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Sample records for human trabecular meshwork

  1. Dexamethasone induced ultrastructural changes in cultured human trabecular meshwork cells.

    PubMed

    Wilson, K; McCartney, M D; Miggans, S T; Clark, A F

    1993-09-01

    Glucocorticoid-induced ocular hypertension has been demonstrated in both animals and humans. It is possible that glucocorticoid-induced changes in trabecular meshwork (TM) cells are responsible for this hypertension. In order to elaborate further the effect of glucocorticoids on the trabecular meshwork, the ultrastructural consequences of dexamethasone (DEX) treatment were examined in three different human TM cell lines. Confluent TM cells were treated with 0.1 microM of DEX for 14 days, and then processed for light, epifluorescent microscopy or transmission electron microscopy (TEM). The effect of DEX treatment on TM cell and nuclear size was quantified using computer assisted morphometrics. Morphometric analysis showed a significant increase in both TM cell and nuclear size after 14 days of DEX treatment. Epifluorescent microscopy of rhodamine-phalloidin stained, control TM cells showed the normal arrangement of stress fibers. In contrast, DEX-treated TM cells showed unusual geodesic dome-like cross-linked actin networks. Control TM cells had the normal complement and arrangement of organelles as well as electron dense inclusions and large vacuoles. DEX-treated TM cells showed stacked arrangements of smooth and rough endoplasmic reticulum, proliferation of the Golgi apparatus, pleomorphic nuclei and increased amounts of extracellular matrix material. The DEX-induced alterations observed in the present study may be an indication of the processes that are occurring in the in vivo disease process.

  2. Oxidative Damage and Autophagy in the Human Trabecular Meshwork as Related with Ageing

    PubMed Central

    Pulliero, Alessandra; Seydel, Anke; Camoirano, Anna; Saccà, Sergio Claudio; Sandri, Marco; Izzotti, Alberto

    2014-01-01

    Autophagy is an intracellular lysosomal degradation process induced under stress conditions. Autophagy also plays a major role in ocular patho-physiology. Molecular aging does occur in the trabecular meshwork, the main regulator of aqueous humor outflow, and trabecular meshwork senescence is accompanied by increased oxidative stress. However, the role of autophagy in trabecular meshwork patho-physiology has not yet been examined in vivo in human ocular tissues. The purpose of the herein presented study is to evaluate autophagy occurrence in ex-vivo collected human trabecular meshwork specimens and to evaluate the relationship between autophagy, oxidative stress, and aging in this tissue. Fresh trabecular meshwork specimens were collected from 28 healthy corneal donors devoid of ocular pathologies and oxidative DNA damage, and LC3 and p62 protein expression analyzed. In a subset of 10 subjects, further to trabecular meshwork proteins, the amounts of cathepesin L and ubiquitin was analyzed by antibody microarray in aqueous humor. Obtained results demonstrate that autophagy activation, measured by LC3II/I ratio, is related with. oxidative damage occurrence during aging in human trabecular meshwork. The expression of autophagy marker p62 was lower in subjects older than 60 years as compared to younger subjects. These findings reflect the occurrence of an agedependent increase in the autophagy as occurring in the trabecular meshwork. Furthermore, we showed that aging promotes trabecular-meshwork senescence due to increased oxidative stress paralleled by autophagy increase. Indeed, both oxidative DNA damage and autophagy were more abundant in subjects older than 60 years. These findings shed new light on the role of oxidative damage and autophagy during trabecular-meshwork aging. PMID:24945152

  3. Tissue-Based Imaging Model of Human Trabecular Meshwork

    PubMed Central

    Chu, Edward R.; Gonzalez, Jose M.

    2014-01-01

    Abstract We have developed a tissue-based model of the human trabecular meshwork (TM) using viable postmortem corneoscleral donor tissue. Two-photon microscopy is used to optically section and image deep in the tissue to analyze cells and extracellular matrix (ECM) within the original three-dimensional (3D) environment of the TM. Multimodal techniques, including autofluorescence (AF), second harmonic generation (SHG), intravital dye fluorescence, and epifluorescence, are combined to provide unique views of the tissue at the cellular and subcellular level. SHG and AF imaging are non-invasive tissue imaging techniques with potential for clinical application, which can be modeled in the system. We describe the following in the tissue-based model: analysis of live cellularity to determine tissue viability; characteristics of live cells based on intravital labeling; features and composition of the TM's structural ECM; localization of specific ECM proteins to regions such as basement membrane; in situ induction and expression of tissue markers characteristic of cultured TM cells relevant to glaucoma; analysis of TM actin and pharmacological effects; in situ visualization of TM, inner wall endothelium, and Schlemm's canal; and application of 3D reconstruction, modeling, and quantitative analysis to the TM. The human model represents a cost-effective use of valuable and scarce yet available human tissue that allows unique cell biology, pharmacology, and translational studies of the TM. PMID:24517246

  4. Comparative Phospholipid Profiles of Control and Glaucomatous Human Trabecular Meshwork

    PubMed Central

    Aribindi, Katyayini; Guerra, Yenifer; Lee, Richard K.; Bhattacharya, Sanjoy K.

    2013-01-01

    Purpose. We compared phospholipid (phosphatidylcholine, phosphatidylserine, phosphatidylethanolamine, and phosphatidylinositol) profiles of control and glaucomatous trabecular meshwork (TM) derived from human donors. Methods. Control TM and most primary open angle glaucoma (POAG) TM were collected from cadaver donors. A select subset of POAG surgical TM samples also were collected for analyses. Lipid extraction was performed using a modification of the Bligh and Dyer method, protein concentrations were determined using the Bradford method, and for select samples confirmed with densitometry of PHAST gels. Lipids were identified and subjected to ratiometric quantification using a TSQ quantum Access Max triple quadrupole mass spectrometer with precursor ion scan (PIS) or neutral ion loss scan (NLS), using appropriate class specific lipid standards. Results. The comparative profiles of phosphatidylcholine, phosphatidylserine, phosphoethanolamine, and phosphatidylinositol between control and glaucomatous TM showed several species common between them. A number of unique lipids in all four phospholipid classes also were identified in control TM that were absent in glaucoma TM and vice versa. Conclusions. A number of phospholipids were found to be uniquely present in control but absent in glaucomatous TM and vice versa. Compared to a previous study of control and POAG blood, a number of these phospholipids are absent locally (TM), as well as systemically (in blood). PMID:23557733

  5. Effect of H-7 on cultured human trabecular meshwork cells.

    PubMed

    Liu, X; Cai, S; Glasser, A; Volberg, T; Polansky, J R; Fauss, D J; Brandt, C R; Geiger, B; Kaufman, P L

    2001-06-27

    To determine the effect of the serine-threonine kinase inhibitor H-7, which blocks actomyosin contractility and increases outflow facility in live monkeys, on morphology, cytoskeleton, and cellular adhesions of human trabecular meshwork (HTM) cells in culture. Cultured HTM cells were videographically recorded and evaluated before and after exposure to H-7 at different concentrations. The subcellular distribution of the actin-based cytoskeleton and associated anchor proteins including vinculin, paxillin, and beta-catenin, as well as phosphotyrosine-containing proteins were evaluated by fluorescence immunocytochemistry and digital fluorescence microscopy. H-7 induced pronounced but reversible HTM cell thickening toward the cell center and deterioration of the actin cytoskeletal network. Cell-extracellular matrix (ECM) and cell-cell adhesions were also affected, but the beta-catenin-rich, vinculin-containing adherens junctions were clearly more resistant than focal contacts. Phosphotyrosine labeling in focal contacts was highly sensitive to H-7. H-7 induces alterations in cell shape, actin cytoskeleton, and associated focal adhesions in cultured HTM cells, which may be responsible for the effects of H-7 on outflow facility in live monkey eyes.

  6. In situ localization of cytoskeletal elements in the human trabecular meshwork and cornea.

    PubMed

    Weinreb, R N; Ryder, M I

    1990-09-01

    The authors compared cytoskeletal elements of the in situ human trabecular-meshwork cell with in situ human corneal cells using indirect immunofluorescence staining for tubulin and intermediate filaments (vimentin, cytokeratin, and desmin) and NBD-phallacidin staining for f-actin using both fixed frozen and unfixed frozen sections from postmortem eyes. Both f-actin and tubulin were found throughout the cell body of trabecular-meshwork cells, keratocytes, corneal endothelium, and corneal epithelium. The f-actin staining pattern was concentrated at the cell periphery of these four cell types. Vimentin stain was intensely localized in focal areas of the trabecular-meshwork cell, keratocytes, and throughout the corneal endothelium. A general anticytokeratin antibody was intensely localized in corneal epithelium and endothelium. However, PKK-1 anticytokeratin antibody was seen only in superficial layers of corneal epithelium and not in corneal endothelium. The 4.62 anticytokeratin antibody was not observed in either corneal epithelium or endothelium. None of these three cytokeratin antibodies were seen in trabecular-meshwork cells or keratocytes. Desmin stain was not noted in any of these cell types. In general, cytoskeletal staining of unfixed frozen sections showed a similar staining pattern for f-actin and tubulin but a more uniform and intense staining pattern for vimentin and cytokeratin compared with fixed frozen material. The authors conclude that these cytoskeletal stains can differentiate human trabecular-meshwork cells from cells of the cornea in situ.

  7. Three-dimensional architecture of collagen type VI in the human trabecular meshwork

    PubMed Central

    Koudouna, Elena; Young, Robert D.; Ueno, Morio; Kinoshita, Shigeru; Knupp, Carlo

    2014-01-01

    Purpose Type VI collagen is a primary component of the extracellular matrix of many connective tissues. It can form distinct aggregates depending on tissue structure, chemical environment, and physiology. In the current study we examine the ultrastructure and mode of aggregation of type VI collagen molecules in the human trabecular meshwork. Methods Trabecular meshwork was dissected from donor human eyes, and three-dimensional transmission electron microscopy of type VI collagen aggregates was performed. Results Electron-dense collagen structures were detected in the human trabecular meshwork and identified as collagen type VI assemblies based on the three-dimensional spatial arrangement of the type VI collagen molecules, the 105-nm axial periodicity of the assemblies themselves, and their characteristic double bands, which arose from the globular domains of the type VI collagen molecules. Sulfated proteoglycans were also seen to associate with the assemblies either with the globular domain or the inner rod-like segments of the tetramers. Conclusions No extended structural regularity in the organization of type VI collagen assemblies within the trabecular meshwork was evident, and the lateral separation of the tetramers forming the assemblies varied, as did the angle formed by the main axes of adjacent tetramers. This is potentially reflective of the specific nature of the trabecular meshwork environment, which facilitates aqueous outflow from the eye, and we speculate that extracellular matrix ions and proteins might prevent a more tight packing of type VI collagen tetramers that form the assemblies. PMID:24868138

  8. Mechanism of Fibronectin Binding to Human Trabecular Meshwork Exosomes and Its Modulation by Dexamethasone

    PubMed Central

    Klingeborn, Mikael; Stamer, W. Daniel

    2016-01-01

    Exosomes are emerging as important mediators of cell-matrix interactions by means of specific adhesion proteins. Changes in the tissue-specific exosomal protein expression may underlie pathological conditions whereby extracellular matrix turnover and homeostasis is disrupted. Ocular hypertension due to extracellular matrix accumulation in the trabecular meshwork is a hallmark of glucocorticoid-induced glaucoma. In the trabecular meshwork, exosomal fibronectin mediates cell matrix interactions at cellular structures called “invadosomes”. Trabecular meshwork cells use invadosomes to turn over their surrounding matrix and maintain passageways for flow of aqueous humor. In this study, we observed that human trabecular meshwork explants treated with dexamethasone released exosomes with significantly reduced amounts of fibronectin bound per exosome. Further, we found that exosome-fibronectin binding is heparan sulfate-dependent, consistent with our observation that trabecular meshwork exosomes are enriched in the heparin/heparan sulfate binding annexins A2 and A6. In this way, dexamethasone-treated explants released exosomes with a significant reduction in annexin A2 and A6 per exosome. Interestingly, we did not detect exosomal matrix metalloproteinases, but we identified abundant dipeptidyl peptidase 4, a serine protease whose activity was reduced on exosomes isolated from dexamethasone-treated explants. Together, our findings demonstrate mechanistically how corticosteroid-induced alterations in exosomal adhesion cargo and properties can account for the pathological matrix accumulation seen in many glaucoma patients. PMID:27783649

  9. Regulatory Roles of Anoctamin-6 in Human Trabecular Meshwork Cells

    PubMed Central

    Banerjee, Juni; Leung, Chi-Ting; Li, Ang; Peterson-Yantorno, Kim; Ouyang, Huan; Stamer, W. Daniel; Civan, Mortimer M.

    2017-01-01

    Purpose Trabecular meshwork (TM) cell volume is a determinant of aqueous humor outflow resistance, and thereby IOP. Regulation of TM cell volume depends on chloride ion (Cl−) release through swelling-activated channels (ICl,Swell), whose pore is formed by LRRC8 proteins. Chloride ion release through swelling-activated channels has been reported to be regulated by calcium-activated anoctamins, but this finding is controversial. Particularly uncertain has been the effect of anoctamin Ano6, reported as a Ca2+-activated Cl− (CaCC) or cation channel in other cells. The current study tested whether anoctamin activity modifies volume regulation of primary TM cell cultures and cell lines. Methods Gene expression was studied with quantitative PCR, supplemented by reverse-transcriptase PCR and Western immunoblots. Currents were measured by ruptured whole-cell patch clamping and volume by electronic cell sizing. Results Primary TM cell cultures and the TM5 and GTM3 cell lines expressed Ano6 3 to 4 orders of magnitude higher than the other anoctamin CaCCs (Ano1 and Ano2). Ionomycin increased cell Ca2+ and activated macroscopic currents conforming to CaCCs in other cells, but displayed significantly more positive mean reversal potentials (+5 to +12 mV) than those displayed by ICl,Swell (−14 to −21 mV) in the same cells. Nonselective CaCC inhibitors (tannic acid>CaCCinh−A01) and transient Ano6 knockdown strongly inhibited ionomycin-activated currents, ICl,Swell and the regulatory volume response to hyposmotic swelling. Conclusions Ionomycin activates CaCCs associated with net cation movement in TM cells. These currents, ICl,Swell, and cell volume are regulated by Ano6. The findings suggest a novel clinically-relevant approach for altering cell volume, and thereby outflow resistance, by targeting Ano6. PMID:28125837

  10. Serial analysis of gene expression (SAGE) in normal human trabecular meshwork.

    PubMed

    Liu, Yutao; Munro, Drew; Layfield, David; Dellinger, Andrew; Walter, Jeffrey; Peterson, Katherine; Rickman, Catherine Bowes; Allingham, R Rand; Hauser, Michael A

    2011-04-08

    To identify the genes expressed in normal human trabecular meshwork tissue, a tissue critical to the pathogenesis of glaucoma. Total RNA was extracted from human trabecular meshwork (HTM) harvested from 3 different donors. Extracted RNA was used to synthesize individual SAGE (serial analysis of gene expression) libraries using the I-SAGE Long kit from Invitrogen. Libraries were analyzed using SAGE 2000 software to extract the 17 base pair sequence tags. The extracted sequence tags were mapped to the genome using SAGE Genie map. A total of 298,834 SAGE tags were identified from all HTM libraries (96,842, 88,126, and 113,866 tags, respectively). Collectively, there were 107,325 unique tags. There were 10,329 unique tags with a minimum of 2 counts from a single library. These tags were mapped to known unique Unigene clusters. Approximately 29% of the tags (orphan tags) did not map to a known Unigene cluster. Thirteen percent of the tags mapped to at least 2 Unigene clusters. Sequence tags from many glaucoma-related genes, including myocilin, optineurin, and WD repeat domain 36, were identified. This is the first time SAGE analysis has been used to characterize the gene expression profile in normal HTM. SAGE analysis provides an unbiased sampling of gene expression of the target tissue. These data will provide new and valuable information to improve understanding of the biology of human aqueous outflow.

  11. [Ultrastructural characteristics of glaucomatous trabecular meshwork].

    PubMed

    Potau, J M; Canals, M; Costa, J; Merindano, M D; Ruano, D

    2000-01-01

    To compare the normal and glaucomatous trabecular meshwork ultrastructure and to relate the observed changes with the intraocular pressure increase characteristic of the primary open angle glaucoma. 21 non glaucomatous trabecular meshworks, aged 23 to 99 years, and 5 from patients diagnosed of primary open angle glaucoma, aged 40 to 65 years, were fixed by Karnovsky's solution and processed and observed by transmission electron microscopy and their morphological characteristics were qualitatively compared. Ultrastructural changes of glaucomatous trabecular meshworks are similar, but much more intense, than those observed in the aged normal trabecular meshworks. These changes are loss of endothelial cells, thickening of basal membranes and trabecular beam central nucleus changes such as an increase of electrodense plaques and collagen degenerative processes. Ultrastructural changes observed in glaucomatous trabecular meshworks are comparable to an early aging of them. These changes can be related with the mechanisms that increase the intraocular pressure in primary open-angle glaucoma.

  12. Dexamethasone Stiffens Trabecular Meshwork, Trabecular Meshwork Cells, and Matrix

    PubMed Central

    Raghunathan, Vijay Krishna; Morgan, Joshua T.; Park, Shin Ae; Weber, Darren; Phinney, Brett S.; Murphy, Christopher J.; Russell, Paul

    2015-01-01

    Purpose Treatment with corticosteroids can result in ocular hypertension and may lead to the development of steroid-induced glaucoma. The extent to which biomechanical changes in trabecular meshwork (TM) cells and extracellular matrix (ECM) contribute toward this dysfunction is poorly understood. Methods Primary human TM (HTM) cells were cultured for either 3 days or 4 weeks in the presence or absence of dexamethasone (DEX), and cell mechanics, matrix mechanics and proteomics were determined, respectively. Adult rabbits were treated topically with either 0.1% DEX or vehicle over 3 weeks, and mechanics of the TM were determined. Results Treatment with DEX for 3 days resulted in a 2-fold increase in HTM cell stiffness, and this correlated with activation of extracellular signal-related kinase 1/2 (ERK1/2) and overexpression of α-smooth muscle actin (αSMA). Further, the matrix deposited by HTM cells chronically treated with DEX is approximately 4-fold stiffer, more organized, and has elevated expression of matrix proteins commonly implicated in glaucoma (decorin, myocilin, fibrillin, secreted frizzle-related protein [SFRP1], matrix-gla). Also, DEX treatment resulted in a 3.5-fold increase in stiffness of the rabbit TM. Discussion This integrated approach clearly demonstrates that DEX treatment increases TM cell stiffness concurrent with elevated αSMA expression and activation of the mitogen-activated protein kinase (MAPK) pathway, stiffens the ECM in vitro along with upregulation of Wnt antagonists and fibrotic markers embedded in a more organized matrix, and increases the stiffness of TM tissues in vivo. These results demonstrate glucocorticoid treatment can initiate the biophysical alteration associated with increased resistance to aqueous humor outflow and the resultant increase in IOP. PMID:26193921

  13. Pharmacological Regulation of SPARC by Lovastatin in Human Trabecular Meshwork Cells

    PubMed Central

    Villarreal, Guadalupe; Chatterjee, Ayan; Oh, Sarah S.; Oh, Dong-Jin; Rhee, Douglas J.

    2014-01-01

    Purpose. Statins have been shown to increase aqueous outflow facility. The matricellular protein SPARC (secreted protein acidic and rich in cysteine) is a critical mediator of aqueous outflow and intraocular pressure (IOP). Here, we examine the effects of lovastatin on SPARC expression in trabecular meshwork (TM) cells, exploring the molecular mechanisms involved. Methods. Primary cultured human TM cells were incubated for 24, 48, and 72 hours with 10 μM lovastatin. In separate cultures, media was supplemented with either farnesyl pyrophosphate (FPP) or geranylgeranyl pyrophosphate (GGPP) for the duration of the 72-hour time point experiment. Trabecular meshwork cells were also pretreated for 24 hours with lovastatin followed by 24-hour stimulation with 3 ng/mL TGF-β2. Cell lysates and media were harvested and relative mRNA and protein level changes were determined. Krüppel-like factor 4 (KLF4) localization in normal human anterior segments was examined by immunofluorescence. Adenovirus expressing human KLF4 was used and relative changes in SPARC mRNA and protein levels were assessed. Results. Incubating TM cells with lovastatin suppressed SPARC mRNA and protein levels. This effect was reversed upon media supplementation with GGPP but not FPP. Pretreating cells with lovastatin inhibited TGF-β2 induction of SPARC. The KLF4 transcription factor was expressed throughout the TM and the inner and outer walls of Schlemm's canal. Lovastatin treatment upregulated KLF4 mRNA and protein levels. Overexpression of KLF4 downregulated SPARC expression. Conclusions. Collectively, our data identify lovastatin as an important pharmacological suppressor of SPARC expression in TM cells, and provide further insight into the molecular mechanisms mediating statin enhancement of aqueous outflow facility. PMID:24474275

  14. Pharmacological regulation of SPARC by lovastatin in human trabecular meshwork cells.

    PubMed

    Villarreal, Guadalupe; Chatterjee, Ayan; Oh, Sarah S; Oh, Dong-Jin; Rhee, Douglas J

    2014-03-19

    Statins have been shown to increase aqueous outflow facility. The matricellular protein SPARC (secreted protein acidic and rich in cysteine) is a critical mediator of aqueous outflow and intraocular pressure (IOP). Here, we examine the effects of lovastatin on SPARC expression in trabecular meshwork (TM) cells, exploring the molecular mechanisms involved. Primary cultured human TM cells were incubated for 24, 48, and 72 hours with 10 μM lovastatin. In separate cultures, media was supplemented with either farnesyl pyrophosphate (FPP) or geranylgeranyl pyrophosphate (GGPP) for the duration of the 72-hour time point experiment. Trabecular meshwork cells were also pretreated for 24 hours with lovastatin followed by 24-hour stimulation with 3 ng/mL TGF-β2. Cell lysates and media were harvested and relative mRNA and protein level changes were determined. Krüppel-like factor 4 (KLF4) localization in normal human anterior segments was examined by immunofluorescence. Adenovirus expressing human KLF4 was used and relative changes in SPARC mRNA and protein levels were assessed. Incubating TM cells with lovastatin suppressed SPARC mRNA and protein levels. This effect was reversed upon media supplementation with GGPP but not FPP. Pretreating cells with lovastatin inhibited TGF-β2 induction of SPARC. The KLF4 transcription factor was expressed throughout the TM and the inner and outer walls of Schlemm's canal. Lovastatin treatment upregulated KLF4 mRNA and protein levels. Overexpression of KLF4 downregulated SPARC expression. Collectively, our data identify lovastatin as an important pharmacological suppressor of SPARC expression in TM cells, and provide further insight into the molecular mechanisms mediating statin enhancement of aqueous outflow facility.

  15. Bioengineered Glaucomatous 3D Human Trabecular Meshwork as an in vitro Disease Model

    PubMed Central

    Torrejon, Karen Y.; Papke, Ellen L.; Halman, Justin R.; Stolwijk, Judith; Dautriche, Cula N.; Bergkvist, Magnus; Danias, John; Sharfstein, Susan T.; Xie, Yubing

    2016-01-01

    Intraocular pressure (IOP) is mostly regulated by aqueous humor outflow through the human trabecular meshwork (HTM) and represents the only modifiable risk factor of glaucoma. The lack of IOP-modulating therapeutics that targets HTM underscores the need of engineering HTM for understanding the outflow physiology and glaucoma pathology in vitro. Using a 3D HTM model that allows for regulation of outflow in response to a pharmacologic steroid, a fibrotic state has been induced resembling that of glaucomatous HTM. This disease model exhibits HTM marker expression, ECM overproduction, impaired HTM cell phagocytic activity and outflow resistance, which represent characteristics found in steroid-induced glaucoma. In particular, steroid-induced ECM alterations in the glaucomatous model can be modified by a ROCK inhibitor. Altogether, this work presents a novel in vitro disease model that allows for physiological and pathological studies pertaining to regulating outflow, leading to improved understanding of steroid-induced glaucoma and accelerated discovery of new therapeutic targets. PMID:26615056

  16. Cellular Fibronectin Expression in Human Trabecular Meshwork and Induction by Transforming Growth Factor-β2

    PubMed Central

    Medina-Ortiz, Wanda E.; Belmares, Ricardo; Neubauer, Sandra; Wordinger, Robert J.; Clark, Abbot F.

    2013-01-01

    Purpose. Levels of TGF-β2 are higher in POAG aqueous humor, causing deposition of extracellular matrix (ECM) proteins, including fibronectin (FN), in the glaucomatous human trabecular meshwork (HTM) that may be responsible for elevated IOP. The purpose of this study was to identify the expression of cellular FN (cFN) isoforms (EDA and EDB) in HTM cells and tissues, and to determine whether TGF-β2 can induce cFN expression and fibril formation in cultured HTM cells. Methods. Expression of cFN mRNA isoforms and induction by recombinant TGF-β2 (5 ng/mL) were determined by quantitative RT-PCR. The TGF-β2 induction of EDA isoform protein expression and FN fibril formation were analyzed using Western immunoblots and immunocytochemistry (ICC), respectively. Immunohistochemistry (IHC) analysis was used to examine total FN and EDA isoform expression in normal (NTM) and glaucomatous (GTM) trabecular meshwork (TM) tissues. Results. Both cFN mRNA isoforms were expressed in cultured HTM cells and were induced by TGF-β2 after 2, 4, and 7 days (P < 0.05). Similarly, EDA isoform protein and fibril formation were increased after 4 and 7 days of TGF-β2 treatment. Finally, GTM tissues had significantly greater EDA isoform protein levels (1.7-fold, P < 0.05) compared to NTM tissues. Conclusions. This study demonstrated that cFN isoforms are expressed and induced in HTM cells by TGF-β2. Also, increased EDA isoform protein levels were seen in GTM tissues. Our findings suggest that induction of cFN isoform expression in the TM ECM may be a novel pathologic mechanism involved in the TM changes associated with glaucoma. PMID:24030464

  17. Trans-scleral imaging of the human trabecular meshwork by two-photon microscopy

    PubMed Central

    Ammar, David A.; Lei, Tim C.; Masihzadeh, Omid; Gibson, Emily A.

    2011-01-01

    Purpose To image the native (unfixed) human trabecular meshwork (TM) through the overlying sclera using a non-invasive, non-destructive technique. Methods Two-photon microscopic (2PM) methods, including two-photon autofluorescence (2PAF) and second harmonic generation (SHG), were used to image through the sclera of a human cadaver eye into the TM region. Multiple images were analyzed along the tissue axis (z-axis) to generate a three-dimensional (3D) model of the region. The tissue was subsequently fixed, paraffin embedded, and histological sections were photographed for comparison to the 2PM images. Results 3D analysis of multiple 2PM SHG images revealed an open region deep within the TM consistent with the location of Schlemm’s canal (SC). Images of the scleral spur and surrounding tissues were also obtained. The SC, TM, scleral spur, and surrounding tissue images obtained with 2PM matched with histologically stained sections of the same tissue. Conclusions 2PM imaging of the outflow system of the human eye documented collagenous structures solely from inherent optical properties. 2PM successfully imaged through the sclera into the SC/TM without the need for fixation, embedding, or histological processing. This work reveals that 2PM imaging has potential as a new metric for evaluating the aqueous outflow region of the human eye and is worthy of further exploration. PMID:21386924

  18. Role of TGFβ/Smad Signaling in Gremlin Induction of Human Trabecular Meshwork Extracellular Matrix Proteins

    PubMed Central

    Sethi, Anirudh; Jain, Ankur; Zode, Gulab S.; Wordinger, Robert J.

    2011-01-01

    Purpose. The bone morphogenic protein (BMP) antagonist gremlin is elevated in glaucomatous trabecular meshwork (TM) cells and tissues and elevates intraocular pressure (IOP). Gremlin also blocks BMP4 inhibition of transforming growth factor (TGF)-β2 induction of TM extracellular matrix (ECM) proteins. The purpose of this study was to determine whether Gremlin regulates ECM proteins in cultured human TM cells. Methods. Human TM cells were treated with recombinant gremlin to determine the effects on ECM gene and protein expression. Expression of the ECM genes FN, COL1, PAI1, and ELN was examined in cultured human TM cells by quantitative RT-PCR and Western immunoblot analysis. TM cells were pretreated with TGFBR inhibitors (LY364947, SB431542 or TGFBR1/TGFB2 siRNAs), inhibitors of the Smad signaling pathway (SIS3 or Smad2/3/4 siRNAs), or CTGF siRNA to identify the signaling pathway(s) involved in gremlin induction of ECM gene and protein expression. Results. All ECM genes analyzed (FN, COL1, PAI1, and ELN) were induced by gremlin. This gremlin induction of ECM genes and protein expression was blocked by inhibitors of TGFBR and the canonical Smad2/3/4 and CTGF signaling pathways. Conclusions. Gremlin employs canonical TGFβ2/Smad signaling to induce ECM genes and proteins in cultured human TM cells. Gremlin also induces both TGFβ2 and CTGF, which can act downstream to mediate some of these ECM changes in TM cells. PMID:21642622

  19. Enhanced cytomegalovirus infection in human trabecular meshwork cells and its implication in glaucoma pathogenesis

    PubMed Central

    Choi, Jin A; Kim, Ju-Eun; Noh, Seung-Jun; Kyoung Kim, Eun; Park, Chan Kee; Paik, Soon-Young

    2017-01-01

    Cytomegalovirus (CMV) is one of the infectious causes of hypertensive anterior uveitis, which is characterized by recurrent episodes of elevated intraocular pressure (IOP) and mild anterior uveitis. Despite the potentially vision-threatening complications of this disease, the underlying mechanisms remain largely undefined. We aimed to investigate whether human trabecular meshwork (TM) cells, the key cell type that regulates IOP, could support CMV replication, as well as demonstrate the relevant pathological changes in TM. When human TM cells were infected with CMV AD169, immediate early antigens were detected 1 day post-infection (dpi); cytopathic changes including rounding, a ballooned appearance with disorganization, and a decreased number of stress fibers were noted in TM cells. The marked increase in viral DNA accumulation was observed most notably at 5 and 7 dpi, suggesting that the active viral infection in human TM cells could be the key mechanism underlying the elevation of IOP in anterior viral uveitis. Notably, CMV infection enhanced the production of transforming growth factor (TGF)-β1, an upstream molecule that increases the resistance of the outflow pathway in human TM cells. The increase of TGF-β1 was countervailed by additional treatment with corticosteroids. Our results provide a pathogenic mechanism for IOP elevation in viral anterior uveitis. PMID:28240260

  20. The formation of cortical actin arrays in human trabecular meshwork cells in response to cytoskeletal disruption.

    PubMed

    Murphy, Kaitlin C; Morgan, Joshua T; Wood, Joshua A; Sadeli, Adeline; Murphy, Christopher J; Russell, Paul

    2014-10-15

    The cytoskeleton of human trabecular meshwork (HTM) cells is known to be altered in glaucoma and has been hypothesized to reduce outflow facility through contracting the HTM tissue. Latrunculin B (Lat-B) and Rho-associated protein kinase (ROCK) inhibitors disrupt the actin cytoskeleton and are in clinical trials as glaucoma therapeutics. We have previously reported a transient increase in HTM cell stiffness peaking at 90 min after Lat-B treatment with a return to pretreatment values after 270 min. We hypothesize that changes in actin morphology correlate with alterations in cell stiffness induced by Lat-B but this is not a general consequence of other cytoskeletal disrupting agents such as Rho kinase inhibitors. We treated HTM cells with 2 µM Lat-B or 100 µM Y-27632 and allowed the cells to recover for 30-270 min. While examining actin morphology in Lat-B treated cells, we observed striking cortical actin arrays (CAAs). The percentage of CAA positive cells (CPCs) was time dependent and exceeded 30% at 90 min and decreased after 270 min. Y-27632 treated cells exhibited few CAAs and no changes in cell stiffness. Together, these data suggest that the increase in cell stiffness after Lat-B treatment is correlated with CAAs.

  1. The intrinsic stiffness of human trabecular meshwork cells increases with senescence

    PubMed Central

    Chang, Yow-Ren; Murphy, Christopher J.; Russell, Paul

    2015-01-01

    Dysfunction of the human trabecular meshwork (HTM) plays a central role in the age-associated disease glaucoma, a leading cause of irreversible blindness. The etiology remains poorly understood but cellular senescence, increased stiffness of the tissue, and the expression of Wnt antagonists such as secreted frizzled related protein-1 (SFRP1) have been implicated. However, it is not known if senescence is causally linked to either stiffness or SFRP1 expression. In this study, we utilized in vitro HTM senescence to determine the effect on cellular stiffening and SFRP1 expression. Stiffness of cultured cells was measured using atomic force microscopy and the morphology of the cytoskeleton was determined using immunofluorescent analysis. SFRP1 expression was measured using qPCR and immunofluorescent analysis. Senescent cell stiffness increased 1.88±0.14 or 2.57±0.14 fold in the presence or absence of serum, respectively. This was accompanied by increased vimentin expression, stress fiber formation, and SFRP1 expression. In aggregate, these data demonstrate that senescence may be a causal factor in HTM stiffening and elevated SFRP1 expression, and contribute towards disease progression. These findings provide insight into the etiology of glaucoma and, more broadly, suggest a causal link between senescence and altered tissue biomechanics in aging-associated diseases. PMID:25915531

  2. Bioengineered glaucomatous 3D human trabecular meshwork as an in vitro disease model.

    PubMed

    Torrejon, Karen Y; Papke, Ellen L; Halman, Justin R; Stolwijk, Judith; Dautriche, Cula N; Bergkvist, Magnus; Danias, John; Sharfstein, Susan T; Xie, Yubing

    2016-06-01

    Intraocular pressure (IOP) is mostly regulated by aqueous humor outflow through the human trabecular meshwork (HTM) and represents the only modifiable risk factor of glaucoma. The lack of IOP-modulating therapeutics that targets HTM underscores the need of engineering HTM for understanding the outflow physiology and glaucoma pathology in vitro. Using a 3D HTM model that allows for regulation of outflow in response to a pharmacologic steroid, a fibrotic state has been induced resembling that of glaucomatous HTM. This disease model exhibits HTM marker expression, ECM overproduction, impaired HTM cell phagocytic activity and outflow resistance, which represent characteristics found in steroid-induced glaucoma. In particular, steroid-induced ECM alterations in the glaucomatous model can be modified by a ROCK inhibitor. Altogether, this work presents a novel in vitro disease model that allows for physiological and pathological studies pertaining to regulating outflow, leading to improved understanding of steroid-induced glaucoma and accelerated discovery of new therapeutic targets. Biotechnol. Bioeng. 2016;113: 1357-1368. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

  3. Estimating Human Trabecular Meshwork Stiffness by Numerical Modeling and Advanced OCT Imaging.

    PubMed

    Wang, Ke; Johnstone, Murray A; Xin, Chen; Song, Shaozhen; Padilla, Steven; Vranka, Janice A; Acott, Ted S; Zhou, Kai; Schwaner, Stephen A; Wang, Ruikang K; Sulchek, Todd; Ethier, C Ross

    2017-09-01

    The purpose of this study was to estimate human trabecular meshwork (hTM) stiffness, thought to be elevated in glaucoma, using a novel indirect approach, and to compare results with direct en face atomic force microscopy (AFM) measurements. Postmortem human eyes were perfused to measure outflow facility and identify high- and low-flow regions (HF, LF) by tracer. Optical coherence tomography (OCT) images were obtained as Schlemm's canal luminal pressure was directly manipulated. TM stiffness was deduced by an inverse finite element modeling (FEM) approach. A series of AFM forcemaps was acquired along a line traversing the anterior angle on a radially cut flat-mount corneoscleral wedge with TM facing upward. The elastic modulus of normal hTM estimated by inverse FEM was 70 ± 20 kPa (mean ± SD), whereas glaucomatous hTM was slightly stiffer (98 ± 19 kPa). This trend was consistent with TM stiffnesses measured by AFM: normal hTM stiffness = 1.37 ± 0.56 kPa, which was lower than glaucomatous hTM stiffness (2.75 ± 1.19 kPa). None of these differences were statistically significant. TM in HF wedges was softer than that in LF wedges for both normal and glaucomatous eyes based on the inverse FEM approach but not by AFM. Outflow facility was significantly correlated with TM stiffness estimated by FEM in six human eyes (P = 0.018). TM stiffness is higher, but only modestly so, in glaucomatous patients. Outflow facility in both normal and glaucomatous human eyes appears to associate with TM stiffness. This evidence motivates further studies to investigate factors underlying TM biomechanical property regulation.

  4. Estimating Human Trabecular Meshwork Stiffness by Numerical Modeling and Advanced OCT Imaging

    PubMed Central

    Wang, Ke; Johnstone, Murray A.; Xin, Chen; Song, Shaozhen; Padilla, Steven; Vranka, Janice A.; Acott, Ted S.; Zhou, Kai; Schwaner, Stephen A.; Wang, Ruikang K.; Sulchek, Todd; Ethier, C. Ross

    2017-01-01

    Purpose The purpose of this study was to estimate human trabecular meshwork (hTM) stiffness, thought to be elevated in glaucoma, using a novel indirect approach, and to compare results with direct en face atomic force microscopy (AFM) measurements. Methods Postmortem human eyes were perfused to measure outflow facility and identify high- and low-flow regions (HF, LF) by tracer. Optical coherence tomography (OCT) images were obtained as Schlemm's canal luminal pressure was directly manipulated. TM stiffness was deduced by an inverse finite element modeling (FEM) approach. A series of AFM forcemaps was acquired along a line traversing the anterior angle on a radially cut flat-mount corneoscleral wedge with TM facing upward. Results The elastic modulus of normal hTM estimated by inverse FEM was 70 ± 20 kPa (mean ± SD), whereas glaucomatous hTM was slightly stiffer (98 ± 19 kPa). This trend was consistent with TM stiffnesses measured by AFM: normal hTM stiffness = 1.37 ± 0.56 kPa, which was lower than glaucomatous hTM stiffness (2.75 ± 1.19 kPa). None of these differences were statistically significant. TM in HF wedges was softer than that in LF wedges for both normal and glaucomatous eyes based on the inverse FEM approach but not by AFM. Outflow facility was significantly correlated with TM stiffness estimated by FEM in six human eyes (P = 0.018). Conclusions TM stiffness is higher, but only modestly so, in glaucomatous patients. Outflow facility in both normal and glaucomatous human eyes appears to associate with TM stiffness. This evidence motivates further studies to investigate factors underlying TM biomechanical property regulation.

  5. Tissue-based multiphoton analysis of actomyosin and structural responses in human trabecular meshwork

    PubMed Central

    Gonzalez, Jose M.; Ko, Minhee K.; Pouw, Andrew; Tan, James C. H.

    2016-01-01

    The contractile trabecular meshwork (TM) modulates aqueous humor outflow resistance and intraocular pressure. The primary goal was to visualize and quantify human TM contractile state by analyzing actin polymerization (F-actin) by 2-photon excitation fluorescence imaging (TPEF) in situ. A secondary goal was to ascertain if structural extracellular matrix (ECM) configuration changed with contractility. Viable ex vivo human TM was incubated with latrunculin-A (Lat-A) or vehicle prior to Alexa-568-phalloidin labeling and TPEF. Quantitative image analysis was applied to 2-dimensional (2D) optical sections and 3D image reconstructions. After Lat-A exposure, (a) the F-actin network reorganized as aggregates; (b) F-actin-associated fluorescence intensity was reduced by 48.6% (mean; p = 0.007; n = 8); (c) F-actin 3D distribution was reduced by 68.9% (p = 0.040); (d) ECM pore cross-sectional area and volume were larger by 36% (p = 0.032) and 65% (p = 0.059) respectively and pores appeared more interconnected; (e) expression of type I collagen and elastin, key TM structural ECM proteins, were unaltered (p = 0.54); and (f) tissue viability was unchanged (p = 0.39) relative to vehicle controls. Thus Lat-A-induced reduction of actomyosin contractility was associated with TM porous expansion without evidence of reduced structural ECM protein expression or cellular viability. These important subcellular-level dynamics could be visualized and quantified within human tissue by TPEF. PMID:26883567

  6. Fluorescent Protein–Labeled Glucocorticoid Receptor alpha Isoform Trafficking in Cultured Human Trabecular Meshwork Cells

    PubMed Central

    Dibas, Adnan; Jiang, Ming; Fudala, Rafal; Gryczynski, Ignacy; Gryczynski, Zygmunt; Clark, Abbot F.; Yorio, Thomas

    2012-01-01

    Purpose. To characterize the roles of the cytoskeleton and heat shock protein 90 (HSP90) in steroid-induced glucocorticoid receptor alpha (GRα) translocation in cultured human trabecular meshwork cells. Methods. Stably transfected red fluorescent protein (RFP)-GRα NTM5 cell lines were developed. Nuclear localization of RFP-GRα in NTM5 cells treated with vehicle (ethanol), dexamethasone (DEX), or RU486 was measured in cytosolic and nuclear fractions by western blotting and laser confocal microscopy. Cytochalasin D, colchicine, and 17-demethoxygeldanamycin (17AAG, an HSP90 inhibitor), were tested for their abilities to affect GRα trafficking. Nuclear export of RFP-GRα was studied using confocal microscopy following DEX or RU486 removal. Results. NTM5 cells transfected with RFP-GRα showed a clear cytosolic localization of receptor that underwent nuclear localization after DEX treatment. RFP-GRα translocation was temperature sensitive, occurring at 37°C but not at room temperature. Neither cytochalasin D nor colchicine blocked DEX-induced or RU486-induced RFP-GRα nuclear translocation; however, 17AAG prevented DEX-induced RFP-GRα nuclear translocation. Both nuclear import and export of DEX-induced RFP-GRα were faster than RU-486–induced nuclear shuttling. Conclusions. RFP-GRα receptor behaves similarly to the wild-type GRα with its cytosolic localization and shuttling to nucleus after DEX or RU486 treatment. HSP90 is required for nuclear translocation, but the disruption of cytoskeleton had no effect on nuclear translocation of RFP-GRα. PMID:22447868

  7. Morphological changes and viability of primary cultured human ocular trabecular meshwork cells after exposure to air.

    PubMed

    Kopsachilis, Nikolaos; Tsaousis, Konstantinos T; Carifi, Gianluca; Welge-Luessen, Ulrich

    2014-06-01

    To investigate the possible toxic effect of air exposure for an in vitro model of primary human ocular trabecular meshwork cells (HTM). HTM were isolated from five donor eyes and cultivated at 37 °C. After reaching confluence the cells were seeded on two well chamber slides. The chamber slides were turned upside down in a Petri culture dish full of culture medium and filled with air using a 5 ml syringe, starting this way the exposure of the cells to the air. Subsequently they were placed in the incubation chamber at 37 °C. Six groups of HTM cultures were set up: group 1 consisted of samples in which HTM were exposed to air for 30 min, group 2 for 1 h, group 3 for 3 h, group 4 for 6 h, group 5 for 12 h and group 6 for 24 h. At 3 h after exposure, the morphology of the cells was still intact, at 6 h few cells appeared deformed and exhibited characteristics of more senescent cells. At 12 h after exposure to air the HTM cells started losing their typical morphology and appeared enlarged and compromised. Viability was superior to 94% in groups 1-3 while for groups 4, 5, 6 it was 82.7%, 39.5% and 12.7% respectively. The toxic effect of air exposure for the studied in vitro model of HTM is not significant for the time period of one to three hours. However it starts reducing viability and alternating morphology 6 h after exposure until the time period of 24 h, where the percentage of living cells is drastically decreased. Therefore, we suggest that the use of an air bubble especially in glaucomatous patients should be applied with caution. Copyright © 2014 Elsevier Ltd. All rights reserved.

  8. Surgery on the Trabecular Meshwork: Histopathological Evidence

    PubMed Central

    Bhartiya, Shibal; Ichhpujani, Parul

    2015-01-01

    ABSTRACT Juxtacanalicular (JXT) trabecular meshwork and endothelial lining of Schlemm’s canal have been cited as the loci of aqueous outflow resistance, both in a normal as well as a glaucomatous eye. In this review, we attempt to understand the currently available surgical modalities in light of the available histopathological evidence, regarding localization of outflow resistance. How to cite this article: Bhartiya S, Ichhpujani P, Shaarawy T. Surgery on the Trabecular Meshwork: Histopathological Evidence. J Curr Glaucoma Pract 2015;9(2):51-61. PMID:26997835

  9. Cross-talk between TGF-beta1 and IL-6 in human trabecular meshwork cells.

    PubMed

    Liton, Paloma B; Li, Guorong; Luna, Coralia; Gonzalez, Pedro; Epstein, David L

    2009-01-01

    To investigate the relationship between transforming growth factor beta-1 (TGF-beta1) and interleukin-6 (IL-6) in human trabecular meshwork (HTM) cells as well as to identify the signaling pathway/s involved in the increased IL-6 expression that occurs in response to mechanical stress and TGF-beta1. All experiments were performed in confluent monolayers of HTM cells at passage 3. Secreted IL-6 was quantified by ELISA. Levels of IL-6 mRNA were evaluated by polymerase chain reaction (PCR) analysis. Activation of the IL-6 and TGF-beta1 promoters was monitored by measuring secreted alkaline phosphatase protein (SEAP) released into the culture medium by HTM cells infected with an adenovirus expressing the SEAP reporter gene that was controlled by either the IL-6 promoter (AdIL6-SEAP) or the TGF-beta1 promoter (AdTGFbeta1-SEAP). Cyclic mechanical stress (5% elongation, one cycle per second) was applied using the Flexcell System. Reagents used in this study included human TGF-beta1, human IL-6, and the inhibitors for the p38 mitogen-activated protein kinase (MAPK; SB202190), c-jun NH2-terminal kinase (JNK; SP600125), extracellular-regulating kinase (ERK; PD98059), and TGF type I activin receptor (SB431542). Incubation of HTM cells with TGF-beta1 (5 ng/ml) resulted in a significant increase in the protein and mRNA levels of IL-6, which was significantly diminished in the presence of the inhibitors for p38 MAPK or JNK. No transcriptional activation of the exogenous IL-6 promoter was observed following TGF-beta1 treatment. In addition, the presence of inhibitors for the p38 MAPK, ERK, and TGF-beta1 pathways significantly decreased the increased expression of IL-6 by cyclic mechanical stress. Furthermore, exposure of HTM cells to IL-6 (100 ng/ml) demonstrated the transcriptional activation of TGF-beta1 promoter, which was severely impaired by blocking the p38 MAPK pathway. Our results indicate that TGF-beta1 participates in the regulation of basal expression and the stretch

  10. Increased Endoplasmic Reticulum Stress in Human Glaucomatous Trabecular Meshwork Cells and Tissues.

    PubMed

    Peters, Joseph C; Bhattacharya, Sanjoy; Clark, Abbot F; Zode, Gulab S

    2015-06-01

    Primary open-angle glaucoma (POAG) is the most common form of glaucoma and is accompanied by elevated intraocular pressure (IOP) resulting from increased aqueous humor outflow resistance through the trabecular meshwork (TM). The pathological mechanisms underlying increased outflow resistance have not been fully delineated. We recently demonstrated that chronic endoplasmic reticulum (ER) stress in the TM is associated with ocular hypertension in mouse models of glaucoma. The purpose of this study was to determine whether ER stress is also increased in human glaucomatous TM cells and tissues. Endoplasmic reticulum stress markers including GRP78, GRP94, and C/EBP homologous protein (CHOP) were examined by immunohistochemistry in the TM of age-matched normal (n = 18) and open-angle glaucoma donors (n = 18). GRP78, GRP94, activating transcription factor (ATF)-4, endoplasmic oxidoreductin-1alpha (ERO-1α), phosphorylated eukaryotic translation initiation factor 2α (EIF-2α), and CHOP were examined by Western blot analysis in TM tissue lysates from age-matched normal (n = 4) and POAG donors (n = 5). In addition, ER stress markers were examined in primary TM cells isolated from normal (n = 4 NTM) and glaucoma (n = 4 GTM) human donors. Immunohistochemical analysis demonstrated a significant increase in GRP78 and GRP94 in the glaucomatous TM (n = 18) compared to normal TM (P < 0.0001, n = 18). Interestingly, there was minimum CHOP immunostaining observed in normal TM tissues. However, there was a 3-fold increase in CHOP levels in the glaucomatous TM (P < 0.0001; n = 18), indicating the presence of chronic ER stress in the glaucomatous TM. Western blot analysis of TM tissue lysates also demonstrated increased ER stress markers in the glaucomatous TM tissues including GRP78, GRP94, ATF-4, ERO-1α, and CHOP. Densitometric analysis of Western blots showed a significant increase in ATF-4, ERO-1α, and CHOP expression in the glaucomatous TM (n = 5) compared to age-matched normal

  11. OCT Study of Mechanical Properties Associated with Trabecular Meshwork and Collector Channel Motion in Human Eyes

    PubMed Central

    Xin, Chen; Johnstone, Murray; Wang, Ningli; Wang, Ruikang K.

    2016-01-01

    We report the use of a high-resolution optical coherence tomography (OCT) imaging platform to identify and quantify pressure-dependent aqueous outflow system (AOS) tissue relationships and to infer mechanical stiffness through examination of tissue properties in ex vivo human eyes. Five enucleated human eyes are included in this study, with each eye prepared with four equal-sized quadrants, each encompassing 90 degrees of the limbal circumference. In radial limbal segments perfusion pressure within Schlemm’s canal (SC) is controlled by means of a perfusion cannula inserted into the canal lumen, while the other end of the cannula leads to a reservoir at a height that can control the pressure in the cannula. The OCT system images the sample with a spatial resolution of about 5 μm from the trabecular meshwork (TM) surface. Geometric parameters are quantified from the 2D OCT images acquired from the sample subjected to controlled changes in perfusion pressures; parameters include area and height of the lumen of SC, collector channel entrances (CCE) and intrascleral collector channels (ISCC). We show that 3D OCT imaging permits the identification of 3-D relationships of the SC, CCE and ISCC lumen dimensions. Collagen flaps or leaflets are found at CCE that are attached or hinged at only one end, whilst the flaps are connected to the TM by cylindrical structures spanning SC. Increasing static SC pressures resulted in SC lumen enlargement with corresponding enlargement of the CCE and ISCC lumen. Pressure-dependent SC lumen area and height changes are significant at the 0.01 levels for ANOVA, and at the 0.05 for both polynomial curves and Tukey paired comparisons. Dynamic measurements demonstrate a synchronous increase in SC, CCE and ISCC lumen height in response to pressure changes from 0 to 10, 30 or 50 mm Hg, respectively, and the response time is within the 50-millisecond range. From the measured SC volume and corresponding IOP values, we demonstrate that an

  12. Pressure-induced expression changes in segmental flow regions of the human trabecular meshwork.

    PubMed

    Vranka, Janice A; Acott, Ted S

    2016-06-19

    Elevated intraocular pressure (IOP) is thought to create distortion or stretching of the juxtacanalicular and Schlemm's canal cells and their extracellular matrix (ECM) leading to a cascade of events that restore IOP to normal levels, a process termed IOP homeostasis. The ECM of the trabecular meshwork (TM) is intricately involved in the regulation of outflow resistance and IOP homeostasis, as matrix metalloproteinase (MMP)-initiated ECM turnover in the TM is necessary to maintain outflow facility. Previous studies have shown ECM gene expression and mRNA splice form differences in TM cells in response to sustained stretch, implicating their involvement in the dynamic process of IOP homeostasis. The observation that outflow is segmental around the circumference of the eye adds another layer of complexity to understanding the molecular events necessary to maintaining proper outflow facility. The aim of this work was to identify molecular expression differences between segmental flow regions of the TM from anterior segments perfused at either physiological or elevated pressure. Human anterior segments were perfused in an ex vivo model system, TM tissues were extracted and quantitative PCR arrays were performed. Comparisons were made between high flow and low flow regions of the TM from anterior segments perfused either at normal (8.8 mmHg) or at elevated (17.6 mmHg) perfusion pressure for 48 h. The results are presented here as independent sets: 1) fold change gene expression between segmental flow regions at a single perfusion pressure, and 2) fold change gene expression in response to elevated perfusion pressure in a single flow region. Multiple genes from the following functional families were found to be differentially expressed in segmental regions and in response to elevated pressure: collagens, ECM glycoproteins including matricellular proteins, ECM receptors such as integrins and adhesion molecules and ECM regulators, such as matrix metalloproteinases. In

  13. Agonist-dependent cannabinoid receptor signalling in human trabecular meshwork cells

    PubMed Central

    McIntosh, B T; Hudson, B; Yegorova, S; Jollimore, C A B; Kelly, M E M

    2007-01-01

    Background and purpose: Trabecular meshwork (TM) is an ocular tissue involved in the regulation of aqueous humour outflow and intraocular pressure (IOP). CB1 receptors (CB1) are present in TM and cannabinoid administration decreases IOP. CB1 signalling was investigated in a cell line derived from human TM (hTM). Experimental approach: CB1 signalling was investigated using ratiometric Ca2+ imaging, western blotting and infrared In-Cell Western analysis. Key results: WIN55212-2, a synthetic aminoalkylindole cannabinoid receptor agonist (10–100 μM) increased intracellular Ca2+ in hTM cells. WIN55,212-2-mediated Ca2+ increases were blocked by AM251, a CB1 antagonist, but were unaffected by the CB2 antagonist, AM630. The WIN55,212-2-mediated increase in [Ca2+]i was pertussis toxin (PTX)-insensitive, therefore, independent of Gi/o coupling, but was attenuated by a dominant negative Gαq/11 subunit, implicating a Gq/11 signalling pathway. The increase in [Ca2+]i was dependent upon PLC activation and mobilization of intracellular Ca2+ stores. A PTX-sensitive increase in extracellular signal-regulated kinase (ERK1/2) phosphorylation was also observed in response to WIN55,212-2, indicative of a Gi/o signalling pathway. CB1-Gq/11 coupling to activate PLC-dependent increases in Ca2+ appeared to be specific to WIN55,212-2 and were not observed with other CB1 agonists, including CP55,940 and methanandamide. CP55940 produced PTX-sensitive increases in [Ca2+]i at concentrations ≥15 μM, and PTX-sensitive increases in ERK1/2 phosphorylation. Conclusions and implications: This study demonstrates that endogenous CB1 couples to both Gq/11 and Gi/o in hTM cells in an agonist-dependent manner. Cannabinoid activation of multiple CB1 signalling pathways in TM tissue could lead to differential changes in aqueous humour outflow and IOP. PMID:17922024

  14. Effects of triamcinolone acetonide on human trabecular meshwork cells in vitro

    PubMed Central

    Sharma, Ashish; Patil, A Jayaprakash; Gupta, Navin; Estrago-Franco, MF; Mansoor, Saffar; Raymond, Vincent; Kenney, M Cristina; Kuppermann, Baruch D

    2014-01-01

    Aim: To study the effects of triamcinolone acetonide (TA) on cultured human trabecular meshwork (HTM) cells. Materials and Methods: HTM cells were cultured and treated with 125, 250, 500 and 1000 μg/mL concentration of TA for 24 h. The cells were treated with both crystalline TA (TA-C) (commercial preparation) and solubilized TA (TA-S). Cell viability was measured by a trypan blue dye exclusion test. The activity of caspse-3/7 was measured by a fluorescence caspase kit and DNA laddering was evaluated by electrophoresis on 3% agarose gel. Levels of lactate dehydrogenase (LDH) were assessed with LDH cytotoxicity assay kit-II. Results: Mean cell viabilities of HTM cells after 24 h exposure to TA-C 125, 250, 500, and 1000 μg/mL were 75.4 ±2.45% (P < 0.0001), 49.43 ± 1.85% (P < 0.0001), 17.07 ± 2.39% (P < 0.0001), and 3.7 ± 0.9% (P < 0.0001), respectively, compared with the untreated HTM cells 92.49 ± 1.21%. The mean cell viabilities with 125, 250, 500, and 1000 μg/mL of TA-S were 94.47 ± 1.60% (P > 0.05), 90.13 ± 0.40% (P < 0.01), 85.57 ± 0.47% (P < 0.001), and 71.67 ± 3.30% (P < 0.0001), respectively, compared to DMSO-equivalent cultures. Untreated HTM control had a cell viability of 96.57 ± 1.98%. DMSO-treated controls of 125, 250, 500, and 1000 μg/mL had a cell viability of 94.73 ± 0.57%, 96.97 ± 1.08%, 93.97 ± 1.85%, and 97.27 ± 1.15%, respectively. There was no increase of caspase-3/7 activity in cultures treated with either TA-C or TA-S. DNA laddering showed no bands in the TA-C or TA-S treated cultures. There were significantly higher LDH release rates at all concentrations of TA-C compared to TA-S. Conclusions: Results show that the effect of TA-C and TA-S on HTM cells is due to cell death by necrosis at all concentrations except 125 μg/mL of TA-S. Elevated levels of LDH confirmed necrotic cell death. Our study also infers the relative safety of TA-S over TA-C. PMID:24817746

  15. [Morphopathological changes in glaucoma-induced trabecular meshwork].

    PubMed

    Petraru, D; Indrei, Anca; Costin, D; Mihalache, G

    2011-01-01

    Glaucoma causes trabecular meshwork and Schlemm canal changes, resulting in the obstruction of the aqueous flow at this level. To show the histological changes in the surgically removed trabecular meshwork tissues. Trabecular meshwork fragments were histologically processed for histological diagnosis. 29.87% of all patients had ordered structure with high eosinophilia, 20.12% a rare structure with high eosinophilia, 21.34% a voluminous trabecular meshwork with fusiform cells, 21.03% tissue fibrosis and 7.62% had tissue necrosis. Aqueous flow obstruction in trabecular meshwork is produced by the histological changes at this level, found in all tissue specimens removed during surgery.

  16. Mechanotransduction channels of the trabecular meshwork.

    PubMed

    Tran, Vu T; Ho, Phi T; Cabrera, Lais; Torres, Juan E; Bhattacharya, Sanjoy K

    2014-03-01

    To determine whether the trabecular meshwork (TM), like the other organs engaged in filter like activities (such as kidneys), show the expression of known mechanotransduction channels at protein level. Human donor eye globes (n = 20), Donor eye derived TM tissue and primary TM cells were utilized for these studies. Commercially available antibodies to channels, immunohisto- and immunocytochemistry, Western blot and mass spectrometric analyses were performed to determine the presence of mechanosensitive channels at protein level. The study was performed adhering to tenets of declaration of Helsinki. We demonstrate here the presence of 11 mechanotransduction channels (Piezo1, Piezo2, TASK1, TREK1, TRPA1, TRPC1, TRPC2, TRPC3, TRPC6, TRPM2, TRPP2) as expressed protein in the TM tissue and at the isolated TM cell level. Presence of at least one known isoform of these channels was demonstrated using Western blot analyses. We demonstrated the presence of 11 mechanotransduction channels in the TM and in isolated TM cells at protein level. Demonstration of these channels as proteins at tissue and cellular level will pave the way for further experimentation.

  17. Rho GTPase signaling promotes constitutive expression and release of TGF-β2 by human trabecular meshwork cells.

    PubMed

    Pervan, Cynthia L; Lautz, Jonathan D; Blitzer, Andrea L; Langert, Kelly A; Stubbs, Evan B

    2016-05-01

    Elevated intraocular pressure (IOP) is causally implicated in the pathophysiology of primary open-angle glaucoma (POAG). The molecular mechanisms responsible for elevated IOP remain elusive, but may involve aberrant expression and signaling of transforming growth factor (TGF)-β2 within the trabecular meshwork (TM). Consistent with previously published studies, we show here that exogenous addition of TGF-β2 to cultured porcine anterior segments significantly attenuates outflow facility in a time-dependent manner. By comparison, perfusing segments with a TGFβRI/ALK-5 antagonist (SB-431542) unexpectedly elicited a significant and sustained increase in outflow facility, implicating a role for TM-localized constitutive expression and release of TGF-β2. Consistent with this thesis, cultured primary or transformed (GTM3) quiescent human TM cells were found to constitutively express and secrete measurable amounts of biologically-active TGF-β2. Disrupting monomeric GTPase post-translational prenylation and activation with lovastatin or GGTI-298 markedly reduced constitutive TGF-β2 expression and release. Specifically, inhibiting the Rho subfamily of GTPases with C3 exoenzyme similarly reduced constitutive expression and secretion of TGF-β2. These findings suggest that Rho GTPase signaling, in part, regulates constitutive expression and release of biologically-active TGF-β2 from human TM cells. Localized constitutive expression and release of TGF-β2 by TM cells may promote or exacerbate elevation of IOP in POAG.

  18. Dexamethasone alters F-actin architecture and promotes cross-linked actin network formation in human trabecular meshwork tissue.

    PubMed

    Clark, Abbot F; Brotchie, Daniel; Read, A Thomas; Hellberg, Peggy; English-Wright, Sherry; Pang, Iok-Hou; Ethier, C Ross; Grierson, Ian

    2005-02-01

    Elevated intraocular pressure is an important risk factor for the development of glaucoma, a leading cause of irreversible blindness. This ocular hypertension is due to increased hydrodynamic resistance to the drainage of aqueous humor through specialized outflow tissues, including the trabecular meshwork (TM) and the endothelial lining of Schlemm's canal. We know that glucocorticoid therapy can cause increased outflow resistance and glaucoma in susceptible individuals, that the cytoskeleton helps regulate aqueous outflow resistance, and that glucocorticoid treatment alters the actin cytoskeleton of cultured TM cells. Our purpose was to characterize the actin cytoskeleton of cells in outflow pathway tissues in situ, to characterize changes in the cytoskeleton due to dexamethasone treatment in situ, and to compare these with changes observed in cell culture. Human ocular anterior segments were perfused with or without 10(-7) M dexamethasone, and F-actin architecture was investigated by confocal laser scanning microscopy. We found that outflow pathway cells contained stress fibers, peripheral actin staining, and occasional actin "tangles." Dexamethasone treatment caused elevated IOP in several eyes and increased overall actin staining, with more actin tangles and the formation of cross-linked actin networks (CLANs). The actin architecture in TM tissues was remarkably similar to that seen in cultured TM cells. Although CLANs have been reported previously in cultured cells, this is the first report of CLANs in tissue. These cytoskeletal changes may be associated with increased aqueous humor outflow resistance after ocular glucocorticoid treatment.

  19. Growth Differentiation Factor-15–Induced Contractile Activity and Extracellular Matrix Production in Human Trabecular Meshwork Cells

    PubMed Central

    Muralidharan, Arumugam Ramachandran; Maddala, Rupalatha; Skiba, Nikolai P.; Rao, Ponugoti Vasantha

    2016-01-01

    Purpose To determine the role and regulation of growth differentiation factor-15 (GDF-15), a TGF-β–related cytokine in human trabecular meshwork (TM) cells in the context of aqueous humor (AH) outflow and IOP. Methods Regulation of expression by external cues, and the distribution and secretion of GDF-15 by human TM primary cell cultures, and the effects of recombinant (r) GDF-15 on TM cell contractile characteristics, actin cytoskeleton, cell adhesion, extracellular matrix (ECM), α-smooth muscle actin (αSMA), SMAD signaling, and gene expression were determined by immunoblot, immunofluorescence, mass spectrometry, cDNA microarray, and real-time quantitative PCR (RT-qPCR) analyses. Results Growth differentiation factor-15, a common constituent of ECM derived from the human TM cells, was confirmed to be distributed throughout the conventional aqueous humor outflow pathway of the human eye. Growth differentiation factor-15 protein levels were significantly increased in human TM cells in response to TGF-β2, dexamethasone, endothelin-1, lysophosphatidic acid, TNF-α, IL-1β treatment, and by cyclic mechanical stretch. Stimulation of human TM cells with rGDF-15 caused a significant increase in the formation of actin stress fibers and focal adhesions, myosin light chain phosphorylation, SMAD signaling, gene expression, and the levels of αSMA and ECM proteins. Conclusions The results of this study, including a robust induction of GDF-15 expression by several external factors known to elevate IOP, and rGDF-15–induced increase in contractility, cell adhesion, and the levels of ECM proteins and αSMA in TM cells, collectively suggest a potential role for GDF-15 in homeostasis and dysregulation of AH outflow and IOP in normal and glaucomatous eyes, respectively. PMID:27918822

  20. Prenylation of Rho G-proteins: a novel mechanism regulating gene expression and protein stability in human trabecular meshwork cells.

    PubMed

    Stubbs, Evan B; Von Zee, Cynthia L

    2012-08-01

    Endogenous prenylation with sesquiterpene or diterpene isoprenoids facilitates membrane localization and functional activation of small monomeric GTP-binding proteins. A direct effect of isoprenoids on regulation of gene expression and protein stability has also been proposed. In this study, we determined the role of sesquiterpene or diterpene isoprenoids on the regulation of Rho G-protein expression, activation, and stability in human trabecular meshwork (TM) cells. In both primary and transformed human TM cells, limiting endogenous isoprenoid synthesis with lovastatin, a potent HMG-CoA reductase inhibitor, elicited marked increases in RhoA and RhoB mRNA and protein content. The effect of lovastatin was dose-dependent with newly synthesized inactive protein accumulating in the cytosol. Supplementation with geranylgeranyl pyrophosphate (GGPP) prevented, while inhibition of geranylgeranyl transferase-I mimicked, the effects of lovastatin on RhoA and RhoB protein content. Similarly, lovastatin-dependent increases in RhoA and RhoB mRNA expression were mimicked by geranylgeranyl transferase-I inhibition. Interestingly, GGPP supplementation selectively promoted the degradation of newly synthesized Rho proteins which was mediated, in part, through the 20S proteasome. Functionally, GGPP supplementation prevented lovastatin-dependent decreases in actin stress fiber organization while selectively facilitating the subcellular redistribution of accumulated Rho proteins from the cytosol to the membrane and increasing RhoA activation. Post-translational prenylation with geranylgeranyl diterpenes selectively facilitates the expression, membrane translocation, functional activation, and turnover of newly synthesized Rho proteins. Geranylgeranyl prenylation represents a novel mechanism by which active Rho proteins are targeted to the 20S proteasome for degradation in human TM cells.

  1. Mechanisms of ATP Release by Human Trabecular Meshwork Cells, the Enabling Step in Purinergic Regulation of Aqueous Humor Outflow

    PubMed Central

    LI, ANG; LEUNG, CHI TING; PETERSON-YANTORNO, KIM; STAMER, W. DANIEL; MITCHELL, CLAIRE H.; CIVAN, MORTIMER M.

    2011-01-01

    Our guiding hypothesis is that ecto-enzymatic conversion of extracellular ATP to adenosine activates A1 adenosine receptors, reducing resistance to aqueous humor outflow and intraocular pressure. The initial step in this purinergic regulation is ATP release from outflow-pathway cells by mechanisms unknown. We measured similar ATP release from human explant-derived primary trabecular meshwork (TM) cells (HTM) and a human TM cell line (TM5). Responses to 21 inhibitors indicated that pannexin-1 (PX1) and connexin (Cx) hemichannels and P2X7 receptors (P2RX7) were comparably important in modulating ATP release induced by hypotonic swelling, whereas vesicular release was insignificant. Consistent with prior studies of PX1 activity in certain other cells, ATP release was lowered by the reducing agent dithiothreitol. Overexpressing PX1 in HEK293T cells promoted, while partial knockdown (KD) in both HEK293T and TM5 cells inhibited hypotonicity-activated ATP release. Additionally, KD reduced the pharmacologically-defined contribution of PX1 and enhanced those of Cx and P2RX7. ATP release was also triggered by raising intracellular Ca2+ activity with ionomycin after a prolonged lag time and was unaffected by the PX1 blocker probenecid, but nearly abolished by P2RX7 antagonists. We conclude that swelling-stimulated ATP release from human TM cells is physiologically mediated by PX1 and Cx hemichannels and P2X7 receptors, but not by vesicular release. PX1 appears not to be stimulated by intracellular Ca2+ in TM cells, but can be modulated by oxidation-reduction state. The P2RX7-dependent component of swelling-activated release may be mediated by PX1 hemichannels or reflect apoptotic magnification of ATP release, either through itself and/or hemichannels. PMID:21381023

  2. Gremlin utilizes canonical and non-canonical TGFβ signaling to induce lysyl oxidase (LOX) genes in human trabecular meshwork cells☆

    PubMed Central

    Sethi, Anirudh; Wordinger, Robert J.; Clark, Abbot F.

    2013-01-01

    The TGFβ/BMP signaling pathways are involved in glaucomatous damage to the trabecular meshwork (TM) leading to elevated intraocular pressure (IOP), which is a major risk factor for the development and progression of glaucoma. The BMP antagonist gremlin is elevated in glaucomatous TM cells and tissues and can directly elevate IOP. Gremlin utilizes the TGFβ2/SMAD pathway to induce TM extracellular matrix (ECM) proteins. The purpose of this study is to determine whether expression of the ECM cross-linking lysyl oxidase (LOX) genes is regulated by gremlin in cultured human TM cells. Human TM cells were treated with recombinant gremlin, and expression of the LOX genes was examined by quantitative RT-PCR and western immunoblotting. TM cells were pretreated with TGFBR inhibitors (LY364947 or SB431542), an inhibitor of the SMAD signaling pathway (SIS3), or with JNK (SP600125) and p38 MAPK (SB203580) inhibitors to identify the signaling pathway(s) involved in gremlin induction of LOX protein expression. All five LOX genes (LOX and LOXL1–4) were induced by gremlin. Gremlin induction of LOX genes and protein expression was blocked by TGFBR inhibitors as well as by inhibitors of the SMAD3, JNK and p38 MAPK signaling pathways. We conclude that gremlin employs both canonical TGFβ/SMAD and the non-canonical JNK and p38 MAPK signaling pathways to induce LOX genes and proteins in cultured human TM cells. Increased LOX levels may be at least partially responsible for gremlin-mediated IOP elevation and increased aqueous humor outflow resistance leading to glaucoma. PMID:23748100

  3. Human Trabecular Meshwork Cells Exhibit Several Characteristics of, but Are Distinct from, Adipose-Derived Mesenchymal Stem Cells

    PubMed Central

    Morgan, Joshua T.; Wood, Joshua A.; Walker, Naomi J.; Raghunathan, Vijay Krishna; Borjesson, Dori L.; Murphy, Christopher J.

    2014-01-01

    Abstract Purpose: To support the growing promise of regenerative medicine in glaucoma, we characterized the similarities and differences between human trabecular meshwork (HTM) cells and human mesenchymal stem cells (hMSCs). Methods: HTM cells and hMSCs were phenotypically characterized by flow cytometry. Using quantitative polymerase chain reaction, the expression of myoc, angptl7, sox2, pou5f1, and notch1 was determined in both cell types with and without dexamethasone (Dex). Immunosuppressive behavior of HTM cells and hMSCs was determined using T cells activated with phytohemagglutinin. T-cell proliferation was determined using BrdU incorporation and flow cytometry. Multipotency of HTM cells and hMSCs was determined using adipogenic and osteogenic differentiation media as well as aqueous humor (AH). Alpha-smooth muscle actin (αSMA) expression was determined in HTM cells, hMSCs, and HTM tissue. Results: Phenotypically, HTM and hMSCs expressed CD73, CD90, CD105, and CD146 but not CD31, CD34, and CD45 and similar sox2, pou5f1, and notch1 expression. Both cell types suppressed T-cell proliferation. However, HTM cells, but not hMSCs, upregulated myoc and angptl7 in response to Dex. Additionally, HTM cells did not differentiate into adipocytes or osteocytes. Culture of hMSCs in 20%, but not 100%, AH potently induced alkaline phosphatase activity. HTM cells in culture possessed uniformly strong expression of αSMA, which contrasted with the limited expression in hMSCs and spatially discrete expression in HTM tissue. Conclusions: HTM cells possess a number of important similarities with hMSCs but lack multipotency, one of the defining characteristics of stem cells. Further work is needed to explore the molecular mechanisms and functional implications underlying the phenotypic similarities. PMID:24456002

  4. Effects of novel ethacrynic acid derivatives on human trabecular meshwork cell shape, actin cytoskeletal organization, and transcellular fluid flow.

    PubMed

    Rao, Ponugoti Vasantha; Shimazaki, Atsushi; Ichikawa, Masaki; Franse-Carman, Linda; Alvarado, Jorge A; Epstein, David L

    2005-12-01

    To determine efficacy and therapeutic index in the context of ocular hypotensive activity of the new ethacrynic acid (ECA) derivatives of the series (SA8,248 and SA8,389), 9,000 series (SA9,000, SA9,622 and SA9,995) and ticrynafen, we undertook a comparative evaluation of the dose-dependent effects of these compounds on human trabecular meshwork (HTM) cell shape, actin cytoskeletal organization, focal adhesions and transcellular fluid flow. Responses were either scored using an arbitrary scale of 1-5 or quantified. Compounds of the 9000 series (SA9,995>SA9,000>SA9,622) were found to be 14- to 20-fold more potent than ECA, ticrynafen or analogs from the 8,000 series (SA8,389>SA8,248) in terms of ability to induce cell shape alterations in HTM cells. Similarly, compounds of the 9,000 series (SA9,995>SA9,622>SA9,000) were found to be much stronger (2 to 20 fold) than ECA, ticrynafen or analogs of the 8000 series in terms of affecting decreases in actin stress fiber content in HTM cells. Analogs of the 9000 series (SA9,622>SA9,995>SA9,000) were also observed to be 8 to 10 fold more potent than ECA (SA8,389>ECA>SA8,248>ticrynafen) at eliciting decreases in cellular focal adhesions. Interestingly, analogs of the 9000 series (SA9,000>SA9,622>SA9,995) and SA8,248 demonstrated a huge increase (by many folds) in transcellular fluid flow of HTM cell monolayers as compared to ECA and ticrynafen. Collectively, these analyses revealed that the structural modification of ECA improves its ocular hypotensive efficacy, indicating that the SA9,000 series compounds might be promising novel ocular hypotensive drugs.

  5. Temperature Oscillations Drive Cycles in the Activity of MMP-2,9 Secreted by a Human Trabecular Meshwork Cell Line

    PubMed Central

    Li, Stanley Ka-lok; Banerjee, Juni; Jang, Christopher; Sehgal, Amita; Stone, Richard A.; Civan, Mortimer M.

    2015-01-01

    Purpose. Aqueous humor inflow falls 50% during sleeping hours without proportional fall in IOP, partly reflecting reduced outflow facility. The mechanisms underlying outflow facility cycling are unknown. One outflow facility regulator is matrix metalloproteinase (MMP) release from trabecular meshwork (TM) cells. Because anterior segment temperature must oscillate due to core temperature cycling and eyelid closure during sleep, we tested whether physiologically relevant temperature oscillations drive cycles in the activity of secreted MMP. Methods. Temperature of transformed normal human TM cells (hTM5 line) was fixed or alternated 12 hours/12 hours between 33°C and 37°C. Activity of secreted MMP-2 and MMP-9 was measured by zymography, and gene expression by RT-PCR and quantitative PCR. Results. Raising temperature to 37°C increased, and lowering to 33°C reduced, activity of secreted MMP. Switching between 37°C and 33°C altered MMP-9 by 40% ± 3% and MMP-2 by 22% ± 2%. Peripheral circadian clocks did not mediate temperature-driven cycling of MMP secretion because MMP-release oscillations did not persist at constant temperature after 3 to 6 days of alternating temperatures, and temperature cycles did not entrain clock-gene expression in these cells. Furthermore, inhibiting heat shock transcription factor 1, which links temperature and peripheral clock-gene oscillations, inhibited MMP-9 but not MMP-2 temperature-driven MMP cycling. Inhibition of heat-sensitive TRPV1 channels altered total MMP secretion but not temperature-induced modulations. Inhibiting cold-sensitive TRPM-8 channels had no effect. Conclusions. Physiologically relevant temperature oscillations drive fluctuations of secreted MMP-2 and MMP-9 activity in hTM5 cells independent of peripheral clock genes and temperature-sensitive TRP channels. PMID:25655795

  6. Temperature oscillations drive cycles in the activity of MMP-2,9 secreted by a human trabecular meshwork cell line.

    PubMed

    Li, Stanley Ka-Lok; Banerjee, Juni; Jang, Christopher; Sehgal, Amita; Stone, Richard A; Civan, Mortimer M

    2015-02-05

    Aqueous humor inflow falls 50% during sleeping hours without proportional fall in IOP, partly reflecting reduced outflow facility. The mechanisms underlying outflow facility cycling are unknown. One outflow facility regulator is matrix metalloproteinase (MMP) release from trabecular meshwork (TM) cells. Because anterior segment temperature must oscillate due to core temperature cycling and eyelid closure during sleep, we tested whether physiologically relevant temperature oscillations drive cycles in the activity of secreted MMP. Temperature of transformed normal human TM cells (hTM5 line) was fixed or alternated 12 hours/12 hours between 33°C and 37°C. Activity of secreted MMP-2 and MMP-9 was measured by zymography, and gene expression by RT-PCR and quantitative PCR. Raising temperature to 37°C increased, and lowering to 33°C reduced, activity of secreted MMP. Switching between 37°C and 33°C altered MMP-9 by 40% ± 3% and MMP-2 by 22% ± 2%. Peripheral circadian clocks did not mediate temperature-driven cycling of MMP secretion because MMP-release oscillations did not persist at constant temperature after 3 to 6 days of alternating temperatures, and temperature cycles did not entrain clock-gene expression in these cells. Furthermore, inhibiting heat shock transcription factor 1, which links temperature and peripheral clock-gene oscillations, inhibited MMP-9 but not MMP-2 temperature-driven MMP cycling. Inhibition of heat-sensitive TRPV1 channels altered total MMP secretion but not temperature-induced modulations. Inhibiting cold-sensitive TRPM-8 channels had no effect. Physiologically relevant temperature oscillations drive fluctuations of secreted MMP-2 and MMP-9 activity in hTM5 cells independent of peripheral clock genes and temperature-sensitive TRP channels. Copyright 2015 The Association for Research in Vision and Ophthalmology, Inc.

  7. Effects of benzalkonium chloride- or polyquad-preserved fixed combination glaucoma medications on human trabecular meshwork cells

    PubMed Central

    Ammar, David A.

    2011-01-01

    Purpose We investigated the potential short and long-term effects in cultured human trabecular meshwork (TM) cells of various topical glaucoma formulations containing different preservatives. Methods We tested the fixed combination medications 0.004% travoprost plus 0.5% timolol preserved with either 0.015% benzalkonium chloride (BAK; DuoTrav®), or with 0.001% polyquad (PQ; DuoTrav® BAK-free); and 0.005% latanoprost plus 0.5% timolol preserved with 0.020% BAK (Xalacom®). Also tested was a range of BAK concentrations (0.001%–0.020%) in balanced salt solution (BSS). Cells were treated for 25 min at 37 °C with solutions diluted 1:10 and 1:100 to mimic the reduced penetration of topical preparations to the anterior chamber. The percentage of live cells was determined immediately after treatment through the uptake of the fluorescent vital dye calcein-AM. To determine any long-term effects, we assayed release of matrix metalloproteinase 9 (MMP-9) and apoptosis 24 h after treatments. Results BAK demonstrated a dose-dependent reduction in TM cell viability, ranging from 71±5% live cells at 0.001% BAK (diluted 1:10) to 33±3% live cells at 0.020% BAK (diluted 1:10). Travoprost (0.004%) plus 0.5% timolol preserved with 0.015% BAK had statistically fewer live TM cells (79±7%) than the same preparation preserved with 0.001% polyquad® (PQ; 93±1%; p<0.001). Latanoprost plus timolol preserved with 0.020% BAK (29±9% live cells) was similar to the 0.020% BAK (33±3%) treatment. However, travoprost plus timolol preserved in 0.015% BAK had significantly more live cells (83±12%) than the 1:10 dilution of 0.015% BAK (49±10%). We also found 0.020% BAK (diluted 1:100) resulted in elevated levels of extracellular MMP-9 at 24 h. Conclusions These results demonstrate that the substitution of the preservative BAK from topical ophthalmic drugs results in greater in vitro viability of TM cells. Travoprost with timolol, but not latanoprost with timolol, countered some of the toxic

  8. Characterization of free-floating spheres from human trabecular meshwork (HTM) cell culture in vitro.

    PubMed

    Gonzalez, P; Epstein, D L; Luna, C; Liton, P B

    2006-06-01

    It has been observed in several tissues that direct isolation of cells in serum-free media and on nonadhesive substrates results in the formation of spherical clusters of cells known as free-floating spheres. Such free-floating spheres have been hypothesized to contain undifferentiated multipotent progenitor cells. Our goal was to isolate and characterize such free-floating spheres from HTM cell primary cultures. For this purpose, HTM cells were incubated in serum-free media and on a nonadhesive substrate. Individual free-floating spheres generated in these conditions were isolated in 96-well plates, and their proliferative capacity was evaluated by monitoring their size increase over time. The expression of the TM markers, MGP and CHI3L1, was examined using recombinant adenoviruses containing the respective promoters. Morphology of the free-floating spheres was analysed in semithin sections, and the gene expression profile was obtained using Human Genome U133 Plus 2.0 Affymetrix microarrays. HTM cells incubated in serum-free media and on nonadhesive substrate generated free-floating spheres that could be grown for more than 3 months. Addition of serum to the culture media promoted the attachment of the spheres to the substrate, migration of cells from the spheres, and differentiation into cells phenotypically similar to normal TM cells. Gene profiling analysis demonstrated strong similarities between the gene expression profiles of the spheres and HTM cell monolayers. Both infection with the recombinant adenoviruses and gene array analysis demonstrated the expression of CHI3L1 and MGP, indicating that free-floating spheres likely originate from HTM cells. Gene array analysis also showed expression of the marker for neural precursor cells nestin, as well as leukemia inhibitory factor, a gene involved in the maintenance of the undifferentiated state of progenitor cells. Analysis of semithin sections indicated that these TM free-floating spheres were highly dynamic

  9. Characterization of free-floating spheres from human trabecular meshwork (HTM) cell culture in vitro

    PubMed Central

    Gonzalez, P.; Epstein, D.L.; Luna, C.; Liton, P.B.

