Science.gov

Sample records for individual collagen fibrils

  1. Stress-strain experiments on individual collagen fibrils.

    PubMed

    Shen, Zhilei L; Dodge, Mohammad Reza; Kahn, Harold; Ballarini, Roberto; Eppell, Steven J

    2008-10-01

    Collagen, a molecule consisting of three braided protein helices, is the primary building block of many biological tissues including bone, tendon, cartilage, and skin. Staggered arrays of collagen molecules form fibrils, which arrange into higher-ordered structures such as fibers and fascicles. Because collagen plays a crucial role in determining the mechanical properties of these tissues, significant theoretical research is directed toward developing models of the stiffness, strength, and toughness of collagen molecules and fibrils. Experimental data to guide the development of these models, however, are sparse and limited to small strain response. Using a microelectromechanical systems platform to test partially hydrated collagen fibrils under uniaxial tension, we obtained quantitative, reproducible mechanical measurements of the stress-strain curve of type I collagen fibrils, with diameters ranging from 150-470 nm. The fibrils showed a small strain (epsilon < 0.09) modulus of 0.86 +/- 0.45 GPa. Fibrils tested to strains as high as 100% demonstrated strain softening (sigma(yield) = 0.22 +/- 0.14 GPa; epsilon(yield) = 0.21 +/- 0.13) and strain hardening, time-dependent recoverable residual strain, dehydration-induced embrittlement, and susceptibility to cyclic fatigue. The results suggest that the stress-strain behavior of collagen fibrils is dictated by global characteristic dimensions as well as internal structure. PMID:18641067

  2. Stress-Strain Experiments on Individual Collagen Fibrils

    PubMed Central

    Shen, Zhilei L.; Dodge, Mohammad Reza; Kahn, Harold; Ballarini, Roberto; Eppell, Steven J.

    2008-01-01

    Collagen, a molecule consisting of three braided protein helices, is the primary building block of many biological tissues including bone, tendon, cartilage, and skin. Staggered arrays of collagen molecules form fibrils, which arrange into higher-ordered structures such as fibers and fascicles. Because collagen plays a crucial role in determining the mechanical properties of these tissues, significant theoretical research is directed toward developing models of the stiffness, strength, and toughness of collagen molecules and fibrils. Experimental data to guide the development of these models, however, are sparse and limited to small strain response. Using a microelectromechanical systems platform to test partially hydrated collagen fibrils under uniaxial tension, we obtained quantitative, reproducible mechanical measurements of the stress-strain curve of type I collagen fibrils, with diameters ranging from 150–470 nm. The fibrils showed a small strain (ɛ < 0.09) modulus of 0.86 ± 0.45 GPa. Fibrils tested to strains as high as 100% demonstrated strain softening (σyield = 0.22 ± 0.14 GPa; ɛyield = 0.21 ± 0.13) and strain hardening, time-dependent recoverable residual strain, dehydration-induced embrittlement, and susceptibility to cyclic fatigue. The results suggest that the stress-strain behavior of collagen fibrils is dictated by global characteristic dimensions as well as internal structure. PMID:18641067

  3. Two-Dimensional Nanoscale Structural and Functional Imaging in Individual Collagen Type I Fibrils

    PubMed Central

    Harnagea, Catalin; Vallières, Martin; Pfeffer, Christian P.; Wu, Dong; Olsen, Bjorn R.; Pignolet, Alain; Légaré, François; Gruverman, Alexei

    2010-01-01

    Abstract The piezoelectric properties of single collagen type I fibrils in fascia were imaged with sub-20 nm spatial resolution using piezoresponse force microscopy. A detailed analysis of the piezoresponse force microscopy signal in controlled tip-fibril geometry revealed shear piezoelectricity parallel to the fibril axis. The direction of the displacement is preserved along the whole fiber length and is independent of the fiber conformation. It is shown that individual fibrils within bundles in skeletal muscle fascia can have opposite polar orientations and are organized into domains, i.e., groups of several fibers having the same polar orientation. We were also able to detect piezoelectric activity of collagen fibrils in the high-frequency range up to 200 kHz, suggesting that the mechanical response time of biomolecules to electrical stimuli can be ∼5 μs. PMID:20550920

  4. Nano-mechanical properties of individual mineralized collagen fibrils from bone tissue.

    PubMed

    Hang, Fei; Barber, Asa H

    2011-04-01

    Mineralized collagen fibrils (MCFs) are distinct building blocks for bone material and perform an important mechanical function. A novel experimental technique using combined atomic force microscopy and scanning electron microscopy is used to manipulate and measure the mechanical properties of individual MCFs from antler, which is a representative bone tissue. The recorded stress-strain response of individual MCFs under tension shows an initial linear deformation region for all fibrils, followed by inhomogeneous deformation above a critical strain. This inhomogeneous deformation is indicative of fibrils exhibiting either yield or strain hardening and suggests possible mineral compositional changes within each fibril. A phenomenological model is used to describe the fibril nano-mechanical behaviour. PMID:20961895

  5. Nanoscale characterization of isolated individual type I collagen fibrils: polarization and piezoelectricity

    NASA Astrophysics Data System (ADS)

    Minary-Jolandan, Majid; Yu, Min-Feng

    2009-02-01

    Piezoresponse force microscopy was applied to directly study individual type I collagen fibrils with diameters of ~100 nm isolated from bovine Achilles tendon. It was revealed that single collagen fibrils behave predominantly as shear piezoelectric materials with a piezoelectric coefficient on the order of 1 pm V-1, and have unipolar axial polarization throughout their entire length. It was estimated that, under reasonable shear load conditions, the fibrils were capable of generating an electric potential up to tens of millivolts. The result substantiates the nanoscale origin of piezoelectricity in bone and tendons, and implies also the potential importance of the shear load-transfer mechanism, which has been the principle basis of the nanoscale mechanics model of collagen, in mechanoelectric transduction in bone.

  6. Large Deformation Mechanisms, Plasticity, and Failure of an Individual Collagen Fibril With Different Mineral Content.

    PubMed

    Depalle, Baptiste; Qin, Zhao; Shefelbine, Sandra J; Buehler, Markus J

    2016-02-01

    Mineralized collagen fibrils are composed of tropocollagen molecules and mineral crystals derived from hydroxyapatite to form a composite material that combines optimal properties of both constituents and exhibits incredible strength and toughness. Their complex hierarchical structure allows collagen fibrils to sustain large deformation without breaking. In this study, we report a mesoscale model of a single mineralized collagen fibril using a bottom-up approach. By conserving the three-dimensional structure and the entanglement of the molecules, we were able to construct finite-size fibril models that allowed us to explore the deformation mechanisms which govern their mechanical behavior under large deformation. We investigated the tensile behavior of a single collagen fibril with various intrafibrillar mineral content and found that a mineralized collagen fibril can present up to five different deformation mechanisms to dissipate energy. These mechanisms include molecular uncoiling, molecular stretching, mineral/collagen sliding, molecular slippage, and crystal dissociation. By multiplying its sources of energy dissipation and deformation mechanisms, a collagen fibril can reach impressive strength and toughness. Adding mineral into the collagen fibril can increase its strength up to 10 times and its toughness up to 35 times. Combining crosslinks with mineral makes the fibril stiffer but more brittle. We also found that a mineralized fibril reaches its maximum toughness to density and strength to density ratios for a mineral density of around 30%. This result, in good agreement with experimental observations, attests that bone tissue is optimized mechanically to remain lightweight but maintain strength and toughness. PMID:26866939

  7. Large Deformation Mechanisms, Plasticity, and Failure of an Individual Collagen Fibril With Different Mineral Content

    PubMed Central

    Depalle, Baptiste; Qin, Zhao; Shefelbine, Sandra J

    2016-01-01

    ABSTRACT Mineralized collagen fibrils are composed of tropocollagen molecules and mineral crystals derived from hydroxyapatite to form a composite material that combines optimal properties of both constituents and exhibits incredible strength and toughness. Their complex hierarchical structure allows collagen fibrils to sustain large deformation without breaking. In this study, we report a mesoscale model of a single mineralized collagen fibril using a bottom‐up approach. By conserving the three‐dimensional structure and the entanglement of the molecules, we were able to construct finite‐size fibril models that allowed us to explore the deformation mechanisms which govern their mechanical behavior under large deformation. We investigated the tensile behavior of a single collagen fibril with various intrafibrillar mineral content and found that a mineralized collagen fibril can present up to five different deformation mechanisms to dissipate energy. These mechanisms include molecular uncoiling, molecular stretching, mineral/collagen sliding, molecular slippage, and crystal dissociation. By multiplying its sources of energy dissipation and deformation mechanisms, a collagen fibril can reach impressive strength and toughness. Adding mineral into the collagen fibril can increase its strength up to 10 times and its toughness up to 35 times. Combining crosslinks with mineral makes the fibril stiffer but more brittle. We also found that a mineralized fibril reaches its maximum toughness to density and strength to density ratios for a mineral density of around 30%. This result, in good agreement with experimental observations, attests that bone tissue is optimized mechanically to remain lightweight but maintain strength and toughness. © 2015 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research (ASBMR). PMID:26866939

  8. Effects of hydration on the mechanical response of individual collagen fibrils

    NASA Astrophysics Data System (ADS)

    Grant, Colin A.; Brockwell, David J.; Radford, Sheena E.; Thomson, Neil H.

    2008-06-01

    Collagen fibrils prepared from bovine Achilles tendon have been mechanically tested through nanoindentation by an atomic force microscope using force volume analysis. In ambient conditions where the fibrils are expected to be dehydrated, the elastic modulus was determined to be 1.9±0.5GPa, while under aqueous fluid, it decreased by three orders of magnitude to 1.2±0.1MPa. In air, fibril fracture occurred along the axis and the crack lengths were quantized to the D-banding periodicity. The apparent hardness of the fibrils was estimated to be in the range of 0.35-0.6GPa.

  9. Electrostatic effects in collagen fibrillization

    NASA Astrophysics Data System (ADS)

    Morozova, Svetlana; Muthukumar, Murugappan

    2014-03-01

    Using light scattering and AFM techniques, we have measured the kinetics of fibrillization of collagen (pertinent to the vitreous of human eye) as a function of pH and ionic strength. At higher and lower pH, collagen triple-peptides remain stable in solution without fibrillization. At neutral pH, the fibrillization occurs and its growth kinetics is slowed upon either an increase in ionic strength or a decrease in temperature. We present a model, based on polymer crystallization theory, to describe the observed electrostatic nature of collagen assembly.

  10. Collagen fibril formation during development

    SciTech Connect

    Fleischmajer, R.; Perlish, J.S.; Timpl, R.; Olsen, B.R.

    1987-05-01

    Studies with embryonic skin and bone suggested that the aminopropeptide (AP) and carboxylpropeptide (CP) of type I pro-callagen (pro-col) play a role in fibril formation. Chick leg metatarsal tendons were studied by electron microscopy. AP and CP of type I pro-col were purified from chick leg tendons; antibodies developed in rabbits and purity tested by radioimmunoassays. Antibodies were used for immunofluorescence microscopy (IFM) and immunoblotting (IB). The peritendineum, consisting of thin 20-30 nm fibrils, revealed the AP of type I and type III procol. In the tendon area, collagen fibrils were arranged within small compartments and were of uniform diameter at 10d, 14d and 18d. However, beyond 21d, there was confluency of the compartments and a wide range of fibril diameters. IFM revealed fine streaks of collagen, staining with the AP of type I throughout the tendon. The CP was mainly intracellular with only a small amount present in the extracellular space. IB revealed procollagen, pN-collagen (AP+collagen) and pC-collagen, (CP+collagen) at all stages of development. Ratios of pN/pC collagen, determined by spectrophotometric scanning of autoradiographs, correlated well with the distribution of fibril diameter. This study suggests the hypothesis that AP initiates fibrillogenesis while CP may regulate additional fibril growth.

  11. Study of Native Type I Collagen Fibrils

    NASA Astrophysics Data System (ADS)

    Heim, August

    2006-03-01

    Presented in this work is direct imaging and force microscopy of native, intact type I collagen fibrils extracted from the sea cucumber Cucumaria frondosa dermis with affiliated proteoglycan molecules. The prototypical collagen fibril structure is well conserved through higher mammalian species and presents a model for study of the mechanical properties of the primary individual components of the dermis and skeletal ligature. Common practice is to use reconstituted fibrils which lack the precise conformal structure and affiliated proteoglycans. We have performed force microscopy to probe the mechanical properties of native fibrils and extract the elastic modulus under natural conditions. This knowledge is combined transmission and atomic force imaging, in conjunction with applied computation models, to demonstrate an inherent semitubular structure of these fibrils.

  12. Nature designs tough collagen: Explaining the nanostructure of collagen fibrils

    PubMed Central

    Buehler, Markus J.

    2006-01-01

    Collagen is a protein material with superior mechanical properties. It consists of collagen fibrils composed of a staggered array of ultra-long tropocollagen (TC) molecules. Theoretical and molecular modeling suggests that this natural design of collagen fibrils maximizes the strength and provides large energy dissipation during deformation, thus creating a tough and robust material. We find that the mechanics of collagen fibrils can be understood quantitatively in terms of two critical molecular length scales χS and χR that characterize when (i) deformation changes from homogeneous intermolecular shear to propagation of slip pulses and when (ii) covalent bonds within TC molecules begin to fracture, leading to brittle-like failure. The ratio χS/χR indicates which mechanism dominates deformation. Our modeling rigorously links the chemical properties of individual TC molecules to the macroscopic mechanical response of fibrils. The results help to explain why collagen fibers found in nature consist of TC molecules with lengths in the proximity of 300 nm and advance the understanding how collagen diseases that change intermolecular adhesion properties influence mechanical properties. PMID:16895989

  13. Type V collagen controls the initiation of collagen fibril assembly.

    PubMed

    Wenstrup, Richard J; Florer, Jane B; Brunskill, Eric W; Bell, Sheila M; Chervoneva, Inna; Birk, David E

    2004-12-17

    Vertebrate collagen fibrils are heterotypically composed of a quantitatively major and minor fibril collagen. In non-cartilaginous tissues, type I collagen accounts for the majority of the collagen mass, and collagen type V, the functions of which are poorly understood, is a minor component. Type V collagen has been implicated in the regulation of fibril diameter, and we reported recently preliminary evidence that type V collagen is required for collagen fibril nucleation (Wenstrup, R. J., Florer, J. B., Cole, W. G., Willing, M. C., and Birk, D. E. (2004) J. Cell. Biochem. 92, 113-124). The purpose of this study was to define the roles of type V collagen in the regulation of collagen fibrillogenesis and matrix assembly. Mouse embryos completely deficient in pro-alpha1(V) chains were created by homologous recombination. The col5a1-/- animals die in early embryogenesis, at approximately embryonic day 10. The type V collagen-deficient mice demonstrate a virtual lack of collagen fibril formation. In contrast, the col5a1+/- animals are viable. The reduced type V collagen content is associated with a 50% reduction in fibril number and dermal collagen content. In addition, relatively normal, cylindrical fibrils are assembled with a second population of large, structurally abnormal collagen fibrils. The structural properties of the abnormal matrix are decreased relative to the wild type control animals. These data indicate a central role for the evolutionary, ancient type V collagen in the regulation of fibrillogenesis. The complete dependence of fibril formation on type V collagen is indicative of the critical role of the latter in early fibril initiation. In addition, this fibril collagen is important in the determination of fibril structure and matrix organization. PMID:15383546

  14. The collagen fibril organization in human articular cartilage.

    PubMed Central

    Minns, R J; Steven, F S

    1977-01-01

    In this scanning electron microscopic study blocks of collagen fibrils were prepared from human articular cartilage, using two techinques which selectively removed either the proteoglycans alone, or both the proteoglycans and the collagen fibrils, of the non-calcified cartilage layer. Amino acid analysis of the fibrils confirmed the purity of the collagen after proteoglycan extraction. The cartilage was scanned in four different ways: (1) normal to the articular surface, (2) in superficial sections, (3) on surfaces of blocks which had been broken in planes parallel to artificial splits make by the insertion of a pin, and (4) on fracture surfaces which traversed the calcified cartilage and the subchondral bone. Five features of the organization of the collagen fibrils were specially noted: (1) Individual fibrils within the trabeculae joined to form small fibre bundles which became grouped into larger bundles at the calcified/uncalcified interface. (2) Fibrils in the deep and middle zones which, exhibiting the characteristic surface periodicity of collagen, were generally oriented towars the articular surface in large bundles approximately 55 micronm across. (3) In the superficial zone, fibrils ran parallel to the surface. (4) The surface fibrils had random orientation, even at the bases of empty lacunae vacated by chondrocytes during specimen preparation. (5) The collagen fibrils of the lacunar walls appeared to be thinner and more closely packed than thos between the lacunae. The fine collagen fibrils associated with the lacunar walls were frequently observed to pass through a large lacunar space, resulting in the formation of two or more compartments, each of which was presumably filled with a chondrocyte in the living cartilage. Images Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 9 Fig. 10 Fig. 11 Fig. 12 Fig. 13 Fig. 14 PMID:870478

  15. Nanointerfacial strength between non-collagenous protein and collagen fibrils in antler bone

    PubMed Central

    Hang, Fei; Gupta, Himadri S.; Barber, Asa H.

    2014-01-01

    Antler bone displays considerable toughness through the use of a complex nanofibrous structure of mineralized collagen fibrils (MCFs) bound together by non-collagenous proteins (NCPs). While the NCP regions represent a small volume fraction relative to the MCFs, significant surface area is evolved upon failure of the nanointerfaces formed at NCP–collagen fibril boundaries. The mechanical properties of nanointerfaces between the MCFs are investigated directly in this work using an in situ atomic force microscopy technique to pull out individual fibrils from the NCP. Results show that the NCP–fibril interfaces in antler bone are weak, which highlights the propensity for interface failure at the nanoscale in antler bone and extensive fibril pullout observed at antler fracture surfaces. The adhesion between fibrils and NCP is additionally suggested as being rate dependent, with increasing interfacial strength and fracture energy observed when pullout velocity decreases. PMID:24352676

  16. Tension tests on mammalian collagen fibrils.

    PubMed

    Liu, Yehe; Ballarini, Roberto; Eppell, Steven J

    2016-02-01

    A brief overview of isolated collagen fibril mechanics testing is followed by presentation of the first results testing fibrils isolated from load-bearing mammalian tendons using a microelectromechanical systems platform. The in vitro modulus (326 ± 112 MPa) and fracture stress (71 ± 23 MPa) are shown to be lower than previously measured on fibrils extracted from sea cucumber dermis and tested with the same technique. Scanning electron microscope images show the fibrils can fail with a mechanism that involves circumferential rupture, whereas the core of the fibril stays at least partially intact. PMID:26855757

  17. Fibril-forming collagens in lamprey.

    PubMed

    Kelly, J; Tanaka, S; Hardt, T; Eikenberry, E F; Brodsky, B

    1988-01-15

    Five types of collagen with triple-helical regions approximately 300 nm in length were found in lamprey tissues which show characteristic D-periodic collagen fibrils. These collagens are members of the fibril forming family of this primitive vertebrate. Lamprey collagens were characterized with respect to solubility, mobility on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, carboxylmethyl-cellulose chromatography, peptide digestion patterns, composition, susceptibility to vertebrate collagenase, thermal stability, and segment long spacing-banding pattern. Comparison with fibril-forming collagens in higher vertebrates (types I, II, III, V, and XI) identified three lamprey collagens as types II, V, and XI. Both lamprey dermis and major body wall collagens had properties similar to type I but not the typical heterotrimer composition. Dermis molecules had only alpha 1(I)-like chains, while body wall molecules had alpha 2(I)-like chains combined with chains resembling lamprey type II. Neither collagen exhibited the interchain disulfide linkages or solubility properties of type III. The conservation of fibril organization in type II/type XI tissues in contrast to the major developments in type I and type III tissues after the divergence of lamprey and higher vertebrates is consistent with these results. The presence of type II and type I-like molecules as major collagens and types V and XI as minor collagens in the lamprey, and the differential susceptibility of these molecules to vertebrate collagenase is analogous to the findings in higher vertebrates. PMID:3335531

  18. Mechanical Properties of Mineralized Collagen Fibrils As Influenced By Demineralization

    SciTech Connect

    Balooch, M.; Habelitz, S.; Kinney, J.H.; Marshall, S.J.; Marshall, G.W.

    2009-05-11

    Dentin and bone derive their mechanical properties from a complex arrangement of collagen type-I fibrils reinforced with nanocrystalline apatite mineral in extra- and intrafibrillar compartments. While mechanical properties have been determined for the bulk of the mineralized tissue, information on the mechanics of the individual fibril is limited. Here, atomic force microscopy was used on individual collagen fibrils to study structural and mechanical changes during acid etching. The characteristic 67 nm periodicity of gap zones was not observed on the mineralized fibril, but became apparent and increasingly pronounced with continuous demineralization. AFM-nanoindentation showed a decrease in modulus from 1.5 GPa to 50 MPa during acid etching of individual collagen fibrils and revealed that the modulus profile followed the axial periodicity. The nanomechanical data, Raman spectroscopy and SAXS support the hypothesis that intrafibrillar mineral etches at a substantially slower rate than the extrafibrillar mineral. These findings are relevant for understanding the biomechanics and design principles of calcified tissues derived from collagen matrices.

  19. Structure-mechanics relationships of collagen fibrils in the osteogenesis imperfecta mouse model.

    PubMed

    Andriotis, O G; Chang, S W; Vanleene, M; Howarth, P H; Davies, D E; Shefelbine, S J; Buehler, M J; Thurner, P J

    2015-10-01

    The collagen molecule, which is the building block of collagen fibrils, is a triple helix of two α1(I) chains and one α2(I) chain. However, in the severe mouse model of osteogenesis imperfecta (OIM), deletion of the COL1A2 gene results in the substitution of the α2(I) chain by one α1(I) chain. As this substitution severely impairs the structure and mechanics of collagen-rich tissues at the tissue and organ level, the main aim of this study was to investigate how the structure and mechanics are altered in OIM collagen fibrils. Comparing results from atomic force microscopy imaging and cantilever-based nanoindentation on collagen fibrils from OIM and wild-type (WT) animals, we found a 33% lower indentation modulus in OIM when air-dried (bound water present) and an almost fivefold higher indentation modulus in OIM collagen fibrils when fully hydrated (bound and unbound water present) in phosphate-buffered saline solution (PBS) compared with WT collagen fibrils. These mechanical changes were accompanied by an impaired swelling upon hydration within PBS. Our experimental and atomistic simulation results show how the structure and mechanics are altered at the individual collagen fibril level as a result of collagen gene mutation in OIM. We envisage that the combination of experimental and modelling approaches could allow mechanical phenotyping at the collagen fibril level of virtually any alteration of collagen structure or chemistry. PMID:26468064

  20. Structure–mechanics relationships of collagen fibrils in the osteogenesis imperfecta mouse model

    PubMed Central

    Andriotis, O. G.; Chang, S. W.; Vanleene, M.; Howarth, P. H.; Davies, D. E.; Shefelbine, S. J.; Buehler, M. J.; Thurner, P. J.

    2015-01-01

    The collagen molecule, which is the building block of collagen fibrils, is a triple helix of two α1(I) chains and one α2(I) chain. However, in the severe mouse model of osteogenesis imperfecta (OIM), deletion of the COL1A2 gene results in the substitution of the α2(I) chain by one α1(I) chain. As this substitution severely impairs the structure and mechanics of collagen-rich tissues at the tissue and organ level, the main aim of this study was to investigate how the structure and mechanics are altered in OIM collagen fibrils. Comparing results from atomic force microscopy imaging and cantilever-based nanoindentation on collagen fibrils from OIM and wild-type (WT) animals, we found a 33% lower indentation modulus in OIM when air-dried (bound water present) and an almost fivefold higher indentation modulus in OIM collagen fibrils when fully hydrated (bound and unbound water present) in phosphate-buffered saline solution (PBS) compared with WT collagen fibrils. These mechanical changes were accompanied by an impaired swelling upon hydration within PBS. Our experimental and atomistic simulation results show how the structure and mechanics are altered at the individual collagen fibril level as a result of collagen gene mutation in OIM. We envisage that the combination of experimental and modelling approaches could allow mechanical phenotyping at the collagen fibril level of virtually any alteration of collagen structure or chemistry. PMID:26468064

  1. Viscoelastic Properties of Isolated Collagen Fibrils

    PubMed Central

    Shen, Zhilei Liu; Kahn, Harold; Ballarini, Roberto; Eppell, Steven J.

    2011-01-01

    Understanding the viscoelastic behavior of collagenous tissues with complex hierarchical structures requires knowledge of the properties at each structural level. Whole tissues have been studied extensively, but less is known about the mechanical behavior at the submicron, fibrillar level. Using a microelectromechanical systems platform, in vitro coupled creep and stress relaxation tests were performed on collagen fibrils isolated from the sea cucumber dermis. Stress-strain-time data indicate that isolated fibrils exhibit viscoelastic behavior that could be fitted using the Maxwell-Weichert model. The fibrils showed an elastic modulus of 123 ± 46 MPa. The time-dependent behavior was well fit using the two-time-constant Maxwell-Weichert model with a fast time response of 7 ± 2 s and a slow time response of 102 ± 5 s. The fibrillar relaxation time was smaller than literature values for tissue-level relaxation time, suggesting that tissue relaxation is dominated by noncollagenous components (e.g., proteoglycans). Each specimen was tested three times, and the only statistically significant difference found was that the elastic modulus is larger in the first test than in the subsequent two tests, indicating that viscous properties of collagen fibrils are not sensitive to the history of previous tests. PMID:21689535

  2. Elastic model for crimped collagen fibrils

    NASA Technical Reports Server (NTRS)

    Freed, Alan D.; Doehring, Todd C.

    2005-01-01

    A physiologic constitutive expression is presented in algorithmic format for the nonlinear elastic response of wavy collagen fibrils found in soft connective tissues. The model is based on the observation that crimped fibrils in a fascicle have a three-dimensional structure at the micron scale that we approximate as a helical spring. The symmetry of this wave form allows the force/displacement relationship derived from Castigliano's theorem to be solved in closed form: all integrals become analytic. Model predictions are in good agreement with experimental observations for mitral-valve chordae tendinece.

  3. Elastic Response of Crimped Collagen Fibrils

    NASA Technical Reports Server (NTRS)

    Freed, Alan D.; Doehring, Todd C.

    2005-01-01

    A physiologic constitutive expression is presented in algorithmic format for the elastic response of wavy collagen fibrils found in soft connective tissues. The model is based on the observation that crimped fibrils have a three-dimensional structure at the micrometer scale that we approximate as a helical spring. The symmetry of this waveform allows the force/displacement relationship derived from Castigliano's theorem to be solved in closed form. Model predictions are in good agreement with experimental observations for mitral-valve chordae tendineae

  4. Collagen fibril biosynthesis in tendon: a review and recent insights.

    PubMed

    Canty, E G; Kadler, K E

    2002-12-01

    The development and evolution of multicellular animals relies on the ability of certain cell types to synthesise an extracellular matrix (ECM) comprising very long collagen fibrils that are arranged in very ordered 3-dimensional scaffolds. Tendon is a good example of a highly ordered ECM, in which tens of millions of collagen fibrils, each hundreds of microns long, are synthesised parallel to the tendon long axis. This review highlights recent discoveries showing that the assembly of collagen fibrils in tendon is hierarchical, and involves the formation of fairly short "collagen early fibrils" that are the fusion precursors of the very long fibrils that occur in mature tendon. PMID:12485687

  5. Thermal Memory in Self-Assembled Collagen Fibril Networks

    PubMed Central

    de Wild, Martijn; Pomp, Wim; Koenderink, Gijsje H.

    2013-01-01

    Collagen fibrils form extracellular networks that regulate cell functions and provide mechanical strength to tissues. Collagen fibrillogenesis is an entropy-driven process promoted by warming and reversed by cooling. Here, we investigate the influence of noncovalent interactions mediated by the collagen triple helix on fibril stability. We measure the kinetics of cold-induced disassembly of fibrils formed from purified collagen I using turbimetry, probe the fibril morphology by atomic force microscopy, and measure the network connectivity by confocal microscopy and rheometry. We demonstrate that collagen fibrils disassemble by subunit release from their sides as well as their ends, with complex kinetics involving an initial fast release followed by a slow release. Surprisingly, the fibrils are gradually stabilized over time, leading to thermal memory. This dynamic stabilization may reflect structural plasticity of the collagen fibrils arising from their complex structure. In addition, we propose that the polymeric nature of collagen monomers may lead to slow kinetics of subunit desorption from the fibril surface. Dynamic stabilization of fibrils may be relevant in the initial stages of collagen assembly during embryogenesis, fibrosis, and wound healing. Moreover, our results are relevant for tissue repair and drug delivery applications, where it is crucial to control fibril stability. PMID:23823240

  6. Structural investigations on native collagen type I fibrils using AFM

    SciTech Connect

    Strasser, Stefan; Zink, Albert; Janko, Marek; Heckl, Wolfgang M.; Thalhammer, Stefan . E-mail: stefan.thalhammer@gsf.de

    2007-03-02

    This study was carried out to determine the elastic properties of single collagen type I fibrils with the use of atomic force microscopy (AFM). Native collagen fibrils were formed by self-assembly in vitro characterized with the AFM. To confirm the inner assembly of the collagen fibrils, the AFM was used as a microdissection tool. Native collagen type I fibrils were dissected and the inner core uncovered. To determine the elastic properties of collagen fibrils the tip of the AFM was used as a nanoindentor by recording force-displacement curves. Measurements were done on the outer shell and in the core of the fibril. The structural investigations revealed the banding of the shell also in the core of native collagen fibrils. Nanoindentation experiments showed the same Young's modulus on the shell as well as in the core of the investigated native collagen fibrils. In addition, the measurements indicate a higher adhesion in the core of the collagen fibrils compared to the shell.

  7. Micromechanical analysis of native and cross-linked collagen type I fibrils supports the existence of microfibrils.

    PubMed

    Yang, L; van der Werf, K O; Dijkstra, P J; Feijen, J; Bennink, M L

    2012-02-01

    The mechanical properties of individual collagen fibrils of approximately 200 nm in diameter were determined using a slightly adapted AFM system. Single collagen fibrils immersed in PBS buffer were attached between an AFM cantilever and a glass surface to perform tensile tests at different strain rates and stress relaxation measurements. The stress-strain behavior of collagen fibrils immersed in PBS buffer comprises a toe region up to a stress of 5 MPa, followed by the heel and linear region at higher stresses. Hysteresis and strain-rate dependent stress-strain behavior of collagen fibrils were observed, which suggest that single collagen fibrils have viscoelastic properties. The stress relaxation process of individual collagen fibrils could be best fitted using a two-term Prony series. Furthermore, the influence of different cross-linking agents on the mechanical properties of single collagen fibrils was investigated. Based on these results, we propose that sliding of microfibrils with respect to each other plays a role in the viscoelastic behavior of collagen fibrils in addition to the sliding of collagen molecules with respect to each other. Our finding provides a better insight into the relationship between the structure and mechanical properties of collagen and the micro-mechanical behavior of tissues. PMID:22301184

  8. Poisson's ratio of collagen fibrils measured by small angle X-ray scattering of strained bovine pericardium

    SciTech Connect

    Wells, Hannah C.; Sizeland, Katie H.; Kayed, Hanan R.; Haverkamp, Richard G.; Kirby, Nigel; Hawley, Adrian; Mudie, Stephen T.

    2015-01-28

    Type I collagen is the main structural component of skin, tendons, and skin products, such as leather. Understanding the mechanical performance of collagen fibrils is important for understanding the mechanical performance of the tissues that they make up, while the mechanical properties of bulk tissue are well characterized, less is known about the mechanical behavior of individual collagen fibrils. In this study, bovine pericardium is subjected to strain while small angle X-ray scattering (SAXS) patterns are recorded using synchrotron radiation. The change in d-spacing, which is a measure of fibril extension, and the change in fibril diameter are determined from SAXS. The tissue is strained 0.25 (25%) with a corresponding strain in the collagen fibrils of 0.045 observed. The ratio of collagen fibril width contraction to length extension, or the Poisson's ratio, is 2.1 ± 0.7 for a tissue strain from 0 to 0.25. This Poisson's ratio indicates that the volume of individual collagen fibrils decreases with increasing strain, which is quite unlike most engineering materials. This high Poisson's ratio of individual fibrils may contribute to high Poisson's ratio observed for tissues, contributing to some of the remarkable properties of collagen-based materials.

  9. Poisson's ratio of collagen fibrils measured by small angle X-ray scattering of strained bovine pericardium

    NASA Astrophysics Data System (ADS)

    Wells, Hannah C.; Sizeland, Katie H.; Kayed, Hanan R.; Kirby, Nigel; Hawley, Adrian; Mudie, Stephen T.; Haverkamp, Richard G.

    2015-01-01

    Type I collagen is the main structural component of skin, tendons, and skin products, such as leather. Understanding the mechanical performance of collagen fibrils is important for understanding the mechanical performance of the tissues that they make up, while the mechanical properties of bulk tissue are well characterized, less is known about the mechanical behavior of individual collagen fibrils. In this study, bovine pericardium is subjected to strain while small angle X-ray scattering (SAXS) patterns are recorded using synchrotron radiation. The change in d-spacing, which is a measure of fibril extension, and the change in fibril diameter are determined from SAXS. The tissue is strained 0.25 (25%) with a corresponding strain in the collagen fibrils of 0.045 observed. The ratio of collagen fibril width contraction to length extension, or the Poisson's ratio, is 2.1 ± 0.7 for a tissue strain from 0 to 0.25. This Poisson's ratio indicates that the volume of individual collagen fibrils decreases with increasing strain, which is quite unlike most engineering materials. This high Poisson's ratio of individual fibrils may contribute to high Poisson's ratio observed for tissues, contributing to some of the remarkable properties of collagen-based materials.

  10. Molecular packing in bone collagen fibrils prior to mineralization

    NASA Astrophysics Data System (ADS)

    Hsiao, Benjamin; Zhou, Hong-Wen; Burger, Christian; Chu, Benjamin; Glimcher, Melvin J.