    2011-01-01

    It has been observed in several tissues that direct isolation of cells in serum-free media and on nonadhesive substrates results in the formation of spherical clusters of cells known as free-floating spheres. Such free-floating spheres have been hypothesized to contain undifferentiated multipotent progenitor cells. Our goal was to isolate and characterize such free-floating spheres from HTM cell primary cultures. For this purpose, HTM cells were incubated in serum-free media and on a nonadhesive substrate. Individual free-floating spheres generated in these conditions were isolated in 96-well plates, and their proliferative capacity was evaluated by monitoring their size increase over time. The expression of the TM markers, MGP and CHI3L1, was examined using recombinant adenoviruses containing the respective promoters. Morphology of the free-floating spheres was analysed in semithin sections, and the gene expression profile was obtained using Human Genome U133 Plus 2.0 Affymetrix microarrays. HTM cells incubated in serum-free media and on nonadhesive substrate generated free-floating spheres that could be grown for more than 3 months. Addition of serum to the culture media promoted the attachment of the spheres to the substrate, migration of cells from the spheres, and differentiation into cells phenotypically similar to normal TM cells. Gene profiling analysis demonstrated strong similarities between the gene expression profiles of the spheres and HTM cell monolayers. Both infection with the recombinant adenoviruses and gene array analysis demonstrated the expression of CHI3L1 and MGP, indicating that free-floating spheres likely originate from HTM cells. Gene array analysis also showed expression of the marker for neural precursor cells nestin, as well as leukemia inhibitory factor, a gene involved in the maintenance of the undifferentiated state of progenitor cells. Analysis of semithin sections indicated that these TM free-floating spheres were highly dynamic

  10. New ethacrynic acid derivatives as potent cytoskeletal modulators in trabecular meshwork cells.

    PubMed

    Shimazaki, Atsushi; Suhara, Hiroshi; Ichikawa, Masaki; Matsugi, Takeshi; Konomi, Koji; Takagi, Yasutaka; Hara, Hideaki; Rao, Ponugoti Vasantha; Epstein, David Lee

    2004-06-01

    A series of ethacrynic acid (ECA) derivatives were synthesized and examined for ocular hypotensive activity. Efficacy was evaluated in a cell-shape assay, using human trabecular meshwork cells, and cytotoxicity in a (3-(4,5-dimethylthiazole-2-yl)-5-(3-carboxymethoxy phenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay, using cultured bovine trabecular meshwork cells. Many of the derivatives demonstrated efficacy equal to or greater than that of ECA. SA9000 was selected as the most promising candidate for a novel ocular hypotensive drug with few side effects.

  11. [Morphological alterations of the trabecular meshwork in primary open angle glaucoma].

    PubMed

    Potau, J M; Canals, M; Costa, J; Merindano, M D; Ruano, D

    2000-03-01

    In the present essay we have compared the morphology and structure of normal trabecular meshworks and glaucomatous trabecular meshworks with the purpose of obtaining information about the etiopathogeny of primary open angle glaucoma. We have observed by conventional light microscopy and scanning electron microscopy a total amount of 20 trabecular meshworks from non-glaucomatous patients and 35 trabecular meshworks from surgical pieces of trabeculectomy performed in patients diagnosed of primary open angle glaucoma. We have observed that glaucomatous trabecular meshworks show morphological and structural alterations of their trabecular beams, as their enlarging, collapse, the partial loss of endothelial cells and the existence of plenty of material accumulated on them, like pigment granules and calcium precipitates. Glaucomatous trabecular meshworks present morphological and structural alterations which can be related to etiopathogeny of primary open angle glaucoma since they modify the normal conditions of drainage of aqueous humour to Schlemm's channel.

  12. Trabecular meshwork and lens partitioning of corticosteroids: implications for elevated intraocular pressure and cataracts.

    PubMed

    Thakur, Ashish; Kadam, Rajendra; Kompella, Uday B

    2011-07-01

    To determine whether adverse effects such as elevated intraocular pressure and cataracts, which are lower with dexamethasone when compared with fluocinolone acetonide or triamcinolone acetonide, may be explained in part by the differences in drug lipophilicity and partitioning of these drugs into the trabecular meshwork and lens. The n-octanol/phosphate-buffered saline (pH 7.4) partition coefficient (log distribution coefficient [D]) and bovine/human ocular tissue partition coefficients were determined for triamcinolone, prednisolone, dexamethasone, fluocinolone acetonide, triamcinolone acetonide, and budesonide at 37°C. The log D of the corticosteroids ranged from 0.712 to 2.970. The ranges of tissue:PBS partition coefficients following drug incubation at 0.4, 2.0, and 10.0 μg/mL were 0.35 to 1.56, 0.30 to 2.12, and 0.30 to 1.95, respectively, for the bovine lens, 0.87 to 4.18, 0.71 to 4.40, and 0.69 to 5.86, respectively, for the human lens, and 2.98 to 9.48, 2.41 to 9.16, and 1.71 to 9.96, respectively, for the bovine trabecular meshwork. In general, tissue partitioning showed a positive correlation with log D. Dexamethasone, with lipophilicity less than triamcinolone acetonide and fluocinolone acetonide, exhibited the least amount of partitioning in the trabecular meshwork and lens among these 3 corticosteroids commonly used for treating diseases at the back of the eye. Binding of corticosteroids to the trabecular meshwork and lens increases as drug lipophilicity increases. Less lipophilic corticosteroids with limited partitioning to the trabecular meshwork and lens may result in reduced incidence of elevated intraocular pressure and cataracts.

  13. The trabecular meshwork outflow pathways: structural and functional aspects.

    PubMed

    Tamm, Ernst R

    2009-04-01

    The major drainage structures for aqueous humor (AH) are the conventional or trabecular outflow pathways, which are comprised of the trabecular meshwork (made up by the uveal and corneoscleral meshworks), the juxtacanalicular connective tissue (JCT), the endothelial lining of Schlemm's canal (SC), the collecting channels and the aqueous veins. The trabecular meshwork (TM) outflow pathways are critical in providing resistance to AH outflow and in generating intraocular pressure (IOP). Outflow resistance in the TM outflow pathways increases with age and primary open-angle glaucoma. Uveal and corneoscleral meshworks form connective tissue lamellae or beams that are covered by flat TM cells which rest on a basal lamina. TM cells in the JCT are surrounded by fibrillar elements of the extracellular matrix (ECM) to form a loose connective tissue. In contrast to the other parts of the TM, JCT cells and ECM fibrils do not form lamellae, but are arranged more irregularly. SC inner wall endothelial cells form giant vacuoles in response to AH flow, as well as intracellular and paracellular pores. In addition, minipores that are covered with a diaphragm are observed. There is considerable evidence that normal AH outflow resistance resides in the inner wall region of SC, which is formed by the JCT and SC inner wall endothelium. Modulation of TM cell tone by the action of their actomyosin system affects TM outflow resistance. In addition, the architecture of the TM outflow pathways and consequently outflow resistance appear to be modulated by contraction of ciliary muscle and scleral spur cells. The scleral spur contains axons that innervate scleral spur cells or that have the ultrastructural characteristics of mechanosensory nerve endings.

  14. Preventive Effects of Omega-3 and Omega-6 Fatty Acids on Peroxide Mediated Oxidative Stress Responses in Primary Human Trabecular Meshwork Cells

    PubMed Central

    Kruse, Friedrich E.; Welge-Lüssen, Ulrich-Christoph; Birke, Kerstin

    2012-01-01

    Pathologic processes in glaucoma include increased apoptosis, accumulation of extracellular material in the trabecular meshwork and optic nerve, condensations of the cytoskeleton and precocious cellular senescence. Oxidative stress was shown to generate these alterations in primary ocular cells. Fatty acids omega-3 and -6 are alleged to constitute a prophylaxis against these deleterious effects. Here, we tested actual preventive effects omega-3 and -6 against peroxide induced stress responses in primary human trabecular meshwork cells. Changes of mitochondrial activity, proliferation, heat shock proteins, extracellular matrix components, and inflammatory markers were evaluated. Alterations of the cytoskeleton were evaluated by phalloidin labeling. Here we report a repressive effect of omega-6 on metabolic activity and proliferation, which was not detected for omega-3. Both agents were able to prevent the anti-proliferative effect of H2O2, but only omega-3 prevented metabolic repression. Expression of heat shock protein 27 was unaltered by both fatty acids, whereas heat shock protein 90 was significantly induced by both. Omega-6 increased fibronectin and connective tissue growth factor synthesis, as well as the amount of secreted fibronectin. Omega-3, instead, induced plasminogen activator inhibitor 1 synthesis. H2O2 further increased fibronectin production in omega-6 supplemented cells, which was not the case in omega-3 treated cells. H2O2 stimulation of plasminogen activator inhibitor 1 and connective tissue growth factor was repressed by both fatty acids. Both fatty acids appeared to abolish H2O2 mediated stimulation of nuclear factor κB and IL-6, but not IL-1α and IL-8. H2O2 induced formation of cross-linked actin networks and stress fibers, which was reduced by preemptive application of omega-3. Omega-6, in contrast, had no protective effect on that, and even seemed to promote condensation. Based on the observed side effects of omega-6, omega-3 appears to be

  15. Proteomics Reveal Cochlin Deposits Associated with Glaucomatous Trabecular Meshwork* S

    PubMed Central

    Bhattacharya, Sanjoy K.; Rockwood, Edward J.; Smith, Scott D.; Bonilha, Vera L.; Crabb, John S.; Kuchtey, Rachel W.; Robertson, Nahid G.; Peachey, Neal S.; Morton, Cynthia C.; Crabb, John W.

    2006-01-01

    The etiology of primary open angle glaucoma, a leading cause of age-related blindness, remains poorly defined, although elevated intraocular pressure (IOP) contributes to the disease progression. To better understand the mechanisms causing elevated IOP from aqueous humor circulation, we pursued proteomic analyses of trabecular meshwork (TM) from glaucoma and age-matched control donors. These analyses demonstrated that Cochlin, a protein associated with deafness disorder DFNA9, is present in glaucomatous but absent in normal TM. Cochlin was also detected in TM from the glaucomatous DBA/2J mouse preceding elevated IOP but found to be absent in three other mouse lines that do not develop elevated IOP. Histochemical analyses revealed co-deposits of Cochlin and mucopolysaccharide in human TM around Schlemm’s canal, similar to that observed in the cochlea in DFNA9 deafness. Purified Cochlin was found to aggregate after sheer stress and to induce the aggregation of TM cells in vitro. Age-dependent in vivo increases in Cochlin were observed in glaucomatous TM, concomitant with a decrease in type II collagen, suggesting that Cochlin may disrupt the TM architecture and render components like collagen more susceptible to degradation and collapse. Overall, these observations suggest that Cochlin contributes to elevated IOP in primary open angle glaucoma through altered interactions within the TM extracellular matrix, resulting in cell aggregation, mucopolysaccharide deposition, and significant obstruction of the aqueous humor circulation. PMID:15579465

  16. Matricellular Proteins in the Trabecular Meshwork: Review and Update

    PubMed Central

    Chatterjee, Ayan; Villarreal, Guadalupe

    2014-01-01

    Abstract Primary open-angle glaucoma (POAG) is a leading cause of blindness worldwide, and intraocular pressure (IOP) is an important modifiable risk factor. IOP is a function of aqueous humor production and aqueous humor outflow, and it is thought that prolonged IOP elevation leads to optic nerve damage over time. Within the trabecular meshwork (TM), the eye's primary drainage system for aqueous humor, matricellular proteins generally allow cells to modulate their attachments with and alter the characteristics of their surrounding extracellular matrix (ECM). It is now well established that ECM turnover in the TM affects outflow facility, and matricellular proteins are emerging as significant players in IOP regulation. The formalized study of matricellular proteins in TM has gained increased attention. Secreted protein acidic and rich in cysteine (SPARC), myocilin, connective tissue growth factor (CTGF), and thrombospondin-1 and -2 (TSP-1 and -2) have been localized to the TM, and a growing body of evidence suggests that these matricellular proteins play an important role in IOP regulation and possibly the pathophysiology of POAG. As evidence continues to emerge, these proteins are now seen as potential therapeutic targets. Further study is warranted to assess their utility in treating glaucoma in humans. PMID:24901502

  17. Direct trabecular meshwork imaging in porcine eyes through multiphoton gonioscopy

    NASA Astrophysics Data System (ADS)

    Masihzadeh, Omid; Ammar, David A.; Kahook, Malik Y.; Gibson, Emily A.; Lei, Tim C.

    2013-03-01

    The development of technologies to characterize the ocular aqueous outflow system (AOS) is important for the understanding of the pathophysiology of glaucoma. Multiphoton microscopy (MPM) offers the advantage of high-resolution, label-free imaging with intrinsic image contrast because the emitted signals result from the specific biomolecular content of the tissue. Previous attempts to use MPM to image the murine irido-corneal region directly through the sclera have suffered from degradation in image resolution due to scattering of the focused laser light. As a result, transscleral MPM has limited ability to observe fine structures in the AOS. In this work, the porcine irido-corneal angle was successfully imaged through the transparent cornea using a gonioscopic lens to circumvent the highly scattering scleral tissue. The resulting high-resolution images allowed the detailed structures in the trabecular meshwork (TM) to be observed. Multimodal imaging by two-photon autofluorescence and second harmonic generation allowed visualization of different features in the TM without labels and without disruption of the TM or surrounding tissues. MPM gonioscopy is a promising noninvasive imaging tool for high-resolution studies of the AOS, and research continues to explore the potential for future clinical applications in humans.

  18. Evidence for a calcification process in the trabecular meshwork.

    PubMed

    Borrás, Teresa; Comes, Núria

    2009-04-01

    The human trabecular meshwork (TM) expresses many genes that have been associated with physiological (bone, cartilage, teeth) and pathological (vascular systems, kidney) calcification. In particular, the TM highly expresses the inhibitor of calcification Matrix Gla (MGP) gene, which encodes a vitamin K-dependent protein that requires post-translational activation to inhibit the formation of calcium precipitates. TM cells have high activity of the activating gamma-carboxylase enzyme and produce active MGP. Silencing MGP increases the activity of alkaline phosphatase (ALP), an enzyme of the matrix vesicles and marker of calcification. Overexpressing MGP reduces the ALP activity induced by bone morphogenetic 2 (BMP2), a potent inducer of calcification. In this review we gathered evidence for the existence of a mineralization process in the TM. We selected twenty regulatory calcification genes, reviewed their functions in their original tissues and looked at their relative abundance in the TM by heat maps derived from existing microarrays. Although results are not yet fully conclusive and more experiments are needed, examining TM expression in the light of the calcification literature brings up many similarities. One such parallel is the role of mechanical forces in bone induction and the high levels of mineralization inhibitors found in the constantly mechanically stressed TM. During the next few years, examination of other calcification-related regulatory genes and pathways, as well as morphological examination of knockout animals, would help to elucidate the relevance of a calcification process to TM's overall function.

  19. Low-dose rotenone exposure induces early senescence leading to late apoptotic signaling cascade in human trabecular meshwork (HTM) cell line: An in vitro glaucoma model.

    PubMed

    Maurya, Nancy; Agarwal, Nupur Rani; Ghosh, Ilora

    2016-01-01

    This study aimed to determine whether the prolonged exposure of the human trabecular meshwork (HTM) cell line to a low dose (1 nM) of rotenone could simulate a glaucomatous-like condition and serve as a cellular model for its etiological analysis. Under 1-nM rotenone exposure for 24-72 h, HTM cells showed a decrease in cell viability as assessed by an MTT assay and showed mitochondrial dysfunction as assessed by measuring H2 DCFDA fluorescence; a decrease in ATP level was also observed. Flow cytometric analysis showed an increase in cellular size and granularity. Elevated AF showed initial senescence. LF staining with SBB and its spectrofluorometric quantification confirmed growth arrest. An accumulation of cytoplasmic myocilin, IL-6, and MMP-9 at 72 h of exposure supported glaucomatous induction. TEM revealed morphological changes in mitochondria and nuclei of treated cells. Signaling cascades were assessed by immunoblotting and immunocytochemical analysis. This study showed a shift in status of the cells from initial senescence to induction of apoptosis in the HTM cell line due to continuous low-dose exposure to rotenone; however, at 72 h, both senescence and apoptotic features are apparent in these cells. This is the first report that reveals the potential of a prolonged low-dose exposure of rotenone to simulate senescence in the HTM cell line to cause a glaucomatous condition. © 2015 International Federation for Cell Biology.

  20. Involvement of Tiam1, RhoG and ELMO2/ILK in Rac1-mediated phagocytosis in human trabecular meshwork cells.

    PubMed

    Peotter, Jennifer L; Phillips, Jenny; Tong, Tiegang; Dimeo, Kaylee; Gonzalez, Jose M; Peters, Donna M

    2016-10-01

    We previously demonstrated that an αvβ5 integrin/FAK- mediated pathway regulated the phagocytic properties of human trabecular meshwork (HTM) cells. Here we demonstrate that this process is mediated by Rac-1 and a previously unreported signaling pathway that utilizes the Tiam1 as well as a novel ILK/RhoG/ELMO2 signaling pathway. Phagocytosis in both a TM-1 cell line and normal HTM cells was mediated by Rac1 and could be significantly decreased by >75% using the Rac1 inhibitor EHop-016. Knockdown of Rac1 in TM-1 cells also inhibited phagocytosis by 40% whereas overexpression of a constitutively active Rac1 or stimulation with PDGF increased phagocytosis by 83% and 32% respectively. Tiam1 was involved in regulating phagocytosis. Knockdown of Tiam1 inhibited phagocytosis by 72% while overexpression of Tiam1 C1199 increased phagocytosis by 75%. Other upstream effectors of Rac1 found to be involved included ELMO2, RhoG, and ILK. Knockdowns of ELMO2, ILK, and RhoG caused a reduction in phagocytosis by 51%, 55% and 46% respectively. In contrast, knockdown of Vav2 and Dock1 or overexpression of Vav2 Y159/172F did not cause a significant change in phagocytosis. These data suggest a novel link between Tiam1 and RhoG/ILK /ELMO2 pathway as upstream effectors of the Rac1-mediated phagocytic process in TM cells. Copyright © 2016 Elsevier Inc. All rights reserved.

  1. Cyclic Mechanical Stress and Trabecular Meshwork Cell Contractility

    PubMed Central

    Ramos, Renata F.; Sumida, Grant M.; Stamer, W. Daniel

    2009-01-01

    Purpose Ocular pulse decreases outflow facility of perfused anterior segments. However, the mechanism by which conventional outflow tissues respond to cyclic intraocular pressure oscillations is unknown. The purpose of the present study was to examine responses of trabecular meshwork (TM) cells to cyclic biomechanical stress in the presence and absence of compounds known to affect cell contractility. Methods To model flow in the juxtacanalicular region of the TM and to measure changes in transendothelial flow, human TM cell monolayers on permeable filters were perfused at a constant flow rate until reaching a stable baseline pressure and then were exposed to cyclic stress with an average amplitude of 2.7 mm Hg peak to peak at a 1-Hz frequency for 2 hours in the presence or absence of compounds known to affect cell contractility (isoproterenol, Y27632, pilocarpine, and nifedipine). Pressure was recorded continuously. Immunocytochemistry staining was used to determine filamentous actin stress fiber content, whereas Western blot analysis was used to measure the extent of myosin light chain (p-MLC) phosphorylation and ratio of filamentous to globular actin. Results Human TM cells respond to cyclic pressure oscillations by increasing mean intrachamber pressure (decreasing hydraulic conductivity) (126.13% ± 2.4%; P < 0.05), a response blocked in the presence of Y27632, a rho-kinase inhibitor (101.35 ± 0.59; P = 0.234), but not isoproterenol, pilocarpine, or nifedipine. Although mechanical stress appeared to have no effect, Y27632 decreased phosphorylated myosin light chain, filamentous/globular actin ratio, and stress fiber formation in TM cells. Conclusions Human TM cells respond to cyclic mechanical stress by increasing intrachamber pressure. Pulse-mediated effects are blocked by Y27632, implicating a role for Rho-kinase-mediated signaling and cellular contractility in ocular pulse-associated changes in outflow facility. PMID:19339745

  2. Induction of Trabecular Meshwork Cells From Induced Pluripotent Stem Cells

    PubMed Central

    Ding, Qiong J.; Zhu, Wei; Cook, Amy C.; Anfinson, Kristin R.; Tucker, Budd A.; Kuehn, Markus H.

    2014-01-01

    Purpose. Loss or dysfunction of trabecular meshwork (TM) cells has been associated with the development of pathologically elevated IOP, and it is conceivable that replacement of damaged TM cells could restore function to the TM. We propose that the use of TM-like cells derived from induced pluripotent stem cells (iPSCs) created from a patient's own dermal fibroblasts offers the best solution to this challenge. Here we demonstrate that mouse iPSCs can be induced to differentiate into TM-like cells suitable for autologous transplantation. Methods. Directed induction of stem cell differentiation was achieved through coculture of mouse iPSCs with human TM cells for up to 21 days. The resultant TM-like cells (iPSC-TM) were characterized morphologically, immunohistochemically, and functionally. Results. The iPSC-TM cells closely resembled cultured human TM cells morphologically and began to express many markers of TM cells while ceasing to express pluripotency markers such as Nanog, Oct4, and Sox2. Functionally, these cells developed the ability to phagocytose particles. Finally, exposure to dexamethasone or phorbol 12-myristate acetate caused a distinct increase in the production and secretion of myocilin and matrix metalloproteinase-3, respectively, behavior characteristic of TM cells. Conclusions. Our data demonstrate that iPSCs can be induced to assume a phenotype that resembles native TM cells in many important aspects. Not only do these cells represent a valuable research tool, but transplantation into glaucomatous eyes with elevated IOP may also restore function to the TM, resulting in re-establishment of IOP. PMID:25298418

  3. The Effects of Transforming Growth Factor-β2 on the Expression of Follistatin and Activin A in Normal and Glaucomatous Human Trabecular Meshwork Cells and Tissues

    PubMed Central

    Fitzgerald, Ashley M.; Benz, Cecilia; Clark, Abbot F.; Wordinger, Robert J.

    2012-01-01

    Purpose. To compare follistatin (FST) and activin (Act) expression in normal and glaucomatous trabecular meshwork (TM) cells and tissues and determine if exogenous TGF-β2 regulates the expression of FST and Act in TM cells. Methods. Total RNA was isolated from TM cell strains, and mRNA expression for FST 317/344 isoforms and Act was determined via RT-PCR and quantitative PCR (qPCR). Western immunoblotting and immunocytochemistry determined FST and Act A protein levels in normal TM (NTM) and glaucomatous TM (GTM) cells. Cells were treated with recombinant human TGF-β2 protein at 0 to 10 ng/mL for 0 to 72 hours. qPCR, Western immunoblotting, immunocytochemistry, and ELISA immunoassay were utilized to determine changes in FST and Act A mRNA and protein levels. In addition, NTM and GTM tissue samples were examined by immunohistochemistry for expression of FST, FST 315, FST 288, and Act A. Results. Both FST mRNA and protein levels were significantly elevated in GTM cells. FST mRNA transcripts FST 317/344 were also significantly elevated in GTM cells. Immunohistochemistry showed FST levels were significantly elevated in GTM tissues. Exogenous TGF-β2 significantly induced FST mRNA and protein expression. Immunohistochemistry demonstrated that Act A protein levels were significantly higher in NTM tissues compared to GTM tissues. Conclusions. FST is elevated in GTM cells and tissues. FST is known to be an inhibitor of bone morphogenetic proteins (BMPs), which, coupled with the ability of TGF-β2 to upregulate FST levels, may indicate a possible role of FST in the pathogenesis of glaucoma. These results suggest that additional endogenous molecules in human TM may regulate TGF-β2 signaling via inhibition of BMP family members. PMID:23010638

  4. Functional pharmacological evidence for EP2 and EP4 prostanoid receptors in immortalized human trabecular meshwork and non-pigmented ciliary epithelial cells.

    PubMed

    Crider, J Y; Sharif, N A

    2001-02-01

    The aim of these studies was to characterize the molecular pharmacology of the prostanoid receptors positively coupled to stimulation of adenylyl cyclase activity in immortalized human trabecular meshwork (TM-3) cells and to compare these results with that of the receptors in immortalized human nonpigmented epithelial (NPE) cells. In general, the TM-3 and NPE cells showed a similar profile with respect to their responses to various prostaglandin (PG) receptor agonists. The rank order of potency (EC50; means +/- SEM) for these compounds in the TM-3 cells was: PGE2 (124 +/- 21 nM) > 13,14-dihydro-PGE1 (430 +/- 110 nM) = PGE1 (522 +/- 345 nM) > 11-deoxy-PGE1 (1063 +/- 118 nM) = 16,16-dimethyl-PGE2 (1776 +/- 460 nM) = butaprost (1920 +/- 527 nM) > PGD2 = PGI2 = PGF2alpha (n = 3 - 12). While the agonist profile indicated the presence of EP2 receptors, the effects of the EP4 receptor antagonists suggested the additional expression of EP4 receptors in both of these cells. Thus, the EP4 receptor antagonist, AH23848B, at a concentration of 30 microM, caused a dextral shift in the PGE2 concentration-response curves in both TM-3 and NPE cells coupled with a 20-28% decrease in the maximal response of PGE2, indicating apparent noncompetitive antagonism profiles. The antagonist potency of AH23848B in these cells was: Kb = 38.4 +/- 14.8 microM and 23.5 +/- 4.5 microM; -log Kb = 4.7. The other EP4 receptor antagonist, AH22921 (-log Kb = 4.1 - 4.7), was weaker than AH23848B. Taken together, these pharmacological studies have shown than TM-3 and NPE cells apparently contain functional EP2 and EP4 prostanoid receptors positively coupled to adenylyl cyclase.

  5. A Porcine Anterior Segment Perfusion and Transduction Model With Direct Visualization of the Trabecular Meshwork

    PubMed Central

    Loewen, Ralitsa T.; Roy, Pritha; Park, Daniel B.; Jensen, Adrianna; Scott, Gordon; Cohen-Karni, Devora; Fautsch, Michael P.; Schuman, Joel S.; Loewen, Nils A.

    2016-01-01

    Purpose To establish a consistent and affordable, high quality porcine anterior segment perfusion and transduction model that allows direct visualization of the trabecular meshwork. Methods Porcine anterior segments were cultured within 2 hours of death by removing lens and uvea and securing in a specially designed petri dish with a thin bottom to allow direct visualization of the trabecular meshwork with minimal distortion. Twenty-two control eyes (CO) with a constant flow rate were compared to eight gravity perfused eyes (COgr, 15 mm Hg). We established gene delivery to the TM using eGFP expressing feline immunodeficiency virus (FIV) vector GINSIN at 108 transducing units (TU) per eye (GINSIN_8, n = 8) and 107 TU (GINSIN_7, n = 8). Expression was assessed for 14 days before histology was obtained. Results Pig eyes were a reliable source for consistent and high quality anterior segment cultures with a low failure rate of 12%. Control eyes had an intraocular pressure (IOP) of 15.8 ± 1.9 mm Hg at fixed pump perfusion with 3 μL/min compared to gravity perfused COgr with imputed 3.7 ± 1.6 μL/min. Vector GINSIN_8 eyes experienced a transient posttransduction IOP increase of 44% that resolved at 48 hours; this was not observed in GINSIN_7 eyes. Expression was higher in GINSIN_8 than in GINSIN_7 eyes. Trabecular meshwork architecture was well preserved. Conclusions Compared with previously used human donor eyes, this inexpensive porcine anterior segment perfusion model is of sufficient, repeatable high quality to develop strategies of TM bioengineering. Trabecular meshwork could be observed directly. Despite significant anatomic differences, effects of transduction replicate the main aspects of previously explored human, feline and rodent models. PMID:27002293

  6. The Effects of Myocilin Expression on Functionally Relevant Trabecular Meshwork Genes: A Mini-Review

    PubMed Central

    2014-01-01

    Abstract Myocilin is a secreted glaucoma-associated protein, specifically induced by dexamethasone in human trabecular meshwork cells, where it was discovered. Myocilin is expressed in several tissues of the body, but it causes disease only in the eye. The protein contains two domains: an N-terminal region with significant homologies to nonmuscle myosin, and a C-terminal region, which is similar to the olfactomedin proteins. Forty percent of myocilin undergoes an intracellular endoproteolytic cleavage by calpain II, a calcium-dependent cysteine protease, which releases the 2 domains. The protein is known to interact with intracellular and extracellular matrix proteins, and some is released into the extracellular space associated with exosomes. Myocilin mutations are linked to glaucoma and induce elevated intraocular pressure. Most of the glaucoma-causative mutations map to the olfactomedin domain, which appears to be a critical domain for the function of the protein. Myocilin mutants are misfolded, aggregate in the endoplasmic reticulum, and are not secreted. Overexpression of myocilin and of its mutants in primary human trabecular meshwork cells triggers changes in the expression of numerous genes, many of which have been known to be involved in mechanisms important for the physiology and pathology of the tissue. Here we review recent studies from our laboratory and those of others that deal with trabecular meshwork genes, which are altered by the overexpression of wild-type and glaucoma-causative mutant myocilin genes. PMID:24564495

  7. TGFβ2 Induces the Formation of Cross-Linked Actin Networks (CLANs) in Human Trabecular Meshwork Cells Through the Smad and Non-Smad Dependent Pathways

    PubMed Central

    Montecchi-Palmer, Michela; Bermudez, Jaclyn Y.; Webber, Hannah C.; Patel, Gaurang C.; Clark, Abbot F.; Mao, Weiming

    2017-01-01

    Purpose Increased intraocular pressure results from increased aqueous humor (AH) outflow resistance at the trabecular meshwork (TM) due to pathologic changes including the formation of cross-linked actin networks (CLANs). Transforming growth factor β2 (TGFβ2) is elevated in the AH and TM of primary open angle glaucoma (POAG) patients and induces POAG-associated TM changes, including CLANs. We determined the role of individual TGFβ2 signaling pathways in CLAN formation. Methods Cultured nonglaucomatous human TM (NTM) cells were treated with control or TGFβ2, with or without the inhibitors of TGFβ receptor, Smad3, c-Jun N-terminal kinases (JNK), extracellular signal regulated kinase (ERK), P38, or Rho-associated protein kinase (ROCK). NTM cells were cotreated with TGFβ2 plus inhibitors for 10 days or pretreated with TGFβ2 for 10 days followed by 1-hour inhibitor treatment. NTM cells were immunostained with phalloidin-Alexa-488 and 4′,6-diamidino-2-phenylindole (DAPI). Data were analyzed using 1-way ANOVA and Dunnett's post hoc test. Results TGFβ2 significantly induced CLAN formation (n = 6 to 12, P < 0.05), which was completely inhibited by TGFβ receptor, Smad3, and ERK inhibitors, as well as completely or partially inhibited by JNK, P38, and ROCK inhibitors, depending on cell strains. One-hour exposure to ROCK inhibitor completely resolved formed CLANs (P < 0.05), whereas TGFβ receptor, Smad3 inhibitor, and ERK inhibitors resulted in partial or complete resolution. The JNK and P38 inhibitors showed partial or no resolution. Among these inhibitors, the ROCK inhibitor was the most disruptive to the actin stress fibers, whereas ERK inhibition showed the least disruption. Conclusions TGFβ2-induced CLANs in NTM cells were prevented and resolved using various pathway inhibitors. Apart from CLAN inhibition, some of these inhibitors also had different effects on actin stress fibers. PMID:28241317

  8. Vesicular stomatitis virus glycoprotein- and Venezuelan equine encephalitis virus-derived glycoprotein-pseudotyped lentivirus vectors differentially transduce corneal endothelium, trabecular meshwork, and human photoreceptors.

    PubMed

    Lipinski, Daniel M; Barnard, Alun R; Charbel Issa, Peter; Singh, Mandeep S; De Silva, Samantha R; Trabalza, Antonio; Eleftheriadou, Ioanna; Ellison, Stuart M; Mazarakis, Nicholas D; MacLaren, Robert E

    2014-01-01

    The ability to deliver a large transgene efficiently to photoreceptors using viral vectors remains problematic and yet is critical for the future therapy of inherited retinal diseases such as Stargardt's and Usher's 1B. Herein, we examine the ocular tropism of a HIV-1-based lentivirus vector pseudotyped with Venezuelan equine encephalitis virus-derived glycoprotein (VEEV-G) after intraocular delivery to the posterior and anterior chambers of C57BL/6 wild-type mice. Reporter gene (EGFP) expression was evaluated using in vivo fluorescence imaging followed by postmortem immunohistochemistry and retinal function assessed by electroretinography. Intracameral administration of VEEV-G and vesicular stomatitis virus glycoprotein (VSV-G)-pseudotyped vectors resulted in robust transgene expression in the corneal endothelium and trabecular meshwork. After subretinal administration, onset of transgene expression was observed in the retinal pigment epithelium (RPE) 1 day postinjection with both VEEV-G and control VSV-G pseudotypes, but no significant photoreceptor transduction was apparent. Substantial degeneration of the outer nuclear layer was observed with VEEV-G-pseudotyped vector, which corresponded to ablation of retinal function. Subretinal administration of VSV-G was observed to result in significant suppression of electrophysiological function compared with buffer-injected and uninjected control eyes. Suppression of the c-wave amplitude, in addition to reduced RPE65 expression, indicated potential RPE dysfunction. Ex vivo tropism of VSV-G was assessed using organotypic culture of explanted retina harvested from wild-type mice and human patients undergoing retinal detachment surgery to examine the prevention of transduction by physical barriers and species differences in tropism.

  9. Effect of benzalkonium chloride on trabecular meshwork cells in a new in vitro 3D trabecular meshwork model for glaucoma.

    PubMed

    Bouchemi, Meryem; Roubeix, Christophe; Kessal, Karima; Riancho, Luisa; Raveu, Anne-Laure; Soualmia, Hayet; Baudouin, Christophe; Brignole-Baudouin, Françoise

    2017-06-01

    To validate a new culture model of primary human trabecular meshwork cells (p-hTMCs) using Matrigel®, in order to mimic in vitro 3D-TM organization, and to investigate the proinflammatory effect of benzalkonium chloride (BAK) in 3D p-hTMC cultures. p-hTMCs, seeded onto Matrigel®-coated inserts were stimulated with BAK (10(-4)%), dexamethasone (DEX) (10(-6)M) or transforming growth factor-beta 2 (TGF-β2) (5ng/ml) for 48h and observed with confocal microscopy. The BAK effect at 10(-4)% or 5.10(-3)% on the gene expressions of interleukin-6 (IL-6), interleukin-8 (IL-8) and matrix metalloproteinase (MMP-9) was investigated using qRT-PCR in 2D and 3D p-hTMC cultures. p-hTMCs seeded in Matrigel® were able to organize themselves in a 3D-spatial conformation in the different conditions tested with cross-linked actin network (CLAN) formation in presence of DEX or TGF-β2 and intercellular space contraction with TGF-β2. IL-6 and IL-8 gene expressions increased in presence of BAK in 2D and in 3D p-hTMC cultures. BAK 10(-4)% only showed a tendency to stimulate MMP-9 expression in p-hTMCs after 24h-recovery. We investigated this new 3D-TM in vitro model in Matrigel(®) matrix for pathophysiological and toxicological purposes. It appears as a new promising tool for a better understanding of TM behavior in physiological and stress conditions, as well as toxicological evaluations of antiglaucoma eyedrops and preservatives. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. σ-1 receptor stimulation protects against pressure-induced damage through InsR-MAPK signaling in human trabecular meshwork cells

    PubMed Central

    Meng, Bo; Li, Hongyi; Sun, Xian; Qu, Wei; Yang, Binbin; Cheng, Fang; Shi, Liping; Yuan, Huiping

    2017-01-01

    The purpose of the present study was to investigate the protective effect of the σ-1 receptor (Sig-1R) agonist (+)-pentazocin (PTZ) on pressure-induced apoptosis and death of human trabecular meshwork cells (hTMCs). The expression levels of Sig-1R and insulin receptor (InsR) were examined in hTMCs. Cells were cultured under a pressure of 0, 20, 40, 60 and 80 mmHg for 48 h, and under 80 mmHg for 44 h, after which the cells were treated with (+)-PTZ (20 µM), N-(2-(3,4-dichlorophenyl)ethyl)-N-methyl-2-(dimethylamino) ethylamine (BD-1063; 20 µM) administered 30 min prior to (+)-PTZ, or BD-1063 (20 µM) and then exposed to 80 mmHg again until the 48 h time-point. The changes of the cells were observed by optical and electron microscopy, the apoptosis and death of hTMCs were detected by ethidium bromide/acridine orange dual staining assay and the expression of Sig-1R and InsR by reverse transcription-quantitative polymerase chain reaction and western blot analysis. The phosphorylation of extracellular signal-regulated kinase (ERK), an important downstream protein of the InsR-mitogen-activated protein kinases (MAPK) signaling pathway, was also detected by western blot analysis when (+)-PTZ and BD-1063 were added to the 80 mmHg-treated cells. Sig-1Rs and InsRs were expressed in hTMCs. The apoptosis and death of hTMCs increased from 40 mmHg with 50% cell death when the pressure was at 80 mmHg and the structure of the cells noticeably changed. The expression of Sig-1R and InsR increased along with the elevation of pressure. (+)-PTZ decreased the apoptosis and death of hTMCs and increased the expression of Sig-1R and InsR, and the phosphorylation of ERK. Such effects were blocked by BD-1063. The present study suggested that Sig-1R agonist (+)-PTZ can protect hTMCs from pressure-induced apoptosis and death by activating InsR and the MAPK signal pathway. PMID:28560459

  11. Age-Related Changes in Trabecular Meshwork Imaging

    PubMed Central

    Gold, Mark E.; Nagi, Kundandeep S.; Bell, Nicholas P.; Blieden, Lauren S.; Chuang, Alice Z.; Baker, Laura A.; Mankiewicz, Kimberly A.; Feldman, Robert M.

    2013-01-01

    Purpose. To evaluate the normal aging effects on trabecular meshwork (TM) parameters using Fourier domain anterior segment optical coherence tomography (ASOCT) images. Patients and Methods. One eye from 45 participants with open angles was imaged. Two independent readers measured TM area, TM length, and area and length of the TM interface shadow from 3 age groups (18–40, 41–60, and 61–80). Measurements were compared using stepwise regression analysis. Results. The average TM parameters were 0.0487 (±0.0092) mm2 for TM area, 0.5502 (±0.1033) mm for TM length, 0.1623 (±0.341) mm2 for TM interface shadow area, and 0.7755 (±0.1574) mm for TM interface shadow length. Interobserver reproducibility coefficients ranged from 0.45 (TM length) to 0.82 (TM area). TM area and length were not correlated with age. While the TM interface shadow length did not correlate with age, the TM interface shadow area increased with age. Race, sex, intraocular pressure, and gonioscopy score were not correlated with any TM parameters. Conclusion. Although the TM measurements were not correlated with age, the TM interface shadow area increased with age. Further study is required to determine whether there is any relationship between the age-related ASOCT findings of the TM interface shadow area and physiologic function. PMID:24163814

  12. Multiphoton gonioscopy to image the trabecular meshwork of porcine eyes

    NASA Astrophysics Data System (ADS)

    Masihzadeh, Omid; Ammar, David A.; Kahook, Malik Y.; Gibson, Emily A.; Lei, Tim C.

    2013-03-01

    The aqueous outflow system (AOS), including the trabecular meshwork (TM), the collector channels (CC) and the Schlemm's canal (SC), regulates intraocular pressure (IOP) through the drainage of the aqueous humor (AH). Abnormal IOP elevation leads to increased pressure stress to retinal ganglion cells, resulting in cell loss that can ultimately lead to complete loss of eyesight. Therefore, development of imaging tools to detect abnormal structural and functional changes of the AOS is important in early diagnosis and prevention of glaucoma. Multiphoton microscopy (MPM), including twophoton autofluorescence (TPAF) and second harmonic generation (SHG), is a label-free microscopic technique that allows molecular specific imaging of biological tissues like the TM. Since the TM and other AOS structures are located behind the highly scattering scleral tissue, transscleral imaging of the TM does not provide enough optical resolution. In this work, a gonioscopic lens is used to allow direct optical access of the TM through the cornea for MPM imaging. Compared to transscleral imaging, the acquired MPM images show improved resolution as individual collagen fiber bundles of the TM can be observed. MPM gonioscopy may have the potential to be developed as a future clinical imaging tool for glaucoma diagnostics.

  13. Elevation of intraocular pressure in rodents using viral vectors targeting the trabecular meshwork.

    PubMed

    Pang, Iok-Hou; Millar, J Cameron; Clark, Abbot F

    2015-12-01

    Rodents are increasingly being used as glaucoma models to study ocular hypertension, optic neuropathy, and retinopathy. A number of different techniques are used to elevate intraocular pressure in rodent eyes by artificially obstructing the aqueous outflow pathway. Another successful technique to induce ocular hypertension is to transduce the trabecular meshwork of rodent eyes with viral vectors expressing glaucoma associated transgenes to provide more relevant models of glaucomatous damage to the trabecular meshwork. This technique has been used to validate newly discovered glaucoma pathogenesis pathways as well as to develop rodent models of primary open angle glaucoma. Ocular hypertension has successfully been induced by adenovirus 5 mediated delivery of mutant MYOC, bioactivated TGFβ2, SFRP1, DKK1, GREM1, and CD44. Advantages of this approach are: selective tropism for the trabecular meshwork, the ability to use numerous mouse strains, and the relatively rapid onset of IOP elevation. Disadvantages include mild-to-moderate ocular inflammation induced by the Ad5 vector and sometimes transient transgene expression. Current efforts are focused at discovering less immunogenic viral vectors that have tropism for the trabecular meshwork and drive sufficient transgene expression to induce ocular hypertension. This viral vector approach allows rapid proof of concept studies to study glaucomatous damage to the trabecular meshwork without the expensive and time-consuming generation of transgenic mouse lines.

  14. Walking through trabecular meshwork biology: Toward engineering design of outflow physiology.

    PubMed

    Dautriche, Cula N; Xie, Yubing; Sharfstein, Susan T

    2014-01-01

    According to the World Health Organization, glaucoma remains the second leading cause of blindness in the world. Glaucoma belongs to a group of optic neuropathies that is characterized by chronic degeneration of the optic nerve along with its supporting glia and vasculature. Despite significant advances in the field, there is no available cure for glaucoma. The trabecular meshwork has been implicated as the primary site for regulation of intraocular pressure, the only known modifiable factor in glaucoma development. In this review, we describe the current models for glaucoma studies, primary culture, anterior eye segments, and animal studies and their limitations. These models, especially anterior eye segments and animal tissues, often require careful interpretation given the inter-species variation and are cumbersome and expensive. The lack of an available in vitro 3D model to study trabecular meshwork cells and detailed mechanisms of their regulation of intraocular pressure has limited progress in the field of glaucoma research. In this paper, we review the current status of knowledge of the trabecular meshwork and how the current advances in tissue engineering techniques might be applied in an effort to engineer a synthetic trabecular meshwork as a 3D in vitro model to further advance glaucoma research. In addition, we describe strategies for selection and design of biomaterials for scaffold fabrication as well as extracellular matrix components to mimic and support the trabecular architecture. We also discuss possible uses for a bioengineered trabecular meshwork for both developing a fundamental understanding of trabecular meshwork biology as well as high-throughput screening of glaucoma drugs.

  15. Disruption of fibronectin matrix affects type IV collagen, fibrillin and laminin deposition into extracellular matrix of human trabecular meshwork (HTM) cells.

    PubMed

    Filla, Mark S; Dimeo, Kaylee D; Tong, Tiegang; Peters, Donna M

    2017-08-28

    Fibronectin fibrils are a major component of the extracellular matrix (ECM) of the trabecular meshwork (TM). They are a key mediator of the formation of the ECM which controls aqueous humor outflow and contributes to the pathogenesis of glaucoma. The purpose of this work was to determine if a fibronectin-binding peptide called FUD, derived from the Streptococcus pyogenes Functional Upstream Domain of the F1 adhesin protein, could be used to control fibronectin fibrillogenesis and hence ECM formation under conditions where its expression was induced by treatment with the glucocorticoid dexamethasone. FUD was very effective at preventing fibronectin fibrillogenesis in the presence or absence of steroid treatment as well as the removal of existing fibronectin fibrils. Disruption of fibronectin fibrillogenesis by FUD also disrupted the incorporation of type IV collagen, laminin and fibrillin into the ECM. The effect of FUD on these other protein matrices, however, was found to be dependent upon the maturity of the ECM when FUD was added. FUD effectively disrupted the incorporation of these other proteins into matrices when added to newly confluent cells that were forming a nascent ECM. In contrast, FUD had no effect on these other protein matrices if the cell cultures already possessed a pre-formed, mature ECM. Our studies indicate that FUD can be used to control fibronectin fibrillogenesis and that these fibrils play a role in regulating the assembly of other ECM protein into matrices involving type IV collagen, laminin, and fibrillin within the TM. This suggests that under in vivo conditions, FUD would selectively disrupt fibronectin fibrils and de novo assembly of other proteins into the ECM. Finally, our studies suggest that targeting fibronectin fibril assembly may be a viable treatment for POAG as well as other glaucomas involving excessive or abnormal matrix deposition of the ECM. Copyright © 2017. Published by Elsevier Ltd.

  16. Scanning electron microscopy of the trabecular meshwork: understanding the pathogenesis of primary angle closure glaucoma.

    PubMed

    Sihota, Ramanjit; Goyal, Amita; Kaur, Jasbir; Gupta, Viney; Nag, Tapas C

    2012-01-01

    To study ultrastructural changes of the trabecular meshwork in acute and chronic primary angle closure glaucoma (PACG) and primary open angle glaucoma (POAG) eyes by scanning electron microscopy. Twenty-one trabecular meshwork surgical specimens from consecutive glaucomatous eyes after a trabeculectomy and five postmortem corneoscleral specimens were fixed immediately in Karnovsky solution. The tissues were washed in 0.1 M phosphate buffer saline, post-fixed in 1% osmium tetraoxide, dehydrated in acetone series (30-100%), dried and mounted. Normal trabecular tissue showed well-defined, thin, cylindrical uveal trabecular beams with many large spaces, overlying flatter corneoscleral beams and numerous smaller spaces. In acute PACG eyes, the trabecular meshwork showed grossly swollen, irregular trabecular endothelial cells with intercellular and occasional basal separation with few spaces. Numerous activated macrophages, leucocytes and amorphous debris were present. Chronic PACG eyes had a few, thickened posterior uveal trabecular beams visible. A homogenous deposit covered the anterior uveal trabeculae and spaces. Converging, fan-shaped trabecular beam configuration corresponded to gonioscopic areas of peripheral anterior synechiae. In POAG eyes, anterior uveal trabecular beams were thin and strap-like, while those posteriorly were wide, with a homogenous deposit covering and bridging intertrabecular spaces, especially posteriorly. Underlying corneoscleral trabecular layers and spaces were visualized in some areas. In acute PACG a marked edema of the endothelium probably contributes for the acute and marked intraocular pressure (IOP) elevation. Chronically raised IOP in chronic PACG and POAG probably results, at least in part, from decreased aqueous outflow secondary to widening and fusion of adjacent trabecular beams, together with the homogenous deposit enmeshing trabecular beams and spaces.

  17. RhoA GTPase-Induced Ocular Hypertension in a Rodent Model Is Associated with Increased Fibrogenic Activity in the Trabecular Meshwork

    PubMed Central

    Pattabiraman, Padmanabhan P.; Rinkoski, Tommy; Poeschla, Eric; Proia, Alan; Challa, Pratap; Rao, Ponugoti V.

    2016-01-01

    Ocular hypertension arising from increased resistance to aqueous humor (AH) outflow through the trabecular meshwork is a primary risk factor for open-angle glaucoma, a leading cause of blindness. Ongoing efforts have found little about the molecular and cellular bases of increased resistance to AH outflow through the trabecular meshwork in ocular hypertension patients. To test the hypothesis that dysregulated Rho GTPase signaling and a resulting fibrotic activity within the trabecular meshwork may result in ocular hypertension, we investigated the effects of expressing a constitutively active RhoA GTPase (RhoAV14) in the AH outflow pathway in Sprague-Dawley rats by using lentiviral vector-based gene delivery. Rats expressing RhoAV14 in the iridocorneal angle exhibited a significantly elevated intraocular pressure. Elevated intraocular pressure in the RhoAV14-expressing rats was associated with fibrotic trabecular meshwork and increased levels of F-actin, phosphorylated myosin light chain, α-smooth muscle actin, collagen-1A, and total collagen in the trabecular AH outflow pathway. Most of these changes were ameliorated by topical application of Rho kinase inhibitor. Human autopsy eyes from patients with glaucoma exhibited significant increases in levels of collagen-1A and total collagen in the trabecular AH outflow pathway. Collectively, these observations indicate that increased fibrogenic activity because of dysregulated RhoA GTPase activity in the trabecular AH outflow pathway increases intraocular pressure in a Rho kinase-dependent manner. PMID:25499974

  18. New Insight of Common Regulatory Pathways in Human Trabecular Meshwork Cells in Response to Dexamethasone and Prednisolone Using an Integrated Quantitative Proteomics: SWATH and MRM-HR Mass Spectrometry.

    PubMed

    Shan, Sze Wan; Do, Chi Wai; Lam, Thomas Chuen; Kong, Ricky Pak Wing; Li, King Kit; Chun, Ka Man; Stamer, William Daniel; To, Chi Ho

    2017-09-27

    The molecular pathophysiology of corticosteroid-induced ocular hypertension (CIH) is not well understood. To determine the biological mechanisms of CIH, this study investigated protein expression profiles of human trabecular meshwork (hTM) cells in response to dexamethasone and prednisolone treatment. Both discovery-based sequential windowed data independent acquisition of the total high-resolution mass spectra (SWATH-MS) and targeted based high resolution multiple reaction monitoring (MRM-HR) confirmation were applied using a hybrid quadrupole-time-of-flight mass spectrometer. A comprehensive list of 1759 proteins (1% FDR) was generated from the hTM. Quantitative proteomics revealed 20 differentially expressed proteins (p-value ≤ 0.05 and fold-change ≥ 1.5 or ≤ 0.67) commonly induced by prednisolone and dexamethasone, both at 300 nM. These included connective tissue growth factor (CTGF) and thrombospondin-1 (THBS1), two proteins previously implicated in ocular hypertension, glaucoma, and the transforming growth factor-β pathway. Their gene expressions in response to corticosteroids were further confirmed using reverse-transcription polymerase chain reaction. Together with other novel proteins identified in the data sets, additional pathways implicated by these regulated proteins were the phosphatidylinositol 3-kinase (PI3K)-protein kinase B (Akt) signaling pathway, integrin cell surface interaction, extracellular matrix (ECM) proteoglycans, and ECM-receptor interaction. Our results indicated that an integrated platform of SWATH-MS and MRM-HR allows high throughput identification and confirmation of novel and known corticosteroid-regulated proteins in trabecular meshwork cells, demonstrating the power of this technique in extending the current understanding of the pathogenesis of CIH.

  19. Hyaluronan cable formation by ocular trabecular meshwork cells.

    PubMed

    Sun, Ying Ying; Keller, Kate E

    2015-10-01

    Hyaluronan (HA) in the ocular trabecular meshwork (TM) is a critical modulator of aqueous humor outflow. Individual HA strands in the pericellular matrix can coalesce to form cable-like structures, which have different functional properties. Here, we investigated HA structural configuration by TM cells in response to various stimuli known to stimulate extracellular matrix (ECM) remodeling. In addition, the effects of HA cable induction on aqueous outflow resistance was determined. Primary TM cell cultures grown on tissue culture-treated plastic were treated for 12-48 h with TNFα, IL-1α, or TGFβ2. TM cells grown on silicone membranes were subject to mechanical stretch, which induces synthesis and activation of ECM proteolytic enzymes. HA structural configuration was investigated by HA binding protein (HAbp) staining and confocal microscopy. HAbp-labeled cables were induced by TNFα, TGFβ2 and mechanical stretch, but not by IL-1α. HA synthase (HAS) gene expression was quantitated by quantitative RT-PCR and HA concentration was measured by ELISA assay. By quantitative RT-PCR, HAS-1, -2, and -3 genes were differentially up-regulated and showed temporal differences in response to each treatment. HA concentration was increased in the media by TNFα, TGFβ2 and IL-1α, but mechanical stretch decreased pericellular HA concentrations. Immunofluorescence and Western immunoblotting were used to investigate the distribution and protein levels of the HA-binding proteins, tumor necrosis factor-stimulated gene-6 (TSG-6) and inter-α-inhibitor (IαI). Western immunoblotting showed that TSG-6 and IαI were increased by TNFα, TGFβ2 and IL-1α, but mechanical stretch reduced their levels. The underlying substrate appears to affect the identity of IαI·TSG-6·HA complexes since different complexes were detected when TM cells were grown on a silicone substrate compared to a rigid plastic surface. Porcine anterior segments were perfused with 10 μg/ml polyinosinic

  20. Phase-sensitive optical coherence tomography characterization of pulse-induced trabecular meshwork displacement in ex vivo non-human primate eyes

    NASA Astrophysics Data System (ADS)

    Li, Peng; Reif, Roberto; Zhi, Zhongwei; An, Lin; Martin, Elizabeth; Shen, Tueng T.; Johnstone, Murray; Wang, Ruikang K.

    2013-03-01

    Purpose. It is suspected that the abnormalities of aqueous outflow pump composed of trabecular meshwork (TM) and Schlemm's canal (SC) results in the increased outflow resistance and then elevated intraocular pressure (IOP) in initial glaucoma. In order to explore the casual mechanism and the early diagnosis of glaucoma, the dynamic characterizations of aqueous outflow pump were explored. Methods. As a functional extension of optical coherence tomography (OCT), tissue Doppler OCT (tissue-DOCT) method capable of measuring the slow tissue movement was developed. The tissue-DOCT imaging was conducted on the corneo-scleral limbus of 4 monkey eyes. The eye was mounted in an anterior segment holder, together with a perfusion system to control the mean IOP and to induce the cyclic IOP transients with amplitude 3 mm Hg at frequency 1 pulse/second. IOP was monitored on-line by a pressure transducer. Tissue-DOCT data and pressure data were recorded simultaneously. The IOP-transient induced Doppler velocity, displacement and strain rate of TM and the normalized area of SC were quantified at 7 different mean IOPs (5, 8, 10, 20, 30, 40, 50 mm Hg). Results. The outflow system, including TM, SC and CCs, was visualized in the micro-structural imaging. The IOP-transient induced pulsatile TM movement and SC deformation were detected and quantified by tissue-DOCT. The TM movement was depth-dependent and the largest movement was located in the area closest to SC endothelium (SCE). Both the pulsations of TM and SC were found to be synchronous with the IOP pulse wave. At 8 mm Hg IOP, the global TM movement was around 0.65μm during one IOP transient. As IOP elevated, a gradual attenuation of TM movement and SC deformation was observed. Conclusions. The observed pulsation of TM and SC induced by the pulsatile IOP transients was in good agreement with the predicated role of TM and SC acting as a biomechanical pump (pumping

  1. Interleukin-20 receptor expression in the trabecular meshwork and its implication in glaucoma.

    PubMed

    Keller, Kate E; Yang, Yong-Feng; Sun, Ying Ying; Sykes, Renee; Gaudette, Natalie Donna; Samples, John R; Acott, Ted S; Wirtz, Mary K

    2014-01-01

    To determine whether interleukin-20 receptors (IL-20R) are expressed in trabecular meshwork cells and the effect of a T104M mutation in IL-20R2 on downstream cellular functions. Evaluation of signal transducer and activator of transcription (STAT)3 phosphorylation and generic matrix metalloproteinase (MMP) activity in primary open angle glaucoma (POAG) dermal fibroblasts (pHDF) with the T104M IL-20R2 mutation were compared with normal human dermal fibroblasts (HDF). Expression of IL-20R1 and IL-20R2 in human trabecular meshwork (HTM) cells was determined by immunohistochemistry and western immunoblotting. A T104M mutation in IL20-R2 was identified in a large POAG family in which the GLC1C locus was originally mapped. pHDFs harboring this mutation had significantly increased phosphorylated STAT3 (pSTAT3) activity compared with normal HDFs. However, stimulation with either IL-19 or IL-20 for 15 min resulted in significantly decreased levels of pSTAT3 in pHDFs compared with controls. Generic MMP activity was significantly decreased in pHDFs compared with controls after stimulation with IL-20 for 24 h. Both IL-20R1 and IL-20R2 receptors were expressed in HTM cells by western immunoblot and immunofluorescence, and they appeared to be up-regulated in response to cytokine treatment. A T104M mutation in IL-20R2 significantly impacts the function of this receptor as shown by decreased pSTAT3 levels and generic MMP activity. Reduced MMP activity may affect the ability of glaucoma patients to alter outflow resistance in response to elevated intraocular pressure.

  2. Interleukin-20 Receptor Expression in the Trabecular Meshwork and Its Implication in Glaucoma

    PubMed Central

    Keller, Kate E.; Yang, Yong-Feng; Sun, Ying Ying; Sykes, Renee; Gaudette, Natalie Donna; Samples, John R.; Acott, Ted S.

    2014-01-01

    Abstract Purpose: To determine whether interleukin-20 receptors (IL-20R) are expressed in trabecular meshwork cells and the effect of a T104M mutation in IL-20R2 on downstream cellular functions. Methods: Evaluation of signal transducer and activator of transcription (STAT)3 phosphorylation and generic matrix metalloproteinase (MMP) activity in primary open angle glaucoma (POAG) dermal fibroblasts (pHDF) with the T104M IL-20R2 mutation were compared with normal human dermal fibroblasts (HDF). Expression of IL-20R1 and IL-20R2 in human trabecular meshwork (HTM) cells was determined by immunohistochemistry and western immunoblotting. Results: A T104M mutation in IL20-R2 was identified in a large POAG family in which the GLC1C locus was originally mapped. pHDFs harboring this mutation had significantly increased phosphorylated STAT3 (pSTAT3) activity compared with normal HDFs. However, stimulation with either IL-19 or IL-20 for 15 min resulted in significantly decreased levels of pSTAT3 in pHDFs compared with controls. Generic MMP activity was significantly decreased in pHDFs compared with controls after stimulation with IL-20 for 24 h. Both IL-20R1 and IL-20R2 receptors were expressed in HTM cells by western immunoblot and immunofluorescence, and they appeared to be up-regulated in response to cytokine treatment. Conclusions: A T104M mutation in IL-20R2 significantly impacts the function of this receptor as shown by decreased pSTAT3 levels and generic MMP activity. Reduced MMP activity may affect the ability of glaucoma patients to alter outflow resistance in response to elevated intraocular pressure. PMID:24455976

  3. [Effects of porcine pancreatic elastase-1 on elastin in human trabecular meshwork--immunohistochemical studies: Report 3. Primary open angle glaucoma].

    PubMed

    Hoya, T

    1994-06-01

    The aim of this study was to determine the location of elastin in the extracellular material and to estimate the influence of porcine pancreatic elastase-1 (PPE) on the elastin in human trabecular tissue. Trabecular tissues obtained from normal post-mortem eyes and trabeculectomy specimens of primary open angle glaucoma (POAG) were used in this study. The tissues were embedded in Lowicryl K4M and sectioned for electron microscopy. First, the sections were subjected to protein A-gold immunohistochemical staining to determine the location of elastin in the tissues. Second, the sections were exposed to PPE, before immunostaining, to evaluate the change of immunolocalization of the gold particles in the tissue. The results were as follows. In POAG specimens, gold particles indicating the presence of elastin were located in the area of fine fibrillar-like material in the subendothelial layers of Schlemm's canal in POAG specimens. In normal eyes, few gold particles were localized in the area. The density of gold particles in the area was reduced by PPE in POAG specimens. These results show that elastin is localized in the area of fine fibrillar-like material in the subendothelial layers of Schlemm's canal of POAG, and that PPE dissolves the elastin in the area.

  4. Intraoperative optical coherence tomography and ab interno trabecular meshwork surgery with the Trabectome

    PubMed Central

    Junker, Bernd; Jordan, Jens F; Framme, Carsten; Pielen, Amelie

    2017-01-01

    Importance This study is the first description of the use of the intraoperative optical coherence tomography (iOCT) for trabecular meshwork surgery with the Trabectome in a regular clinical setting. Background The aim of this study is to evaluate intraoperatively the immediate success of ab interno trabeculotomy with the Trabectome defined as a removal of the trabecular meshwork. Design This is a retrospective clinical study performed in the University Eye Hospital, Medical School Hannover. Participants A total of nine consecutive Caucasian patients suffering from primary open angle glaucoma, pigment dispersion glaucoma, or pseudoexfoliation glaucoma took part in the study. Methods All patients underwent ab interno trabeculotomy surgery with the Trabectome using a commercially available iOCT to visualize the anterior chamber angle (ACA) before and after the procedure. The visualization was done using a modified Swan-Jacobs lens (all nine patients) or without lens (view from above, five patients). Main outcome measures The main outcome of this study is the success of visualization of the ACA on iOCT, especially the postprocedural visualization of the wound gap after removal of the trabecular meshwork. Results Using the view from above, the ACA could be visualized before and after the procedure in only two of the five cases. Using the modified Swan-Jacobs lens, the ACA could be visualized before the procedure and the trabecular meshwork opening after the procedure in all nine patients. Conclusion The iOCT can be used to objectify the immediate success of the surgical procedure, ie, the removal of the trabecular meshwork, of ab interno trabeculotomy with the Trabectome. The procedure itself cannot be captured sufficiently via iOCT.

  5. Extracellular matrix in the trabecular meshwork: Intraocular pressure regulation and dysregulation in glaucoma

    PubMed Central

    Vranka, Janice A.; Kelley, Mary J.; Acott, Ted S.; Keller, Kate E.

    2014-01-01

    The trabecular meshwork (TM) is located in the anterior segment of the eye and is responsible for regulating the outflow of aqueous humor. Increased resistance to aqueous outflow causes intraocular pressure to increase, which is the primary risk factor for glaucoma. TM cells reside on a series of fenestrated beams and sheets through which the aqueous humor flows to exit the anterior chamber via Schlemm’s canal. The outer trabecular cells are phagocytic and are thought to function as a pre-filter. However, most of the outflow resistance is thought to be from the extracellular matrix (ECM) of the juxtacanalicular region, the deepest portion of the TM, and from the inner wall basement membrane of Schlemm’s canal. It is becoming increasingly evident that the extracellular milieu is important in maintaining the integrity of the TM. Not only have ultrastructural changes been observed in the ECM of the TM in glaucoma, and a significant number of mutations in ECM genes are known to be associated with glaucoma, but the stiffness of glaucomatous TM appears to be greater than that of normal tissue. Additionally, TGFβ2 has been found to be elevated in the aqueous humor of glaucoma patients and is assumed to be involved in ECM changes deep with the juxtacanalicular region of the TM. This review summarizes the current literature on trabecular ECM as well as the development and function of the TM. Animal models and organ culture models targeting specific ECM molecules to investigate the mechanisms of glaucoma are described. Finally, the growing number of mutations that have been identified in ECM genes and genes that modulate ECM in humans with glaucoma are documented. PMID:25819459

  6. The development of the trabecular meshwork and its abnormality in primary infantile glaucoma.

    PubMed Central

    Anderson, D R

    1981-01-01

    Tissue from ten eyes with infantile glaucoma and from 40 normal eyes of fetuses and infants without glaucoma were examined by light and electron microscopy. In normal development, the corneoscleral coat grows faster than the uveal tract during the last trimester, leading to a posterior migration of the ciliary body attachment from Schwalbe's line (5th month) to the scleral spur (9th month), and then to a location behind the scleral spur (postnatally). In infantile glaucoma, the insertion of the anterior ciliary body and iris overlaps the trabecular meshwork, similar to the late fetal position. The trabecular sheets are perforated, and there is no membrane over the surface of the trabecular meshwork. The trabecular beams are thicker than in normal infant eyes. There is both histologic and clinical evidence of traction on the iris root exerted by the thickened trabecular beams. These findings suggest that in congenital glaucoma the thickened beams had prevented the normal posterior migration of the ciliary body and iris root. This traction may compact the thickened trabecular beams, obstructing aqueous humor outflow. Release of the traction by an incision (goniotomy or trabeculotomy) of the thickened meshwork may relieve the obstruction. Of uncertain pathological significance is that there are no vacuoles in the endothelium of Schlemm's canal and there is a broad layer of collagen and amorphous material in the juxtacanalicular connective tissue. The ciliary processes are elongated inward, as if they were pulled by zonular traction (perhaps created by an enlarging diameter of the limbus with a fixed lens diameter). Images FIGURE 7 FIGURE 8 FIGURE 10 FIGURE 11 FIGURE 20 A FIGURE 20 B FIGURE 1 FIGURE 3 FIGURE 4 A FIGURE 4 B FIGURE 5 A FIGURE 5 B FIGURE 6 FIGURE 9 FIGURE 12 FIGURE 13 FIGURE 14 FIGURE 15 FIGURE 16 FIGURE 17 FIGURE 18 FIGURE 19 PMID:7342408

  7. Confocal microscopic examination of trabecular meshwork removed during ab externo trabeculectomy

    PubMed Central

    Hamard, P; Valtot, F; Sourdille, P; Bourles-Dagonet, F; Baudouin, C

    2002-01-01

    Aims: The aim of the ab externo trabeculectomy (AET) is to remove the external portion of the trabecular meshwork (ETM) responsible for the main aqueous outflow resistance in glaucoma patients, with no opening of the anterior chamber. ETM characteristics were evaluated with a confocal microscope. Methods: A prospective comparative observational case series was performed in 60 consecutive medically treated patients with primary open angle glaucoma and eight postmortem normal donors’ eyes that underwent AET. Once deroofing the Schlemm’ s canal (SC), a deeper dissection led to removal of a coherent membrane (ETM) which allowed satisfactory aqueous egress through the remaining intact internal trabecular meshwork (TM) layers. After fixation with acetone and immunostaining with anti-vimentin antibody, ETM were analysed with a confocal microscope. Results: Glaucomatous ETM (mean thickness: 29.5 (7.6) μm) were characterised by a severe paucicellularity compared with the controls (respectively 37.3 (9.7) cells/area and 167.5 (24.9) cells/area, p<10−4). ETM analysis showed involvement of both cribriform and corneoscleral layers. ETM cell density was significantly decreased in case of preoperative fluorometholone instillation. Conclusion: Paucicellularity of glaucomatous TM is confirmed by this original technique. Structural characteristics of the ETM, whose removal allows satisfactory aqueous egress, suggest that aqueous outflow resistance not only involves inner wall of SC and juxtacanalicular meshwork but also corneoscleral trabecular layers. PMID:12185136

  8. Numerical simulations of ethacrynic acid transport from precorneal region to trabecular meshwork.

    PubMed

    Lin, Cheng-Wen; Yuan, Fan

    2010-03-01

    Topical application of drugs for treatment of intraocular diseases is often limited by inadequate transport and induced toxicity in corneal tissues. To improve the drug delivery, a mathematical model was developed to numerically simulate the transport process of ethacrynic acid (ECA), a potential drug for glaucoma treatment, in the anterior segment of a typical human eye. The model considered diffusion of ECA in all tissues and the aqueous humor (AH) as well as convection of ECA in the AH. The simulation results showed that ECA concentration in the eye depended on the rate of AH production, the half-life of ECA in the precorneal tear film, and the transport parameters in the model. In addition, the main pathway for ECA clearance from the eye was the trabecular meshwork (TM) and the rate of clearance was approximately proportional to the AH production rate. The model predicted that the most effective approach to improving topical drug delivery was to prolong its half-life in the precorneal tear film. These simulation results and model prediction, which could be verified experimentally, might be useful for improving delivery of ECA and other therapeutic agents to the TM as well as other tissues in the anterior segment of the eye.

  9. Cyp1b1 Mediates Periostin Regulation of Trabecular Meshwork Development by Suppression of Oxidative Stress

    PubMed Central

    Zhao, Yun; Wang, Shoujian; Sorenson, Christine M.; Teixeira, Leandro; Dubielzig, Richard R.; Peters, Donna M.; Conway, Simon J.; Jefcoate, Colin R.

    2013-01-01

    Mutation in CYP1B1 has been reported for patients with congenital glaucoma. However, the underlying mechanisms remain unknown. Here we show increased diurnal intraocular pressure (IOP) in Cyp1b1-deficient (Cyp1b1−/−) mice. Cyp1b1−/− mice presented ultrastructural irregular collagen distribution in their trabecular meshwork (TM) tissue along with increased oxidative stress and decreased levels of periostin (Postn). Increased levels of oxidative stress and decreased levels of Postn were also detected in human glaucomatous TM tissues. Furthermore, Postn-deficient mice exhibited TM tissue ultrastructural abnormalities similar to those of Cyp1b1−/− mice. Administration of the antioxidant N-acetylcysteine (NAC) restored structural abnormality of TM tissue in Cyp1b1−/− mice. In addition, TM cells prepared from Cyp1b1−/− mice exhibited increased oxidative stress, altered adhesion, and decreased levels of Postn. These aberrant cellular responses were reversed in the presence of NAC or by restoration of Cyp1b1 expression. Cyp1b1 knockdown or inhibition of CYP1B1 activity in Cyp1b1+/+ TM cells resulted in a Cyp1b1−/− phenotype. Thus, metabolic activity of CYP1B1 contributes to oxidative homeostasis and ultrastructural organization and function of TM tissue through modulation of Postn expression. PMID:23979599

  10. Translimbal laser photocoagulation to the trabecular meshwork as a model of glaucoma in rats.

    PubMed

    Levkovitch-Verbin, Hana; Quigley, Harry A; Martin, Keith R G; Valenta, Danielle; Baumrind, Lisa A; Pease, Mary Ellen

    2002-02-01

    To develop and characterize a model of pressure-induced optic neuropathy in rats. Experimental glaucoma was induced unilaterally in 174 Wistar rats, using a diode laser with wavelength of 532 nm aimed at the trabecular meshwork and episcleral veins (combination treatment group) or only at the trabecular meshwork (trabecular group) through the external limbus. Intraocular pressure (IOP) was measured by a tonometer in rats under ketamine-xylazine anesthesia. Possible retinal vascular compromise was evaluated by repeated fundus examinations and by histology. The degree of retinal ganglion cell (RGC) loss was assessed by a masked, semiautomated counting of optic nerve axons. Effects of laser treatment on anterior ocular structures and retina were judged by light microscopy. After the laser treatment, IOP was increased in all eyes to higher than the normal mean IOP of 19.4 +/- 2.1 mm Hg (270 eyes). Peak IOP was 49.0 +/- 6.1 mm Hg (n = 108) in the combination group that was treated by a laser setting of 0.7 seconds and 0.4 W and 34.0 +/- 5.7 mm Hg (n = 46) in the trabecular group. Mean IOP after 6 weeks was 25.5 +/- 2.9 mm Hg in glaucomatous eyes in the combination group compared with 22.0 +/- 1.8 mm Hg in the trabecular group. IOP in the glaucomatous eyes was typically higher than in the control eyes for at least 3 weeks. In the combination group, RGC loss was 16.1% +/- 14.4% at 1 week (n = 8, P = 0.01), 59.7% +/- 25.7% at 6 weeks (n = 88, P < 0.001), and 70.9% +/- 23.6% at 9 weeks (n = 12, P < 0.001). The trabecular group had mean axonal loss of 19.1% +/- 14.0% at 3 weeks (n = 9, P = 0.004) and 24.3% +/- 20.2% at 6 weeks (n = 25, P < 0.001), increasing to 48.4% +/- 32.8% at 9 weeks (n = 12, P < 0.001). Laser treatment led to closure of intertrabecular spaces and the major outflow channel. The retina and choroid were normal by ophthalmoscopy at all times after treatment. Light microscopic examination showed only loss of RGCs and their nerve fibers. Increased IOP caused

  11. Protein expression in a transformed trabecular meshwork cell line: proteome analysis.

    PubMed

    Steely, H Thomas; Dillow, Glen W; Bian, Liangqian; Grundstad, Jason; Braun, Terry A; Casavant, Thomas L; McCartney, Mitchell D; Clark, Abbot F

    2006-04-18

    Characterization of the human trabecular meshwork (TM) proteome is hindered by the small mass of intact tissue and the slow growth of cultured cell strains. We have previously characterized a transformed TM cell strain (GTM3) that demonstrates many of the same protein expression and cell signaling systems of nontransformed cell strains. The aim of this study was to initiate a proteomic survey of GTM3 cells as the initial step toward characterization of the complete human TM proteome. GTM3 cells were cultured to confluence, harvested and solubilized in urea/Nonidet. The protein extract (600 mug) was focused in immobilized isoelectric focusing (IEF) strips, separated by 10% SDS PAGE, and visualized with colloidal Coomassie Blue. Spots of interest were excised, destained, and the contained proteins subjected to in-gel reduction, derivatization, and tryptic digestion. Tryptic peptides were extracted and analyzed by electrospray LC/MS/MS. Protein identification was made using the TurboSequest search algorithm and a recent version of the nonredundant human protein database downloaded from the National Center for Biotechnology Information (NCBI). Eighty-seven (87) primary proteins and 93 variants of these proteins were identified. A website was created (TM proteome) that combines data such as graphic spot location within the gel, peptide sequence, apparent and calculated pI, apparent and calculated mass, percentage of coverage, and protein informatic website links. Proteomic analysis of a transformed human TM cell line has been initiated combining preparative two-dimensional PAGE separation, LC/MS/MS analysis of major proteins, and bioinformatic cataloging of the data. Further investigation of data from the transformed cell strain will be used in a comparative fashion for spot identification of analytical proteomic gels of human TM tissue and cultured normal cells. These initial data will form the base from which the characterization of protein expression in the normal

  12. Inhibition of Hyaluronan Synthesis Reduces Versican and Fibronectin Levels in Trabecular Meshwork Cells

    PubMed Central

    Keller, Kate E.; Sun, Ying Ying; Vranka, Janice A.; Hayashi, Lauren; Acott, Ted S.

    2012-01-01

    Hyaluronan (HA) is a major component of the extracellular matrix (ECM) and is synthesized by three HA synthases (HAS). Similarities between the HAS2 knockout mouse and the hdf mutant mouse, which has a mutation in the versican gene, suggest that HA and versican expression may be linked. In this study, the relationship between HA synthesis and levels of versican, fibronectin and several other ECM components in trabecular meshwork cells from the anterior segment of the eye was investigated. HA synthesis was inhibited using 4-methylumbelliferone (4MU), or reduced by RNAi silencing of each individual HAS gene. Quantitative RT-PCR and immunoblotting demonstrated a reduction in mRNA and protein levels of versican and fibronectin. Hyaluronidase treatment also reduced versican and fibronectin levels. These effects could not be reversed by addition of excess glucose or glucosamine or exogenous HA to the culture medium. CD44, tenascin C and fibrillin-1 mRNA levels were reduced by 4MU treatment, but SPARC and CSPG6 mRNA levels were unaffected. Immunostaining of trabecular meshwork tissue after exposure to 4MU showed an altered localization pattern of HA-binding protein, versican and fibronectin. Reduction of versican by RNAi silencing did not affect HA concentration as assessed by ELISA. Together, these data imply that HA concentration affects synthesis of certain ECM components. Since precise regulation of the trabecular meshwork ECM composition and organization is required to maintain the aqueous humor outflow resistance and intraocular pressure homeostasis in the eye, coordinated coupling of HA levels and several of its ECM binding partners should facilitate this process. PMID:23139787

  13. The Effects of Tenascin C Knockdown on Trabecular Meshwork Outflow Resistance

    PubMed Central

    Keller, Kate E.; Vranka, Janice A.; Haddadin, Ramez I.; Kang, Min-Hyung; Oh, Dong-Jin; Rhee, Douglas J.; Yang, Yong-feng; Sun, Ying Ying; Kelley, Mary J.; Acott, Ted S.

    2013-01-01

    Purpose. Tenascin C (TNC) is a matricellular glycoprotein whose expression in adult tissue is indicative of tissue remodeling. The purpose of the current study was to determine the localization of TNC in trabecular meshwork (TM) tissue and to analyze the effects of TNC on intraocular pressure (IOP). Methods. Human TM frontal sections were immunostained with anti-TNC and imaged by confocal microscopy. TNC mRNA and protein levels were quantitated in anterior segments perfused at physiological and elevated pressure. Short, hairpin RNA (shRNA) silencing lentivirus targeting full-length TNC (shTNC) was applied to anterior segment perfusion organ cultures. The IOPs and central corneal thickness (CCT) of wild-type, TNC−/−, and tenascin X (TNX−/−) knockout mice were measured. Results. TNC was distributed in the juxtacanalicular (JCT) region of adult human TM, predominantly in the basement membrane underlying the inner wall of Schlemm's canal. Application of shTNC lentivirus to human and porcine anterior segments in perfusion culture did not significantly affect outflow rate. Although TNC was upregulated in response to pressure, there was no difference in outflow rate when shTNC-silenced anterior segments were subjected to elevated pressure. Furthermore, IOPs and CCTs were not significantly different between TNC−/− or TNX−/− and wild-type mice. Conclusions. TNC does not appear to contribute directly to outflow resistance. However, TNC immunolocalization in the JCT of adult human eyes suggests that certain areas of the TM are being continuously remodeled with or without an IOP increase. PMID:23882691

  14. Regulation of myosin light chain phosphorylation in the trabecular meshwork: role in aqueous humour outflow facility.

    PubMed

    Rao, P Vasantha; Deng, Peifeng; Sasaki, Yasuharu; Epstein, David L

    2005-02-01

    Cellular contraction and relaxation and integrity of the actin cytoskeleton in trabecular meshwork (TM) tissue have been thought to influence aqueous humour outflow. However, the cellular pathways that regulate these events in TM cells are not well understood. In this study, we investigated physiological agonist-mediated regulation of myosin light chain (MLC) phosphorylation in the TM, and correlated such effects with alterations in aqueous outflow facility, since MLC phosphorylation is a critical biochemical determinant of cellular contraction in TM cells. Treatment of serum starved human TM cells with endothelin-1 (0.1 microM), thromboxane A2 mimetic U-46619 (1.0 microM), or angiotensin II (1 microM), all of which are agonists of G-protein coupled receptors, triggered activation of MLC phosphorylation, as determined by urea/glycerol-based Western blot analysis. Agonist-stimulated increase in MLC phosphorylation was associated with activation of Rho GTPase in TM cells, as determined in pull-down assays. In contrast, treatment of human TM cells with a novel Rho-kinase inhibitor H-1152 (0.1-2 microM), in the presence of serum reduced basal MLC phosphorylation. H-1152 also increased aqueous outflow facility significantly in a dose-dependent fashion, in perfusion studies with cadaver porcine eyes. This effect of H-1152 on outflow facility was associated with decreased MLC phosphorylation in TM tissue of drug-perfused eyes. Collectively, this study identifies potential physiological regulators of MLC phosphorylation in human TM cells and demonstrates the significance of Rho/Rho-kinase pathway-mediated MLC phosphorylation in modulation of aqueous outflow facility through TM.