    2012-02-01

    The three-dimensional packing of collagen molecules in bone collagen fibrils has been largely unknown because even in moderately mineralized bone tissues, the organic matrix structure is severely perturbed by the deposition of mineral crystals. During the past decades, the structure of tendon collagen (e.g. rat tail) --- a tissue that cannot mineralize in vivo, has been assumed to be representative for bone collagen fibrils. Small-angle X-ray diffraction analysis of the native, uncalcified intramuscular fish bone has revealed a new molecular packing scheme, significantly different from the quasi-hexagonal arrangement often found in tendons. The deduced structure in bone collagen fibrils indicates the presence of spatially discrete microfibrils, and an arrangement of intrafibrillar space to form ``channels'', which could accommodate crystals with dimensions typically found in bone apatite.

  11. Fracture Mechanics of Collagen Fibrils: Influence of Natural Cross-Links

    PubMed Central

    Svensson, Rene B.; Mulder, Hindrik; Kovanen, Vuokko; Magnusson, S. Peter

    2013-01-01

    Tendons are important load-bearing structures, which are frequently injured in both sports and work. Type I collagen fibrils are the primary components of tendons and carry most of the mechanical loads experienced by the tissue, however, knowledge of how load is transmitted between and within fibrils is limited. The presence of covalent enzymatic cross-links between collagen molecules is an important factor that has been shown to influence mechanical behavior of the tendons. To improve our understanding of how molecular bonds translate into tendon mechanics, we used an atomic force microscopy technique to measure the mechanical behavior of individual collagen fibrils loaded to failure. Fibrils from human patellar tendons, rat-tail tendons (RTTs), NaBH4 reduced RTTs, and tail tendons of Zucker diabetic fat rats were tested. We found a characteristic three-phase stress-strain behavior in the human collagen fibrils. There was an initial rise in modulus followed by a plateau with reduced modulus, which was finally followed by an even greater increase in stress and modulus before failure. The RTTs also displayed the initial increase and plateau phase, but the third region was virtually absent and the plateau continued until failure. The importance of cross-link lability was investigated by NaBH4 reduction of the rat-tail fibrils, which did not alter their behavior. These findings shed light on the function of cross-links at the fibril level, but further studies will be required to establish the underlying mechanisms. PMID:23746520

  12. Collagen fibrils as skeletal frame in monkey trabecular meshwork.

    PubMed

    Nishida, S; Mizutani, S

    1994-01-01

    In an attempt to identify the characteristic skeletal frame of the trabecular meshwork, the three-dimensional architecture of collagen fibrillar bundles (collagen bundles) was studied by applying the NaOH cell-maceration method to the anterior segment of cynomolgus monkey eyes. Collagen bundles in the trabecular meshwork were found to be continuous with thinner collagen lamellae in the peripheral cornea and with the collagen fibril plexus in the ciliary body. The collagen core in the uveal cord was columnar in shape and was arranged parallel to the long axis. Collagen bundles were arranged as the layered network forming the fundamental framework of the trabecular meshwork. Most collagen bundles of the corneoscleral sheet were arranged circularly, parallel to the circumference of the limbus, and numerous slender bundles were observed side by side, forming the flat and membranous configuration of the sheet. The endothelial meshwork consisted of a network of fine and sparse collagen fibrils forming extracellular spaces and intercommunicating openings. The inner wall of the canal of Schlemm was seen as a netlike surface of sparse collagen fibrils with variously sized circular openings. The openings suggested the possibility that development of giant vacuoles corresponds to the circular openings under the inner endothelial cell lining. PMID:7933694

  13. Characterization of type I collagen fibril formation using thioflavin T fluorescent dye.

    PubMed

    Morimoto, Koichi; Kawabata, Kazuya; Kunii, Saori; Hamano, Kaori; Saito, Takuya; Tonomura, Ben'ichiro

    2009-05-01

    Collagen is composed of fibrils that are formed by self-assembly of smaller units, monomers which are triple-helical polypeptide. However, the mechanism of fibril formation at the level of individual molecules has remained to be clarified. We found that the fluorescence of thioflavin T, which has been widely used as a specific dye for amyloid fibrils, also increased by binding with fibrils of atelocollagen prepared from yellowfin tuna skin. There was a linear correlation between the fluorescence increase and the amount of atelocollagen within a collagen concentration range of 0-0.15 mg/ml at pH 6.5 with 50 microM thioflavin T. In contrast, neither actinidain-processed collagen that keeps monomeric nature nor heat-denatured collagen could cause the fluorescence increase of thioflavin T at all. The relationship between the fluorescence increase and thioflavin T concentration was fit to a theoretical binary binding curve. An apparent dissociation constant, K(d), and a maximal fluorescence increase, DeltaF(max), were calculated at various pHs. The values of K(d) and DeltaF(max) were dependent on pH (K(d) was 9.4 microM at pH 6.5). The present finding demonstrates that thioflavin T specifically binds to collagen fibrils and may be used as a sensitive tool for the study of collagen structure. PMID:19204013

  14. Stabilization and Anomalous Hydration of Collagen Fibril under Heating

    PubMed Central

    Gevorkian, Sasun G.; Allahverdyan, Armen E.; Gevorgyan, David S.; Simonian, Aleksandr L.; Hu, Chin-Kun

    2013-01-01

    Background Type I collagen is the most common protein among higher vertebrates. It forms the basis of fibrous connective tissues (tendon, chord, skin, bones) and ensures mechanical stability and strength of these tissues. It is known, however, that separate triple-helical collagen macromolecules are unstable at physiological temperatures. We want to understand the mechanism of collagen stability at the intermolecular level. To this end, we study the collagen fibril, an intermediate level in the collagen hierarchy between triple-helical macromolecule and tendon. Methodology/Principal Finding When heating a native fibril sample, its Young’s modulus decreases in temperature range 20–58°C due to partial denaturation of triple-helices, but it is approximately constant at 58–75°C, because of stabilization by inter-molecular interactions. The stabilization temperature range 58–75°C has two further important features: here the fibril absorbs water under heating and the internal friction displays a peak. We relate these experimental findings to restructuring of collagen triple-helices in fibril. A theoretical description of the experimental results is provided via a generalization of the standard Zimm-Bragg model for the helix-coil transition. It takes into account intermolecular interactions of collagen triple-helices in fibril and describes water adsorption via the Langmuir mechanism. Conclusion/Significance We uncovered an inter-molecular mechanism that stabilizes the fibril made of unstable collagen macromolecules. This mechanism can be relevant for explaining stability of collagen. PMID:24244320

  15. Measurement of the Mechanical Properties of Intact Collagen Fibrils

    NASA Astrophysics Data System (ADS)

    Mercedes, H.; Heim, A.; Matthews, W. G.; Koob, T.

    2006-03-01

    Motivated by the genetic disorder Ehlers-Danlos syndrome (EDS), in which proper collagen synthesis is interrupted, we are investigating the structural and mechanical properties of collagen fibrils. The fibrous glycoprotein collagen is the most abundant protein found in the human body and plays a key role in the extracellular matrix of the connective tissue, the properties of which are altered in EDS. We have selected as our model system the collagen fibrils of the sea cucumber dermis, a naturally mutable tissue. This system allows us to work with native fibrils which have their proteoglycan complement intact, something that is not possible with reconstituted mammalian collagen fibrils. Using atomic force microscopy, we measure, as a function of the concentration of divalent cations, the fibril diameter, its response to force loading, and the changes in its rigidity. Through these experiments, we will shed light on the mechanisms which control the properties of the sea cucumber dermis and hope to help explain the altered connective tissue extracellular matrix properties associated with EDS.

  16. Collagen XII: Protecting bone and muscle integrity by organizing collagen fibrils.

    PubMed

    Chiquet, Matthias; Birk, David E; Bönnemann, Carsten G; Koch, Manuel

    2014-08-01

    Collagen XII, largest member of the fibril-associated collagens with interrupted triple helix (FACIT) family, assembles from three identical α-chains encoded by the COL12A1 gene. The molecule consists of three threadlike N-terminal noncollagenous NC3 domains, joined by disulfide bonds and a short interrupted collagen triple helix toward the C-terminus. Splice variants differ considerably in size and properties: "small" collagen XIIB (220 kDa subunit) is similar to collagen XIV, whereas collagen XIIA (350 kDa) has a much larger NC3 domain carrying glycosaminoglycan chains. Collagen XII binds to collagen I-containing fibrils via its collagenous domain, whereas its large noncollagenous arms interact with other matrix proteins such as tenascin-X. In dense connective tissues and bone, collagen XII is thought to regulate organization and mechanical properties of collagen fibril bundles. Accordingly, recent findings show that collagen XII mutations cause Ehlers-Danlos/myopathy overlap syndrome associated with skeletal abnormalities and muscle weakness in mice and humans. PMID:24801612

  17. Molecules in Focus: Collagen XII: Protecting bone and muscle integrity by organizing collagen fibrils

    PubMed Central

    Chiquet, Matthias; Birk, David E.; Bönnemann, Carsten G.; Koch, Manuel

    2014-01-01

    Collagen XII, largest member of the fibril-associated collagens with interrupted triple helix (FACIT) family, assembles from three identical α-chains encoded by the COL12A1 gene. The molecule consists of three threadlike N-terminal noncollagenous NC3 domains, joined by disulfide bonds and a short interrupted collagen triple helix towards the C-terminus. Splice variants differ considerably in size and properties: "small" collagen XIIB (220 kDa subunit) is similar to collagen XIV, whereas collagen XIIA (350 kDa) has a much larger NC3 domain carrying glycosaminoglycan chains. Collagen XII binds to collagen I-containing fibrils via its collagenous domain, whereas its large noncollagenous arms interact with other matrix proteins such as tenascin-X. In dense connective tissues and bone, collagen XII is thought to regulate organization and mechanical properties of collagen fibril bundles. Accordingly, recent findings show that collagen XII mutations cause Ehlers-Danlos/myopathy overlap syndrome associated with skeletal abnormalities and muscle weakness in mice and humans. PMID:24801612

  18. Effects of photochemical riboflavin-mediated crosslinks on the physical properties of collagen constructs and fibrils.

    PubMed

    Rich, Harvey; Odlyha, Marianne; Cheema, Umber; Mudera, Vivek; Bozec, Laurent

    2014-01-01

    The use of collagen scaffold in tissue engineering is on the rise, as modifications to mechanical properties are becoming more effective in strengthening constructs whilst preserving the natural biocompatibility. The combined technique of plastic compression and cross-linking is known to increase the mechanical strength of the collagen construct. Here, a modified protocol for engineering these collagen constructs is used to bring together a plastic compression method, combined with controlled photochemical crosslinking using riboflavin as a photoinitiator. In order to ascertain the effects of the photochemical crosslinking approach and the impact of the crosslinks created upon the properties of the engineered collagen constructs, the constructs were characterized both at the macroscale and at the fibrillar level. The resulting constructs were found to have a 2.5 fold increase in their Young's modulus, reaching a value of 650 ± 73 kPa when compared to non-crosslinked control collagen constructs. This value is not yet comparable to that of native tendon, but it proves that combining a crosslinking methodology to collagen tissue engineering may offer a new approach to create stronger, biomimetic constructs. A notable outcome of crosslinking collagen with riboflavin is the collagen's greater affinity for water; it was demonstrated that riboflavin crosslinked collagen retains water for a longer period of time compared to non-cross-linked control samples. The affinity of the cross-linked collagen to water also resulted in an increase of individual collagen fibrils' cross-sectional area as function of the crosslinking. These changes in water affinity and fibril morphology induced by the process of crosslinking could indicate that the crosslinked chains created during the photochemical crosslinking process may act as intermolecular hydrophilic nanosprings. These intermolecular nanosprings would be responsible for a change in the fibril morphology to accommodate variable

  19. Interpreting Second-Harmonic Generation Images of Collagen I Fibrils

    PubMed Central

    Williams, Rebecca M.; Zipfel, Warren R.; Webb, Watt W.

    2005-01-01

    Fibrillar collagen, being highly noncentrosymmetric, possesses a tremendous nonlinear susceptibility. As a result, second-harmonic generation (SHG) microscopy of collagen produces extremely bright and robust signals, providing an invaluable tool for imaging tissue structure with submicron resolution. Here we discuss fundamental principles governing SHG phase matching with the tightly focusing optics used in microscopy. Their application to collagen imaging yields several biophysical features characteristic of native collagen structure: SHG radiates from the shell of a collagen fibril, rather than from its bulk. This SHG shell may correspond to the supporting element of the fibril. Physiologically relevant changes in solution ionic strength alter the ratio of forward-to-backward propagating SHG, implying a resulting change in the SHG shell thickness. Fibrillogenesis can be resolved in immature tissue by directly imaging backward-propagating SHG. Such findings are crucial to the design and development of forthcoming diagnostic and research tools. PMID:15533922

  20. Supramolecular assembly of collagen fibrils into collagen fiber in fish scales of red seabream, Pagrus major.

    PubMed

    Youn, Hwa Shik; Shin, Tae Joo

    2009-11-01

    Supramolecular assembly of collagen fibrils into collagen fiber and its distribution in fish scales of red seabream, Pagrus major, were investigated. By virtue of Zernike phase-contrast hard X-ray microscopy, it has been firstly observed that collagen fiber consists of helical substructures of collagen fibrils wrapped with incrustation. As it close to the scalar focus (that is, with aging), loosened- and deteriorated-helical assemblies started to be observed with loosing wrapping incrustation, indicative of the distortion of the basic helical assembly. Various distributions and packing arrangements of collagen fibers were observed dependent on subdivisions of fish scale. Freshly growing edge region of fish scale, embedded into fish skin, showed rarely patched and one directionally arranged collagen fibers, in which specifically triple helical assemblies of collagen fibrils were found. On the contrary, relatively aged region of the rostral field close to the scalar focus displayed randomly directed and densely packed collagen fibers, in which loosened- and deteriorated-helical assemblies of collagen fibrils were mostly found. Our results have demonstrated that hard X-ray microscope can be a powerful tool to study in situ internal structure of biological specimens in an atmospheric pressure. PMID:19666125

  1. Dissolution of type I collagen fibrils by gingival fibroblasts isolated from patients of various periodontitis categories.

    PubMed

    Havemose-Poulsen, A; Holmstrup, P; Stoltze, K; Birkedal-Hansen, H

    1998-07-01

    The classification of periodontitis in various disease categories, including juvenile periodontitis, rapidly progressive adult periodontitis and slowly progressive adult periodontitis is based mainly on differences in disease progression and age group susceptibility. Because dissolution of collagen fibers is an integral part of periodontal attachment loss, we investigated whether the clinical differences among these periodontitis/control groups are reflected in the collagen-degrading activity of gingival fibroblasts isolated from affected tissues. All fibroblast strains isolated from the 4 groups (n = 48) displayed cell-associated collagenolytic activity when seeded in contact with a reconstituted film of type I collagen fibrils. Cells from the control group (n = 14) dissolved the collagen fibril film twice as fast as those from each of the 3 disease groups (juvenile periodontitis (n = 13), rapidly progressive adult periodontitis (n = 7), and slowly progressive adult periodontitis (n = 14)). Both interleukin-1 beta and phorbolester accelerated the rate of dissolution 2-4-fold, but even after cytokine or phorbolester stimulation control cells were still considerably more effective in dissolving the collagen fibrils than cells from the disease groups. The observation made in this study, that dissolution of collagen fibrils by gingival fibroblasts from periodontally diseased individuals is significantly slower than by cells from healthy control subjects, challenges disease paradigms based on a direct relationship between collagenolytic potential and disease activity. PMID:9777595

  2. Viscoelastic behavior of discrete human collagen fibrils.

    PubMed

    Svensson, René B; Hassenkam, Tue; Hansen, Philip; Peter Magnusson, S

    2010-01-01

    Whole tendon and fibril bundles display viscoelastic behavior, but to the best of our knowledge this property has not been directly measured in single human tendon fibrils. In the present work an atomic force microscopy (AFM) approach was used for tensile testing of two human patellar tendon fibrils. Fibrils were obtained from intact human fascicles, without any pre-treatment besides frozen storage. In the dry state a single isolated fibril was anchored to a substrate using epoxy glue, and the end of the fibril was glued on to an AFM cantilever for tensile testing. In phosphate buffered saline, cyclic testing was performed in the pre-yield region at different strain rates, and the elastic response was determined by a stepwise stress relaxation test. The elastic stress-strain response corresponded to a second-order polynomial fit, while the viscous response showed a linear dependence on the strain. The slope of the viscous response showed a strain rate dependence corresponding to a power function of powers 0.242 and 0.168 for the two patellar tendon fibrils, respectively. In conclusion, the present work provides direct evidence of viscoelastic behavior at the single fibril level, which has not been previously measured. PMID:19878908

  3. Surface-Sensitive Raman Spectroscopy of Collagen I Fibrils

    PubMed Central

    Gullekson, Corinne; Lucas, Leanne; Hewitt, Kevin; Kreplak, Laurent

    2011-01-01

    Collagen fibrils are the main constituent of the extracellular matrix surrounding eukaryotic cells. Although the assembly and structure of collagen fibrils is well characterized, very little appears to be known about one of the key determinants of their biological function—namely, the physico-chemical properties of their surface. One way to obtain surface-sensitive structural and chemical data is to take advantage of the near-field nature of surface- and tip-enhanced Raman spectroscopy. Using Ag and Au nanoparticles bound to Collagen type-I fibrils, as well as tips coated with a thin layer of Ag, we obtained Raman spectra characteristic to the first layer of collagen molecules at the surface of the fibrils. The most frequent Raman peaks were attributed to aromatic residues such as phenylalanine and tyrosine. In several instances, we also observed Amide I bands with a full width at half-maximum of 10–30 cm−1. The assignment of these Amide I band positions suggests the presence of 310-helices as well as α- and β-sheets at the fibril's surface. PMID:21463598

  4. Exploring a Role in Tanning for the Gap Region of the Collagen Fibril: Catechin-Collagen Interactions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Electron micrographs of stained collagen fibrils display a pattern of alternating light and dark bands perpendicular to the axis of the collagen fibril. Light bands correspond to regions of more dense lateral packing where adjacent collagen monomers overlap, and dark bands correspond to 'gap' regio...

  5. In Vitro Fracture Testing of Submicron Diameter Collagen Fibril Specimens

    PubMed Central

    Shen, Zhilei Liu; Dodge, Mohammad Reza; Kahn, Harold; Ballarini, Roberto; Eppell, Steven J.

    2010-01-01

    Mechanical testing of collagenous tissues at different length scales will provide improved understanding of the mechanical behavior of structures such as skin, tendon, and bone, and also guide the development of multiscale mechanical models. Using a microelectromechanical-systems (MEMS) platform, stress-strain response curves up to failure of type I collagen fibril specimens isolated from the dermis of sea cucumbers were obtained in vitro. A majority of the fibril specimens showed brittle fracture. Some displayed linear behavior up to failure, while others displayed some nonlinearity. The fibril specimens showed an elastic modulus of 470 ± 410 MPa, a fracture strength of 230 ± 160 MPa, and a fracture strain of 80% ± 44%. The fibril specimens displayed significantly lower elastic modulus in vitro than previously measured in air. Fracture strength/strain obtained in vitro and in air are both significantly larger than those obtained in vacuo, indicating that the difference arises from the lack of intrafibrillar water molecules produced by vacuum drying. Furthermore, fracture strength/strain of fibril specimens were different from those reported for collagenous tissues of higher hierarchical levels, indicating the importance of obtaining these properties at the fibrillar level for multiscale modeling. PMID:20858445

  6. In vitro fracture testing of submicron diameter collagen fibril specimens.

    PubMed

    Shen, Zhilei Liu; Dodge, Mohammad Reza; Kahn, Harold; Ballarini, Roberto; Eppell, Steven J

    2010-09-22

    Mechanical testing of collagenous tissues at different length scales will provide improved understanding of the mechanical behavior of structures such as skin, tendon, and bone, and also guide the development of multiscale mechanical models. Using a microelectromechanical-systems (MEMS) platform, stress-strain response curves up to failure of type I collagen fibril specimens isolated from the dermis of sea cucumbers were obtained in vitro. A majority of the fibril specimens showed brittle fracture. Some displayed linear behavior up to failure, while others displayed some nonlinearity. The fibril specimens showed an elastic modulus of 470 ± 410 MPa, a fracture strength of 230 ± 160 MPa, and a fracture strain of 80% ± 44%. The fibril specimens displayed significantly lower elastic modulus in vitro than previously measured in air. Fracture strength/strain obtained in vitro and in air are both significantly larger than those obtained in vacuo, indicating that the difference arises from the lack of intrafibrillar water molecules produced by vacuum drying. Furthermore, fracture strength/strain of fibril specimens were different from those reported for collagenous tissues of higher hierarchical levels, indicating the importance of obtaining these properties at the fibrillar level for multiscale modeling. PMID:20858445

  7. Constitutive modeling of crimped collagen fibrils in soft tissues.

    PubMed

    Grytz, Rafael; Meschke, Günther

    2009-10-01

    A microstructurally oriented constitutive formulation for the hyperelastic response of crimped collagen fibrils existing in soft connective tissues is proposed. The model is based on observations that collagen fibrils embedded in a soft matrix crimp into a smooth three-dimensional pattern when unloaded. Following ideas presented by Beskos and Jenkins [Beskos, D., Jenkins, J., 1975. A mechanical model for mammalian tendon. ASME Journal of Applied Mechanics 42, 755-758] and Freed and Doehring [Freed, A., Doehring, T., 2005. Elastic model for crimped collagen fibrils. Journal of Biomechanical Engineering 127, 587-593] the collagen fibril crimp is approximated by a cylindrical helix to represent the constitutive behavior of the hierarchical organized substructure of biological tissues at the fibrillar level. The model is derived from the nonlinear axial force-stretch relationship of an extensible helical spring, including the full extension of the spring as a limit case. The geometrically nonlinear solution of the extensible helical spring is carried out by an iterative procedure. The model only requires one material parameter and two geometrical parameters to be determined from experiments. The ability of the proposed model to reproduce the biomechanical response of fibrous tissues is demonstrated for fascicles from rat tail tendons, for porcine cornea strips, and for bovine Achilles tendons. PMID:19627859

  8. Collagen fibril surface displays a constellation of sites capable of promoting fibril assembly, stability, and hemostasis

    SciTech Connect

    Orgel, J.P.; Antipova, O.; Sagi, I.; Bitler, A.; Qiu, D.; Wang, R.; Xu, Y.; San Antonio, J.D.

    2011-12-14

    Fibrillar collagens form the structural basis of organs and tissues including the vasculature, bone, and tendon. They are also dynamic, organizational scaffolds that present binding and recognition sites for ligands, cells, and platelets. We interpret recently published X-ray diffraction findings and use atomic force microscopy data to illustrate the significance of new insights into the functional organization of the collagen fibril. These data indicate that collagen's most crucial functional domains localize primarily to the overlap region, comprising a constellation of sites we call the 'master control region.' Moreover, the collagen's most exposed aspect contains its most stable part - the C-terminal region that controls collagen assembly, cross-linking, and blood clotting. Hidden beneath the fibril surface exists a constellation of 'cryptic' sequences poised to promote hemostasis and cell - collagen interactions in tissue injury and regeneration. These findings begin to address several important, and previously unresolved, questions: How functional domains are organized in the fibril, which domains are accessible, and which require proteolysis or structural trauma to become exposed? Here we speculate as to how collagen fibrillar organization impacts molecular processes relating to tissue growth, development, and repair.

  9. Exploring a role in tanning for the gap region of the collagen fibril

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Three-dimensional structures of fibrillar collagens have been the subject of numerous studies for more than 60 years. Electron micrographs of stained collagen fibrils display a pattern of alternating light and dark bands perpendicular to the axis of the collagen fibril. Light bands correspond to r...

  10. Exploring a role in tanning for the gap region of the collagen fibril

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Three-dimensional structures of fibrillar collagens have been the subject of numerous studies for more than 60 years. Electron micrographs of stained collagen fibrils display a pattern of alternating light and dark bands perpendicular to the axis of the collagen fibril. Light bands correspond to reg...

  11. Small-Angle X-ray Scattering Study of Intramuscular Fish Bone: Collagen Fibril Superstructure Determined from Equidistant Meridional Reflections

    SciTech Connect

    Burger,C.; Zhou, H.; Sics, I.; Hsiao, B.; Chu, B.; Graham, L.; Glimcher, M.

    2008-01-01

    New insights into the bone collagen fibril superstructure have been obtained by novel small-angle X-ray scattering analysis. The analysis was carried out on the small-angle equidistant meridional reflections resulting from the periodic structure of collagen fibrils in their axial direction. Conventional two-dimensional analysis is difficult because of the large discrepancy of longitudinal and lateral length scales for individual fibrils, as well as their preferred orientation. The new approach represents an unapproximated analysis of the equidistant meridional reflections, which takes the exact separation of preferred orientation and fibril size effects into account. The analytical results (e.g. axial period, fibril diameter etc.) agree well with the parameters obtained from transmission electron microscopy.

  12. In vitro formation and thermal transition of novel hybrid fibrils from type I fish scale collagen and type I porcine collagen

    NASA Astrophysics Data System (ADS)

    Chen, Song; Ikoma, Toshiyuki; Ogawa, Nobuhiro; Migita, Satoshi; Kobayashi, Hisatoshi; Hanagata, Nobutaka

    2010-06-01

    Novel type I collagen hybrid fibrils were fabricated by neutralizing a mixture of type I fish scale collagen solution and type I porcine collagen solution with a phosphate buffer saline at 28 °C. Their structure was discussed in terms of the volume ratio of fish/porcine collagen solution. Scanning electron and atomic force micrographs showed that the diameter of collagen fibrils derived from the collagen mixture was larger than those derived from each collagen, and all resultant fibrils exhibited a typical D-periodic unit of ~67 nm, irrespective of volume ratio of both collagens. Differential scanning calorimetry revealed only one endothermic peak for the fibrils derived from collagen mixture or from each collagen solution, indicating that the resultant collagen fibrils were hybrids of type I fish scale collagen and type I porcine collagen.

  13. Candidate Cell and Matrix Interaction Domains on the Collagen Fibril, the Predominant Protein of Vertebrates

    SciTech Connect

    Sweeney, Shawn M.; Orgel, Joseph P.; Fertala, Andrzej; McAuliffe, Jon D.; Turner, Kevin R.; Di Lullo, Gloria A.; Chen, Steven; Antipova, Olga; Perumal, Shiamalee; Ala-Kokko, Leena; Forlinoi, Antonella; Cabral, Wayne A.; Barnes, Aileen M.; Marini, Joan C.; San Antonio, James D.

    2008-07-18

    Type I collagen, the predominant protein of vertebrates, polymerizes with type III and V collagens and non-collagenous molecules into large cable-like fibrils, yet how the fibril interacts with cells and other binding partners remains poorly understood. To help reveal insights into the collagen structure-function relationship, a data base was assembled including hundreds of type I collagen ligand binding sites and mutations on a two-dimensional model of the fibril. Visual examination of the distribution of functional sites, and statistical analysis of mutation distributions on the fibril suggest it is organized into two domains. The 'cell interaction domain' is proposed to regulate dynamic aspects of collagen biology, including integrin-mediated cell interactions and fibril remodeling. The 'matrix interaction domain' may assume a structural role, mediating collagen cross-linking, proteoglycan interactions, and tissue mineralization. Molecular modeling was used to superimpose the positions of functional sites and mutations from the two-dimensional fibril map onto a three-dimensional x-ray diffraction structure of the collagen microfibril in situ, indicating the existence of domains in the native fibril. Sequence searches revealed that major fibril domain elements are conserved in type I collagens through evolution and in the type II/XI collagen fibril predominant in cartilage. Moreover, the fibril domain model provides potential insights into the genotype-phenotype relationship for several classes of human connective tissue diseases, mechanisms of integrin clustering by fibrils, the polarity of fibril assembly, heterotypic fibril function, and connective tissue pathology in diabetes and aging.

  14. Characterization of the viscoelastic behavior of a simplified collagen micro-fibril based on molecular dynamics simulations.

    PubMed

    Ghodsi, Hossein; Darvish, Kurosh

    2016-10-01

    Collagen fibril is a major component of connective tissues such as bone, tendon, blood vessels, and skin. The mechanical properties of this highly hierarchical structure are greatly influenced by the presence of covalent cross-links between individual collagen molecules. This study investigates the viscoelastic behavior of a collagen lysine-lysine cross-link based on creep simulations with applied forces in the range or 10 to 2000pN using steered molecular dynamics (SMD). The viscoelastic model of the cross-link was combined with a system composed by two segments of adjacent collagen molecules hence representing a reduced viscoelastic model for a simplified micro-fibril. It was found that the collagen micro-fibril assembly had a steady-state Young׳s modulus ranging from 2.24 to 3.27GPa, which is in agreement with reported experimental measurements. The propagation of longitudinal force wave along the molecule was implemented by adding a delay element to the model. The force wave speed was found to be correlated with the speed of one-dimensional elastic waves in rods. The presented reduced model with three degrees of freedom can serve as a building block for developing models of the next level of hierarchy, i.e., a collagen fibril. PMID:27341288

  15. Rapid Patterning of 1-D Collagenous Topography as an ECM Protein Fibril Platform for Image Cytometry

    PubMed Central

    Xue, Niannan; Li, Xia; Bertulli, Cristina; Li, Zhaoying; Patharagulpong, Atipat; Sadok, Amine; Huang, Yan Yan Shery

    2014-01-01

    Cellular behavior is strongly influenced by the architecture and pattern of its interfacing extracellular matrix (ECM). For an artificial culture system which could eventually benefit the translation of scientific findings into therapeutic development, the system should capture the key characteristics of a physiological microenvironment. At the same time, it should also enable standardized, high throughput data acquisition. Since an ECM is composed of different fibrous proteins, studying cellular interaction with individual fibrils will be of physiological relevance. In this study, we employ near-field electrospinning to create ordered patterns of collagenous fibrils of gelatin, based on an acetic acid and ethyl acetate aqueous co-solvent system. Tunable conformations of micro-fibrils were directly deposited onto soft polymeric substrates in a single step. We observe that global topographical features of straight lines, beads-on-strings, and curls are dictated by solution conductivity; whereas the finer details such as the fiber cross-sectional profile are tuned by solution viscosity. Using these fibril constructs as cellular assays, we study EA.hy926 endothelial cells' response to ROCK inhibition, because of ROCK's key role in the regulation of cell shape. The fibril array was shown to modulate the cellular morphology towards a pre-capillary cord-like phenotype, which was otherwise not observed on a flat 2-D substrate. Further facilitated by quantitative analysis of morphological parameters, the fibril platform also provides better dissection in the cells' response to a H1152 ROCK inhibitor. In conclusion, the near-field electrospun fibril constructs provide a more physiologically-relevant platform compared to a featureless 2-D surface, and simultaneously permit statistical single-cell image cytometry using conventional microscopy systems. The patterning approach described here is also expected to form the basics for depositing other protein fibrils, seen among

  16. A micro-mechanical model to determine changes of collagen fibrils under cyclic loading

    NASA Astrophysics Data System (ADS)

    Chen, Michelle L.; Susilo, Monica E.; Ruberti, Jeffrey A.; Nguyen, Thao D.

    Dynamic mechanical loading induces growth and remodeling in biological tissues. It can alter the degradation rate and intrinsic mechanical properties of collagen through cellular activity. Experiments showed that repeated cyclic loading of a dense collagen fibril substrate increased collagen stiffness and strength, lengthened the substrate, but did not significantly change the fibril areal fraction or fibril anisotropy (Susilo, et al. ``Collagen Network Hardening Following Cyclic Tensile Loading'', Interface Focus, submitted). We developed a model for the collagen fibril substrate (Tonge, et al. ``A micromechanical modeling study of the mechanical stabilization of enzymatic degradation of collagen tissues'', Biophys J, in press.) to probe whether changes in the fibril morphology and mechanical properties can explain the tissue-level properties observed during cyclic loading. The fibrils were modeled as a continuous distribution of wavy elastica, based on experimental measurements of fibril density and collagen anisotropy, and can experience damage after a critical stress threshold. Other mechanical properties in the model were fit to the stress response measured before and after the extended cyclic loading to determine changes in the strength and stiffness of collagen fibrils.

  17. Collagen fibril architecture, domain organization, and triple-helical conformation govern its proteolysis

    SciTech Connect

    Perumal, Shiamalee; Antipova, Olga; Orgel, Joseph P.R.O.

    2008-06-24

    We describe the molecular structure of the collagen fibril and how it affects collagen proteolysis or 'collagenolysis.' The fibril-forming collagens are major components of all mammalian connective tissues, providing the structural and organizational framework for skin, blood vessels, bone, tendon, and other tissues. The triple helix of the collagen molecule is resistant to most proteinases, and the matrix metalloproteinases that do proteolyze collagen are affected by the architecture of collagen fibrils, which are notably more resistant to collagenolysis than lone collagen monomers. Until now, there has been no molecular explanation for this. Full or limited proteolysis of the collagen fibril is known to be a key process in normal growth, development, repair, and cell differentiation, and in cancerous tumor progression and heart disease. Peptide fragments generated by collagenolysis, and the conformation of exposed sites on the fibril as a result of limited proteolysis, regulate these processes and that of cellular attachment, but it is not known how or why. Using computational and molecular visualization methods, we found that the arrangement of collagen monomers in the fibril (its architecture) protects areas vulnerable to collagenolysis and strictly governs the process. This in turn affects the accessibility of a cell interaction site located near the cleavage region. Our observations suggest that the C-terminal telopeptide must be proteolyzed before collagenase can gain access to the cleavage site. Collagenase then binds to the substrate's 'interaction domain,' which facilitates the triple-helix unwinding/dissociation function of the enzyme before collagenolysis.