  15. Aberrant Collagen Composition of the Trabecular Meshwork Results in Reduced Aqueous Humor Drainage and Elevated IOP in MMP-9 Null Mice

    PubMed Central

    De Groef, Lies; Andries, Lien; Siwakoti, Anuja; Geeraerts, Emiel; Bollaerts, Ilse; Noterdaeme, Lut; Etienne, Isabelle; Papageorgiou, Anna-Pia; Stalmans, Ingeborg; Billen, Johan; West-Mays, Judith A.; Moons, Lieve

    2016-01-01

    Purpose Homeostatic turnover of the trabecular meshwork extracellular matrix (ECM) is essential to regulate aqueous humor outflow and to maintain intraocular pressure homeostasis. In this study, we evaluated aqueous humor turnover, intraocular pressure, and trabecular meshwork organization in MMP-9 null mice. Methods Intraocular pressure and aqueous humor turnover were measured in MMP-9 null versus wild-type mice. Morphology of the anterior segment of the eye, with special attention to the structural organization of the trabecular meshwork, was investigated by means of optical coherence tomography, light microscopy, and transmission electron microscopy. Furthermore, using quantitative real-time polymerase chain reaction and immunostainings, we evaluated the ECM composition of the trabecular meshwork. Finally, the integrity and function of the retina and optic nerve were assessed, via optical coherence tomography, histologic techniques, and optomotor testing. Results MMP-9 null mice displayed early-onset ocular hypertension and reduced aqueous humor turnover. While transmission electron microscopic analysis did not reveal any abnormalities in the cellular organization of the trabecular meshwork, detailed investigation of collagen expression indicated that there is an aberrant trabecular meshwork ECM composition in MMP-9 null mice. Notably, at the age of 13 months, no glaucomatous neurodegeneration was seen in MMP-9 null mice. Conclusions Our observations corroborate MMP-9 as an important remodeler of the collagenous composition of the trabecular meshwork and provide evidence for a causal link between MMP-9 deficiency, trabecular meshwork ultrastructure, and ocular hypertension. PMID:27820954

  16. Role of Aquaporin-1 in Trabecular Meshwork Cell Homeostasis during Mechanical Strain

    PubMed Central

    Baetz, NW; Hoffman, EA; Yool, AJ; Stamer, WD

    2009-01-01

    Aquaporin-1 (AQP1) channels are expressed by trabecular meshwork (TM) and Schlemm’s canal cells of the conventional outflow pathway where fluid movement is predominantly paracellular, suggesting a non-canonical role for AQP1. We hypothesized that AQP1 functions to protect TM cells during periods of mechanical strain. To test this idea, primary cultures of confluent human TM cells on Bioflex membranes were exposed to static and cyclic stretch for 8 and 24 hours using the Flexcell system. AQP1 expression in TM cells was assessed by SDS-PAGE and western blot using anti-AQP1 IgGs. AQP1 protein bands were analyzed using densitometry and normalized to β-actin expression. Cell damage was monitored by measuring lactate dehydrogenase (LDH) and histone deacetylase appearance in conditioned media. Recombinant expression of AQP1 in TM cell cultures was facilitated by transduction with adenovirus. Results show that AQP1 expression significantly increased by 2 fold with 10% static stretch and 3.5 fold with 20% static stretch at 8 h (n=4, p<0.05) and 24 h (n=6, p<0.05). While histone deacetylase levels were unaffected by treatments, release of LDH from TM cells was the most profound at the 20% static stretch level (n=4 p<0.05). Significantly, cells were refractory to the 20% static stretch level when AQP1 expression was increased to near tissue levels. Analysis of LDH release with respect to AQP1 expression revealed an inverse linear relationship (r2 = 0.7780). Taken together, AQP1 in human TM appears to serve a protective role by facilitating improved cell viability during conditions of mechanical strain. PMID:19268465

  17. Galectin-8 Promotes Cytoskeletal Rearrangement in Trabecular Meshwork Cells through Activation of Rho Signaling

    PubMed Central

    Cao, Zhiyi; Gyawali, Smita; Gong, Haiyan; Soza, Andrea; González, Alfonso; Panjwani, Noorjahan

    2012-01-01

    Purpose The trabecular meshwork (TM) cell-matrix interactions and factors that influence Rho signaling in TM cells are thought to play a pivotal role in the regulation of aqueous outflow. The current study was designed to evaluate the role of a carbohydrate-binding protein, galectin-8 (Gal8), in TM cell adhesion and Rho signaling. Methods Normal human TM cells were assayed for Gal8 expression by immunohistochemistry and Western blot analysis. To assess the role of Gal8 in TM cell adhesion and Rho signaling, the cell adhesion and spreading assays were performed on Gal8-coated culture plates in the presence and the absence of anti-β1 integrin antibody and Rho and Rho-kinase inhibitors. In addition, the effect of Gal8-mediated cell-matrix interactions on TM cell cytoskeleton arrangement and myosin light chain 2 (MLC2) phosphorylation was examined. Principal Findings We demonstrate here that Gal8 is expressed in the TM and a function-blocking anti-β1 integrin antibody inhibits the adhesion and spreading of TM cells to Gal8-coated wells. Cell spreading on Gal8 substratum was associated with the accumulation of phosphorylated myosin light chain and the formation of stress fibers that was inhibited by the Rho inhibitor, C3 transferase, as well as by the Rho-kinase inhibitor, Y27632. Conclusions/Significance The above findings present a novel function for Gal8 in activating Rho signaling in TM cells. This function may allow Gal8 to participate in the regulation of aqueous outflow. PMID:22973445

  18. Experimental erbium: YAG laser photoablation of trabecular meshwork in rabbits: an in-vivo study.

    PubMed

    Dietlein, T S; Jacobi, P C; Schröder, R; Krieglstein, G K

    1997-05-01

    Photoablative laser trabecular surgery has been proposed as an outflow-enhancing treatment for open-angle glaucoma. The aim of the study was to investigate the time course of repair response following low-thermal Erbium: YAG laser trabecular ablation. In 20 anaesthetized rabbits gonioscopically controlled ab-interno photoablation of the ligamenta pectinata and underlying trabecular meshwork (TM) was performed with a single-pulsed (200 microseconds) Erbium: YAG (2.94 microns) laser. The right eye received 12-15 single laser pulses (2 mJ) delivered through an articulated zirconium fluoride fiberoptic and a 200 microns (core diameter) quartz fiber tip, the left unoperated eye served as control. At time intervals of 30 minutes, 2, 10, 30, and 60 days after laser treatment, eyes were processed for light- and scanning electron microscopy. The applied energy density of 6-4 J cm-2 resulted in visible dissection of the ligamenta pectinata and reproducible microperforations of the TM exposing scleral tissue accompanied by blood reflux from the aqueous plexus. The initial ablation zones measured 154 +/- 36 microns in depth and 45 +/- 6 microns in width. Collateral thermal damage zones were 22 +/- 8 microns. At two days post-operative, ablation craters were still blood- and fibrin-filled. The inner surface of the craters were covered with granulocytes. No cellular infiltration of the collateral thermal damage zone was observed. At 10 days post-operative, progressive fibroblastic proliferation was observed, resulting in dense scar tissue formation with anterior synechiae, proliferating capillaries and loss of intertrabecular spaces inside the range of former laser treatment at 60 days post-operative. Trabecular microperforations were closed 60 days after laser treatment in all rabbits. IOP in treated and contralateral eyes did not significantly change its level during whole period of observation. Low-thermal infrared laser energy with minimal thermal damage to collateral

  19. Ascorbic acid modulates collagen type I gene expression by cells from an eye tissue--trabecular meshwork.

    PubMed

    Sawaguchi, S; Yue, B Y; Chang, I L; Wong, F; Higginbotham, E J

    1992-09-01

    The trabecular meshwork, a specialized tissue in the anterior chamber of the eye, plays a major role in the regulation of aqueous humor outflow. We studied the effects of ascorbic acid, a significant component in the aqueous humor, on gene expression of type I collagen in cultures of bovine trabecular meshwork cells. These cells were plated for 6 days, exposed to ascorbic acid in concentrations of 100, 250 and 500 micrograms/ml for 3 days and labeled with (3H)proline for the last 24 hrs. Cultures that did not receive ascorbic acid served as controls. Bacterial collagenase assays showed enhanced incorporation of (3H)proline into collagenous proteins in cultures treated with 100 and 250 micrograms/ml of ascorbic acid. Gel electrophoresis and fluorography revealed that ascorbic acid caused a 2.6- to 4.9-fold increase in production of alpha 1 (I) and alpha 2(I) collagen chains by trabecular meshwork cells. Such an increase was found, using a cDNA probe specific for pro alpha 1(I) chains, to be accompanied by an increase in steady-state mRNA levels. Similar findings were also yielded from in situ hybridization experiments. These results, coupled with previously demonstrated ascorbate-induced effects on glycosaminoglycan, fibronectin and laminin synthesis, suggest that ascorbic acid is a key mediator of the extracellular matrix production by trabecular meshwork cells. Fluctuations in its concentration may lead to alterations in the makeup and assembly of matrices underlying the cells.

  20. Effect of persistent high intraocular pressure on microstructure and hydraulic permeability of trabecular meshwork

    NASA Astrophysics Data System (ADS)

    Mei, Xi; Ren, Lin; Xu, Qiang; Zheng, Wei; Liu, Zhi-Cheng

    2015-05-01

    As the aqueous humor leaves the eye, it first passes through the trabecular meshwork (TM). Increased flow resistance in this region causes elevation of intraocular pressure (IOP), which leads to the occurrence of glaucoma. To quantitatively evaluate the effect of high IOP on the configuration and hydraulic permeability of the TM, second harmonic generation (SHG) microscopy was used to image the microstructures of the TM and adjacent tissues in control (normal) and high IOP conditions. Enucleated rabbit eyes were perfused at a pressure of 60 mmHg to achieve the high IOP. Through the anterior chamber of the eye, in situ images were obtained from different depths beneath the surface of the TM. Porosity and specific surface area of the TM in control and high IOP conditions were then calculated to estimate the effect of the high pressure on the permeability of tissue in different depths. We further photographed the histological sections of the TM and compared the in situ images. The following results were obtained in the control condition, where the region of depth was less than 55 μm with crossed branching beams and large pores in the superficial TM. The deeper meshwork is a silk-like tissue with abundant fluorescence separating the small size of pores. The total thickness of pathway tissues composed of TM and juxtacanalicular (JCT) is more than 100 μm. After putting a high pressure on the inner wall of the eye, the TM region progressively collapses and decreases to be less than 40 μm. Fibers of the TM became dense, and the porosity at 34 μm in the high IOP condition is comparable to that at 105 μm in the control condition. As a consequent result, the permeability of the superficial TM decreases rapidly from 120 μm2 to 49.6 μm2 and that of deeper TM decreases from 1.66 μm2 to 0.57 μm2. Heterogeneity reflected by descent in permeability reduces from 12.4 μm of the control condition to 3.74 μm of the high IOP condition. The persistently high IOP makes the TM

  1. Effect of Nitric Oxide on the Expression of Matrix Metalloproteinase and Its Association with Migration of Cultured Trabecular Meshwork Cells

    PubMed Central

    2016-01-01

    Purpose To determine the effect of exogenous nitric oxide (NO) on the migration of trabecular meshwork (TM) cells and its association with expression of matrix metalloproteinases (MMPs). Methods Primary human TM cells treated with 1 or 10 µM S-nitroso-N-acetyl-penicillamine (SNAP) and examined for changes in adherence. TM cells were seeded onto transwell culture inserts, and changes in their migratory activity were quantified. Reverse transcription polymerase chain reaction was performed to determine the relative changes in mRNA expression of MMPs and tissue inhibitor of metalloproteinases (TIMPs). Results Treatment with SNAP did not significantly suppress TM cell adhesion or migration (p > 0.05). Treatment of TM cells with 10 µM SNAP decreased expression of MMP-2 and increased expression of membrane type MMP-1 and TIMP-2. Treatment with interleukin-1α triggered MMP-3 expression but did not exert significant effects on MMP-3 activation in response to SNAP. Conclusions These data suggest that NO revealed no significant effect on the migration of TM cells because NO decreased MMP-2 and increased TIMP-2 expression. Although expression of certain MMPs and TIMPs change in response to NO donors, NO may modulate trabecular outflow by changing the cellular production of extracellular matrix without having a significant effect on the migration of TM cells. PMID:26865806

  2. Elevated Intraocular Pressure Induces Rho GTPase Mediated Contractile Signaling in the Trabecular Meshwork

    PubMed Central

    Pattabiraman, Padmanabhan P; Inoue, Toshihiro; Rao, P. Vasantha

    2015-01-01

    Rho GTPase regulated contractile signaling in the trabecular meshwork (TM) has been shown to modulate aqueous humor (AH) outflow and intraocular pressure (IOP). To explore whether elevated IOP, a major risk factor for primary open angle glaucoma (POAG) influences Rho GTPase signaling in the TM, we recorded AH outflow in enucleated contralateral porcine eyes perfused for 4–5 hours at either 15 mm or 50 mm Hg pressure. After perfusion, TM tissue extracted from perfused eyes was evaluated for the activation status of Rho GTPase, myosin light chain (MLC), myosin phosphatase target substrate 1 (MYPT1), myristoylated alanine-rich C-kinase substrate (MARCKS) and paxillin. Eyes perfused at 50 mm Hg exhibited a significant decrease in AH outflow facility compared with those perfused at 15 mm Hg. Additionally, TM tissue from eyes perfused at 50 mm Hg revealed significantly increased levels of activated RhoA and phosphorylated MLC, MYPT1, MARCKS and paxillin compared to TM tissue derived from eyes perfused at 15 mm Hg. Taken together, these observations indicate that elevated IOP-induced activation of Rho GTPase-dependent contractile signaling in the TM is associated with increased resistance to AH outflow through the trabecular pathway, and demonstrate the sensitivity of Rho GTPase signaling to mechanical force in the AH outflow pathway. PMID:25956210

  3. Label-free imaging of trabecular meshwork cells using Coherent Anti-Stokes Raman Scattering (CARS) microscopy

    PubMed Central

    Lei, Tim C.; Ammar, David A.; Masihzadeh, Omid; Gibson, Emily A.

    2011-01-01

    Purpose To image the human trabecular meshwork (TM) using a non-invasive, non-destructive technique without the application of exogenous label. Methods Flat-mounted TM samples from a human cadaver eye were imaged using two nonlinear optical techniques: coherent anti-Stokes Raman scattering (CARS) and two-photon autofluorescence (TPAF). In TPAF, two optical photons are simultaneously absorbed and excite molecules in the sample that then emit a higher energy photon. The signal is predominately from collagen and elastin. The CARS technique uses two laser frequencies to specifically excite carbon-hydrogen bonds, allowing the visualization of lipid-rich cell membranes. Multiple images were taken along an axis perpendicular to the surface of the TM for subsequent analysis. Results Analysis of multiple TPAF images of the TM reveals the characteristic overlapping bundles of collagen of various sizes. Simultaneous CARS imaging revealed elliptical structures of ~7×10 µm in diameter populating the meshwork which were consistent with TM cells. Irregularly shaped objects of ~4 µm diameter appeared in both the TPAF and CARS channels, and are consistent with melanin granules. Conclusions CARS techniques were successful in imaging live TM cells in freshly isolated human TM samples. Similar images have been obtained with standard histological techniques, however the method described here has the advantage of being performed on unprocessed, unfixed tissue free from the potential distortions of the fine tissue morphology that can occur due to infusion of fixatives and treatment with alcohols. CARS imaging of the TM represents a new avenue for exploring details of aqueous outflow and TM cell physiology. PMID:22025898

  4. Freeze-thaw decellularization of the trabecular meshwork in an ex vivo eye perfusion model

    PubMed Central

    Dang, Yalong; Waxman, Susannah; Wang, Chao; Jensen, Adrianna; Loewen, Ralitsa T.; Bilonick, Richard A.

    2017-01-01

    Objective The trabecular meshwork (TM) is the primary substrate of outflow resistance in glaucomatous eyes. Repopulating diseased TM with fresh, functional TM cells might be a viable therapeutic approach. Decellularized TM scaffolds have previously been produced by ablating cells with suicide gene therapy or saponin, which risks incomplete cell removal or dissolution of the extracellular matrix, respectively. We hypothesized that improved trabecular meshwork cell ablation would result from freeze-thaw cycles compared to chemical treatment. Materials and Methods We obtained 24 porcine eyes from a local abattoir, dissected and mounted them in an anterior segment perfusion within two hours of sacrifice. Intraocular pressure (IOP) was recorded continuously by a pressure transducer system. After 72 h of IOP stabilization, eight eyes were assigned to freeze-thaw (F) ablation (−80 °C × 2), to 0.02% saponin (S) treatment, or the control group (C), respectively. The TM was transduced with an eGFP expressing feline immunodeficiency viral (FIV) vector and tracked via fluorescent microscopy to confirm ablation. Following treatment, the eyes were perfused with standard tissue culture media for 180 h. TM histology was assessed by hematoxylin and eosin staining. TM viability was evaluated by a calcein AM/propidium iodide (PI) assay. The TM extracellular matrix was stained with Picro Sirius Red. We measured IOP and modeled it with a linear mixed effects model using a B-spline function of time with five degrees of freedom. Results F and S experienced a similar IOP reduction of 30% from baseline (P = 0.64). IOP reduction of about 30% occurred in F within 24 h and in S within 48 h. Live visualization of eGFP demonstrated that F conferred a complete ablation of all TM cells and only a partial ablation in S. Histological analysis and Picro Sirius staining confirmed that no TM cells survived in F while the extracellular matrix remained. The viability assay showed very low

  5. Crosstalk Between Transforming Growth Factor Beta-2 and Toll-Like Receptor 4 in the Trabecular Meshwork

    PubMed Central

    Hernandez, Humberto; Medina-Ortiz, Wanda E.; Luan, Tomi; Clark, Abbot F.; McDowell, Colleen M.

    2017-01-01

    Purpose The trabecular meshwork (TM) is involved in the outflow of aqueous humor and intraocular pressure (IOP) regulation. Regulation of the extracellular matrix (ECM) by TGFβ2 signaling pathways in the TM has been extensively studied. Recent evidence has implicated toll-like receptor 4 (TLR4) in the regulation of ECM and fibrogenesis in liver, kidney, lung, and skin. Here, we investigated the role of TGFβ2–TLR4 signaling crosstalk in the regulation of the ECM in the TM and ocular hypertension. Methods Cross sections of human donor eyes, primary human TM cells in culture, and dissected mouse TM rings were used to determine Tlr4 expression in the TM. Trabecular meshwork cells in culture were treated with TGFβ2 (5 ng/mL), TLR4 inhibitor (TAK-242, 15 μM), and a TLR4 ligand (cellular fibronectin isoform [cFN]-EDA). A/J (n = 13), AKR/J (n = 7), BALBc/J (n = 8), C3H/HeJ (n = 20), and C3H/HeOuJ (n = 10) mice were injected intravitreally with adenovirus 5 (Ad5).hTGFβ2c226s/c228s in one eye, with the uninjected contralateral eye serving as a control. Conscious IOP measurements were taken using a TonoLab rebound tonometer. Results Toll-like receptor 4 is expressed in the human and mouse TM. Inhibition of TLR4 signaling in the presence of TGFβ2 decreases fibronectin expression. Activation of TLR4 by cFN-EDA in the presence of TGFβ2 further increases fibronectin, laminin, and collagen-1 expression, and TLR4 signaling inhibition blocks this effect. Ad5.hTGFβ2c226s/c228s induces ocular hypertension in wild-type mice but has no effect in Tlr4 mutant (C3H/HeJ) mice. Conclusions These studies identify TGFβ2–TLR4 crosstalk as a novel pathway involved in ECM regulation in the TM and ocular hypertension. These data further explain the complex mechanisms involved in the development of glaucomatous TM damage. PMID:28346614

  6. Mathematical Modeling of Outflow Facility Increase With Trabecular Meshwork Bypass and Schlemm Canal Dilation.

    PubMed

    Yuan, Fan; Schieber, Andrew T; Camras, Lucinda J; Harasymowycz, Paul J; Herndon, Leon W; Allingham, R Rand

    2016-04-01

    To mathematically model the conventional aqueous humor outflow system with trabecular meshwork (TM) bypass and Schlemm canal (SC) dilation. The SC was modeled as a rectangular channel with the TM modeled as a permeable membrane. The collector channels (CCs) were modeled as fluid sinks distributed along the outer wall of SC. Two different implants were investigated in this study. The Hydrus Microstent (scaffold) was modeled with a TM bypass and a dilated region in SC that was 7 or 15 mm long and approximately 5-fold larger than the normal height of SC (h0). The iStent trabecular microbypass was modeled with a similar structure except that the dilated region in SC was 1 mm long and 25% larger than h0. Creation of a TM bypass structure would increase the pressure in the surrounding regions inside the SC and make it close to the intraocular pressure. SC dilation would increase the pressure more uniformly in the dilated region. The pressure increase led to higher flow rates in SC and CCs, and subsequently increased outflow facility (C). If CCs were uniformly distributed, the increase in C was the smallest after implantation of 1 microbypass, compared with that after implantation of 2 microbypasses or 1 scaffold. If CCs were nonuniformly distributed, the magnitude of increase in C was sensitive to the location of implant, and the sensitivity was higher for the microbypass than the scaffold. The study showed that creation of TM bypass and SC dilation significantly increased outflow facility, and the amount of increase correlated with the length of dilated regions in SC.

  7. Visibility of trabecular meshwork by standard and polarization-sensitive optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Yasuno, Yoshiaki; Yamanari, Masahiro; Kawana, Keisuke; Miura, Masahiro; Fukuda, Shinichi; Makita, Shuichi; Sakai, Shingo; Oshika, Tetsuro

    2010-11-01

    Polarization-sensitive optical coherence tomography (PS-OCT) is known to be advantageous because of its additional tissue-specific contrast of the anterior eye. So far, this advantage has been shown only qualitatively. We evaluate the improved visibility afforded by 3-D PS corneal and anterior eye segment OCT (PS-CAS-OCT) in visualizing the trabecular meshwork (TM) based on statistical evidences. A total of 31 normal subjects participated in this study. The anterior eye segments of both the eyes of the subjects are scanned using a custom-made PS-CAS-OCT and the standard-scattering OCT (S-OCT) and polarization-sensitive phase-retardation OCT (P-OCT) images are obtained. Three graders grade the visibility of the TM using a four-leveled grading system. The intergrader agreement, intermodality differences, and interquadrant dependence of visibility are statistically examined. All three of three combinations of graders show substantial agreement in visibility with P-OCT (ρ = 0.74, 0.70, and 0.68, Spearman's correlation), while only one of three shows substantial agreement with S-OCT (ρ = 0.72). Significant dependence of the visibility on the modality (S-OCT versus P-OCT) and quadrants are found by the analysis of variance. A subsequent Wilcoxon signed-rank test reveals significantly improved visibility. PS-CAS-OCT may become a useful tool for screening angle-closure glaucoma.

  8. MTOR-independent induction of autophagy in trabecular meshwork cells subjected to biaxial stretch.

    PubMed

    Porter, Kristine M; Jeyabalan, Nallathambi; Liton, Paloma B

    2014-06-01

    The trabecular meshwork (TM) is part of a complex tissue that controls the exit of aqueous humor from the anterior chamber of the eye, and therefore helps maintaining intraocular pressure (IOP). Because of variations in IOP with changing pressure gradients and fluid movement, the TM and its contained cells undergo morphological deformations, resulting in distention and stretching. It is therefore essential for TM cells to continuously detect and respond to these mechanical forces and adapt their physiology to maintain proper cellular function and protect against mechanical injury. Here we demonstrate the activation of autophagy, a pro-survival pathway responsible for the degradation of long-lived proteins and organelles, in TM cells when subjected to biaxial static stretch (20% elongation), as well as in high-pressure perfused eyes (30mmHg). Morphological and biochemical markers for autophagy found in the stretched cells include elevated LC3-II levels, increased autophagic flux, and the presence of autophagic figures in electron micrographs. Furthermore, our results indicate that the stretch-induced autophagy in TM cells occurs in an MTOR- and BAG3-independent manner. We hypothesize that activation of autophagy is part of the physiological response that allows TM cells to cope and adapt to mechanical forces.

  9. Imaging of trabecular meshwork using Bessel-Gauss light sheet with fluorescence

    NASA Astrophysics Data System (ADS)

    Jie Jeesmond Hong, Xun; Shinoj, V. K.; Murukeshan, V. M.; Baskaran, M.; Aung, Tin

    2017-03-01

    Ocular imaging technology that holds promise for both fundamental investigation and clinical detection of glaucoma is still a challenging research area. A direct view of the trabecular meshwork (TM) with high resolution is not generally possible because the iridocorneal angle region is obstructed by the sclera overlap. The best approach to observe the aqueous outflow system (AOS) is therefore to view from the opposite angle. In this research work, we developed two imaging systems for the high resolution ex vivo studies of the AOS inside porcine eye, based on a Gaussian illuminated and a digitally scanned Bessel-Gauss beam light sheet fluorescence configurations. The digitally scanned Bessel-Gauss beam is able to overcome the trade-off between the length and thickness of the Gaussian light sheet to give better imaging performance. It has adequate spatial resolution to resolve critical anatomical structures such as the TM, thereby enabling objective information about the AOS. This non-contact and non-invasive imaging methodology with excellent safety profile is expected to be well received by vision researchers and clinicians in the evaluation and management of glaucoma.

  10. Technical Brief: a novel strategy for enrichment of trabecular meshwork protease proteome.

    PubMed

    Picciani, Renata; Junk, Anna K; Bhattacharya, Sanjoy K

    2008-05-14

    We present a novel and simple enrichment strategy to capture trabecular meshwork (TM) protease proteome. The method relies on fractionation of TM tissue into cytosolic and nuclear extracts and subsequent affinity enrichment of proteases on peptide inhibitors. A large repertoire of available protease substrate analog peptides enables an improved capture of TM protease proteome compared to SDS-PAGE fractionation alone. Peptide analog inhibitors of protease substrates are immobilized on a protein A or G column using 254 nm intense ultraviolet (UV) light. The TM cytosolic protein extract incubated on the column is eluted with salt or a buffer with a low hydrogen ion concentration. The resultant protein solution is precipitated with acetone, fractionated on SDS-PAGE, in situ trypsin digested, and subjected to mass spectrometry. This relatively simple protocol enables improved capture of cytosolic proteases. We identified 20 previously reported TM proteins from a single donor tissue using affinity enrichment. The majority of identified proteins were either intracellular proteases or known protease inhibitors. Both serine and cysteine proteases were captured using this strategy with improved coverage compared to our previous identification without affinity enrichment.

  11. Durable, safe, multi-gene lentiviral vector expression in feline trabecular meshwork.

    PubMed

    Khare, Pranay D; Loewen, Nils; Teo, Wulin; Barraza, Román A; Saenz, Dyana T; Johnson, Douglas H; Poeschla, Eric M

    2008-01-01

    Multiple disease-specific considerations have led to interest in the potential of gene therapy to permanently correct elevated intraocular pressure (IOP), the main causal risk factor for primary open angle glaucoma (POAG). Since IOP elevation results from abnormal resistance to aqueous humor outflow from the eye through the trabecular meshwork (TM), a means to genetically modify this specialized outflow organ permanently and safely is a prioritized goal. Here we tested different lentiviral vector designs and doses for long-term transgene expression in a large animal model, and investigated whether exogenously introduced myocilin proteins influenced IOP. The anterior chambers of 18 domestic cats (36 eyes) were injected with dual-gene feline immunodeficiency virus (FIV) vectors. Substantial, well-tolerated green fluorescent protein (GFP) expression was achieved in TM and monitored non-invasively in vivo for 1.2-2.3 years, using both 5' cap-translation and internal ribosome entry site (IRES)-translation. In all 36 eyes, post-mortem examination revealed substantial TM transgene expression (which often greatly exceeded that observable non-invasively during life). However, co-expression with enhanced GFP of myocilin or a juvenile glaucoma-associated mutant myocilin did not elevate IOP. These results demonstrate a safe, long-term single and dual gene expression in TM and establish an experimental system for testing candidate therapeutic transgenes for POAG.

  12. Targeting the ER-Autophagy System in the Trabecular Meshwork to Treat Glaucoma

    PubMed Central

    Stothert, Andrew R.; Fontaine, Sarah N.; Sabbagh, Jonathan J.; Dickey, Chad A.

    2015-01-01

    A major drainage network involved in aqueous humor dynamics is the conventional outflow pathway, which is gated by the trabecular meshwork (TM). The TM acts as a molecular sieve, providing resistance to aqueous outflow, which is responsible for regulating intraocular pressure (IOP). If the TM is damaged, aqueous outflow is impaired, IOP increases and glaucoma can manifest. Mutations in the MYOC gene cause hereditary primary open-angle glaucoma (POAG) by promoting the abnormal amyloidosis of the myocilin protein in the endoplasmic reticulum (ER), leading to ER stress-induced TM cell death. Myocilin accumulation is observed in approximately 70–80% of all glaucoma cases suggesting that environmental or other genetic factors may also promote myocilin toxicity. For example, simply preventing myocilin glycosylation is sufficient to promote its abnormal accretion. These myocilin amyloids are unique as there are no other known pathogenic proteins that accumulate within the ER of TM cells and cause toxicity. Moreover, this pathogenic accumulation only kills TM cells, despite expression of this protein in other cell types, suggesting that another modifier exclusive to the TM participates in the proteotoxicity of myocilin. ER autophagy (reticulophagy) is one of the pathways essential for myocilin clearance that can be impacted dramatically by aging and other environmental factors such as nutrition. This review will discuss the link between myocilin and autophagy, evaluating the role of this degradation pathway in glaucoma as well as its potential as a therapeutic target. PMID:26302411

  13. TGFβ2-induced outflow alterations in a bioengineered trabecular meshwork are offset by a rho-associated kinase inhibitor

    PubMed Central

    Torrejon, Karen Y.; Papke, Ellen L.; Halman, Justin R.; Bergkvist, Magnus; Danias, John; Sharfstein, Susan T.; Xie, Yubing

    2016-01-01

    Members of the transforming growth factor beta (TGFβ) cytokine family have long been associated with affecting several cellular functions, including cell proliferation, differentiation and extracellular matrix (ECM) turnover. Of particular interest to this work, TGFβ2 has been linked to most types of glaucomas as a potential fibrotic agent that can cause elevation of intraocular pressure (IOP). Given that the trabecular meshwork (TM) provides most of aqueous humor outflow resistance in the eye, an in vitro bioengineered human TM (HTM) model has been created and validated by analyzing effects of TGFβ2 on transcellular pressure changes and outflow facility. These changes were correlated with several biological alterations induced by this cytokine, including ECM production and overexpression of HTM-marker myocillin. Furthermore, this TM model has been used to extend current knowledge of gene expression of cytokines involved in TGFβ-induced ECM turnover over time. In particular, the ability for a ROCK-inhibitor to diminish the effect of TGFβ on TM was demonstrated. This work supports the notion that anti-fibrotic activities of ROCK-inhibitors could counteract the elevation of IOP and increased strain observed in glaucomatous TM. PMID:27924833

  14. Tissue plasminogen activator in trabecular meshwork attenuates steroid induced outflow resistance in mice.

    PubMed

    Kumar, Sandeep; Shah, Shaily; Tang, Hai Michael; Smith, Matthew; Borrás, Teresa; Danias, John

    2013-01-01

    Tissue plasminogen activator, a serine protease encoded by the PLAT gene is present in the trabecular meshwork (TM) and other ocular tissues and has been reported to be downregulated by treatment with steroids in vitro. Steroids are known to cause changes in outflow facility of aqueous humor in many species. In the present study, we tested whether overexpression of PLAT can prevent and/or reverse the outflow facility of mouse eyes treated with steroids. Animals received bilateral injection with 20 µl of triamcinolone acetonide (TA) (40 mg/ml) suspension subconjunctivally to induce outflow facility changes. Some animals received unilateral intracameral injection with 2 µl of adenoviral suspension [3-4 x 10(12) virus genomes per milliliter (vg/ml)] carrying sheep PLAT cDNA (AdPLAT) either concurrently with TA injection or one week after TA injection, whereas others received bilateral intracameral injection with 2 µl of adenoviral suspension (9 x 10(12) vg/ml) carrying no transgene (AdNull) concurrently with TA injection. Animals were sacrificed one week after AdPLAT or AdNull treatment. Endogenous mRNA expression levels of mouse PAI-1 and MMP-2, -9 and -13 were also measured using qRT-PCR. Outflow facility one week after AdPLAT administration was increased by 60% and 63% respectively for animals that had not or had been pretreated with steroids. Overexpression of PLAT significantly upregulated expression of PAI-1, MMP-2, -9 and -13 compared to the levels found in TA only treated eyes. These findings suggest that overexpression of PLAT in TM of mouse eyes can both prevent and reverse the decrease in outflow facility caused by steroid treatment and is associated with upregulation of MMPs.

  15. HDAC Inhibitor-Mediated Epigenetic Regulation of Glaucoma-Associated TGFβ2 in the Trabecular Meshwork

    PubMed Central

    Bermudez, Jaclyn Y.; Webber, Hannah C.; Patel, Gaurang C.; Liu, Xiangyang; Cheng, Yi-Qiang; Clark, Abbot F.; Mao, Weiming

    2016-01-01

    Purpose Elevated intraocular pressure (IOP) in primary open-angle glaucoma (POAG) results from glaucomatous damage to the trabecular meshwork (TM). The glaucoma-associated factor TGFβ2 is increased in aqueous humor and TM of POAG patients. We hypothesize that histone acetylation has a role in dysregulated TGFβ2 expression. Methods Protein acetylation was compared between nonglaucomatous TM (NTM) and glaucomatous TM (GTM) cells using Western immunoblotting (WB). Nonglaucomatous TM cells were treated with 10 nM thailandepsin-A (TDP-A), a potent histone deacetylase inhibitor for 4 days. Total and nuclear proteins, RNA, and nuclear protein-DNA complexes were harvested for WB, quantitative PCR (qPCR), and chromatin immunoprecipitation (ChIP) assays, respectively. Paired bovine eyes were perfused with TDP-A versus DMSO, or TDP-A versus TDP-A plus the TGFβ pathway inhibitor LY364947 for 5 to 9 days. Intraocular pressure, TM, and perfusate proteins were compared. Results We found increased acetylated histone 3 and total protein acetylation in the GTM cells and TDP-A treated NTM cells. Chromatin immunoprecipitation assays showed that TDP-A induced histone hyperacetylation associated with the TGFβ2 promoter. This change of acetylation significantly increased TGFβ2 mRNA and protein expression in NTM cells. In perfusion-cultured bovine eyes, TDP-A increased TGFβ2 in the perfusate as well as elevated IOP. Histologic and immunofluorescent analyses showed increased extracellular matrix and cytoskeletal proteins in the TM of TDP-A treated bovine eyes. Cotreatment with the TGFβ pathway inhibitor LY364947 blocked TDP-A–induced ocular hypertension. Conclusions Our results suggest that histone acetylation has an important role in increased expression of the glaucoma-associated factor TGFβ2. Histone hyperacetylation may be the initiator of glaucomatous damage to the TM. PMID:27403998

  16. In Vitro and in Vivo Experimental Studies on Trabecular Meshwork Degeneration Induced by Benzalkonium Chloride (An American Ophthalmological Society Thesis)

    PubMed Central

    Baudouin, Christophe; Denoyer, Alexandre; Desbenoit, Nicolas; Hamm, Gregory; Grise, Alice

    2012-01-01

    Purpose: Long-term antiglaucomatous drug administration may cause irritation, dry eye, allergy, subconjunctival fibrosis, or increased risk of glaucoma surgery failure, potentially due to the preservative benzalkonium chloride (BAK), whose toxic, proinflammatory, and detergent effects have extensively been shown experimentally. We hypothesize that BAK also influences trabecular meshwork (TM) degeneration. Methods: Trabecular specimens were examined using immunohistology and reverse transcriptase–polymerase chain reaction. A trabecular cell line was stimulated by BAK and examined for apoptosis, oxidative stress, fractalkine and SDF-1 expression, and modulation of their receptors. An experimental model was developed with BAK subconjunctival injections to induce TM degeneration. Mass spectrometry (MS) imaging assessed BAK penetration after repeated instillations in rabbit eyes. Results: Trabecular specimens showed extremely low densities of trabecular cells and presence of cells expressing fractalkine and fractalkine receptor and their respective mRNAs. Benzalkonium in vitro induced apoptosis, oxidative stress, and fractalkine expression and inhibited the protective chemokine SDF-1 and Bcl2, also inducing a sustained intraocular pressure (IOP) increase, with dramatic apoptosis of trabecular cells and reduction of aqueous outflow. MS imaging showed that BAK could access the TM at measurable levels after repeated instillations. Conclusion: BAK enhances all characteristics of TM degeneration typical of glaucoma—trabecular apoptosis, oxidative stress, induction of inflammatory chemokines—and causes degeneration in acute experimental conditions, potentially mimicking long-term accumulation. BAK was also shown to access the TM after repeated instillations. These findings support the hypothesis that antiglaucoma medications, through toxicity of their preservative, may cause further long-term trabecular degeneration and therefore enhance outflow resistance, reducing the

  17. Intraocular Pressure and the Mechanisms Involved in Resistance of the Aqueous Humor Flow in the Trabecular Meshwork Outflow Pathways.

    PubMed

    Tamm, Ernst R; Braunger, Barbara M; Fuchshofer, Rudolf

    2015-01-01

    Intraocular pressure (IOP), the critical risk factor for glaucoma, is generated and maintained by the aqueous humor circulation system. Aqueous humor is secreted from the epithelial layers of the ciliary body and exits the eye through the trabecular meshwork or the uveoscleral outflow pathways. IOP builds up in response to a resistance to aqueous humor flow in the trabecular outflow pathways. The trabecular outflow resistance is localized in the inner wall region, which comprises the juxtacanalicular connective tissue (JCT) and the inner wall endothelium of Schlemm's canal (SC). Outflow resistance in this region is lowered through the relaxation of contractile myofibroblast-like cells in trabecular meshwork and the adjacent scleral spur, or the contraction of the ciliary muscle. In primary open-angle glaucoma, the most frequent form of glaucoma, outflow resistance of the inner wall region is typically higher than normal. There is evidence that the increase in resistance is related to characteristic biological changes in the resident cells of the JCT, which more and more acquire the structural and functional characteristics of contractile myofibroblasts. The changes involve an augmentation of their actin cytoskeleton and of their surrounding fibrillary extracellular matrix, which connects to JCT cells via integrins. This scenario leads to an overall stiffening of the inner wall region, and is modulated by transforming growth factor-β/connective tissue growth factor signaling. Essentially comparable changes appear to occur in SC endothelial cells. Stiffening of JCT and SC cells is very likely a critical causative factor for the increase in trabecular outflow resistance in POAG.

  18. Cross-Talk between Ciliary Epithelium and Trabecular Meshwork Cells In-Vitro: A New Insight into Glaucoma

    PubMed Central

    Lerner, Natalie; Beit-Yannai, Elie

    2014-01-01

    Purpose It is assumed that the non-pigmented ciliary epithelium plays a role in regulating intraocular pressure via its neuroendocrine activities. To test this hypothesis, we investigated the effect on a human trabecular meshwork (TM) cell line (NTM) of co-culture with a human non-pigmented ciliary epithelium cell line (ODM-2). Methods The cellular cross-talk between ODM-2 and NTM cells was studied in a co-culture system in which the two cell types were co-cultured for 5 to 60min or 2, 4 and 8h and then removed from the co-culture and analyzed. Analyses of the ERK and p38 mitogen-activated protein kinase (MAPK) pathways and of the activity of TM phosphatases and matrix metalloproteins (MMPs) were performed. Acid and alkaline phosphatase activity was determined by the DiFMUP (6, 8-difluoro-4-methylumbelliferyl phosphate) assay. MMP levels were determined by gelatin zymography. Results Exposure of NTM cells to ODM-2 cells led to the activation of the MAPK signal transduction pathways in NTM cells within 5min of co-culture. Phosphorylation of ERK1/ERK2 and p38 peaked at 10 and 15min and then decreased over time. Interaction between ODM-2 and NTM cells promoted the expression of MMP-9 in the NTM cells after 4h of co-culture. Conclusions Our findings provide support for the hypothesis that crosstalk does indeed take place between ODM-2 and NTM cells. Future studies should be designed to determine the relationship between the MMP system, MAPK kinases and phosphatases. Manipulation of these signaling molecules and the related NTM signal transduction pathways may provide targets for developing improved treatments for glaucoma. PMID:25389776

  19. Cross-talk between ciliary epithelium and trabecular meshwork cells in-vitro: a new insight into glaucoma.

    PubMed

    Lerner, Natalie; Beit-Yannai, Elie

    2014-01-01

    It is assumed that the non-pigmented ciliary epithelium plays a role in regulating intraocular pressure via its neuroendocrine activities. To test this hypothesis, we investigated the effect on a human trabecular meshwork (TM) cell line (NTM) of co-culture with a human non-pigmented ciliary epithelium cell line (ODM-2). The cellular cross-talk between ODM-2 and NTM cells was studied in a co-culture system in which the two cell types were co-cultured for 5 to 60 min or 2, 4 and 8h and then removed from the co-culture and analyzed. Analyses of the ERK and p38 mitogen-activated protein kinase (MAPK) pathways and of the activity of TM phosphatases and matrix metalloproteins (MMPs) were performed. Acid and alkaline phosphatase activity was determined by the DiFMUP (6, 8-difluoro-4-methylumbelliferyl phosphate) assay. MMP levels were determined by gelatin zymography. Exposure of NTM cells to ODM-2 cells led to the activation of the MAPK signal transduction pathways in NTM cells within 5 min of co-culture. Phosphorylation of ERK1/ERK2 and p38 peaked at 10 and 15 min and then decreased over time. Interaction between ODM-2 and NTM cells promoted the expression of MMP-9 in the NTM cells after 4h of co-culture. Our findings provide support for the hypothesis that crosstalk does indeed take place between ODM-2 and NTM cells. Future studies should be designed to determine the relationship between the MMP system, MAPK kinases and phosphatases. Manipulation of these signaling molecules and the related NTM signal transduction pathways may provide targets for developing improved treatments for glaucoma.

  20. Hic-5 Regulates Actin Cytoskeletal Reorganization and Expression of Fibrogenic Markers and Myocilin in Trabecular Meshwork Cells

    PubMed Central

    Pattabiraman, Padmanabhan Paranji; Rao, Ponugoti Vasantha

    2015-01-01

    Purpose To explore the role of inducible focal adhesion (FA) protein Hic-5 in actin cytoskeletal reorganization, FA formation, fibrogenic activity, and expression of myocilin in trabecular meshwork (TM) cells. Methods Using primary cultures of human TM (HTM) cells, the effects of various external factors on Hic-5 protein levels, as well as the effects of recombinant Hic-5 and Hic-5 small interfering RNA (siRNA) on actin cytoskeleton, FAs, myocilin, α-smooth muscle actin (αSMA), and collagen-1 were determined by immunofluorescence and immunoblot analyses. Results Hic-5 distributes discretely to the FAs in HTM cells and throughout the TM and Schlemm's canal of the human aqueous humor (AH) outflow pathway. Transforming growth factor-β2 (TGF-β2), endothelin-1, lysophosphatidic acid, hydrogen peroxide, and RhoA significantly increased Hic-5 protein levels in HTM cells in association with reorganization of actin cytoskeleton and FAs. While recombinant Hic-5 induced actin stress fibers, FAs, αv integrin redistribution to the FAs, increased levels of αSMA, collagen-1, and myocilin, Hic-5 siRNA suppressed most of these responses in HTM cells. Hic-5 siRNA also suppressed TGF-β2-induced fibrogenic activity and dexamethasone-induced myocilin expression in HTM cells. Conclusions Taken together, these results reveal that Hic-5, whose levels were increased by various external factors implicated in elevated intraocular pressure, induces actin cytoskeletal reorganization, FAs, expression of fibrogenic markers, and myocilin in HTM cells. These characteristics of Hic-5 in TM cells indicate its importance in regulation of AH outflow through the TM in both normal and glaucomatous eyes. PMID:26313302

  1. A Comparison of Gene Expression Profiles between Glucocorticoid Responder and Non-Responder Bovine Trabecular Meshwork Cells Using RNA Sequencing

    PubMed Central

    Bermudez, Jaclyn Y.; Webber, Hannah C.; Brown, Bartley; Braun, Terry A.; Clark, Abbot F.; Mao, Weiming

    2017-01-01

    The most common ocular side effect of glucocorticoid (GC) therapy is GC-induced ocular hypertension (OHT) and GC-induced glaucoma (GIG). GC-induced OHT occurs in about 40% of the general population, while the other 60% are resistant. This study aims to determine the genes and pathways involved in differential GC responsiveness in the trabecular meshwork (TM). Using paired bovine eyes, one eye was perfusion-cultured with 100nM dexamethasone (DEX), while the fellow eye was used to establish a bovine TM (BTM) cell strain. Based on maximum IOP change in the perfused eye, the BTM cell strain was identified as a DEX-responder or non-responder strain. Three responder and three non-responder BTM cell strains were cultured, treated with 0.1% ethanol or 100nM DEX for 7 days. RNA and proteins were extracted for RNA sequencing (RNAseq), qPCR, and Western immunoblotting (WB), respectively. Data were analyzed using the human and bovine genome databases as well as Tophat2 software. Genes were grouped and compared using Student’s t-test. We found that DEX induced fibronectin expression in responder BTM cells but not in non-responder cells using WB. RNAseq showed between 93 and 606 differentially expressed genes in different expression groups between responder and non-responder BTM cells. The data generated by RNAseq were validated using qPCR. Pathway analyses showed 35 pathways associated with differentially expressed genes. These genes and pathways may play important roles in GC-induced OHT and will help us to better understand differential ocular responsiveness to GCs. PMID:28068412

  2. Imaging the Effects of Prostaglandin Analogues on Cultured Trabecular Meshwork Cells by Coherent Anti-Stokes Raman Scattering

    PubMed Central

    Lei, Tim C.; Masihzadeh, Omid; Kahook, Malik Y.; Ammar, David A.

    2013-01-01

    Purpose. The aim of this study was to nondestructively monitor morphological changes to the lipid membranes of primary cultures of living human trabecular meshwork cells (hTMC) without the application of exogenous label. Methods. Live hTMC were imaged using two nonlinear optical techniques: coherent anti-Stokes Raman scattering (CARS) and two-photon autofluorescence (TPAF). The hTMC were treated with a commercial formulation of latanoprost (0.5 μg/mL) for 24 hours before imaging. Untreated cells and cells treated with vehicle containing the preservative benzalkonium chloride (BAK; 2 μg/mL) were imaged as controls. After CARS/TPAF imaging, hTMC were fixed, stained with the fluorescent lipid dye Nile Red, and imaged by conventional confocal microscopy to verify lipid membrane structures. Results. Analysis of CARS/TPAF images of hTMC treated with latanoprost revealed multiple intracellular lipid membranes absent from untreated or BAK-treated hTMC. Treatment of hTMC with sodium fluoride or ouabain, agents shown to cause morphological changes to hTMC, also did not induce formation of intracellular lipid membranes. Conclusions. CARS microscopy detected changes in living hTMC morphology that were validated by subsequent histological stain. Prostaglandin-induced changes to hTMC involved rearrangement of lipid membranes within these cells. These in vitro results identify a novel biological response to a class of antiglaucoma drugs, and further experiments are needed to establish how this effect is involved in the hypotensive action of prostaglandin analogues in vivo. PMID:23900606

  3. Effects of TGF-beta2, BMP-4, and gremlin in the trabecular meshwork: implications for glaucoma.

    PubMed

    Wordinger, Robert J; Fleenor, Debra L; Hellberg, Peggy E; Pang, Iok-Hou; Tovar, Tara O; Zode, Gulab S; Fuller, John A; Clark, Abbot F

    2007-03-01

    The primary causative factor of primary open-angle glaucoma (POAG) is elevated intraocular pressure (IOP) due to increased aqueous humor (AH) outflow resistance, which is associated with morphologic and biochemical changes in the trabecular meshwork (TM). Patients with glaucoma have elevated levels of transforming growth factor (TGF)-beta2 in their AH, and TGF-beta has been shown to increase TM extracellular matrix (ECM) production. The bone morphogenetic protein (BMP) signaling pathway modifies TGF-beta signaling in several different tissues, and a prior study demonstrated that TM cells and tissues express members of the BMP gene family. The purpose of this study was to determine whether BMPs can alter TGF-beta2 signaling in the TM and whether there are defects in BMP signaling in glaucoma. ELISA, Western immunoblot analysis, and immunohistochemistry were used to evaluate the expression of BMP proteins in TM cells and tissues. ELISA was used to determine the effects of TGF-beta2 and BMPs on TM fibronectin (FN) secretion. Gene expression was determined by gene microarrays and quantitative (q)PCR. Perfusion-cultured human anterior segments were used to study the effects of altered BMP signaling on IOP. The human TM synthesized and secreted BMP-4 as well as expressed BMP receptor subtypes BMPRI and BMPRII. TM cells responded to exogenous BMP-4 by phosphorylating Smad signaling proteins. Cultured human TM cells treated with TGF-beta2 significantly increased FN levels, and BMP-4 blocked this FN induction. The expression of BMP family genes in normal and glaucomatous TM cells was profiled and significant elevation of mRNA and protein levels of the BMP antagonist gremlin were found in glaucomatous TM cells. In addition, Gremlin was present in human aqueous humor and in the perfusate medium of perfusion-cultured human eyes. Gremlin blocked the negative effect of BMP-4 on TGF-beta-induction of FN. Recombinant Gremlin added to the medium of ex vivo perfusion-cultured human

  4. Effects of K-115 (Ripasudil), a novel ROCK inhibitor, on trabecular meshwork and Schlemm’s canal endothelial cells

    PubMed Central

    Kaneko, Yoshio; Ohta, Masayuki; Inoue, Toshihiro; Mizuno, Ken; Isobe, Tomoyuki; Tanabe, Sohei; Tanihara, Hidenobu

    2016-01-01

    Ripasudil hydrochloride hydrate (K-115), a specific Rho-associated coiled-coil containing protein kinase (ROCK) inhibitor, was the first ophthalmic solution developed for the treatment of glaucoma and ocular hypertension in Japan. Topical administration of K-115 decreased intraocular pressure (IOP) and increased outflow facility in rabbits. This study evaluated the effect of K-115 on monkey trabecular meshwork (TM) cells and Schlemm’s canal endothelial (SCE) cells. K-115 induced retraction and rounding of cell bodies as well as disruption of actin bundles in TM cells. In SCE-cell monolayer permeability studies, K-115 significantly decreased transendothelial electrical resistance (TEER) and increased the transendothelial flux of FITC-dextran. Further, K-115 disrupted cellular localization of ZO-1 expression in SCE-cell monolayers. These results indicate that K-115 decreases IOP by increasing outflow facility in association with the modulation of TM cell behavior and SCE cell permeability in association with disruption of tight junction. PMID:26782355

  5. Non-contact high resolution Bessel beam probe for diagnostic imaging of cornea and trabecular meshwork region in eye

    NASA Astrophysics Data System (ADS)

    Murukeshan, V. M.; Jesmond, Hong Xun J.; Shinoj, V. K.; Baskaran, M.; Tin, Aung

    2015-07-01

    Primary angle closure glaucoma is a major form of disease that causes blindness in Asia and worldwide. In glaucoma, irregularities in the ocular aqueous outflow system cause an elevation in intraocular pressure (IOP) with subsequent death of retinal ganglion cells, resulting in loss of vision. High resolution visualization of the iridocorneal angle region has great diagnostic value in understanding the disease condition which enables monitoring of surgical interventions that decrease IOP. None of the current diagnostic techniques such as goniophotography, ultrasound biomicroscopy (UBM), anterior segment optical coherence tomography (AS-OCT) and RetCam™ can image with molecular specificity and required spatial resolution that can delineate the trabecular meshwork structures. This paper in this context proposes new concepts and methodology using Bessel beams based illumination and imaging for such diagnostic ocular imaging applications. The salient features using Bessel beams instead of the conventional Gaussian beam, and the optimization challenges in configuring the probe system will be illustrated with porcine eye samples.

  6. Interaction of cochlin and mechanosensitive channel TREK-1 in trabecular meshwork cells influences the regulation of intraocular pressure.

    PubMed

    Carreon, Teresia A; Castellanos, Aida; Gasull, Xavier; Bhattacharya, Sanjoy K

    2017-03-28

    This work was funded by National Institute of Health Grants R01 EY016112, EY015266, and EY014801 and an unrestricted grant to the University of Miami's Bascom Palmer Eye Institute from Research to Prevent Blindness. Financial support from Fight for Sight is gratefully acknowledged. Funding to XG was provided by Instituto de Salud Carlos III, Spain (FIS PI14/00141 and RETIC RD12/0034/0003) and Generalitat de Catalunya (2014SGR1165). In the eye, intraocular pressure (IOP) is tightly regulated and its persistent increase leads to ocular hypertension and glaucoma. We have previously shown that trabecular meshwork (TM) cells might detect aqueous humor fluid shear stress via interaction of the extracellular matrix (ECM) protein cochlin with the cell surface bound and stretch-activated channel TREK-1. We provide evidence here that interaction between both proteins are involved in IOP regulation. Silencing of TREK-1 in mice prevents the previously demonstrated cochlin-overexpression mediated increase in IOP. Biochemical and electrophysiological experiments demonstrate that high shear stress-induced multimeric cochlin produces a qualitatively different interaction with TREK-1 compared to monomeric cochlin. Physiological concentrations of multimeric but not monomeric cochlin reduce TREK-1 current. Results presented here indicate that the interaction of TREK-1 and cochlin play an important role for maintaining IOP homeostasis.

  7. Cathepsin B Is Up-Regulated and Mediates Extracellular Matrix Degradation in Trabecular Meshwork Cells Following Phagocytic Challenge

    PubMed Central

    Porter, Kristine; Lin, Yizhi; Liton, Paloma B.

    2013-01-01

    Cells in the trabecular meshwork (TM), a tissue responsible for draining aqueous humor out of the eye, are known to be highly phagocytic. Phagocytic activity in TM cells is thought to play an important role in outflow pathway physiology. However, the molecular mechanisms triggered by phagocytosis in TM cells are unknown. Here we investigated the effects of chronic phagocytic stress on lysosomal function using different phagocytic ligands (E. coli, carboxylated beads, collagen I-coated beads, and pigment). Lysotracker red co-localization and electron micrographs showed the maturation of E. coli- and collagen I-coated beads-containing phagosomes into phagolysosomes. Maturation of phagosomes into phagolysosomes was not observed with carboxylated beads or pigment particles. In addition, phagocytosis of E. coli and collagen I-coated beads led to increased lysosomal mass, and the specific up-regulation and activity of cathepsin B (CTSB). Higher levels of membrane-bound and secreted CTSB were also detected. Moreover, in vivo zymography showed the intralysosomal degradation of ECM components associated with active CTSB, as well as an overall increased gelatinolytic activity in phagocytically challenged TM cells. This increased gelatinolytic activity with phagocytosis was partially blocked with an intracellular CTSB inhibitor. Altogether, these results suggest a potential role of phagocytosis in outflow pathway tissue homeostasis through the up-regulation and/or proteolytic activation of extracellular matrix remodeling genes. PMID:23844232

  8. The Juxtacanalicular Region of Ocular Trabecular Meshwork: A Tissue with a Unique Extracellular Matrix and Specialized Function.

    PubMed

    Keller, Kate E; Acott, Ted S

    2013-06-01

    The trabecular meshwork (TM) is a filter-like tissue located in the anterior segment of the eye. It is composed of a series of fenestrated beams through which aqueous humor flows to exit the anterior chamber via Schlemm's canal. The primary function of the TM is to regulate the flow of aqueous humor in order to establish intraocular pressure (IOP). Dysregulated aqueous humor outflow causes elevated IOP, which is a primary risk factor for glaucoma. The region of the TM implicated in establishing IOP lies adjacent to Schlemm's canal and is called the juxtacanalicular tissue (JCT) or cribriform region. Recent advanced light microscopy studies suggest that the JCT can be subdivided into inner and outer zones based on the localization of certain extracellular matrix (ECM) molecules. By comparing the ECM of the JCT to other connectives tissues and disease processes, this review outlines the evidence for two new concepts in TM biology: (1) continuous maintenance ECM remodeling, which may be critical in order to preserve open aqueous humor flow channels by releasing trapped debris and associated ECM fragments from the outflow pathways; (2) the JCT ECM as a barrier to functionally isolate the aqueous outflow channels. The ECM surrounding the outflow channels in the JCT may function to sequester small active regulatory molecules and prevent them from aberrantly modulating outflow resistance. These adaptations point to a distinctive tissue that has evolved transient ECM remodeling processes in order to regulate aqueous humor outflow and maintain rigorous control of IOP.

  9. Effects of induction and inhibition of matrix cross-linking on remodeling of the aqueous outflow resistance by ocular trabecular meshwork cells

    PubMed Central

    Yang, Yong-Feng; Sun, Ying Ying; Acott, Ted S.; Keller, Kate E.

    2016-01-01

    The trabecular meshwork (TM) tissue controls drainage of aqueous humor from the anterior chamber of the eye primarily by regulating extracellular matrix (ECM) remodeling by matrix metalloproteinases (MMPs). Glaucomatous TM tissue is stiffer than age-matched controls, which may be due to alterations in ECM cross-linking. In this study, we used genipin or beta-aminopropionitrile (BAPN) agents to induce or inhibit matrix cross-linking, respectively, to investigate the effects on outflow resistance and ECM remodeling. Treatment with BAPN increased outflow rates in perfused human and porcine anterior segments, whereas genipin reduced outflow. Using a fluorogenic peptide assay, MMP activity was increased with BAPN treatment, but reduced with genipin treatment. In genipin-treated TM cells, Western immunoblotting showed a reduction of active MMP2 and MMP14 species and the presence of TIMP2-MMP14 higher molecular weight complexes. BAPN treatment increased collagen type I mRNA and protein levels, but genipin reduced the levels of collagen type I, tenascin C, elastin and versican. CD44 and fibronectin levels were unaffected by either treatment. Collectively, our results show that matrix cross-linking has profound effects on outflow resistance and ECM composition and are consistent with the emerging paradigm that the stiffer the ECM, the lower the aqueous outflow facility through the TM. PMID:27465745

  10. Intraocular pressure regulation: findings of pulse-dependent trabecular meshwork motion lead to unifying concepts of intraocular pressure homeostasis.

    PubMed

    Johnstone, Murray A

    2014-01-01

    Intraocular pressure (IOP) is the only treatable risk factor in glaucoma, one of the world's leading causes of blindness. Mechanisms that maintain IOP within a normal range have been poorly understood in contrast to intrinsic mechanisms that regulate systemic blood pressure. Vessel walls experience continuous pulse-induced cyclic pressure and flow. Pressure-dependent wall stress and flow-dependent shear stress provide sensory signals that initiate mechanotransduction responses. The responses optimize vessel wall elasticity, compliance and lumen size, providing a feedback loop to maintain intrinsic pressure homeostasis. Aqueous humor is part of a vascular circulatory loop, being secreted into the anterior chamber of the eye from the vasculature, then returning to the vasculature by passing through the trabecular meshwork (TM), a uniquely modified vessel wall interposed between the anterior chamber and a vascular sinus called Schlemm's canal (SC). Since pressure in circulatory loops elsewhere is modulated by cyclic stresses, one might predict similar pressure modulation in the aqueous outflow system. Recent laboratory evidence in fact demonstrates that cyclic IOP changes alter aqueous outflow while increasing cellularity and contractility of TM cells. Cyclic changes also lead to alterations in gene expression, changes in cytoskeletal networks and modulation of signal transduction. A new technology, phase-based optical coherence tomography, demonstrates in vivo pulse-dependent TM motion like that elsewhere in the vasculature. Recognition of pulse-dependent TM motion provides a linkage to well-characterized mechanisms that provide pressure homeostasis in the systemic vasculature. The linkage may permit unifying concepts of pressure control and provide new insights into IOP homeostatic mechanisms.

  11. Dual-purpose laser irradiation and perfusion testing system for in-vitro experiments using cultured trabecular meshwork endothelial cells

    NASA Astrophysics Data System (ADS)

    Rivera, Brian K.; Roberts, Cynthia J.; Weber, Paul A.

    1998-06-01

    The means by which Argon laser trabeculoplasty (ALT) lowers intraocular pressure (IOP) is a matter of debate. Mechanical and biological laser-tissue interaction theories have been proposed. To investigate the effect laser irradiation has upon the aqueous outflow facility of trabecular meshwork (TM) cells, a suitable in-vitro model is required. Therefore the purpose of this study was to design, construct, and validate a laser irradiation and perfusion testing apparatus. The system was designed to utilize cultured TM cells seeded onto filter supports. Outflow facility will be quantified by calculating the hydraulic conductivity of the monolayer. An appropriate filter support was located, and its perfusion characteristics determined using water. Afterwards, the steady state perfusion flow rate of the filter was ascertained to be 0.096 plus or minus 0.008 ml/min when culture medium is used. Following these tests a single, baseline perfusion experiment was conducted using a TM cell monolayer. Analysis of the data produced a baseline hydraulic conductivity of 0.673 plus or minus 0.076 (mu) l/min/mm Hg/cm2, well within the range found in previous reports. A dual purpose, in vitro-cellular perfusion and laser irradiation testing apparatus has been developed, tested and validates using known baseline cellular perfusion and laser irradiation testing apparatus has been developed, tested, and validated using known baseline cellular perfusion values. Future experiments will be conducted to verify these initial findings, and further experiments will be conducted using Argon laser irradiation. The response of the TM cell monolayer will then be compared to the baseline figures.

  12. Novel device for expanding Schlemm's canal: a morphological study: Implantation of the Stegmann Canal Expander following viscodilation of Schlemm's canal resulted in permanent expansion of the canal lumen and distension of the trabecular meshwork without complications.

    PubMed

    Grieshaber, Matthias C; Stegmann, Robert; Grieshaber, Hans R; Meyer, Peter

    2015-07-01

    This study was performed to assess any changes in Schlemm's canal (SC) in human autopsy eyes possibly resulting from the injection of a viscoelastic substance and implantation of a new device (the Stegmann Canal Expander, SCE) into SC. After the surgical procedure, eyes were fixed, dissected into quartered segments and examined using light and scanning electron microscopy. Tissue sections displayed a marked dilation of SC and of the collector channels compared with untreated control sections. The SC walls were disrupted in some areas due to viscodilation, but not due to SCE implantation. In all eyes, the entire 9-mm length of the SCE was positioned inside the canal, keeping the canal wide open. The SCE diameter of 240 μm remained unchanged after implantation. Injection of a viscoelastic substance into SC leads to marked dilation of SC and collector channels. Implanting the SCE into SC allowed persistent expansion of SC and stretching of the trabecular meshwork. This may increase the permeability of the trabecular meshwork, reduce its resistance to aqueous humour and maintain circumferential flow within SC. Experimental and clinical studies should determine the impact of this new canal expander in terms of lowering intraocular pressure in glaucoma surgery. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

  13. Activated αvβ3 Integrin Regulates αvβ5 Integrin–Mediated Phagocytosis in Trabecular Meshwork Cells

    PubMed Central

    Gagen, Debjani; Filla, Mark S.; Clark, Ross; Liton, Paloma; Peters, Donna M.

    2013-01-01

    Purpose. To investigate the roles of αvβ3 and αvβ5 integrins in phagocytosis in human trabecular meshwork (HTM) cells. Methods. Immunofluorescence microscopy and FACS analysis were used to determine levels of αvβ3 and αvβ5 integrins in TM tissue and cultures of normal and immortalized TM cells. Phagocytosis was measured using pHrodo-labeled S. aureus bioparticles followed by FACS analysis. The role of αvβ5 integrin in phagocytosis was evaluated by knocking down αvβ5 integrin expression with siRNA against the human β5 gene. Signaling from focal adhesion kinase (FAK) was blocked using FAK inhibitor 14. The role of αvβ3 integrins in phagocytosis was determined by treating HTM cells with dexamethasone (DEX) or ethanol (EtOH) and by generating stable cell lines that overexpressed either wild type (WT) or constitutively active (CA) β3 integrin subunit. Results. Both TM tissue and cell lines expressed αvβ3 and αvβ5 integrins. Knockdown of αvβ5 integrin reduced phagocytosis by ∼60% and FAK inhibition significantly reduced phagocytosis up to 84%, in a dose-dependent manner. DEX treatment increased αvβ3 integrin expression in HTM cells but reduced phagocytosis by ∼50% compared with untreated and EtOH-treated cells. The CA β3 integrin–expressing cell line showed increased αvβ3 integrin levels and decreased phagocytosis by ∼50% compared with the control. Conclusions. The αvβ5 integrin-FAK–mediated pathway regulates phagocytosis in TM cells and this pathway is inhibited by activation of αvβ3 integrins. This suggests that changes in integrin expression and activity may be responsible for alterations in phagocytosis observed in steroid induced glaucoma. PMID:23821196

  14. Perturbation of Hyaluronan Synthesis in the Trabecular Meshwork and the Effects on Outflow Facility

    PubMed Central

    Keller, Kate E.; Sun, Ying Ying; Yang, Yong-Feng; Bradley, John M.; Acott, Ted S.

    2012-01-01

    Purpose. Hyaluronan (HA) is a major component of the aqueous outflow pathway. However, the contribution of HA to human outflow resistance remains unclear. Three HA synthase genes (HAS1-3) have been identified. Here, we evaluate the contribution of each of the HAS proteins to outflow facility in anterior segment perfusion culture. Methods. Two methods were used to reduce HA synthesis: 1 mM 4-methylumbelliferone (4MU) was used to inhibit all HAS synthases and shRNA silencing lentivirus was generated to knock down expression of each HAS individually. Quantitative RT-PCR, Western immunoblotting and an HA ELISA assay were used to assess HAS mRNA and protein levels and HA concentration, respectively. The effects of 4MU treatment and HAS gene silencing on outflow facility were assessed in human and porcine perfusion culture. Results. Quantitative RT-PCR and Western immunoblotting showed a reduction of each HAS in response to their respective silencing and 4MU treatment. HA concentration was concomitantly reduced. Treatment with 4MU decreased outflow facility in human anterior segments but increased outflow facility in porcine eyes. Lentiviral delivery of HAS1 and HAS2 silencing vectors caused similar opposite effects on outflow facility. Silencing of HAS3 did not significantly affect outflow resistance in either species. Conclusions. This is the first conclusive evidence for a significant role of HA in the human outflow pathway. HA chains synthesized by HAS1 and HAS2 contribute to outflow resistance, while hyaluronan produced by HAS3 does not appear to play a significant role. PMID:22695958

  15. Shear Strength Behavior of Human Trabecular Bone

    PubMed Central

    Sanyal, Arnav; Gupta, Atul; Bayraktar, Harun H.; Kwon, Ronald Y.; Keaveny, Tony M.

    2012-01-01

    The shear strength of human trabecular bone may influence overall bone strength under fall loading conditions and failure at bone-implant interfaces. Here, we sought to compare shear and compressive yield strengths of human trabecular bone and elucidate the underlying failure mechanisms. We analyzed 54 specimens (5-mm cubes), all aligned with the main trabecular orientation and spanning four anatomic sites, 44 different cadavers, and a wide range of bone volume fraction (0.06–0.38). Micro-CT-based non-linear finite element analysis was used to assess the compressive and shear strengths and the spatial distribution of yielded tissue; the tissue-level constitutive model allowed for kinematic non-linearity and yielding with strength asymmetry. We found that the computed values of both the shear and compressive strengths depended on bone volume fraction via power law relations having an exponent of 1.7 (R2=0.95 shear; R2=0.97 compression). The ratio of shear to compressive strengths (mean ± SD, 0.44 ± 0.16) did not depend on bone volume fraction (p=0.24) but did depend on microarchitecture, most notably the intra-trabecular standard deviation in trabecular spacing (R2=0.23, p<0.005). For shear, the main tissue-level failure mode was tensile yield of the obliquely oriented trabeculae. By contrast, for compression, specimens having low bone volume fraction failed primarily by large-deformation-related tensile yield of horizontal trabeculae and those having high bone volume failed primarily by compressive yield of vertical trabeculae. We conclude that human trabecular bone is generally much weaker in shear than compression at the apparent level, reflecting different failure mechanisms at the tissue level. PMID:22884967

  16. Ankyrin repeat and suppressor of cytokine signaling box containing protein-10 is associated with ubiquitin-mediated degradation pathways in trabecular meshwork cells.

    PubMed

    Keller, Kate E; Yang, Yong-Feng; Sun, Ying Ying; Sykes, Renee; Acott, Ted S; Wirtz, Mary K

    2013-01-01

    Ankyrin repeat and suppressor of cytokine signaling (SOCS) box containing protein-10 (ASB10) was recently identified as a gene that causes primary open-angle glaucoma. Here, we investigated endogenous ASB10 protein expression in human trabecular meshwork (HTM) cells to provide the first clues to the biologic function of this protein. Primary HTM cells were cultured and immunostained with anti-ASB10 and various biomarkers of the ubiquitin-mediated proteasomal and autophagy-lysosomal degradation pathways. Cells were imaged with confocal and high-resolution structured illumination microscopy. Colocalization was quantified using Imaris Bitplane software, which generated a Pearson's correlation coefficient value. Coimmunoprecipitation of ASB10-transfected cells was performed. Immunofluorescence and confocal analysis showed that ASB10 was localized in intracellular structures in HTM cells. Two populations were observed: small, spherical vesicles and larger, less abundant structures. In the ASB10-silenced cells, the number of large structures was significantly decreased. ASB10 partially colocalized with biomarkers of the ubiquitin-mediated proteasomal pathway including ubiquitin and the α4 subunit of the 20S proteasome. However, ASB10 itself was not ubiquitinated. ASB10 also colocalized with numerous biomarkers of specific autophagic structures: aggresomes (histone deacetylase 6 [HDAC6] and heat shock protein 70 [HSP70]), autophagosomes (light chain 3 [LC3] and p62), amphisomes (Rab7), and lysosomes (lysosomal-associated membrane protein 1 [LAMP1]). Pearson coefficients indicated strong colocalization of large ASB10-stained structures with the α4 subunit of the 20S proteasome, K48 and K63-linked ubiquitin antibodies, p62, HSP70, and HDAC6 (Pearson's range, 0.59-0.82). Coimmunoprecipitation assays showed a positive interaction of ASB10 with HSP70 and with the α4 subunit of the 20S proteasome. Super-resolution structured illumination confocal microscopy suggested that

  17. The trabecular structure of developing human mandible.

    PubMed

    Wojtowicz, A.; Chaberek, S.; Pirino, A.; Montella, A.; Bandiera, P.; Kinsner, A.; Ostrowski, K.

    2001-08-01

    In this paper we tried to analyse in quantitative terms the differences in trabecular structure of human mandibles 8, 10 and 12 weeks old. The analysis was performed on decalcified Sirius-red stained trabeculae, photographed in polarised light. The data obtained from Fourier transforms of scanned pictures were evaluated by discriminant analysis to show the differences between the analysed stages of development. Also, various parts of the mandible were compared because the clinical experience shows that the frequency of pathological changes is different in different parts of mandible bone. The complexity of trabecular structure of bone samples was measured by fractal dimension. It is concluded that this quantitative approach is reliable and, in the future, could be used for physiological and pathological analyses of bone biopsies.

  18. Ultrasonic characterization of human trabecular bone microstructure.

    PubMed

    Hakulinen, Mikko A; Day, Judd S; Töyräs, Juha; Weinans, Harrie; Jurvelin, Jukka S

    2006-03-21

    New quantitative ultrasound (QUS) techniques involving ultrasound backscattering have been introduced for the assessment of bone quality. QUS parameters are affected by the transducer characteristics, e.g. frequency range, wave and pulse length. Although frequency-dependent backscattering has been studied extensively, understanding of the ultrasound scattering phenomenon in trabecular bone is still limited. In the present study, the relationships between QUS parameters and the microstructure of human trabecular bone were investigated experimentally and by using numerical simulations. Speed of sound (SOS), normalized broadband ultrasound attenuation (nBUA), average attenuation, integrated reflection coefficient (IRC) and broadband ultrasound backscatter (BUB) were measured for 26 human trabecular bone cylinders. Subsequently, a high-resolution microCT system was used to determine the microstructural parameters. Moreover, based on the sample-specific microCT data, a numerical model for ultrasound propagation was developed for the simulation of experimental measurements. Experimentally, significant relationships between the QUS parameters and microstructural parameters were demonstrated. The relationships were dependent on the frequency, and the strongest association (r = 0.88) between SOS and structural parameters was observed at a centre frequency of 5 MHz. nBUA, average attenuation, IRC and BUB showed somewhat lower linear correlations with the structural properties at a centre frequency of 5 MHz, as compared to those determined at lower frequencies. Multiple regression analyses revealed that the variation of acoustic parameters could best be explained by parameters reflecting the amount of mineralized tissue. A principal component analysis demonstrated that the strongest determinants of BUB and IRC were related to the trabecular structure. However, other structural characteristics contributed significantly to the prediction of the acoustic parameters as well. The

  19. Trabecular Plates and Rods Determine Elastic Modulus and Yield Strength of Human Trabecular Bone

    PubMed Central

    Wang, Ji; Zhou, Bin; Liu, X. Sherry; Fields, Aaron J.; Sanyal, Arnav; Shi, Xiutao; Adams, Mark; Keaveny, Tony M.; Guo, X. Edward

    2014-01-01

    The microstructure of trabecular bone is usually perceived as a collection of plate-like and rod-like trabeculae, which can be determined from the emerging high-resolution skeletal imaging modalities such as micro computed tomography (μCT) or clinical high-resolution peripheral quantitative CT (HR-pQCT) using the individual trabecula segmentation (ITS) technique. It has been shown that the ITS-based plate and rod parameters are highly correlated with elastic modulus and yield strength of human trabecular bone. In the current study, plate-rod (PR) finite element (FE) models were constructed completely based on ITS-identified individual trabecular plates and rods. We hypothesized that PR FE can accurately and efficiently predict elastic modulus and yield strength of human trabecular bone. Human trabecular bone cores from proximal tibia (PT), femoral neck (FN) and greater trochanter (GT) were scanned by micro computed tomography (μCT). Specimen-specific ITS-based PR FE models were generated for each μCT image and corresponding voxel-based FE models were also generated in comparison. Both types of specimen-specific models were subjected to nonlinear FE analysis to predict the apparent elastic modulus and yield strength using the same trabecular bone tissue properties. Then, mechanical tests were performed to experimentally measure the apparent modulus and yield strength. Strong linear correlations for both elastic modulus (r2=0.97) and yield strength (r2=0.96) were found between the PR FE model predictions and experimental measures, suggesting that trabecular plates and rods morphology adequately captures three-dimensional (3D) microarchitecture of human trabecular bone. In addition, the PR FE model predictions in both elastic modulus and yield strength were highly correlated with the voxel-based FE models (r2=0.99, r2=0.98, respectively), resulted from the original 3D images without the PR segmentation. In conclusion, the ITS-based PR models predicted accurately

  20. Trabecular plates and rods determine elastic modulus and yield strength of human trabecular bone.

    PubMed

    Wang, Ji; Zhou, Bin; Liu, X Sherry; Fields, Aaron J; Sanyal, Arnav; Shi, Xiutao; Adams, Mark; Keaveny, Tony M; Guo, X Edward

    2015-03-01

    The microstructure of trabecular bone is usually perceived as a collection of plate-like and rod-like trabeculae, which can be determined from the emerging high-resolution skeletal imaging modalities such as micro-computed tomography (μCT) or clinical high-resolution peripheral quantitative CT (HR-pQCT) using the individual trabecula segmentation (ITS) technique. It has been shown that the ITS-based plate and rod parameters are highly correlated with elastic modulus and yield strength of human trabecular bone. In the current study, plate-rod (PR) finite element (FE) models were constructed completely based on ITS-identified individual trabecular plates and rods. We hypothesized that PR FE can accurately and efficiently predict elastic modulus and yield strength of human trabecular bone. Human trabecular bone cores from proximal tibia (PT), femoral neck (FN) and greater trochanter (GT) were scanned by μCT. Specimen-specific ITS-based PR FE models were generated for each μCT image and corresponding voxel-based FE models were also generated in comparison. Both types of specimen-specific models were subjected to nonlinear FE analysis to predict the apparent elastic modulus and yield strength using the same trabecular bone tissue properties. Then, mechanical tests were performed to experimentally measure the apparent modulus and yield strength. Strong linear correlations for both elastic modulus (r(2) = 0.97) and yield strength (r(2) = 0.96) were found between the PR FE model predictions and experimental measures, suggesting that trabecular plate and rod morphology adequately captures three-dimensional (3D) microarchitecture of human trabecular bone. In addition, the PR FE model predictions in both elastic modulus and yield strength were highly correlated with the voxel-based FE models (r(2) = 0.99, r(2) = 0.98, respectively), resulted from the original 3D images without the PR segmentation. In conclusion, the ITS-based PR models predicted accurately both elastic

  1. Differential Effects of Caveolin-1 and -2 Knockdown on Aqueous Outflow and Altered Extracellular Matrix Turnover in Caveolin-Silenced Trabecular Meshwork Cells

    PubMed Central

    Aga, Mini; Bradley, John M.; Wanchu, Rohan; Yang, Yong-feng; Acott, Ted S.; Keller, Kate E.