  18. Tyrosine-rich acidic matrix protein (TRAMP) accelerates collagen fibril formation in vitro.

    PubMed

    MacBeath, J R; Shackleton, D R; Hulmes, D J

    1993-09-15

    Tyrosine-rich acidic matrix protein (TRAMP) is a recently discovered protein that co-purifies with porcine skin lysyl oxidase and is equivalent to the M(r) 22,000 extracellular matrix protein from bovine skin that co-purifies with dermatan sulfate proteoglycans (Cronshaw, A. D., MacBeath, J. R. E., Shackleton, D. R., Collins, J. F., Fothergill-Gilmore, L. A., and Hulmes, D. J. S. (1993) Matrix 13, 255-266; Neame, P. J., Choi, H. U., and Rosenberg, L. C. (1989) J. Biol. Chem. 264, 5474-5479). The effect of TRAMP on collagen fibril formation was studied in vitro by reconstitution of fibrils from lathyritic rat skin collagen I. Fibril formation was initiated by the warm start procedure, in which acidic collagen solutions and double strength neutral buffer, both preincubated separately at 34 degrees C, were mixed. When monitored by turbidimetry, TRAMP was found to accelerate collagen fibril formation. Acceleration occurred at sub-stoichiometric molar ratios of TRAMP collagen, and the presence of TRAMP stabilized the fibrils against low temperature dissociation. It was confirmed by centrifugation that the amount of fibrillar collagen formed in the presence of TRAMP was greater than in its absence. By SDS-polyacrylamide gel electrophoresis and scanning densitometry, binding of TRAMP to collagen was detected that approached saturation with a molar ratio of TRAMP to collagen of approximately 1:2. Fibrils formed in the presence of TRAMP were normal when observed by electron microscopy, although fibril diameters were smaller than the controls. TRAMP was found to partially reverse the inhibitory effects of urea and increased ionic strength on the kinetics of fibril formation, although inhibition by glucose was unaffected. TRAMP also accelerated the assembly of pepsin-treated collagen, where the non-helical, telopeptide regions were partially removed. Acceleration of collagen fibril formation by TRAMP is discussed in the light of the known effects of other extracellular matrix

  19. Coalignment of microtubules, cytokeratin intermediate filaments, and collagen fibrils in a collagen-secreting cell system.

    PubMed

    McBeath, E; Fujiwara, K

    1989-12-01

    The distribution of microtubules and intermediate filaments in the collagen-secreting scleroblasts of the goldfish scale was investigated by immunofluorescence and electron microscopy. Many of the microtubules and cytokeratin type intermediate filaments formed bundles that were aligned with the underlying, parallel collagen fibrils. The intermediate filament bundles were evenly spaced and located adjacent to the basal plasma membrane. The microtubules, on the other hand, were located further away from the membrane, although many were found very close to the intermediate filament bundles. No detectable change was observed in scleroblast microtubules when cells on scales were treated with colchicine or cooled (greater than or equal to 0 degrees C) for up to 1 h. Cells had to be cooled overnight before the microtubules were affected. The final number and length of the microtubules in the cell depended only on the final steady-state temperature and not the temperature history of the scale cell, and steady state was reached more slowly at colder temperatures. The microtubules but not the intermediate filaments rapidly (within 5 min) and reversibly depolymerized when cells were chilled to -2 approximately -4 degrees C. When chilled cells were warmed, the microtubules polymerized back, within 15 min at room temperature, to the same pattern of parallel coalignment with the underlying collagen. They appeared to repolymerize via two different pathways: (1) a radial growth outwards from the microtubule organizing center followed by a progressive realignment with the underlying collagen and (2) a gradual and simultaneous polymerization along cold-stable, antitubulin staining fibers. These fibers were also aligned with the collagen fibrils and may be related to the aligned intermediate filaments. PMID:2483378

  20. Structural changes in collagen fibrils across a mineralized interface revealed by cryo-TEM.

    PubMed

    Quan, Bryan D; Sone, Eli D

    2015-08-01

    The structure of the mineralized collagen fibril, which is the basic building block of mineralized connective tissues, is critical to its function. We use cryo-TEM to study collagen structure at a well-defined hard-soft tissue interface, across which collagen fibrils are continuous, in order to evaluate changes to collagen upon mineralization. To establish a basis for the analysis of collagen banding, we compared cryo-TEM images of rat-tail tendon collagen to a model based on the X-ray structure. While there is close correspondence of periodicity, differences in band intensity indicate fibril regions with high density but lacking order, providing new insight into collagen fibrillar structure. Across a mineralized interface, we show that mineralization results in an axial contraction of the fibril, concomitant with lateral expansion, and that this contraction occurs only in the more flexible gap region of the fibril. Nevertheless, the major features of the banding pattern are not significantly changed, indicating that the axial arrangement of molecules remains largely intact. These results suggest a mechanism by which collagen fibrils are able to accommodate large amounts of mineral without significant disruption of their molecular packing, leading to synergy of mechanical properties. PMID:25892483

  1. Enzyme-etching technique to fabricate micropatterns of aligned collagen fibrils

    PubMed Central

    Liu, Honghai; Chen, Ruikai; Yang, Huaxiao; Qin, Wan; Borg, Thomas K.; Dean, Delphine; Xu, Meifeng; Gao, Bruce Z.

    2014-01-01

    A technique to tailor-make pre-coated, pre-aligned bovine collagen fibrils, derived from neonatal cardiomyocytes, on the surface of a glass slide into a designated pattern is reported. The unwanted collagen-coated area was erased by a collagenase solution and the tailored area was retained by attaching a microfabricated polydimethylsiloxane stamp directly to the collagen-coated surface. Using this technique, collagen patterns with designated orientations and with clear pattern boundaries and defined shapes were fabricated. PMID:24562408

  2. An equilibrium double-twist model for the radial structure of collagen fibrils.

    PubMed

    Brown, Aidan I; Kreplak, Laurent; Rutenberg, Andrew D

    2014-11-14

    Mammalian tissues contain networks and ordered arrays of collagen fibrils originating from the periodic self-assembly of helical 300 nm long tropocollagen complexes. The fibril radius is typically between 25 to 250 nm, and tropocollagen at the surface appears to exhibit a characteristic twist-angle with respect to the fibril axis. Similar fibril radii and twist-angles at the surface are observed in vitro, suggesting that these features are controlled by a similar self-assembly process. In this work, we propose a physical mechanism of equilibrium radius control for collagen fibrils based on a radially varying double-twist alignment of tropocollagen within a collagen fibril. The free-energy of alignment is similar to that of liquid crystalline blue phases, and we employ an analytic Euler-Lagrange and numerical free energy minimization to determine the twist-angle between the molecular axis and the fibril axis along the radial direction. Competition between the different elastic energy components, together with a surface energy, determines the equilibrium radius and twist-angle at the fibril surface. A simplified model with a twist-angle that is linear with radius is a reasonable approximation in some parameter regimes, and explains a power-law dependence of radius and twist-angle at the surface as parameters are varied. Fibril radius and twist-angle at the surface corresponding to an equilibrium free-energy minimum are consistent with existing experimental measurements of collagen fibrils. Remarkably, in the experimental regime, all of our model parameters are important for controlling equilibrium structural parameters of collagen fibrils. PMID:25238208

  3. Determination of the elastic modulus of native collagen fibrils via radial indentation

    NASA Astrophysics Data System (ADS)

    Heim, August J.; Matthews, William G.; Koob, Thomas J.

    2006-10-01

    The authors studied the elastic response of single, native collagen fibrils extracted from tissues of the inner dermis of the sea cucumber, Cucumaria frondosa, via local nanoscale indentation with an atomic force microscope (AFM). AFM imaging of fibrils under ambient conditions are presented, demonstrating a peak-to-peak periodicity, the d band, of dehydrated, unfixed fibrils to be ˜64.5nm. Radial indentation experiments were performed, and the measured value for the reduced modulus is 1-2GPa.

  4. Chondroitin sulfate perlecan enhances collagen fibril formation. Implications for perlecan chondrodysplasias.

    PubMed

    Kvist, Alexander J; Johnson, Anna E; Mörgelin, Matthias; Gustafsson, Erika; Bengtsson, Eva; Lindblom, Karin; Aszódi, Attila; Fässler, Reinhard; Sasaki, Takako; Timpl, Rupert; Aspberg, Anders

    2006-11-01

    Inactivation of the perlecan gene leads to perinatal lethal chondrodysplasia. The similarity to the phenotypes of the Col2A1 knock-out and the disproportionate micromelia mutation suggests perlecan involvement in cartilage collagen matrix assembly. We now present a mechanism for the defect in collagen type II fibril assembly by perlecan-null chondrocytes. Cartilage perlecan is a heparin sulfate or a mixed heparan sulfate/chondroitin sulfate proteoglycan. The latter form binds collagen and accelerates fibril formation in vitro, with more defined fibril morphology and increased fibril diameters produced in the presence of perlecan. Interestingly, the enhancement of collagen fibril formation is independent on the core protein and is mimicked by chondroitin sulfate E but neither by chondroitin sulfate D nor dextran sulfate. Furthermore, perlecan chondroitin sulfate contains the 4,6-disulfated disaccharides typical for chondroitin sulfate E. Indeed, purified glycosaminoglycans from perlecan-enriched fractions of cartilage extracts contain elevated levels of 4,6-disulfated chondroitin sulfate disaccharides and enhance collagen fibril formation. The effect on collagen assembly is proportional to the content of the 4,6-disulfated disaccharide in the different cartilage extracts, with growth plate cartilage glycosaminoglycan being the most efficient enhancer. These findings demonstrate a role for perlecan chondroitin sulfate side chains in cartilage extracellular matrix assembly and provide an explanation for the perlecan-null chondrodysplasia. PMID:16956876

  5. Thermal denaturation behavior of collagen fibrils in wet and dry environment.

    PubMed

    Suwa, Yosuke; Nam, Kwangwoo; Ozeki, Kazuhide; Kimura, Tsuyoshi; Kishida, Akio; Masuzawa, Toru

    2016-04-01

    We have developed a new minimally invasive technique--integrated low-level energy adhesion technique (ILEAT)--which uses heat, pressure, and low-frequency vibrations for binding living tissues. Because the adhesion mechanism of the living tissues is not fully understood, we investigated the effect of thermal energy on the collagen structure in living tissues using ILEAT. To study the effect of thermal energy and heating time on the structure of the collagen fibril, samples were divided in two categories-wet and dry. Further, atomic force microscopy was used to analyze the collagen fibril structure before and after heating. Results showed that collagen fibrils in water denatured after 1 minute at temperatures higher than 80 °C, while partial denaturation was observed at temperatures of 80 °C and a heating time of 1 min. Furthermore, complete denaturation was achieved after 90 min, suggesting that the denaturation rate is temperature and time dependent. Moreover, the collagen fibrils in dry condition maintained their native structure even after being heated to 120 °C for 90 min in the absence of water, which specifically suppressed denaturation. However, partial denaturation of collagen fibrils could not be prevented, because this determines the adhesion between the collagen molecules, and stabilizes tissue bonding. PMID:25952296

  6. Second harmonic generation quantitative measurements on collagen fibrils through correlation to electron microscopy

    NASA Astrophysics Data System (ADS)

    Bancelin, S.; Aimé, C.; Gusachenko, I.; Kowalczuk, L.; Latour, G.; Coradin, T.; Schanne-Klein, M.-C.

    2015-03-01

    Type I collagen is a major structural protein in mammals that shows highly structured macromolecular organizations specific to each tissue. This biopolymer is synthesized as triple helices, which self-assemble into fibrils (Ø =10-300 nm) and further form various 3D organization. In recent years, Second Harmonic Generation (SHG) microscopy has emerged as a powerful technique to probe in situ the fibrillar collagenous network within tissues. However, this optical technique cannot resolve most of the fibrils and is a coherent process, which has impeded quantitative measurements of the fibril diameter so far. In this study, we correlated SHG microscopy with Transmission Electron Microscopy to determine the sensitivity of SHG microscopy and to calibrate SHG signals as a function of the fibril diameter in reconstructed collagen gels. To that end, we synthetized isolated fibrils with various diameters and successfully imaged the very same fibrils with both techniques, down to 30 nm diameter. We observed that SHG signals scaled as the fourth power of the fibril diameter, as expected from analytical and numerical calculations. This calibration was then applied to diabetic rat cornea in which we successfully recovered the diameter of hyperglycemia-induced fibrils in the Descemet's membrane without having to resolve them. Finally we derived the first hyperpolarizability from a single collagen triple helix which validates the bottom-up approach used to calculate the non-linear response at the fibrillar scale and denotes a parallel alignment of triple helices within the fibrils. These results represent a major step towards quantitative SHG imaging of nm-sized collagen fibrils.

  7. Characterization via atomic force microscopy of discrete plasticity in collagen fibrils from mechanically overloaded tendons: Nano-scale structural changes mimic rope failure.

    PubMed

    Baldwin, Samuel J; Kreplak, Laurent; Lee, J Michael

    2016-07-01

    Tendons exposed to tensile overload show a structural alteration at the fibril scale termed discrete plasticity. Serial kinks appear along individual collagen fibrils that are susceptible to enzymatic digestion and are thermally unstable. Using atomic force microscopy we mapped the topography and mechanical properties in dehydrated and hydrated states of 25 control fibrils and 25 fibrils displaying periodic kinks, extracted from overloaded bovine tail tendons. Using the measured modulus of the hydrated fibrils as a probe of molecular density, we observed a non-linear negative correlation between molecular density and kink density of individual fibrils. This is accompanied by an increase in water uptake with kink density and a doubling of the coefficient of variation of the modulus between kinked, and control fibrils. The mechanical property maps of kinked collagen fibrils show radial heterogeneity that can be modeled as a high-density core surrounded by a low-density shell. The core of the fibril contains the kink structures characteristic of discrete plasticity; separated by inter-kink regions, which often retain the D-banding structure. We propose that the shell and kink structures mimic characteristic damage motifs observed in laid rope strands. PMID:26925699

  8. Nanoscale characterization of the biomechanical properties of collagen fibrils in the sclera

    SciTech Connect

    Papi, M.; Paoletti, P.; Geraghty, B.; Akhtar, R.

    2014-03-10

    We apply the PeakForce Quantitative Nanomechanical Property Mapping (PFQNM) atomic force microscopy mode for the investigation of regional variations in the nanomechanical properties of porcine sclera. We examine variations in the collagen fibril diameter, adhesion, elastic modulus and dissipation in the posterior, equatorial and anterior regions of the sclera. The mean fibril diameter, elastic modulus and dissipation increased from the posterior to the anterior region. Collagen fibril diameter correlated linearly with elastic modulus. Our data matches the known macroscopic mechanical behavior of the sclera. We propose that PFQNM has significant potential in ocular biomechanics and biophysics research.

  9. Bowstring Stretching and Quantitative Imaging of Single Collagen Fibrils via Atomic Force Microscopy.

    PubMed

    Quigley, Andrew S; Veres, Samuel P; Kreplak, Laurent

    2016-01-01

    Collagen is the primary structural protein in animals. Serving as nanoscale biological ropes, collagen fibrils are responsible for providing strength to a variety of connective tissues such as tendon, skin, and bone. Understanding structure-function relationships in collagenous tissues requires the ability to conduct a variety of mechanical experiments on single collagen fibrils. Though significant advances have been made, certain tests are not possible using the techniques currently available. In this report we present a new atomic force microscopy (AFM) based method for tensile manipulation and subsequent nanoscale structural assessment of single collagen fibrils. While the method documented here cannot currently capture force data during loading, it offers the great advantage of allowing structural assessment after subrupture loading. To demonstrate the utility of this technique, we describe the results of 23 tensile experiments in which collagen fibrils were loaded to varying levels of strain and subsequently imaged in both the hydrated and dehydrated states. We show that following a dehydration-rehydration cycle (necessary for sample preparation), fibrils experience an increase in height and decrease in radial modulus in response to one loading-unloading cycle to strain <5%. This change is not altered by a second cycle to strain >5%. In fibril segments that ruptured during their second loading cycle, we show that the fibril structure is affected away from the rupture site in the form of discrete permanent deformations. By comparing the severity of select damage sites in both hydrated and dehydrated conditions, we demonstrate that dehydration masks damage features, leading to an underestimate of the degree of structural disruption. Overall, the method shows promise as a powerful tool for the investigation of structure-function relationships in nanoscale fibrous materials. PMID:27598334

  10. Decorin Core Protein (Decoron) Shape Complements Collagen Fibril Surface Structure and Mediates Its Binding

    SciTech Connect

    Orgel, Joseph P.R.O.; Eid, Aya; Antipova, Olga; Bella, Jordi; Scott, John E.

    2010-02-11

    Decorin is the archetypal small leucine rich repeat proteoglycan of the vertebrate extracellular matrix (ECM). With its glycosaminoglycuronan chain, it is responsible for stabilizing inter-fibrillar organization. Type I collagen is the predominant member of the fibrillar collagen family, fulfilling both organizational and structural roles in animal ECMs. In this study, interactions between decoron (the decorin core protein) and binding sites in the d and e1 bands of the type I collagen fibril were investigated through molecular modeling of their respective X-ray diffraction structures. Previously, it was proposed that a model-based, highly curved concave decoron interacts with a single collagen molecule, which would form extensive van der Waals contacts and give rise to strong non-specific binding. However, the large well-ordered aggregate that is the collagen fibril places significant restraints on modes of ligand binding and necessitates multi-collagen molecular contacts. We present here a relatively high-resolution model of the decoron-fibril collagen complex. We find that the respective crystal structures complement each other well, although it is the monomeric form of decoron that shows the most appropriate shape complementarity with the fibril surface and favorable calculated energies of interaction. One molecule of decoron interacts with four to six collagen molecules, and the binding specificity relies on a large number of hydrogen bonds and electrostatic interactions, primarily with the collagen motifs KXGDRGE and AKGDRGE (d and e{sub 1} bands). This work helps us to understand collagen-decorin interactions and the molecular architecture of the fibrillar ECM in health and disease.

  11. 3D Raman mapping of the collagen fibril orientation in human osteonal lamellae.

    PubMed

    Schrof, Susanne; Varga, Peter; Galvis, Leonardo; Raum, Kay; Masic, Admir

    2014-09-01

    Chemical composition and fibrillar organization are the major determinants of osteonal bone mechanics. However, prominent methodologies commonly applied to investigate mechanical properties of bone on the micro scale are usually not able to concurrently describe both factors. In this study, we used polarized Raman spectroscopy (PRS) to simultaneously analyze structural and chemical information of collagen fibrils in human osteonal bone in a single experiment. Specifically, the three-dimensional arrangement of collagen fibrils in osteonal lamellae was assessed. By analyzing the anisotropic intensity of the amide I Raman band of collagen as a function of the orientation of the incident laser polarization, different parameters related to the orientation of the collagen fibrils and the degree of alignment of the fibrils were derived. Based on the analysis of several osteons, two major fibrillar organization patterns were identified, one with a monotonic and another with a periodically changing twist direction. These results confirm earlier reported twisted and oscillating plywood arrangements, respectively. Furthermore, indicators of the degree of alignment suggested the presence of disordered collagen within the lamellar organization of the osteon. The results show the versatility of the analytical PRS approach and demonstrate its capability in providing not only compositional, but also 3D structural information in a complex hierarchically structured biological material. The concurrent assessment of chemical and structural features may contribute to a comprehensive characterization of the microstructure of bone and other collagen-based tissues. PMID:25025981

  12. Nanostructural and nanomechanical responses of collagen fibrils in the collagenase-induced Achilles tendinitis rat model.

    PubMed

    Lee, Gi-Ja; Choi, Samjin; Chon, Jinmann; Yoo, Seung Don; Kim, Hee-Sang; Park, Hun-Kuk; Chung, Joo Ho

    2013-11-01

    Achilles tendons are vulnerable to acute or chronic injuries that lead to inflammation. We investigated nanostructural and nanomechanical changes in collagen fibrils from rat Achilles tendons over a period of 9 weeks after injury using atomic force microscopy (AFM). To evaluate the nanostructural changes in Achilles tendons, we measured the diameter and D-banding of collagen fibrils by AFM. And the adhesion forces, which were related to cross-linking of collagen, were calculated from the retraction process of a force-distance curve. We successfully observed the time course of changes in collagen fibrils during healing using AFM. The diameters and D-banding in healed tendons were similar to those of uninjured tendons at 9 weeks after injury, but the adhesion forces remained different from those of uninjured tendons. Our AFM results depicted the minute changes in Achilles tendon surface by natural healing quite well, even drawbacks to naturally healed tendon. Understanding changes in collagen cross-linking and structure while healing will lead to better understanding of healing mechanisms and subsequent improvements in treatment. And AFM can be applied as powerful tool to evaluate structural and property changes in collagen fibrils before and after injury and/or treatment in Achilles tendon. PMID:24245243

  13. Intracellular collagen fibrils: evidence of an intracellular source from experiments with tendon fibroblasts and fibroblastic tumour cells.

    PubMed Central

    Michna, H

    1988-01-01

    This study was designed to substantiate one or both of the two hypotheses for the explanation of intracellular collagen fibrils in collagen-producing cells. The more obvious is the phagocytosis of extracellular collagen fibrils by the cell and the other is a form of autophagocytosis of newly synthesised collagenous products. Information was collected on fibroblasts from murine tendons after exercise and simultaneously stimulating collagen synthesis by treatment with an anabolic steroid hormone. Moreover, in vivo and in vitro fibroblastic tumour cells which demonstrate enhanced protein synthesis were also treated with the anabolic steroid. The findings of intracellular collagen fibrils in tendon fibroblasts and the sarcoma cells after experimentally stimulating collagen synthesis are discussed in the light of the hypothesis that the findings may represent steps of autophagocytosis of newly synthesised collagenous products in the absence of a control mechanism to remove collagenous products which cannot be secreted. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 PMID:3225213

  14. Techniques to assess bone ultrastructure organization: orientation and arrangement of mineralized collagen fibrils.

    PubMed

    Georgiadis, Marios; Müller, Ralph; Schneider, Philipp

    2016-06-01

    Bone's remarkable mechanical properties are a result of its hierarchical structure. The mineralized collagen fibrils, made up of collagen fibrils and crystal platelets, are bone's building blocks at an ultrastructural level. The organization of bone's ultrastructure with respect to the orientation and arrangement of mineralized collagen fibrils has been the matter of numerous studies based on a variety of imaging techniques in the past decades. These techniques either exploit physical principles, such as polarization, diffraction or scattering to examine bone ultrastructure orientation and arrangement, or directly image the fibrils at the sub-micrometre scale. They make use of diverse probes such as visible light, X-rays and electrons at different scales, from centimetres down to nanometres. They allow imaging of bone sections or surfaces in two dimensions or investigating bone tissue truly in three dimensions, in vivo or ex vivo, and sometimes in combination with in situ mechanical experiments. The purpose of this review is to summarize and discuss this broad range of imaging techniques and the different modalities of their use, in order to discuss their advantages and limitations for the assessment of bone ultrastructure organization with respect to the orientation and arrangement of mineralized collagen fibrils. PMID:27335222

  15. Techniques to assess bone ultrastructure organization: orientation and arrangement of mineralized collagen fibrils

    PubMed Central

    Georgiadis, Marios; Müller, Ralph; Schneider, Philipp

    2016-01-01

    Bone's remarkable mechanical properties are a result of its hierarchical structure. The mineralized collagen fibrils, made up of collagen fibrils and crystal platelets, are bone's building blocks at an ultrastructural level. The organization of bone's ultrastructure with respect to the orientation and arrangement of mineralized collagen fibrils has been the matter of numerous studies based on a variety of imaging techniques in the past decades. These techniques either exploit physical principles, such as polarization, diffraction or scattering to examine bone ultrastructure orientation and arrangement, or directly image the fibrils at the sub-micrometre scale. They make use of diverse probes such as visible light, X-rays and electrons at different scales, from centimetres down to nanometres. They allow imaging of bone sections or surfaces in two dimensions or investigating bone tissue truly in three dimensions, in vivo or ex vivo, and sometimes in combination with in situ mechanical experiments. The purpose of this review is to summarize and discuss this broad range of imaging techniques and the different modalities of their use, in order to discuss their advantages and limitations for the assessment of bone ultrastructure organization with respect to the orientation and arrangement of mineralized collagen fibrils. PMID:27335222

  16. Extracellular compartments in matrix morphogenesis: collagen fibril, bundle, and lamellar formation by corneal fibroblasts.

    PubMed

    Birk, D E; Trelstad, R L

    1984-12-01

    The regulation of collagen fibril, bundle, and lamella formation by the corneal fibroblasts, as well as the organization of these elements into an orthogonal stroma, was studied by transmission electron microscopy and high voltage electron microscopy. Transmission and high voltage electron microscopy of chick embryo corneas each demonstrated a series of unique extracellular compartments. Collagen fibrillogenesis occurred within small surface recesses. These small recesses usually contained between 5 and 12 collagen fibrils with typically mature diameters and constant intrafibrillar spacing. The lateral fusion of the recesses resulted in larger recesses and consequent formation of prominent cell surface foldings. Within these surface foldings, bundles that contained 50-100 collagen fibrils were formed. The surface foldings continued to fuse and the cell surface retracted, forming large surface-associated compartments in which bundles coalesced to form lamellae. High voltage electron microscopy of 0.5 micron sections cut parallel to the corneal surface revealed that the corneal fibroblasts and their processes had two major axes at approximately right angles to one another. The surface compartments involved in the production of the corneal stroma were aligned along the fibroblast axes and the orthogonality of the cell was in register with that of the extracellular matrix. In this manner, corneal fibroblasts formed collagen fibrils, bundles, and lamellae within a controlled environment and thereby determined the architecture of the corneal stroma by the configuration of the cell and its associated compartments. PMID:6542105

  17. Second harmonic generation imaging of the collagen in myocardium for atrial fibrillation diagnosis

    NASA Astrophysics Data System (ADS)

    Tsai, Ming-Rung; Chiou, Yu-We; Sun, Chi-Kuang

    2009-02-01

    Myocardial fibrosis, a common sequela of cardiac hypertrophy, has been shown to be associated with arrhythmias in experimental models. Some research has indicated that myocardial fibrosis plays an important role in predisposing patients to atrial fibrillation. Second harmonic generation (SHG) is an optically nonlinear coherent process to image the collagen network. In this presentation, we observe the SHG images of the collagen matrix in atrial myocardium and we analyzed of collagen fibers arrangement by using Fourier-transform analysis. Moreover, comparing the SHG images of the collagen fibers in atrial myocardium between normal sinus rhythm (NSR) and atrial fibrillation (AF), our result indicated that it is possible to realize the relation between myocardial fibrosis and AF.

  18. Effect of γ-PGA on the formation of collagen fibrils in vitro.

    PubMed

    Ding, Cuicui; Zheng, Zhigong; Liu, Xinzhong; Li, Hengda; Zhang, Min

    2016-07-01

    The effect of γ-poly(glutamic acid) (γ-PGA) on the self-assembly of collagen was studied. Under physiological conditions, the kinetic curves for fibril formation showed that the turbidity of collagen/γ-PGA blends at 313 nm was increased with the addition of γ-PGA. Furthermore, it was shown using both field-emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) that fibrils with a larger diameter were obtained following the addition of γ-PGA, probably due to the electrostatic and hydrogen bond interactions between collagen and γ-PGA, which promoted the lateral association of collagen molecules. In addition, both the thermal stability and viscoelastic properties of the hybrid hydrogels, which were evaluated by differential scanning calorimetry and rheological measurements, respectively, were improved by the addition of γ-PGA. PMID:26940941

  19. Structure and formation of the twisted plywood pattern of collagen fibrils in rat lamellar bone.

    PubMed

    Yamamoto, Tsuneyuki; Hasegawa, Tomoka; Sasaki, Muneteru; Hongo, Hiromi; Tabata, Chihiro; Liu, Zhusheng; Li, Minqi; Amizuka, Norio

    2012-04-01

    This study was designed to elucidate details of the structure and formation process of the alternate lamellar pattern known to exist in lamellar bone. For this purpose, we examined basic internal lamellae in femurs of young rats by transmission and scanning electron microscopy, the latter employing two different macerations with NaOH at concentrations of 10 and 24%. Observations after the maceration with 10% NaOH showed that the regular and periodic rotation of collagen fibrils caused an alternation between two types of lamellae: one consisting of transversely and nearly transversely cut fibrils, and the other consisting of longitudinally and nearly longitudinally cut fibrils. This finding confirms the consistency of the twisted plywood model. The maceration method with 24% NaOH removed bone components other than cells, thus allowing for three-dimensional observations of osteoblast morphology. Osteoblasts extended finger-like processes paralleling the inner bone surface, and grouped in such a way that, within a group, the processes arranged in a similar direction. Transmission electron microscopy showed that newly deposited fibrils were arranged alongside these processes. For the formation of the alternating pattern, our findings suggest that: (1) osteoblasts control the collagen fibril arrangement through their finger-like process position; (2) osteoblasts behave similarly within a group; (3) osteoblasts move their processes synchronously and periodically to promote alternating different fibril orientation; and (4) this dynamic sequential deposition of fibrils results in the alternate lamellar (or twisted plywood) pattern. PMID:22362877

  20. Second-harmonic generation imaging of collagen fibers in myocardium for atrial fibrillation diagnosis

    NASA Astrophysics Data System (ADS)

    Tsai, Ming-Rung; Chiu, Yu-Wei; Lo, Men Tzung; Sun, Chi-Kuang

    2010-03-01

    Atrial fibrillation (AF) is the most common irregular heart rhythm and the mortality rate for patients with AF is approximately twice the mortality rate for patients with normal sinus rhythm (NSR). Some research has indicated that myocardial fibrosis plays an important role in predisposing patients to AF. Therefore, realizing the relationship between myocardial collagen fibrosis and AF is significant. Second-harmonic generation (SHG) is an optically nonlinear coherent process to image the collagen network. We perform SHG microscopic imaging of the collagen fibers in the human atrial myocardium. Utilizing the SHG images, we can identify the differences in morphology and the arrangement of collagen fibers between NSR and AF tissues. We also quantify the arrangement of the collagen fibers using Fourier transform images and calculating the values of angle entropy. We indicate that SHG imaging, a nondestructive and reproducible method to analyze the arrangement of collagen fibers, can provide explicit information about the relationship between myocardial fibrosis and AF.

  1. Three-dimensional imaging of collagen fibril organization in rat circumferential lamellar bone using a dual beam electron microscope reveals ordered and disordered sub-lamellar structures.

    PubMed

    Reznikov, Natalie; Almany-Magal, Rotem; Shahar, Ron; Weiner, Steve

    2013-02-01

    Lamellar bone is a major component of most mammalian skeletons. A prominent component of individual lamellae are parallel arrays of mineralized type I collagen fibrils, organized in a plywood like motif. Here we use a dual beam microscope and the serial surface view (SSV) method to investigate the three dimensional collagen organization of circumferential lamellar bone from rat tibiae after demineralization and osmium staining. Fast Fourier transform analysis is used to quantitatively identify the mean collagen array orientations and local collagen fibril dispersion. Based on collagen fibril array orientations and variations in fibril dispersion, we identify 3 distinct sub-lamellar structural motifs: a plywood-like fanning sub-lamella, a unidirectional sub-lamella and a disordered sub-lamella. We also show that the disordered sub-lamella is less mineralized than the other sub-lamellae. The hubs and junctions of the canalicular network, which connect radially oriented canaliculi, are intimately associated with the disordered sub-lamella. We also note considerable variations in the proportions of these 3 sub-lamellar structural elements among different lamellae. This new application of Serial Surface View opens the way to quantitatively compare lamellar bone from different sources, and to clarify the 3-dimensional structures of other bone types, as well as other biological structural materials. PMID:23153959

  2. Rapid oriented fibril formation of fish scale collagen facilitates early osteoblastic differentiation of human mesenchymal stem cells.

    PubMed

    Matsumoto, Rena; Uemura, Toshimasa; Xu, Zhefeng; Yamaguchi, Isamu; Ikoma, Toshiyuki; Tanaka, Junzo

    2015-08-01

    We studied the effect of fibril formation of fish scale collagen on the osteoblastic differentiation of human mesenchymal stem cells (hMSCs). We found that hMSCs adhered easily to tilapia scale collagen, which remarkably accelerated the early stage of osteoblastic differentiation in hMSCs during in vitro cell culture. Osteoblastic markers such as ALP activity, osteopontin, and bone morphogenetic protein 2 were markedly upregulated when the hMSCs were cultured on a tilapia collagen surface, especially in the early osteoblastic differentiation stage. We hypothesized that this phenomenon occurs due to specific fibril formation of tilapia collagen. Thus, we examined the time course of collagen fibril formation using high-speed atomic force microscopy. Moreover, to elucidate the effect of the orientation of fibril formation on the differentiation of hMSCs, we measured ALP activity of hMSCs cultured on two types of tilapia scale collagen membranes with different degrees of fibril formation. The ALP activity in hMSCs cultured on a fibrous collagen membrane was significantly higher than on a non-fibrous collagen membrane even before adding osteoblastic differentiation medium. These results showed that the degree of the fibril formation of tilapia collagen was essential for the osteoblastic differentiation of hMSCs. PMID:25546439

  3. A new model to simulate the elastic properties of mineralized collagen fibril.

    SciTech Connect

    Yuan, F.; Stock, S.R.; Haeffner, D.R.; Almer, J.D.; Dunand , D.C.; Brinson, K.

    2011-01-01

    Bone, because of its hierarchical composite structure, exhibits an excellent combination of stiffness and toughness, which is due substantially to the structural order and deformation at the smaller length scales. Here, we focus on the mineralized collagen fibril, consisting of hydroxyapatite plates with nanometric dimensions aligned within a protein matrix, and emphasize the relationship between the structure and elastic properties of a mineralized collagen fibril. We create two- and three-dimensional representative volume elements to represent the structure of the fibril and evaluate the importance of the parameters defining its structure and properties of the constituent mineral and collagen phase. Elastic stiffnesses are calculated by the finite element method and compared with experimental data obtained by synchrotron X-ray diffraction. The computational results match the experimental data well, and provide insight into the role of the phases and morphology on the elastic deformation characteristics. Also, the effects of water, imperfections in the mineral phase and mineral content outside the mineralized collagen fibril upon its elastic properties are discussed.

  4. A new model to simulate the elastic properties of mineralized collagen fibril

    SciTech Connect

    Yuan, F.; Stock, S.R.; Haeffner, D.R.; Almer, J.D.; Dunand, D.C.; Brinson, L.C.

    2012-05-02

    Bone, because of its hierarchical composite structure, exhibits an excellent combination of stiffness and toughness, which is due substantially to the structural order and deformation at the smaller length scales. Here, we focus on the mineralized collagen fibril, consisting of hydroxyapatite plates with nanometric dimensions aligned within a protein matrix, and emphasize the relationship between the structure and elastic properties of a mineralized collagen fibril. We create two- and three-dimensional representative volume elements to represent the structure of the fibril and evaluate the importance of the parameters defining its structure and properties of the constituent mineral and collagen phase. Elastic stiffnesses are calculated by the finite element method and compared with experimental data obtained by synchrotron X-ray diffraction. The computational results match the experimental data well, and provide insight into the role of the phases and morphology on the elastic deformation characteristics. Also, the effects of water, imperfections in the mineral phase and mineral content outside the mineralized collagen fibril upon its elastic properties are discussed.