    2014-01-01

    Purpose. A single nucleotide polymorphism (SNP) identified between caveolin-1 (CAV1) and caveolin-2 (CAV2) on chromosome 7 is associated with glaucoma. One function of CAVs is endocytosis and recycling of extracellular matrix (ECM) components. Here, we generated CAV-silencing lentivirus to evaluate the effects on ECM turnover by trabecular meshwork (TM) cells and to measure the effect on outflow facility in anterior segment perfusion culture. Methods. Short hairpin CAV1 and CAV2 silencing and control lentivirus were generated, characterized, and applied to anterior segments in perfusion culture. Colocalization of CAVs with various ECM molecules in TM cells was investigated using immunofluorescence and confocal microscopy. Western immunoblotting and fluorogenic-based enzyme activity assays were used to investigate ECM protein levels and degradation, respectively. Results. Endogenous CAVs colocalized with cortactin at podosome- or invadopodia-like structures (PILS), which are areas of focal ECM degradation. In perfusion culture, outflow rates increased significantly in CAV1-silenced anterior segments, whereas outflow significantly decreased in CAV2-silenced anterior segments. Matrix metalloproteinase (MMP)2 and MMP14, and a disintegrin and metalloproteinase with thrombospondin motifs-4 (ADAMTS4) colocalized with both CAVs in TM cells. Protein levels and enzyme activities of MMP/ADAMTS4, fibronectin protein levels, actin stress fibers, and α-smooth muscle actin were all increased in CAV-silenced cells. Conclusions. Caveolin-mediated endocytosis is one mechanism by which TM cells can alter the physiological catabolism of ECM in order to change the composition of the outflow channels in the TM to regulate aqueous outflow resistance. Dysregulation of CAV function could contribute to the pathological changes in ECM that are observed in glaucoma. PMID:25103269

  2. The Structure of the Trabecular Meshwork, Its Connections to the Ciliary Muscle, and the Effect of Pilocarpine on Outflow Facility in Mice

    PubMed Central

    Overby, Darryl R.; Bertrand, Jacques; Schicht, Martin; Paulsen, Friedrich; Stamer, W. Daniel; Lütjen-Drecoll, Elke

    2014-01-01

    Purpose. To determine the connections between the ciliary muscle (CM), trabecular meshwork (TM), and Schlemm's canal (SC) and their innervations that allows CM contraction (by pilocarpine) to influence conventional outflow in mice. Methods. Sequential sections and whole mounts of murine corneoscleral angles were stained for elastin, α-smooth muscle actin (αSMA), vesicular acetylcholine transporter (VAChT), neuronal nitric oxide synthase (nNOS), vasoactive intestinal peptide (VIP), and tyrosine hydroxylase (TH). Elastic (EL) fibers between the CM, TM, and SC were examined in ultrathin, sequential sections from different planes. The effect of pilocarpine (100 μM) on conventional outflow facility was measured by perfusion of enucleated mouse eyes. Results. The mouse TM contains a three-dimensional (3D) net of EL fibers connecting the inner wall of SC to the cornea anteriorly, the ciliary body (CB) internally and the choroid and CM posteriorly. The CM bifurcates near the posterior TM, extending outer tendons to the juxtacanalicular tissue and inner wall of SC and internal connections to the lamellated TM and CB. Ciliary muscle and lamellated TM cells stain with αSMA and are innervated by VAChT-containing nerve fibers, without TH, VIP, or nNOS. Pilocarpine doubled outflow facility. Conclusions. Mouse eyes resemble primate eyes not only by their well developed SC and TM, but also by their 3D EL net tethering together the TM and SC inner wall and by the tendinous insertion of the CM into this net. The increase in outflow facility following cholinergic stimulation in mice, as in primates, supports using mice for studies of aqueous humor dynamics and glaucoma. PMID:24833737

  3. Mechanical properties of human trabecular bone lamellae quantified by nanoindentation.

    PubMed

    Zysset, P K; Guo, X E; Hoffler, C E; Moore, K E; Goldstein, S A

    1998-12-01

    Improved preventive and therapeutic strategies for skeletal diseases such as osteoporosis rely on a better understanding of the mechanical properties of trabecular bone and their influence on cell mediated adaptation processes. The mechanical properties of trabecular bone are determined by composition as well as structural (trabecular architecture), microstructural (trabecular packets) and nanostructural (lamellae) organization. Density is the major predictor of the mechanical properties of trabecular structures and has been extended to the concept of fabric to include architectural anisotropy and improve even further the power of prediction. Recent advances in QCT and MRI technologies allow for precise assessment of 3D trabecular architecture and the mechanical consequences of structural changes can be increasingly well quantified by the means of computational methods. While single trabeculae have been tested using various techniques with contrasting results, little is known about the intrinsic mechanical properties of trabecular bone lamellae on which these computational methods rely. For instance, water and mineral content have a significant effect on the elastic, viscous, yield and postyield properties of bone tissue. In addition, collagen fiber orientation affects the mechanics of single remodeling units. Variations in composition and organization determined by age, accumulated damage or disease may therefore reduce the mechanical integrity of trabecular bone and deserve more attention. The aim of this work was to utilize a nanoindentation technique to quantify elastic modulus and hardness of human trabecular bone lamellae.

  4. [Human trabecular cells and apoptosis: in vitro evaluation of the effect of betaxolol with or without preservative].

    PubMed

    Hamard, P; Debbasch, C; Blondin, C; Brignole, F; Loison-Dayma, K; Warnet, J M; Baudouin, C

    2002-10-01

    Trabecular meshwork, which is involved in aqueous outflow resistance, is deeply modified in glaucoma patients, with a decrease in the trabecular cell number. Trabecular toxicity of antiglaucoma medications cannot be excluded. On a human cultured trabecular cell line, we investigated the potential proapoptotic effect of a beta-blocker with or without preservative, benzalkonium chloride (0.01% BAC), by flow cytometry and confocal microscopy. and A human immortalized trabecular cell line (HTM-5) obtained from a normal donor was cultured under normal conditions. Preserved 0.25% betaxolol suspension (betaxolol BAC +), unpreserved 0.25% betaxolol suspension, and 0.01% BAC were respectively added to the culture medium in a 1/10 or 1/100 dilution for 15 minutes. After a 24-hour recovery period in normal culture conditions, cell size and the expression of an apoptotic marker, Apo 2.7, were evaluated by flow cytometry and confocal microscopy. Untreated trabecular cells were used as control cells. Preserved and unpreserved betaxolol in a 1/10 dilution induced a significant decrease in trabecular cell size compared to controls. However, this cell size decrease was less pronounced than that induced by BAC at the same dilution. Similar results were obtained with betaxolol and BAC in a 1/100 dilution. Trabecular cell Apo 2.7 expression was significantly increased after treatment with betaxolol BAC + and BAC- in a 1/10 dilution compared to controls (36.8%, 28.1%, and 15.4%, respectively p<0.005). However, this proapoptotic activity was much less pronounced than that induced by BAC- at the same dilution (96.9%, p<10(-4)). Unpreserved betaxolol in a 1/100 dilution had no apoptotic activity on trabecular cells. Trabecular cell Apo 2.7 expression slightly increased with betaxolol BAC + at a 1/100 dilution (24.9%, p=0.04), while it was greatly increased with BAC at the same dilution (39.9%; p<10(-4)). In our model, unpreserved betaxolol at a low concentration displayed no proapoptotic

  5. Recent origin of low trabecular bone density in modern humans.

    PubMed

    Chirchir, Habiba; Kivell, Tracy L; Ruff, Christopher B; Hublin, Jean-Jacques; Carlson, Kristian J; Zipfel, Bernhard; Richmond, Brian G

    2015-01-13

    Humans are unique, compared with our closest living relatives (chimpanzees) and early fossil hominins, in having an enlarged body size and lower limb joint surfaces in combination with a relatively gracile skeleton (i.e., lower bone mass for our body size). Some analyses have observed that in at least a few anatomical regions modern humans today appear to have relatively low trabecular density, but little is known about how that density varies throughout the human skeleton and across species or how and when the present trabecular patterns emerged over the course of human evolution. Here, we test the hypotheses that (i) recent modern humans have low trabecular density throughout the upper and lower limbs compared with other primate taxa and (ii) the reduction in trabecular density first occurred in early Homo erectus, consistent with the shift toward a modern human locomotor anatomy, or more recently in concert with diaphyseal gracilization in Holocene humans. We used peripheral quantitative CT and microtomography to measure trabecular bone of limb epiphyses (long bone articular ends) in modern humans and chimpanzees and in fossil hominins attributed to Australopithecus africanus, Paranthropus robustus/early Homo from Swartkrans, Homo neanderthalensis, and early Homo sapiens. Results show that only recent modern humans have low trabecular density throughout the limb joints. Extinct hominins, including pre-Holocene Homo sapiens, retain the high levels seen in nonhuman primates. Thus, the low trabecular density of the recent modern human skeleton evolved late in our evolutionary history, potentially resulting from increased sedentism and reliance on technological and cultural innovations.

  6. Recent origin of low trabecular bone density in modern humans

    PubMed Central

    Chirchir, Habiba; Kivell, Tracy L.; Ruff, Christopher B.; Hublin, Jean-Jacques; Carlson, Kristian J.; Zipfel, Bernhard; Richmond, Brian G.

    2015-01-01

    Humans are unique, compared with our closest living relatives (chimpanzees) and early fossil hominins, in having an enlarged body size and lower limb joint surfaces in combination with a relatively gracile skeleton (i.e., lower bone mass for our body size). Some analyses have observed that in at least a few anatomical regions modern humans today appear to have relatively low trabecular density, but little is known about how that density varies throughout the human skeleton and across species or how and when the present trabecular patterns emerged over the course of human evolution. Here, we test the hypotheses that (i) recent modern humans have low trabecular density throughout the upper and lower limbs compared with other primate taxa and (ii) the reduction in trabecular density first occurred in early Homo erectus, consistent with the shift toward a modern human locomotor anatomy, or more recently in concert with diaphyseal gracilization in Holocene humans. We used peripheral quantitative CT and microtomography to measure trabecular bone of limb epiphyses (long bone articular ends) in modern humans and chimpanzees and in fossil hominins attributed to Australopithecus africanus, Paranthropus robustus/early Homo from Swartkrans, Homo neanderthalensis, and early Homo sapiens. Results show that only recent modern humans have low trabecular density throughout the limb joints. Extinct hominins, including pre-Holocene Homo sapiens, retain the high levels seen in nonhuman primates. Thus, the low trabecular density of the recent modern human skeleton evolved late in our evolutionary history, potentially resulting from increased sedentism and reliance on technological and cultural innovations. PMID:25535354

  7. Trabecular network arrangement within the human patella: how osteoarthritis remodels the 3D trabecular structure

    NASA Astrophysics Data System (ADS)

    Hoechel, Sebastian; Deyhle, Hans; Toranelli, Mireille; Müller-Gerbl, Magdalena

    2016-10-01

    Following the principles of "morphology reveals biomechanics", the anatomical structure of the cartilage-osseous interface and the supporting trabecular network show defined adaptation in their architectural properties to physiological loading. In case of a faulty relationship, the ability to support the load diminishes and the onset of osteoarthritis (OA) may arise and disturb the balanced formation and resorption processes. To describe and quantify the changes occurring, 10 human OA patellae were analysed concerning the architectural parameters of the trabecular network within the first five mms by the evaluation of 3Dmicro-CT datasets. The analysed OA-samples showed a strong irregularity for all trabecular parameters across the trabecular network, no regularity in parameter distribution was found. In general, we saw a decrease of material in the OA population as BV/TV, BS/TV, Tb.N and Tb.Th were decreased and the spacing increased. The development into depth showed a logarithmic dependency, which revealed the greatest difference for all parameters within the first mm in comparison to the physiologic samples. The differences decreased towards the 5th mm. The interpretation of the mathematic dependency leads to the conclusion that the main impact of OA is beneath the subchondral bone plate (SBP) and lessens with depth. Next to the clear difference in material, the architectural arrangement is more rod-like and isotropic just beneath the SBP in comparison to the plate-like and more anisotropic physiological arrangement.

  8. Gene expression profiling of TGFβ2- and/or BMP7-treated trabecular meshwork cells: Identification of Smad7 as a critical inhibitor of TGF-β2 signaling

    PubMed Central

    Fuchshofer, Rudolf; Stephan, Dietrich A.; Russell, Paul; Tamm, Ernst R.

    2009-01-01

    A distinct structural change in the trabecular meshwork (TM) of patients with primary open-angle glaucoma (POAH) is the increase in fibrillar extracellular matrix (ECM) in the juxtacanalicular region of the TM. Transforming growth factor (TGF)-β2 signaling may be involved, as TGF-β2 is significantly increased in the aqueous humor of patients with POAG. In cultured human TM cells, TGF-β2 causes an increase in ECM deposition, an effect that is blunted or prevented, if BMP7 is added in combination with TGF-β2. In order to know more about the signaling network that is induced in HTM cells treated with BMP7, TGF-β2 or the combination of both factors, we identified differentially regulated genes by microarray analysis, and confirmed selected genes by quantitative RT-PCR, Western blotting, or immunohistochemistry. We observed multiple effects of both TGF-β2 and BMP7 on the expression of a considerable number of genes involved in growth factor signaling, ECM structure and turnover, and modification of the cytoskeleton. Among the genes that were found to be regulated were CAPZA1, CDC42BPB, EFEMP1, FGF5, FSTL3, HBEGF, LTBP1, LTBP2, MATN2, NRP1, SERPINE1, SH3MD1, SMTN, SMAD7, TFPI2, TNFAIP6, and VEGF. Since SMAD7 encodes for Smad7, an inhibitory Smad that acts in a negative feedback loop to inhibit TGF-β activity, we silenced Smad7 mRNA in cultured human TM cells by a specific small interfering RNA. Silencing of its mRNA caused a substantial knock down of Smad7 in TM cells. Following combined BMP7/TGF-β2 treatment, the antagonizing effect of BMP7 on TGF-β2 induced CTGF expression was abolished. We conclude that Smad7 is the key molecular switch that inhibits TGF-β2 signaling, and mediates the blunting effects of BMP7 on TGF-β2 in TM cells. A therapeutic modulation of Smad7 might be a promising approach to influence ECM turnover in the TM and to treat POAG. PMID:19450457

  9. Purines in the eye: recent evidence for the physiological and pathological role of purines in the RPE, retinal neurons, astrocytes, Müller cells, lens, trabecular meshwork, cornea and lacrimal gland

    PubMed Central

    Sanderson, Julie; Dartt, Darlene A.; Trinkaus-Randall, Vickery; Pintor, Jesus; Civan, Mortimer M.; Delamere, Nicholas A.; Fletcher, Erica L.; Salt, Thomas E.; Grosche, Antje; Mitchell, Claire H.

    2014-01-01

    This review highlights recent findings that describe how purines modulate the physiological and pathophysiological responses of ocular tissues. For example, in lacrimal glands the cross-talk between P2X7 receptors and both M3 muscarinic receptors and α1D-adrenergic receptors can influence tear secretion. In the cornea, purines lead to post-translational modification of EGFR and structural proteins that participate in wound repair in the epithelium and influence the expression of matrix proteins in the stroma. Purines act at receptors on both the trabecular meshwork and ciliary epithelium to modulate intraocular pressure (IOP); ATP-release pathways of inflow and outflow cells differ, possibly permitting differential modulation of adenosine delivery. Modulators of trabecular meshwork cell ATP release include cell volume, stretch, extracellular Ca2+ concentration, oxidation state, actin remodeling and possibly endogenous cardiotonic steroids. In the lens, osmotic stress leads to ATP release following TRPV4 activation upstream of hemichannel opening. In the anterior eye, diadenosine polyphosphates such as Ap4A act at P2 receptors to modulate the rate and composition of tear secretion, impact corneal wound healing and lower IOP. The Gq11-coupled P2Y1-receptor contributes to volume control in Müller cells and thus the retina. P2X receptors are expressed in neurons in the inner and outer retina and contribute to visual processing as well as the demise of retinal ganglion cells. In RPE cells, the balance between extracellular ATP and adenosine may modulate lysosomal pH and the rate of lipofuscin formation. In optic nerve head astrocytes, mechanosensitive ATP release via pannexin hemichannels, coupled with stretch-dependent upregulation of pannexins, provides a mechanism for ATP signaling in chronic glaucoma. With so many receptors linked to divergent functions throughout the eye, ensuring the transmitters remain local and stimulation is restricted to the intended target

  10. Determinants of Microdamage in Elderly Human Vertebral Trabecular Bone

    PubMed Central

    Follet, Hélène; Farlay, Delphine; Bala, Yohann; Viguet-Carrin, Stéphanie; Gineyts, Evelyne; Burt-Pichat, Brigitte; Wegrzyn, Julien; Delmas, Pierre; Boivin, Georges; Chapurlat, Roland

    2013-01-01

    Previous studies have shown that microdamage accumulates in bone as a result of physiological loading and occurs naturally in human trabecular bone. The purpose of this study was to determine the factors associated with pre-existing microdamage in human vertebral trabecular bone, namely age, architecture, hardness, mineral and organic matrix. Trabecular bone cores were collected from human L2 vertebrae (n = 53) from donors 54–95 years of age (22 men and 30 women, 1 unknown) and previous cited parameters were evaluated. Collagen cross-link content (PYD, DPD, PEN and % of collagen) was measured on surrounding trabecular bone. We found that determinants of microdamage were mostly the age of donors, architecture, mineral characteristics and mature enzymatic cross-links. Moreover, linear microcracks were mostly associated with the bone matrix characteristics whereas diffuse damage was associated with architecture. We conclude that linear and diffuse types of microdamage seemed to have different determinants, with age being critical for both types. PMID:23457465

  11. Limited Trabecular Bone Density Heterogeneity in the Human Skeleton.

    PubMed

    Chirchir, Habiba

    2016-01-01

    There is evidence for variation in trabecular bone density and volume within an individual skeleton, albeit in a few anatomical sites, which is partly dependent on mechanical loading. However, little is known regarding the basic variation in trabecular bone density throughout the skeleton in healthy human adults. This is because research on bone density has been confined to a few skeletal elements, which can be readily measured using available imaging technology particularly in clinical settings. This study comprehensively investigates the distribution of trabecular bone density within the human skeleton in nine skeletal sites (femur, proximal and distal tibia, third metatarsal, humerus, ulna, radius, third metacarpal, and axis) in a sample of N = 20 individuals (11 males and 9 females). pQCT results showed that the proximal ulna (mean = 231.3 mg/cm(3)) and axis vertebra (mean = 234.3 mg/cm(3)) displayed significantly greater (p < 0.01) trabecular bone density than other elements, whereas there was no significant variation among the rest of the elements (p > 0.01). The homogeneity of the majority of elements suggests that these sites are potentially responsive to site-specific genetic factors. Secondly, the lack of correlation between elements (p > 0.05) suggests that density measurements of one anatomical region are not necessarily accurate measures of other anatomical regions.

  12. Limited Trabecular Bone Density Heterogeneity in the Human Skeleton

    PubMed Central

    Chirchir, Habiba

    2016-01-01

    There is evidence for variation in trabecular bone density and volume within an individual skeleton, albeit in a few anatomical sites, which is partly dependent on mechanical loading. However, little is known regarding the basic variation in trabecular bone density throughout the skeleton in healthy human adults. This is because research on bone density has been confined to a few skeletal elements, which can be readily measured using available imaging technology particularly in clinical settings. This study comprehensively investigates the distribution of trabecular bone density within the human skeleton in nine skeletal sites (femur, proximal and distal tibia, third metatarsal, humerus, ulna, radius, third metacarpal, and axis) in a sample of N = 20 individuals (11 males and 9 females). pQCT results showed that the proximal ulna (mean = 231.3 mg/cm3) and axis vertebra (mean = 234.3 mg/cm3) displayed significantly greater (p < 0.01) trabecular bone density than other elements, whereas there was no significant variation among the rest of the elements (p > 0.01). The homogeneity of the majority of elements suggests that these sites are potentially responsive to site-specific genetic factors. Secondly, the lack of correlation between elements (p > 0.05) suggests that density measurements of one anatomical region are not necessarily accurate measures of other anatomical regions. PMID:27148458

  13. Multi-axial mechanical properties of human trabecular bone.

    PubMed

    Rincón-Kohli, Liliana; Zysset, Philippe K

    2009-06-01

    In the context of osteoporosis, evaluation of bone fracture risk and improved design of epiphyseal bone implants rely on accurate knowledge of the mechanical properties of trabecular bone. A multi-axial loading chamber was designed, built and applied to explore the compressive multi-axial yield and strength properties of human trabecular bone from different anatomical locations. A thorough experimental protocol was elaborated for extraction of cylindrical bone samples, assessment of their morphology by micro-computed tomography and application of different mechanical tests: torsion, uni-axial traction, uni-axial compression and multi-axial compression. A total of 128 bone samples were processed through the protocol and subjected to one of the mechanical tests up to yield and failure. The elastic data were analyzed using a tensorial fabric-elasticity relationship, while the yield and strength data were analyzed with fabric-based, conewise generalized Hill criteria. For each loading mode and more importantly for the combined results, strong relationships were demonstrated between volume fraction, fabric and the elastic, yield and strength properties of human trabecular bone. Despite the reviewed limitations, the obtained results will help improve the simulation of the damage behavior of human bones and bone-implant systems using the finite element method.

  14. Purines in the eye: recent evidence for the physiological and pathological role of purines in the RPE, retinal neurons, astrocytes, Müller cells, lens, trabecular meshwork, cornea and lacrimal gland.

    PubMed

    Sanderson, Julie; Dartt, Darlene A; Trinkaus-Randall, Vickery; Pintor, Jesus; Civan, Mortimer M; Delamere, Nicholas A; Fletcher, Erica L; Salt, Thomas E; Grosche, Antje; Mitchell, Claire H

    2014-10-01

    This review highlights recent findings that describ how purines modulate the physiological and pathophysiological responses of ocular tissues. For example, in lacrimal glands the cross-talk between P2X7 receptors and both M3 muscarinic receptors and α1D-adrenergic receptors can influence tear secretion. In the cornea, purines lead to post-translational modification of EGFR and structural proteins that participate in wound repair in the epithelium and influence the expression of matrix proteins in the stroma. Purines act at receptors on both the trabecular meshwork and ciliary epithelium to modulate intraocular pressure (IOP); ATP-release pathways of inflow and outflow cells differ, possibly permitting differential modulation of adenosine delivery. Modulators of trabecular meshwork cell ATP release include cell volume, stretch, extracellular Ca(2+) concentration, oxidation state, actin remodeling and possibly endogenous cardiotonic steroids. In the lens, osmotic stress leads to ATP release following TRPV4 activation upstream of hemichannel opening. In the anterior eye, diadenosine polyphosphates such as Ap4A act at P2 receptors to modulate the rate and composition of tear secretion, impact corneal wound healing and lower IOP. The Gq11-coupled P2Y1-receptor contributes to volume control in Müller cells and thus the retina. P2X receptors are expressed in neurons in the inner and outer retina and contribute to visual processing as well as the demise of retinal ganglion cells. In RPE cells, the balance between extracellular ATP and adenosine may modulate lysosomal pH and the rate of lipofuscin formation. In optic nerve head astrocytes, mechanosensitive ATP release via pannexin hemichannels, coupled with stretch-dependent upregulation of pannexins, provides a mechanism for ATP signaling in chronic glaucoma. With so many receptors linked to divergent functions throughout the eye, ensuring the transmitters remain local and stimulation is restricted to the intended target

  15. Creep of trabecular bone from the human proximal tibia.

    PubMed

    Novitskaya, Ekaterina; Zin, Carolyn; Chang, Neil; Cory, Esther; Chen, Peter; D'Lima, Darryl; Sah, Robert L; McKittrick, Joanna

    2014-07-01

    Creep is the deformation that occurs under a prolonged, sustained load and can lead to permanent damage in bone. Creep in bone is a complex phenomenon and varies with type of loading and local mechanical properties. Human trabecular bone samples from proximal tibia were harvested from a 71-year old female cadaver with osteoporosis. The samples were initially subjected to one cycle load up to 1% strain to determine the creep load. Samples were then loaded in compression under a constant stress for 2h and immediately unloaded. All tests were conducted with the specimens soaked in phosphate buffered saline with proteinase inhibitors at 37 °C. Steady state creep rate and final creep strain were estimated from mechanical testing and compared with published data. The steady state creep rate correlated well with values obtained from bovine tibial and human vertebral trabecular bone, and was higher for lower density samples. Tissue architecture was analyzed by micro-computed tomography (μCT) both before and after creep testing to assess creep deformation and damage accumulated. Quantitative morphometric analysis indicated that creep induced changes in trabecular separation and the structural model index. A main mode of deformation was bending of trabeculae. Copyright © 2014 Elsevier B.V. All rights reserved.

  16. Creep of trabecular bone from the human proximal tibia

    PubMed Central

    Novitskaya, Ekaterina; Zin, Carolyn; Chang, Neil; Cory, Esther; Chen, Peter; D'Lima, Darryl; Sah, Robert L.; McKittrick, Joanna

    2014-01-01

    Creep is the deformation that occurs under a prolonged, sustained load and can lead to permanent damage in bone. Creep in bone is a complex phenomenon and varies with type of loading and local mechanical properties. Human trabecular bone samples from proximal tibia were harvested from a 71-year old female cadaver with osteoporosis. The samples were initially subjected to one cycle load up to 1% strain to determine the creep load. Samples were then loaded in compression under a constant stress for two hours and immediately unloaded. All tests were conducted with the specimens soaked in phosphate buffered saline with proteinase inhibitors at 37°C. Steady state creep rate and final creep strain were estimated from mechanical testing and compared with published data. The steady state creep rate correlated well with values obtained from bovine tibial and human vertebral trabecular bone, and was higher for lower density samples. Tissue architecture was analyzed by micro-computed tomography (μCT) both before and after creep testing to assess creep deformation and damage accumulated. Quantitative morphometric analysis indicated that creep induced changes in trabecular separation and the structural model index. A main mode of deformation was bending of trabeculae. PMID:24857486

  17. Elastic Anisotropy of Trabecular Bone in the Elderly Human Vertebra

    PubMed Central

    Unnikrishnan, Ginu U.; Gallagher, John A.; Hussein, Amira I.; Barest, Glenn D.; Morgan, Elise F.

    2015-01-01

    Knowledge of the nature of the elastic symmetry of trabecular bone is fundamental to the study of bone adaptation and failure. Previous studies have classified human vertebral trabecular bone as orthotropic or transversely isotropic but have typically obtained samples from only selected regions of the centrum. In this study, the elastic symmetry of human vertebral trabecular bone was characterized using microfinite element (μFE) analyses performed on 1019 cubic regions of side length equal to 5 mm, obtained via thorough sampling of the centrums of 18 human L1 vertebrae (age = 81.17 ± 7.7 yr; eight males and ten females). An optimization procedure was used to find the closest orthotropic representation of the resulting stiffness tensor for each cube. The orthotropic elastic constants and orientation of the principal elastic axes were then recorded for each cube and were compared to the constants predicted from Cowin's fabric-based constitutive model (Cowin, 1985, “The Relationship Between the Elasticity Tensor and the Fabric Tensor,” Mech. Mater., 4(2), pp. 137–147.) and the orientation of the principal axes of the fabric tensor, respectively. Deviations from orthotropy were quantified by the “orthotropic error” (van Rietbergen et al., 1996, “Direct Mechanics Assessment of Elastic Symmetries and Properties of Trabecular Bone Architecture,” J. Biomech., 29(12), pp. 1653–1657), and deviations from transverse isotropy were determined by statistical comparison of the secondary and tertiary elastic moduli. The orthotropic error was greater than 50% for nearly half of the cubes, and the secondary and tertiary moduli differed from one another (p < 0.0001). Both the orthotropic error and the difference between secondary and tertiary moduli decreased with increasing bone volume fraction (BV/TV; p ≤ 0.007). Considering only the cubes with an orthotropic error less than 50%, only moderate correlations were observed between the fabric

  18. Elastic Anisotropy of Trabecular Bone in the Elderly Human Vertebra.

    PubMed

    Unnikrishnan, Ginu U; Gallagher, John A; Hussein, Amira I; Barest, Glenn D; Morgan, Elise F

    2015-11-01

    Knowledge of the nature of the elastic symmetry of trabecular bone is fundamental to the study of bone adaptation and failure. Previous studies have classified human vertebral trabecular bone as orthotropic or transversely isotropic but have typically obtained samples from only selected regions of the centrum. In this study, the elastic symmetry of human vertebral trabecular bone was characterized using microfinite element (μFE) analyses performed on 1019 cubic regions of side length equal to 5 mm, obtained via thorough sampling of the centrums of 18 human L1 vertebrae (age = 81.17 ± 7.7 yr; eight males and ten females). An optimization procedure was used to find the closest orthotropic representation of the resulting stiffness tensor for each cube. The orthotropic elastic constants and orientation of the principal elastic axes were then recorded for each cube and were compared to the constants predicted from Cowin's fabric-based constitutive model (Cowin, 1985, "The Relationship Between the Elasticity Tensor and the Fabric Tensor," Mech. Mater., 4(2), pp. 137-147.) and the orientation of the principal axes of the fabric tensor, respectively. Deviations from orthotropy were quantified by the "orthotropic error" (van Rietbergen et al., 1996, "Direct Mechanics Assessment of Elastic Symmetries and Properties of Trabecular Bone Architecture," J. Biomech., 29(12), pp. 1653-1657), and deviations from transverse isotropy were determined by statistical comparison of the secondary and tertiary elastic moduli. The orthotropic error was greater than 50% for nearly half of the cubes, and the secondary and tertiary moduli differed from one another (p < 0.0001). Both the orthotropic error and the difference between secondary and tertiary moduli decreased with increasing bone volume fraction (BV/TV; p ≤ 0.007). Considering only the cubes with an orthotropic error less than 50%, only moderate correlations were observed between the fabric-based and the

  19. Topology optimization of trabecular bone in the human spine

    NASA Astrophysics Data System (ADS)

    Elbanna, Ahmed

    2015-03-01

    It is widely believed in the realm of biology that the trabecular structure of long bones self-optimizes in response to mechanical loads, in accordance with Wolff's law. Here, we examine this idea by applying techniques from topology optimization the human spine. We consider different domain geometries as well as different load cases to account for the various loading conditions and changes in shape that take place within the spine during day-to-day activities and over the years. We show that the classical approach of minimizing compliance subject to a volume constraint does not yield a sponge-like architecture but results in only vertical trabeculae. Additional constraints/objective functions have to be considered simultaneously. We show that more realistic trabecular geometries may be produced by taking into consideration the function of trabecular bone as a reservoir for minerals and bone marrow production. By maximizing the surface area of the generated voids while minimizing the total volume of the trabeculae subject to a constraint on their buckling strength, we recover the sponge-like structure. Our results shed light on the optimizing conditions for bone structure beyond Wolff's law and provide guidelines for biomimetic material design.

  20. Complete Volumetric Decomposition of Individual Trabecular Plates and Rods and Its Morphological Correlations With Anisotropic Elastic Moduli in Human Trabecular Bone

    PubMed Central

    Liu, X Sherry; Sajda, Paul; Saha, Punam K; Wehrli, Felix W; Bevill, Grant; Keaveny, Tony M; Guo, X Edward

    2008-01-01

    Trabecular plates and rods are important microarchitectural features in determining mechanical properties of trabecular bone. A complete volumetric decomposition of individual trabecular plates and rods was used to assess the orientation and morphology of 71 human trabecular bone samples. The ITS-based morphological analyses better characterize microarchitecture and help predict anisotropic mechanical properties of trabecular bone. Introduction Standard morphological analyses of trabecular architecture lack explicit segmentations of individual trabecular plates and rods. In this study, a complete volumetric decomposition technique was developed to segment trabecular bone microstructure into individual plates and rods. Contributions of trabecular type–associated morphological parameters to the anisotropic elastic moduli of trabecular bone were studied. Materials and Methods Seventy-one human trabecular bone samples from the femoral neck (FN), tibia, and vertebral body (VB) were imaged using μCT or serial milling. Complete volumetric decomposition was applied to segment trabecular bone microstructure into individual plates and rods. The orientation of each individual trabecula was determined, and the axial bone volume fractions (aBV/TV), axially aligned bone volume fraction along each orthotropic axis, were correlated with the elastic moduli. The microstructural type–associated morphological parameters were derived and compared with standard morphological parameters. Their contributions to the anisotropic elastic moduli, calculated by finite element analysis (FEA), were evaluated and compared. Results The distribution of trabecular orientation suggested that longitudinal plates and transverse rods dominate at all three anatomic sites. aBV/TV along each axis, in general, showed a better correlation with the axial elastic modulus (r 2 = 0.95∼0.99) compared with BV/TV (r 2 = 0.93∼0.94). The plate-associated morphological parameters generally showed higher

  1. Trabecular shear stress amplification and variability in human vertebral cancellous bone: relationship with age, gender, spine level and trabecular architecture.

    PubMed

    Yeni, Yener N; Zelman, Eric A; Divine, George W; Kim, Do-Gyoon; Fyhrie, David P

    2008-03-01

    Trabecular shear stress magnitude and variability have been implicated in damage formation and reduced bone strength associated with bone loss for human vertebral bone. This study addresses the issue of whether these parameters change with age, gender or anatomical location, and if so whether this is independent of bone mass. Additionally, 3D-stereology-based architectural parameters were examined in order to establish the relationship between stress distribution parameters and trabecular architecture. Eighty cancellous bone specimens were cored from the anterior region of thoracic 12 and donor-matched lumbar 1 vertebrae from a randomly selected population of 40 cadavers. The specimens were scanned at 21-microm voxel size using microcomputed tomography (microCT) and reconstructed at 50microm. Bone volume fraction (BV/TV), trabecular number (Tb.N), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp), bone surface-to-volume ratio (BS/BV), degree of anisotropy (MIL1/MIL3), and connectivity density (-#Euler/Vol) were calculated directly from micro-CT images. Large-scale finite element models were constructed and superoinferior compressive loading was simulated. Apparent cancellous modulus (EFEM) was calculated. The average trabecular von Mises stress generated per uniaxial apparent stress (sigma (-)VM / sigmaapp) and coefficient of variation of trabecular von Mises stresses (COV) were calculated as measures of the magnitude and variability of shear stresses in the trabeculae. Mixed-models and regression were used for analysis. sigma(-)VM / sigmaapp and COV were not different between genders and vertebrae. Both sigma(-)VM / sigmaapp and COV increased with age accompanied by a decrease in BV/TV. Strong relationship of sigma(-)VM / sigmaapp with BV/TV was found whereas COV was strongly related to EFEM/(BV/TV). The results from T12 and L1 were not different and highly correlated with each other. The relationship of sigma(-)VM / sigmaapp with COV was observed to be

  2. Visualization of Neutrophil Extracellular Traps and Fibrin Meshwork in Human Fibrinopurulent Inflammatory Lesions: II. Ultrastructural Study

    PubMed Central

    Onouchi, Takanori; Shiogama, Kazuya; Matsui, Takahiro; Mizutani, Yasuyoshi; Sakurai, Kouhei; Inada, Ken-ichi; Tsutsumi, Yutaka

    2016-01-01

    Neutrophil extracellular traps (NETs) represent an extracellular, spider’s web-like structure resulting from cell death of neutrophils. NETs play an important role in innate immunity against microbial infection, but their roles in human pathological processes remain largely unknown. NETs and fibrin meshwork both showing fibrillar structures are observed at the site of fibrinopurulent inflammation, as described in our sister paper [Acta Histochem. Cytochem. 49; 109–116, 2016]. In the present study, immunoelectron microscopic study was performed for visualizing NETs and fibrin fibrils (thick fibrils in our tongue) in formalin-fixed, paraffin-embedded sections of autopsied lung tissue of legionnaire’s pneumonia. Lactoferrin and fibrinogen gamma chain were utilized as markers of NETs and fibrin, respectively. Analysis of immuno-scanning electron microscopy indicated that NETs constructed thin fibrils and granular materials were attached onto the NETs fibrils. The smooth-surfaced fibrin fibrils were much thicker than the NETs fibrils. Pre-embedding immunoelectron microscopy demonstrated that lactoferrin immunoreactivities were visible as dots on the fibrils, whereas fibrinogen gamma chain immunoreactivities were homogeneously observed throughout the fibrils. Usefulness of immunoelectron microscopic analysis of NETs and fibrin fibrils should be emphasized. PMID:27682015

  3. Patterns of activity adaptation in humeral trabecular bone in Neolithic humans and present-day people.

    PubMed

    Scherf, Heike; Wahl, Joachim; Hublin, Jean-Jacques; Harvati, Katerina

    2016-01-01

    The annual turnover rate of trabecular bone by far exceeds that of cortical bone and, therefore, is very sensitive to its daily loading regime. Here we test the hypothesis that the study of the trabecular bone architecture of the human humerus is able to differentiate between different habitual manual activities. For this purpose, we compared the trabecular architecture of the humeral head in a Neolithic population to that of a sample of contemporary Europeans using micro-computed tomography (microCT). We defined in each specimen a spherical volume of interest with a diameter of 57.5 ± 2.5% of the maximal diameter of the humeral head to metrically analyze the bulk of humeral head trabecular architecture. We subsequently quantified the trabecular architectures in the VOIs, measuring seven standard 3D-morphometric parameters, and used univariate and multivariate statistical analyses for comparisons within and between populations. Univariate statistical analysis showed significant differences in a combination of 3D-morphometric parameters. A principal components analysis of the 3D-morphometrics of the trabecular architectures separated the Neolithic from the contemporary samples on the basis of differences in their gross trabecular architecture, including differences in the bone volume fraction (BV/TV), the number of trabeculae per unit length (Tb N), and the distance between trabeculae (Tb Sp). We interpret the significant differences found in the humeral trabecular bone of the Neolithic and the contemporary group as likely reflecting the distinct manual working routines. The trabecular bone configuration in the Neolithic sample shows presumably functional signatures of prehistoric subsistence techniques and activity levels. © 2015 Wiley Periodicals, Inc.

  4. Finite element dependence of stress evaluation for human trabecular bone.

    PubMed

    Depalle, B; Chapurlat, R; Walter-Le-Berre, H; Bou-Saïd, B; Follet, H

    2013-02-01

    Numerical simulation using finite element models (FEM) has become more and more suitable to estimate the mechanical properties of trabecular bone. The size and kind of elements involved in the models, however, may influence the results. The purpose of this study is to analyze the influence of hexahedral elements formulation on the evaluation of mechanical stress applied to trabeculae bone during a compression test simulation. Trabecular bone cores were extracted from 18 L2 vertebrae (12 women and 6 men, mean age: 76 ± 11, BV/TV=7.5 ± 1.9%). Samples were micro-CT scanned at 20 μm isotropic voxel size. Micro-CT images have been sub-sampled (20, 40 and 80 μm) to create 5.6 mm cubic FEM. For each sample, a compression test FEM has been created, using either 8-nodes linear hexahedral elements with full or reduced integration or 20-nodes quadratic hexahedral elements fully integrated, resulting in nine models per samples. Bone mechanical properties have been assumed isotropic, homogenous and to follow a linear elastic behavior law (Young modulus: 8 GPa, Poisson ratio: 0.3). Despite micro-architecture modifications (loss of connectivity, trabeculae thickening) due to voxel size increase, apparent mechanical properties calculated with low resolution models are significantly correlated with high resolution results, no matter the element formulation. However, stress distributions are more sensitive to both resolution and element formulation modifications. With linear elements, increasing voxel size leads to an alteration of stress concentration areas due to stiffening errors. On the opposite, the use of reduced integration induces severe smoothing and underestimation of stress fields resulting in stress raisers loss. Notwithstanding their high computational cost, quadratic elements are most appropriate for stress prediction in low resolution trabecular bone FEM. These observations are dependent on trabecular bone micro-architecture, and are more significant for low

  5. Cortical and trabecular load sharing in the human femoral neck.

    PubMed

    Nawathe, Shashank; Nguyen, Bich Phuong; Barzanian, Nasim; Akhlaghpour, Hosna; Bouxsein, Mary L; Keaveny, Tony M

    2015-03-18

    The relative role of the cortical vs trabecular bone in the load-carrying capacity of the proximal femur-a fundamental issue in both basic-science and clinical biomechanics-remains unclear. To gain insight into this issue, we performed micro-CT-based, linear elastic finite element analysis (61.5-micron-sized elements; ~280 million elements per model) on 18 proximal femurs (5M, 13F, ages 61-93 years) to quantify the fraction of frontal-plane bending moment shared by the cortical vs trabecular bone in the femoral neck, as well as the associated spatial distributions of stress. Analyses were performed separately for a sideways fall and stance loading. For both loading modes and across all 18 bones, we found consistent patterns of load-sharing in the neck: most proximally, the trabecular bone took most of the load; moving distally, the cortical bone took increasingly more of the load; and more distally, there was a region of uniform load-sharing, the cortical bone taking the majority of the load. This distal region of uniform load-sharing extended more for fall than stance loading (77 ± 8% vs 51 ± 6% of the neck length for fall vs. stance; mean ± SD) but the fraction of total load taken by the cortical bone in that region was greater for stance loading (88 ± 5% vs. 64 ± 9% for stance vs. fall). Locally, maximum stress levels occurred in the cortical bone distally, but in the trabecular bone proximally. Although the distal cortex showed qualitative stress distributions consistent with the behavior of an Euler-type beam, quantitatively beam theory did not apply. We conclude that consistent and well-delineated regions of uniform load-sharing and load-transfer between the cortical and trabecular bone exist within the femoral neck, the details of which depend on the external loading conditions.

  6. A comparative study of the trabecular bony architecture of the talus in humans, non-human primates, and Australopithecus.

    PubMed

    DeSilva, Jeremy M; Devlin, Maureen J

    2012-09-01

    This study tested the hypothesis that talar trabecular microarchitecture reflects the loading patterns in the primate ankle joint, to determine whether talar trabecular morphology might be useful for inferring locomotor behavior in fossil hominins. Trabecular microarchitecture was quantified in the anteromedial, anterolateral, posteromedial, and posterolateral quadrants of the talar body in humans and non-human primates using micro-computed tomography. Trabecular bone parameters, including bone volume fraction, trabecular number and thickness, and degree of anisotropy differed between primates, but not in a manner entirely consistent with hypotheses derived from locomotor kinematics. Humans have highly organized trabecular struts across the entirety of the talus, consistent with the compressive loads incurred during bipedal walking. Chimpanzees possess a high bone volume fraction, consisting of plate-like trabecular struts. Orangutan tali are filled with a high number of thin, connected trabeculae, particularly in the anterior portion of the talus. Gorillas and baboons have strikingly similar internal architecture of the talus. Intraspecific analyses revealed no regional differences in trabecular architecture unique to bipedal humans. Of the 22 statistically significant regional differences in the human talus, all can also be found in other primates. Trabecular thickness, number, spacing, and connectivity density had the same regional relationship in the talus of humans, chimpanzees, gorillas, and baboons, suggesting a deeply conserved architecture in the primate talus. Australopithecus tali are human-like in most respects, differing most notably in having more oriented struts in the posteromedial quadrant of the body compared with the posterolateral quadrant. Though this result could mean that australopiths loaded their ankles in a unique manner during bipedal gait, the regional variation in degree of anisotropy was similar in humans, chimpanzees, and gorillas

  7. Computational study of Wolff's law with trabecular architecture in the human proximal femur using topology optimization.

    PubMed

    Jang, In Gwun; Kim, Il Yong

    2008-08-07

    In the field of bone adaptation, it is believed that the morphology of bone is affected by its mechanical loads, and bone has self-optimizing capability; this phenomenon is well known as Wolff's law of the transformation of bone. In this paper, we simulated trabecular bone adaptation in the human proximal femur using topology optimization and quantitatively investigated the validity of Wolff's law. Topology optimization iteratively distributes material in a design domain producing optimal layout or configuration, and it has been widely and successfully used in many engineering fields. We used a two-dimensional micro-FE model with 50 microm pixel resolution to represent the full trabecular architecture in the proximal femur, and performed topology optimization to study the trabecular morphological changes under three loading cases in daily activities. The simulation results were compared to the actual trabecular architecture in previous experimental studies. We discovered that there are strong similarities in trabecular patterns between the computational results and observed data in the literature. The results showed that the strain energy distribution of the trabecular architecture became more uniform during the optimization; from the viewpoint of structural topology optimization, this bone morphology may be considered as an optimal structure. We also showed that the non-orthogonal intersections were constructed to support daily activity loadings in the sense of optimization, as opposed to Wolff's drawing.

  8. Basal nitric oxide production is enhanced by hydraulic pressure in cultured human trabecular cells

    PubMed Central

    Matsuo, T.

    2000-01-01

    BACKGROUND/AIMS—Nitric oxide donors reduce intraocular pressure. Human trabecular cells in culture were examined for their nitric oxide production in response to hydraulic pressure.
METHODS—Human trabecular cells were cultured from trabeculum tissue fragments excised during trabeculectomy and exposed to hydraulic pressure change in a culture flask connected to a glass syringe. The pressure was exerted by automatic infusion of the piston of the syringe and monitored by a pressure gauge. The intracellular nitric oxide level was measured in real time with a nitric oxide binding fluorescent dye, diaminofluorescein-2.
RESULTS—Intracellular nitric oxide levels in cultured trabecular cells showed spontaneous fluctuation during 400 seconds of observation. Peak levels of intracellular nitric oxide were significantly higher at hydraulic pressure of 30, 40, and 50 mm Hg, compared with 0 and 25 mm Hg (p<0.0001, one way ANOVA, and p<0.05, Tukey-Kramer test). The fluctuation was completely abolished by the presence of N-methyl-L-arginine (L-NMMA), a nitric oxide synthase inhibitor. The cultured trabecular cells were shown by immunohistochemistry to express brain nitric oxide synthase (bNOS).
CONCLUSION—Higher levels of hydraulic pressure enhanced basal production of nitric oxide in human trabecular cells. Nitric oxide would be a physiological mediator in the regulation of intraocular pressure.

 PMID:10837391

  9. Fourier analysis methodology of trabecular orientation measurement in the human tibial epiphysis

    PubMed Central

    HERRERA, M.; PONS, A. M.; ILLUECA, C.; ERADES, D.

    2001-01-01

    Methods to quantify trabecular orientation are crucial in order to assess the exact trajectory of trabeculae in anatomical and histological sections. Specific methods for evaluating trabecular orientation include the ‘point counting’ technique (Whitehouse, 1974), manual tracing of trabecular outlines on a digitising board (Whitehouse, 1980), textural analysis (Veenland et al. 1998), graphic representation of vectors (Shimizu et al. 1993; Kamibayashi et al. 1995) and both mathematical (Geraets, 1998) and fractal analysis (Millard et al. 1998). Optical and computer-assisted methods to detect trabecular orientation of bone using the Fourier transform were introduced by Oxnard (1982) later refined by Kuo & Carter (1991) (see also Oxnard, 1993, for a review), in the analysis of planar sections of vertebral bodies as well as in planar radiographs of cancellous bone in the distal radius (Wigderowitz et al. 1997). At present no studies have applied this technique to 2-D images or to the study of dried bones. We report a universal computer-automated technique for assessing the preferential orientation of the tibial subarticular trabeculae based on Fourier analysis, emphasis being placed on the search for improvements in accuracy over previous methods and applied to large stereoscopic (2-D) fields of anatomical sections of dried human tibiae. Previous studies on the trajectorial architecture of the tibial epiphysis (Takechi, 1977; Maquet, 1984) and research data about trabecular orientation (Kamibayashi et al. 1995) have not employed Fourier analysis. PMID:11273050

  10. Pore cross-section area on predicting elastic properties of trabecular bovine bone for human implants.

    PubMed

    Maciel, Alfredo; Presbítero, Gerardo; Piña, Cristina; del Pilar Gutiérrez, María; Guzmán, José; Munguía, Nadia

    2015-01-01

    A clear understanding of the dependence of mechanical properties of bone remains a task not fully achieved. In order to estimate the mechanical properties in bones for implants, pore cross-section area, calcium content, and apparent density were measured in trabecular bone samples for human implants. Samples of fresh and defatted bone tissue, extracted from one year old bovines, were cut in longitudinal and transversal orientation of the trabeculae. Pore cross-section area was measured with an image analyzer. Compression tests were conducted into rectangular prisms. Elastic modulus presents a linear tendency as a function of pore cross-section area, calcium content and apparent density regardless of the trabecular orientation. The best variable to estimate elastic modulus of trabecular bone for implants was pore cross-section area, and affirmations to consider Nukbone process appropriated for marrow extraction in trabecular bone for implantation purposes are proposed, according to bone mechanical properties. Considering stress-strain curves, defatted bone is stiffer than fresh bone. Number of pores against pore cross-section area present an exponential decay, consistent for all the samples. These graphs also are useful to predict elastic properties of trabecular samples of young bovines for implants.

  11. Trabecular microstructure of the human lunate in Kienbock's disease.

    PubMed

    Han, K-J; Kim, J Y; Chung, N-S; Lee, H R; Lee, Y S

    2012-05-01

    The trabecular microstructure of normal lunates and lunates with Kienböck's disease was investigated using micro-computed tomography (micro-CT). Five lunates with advanced Kienböck's disease were obtained during lunate excision and scaphocapitate fusion, and five control lunates were from embalmed cadavers. Microstructural morphometric parameters were measured using micro-CT images. Trabeculations of lunates with Kienböck's disease were 2.67 times denser and 1.84 times thicker than those of normal lunates. Furthermore, bone surface areas were 1.43 times greater and bone volume 2.67 times greater, and structural model indices were significantly lower in lunates with Kienböck's disease. The study estimated that high mechanical stress would be applied to lunates with Kienböck's disease, and suggests that new bone formation and collapse may play important roles in the microstructural changes in the lunate with advanced Kienböck's disease.

  12. Aqueous Angiography-Mediated Guidance of Trabecular Bypass Improves Angiographic Outflow in Human Enucleated Eyes.

    PubMed

    Huang, Alex S; Saraswathy, Sindhu; Dastiridou, Anna; Begian, Alan; Mohindroo, Chirayu; Tan, James C H; Francis, Brian A; Hinton, David R; Weinreb, Robert N

    2016-09-01

    To assess the ability of trabecular micro-bypass stents to improve aqueous humor outflow (AHO) in regions initially devoid of AHO as assessed by aqueous angiography. Enucleated human eyes (14 total from 7 males and 3 females [ages 52-84]) were obtained from an eye bank within 48 hours of death. Eyes were oriented by inferior oblique insertion, and aqueous angiography was performed with indocyanine green (ICG; 0.4%) or fluorescein (2.5%) at 10 mm Hg. With an angiographer, infrared and fluorescent images were acquired. Concurrent anterior segment optical coherence tomography (OCT) was performed, and fixable fluorescent dextrans were introduced into the eye for histologic analysis of angiographically positive and negative areas. Experimentally, some eyes (n = 11) first received ICG aqueous angiography to determine angiographic patterns. These eyes then underwent trabecular micro-bypass sham or stent placement in regions initially devoid of angiographic signal. This was followed by fluorescein aqueous angiography to query the effects. Aqueous angiography in human eyes yielded high-quality images with segmental patterns. Distally, angiographically positive but not negative areas demonstrated intrascleral lumens on OCT images. Aqueous angiography with fluorescent dextrans led to their trapping in AHO pathways. Trabecular bypass but not sham in regions initially devoid of ICG aqueous angiography led to increased aqueous angiography as assessed by fluorescein (P = 0.043). Using sequential aqueous angiography in an enucleated human eye model system, regions initially without angiographic flow or signal could be recruited for AHO using a trabecular bypass stent.

  13. Three-dimensional microstructure of human alveolar trabecular bone: a micro-computed tomography study

    PubMed Central

    2017-01-01

    Purpose The microstructural characteristics of trabecular bone were identified using micro-computed tomography (micro-CT), in order to develop a potential strategy for implant surface improvement to facilitate osseointegration. Methods Alveolar bone specimens from the cadavers of 30 humans were scanned by high-resolution micro-CT and reconstructed. Volumes of interest chosen within the jaw were classified according to Hounsfield units into 4 bone quality categories. Several structural parameters were measured and statistically analyzed. Results Alveolar bone specimens with D1 bone quality had significantly higher values for all structural parameters than the other bone quality categories, except for trabecular thickness (Tb.Th). The percentage of bone volume, trabecular separation (Tb.Sp), and trabecular number (Tb.N) varied significantly among bone quality categories. Tb.Sp varied markedly across the bone quality categories (D1: 0.59±0.22 mm, D4: 1.20±0.48 mm), whereas Tb.Th had similar values (D1: 0.30±0.08 mm, D4: 0.22±0.05 mm). Conclusions Bone quality depended on Tb.Sp and number—that is, endosteal space architecture—rather than bone surface and Tb.Th. Regardless of bone quality, Tb.Th showed little variation. These factors should be taken into account when developing individualized implant surface topographies. PMID:28261521

  14. The role of fabric in the large strain compressive behavior of human trabecular bone.

    PubMed

    Charlebois, Mathieu; Pretterklieber, Michael; Zysset, Philippe K

    2010-12-01

    Osteoporosis-related vertebral body fractures involve large compressive strains of trabecular bone. The small strain mechanical properties of the trabecular bone such as the elastic modulus or ultimate strength can be estimated using the volume fraction and a second order fabric tensor, but it remains unclear if similar estimations may be extended to large strain properties. Accordingly, the aim of this work is to identify the role of volume fraction and especially fabric in the large strain compressive behavior of human trabecular bone from various anatomical locations. Trabecular bone biopsies were extracted from human T12 vertebrae (n=31), distal radii (n=43), femoral head (n=44), and calcanei (n=30), scanned using microcomputed tomography to quantify bone volume fraction (BV/TV) and the fabric tensor (M), and tested either in unconfined or confined compression up to very large strains (∼70%). The mechanical parameters of the resulting stress-strain curves were analyzed using regression models to examine the respective influence of BV/TV and fabric eigenvalues. The compressive stress-strain curves demonstrated linear elasticity, yielding with hardening up to an ultimate stress, softening toward a minimum stress, and a steady rehardening followed by a rapid densification. For the pooled experiments, the average minimum stress was 1.89 ± 1.77 MPa, while the corresponding mean strain was 7.15 ± 1.84%. The minimum stress showed a weaker dependence with fabric as the elastic modulus or ultimate strength. For the confined experiments, the stress at a logarithmic strain of 1.2 was 8.08 ± 7.91 MPa, and the dissipated energy density was 5.67 ± 4.42 MPa. The latter variable was strongly related to the volume fraction (R(2)=0.83) but the correlation improved only marginally with the inclusion of fabric (R(2)=0.84). The influence of fabric on the mechanical properties of human trabecular bone decreases with increasing strain, while the role of volume fraction remains

  15. Aqueous Angiography–Mediated Guidance of Trabecular Bypass Improves Angiographic Outflow in Human Enucleated Eyes

    PubMed Central

    Huang, Alex S.; Saraswathy, Sindhu; Dastiridou, Anna; Begian, Alan; Mohindroo, Chirayu; Tan, James C. H.; Francis, Brian A.; Hinton, David R.; Weinreb, Robert N.

    2016-01-01

    Purpose To assess the ability of trabecular micro-bypass stents to improve aqueous humor outflow (AHO) in regions initially devoid of AHO as assessed by aqueous angiography. Methods Enucleated human eyes (14 total from 7 males and 3 females [ages 52–84]) were obtained from an eye bank within 48 hours of death. Eyes were oriented by inferior oblique insertion, and aqueous angiography was performed with indocyanine green (ICG; 0.4%) or fluorescein (2.5%) at 10 mm Hg. With an angiographer, infrared and fluorescent images were acquired. Concurrent anterior segment optical coherence tomography (OCT) was performed, and fixable fluorescent dextrans were introduced into the eye for histologic analysis of angiographically positive and negative areas. Experimentally, some eyes (n = 11) first received ICG aqueous angiography to determine angiographic patterns. These eyes then underwent trabecular micro-bypass sham or stent placement in regions initially devoid of angiographic signal. This was followed by fluorescein aqueous angiography to query the effects. Results Aqueous angiography in human eyes yielded high-quality images with segmental patterns. Distally, angiographically positive but not negative areas demonstrated intrascleral lumens on OCT images. Aqueous angiography with fluorescent dextrans led to their trapping in AHO pathways. Trabecular bypass but not sham in regions initially devoid of ICG aqueous angiography led to increased aqueous angiography as assessed by fluorescein (P = 0.043). Conclusions Using sequential aqueous angiography in an enucleated human eye model system, regions initially without angiographic flow or signal could be recruited for AHO using a trabecular bypass stent. PMID:27588614

  16. Biomarkers and special features of oxidative stress in the anterior segment of the eye linked to lens cataract and the trabecular meshwork injury in primary open-angle glaucoma: challenges of dual combination therapy with N-acetylcarnosine lubricant eye drops and oral formulation of nonhydrolyzed carnosine.

    PubMed

    Babizhayev, Mark A

    2012-02-01

    The implication of oxidative stress associated with increased oxidant production in mammalian and human cells characterized by the release of free radicals, resulting in cellular degeneration, is involved in many ocular diseases, such as age-related macular degeneration, retinopathy of prematurity, retinal light damage, primary open-angle glaucoma (POAG), and cataract. Cataract is the leading cause of blindness, accounting for 50% of blindness worldwide. Glaucoma, the leading cause of irreversible blindness, is considered as a progressive optic neuropathy often caused by elevated intraocular pressure (IOP) consequent to abnormally high resistance to aqueous humor (AH) drainage via the trabecular meshwork (TM) and Schlemm's canal. Morphological and biochemical analyses of the TM of patients with POAG revealed the loss of cells, increased accumulation of extracellular matrix proteins (ECM), changes in the cytoskeleton, cellular senescence, and the process of subclinical inflammation. The TM is the target tissue of glaucoma in the anterior chamber, and the development and progression of glaucoma are accompanied by the accumulation of oxidative damage in this tissue. The separate studies were conducted to comparatively evaluate the sensitivity to oxidative stress and lipid peroxidation (LPO) of anterior chamber tissues including TM. Accumulation of the primary, secondary, and end products of LPO (diene and triene conjugates, Schiff's bases) was noted in the studied extracts. Significant differences in the levels of all mentioned LPO products in comparison with the control were observed. The data may be considered as an evidence of LPO participation in the destruction of the trabecule and Schlemm's canal in POAG. Treatment of TM cells with oxidative stress induced POAG-typical changes such as ECM accumulation, cell death, disarrangement of the cytoskeleton, advanced senescence, and the release of inflammatory markers. By pretreatment with antioxidants, prostaglandin

  17. Trabecular Evidence for a Human-Like Gait in Australopithecus africanus

    PubMed Central

    Raichlen, David; Pontzer, Herman; Warrener, Anna G.; Hublin, Jean-Jacques

    2013-01-01

    Although the earliest known hominins were apparently upright bipeds, there has been mixed evidence whether particular species of hominins including those in the genus Australopithecus walked with relatively extended hips, knees and ankles like modern humans, or with more flexed lower limb joints like apes when bipedal. Here we demonstrate in chimpanzees and humans a highly predictable and sensitive relationship between the orientation of the ankle joint during loading and the principal orientation of trabecular bone struts in the distal tibia that function to withstand compressive forces within the joint. Analyses of the orientation of these struts using microCT scans in a sample of fossil tibiae from the site of Sterkfontein, of which two are assigned to Australopithecus africanus, indicate that these hominins primarily loaded their ankles in a relatively extended posture like modern humans and unlike chimpanzees. In other respects, however, trabecular properties in Au africanus are distinctive, with values that mostly fall between those of chimpanzees and humans. These results indicate that Au. africanus, like Homo, walked with an efficient, extended lower limb. PMID:24223719

  18. Trabecular evidence for a human-like gait in Australopithecus africanus.

    PubMed

    Barak, Meir M; Lieberman, Daniel E; Raichlen, David; Pontzer, Herman; Warrener, Anna G; Hublin, Jean-Jacques

    2013-01-01

    Although the earliest known hominins were apparently upright bipeds, there has been mixed evidence whether particular species of hominins including those in the genus Australopithecus walked with relatively extended hips, knees and ankles like modern humans, or with more flexed lower limb joints like apes when bipedal. Here we demonstrate in chimpanzees and humans a highly predictable and sensitive relationship between the orientation of the ankle joint during loading and the principal orientation of trabecular bone struts in the distal tibia that function to withstand compressive forces within the joint. Analyses of the orientation of these struts using microCT scans in a sample of fossil tibiae from the site of Sterkfontein, of which two are assigned to Australopithecus africanus, indicate that these hominins primarily loaded their ankles in a relatively extended posture like modern humans and unlike chimpanzees. In other respects, however, trabecular properties in Au africanus are distinctive, with values that mostly fall between those of chimpanzees and humans. These results indicate that Au. africanus, like Homo, walked with an efficient, extended lower limb.

  19. The three-dimensional microstructure of trabecular bone: Analysis of site-specific variation in the human jaw bone

    PubMed Central

    Kim, Jo-Eun; Shin, Jae-Myung; Oh, Sung-Ook; Yi, Won-Jin; Heo, Min-Suk; Lee, Sam-Sun; Choi, Soon-Chul

    2013-01-01

    Purpose This study was performed to analyze human maxillary and mandibular trabecular bone using the data acquired from micro-computed tomography (micro-CT), and to characterize the site-specific microstructures of trabeculae. Materials and Methods Sixty-nine cylindrical bone specimens were prepared from the mandible and maxilla. They were divided into 5 groups by region: the anterior maxilla, posterior maxilla, anterior mandible, posterior mandible, and mandibular condyle. After the specimens were scanned using a micro-CT system, three-dimensional microstructural parameters such as the percent bone volume, bone specific surface, trabecular thickness, trabecular separation, trabecular number, structure model index, and degrees of anisotropy were analyzed. Results Among the regions other than the condylar area, the anterior mandibular region showed the highest trabecular thickness and the lowest value for the bone specific surface. On the other hand, the posterior maxilla region showed the lowest trabecular thickness and the highest value for the bone specific surface. The degree of anisotropy was lowest at the anterior mandible. The condyle showed thinner trabeculae with a more anisotropic arrangement than the other mandibular regions. Conclusion There were microstructural differences between the regions of the maxilla and mandible. These results suggested that different mechanisms of external force might exist at each site. PMID:24380061

  20. Distinct Tissue Mineral Density in Plate- and Rod-like Trabeculae of Human Trabecular Bone.

    PubMed

    Wang, Ji; Kazakia, Galateia J; Zhou, Bin; Shi, X Tony; Guo, X Edward

    2015-09-01

    Trabecular bone quality includes both microstructural and intrinsic tissue mineralization properties. However, the tissue mineralization in individual trabeculae of different trabecular types and orientations has not yet been investigated. The aim of this study was to develop an individual trabecula mineralization (ITM) analysis technique to determine tissue mineral density (TMD) distributions in plate- and rod-like trabeculae, respectively, and to compare the TMD of trabeculae along various orientations in micro-computed tomography (μCT) images of trabecular bone samples from the femoral neck, greater trochanter, and proximal tibia. ITM analyses indicated that trabecular plates, on average, had significantly higher TMD than trabecular rods. In addition, the distribution of TMD in trabecular plates depended on trabecular orientation with the lowest TMD in longitudinal plates and the highest TMD in transverse plates. Conversely, there was a relatively uniform distribution of TMD among trabecular rods, with respect to trabecular orientation. Further analyses of TMD distribution revealed that trabecular plates had higher mean and peak TMD, whereas trabecular rods had a wider TMD distribution and a larger portion of low mineralized trabeculae. Comparison of apparent Young's moduli derived from micro-finite element models with and without heterogeneous TMD demonstrated that heterogeneous TMD in trabecular plates had a significant influence on the elastic mechanical property of trabecular bone. In conclusion, this study revealed differences in TMD between plate- and rod-like trabeculae and among various trabecular orientations. The observation of less mineralized longitudinal trabecular plates suggests interesting implications of these load-bearing plates in bone remodeling. The newly developed ITM analysis can be a valuable technique to assess the influence of metabolic bone diseases and their pharmaceutical treatments on not only microstructure of trabecular bone but

  1. The quartic piecewise-linear criterion for the multiaxial yield behavior of human trabecular bone.

    PubMed

    Sanyal, Arnav; Scheffelin, Joanna; Keaveny, Tony M

    2015-01-01

    Prior multiaxial strength studies on trabecular bone have either not addressed large variations in bone volume fraction and microarchitecture, or have not addressed the full range of multiaxial stress states. Addressing these limitations, we utilized micro-computed tomography (lCT) based nonlinear finite element analysis to investigate the complete 3D multiaxial failure behavior of ten specimens (5mm cube) of human trabecular bone, taken from three anatomic sites and spanning a wide range of bone volume fraction (0.09–0.36),mechanical anisotropy (range of E3/E1¼3.0–12.0), and microarchitecture. We found that most of the observed variation in multiaxial strength behavior could be accounted for by normalizing the multiaxial strength by specimen-specific values of uniaxial strength (tension,compression in the longitudinal and transverse directions). Scatter between specimens was reduced further when the normalized multiaxial strength was described in strain space.The resulting multiaxial failure envelope in this normalized-strain space had a rectangular boxlike shape for normal–normal loading and either a rhomboidal box like shape or a triangular shape for normal-shear loading, depending on the loading direction. The finite element data were well described by a single quartic yield criterion in the 6D normalized strain space combined with a piecewise linear yield criterion in two planes for normalshear loading (mean error SD: 4.660.8% for the finite element data versus the criterion).This multiaxial yield criterion in normalized-strain space can be used to describe the complete 3D multiaxial failure behavior of human trabecular bone across a wide range of bone volume fraction, mechanical anisotropy, and microarchitecture.

  2. Micro-CT characterization of human trabecular bone in osteogenesis imperfecta

    NASA Astrophysics Data System (ADS)

    Jameson, John; Albert, Carolyne; Smith, Peter; Molthen, Robert; Harris, Gerald

    2011-03-01

    Osteogenesis imperfecta (OI) is a genetic syndrome affecting collagen synthesis and assembly. Its symptoms vary widely but commonly include bone fragility, reduced stature, and bone deformity. Because of the small size and paucity of human specimens, there is a lack of biomechanical data for OI bone. Most literature has focused on histomorphometric analyses, which rely on assumptions to extrapolate 3-D properties. In this study, a micro-computed tomography (μCT) system was used to directly measure structural and mineral properties in pediatric OI bone collected during routine surgical procedures. Surface renderings suggested a poorly organized, plate-like orientation. Patients with a history of bone-augmenting drugs exhibited increased bone volume fraction (BV/TV), trabecular number (Tb.N), and connectivity density (Eu.Conn.D). The latter two parameters appeared to be related to OI severity. Structural results were consistently higher than those reported in a previous histomorphometric study, but these differences can be attributed to factors such as specimen collection site, drug therapy, and assumptions associated with histomorphometry. Mineral testing revealed strong correlations with several structural parameters, highlighting the importance of a dual approach in trabecular bone testing. This study reports some of the first quantitative μCT data of human OI bone, and it suggests compelling possibilities for the future of OI bone assessment.

  3. Heterogeneity of yield strain in low-density versus high-density human trabecular bone

    PubMed Central

    Bevill, Grant; Farhamand, Farhad; Keaveny, Tony M.

    2010-01-01

    Understanding the off-axis behavior of trabecular yield strains may lend unique insight into the etiology of fractures since yield strains provide measures of failure independent of elastic behavior. We sought to address anisotropy of trabecular yield strains while accounting for variations in both density and anatomic site and to determine the mechanisms governing this behavior. Cylindrical specimens were cored from vertebral bodies (n=22, BV/TV=0.11±0.02) and femoral necks (n=28, BV/TV=0.22±0.06) with the principal trabecular orientation either aligned along the cylinder axis (on-axis, n=22) or at an oblique angle of 15° or 45° (off-axis, n=28). Each specimen was scanned with micro-CT, mechanically compressed to failure, and analyzed with nonlinear micro-CT-based finite element analysis. Yield strains depended on anatomic site (p=0.03, ANOVA), and the effect of off-axis loading was different for the two sites (p=0.04) – yield strains increased for off-axis loading of the vertebral bone (p=0.04), but were isotropic for the femoral bone (p=0.66). With sites pooled together, yield strains were positively correlated with BV/TV for on-axis loading (R2=58%, p<0.0001), but no such correlation existed for off-axis loading (p=0.79). Analysis of the modulus-BV/TV and strength-BV/TV relationships indicated that, for the femoral bone, the reduction in strength associated with off-axis loading was greater than that for modulus, while the opposite trend occurred for the vertebral bone. The micro-FE analyses indicated that these trends were due to different failure mechanisms for the two types of bone and the different loading modes. Taken together, these results provide unique insight into the failure behavior of human trabecular bone and highlight the need for a multiaxial failure criterion that accounts for anatomic site and bone volume fraction. PMID:19700162

  4. Stochastic predictors from the DXA scans of human lumbar vertebrae are correlated with the microarchitecture parameters of trabecular bone.

    PubMed

    Dong, Xuanliang Neil; Pinninti, Rajeshwar; Tvinnereim, Amy; Lowe, Timothy; Di Paolo, David; Shirvaikar, Mukul

    2015-09-18

    The purpose of this study was to provide a novel stochastic assessment of inhomogeneous distribution of bone mineral density (BMD) from the Dual-energy X-ray Absorptiometry (DXA) scans of human lumbar vertebrae and identify the stochastic predictors that were correlated with the microarchitecture parameters of trabecular bone. Eighteen human lumbar vertebrae with intact posterior elements from 5 cadaveric spines were scanned in the posterior-anterior projection using a Hologic densitometer. The BMD map of human vertebrae was obtained from the raw data of DXA scans by directly operating on the transmission measurements of low- and high-energy X-ray beams. Stochastic predictors were calculated by fitting theoretical models onto the experimental variogram of the BMD map, rather than grayscale images, from DXA scans. In addition, microarchitecture parameters of trabecular bone were measured from the 3D images of human vertebrae acquired using a Micro-CT scanner. Significant correlations were observed between stochastic predictors and microarchitecture parameters. The sill variance, representing the standard deviation of the BMD map to some extent, had significantly positive correlations with bone volume, trabecular thickness, trabecular number and connectivity density. The sill variance was also negatively associated with bone surface to volume ratio and trabecular separation. This study demonstrates that the stochastic assessment of the inhomogeneous distribution of BMD from DXA scans of human lumbar vertebrae can reveal microarchitecture information of trabecular bone. However, future studies are needed to examine the potential of stochastic predictors from routine clinical DXA scans in providing bone fragility information complementary to BMD.

  5. Comparison of the trabecular and cortical tissue moduli from human iliac crests.

    PubMed

    Kuhn, J L; Goldstein, S A; Choi, K; London, M; Feldkamp, L A; Matthews, L S

    1989-01-01

    The purpose of this study was to design a method to produce and test mechanically microspecimens of trabecular and cortical tissue from human iliac crests, and compare their measured moduli. Rectangular beam specimens were prepared on a low-speed diamond blade saw and a miniature milling machine. The final specimen dimensions ranged from approximately 50-200 microns for base and height. The modulus of each specimen was measured using three-point bending tests across a span length of 1.04 mm and performed at a constant rate of displacement. A subset of specimens was recovered for a radiographic estimation of degree of mineralization. The results showed the mean trabecular tissue modulus of all iliac crest specimens to be 3.81 GPa, whereas cortical tissue specimens averaged 4.89 GPa. This was a significant difference according to a two-way analysis of variance that controlled for differences between donors. No strong correlations were found between modulus and mineral density. Future investigations that consider other microstructural characteristics and their contributions to modulus, and specimen size effects, are indicated.

  6. Feasibility of micro-crack detection in human trabecular bone images from 3D synchrotron microtomography.

    PubMed

    Larrue, Aymeric; Rattner, Aline; Laroche, Norbert; Vico, Laurence; Peyrin, Françoise

    2007-01-01

    Bone micro-cracks receive an increasing attention to explain bone quality. They have mainly been observed in 2D with microscopic techniques. In this paper, we propose a method based on 3D Synchrotron Radiation micro-CT to analyze micro-cracks in human trabecular bone samples. Samples were imaged with a voxel size of 1.4 microm. Despite micro-cracks are visible, their automatic detection is challenging because of noise, artifacts, low-contrast, and partial volume effect. We propose a two-steps procedure, based on image enhancement and segmentation to address this problem. The method enables to get the 3D morphology of micro-cracks, shown for the first time with this precision. Future work will be devoted to extract quantitative parameters on the crack morphology.

  7. Visualization of Neutrophil Extracellular Traps and Fibrin Meshwork in Human Fibrinopurulent Inflammatory Lesions: III. Correlative Light and Electron Microscopic Study

    PubMed Central

    Onouchi, Takanori; Shiogama, Kazuya; Mizutani, Yasuyoshi; Takaki, Takashi; Tsutsumi, Yutaka

    2016-01-01

    Neutrophil extracellular traps (NETs) released from dead neutrophils at the site of inflammation represent webs of neutrophilic DNA stretches dotted with granule-derived antimicrobial proteins, including lactoferrin, and play important roles in innate immunity against microbial infection. We have shown the coexistence of NETs and fibrin meshwork in varied fibrinopurulent inflammatory lesions at both light and electron microscopic levels. In the present study, correlative light and electron microscopy (CLEM) employing confocal laser scanning microscopy and scanning electron microscopy was performed to bridge light and electron microscopic images of NETs and fibrin fibrils in formalin-fixed, paraffin-embedded, autopsied lung sections of legionnaire’s pneumonia. Lactoferrin immunoreactivity and 4'-6-diamidino-2-phenylindole (DAPI) reactivity were used as markers of NETs, and fibrin was probed by fibrinogen gamma chain. Of note is that NETs light microscopically represented as lactoferrin and DAPI-colocalized dots, 2.5 μm in diameter. CLEM gave super-resolution images of NETs and fibrin fibrils: “Dotted” NETs were ultrastructurally composed of fine filaments and masses of 58 nm-sized globular materials. A fibrin fibril consisted of clusters of smooth-surfaced filaments. NETs filaments (26 nm in diameter) were significantly thinner than fibrin filaments (295 nm in diameter). Of note is that CLEM was applicable to formalin-fixed, paraffin-embedded sections of autopsy material. PMID:27917008

  8. A system for culture of human trabecular bone and hormone response profiles of derived cells.

    PubMed Central

    Crisp, A. J.; McGuire-Goldring, M. B.; Goldring, S. R.

    1984-01-01

    Specimens of human trabecular bone from II patients were processed for tissue culture. In 10 out of 11 samples both cellular and matrix outgrowths were noted at the surfaces of explanted fragments after the first week in culture. During the second week adherent cells extended beyond the margins of the bone fragments and appeared to replicate. Plates achieved confluence in 30-36 days and cells were subcultured. In passaged cells doubling times were 5-7 days. Six cell cultures were examined for the presence of alkaline and acid phosphatase activity employing histochemical techniques. All six cultures contained cells which stained positively for alkaline phosphatase (10-80%). A small number of cells in one culture demonstrated tartrate-resistant acid phosphatase activity. Responses to hormones known to regulate the biological activities of skeletal tissues were also tested. Intracellular cyclic AMP was significantly increased by parathyroid hormone in three cultures, by salmon calcitonin in three cultures and by prostaglandin E2 in all 10 cultures. All three hormones increased the cyclic AMP content of cells cultured from human periosteum. It is concluded that cells cultured by this method demonstrate biochemical and morphological characteristics consistent with a skeletal tissue origin. Furthermore, such an approach may permit isolation and further characterization of individual subpopulations of bone cells of human origin. Images Fig. 1 Fig. 2 PMID:6093841

  9. Differences in acoustic impedance of fresh and embedded human trabecular bone samples-Scanning acoustic microscopy and numerical evaluation.

    PubMed

    Ojanen, Xiaowei; Töyräs, Juha; Inkinen, Satu I; Malo, Markus K H; Isaksson, Hanna; Jurvelin, Jukka S

    2016-09-01

    Trabecular bone samples are traditionally embedded and polished for scanning acoustic microscopy (SAM). The effect of sample processing, including dehydration, on the acoustic impedance of bone is unknown. In this study, acoustic impedance of human trabecular bone samples (n = 8) was experimentally assessed before (fresh) and after embedding using SAM and two-dimensional (2-D) finite-difference time domain simulations. Fresh samples were polished with sandpapers of different grit (P1000, P2500, and P4000). Experimental results indicated that acoustic impedance of samples increased significantly after embedding [mean values 3.7 MRayl (fresh), 6.1 MRayl (embedded), p < 0.001]. After polishing with different papers, no significant changes in acoustic impedance were found, even though higher mean values were detected after polishing with finer (P2500 and P4000) papers. A linear correlation (r = 0.854, p < 0.05) was found between the acoustic impedance values of embedded and fresh bone samples polished using P2500 SiC paper. In numerical simulations dehydration increased the acoustic impedance of trabecular bone (38%), whereas changes in surface roughness of bone had a minor effect on the acoustic impedance (-1.56%/0.1 μm). Thereby, the numerical simulations corroborated the experimental findings. In conclusion, acoustic impedance measurement of fresh trabecular bone is possible and may provide realistic material values similar to those of living bone.

  10. Within subject heterogeneity in tissue-level post-yield mechanical and material properties in human trabecular bone.

    PubMed

    Carretta, Roberto; Stüssi, Edgar; Müller, Ralph; Lorenzetti, Silvio

    2013-08-01

    The ability to determine patient-specific mechanical properties of trabecular bone is needed for a reliable estimation of fracture risks. Tissue mechanics and material composition are important factors that contribute to trabecular bone performance, but only a few studies have investigated the post-yield behaviour of human trabecular bone, and limited knowledge for modelling is available about ultimate properties needed. Aim of this paper was to investigate absolute values and deviation of mechanical and material properties of human trabecular bone at the tissue level, in a healthy and osteoporotic donor. A combination of tensile and bending tests of single trabeculae up to failure, μCT measurement of sample geometry and finite element analysis were incorporated to determine mechanical properties. The samples were analysed with Raman spectroscopy to evaluate the material composition. High within-subject variability was found, for both the healthy and osteoporotic donor. Nevertheless, the two donors could be separated by analysing the ultimate strain and post-yield work, as well as two of the material parameters (B-type carbonate substitution ratio and collagen cross-link ratio). It indicates that tissue level properties seem to be relevant also for macroscopic mechanical behaviour. These findings also suggest that the mechanical variability for the inelastic region at the tissue level may be associated with varying material properties, while until yielding occurs our data does not suggest any connection between the mechanical and the investigated material. Finally, a set of mechanical properties of human bone have been reported that are a relevant reference for computational studies and FE analysis.

  11. Osteoblast-Specific Overexpression of Human WNT16 Increases Both Cortical and Trabecular Bone Mass and Structure in Mice

    PubMed Central

    Alkhouli, Mohammed; Gerard-O'Riley, Rita L.; Wright, Weston B.; Acton, Dena; Gray, Amie K.; Patel, Bhavmik; Reilly, Austin M.; Lim, Kyung-Eun; Robling, Alexander G.; Econs, Michael J.

    2016-01-01

    Previous genome-wide association studies have identified common variants in genes associated with bone mineral density (BMD) and risk of fracture. Recently, we identified single nucleotide polymorphisms (SNPs) in Wingless-type mouse mammary tumor virus integration site (WNT)16 that were associated with peak BMD in premenopausal women. To further identify the role of Wnt16 in bone mass regulation, we created transgenic (TG) mice overexpressing human WNT16 in osteoblasts. We compared bone phenotypes, serum biochemistry, gene expression, and dynamic bone histomorphometry between TG and wild-type (WT) mice. Compared with WT mice, WNT16-TG mice exhibited significantly higher whole-body areal BMD and bone mineral content (BMC) at 6 and 12 weeks of age in both male and female. Microcomputer tomography analysis of trabecular bone at distal femur revealed 3-fold (male) and 14-fold (female) higher bone volume/tissue volume (BV/TV), and significantly higher trabecular number and trabecular thickness but lower trabecular separation in TG mice compared with WT littermates in both sexes. The cortical bone at femur midshaft also displayed significantly greater bone area/total area and cortical thickness in the TG mice in both sexes. Serum biochemistry analysis showed that male TG mice had higher serum alkaline phosphatase, osteocalcin, osteoprotegerin (OPG), OPG to receptor activator of NF-kB ligand (tumor necrosis family ligand superfamily, number 11; RANKL) ratio as compared with WT mice. Also, lower carboxy-terminal collagen cross-link (CTX) to tartrate-resistant acid phosphatase 5, isoform b (TRAPc5b) ratio was observed in TG mice compared with WT littermates in both male and female. Histomorphometry data demonstrated that both male and female TG mice had significantly higher cortical and trabecular mineralizing surface/bone surface and bone formation rate compared with sex-matched WT mice. Gene expression analysis demonstrated higher expression of Alp, OC, Opg, and Opg to

  12. In vivo microdamage is an indicator of susceptibility to initiation and propagation of microdamage in human femoral trabecular bone

    PubMed Central

    Wu, Ziheng; LaNeve, Anthony J.; Niebur, Glen L.

    2013-01-01

    Microdamage has been cited as an important element of trabecular bone quality and fracture risk, as materials with flaws have lower modulus and strength than equivalent undamaged materials. However, the magnitude of the effect of damage on failure properties depends on its tendency to propagate. Human femoral trabecular bone from the neck and greater trochanter was subjected to one of compressive, torsional, or combined compression and torsion. The in vivo, new, and propagating damage were then quantified in thick sections under epifluorescent microscopy. Multiaxial loading, which was intended to represent an off-axis load such as a fall or accident, caused much more damage than either simple compression or shear, and similarly caused the greatest stiffness loss. In all cases, initiation of new damage far exceeded the propagation of existing damage. This may reflect stress redistribution away from damaged trabeculae, resulting in new damage sites. However, the accumulation of new damage was positively correlated with the quantity of pre-existing damage in all loading modes, indicating that damaged bone is inherently more prone to further damage formation. Moreover, about 50% of in vivo microcracks propagated under each type of loading. Finally, damage formation was positively correlated to decreased compressive stiffness following both axial and shear loading. Taken together, these results demonstrate that damage in trabecular bone adversely affects its mechanical properties, and is indicative of bone that is more susceptible to further damage. PMID:23459314

  13. Skeletal site-related variation in human trabecular bone transcriptome and signaling.

    PubMed

    Varanasi, Satya S; Olstad, Ole K; Swan, Daniel C; Sanderson, Paul; Gautvik, Vigdis T; Reppe, Sjur; Francis, Roger M; Gautvik, Kaare M; Datta, Harish K

    2010-05-18

    The skeletal site-specific influence of multiple genes on bone morphology is recognised, but the question as to how these influences may be exerted at the molecular and cellular level has not been explored. To address this question, we have compared global gene expression profiles of human trabecular bone from two different skeletal sites that experience vastly different degrees of mechanical loading, namely biopsies from iliac crest and lumbar spinal lamina. In the lumbar spine, compared to the iliac crest, the majority of the differentially expressed genes showed significantly increased levels of expression; 3406 transcripts were up- whilst 838 were down-regulated. Interestingly, all gene transcripts that have been recently demonstrated to be markers of osteocyte, as well as osteoblast and osteoclast-related genes, were markedly up-regulated in the spine. The transcriptome data is consistent with osteocyte numbers being almost identical at the two anatomical sites, but suggesting a relatively low osteocyte functional activity in the iliac crest. Similarly, osteoblast and osteoclast expression data suggested similar numbers of the cells, but presented with higher activity in the spine than iliac crest. This analysis has also led to the identification of expression of a number of transcripts, previously known and novel, which to our knowledge have never earlier been associated with bone growth and remodelling. This study provides molecular evidence explaining anatomical and micro-architectural site-related changes in bone cell function, which is predominantly attributable to alteration in cell transcriptional activity. A number of novel signaling molecules in critical pathways, which have been hitherto not known to be expressed in bone cells of mature vertebrates, were identified.

  14. Regional Variations in Shear Strength and Density of the Human Thoracic Vertebral Endplate and Trabecular Bone

    PubMed Central

    Jauregui, Julio J.; Cornish, Nathan; Jason-Rousseau, Rebecca; Chatterjee, Dipal; Feuer, Gavriel; Hayes, Westley; Kapadia, Bhaveen H.; Carter, John N.; Yoshihara, Hiroyuki; Saha, Subrata

    2017-01-01

    Background Previous studies investigated the overall mechanical strength of the vertebral body; however, limited information is available on the biomechanical properties of different regions within the vertebral endplate and cancellous bone. In addition, the correlation between mechanical strength and various density measurements has not been studied yet. Methods Thoracic (T10) vertebrae were harvested from fifteen human cadaveric spines (average age: 77 years old). Twelve cylindrical cores of 7.2 mm (diameter) by 3.2 mm (height) were prepared from each vertebral body. Shear was produced using a stainless steel tubular blade and measured with a load cell from a mechanical testing machine. Optical and bulk densities were calculated before mechanical testing. Apparent, material, and ash densities were measured after testing. Results Material density and shear strength increased from anterior to lateral regions of both endplate and cancellous bone. Endplate shear strength was significantly lower in the anterior (0.52 ± 0.08 MPa) than in the lateral region (2.72 ± 0.59 MPa) (p=0.017). Trabecular bone maximum load carrying capacity was 5 times higher in the lateral (12 ± 2.74 N) (p=0.09) and 4.5 times higher in the central (10 ± 2.24 N) (p=0.2) than in the anterior (2 ± 0.60 N) regions. Mechanical strength positively correlated with ash density, and even moreso with material density. Conclusion Shear strength was the lowest at the anterior region and highest at the lateral region for both endplate and cancellous bone. Material density had the best correlation with mechanical strength. Newer spinal implants could optimize the loading in the lateral aspects of both endplate and cancellous bone to reduce the likelihood of screw loosening and the subsidence of disc replacement devices. This study was reviewed by the SUNY Downstate Medical Center IRB Committee; IRB#: 533603-2. PMID:28377865

  15. Influence of bone volume fraction and architecture on computed large-deformation failure mechanisms in human trabecular bone.

    PubMed

    Bevill, Grant; Eswaran, Senthil K; Gupta, Atul; Papadopoulos, Panayiotis; Keaveny, Tony M

    2006-12-01

    Large-deformation bending and buckling have long been proposed as failure mechanisms by which the strength of trabecular bone can be affected disproportionately to changes in bone density, and thus may represent an important aspect of bone quality. We sought here to quantify the contribution of large-deformation failure mechanisms on strength, to determine the dependence of these effects on bone volume fraction and architecture, and to confirm that the inclusion of large-deformation effects in high-resolution finite element models improves predictions of strength versus experiment. Micro-CT-based finite element models having uniform hard tissue material properties were created from 54 cores of human trabecular bone taken from four anatomic sites (age = 70+/-11; 24 male, 27 female donors), which were subsequently biomechanically tested to failure. Strength predictions were made from the models first including, then excluding, large-deformation failure mechanisms, both for compressive and tensile load cases. As expected, strength predictions versus experimental data for the large-deformation finite element models were significantly improved (p < 0.001) relative to the small deformation models in both tension and compression. Below a volume fraction of about 0.20, large-deformation failure mechanisms decreased trabecular strength from 5-80% for compressive loading, while effects were negligible above this volume fraction. Step-wise nonlinear multiple regression revealed that structure model index (SMI) and volume fraction (BV/TV) were significant predictors of these reductions in strength (R2 = 0.83, p < 0.03). Even so, some low-density specimens having nearly identical volume fraction and SMI exhibited up to fivefold differences in strength reduction. We conclude that within very low-density bone, the potentially important biomechanical effect of large-deformation failure mechanisms on trabecular bone strength is highly heterogeneous and is not well explained by

  16. Human trabecular bone microarchitecture can be assessed independently of density with second generation HR-pQCT.

    PubMed

    Manske, Sarah L; Zhu, Ying; Sandino, Clara; Boyd, Steven K

    2015-10-01

    The second generation HR-pQCT scanner (XtremeCTII, Scanco Medical) can assess human bone microarchitecture of peripheral limbs with a 61 μm nominal isotropic voxel size. This is a marked improvement from the first generation HR-pQCT that had a nominal isotropic voxel size of 82 μm, which is at the limit to accurately determine the thickness of individual human trabeculae. We sought to determine the accuracy of a direct morphometric approach to measure trabecular bone microarchitecture with three-dimensional morphological techniques using second generation HR-pQCT, and to compare this with the approach currently applied by the first generation HR-pQCT scanner based on derived indices using ex vivo scans of human cadaveric radii. We also compared images acquired and resampled to mimic the first generation HR-pQCT with those obtained directly from the first generation HR-pQCT. We evaluated 20 human cadaveric radii and a micro-CT performance phantom using the first (XtremeCT, Scanco Medical) and second generation HR-pQCT scanner (XtremeCTII) and compared a patient evaluation (XCTII, 61 μm) with a high resolution ex vivo protocol (HR, 30μm). We generated 82 μm scans of the same specimens to mimic a first-generation HR-pQCT evaluation (XCTIM, 82 μm) and compared these with a first-generation patient evaluation (XCTI, 82 μm). A standard structural extraction approach was applied to both XCTII and HR evaluations for assessment of bone volume fraction (BV/TV), and a distance transform was used to assess trabecular number (Tb.N), trabecular thickness (Tb.Th) and trabecular separation (Tb.Sp). For XCTI and XCTIM evaluations we followed the manufacturer's standard procedure and assessed bone mineral density (BMD), Tb.N with a distance transform, and then derived bone volume ratio (BV/TV(d)), trabecular thickness (Tb.Th(d)) and separation (Tb.Sp(d)). The spatial resolution (10% MTF) was 142.2 μm for XCTI, 108.9 μm for XCTIM, 95.2μm for XCTII, and 55.9 μm for HR. XCTI

  17. Static histomorphometry of human iliac crest and vertebral trabecular bone: a comparative study.

    PubMed

    Thomsen, J S; Ebbesen, E N; Mosekilde, Li

    2002-01-01

    We recently developed a new, rapid method for conducting static histomorphometry on large histologic sections. This method has now been applied on both iliac crest and lumbar vertebral bone to compare the age-related changes at these two skeletal sites and to investigate the correlation between the histomorphometric measures at the iliac crest and the vertebral body. The material comprised matched sets of unilateral transiliac crest bone biopsies and lumbar vertebral bodies (L-2) from 24 women (19-96 years) and 24 men (23-95 years) selected from a larger autopsy material. Three female subjects (80, 88, and 90 years) had a known vertebral fracture of L-2. The iliac crest biopsies and 9-mm-thick mediolateral slices of half the entire vertebral bodies were embedded in methylmetacrylate, stained with aniline blue, and scanned into a computer with a flatbed image scanner at a high resolution. With a custom-made computer program the following static histomorphometric measures were determined: trabecular bone volume; marrow and bone space star volume; node-strut analysis; trabecular bone pattern factor; trabecular thickness; trabecular number; trabecular separation; and anisotropy of bone and marrow phase. In addition, connectivity density was measured (ConnEulor method). The results showed that the age-related changes in the static histomorphometric measures are generally similar in the iliac crest and the vertebral body, and that these age-related changes are independent of gender. An exception, however, is connectivity density, where the age-related changes are similar for women and men in the vertebral body but significantly different in the iliac crest. Furthermore, the results showed that the histomorphometric measures were weakly intercorrelated between the iliac crest and the vertebral body, despite the generally similar pattern in age-related changes at these two skeletal sites. The highest correlation coefficient was found for trabecular separation (Tb.Sp; r = 0

  18. Comparison of synchrotron radiation and conventional x-ray microcomputed tomography for assessing trabecular bone microarchitecture of human femoral heads

    SciTech Connect

    Chappard, Christine; Basillais, Armelle; Benhamou, Laurent; Bonassie, Alexandra; Brunet-Imbault, Barbara; Bonnet, Nicolas; Peyrin, Francoise

    2006-09-15

    Microcomputed tomography ({mu}CT) produces three-dimensional (3D) images of trabecular bone. We compared conventional {mu}CT (C{mu}CT) with a polychromatic x-ray cone beam to synchrotron radiation (SR) {mu}CT with a monochromatic parallel beam for assessing trabecular bone microarchitecture of 14 subchondral femoral head specimens from patients with osteoarthritis (n=10) or osteoporosis (n=4). SR{mu}CT images with a voxel size of 10.13 {mu}m were reconstructed from 900 2D radiographic projections (angular step, 0.2 deg. ). C{mu}CT images with a voxel size of 10.77 {mu}m were reconstructed from 205, 413, and 825 projections obtained using angular steps of 0.9 deg., 0.45 deg., and 0.23 deg., respectively. A single threshold was used to binarize the images. We computed bone volume/tissue volume (BV/TV), bone surface/bone volume (BS/BV), trabecular number (Tb.N), trabecular thickness (Tb.Th and Tb.Th*), trabecular spacing (Tb.Sp), degree of anisotropy (DA), and Euler density. With the 0.9 deg. angular step, all C{mu}CT values were significantly different from SR{mu}CT values. With the 0.23 deg. and 0.45 deg. rotation steps, BV/TV, Tb.Th, and BS/BV by C{mu}CT differed significantly from the values by SR{mu}CT. The error due to slice matching (visual site matching {+-}10 slices) was within 1% for most parameters. Compared to SR{mu}CT, BV/TV, Tb.Sp, and Tb.Th by C{mu}CT were underestimated, whereas Tb.N and Tb.Th* were overestimated. A Bland and Altman plot showed no bias for Tb.N or DA. Bias was -0.8{+-}1.0%, +5.0{+-}1.1 {mu}m, -5.9{+-}6.3 {mu}m, and -5.7{+-}29.1 {mu}m for BV/TV, Tb.Th*, Tb.Th, and Tb.Sp, respectively, and the differences did not vary over the range of values. Although systematic differences were noted between SR{mu}CT and C{mu}CT values, correlations between the techniques were high and the differences would probably not change the discrimination between study groups. C{mu}CT provides a reliable 3D assessment of human defatted bone when working at the 0

  19. Early Trabecular Development in Human Vertebrae: Overproduction, Constructive Regression, and Refinement

    PubMed Central

    Acquaah, Frank; Robson Brown, Katharine A.; Ahmed, Farah; Jeffery, Nathan; Abel, Richard L.

    2015-01-01

    Early bone development may have a significant impact upon bone health in adulthood. Bone mineral density (BMD) and bone mass are important determinants of adult bone strength. However, several studies have shown that BMD and bone mass decrease after birth. If early development is important for strength, why does this reduction occur? To investigate this, more data characterizing gestational, infant, and childhood bone development are needed in order to compare with adults. The aim of this study is to document early vertebral trabecular bone development, a key fragility fracture site, and infer whether this period is important for adult bone mass and structure. A series of 120 vertebrae aged between 6 months gestation and 2.5 years were visualized using microcomputed tomography. Spherical volumes of interest were defined, thresholded, and measured using 3D bone analysis software (BoneJ, Quant3D). The findings showed that gestation was characterized by increasing bone volume fraction whilst infancy was defined by significant bone loss (≈2/3rds) and the appearance of a highly anisotropic trabecular structure with a predominantly inferior–superior direction. Childhood development progressed via selective thickening of some trabeculae and the loss of others; maintaining bone volume whilst creating a more anisotropic structure. Overall, the pattern of vertebral development is one of gestational overproduction followed by infant “sculpting” of bone tissue during the first year of life (perhaps in order to regulate mineral homeostasis or to adapt to loading environment) and then subsequent refinement during early childhood. Comparison of early bone developmental data in this study with adult bone volume values taken from the literature shows that the loss in bone mass that occurs during the first year of life is never fully recovered. Early development could therefore be important for developing bone strength, but through structural changes in trabecular

  20. Regional variations in human patellar trabecular architecture and the structure of the proximal patellar tendon enthesis

    PubMed Central

    Toumi, H; Higashiyama, I; Suzuki, D; Kumai, T; Bydder, G; McGonagle, D; Emery, P; Fairclough, J; Benjamin, M

    2006-01-01

    Proximal patellar tendinopathy occurs as an overuse injury in sport and is also characteristic of ankylosing spondylitis patients. It particularly affects the posteromedial part of the patellar tendon enthesis, although the reason for this is unclear. We investigated whether there are regional differences in the trabecular architecture of the patella or in the histology of the patellar tendon enthesis that could suggest unequal force transmission from bone to tendon. Trabecular architecture was analysed from X-rays taken with a Faxitron radiography system of the patellae of dissecting room cadavers and in magnetic resonance images of the knees of living volunteers. Structural and fractal analyses were performed on the Faxitron digital images using MatLab software. Regional differences at the enthesis in the thickness of the uncalcified fibrocartilage and the subchondral plate were evaluated histologically in cadaveric material. The radiological studies showed that the quantity of bone and the apparent trabecular thickness in the patella were greatest medially, and that in the lateral part of the patella there were fewer trabeculae which were orientated either antero-posteriorly or superiorly inferiorly. The histological study showed that the uncalcified fibrocartilage was most prominent medially and that the subchondral plate was thinner laterally. Overall, the results indicate that mechanical stress at the proximal patellar tendon enthesis is asymmetrically distributed and greater on the medial than on the lateral side. Thus, we suggest that the functional anatomy of the knee is closely related to regional variations in force transmission, which in turn relates to the posteromedial site of pathology in proximal patellar tendinopathy. PMID:16420378

  1. Slow and fast ultrasonic wave detection improvement in human trabecular bones using Golay code modulation.

    PubMed

    Lashkari, Bahman; Manbachi, Amir; Mandelis, Andreas; Cobbold, Richard S C

    2012-09-01

    The identification of fast and slow waves propagating through trabecular bone is a challenging task due to temporal wave overlap combined with the high attenuation of the fast wave in the presence of noise. However, it can provide valuable information about bone integrity and become a means for monitoring osteoporosis. The objective of this work is to apply different coded excitation methods for this purpose. The results for single-sine cycle pulse, Golay code, and chirp excitations are compared. It is shown that Golay code is superior to the other techniques due to its signal enhancement while exhibiting excellent resolution without the ambiguity of sidelobes.

  2. Glaukos iStent® Trabecular Micro-Bypass

    PubMed Central

    Nichamin, Louis D.

    2009-01-01

    The iStent trabecular micro-bypass system (Glaukos Corp. Laguna Hills, CA) was developed to address the limitations of current medical and surgical therapies for glaucoma treatment. The iStent® is inserted ab interno through a small temporal clear corneal incision, bypassing the trabecular meshwork and placed in Schlemm's canal at the lower nasal quadrant. Implantation of this stent into Schlemm's canal allows aqueous humor to drain directly from the anterior chamber into Schlemm's canal bypassing the obstructed trabecular meshwork. For this review, a Medline search was performed using the terms “trabecular micro-bypass stent” and “trabecular bypass stent.” The online abstract database for the American Academy of Ophthalmology was also reviewed. Abstracts which duplicated published articles were excluded. All relevant papers (n is equal to three) and abstracts (n is equal to one) were included in this review. Multiple, prospective multi-country, clinical trials have demonstrated the safety and efficacy of iStent in reducing IOP, when compared to traditional treatment modalities, while reducing/ eliminating the need for ocular antihypertensive drugs when implanted in OAG patients during combined cataract surgery or in patients with glaucoma refractory to traditional treatment modalities. PMID:20142980

  3. Comparison of diffraction-enhanced computed tomography and monochromatic synchrotron radiation computed tomography of human trabecular bone.

    PubMed

    Connor, D M; Hallen, H D; Lalush, D S; Sumner, D R; Zhong, Z

    2009-10-21

    Diffraction-enhanced imaging (DEI) is an x-ray-based medical imaging modality that, when used in tomography mode (DECT), can generate a three-dimensional map of both the apparent absorption coefficient and the out-of-plane gradient of the index of refraction of the sample. DECT is known to have contrast gains over monochromatic synchrotron radiation CT (SRCT) for soft tissue structures. The goal of this experiment was to compare contrast-to-noise ratio (CNR) and resolution in images of human trabecular bone acquired using SRCT with images acquired using DECT. All images were acquired at the National Synchrotron Light Source (Upton, NY, USA) at beamline X15 A at an x-ray energy of 40 keV and the silicon [3 3 3] reflection. SRCT, apparent absorption DECT and refraction DECT slice images of the trabecular bone were created. The apparent absorption DECT images have significantly higher spatial resolution and CNR than the corresponding SRCT images. Thus, DECT will prove to be a useful tool for imaging applications in which high contrast and high spatial resolution are required for both soft tissue features and bone.

  4. Occlusal load distribution through the cortical and trabecular bone of the human mid-facial skeleton in natural dentition: a three-dimensional finite element study.

    PubMed

    Janovic, Aleksa; Saveljic, Igor; Vukicevic, Arso; Nikolic, Dalibor; Rakocevic, Zoran; Jovicic, Gordana; Filipovic, Nenad; Djuric, Marija

    2015-01-01

    Understanding of the occlusal load distribution through the mid-facial skeleton in natural dentition is essential because alterations in magnitude and/or direction of occlusal forces may cause remarkable changes in cortical and trabecular bone structure. Previous analyses by strain gauge technique, photoelastic and, more recently, finite element (FE) methods provided no direct evidence for occlusal load distribution through the cortical and trabecular bone compartments individually. Therefore, we developed an improved three-dimensional FE model of the human skull in order to clarify the distribution of occlusal forces through the cortical and trabecular bone during habitual masticatory activities. Particular focus was placed on the load transfer through the anterior and posterior maxilla. The results were presented in von Mises stress (VMS) and the maximum principal stress, and compared to the reported FE and strain gauge data. Our qualitative stress analysis indicates that occlusal forces distribute through the mid-facial skeleton along five vertical and two horizontal buttresses. We demonstrated that cortical bone has a priority in the transfer of occlusal load in the anterior maxilla, whereas both cortical and trabecular bone in the posterior maxilla are equally involved in performing this task. Observed site dependence of the occlusal load distribution may help clinicians in creating strategies for implantology and orthodontic treatments. Additionally, the magnitude of VMS in our model was significantly lower in comparison to previous FE models composed only of cortical bone. This finding suggests that both cortical and trabecular bone should be modeled whenever stress will be quantitatively analyzed.

  5. Trabecular orientation in the human femur and tibia and the relationship with lower-limb alignment for patients with osteoarthritis of the knee.

    PubMed

    Sampath, Shameem A; Lewis, Sandra; Fosco, Matteo; Tigani, Domenico

    2015-04-13

    Wolff׳s Law suggests that the orientation of trabeculae in human bone changes in response to altered loading patterns. The aim of this study was to investigate trabecular orientation in both the femur and tibia and to compare this with the mechanical axis of the leg. The study involved analysis of radiographs from patients with osteoarthritis of the knee (n=91). For each patient, the trabecular orientation in both the distal femur and proximal tibia was measured from a standard anteroposterior radiograph of the knee and the mechanical axis of the leg was calculated from a long leg view taken while weight bearing. There was a significant correlation between the mechanical axis and the trabecular orientation in each of the regions considered in the femur (r=-0.41, -0.30, 0.52, and 0.23) and tibia (r=-0.27 and 0.31). Multiple regression analysis, with mechanical axis as the dependent variable, produced an R(2) of 0.62. Greater trabecular anisotropy (i.e. greater alignment) was observed in the medial femur and tibia compared to the lateral side (p<0.01). The results give an insight into the trabecular changes that may take place during development of osteoarthritis and following surgery. In particular, we propose that the orientation of the trabeculae in both the distal femur and proximal tibia will reflect the angle of mechanical loading through the knee.

  6. Enhancing trabecular outflow by disrupting the actin cytoskeleton, increasing uveoscleral outflow with prostaglandins, and understanding the pathophysiology of presbyopia

    PubMed Central

    Kaufman, Paul L.

    2008-01-01

    Several major areas of work by the author and his international collaborators are reviewed. 1) The ciliary muscle in the nonhuman primate eye was disinserted at the scleral spur. Pilocarpine was then ineffective in increasing outflow facility, indicating that ciliary muscle contraction mediated the IOP-lowering effect of muscarinic cholinergics. 2) Compounds such as cytochalasins, H-7 and latrunculin A/B, which alter the actin cytoskeleton, cellular contractility and cellular adhesions in cultured trabecular meshwork cells, relaxed trabecular pathway cells and consequently the meshwork itself so as to decrease IOP and enhance trabecular outflow facility in nonhuman primates. Gene transfer approaches utilizing C3 and caldesmon over-expression by viral vectors to target specific steps in the cellular contractility/cytoskeleton/cell adhesion cascades characteristically altered trabecular meshwork cell morphology and increased outflow facility in organ-cultured anterior segments. 3) Prostaglandin F2α analogues enhanced matrix metalloproteinase production by ciliary muscle cells and scleral fibroblasts, leading to remodeling of the extracellular matrix of the ciliary muscle and sclera and consequently to increased uveoslceral outflow and decreased IOP in primates. 4) The rhesus monkey was an excellent model for human presbyopia, losing the accommodative response to cholinergic stimulation in the same timeframe relative to lifespan. No changes were found in ciliary muscle enzymes involved in acetylcholine biosynthesis or degradation or in muscarinic receptor numbers or affinity. Contractility of isolated ciliary muscle did not diminish with age, but posterior ciliary muscle attachments stiffened, suggesting a possible role in restricting muscle and consequently lens movement during accommodation. A model to reproducibly stimulate accommodation through central stimulation of the Edinger-Westphal nucleus was developed. Goniovideography and ultrasound biomicroscopic

  7. Digital tomosynthesis (DTS) for quantitative assessment of trabecular microstructure in human vertebral bone.

    PubMed

    Kim, Woong; Oravec, Daniel; Nekkanty, Srikant; Yerramshetty, Janardhan; Sander, Edward A; Divine, George W; Flynn, Michael J; Yeni, Yener N

    2015-01-01

    Digital tomosynthesis (DTS) provides slice images of an object using conventional radiographic methods with high in-plane resolution. The objective of this study was to explore the potential of DTS for describing microstructural, stiffness and stress distribution properties of vertebral cancellous bone. Forty vertebrae (T6, T8, T11, and L3) from 10 cadavers (63-90 years) were scanned using microCT and DTS. Anisotropy (μCT.DA), and the specimen-average and standard deviation of trabecular bone volume fraction (BV/TV), thickness (Tb.Th), number (Tb.N) and separation (Tb.Sp) were obtained using stereology. Apparent modulus (EFEM), and the magnitude (VMExp/σapp) and variability (VMCV) of trabecular stresses were calculated using microCT-based finite element modeling. Mean intercept length, line fraction deviation and fractal parameters were obtained from coronal DTS slices, then correlated with stereological and finite element parameters using linear regression models. Twenty-one DTS parameters (out of 27) correlated to BV/TV, Tb.Th, Tb.N, Tb.Sp and/or μCT.DA (p<0.0001-p<0.05). DTS parameters increased the explained variability in EFEM and VMCV (by 9-11% and 13-19%, respectively; p<0.0001-p<0.04) over that explained by BV/TV. In conclusion, DTS has potential for quantitative assessment of cancellous bone and may be used as a modality complementary to those measuring bone mass for assessing spinal fracture risk.

  8. Relationship between sample volumes and modulus of human vertebral trabecular bone in micro-finite element analysis.

    PubMed

    Wen, Xin-Xin; Xu, Chao; Zong, Chun-Lin; Feng, Ya-Fei; Ma, Xiang-Yu; Wang, Fa-Qi; Yan, Ya-Bo; Lei, Wei

    2016-07-01

    Micro-finite element (μFE) models have been widely used to assess the biomechanical properties of trabecular bone. How to choose a proper sample volume of trabecular bone, which could predict the real bone biomechanical properties and reduce the calculation time, was an interesting problem. Therefore, the purpose of this study was to investigate the relationship between different sample volumes and apparent elastic modulus (E) calculated from μFE model. 5 Human lumbar vertebral bodies (L1-L5) were scanned by micro-CT. Cubic concentric samples of different lengths were constructed as the experimental groups and the largest possible volumes of interest (VOI) were constructed as the control group. A direct voxel-to-element approach was used to generate μFE models and steel layers were added to the superior and inferior surface to mimic axial compression tests. A 1% axial strain was prescribed to the top surface of the model to obtain the E values. ANOVA tests were performed to compare the E values from the different VOIs against that of the control group. Nonlinear function curve fitting was performed to study the relationship between volumes and E values. The larger cubic VOI included more nodes and elements, and more CPU times were needed for calculations. E values showed a descending tendency as the length of cubic VOI decreased. When the volume of VOI was smaller than (7.34mm(3)), E values were significantly different from the control group. The fit function showed that E values approached an asymptotic values with increasing length of VOI. Our study demonstrated that apparent elastic modulus calculated from μFE models were affected by the sample volumes. There was a descending tendency of E values as the length of cubic VOI decreased. Sample volume which was not smaller than (7.34mm(3)) was efficient enough and timesaving for the calculation of E.

  9. Fabrication, pore structure and compressive behavior of anisotropic porous titanium for human trabecular bone implant applications.

    PubMed

    Li, Fuping; Li, Jinshan; Xu, Guangsheng; Liu, Gejun; Kou, Hongchao; Zhou, Lian

    2015-06-01

    Porous titanium with average pore size of 100-650 μm and porosity of 30-70% was fabricated by diffusion bonding of titanium meshes. Pore structure was characterized by Micro-CT scan and SEM. Compressive behavior of porous titanium in the out-of-plane direction was studied. The effect of porosity and pore size on the compressive properties was also discussed based on the deformation mode. The results reveal that the fabrication process can control the porosity precisely. The average pore size of porous titanium can be tailored by adjusting the pore size of titanium meshes. The fabricated porous titanium possesses an anisotropic structure with square pores in the in-plane direction and elongated pores in the out-of-plane direction. The compressive Young's modulus and yield stress are in the range of 1-7.5 GPa and 10-110 MPa, respectively. The dominant compressive deformation mode is buckling of mesh wires, but some uncoordinated buckling is present in porous titanium with lower porosity. Relationship between compressive properties and porosity conforms well to the Gibson-Ashby model. The effect of pore size on compressive properties is fundamentally ascribed to the aspect ratio of titanium meshes. Porous titanium with 60-70% porosity has potential for trabecular bone implant applications.

  10. Does skeletal anatomy reflect adaptation to locomotor patterns? Cortical and trabecular architecture in human and nonhuman anthropoids.

    PubMed

    Shaw, Colin N; Ryan, Timothy M

    2012-02-01

    Although the correspondence between habitual activity and diaphyseal cortical bone morphology has been demonstrated for the fore- and hind-limb long bones of primates, the relationship between trabecular bone architecture and locomotor behavior is less certain. If sub-articular trabecular and diaphyseal cortical bone morphology reflects locomotor patterns, this correspondence would be a valuable tool with which to interpret morphological variation in the skeletal and fossil record. To assess this relationship, high-resolution computed tomography images from both the humeral and femoral head and midshaft of 112 individuals from eight anthropoid genera (Alouatta, Homo, Macaca, Pan, Papio, Pongo, Trachypithecus, and Symphalangus) were analyzed. Within-bone (sub-articular trabeculae vs. mid-diaphysis), between-bone (forelimb vs. hind limb), and among-taxa relative distributions (femoral:humeral) were compared. Three conclusions are evident: (1) Correlations exists between humeral head sub-articular trabecular bone architecture and mid-humerus diaphyseal bone properties; this was not the case in the femur. (2) In contrast to comparisons of inter-limb diaphyseal bone robusticity, among all species femoral head trabecular bone architecture is significantly more substantial (i.e., higher values for mechanically relevant trabecular bone architectural features) than humeral head trabecular bone architecture. (3) Interspecific comparisons of femoral morphology relative to humeral morphology reveal an osteological "locomotor signal" indicative of differential use of the forelimb and hind limb within mid-diaphysis cortical bone geometry, but not within sub-articular trabecular bone architecture. Copyright © 2011 Wiley Periodicals, Inc.

  11. Tantalum trabecular metal - addition of human skeletal cells to enhance bone implant interface strength and clinical application.

    PubMed

    Smith, J O; Sengers, B G; Aarvold, A; Tayton, E R; Dunlop, D G; Oreffo, R O C

    2014-04-01

    The osteo-regenerative properties of allograft have recently been enhanced by addition of autogenous human bone marrow stromal cells (HBMSCs). Limitations in the use of allograft have prompted the investigation of tantalum trabecular metal (TTM) as a potential alternative. TTM is already in widespread orthopaedic use, although in applications where there is poor initial stability, or when TTM is used in conjunction with bone grafting, initial implant loading may need to be limited. The aim of this study was to evaluate the osteo-regenerative potential of TTM with HBMSCs, in direct comparison to human allograft and autograft. HBMSCs were cultured on blocks of TTM, allograft or autograft in basal and osteogenic media. Molecular profiling, confocal and scanning electron microscopy (SEM) and biochemical assays were used to characterize cell adherence, proliferation and phenotype. Mechanical testing was used to define the tensile characteristics of the constructs. HBMSCs displayed adherence and proliferation throughout TTM, evidenced by immunocytochemistry and SEM, with significant cellular ingrowth and matrix production through TTM. In contrast to cells cultured with allograft, cell proliferation assays showed significantly higher activity with TTM (p < 0.001), although molecular profiling confirmed no significant difference in expression of osteogenic genes. In contrast to acellular constructs, mechanical testing of cell-TTM constructs showed enhanced tensile characteristics, which compared favourably to cell-allograft constructs. These studies demonstrated the ability of TTM to support HBMSC growth and osteogenic differentiation comparable to allograft. Thus, TTM represents an alternative to allograft for osteo-regenerative strategies, extending its clinical applications as a substitute for allograft. Copyright © 2012 John Wiley & Sons, Ltd.

  12. Three-dimensional micro-level computational study of Wolff's law via trabecular bone remodeling in the human proximal femur using design space topology optimization.

    PubMed

    Boyle, Christopher; Kim, Il Yong

    2011-03-15

    The law of bone remodeling, commonly referred to as Wolff's Law, asserts that the internal trabecular bone adapts to external loadings, reorienting with the principal stress trajectories to maximize mechanical efficiency creating a naturally optimum structure. The goal of the current study was to utilize an advanced structural optimization algorithm, called design space optimization (DSO), to perform a micro-level three-dimensional finite element bone remodeling simulation on the human proximal femur and analyse the results to determine the validity of Wolff's hypothesis. DSO optimizes the layout of material by iteratively distributing it into the areas of highest loading, while simultaneously changing the design domain to increase computational efficiency. The result is a "fully stressed" structure with minimized compliance and increased stiffness. The large-scale computational simulation utilized a 175 μm mesh resolution and the routine daily loading activities of walking and stair climbing. The resulting anisotropic trabecular architecture was compared to both Wolff's trajectory hypothesis and natural femur samples from literature using a variety of visualization techniques, including radiography and computed tomography (CT). The results qualitatively revealed several anisotropic trabecular regions, that were comparable to the natural human femurs. Quantitatively, the various regional bone volume fractions from the computational results were consistent with quantitative CT analyses. The global strain energy proceeded to become more uniform during optimization; implying increased mechanical efficiency was achieved. The realistic simulated trabecular geometry suggests that the DSO method can accurately predict bone adaptation due to mechanical loading and that the proximal femur is an optimum structure as the Wolff hypothesized. Crown Copyright © 2010. Published by Elsevier Ltd. All rights reserved.

  13. Strong similarities in the creep and damage behaviour of a synthetic bone model compared to human trabecular bone under compressive cyclic loading.

    PubMed

    Purcell, Philip; Tiernan, Stephen; McEvoy, Fiona; Morris, Seamus

    2015-08-01

    Understanding the failure modes which instigate vertebral collapse requires the determination of trabecular bone fatigue properties, since many of these fractures are observed clinically without any preceding overload event. Alternatives to biological bone tissue for in-vitro fatigue studies are available in the form of commercially available open cell polyurethane foams. These test surrogates offer particular advantages compared to biological tissue such as a controllable architecture and greater uniformity. The present study provides a critical evaluation of these models as a surrogate to human trabecular bone tissue for the study of vertebral augmentation treatments such as balloon kyphoplasty. The results of this study show that while statistically significant differences were observed for the damage response of the two materials, both share a similar three phase modulus reduction over their life span with complete failure rapidly ensuing at damage levels above 30%. No significant differences were observed for creep accumulation properties, with greater than 50% of creep strains being accumulated during the first quarter of the life span for both materials. A significant power law relationship was identified between damage accumulation rate and cycles to failure for the synthetic bone model along with comparable microarchitectural features and a hierarchical composite structure consistent with biological bone. These findings illustrate that synthetic bone models offer potential as a surrogate for trabecular bone to an extent that warrants a full validation study to define boundaries of use which compliment traditional tests using biological bone. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. Region-dependent patterns of trabecular bone growth in the human proximal femur: A study of 3D bone microarchitecture from early postnatal to late childhood period.

    PubMed

    Milovanovic, Petar; Djonic, Danijela; Hahn, Michael; Amling, Michael; Busse, Björn; Djuric, Marija

    2017-10-01

    Parallel with body growth and development, bone structure in non-adults is reorganized to achieve the particular design observed in mature individuals. We traced the changes in three-dimensional trabecular microarchitectural design during the phases of locomotor maturation to clarify how human bone adapts to mechanical demands. Micro-CT was performed on biomechanically-relevant subregions of the proximal femur (medial, intermediate and lateral neck regions, intertrochanteric region, metaphyseal region) from early postnatal period to late childhood. Developmental patterns of trabecular microarchitecture showed that gestationally overproduced bone present at birth underwent the most dramatic reduction during the first year, followed by a reversing trend in some of the quantitative parameters (e.g., bone volume fraction, trabecular anisotropy). Certain regional anisotropy already present at birth is further accentuated into the childhood suggesting an adaptation to differential loading environments. Trabecular eccentricity in the femoral neck was particularly accentuated during childhood, giving the medial neck-the site mostly loaded in walking-superior microarchitectural design (high bone volume fraction and anisotropy, the earliest appearance and predominance of plate- and honeycomb-shaped trabeculae). While providing quantitative data on how bone microarchitecture adapts to increasing mechanical demands occurring during the phases of locomotor maturation, the study reveals how regional anisotropy develops in the proximal femur to ensure a functional and competent bone structure. Decomposing the region-specific patterns of bone mass accrual is important in understanding skeletal adaptations to bipedalism, as well for understanding why fractures often occur location-dependent, both in pediatric and elderly individuals. © 2017 Wiley Periodicals, Inc.

  15. Tomography of human trabecular bone with a laser-wakefield driven x-ray source

    NASA Astrophysics Data System (ADS)

    Cole, J. M.; Wood, J. C.; Lopes, N. C.; Poder, K.; Abel, R. L.; Alatabi, S.; Bryant, J. S. J.; Jin, A.; Kneip, S.; Mecseki, K.; Parker, S.; Symes, D. R.; Sandholzer, M. A.; Mangles, S. P. D.; Najmudin, Z.

    2016-01-01

    A laser-wakefield driven x-ray source is used for the radiography of human bone. The betatron motion of accelerated electrons generates x-rays which are hard (critical energy {{E}\\text{crit}}>30 keV), have small source size (<3 μm) and high average brightness. The x-rays are generated from a helium gas cell which is near-instantly replenishable, and thus the average photon flux is limited by the repetition rate of the driving laser rather than the breakdown of the x-ray source. A tomograph of a human bone sample was recorded with a resolution down to 50 μm. The photon flux was sufficiently high that a radiograph could be taken with each laser shot, and the fact that x-ray beams were produced on 97% of shots minimised failed shots and facilitated full micro-computed tomography in a reasonable time scale of several hours, limited only by the laser repetition rate. The x-ray imaging beamline length (not including the laser) is shorter than that of a synchrotron source due to the high accelerating fields and small source size. Hence this interesting laboratory-based source may one day bridge the gap between small microfocus x-ray tubes and large synchrotron facilities.

  16. The classic: The architecture of the trabecular bone (tenth contribution on the mechanics of the human skeletal framework).

    PubMed

    von Meyer, Georg Hermann

    2011-11-01

    Hermann von Meyer may rightfully be considered the original proposer of the concept of trabecular architecture following patterns suggesting the directions of principle compressive and tensile stresses in a similarly shaped trabecular structure. Until the mid 19th Century, few had observed trabecular architecture, and when depicted was generally considered to have little regularity. In the 1830s Bourgery, Ward, and Wyman independently described the regularity of trabecular architecture, but according to Koch (1917) the proposed explanations were in error or overly simplified. Karl Culmann, an engineer and the developer of "graphic statics," attended a lecture of von Meyer and made the connection, which was then developed by the latter in this seminal paper. We present the paper in translation here. The original German article entitled "Die Architectur der Spongiosa" was often written in long, cumbersome sentences, with sometimes obscure meanings. We have taken considerable license in translating, rearranging punctuation, and condensing the material into modern terminology and style, while attempting to maintain the flavor of von Meyer's writing. We thank Dr. Per K. Amundson for the original translation; Drs. John Skedros and Richard Brand made additional suggestions. An accompanying biographical sketch of Hermann von Meyer is available at DOI 10.1007/s11999-011-2040-6.

  17. Finite element micro-modelling of a human ankle bone reveals the importance of the trabecular network to mechanical performance: new methods for the generation and comparison of 3D models.

    PubMed

    Parr, W C H; Chamoli, U; Jones, A; Walsh, W R; Wroe, S

    2013-01-04

    Most modelling of whole bones does not incorporate trabecular geometry and treats bone as a solid non-porous structure. Some studies have modelled trabecular networks in isolation. One study has modelled the performance of whole human bones incorporating trabeculae, although this required considerable computer resources and purpose-written code. The difference between mechanical behaviour in models that incorporate trabecular geometry and non-porous models has not been explored. The ability to easily model trabecular networks may shed light on the mechanical consequences of bone loss in osteoporosis and remodelling after implant insertion. Here we present a Finite Element Analysis (FEA) of a human ankle bone that includes trabecular network geometry. We compare results from this model with results from non-porous models and introduce protocols achievable on desktop computers using widely available softwares. Our findings show that models including trabecular geometry are considerably stiffer than non-porous whole bone models wherein the non-cortical component has the same mass as the trabecular network, suggesting inclusion of trabecular geometry is desirable. We further present new methods for the construction and analysis of 3D models permitting: (1) construction of multi-property, non-porous models wherein cortical layer thickness can be manipulated; (2) maintenance of the same triangle network for the outer cortical bone surface in both 3D reconstruction and non-porous models allowing exact replication of load and restraint cases; and (3) creation of an internal landmark point grid allowing direct comparison between 3D FE Models (FEMs).

  18. Synchrotron radiation micro-CT at the micrometer scale for the analysis of the three-dimensional morphology of microcracks in human trabecular bone.

    PubMed

    Larrue, Aymeric; Rattner, Aline; Peter, Zsolt-Andrei; Olivier, Cécile; Laroche, Norbert; Vico, Laurence; Peyrin, Françoise

    2011-01-01

    Bone quality is an important concept to explain bone fragility in addition to bone mass. Among bone quality factors, microdamage which appears in daily life is thought to have a marked impact on bone strength and plays a major role in the repair process. The starting point for all studies designed to further our understanding of how bone microdamage initiate or dissipate energy, or to investigate the impact of age, gender or disease, remains reliable observation and measurement of microdamage. In this study, 3D Synchrotron Radiation (SR) micro-CT at the micrometric scale was coupled to image analysis for the three-dimensional characterization of bone microdamage in human trabecular bone specimens taken from femoral heads. Specimens were imaged by 3D SR micro-CT with a voxel size of 1.4 µm. A new tailored 3D image analysis technique was developed to segment and quantify microcracks. Microcracks from human trabecular bone were observed in different tomographic sections as well as from 3D renderings. New 3D quantitative measurements on the microcrack density and morphology are reported on five specimens. The 3D microcrack density was found between 3.1 and 9.4/mm3 corresponding to a 2D density between 0.55 and 0.76 /mm2. The microcrack length and width measured in 3D on five selected microcrack ranged respectively from 164 µm to 209 µm and 100 µm to 120 µm. This is the first time that various microcracks in unloaded human trabecular bone--from the simplest linear crack to more complex cross-hatch cracks--have been examined and quantified by 3D imaging at this scale. The suspected complex morphology of microcracks is here considerably more evident than in the 2D observations. In conclusion, this technique opens new perspective for the 3D investigation of microcracks and the impact of age, disease or treatment.

  19. Sealing the live part of the skin: the integrated meshwork of desmosomes, tight junctions and curvilinear ridge structures in the cells of the uppermost granular layer of the human epidermis.

    PubMed

    Schlüter, Holger; Wepf, Roger; Moll, Ingrid; Franke, Werner W

    2004-12-01

    In the literature the question of whether a system structurally and functionally related to the barrier function of the tight junctions (TJs) of polarized epithelia exists in the epidermis has been and still is controversially discussed. We have systematically addressed this question in a study of the granular layer of fetal and adult human epidermis, combining different light and electron microscopic methods. We show that the lateral membranes of the cells of the stratum granulosum are connected by an extended subapical complex system integrating desmosomes and TJ structures identified as sites of close membrane-membrane contact and as regions of membrane-to-membrane apposition that in immunoelectron microscopy are positive for TJ marker proteins, notably occludin, indicative of an extended, probably continuous TJ barrier. In addition, we have noted in freeze-fractures of the apical membrane attaching this layer to the basalmost membrane of the stratum corneum an extended system integrating desmosomes with intramembraneous ridge configurations that appear as strands, circles, lariats or complex meshworks showing numerous continuities with the desmosomes. In some regions this system interconnecting desmosomes with curvilinear ridge structures occupies the major part of the plasma membrane. The molecular organizations and possible functional contributions of both structural systems positioned at the border between the living portion of the epidermis and the corneal layer are discussed, in particular in relation to the formation of a stable association between the two layers and of a barrier to the paracellular flow of molecules and particles. It is also discussed whether similar structures occur in other keratinizing stratified squamous epithelia, in squamous metaplasias and in tumors derived from such tissues.

  20. Variations in active outflow along the trabecular outflow pathway.

    PubMed

    Cha, Elliott D K; Xu, Jia; Gong, Lihua; Gong, Haiyan

    2016-05-01

    Previous tracer studies have shown segmental outflow in the trabecular meshwork (TM) and along the inner wall (IW) of Schlemm's canal (SC). Whether segmental outflow is conserved distal to SC has not yet been investigated. This study aims to investigate whether the segmented pattern of outflow is conserved in distal outflow pathways by using a newly developed global imaging method and to evaluate variations of active outflow in three distinct regions along trabecular outflow pathway. Six normal whole globe human eyes were first perfused at 15 mmHg to establish a stable baseline outflow facility. The anterior chamber was then exchanged (5 mL) and perfused with fluorescent microspheres (0.002% v/v, 200 μL) to label areas of active outflow. All eyes were perfusion fixed and dissected into anterior segments. The TM and scleral surface were en face imaged globally. Effective filtration area (EFA) and fluorescent tracer distribution and intensity were analyzed in global images for both the TM and episcleral veins (EPVs). Anterior segments were further dissected into a minimum of 16 radial wedges, from which frontal sections were cut, stained, and imaged, using confocal microscopy. EFA from all three locations along the trabecular outflow pathway were measured and compared. Additionally, TM thickness, SC height, and total number of collector channels (CC) were analyzed and compared between active and inactive areas of outflow. Statistical analysis was performed using Student's t-tests and Wilcoxon signed-rank test with a required significance of p ≤ 0.05. All three locations showed a segmental outflow pattern. The TM had a significantly higher mean EFA (86.3 ± 3.5%) compared to both the IW (34.7 ± 2.9%; p ≤ 0.01) and EPVs (41.1 ± 3.8%; p ≤ 0.01). No significant difference in mean EFA was found between IW and EPVs. Preferential active outflow was observed in the nasal and inferior quadrants. TM thickness was significantly larger in areas of active

  1. An Orientation Distribution Function for Trabecular Bone

    SciTech Connect

    Lawrence Livermore National Laboratory

    2004-10-08

    We describe a new method for quantifying the orientation of trabecular bone from three-dimensional images. Trabecular lattices from five human vertebrae were decomposed into individual trabecular elements, and the orientation, mass, and thickness of each element were recorded. Continuous functions that described the total mass (M({var_phi},{theta})) and mean thickness ({tau}({var_phi},{theta})) of all trabeculae as a function of orientation were derived. The results were compared with experimental measurements of the elastic modulus in the three principal anatomic directions. A power law scaling relationship between the anisotropies in mass and elastic modulus was observed; the scaling exponent was 1.41 (R{sup 2} = 0.88). As expected, the preponderance of trabecular mass was oriented along the cranial-caudal direction; on average, there was 3.4 times more mass oriented vertically than horizontally. Moreover, the vertical trabeculae were 30% thicker, on average, than the horizontal trabeculae. The vertical trabecular thickness was inversely related to the connectivity (R{sup 2} = 0.70; p = 0.07), suggesting a possible organization into either few, thick trabeculae or many thin trabeculae. The method, which accounts for the mechanical connectedness of the lattice, provides a rapid way to both visualize and quantify the three-dimensional organization of trabecular bone.

  2. Material Properties of the Mandibular Trabecular Bone

    PubMed Central

    Lakatos, Éva; Magyar, Lóránt; Bojtár, Imre

    2014-01-01

    The present paper introduces a numerical simulation aided, experimental method for the measurement of Young's modulus of the trabecular substance in the human mandible. Compression tests were performed on fresh cadaveric samples containing trabecular bone covered with cortical layer, thus avoiding the destruction caused by the sterilization, preservation, and storage and the underestimation of the stiffness resulting from the individual failure of the trabeculae cut on the surfaces. The elastic modulus of the spongiosa was determined by the numerical simulation of each compression test using a specimen specific finite element model of each sample. The received mandibular trabecular bone Young's modulus values ranged from 6.9 to 199.5 MPa. PMID:27006933

  3. Immunohistochemical Detection of CTGF in the Human Eye.

    PubMed

    van Setten, Gysbert B; Trost, Andrea; Schrödl, Falk; Kaser-Eichberger, Alexandra; Bogner, Barbara; van Setten, Mercedes; Heindl, Ludwig M; Grabner, Günther; Reitsamer, Herbert A

    2016-12-01

    Purpose/Aim of the study: Connective tissue growth factor (CTGF) is a key player in the control of extracellular matrix remodeling, fibrosis, and angiogenesis. It is also involved in the modification of the trabecular meshwork, thus potentially modulating outflow facility and intraocular pressure (IOP). As a consequence, CTGF might be relevant for the development of elevated IOP, a major risk factor in glaucoma-pathogenesis. While comprehensive information on the origins of CTGF in the human eye is not available, the goal of this study is to identify ocular sources of CTGF using morphological methods.

  4. Trabecular architecture analysis in femur radiographic images using fractals.

    PubMed

    Udhayakumar, G; Sujatha, C M; Ramakrishnan, S

    2013-04-01

    Trabecular bone is a highly complex anisotropic material that exhibits varying magnitudes of strength in compression and tension. Analysis of the trabecular architectural alteration that manifest as loss of trabecular plates and connection has been shown to yield better estimation of bone strength. In this work, an attempt has been made toward the development of an automated system for investigation of trabecular femur bone architecture using fractal analysis. Conventional radiographic femur bone images recorded using standard protocols are used in this study. The compressive and tensile regions in the images are delineated using preprocessing procedures. The delineated images are analyzed using Higuchi's fractal method to quantify pattern heterogeneity and anisotropy of trabecular bone structure. The results show that the extracted fractal features are distinct for compressive and tensile regions of normal and abnormal human femur bone. As the strength of the bone depends on architectural variation in addition to bone mass, this study seems to be clinically useful.

  5. Mechanical model of blebbing in nuclear lamin meshworks.

    PubMed

    Funkhouser, Chloe M; Sknepnek, Rastko; Shimi, Takeshi; Goldman, Anne E; Goldman, Robert D; Olvera de la Cruz, Monica

    2013-02-26

    Much of the structural stability of the nucleus comes from meshworks of intermediate filament proteins known as lamins forming the inner layer of the nuclear envelope called the nuclear lamina. These lamin meshworks additionally play a role in gene expression. Abnormalities in nuclear shape are associated with a variety of pathologies, including some forms of cancer and Hutchinson-Gilford Progeria Syndrome, and often include protruding structures termed nuclear blebs. These nuclear blebs are thought to be related to pathological gene expression; however, little is known about how and why blebs form. We have developed a minimal continuum elastic model of a lamin meshwork that we use to investigate which aspects of the meshwork could be responsible for bleb formation. Mammalian lamin meshworks consist of two types of lamin proteins, A type and B type, and it has been reported that nuclear blebs are enriched in A-type lamins. Our model treats each lamin type separately and thus, can assign them different properties. Nuclear blebs have been reported to be located in regions where the fibers in the lamin meshwork have a greater separation, and we find that this greater separation of fibers is an essential characteristic for generating nuclear blebs. The model produces structures with comparable morphologies and distributions of lamin types as real pathological nuclei. Thus, preventing this opening of the meshwork could be a route to prevent bleb formation, which could be used as a potential therapy for the pathologies associated with nuclear blebs.

  6. Aquaporin-1 Expression and Conventional Aqueous Outflow in Human Eyes

    PubMed Central

    Stamer, W. Daniel; Chan, Darren W.H.; Conley, Shannon M.; Coons, Serena; Ethier, C. Ross

    2008-01-01

    Aquaporin channels facilitate the enhanced permeability of secretory and absorptive tissues to water. In the conventional drainage tract, aquaporin-1 is expressed but its contribution to outflow facility is unknown. The purpose of the present study was to determine the effect of elevated aquaporin-1 expression by cells of the human conventional drainage pathway on outflow facility. Using thirteen pairs of human anterior segments in organ culture, we modified aquaporin-1 protein expression in outflow cells using adenovirus encoding human aquaporin-1. Contralateral anterior segments served as controls and were transduced with adenovirus encoding beta galactosidase. By confocal immunofluorescence microscopy, we observed that inner trabecular meshwork cells from anterior segments exposed to adenovirus (via injection into the inlet tubing during perfusion) had increased aquaporin-1 protein expression compared to endogenous levels. In contrast, elevation of aquaporin-1 protein in outer meshwork cells (juxtacanalicular region) and Schlemm’s canal required transduction of adenovirus into anterior segments using retroperfusion via episcleral veins. Regardless of exposure route, outflow facility of experimental segments was not different than control. Specifically, overexpression of aquaporin-1 in the inner meshwork resulted in an average facility change of −2.0 ± 9.2 %, while overexpression of aquaporin-1 in the resistance-generating region changed outflow facility by −3.2 ± 11.2 %. Taken together, these results indicate that a transcellular pathway, mediated by aquaporin-1, does not contribute significantly to bulk outflow through the conventional aqueous outflow tract of human eyes. PMID:18657536

  7. An Elastic Model of Blebbing in Nuclear Lamin Meshworks

    NASA Astrophysics Data System (ADS)

    Funkhouser, Chloe; Sknepnek, Rastko; Shimi, Takeshi; Goldman, Anne; Goldman, Robert; Olvera de La Cruz, Monica

    2013-03-01

    A two-component continuum elastic model is introduced to analyze a nuclear lamin meshwork, a structural element of the lamina of the nuclear envelope. The main component of the lamina is a meshwork of lamin protein filaments providing mechanical support to the nucleus and also playing a role in gene expression. Abnormalities in nuclear shape are associated with a variety of pathologies, including some forms of cancer and Hutchinson-Gilford progeria syndrome, and are often characterized by protruding structures termed nuclear blebs. Nuclear blebs are rich in A-type lamins and may be related to pathological gene expression. We apply the two-dimensional elastic shell model to determine which characteristics of the meshwork could be responsible for blebbing, including heterogeneities in the meshwork thickness and mesh size. We find that if one component of the lamin meshwork, rich in A-type lamins, has a tendency to form a larger mesh size than that rich in B-type lamins, this is sufficient to cause segregation of the lamin components and also to form blebs rich in A-type lamins. The model produces structures with comparable morphologies and mesh size distributions as the lamin meshworks of real, pathological nuclei. Funded by US DoE Award DEFG02-08ER46539 and by the DDR&E and AFOSR under Award FA9550-10-1-0167; simulations performed on NU Quest cluster

  8. Automated trabecular bone histomorphometry

    NASA Technical Reports Server (NTRS)

    Polig, E.; Jee, W. S. S.

    1985-01-01

    The toxicity of alpha-emitting bone-seeking radionuclides and the relationship between bone tumor incidence and the local dosimetry of radionuclides in bone are investigated. The microdistributions of alpha-emitting radionuclides in the trabecular bone from the proximal humerus, distal humerus, proximal ulna, proximal femur, and distal femur of six young adult beagles injected with Am-241 (three with 2.8 micro-Ci/kg and three with 0.9 micro-Ci/kg) are estimated using a computer-controlled microscope photometer system; the components of the University of Utah Optical Track Scanner are described. The morphometric parameters for the beagles are calculated and analyzed. It is observed that the beagles injected with 0.9 micro-Ci of Am-241/kg showed an increase in the percentage of bone and trabecular bone thickness, and a reduction in the width of the bone marrow space and surface/volume ratio. The data reveal that radiation damage causes abnormal bone structure.

  9. iStent® Trabecular Microbypass Stent: An Update

    PubMed Central

    Resende, Arthur Fernandes; Patel, Neal Sanjay; Waisbourd, Michael; Katz, L. Jay

    2016-01-01

    Due to the high rates of complications and failure experienced with current glaucoma procedures, there is a continuous search for a safer and more effective glaucoma surgery. A new class of procedures termed minimally invasive glaucoma surgeries (MIGS) aim to fill this void by offering an alternative method of IOP reduction associated with markedly reduced complication rates and shorter recovery times. The iStent, a trabecular microbypass stent, is a MIGS device that has quickly gained popularity. The device allows aqueous humor to directly drain from the anterior chamber into Schlemm's canal by bypassing an obstructed trabecular meshwork. This review examines publications about the iStent, focusing on the device's efficacy, safety, and cost when a single iStent or multiple iStents are implanted in combination with cataract surgery or as a solo procedure. Current data suggest that the iStent is a safe and effective tool in the management of mild-to-moderate glaucoma, notable for its limited complications and absence of serious adverse events following implantation. As valuable experience is gained performing ab interno MIGS, increasing familiarity with angle anatomy and iStent placement, and as newer stent designs are developed, there is promise of continual improvement in the surgical management of glaucoma. PMID:27413541

  10. Comparison of the abilities of human parathyroid hormone (hPTH)-(1-34) and [Leu27]-cyclo(Glu22-Lys26)-hPTH-(1-31)NH2 to stimulate femoral trabecular bone growth in ovariectomized rats.

    PubMed

    Whitfield, J F; Morley, P; Willick, G; MacLean, S; Ross, V; Isaacs, R J; Barbier, J R

    1998-11-01

    hPTH-(1-31)NH2, so far the smallest of the potently anabolic N-terminal fragments of the human parathyroid hormone, stimulates trabecular growth in the distal femurs of ovariectomized (OVX) rats as strongly as hPTH-(1-34) when injected at a high daily dose such as 1 nmol/100 g of body weight, but it is only about 70% as effective as hPTH-(1-34) when injected at the suboptimal 0.6 nmol/100 g of body weight. A lactam derivative of hPTH-(1-31)-NH2, [Leu27]-cyclo(Glu22-Lys26)-hPTH-(1-31)NH2, is a much more effective stimulator of adenylyl cyclase in ROS 17/2 rat osteoblast-like cells and a significantly more effective stimulator of femoral trabecular growth in OVX rats than hPTH-(1-31)NH2. We have now shown that [Leu27]-cyclo(Glu22-Lys26)-hPTH-(1-31)NH2 prevents the OVX-induced loss of femoral trabeculae significantly more effectively than hPTH-(1-34) and stimulates the thickening of the trabeculae remaining in severely depleted femoral trabecular bone of OVX rats as effectively as hPTH-(1-34) when injected at 0.6 nmol/100 g of body weight.

  11. Calculations of flow resistance in the juxtacanalicular meshwork.

    PubMed

    Ethier, C R; Kamm, R D; Palaszewski, B A; Johnson, M C; Richardson, T M

    1986-12-01

    The structure of the juxtacanalicular meshwork (JCM) was analyzed morphometrically, and the resulting data were used to calculate the resistance to flow through this tissue. Two models of the JCM were presented and compared. In the first (Model A), aqueous humor was assumed to flow via open channels within a solid framework, while, in the second (Model B), these open spaces were assumed to be filled with extracellular matrix gel. An expression giving the resistance of such a gel as a function of gel concentration was presented and tested on corneal and scleral stroma. Morphometry of normal and glaucomatous human eyes showed that Model A underpredicted the resistance of the JCM by factors of 10-100, suggesting that a GAG or proteoglycan gel may control the flow resistance of this tissue. This was supported by Model B, which showed that measured bulk concentrations of GAGs were consistent with gel concentrations needed to account for the estimated resistance of the JCM in vivo. Some limitations and implications of Model B were discussed.

  12. Creep does not contribute to fatigue in bovine trabecular bone.

    PubMed

    Moore, T L A; O'Brien, F J; Gibson, L J

    2004-06-01

    In both cortical and trabecular bone loaded in fatigue, the stress-strain loops translate along the strain axis. Previous studies have suggested that this translation is the result of creep associated with the mean stress applied in the fatigue test. In this study, we measured the residual strrain (corresponding to the translation of the stress-strain loops) in fatigue tests on bovine trabecular bone and compared it to an upper bound estimate of the creep strain in each test. Our results indicate that the contribution of creep to the translation of the stress-strain loops is negligible in bovine trabecular bone. These results, combined with models for fatigue in lower density bone, suggest that that creep does not contribute to the fatigue of normal human bone. Creep may make a significant contribution to fatigue in low-density osteoporotic bone in which trabeculae have resorbed, reducing the connectivity of the trabecular structure.

  13. Experimental Study of Diffusion Coefficients of Water through the Collagen: Apatite Porosity in Human Trabecular Bone Tissue

    PubMed Central

    Bini, Fabiano; Marinozzi, Andrea

    2014-01-01

    We firstly measured the swelling of single trabeculae from human femur heads during water imbibition. Since the swelling is caused by water diffusing from external surfaces to the core of the sample, by measuring the sample swelling over time, we obtained direct information about the transport of fluids through the intimate constituents of bone, where the mineralization process takes place. We developed an apparatus to measure the free expansion of the tissue during the imbibition. In particular, we measured the swelling along three natural axes (length L, width W, and thickness T) of plate-like trabeculae. For this aim, we developed a 3D analytical model of the water uptake by the sample that was performed according to Fickian transport mechanism. The results were then utilized to predict the swelling over time along the three sample directions (L, W, T) and the apparent diffusion coefficients DT, DW, and DL. PMID:24967405

  14. Comparative forefoot trabecular bone architecture in extant hominids.

    PubMed

    Griffin, Nicole L; D'Août, Kristiaan; Ryan, Timothy M; Richmond, Brian G; Ketcham, Richard A; Postnov, Andrei

    2010-08-01

    The appearance of a forefoot push-off mechanism in the hominin lineage has been difficult to identify, partially because researchers disagree over the use of the external skeletal morphology to differentiate metatarsophalangeal joint functional differences in extant great apes and humans. In this study, we approach the problem by quantifying properties of internal bone architecture that may reflect different loading patterns in metatarsophalangeal joints in humans and great apes. High-resolution x-ray computed tomography data were collected for first and second metatarsal heads of Homo sapiens (n = 26), Pan paniscus (n = 17), Pan troglodytes (n = 19), Gorilla gorilla (n = 16), and Pongo pygmaeus (n = 20). Trabecular bone fabric structure was analyzed in three regions of each metatarsal head. While bone volume fraction did not significantly differentiate human and great ape trabecular bone structure, human metatarsal heads generally show significantly more anisotropic trabecular bone architectures, especially in the dorsal regions compared to the corresponding areas of the great ape metatarsal heads. The differences in anisotropy between humans and great apes support the hypothesis that trabecular architecture in the dorsal regions of the human metatarsals are indicative of a forefoot habitually used for propulsion during gait. This study provides a potential route for predicting forefoot function and gait in fossil hominins from metatarsal head trabecular bone architecture. Copyright 2010 Elsevier Ltd. All rights reserved.

  15. Denosumab, a fully human RANKL antibody, reduced bone turnover markers and increased trabecular and cortical bone mass, density, and strength in ovariectomized cynomolgus monkeys.

    PubMed

    Ominsky, Michael S; Stouch, Brian; Schroeder, Joseph; Pyrah, Ian; Stolina, Marina; Smith, Susan Y; Kostenuik, Paul J

    2011-08-01

    similar or greater load values at given BMC values compared with OVX-Veh or Sham. In summary, denosumab markedly reduced biochemical markers of bone remodeling and increased cortical and trabecular bone mass in adult OVX cynos. Denosumab improved structural bone strength parameters at all sites analyzed, and strength remained highly correlated with bone mass. There was no evidence for reduced material strength properties of cortical bone with denosumab over this time period, which approximates to 4years of remodeling in the slower-remodeling adult human skeleton. These data indicate that denosumab increased bone strength by increasing bone mass and preserving bone quality. Copyright © 2011 Elsevier Inc. All rights reserved.

  16. Characterization of trabecular bone plate-rod microarchitecture using multirow detector CT and the tensor scale: Algorithms, validation, and applications to pilot human studies

    PubMed Central

    Saha, Punam K.; Liu, Yinxiao; Chen, Cheng; Jin, Dakai; Letuchy, Elena M.; Xu, Ziyue; Amelon, Ryan E.; Burns, Trudy L.; Torner, James C.; Levy, Steven M.; Calarge, Chadi A.

    2015-01-01

    Purpose: Osteoporosis is a common bone disease associated with increased risk of low-trauma fractures leading to substantial morbidity, mortality, and financial costs. Clinically, osteoporosis is defined by low bone mineral density (BMD); however, increasing evidence suggests that trabecular bone (TB) microarchitectural quality is an important determinant of bone strength and fracture risk. A tensor scale based algorithm for in vivo characterization of TB plate-rod microarchitecture at the distal tibia using multirow detector CT (MD-CT) imaging is presented and its performance and applications are examined. Methods: The tensor scale characterizes individual TB on the continuum between a perfect plate and a perfect rod and computes their orientation using optimal ellipsoidal representation of local structures. The accuracy of the method was evaluated using computer-generated phantom images at a resolution and signal-to-noise ratio achievable in vivo. The robustness of the method was examined in terms of stability across a wide range of voxel sizes, repeat scan reproducibility, and correlation between TB measures derived by imaging human ankle specimens under ex vivo and in vivo conditions. Finally, the application of the method was evaluated in pilot human studies involving healthy young-adult volunteers (age: 19 to 21 yr; 51 females and 46 males) and patients treated with selective serotonin reuptake inhibitors (SSRIs) (age: 19 to 21 yr; six males and six females). Results: An error of (3.2% ± 2.0%) (mean ± SD), computed as deviation from known measures of TB plate-width, was observed for computer-generated phantoms. An intraclass correlation coefficient of 0.95 was observed for tensor scale TB measures in repeat MD-CT scans where the measures were averaged over a small volume of interest of 1.05 mm diameter with limited smoothing effects. The method was found to be highly stable at different voxel sizes with an error of (2.29% ± 1.56%) at an in vivo voxel size

  17. Characterization of trabecular bone plate-rod microarchitecture using multirow detector CT and the tensor scale: Algorithms, validation, and applications to pilot human studies.

    PubMed

    Saha, Punam K; Liu, Yinxiao; Chen, Cheng; Jin, Dakai; Letuchy, Elena M; Xu, Ziyue; Amelon, Ryan E; Burns, Trudy L; Torner, James C; Levy, Steven M; Calarge, Chadi A

    2015-09-01

    Osteoporosis is a common bone disease associated with increased risk of low-trauma fractures leading to substantial morbidity, mortality, and financial costs. Clinically, osteoporosis is defined by low bone mineral density (BMD); however, increasing evidence suggests that trabecular bone (TB) microarchitectural quality is an important determinant of bone strength and fracture risk. A tensor scale based algorithm for in vivo characterization of TB plate-rod microarchitecture at the distal tibia using multirow detector CT (MD-CT) imaging is presented and its performance and applications are examined. The tensor scale characterizes individual TB on the continuum between a perfect plate and a perfect rod and computes their orientation using optimal ellipsoidal representation of local structures. The accuracy of the method was evaluated using computer-generated phantom images at a resolution and signal-to-noise ratio achievable in vivo. The robustness of the method was examined in terms of stability across a wide range of voxel sizes, repeat scan reproducibility, and correlation between TB measures derived by imaging human ankle specimens under ex vivo and in vivo conditions. Finally, the application of the method was evaluated in pilot human studies involving healthy young-adult volunteers (age: 19 to 21 yr; 51 females and 46 males) and patients treated with selective serotonin reuptake inhibitors (SSRIs) (age: 19 to 21 yr; six males and six females). An error of (3.2% ± 2.0%) (mean ± SD), computed as deviation from known measures of TB plate-width, was observed for computer-generated phantoms. An intraclass correlation coefficient of 0.95 was observed for tensor scale TB measures in repeat MD-CT scans where the measures were averaged over a small volume of interest of 1.05 mm diameter with limited smoothing effects. The method was found to be highly stable at different voxel sizes with an error of (2.29% ± 1.56%) at an in vivo voxel size as compared to the original

  18. The effective elastic properties of human trabecular bone may be approximated using micro-finite element analyses of embedded volume elements.

    PubMed

    Daszkiewicz, Karol; Maquer, Ghislain; Zysset, Philippe K

    2017-06-01

    Boundary conditions (BCs) and sample size affect the measured elastic properties of cancellous bone. Samples too small to be representative appear stiffer under kinematic uniform BCs (KUBCs) than under periodicity-compatible mixed uniform BCs (PMUBCs). To avoid those effects, we propose to determine the effective properties of trabecular bone using an embedded configuration. Cubic samples of various sizes (2.63, 5.29, 7.96, 10.58 and 15.87 mm) were cropped from [Formula: see text] scans of femoral heads and vertebral bodies. They were converted into [Formula: see text] models and their stiffness tensor was established via six uniaxial and shear load cases. PMUBCs- and KUBCs-based tensors were determined for each sample. "In situ" stiffness tensors were also evaluated for the embedded configuration, i.e. when the loads were transmitted to the samples via a layer of trabecular bone. The Zysset-Curnier model accounting for bone volume fraction and fabric anisotropy was fitted to those stiffness tensors, and model parameters [Formula: see text] (Poisson's ratio) [Formula: see text] and [Formula: see text] (elastic and shear moduli) were compared between sizes. BCs and sample size had little impact on [Formula: see text]. However, KUBCs- and PMUBCs-based [Formula: see text] and [Formula: see text], respectively, decreased and increased with growing size, though convergence was not reached even for our largest samples. Both BCs produced upper and lower bounds for the in situ values that were almost constant across samples dimensions, thus appearing as an approximation of the effective properties. PMUBCs seem also appropriate for mimicking the trabecular core, but they still underestimate its elastic properties (especially in shear) even for nearly orthotropic samples.

  19. Incorporation of tenascin-C into the extracellular matrix by periostin underlies an extracellular meshwork architecture.

    PubMed

    Kii, Isao; Nishiyama, Takashi; Li, Minqi; Matsumoto, Ken-Ichi; Saito, Mitsuru; Amizuka, Norio; Kudo, Akira

    2010-01-15

    Extracellular matrix (ECM) underlies a complicated multicellular architecture that is subjected to significant forces from mechanical environment. Although various components of the ECM have been enumerated, mechanisms that evolve the sophisticated ECM architecture remain to be addressed. Here we show that periostin, a matricellular protein, promotes incorporation of tenascin-C into the ECM and organizes a meshwork architecture of the ECM. We found that both periostin null mice and tenascin-C null mice exhibited a similar phenotype, confined tibial periostitis, which possibly corresponds to medial tibial stress syndrome in human sports injuries. Periostin possessed adjacent domains that bind to tenascin-C and the other ECM protein: fibronectin and type I collagen, respectively. These adjacent domains functioned as a bridge between tenascin-C and the ECM, which increased deposition of tenascin-C on the ECM. The deposition of hexabrachions of tenascin-C may stabilize bifurcations of the ECM fibrils, which is integrated into the extracellular meshwork architecture. This study suggests a role for periostin in adaptation of the ECM architecture in the mechanical environment.

  20. Olfactomedin-like 3 (OLFML3) gene expression in baboon and human ocular tissues: cornea, lens, uvea and retina

    PubMed Central

    Rodríguez-Sánchez, Iràm Pablo; Garza-Rodríguez, Maria Lourdes; Mohamed-Noriega, Karim; Voruganti, Venkata Saroja; Tejero, Maria Elizabeth; Delgado-Enciso, Ivan; Ibave, Diana Cristina Perez; Schlabritz-Loutsevitch, Natalia E.; Mohamed-Noriega, Jibran; Martinez-Fierro, Margarita L; Reséndez-Pérez, Diana; Cole, Shelley A; Cavazos-Adame, Humberto; Comuzzie, Anthony G.; Mohamed-Hamsho, Jesús; Barrera-Saldaña, Hugo Alberto

    2013-01-01

    Background Olfactomedin-like is a polyfunctional polymeric glycoprotein. This family has at least four members. One member of this family is OLFML3, which is preferentially expressed in placenta but is also detected in other adult tissues including the liver and heart. However, the orthologous rat gene is expressed in the iris, sclera, trabecular meshwork, retina, and optic nerve. Methods OLFML3 amplification was performed by RT-PCR from human and baboon ocular tissues. The products were cloned and sequenced. Results We report OFML3 expression in human and baboon eye. The full CDS has 1221 bp, from which a OFR of 406 amino acid was obtained. The baboon OLFML3 gene nucleotidic sequence has 98%, and amino acidic 99% similarity with humans. Conclusions OLFML3 expression in human and baboon ocular tissues and its high similarity make the baboon a powerful model to deduce the physiological and/or metabolic function of this protein in the eye. PMID:23398349

  1. Immunolocalization of CYP1B1 in normal, human, fetal and adult eyes.

    PubMed

    Doshi, Manali; Marcus, Craig; Bejjani, Bassem A; Edward, Deepak P

    2006-01-01

    CYP1B1 is a cytochrome P450 enzyme implicated in autosomal recessive primary congenital glaucoma (PCG). The mechanism and function of CYP1B1 in the development of the PCG phenotype is unknown. Previously, investigators have reported detection of Cyp1b1 mRNA in the ciliary body and epithelium and neuroepithelium in the developing mouse eye, employing in situ hybridization techniques. Similarly, additional investigators have detected CYP1B1 mRNA in the iris, ciliary body, non-pigmented ciliary epithelial line, cornea, retinal-pigment epithelium, and retina in the human adult eye, using Northern blotting. This study was designed to immunolocalize CYP1B1 protein in the various ocular structures of normal, human fetal and adult eyes. Normal fetal and adult eyes were immunolabeled with a polyclonal antibody against human CYP1B1 using indirect immunofluorescence, and then compared with appropriate controls. The intensity of immunolabeling of the various ocular structures was assessed by qualitative and semi-quantitative techniques. In the anterior segment anti-CYP1B1 immunoreactivity (IR) was detected early in fetal development in the primitive ciliary epithelium. As well, the most intense CYP1B1 IR was in the non-pigmented ciliary epithelium. In addition, CYP1B1 IR was also present in the corneal epithelium and keratocytes, both layers of the iris pigmented epithelium, and retina. However, CYP1B1 IR was absent in the trabecular meshwork in all of the samples. In general, CYP1B1 immunolabeling in the human fetal eyes was more intense when compared to adult eyes. CYP1B1 IR was primarily immunolocalized to the non-pigmented ciliary epithelium and early in fetal development. In addition, CYP1B1 IR was not detected in the trabecular meshwork. These findings suggest that the abnormalities in the development of the trabecular meshwork in PCG may result from diminished or absent metabolism of important endogenous substrates in the ciliary epithelium due to non-functional CYP1B1

  2. Bone formation in trabecular bone cell seeded scaffolds used for reconstruction of the rat mandible.

    PubMed

    Schliephake, H; Zghoul, N; Jäger, V; van Griensven, M; Zeichen, J; Gelinsky, M; Szubtarsky, N

    2009-02-01

    This study tested whether different in vitro cultivation techniques for tissue-engineered scaffolds seeded with human trabecular bone cells affect in vivo bone formation when implanted into critical-size defects in rat mandibles. Human trabecular cells were isolated and seeded into three types of scaffolds (porous CaCO(3), mineralized collagen, porous tricalcium phosphate). Four in vitro groups were produced: empty control scaffolds incubated with cell culture medium for 24 h; scaffolds seeded with trabecular bone cells, cultivated under static conditions for 24 h; scaffolds seeded with trabecular bone cells, cultivated for 14 days under static conditions; scaffolds seeded with trabecular bone cells, cultivated for 14 days in a continuous flow perfusion bioreactor. The scaffolds were implanted press fit into non-healing defects, 5 mm diameter, in rat mandibles. After 6 weeks the presence of human cells was assessed; none were detected. Histomorphometric evaluation showed that neither seeding human trabecular bone cells nor the culturing technique increased the amount of early bone formation compared with the level provided by osteoconductive bone ingrowth from the defect edges. It is concluded that human bone marrow stroma cells in tissue-engineered scaffolds and associated in vitro technology are difficult to test in the mandible in animal models.

  3. Simulating the transport of heavy charged particles through trabecular spongiosa

    NASA Astrophysics Data System (ADS)

    Gersh, Jacob A.

    As planning continues for manned missions far beyond Low Earth Orbit, a paramount concern remains the flight crew's exposure to galactic cosmic radiation. When humans exit the protective magnetic field of Earth, they become subject to bombardment by highly-reactive heavy charged (HZE) particles. A possible consequence of this two- to three-year-long mission is the onset of radiation-induced leukemia, a disorder with a latency period as short as two to three years. Because data on risk to humans from exposure to HZE particles is non-existent, studies of leukemia in animals are now underway to investigate the relative effectiveness of HZE exposures. Leukemogenesis can result from energy depositions occurring within marrow contained in the trabecular spongiosa. Trabecular spongiosa is found in flat bones and within the ends of long bones, and is characterized by an intricate matrix of interconnected bone tissue forming cavities that house marrow. The microscopic internal dimensions of spongiosa vary between species. As radiation traverses this region, interface-induced dose perturbations that occur at the interfaces between bone and marrow affect the patterns of energy deposition within the region. An aim of this project is to determine the extent by which tissue heterogeneity and microscopic dimensions have on patterns of energy deposition within the trabecular spongiosa. This leads to the development of PATHFIT, a computer code capable of generating simple quadric-based geometric models of trabecular spongiosa for both humans and mice based on actual experimentally-determined internal dimensions of trabecular spongiosa. Following the creation of spongiosa models, focus is placed on the development of HITSPAP, a hybrid Monte Carlo (MC) radiation transport code system that combines capabilities of the MC code PENELOPE and MC code PARTRAC. This code is capable of simulating the transport of HZE particles through accurate models of trabecular spongiosa. The final and

  4. Long-Term Dose Response of Trabecular Bone in Mice to Proton Radiation

    PubMed Central

    Bandstra, Eric R.; Pecaut, Michael J.; Anderson, Erica R.; Willey, Jeffrey S.; De Carlo, Francesco; Stock, Stuart R.; Gridley, Daila S.; Nelson, Gregory A.; Levine, Howard G.; Bateman, Ted A.

    2015-01-01

    Astronauts on exploratory missions will experience a complex environment, including microgravity and radiation. While the deleterious effects of unloading on bone are well established, fewer studies have focused on the effects of radiation. We previously demonstrated that 2 Gy of ionizing radiation has deleterious effects on trabecular bone in mice 4 months after exposure. The present study investigated the skeletal response after total doses of proton radiation that astronauts may be exposed to during a solar particle event. We exposed mice to 0.5, 1 or 2 Gy of whole-body proton radiation and killed them humanely 117 days later. Tibiae and femora were analyzed using microcomputed tomography, mechanical testing, mineral composition and quantitative histomorphometry. Relative to control mice, mice exposed to 2 Gy had significant differences in trabecular bone volume fraction (−20%), trabecular separation (+11%), and trabecular volumetric bone mineral density (−19%). Exposure to 1 Gy radiation induced a nonsignificant trend in trabecular bone volume fraction (−13%), while exposure to 0.5 Gy resulted in no differences. No response was detected in cortical bone. Further analysis of the 1-Gy mice using synchrotron microCT revealed a significantly lower trabecular bone volume fraction (−13%) than in control mice. Trabecular bone loss 4 months after exposure to 1 Gy highlights the importance of further examination of how space radiation affects bone. PMID:18494551

  5. Long-term dose response of trabecular bone in mice to proton radiation.

    PubMed

    Bandstra, Eric R; Pecaut, Michael J; Anderson, Erica R; Willey, Jeffrey S; De Carlo, Francesco; Stock, Stuart R; Gridley, Daila S; Nelson, Gregory A; Levine, Howard G; Bateman, Ted A

    2008-06-01

    Astronauts on exploratory missions will experience a complex environment, including microgravity and radiation. While the deleterious effects of unloading on bone are well established, fewer studies have focused on the effects of radiation. We previously demonstrated that 2 Gy of ionizing radiation has deleterious effects on trabecular bone in mice 4 months after exposure. The present study investigated the skeletal response after total doses of proton radiation that astronauts may be exposed to during a solar particle event. We exposed mice to 0.5, 1 or 2 Gy of whole-body proton radiation and killed them humanely 117 days later. Tibiae and femora were analyzed using microcomputed tomography, mechanical testing, mineral composition and quantitative histomorphometry. Relative to control mice, mice exposed to 2 Gy had significant differences in trabecular bone volume fraction (-20%), trabecular separation (+11%), and trabecular volumetric bone mineral density (-19%). Exposure to 1 Gy radiation induced a nonsignificant trend in trabecular bone volume fraction (-13%), while exposure to 0.5 Gy resulted in no differences. No response was detected in cortical bone. Further analysis of the 1-Gy mice using synchrotron microCT revealed a significantly lower trabecular bone volume fraction (-13%) than in control mice. Trabecular bone loss 4 months after exposure to 1 Gy highlights the importance of further examination of how space radiation affects bone.

  6. MiRNA profiling of whole trabecular bone: identification of osteoporosis-related changes in MiRNAs in human hip bones.