  5. High-speed atomic force microscopy reveals strongly polarized movement of clostridial collagenase along collagen fibrils.

    PubMed

    Watanabe-Nakayama, Takahiro; Itami, Masahiro; Kodera, Noriyuki; Ando, Toshio; Konno, Hiroki

    2016-01-01

    Bacterial collagenases involved in donor infection are widely applied in many fields due to their high activity and specificity; however, little is known regarding the mechanisms by which bacterial collagenases degrade insoluble collagen in host tissues. Using high-speed atomic force microscopy, we simultaneously visualized the hierarchical structure of collagen fibrils and the movement of a representative bacterial collagenase, Clostridium histolyticum type I collagenase (ColG), to determine the relationship between collagen structure and collagenase movement. Notably, ColG moved ~14.5 nm toward the collagen N terminus in ~3.8 s in a manner dependent on a catalytic zinc ion. While ColG was engaged, collagen molecules were not only degraded but also occasionally rearranged to thicken neighboring collagen fibrils. Importantly, we found a similarity of relationship between the enzyme-substrate interface structure and enzyme migration in collagen-collagenase and DNA-nuclease systems, which share a helical substrate structure, suggesting a common strategy in enzyme evolution. PMID:27373458

  6. High-speed atomic force microscopy reveals strongly polarized movement of clostridial collagenase along collagen fibrils

    PubMed Central

    Watanabe-Nakayama, Takahiro; Itami, Masahiro; Kodera, Noriyuki; Ando, Toshio; Konno, Hiroki

    2016-01-01

    Bacterial collagenases involved in donor infection are widely applied in many fields due to their high activity and specificity; however, little is known regarding the mechanisms by which bacterial collagenases degrade insoluble collagen in host tissues. Using high-speed atomic force microscopy, we simultaneously visualized the hierarchical structure of collagen fibrils and the movement of a representative bacterial collagenase, Clostridium histolyticum type I collagenase (ColG), to determine the relationship between collagen structure and collagenase movement. Notably, ColG moved ~14.5 nm toward the collagen N terminus in ~3.8 s in a manner dependent on a catalytic zinc ion. While ColG was engaged, collagen molecules were not only degraded but also occasionally rearranged to thicken neighboring collagen fibrils. Importantly, we found a similarity of relationship between the enzyme-substrate interface structure and enzyme migration in collagen-collagenase and DNA-nuclease systems, which share a helical substrate structure, suggesting a common strategy in enzyme evolution. PMID:27373458

  7. Cross-linking connectivity in bone collagen fibrils: the COOH-terminal locus of free aldehyde

    NASA Technical Reports Server (NTRS)

    Otsubo, K.; Katz, E. P.; Mechanic, G. L.; Yamauchi, M.

    1992-01-01

    Quantitative analyses of the chemical state of the 16c residue of the alpha 1 chain of bone collagen were performed on samples from fetal (4-6-month embryo) and mature (2-3 year old) bovine animals. All of this residue could be accounted for in terms of three chemical states, in relative amounts which depended upon the age of the animal. Most of the residue was incorporated into either bifunctional or trifunctional cross-links. Some of it, however, was present as free aldehyde, and the content increased with maturation. This was established by isolating and characterizing the aldehyde-containing peptides generated by tryptic digestion of NaB3H4-reduced mature bone collagen. We have concluded that the connectivity of COOH-terminal cross-linking in bone collagen fibrils changes with maturation in the following way: at first, each 16c residue in each of the two alpha 1 chains of the collagen molecule is incorporated into a sheet-like pattern of intermolecular iminium cross-links, which stabilizes the young, nonmineralized fibril as a whole. In time, some of these labile cross-links maturate into pyridinoline while others dissociate back to their precursor form. The latter is likely due to changes in the molecular packing brought about by the mineralization of the collagen fibrils. The resultant reduction in cross-linking connectivity may provide a mechanism for enhancing certain mechanical characteristics of the skeleton of a mature animal.

  8. Characteristics and Young's Modulus of Collagen Fibrils from Expanded Skin Using Anisotropic Controlled Rate Self-Inflating Tissue Expander.

    PubMed

    Manssor, Nur Aini S; Radzi, Zamri; Yahya, Noor Azlin; Mohamad Yusof, Loqman; Hariri, Firdaus; Khairuddin, Nurul Hayah; Abu Kasim, Noor Hayaty; Czernuszka, Jan T

    2016-01-01

    Mechanical properties of expanded skin tissue are different from normal skin, which is dependent mainly on the structural and functional integrity of dermal collagen fibrils. In the present study, mechanical properties and surface topography of both expanded and nonexpanded skin collagen fibrils were evaluated. Anisotropic controlled rate self-inflating tissue expanders were placed beneath the skin of sheep's forelimbs. The tissue expanders gradually increased in height and reached equilibrium in 2 weeks. They were left in situ for another 2 weeks before explantation. Expanded and normal skin samples were surgically harvested from the sheep (n = 5). Young's modulus and surface topography of collagen fibrils were measured using an atomic force microscope. A surface topographic scan showed organized hierarchical structural levels: collagen molecules, fibrils and fibers. No significant difference was detected for the D-banding pattern: 63.5 ± 2.6 nm (normal skin) and 63.7 ± 2.7 nm (expanded skin). Fibrils from expanded tissues consisted of loosely packed collagen fibrils and the width of the fibrils was significantly narrower compared to those from normal skin: 153.9 ± 25.3 and 106.7 ± 28.5 nm, respectively. Young's modulus of the collagen fibrils in the expanded and normal skin was not statistically significant: 46.5 ± 19.4 and 35.2 ± 27.0 MPa, respectively. In conclusion, the anisotropic controlled rate self-inflating tissue expander produced a loosely packed collagen network and the fibrils exhibited similar D-banding characteristics as the control group in a sheep model. However, the fibrils from the expanded skin were significantly narrower. The stiffness of the fibrils from the expanded skin was higher but it was not statistically different. PMID:26836267

  9. Individualized approaches to thromboprophylaxis in atrial fibrillation.

    PubMed

    Ziff, Oliver J; Camm, A John

    2016-03-01

    Atrial fibrillation (AF) is the most common arrhythmia worldwide. The prevalence of AF in persons older than 55 years is at least 33.5 million globally and is predicted to more than double in the next half-century. Anticoagulation, heart rate control, and heart rhythm control comprise the 3 main treatment strategies in AF. Anticoagulation is aimed at preventing debilitating stroke, systemic embolism, and associated mortality. Historically, anticoagulation in AF was achieved with a vitamin K antagonist such as warfarin, which is supported by evidence demonstrating reduced incident stroke and all-cause mortality. However, warfarin has unpredictable pharmacokinetics with many drug-drug interactions that require regular monitoring to ensure patients remain in the therapeutic anticoagulant range. Non-vitamin K antagonist oral anticoagulants including dabigatran, rivaroxaban, apixaban, and edoxaban provide a possible solution to these issues with their more predictable pharmacokinetics, rapid onset of action, and greater specificity. Results from large randomized, controlled trials indicate that these agents are at least noninferior to warfarin in prevention of stroke. These trials also demonstrate a consistently lower incidence of intracranial hemorrhage, almost always all life-threatening bleeds, and many forms of major bleeds with the possible exception of gastrointestinal and some other forms of mucosal bleeding, compared with warfarin. Patients with AF are a heterogeneous population with diverse risk of stroke and bleeding, and different subgroups respond differently to anticoagulation. Important clinical questions have arisen regarding optimal anticoagulation drug selection in distinct populations such as those with renal impairment, older age, coronary artery disease, and heart failure as well as those at particularly high risk for bleeding or thromboembolism. In this review, treatment strategies in AF management are discussed in the context of different

  10. Acellular and cellular high-density, collagen-fibril constructs with suprafibrillar organization.

    PubMed

    Blum, Kevin M; Novak, Tyler; Watkins, Lauren; Neu, Corey P; Wallace, Joseph M; Bart, Zachary R; Voytik-Harbin, Sherry L

    2016-04-22

    Collagen is used extensively for tissue engineering due to its prevalence in connective tissues and its role in defining tissue biophysical and biological signalling properties. However, traditional collagen-based materials fashioned from atelocollagen and telocollagen have lacked collagen densities, multi-scale organization, mechanical integrity, and proteolytic resistance found within tissues in vivo. Here, highly interconnected low-density matrices of D-banded fibrils were created from collagen oligomers, which exhibit fibrillar as well as suprafibrillar assembly. Confined compression then was applied to controllably reduce the interstitial fluid while maintaining fibril integrity. More specifically, low-density (3.5 mg mL(-1)) oligomer matrices were densified to create collagen-fibril constructs with average concentrations of 12.25 mg mL(-1) and 24.5 mg mL(-1). Control and densified constructs exhibited nearly linear increases in ultimate stress, Young's modulus, and compressive modulus over the ranges of 65 to 213 kPa, 400 to 1.26 MPa, and 20 to 150 kPa, respectively. Densification also increased construct resistance to collagenase degradability. Finally, this process was amenable to creating high-density cellularized tissues; all constructs maintained high cell viability (at least 97%) immediately following compression as well as after 1 day and 7 days of culture. This method, which integrates the suprafibrillar assembly capacity of oligomers and controlled fluid reduction by confined compression, supports the rational and scalable design of a broad range of collagen-fibril materials and cell-encapsulated tissue constructs for tissue engineering applications. PMID:26902645

  11. Mechanisms of collagen fibril alignment in tendon injury: from tendon regeneration to artificial tendon.

    PubMed

    Torigoe, Kojun; Tanaka, Hirohito F; Yonenaga, Kazumichi; Ohkochi, Hiroki; Miyasaka, Muneo; Sato, Ryota; Kuzumaki, Toru; Yoshida, Kazuharu; Yoshida, Toshiko

    2011-12-01

    The process by which collagen fibrils are aligned following tendon injury remains unknown. Therefore, we analyzed the process of tendon regeneration by transmission electron microscopy, using a film model method. In mice, the Achilles tendon of medial head was transected. On day 3, after only the proximal end of the transected tendon was placed on film and kept in vivo, a translucent substance containing granules, called tendon gel, was secreted. On day 5, the granules assembled in a loose (L) layer, and coalesced tightly in a dense (D) layer, forming an L-D-L layered pattern. On day 10, granules showed high electron density in H layers, which developed into D-H-D layers on day 13. The distal end was placed on film to face the proximal end. On day 10, the tendon gel showed a D-H-D layer pattern. On day 11, mechanical stress from muscular constriction changed the tendon gel to aligned collagen fibrils (6 ± 2 nm in diameter). Thereafter, the diameter of the fibrils increased. Tendon gel harvested on day 5 or day 10 was pulled manually or by hanging weights (about 0.6 MPa). Aligned collagen fibrils (32 ± 7 nm in diameter) were created by traction using tendon gel harvested on day 10. PMID:21618275

  12. Influence of the mineral staggering on the elastic properties of the mineralized collagen fibril in lamellar bone.

    PubMed

    Vercher-Martínez, Ana; Giner, Eugenio; Arango, Camila; Fuenmayor, F Javier

    2015-02-01

    In this work, a three-dimensional finite element model of the staggered distribution of the mineral within the mineralized collagen fibril has been developed to characterize the lamellar bone elastic behavior at the sub-micro length scale. Minerals have been assumed to be embedded in a collagen matrix, and different degrees of mineralization have been considered allowing the growth of platelet-shaped minerals both in the axial and the transverse directions of the fibril, through the variation of the lateral space between platelets. We provide numerical values and trends for all the elastic constants of the mineralized collagen fibril as a function of the volume fraction of mineral. In our results, we verify the high influence of the mineral overlapping on the mechanical response of the fibril and we highlight that the lateral distance between crystals is relevant to the mechanical behavior of the fibril and not only the mineral overlapping in the axial direction. PMID:25498297

  13. The Relation Between Collagen Fibril Kinematics and Mechanical Properties in the Mitral Valve Anterior Leaflet

    SciTech Connect

    Liao,J.; Yang, L.; Grashow, J.; Sacks, M.

    2007-01-01

    We have recently demonstrated that the mitral valve anterior leaflet (MVAL) exhibited minimal hysteresis, no strain rate sensitivity, stress relaxation but not creep (Grashow et al., 2006, Ann Biomed Eng., 34(2), pp. 315-325; Grashow et al., 2006, Ann Biomed. Eng., 34(10), pp. 1509-1518). However, the underlying structural basis for this unique quasi-elastic mechanical behavior is presently unknown. As collagen is the major structural component of the MVAL, we investigated the relation between collagen fibril kinematics (rotation and stretch) and tissue-level mechanical properties in the MVAL under biaxial loading using small angle X-ray scattering. A novel device was developed and utilized to perform simultaneous measurements of tissue level forces and strain under a planar biaxial loading state. Collagen fibril D-period strain ({epsilon}{sub D}) and the fibrillar angular distribution were measured under equibiaxial tension, creep, and stress relaxation to a peak tension of 90 N/m. Results indicated that, under equibiaxial tension, collagen fibril straining did not initiate until the end of the nonlinear region of the tissue-level stress-strain curve. At higher tissue tension levels, {epsilon}{sub D} increased linearly with increasing tension. Changes in the angular distribution of the collagen fibrils mainly occurred in the tissue toe region. Using {epsilon}{sub D}, the tangent modulus of collagen fibrils was estimated to be 95.5{+-}25.5 MPa, which was {approx}27 times higher than the tissue tensile tangent modulus of 3.58{+-}1.83 MPa. In creep tests performed at 90 N/m equibiaxial tension for 60 min, both tissue strain and D remained constant with no observable changes over the test length. In contrast, in stress relaxation tests performed for 90 min {epsilon}{sub D} was found to rapidly decrease in the first 10 min followed by a slower decay rate for the remainder of the test. Using a single exponential model, the time constant for the reduction in collagen

  14. Influence of telopeptides, fibrils and crosslinking on physicochemical properties of type I collagen films.

    PubMed

    Walton, Robin S; Brand, David D; Czernuszka, Jan T

    2010-02-01

    Type I collagen is widely used in various different forms for research and commercial applications. Different forms of collagen may be classified according to their source, extraction method, crosslinking and resultant ultrastructure. In this study, afibrillar and reconstituted fibrillar films, derived from acid soluble and pepsin digested Type I collagen, were analysed using Lateral Force Microscopy (LFM), Fourier Transform Infra-Red Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC) and enzymatic stability assays to asses the influence of telopeptides, fibrils and crosslinking. LFM proved to be a useful technique to confirm an afibrillar/fibrillar ultrastructure and to elucidate fibril diameters. FTIR has proved insensitive to ultrastructural differences involving telopeptides and fibrils. DSC results showed a significant increase in T(d) for crosslinked samples (+22-28 degrees C), and demonstrated that the thermal behaviour of hydrated, afibrillar films is more akin to reconstituted fibrillar films than monomeric solutions. The enzymatic stability assay has provided new evidence to show that afibrillar films of Type I collagen can be significantly more resistant to collagenase (by up to 3.5 times), than reconstituted fibrillar films, as a direct consequence of the different spatial arrangement of collagen molecules. A novel mechanism for this phenomenon is proposed and discussed. Additionally, the presence of telopeptide regions in afibrillar tropocollagen samples has been shown to increase resistance to collagenase by greater than 3.5 times compared to counterpart afibrillar atelocollagen samples. One-factor ANOVA analysis, with Fisher's LSD post-hoc test, confirms these key findings to be of statistical significance (P < 0.05). The profound physicochemical effects of collagen ultrastructure demonstrated in this study reiterates the need for comprehensive materials disclosure and classification when using these biomaterials. PMID:19851839

  15. Interfibrillar shear stress is the loading mechanism of collagen fibrils in tendon

    PubMed Central

    Szczesny, Spencer E.; Elliott, Dawn M.

    2014-01-01

    Despite the critical role tendons play in transmitting loads throughout the musculoskeletal system, little is known about the microstructural mechanisms underlying their mechanical function. Of particular interest is whether collagen fibrils in tendon fascicles bear load independently or if load is transferred between fibrils through interfibrillar shear forces. We conducted multiscale experimental testing and developed a microstructural shear lag model to explicitly test whether interfibrillar shear load transfer is indeed the fibrillar loading mechanism in tendon. Experimental correlations between fascicle macroscale mechanics and microscale interfibrillar sliding suggest that fibrils are discontinuous and share load. Moreover, for the first time, we demonstrate that a shear lag model can replicate the fascicle macroscale mechanics as well as predict the microscale fibrillar deformations. Since interfibrillar shear stress is the fundamental loading mechanism assumed in the model, this result provides strong evidence that load is transferred between fibrils in tendon and possibly other aligned collagenous tissues. Conclusively establishing this fibrillar loading mechanism and identifying the involved structural components should help develop repair strategies for tissue degeneration and guide the design of tissue engineered replacements. PMID:24530560

  16. Homogenized stiffness matrices for mineralized collagen fibrils and lamellar bone using unit cell finite element models.