    PubMed

    De-Ugarte, Laura; Yoskovitz, Guy; Balcells, Susana; Güerri-Fernández, Robert; Martinez-Diaz, Santos; Mellibovsky, Leonardo; Urreizti, Roser; Nogués, Xavier; Grinberg, Daniel; García-Giralt, Natalia; Díez-Pérez, Adolfo

    2015-11-10

    MicroRNAs (miRNAs) are important regulators of gene expression, with documented roles in bone metabolism and osteoporosis, suggesting potential therapeutic targets. Our aim was to identify miRNAs differentially expressed in fractured vs nonfractured bones. Additionally, we performed a miRNA profiling of primary osteoblasts to assess the origin of these differentially expressed miRNAs. Total RNA was extracted from (a) fresh femoral neck trabecular bone from women undergoing hip replacement due to either osteoporotic fracture (OP group, n = 6) or osteoarthritis in the absence of osteoporosis (Control group, n = 6), matching the two groups by age and body mass index, and (b) primary osteoblasts obtained from knee replacement due to osteoarthritis (n = 4). Samples were hybridized to a microRNA array containing more than 1900 miRNAs. Principal component analysis (PCA) plots and heat map hierarchical clustering were performed. For comparison of expression levels, the threshold was set at log fold change > 1.5 and a p-value < 0.05 (corrected for multiple testing). Both PCA and heat map analyses showed that the samples clustered according to the presence or absence of fracture. Overall, 790 and 315 different miRNAs were detected in fresh bone samples and in primary osteoblasts, respectively, 293 of which were common to both groups. A subset of 82 miRNAs was differentially expressed (p < 0.05) between osteoporotic and control osteoarthritic samples. The eight miRNAs with the lowest p-values (and for which a validated miRNA qPCR assay was available) were assayed, and two were confirmed: miR-320a and miR-483-5p. Both were over-expressed in the osteoporotic samples and expressed in primary osteoblasts. miR-320a is known to target CTNNB1 and predicted to regulate RUNX2 and LEPR, while miR-483-5p down-regulates IGF2. We observed a reduction trend for this target gene in the osteoporotic bone. We identified two osteoblast miRNAs over-expressed in osteoporotic fractures, which

  7. Trabecular Bone Structure Correlates with Hand Posture and Use in Hominoids

    PubMed Central

    Tsegai, Zewdi J.; Kivell, Tracy L.; Gross, Thomas; Nguyen, N. Huynh; Pahr, Dieter H.; Smaers, Jeroen B.; Skinner, Matthew M.

    2013-01-01

    Bone is capable of adapting during life in response to stress. Therefore, variation in locomotor and manipulative behaviours across extant hominoids may be reflected in differences in trabecular bone structure. The hand is a promising region for trabecular analysis, as it is the direct contact between the individual and the environment and joint positions at peak loading vary amongst extant hominoids. Building upon traditional volume of interest-based analyses, we apply a whole-epiphysis analytical approach using high-resolution microtomographic scans of the hominoid third metacarpal to investigate whether trabecular structure reflects differences in hand posture and loading in knuckle-walking (Gorilla, Pan), suspensory (Pongo, Hylobates and Symphalangus) and manipulative (Homo) taxa. Additionally, a comparative phylogenetic method was used to analyse rates of evolutionary changes in trabecular parameters. Results demonstrate that trabecular bone volume distribution and regions of greatest stiffness (i.e., Young's modulus) correspond with predicted loading of the hand in each behavioural category. In suspensory and manipulative taxa, regions of high bone volume and greatest stiffness are concentrated on the palmar or distopalmar regions of the metacarpal head, whereas knuckle-walking taxa show greater bone volume and stiffness throughout the head, and particularly in the dorsal region; patterns that correspond with the highest predicted joint reaction forces. Trabecular structure in knuckle-walking taxa is characterised by high bone volume fraction and a high degree of anisotropy in contrast to the suspensory brachiators. Humans, in which the hand is used primarily for manipulation, have a low bone volume fraction and a variable degree of anisotropy. Finally, when trabecular parameters are mapped onto a molecular-based phylogeny, we show that the rates of change in trabecular structure vary across the hominoid clade. Our results support a link between inferred

  8. Trabecular Microstructure and Damage Affect Cement Leakage From the Basivertebral Foramen During Vertebral Augmentation.

    PubMed

    Li, Shengyun; Wang, Chongyan; Shan, Zhi; Liu, Junhui; Yu, Tianming; Zhang, Xuyang; Fan, Shunwu; Christiansen, Blaine A; Ding, Wenyuan; Zhao, Fengdong

    2017-08-15

    A prospective study on cadaver specimens. To explore why cement leakage from basivertebral foramen (BF) easily occurs during vertebral augmentation procedures. Type B (through BF, basivertebral foramen) cement leakage is the most common type after vertebral augmentation, but the mechanism of this is still controversial. The contribution of vertebral trabecular bone orientation and trabecular damage during compression fracture to cement leakage is still unknown. In this study, 12 fresh-frozen human lumbar spines (T12-L5) were collected and divided into 24 three-segment units. Mechanical testing was performed to simulate a compression fracture. MicroCT were performed on all segments before and after mechanical testing, and trabecular microstructure of the superior, middle (containing BF), and inferior 1/3 of each vertebral body was analyzed. The diameter variation of intertrabecular space before and after compression fracture was used to quantify trabecular injury. After mechanical testing, vertebral augmentation, and imaging-based diagnosis were used to evaluate cement leakage. Trabecular bone microstructural parameters in middle region (containing BF) were lower than those of the superior or inferior regions (P < 0.01). After compressive failure, 3D-reconstruction of the vertebral body by MicroCT demonstrated that intertrabecular distance in the middle region was markedly increased. Type B cement leakage was the most common type after vertebral augmentation, as found previously in Wang et al. (Spine J 2014;14: 1551-1558). The presence of the BF and the relative sparsity of trabecular bone make the middle region of the vertebral body the mechanically weakest region. Trabecular bone in middle region suffered the most severe damage during compressive failure of the vertebral body, which resulted in the greatest intervertebral spacing, and subsequently the highest percentage of type B cement leakage. These data suggest specific mechanisms by which cement may leak

  9. A review of trabecular bone functional adaptation: what have we learned from trabecular analyses in extant hominoids and what can we apply to fossils?

    PubMed

    Kivell, Tracy L

    2016-04-01

    Many of the unresolved debates in palaeoanthropology regarding evolution of particular locomotor or manipulative behaviours are founded in differing opinions about the functional significance of the preserved external fossil morphology. However, the plasticity of internal bone morphology, and particularly trabecular bone, allowing it to respond to mechanical loading during life means that it can reveal greater insight into how a bone or joint was used during an individual's lifetime. Analyses of trabecular bone have been commonplace for several decades in a human clinical context. In contrast, the study of trabecular bone as a method for reconstructing joint position, joint loading and ultimately behaviour in extant and fossil non-human primates is comparatively new. Since the initial 2D studies in the late 1970s and 3D analyses in the 1990 s, the utility of trabecular bone to reconstruct behaviour in primates has grown to incorporate experimental studies, expanded taxonomic samples and skeletal elements, and improved methodologies. However, this work, in conjunction with research on humans and non-primate mammals, has also revealed the substantial complexity inherent in making functional inferences from variation in trabecular architecture. This review addresses the current understanding of trabecular bone functional adaptation, how it has been applied to hominoids, as well as other primates and, ultimately, how this can be used to better interpret fossil hominoid and hominin morphology. Because the fossil record constrains us to interpreting function largely from bony morphology alone, and typically from isolated bones, analyses of trabecular structure, ideally in conjunction with that of cortical structure and external morphology, can offer the best resource for reconstructing behaviour in the past. © 2016 Anatomical Society.

  10. Fractal dimension and architecture of trabecular bone.

    PubMed

    Fazzalari, N L; Parkinson, I H

    1996-01-01

    The fractal dimension of trabecular bone was determined for biopsies from the proximal femur of 25 subjects undergoing hip arthroplasty. The average age was 67.7 years. A binary profile of the trabecular bone in the biopsy was obtained from a digitized image. A program written for the Quantimet 520 performed the fractal analysis. The fractal dimension was calculated for each specimen, using boxes whose sides ranged from 65 to 1000 microns in length. The mean fractal dimension for the 25 subjects was 1.195 +/- 0.064 and shows that in Euclidean terms the surface extent of trabecular bone is indeterminate. The Quantimet 520 was also used to perform bone histomorphometric measurements. These were bone volume/total volume (BV/TV) (per cent) = 11.05 +/- 4.38, bone surface/total volume (BS/TV) (mm2/mm3) = 1.90 +/- 0.51, trabecular thickness (Tb.Th) (mm) = 0.12 +/- 0.03, trabecular spacing (Tb.Sp) (mm) = 1.03 +/- 0.36, and trabecular number (Tb.N) (number/mm) = 0.95 +/- 0.25. Pearsons' correlation coefficients showed a statistically significant relationship between the fractal dimension and all the histomorphometric parameters, with BV/TV (r = 0.85, P < 0.0001), BS/TV (r = 0.74, P < 0.0001), Tb.Th (r = 0.50, P < 0.02), Tb.Sp (r = -0.81, P < 0.0001), and Tb.N (r = 0.76, P < 0.0001). This method for calculating fractal dimension shows that trabecular bone exhibits fractal properties over a defined box size, which is within the dimensions of a structural unit for trabecular bone. Therefore, the fractal dimension of trabecular bone provides a measure which does not rely on Euclidean descriptors in order to describe a complex geometry.

  11. Trabecular bone of growth plate origin influences both trabecular and cortical morphology in adulthood.

    PubMed

    Wang, Qingju; Ghasem-Zadeh, Ali; Wang, Xiao-Fang; Iuliano-Burns, Sandra; Seeman, Ego

    2011-07-01

    Skeletal fragility is common at metaphyseal regions of long bones. The cortices of this region are derived by coalescence of trabeculae around the periphery of the growth plate, not by periosteal apposition, as occurs in the diaphyses. We therefore hypothesized that trabecular bone in childhood predicted both cortical and trabecular morphology in adulthood. To test this hypothesis, we measured distal radial and tibial structure using high-resolution peripheral quantitative computed tomography in 61 daughter-mother pairs, mean age 12.5 years (range 7 to 19 years) and 44.1 years (range 32 to 50 years), respectively. The daughters' trabecular bone volume (BV/TV), thickness, number, and separation predicted the corresponding traits in their mothers. Their trabecular BV/TV also predicted their mothers' cortical thickness (r = 0.32, p = .02). By contrast, the daughters' cortical thickness did not predict their mothers' cortical thickness. The daughters had higher trabecular BV/TV than their mothers (mean ± SD, radius 0.134 ± 0.024 versus 0.124 ± 0.033, p = .03; tibia 0.145 ± 0.021 versus 0.135 ± 0.032, p < .01) owing to greater trabecular number, not thickness, and less trabecular separation. Abnormalities in the development of metaphyseal trabecular bone are likely to influence fragility in both trabecular and cortical bone of this region in adulthood.

  12. The metaphyseal bone defect in distal radius fractures and its implication on trabecular remodeling-a histomorphometric study (case series).

    PubMed

    Lutz, Martin; Steck, Roland; Sitte, Ingrid; Rieger, Michael; Schuetz, Michael; Klestil, Thomas

    2015-05-09

    The invention of the locking plate technology leads to alterations of treatment strategies at metaphyseal fracture sites with the concept of spontaneous remodeling of trabecular bone voids. Whereas trabecular regeneration has been proven in experimental animal studies, no histologic data exist on human fracture healing with special emphasis on bone voids. In order to qualify the trabecular bone remodeling capacity in vivo, bone specimens from the metaphyseal bone void were analyzed 14 months after trauma using quantitative histomorphometry. Twenty-five patients with an unstable dorsally displaced distal radius fracture were fixed with a palmar locking plate without additional bone graft or substitute. At implant removal, specimens from the previous compression void were harvested with a trephine in a volar-dorsal direction. In 16 patients, histomorphometric analysis could be performed, comparing the dorsal trabecular network with the volar, non-compressed ultrastructure. Significant differences for bone volume/total volume (BV/TV), trabecular number (TbN) and trabecular separation (TbSp), but not for trabecular thickness (TbTh) and osteoid volume/total volume (OV/TV), were detected. Neither patient age, defect size nor gender had a significant influence on bone remodeling. The results of this study indicate that trabecular bone remodeling does not lead to pre-trauma bone quality in metaphyseal bone compression voids following reduction and application of a locking plate.

  13. Nonlinear viscoelastic characterization of bovine trabecular bone.

    PubMed

    Manda, Krishnagoud; Wallace, Robert J; Xie, Shuqiao; Levrero-Florencio, Francesc; Pankaj, Pankaj

    2017-02-01

    The time-independent elastic properties of trabecular bone have been extensively investigated, and several stiffness-density relations have been proposed. Although it is recognized that trabecular bone exhibits time-dependent mechanical behaviour, a property of viscoelastic materials, the characterization of this behaviour has received limited attention. The objective of the present study was to investigate the time-dependent behaviour of bovine trabecular bone through a series of compressive creep-recovery experiments and to identify its nonlinear constitutive viscoelastic material parameters. Uniaxial compressive creep and recovery experiments at multiple loads were performed on cylindrical bovine trabecular bone samples ([Formula: see text]). Creep response was found to be significant and always comprised of recoverable and irrecoverable strains, even at low stress/strain levels. This response was also found to vary nonlinearly with applied stress. A systematic methodology was developed to separate recoverable (nonlinear viscoelastic) and irrecoverable (permanent) strains from the total experimental strain response. We found that Schapery's nonlinear viscoelastic constitutive model describes the viscoelastic response of the trabecular bone, and parameters associated with this model were estimated from the multiple load creep-recovery (MLCR) experiments. Nonlinear viscoelastic recovery compliance was found to have a decreasing and then increasing trend with increasing stress level, indicating possible stiffening and softening behaviour of trabecular bone due to creep. The obtained parameters from MLCR tests, expressed as second-order polynomial functions of stress, showed a similar trend for all the samples, and also demonstrate stiffening-softening behaviour with increasing stress.

  14. Anisotropic Permeability of Trabecular Bone and its Relationship to Fabric and Architecture: A Computational Study.

    PubMed

    Kreipke, T C; Niebur, G L

    2017-02-02

    Trabecular bone is a porous, mineralized tissue found in vertebral bodies, the metaphyses and epiphyses of long bones, and in the irregular and flat shaped bones. The pore space is filled with bone marrow, a highly cellular fluid. Together, the bone and marrow behave as a poroelastic solid. In poroelasticity theory, the permeability is the primary material property that governs the momentum transfer between the solid and fluid constituents. In the linearized theory, the permeability of a material depends on the shape and connectivity of the pores. Developing a model of the relationship between trabecular microarchitecture and permeability could lead to improved simulations of trabecular bone mechanical response, which can be used to investigate bone adaptation, mechanobiological signaling, and progression of diseases such as osteoporosis. This study used finite element models of the trabecular pore space to calculate the complete anisotropic permeability tensor of 12 human and 18 porcine femoral trabecular bone samples. The sensitivity of the simulations to model assumptions and post-processing was analyzed to improve confidence in the result. The orthotropic permeability tensor depended on the fabric tensor, trabecular spacing, and structure model index through a power law relationship. Porosity and fabric alone also provided a reasonable prediction, which may be useful in cases where the image resolution is insufficient to obtain detailed measures of architecture.

  15. Expression profile of the matricellular protein osteopontin in primary open-angle glaucoma and the normal human eye.

    PubMed

    Chowdhury, Uttio Roy; Jea, Seung-Youn; Oh, Dong-Jin; Rhee, Douglas J; Fautsch, Michael P

    2011-08-16

    PURPOSE. To characterize the role of osteopontin (OPN) in primary open-angle glaucoma (POAG) and normal eyes. METHODS. OPN quantification was performed by enzyme-linked immunosorbent assay in aqueous humor (AH) obtained from human donor eyes (POAG and normal) and surgical samples (POAG and elective cataract removal). OPN expression and localization in whole eye tissue sections and primary normal human trabecular meshwork (NTM) cells were studied by Western blot and immunohistochemistry. Latanoprost-free acid (LFA)-treated NTM cells were analyzed for OPN gene and protein expression. Intraocular pressure was measured by tonometry, and central corneal thickness was measured by optical coherence tomography in young OPN(-/-) and wild-type mice. RESULTS. OPN levels were significantly reduced in donor POAG AH compared with normal AH (0.54 ± 0.18 ng/μg [n = 8] vs. 0.77 ± 0.23 ng/μg [n = 9]; P = 0.039). A similar trend was observed in surgical AH (1.05 ± 0.31 ng/μg [n = 20] vs. 1.43 ± 0.88 ng/μg [n = 20]; P = 0.083). OPN was present in the trabecular meshwork, corneal epithelium and endothelium, iris, ciliary body, retina, vitreous humor, and optic nerve. LFA increased OPN gene expression, but minimal change in OPN protein expression was observed. No difference in intraocular pressure (17.5 ± 2.0 mm Hg [n = 56] vs. 17.3 ± 1.9 mm Hg [n = 68]) but thinner central corneal thickness (91.7 ± 3.6 μm [n = 50] vs. 99.2 ± 5.5 μm [n = 70]) was noted between OPN(-/-) and wild-type mice. CONCLUSIONS. OPN is widely distributed in the human eye and was found in lower concentrations in POAG AH. Reduction of OPN in young mice does not affect IOP.

  16. Micro-CT finite element model and experimental validation of trabecular bone damage and fracture.

    PubMed

    Hambli, Ridha

    2013-10-01

    Most micro-CT finite element modeling of human trabecular bone has focused on linear and non-linear analysis to evaluate bone failure properties. However, prediction of the apparent failure properties of trabecular bone specimens under compressive load, including the damage initiation and its progressive propagation until complete bone failure into consideration, is still lacking. In the present work, an isotropic micro-CT FE model at bone tissue level coupled to a damage law was developed in order to simulate the failure of human trabecular bone specimens under quasi-static compressive load and predict the apparent stress and strain. The element deletion technique was applied in order to simulate the progressive fracturing process of bone tissue. To prevent mesh-dependence that generally affects the damage propagation rate, regularization technique was applied in the current work. The model was validated with experimental results performed on twenty-three human trabecular specimens. In addition, a sensitivity analysis was performed to investigate the impact of the model factors' sensitivities on the predicted ultimate stress and strain of the trabecular specimens. It was found that the predicted failure properties agreed very well with the experimental ones. © 2013.

  17. Tensile strength of bovine trabecular bone.

    PubMed

    Kaplan, S J; Hayes, W C; Stone, J L; Beaupré, G S

    1985-01-01

    Data on the tensile and compressive properties of trabecular bone are needed to define input parameters and failure criteria for modeling total joint replacements. To help resolve differences in reports comparing tensile and compressive properties of trabecular bone, we have developed new methods, based on porous foam technology, for tensile testing of fresh/frozen trabecular bone specimens. Using bovine trabecular bone from an isotropic region from the proximal humerus as a model material, we measured ultimate strengths in tension and compression for two groups of 24 specimens each. The average ultimate strength in tension was 7.6 +/- 2.2 (95% C.I.) MPa and in compression was 12.4 +/- 3.2 MPa. This difference was statistically significant (p = 0.013) and was not related to density differences between the test groups (p = 0.28). Strength was related by a power-law function of the local apparent density, but, even accounting for density influences, isotropic bovine trabecular bone exhibits significantly lower strengths in tension than in compression.

  18. Assessment of trabecular bone quality in human cadaver calcaneus using scanning confocal ultrasound and dual x-ray absorptiometry (DEXA) measurements

    NASA Astrophysics Data System (ADS)

    Qin, Yixian; Xia, Yi; Lin, Wei; Rubin, Clinton; Gruber, Barry

    2004-10-01

    Microgravity and aging induced bone loss is a critical skeleton complication, occurring particularly in the weight-supporting skeleton, which leads to osteoporosis and fracture. Advents in quantitative ultrasound (QUS) provide a unique method for evaluating bone strength and density. Using a newly developed scanning confocal acoustic diagnostic (SCAD) system, QUS assessment for bone quality in the real body region was evaluated. A total of 19 human cadaver calcanei, age 66 to 97 years old, were tested by both SCAD and nonscan mode. The scanning region covered an approximate 40×40 mm2 with 0.5 mm resolution. Broadband ultrasound attenuation (BUA, dB/MHz), energy attenuation (ATT, dB), and ultrasound velocity (UV, m/s) were measured. The QUS properties were then correlated to the bone mineral density (BMD) measured by DEXA. Correlations between BMD and QUS parameters were significantly improved by using SCAD as compared to nonscan mode, yielding correlations between BMD and SCAD QUS parameters as R=0.82 (BUA), and R=0.86 (est. BMD). It is suggested that SCAD is feasible for in vivo bone quality mapping. It can be potentially used for monitoring instant changes of bone strength and density. [Work supported by the National Space Biomedical Research Institute (TD00207), and New York Center for Biotechnology.

  19. Fractal analysis of radiographs: assessment of trabecular bone structure and prediction of elastic modulus and strength.

    PubMed

    Majumdar, S; Lin, J; Link, T; Millard, J; Augat, P; Ouyang, X; Newitt, D; Gould, R; Kothari, M; Genant, H

    1999-07-01

    The purpose of this study was to determine whether fractal dimension of radiographs provide measures of trabecular bone structure which correlate with bone mineral density (BMD) and bone biomechanics, and whether these relationships depend on the technique used to calculate the fractal dimension. Eighty seven cubic specimen of human trabecular bone were obtained from the vertebrae and femur. The cubes were radiographed along all three orientations--superior-inferior (SI), medial-lateral (ML), and anterior-posterior (AP), digitized, corrected for background variations, and fractal based techniques were applied to quantify trabecular structure. Three different techniques namely, semivariance, surface area, and power spectral methods were used. The specimens were tested in compression along three orientations and the Young's modulus (YM) was determined. Compressive strength was measured along the SI direction. Quantitative computed tomography was used to measure trabecular BMD. High-resolution magnetic-resonance images were used to obtain three-dimensional measures of trabecular architecture such as the apparent bone volume fraction, trabecular thickness, spacing, and number. The measures of trabecular structure computed in the different directions showed significant differences (p<0.05). The correlation between BMD, YM, strength, and the fractal dimension were direction and technique dependent. The trends of variation of the fractal dimension with BMD and biomechanical properties also depended on the technique and the range of resolutions over which the data was analyzed. The fractal dimension showed varying trends with bone mineral density changes, and these trends also depended on the range of frequencies over which the fractal dimension was measured. For example, using the power spectral method the fractal dimension increased with BMD when computed over a lower range of spatial frequencies and decreased for higher ranges. However, for the surface area technique

  20. Internal channel structures in trabecular bone

    NASA Astrophysics Data System (ADS)

    Scherf, Heike; Beckmann, Felix; Fischer, Jens; Witte, Frank

    2004-10-01

    Material properties of bone are crucial for studies regarding the mechanical behavior of bone. The mechanical behavior depends on the macro- and micro-architecture as well as the organic and mineral content of bone. The marco-architecture of bone is normally analyzed by plane radiographs. The micro-architecture of the trabecular bone can be imaged by high resolution CT imaging techniques using conventional x-ray tubes. However, fine structures in bone architecture cannot be sufficiently analyzed by this technique due to its limited resolution. High resolution CT imaging technique using synchrotron radiation generates images with a high spatial resolution of bone structures on a micron scale. Additionally, this imaging technique provides superior determination of local differences in the bone mineral density. Two microtomography techniques, first: based on conventional x-ray tubes and second: based on synchrotron radiation were compared in this study to detect fine bone structures such as inner trabecular channels. In two red howler monkeys (Alouatta seniculus) femora channel structures were found inside the trabecular bone by both techniques. Only synchrotron-based microtomography was able to detect layers of lower mineral density in the channel walls. The found structures in trabecular bone are normally expected in the Haversian channel walls of the cortical bone. However, the origin of the trabecular channel structure is not fully understood. We found, that synchrotron-based microtomography is a very valuable technique in the research of fine bone structures. Further research should focus on the impact of these findings on the mechanical properties of trabecular bone.

  1. Geodesic topological analysis of trabecular bone microarchitecture from high-spatial resolution magnetic resonance images.

    PubMed

    Carballido-Gamio, Julio; Krug, Roland; Huber, Markus B; Hyun, Ben; Eckstein, Felix; Majumdar, Sharmila; Link, Thomas M

    2009-02-01

    In vivo assessment of trabecular bone microarchitecture could improve the prediction of fracture risk and the efficacy of osteoporosis treatment and prevention. Geodesic topological analysis (GTA) is introduced as a novel technique to quantify the trabecular bone microarchitecture from high-spatial resolution magnetic resonance (MR) images. Trabecular bone parameters that quantify the scale, topology, and anisotropy of the trabecular bone network in terms of its junctions are the result of GTA. The reproducibility of GTA was tested with in vivo images of human distal tibiae and radii (n = 6) at 1.5 Tesla; and its ability to discriminate between subjects with and without vertebral fracture was assessed with ex vivo images of human calcanei at 1.5 and 3.0 Tesla (n = 30). GTA parameters yielded an average reproducibility of 4.8%, and their individual areas under the curve (AUC) of the receiver operating characteristic curve analysis for fracture discrimination performed better at 3.0 than at 1.5 Tesla reaching values of up to 0.78 (p < 0.001). Logistic regression analysis demonstrated that fracture discrimination was improved by combining GTA parameters, and that GTA combined with bone mineral density (BMD) allow for better discrimination than BMD alone (AUC = 0.95; p < 0.001). Results indicate that GTA can substantially contribute in studies of osteoporosis involving imaging of the trabecular bone microarchitecture.

  2. Chloroplast actin filaments organize meshwork on the photorelocated chloroplasts in the moss Physcomitrella patens.

    PubMed

    Yamashita, Hiroko; Sato, Yoshikatsu; Kanegae, Takeshi; Kagawa, Takatoshi; Wada, Masamitsu; Kadota, Akeo

    2011-02-01

    Cytoskeleton dynamics during phototropin-dependent chloroplast photorelocation movement was analyzed in protonemal cells of actin- and microtubule-visualized lines of Physcomitrella patens expressing GFP- or tdTomato-talin and GFP-tubulin. Using newly developed epi- and trans-microbeam irradiation systems that permit fluorescence observation of the cell under blue microbeam irradiation inducing chloroplast relocation, it was revealed that meshwork of actin filaments formed at the chloroplast-accumulating area both in the avoidance and accumulation movements. The structure disappeared soon when blue microbeam was turned off, and it was not induced under red microbeam irradiation that did not evoke chloroplast relocation movement. In contrast, no apparent change in microtubule organization was detected during the movements. The actin meshwork was composed of short actin filaments distinct from the cytoplasmic long actin cables and was present between the chloroplasts and plasma membrane. The short actin filaments emerged from around the chloroplast periphery towards the center of chloroplast. Showing highly dynamic behavior, the chloroplast actin filaments (cp-actin filaments) were rapidly organized into meshwork on the chloroplast surface facing plasma membrane. The actin filament configuration on a chloroplast led to the formation of actin meshwork area in the cell as the chloroplasts arrived at and occupied the area. After establishment of the meshwork, cp-actin filaments were still highly dynamic, showing appearance, disappearance, severing and bundling of filaments. These results indicate that the cp-actin filaments have significant roles in the chloroplast movement and positioning in the cell.

  3. Hip bone trabecular architecture shows uniquely distinctive locomotor behaviour in South African australopithecines.

    PubMed

    Macchiarelli, R; Bondioli, L; Galichon, V; Tobias, P V

    1999-02-01

    Cancellous bone retains structural and behavioural properties which are time and strain-rate dependent. As the orientation of the trabeculae (trajectories) follows the direction of the principal strains imposed by daily loadings, habitual postural and locomotor behaviours are responsible for a variety of trabecular architectures and site-specific textural arrangements of the pelvic cancellous network. With respect to the great ape condition, the human trabecular pattern is characterized by a distinctive ilioischial bundle, an undivided sacropubic bundle, and a full diagonal crossing (approximately 100 degrees) over the acetabulum between the ilioischial and the sacropubic bundles. Advanced digital image processing (DIP) of hip bone radiographs has revealed that adolescent and adult South African australopithecines retained an incompletely developed human-like trabecular pattern associated with gait-related features that are unique among the extant primates.

  4. Dependences of ultrasonic properties on frequency and trabecular spacing in trabecular-bone-mimicking phantoms.

    PubMed

    Lee, Kang Il

    2015-02-01

    The dependences of ultrasonic properties on the frequency and the trabecular spacing were investigated in 20 trabecular-bone-mimicking phantoms consisting of cellular copper foams. The strong slow waves were consistently observed in the signals transmitted through all of the phantoms. The frequency-dependent phase velocity and attenuation coefficient of the slow wave were measured at frequencies from 0.7 to 1.3 MHz. The phase velocity decreased approximately linearly with increasing frequency while the attenuation coefficients increased with increasing frequency. The phase velocity increased monotonically with increasing trabecular spacing from 1337 to 2931 μm while the attenuation coefficient decreased with increasing spacing.

  5. Aqueous outflow: Segmental and distal flow

    PubMed Central

    Swaminathan, Swarup S.; Oh, Dong-Jin; Kang, Min Hyung; Rhee, Douglas J.

    2014-01-01

    A prominent risk factor of primary open-angle glaucoma is ocular hypertension, a pathologic state caused by impaired outflow of aqueous humor through the trabecular meshwork within the iridocorneal angle. The juxtacanalicular region of the trabecular meshwork and the inner wall of Schlemm canal have been identified as the main contributors to aqueous outflow resistance, and both extracellular matrix within the trabecular meshwork and trabecular meshwork cell shape have been shown to affect outflow. Overexpression of multiple ECM proteins in perfused cadaveric human eyes has led to increased outflow resistance and elevated IOP. Pharmacologic agents targeting trabecular meshwork cytoskeletal arrangements have been developed after multiple studies demonstrated the importance of cell shape on outflow. Several groups have shown that aqueous outflow occurs only at certain segments of the trabecular meshwork circumferentially, a concept known as segmental flow. This is based on the theory that aqueous outflow is dependent on the presence of discrete pores within the Schlemm canal. Segmental flow has been described in the eyes of multiple species, including primate, bovine, mouse, and human samples. While the trabecular meshwork appears to be the major source of resistance, trabecular meshwork bypass procedures have been unable to achieve the degree of IOP reduction observed with trabeculectomy, reflecting the potential impact of distal flow, or flow through Schlemm canal and collector channels, on outflow. Multiple studies have demonstrated that outflow occurs preferentially near collector channels, suggesting that these distal structures may be more important to aqueous outflow than previously believed. PMID:25088623

  6. Mesenchymal stem cell proliferation and differentiation on load-bearing trabecular Nitinol scaffolds.

    PubMed

    Gotman, Irena; Ben-David, Dror; Unger, Ronald E; Böse, Thomas; Gutmanas, Elazar Y; Kirkpatrick, C James

    2013-09-01

    Bone tissue regeneration in load-bearing regions of the body requires high-strength porous scaffolds capable of supporting angiogenesis and osteogenesis. 70% porous Nitinol (NiTi) scaffolds with a regular 3-D architecture resembling trabecular bone were produced from Ni foams using an original reactive vapor infiltration technique. The "trabecular Nitinol" scaffolds possessed a high compressive strength of 79 MPa and high permeability of 6.9×10(-6) cm2. The scaffolds were further modified to produce a near Ni-free surface layer and evaluated in terms of Ni ion release and human mesenchymal stem cell (hMSC) proliferation (AlamarBlue), differentiation (alkaline phosphatase activity, ALP) and mineralization (Alizarin Red S staining). Scanning electron microscopy was employed to qualitatively corroborate the results. hMSCs were able to adhere and proliferate on both as-produced and surface-modified trabecular NiTi scaffolds, to acquire an osteoblastic phenotype and produce a mineralized extracellular matrix. Both ALP activity and mineralization were increased on porous scaffolds compared to control polystyrene plates. Experiments in a model coculture system of microvascular endothelial cells and hMSCs demonstrated the formation of prevascular structures in trabecular NiTi scaffolds. These data suggest that load-bearing trabecular Nitinol scaffolds could be effective in regenerating damaged or lost bone tissue.

  7. Effects of trabecular type and orientation on microdamage susceptibility in trabecular bone.

    PubMed

    Shi, Xiutao; Liu, X Sherry; Wang, Xiang; Guo, X Edward; Niebur, Glen L

    2010-05-01

    Trabecular architecture becomes more rod-like and anisotropic in osteoporotic and aging trabecular bone. In order to address the effects of trabecular type and orientation on trabecular bone damage mechanics, microstructural finite element modeling was used to identify the yielded tissue in ten bovine tibial trabecular bone samples compressed to 1.2% on-axis apparent strain. The yielded tissue was mapped onto individual trabeculae identified by an Individual Trabeculae Segmentation (ITS) technique, and the distribution of the predicted yielding among trabecular types and orientations was compared to the experimentally measured microdamage. Although most of the predicted yielded tissue was found in longitudinal plates (73+/-11%), the measured microcrack density was positively correlated with the proportion of the yielded tissue in longitudinal rods (R(2)=0.52, p=0.02), but not in rods of other directions or plates. The overall fraction of rods and the fractions of rods along the longitudinal and transverse axes were also correlated with the measured microcrack density. In contrast, diffuse damage area did not correlate with any of these quantities. These results agree with the findings that both in vitro and in vivo microcrack densities are correlated with Structure Model Index (SMI), and are also consistent with decreased energy to failure in more rod-like trabecular bone. Together the results suggest that bending or buckling deformations of rod-like trabeculae may make trabecular structures more susceptible to microdamage formation. Moreover, while simple strain-based tissue yield criteria may account for macroscopic yielding, they may not be suitable for identifying damage.

  8. TECHNIQUES AND OUTCOMES OF MINIMALLY-INVASIVE TRABECULAR ABLATION AND BYPASS SURGERY

    PubMed Central

    Kaplowitz, Kevin; Schuman, Joel S.; Loewen, Nils A.

    2014-01-01

    Minimally invasive glaucoma surgeries (MIGS) can improve the conventional, pressure dependent outflow by bypassing or ablating the trabecular meshwork or create alternative drainage routes into the suprachoroidal or subconjunctival space. They have a highly favorable risk profile compared to penetrating surgeries and lower intraocular pressure with variable efficacy that may depend on the extent of outflow segments accessed. Since they are highly standardized procedures that use clear corneal incisions, they can elegantly be combined with cataract and refractive procedures to improve vision in the same session. There is a growing need for surgeons to become proficient in MIGS to address the increasing prevalence of glaucoma and cataracts in a well-informed, aging population. Techniques of visualization and instrumentation in an anatomically highly confined space with semi-transparent tissues are fundamentally different from other anterior segment surgeries and present even experienced surgeons with a substantial learning curve. Here, we provide practical tips and review techniques and outcomes of TM bypass and ablation MIGS. PMID:24338085

  9. The trabecular bypass stent in a pseudophakic glaucoma patient: A 1-year follow-up

    PubMed Central

    Fea, Antonio M; Dogliani, Monica; Machetta, Federica; Lale-Lacroix, Gabriella; Brogliatti, Beatrice; Grignolo, Federico M

    2008-01-01

    Purpose To describe the 1-year success of a trabecular stent implant in a pseudophakic glaucoma patient. The stent is implanted through a small corneal incision under gonioscopic control. Intraocular pressure control was reported in cultured human anterior segment. Design Observational case report. Methods We report the case of a patient who was implanted and followed-up for 1 year at the Dipartimento di Fisiopatologia Clinica. The main outcome measures were intraocular pressure and visual field. Results The patient’s intraocular pressure was controlled with topical beta-blockers for 6 months and without therapy for 6 months. Two diurnal curves demonstrated achievement of target pressure during the day. The 1-year visual field was unchanged. Conclusions We are not aware of previous reports of trabecular stent implantation in pseudophakic patients. The trabecular stent had minimal peri-operative morbidity. Identification of the implantation site is challenging and reduction of efficacy over time may occur. PMID:19668446

  10. The trabecular bypass stent in a pseudophakic glaucoma patient: A 1-year follow-up.

    PubMed

    Fea, Antonio M; Dogliani, Monica; Machetta, Federica; Lale-Lacroix, Gabriella; Brogliatti, Beatrice; Grignolo, Federico M

    2008-12-01

    To describe the 1-year success of a trabecular stent implant in a pseudophakic glaucoma patient. The stent is implanted through a small corneal incision under gonioscopic control. Intraocular pressure control was reported in cultured human anterior segment. Observational case report. We report the case of a patient who was implanted and followed-up for 1 year at the Dipartimento di Fisiopatologia Clinica. The main outcome measures were intraocular pressure and visual field. The patient's intraocular pressure was controlled with topical beta-blockers for 6 months and without therapy for 6 months. Two diurnal curves demonstrated achievement of target pressure during the day. The 1-year visual field was unchanged. We are not aware of previous reports of trabecular stent implantation in pseudophakic patients. The trabecular stent had minimal peri-operative morbidity. Identification of the implantation site is challenging and reduction of efficacy over time may occur.

  11. Trabecular bone volume fraction mapping by low-resolution MRI.

    PubMed

    Fernández-Seara, M A; Song, H K; Wehrli, F W

    2001-07-01

    Trabecular bone volume fraction (TBVF) is highly associated with the mechanical competence of trabecular bone. TBVF is ordinarily measured by histomorphometry from bone biopsies or, noninvasively, by means of high-resolution microcomputed tomography and, more recently, by micro-MRI. The latter methods require spatial resolution sufficient to resolve trabeculae, along with segmentation techniques that allow unambiguous assignment of the signal to bone or bone marrow. In this article it is shown that TBVF can be measured under low-resolution conditions by exploiting the attenuation of the MR signal resulting from fractional occupancy of the imaging voxel by bone and bone marrow, provided that a reference signal is available from a marrow volume devoid of trabeculation. The method requires accurate measurement of apparent proton density, which entails correction for various sources of error. Key among these are the spatial nonuniformity in the RF field amplitude and effects of the slice profile, which are determined by B(1) field mapping and numerical integration of the Bloch equations, respectively. By contrast, errors from variations in bone marrow composition (hematopoietic vs. fatty) between trabecular and reference site are predicted to be small and usually negligible. The method was evaluated in phantoms and in vivo in the distal radius and found to be accurate to 1% in marrow volume fraction. Finally, in a group of 12 patients of varying skeletal status, TBVF in the calcaneus was found to strongly correlate with integral bone mineral density of the lumbar vertebrae (r(2) = 0.83, p < 0.0001). The method may fail in large imaging objects such as the human trunk at high magnetic field where standing wave and RF penetration effects cause intensity variations that cannot be corrected. Magn Reson Med 46:103-113, 2001.

  12. Measurement of the speed of sound in trabecular bone by using a time reversal acoustics focusing system

    NASA Astrophysics Data System (ADS)

    Lee, Kang Il; Choi, Bok Kyoung

    2014-10-01

    A new method for measuring the speed of sound (SOS) in trabecular bone by using a time reversal acoustics (TRA) focusing system was proposed and validated with measurements obtained by using the conventional pulse-transmission technique. The SOS measured in 14 bovine femoral trabecular bone samples by using the two methods was highly correlated each other, although the SOS measured by using the TRA focusing system was slightly lower by an average of 2.2 m/s. The SOS measured by using the two methods showed high correlation coefficients of r = 0.92 with the apparent bone density, consistent with the behavior in human trabecular bone in vitro. These results prove the efficacy of the new method based on the principle of TRA to measure the SOS in trabecular bone.

  13. Imaging the Aqueous Humor Outflow Pathway in Human Eyes by Three-dimensional Micro-computed Tomography (3D micro-CT)

    SciTech Connect

    C Hann; M Bentley; A Vercnocke; E Ritman; M Fautsch

    2011-12-31

    The site of outflow resistance leading to elevated intraocular pressure in primary open-angle glaucoma is believed to be located in the region of Schlemm's canal inner wall endothelium, its basement membrane and the adjacent juxtacanalicular tissue. Evidence also suggests collector channels and intrascleral vessels may have a role in intraocular pressure in both normal and glaucoma eyes. Traditional imaging modalities limit the ability to view both proximal and distal portions of the trabecular outflow pathway as a single unit. In this study, we examined the effectiveness of three-dimensional micro-computed tomography (3D micro-CT) as a potential method to view the trabecular outflow pathway. Two normal human eyes were used: one immersion fixed in 4% paraformaldehyde and one with anterior chamber perfusion at 10 mmHg followed by perfusion fixation in 4% paraformaldehyde/2% glutaraldehyde. Both eyes were postfixed in 1% osmium tetroxide and scanned with 3D micro-CT at 2 {mu}m or 5 {mu}m voxel resolution. In the immersion fixed eye, 24 collector channels were identified with an average orifice size of 27.5 {+-} 5 {mu}m. In comparison, the perfusion fixed eye had 29 collector channels with a mean orifice size of 40.5 {+-} 13 {mu}m. Collector channels were not evenly dispersed around the circumference of the eye. There was no significant difference in the length of Schlemm's canal in the immersed versus the perfused eye (33.2 versus 35.1 mm). Structures, locations and size measurements identified by 3D micro-CT were confirmed by correlative light microscopy. These findings confirm 3D micro-CT can be used effectively for the non-invasive examination of the trabecular meshwork, Schlemm's canal, collector channels and intrascleral vasculature that comprise the distal outflow pathway. This imaging modality will be useful for non-invasive study of the role of the trabecular outflow pathway as a whole unit.

  14. Sparseness of the trabecular pattern on dental radiographs: visual assessment compared with semi-automated measurements

    PubMed Central

    Geraets, W G M; Lindh, C; Verheij, H

    2012-01-01

    Objective In diagnostic imaging; human perception is the most prominent, yet least studied, source of error. A better understanding of image perception will help to improve diagnostic performance. This study focuses on the perception of coarseness of trabecular patterns on dental radiographs. Comparison of human vision with machine vision should yield knowledge on human perception. Method In a study on identifying osteoporotic patients, dental radiographs were made from 505 post-menopausal women aged 45–70 years. Intra-oral radiographs of the lower and upper jaws were made. Five observers graded the trabecular pattern as dense, sparse or mixed. The five gradings were combined into a single averaged observer score per jaw. The radiographs were scanned and a region of interest (ROI) was indicated on each. The ROIs were processed with image analysis software measuring 25 image features. Pearson correlation and multiple linear regression were used to compare the averaged observer score with the image features. Results 14 image features correlated significantly with the observer judgement for both jaws. The strongest correlation was found for the average grey value in the ROI. Other features, describing that osteoporotic patients have fewer but bigger marrow spaces than controls, correlated less with the sparseness of the trabecular pattern than a rather crude measure for structure such as the average grey value. Conclusion Human perception of the sparseness of trabecular patterns is based more on average grey values of the ROI than on geometric details within the ROI. PMID:22374281

  15. Three-dimensional trabecular alignment model.

    PubMed

    Bono, Eric S; Smolinski, Patrick; Casagranda, Al; Xu, Junde

    2003-04-01

    Trabecular alignment theory has been used to quantify Wolff's Law of bone remodeling. A three-dimensional finite element scheme was developed to analyze the bone remodeling phenomenon. The mathematical model proposed by Mullender et al. and later modified by Smith et al. was adopted to simulate the surface-based trabecular resorption and formation processes. Enhancements incorporated into the previous model include: mapping into three-dimensions, controlling the remodeling signal's passage through marrow, controlling the finite distance the signal may pass through the bone matrix, and including non-bone material in the finite element model. After the model is explained and thoroughly studied, three-dimensional implant surface geometries are simulated.

  16. Vibrational testing of trabecular bone architectures using rapid prototype models.

    PubMed

    Mc Donnell, P; Liebschner, M A K; Tawackoli, Wafa; Mc Hugh, P E

    2009-01-01

    The purpose of this study was to investigate if standard analysis of the vibrational characteristics of trabecular architectures can be used to detect changes in the mechanical properties due to progressive bone loss. A cored trabecular specimen from a human lumbar vertebra was microCT scanned and a three-dimensional, virtual model in stereolithography (STL) format was generated. Uniform bone loss was simulated using a surface erosion algorithm. Rapid prototype (RP) replicas were manufactured from these virtualised models with 0%, 16% and 42% bone loss. Vibrational behaviour of the RP replicas was evaluated by performing a dynamic compression test through a frequency range using an electro-dynamic shaker. The acceleration and dynamic force responses were recorded and fast Fourier transform (FFT) analyses were performed to determine the response spectrum. Standard resonant frequency analysis and damping factor calculations were performed. The RP replicas were subsequently tested in compression beyond failure to determine their strength and modulus. It was found that the reductions in resonant frequency with increasing bone loss corresponded well with reductions in apparent stiffness and strength. This suggests that structural dynamics has the potential to be an alternative diagnostic technique for osteoporosis, although significant challenges must be overcome to determine the effect of the skin/soft tissue interface, the cortex and variabilities associated with in vivo testing.

  17. Variations in mineralization affect the stress and strain distributions in cortical and trabecular bone.

    PubMed

    van Ruijven, L J; Mulder, L; van Eijden, T M G J

    2007-01-01

    The mechanical properties of bone depend largely on its degree and distribution of mineralization. The present study analyzes the effect of an inhomogeneous distribution of mineralization on the stress and strain distributions in the human mandibular condyle during static clenching. A condyle was scanned with a micro-CT scanner to create a finite element model. For every voxel the degree of mineralization (DMB) was determined from the micro-CT scan. The Young's moduli of the elements were calculated from the DMB using constant, linear, and cubic relations, respectively. Stresses, strains, and displacements in cortical and trabecular bone, as well as the condylar deformation (extension along the antero-posterion axis) and compliance were compared. Over 90% of the bone mineral was located in the cortical bone. The DMB showed large variations in both cortical bone (mean: 884, SD: 111 mg/cm(3)) and trabecular bone (mean: 738, SD: 101 mg/cm(3)). Variations of the stresses and the strains were small in cortical bone, but large in trabecular bone. In the cortical bone an inhomogeneous mineral distribution increased the stresses and the strains. In the trabecular bone, however, it decreased the stresses and increased the strains. Furthermore, the condylar compliance remained relatively constant, but the condylar deformation doubled. It was concluded that neglect of the inhomogeneity of the mineral distribution results in a large underestimation of the stresses and strains of possibly more than 50%. The stiffness of trabecular bone strongly influences the condylar deformation. Vice versa, the condylar deformation largely determines the magnitude of the strains in the trabecular bone.

  18. The effects of side-artifacts on the elastic modulus of trabecular bone.

    PubMed

    Un, Kerem; Bevill, Grant; Keaveny, Tony M

    2006-01-01

    Determining accurate density-mechanical property relationships for trabecular bone is critical for correct characterization of this important structure-function relation. When testing any excised specimen of trabecular bone, an unavoidable experimental artifact originates from the sides of the specimen where peripheral trabeculae lose their vertical load-bearing capacity due to interruption of connectivity, a phenomenon denoted here as the 'side-artifact'. We sought in this study to quantify the magnitude of such side-artifact errors in modulus measurement and to do so as a function of the trabecular architecture and specimen size. Using parametric computational analysis of high-resolution micro-CT-based finite-element models of cores of elderly human vertebral trabecular bone, a specimen-specific correction factor for the side-artifact was quantified as the ratio of the side-artifact-free apparent modulus (Etrue) to the apparent modulus that would be measured in a typical experiment (Emeasured). We found that the width over which the peripheral trabeculae were mostly unloaded was between 0.19 and 0.58 mm. The side-artifact led to an underestimation error in Etrue of over 50% in some specimens, having a mean (+/-SD) of 27+/-11%. There was a trend for the correction factor to linearly increase as volume fraction decreased (p=0.001) and as mean trabecular separation increased (p<0.001). Further analysis indicated that the error increased substantially as specimen size decreased. Two methods used for correcting for the side-artifact were both successful in bringing Emeasured into statistical agreement with Etrue. These findings have important implications for the interpretation of almost all literature data on trabecular bone mechanical properties since they indicate that such properties need to be adjusted to eliminate the substantial effects of side-artifacts in order to provide more accurate estimates of in situ behavior.

  19. Trabecular bone texture classification using wavelet leaders

    NASA Astrophysics Data System (ADS)

    Zou, Zilong; Yang, Jie; Megalooikonomou, Vasileios; Jennane, Rachid; Cheng, Erkang; Ling, Haibin

    2016-03-01

    In this paper we propose to use the Wavelet Leader (WL) transformation for studying trabecular bone patterns. Given an input image, its WL transformation is defined as the cross-channel-layer maximum pooling of an underlying wavelet transformation. WL inherits the advantage of the original wavelet transformation in capturing spatial-frequency statistics of texture images, while being more robust against scale and orientation thanks to the maximum pooling strategy. These properties make WL an attractive alternative to replace wavelet transformations which are used for trabecular analysis in previous studies. In particular, in this paper, after extracting wavelet leader descriptors from a trabecular texture patch, we feed them into two existing statistic texture characterization methods, namely the Gray Level Co-occurrence Matrix (GLCM) and the Gray Level Run Length Matrix (GLRLM). The most discriminative features, Energy of GLCM and Gray Level Non-Uniformity of GLRLM, are retained to distinguish two different populations between osteoporotic patients and control subjects. Receiver Operating Characteristics (ROC) curves are used to measure performance of classification. Experimental results on a recently released benchmark dataset show that WL significantly boosts the performance of baseline wavelet transformations by 5% in average.

  20. Trabecular Bone Mechanical Properties and Fractal Dimension

    NASA Technical Reports Server (NTRS)

    Hogan, Harry A.

    1996-01-01

    Countermeasures for reducing bone loss and muscle atrophy due to extended exposure to the microgravity environment of space are continuing to be developed and improved. An important component of this effort is finite element modeling of the lower extremity and spinal column. These models will permit analysis and evaluation specific to each individual and thereby provide more efficient and effective exercise protocols. Inflight countermeasures and post-flight rehabilitation can then be customized and targeted on a case-by-case basis. Recent Summer Faculty Fellowship participants have focused upon finite element mesh generation, muscle force estimation, and fractal calculations of trabecular bone microstructure. Methods have been developed for generating the three-dimensional geometry of the femur from serial section magnetic resonance images (MRI). The use of MRI as an imaging modality avoids excessive exposure to radiation associated with X-ray based methods. These images can also detect trabecular bone microstructure and architecture. The goal of the current research is to determine the degree to which the fractal dimension of trabecular architecture can be used to predict the mechanical properties of trabecular bone tissue. The elastic modulus and the ultimate strength (or strain) can then be estimated from non-invasive, non-radiating imaging and incorporated into the finite element models to more accurately represent the bone tissue of each individual of interest. Trabecular bone specimens from the proximal tibia are being studied in this first phase of the work. Detailed protocols and procedures have been developed for carrying test specimens through all of the steps of a multi-faceted test program. The test program begins with MRI and X-ray imaging of the whole bones before excising a smaller workpiece from the proximal tibia region. High resolution MRI scans are then made and the piece further cut into slabs (roughly 1 cm thick). The slabs are X-rayed again

  1. Fabrication of Trabecular Bone-Templated Tissue-Engineered Constructs by 3D Inkjet Printing.

    PubMed

    Vanderburgh, Joseph P; Fernando, Shanik J; Merkel, Alyssa R; Sterling, Julie A; Guelcher, Scott A

    2017-09-11

    3D printing enables the creation of scaffolds with precisely controlled morphometric properties for multiple tissue types, including musculoskeletal tissues such as cartilage and bone. Computed tomography (CT) imaging has been combined with 3D printing to fabricate anatomically scaled patient-specific scaffolds for bone regeneration. However, anatomically scaled scaffolds typically lack sufficient resolution to recapitulate the <100 micrometer-scale trabecular architecture essential for investigating the cellular response to the morphometric properties of bone. In this study, it is hypothesized that the architecture of trabecular bone regulates osteoblast differentiation and mineralization. To test this hypothesis, human bone-templated 3D constructs are fabricated via a new micro-CT/3D inkjet printing process. It is shown that this process reproducibly fabricates bone-templated constructs that recapitulate the anatomic site-specific morphometric properties of trabecular bone. A significant correlation is observed between the structure model index (a morphometric parameter related to surface curvature) and the degree of mineralization of human mesenchymal stem cells, with more concave surfaces promoting more extensive osteoblast differentiation and mineralization compared to predominately convex surfaces. These findings highlight the significant effects of trabecular architecture on osteoblast function. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. A novel flexible microfluidic meshwork to reduce fibrosis in glaucoma surgery.

    PubMed

    Amoozgar, Behzad; Wei, Xiaoling; Hui Lee, Jun; Bloomer, Michele; Zhao, Zhengtuo; Coh, Paul; He, Fei; Luan, Lan; Xie, Chong; Han, Ying

    2017-01-01

    Fibrosis and hence capsule formation around the glaucoma implants are the main reasons for glaucoma implant failure. To address these issues, we designed a microfluidic meshwork and tested its biocompatibility in a rabbit eye model. The amount of fibrosis elicited by the microfluidic meshwork was compared to the amount elicited by the plate of conventional glaucoma drainage device. Six eyes from 3 New Zealand albino rabbits were randomized to receive either the novel microfluidic meshwork or a plate of Ahmed glaucoma valve model PF7 (AGV PF7). The flexible microfluidic implant was made from negative photoresist SU-8 by using micro-fabrication techniques. The overall size of the meshwork was 7 mm × 7 mm with a grid period of 100 μm. Both implants were placed in the subtenon space at the supratemporal quadrant in a standard fashion. There was no communication between the implants and the anterior chamber via a tube. All animal eyes were examined for signs of infection and implant erosion on days 1, 3, 7, and 14 and then monthly. Exenterations were performed in which the entire orbital contents were removed at 3 months. Histology slides of the implant and the surrounding tissues were prepared and stained with hematoxylin-eosin. Thickness of the fibrous capsules beneath the implants were measured and compared with paired student's t-test between the two groups. The gross histological sections showed that nearly no capsule formed around the microfluidic meshwork in contrast to the thick capsule formed around the plate of AGV PF7. Thickness of the fibrotic capsules beneath the AGV PF7 plate from the 3 rabbit eyes was 90μm, 82μm, and 95 μm, respectively. The thickness at the bottom of fibrotic capsules around the new microfluidic implant were 1μm, 2μm, and 1μm, respectively. The difference in thickness of capsule between the two groups was significant (P = 0.002). No complications were noticed in the 6 eyes, and both implants were tolerated well by all rabbits

  3. A novel flexible microfluidic meshwork to reduce fibrosis in glaucoma surgery

    PubMed Central

    Hui Lee, Jun; Bloomer, Michele; Zhao, Zhengtuo; Coh, Paul; He, Fei; Luan, Lan; Xie, Chong

    2017-01-01

    Purpose/Relevance Fibrosis and hence capsule formation around the glaucoma implants are the main reasons for glaucoma implant failure. To address these issues, we designed a microfluidic meshwork and tested its biocompatibility in a rabbit eye model. The amount of fibrosis elicited by the microfluidic meshwork was compared to the amount elicited by the plate of conventional glaucoma drainage device. Methods Six eyes from 3 New Zealand albino rabbits were randomized to receive either the novel microfluidic meshwork or a plate of Ahmed glaucoma valve model PF7 (AGV PF7). The flexible microfluidic implant was made from negative photoresist SU-8 by using micro-fabrication techniques. The overall size of the meshwork was 7 mm × 7 mm with a grid period of 100 μm. Both implants were placed in the subtenon space at the supratemporal quadrant in a standard fashion. There was no communication between the implants and the anterior chamber via a tube. All animal eyes were examined for signs of infection and implant erosion on days 1, 3, 7, and 14 and then monthly. Exenterations were performed in which the entire orbital contents were removed at 3 months. Histology slides of the implant and the surrounding tissues were prepared and stained with hematoxylin-eosin. Thickness of the fibrous capsules beneath the implants were measured and compared with paired student’s t-test between the two groups. Results The gross histological sections showed that nearly no capsule formed around the microfluidic meshwork in contrast to the thick capsule formed around the plate of AGV PF7. Thickness of the fibrotic capsules beneath the AGV PF7 plate from the 3 rabbit eyes was 90μm, 82μm, and 95 μm, respectively. The thickness at the bottom of fibrotic capsules around the new microfluidic implant were 1μm, 2μm, and 1μm, respectively. The difference in thickness of capsule between the two groups was significant (P = 0.002). No complications were noticed in the 6 eyes, and both implants

  4. Relationships of linear and nonlinear ultrasound parameters with porosity and trabecular spacing in trabecular-bone-mimicking phantoms.

    PubMed

    Lee, Kang Il

    2016-12-01

    The speed of sound (SOS), the normalized broadband ultrasound attenuation (nBUA), and the nonlinear parameter (B/A) were measured in 18 trabecular-bone-mimicking phantoms consisting of water-saturated aluminum foams. The strong slow wave and the very weak fast wave were consistently observed in the signals transmitted through all of the phantoms. It was found that the SOS increased as the porosity and the trabecular spacing increased. In contrast, both the nBUA and the B/A showed opposite dependences on the porosity and the trabecular spacing. All three ultrasound parameters exhibited high correlation coefficients with the porosity and the trabecular spacing.

  5. Genetic Determinants of Trabecular and Cortical Volumetric Bone Mineral Densities and Bone Microstructure

    PubMed Central

    Kähönen, Mika; Raitakari, Olli; Laaksonen, Marika; Sievänen, Harri; Viikari, Jorma; Lyytikäinen, Leo-Pekka; Mellström, Dan; Karlsson, Magnus; Ljunggren, Östen; Grundberg, Elin; Kemp, John P.; Sayers, Adrian; Nethander, Maria; Evans, David M.; Vandenput, Liesbeth; Tobias, Jon H.; Ohlsson, Claes

    2013-01-01

    Most previous genetic epidemiology studies within the field of osteoporosis have focused on the genetics of the complex trait areal bone mineral density (aBMD), not being able to differentiate genetic determinants of cortical volumetric BMD (vBMD), trabecular vBMD, and bone microstructural traits. The objective of this study was to separately identify genetic determinants of these bone traits as analysed by peripheral quantitative computed tomography (pQCT). Separate GWA meta-analyses for cortical and trabecular vBMDs were performed. The cortical vBMD GWA meta-analysis (n = 5,878) followed by replication (n = 1,052) identified genetic variants in four separate loci reaching genome-wide significance (RANKL, rs1021188, p = 3.6×10−14; LOC285735, rs271170, p = 2.7×10−12; OPG, rs7839059, p = 1.2×10−10; and ESR1/C6orf97, rs6909279, p = 1.1×10−9). The trabecular vBMD GWA meta-analysis (n = 2,500) followed by replication (n = 1,022) identified one locus reaching genome-wide significance (FMN2/GREM2, rs9287237, p = 1.9×10−9). High-resolution pQCT analyses, giving information about bone microstructure, were available in a subset of the GOOD cohort (n = 729). rs1021188 was significantly associated with cortical porosity while rs9287237 was significantly associated with trabecular bone fraction. The genetic variant in the FMN2/GREM2 locus was associated with fracture risk in the MrOS Sweden cohort (HR per extra T allele 0.75, 95% confidence interval 0.60–0.93) and GREM2 expression in human osteoblasts. In conclusion, five genetic loci associated with trabecular or cortical vBMD were identified. Two of these (FMN2/GREM2 and LOC285735) are novel bone-related loci, while the other three have previously been reported to be associated with aBMD. The genetic variants associated with cortical and trabecular bone parameters differed, underscoring the complexity of the genetics of bone parameters. We propose that a genetic

  6. Trabecular bone structure analysis in the limited spatial resolution regime of in vivo MRI.

    PubMed

    Magland, Jeremy F; Wehrli, Felix W

    2008-12-01

    To develop a method for processing and visualization of trabecular bone networks on the basis of magnetic resonance (MR) images acquired in the limited spatial resolution regime of in vivo imaging at which trabecular thickness is comparable to voxel size. A sequence of processing steps for analyzing the topologic structure of trabecular bone networks is presented and evaluated using three types of datasets: images of synthetic structures with various levels of superimposed Gaussian noise, micro-computed tomographic images of human trabecular bone downsampled to in vivo resolution, and in vivo micro-MR images from a prior longitudinal study investigating the structural implications of testosterone treatment of hypogonadal men. The simulated images were analyzed at a voxel size of 150 microm(3), the clinical MR image data had been acquired with 137 x 137 x 410 microm(3) voxel size. The technique is a modification to the virtual bone biopsy processing chain that involves a sinc convolution step immediately preceding binarization, and employs the Manzanera-Bernard thinning algorithm for obtaining the three-dimensional skeleton before topologic classification. The detectability of plate and rod bone elements was also analyzed theoretically. As compared with previously published techniques, the approach produced a more accurate bone skeleton in the micro-computed tomographic and simulation experiments, with clear improvement in preservation of rod and plate elements. Simulations suggest that rods are detectable down to a diameter of approximately 50% of the MR image voxel length, whereas plates can be detected at thicknesses of 20% or more of voxel length. For in vivo studies, it was shown that the method could recover the treatment response in terms of the ensuing topologic changes in patients undergoing antiresorptive treatment. The algorithm for processing of in vivo micro-MR images of trabecular bone is superior to prior approaches in preserving the topology of the

  7. Structural adaptation of trabecular bone revealed by position resolved analysis of proximal femora of different primates.

    PubMed

    Saparin, Peter; Scherf, Heike; Hublin, Jean-Jacques; Fratzl, Peter; Weinkamer, Richard

    2011-01-01

    The anisotropic arrangement of trabeculae in the proximal femur of humans and primates is seen as striking evidence for the functional adaptation of trabecular bone architecture. Quantitative evidence to demonstrate this adaptation for trabecular bone is still scarce, because experimental design of controlled load change is difficult. In this work, we use the natural variation of loading caused by a different main locomotor behavior of primates. Using high-resolution computed tomography and advanced image analysis techniques, we analyze the heterogeneity of the architecture in four proximal femora of four primate species. Although the small sample number does not allow an interspecies comparison, the very differently loaded bones are well suited to search for common structural features as a result of adaptation. A cubic volume of interest of size (5 mm)(3) was moved through the proximal femur and a morphometric analysis including local anisotropy was performed on 209 positions on average. The correlation of bone volume fraction (BV/TV) with trabecular number (Tb.N) and trabecular thickness (Tb.Th) leads to the suggestion of two different mechanisms of trabecular bone adaptation. Higher values of BV/TV in highly loaded regions of the proximal femur are due to a thickening of the trabeculae, whereas Tb.N does not change. In less loaded regions, however, lower values of BV/TV are found, caused by a reduction of the number of the trabeculae, whereas Tb.Th remains constant. This reduction in Tb.N goes along with an increase in the degree of anisotropy, indicating an adaptive selection of trabeculae. 2010 Wiley-Liss, Inc.

  8. A cellular solid criterion for predicting the axial-shear failure properties of bovine trabecular bone.

    PubMed

    Fenech, C M; Keaveny, T M

    1999-08-01

    In a long-term effort to develop a complete multi-axial failure criterion for human trabecular bone, the overall goal of this study was to compare the ability of a simple cellular solid mechanistic criterion versus the Tsai-Wu, Principal Strain, and von Mises phenomenological criteria--all normalized to minimize effects of interspecimen heterogeneity of strength--to predict the on-axis axial-shear failure properties of bovine trabecular bone. The Cellular Solid criterion that was developed here assumed that vertical trabeculae failed due to a linear superposition of axial compression/tension and bending stresses, induced by the apparent level axial and shear loading, respectively. Twenty-seven bovine tibial trabecular bone specimens were destructively tested on-axis without end artifacts, loaded either in combined tension-torsion (n = 10), compression-torsion (n = 11), or uniaxially (n = 6). For compression-shear, the mean (+/- S.D.) percentage errors between measured values and criterion predictions were 7.7 +/- 12.6 percent, 19.7 +/- 23.2 percent, 22.8 +/- 18.9 percent, and 82.4 +/- 64.5 percent for the Cellular Solid, Tsai-Wu, Principal Strain, and von Mises criteria, respectively; corresponding mean errors for tension-shear were -5.2 +/- 11.8 percent, 14.3 +/- 12.5 percent, 6.9 +/- 7.6 percent, and 57.7 +/- 46.3 percent. Statistical analysis indicated that the Cellular Solid criterion was the best performer for compression-shear, and performed as well as the Principal Strain criterion for tension-shear. These data should substantially improve the ability to predict axial-shear failure of dense trabecular bone. More importantly, the results firmly establish the importance of cellular solid analysis for understanding and predicting the multiaxial failure behavior of trabecular bone.

  9. Reduced tissue hardness of trabecular bone is associated with severe osteoarthritis.

    PubMed

    Dall'Ara, Enrico; Ohman, Caroline; Baleani, Massimiliano; Viceconti, Marco

    2011-05-17

    This study investigated whether changes in hardness of human trabecular bone are associated with osteoarthritis. Twenty femoral heads extracted from subjects without musculoskeletal diseases (subject age: 49-83 years) and twenty femoral heads extracted from osteoarthritic subjects (subject age: 42-85 years) were tested. Sixty indentations were performed along the main trabecular direction of each sample at a fixed relative distance. Two microstructures were found on the indenting locations: packs of parallel-lamellae (PL) and secondary osteons (SO). A 25gf load was applied for 15s and the Vickers Hardness (HV) was assessed. Trabecular tissue extracted from osteoarthritic subjects was found to be about 13% less hard compared to tissue extracted from non-pathologic subjects. However, tissue hardness was not significantly affected by gender or age. The SO was 10% less hard than the PL for both pathologic and non-pathologic tissues. A hardness of 34.1HV for PL and 30.8HV for SO was found for the non-pathologic tissue. For osteoarthritic tissue, the hardness was 30.2HV for PL and 27.1HV for SO. In the bone tissue extracted from osteoarthritic subjects the occurrence of indenting a SO (28%) was higher than that observed in the non-pathological tissue (15%). Osteoarthritis is associated with reduced tissue hardness and alterations in microstructure of the trabecular bone tissue. Gender does not significantly affect trabecular bone hardness either in non-pathological or osteoarthritic subjects. A similar conclusion can be drawn for age, although a larger donor sample size would be necessary to definitively exclude the existence of a slight effect.

  10. Quantifying trabecular bone material anisotropy and orientation using low resolution clinical CT images: A feasibility study.

    PubMed

    Nazemi, S Majid; Cooper, David M L; Johnston, James D

    2016-09-01

    Accounting for spatial variation of trabecular material anisotropy and orientation can improve the accuracy of quantitative computed tomography-based finite element (FE) modeling of bone. The objective of this study was to investigate the feasibility of quantifying trabecular material anisotropy and orientation using clinical computed tomography (CT). Forty four cubic volumes of interest were obtained from micro-CT images of the human radius. Micro-FE modeling was performed on the samples to obtain orthotropic stiffness entries as well as trabecular orientation. Simulated computed tomography images (0.32, 0.37, and 0.5mm isotropic voxel sizes) were created by resampling micro-CT images with added image noise. The gray-level structure tensor was used to derive fabric eigenvalues and eigenvectors in simulated CT images. For 'best case' comparison purposes, Mean Intercept Length was used to define fabric from micro-CT images. Regression was used in combination with eigenvalues, imaged density and FE to inversely derive the constants used in Cowin and Zysset-Curnier fabric-elasticity equations, and for comparing image derived fabric-elasticity stiffness entries to those obtained using micro-FE. Image derived eigenvectors (which indicated trabecular orientation) were then compared to orientation derived using micro-FE. When using clinically available voxel sizes, gray-level structure tensor derived fabric combined with Cowin's equations was able to explain 94-97% of the variance in orthotropic stiffness entries while Zysset-Curnier equations explained 82-88% of the variance in stiffness. Image derived orientation deviated by 4.4-10.8° from micro-FE derived orientation. Our results indicate potential to account for spatial variation of trabecular material anisotropy and orientation in subject-specific finite element modeling of bone using clinically available CT.

  11. Modeling orthotropic elasticity, localized plasticity and fracture in trabecular bone

    NASA Astrophysics Data System (ADS)

    O'Connor, D. T.; Elkhodary, K. I.; Fouad, Y.; Greene, M. S.; Sabet, F. A.; Qian, J.; Zhang, Y.; Liu, W. K.; Jasiuk, I.

    2016-09-01

    This work develops a model for the mechanical response of trabecular bone including plasticity, damage and fracture. It features a resultant lamellar orientation that captures trabecular strut anisotropic elasticity, and introduces asymmetric J2 plasticity with isotropic hardening to capture evolving strut tensile and compressive dissipative properties. A continuum compatibility based damage and fracture criterion is also proposed to model fracture surface generation. We investigated fracture of a trabecular bone network under a compressive load, for which failure modes of both tension and compression were identified at the strut level. The predicted trabecular network response was found to fall within the range of experimental results reported in literature. We also investigated the response of idealized struts under compression, tension and bending using our model. Individual struts were found to exhibit micro-buckling under compression and micro-necking under tension. These instabilities are however masked by the multiplicity and complexity of strut orientations at the trabecular network level.

  12. Trabecular bone scales allometrically in mammals and birds

    PubMed Central

    Doube, Michael; Kłosowski, Michał M.; Wiktorowicz-Conroy, Alexis M.; Hutchinson, John R.; Shefelbine, Sandra J.

    2011-01-01

    Many bones are supported internally by a latticework of trabeculae. Scaling of whole bone length and diameter has been extensively investigated, but scaling of the trabecular network is not well characterized. We analysed trabecular geometry in the femora of 90 terrestrial mammalian and avian species with body masses ranging from 3 g to 3400 kg. We found that bone volume fraction does not scale substantially with animal size, while trabeculae in larger animals' femora are thicker, further apart and fewer per unit volume than in smaller animals. Finite element modelling indicates that trabecular scaling does not alter the bulk stiffness of trabecular bone, but does alter strain within trabeculae under equal applied loads. Allometry of bone's trabecular tissue may contribute to the skeleton's ability to withstand load, without incurring the physiological or mechanical costs of increasing bone mass. PMID:21389033

  13. Trabecular bone scales allometrically in mammals and birds.

    PubMed

    Doube, Michael; Klosowski, Michal M; Wiktorowicz-Conroy, Alexis M; Hutchinson, John R; Shefelbine, Sandra J

    2011-10-22

    Many bones are supported internally by a latticework of trabeculae. Scaling of whole bone length and diameter has been extensively investigated, but scaling of the trabecular network is not well characterized. We analysed trabecular geometry in the femora of 90 terrestrial mammalian and avian species with body masses ranging from 3 g to 3400 kg. We found that bone volume fraction does not scale substantially with animal size, while trabeculae in larger animals' femora are thicker, further apart and fewer per unit volume than in smaller animals. Finite element modelling indicates that trabecular scaling does not alter the bulk stiffness of trabecular bone, but does alter strain within trabeculae under equal applied loads. Allometry of bone's trabecular tissue may contribute to the skeleton's ability to withstand load, without incurring the physiological or mechanical costs of increasing bone mass.

  14. Trabecular architecture in the StW 352 fossil hominin calcaneus.

    PubMed

    Zeininger, Angel; Patel, Biren A; Zipfel, Bernhard; Carlson, Kristian J

    2016-08-01

    Australopithecus africanus has been interpreted as having a rigid lateral foot. One mechanism contributing to a rigid foot during push-off in humans is a calcaneocuboid joint (CCJ) with limited dorsiflexion and a "close-packed" talocalcaneal joint (TCJ). In contrast, apes likely have a greater CCJ range of motion and lack a close-packed TCJ. Differences in tarsal arthrokinematics may result in different joint loading environments. In Homo sapiens, we tested the hypothesis that dorsal and plantar CCJ and the TCJ show evidence of predictable habitual loading. In Pan troglodytes, Gorilla gorilla, Gorilla beringei, and Papio ursinus, we tested the hypothesis that only the dorsal CCJ shows evidence of predictable loading. Specifically, we predicted similarity in trabecular properties across the dorsal and plantar CCJ in H. sapiens, but dissimilarity in non-humans. Additionally, we investigated trabecular properties of an A. africanus calcaneus (StW 352) to evaluate joint loading patterns in this hominin and ultimately address the evolution of these properties in H. sapiens. Contrary to predictions, the H. sapiens dorsal CCJ has a significantly higher elongation index, bone volume fraction, trabecular thickness, and trabecular number than the plantar CCJ, while trabecular properties in non-humans do not always differ as predicted between regions. H. sapiens exhibits trabecular morphology indicative of less variable TCJ loading than other groups, having the most anisotropic and rod-like struts oriented in line with predicted principal loads. Multivariate analysis shows that the StW 352 dorsal CCJ matches P. ursinus best, while the plantar CCJ matches G. beringei best and the TCJ matches that of G. gorilla best. Overall patterns suggest that the StW 352 calcaneus experienced more variable loading than H. sapiens, but less variable loading than P. troglodytes, G. gorilla, G. beringei, and P. ursinus, consistent with a large range of foot movements, probably

  15. Frequency Specific Ultrasound Attenuation Is Sensitive to Trabecular Bone Structure

    PubMed Central

    Lin, Wei; Serra-Hsu, Frederick; Chen, Jiqi; Qin, Yi-Xian

    2012-01-01

    This study investigated the efficacy of frequency modulated ultrasound attenuation in the assessment of the trabecular structural properties. Four frequency modulated signals were created to represent four frequency bands centered at 500 kHz, 900 kHz, 1.3 MHz and 1.7 MHz with the bandwidth of 400 kHz. Five one-centimeter trabecular cubes were harvested from fresh bovine distal femur. The cubes underwent four steps of demineralization process to expand the sample size to twenty five with the greater variations of the structural properties for the better correlation study. Pearson correlation study was performed between the ultrasound attenuation in four frequency bands and the trabecular structural properties. The results showed that correlations of frequency modulated ultrasound attenuation to the trabecular structural properties are dependent on frequency bands. The attenuation in proximal-distal orientation had the highest correlation to BV/TV (R2=0.73, p<0.001) and trabecular thickness (R2=0.50, p<0.001) at the frequency band centered at 1.7 MHz. It was equivalent in the four frequency bands in correlation to the trabecular number (average R2=0.80, p<0.001) and to the trabecular separation (average R2 =0.83, p<0.001). The attenuation in anterio-posterial orientation had the highest correlation to BV/TV (R2=0.80, p<0.001) and trabecular thickness (R2=0.71, p<0.001) at the frequency band centered at 1.3 MHz. The attenuation in the first frequency band was the most sensitive to the trabecular number (R2=0.71, p<0.001) and trabecular separation (R2=0.80, p<0.001). No significant correlation was observed for the attenuation in medial-lateral orientation across the four frequency bands. PMID:22975035

  16. A Novel 3D Microstructural Model for Trabecular Bone: I. The Relationship between Fabric and Elasticity.

    PubMed

    Zysset, P. K.; Ominsky, M. S.; Goldstein, S. A.

    1998-01-01

    A novel 3D microstructural model is proposed to investigate the relationship between morphology and mechanical properties of trabecular bone. Open and closed cell geometries were selected with varying volume fractions and degrees of anisotropy that simulate the architectures of human cancellous bone over a broad range of anatomical locations. Finite element models of both cells were developed using beams and shells. Volume fraction and mean intercept length were calculated analytically and the effective elastic tensors were computed with linear tissue properties and periodic boundary conditions. Distinct, but strong relationships were obtained between fabric and the elastic tensors for open and closed cell geometries, which bound the experimental results obtained for human bone and support the relevance of the selected model to address trabecular bone fragility.

  17. Dependences of ultrasonic properties on the propagation angle with respect to the trabecular alignment in trabecular bone

    NASA Astrophysics Data System (ADS)

    Lee, Kang Il

    2014-06-01

    The present study aims to investigate the dependences of ultrasonic properties on the propagation angle with respect to the trabecular alignment in 12 bovine femoral trabecular bone samples. The phase velocity and the attenuation coefficient of the fast wave measured at 0.5 MHz were found to decrease significantly with increasing angle and had their maximum values at 0°, i.e., for wave propagation in a direction parallel to the predominant trabecular alignment. The present study applied the angle-dependent Biot model by introducing anisotropy into the Biot model through the angle-dependent Young's, bulk, and shear moduli of the skeletal frame for trabecular bone to predict the measurements. Good agreement between the measurements and the prediction of the fast wave velocity suggests that the anisotropic fast wave velocity as a function of the propagation angle is mainly due to the variation in the elastic moduli of the skeletal frame with respect to the trabecular alignment.

  18. Heme compounds in dinosaur trabecular bone.

    PubMed

    Schweitzer, M H; Marshall, M; Carron, K; Bohle, D S; Busse, S C; Arnold, E V; Barnard, D; Horner, J R; Starkey, J R

    1997-06-10

    Six independent lines of evidence point to the existence of heme-containing compounds and/or hemoglobin breakdown products in extracts of trabecular tissues of the large theropod dinosaur Tyrannosaurus rex. These include signatures from nuclear magnetic resonance and electron spin resonance that indicate the presence of a paramagnetic compound consistent with heme. In addition, UV/visible spectroscopy and high performance liquid chromatography data are consistent with the Soret absorbance characteristic of this molecule. Resonance Raman profiles are also consistent with a modified heme structure. Finally, when dinosaurian tissues were extracted for protein fragments and were used to immunize rats, the resulting antisera reacted positively with purified avian and mammalian hemoglobins. The most parsimonious explanation of this evidence is the presence of blood-derived hemoglobin compounds preserved in the dinosaurian tissues.

  19. Trabecular Pattern Analysis Using Fractal Dimension

    NASA Astrophysics Data System (ADS)

    Ishida, Takayuki; Yamashita, Kazuya; Takigawa, Atsushi; Kariya, Komyo; Itoh, Hiroshi

    1993-04-01

    Feature extraction from a digitized image is advantageous for the detection of signs of disease. In this work, we attempted to evaluate bone trabecular pattern changes in osteoporosis using the fractal dimension and the root mean square (RMS) values. The relationship between the fractal dimension and the 1st moment of the power spectrum is explored, and we investigated the relationship between the results of this analysis and the bone mineral density (BMD) value which was measured using dual-energy X-ray absorptiometry (DEXA). As a result, we were able to extract useful information, using the fractal dimension and the RMS value of the radiographs (lateral view of the lumbar vertebrae), for the diagnosis of osteoporosis. Abnormal clinical cases were separated from normal cases based on the evaluation values. Negligible correlation between the BMD value and these indexes was observed.

  20. Measurement of the normalized broadband ultrasound attenuation in trabecular bone by using a bidirectional transverse transmission technique

    NASA Astrophysics Data System (ADS)

    Lee, Kang Il

    2015-01-01

    A new method for measuring the normalized broadband ultrasound attenuation (nBUA) in trabecular bone by using a bidirectional transverse transmission technique was proposed and validated with measurements obtained by using the conventional transverse transmission technique. There was no significant difference between the nBUA measurements obtained for 14 bovine femoral trabecular bone samples by using the bidirectional and the conventional transverse transmission techniques. The nBUA measured by using the two transverse transmission techniques showed strong positive correlations of r = 0.87 to 0.88 with the apparent bone density, consistent with the behavior in human trabecular bone invitro. We expect that the new method can be usefully applied for improved accuracy and precision in clinical measurements.

  1. Biomechanics and Mechanobiology of Trabecular Bone: A Review

    PubMed Central

    Oftadeh, Ramin; Perez-Viloria, Miguel; Villa-Camacho, Juan C.; Vaziri, Ashkan; Nazarian, Ara

    2015-01-01

    Trabecular bone is a highly porous, heterogeneous, and anisotropic material which can be found at the epiphyses of long bones and in the vertebral bodies. Studying the mechanical properties of trabecular bone is important, since trabecular bone is the main load bearing bone in vertebral bodies and also transfers the load from joints to the compact bone of the cortex of long bones. This review article highlights the high dependency of the mechanical properties of trabecular bone on species, age, anatomic site, loading direction, and size of the sample under consideration. In recent years, high resolution micro finite element methods have been extensively used to specifically address the mechanical properties of the trabecular bone and provide unique tools to interpret and model the mechanical testing experiments. The aims of the current work are to first review the mechanobiology of trabecular bone and then present classical and new approaches for modeling and analyzing the trabecular bone microstructure and macrostructure and corresponding mechanical properties such as elastic properties and strength. PMID:25412137

  2. Remodeling of the Inner Hair Cell Microtubule Meshwork in a Mouse Model of Auditory Neuropathy AUNA1

    PubMed Central

    Surel, Clément; Guillet, Marie; Lenoir, Marc; Bourien, Jérôme; Sendin, Gaston; Joly, Willy; Delprat, Benjamin; Lesperance, Marci M.; Puel, Jean-Luc

    2016-01-01

    Abstract Auditory neuropathy 1 (AUNA1) is a form of human deafness resulting from a point mutation in the 5′ untranslated region of the Diaphanous homolog 3 (DIAPH3) gene. Notably, the DIAPH3 mutation leads to the overexpression of the DIAPH3 protein, a formin family member involved in cytoskeleton dynamics. Through study of diap3-overexpressing transgenic (Tg) mice, we examine in further detail the anatomical, functional, and molecular mechanisms underlying AUNA1. We identify diap3 as a component of the hair cells apical pole in wild-type mice. In the diap3-overexpressing Tg mice, which show a progressive threshold shift associated with a defect in inner hair cells (IHCs), the neurotransmitter release and potassium conductances are not affected. Strikingly, the overexpression of diap3 results in a selective and early-onset alteration of the IHC cuticular plate. Molecular dissection of the apical components revealed that the microtubule meshwork first undergoes aberrant targeting into the cuticular plate of Tg IHCs, followed by collapse of the stereociliary bundle, with eventual loss of the IHC capacity to transmit incoming auditory stimuli. PMID:28058271

  3. Anticipating bipedalism: trabecular organization in the newborn ilium

    PubMed Central

    Cunningham, Craig A; Black, Sue M

    2009-01-01

    Trabecular bone structural organization is considered to be predominantly influenced by localized temporal forces which act to maintain and remodel the trabecular architecture into a biomechanically optimal configuration. In the adult pelvis, the most significant remodelling forces are believed to be those generated during bipedal locomotion. However, during the fetal and neonatal period the pelvic complex is non-weight bearing and, as such, structural organization of iliac trabecular bone cannot reflect direct stance-related forces. In this study, micro-computed tomography scans from 28 neonatal ilia were analysed, using a whole bone approach, to investigate the trabecular characteristics present within specific volumes of interest relevant to density gradients highlighted in a previous radiographic study. Analysis of the structural indices bone volume fraction, trabecular thickness, trabecular spacing and trabecular number was carried out to quantitatively investigate structural composition. Quantification of the neonatal trabecular structure reinforced radiographic observations by highlighting regions of significant architectural form which grossly parallel architectural differences in the adult pattern but which have previously been attributed to stance-related forces. It is suggested that the seemingly organized rudimentary scaffold observed in the neonatal ilium may be attributable to other non-weight bearing anatomical interactions or even to a predetermined genetic blueprint. It must also be postulated that whilst the observed patterning may be indicative of a predetermined inherent template, early non-weight bearing and late stance-related locomotive influences may subsequently be superimposed upon this scaffolding and perhaps reinforced and likely remodelled at a later age. Ultimately, the analysis of this fundamental primary pattern has core implications for understanding the earliest changes in pelvic trabecular architecture and provides a baseline

  4. Netarsudil Increases Outflow Facility in Human Eyes Through Multiple Mechanisms

    PubMed Central

    Ren, Ruiyi; Li, Guorong; Le, Thuy Duong; Kopczynski, Casey; Stamer, W. Daniel; Gong, Haiyan

    2016-01-01

    Purpose Netarsudil is a Rho kinase/norepinephrine transporter inhibitor currently in phase 3 clinical development for glaucoma treatment. We investigated the effects of its active metabolite, netarsudil-M1, on outflow facility (C), outflow hydrodynamics, and morphology of the conventional outflow pathway in enucleated human eyes. Methods Paired human eyes (n = 5) were perfused with either 0.3 μM netarsudil-M1 or vehicle solution at constant pressure (15 mm Hg). After 3 hours, fluorescent microspheres were added to perfusion media to trace the outflow patterns before perfusion-fixation. The percentage effective filtration length (PEFL) was calculated from the measured lengths of tracer distribution in the trabecular meshwork (TM), episcleral veins (ESVs), and along the inner wall (IW) of Schlemm's canal after global and confocal imaging. Morphologic changes along the trabecular outflow pathway were investigated by confocal, light, and electron microscopy. Results Perfusion with netarsudil-M1 significantly increased C when compared to baseline (51%, P < 0.01) and to paired controls (102%, P < 0.01), as well as significantly increased PEFL in both IW (P < 0.05) and ESVs (P < 0.01). In treated eyes, PEFL was significantly higher in ESVs than in the IW (P < 0.01) and was associated with increased cross-sectional area of ESVs (P < 0.01). Percentage effective filtration length in ESVs positively correlated with the percentage change in C (R2 = 0.58, P = 0.01). A significant increase in juxtacanalicular connective tissue (JCT) thickness (P < 0.05) was found in treated eyes compared to controls. Conclusions Netarsudil acutely increased C by expansion of the JCT and dilating the ESVs, which led to redistribution of aqueous outflow through a larger area of the IW and ESVs. PMID:27842161

  5. Romosozumab Treatment Converts Trabecular Rods into Trabecular Plates in Male Cynomolgus Monkeys.

    PubMed

    Matheny, Jonathan B; Torres, Ashley M; Ominsky, Michael S; Hernandez, Christopher J

    2017-02-28

    Treatment with sclerostin antibody (romosozumab) increases bone formation while reducing bone resorption, leading to increases in bone volume and bone mineral density. Sclerostin antibody treatment may also provide beneficial changes in trabecular microarchitecture and strength that are not reflected in bone volume and density. Here we use three-dimensional dynamic histomorphometry to determine longitudinal changes in vertebral trabecular microarchitecture in adolescent male cynomolgus monkeys (4-5 years old) treated with sclerostin antibody. Animals were treated bi-weekly with either sclerostin antibody (30 mg/kg, sc, n = 6) or vehicle (n = 6) for 10 weeks. Animals were administered fluorochrome bone formation labels on days 14 and 24 (tetracycline) and on days 56 and 66 (calcein), followed by necropsy on day 70. Cylindrical specimens of cancellous bone from the 5th lumbar vertebrae were used to generate high-resolution, three-dimensional images of bone and fluorescent labels of bone formation (0.7 × 0.7 × 5.0 µm/voxel). The three-dimensional images of the bone formation labels were used to determine the bone volume formed between days 14 and 66 and the resulting alterations in trabecular microarchitecture within each bone. Treatment with sclerostin antibody resulted in a conversion of rod-like trabeculae into plate-like trabeculae at a higher rate than in vehicle-treated animals (p = 0.01). Plate bone volume fraction was greater in the sclerostin antibody group relative to vehicle (mean 43 vs. 30%, p < 0.05). Bone formation increased the thickness of trabeculae in all three trabecular orientations (axial, oblique, and transverse, p < 0.05). The volume of bone formed between days 14 to 66 was greater in sclerostin antibody-treated groups (9.0 vs. 5.4%, p = 0.02), and new bone formation due to sclerostin antibody treatment was associated with increased apparent stiffness as determined from finite element models. Our results

  6. Nuclear migration during karyogamy in rice zygotes is mediated by continuous convergence of actin meshwork toward the egg nucleus.

    PubMed

    Ohnishi, Yukinosuke; Okamoto, Takashi

    2017-03-01

    Fertilization is comprised of two sequential fusion processes; plasmogamy and karyogamy. Karyogamy completes with migration and fusion of the male and female nuclei in the fused cell. In animals, microtubules organized by the centrosome control female/male pronuclei migration. In contrast, the nuclear migration in fused gametes of angiosperms is controlled by actin filaments, but the mechanism that regulates actin filament-dependent nuclear migration is not clear. In this study, we prepared fused rice (Oryza sativa L.) gametes/zygotes using in vitro fertilization and observed the spatial and temporal movements of actin filaments and sperm nuclei. Our results show that actin filaments in egg cells form a meshwork structure surrounding the nuclei. Quantitative analysis of the actin meshwork dynamics suggests that actin meshwork converges toward the egg nucleus. In egg cells fused with sperm cells, actin filaments appeared to interact with a portion of the sperm nuclear membrane. The velocity of the actin filaments was positively correlated with the velocity of the sperm nucleus during karyogamy. These results suggest that sperm nuclear membrane and actin filaments physically interact with each other during karyogamy, and that the sperm nucleus migrates toward the egg nucleus through the convergence of the actin meshwork. Interestingly, actin filament velocity increased promptly after gamete fusion and was further elevated during nuclear fusion. In addition to the migration of gamete nuclei, convergence of actin meshwork may also be critical during early zygotic developments.

  7. Experimental and numerical characterisation of the elasto-plastic properties of bovine trabecular bone and a trabecular bone analogue.

    PubMed

    Kelly, Nicola; McGarry, J Patrick

    2012-05-01

    The inelastic pressure dependent compressive behaviour of bovine trabecular bone is investigated through experimental and computational analysis. Two loading configurations are implemented, uniaxial and confined compression, providing two distinct loading paths in the von Mises-pressure stress plane. Experimental results reveal distinctive yielding followed by a constant nominal stress plateau for both uniaxial and confined compression. Computational simulation of the experimental tests using the Drucker-Prager and Mohr-Coulomb plasticity models fails to capture the confined compression behaviour of trabecular bone. The high pressure developed during confined compression does not result in plastic deformation using these formulations, and a near elastic response is computed. In contrast, the crushable foam plasticity models provide accurate simulation of the confined compression tests, with distinctive yield and plateau behaviour being predicted. The elliptical yield surfaces of the crushable foam formulations in the von Mises-pressure stress plane accurately characterise the plastic behaviour of trabecular bone. Results reveal that the hydrostatic yield stress is equal to the uniaxial yield stress for trabecular bone, demonstrating the importance of accurate characterisation and simulation of the pressure dependent plasticity. It is also demonstrated in this study that a commercially available trabecular bone analogue material, cellular rigid polyurethane foam, exhibits similar pressure dependent yield behaviour, despite having a lower stiffness and strength than trabecular bone. This study provides a novel insight into the pressure dependent yield behaviour of trabecular bone, demonstrating the inadequacy of uniaxial testing alone. For the first time, crushable foam plasticity formulations are implemented for trabecular bone. The enhanced understanding of the inelastic behaviour of trabecular bone established in this study will allow for more realistic simulation

  8. Phenotypic integration among trabecular and cortical bone traits establishes mechanical functionality of inbred mouse vertebrae.

    PubMed

    Tommasini, Steven M; Hu, Bin; Nadeau, Joseph H; Jepsen, Karl J

    2009-04-01

    Conventional approaches to identifying quantitative trait loci (QTLs) regulating bone mass and fragility are limited because they examine cortical and trabecular traits independently. Prior work examining long bones from young adult mice and humans indicated that skeletal traits are functionally related and that compensatory interactions among morphological and compositional traits are critical for establishing mechanical function. However, it is not known whether trait covariation (i.e., phenotypic integration) also is important for establishing mechanical function in more complex, corticocancellous structures. Covariation among trabecular, cortical, and compositional bone traits was examined in the context of mechanical functionality for L(4) vertebral bodies across a panel of 16-wk-old female AXB/BXA recombinant inbred (RI) mouse strains. The unique pattern of randomization of the A/J and C57BL/6J (B6) genome among the RI panel provides a powerful tool that can be used to measure the tendency for different traits to covary and to study the biology of complex traits. We tested the hypothesis that genetic variants affecting vertebral size and mass are buffered by changes in the relative amounts of cortical and trabecular bone and overall mineralization. Despite inheriting random sets of A/J and B6 genomes, the RI strains inherited nonrandom sets of cortical and trabecular bone traits. Path analysis, which is a multivariate analysis that shows how multiple traits covary simultaneously when confounding variables like body size are taken into consideration, showed that RI strains that tended to have smaller vertebrae relative to body size achieved mechanical functionality by increasing mineralization and the relative amounts of cortical and trabecular bone. The interdependence among corticocancellous traits in the vertebral body indicated that variation in trabecular bone traits among inbred mouse strains, which is often thought to arise from genetic factors, is also

  9. Particle migration and gap healing around trabecular metal implants

    PubMed Central

    Kold, S.; Zippor, B.; Overgaard, S.; Søballe, K.

    2005-01-01

    Bone on-growth and peri-implant migration of polyethylene particles were studied in an experimental setting using trabecular metal and solid metal implants. Cylindrical implants of trabecular tantalum metal and solid titanium alloy implants with a glass bead blasted surface were inserted either in an exact surgical fit or with a peri-implant gap into a canine knee joint. We used a randomised paired design. Polyethylene particles were injected into the knee joint. In both types of surgical fit we found that the trabecular metal implants had superior bone ongrowth in comparison with solid metal implants (exact fit: 23% vs. 7% [p=0.02], peri-implant gap: 13% vs. 0% [p=0.02]. The number of peri-implant polyethylene particles was significantly reduced around the trabecular metal implants with a peri-implant gap compared with solid implants. PMID:16132987

  10. Trabecular scaffolds created using micro CT guided fused deposition modeling

    PubMed Central

    Tellis, B.C.; Szivek, J.A.; Bliss, C.L.; Margolis, D.S.; Vaidyanathan, R.K.; Calvert, P.

    2009-01-01

    Free form fabrication and high resolution imaging techniques enable the creation of biomimetic tissue engineering scaffolds. A 3D CAD model of canine trabecular bone was produced via micro CT and exported to a fused deposition modeler, to produce polybutylene terephthalate (PBT) trabeculated scaffolds and four other scaffold groups of varying pore structures. The five scaffold groups were divided into subgroups (n=6) and compression tested at two load rates (49 N/s and 294 N/s). Two groups were soaked in a 25 °C saline solution for 7 days before compression testing. Micro CT was used to compare porosity, connectivity density, and trabecular separation of each scaffold type to a canine trabecular bone sample. At 49 N/s the dry trabecular scaffolds had a compressive stiffness of 4.94±1.19 MPa, similar to the simple linear small pore scaffolds and significantly more stiff (p<0.05) than either of the complex interconnected pore scaffolds. At 294 N/s, the compressive stiffness values for all five groups roughly doubled. Soaking in saline had an insignificant effect on stiffness. The trabecular scaffolds matched bone samples in porosity; however, achieving physiologic connectivity density and trabecular separation will require further refining of scaffold processing. PMID:21461176

  11. Radiographic features of mandibular trabecular bone structure in hypodontia.

    PubMed

    Créton, Marijn; Geraets, Wil; Verhoeven, Jan Willem; van der Stelt, Paul F; Verhey, Hans; Cune, Marco

    2012-04-01

    Radiographic parameters of mandibular trabecular bone structure between 67 subjects having hypodontia and those without were studied on digital panoramic radiographs. Three regions of interest (ROI) were defined: the ascending ramus, apical of the mandibular molar and mesial of the first mandibular molar. The effects of the presence of hypodontia and the ROI on the mandibular trabecular bone structure were tested for statistical significance by means of multivariate analysis. Radiographic parameters of trabecular bone architecture were found to differ between various regions of the mandible (p = 0.000), but not between the group of hypodontia subjects and their controls (p = 0.23). There was no interaction effect between the ROIs and the two groups (p = 0.79). For people having hypodontia, some directional parameters of trabecular bone have a reverse correlation with the number of missing teeth. The fractal dimension and the number and perimeter of white segments in the binarized image correlate positively with the number of congenitally missing teeth. A limited number of parameters of radiographic mandibular trabecular bone structure correlate with the number of missing teeth. However, a markable difference in radiographic parameters of mandibular trabecular bone structure between hypodontia and non-hypodontia subjects could not be demonstrated. © 2009 Wiley Periodicals, Inc.

  12. The sensitivity of nonlinear computational models of trabecular bone to tissue level constitutive model.

    PubMed

    Baumann, Andrew P; Shi, Xiutao; Roeder, Ryan K; Niebur, Glen L

    2016-01-01

    Microarchitectural finite element models have become a key tool in the analysis of trabecular bone. Robust, accurate, and validated constitutive models would enhance confidence in predictive applications of these models and in their usefulness as accurate assays of tissue properties. Human trabecular bone specimens from the femoral neck (n = 3), greater trochanter (n = 6), and lumbar vertebra (n = 1) of eight different donors were scanned by μ-CT and converted to voxel-based finite element models. Unconfined uniaxial compression and shear loading were simulated for each of three different constitutive models: a principal strain-based model, Drucker-Lode, and Drucker-Prager. The latter was applied with both infinitesimal and finite kinematics. Apparent yield strains exhibited minimal dependence on the constitutive model, differing by at most 16.1%, with the kinematic formulation being influential in compression loading. At the tissue level, the quantities and locations of yielded tissue were insensitive to the constitutive model, with the exception of the Drucker-Lode model, suggesting that correlation of microdamage with computational models does not improve the ability to discriminate between constitutive laws. Taken together, it is unlikely that a tissue constitutive model can be fully validated from apparent-level experiments alone, as the calculations are too insensitive to identify differences in the outcomes. Rather, any asymmetric criterion with a valid yield surface will likely be suitable for most trabecular bone models.

  13. An ontogenetic framework linking locomotion and trabecular bone architecture with applications for reconstructing hominin life history.

    PubMed

    Raichlen, David A; Gordon, Adam D; Foster, Adam D; Webber, James T; Sukhdeo, Simone M; Scott, Robert S; Gosman, James H; Ryan, Timothy M

    2015-04-01

    The ontogeny of bipedal walking is considered uniquely challenging, due in part to the balance requirements of single limb support. Thus, locomotor development in humans and our bipedal ancestors may track developmental milestones including the maturation of the neuromuscular control system. Here, we examined the ontogeny of locomotor mechanics in children aged 1-8, and bone growth and development in an age-matched skeletal sample to identify bony markers of locomotor development. We show that step-to-step variation in mediolateral tibia angle relative to the vertical decreases with age, an indication that older children increase stability. Analyses of trabecular bone architecture in the distal tibia of an age-matched skeletal sample (the Norris Farms #36 archaeological skeletal collection) show a bony signal of this shift in locomotor stability. Using a grid of eleven cubic volumes of interest (VOI) in the distal metaphysis of each tibia, we show that the degree of anisotropy (DA) of trabecular struts changes with age. Intra-individual variation in DA across these VOIs is generally high at young ages, likely reflecting variation in loading due to kinematic instability. With increasing age, mean DA converges on higher values and becomes less variable across the distal tibia. We believe the ontogeny of distal tibia trabecular architecture reflects the development of locomotor stability in bipeds. We suggest this novel bony marker of development may be used to assess the relationship between locomotor development and other life history milestones in fossil hominins. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. Lacunarity analysis of spatial pattern in CT images of vertebral trabecular bone for assessing osteoporosis.

    PubMed

    Dougherty, Geoffrey; Henebry, Geoffrey M

    2002-03-01

    The structural integrity of vertebral trabecular bone is determined by the continuity of its trabecular network and the size of the holes comprising its marrow space, both of which determine the apparent size of the marrow spaces in a transaxial CT image. A model-independent assessment of the trabeculation pattern was determined from the lacunarity of thresholded CT images. Using test images of lumbar vertebrae from human cadavers, acquired at different slice thicknesses, we determined that both median thresholding and local adaptive thresholding (using a 7 x 7 window) successfully segmented the grey-scale images. Lacunarity analysis indicated a multifractal nature to the images, and a range of marrow space sizes with significant structure around 14-18 mm(2). Preliminary studies of in vivo images from a clinical CT scanner indicate that lacunarity analysis can follow the pattern of bone loss in osteoporosis by monitoring the homogeneity of the marrow spaces, which is related to the connectivity of the trabecular bone network and the marrow space sizes. Although the patient sample was small, derived parameters such as the maximum deviation of the lacunarity from a neutral (fractal) model, and the maximum derivative of this deviation, seem to be sufficiently sensitive to distinguish a range of bone conditions. Our results suggest that these parameters, used with bone mineral density values, may have diagnostic value in characterizing osteoporosis and predicting fracture risk.

  15. In vivo volumetric imaging of the human corneo-scleral limbus with spectral domain OCT

    PubMed Central

    Bizheva, Kostadinka; Hutchings, Natalie; Sorbara, Luigina; Moayed, Alireza A.; Simpson, Trefford

    2011-01-01

    The limbus is the structurally rich transitional region of tissue between the cornea on one side, and the sclera and conjunctiva on the other. This zone, among other things, contains nerves passing to the cornea, blood and lymph vasculature for oxygen and nutrient delivery and for waste, CO2 removal and drainage of the aqueous humour. In addition, the limbus contains stem cells responsible for the existence and healing of the corneal epithelium. Here we present 3D images of the healthy human limbus, acquired in vivo with a spectral domain optical coherence tomography system operating at 1060nm. Cross-sectional and volumetric images were acquired from temporal and nasal locations in the human limbus with ~3µm x 18µm (axial x lateral) resolution in biological tissue at the rate of 92,000 A-scans/s. The imaging enabled detailed mapping of the corneo-scleral tissue morphology, and visualization of structural details such as the Vogt palisades, the blood and lymph vasculature including the Schlemm’s canal and the trabecular meshwork, as well as corneal nerve fiber bundles. Non-invasive, volumetric, high resolution imaging reveals fine details of the normal human limbal structure, and promises to provide invaluable information about its changes in health and disease as well as during and after corneal surgery. PMID:21750758

  16. Investigation of the failure behaviour of vertebral trabecular architectures under uni-axial compression and wedge action loading conditions.

    PubMed

    McDonnell, P; Harrison, N; McHugh, P E

    2010-07-01

    Vertebral wedge fractures are associated with combined compression and flexure loading and are the most common fracture type for human vertebrae. In this study, rapid prototype (RP) biomodels of human vertebral trabecular bone were mechanically tested under uni-axial compression loading and also under wedge action loading (combination of compression and flexure loading) to investigate the mode of failure and the ultimate loads that could be sustained under these different loading conditions. Two types of trabecular bone models were manufactured and tested: baseline models which were directly derived from microCT scans of human thoracic vertebrae, and osteoporotic models which were generated from the baseline models using a custom-developed bone loss algorithm. The ultimate load for each model under compression and wedge action loading was determined and a video was recorded of each test so that failure mechanisms could be evaluated. The results of the RP model mechanical tests showed that the ultimate loads that could be supported by vertebral trabecular architectures under wedge action loading were less than those that could be supported under uni-axial compression loading by up to 26%. Also, the percentage reduction in strength from the baseline value due to osteoporotic bone loss was slightly less for the wedge action loading compared to uni-axial compression loading. Analysis of the videos for each test revealed that failure occurred in localised regions of the trabecular structure due to bending and buckling of thin vertical struts. These results suggest that vertebral trabecular bone is more susceptible to failure from wedge action loading compared to uni-axial compression loading, although this effect is not exacerbated by osteoporotic bone loss.

  17. High Insulin Levels in KK-Ay Diabetic Mice Cause Increased Cortical Bone Mass and Impaired Trabecular Micro-Structure

    PubMed Central

    Fu, Cen; Zhang, Xiaolin; Ye, Fei; Yang, Jianhong

    2015-01-01

    Type 2 diabetes mellitus (T2DM) is a chronic disease characterized by hyperglycemia, hyperinsulinemia and complications, including obesity and osteoporosis. Rodents have been widely used to model human T2DM and investigate its effect on the skeleton. We aimed to investigate skeletal alterations in Yellow Kuo Kondo (KK-Ay) diabetic mice displaying high insulin and glucose levels. Bone mineral density (BMD), micro-architecture and bone metabolism-related genes were analyzed. The total femoral areal BMD (aBMD), cortical volumetric BMD (vBMD) and thickness were significantly increased in KK-Ay mice, while the trabecular vBMD and mineralized bone volume/tissue volume (BV/TV), trabecular thickness and number were decreased compared to C57BL mice. The expression of both osteoblast-related genes, such as osteocalcin (OC), bone sialoprotein, Type I Collagen, osteonectin, RUNX2 and OSX, and osteoclast-related genes, such as TRAP and TCIRG, were up-regulated in KK-Ay mice. Correlation analyses showed that serum insulin levels were positively associated with aBMD, cortical vBMD and thickness and negatively associated with trabecular vBMD and micro-architecture. In addition, serum insulin levels were positively related to osteoblast-related and osteoclast-related gene expression. Our data suggest that high insulin levels in KK-Ay diabetic mice may increase cortical bone mass and impair trabecular micro-structure by up-regulating osteoblast-and osteoclast-related gene expression. PMID:25872143

  18. High insulin levels in KK-Ay diabetic mice cause increased cortical bone mass and impaired trabecular micro-structure.

    PubMed

    Fu, Cen; Zhang, Xiaolin; Ye, Fei; Yang, Jianhong

    2015-04-13

    Type 2 diabetes mellitus (T2DM) is a chronic disease characterized by hyperglycemia, hyperinsulinemia and complications, including obesity and osteoporosis. Rodents have been widely used to model human T2DM and investigate its effect on the skeleton. We aimed to investigate skeletal alterations in Yellow Kuo Kondo (KK-Ay) diabetic mice displaying high insulin and glucose levels. Bone mineral density (BMD), micro-architecture and bone metabolism-related genes were analyzed. The total femoral areal BMD (aBMD), cortical volumetric BMD (vBMD) and thickness were significantly increased in KK-Ay mice, while the trabecular vBMD and mineralized bone volume/tissue volume (BV/TV), trabecular thickness and number were decreased compared to C57BL mice. The expression of both osteoblast-related genes, such as osteocalcin (OC), bone sialoprotein, Type I Collagen, osteonectin, RUNX2 and OSX, and osteoclast-related genes, such as TRAP and TCIRG, were up-regulated in KK-Ay mice. Correlation analyses showed that serum insulin levels were positively associated with aBMD, cortical vBMD and thickness and negatively associated with trabecular vBMD and micro-architecture. In addition, serum insulin levels were positively related to osteoblast-related and osteoclast-related gene expression. Our data suggest that high insulin levels in KK-Ay diabetic mice may increase cortical bone mass and impair trabecular micro-structure by up-regulating osteoblast-and osteoclast-related gene expression.

  19. Plasma Membrane is Compartmentalized by a Self-Similar Cortical Actin Meshwork

    NASA Astrophysics Data System (ADS)

    Sadegh, Sanaz; Higgins, Jenny L.; Mannion, Patrick C.; Tamkun, Michael M.; Krapf, Diego

    2017-01-01

    A broad range of membrane proteins display anomalous diffusion on the cell surface. Different methods provide evidence for obstructed subdiffusion and diffusion on a fractal space, but the underlying structure inducing anomalous diffusion has never been visualized because of experimental challenges. We addressed this problem by imaging the cortical actin at high resolution while simultaneously tracking individual membrane proteins in live mammalian cells. Our data confirm that actin introduces barriers leading to compartmentalization of the plasma membrane and that membrane proteins are transiently confined within actin fences. Furthermore, superresolution imaging shows that the cortical actin is organized into a self-similar meshwork. These results present a hierarchical nanoscale picture of the plasma membrane.

  20. Cohesiveness tunes assembly and morphology of FG nucleoporin domain meshworks – Implications for nuclear pore permeability

    PubMed Central

    Eisele, Nico B.; Labokha, Aksana A.; Frey, Steffen; Görlich, Dirk; Richter, Ralf P.

    2013-01-01

    Nuclear pore complexes control the exchange of macromolecules between the cytoplasm and the nucleus. A selective permeability barrier that arises from a supramolecular assembly of intrinsically unfolded nucleoporin domains rich in phenylalanine-glycine dipeptides (FG domains) fills the nuclear pore. There is increasing evidence that selective transport requires cohesive FG domain interactions. To understand the functional roles of cohesive interactions, we studied monolayers of end-grafted FG domains as a bottom-up nanoscale model system of the permeability barrier. Based on detailed physicochemical analysis of the model films and comparison of the data with polymer theory, we propose that cohesiveness is tuned to promote rapid assembly of the permeability barrier and to generate a stable and compact pore-filling meshwork with a small mesh size. Our results highlight the functional importance of weak interactions, typically a few kBT per chain, and contribute important information to understand the mechanism of size-selective transport. PMID:24138862

  1. Existence of a dense reticular meshwork surrounding the nephron inducer in neonatal rabbit kidney.

    PubMed

    Strehl, R; Trautner, V; Kloth, S; Minuth, W W

    1999-12-01

    While more and more humoral factors involved in nephrogenesis are being discovered, there is no detailed knowledge of the morphological structures at the interface of the nephron inducer and the surrounding mesenchyme. For that reason we examined this area in the cortex of neonatal rabbit kidneys by scanning electron-microscopical and transmission electron-microscopical techniques. Our interest was focused on the basal aspect of the collecting duct ampulla and the surrounding competent mesenchyme, where morphogenic signals are to be exchanged during nephron induction. Close contact between these two tissues involved in nephrogenesis is assumed to allow direct cellular contact or diffusion of soluble factors across a short distance. Our data, however, show the presence of a dense fibrillar meshwork around the collecting duct ampulla, spatially separating the inducer and the competent mesenchyme during nephron induction.

  2. Microsurgical anatomy of the supratentorial arachnoidal trabecular membranes and cisterns.

    PubMed

    Vinas, F C; Fandino, R; Dujovny, M; Chavez, V

    1994-12-01

    We examined the microsurgical anatomy of the supratentorial subarachnoid cisterns with a surgical microscope in 20 brains prepared using the immersion technique. The adult brains were immersed in Ringer's solution and air was injected into the subarachnoid cisterns while the brains remained submerged in solution. We identified nine trabecular membranes that limit the 15 cisterns. We specifically looked at the anatomical relationship between the supratentorial trabecular membranes and cisterns to their corresponding vessels and cranial nerves. The cistern divisions and the dispositions of trabecular membranes were closely related to the vascular division patterns of the principal brain arteries. A clear and thorough understanding of the neuroanatomical structures of the subarachnoid cisterns is important because they provide natural pathways to neurovascular and cranial nerve structures. These pathways allow access to intracranial arteries, veins, and nerves during microvascular procedures without disturbing surrounding important brain structures.

  3. Microsurgical anatomy of the infratentorial trabecular membranes and subarachnoid cisterns.

    PubMed

    Vinas, F C; Dujovny, M; Fandino, R; Chavez, V

    1996-04-01

    The understanding of the anatomy of the subarachnoid cisterns and trabecular membranes is of paramount importance in the surgical treatment of pathology of the posterior fossa. Aneurysms, arteriovenous malformations, and some tumors should be approached through the subarachnoid space. The subarachnoid cisterns provide natural pathways to approach neurovascular and cranial nerve structures. The microsurgical anatomy of the infratentorial subarachnoid cisterns was studied in twenty adult brains, using the 'immersion technique'. Air was injected into the subarachnoid cisterns and brains were dissected under the operative microscope. Six main compartmental trabecular membranes were identified in the infratentorial level. They divide the subarachnoid space into six cisterns. Cisternal divisions and the disposition of the trabecular membranes were closely related to the vascular divisional patterns of the principal arteries. Thorough knowledge of the microsurgical anatomy of the subarachnoid space will aid neurosurgeons during the surgical approach of many vascular and tumoral lesions located in the posterior fossa.

  4. The dependencies of phase velocity and dispersion on trabecular thickness and spacing in trabecular bone-mimicking phantoms.

    PubMed

    Wear, Keith A

    2005-08-01

    Frequency-dependent phase velocity was measured in trabecular-bone-mimicking phantoms consisting of two-dimensional arrays of parallel nylon wires (simulating trabeculae) with thicknesses ranging from 152 to 305 microm and spacings ranging from 700 to 1000 microm. Phase velocity varied approximately linearly with frequency over the range from 400 to 750 kHz. Dispersion was characterized by the slope of a linear least-squares regression fit to phase velocity versus frequency data. The increase in phase velocity (compared with that in water) at 500 kHz was approximately proportional to the (1) square of trabecular thickness, (2) inverse square of trabecular spacing, and (3) volume fraction occupied by nylon wires. The first derivative of phase velocity with respect to frequency was negative and exhibited nonlinear, monotonically decreasing dependencies on trabecular thickness and volume fraction. The dependencies of phase velocity and its first derivative on volume fraction in the phantoms were consistent with those reported in trabecular bone.

  5. The dependencies of phase velocity and dispersion on trabecular thickness and spacing in trabecular bone-mimicking phantoms

    NASA Astrophysics Data System (ADS)

    Wear, Keith A.

    2005-08-01

    Frequency-dependent phase velocity was measured in trabecular-bone-mimicking phantoms consisting of two-dimensional arrays of parallel nylon wires (simulating trabeculae) with thicknesses ranging from 152 to 305 μm and spacings ranging from 700 to 1000 μm. Phase velocity varied approximately linearly with frequency over the range from 400 to 750 kHz. Dispersion was characterized by the slope of a linear least-squares regression fit to phase velocity versus frequency data. The increase in phase velocity (compared with that in water) at 500 kHz was approximately proportional to the (1) square of trabecular thickness, (2) inverse square of trabecular spacing, and (3) volume fraction occupied by nylon wires. The first derivative of phase velocity with respect to frequency was negative and exhibited nonlinear, monotonically decreasing dependencies on trabecular thickness and volume fraction. The dependencies of phase velocity and its first derivative on volume fraction in the phantoms were consistent with those reported in trabecular bone.

  6. Study of trabecular bone microstructure using spatial autocorrelation analysis

    NASA Astrophysics Data System (ADS)

    Wald, Michael J.; Vasilic, Branimir; Saha, Punam K.; Wehrli, Felix W.

    2005-04-01

    The spatial autocorrelation analysis method represents a powerful, new approach to quantitative characterization of structurally quasi-periodic anisotropic materials such as trabecular bone (TB). The method is applicable to grayscale images and thus does not require any preprocessing, such as segmentation which is difficult to achieve in the limited resolution regime of in vivo imaging. The 3D autocorrelation function (ACF) can be efficiently calculated using the Fourier transform. The resulting trabecular thickness and spacing measurements are robust to the presence of noise and produce values within the expected range as determined by other methods from μCT and μMRI datasets. TB features found from the ACF are shown to correlate well with those determined by the Fuzzy Distance transform (FDT) in the transverse plane, i.e. the plane orthogonal to bone"s major axis. The method is further shown to be applicable to in-vivo μMRI data. Using the ACF, we examine data acquired in a previous study aimed at evaluating the structural implications of male hypogonadism characterized by testosterone deficiency and reduced bone mass. Specifically, we consider the hypothesis that eugonadal and hypogonadal men differ in the anisotropy of their trabecular networks. The analysis indicates a significant difference in trabecular bone thickness and longitudinal spacing between the control group and the testosterone deficient group. We conclude that spatial autocorrelation analysis is able to characterize the 3D structure and anisotropy of trabecular bone and provides new insight into the structural changes associated with osteoporotic trabecular bone loss.

  7. Detection of trabecular bone microdamage by micro-computed tomography

    PubMed Central

    Wang, Xiang; Masse, Daniel B.; Leng, Huijie; Hess, Kevin P.; Ross, Ryan D.; Roeder, Ryan K.; Niebur, Glen L.

    2007-01-01

    Microdamage is an important component of bone quality and affects bone remodeling. Improved techniques to assess microdamage without the need for histological sectioning would provide insight into the role of microdamage in trabecular bone strength by allowing the spatial distribution of damage within the trabecular microstructure to be measured. Nineteen cylindrical trabecular bone specimens were prepared and assigned to two groups. The specimens in group I were damaged to 3% compressive strain and labeled with BaSO4. Group II was not loaded, but was labeled with BaSO4. Micro-CT images of the specimens were obtained at 10 μm resolution. The median intensity of the treated bone tissue was compared between groups. Thresholding was also used to measure the damaged area fraction in the micro-CT scans. The histologically measured damaged area fraction, the median CT intensity, and the micro-CT measured damaged area fraction were all higher in the loaded group than in the unloaded group, indicating that the micro-CT images could differentiate the damaged specimen group from the unloaded specimens. The histologically measured damaged area fraction was positively correlated with the micro-CT measured damaged area fraction and with the median CT intensity of the bone, indicating that the micro-CT images can detect microdamage in trabecular bone with sufficient accuracy to differentiate damage levels between samples. This technique provides a means to non-invasively assess the three-dimensional distribution of microdamage within trabecular bone test specimens, and could be used to gain insight into the role of trabecular architecture in microdamage formation. PMID:17588588

  8. Effects of spaceflight on trabecular bone in rats

    NASA Technical Reports Server (NTRS)

    Jee, W. S. S.; Wronski, T. J.; Morey, E. R.; Kimmel, D. B.

    1983-01-01

    Alterations in trabecular bone were observed in growing male Wistar rats after 18.5 days of orbital flight on the COSMOS 1129 biosatellite. Spaceflight induced a decreased mass of mineralized tissue and an increased fat content of the bone marrow in the proximal tibial and humeral metaphyses. The osteoblast population appeared to decline immediately adjacent to the growth cartilage-metaphyseal junction, but osteoclast numbers were unchanged. These results suggested that bone formation may have been inhibited during spaceflight, but resorption remained constant. With the exception of trabecular bone mass in the proximal tibia, the observed skeletal changes returned to normal during a 29-day postflight period.

  9. Multi-scale modelling of elastic moduli of trabecular bone

    PubMed Central

    Hamed, Elham; Jasiuk, Iwona; Yoo, Andrew; Lee, YikHan; Liszka, Tadeusz

    2012-01-01

    We model trabecular bone as a nanocomposite material with hierarchical structure and predict its elastic properties at different structural scales. The analysis involves a bottom-up multi-scale approach, starting with nanoscale (mineralized collagen fibril) and moving up the scales to sub-microscale (single lamella), microscale (single trabecula) and mesoscale (trabecular bone) levels. Continuum micromechanics methods, composite materials laminate theory and finite-element methods are used in the analysis. Good agreement is found between theoretical and experimental results. PMID:22279160

  10. The three-dimensional organisation of the post-trabecular aqueous outflow pathway and limbal vasculature in the mouse.

    PubMed

    van der Merwe, Elizabeth L; Kidson, Susan H

    2014-08-01

    The mouse eye has been used as a model for studies on the microanatomy of the outflow pathways but most of what is known comes from histological sections. These studies have focused mainly on the morphological features of the trabecular meshwork, Schlemm's canal and aqueous channels that link to the superficial episcleral vasculature. However, the anatomical architecture of the aqueous outflow vessels and their relationship to each other and to the general vascular circulation is not well understood. The aim of this study was to provide a detailed description of the microarchitecture of the aqueous outflow vessels and their relationship to the superficial limbal/episcleral vasculature throughout the entire limbus. The aqueous outflow vessels and blood and lymphatic vessels were imaged in PECAM-1 and LYVE-1 immunostained whole anterior segments of adult mice and three-dimensional (3-D) reconstructions of the optical sections were generated to reveal the aqueous, blood and lymphatic architecture. The arterial supply, venous drainage, organisation of perilimbal vasculature, collector channels/aqueous veins and the morphology of Schlemm's canal were revealed in their entirety and the relationships between these structures is described. Schlemm's canal was PECAM-1 positive but there was no affinity for the lymphatic marker LYVE-1. We show that Schlemm's canal is a continuous circular structure and more often seen as a single, broad, varicose vessel with short regions appearing as a plexus. Aqueous veins link Schlemm's canal to the superficial vasculature and there were no direct links seen between the canal and the lymphatic vessels. Copyright © 2014 Elsevier Ltd. All rights reserved.

  11. Trabecular bone structure in the humeral and femoral heads of anthropoid primates.

    PubMed

    Ryan, Timothy M; Walker, Alan

    2010-04-01

    The functional significance of three-dimensional trabecular bone architecture in the primate postcranial skeleton has received significant interest over the last decade. Some previous work has produced promising results, finding significant relationships between femoral head trabecular bone structure and hypothesized locomotor loading in leaping and nonleaping strepsirrhines. Conversely, most studies of anthropoid femoral head bone structure have found broad similarity across taxonomic and locomotor groups. The goal of this study is to expand on past analyses of anthropoid trabecular bone structure by assessing the effects of differential limb usage on the trabecular bone architecture of the forelimb and hindlimb across taxa characterized by diverse locomotor behaviors, including brachiation, quadrupedalism, and climbing. High-resolution x-ray computed tomography scans were collected from the proximal humerus and proximal femur of 55 individuals from five anthropoid primate species, including Symphalangus syndactylus, Papio sp., Presbytis rubicunda, Alouatta caraya, and Pan troglodytes. Trabecular bone structural features including bone volume fraction, anisotropy, trabecular thickness, and trabecular number were quantified in large volumes positioned in the center of the humeral or femoral head. Femoral head trabecular bone volume is consistently and significantly higher than trabecular bone volume in the humerus in all taxa independent of locomotor behavior. Humeral trabecular bone is more isotropic than femoral trabecular bone in all species sampled, possibly reflecting the emphasis on a mobile shoulder joint and manipulative forelimb. The results indicate broad similarity in trabecular bone structure in these bones across anthropoids. (c) 2010 Wiley-Liss, Inc.

  12. Modeling the Mechanical Consequences of Age-Related Trabecular Bone Loss by XFEM Simulation

    PubMed Central

    Fan, Ruoxun; Zhang, Xianbin; Liu, Jun; Jia, Zhengbin; Zhu, Dong

    2016-01-01

    The elderly are more likely to suffer from fracture because of age-related trabecular bone loss. Different bone loss locations and patterns have different effects on bone mechanical properties. Extended finite element method (XFEM) can simulate fracture process and was suited to investigate the effects of bone loss on trabecular bone. Age-related bone loss is indicated by trabecular thinning and loss and may occur at low-strain locations or other random sites. Accordingly, several ideal normal and aged trabecular bone models were created based on different bone loss locations and patterns; then, fracture processes from crack initiation to complete failure of these models were observed by XFEM; finally, the effects of different locations and patterns on trabecular bone were compared. Results indicated that bone loss occurring at low-strain locations was more detrimental to trabecular bone than that occurring at other random sites; meanwhile, the decrease in bone strength caused by trabecular loss was higher than that caused by trabecular thinning, and the effects of vertical trabecular loss on mechanical properties were more severe than horizontal trabecular loss. This study provided a numerical method to simulate trabecular bone fracture and distinguished different effects of the possible occurrence of bone loss locations and patterns on trabecular bone. PMID:27403206

  13. Modeling the Mechanical Consequences of Age-Related Trabecular Bone Loss by XFEM Simulation.

    PubMed

    Fan, Ruoxun; Gong, He; Zhang, Xianbin; Liu, Jun; Jia, Zhengbin; Zhu, Dong

    2016-01-01

    The elderly are more likely to suffer from fracture because of age-related trabecular bone loss. Different bone loss locations and patterns have different effects on bone mechanical properties. Extended finite element method (XFEM) can simulate fracture process and was suited to investigate the effects of bone loss on trabecular bone. Age-related bone loss is indicated by trabecular thinning and loss and may occur at low-strain locations or other random sites. Accordingly, several ideal normal and aged trabecular bone models were created based on different bone loss locations and patterns; then, fracture processes from crack initiation to complete failure of these models were observed by XFEM; finally, the effects of different locations and patterns on trabecular bone were compared. Results indicated that bone loss occurring at low-strain locations was more detrimental to trabecular bone than that occurring at other random sites; meanwhile, the decrease in bone strength caused by trabecular loss was higher than that caused by trabecular thinning, and the effects of vertical trabecular loss on mechanical properties were more severe than horizontal trabecular loss. This study provided a numerical method to simulate trabecular bone fracture and distinguished different effects of the possible occurrence of bone loss locations and patterns on trabecular bone.

  14. Three-dimensional arrangement of elastic fibers in the human corneal stroma.

    PubMed

    Lewis, Philip N; White, Tomas L; Young, Robert D; Bell, James S; Winlove, C Peter; Meek, Keith M

    2016-05-01

    The cornea is the main refracting lens in the eye. As part of the outer tunic it has to be resilient, a property conferred by the organisation of the constituent collagen. It also has to be sufficiently elastic to regain its exact shape when deformed, in order not to distort the retinal image. The basis of this elasticity is not fully understood. The purpose of this study was to characterise in three dimensions the arrangement and distribution of elastic fibers in the human corneal stroma, using serial block face scanning electron microscopy. We have demonstrated that there exists a complex network of elastic fibers that appear to originate in the sclera or limbus. These appear as elastic sheets in the limbus and peripheral cornea immediately above the trabecular meshwork which itself appears to extend above Descemet's membrane in the peripheral stroma. From these sheets, elastic fibers extend into the cornea; moving centrally they bifurcate and trifurcate into narrower fibers and are concentrated in the posterior stroma immediately above Descemet's membrane. We contend that elastic sheets will play an important role in the biomechanical deformation and recovery of the peripheral cornea. The network may also have practical implications for understanding the structural basis behind a number of corneal surgeries.

  15. Prediction of trabecular bone qualitative properties using scanning quantitative ultrasound

    PubMed Central

    Qin, Yi-Xian; Lin, Wei; Mittra, Erik; Xia, Yi; Cheng, Jiqi; Judex, Stefan; Rubin, Clint; Müller, Ralph

    2012-01-01

    Microgravity induced bone loss represents a critical health problem in astronauts, particularly occurred in weight-supporting skeleton, which leads to osteopenia and increase of fracture risk. Lack of suitable evaluation modality makes it difficult for monitoring skeletal status in long term space mission and increases potential risk of complication. Such disuse osteopenia and osteoporosis compromise trabecular bone density, and architectural and mechanical properties. While X-ray based imaging would not be practical in space, quantitative ultrasound may provide advantages to characterize bone density and strength through wave propagation in complex trabecular structure. This study used a scanning confocal acoustic diagnostic and navigation system (SCAN) to evaluate trabecular bone quality in 60 cubic trabecular samples harvested from adult sheep. Ultrasound image based SCAN measurements in structural and strength properties were validated by μCT and compressive mechanical testing. This result indicated a moderately strong negative correlations observed between broadband ultrasonic attenuation (BUA) and μCT-determined bone volume fraction (BV/TV, R2=0.53). Strong correlations were observed between ultrasound velocity (UV) and bone’s mechanical strength and structural parameters, i.e., bulk Young’s modulus (R2=0.67) and BV/TV (R2=0.85). The predictions for bone density and mechanical strength were significantly improved by using a linear combination of both BUA and UV, yielding R2=0.92 for BV/TV and R2=0.71 for bulk Young’s modulus. These results imply that quantitative ultrasound can characterize trabecular structural and mechanical properties through measurements of particular ultrasound parameters, and potentially provide an excellent estimation for bone’s structural integrity. PMID:23976803

  16. Trabecular bone microdamage and microstructural stresses under uniaxial compression.

    PubMed

    Nagaraja, Srinidhi; Couse, Tracey L; Guldberg, Robert E

    2005-04-01

    The balance between local remodeling and accumulation of trabecular bone microdamage is believed to play an important role in the maintenance of skeletal integrity. However, the local mechanical parameters associated with microdamage initiation are not well understood. Using histological damage labeling, micro-CT imaging, and image-based finite element analysis, regions of trabecular bone microdamage were detected and registered to estimated microstructural von Mises effective stresses and strains, maximum principal stresses and strains, and strain energy density (SED). Bovine tibial trabecular bone cores underwent a stepwise uniaxial compression routine in which specimens were micro-CT imaged following each compression step. The results indicate that the mode of trabecular failure observed by micro-CT imaging agreed well with the polarity and distribution of stresses within an individual trabecula. Analysis of on-axis subsections within specimens provided significant positive relationships between microdamage and each estimated tissue stress, strain and SED parameter. In a more localized analysis, individual microdamaged and undamaged trabeculae were extracted from specimens loaded within the elastic region and to the apparent yield point. As expected, damaged trabeculae in both groups possessed significantly higher local stresses and strains than undamaged trabeculae. The results also indicated that microdamage initiation occurred prior to apparent yield at local principal stresses in the range of 88-121 MPa for compression and 35-43 MPa for tension and local principal strains of 0.46-0.63% in compression and 0.18-0.24% in tension. These data provide an important step towards understanding factors contributing to microdamage initiation and establishing local failure criteria for normal and diseased trabecular bone.

  17. Prediction of trabecular bone qualitative properties using scanning quantitative ultrasound.

    PubMed

    Qin, Yi-Xian; Lin, Wei; Mittra, Erik; Xia, Yi; Cheng, Jiqi; Judex, Stefan; Rubin, Clint; Müller, Ralph

    2013-11-01

    Microgravity induced bone loss represents a critical health problem in astronauts, particularly occurred in weight-supporting skeleton, which leads to osteopenia and increase of fracture risk. Lack of suitable evaluation modality makes it difficult for monitoring skeletal status in long term space mission and increases potential risk of complication. Such disuse osteopenia and osteoporosis compromise trabecular bone density, and architectural and mechanical properties. While X-ray based imaging would not be practical in space, quantitative ultrasound may provide advantages to characterize bone density and strength through wave propagation in complex trabecular structure. This study used a scanning confocal acoustic diagnostic and navigation system (SCAN) to evaluate trabecular bone quality in 60 cubic trabecular samples harvested from adult sheep. Ultrasound image based SCAN measurements in structural and strength properties were validated by μCT and compressive mechanical testing. This result indicated a moderately strong negative correlations observed between broadband ultrasonic attenuation (BUA) and μCT-determined bone volume fraction (BV/TV, R(2)=0.53). Strong correlations were observed between ultrasound velocity (UV) and bone's mechanical strength and structural parameters, i.e., bulk Young's modulus (R(2)=0.67) and BV/TV (R(2)=0.85). The predictions for bone density and mechanical strength were significantly improved by using a linear combination of both BUA and UV, yielding R(2)=0.92 for BV/TV and R(2)=0.71 for bulk Young's modulus. These results imply that quantitative ultrasound can characterize trabecular structural and mechanical properties through measurements of particular ultrasound parameters, and potentially provide an excellent estimation for bone's structural integrity.

  18. Prediction of trabecular bone qualitative properties using scanning quantitative ultrasound

    NASA Astrophysics Data System (ADS)

    Qin, Yi-Xian; Lin, Wei; Mittra, Erik; Xia, Yi; Cheng, Jiqi; Judex, Stefan; Rubin, Clint; Müller, Ralph

    2013-11-01

    Microgravity induced bone loss represents a critical health problem in astronauts, particularly occurred in weight-supporting skeleton, which leads to osteopenia and increase of fracture risk. Lack of suitable evaluation modality makes it difficult for monitoring skeletal status in long term space mission and increases potential risk of complication. Such disuse osteopenia and osteoporosis compromise trabecular bone density, and architectural and mechanical properties. While X-ray based imaging would not be practical in space, quantitative ultrasound may provide advantages to characterize bone density and strength through wave propagation in complex trabecular structure. This study used a scanning confocal acoustic diagnostic and navigation system (SCAN) to evaluate trabecular bone quality in 60 cubic trabecular samples harvested from adult sheep. Ultrasound image based SCAN measurements in structural and strength properties were validated by μCT and compressive mechanical testing. This result indicated a moderately strong negative correlations observed between broadband ultrasonic attenuation (BUA) and μCT-determined bone volume fraction (BV/TV, R2=0.53). Strong correlations were observed between ultrasound velocity (UV) and bone's mechanical strength and structural parameters, i.e., bulk Young's modulus (R2=0.67) and BV/TV (R2=0.85). The predictions for bone density and mechanical strength were significantly improved by using a linear combination of both BUA and UV, yielding R2=0.92 for BV/TV and R2=0.71 for bulk Young's modulus. These results imply that quantitative ultrasound can characterize trabecular structural and mechanical properties through measurements of particular ultrasound parameters, and potentially provide an excellent estimation for bone's structural integrity.

  19. Response of trabecular bone, thyroid C and follicular cells to synthetic salmon calcitonin in middle-aged orchidectomized male rats.

    PubMed

    Filipović, Branko; Šošić-Jurjević, Branka; Ajdžanović, Vladimir; Živanović, Jasmina; Ristić, Nataša; Trifunović, Svetlana; Milošević, Verica

    2017-06-01

    In contrast to studies in women, male osteoporosis is poorly understood and strictly related to advancing age. Among the first antiresorptive substances used in the prevention and treatment of osteoporosis is calcitonin (CT), a hypocalcemic hormone that potently inhibits osteoclastic bone resorption. Natural CT is produced and secreted by thyroid C-cells. The other endocrine population of thyroid cells produces thyroid hormones (TH), which also affect bone turnover. The aim of this study was to evaluate the influence of salmon CT on trabecular bone microarchitecture with special reference to effects on the structure and function of both CT- and TH-producing thyroid cells in orchidectomized (Orx) middle-aged rats. Twenty-four male Wistar rats aged 15 months were randomly divided into Orx and sham-operated (SO) groups. One group of Orx animals received (s.c.) synthetic salmon CT (Orx + CT; 100 IU kg(-1) b.w.) subcutaneously every second day for 6 weeks. The second Orx group and SO rats were given the same volume of vehicle alone by the same schedule. Trabecular bone histomorphometrical parameters were: cancellous bone area (B.Ar), trabecular thickness (Tb.Th), trabecular number (Tb.N) and trabecular separation (Tb.Sp) were obtained with an ImageJ public-domain image-processing program. The peroxidase-antiperoxidase method was applied for localization of CT in C-cells. Anti-human CT antisera served as the primary antibodies. For immunohistochemical characterization of vascular endothelial growth factor (VEGF) in thyroid tissue, rabbit antisera against human VEGF, served as primary antibodies. CT-immunopositive thyroid C-cells, thyroid follicular epithelium, interstitium and colloid were evaluated morphometrically. Blood serum samples were analyzed for CT, osteocalcin (OC), and thyroxine (T4 ), and calcium (Ca(2+) ) concentration was determined in urine samples. Salmon CT application significantly increased B.Ar, TbTh and TbN, but markedly decreased Tb

  20. Effect of swimming exercise on three-dimensional trabecular bone microarchitecture in ovariectomized rats.

    PubMed

    Ju, Yong-In; Sone, Teruki; Ohnaru, Kazuhiro; Tanaka, Kensuke; Fukunaga, Masao

    2015-11-01

    Swimming is generally considered ineffective for increasing bone mass in humans, at least compared with weight-bearing sports. However, swimming exercise has sometimes been shown to have a strong positive effect on bone mass in small animals. This study investigated the effects of swimming on bone mass, strength, and microarchitecture in ovariectomized (OVX) rats. OVX or sham operations were performed on 18-wk-old female Fisher 344 rats. Rats were randomly divided into four groups: sham sedentary (Sham-CON), sham swimming exercised (Sham-SWI), OVX sedentary (OVX-CON), and OVX swimming exercised (OVX-SWI). Rats in exercise groups performed swimming in a water bath for 60 min/day, 5 days/wk, for 12 wk. Bone mineral density (BMD) in right femurs was analyzed using dual-energy X-ray absorptiometry. Three-dimensional trabecular architecture at the distal femoral metaphysis was analyzed using microcomputed tomography (μCT). Geometrical properties of diaphyseal cortical bone were evaluated in the midfemoral region using μCT. The biomechanical properties of femurs were analyzed using three-point bending. Femoral BMD was significantly decreased following ovariectomy. This change was suppressed by swimming. Trabecular bone thickness, number, and connectivity were decreased by ovariectomy, whereas structure model index (i.e., ratio of rod-like to plate-like trabeculae) increased. These changes were also suppressed by swimming exercise. Femurs displayed greater cortical width and maximum load in SWI groups than in CON groups. Together, these results demonstrate that swimming exercise drastically alleviated both OVX-induced decreases in bone mass and mechanical strength and the deterioration of trabecular microarchitecture in rat models of osteoporosis. Copyright © 2015 the American Physiological Society.

  1. Aquaporins 6-12 in the human eye.

    PubMed

    Tran, Thuy Linh; Bek, Toke; Holm, Lars; la Cour, Morten; Nielsen, Søren; Prause, Jan Ulrik; Rojek, Aleksandra; Hamann, Steffen; Heegaard, Steffen

    2013-09-01

    Aquaporins (AQPs) are widely expressed and have diverse distribution patterns in the eye. AQPs 0-5 have been localized at the cellular level in human eyes. We investigated the presence of the more recently discovered AQPs 6-12 in the human eye. RT-PCR was performed on fresh tissue from two human eyes divided into the cornea, corneal limbus, ciliary body and iris, lens, choroid, optic nerve, retina and sclera. Each structure was examined to detect the mRNA of AQPs 6-12. Twenty-one human eyes were examined using immunohistochemical and immunofluorescence techniques to determine the topographical localization of AQPs 6-12. mRNA transcripts of AQP7, AQP9 and AQP11 were found in the ciliary body, corneo-limbal tissue, optic nerve, retina and sclera. AQP9 and AQP11 mRNA was also detected in the choroid. No mRNA of AQP6, AQP8, AQP10 or AQP12 was detected. Anti-AQP7 immunolabelling was detected in the corneal epithelium, corneal endothelium, trabecular meshwork endothelium, ciliary epithelia, lens epithelium, the inner and outer limiting membrane of the retina, the retinal pigment epithelium and the capillary endothelium of all parts of the eye. AQP9 immunolabelling was detected in the nonpigmented ciliary epithelium and retinal ganglion cells. AQP11 immunolabelling was detected in the corneo-limbal epithelium, nonpigmented ciliary epithelium and inner limiting membrane of the retina. Selective expression of AQP7, AQP9 and AQP11 was found within various structures of the human eye. The detection of these aquaporins in the eye implies a role that may be related not only to water transport but also to the transport of glycerol, lactate and ammonia, with importance for metabolism, especially in the retina. © 2012 The Authors. Acta Ophthalmologica © 2012 Acta Ophthalmologica Scandinavica Foundation.

  2. Automated selection of trabecular bone regions in knee radiographs

    SciTech Connect

    Podsiadlo, P.; Wolski, M.; Stachowiak, G. W.

    2008-05-15

    Osteoarthritic (OA) changes in knee joints can be assessed by analyzing the structure of trabecular bone (TB) in the tibia. This analysis is performed on TB regions selected manually by a human operator on x-ray images. Manual selection is time-consuming, tedious, and expensive. Even if a radiologist expert or highly trained person is available to select regions, high inter- and intraobserver variabilities are still possible. A fully automated image segmentation method was, therefore, developed to select the bone regions for numerical analyses of changes in bone structures. The newly developed method consists of image preprocessing, delineation of cortical bone plates (active shape model), and location of regions of interest (ROI). The method was trained on an independent set of 40 x-ray images. Automatically selected regions were compared to the ''gold standard'' that contains ROIs selected manually by a radiologist expert on 132 x-ray images. All images were acquired from subjects locked in a standardized standing position using a radiography rig. The size of each ROI is 12.8x12.8 mm. The automated method results showed a good agreement with the gold standard [similarity index (SI)=0.83 (medial) and 0.81 (lateral) and the offset=[-1.78, 1.27]x[-0.65,0.26] mm (medial) and [-2.15, 1.59]x[-0.58, 0.52] mm (lateral)]. Bland and Altman plots were constructed for fractal signatures, and changes of fractal dimensions (FD) to region offsets calculated between the gold standard and automatically selected regions were calculated. The plots showed a random scatter and the 95% confidence intervals were (-0.006, 0.008) and (-0.001, 0.011). The changes of FDs to region offsets were less than 0.035. Previous studies showed that differences in FDs between non-OA and OA bone regions were greater than 0.05. ROIs were also selected by a second radiologist and then evaluated. Results indicated that the newly developed method could replace a human operator and produces bone regions

  3. Automated selection of trabecular bone regions in knee radiographs.

    PubMed

    Podsiadlo, P; Wolski, M; Stachowiak, G W

    2008-05-01

    Osteoarthritic (OA) changes in knee joints can be assessed by analyzing the structure of trabecular bone (TB) in the tibia. This analysis is performed on TB regions selected manually by a human operator on x-ray images. Manual selection is time-consuming, tedious, and expensive. Even if a radiologist expert or highly trained person is available to select regions, high inter- and intraobserver variabilities are still possible. A fully automated image segmentation method was, therefore, developed to select the bone regions for numerical analyses of changes in bone structures. The newly developed method consists of image preprocessing, delineation of cortical bone plates (active shape model), and location of regions of interest (ROI). The method was trained on an independent set of 40 x-ray images. Automatically selected regions were compared to the "gold standard" that contains ROIs selected manually by a radiologist expert on 132 x-ray images. All images were acquired from subjects locked in a standardized standing position using a radiography rig. The size of each ROI is 12.8 x 12.8 mm. The automated method results showed a good agreement with the gold standard [similarity index (SI) = 0.83 (medial) and 0.81 (lateral) and the offset =[-1.78, 1.27]x[-0.65,0.26] mm (medial) and [-2.15, 1.59]x[-0.58, 0.52] mm (lateral)]. Bland and Altman plots were constructed for fractal signatures, and changes of fractal dimensions (FD) to region offsets calculated between the gold standard and automatically selected regions were calculated. The plots showed a random scatter and the 95% confidence intervals were (-0.006, 0.008) and (-0.001, 0.011). The changes of FDs to region offsets were less than 0.035. Previous studies showed that differences in FDs between non-OA and OA bone regions were greater than 0.05. ROIs were also selected by a second radiologist and then evaluated. Results indicated that the newly developed method could replace a human operator and produces bone regions

  4. Comparison of optical coherence tomography, microcomputed tomography, and histology at a three-dimensionally imaged trabecular bone sample

    NASA Astrophysics Data System (ADS)

    Kasseck, Christoph; Kratz, Marita; Torcasio, Antonia; Gerhardt, Nils C.; van Lenthe, G. Harry; Gambichler, Thilo; Hoffmann, Klaus; Jones, David B.; Hofmann, Martin R.

    2010-07-01

    We investigate optical coherence tomography (OCT) as a method for imaging bone. The OCT images are compared directly to those of the standard methods of bone histology and microcomputed tomography (μCT) on a single, fixed human femoral trabecular bone sample. An advantage of OCT over bone histology is its noninvasive nature. OCT also images the lamellar structure of trabeculae at slightly higher contrast than normal bone histology. While μCT visualizes the trabecular framework of the whole sample, OCT can image additionally cells with a penetration depth limited approximately to 1 mm. The most significant advantage of OCT, however, is the absence of toxic effects (no ionizing radiation), i.e., continuous images may be made and individual cell tracking may be performed. The penetration depth of OCT, however, limits its use to small animal models and small bone organ cultures.

  5. Fundamental precision limitations for measurements of frequency dependence of backscatter: Applications in tissue-mimicking phantoms and trabecular bone

    NASA Astrophysics Data System (ADS)

    Wear, Keith A.

    2001-12-01

    Various models for ultrasonic scattering from trabecular bone have been proposed. They may be evaluated to a certain extent by comparison with experimental measurements. In order to appreciate limitations of these comparisons, it is important to understand measurement precision. In this article, an approach proposed by Lizzi and co-workers is adapted to model precision of estimates of frequency-dependent backscatter for scattering targets (such as trabecular bone) that contain many scatterers per resolution cell. This approach predicts uncertainties in backscatter due to the random nature of the interference of echoes from individual scatterers as they are summed at the receiver. The model is validated in experiments on a soft-tissue-mimicking phantom and on 24 human calcaneus samples interrogated in vitro. It is found that while random interference effects only partially explain measured variations in the magnitude of backscatter, they are virtually entirely responsible for observed variations in the frequency dependence (exponent of a power law fit) of backscatter.

  6. A Novel 3D Microstructural Model for Trabecular Bone: II. The Relationship Between Fabric and the Yield Surface.

    PubMed

    Zysset, P. K.; Ominsky, M. S.; Goldstein, S. A.

    1999-01-01

    A novel 3D microstructural model was proposed and validated in part I of this publication. In part II, the model was used to identify the yield surface of a representative volume element of human trabecular bone as a function of volume fraction and degree of anisotropy. Finite element models of open and closed cells geometries were used to calculate effective yield stresses for a variety of loading cases with periodic boundary conditions. The postyield behaviour of the trabecular tissue was assumed from data available for cortical tissue. The yield stresses defined by a 0.2% offset in the global stress-strain curve were fit to an orthotropic Hill criterion and the parameters of the surface calculated. Similarly to the previous elastic analysis, distinct but strong relationships were obtained between volume fraction, fabric and the yield surface parameters for both the open and closed cell geometries. This finding suggests that volume fraction and fabric may be used to predict the initiation of mechanical damage in human trabecular bone at the continuum level.

  7. A three-dimensional ParF meshwork assembles through the nucleoid to mediate plasmid segregation

    PubMed Central

    McLeod, Brett N.; Allison-Gamble, Gina E.; Barge, Madhuri T.; Tonthat, Nam K.; Schumacher, Maria A.; Hayes, Finbarr

    2017-01-01

    Abstract Genome segregation is a fundamental step in the life cycle of every cell. Most bacteria rely on dedicated DNA partition proteins to actively segregate chromosomes and low copy-number plasmids. Here, by employing super resolution microscopy, we establish that the ParF DNA partition protein of the ParA family assembles into a three-dimensional meshwork that uses the nucleoid as a scaffold and periodically shuttles between its poles. Whereas ParF specifies the territory for plasmid trafficking, the ParG partner protein dictates the tempo of ParF assembly cycles and plasmid segregation events by stimulating ParF adenosine triphosphate hydrolysis. Mutants in which this ParG temporal regulation is ablated show partition deficient phenotypes as a result of either altered ParF structure or dynamics and indicate that ParF nucleoid localization and dynamic relocation, although necessary, are not sufficient per se to ensure plasmid segregation. We propose a Venus flytrap model that merges the concepts of ParA polymerization and gradient formation and speculate that a transient, dynamic network of intersecting polymers that branches into the nucleoid interior is a widespread mechanism to distribute sizeable cargos within prokaryotic cells. PMID:28034957

  8. Cohesiveness tunes assembly and morphology of FG nucleoporin domain meshworks - Implications for nuclear pore permeability.

    PubMed

    Eisele, Nico B; Labokha, Aksana A; Frey, Steffen; Görlich, Dirk; Richter, Ralf P

    2013-10-15

    Nuclear pore complexes control the exchange of macromolecules between the cytoplasm and the nucleus. A selective permeability barrier that arises from a supramolecular assembly of intrinsically unfolded nucleoporin domains rich in phenylalanine-glycine dipeptides (FG domains) fills the nuclear pore. There is increasing evidence that selective transport requires cohesive FG domain interactions. To understand the functional roles of cohesive interactions, we studied monolayers of end-grafted FG domains as a bottom-up nanoscale model system of the permeability barrier. Based on detailed physicochemical analysis of the model films and comparison of the data with polymer theory, we propose that cohesiveness is tuned to promote rapid assembly of the permeability barrier and to generate a stable and compact pore-filling meshwork with a small mesh size. Our results highlight the functional importance of weak interactions, typically a few kBT per chain, and contribute important information to understand the mechanism of size-selective transport. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  9. Estimation of anisotropic permeability in trabecular bone based on microCT imaging and pore-scale fluid dynamics simulations.

    PubMed

    Daish, C; Blanchard, R; Gulati, K; Losic, D; Findlay, D; Harvie, D J E; Pivonka, P

    2017-06-01

    In this paper, a comprehensive framework is proposed to estimate the anisotropic permeability matrix in trabecular bone specimens based on micro-computed tomography (microCT) imaging combined with pore-scale fluid dynamics simulations. Two essential steps in the proposed methodology are the selection of (i) a representative volume element (RVE) for calculation of trabecular bone permeability and (ii) a converged mesh for accurate calculation of pore fluid flow properties. Accurate estimates of trabecular bone porosities are obtained using a microCT image resolution of approximately 10 μm. We show that a trabecular bone RVE in the order of 2 × 2 × 2 mm(3) is most suitable. Mesh convergence studies show that accurate fluid flow properties are obtained for a mesh size above 125,000 elements. Volume averaging of the pore-scale fluid flow properties allows calculation of the apparent permeability matrix of trabecular bone specimens. For the four specimens chosen, our numerical results show that the so obtained permeability coefficients are in excellent agreement with previously reported experimental data for both human and bovine trabecular bone samples. We also identified that bone samples taken from long bones generally exhibit a larger permeability in the longitudinal direction. The fact that all coefficients of the permeability matrix were different from zero indicates that bone samples are generally not harvested in the principal flow directions. The full permeability matrix was diagonalized by calculating the eigenvalues, while the eigenvectors showed how strongly the bone sample's orientations deviated from the principal flow directions. Porosity values of the four bone specimens range from 0.83 to 0.86, with a low standard deviation of ± 0.016, principal permeability values range from 0.22 to 1.45 ⋅ 10( -8) m(2), with a high standard deviation of ± 0.33. Also, the anisotropic ratio ranged from 0.27 to 0.83, with high standard deviation. These

  10. Local plate/rod descriptors of 3D trabecular bone micro-CT images from medial axis topologic analysis

    SciTech Connect

    Peyrin, Francoise; Attali, Dominique; Chappard, Christine; Benhamou, Claude Laurent

    2010-08-15

    Purpose: Trabecular bone microarchitecture is made of a complex network of plate and rod structures evolving with age and disease. The purpose of this article is to propose a new 3D local analysis method for the quantitative assessment of parameters related to the geometry of trabecular bone microarchitecture. Methods: The method is based on the topologic classification of the medial axis of the 3D image into branches, rods, and plates. Thanks to the reversibility of the medial axis, the classification is next extended to the whole 3D image. Finally, the percentages of rods and plates as well as their mean thicknesses are calculated. The method was applied both to simulated test images and 3D micro-CT images of human trabecular bone. Results: The classification of simulated phantoms made of plates and rods shows that the maximum error in the quantitative percentages of plate and rods is less than 6% and smaller than with the structure model index (SMI). Micro-CT images of human femoral bone taken in osteoporosis and early or advanced osteoarthritis were analyzed. Despite the large physiological variability, the present method avoids the underestimation of rods observed with other local methods. The relative percentages of rods and plates were not significantly different between osteoarthritis and osteoporotic groups, whereas their absolute percentages were in relation to an increase of rod and plate thicknesses in advanced osteoarthritis with also higher relative and absolute number of nodes. Conclusions: The proposed method is model-independent, robust to surface irregularities, and enables geometrical characterization of not only skeletal structures but entire 3D images. Its application provided more accurate results than the standard SMI on simple simulated phantoms, but the discrepancy observed on the advanced osteoarthritis group raises questions that will require further investigations. The systematic use of such a local method in the characterization of

  11. Intraocular caspofungin: in vitro safety profile for human ocular cells.

    PubMed

    Kernt, M; Kampik, A

    2011-07-01

    Endogenous Candida endophthalmitis is sight-threatening, difficult to treat and sometimes leads to loss of the eye. Only a few therapeutic agents are available for its treatment. Caspofungin is the first of a new class of antifungal drugs (echinocandins) with a high activity against Candida species, the most common pathogens found in endogenous endophthalmitis. This study investigates the safety profile of caspofungin for intraocular application in a cell-culture model. Endothelial toxicity of caspofungin was evaluated in cultured human corneas. Possible toxic effects of caspofungin (5-300 μg ml(-1)) in corneal endothelial cells (CEC), primary human trabecular meshwork cells (TMC) and primary human retinal pigment epithelium (RPE) cells were evaluated after 24 h and under conditions of inflammatory stress by treatment with tumour necrosis factor-alpha (TNF-α), lipopolysaccharides (LPS) or interleukin-6 (IL-6) and hydrogen peroxide (H(2)O(2)). Toxicity was evaluated by tetrazolium dye-reduction assay; cell viability was quantified by a microscopic live-dead assay. No corneal endothelial toxicity could be detected after 30 days of treatment with 75 μg ml(-1) of caspofungin. Concentrations up to 75 μg ml(-1) had no influence on CEC, TMC or RPE cell proliferation, or on cell viability when administered for 24 h. Exposure to H(2)O(2) did not increase cellular toxicity of caspofungin at concentrations of 5-50 μg ml(-1). After preincubation with TNF-α, LPS or IL-6 for 24 h followed by treatment with caspofungin for 24 h, no significant decrease in cell proliferation or viability was observed. This study showed no significant toxicity for caspofungin on CEC, TMC or RPE cells, or human corneal endothelium when administered in therapeutic concentrations up to 50 μg ml(-1).

  12. Intracameral voriconazole: in vitro safety for human ocular cells.

    PubMed

    Kernt, M; Kampik, A

    2009-04-28

    Fungal keratitis is a sight-threatening infection of the cornea. It sometimes leads to loss of the eye. Despite an expanding range of fungal pathogens, there are only few therapeutic agents for its treatment available. Voriconazole is a second-generation synthetic triazole with a broad action against yeasts and molds. The current study investigates the safety of voriconazole for intracameral application in a cell culture model. Endothelial toxicity of voriconazole was evaluated in cultured human corneas. Possible toxic effects of voriconazole (10 microg /mL-10mg/mL) in corneal endothelial cells (CEC), primary human trabecular meshwork cells (TMC), and primary human retinal pigment epithelium (RPE) cells were evaluated after 24h and under conditions of inflammatory stress by treatment with tumor-necrosis-factor alpha (TNF-alpha), lipopolysaccharides (LPS), or interleukin-6 (IL-6) and hydrogen peroxide. Toxicity was evaluated by tetrazolium dye-reduction assay, and cell viability was quantified by a microscopic live-dead assay. No corneal endothelial toxicity could be detected after 30 days of treatment with 250 microg /mL of voriconazole. Concentrations up to 1mg/mL had no influence on CEC, TMC, or RPE cell proliferation, or on cell viability when administered for 24h. Hydrogen peroxide exposure did not increase cellular toxicity of voriconazole at concentrations from 10 to 250 microg /mL. After preincubation with TNF-alpha, LPS, or IL-6 for 24h and subsequent voriconazole treatment for 24h, no significant decrease in proliferation or viability was observed. This study showed no significant toxicity for voriconazole on CEC, TMC, RPE cells, or human corneal endothelium when administered in therapeutic concentrations up to 250 microg /mL.

  13. Cellular basis for bimatoprost effects on human conventional outflow.

    PubMed

    Stamer, W Daniel; Piwnica, David; Jolas, Thierry; Carling, Robert W; Cornell, Clive L; Fliri, Hans; Martos, Jose; Pettit, Simon N; Wang, Jenny W; Woodward, David F

    2010-10-01

    Bimatoprost is a widely used ocular hypotensive agent to treat glaucoma. It lowers intraocular pressure in humans by increasing both pressure-independent (uveoscleral) and pressure-dependent (conventional) aqueous humor outflow. The present study specifically examines bimatoprost effects on the cells that populate human outflow tissues. The authors tested for prostamide receptor activation in primary cultures of human trabecular meshwork (TM), Schlemm's canal (SC), and ciliary smooth muscle (CSM) cells using cellular dielectric spectroscopy (CDS). The authors observed that bimatoprost produced an immediate and concentration-dependent increase in cell monolayer impedance for TM, SC, and CSM cells with EC(50) values of 4.3, 1.2, and 1.7 nM, respectively; corresponding to decreased cell contractility. Notably, in TM, SC, and CSM cells, bimatoprost was approximately equipotent to the selective FP receptor agonists fluprostenol and 17-phenyl PGF(2α). Bimatoprost effects were insensitive to cholera toxin and pertussis toxin but were abolished by phorbol 12-myristate 13-acetate pretreatment, suggesting Gq-involvement in cell signaling. The effects of bimatoprost on TM and SC cells were inhibited by the prostamide receptor antagonist AGN211334, with IC(50) values of 1.2 and 3.3 μM, respectively. Interestingly, AGN211334 behaved as an apparent inverse agonist in CDS assays involving TM cells but as a neutral prostamide antagonist with SC cells. Taken together, results suggest that bimatoprost specifically activates receptors in both cell types of the human conventional outflow pathway to modify intraocular pressure. However, only TM cell monolayers appear to have autocrine, or agonist-independent, receptor signaling that is sensitive to a prostamide receptor antagonist.

  14. Induced Pluripotent Stem Cells Restore Function in a Human Cell Loss Model of Open-Angle Glaucoma

    PubMed Central

    Abu-Hassan, Diala W; Li, Xinbo; Ryan, Eileen I; Acott, Ted S; Kelley, Mary J

    2015-01-01

    Normally, trabecular meshwork (TM) and Schlemm's canal inner wall endothelial cells within the aqueous humor outflow pathway maintain intraocular pressure within a narrow safe range. Elevation in intraocular pressure, because of the loss of homeostatic regulation by these outflow pathway cells, is the primary risk factor for vision loss due to glaucomatous optic neuropathy. A notable feature associated with glaucoma is outflow pathway cell loss. Using controlled cell loss in ex vivo perfused human outflow pathway organ culture, we developed compelling experimental evidence that this level of cell loss compromises intraocular pressure homeostatic function. This function was restored by repopulation of the model with fresh TM cells. We then differentiated induced pluripotent stem cells (iPSCs) and used them to repopulate this cell depletion model. These differentiated cells (TM-like iPSCs) became similar to TM cells in both morphology and expression patterns. When transplanted, they were able to fully restore intraocular pressure homeostatic function. This successful transplantation of TM-like iPSCs establishes the conceptual feasibility of using autologous stem cells to restore intraocular pressure regulatory function in open-angle glaucoma patients, providing a novel alternative treatment option. Stem Cells 2015;33:751–761 PMID:25377070

  15. Induced pluripotent stem cells restore function in a human cell loss model of open-angle glaucoma.

    PubMed

    Abu-Hassan, Diala W; Li, Xinbo; Ryan, Eileen I; Acott, Ted S; Kelley, Mary J

    2015-03-01

    Normally, trabecular meshwork (TM) and Schlemm's canal inner wall endothelial cells within the aqueous humor outflow pathway maintain intraocular pressure within a narrow safe range. Elevation in intraocular pressure, because of the loss of homeostatic regulation by these outflow pathway cells, is the primary risk factor for vision loss due to glaucomatous optic neuropathy. A notable feature associated with glaucoma is outflow pathway cell loss. Using controlled cell loss in ex vivo perfused human outflow pathway organ culture, we developed compelling experimental evidence that this level of cell loss compromises intraocular pressure homeostatic function. This function was restored by repopulation of the model with fresh TM cells. We then differentiated induced pluripotent stem cells (iPSCs) and used them to repopulate this cell depletion model. These differentiated cells (TM-like iPSCs) became similar to TM cells in both morphology and expression patterns. When transplanted, they were able to fully restore intraocular pressure homeostatic function. This successful transplantation of TM-like iPSCs establishes the conceptual feasibility of using autologous stem cells to restore intraocular pressure regulatory function in open-angle glaucoma patients, providing a novel alternative treatment option. © 2014 The Authors. STEM CELLS Published by Wiley Periodicals, Inc. on behalf of AlphaMed Press.

  16. Lattice strains and load partitioning in bovine trabecular bone.

    SciTech Connect

    Akhtar, R.; Daymond, M. R.; Almer, J. D.; Mummery, P. M.

    2012-02-01

    Microdamage and failure mechanisms have been well characterized in bovine trabecular bone. However, little is known about how elastic strains develop in the apatite crystals of the trabecular struts and their relationship with different deformation mechanisms. In this study, wide-angle high-energy synchrotron X-ray diffraction has been used to determine bulk elastic strains under in situ compression. Dehydrated bone is compared to hydrated bone in terms of their response to load. During compression, load is initially borne by trabeculae aligned parallel to loading direction with non-parallel trabeculae deforming by bending. Ineffective load partitioning is noted in dehydrated bone whereas hydrated bone behaves like a plastically yielding foam

  17. Lattice strains and load partitioning in bovine trabecular bone.

    PubMed

    Akhtar, R; Daymond, M R; Almer, J D; Mummery, P M

    2011-02-01

    Microdamage and failure mechanisms have been well characterized in bovine trabecular bone. However, little is known about how elastic strains develop in the apatite crystals of the trabecular struts and their relationship with different deformation mechanisms. In this study, wide-angle high-energy synchrotron X-ray diffraction has been used to determine bulk elastic strains under in situ compression. Dehydrated bone is compared to hydrated bone in terms of their response to load. During compression, load is initially borne by trabeculae aligned parallel to loading direction with non-parallel trabeculae deforming by bending. Ineffective load partitioning is noted in dehydrated bone whereas hydrated bone behaves like a plastically yielding foam.

  18. Trabecular mineral contents of lumbar vertebra in patients with osteoporosis.

    PubMed

    Suzuki, S; Okumura, H; Yamamuro, T

    1990-01-01

    The trabecular mineral contents (TMCs) of the third lumbar vertebra in normal subjects and patients with spinal osteoporosis and with femoral neck fracture were measured by quantitative computed tomography (QCT) using a reference phantom. The present paper describes these results. The TMCs in patients with spinal osteoporosis and with femoral neck fracture were significantly lower than those in normal subjects. When evaluated in terms of the ratio to the mean trabecular mineral content (mTMC) in normal subjects of the same decade groups, it was assumed that there should be a threshold value of vertebral compression fracture, and that value was approximately 50% of the mTMC in normal subjects. A correlation was noted between the data of the QCT method and those of the microdensitometric method in the groups with vertebral compression fracture and with femoral neck fracture, but not in the group without vertebral fracture.

  19. Some effects of basic multicellular unit-based remodelling on photon absorptiometry of trabecular bone.

    PubMed

    Frost, H M

    1989-08-01

    This article offers algorithms and an algebra for estimating effects of bone turnover, remodelling space, undermineralized bone and trabecular surface-to-volume ratio effects on trabecular bone mass estimation by photon absorptiometry. From published histomorphometric data and other evidence the algorithms suggest the amount of mineral in a given bone sample can suggest to absorptiometry an amount of bone that differs from the truth by over 40% in the extreme, and more commonly by 5-15%. They suggest that by reducing a bone's global mineral content high bone turnover causes underestimation of true bone mass. They suggest that by letting mineral return to the remodelling space and undermineralized bone, reduced bone turnover causes apparent gains in bone mass. The commonly suggested 5-15% magnitude of such errors exceeds those assumed in the past. The algorithms suggest that after a challenge to remodelling those bone mineral changes can take from 6 months to over 3 years to reach steady states. Those features could explain why many osteoporosis treatments judged effective from initial absorptiometric evidence failed when used for long periods in patients. Finally the algorithms suggest that a real increase in ideal bone volume can even appear to absorptiometry as no gain or an initial loss, which has already happened in two human experiments.

  20. The sensitivity of nonlinear computational models of trabecular bone to tissue level constitutive model

    PubMed Central

    Baumann, Andrew P.; Shi, Xiutao; Roeder, Ryan K.; Niebur, Glen L.

    2015-01-01

    Microarchitectural finite element models have become a key tool in analyses of trabecular bone. Robust, accurate, and validated constitutive models would enhance confidence in predictive applications of these models, and in their usefulness as accurate assays of tissue properties. Human trabecular bone specimens from the femoral neck (n = 3), greater trochanter (n = 6), and lumbar vertebra (n = 1) of eight different donors were scanned by μ-CT and converted to voxel-based finite element models. Unconfined uniaxial compression and shear loading were simulated for each of three different constitutive models: a principal strain based model, Drucker-Lode, and Drucker-Prager. The latter was applied with both infinitesimal and finite kinematics. Apparent yield strains exhibited minimal dependence on the constitutive model, differing by at most 16.1%, with the kinematic formulation being influential in compression loading. At the tissue level, the quantities and locations of yielded tissue were insensitive to the constitutive model, with the exception of the Drucker-Lode model, suggesting that correlation of microdamage with computational models does not improve the ability to discriminate between constitutive laws. Taken together, it is unlikely that a tissue constitutive model can be fully validated from apparent level experiments alone, as the calculations are too insensitive to identify differences in the outcomes. Rather, any asymmetric criterion with a valid yield surface will likely be suitable for most bone models. PMID:25959510

  1. Cortical and trabecular deterioration in mouse models of Roux-en-Y gastric bypass

    PubMed Central

    Yu, Elaine W.; Carmody, Jill S.; Brooks, Daniel J.; LaJoie, Scott; Kaplan, Lee M.; Bouxsein, Mary L

    2016-01-01

    Roux-en-Y gastric bypass (RYGB) is a profoundly effective treatment for severe obesity, but results in significant bone loss in patients. Developing a murine model that recapitulates this skeletal phenotype will provide a robust tool with which to study the physiologic mechanisms of this bone loss. We studied adult male C57BL/6J mice who underwent either RYGB or sham operation. Twelve weeks after surgery, we characterized biochemical bone markers (parathyroid hormone, PTH; C-telopeptide, CTX; and type 1 procollagen, P1NP) and bone microarchitectural parameters as measured by microcomputed tomography. RYGB-treated mice had significant trabecular and cortical bone deficits compared with sham-operated controls. Although adjustment for final body weight eliminated observed cortical differences, the trabecular bone volume fraction remained significantly lower in RYGB mice even after weight adjustment. PTH levels were similar between groups, but RYGB mice had significantly higher indices of bone turnover than sham controls. These data demonstrate that murine models of RYGB recapitulate patterns of bone loss and turnover that have been observed in human clinical studies. Future studies that exploit this murine model will help delineate the alterations in bone metabolism and mechanisms of bone loss after RYGB. PMID:26806052

  2. Three-dimensional quantification of structures in trabecular bone using measures of complexity

    NASA Astrophysics Data System (ADS)

    Marwan, Norbert; Kurths, Jürgen; Thomsen, Jesper Skovhus; Felsenberg, Dieter; Saparin, Peter

    2009-02-01

    The study of pathological changes of bone is an important task in diagnostic procedures of patients with metabolic bone diseases such as osteoporosis as well as in monitoring the health state of astronauts during long-term space flights. The recent availability of high-resolution three-dimensional (3D) imaging of bone challenges the development of data analysis techniques able to assess changes of the 3D microarchitecture of trabecular bone. We introduce an approach based on spatial geometrical properties and define structural measures of complexity for 3D image analysis. These measures evaluate different aspects of organization and complexity of 3D structures, such as complexity of its surface or shape variability. We apply these measures to 3D data acquired by high-resolution microcomputed tomography (μCT) from human proximal tibiae and lumbar vertebrae at different stages of osteoporotic bone loss. The outcome is compared to the results of conventional static histomorphometry and exhibits clear relationships between the analyzed geometrical features of trabecular bone and loss of bone density, but also indicate that the measures reveal additional information about the structural composition of bone, which were not revealed by the static histomorphometry. Finally, we have studied the dependency of the developed measures of complexity on the spatial resolution of the μCT data sets.

  3. Three-dimensional quantification of structures in trabecular bone using measures of complexity.

    PubMed

    Marwan, Norbert; Kurths, Jürgen; Thomsen, Jesper Skovhus; Felsenberg, Dieter; Saparin, Peter

    2009-02-01

    The study of pathological changes of bone is an important task in diagnostic procedures of patients with metabolic bone diseases such as osteoporosis as well as in monitoring the health state of astronauts during long-term space flights. The recent availability of high-resolution three-dimensional (3D) imaging of bone challenges the development of data analysis techniques able to assess changes of the 3D microarchitecture of trabecular bone. We introduce an approach based on spatial geometrical properties and define structural measures of complexity for 3D image analysis. These measures evaluate different aspects of organization and complexity of 3D structures, such as complexity of its surface or shape variability. We apply these measures to 3D data acquired by high-resolution microcomputed tomography (microCT) from human proximal tibiae and lumbar vertebrae at different stages of osteoporotic bone loss. The outcome is compared to the results of conventional static histomorphometry and exhibits clear relationships between the analyzed geometrical features of trabecular bone and loss of bone density, but also indicate that the measures reveal additional information about the structural composition of bone, which were not revealed by the static histomorphometry. Finally, we have studied the dependency of the developed measures of complexity on the spatial resolution of the microCT data sets.

  4. Fine trabecularized carbon: ideal material and texture for percutaneous device system of permanent left ventricular assist device.

    PubMed

    Tagusari, O; Yamazaki, K; Litwak, P; Kojima, A; Klein, E C; Antaki, J F; Watach, M; Gordon, L M; Kono, K; Mori, T; Koyanagi, H; Griffith, B P; Kormos, R L

    1998-06-01

    The development of a percutaneous artificial internal organ system requires a reliable biocompatible connection between the external environment and the inside of the human body. Such is necessary for the success of a permanent left ventricular assist device. However, the search for a satisfactory interface at the epidermal level has proven to be difficult. Carbon has been proposed for this application, but its texture does not typically promote ingrowth from surrounding tissue. We have therefore employed a new processing method to produce a fine trabecularized carbon implant. The method for preparing the implant involves infiltrating low temperature pyrolytic carbon into the surface of a carbon core which is wrapped with carbon fabric. This results in a tightly woven porous structure of carbon (carbon fiber diameter: 35-50 microm, maximal pore size >200 microm) with gradually increasing porosity from 15-75%. We implanted test samples percutaneously in a calf for in vivo histological evaluation. Thirty days after implantation epidermal downgrowth was minimal. Microscopic analysis revealed that a thin fibrous capsule surrounded the implant, and mature connective tissue with accompanying blood vessels filled the pores of the fine trabecularized carbon layer. From these results we suggest that fine trabecularized carbon is ideally suited for a percutaneous device system in a permanent left ventricular assist device.

  5. Anorexia Nervosa: Analysis of Trabecular Texture with CT.

    PubMed

    Tabari, Azadeh; Torriani, Martin; Miller, Karen K; Klibanski, Anne; Kalra, Mannudeep K; Bredella, Miriam A

    2016-10-31

    Purpose To determine indexes of skeletal integrity by using computed tomographic (CT) trabecular texture analysis of the lumbar spine in patients with anorexia nervosa and normal-weight control subjects and to determine body composition predictors of trabecular texture. Materials and Methods This cross-sectional study was approved by the institutional review board and compliant with HIPAA. Written informed consent was obtained. The study included 30 women with anorexia nervosa (mean age ± standard deviation, 26 years ± 6) and 30 normal-weight age-matched women (control group). All participants underwent low-dose single-section quantitative CT of the L4 vertebral body with use of a calibration phantom. Trabecular texture analysis was performed by using software. Skewness (asymmetry of gray-level pixel distribution), kurtosis (pointiness of pixel distribution), entropy (inhomogeneity of pixel distribution), and mean value of positive pixels (MPP) were assessed. Bone mineral density and abdominal fat and paraspinal muscle areas were quantified with quantitative CT. Women with anorexia nervosa and normal-weight control subjects were compared by using the Student t test. Linear regression analyses were performed to determine associations between trabecular texture and body composition. Results Women with anorexia nervosa had higher skewness and kurtosis, lower MPP (P < .001), and a trend toward lower entropy (P = .07) compared with control subjects. Bone mineral density, abdominal fat area, and paraspinal muscle area were inversely associated with skewness and kurtosis and positively associated with MPP and entropy. Texture parameters, but not bone mineral density, were associated with lowest lifetime weight and duration of amenorrhea in anorexia nervosa. Conclusion Patients with anorexia nervosa had increased skewness and kurtosis and decreased entropy and MPP compared with normal-weight control subjects. These parameters were associated with lowest lifetime weight

  6. Trabecular bone histomorphometry in humans with Type 1 Diabetes Mellitus.

    PubMed

    Armas, Laura A G; Akhter, Mohammed P; Drincic, Andjela; Recker, Robert R

    2012-01-01

    Patients with Type 1 Diabetes Mellitus (DM) have markedly increased risk of fracture, but little is known about abnormalities in bone microarchitecture or remodeling properties that might give insight into the pathogenesis of skeletal fragility in these patients. We report here a case-control study comparing bone histomorphometric and micro-CT results from iliac biopsies in 18 otherwise healthy subjects with Type 1 Diabetes Mellitus with those from healthy age- and sex-matched non-diabetic control subjects. Five of the diabetics had histories of low-trauma fracture. Transilial bone biopsies were obtained after tetracycline labeling. The biopsy specimens were fixed, embedded, and scanned using a desktop μCT at 16 μm resolution. They were then sectioned and quantitative histomorphometry was performed as previously described by Recker et al. [1]. Two sections, >250 μm apart, were read from the central part of each biopsy. Overall there were no significant differences between diabetics and controls in histomorphometric or micro-CT measurements. However, fracturing diabetics had structural and dynamic trends different from nonfracturing diabetics by both methods of analysis. In conclusion, Type 1 Diabetes Mellitus does not result in abnormalities in bone histomorphometric or micro-CT variables in the absence of manifest complications from the diabetes. However, diabetics suffering fractures may have defects in their skeletal microarchitecture that may underlie the presence of excess skeletal fragility.

  7. Stimulation of the growth of femoral trabecular bone in ovariectomized rats by the novel parathyroid hormone fragment, hPTH-(1-31)NH2 (Ostabolin).

    PubMed

    Whitfield, J F; Morley, P; Willick, G E; Ross, V; Barbier, J R; Isaacs, R J; Ohannessian-Barry, L

    1996-02-01

    The human parathyroid hormone, hPTH-(1-84), and its hPTH-(1-34) fragment are promising anabolic agents for treating osteoporosis because they can strongly stimulate the production of biomechanically effective cortical and trabecular bone in osteopenic ovariectomized (OVX) rats and trabecular bone in osteoporotic postmenopausal humans. The ideal PTH fragment for treating osteoporosis would be the smallest and functionally simplest fragment that activates only one signal mechanism and still strongly stimulates trabecular bone growth. A new PTH fragment, hPTH-(1-31)NH2, which only stimulates adenylyl cyclase instead of stimulating both adenylyl cyclase and phospholipase-C as do hPTH-(1-84) and hPTH-(1-34), is this minimum, high-potency anabolic fragment. hPTH-(1-31)NH2 (which we have named Ostabolin) can greatly thicken trabeculae and increase the dry weight and calcium content of trabecular bone in the distal femurs of osteopenic, young, sexually mature OVX Sprague-Dawley rats when injected subcutaneously each day for 6 weeks at doses between 0.4 and 1.6 nmole/100 g of body weight.

  8. Graphene Oxide Induced Perturbation to Plasma Membrane and Cytoskeletal Meshwork Sensitize Cancer Cells to Chemotherapeutic Agents.

    PubMed

    Zhu, Jianqiang; Xu, Ming; Gao, Ming; Zhang, Zhihong; Xu, Yong; Xia, Tian; Liu, Sijin

    2017-03-28

    The outstanding physicochemical properties endow graphene materials (e.g., graphene oxide, GO) with beneficial potentials in diverse biomedical fields such as bioimaging, drug delivery, and biomolecular detection. GO recently emerged as a chemosensitizer; however, the detailed molecular basis underlying GO-conducted sensitization and corresponding biological effects are still elusive. Based on our recent findings that GO treatment at sublethal concentrations could impair the general cellular priming state, including disorders of plasma membrane and cytoskeleton construction, we aimed here to explore the mechanism of GO as a sensitizer to make cancer cells more susceptible to chemotherapeutic agents. We discovered that GO could not only compromise plasma membrane and cytoskeleton in J774A.1 macrophages and A549 lung cancer cells at sublethal concentrations without incurring significant cell death but also dampen a number of biological processes. Using the toxicogenomics approaches, we laid out the gene expression signature affected by GO and further defined those genes involved in membrane and cytoskeletal impairments responding to GO. The mechanistic investigation uncovered that the interactions of GO-integrin occurred on the plasma membrane and consequently activated the integrin-FAK-Rho-ROCK pathway and suppressed the expression of integrin, resulting in compromised cell membrane and cytoskeleton and a subsequent cellular priming state. By making use of this mechanism, the efficacy of chemotherapeutic agents (e.g., doxorubicin and cisplatin) could be enhanced by GO pretreatment in killing cancer cells. This study unveiled a feature of GO in cancer therapeutics: sensitizing cancer cells to chemotherapeutic agents by undermining the resistance capability of tumor cells against chemotherapeutic agents, at least partially, by compromising plasma membrane and cytoskeleton meshwork.

  9. Estimating Trabecular Bone Mechanical Properties From Non-Invasive Imaging

    NASA Technical Reports Server (NTRS)

    Hogan, Harry A.; Webster, Laurie

    1997-01-01

    An important component in developing countermeasures for maintaining musculoskeletal integrity during long-term space flight is an effective and meaningful method of monitoring skeletal condition. Magnetic resonance imaging (MRI) is an attractive non-invasive approach because it avoids the exposure to radiation associated with X-ray based imaging and also provides measures related to bone microstructure rather than just density. The purpose of the research for the 1996 Summer Faculty Fellowship period was to extend the usefulness of the MRI data to estimate the mechanical properties of trabecular bone. The main mechanical properties of interest are the elastic modulus and ultimate strength. Correlations are being investigated between these and fractal analysis parameters, MRI relaxation times, apparent densities, and bone mineral densities. Bone specimens from both human and equine donors have been studied initially to ensure high-quality MR images. Specimens were prepared and scanned from human proximal tibia bones as well as the equine distal radius. The quality of the images from the human bone appeared compromised due to freezing artifact, so only equine bone was included in subsequent procedures since these specimens could be acquired and imaged fresh before being frozen. MRI scans were made spanning a 3.6 cm length on each of 5 equine distal radius specimens. The images were then sent to Dr. Raj Acharya of the State University of New York at Buffalo for fractal analysis. Each piece was cut into 3 slabs approximately 1.2 cm thick and high-resolution contact radiographs were made to provide images for comparing fractal analysis with MR images. Dual energy X-ray absorptiometry (DEXA) scans were also made of each slab for subsequent bone mineral density determination. Slabs were cut into cubes for mechanical using a slow-speed diamond blade wafering saw (Buehler Isomet). The dimensions and wet weights of each cube specimen were measured and recorded. Wet weights

  10. Morphogenetic role of F-actin meshwork in chamber formation: immunolabeling results from symbiont bearing benthic foraminifera

    NASA Astrophysics Data System (ADS)

    Tyszka, Jaroslaw; Raitzsch, Markus; Bijma, Jelle; Höher, Nicole; Bickmeyer, Ulf; Rivera-Ingraham, Georginia; Topa, Paweł; Kaczmarek, Karina; Mewes, Antje; Bowser, Samuel; Travis, Jeffrey

    2015-04-01

    Foraminifera are excellent tracers of palaeoceanographic conditions recorded in their shell (test) morphology and chemical composition. Understanding foraminiferal morphology controlled by chamberwise growth can be reduced to processes of chamber formation. However, little is known about how foraminifera control the shape of the chamber wall to be biosynthesized and precipitated. Searching for fundamental morphogenetic features involved in biomineralization, we focused on foraminifers, which belong to the class Globothalamea. The most critical condition to run experiments was to have convenient access to early stages of chamber formation in any species of cultured benthic foraminifers. We have tested small foraminifers collected from the tidal flats of the North Sea. All species, including Ammonia, Haynesina, and Elphidium, turned out to be unsuitable due to their reproduction seasonality and/or unpredictability. The problem was solved by using symbiont bearing Amphistegina lessonii cultured in small aquaria. In well treated cultures, such foraminifera often reproduce on a glass wall surface, serving as a continuous source of juveniles. They tend to regularly construct chambers. Another important point is that symbiont bearing foraminifers usually do not construct opaque protective cysts from detritus that disturb observations. All these features facilitate immunolabeling experiments observed under confocal microscopy. Therefore, for the first time, we managed to label cytoskeleton proteins during the chamber formation in Foraminifera. The results show that the shape of chamber is predefined by a meshwork of F-actin, which acts as a dynamic organic scaffold most likely responsible for distribution and docking of biomineralizing molecules (glycoproteins). The F-actin meshwork interacts with microtubules and all associated proteins, which are involved in the morphogenesis of biomineralized structures. Foraminifera, like other eukaryotic cells, can form active

  11. Left and right ventricular trabecular patterns. Consequence of ventricular septation and valve development.

    PubMed Central

    Wenink, A C; Gittenberger-de Groot, A C

    1982-01-01

    Study of serial sections of human embryos ranging from 3.6 to 25 mm crown rump length shows that the ventricular septum develops from three sources. The primary septum develops between the inlet and outlet which are the two first discernible segments of the ventricular portion of the primary heart tube. Two other septa develop within the inlet and within the outlet, respectively. Before and during septation all ventricular trabeculations are identical. In later stages, the atrioventricular valves and their tension apparatus develop from the inner myocardial layer of the left and right ventricular inlet parts. The outlet trabeculations do not take part in this process. These observations are suggested to explain the typical trabecular patterns of the apices of the mature left and right ventricles, which develop from the inlet and from the outlet, respectively. Images PMID:7138710

  12. Modeling of the dielectric properties of trabecular bone samples at microwave frequency.

    PubMed

    Irastorza, Ramiro M; Blangino, Eugenia; Carlevaro, Carlos M; Vericat, Fernando

    2014-05-01

    In this paper, the dielectric properties of human trabecular bone are evaluated under physiological condition in the microwave range. Assuming a two components medium, simulation and experimental data are presented and discussed. A special experimental setup is developed in order to deal with inhomogeneous samples. Simulation data are obtained using finite difference time domain from a realistic sample. The bone mineral density of the samples are also measured. The simulation and experimental results of the present study suggest that there is a negative relation between bone volume fraction (BV/TV) and permittivity/conductivity: the higher the BV/TV, the lower the permittivity/conductivity. This is in agreement with the recently published in vivo data.

  13. Juvenile Trabecular Ossifying Fibroma of the Maxilla: a Case Report

    PubMed Central

    Aboujaoude, Samia; Aoun, Georges

    2016-01-01

    Introduction: Juvenile ossifying fibromas are uncommon benign tumors. Their aggressiveness added to their high tendency to recur, provoke real diagnostic and therapeutic challenges for the dental practitioner and make a postoperative follow-up over the years indispensable. Case report: In this report, we present a case of a seven-year-old girl presented with a swelling in the face at the upper right maxillary region. After clinical, radiological, and histopathological examinations the diagnosis of trabecular juvenile ossifying fibroma was made. The lesion was surgically excised and followed up for two years with no evidence of recurrence. PMID:28210024

  14. Abnormalities in Cortical Bone, Trabecular Plates, and Stiffness in Postmenopausal Women Treated With Glucocorticoids

    PubMed Central

    Sutter, Stephanie; Nishiyama, Kyle K.; Kepley, Anna; Zhou, Bin; Wang, Ji; McMahon, Donald J.; Guo, X. Edward

    2014-01-01

    Context: The mechanisms by which glucocorticoids (GCs) increase skeletal fragility are not well understood. Objective: The objective of the study was to evaluate the microarchitecture, trabecular morphology, and biomechanical properties of bone in postmenopausal women treated with GCs. Design: This was a case-control study. Setting: The study was conducted at a university hospital outpatient facility. Patients: Postmenopausal women treated with oral GCs for longer than 3 months (n = 30) and age/race-matched controls (n = 60) participated in the study. Main Outcome Measures: Areal bone mineral density aBMD (BMD) by dual-energy x-ray absorptiometry (DXA) was measured. Trabecular and cortical volumetric BMD (vBMD) and microarchitecture by high-resolution peripheral computed tomography of the distal radius and tibia were also measured. Whole-bone stiffness was estimated by finite element analysis. A novel technique, individual trabecula segmentation, was used to evaluate trabecular type (as plate or rod), orientation, and connectivity. Results: DXA T-scores did not differ significantly at any site. GC subjects had significantly lower total, cortical, and trabecular vBMD and thinner cortices, fewer, thinner, more widely, and irregularly spaced trabeculae. They had fewer trabecular plates, fewer axially aligned trabeculae, and lower trabecular connectivity. Differences ranged from 4% to 65% for these trabecular measures and 5% to 17% for the cortical measures. Whole-bone stiffness was significantly lower (11%–16%) in GC subjects. Markers of bone formation (osteocalcin and amino-terminal propeptide of type I procollagen) and resorption (C-telopeptide) were lower in the GC subjects. Conclusions: Despite similar areal BMD by DXA, GC-treated women had abnormal cortical and trabecular vBMD and microarchitecture at both the radius and tibia, including fewer trabecular plates, a less axially aligned trabecular network, lower trabecular connectivity, thinner cortices, and

  15. Identification of lymphatics in the ciliary body of the human eye: a novel "uveolymphatic" outflow pathway.

    PubMed

    Yücel, Yeni H; Johnston, Miles G; Ly, Tina; Patel, Manoj; Drake, Brian; Gümüş, Ersin; Fraenkl, Stephan A; Moore, Sara; Tobbia, Dalia; Armstrong, Dianna; Horvath, Eva; Gupta, Neeru

    2009-11-01

    Impaired aqueous humor flow from the eye may lead to elevated intraocular pressure and glaucoma. Drainage of aqueous fluid from the eye occurs through established routes that include conventional outflow via the trabecular meshwork, and an unconventional or uveoscleral outflow pathway involving the ciliary body. Based on the assumption that the eye lacks a lymphatic circulation, the possible role of lymphatics in the less well defined uveoscleral pathway has been largely ignored. Advances in lymphatic research have identified specific lymphatic markers such as podoplanin, a transmembrane mucin-type glycoprotein, and lymphatic vessel endothelial hyaluronan receptor-1 (LYVE-1). Lymphatic channels were identified in the human ciliary body using immunofluorescence with D2-40 antibody for podoplanin, and LYVE-1 antibody. In keeping with the criteria for lymphatic vessels in conjunctiva used as positive control, D2-40 and LYVE-1-positive lymphatic channels in the ciliary body had a distinct lumen, were negative for blood vessel endothelial cell marker CD34, and were surrounded by either discontinuous or no collagen IV-positive basement membrane. Cryo-immunogold electron microscopy confirmed the presence D2-40-immunoreactivity in lymphatic endothelium in the human ciliary body. Fluorescent nanospheres injected into the anterior chamber of the sheep eye were detected in LYVE-1-positive channels of the ciliary body 15, 30, and 45 min following injection. Four hours following intracameral injection, Iodine-125 radio-labeled human serum albumin injected into the sheep eye (n = 5) was drained preferentially into cervical, retropharyngeal, submandibular and preauricular lymph nodes in the head and neck region compared to reference popliteal lymph nodes (P < 0.05). These findings collectively indicate the presence of distinct lymphatic channels in the human ciliary body, and that fluid and solutes flow at least partially through this system. The discovery of a uveolymphatic

  16. Cyclic cryopreservation affects the nanoscale material properties of trabecular bone.

    PubMed

    Landauer, Alexander K; Mondal, Sumona; Yuya, Philip A; Kuxhaus, Laurel

    2014-11-07

    Tissues such as bone are often stored via freezing, or cryopreservation. During an experimental protocol, bone may be frozen and thawed a number of times. For whole bone, the mechanical properties (strength and modulus) do not significantly change throughout five freeze-thaw cycles. Material properties at the trabecular and lamellar scales are distinct from whole bone properties, thus the impact of freeze-thaw cycling at this scale is unknown. To address this, the effect of repeated freezing on viscoelastic material properties of trabecular bone was quantified via dynamic nanoindentation. Vertebrae from five cervine spines (1.5-year-old, male) were semi-randomly assigned, three-to-a-cycle, to 0-10 freeze-thaw cycles. After freeze-thaw cycling, the vertebrae were dissected, prepared and tested. ANOVA (factors cycle, frequency, and donor) on storage modulus, loss modulus, and loss tangent, were conducted. Results revealed significant changes between cycles for all material properties for most cycles, no significant difference across most of the dynamic range, and significant differences between some donors. Regression analysis showed a moderate positive correlation between cycles and material property for loss modulus and loss tangent, and weak negative correlation for storage modulus, all correlations were significant. These results indicate that not only is elasticity unpredictably altered, but also that damping and viscoelasticity tend to increase with additional freeze-thaw cycling. Copyright © 2014 Elsevier Ltd. All rights reserved.

  17. Fractal-based image texture analysis of trabecular bone architecture.

    PubMed

    Jiang, C; Pitt, R E; Bertram, J E; Aneshansley, D J

    1999-07-01

    Fractal-based image analysis methods are investigated to extract textural features related to the anisotropic structure of trabecular bone from the X-ray images of cubic bone specimens. Three methods are used to quantify image textural features: power spectrum, Minkowski dimension and mean intercept length. The global fractal dimension is used to describe the overall roughness of the image texture. The anisotropic features formed by the trabeculae are characterised by a fabric ellipse, whose orientation and eccentricity reflect the textural anisotropy of the image. Tests of these methods with synthetic images of known fractal dimension show that the Minkowski dimension provides a more accurate and consistent estimation of global fractal dimension. Tests on bone x-ray (eccentricity range 0.25-0.80) images indicate that the Minkowski dimension is more sensitive to the changes in textural orientation. The results suggest that the Minkowski dimension is a better measure for characterising trabecular bone anisotropy in the x-ray images of thick specimens.

  18. MR imaging and osteoporosis: fractal lacunarity analysis of trabecular bone.

    PubMed

    Zaia, Annamaria; Eleonori, Roberta; Maponi, Pierluigi; Rossi, Roberto; Murri, Roberto

    2006-07-01

    We develop a method of magnetic resonance (MR) image analysis able to provide parameter(s) sensitive to bone microarchitecture changes in aging, and to osteoporosis onset and progression. The method has been built taking into account fractal properties of many anatomic and physiologic structures. Fractal lacunarity analysis has been used to determine relevant parameter(s) to differentiate among three types of trabecular bone structure (healthy young, healthy perimenopausal, and osteoporotic patients) from lumbar vertebra MR images. In particular, we propose to approximate the lacunarity function by a hyperbola model function that depends on three coefficients, alpha, beta, and gamma, and to compute these coefficients as the solution of a least squares problem. This triplet of coefficients provides a model function that better represents the variation of mass density of pixels in the image considered. Clinical application of this preliminary version of our method suggests that one of the three coefficients, beta, may represent a standard for the evaluation of trabecular bone architecture and a potentially useful parametric index for the early diagnosis of osteoporosis.

  19. A potential mechanism for allometric trabecular bone scaling in terrestrial mammals.

    PubMed

    Christen, Patrik; Ito, Keita; van Rietbergen, Bert

    2015-03-01

    Trabecular bone microstructural parameters, including trabecular thickness, spacing, and number, have been reported to scale with animal size with negative allometry, whereas bone volume fraction is animal size-invariant in terrestrial mammals. As for the majority of scaling patterns described in animals, its underlying mechanism is unknown. However, it has also been found that osteocyte density is inversely related to animal size, possibly adapted to metabolic rate, which shows a negative relationship as well. In addition, the signalling reach of osteocytes is limited by the extent of the lacuno-canalicular network, depending on trabecular dimensions and thus also on animal size. Here we propose animal size-dependent variations in osteocyte density and their signalling influence distance as a potential mechanism for negative allometric trabecular bone scaling in terrestrial mammals. Using an established and tested computational model of bone modelling and remodelling, we run simulations with different osteocyte densities and influence distances mimicking six terrestrial mammals covering a large range of body masses. Simulated trabecular structures revealed negative allometric scaling for trabecular thickness, spacing, and number, constant bone volume fraction, and bone turnover rates inversely related to animal size. These results are in agreement with previous observations supporting our proposal of osteocyte density and influence distance variation as a potential mechanism for negative allometric trabecular bone scaling in terrestrial mammals. The inverse relationship between bone turnover rates and animal size further indicates that trabecular bone scaling may be linked to metabolic rather than mechanical adaptations.

  20. A potential mechanism for allometric trabecular bone scaling in terrestrial mammals

    PubMed Central

    Christen, Patrik; Ito, Keita; van Rietbergen, Bert

    2015-01-01

    Trabecular bone microstructural parameters, including trabecular thickness, spacing, and number, have been reported to scale with animal size with negative allometry, whereas bone volume fraction is animal size-invariant in terrestrial mammals. As for the majority of scaling patterns described in animals, its underlying mechanism is unknown. However, it has also been found that osteocyte density is inversely related to animal size, possibly adapted to metabolic rate, which shows a negative relationship as well. In addition, the signalling reach of osteocytes is limited by the extent of the lacuno-canalicular network, depending on trabecular dimensions and thus also on animal size. Here we propose animal size-dependent variations in osteocyte density and their signalling influence distance as a potential mechanism for negative allometric trabecular bone scaling in terrestrial mammals. Using an established and tested computational model of bone modelling and remodelling, we run simulations with different osteocyte densities and influence distances mimicking six terrestrial mammals covering a large range of body masses. Simulated trabecular structures revealed negative allometric scaling for trabecular thickness, spacing, and number, constant bone volume fraction, and bone turnover rates inversely related to animal size. These results are in agreement with previous observations supporting our proposal of osteocyte density and influence distance variation as a potential mechanism for negative allometric trabecular bone scaling in terrestrial mammals. The inverse relationship between bone turnover rates and animal size further indicates that trabecular bone scaling may be linked to metabolic rather than mechanical adaptations. PMID:25655770

  1. Individual Trabeculae Segmentation (ITS)–Based Morphological Analysis of High-Resolution Peripheral Quantitative Computed Tomography Images Detects Abnormal Trabecular Plate and Rod Microarchitecture in Premenopausal Women With Idiopathic Osteoporosis

    PubMed Central

    Liu, X Sherry; Cohen, Adi; Shane, Elizabeth; Stein, Emily; Rogers, Halley; Kokolus, Shannon L; Yin, Perry T; McMahon, Donald J; Lappe, Joan M; Recker, Robert R; Guo, X Edward

    2010-01-01

    Idiopathic osteoporosis (IOP) in premenopausal women is a poorly understood entity in which otherwise healthy women have low-trauma fracture or very low bone mineral density (BMD). In this study, we applied individual trabeculae segmentation (ITS)–based morphological analysis to high-resolution peripheral quantitative computed tomography (HR-pQCT) images of the distal radius and distal tibia to gain greater insight into skeletal microarchitecture in premenopausal women with IOP. HR-pQCT scans were performed for 26 normal control individuals and 31 women with IOP. A cubic subvolume was extracted from the trabecular bone compartment and subjected to ITS-based analysis. Three Young's moduli and three shear moduli were calculated by micro–finite element (µFE) analysis. ITS-based morphological analysis of HR-pQCT images detected significantly decreased trabecular plate and rod bone volume fraction and number, decreased axial bone volume fraction in the longitudinal axis, increased rod length, and decreased rod-to-rod, plate-to-rod, and plate-to-plate junction densities at the distal radius and distal tibia in women with IOP. However, trabecular plate and rod thickness did not differ. A more rod-like trabecular microstructure was found in the distal radius, but not in the distal tibia. Most ITS measurements contributed significantly to the elastic moduli of trabecular bone independent of bone volume fraction (BV/TV). At a fixed BV/TV, plate-like trabeculae contributed positively to the mechanical properties of trabecular bone. The results suggest that ITS-based morphological analysis of HR-pQCT images is a sensitive and promising clinical tool for the investigation of trabecular bone microstructure in human studies of osteoporosis. © 2010 American Society for Bone and Mineral Research. PMID:20200967

  2. Predicting Trabecular Bone Stiffness from Clinical Cone-Beam CT and HR-pQCT Data; an In Vitro Study Using Finite Element Analysis

    PubMed Central

    Moreno, Rodrigo; Brismar, Torkel B.; Pahr, Dieter H.; Smedby, Örjan

    2016-01-01

    Stiffness and shear moduli of human trabecular bone may be analyzed in vivo by finite element (FE) analysis from image data obtained by clinical imaging equipment such as high resolution peripheral quantitative computed tomography (HR-pQCT). In clinical practice today, this is done in the peripheral skeleton like the wrist and heel. In this cadaveric bone study, fourteen bone specimens from the wrist were imaged by two dental cone beam computed tomography (CBCT) devices and one HR-pQCT device as well as by dual energy X-ray absorptiometry (DXA). Histomorphometric measurements from micro-CT data were used as gold standard. The image processing was done with an in-house developed code based on the automated region growing (ARG) algorithm. Evaluation of how well stiffness (Young’s modulus E3) and minimum shear modulus from the 12, 13, or 23 could be predicted from the CBCT and HR-pQCT imaging data was studied and compared to FE analysis from the micro-CT imaging data. Strong correlations were found between the clinical machines and micro-CT regarding trabecular bone structure parameters, such as bone volume over total volume, trabecular thickness, trabecular number and trabecular nodes (varying from 0.79 to 0.96). The two CBCT devices as well as the HR-pQCT showed the ability to predict stiffness and shear, with adjusted R2-values between 0.78 and 0.92, based on data derived through our in-house developed code based on the ARG algorithm. These findings indicate that clinically used CBCT may be a feasible method for clinical studies of bone structure and mechanical properties in future osteoporosis research. PMID:27513664

  3. A novel in silico method to quantify primary stability of screws in trabecular bone.

    PubMed

    Steiner, Juri A; Christen, Patrik; Affentranger, Remo; Ferguson, Stephen J; van Lenthe, Gerrit Harry

    2017-02-27

    Insufficient primary stability of screws in bone leads to screw loosening and failure. Unlike conventional continuum finite-element models, micro-CT based finite-element analysis (micro-FE) is capable of capturing the patient-specific bone micro-architecture, providing accurate estimates of bone stiffness. However, such in silico models for screws in bone highly overestimate the apparent stiffness. We hypothesized that a more accurate prediction of primary implant stability of screws in bone is possible by considering insertion-related bone damage. We assessed two different screw types and loading scenarios in 20 trabecular bone specimens extracted from 12 cadaveric human femoral heads (N = 5 for each case). In the micro-FE model, we predicted specimen-specific Young's moduli of the peri-implant bone damage region based on morphometric parameters such that the apparent stiffness of each in silico model matched the experimentally measured stiffness of the corresponding in vitro specimen as closely as possible. The standard micro-FE models assuming perfectly intact peri-implant bone overestimated the stiffness by over 330%. The consideration of insertion related damaged peri-implant bone corrected the mean absolute percentage error down to 11.4% for both loading scenarios and screw types. Cross-validation revealed a mean absolute percentage error of 14.2%. We present the validation of a novel micro-FE modeling technique to quantify the apparent stiffness of screws in trabecular bone. While the standard micro-FE model overestimated the bone-implant stiffness, the consideration of insertion-related bone damage was crucial for an accurate stiffness prediction. This approach provides an important step toward more accurate specimen-specific micro-FE models. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

  4. Assessment of global morphological and topological changes in trabecular structure under the bone resorption process

    NASA Astrophysics Data System (ADS)

    Sidorenko, Irina N.; Bauer, Jan; Monetti, Roberto; Baum, Thomas; Rummeny, Ernst J.; Eckstein, Felix; Matsuura, Maiko; Lochmueller, Eva-Maria; Zysset, Philippe K.; Raeth, Christoph W.

    2012-03-01

    Osteoporosis is a frequent skeletal disease characterised both by loss of bone mineral mass and deterioration of cancellous bone micro-architecture. It can be caused by mechanical disuse, estrogen deficiency or natural age-related resorption process. Numerical analysis of high-resolution images of the trabecular network is recognised as a powerful tool for assessment of structural characteristics. Using μCT images of 73 thoracic and 78 lumbar human vertebral specimens in vitro with isotropic resolution of 26μm we simulate bone atrophy as random resorption of bone surface voxels. Global morphological and topological characteristics provided by four Minkowski Functionals (MF) are calculated for two numerical resorption models with and without conservation of global topological connectivity of the trabecular network, which simulates different types of bone loss in osteoporosis, as it has been described in males and females. Diagnostic performance of morphological and topological characteristics as a function of relative bone loss is evaluated by a correlation analysis with respect to experimentally measured Maximum Compressive Strength (MCS). In both resorption models the second MF, which coincides with bone surface fraction BS/TV, demonstrates almost constant value of Pearson's correlation coefficient with respect to the relative bone loss ▵BV/TV. This morphological characteristic does not vary considerably under age-related random resorption and can be used for predicting bone strength in the elderly. The third and fourth MF demonstrate an increasing correlation coefficients with MCS after applying random bone surface thinning without preserving topological connectivity, what can be used for improvement of evaluation of the current state of the structure.

  5. The effect of postmortem time on the RNA quality of human ocular tissues

    PubMed Central

    Kim, Byung-Jin; Sprehe, Nicholas; Morganti, Ashley; Wordinger, Robert J.

    2013-01-01

    Purpose Profiling gene expression in human ocular tissues provides invaluable information for understanding ocular biology and investigating numerous ocular diseases. Accurate measurement of gene expression requires high-quality RNA, which often is a challenge with postmortem ocular tissues. Methods We examined the effect of various death to preservation (DP) times on the RNA quality of ten different ocular tissues. We used 16 eyes from eight different human donors. The eyes were preserved immediately in RNAlater or preserved after initial storage at 4 °C to create a range of DP times from 2 to 48 h. Ten ocular tissues were dissected from each eye. After total RNA was extracted from each dissected ocular tissue, the RNA integrity number (RIN) was determined using an Agilent Bioanalyzer. Results The RIN values from corneal and trabecular meshwork tissues were significantly (p<0.05) higher than those from the ciliary body at an earlier DP time (<6 h), but were not different among all tissues after 8 h. Interestingly, the RIN values from non-vascularized tissues were significantly (p=0.0002) higher than those from vascularized ocular tissues at early DP times (<6 h). The RIN value from the cornea was significantly (p<0.05) higher at short DP times compared to longer DP times. The RIN values from corneal tissues were significantly correlated to DP time according to regression analysis (p<0.05). Conclusions In this study, we determined RNA quality from postmortem ocular tissues with various DP times. Our results emphasize the need for rapid preservation and processing of postmortem human donor eye tissues, especially for vascularized ocular tissues. PMID:23805035

  6. A Wolff in sheep's clothing: trabecular bone adaptation in response to changes in joint loading orientation.

    PubMed

    Barak, Meir M; Lieberman, Daniel E; Hublin, Jean-Jacques

    2011-12-01

    This study tests Wolff's law of trabecular bone adaptation by examining if induced changes in joint loading orientation cause corresponding adjustments in trabecular orientation. Two groups of sheep were exercised at a trot, 15 min/day for 34 days on an inclined (7°) or level (0°) treadmills. Incline trotting caused the sheep to extend their tarsal joints by 3-4.5° during peak loading (P<0.01) but has no effect on carpal joint angle (P=0.984). Additionally, tarsal joint angle in the incline group sheep were maintained more extended throughout the day using elevated platform shoes on their forelimbs. A third "sedentary group" group did not run but wore platform shoes throughout the day. As predicted by Wolff's law, trabecular orientation in the distal tibia (tarsal joint) were more obtuse by 2.7 to 4.3° in the incline group compared to the level group; trabecular orientation was not significantly different in the sedentary and level groups. In addition, trabecular orientations in the distal radius (carpal joint) of the sedentary, level and incline groups did not differ between groups, and were aligned almost parallel to the radius long axis, corresponding to the almost straight carpal joint angle at peak loading. Measurements of other trabecular bone parameters revealed additional responses to loading, including significantly higher bone volume fraction (BV/TV), Trabecular number (Tb.N) and trabecular thickness (Tb.Th), lower trabecular spacing (Tb.Sp), and less rod-shaped trabeculae (higher structure model index, SMI) in the exercised than sedentary sheep. Overall, these results demonstrate that trabecular bone dynamically adjusts and realigns itself in very precise relation to changes in peak loading direction, indicating that Wolff's law is not only accurate but also highly sensitive.

  7. Weak Genetic Relationship Between Trabecular Bone Morphology and Obesity in Mice

    PubMed Central

    Carson, E. Ann; Kenney-Hunt, Jane P; Pavlicev, Mihaela; Bouckaert, Kristine A; Chinn, Alex J; Silva, Matthew J; Cheverud, James M

    2012-01-01

    Obesity, in addition to being associated with metabolic diseases, such as diabetes, has also been found to lower the risk of osteoporotic fractures. The relationship between obesity and bone trabecular structure is complex, involving responses to mechanical loading and the effects of adipocyte-derived hormones, both directly interacting with bone tissue and indirectly through central nervous system signaling. Here we examine the effects of sex, a high fat diet, and genetics on the trabecular density and structure of the lumbar and caudal vertebra and the proximal tibia along with body weight, fat pad weight, and serum leptin levels in a murine obesity model, the LGXSM Recombinant Inbred (RI) mouse strains. The sample included 481 mice from 16 RI strains. We found that vertebral trabecular density was higher in males while the females had higher tibial trabecular density. The high fat diet led to only slightly higher trabecular density in both sexes despite its extreme effects on obesity and serum leptin levels. Trait heritabilities are moderate to strong and genetic correlations among trabecular features are high. Most genetic variation contrasts strains with large numbers of thick, closely-spaced, highly interconnected, plate-like trabeculae with a high bone volume to total volume ratio against strains displaying small numbers of thin, widely-spaced, sparsely connected, rod-like trabeculae with a low bone volume to total volume ratio. Genetic correlations between trabecular and obesity-related traits were low and not statistically significant. We mapped trabecular properties to 20 genomic locations. Only one-quarter of these locations also had effects on obesity. In this population obesity has a relatively minor effect on trabecular bone morphology. Key Words: bone; trabecular morphology; obesity; quantitative trait loci; mice PMID:22503703

  8. Skeletal dosimetry based on µCT images of trabecular bone: update and comparisons

    NASA Astrophysics Data System (ADS)

    Kramer, R.; Cassola, V. F.; Vieira, J. W.; Khoury, H. J.; de Oliveira Lira, C. A. B.; Robson Brown, K.

    2012-06-01

    Two skeletal dosimetry methods using µCT images of human bone have recently been developed: the paired-image radiation transport (PIRT) model introduced by researchers at the University of Florida (UF) in the US and the systematic-periodic cluster (SPC) method developed by researchers at the Federal University of Pernambuco in Brazil. Both methods use µCT images of trabecular bone (TB) to model spongiosa regions of human bones containing marrow cavities segmented into soft tissue volumes of active marrow (AM), trabecular inactive marrow and the bone endosteum (BE), which is a 50 µm thick layer of marrow on all TB surfaces and on cortical bone surfaces next to TB as well as inside the medullary cavities. With respect to the radiation absorbed dose, the AM and the BE are sensitive soft tissues for the induction of leukaemia and bone cancer, respectively. The two methods differ mainly with respect to the number of bone sites and the size of the µCT images used in Monte Carlo calculations and they apply different methods to simulate exposure from radiation sources located outside the skeleton. The PIRT method calculates dosimetric quantities in isolated human bones while the SPC method uses human bones embedded in the body of a phantom which contains all relevant organs and soft tissues. Consequently, the SPC method calculates absorbed dose to the AM and to the BE from particles emitted by radionuclides concentrated in organs or from radiation sources located outside the human body in one calculation step. In order to allow for similar calculations of AM and BE absorbed doses using the PIRT method, the so-called dose response functions (DRFs) have been developed based on absorbed fractions (AFs) of energy for electrons isotropically emitted in skeletal tissues. The DRFs can be used to transform the photon fluence in homogeneous spongiosa regions into absorbed dose to AM and BE. This paper will compare AM and BE AFs of energy from electrons emitted in skeletal

  9. A model of trabecular bone and an application to osteoporosis

    NASA Astrophysics Data System (ADS)

    Gunaratne, Gemunu H.; Mohanty, Kishore K.; Wimalawansa, Sunil J.

    2002-11-01

    Large bones consists of an outer compact shaft and an inner porous segment, known as the trabecular architecture (TA). The TA is the principal load carrier in bones from older adults, and the aim of therapeutic interventions is to preserve their strength. It is argued that forms for broad-based diagnostic tools for osteoporosis can be identified through an analysis of simple model systems. A model based on elastic networks is introduced, and shows that weak networks can only utilize a small fraction of themselves for stress transmission. This observation is used to argue that the ratio of linear response of a network to DC and AC strain can be used as a surrogate for bone strength. We discuss the possibility of using this measure to identify osteoporotic bone and to monitor the efficacy of therapy.

  10. Differences in Trabecular Microstructure Between Black and White Women Assessed by Individual Trabecular Segmentation Analysis of HR-pQCT Images.

    PubMed

    Putman, Melissa S; Yu, Elaine W; Lin, David; Darakananda, Karin; Finkelstein, Joel S; Bouxsein, Mary L

    2017-05-01

    Black women have lower fracture risk compared with white women, which may be partly explained by improved volumetric bone mineral density (vBMD) and bone microarchitecture primarily within the cortical bone compartment. To determine if there are differences in trabecular microstructure, connectivity, and alignment according to race/ethnicity, we performed individual trabecular segmentation (ITS) analyses on high-resolution peripheral quantitative computed tomography (HR-pQCT) scans of the distal radius and tibia in 273 peri- and postmenopausal black (n = 100) and white (n = 173) women participating in the Study of Women's Health Across the Nation in Boston. Unadjusted analyses showed that black women had greater trabecular plate volume fraction, plate thickness, plate number density, and plate surface area along with greater axial alignment of trabeculae, whereas white women had greater trabecular rod tissue fraction (p < 0.05 for all). Adjustment for clinical covariates augmented these race/ethnicity-related differences in plates and rods, such that white women had greater trabecular rod number density and rod-rod connectivity, whereas black women continued to have superior plate structural characteristics and axial alignment (p < 0.05 for all). These differences remained significant after adjustment for hip BMD and trabecular vBMD. In conclusion, black women had more plate-like trabecular morphology and higher axial alignment of trabeculae, whereas white women had more rod-like trabeculae. These differences may contribute to the improved bone strength and lower fracture risk observed in black women. © 2016 American Society for Bone and Mineral Research. © 2016 American Society for Bone and Mineral Research.

  11. Heritability of lumbar trabecular bone mechanical properties in baboons.

    PubMed

    Havill, L M; Allen, M R; Bredbenner, T L; Burr, D B; Nicolella, D P; Turner, C H; Warren, D M; Mahaney, M C

    2010-03-01

    Genetic effects on mechanical properties have been demonstrated in rodents, but not confirmed in primates. Our aim was to quantify the proportion of variation in vertebral trabecular bone mechanical properties that is due to the effects of genes. L3 vertebrae were collected from 110 females and 46 male baboons (6-32 years old) from a single extended pedigree. Cranio-caudally oriented trabecular bone cores were scanned with microCT then tested in monotonic compression to determine apparent ultimate stress, modulus, and toughness. Age and sex effects and heritability (h(2)) were assessed using maximum likelihood-based variance components methods. Additive effects of genes on residual trait variance were significant for ultimate stress (h(2)=0.58), toughness (h(2)=0.64), and BV/TV (h(2)=0.55). When BV/TV was accounted for, the residual variance in ultimate stress accounted for by the additive effects of genes was no longer significant. Toughness, however, showed evidence of a non-BV/TV-related genetic effect. Overall, maximum stress and modulus show strong genetic effects that are nearly entirely due to bone volume. Toughness shows strong genetic effects related to bone volume and shows additional genetic effects (accounting for 10% of the total trait variance) that are independent of bone volume. These results support continued use of bone volume as a focal trait to identify genes related to skeletal fragility, but also show that other focal traits related to toughness and variation in the organic component of bone matrix will enhance our ability to find additional genes that are particularly relevant to fatigue-related fractures.

  12. Application of homogenization theory to the study of trabecular bone mechanics.

    PubMed

    Hollister, S J; Fyhrie, D P; Jepsen, K J; Goldstein, S A

    1991-01-01

    It is generally accepted that the strength and stiffness of trabecular bone is strongly affected by trabecular microstructure. It has also been hypothesized that stress induced adaptation of trabecular bone is affected by trabecular tissue level stress and/or strain. At this time, however, there is no generally accepted (or easily accomplished) technique for predicting the effect of microstructure on trabecular bone apparent stiffness and strength or estimating tissue level stress or strain. In this paper, a recently developed mechanics theory specifically designed to analyze microstructured materials, called the homogenization theory, is presented and applied to analyze trabecular bone mechanics. Using the homogenization theory it is possible to perform microstructural and continuum analyses separately and then combine them in a systematic manner. Stiffness predictions from two different microstructural models of trabecular bone show reasonable agreement with experimental results, depending on metaphyseal region, (R2 greater than 0.5 for proximal humerus specimens, R2 less than 0.5 for distal femur and proximal tibia specimens). Estimates of both microstructural strain energy density (SED) and apparent SED show that there are large differences (up to 30 times) between apparent SED (as calculated by standard continuum finite element analyses) and the maximum microstructural or tissue SED. Furthermore, a strut and spherical void microstructure gave very different estimates of maximum tissue SED for the same bone volume fraction (BV/TV). The estimates from the spherical void microstructure are between 2 and 20 times greater than the strut microstructure at 10-20% BV/TV.

  13. Trabecular bone microstructure scales allometrically in the primate humerus and femur.

    PubMed

    Ryan, Timothy M; Shaw, Colin N

    2013-05-07

    Most analyses of trabecular microarchitecture in mammals have focused on the functional significance of interspecific variation, but they have not effectively considered the influence of body size or phylogeny on bone architecture. The goals of this study were to determine the relationship between trabecular bone and body size in the humeral and femoral heads of extant primates, and to assess the influence of phylogeny on bone microstructure. Using a sample of 235 individuals from 34 primate species, ranging in body size from 0.06 to 130 kg, the relationships between trabecular bone structure and body size were assessed by using conventional and phylogenetic regression analyses. Bone volume fraction, trabecular thickness and trabecular spacing increase with body size, whereas bone surface-area-to-volume ratio decreases. Shape variables such as trabecular number, connectivity density and degree of anisotropy scale inversely with size. Most of these variables scale with significant negative allometry, except bone surface-area-to-volume ratio, which scales with slight positive allometry. Phylogenetic regressions indicate a relatively weak phylogenetic signal in some trabecular bone variables. These data demonstrate that, relative to body size, large primates have thinner and more tightly packed trabeculae than small primates. The relatively thin trabeculae in large primates and other mammals, coupled with constraints on trabecular thickness related to osteocyte function, suggest that increased skeletal loads in the postcranial joints of large mammals are probably mitigated not only through alterations in trabecular microarchitecture, but also through other mechanisms such as changes in cortical bone distribution, limb posture and gait speed.

  14. Methodological considerations for analyzing trabecular architecture: an example from the primate hand

    PubMed Central

    Kivell, Tracy L; Skinner, Matthew M; Lazenby, Richard; Hublin, Jean-Jacques

    2011-01-01

    Micro-computed tomographic analyses of trabecular bone architecture have been used to clarify the link between positional behavior and skeletal anatomy in primates. However, there are methodological decisions associated with quantifying and comparing trabecular anatomy across taxa that vary greatly in body size and morphology that can affect characterizations of trabecular architecture, such as choice of the volume of interest (VOI) size and location. The potential effects of these decisions may be amplified in small, irregular-shaped bones of the hands and feet that have more complex external morphology and more heterogeneous trabecular structure compared to, for example, the spherical epiphysis of the femoral head. In this study we investigate the effects of changes in VOI size and location on standard trabecular parameters in two bones of the hand, the capitate and third metacarpal, in a diverse sample of nonhuman primates that vary greatly in morphology, body mass and positional behavior. Results demonstrate that changes in VOI location and, to a lesser extent, changes in VOI size had a dramatic affect on many trabecular parameters, especially trabecular connectivity and structure (rods vs. plates), degree of anisotropy, and the primary orientation of the trabeculae. Although previous research has shown that some trabecular parameters are susceptible to slight variations in methodology (e.g. VOI location, scan resolution), this study provides a quantification of these effects in hand bones of a diverse sample of primates. An a priori understanding of the inherent biases created by the choice of VOI size and particularly location is critical to robust trabecular analysis and functional interpretation, especially in small bones with complex arthroses. PMID:20977475

  15. Clinical Application of Solid Model Based on Trabecular Tibia Bone CT Images Created by 3D Printer.

    PubMed

    Cho, Jaemo; Park, Chan-Soo; Kim, Yeoun-Jae; Kim, Kwang Gi

    2015-07-01

    The aim of this work is to use a 3D solid model to predict the mechanical loads of human bone fracture risk associated with bone disease conditions according to biomechanical engineering parameters. We used special image processing tools for image segmentation and three-dimensional (3D) reconstruction to generate meshes, which are necessary for the production of a solid model with a 3D printer from computed tomography (CT) images of the human tibia's trabecular and cortical bones. We examined the defects of the mechanism for the tibia's trabecular bones. Image processing tools and segmentation techniques were used to analyze bone structures and produce a solid model with a 3D printer. These days, bio-imaging (CT and magnetic resonance imaging) devices are able to display and reconstruct 3D anatomical details, and diagnostics are becoming increasingly vital to the quality of patient treatment planning and clinical treatment. Furthermore, radiographic images are being used to study biomechanical systems with several aims, namely, to describe and simulate the mechanical behavior of certain anatomical systems, to analyze pathological bone conditions, to study tissues structure and properties, and to create a solid model using a 3D printer to support surgical planning and reduce experimental costs. These days, research using image processing tools and segmentation techniques to analyze bone structures to produce a solid model with a 3D printer is rapidly becoming very important.

  16. Clinical Application of Solid Model Based on Trabecular Tibia Bone CT Images Created by 3D Printer

    PubMed Central

    Cho, Jaemo; Park, Chan-Soo; Kim, Yeoun-Jae

    2015-01-01

    Objectives The aim of this work is to use a 3D solid model to predict the mechanical loads of human bone fracture risk associated with bone disease conditions according to biomechanical engineering parameters. Methods We used special image processing tools for image segmentation and three-dimensional (3D) reconstruction to generate meshes, which are necessary for the production of a solid model with a 3D printer from computed tomography (CT) images of the human tibia's trabecular and cortical bones. We examined the defects of the mechanism for the tibia's trabecular bones. Results Image processing tools and segmentation techniques were used to analyze bone structures and produce a solid model with a 3D printer. Conclusions These days, bio-imaging (CT and magnetic resonance imaging) devices are able to display and reconstruct 3D anatomical details, and diagnostics are becoming increasingly vital to the quality of patient treatment planning and clinical treatment. Furthermore, radiographic images are being used to study biomechanical systems with several aims, namely, to describe and simulate the mechanical behavior of certain anatomical systems, to analyze pathological bone conditions, to study tissues structure and properties, and to create a solid model using a 3D printer to support surgical planning and reduce experimental costs. These days, research using image processing tools and segmentation techniques to analyze bone structures to produce a solid model with a 3D printer is rapidly becoming very important. PMID:26279958

  17. The Potential of Human Stem Cells for the Study and Treatment of Glaucoma

    PubMed Central

    Chamling, Xitiz; Sluch, Valentin M.; Zack, Donald J.

    2016-01-01

    Purpose Currently, the only available and approved treatments for glaucoma are various pharmacologic, laser-based, and surgical procedures that lower IOP. Although these treatments can be effective, they are not always sufficient, and they cannot restore vision that has already been lost. The goal of this review is to briefly assess current developments in the application of stem cell biology to the study and treatment of glaucoma and other forms of optic neuropathy. Methods A combined literature review and summary of the glaucoma-related discussion at the 2015 “Sight Restoration Through Stem Cell Therapy” meeting that was sponsored by the Ocular Research Symposia Foundation (ORSF). Results Ongoing advancements in basic and eye-related developmental biology have enabled researchers to direct murine and human stem cells along specific developmental paths and to differentiate them into a variety of ocular cell types of interest. The most advanced of these efforts involve the differentiation of stem cells into retinal pigment epithelial cells, work that has led to the initiation of several human trials. More related to the glaucoma field, there have been recent advances in developing protocols for differentiation of stem cells into trabecular meshwork and retinal ganglion cells. Additionally, efforts are being made to generate stem cell–derived cells that can be used to secrete neuroprotective factors. Conclusions Advancing stem cell technology provides opportunities to improve our understanding of glaucoma-related biology and develop models for drug development, and offers the possibility of cell-based therapies to restore sight to patients who have already lost vision. PMID:27116666

  18. Sphingosine-1-Phosphate Enhancement of Cortical Actomyosin Organization in Cultured Human Schlemm's Canal Endothelial Cell Monolayers

    PubMed Central

    Sumida, Grant M.

    2010-01-01

    Purpose. Perfusion of sphingosine-1-phosphate (S1P) in whole eye organ culture models decreases outflow facility, whereas S1P promotes stress fiber formation and contractility in cultured trabecular meshwork (TM) cells. Because of S1P's known effect of increasing barrier function in endothelial cells, the authors hypothesized that Schlemm's canal (SC) cells in culture respond to S1P by increasing actomyosin organization at the cell cortex. Methods. Using primary cultures of human SC cells, the authors determined S1P activation of the GTP-binding proteins, RhoA and Rac (1,2,3). Time- and dose-dependent myosin light chain (MLC) phosphorylation in response to S1P and total expression of MLC were determined. Immunocytochemistry after S1P treatment was used to monitor filamentous actin (F-actin) and phospho-MLC organization and the localization of β-catenin, a component of adherens junctions. TM and human umbilical vein endothelial cell monolayers were used as controls. Results. S1P (1 μM) activated RhoA and Rac after 5- and 30-minute treatments. S1P increased MLC phosphorylation with a similar time- and dose-dependent response in SC (EC50 = 0.83 μM) compared with TM (EC50 = 1.33 μM), though MLC expression was significantly greater in TM. In response to 1 μM S1P treatment, phospho-MLC concentrated in the SC cell periphery, coincident with cortical actin assembly and recruitment of β-catenin to the cell periphery. Conclusions. Results obtained in this study support the hypothesis that S1P increases actomyosin organization at the SC cell cortex and promotes intercellular junctions at the level of the inner wall of SC to increase transendothelial resistance and in part explains the S1P-induced decrease of outflow facility in organ culture. PMID:20592229

  19. A novel composite material specifically developed for ultrasound bone phantoms: cortical, trabecular and skull

    NASA Astrophysics Data System (ADS)

    Wydra, A.; Maev, R. Gr

    2013-11-01

    In the various stages of developing diagnostic and therapeutic equipment, the use of phantoms can play a very important role in improving the process, help in implementation, testing and calibrations. Phantoms are especially useful in developing new applications and training new doctors in medical schools. However, devices that use different physical factors, such as MRI, Ultrasound, CT Scan, etc will require the phantom to be made of different physical properties. In this paper we introduce the properties of recently designed new materials for developing phantoms for ultrasonic human body investigation, which in today's market make up more than 30% in the world of phantoms. We developed a novel composite material which allows fabrication of various kinds of ultrasound bone phantoms to mimic most of the acoustical properties of human bones. In contrast to the ex vivo tissues, the proposed material can maintain the physical and acoustical properties unchanged for long periods of time; moreover, these properties can be custom designed and created to suit specific needs. As a result, we introduce three examples of ultrasound phantoms that we manufactured in our laboratory: cortical, trabecular and skull bone phantoms. The paper also presents the results of a comparison study between the acoustical and physical properties of actual human bones (reported in the referenced literatures) and the phantoms manufactured by us.

  20. Skeletal Structure in Postmenopausal Women with Osteopenia and Fractures is Characterized by Abnormal Trabecular Plates and Cortical Thinning

    PubMed Central

    Stein, Emily M.; Kepley, Anna; Walker, Marcella; Nickolas, Thomas L.; Nishiyama, Kyle; Zhou, Bin; Liu, X. Sherry; McMahon, Donald J.; Zhang, Chiyuan; Boutroy, Stephanie; Cosman, Felicia; Nieves, Jeri; Guo, X. Edward; Shane, Elizabeth

    2014-01-01

    The majority of fragility fractures occur in women with osteopenia rather than osteoporosis by dual energy x-ray absorptiometry (DXA). However, it is difficult to identify which women with osteopenia are at greatest risk. We performed this study to determine whether osteopenic women with and without fracture had differences in trabecular morphology and biomechanical properties of bone. We hypothesized that women with fractures would have fewer trabecular plates, less trabecular connectivity and lower stiffness. We enrolled 117 postmenopausal women with osteopenia by DXA (mean age 66 years; 58 with fragility fractures and 59 non-fractured controls). All had areal bone mineral density by DXA. Trabecular and cortical volumetric BMD (vBMD), trabecular microarchitecture, and cortical porosity were measured by high resolution peripheral computed tomography (HR-pQCT) of the distal radius and tibia. HR-pQCT scans were subjected to finite element analysis to estimate whole bone stiffness and individual trabecula segmentation (ITS) to evaluate trabecular type (as plate or rod), orientation and connectivity. Groups had similar age, race, BMI, and mean T-scores. Fracture subjects had lower cortical and trabecular vBMD, thinner cortices, and thinner more widely separated trabeculae. By ITS, fracture subjects had fewer trabecular plates, less axially aligned trabeculae and less trabecular connectivity. Whole bone stiffness was lower in women with fractures. Cortical porosity did not differ. Differences in cortical bone were found at both sites, whereas trabecular differences were more pronounced at the radius. In summary, postmenopausal women with osteopenia and fractures had lower cortical and trabecular vBMD, thinner, more widely separated and rod-like trabecular structure, less trabecular connectivity and lower whole bone stiffness compared to controls, despite similar aBMD by DXA. Our results suggest that in addition to trabecular and cortical bone loss, changes in plate and

  1. Effect of micro-computed tomography voxel size and segmentation method on trabecular bone microstructure measures in mice.

    PubMed

    Christiansen, Blaine A

    2016-12-01

    Micro-computed tomography (μCT) is currently the gold standard for determining trabecular bone microstructure in small animal models. Numerous parameters associated with scanning and evaluation of μCT scans can strongly affect morphologic results obtained from bone samples. However, the effect of these parameters on specific trabecular bone outcomes is not well understood. This study investigated the effect of μCT scanning with nominal voxel sizes between 6-30 μm on trabecular bone outcomes quantified in mouse vertebral body trabecular bone. Additionally, two methods for determining a global segmentation threshold were compared: based on qualitative assessment of 2D images, or based on quantitative assessment of image histograms. It was found that nominal voxel size had a strong effect on several commonly reported trabecular bone parameters, in particular connectivity density, trabecular thickness, and bone tissue mineral density. Additionally, the two segmentation methods provided similar trabecular bone outcomes for scans with small nominal voxel sizes, but considerably different outcomes for scans with larger voxel sizes. The Qualitatively Selected segmentation method more consistently estimated trabecular bone volume fraction (BV/TV) and trabecular thickness across different voxel sizes, but the Histogram segmentation method more consistently estimated trabecular number, trabecular separation, and structure model index. Altogether, these results suggest that high-resolution scans be used whenever possible to provide the most accurate estimation of trabecular bone microstructure, and that the limitations of accurately determining trabecular bone outcomes should be considered when selecting scan parameters and making conclusions about inter-group variance or between-group differences in studies of trabecular bone microstructure in small animals.

  2. Analysis of trabecular bone texture by modified Hurst orientation transform method.

    PubMed

    Podsiadlo, P; Stachowiak, G W

    2002-04-01

    There is a growing need for noninvasive and inexpensive methods that can effectively be used on a large scale, to detect an onset of early osteoarthritis in human knee joints. Of many possible options, fractal analysis of two-dimensional projection x-ray images of trabecular bone (TB) texture, appears as one of the best approaches. However, there are some problems associated with the characterization of the roughness and anisotropy of the bone texture. To resolve these problems, a modified Hurst orientation transform (HOT) method, previously developed by the authors, has been used in this study. The advantages of the HOT method over other techniques used to analyze bone texture, are that it calculates a two-dimensional fractal dimension in all possible directions and also provides a measure of anisotropy for both surfaces exhibiting strong anisotropy and surfaces exhibiting weak anisotropy. In this study, the accuracy of the HOT method in measuring the bone texture roughness and anisotropy; together with the effects of image noise, blur, exposure, magnification, and projection angle on its performance were investigated. Computer-generated images of fractal surfaces and x-ray images obtained for a human tibia head were used. Results obtained show that the HOT method can effectively be used to characterize the roughness and anisotropy (isotropy) of TB texture.

  3. Reproducibility of subregional trabecular bone micro-architectural measures derived from 7-Tesla magnetic resonance images.

    PubMed

    Chang, Gregory; Wang, Ligong; Liang, Guoyuan; Babb, James S; Saha, Punam K; Regatte, Ravinder R

    2011-06-01

    High-resolution magnetic resonance imaging (MRI) of trabecular bone combined with quantitative image analysis represents a powerful technique to gain insight into trabecular bone micro-architectural derangements in osteoporosis and osteoarthritis. The increased signal-to-noise ratio of ultra high-field MR (≥7 Tesla) permits images to be obtained with higher resolution and/or decreased scan time compared to scanning at 1.5/3T. In this small feasibility study, we show high measurement precision for subregional trabecular bone micro-architectural analysis performed on 7T knee MR images. The results provide further support for the use of trabecular bone measures as biomarkers in clinical studies of bone disorders.

  4. Microsurgical anatomy of the arachnoidal trabecular membranes and cisterns at the level of the tentorium.

    PubMed

    Vinas, F C; Dujovny, M; Fandino, R; Chavez, V

    1996-08-01

    A clear and thorough understanding of the neuroanatomical structures of the subarachnoid cisterns is important because they provide natural pathways to intracranial arteries, veins, and nerves during microvascular procedures without disturbing surrounding important brain structures. Using a surgical microscope, we examined the microsurgical anatomy of the trabecular membranes and subarachnoid cisterns in 20 adult cadaver brains. The brains were immersed in Ringer's solution and air was injected into the subarachnoid cisterns while the brains remained submerged in solution. We identified seven trabecular membranes that limit six cisterns. We specifically looked at the anatomical relationship between the trabecular membranes and cisterns and their corresponding vessels and cranial nerves. The cistern divisions and the dispositions of trabecular membranes were closely related to the vascular division patterns of the principal brain arteries.

  5. Maternal vitamin D and offspring trabecular bone score.

    PubMed

    Hyde, N K; Brennan-Olsen, S L; Wark, J D; Hosking, S M; Holloway, K L; Pasco, J A

    2017-09-03

    No studies have explored the relationship with maternal vitamin D (25(OH)D) in pregnancy and offspring trabecular bone score (TBS). Our data suggest that maternal 25(OH)D in early pregnancy, but not late, may be associated with offspring TBS in boys. These data act as hypothesis-generating findings for confirmation in larger, longer-term studies. Trabecular bone score (TBS), a novel tool derived from dual-energy X-ray absorptiometry (DXA), reflects the microarchitecture of the vertebrae. It has been shown to predict fracture independent of standard DXA parameters in adult populations. Previously, we demonstrated that maternal serum 25-hydroxyvitamin D (25(OH)D) during pregnancy is associated with offspring bone mineral content at age 11 years. However, associations with TBS have not been explored, thus we aimed to determine associations between maternal 25(OH)D and offspring TBS. Data were collected from the Vitamin D in Pregnancy (VIP) study. Venous blood samples were taken at recruitment and at 28-32 weeks' gestation. Maternal 25(OH)D was measured by radioimmunoassay. Offspring (n = 195, n = 181 with complete measures) underwent spine DXA (GE Lunar), at age 11 years (median = 10.9 (IQR 10.9-11.4)). TBS was calculated using TBS iNsight software. Offspring of mothers with sufficient 25(OH)D levels (≥50 nmol/L) at recruitment had a higher TBS (1.363 vs. 1.340, p = 0.04). In multivariable linear regression models, after adjustment for child relative lean mass, sex and pubertal stage, a 10 nmol/L increase in maternal 25(OH)D was associated with a 0.005 (95% CI 0.000, 0.010, p = 0.04) increase in TBS. However when stratified by sex (p for interaction = 0.16), the association was significant in boys, but not girls. There were no associations with TBS and maternal 25(OH)D at 28-32 weeks. We speculate that maternal 25(OH)D in early pregnancy may be associated with TBS in offspring at age 11 in boys. These hypothesis-generating findings warrant

  6. Numerical investigation of ultrasonic attenuation through 2D trabecular bone structures reconstructed from CT scans and random realizations.

    PubMed

    Gilbert, Robert P; Guyenne, Philippe; Li, Jing

    2014-02-01

    In this paper, we compare ultrasound interrogations of actual CT-scanned images of trabecular bone with artificial randomly constructed bone. Even though it is known that actual bone does not have randomly distributed trabeculae, we find that the ultrasound attenuations are close enough to cast doubt on any microstructural information, such as trabeculae width and distance between trabeculae, being gleaned from such experiments. More precisely, we perform numerical simulations of ultrasound interrogation on cancellous bone to investigate the phenomenon of ultrasound attenuation as a function of excitation frequency and bone porosity. The theoretical model is based on acoustic propagation equations for a composite fluid-solid material and is solved by a staggered-grid finite-difference scheme in the time domain. Numerical experiments are performed on two-dimensional bone samples reconstructed from CT-scanned images of real human calcaneus and from random distributions of fluid-solid particles generated via the turning bands method. A detailed comparison is performed on various parameters such as the attenuation rate and speed of sound through the bone samples as well as the normalized broadband ultrasound attenuation coefficient. Comparing results from these two types of bone samples allows us to assess the role of bone microstructure in ultrasound attenuation. It is found that the random model provides suitable bone samples for ultrasound interrogation in the transverse direction of the trabecular network.

  7. Comparison of micro-CT and cone beam CT on the feasibility of assessing trabecular structures in mandibular condyle.

    PubMed

    Liang, Xin; Zhang, Zuyan; Gu, Jianping; Wang, Zhihui; Vandenberghe, Bart; Jacobs, Reinhilde; Yang, Jie; Ma, Guowu; Ling, Haibin; Ma, Xuchen

    2017-07-01

    To evaluate the accuracy of CBCT in assessing trabecular structures. Two human mandibles were scanned by micro-CT (Skyscan 1173 high-energy spiral scan micro-CT; Skyscan NV, Kontich, Belgium) and CBCT (3D Accuitomo 170; Morita, Japan). The CBCT images were reconstructed with 0.5 and 1 mm thicknesses. The condylar images were selected for registration. A parallel algorithm for histogram computation was introduced to perform the registration. A mutual information (MI) value was used to evaluate the match between the images obtained from micro-CT and CBCT. In comparison with the micro-CT image for the two samples, the CBCT image with 0.5 mm thickness has a MI value of 0.873 and 0.903 while that with 1.0 mm thickness has a MI value of 0.741 and 0.752. The CBCT images with 0.5 mm thickness were better matched with micro-CT images. CBCT shows comparable accuracy with high-resolution micro-CT in assessing trabecular structures. CBCT can be a feasible tool to evaluate osseous changes of jaw bones.

  8. Trabecular bone pattern factor--a new parameter for simple quantification of bone microarchitecture.

    PubMed

    Hahn, M; Vogel, M; Pompesius-Kempa, M; Delling, G

    1992-01-01

    The stability of trabecular bone depends not only on the amount of bone tissue, but also on the three-dimensional orientation and connectedness of trabeculae, which is summarized as trabecular microarchitecture. In previous studies we could demonstrate that in three-dimensional bone tissue the relation of trabecular plates to rods is reflected in the ratio of concave to convex surfaces of the bone pattern in two-dimensional bone sections. For the quantification of the connectedness of these bone patterns we developed a new histomorphometric parameter called Trabecular Bone Pattern factor (TBPf). The basic idea is that the connectedness of structures can be described by the relation of convex to concave surfaces. A lot of concave surfaces represent a well connected spongy lattice, whereas a lot of convex surfaces indicate a badly connected trabecular lattice in two-dimensional sections. By means of an automatic image analysis system we measure trabecular bone area (A1) and perimeter (P1). A second measurement of these two parameters (now A2 and P2) is done after a simulated dilatation of trabeculae on the screen. This dilatation results in a characteristic change of bone area and perimeter depending on the relation of convex to concave surfaces. TBPf is defined as a quotient of the difference of the first and the second measurement: TBPf = (P1 - P2)/(A1 - A2). First measurements of TBPf in 192 iliac crest bone biopsies of autopsy cases show that there is not only age-related loss of bone volume, but also a decrease of trabecular connectedness. By means of TBPf we can demonstrate a significant difference in the age-related loss of trabecular connectivity between male and female individuals.

  9. Attenuating trabecular morphology associated with low magnesium diet evaluated using micro computed tomography

    PubMed Central

    Tu, Shu-Ju; Wang, Shun-Ping; Cheng, Fu-Chou; Weng, Chia-En; Huang, Wei-Tzu; Chang, Wei-Jeng; Chen, Ying-Ju

    2017-01-01

    Objective The literature shows that bone mineral density (BMD) and the geometric architecture of trabecular bone in the femur may be affected by inadequate dietary intake of Mg. In this study, we used microcomputed tomography (micro-CT) to characterize and quantify the impact of a low-Mg diet on femoral trabecular bones in mice. Materials and methods Four-week-old C57BL/6J male mice were randomly assigned to 2 groups and supplied either a normal or low-Mg diet for 8weeks. Samples of plasma and urine were collected for biochemical analysis, and femur tissues were removed for micro-CT imaging. In addition to considering standard parameters, we regarded trabecular bone as a cylindrical rod and used computational algorithms for a technical assessment of the morphological characteristics of the bones. BMD (mg-HA/cm3) was obtained using a standard phantom. Results We observed a decline in the total tissue volume, bone volume, percent bone volume, fractal dimension, number of trabecular segments, number of connecting nodes, bone mineral content (mg-HA), and BMD, as well as an increase in the structural model index and surface-area-to-volume ratio in low-Mg mice. Subsequently, we examined the distributions of the trabecular segment length and radius, and a series of specific local maximums were identified. The biochemical analysis revealed a 43% (96%) decrease in Mg and a 40% (71%) decrease in Ca in plasma (urine excretion). Conclusions This technical assessment performed using micro-CT revealed a lower population of femoral trabecular bones and a decrease in BMD at the distal metaphysis in the low-Mg mice. Examining the distributions of the length and radius of trabecular segments showed that the average length and radius of the trabecular segments in low-Mg mice are similar to those in normal mice. PMID:28369124

  10. Altered trabecular bone morphology in adolescent and young adult athletes with menstrual dysfunction.

    PubMed

    Mitchell, Deborah M; Tuck, Padrig; Ackerman, Kathryn E; Cano Sokoloff, Natalia; Woolley, Ryan; Slattery, Meghan; Lee, Hang; Bouxsein, Mary L; Misra, Madhusmita

    2015-12-01

    Young amenorrheic athletes (AA) have lower bone mineral density (BMD) and an increased prevalence of fracture compared with eumenorrheic athletes (EA) and non-athletes. Trabecular morphology is a determinant of skeletal strength and may contribute to fracture risk. To determine the variation in trabecular morphology among AA, EA, and non-athletes and to determine the association of trabecular morphology with fracture among AA. A cross-sectional study performed at an academic clinical research center. 161 girls and young women aged 14-26 years (97 AA, 32 EA, and 32 non-athletes). We measured volumetric BMD (vBMD) and skeletal microarchitecture using high-resolution peripheral quantitative computed tomography. We evaluated trabecular morphology (plate-like vs. rod-like), orientation, and connectivity by individual trabecula segmentation. At the non-weight-bearing distal radius, the groups did not differ for trabecular vBMD. However, plate-like trabecular bone volume fraction (pBV/TV) was lower in AA vs. EA (p=0.03), as were plate number (p=0.03) and connectivity (p=0.03). At the weight-bearing distal tibia, trabecular vBMD was higher in athletes vs. non-athletes (p=0.05 for AA and p=0.009 for EA vs. non-athletes, respectively). pBV/TV was higher in athletes vs. non-athletes (p=0.04 AA and p=0.005 EA vs. non-athletes), as were axially-aligned trabeculae, plate number, and connectivity. Among AA, those with a history of recurrent stress fracture had lower pBV/TV, axially-aligned trabeculae, plate number, plate thickness, and connectivity at the distal radius. Trabecular morphology and alignment differ among AA, EA, and non-athletes. These differences may be associated with increased fracture risk. Copyright © 2015. Published by Elsevier Inc.

  11. Effect of hydrostatic pressure gradients and Na2EDTA on permeability of human Schlemm's canal cell monolayers.

    PubMed

    Burke, A G; Zhou, W; O'Brien, E T; Roberts, B C; Stamer, W D

    2004-06-01

    Elevated intraocular pressure in those with glaucoma appears to be a function of increased resistance to movement of aqueous humor through the conventional outflow pathway. The majority of resistance in both normal and glaucomatous eyes is generated in the region between the juxtacanalicular trabecular meshwork and the inner wall of Schlemm's canal. To accommodate transient elevations in pressure, we hypothesize that conventional outflow increases rapidly due to changes in complexity of intercellular junctions between cells of the inner wall of Schlemm's canal. To test this hypothesis we examined specifically the effects of hydrostatic pressure gradients and the calcium chelator, Na2EDTA, on permeability of cultured human Schlemm's canal cell monolayers in isolation. Human Schlemm's Canal cells were isolated, cultured and then seeded onto permeable supports and maintained in culture to allow intercellular junctions to mature. With a minimum net transendothelial electrical resistance of 10 Ohm cm2, cells were placed into an Ussing-type chamber and hydraulic conductivity was calculated from pressure and flow measurements that were continuously recorded. Simultaneously, transendothelial electrical resistance was measured manually at fixed intervals. In parallel experiments, cell margins were monitored in real time by videomicroscopy. During the baseline measurement period when cells were exposed to pressure but not Na2EDTA, hydraulic conductivity was constant but transendothelial electrical resistance decreased continuously at rate of 0.24 Ohm cm2/minute. After Na2EDTA treatment, no significant change in transendothelial electrical resistance was measured while, hydraulic conductivity of Schlemm's Canal monolayers increased significantly by 125%; corresponding to noticeable intercellular separations. Restoration of cell-cell contact was observed by videomicroscopy 30 minutes following washout of Na2EDTA and functionally after 2 hours. Responses of Schlemm's Canal

  12. Evaluation of trabecular bone patterns on dental radiographic images: influence of cortical bone

    NASA Astrophysics Data System (ADS)

    Amouriq, Yves; Evenou, Pierre; Arlicot, Aurore; Normand, Nicolas; Layrolle, Pierre; Weiss, Pierre; Guédon, Jean-Pierre

    2010-03-01

    For some authors trabecular bone is highly visible in intraoral radiographs. For other authors, the observed intrabony