    PubMed

    Vercher, Ana; Giner, Eugenio; Arango, Camila; Tarancón, José E; Fuenmayor, F Javier

    2014-04-01

    Mineralized collagen fibrils have been usually analyzed like a two-phase composite material where crystals are considered as platelets that constitute the reinforcement phase. Different models have been used to describe the elastic behavior of the material. In this work, it is shown that when Halpin-Tsai equations are applied to estimate elastic constants from typical constituent properties, not all crystal dimensions yield a model that satisfy thermodynamic restrictions. We provide the ranges of platelet dimensions that lead to positive definite stiffness matrices. On the other hand, a finite element model of a mineralized collagen fibril unit cell under periodic boundary conditions is analyzed. By applying six canonical load cases, homogenized stiffness matrices are numerically calculated. Results show a monoclinic behavior of the mineralized collagen fibril. In addition, a 5-layer lamellar structure is also considered where crystals rotate in adjacent layers of a lamella. The stiffness matrix of each layer is calculated applying Lekhnitskii transformations, and a new finite element model under periodic boundary conditions is analyzed to calculate the homogenized 3D anisotropic stiffness matrix of a unit cell of lamellar bone. Results are compared with the rule-of-mixtures showing in general good agreement. PMID:23793930

  17. Modeling of bovine type-I collagen fibrils: interaction with pickling and retanning agents.

    PubMed

    Bulo, Rosa E; Siggel, Lorenz; Molnar, Ferenc; Weiss, Horst

    2007-02-12

    Bovine Type I collagen was investigated, building on a large scale computer model of a collagen fibril in water, and focusing on two stages of the leather manufacturing process. The effects of different salts (NaCl, CaCl(2), and Na(2)SO(4)) on the swelling behavior of collagen at low pH (the pickling process) were studied. The salts suppress the swelling of the fibrils at low pH and we find specific stabilizing influences for CaCl(2) and Na(2)SO(4), due to weak Ca(2+)/Cl(-) and strong SO(4) (2-)/lysine/arginine interactions, respectively. Using state-of-the-art sampling techniques, such as the metadynamics algorithm, to allow an efficient exploration of configuration space, we were able to investigate the effect of polyacrylate and poly(methyl acrylate) - two polymeric retanning agents - on the fibril. Both polymers interact with the ammonium groups on the surface, but polyacrylate shows significantly stronger interactions. We suggest that it is this stronger interaction that contributes to the reduced suitability of PAA as a tanning agent. PMID:17295396

  18. Epitaxially Grown Collagen Fibrils Reveal Diversity in Contact Guidance Behavior among Cancer Cells

    PubMed Central

    2015-01-01

    Invasion of cancer cells into the surrounding tissue is an important step during cancer progression and is driven by cell migration. Cell migration can be random, but often it is directed by various cues such as aligned fibers composed of extracellular matrix (ECM), a process called contact guidance. During contact guidance, aligned fibers bias migration along the long axis of the fibers. These aligned fibers of ECM are commonly composed of type I collagen, an abundant structural protein around tumors. In this paper, we epitaxially grew several different patterns of organized type I collagen on mica and compared the morphology and contact guidance behavior of two invasive breast cancer cell lines (MDA-MB-231 and MTLn3 cells). Others have shown that these cells randomly migrate in qualitatively different ways. MDA-MB-231 cells exert large traction forces, tightly adhere to the ECM, and migrate with spindle-shaped morphology and thus adopt a mesenchymal mode of migration. MTLn3 cells exert small traction forces, loosely adhere to the ECM, and migrate with a more rounded morphology and thus adopt an amoeboid mode of migration. As the degree of alignment of type I collagen fibrils increases, cells become more elongated and engage in more directed contact guidance. MDA-MB-231 cells perceive the directional signal of highly aligned type I collagen fibrils with high fidelity, elongating to large extents and migrating directionally. Interestingly, behavior in MTLn3 cells differs. While highly aligned type I collagen fibril patterns facilitate spreading and random migration of MTLn3 cells, they do not support elongation or directed migration. Thus, different contact guidance cues bias cell migration differently and the fidelity of contact guidance is cell type dependent, suggesting that ECM alignment is a permissive cue for contact guidance, but requires a cell to have certain properties to interpret that cue. PMID:25531276

  19. Biochemical characterisation and assessment of fibril-forming ability of collagens extracted from Bester sturgeon Huso huso × Acipenser ruthenus.

    PubMed

    Zhang, Xi; Ookawa, Mika; Tan, Yongkai; Ura, Kazuhiro; Adachi, Shinji; Takagi, Yasuaki

    2014-10-01

    Collagens purified from Bester sturgeon organs were characterised biochemically, and their fibril-forming abilities and fibril morphologies formed in vitro clarified. Yields of collagens were 2.1%, 11.9%, 0.4%, 18.1%, 0.4%, 0.8% and 0.03% (collagen dry weight/tissue wet weight) from scales, skin, muscle, swim bladder, digestive tract, notochord and snout cartilage, respectively. Using SDS-PAGE and amino acid composition analyses, collagens from scales, skin, muscle, the swim bladder and digestive tract were characterised as type I, and collagens from the notochord and snout cartilage as type II. Denaturation temperatures of the collagens, measured using circular dichroism, were 29.6, 26.8, 29.0, 32.9, 31.6 and 36.3 °C in scales, skin, muscle, swim bladder, digestive tract, and notochord, respectively. For fibril formation, swim bladder and skin collagen showed a more rapid rate of increase in turbidity, a shorter time to attain the maximum turbidity, and formed thicker fibrils compared with porcine tendon type I collagen. PMID:24799243

  20. Tectorins crosslink type II collagen fibrils and connect the tectorial membrane to the spiral limbus.

    PubMed

    Andrade, Leonardo R; Salles, Felipe T; Grati, M'hamed; Manor, Uri; Kachar, Bechara

    2016-05-01

    All inner ear organs possess extracellular matrix appendices over the sensory epithelia that are crucial for their proper function. The tectorial membrane (TM) is a gelatinous acellular membrane located above the hearing sensory epithelium and is composed mostly of type II collagen, and α and β tectorins. TM molecules self-assemble in the endolymph fluid environment, interacting medially with the spiral limbus and distally with the outer hair cell stereocilia. Here, we used immunogold labeling in freeze-substituted mouse cochleae to assess the fine localization of both tectorins in distinct TM regions. We observed that the TM adheres to the spiral limbus through a dense thin matrix enriched in α- and β-tectorin, both likely bound to the membranes of interdental cells. Freeze-etching images revealed that type II collagen fibrils were crosslinked by short thin filaments (4±1.5nm, width), resembling another collagen type protein, or chains of globular elements (15±3.2nm, diameter). Gold-particles for both tectorins also localized adjacent to the type II collagen fibrils, suggesting that these globules might be composed essentially of α- and β-tectorins. Finally, the presence of gold-particles at the TM lower side suggests that the outer hair cell stereocilia membrane has a molecular partner to tectorins, probably stereocilin, allowing the physical connection between the TM and the organ of Corti. PMID:26806019

  1. Modeling the collagen fibril network of biological tissues as a nonlinearly elastic material using a continuous volume fraction distribution function

    PubMed Central

    Shirazi, Reza; Vena, Pasquale; Sah, Robert L.; Klisch, Stephen M.

    2012-01-01

    Despite distinct mechanical functions, biological soft tissues have a common microstructure in which a ground matrix is reinforced by a collagen fibril network. The microstructural properties of the collagen network contribute to continuum mechanical tissue properties that are strongly anisotropic with tensile-compressive asymmetry. In this study, a novel approach based on a continuous distribution of collagen fibril volume fractions is developed to model fibril reinforced soft tissues as a nonlinearly elastic and anisotropic material. Compared with other approaches that use a normalized number of fibrils for the definition of the distribution function, this representation is based on a distribution parameter (i.e. volume fraction) that is commonly measured experimentally while also incorporating pre-stress of the collagen fibril network in a tissue natural configuration. After motivating the form of the collagen strain energy function, examples are provided for two volume fraction distribution functions. Consequently, collagen second-Piola Kirchhoff stress and elasticity tensors are derived, first in general form and then specifically for a model that may be used for immature bovine articular cartilage. It is shown that the proposed strain energy is a convex function of the deformation gradient tensor and, thus, is suitable for the formation of a polyconvex tissue strain energy function. PMID:23390357

  2. Influence of cross-link structure, density and mechanical properties in the mesoscale deformation mechanisms of collagen fibrils

    PubMed Central

    Depalle, Baptiste; Qin, Zhao; Shefelbine, Sandra J.; Buehler, Markus J.

    2015-01-01

    Collagen is a ubiquitous protein with remarkable mechanical properties. It is highly elastic, shows large fracture strength and enables substantial energy dissipation during deformation. Most of the connective tissue in humans consists of collagen fibrils composed of a staggered array of tropocollagen molecules, which are connected by intermolecular cross-links. In this study, we report a three-dimensional coarse-grained model of collagen and analyze the influence of enzymatic cross-links on the mechanics of collagen fibrils. Two representatives immature and mature cross-links are implemented in the mesoscale model using a bottom-up approach. By varying the number, type and mechanical properties of cross-links in the fibrils and performing tensile test on the models, we systematically investigate the deformation mechanisms of cross-linked collagen fibrils. We find that cross-linked fibrils exhibit a three phase behavior, which agrees closer with experimental results than what was obtained using previous models. The fibril mechanical response is characterized by: (i) an initial elastic deformation corresponding to the collagen molecule uncoiling, (ii) a linear regime dominated by molecule sliding and (iii) the second stiffer elastic regime related to the stretching of the backbone of the tropocollagen molecules until the fibril ruptures. Our results suggest that both cross-link density and type dictate the stiffness of large deformation regime by increasing the number of interconnected molecules while cross-links mechanical properties determine the failure strain and strength of the fibril. These findings reveal that cross-links play an essential role in creating an interconnected fibrillar material of tunable toughness and strength. PMID:25153614

  3. Mineralization of collagen may occur on fibril surfaces: evidence from conventional and high-voltage electron microscopy and three-dimensional imaging

    NASA Technical Reports Server (NTRS)

    Landis, W. J.; Hodgens, K. J.; Song, M. J.; Arena, J.; Kiyonaga, S.; Marko, M.; Owen, C.; McEwen, B. F.

    1996-01-01

    The interaction between collagen and mineral crystals in the normally calcifying leg tendons from the domestic turkey, Meleagris gallopavo, has been investigated at an ultrastructural level with conventional and high-voltage electron microscopy, computed tomography, and three-dimensional image reconstruction methods. Specimens treated by either aqueous or anhydrous techniques and resin-embedded were appropriately sectioned and regions of early tendon mineralization were photographed. On the basis of individual photomicrographs, stereoscopic pairs of images, and tomographic three-dimensional image reconstructions, platelet-shaped crystals may be demonstrated for the first time in association with the surface of collagen fibrils. Mineral is also observed in closely parallel arrays within collagen hole and overlap zones. The mineral deposition at these spatially distinct locations in the tendon provides insight into possible means by which calcification is mediated by collagen as a fundamental event in skeletal and dental formation among vertebrates.

  4. Nanomechanics of Type I Collagen.

    PubMed

    Varma, Sameer; Orgel, Joseph P R O; Schieber, Jay D

    2016-07-12

    Type I collagen is the predominant collagen in mature tendons and ligaments, where it gives them their load-bearing mechanical properties. Fibrils of type I collagen are formed by the packing of polypeptide triple helices. Higher-order structures like fibril bundles and fibers are assembled from fibrils in the presence of other collagenous molecules and noncollagenous molecules. Curiously, however, experiments show that fibrils/fibril bundles are less resistant to axial stress compared to their constituent triple helices-the Young's moduli of fibrils/fibril bundles are an order-of-magnitude smaller than the Young's moduli of triple helices. Given the sensitivity of the Young's moduli of triple helices to solvation environment, a plausible explanation is that the packing of triple helices into fibrils perhaps reduces the Young's modulus of an individual triple helix, which results in fibrils having smaller Young's moduli. We find, however, from molecular dynamics and accelerated conformational sampling simulations that the Young's modulus of the buried core of the fibril is of the same order as that of a triple helix in aqueous phase. These simulations, therefore, suggest that the lower Young's moduli of fibrils/fibril bundles cannot be attributed to the specific packing of triple helices in the fibril core. It is not the fibril core that yields initially to axial stress. Rather, it must be the portion of the fibril exposed to the solvent and/or the fibril-fibril interface that bears the initial strain. Overall, this work provides estimates of Young's moduli and persistence lengths at two levels of collagen's structural assembly, which are necessary to quantitatively investigate the response of various biological factors on collagen mechanics, including congenital mutations, posttranslational modifications and ligand binding, and also engineer new collagen-based materials. PMID:27410733

  5. Effect of cyclic loading on the nanoscale deformation of hydroxyapatite and collagen fibrils in bovine bone.

    PubMed

    Singhal, Anjali; Stock, Stuart R; Almer, Jonathan D; Dunand, David C

    2014-06-01

    Cyclic compressive loading tests were carried out on bovine femoral bones at body temperature (37 °C), with varying mean stresses (-55 to -80 MPa) and loading frequencies (0.5-5 Hz). At various times, the cyclic loading was interrupted to carry out high-energy X-ray scattering measurements of the internal strains developing in the hydroxyapatite (HAP) platelets and the collagen fibrils. The residual strains upon unloading were always tensile in the HAP and compressive in the fibrils, and each increases in magnitude with loading cycles, which can be explained from damage at the HAP–collagen interface and accumulation of plastic deformation within the collagen phase. The samples tested at a higher mean stress and stress amplitude, and at lower loading frequencies exhibit greater plastic deformation and damage accumulation, which is attributed to greater contribution of creep. Synchrotron microcomputed tomography of some of the specimens showed that cracks are produced during cyclic loading and that they mostly occur concentric with Haversian canals. PMID:23958833

  6. Three-dimensional modeling and computational analysis of the human cornea considering distributed collagen fibril orientations.

    PubMed

    Pandolfi, Anna; Holzapfel, Gerhard A

    2008-12-01

    Experimental tests on human corneas reveal distinguished reinforcing collagen lamellar structures that may be well described by a structural constitutive model considering distributed collagen fibril orientations along the superior-inferior and the nasal-temporal meridians. A proper interplay between the material structure and the geometry guarantees the refractive function and defines the refractive properties of the cornea. We propose a three-dimensional computational model for the human cornea that is able to provide the refractive power by analyzing the structural mechanical response with the nonlinear regime and the effect the intraocular pressure has. For an assigned unloaded geometry we show how the distribution of the von Mises stress at the top surface of the cornea and through the corneal thickness and the refractive power depend on the material properties and the fibril dispersion. We conclude that a model for the human cornea must not disregard the peculiar collagen fibrillar structure, which equips the cornea with the unique biophysical, mechanical, and optical properties. PMID:19045535

  7. The Collagen Fibril Structure in the Superficial Zone of Articular Cartilage by μMRI

    PubMed Central

    Zheng, ShaoKuan; Xia, Yang

    2009-01-01

    Objective To investigate the fibril architecture of the collage matrix in the superficial zone of articular cartilage non-destructively by microscopic MRI (μMRI) T2 anisotropy. Method Six specimens of canine humeral cartilage were rotated in such a way that the normal axis of the articular surface of the cartilage specimen remained stationary and perpendicular to the static magnetic field, over a range of 180° and at a step of 15°. At each rotation angle, a quantitative T2 image was constructed at 13μm pixel resolution. Results A set of complex and depth-dependent patterns was found in the μMRI T2 anisotropy along the depth of the tissue. In the superficial zone, the T2 anisotropy is clearly periodic, which demonstrates that the distribution of the collagen fibrils in the superficial zone is not random. In the transitional zone, the periodicity of the T2 anisotropy approximately doubles with respect to that in the superficial zone. In the initial part of the radial zone, the T2 anisotropy is also periodic but inverse to that in the superficial zone. In the deep part of the radial zone, the T2 anisotropy becomes increasingly weaker and eventually disappears. Conclusion There exists a certain degree of collagen anisotropy in all zones of articular cartilage. The anisotropic imaging data can be interpreted with the aid of a collagen architecture model. PMID:19527808

  8. Modelling the mechanics of partially mineralized collagen fibrils, fibres and tissue

    PubMed Central

    Liu, Yanxin; Thomopoulos, Stavros; Chen, Changqing; Birman, Victor; Buehler, Markus J.; Genin, Guy M.

    2014-01-01

    Progressive stiffening of collagen tissue by bioapatite mineral is important physiologically, but the details of this stiffening are uncertain. Unresolved questions about the details of the accommodation of bioapatite within and upon collagen's hierarchical structure have posed a central hurdle, but recent microscopy data resolve several major questions. These data suggest how collagen accommodates bioapatite at the lowest relevant hierarchical level (collagen fibrils), and suggest several possibilities for the progressive accommodation of bioapatite at higher hierarchical length scales (fibres and tissue). We developed approximations for the stiffening of collagen across spatial hierarchies based upon these data, and connected models across hierarchies levels to estimate mineralization-dependent tissue-level mechanics. In the five possible sequences of mineralization studied, percolation of the bioapatite phase proved to be an important determinant of the degree of stiffening by bioapatite. The models were applied to study one important instance of partially mineralized tissue, which occurs at the attachment of tendon to bone. All sequences of mineralization considered reproduced experimental observations of a region of tissue between tendon and bone that is more compliant than either tendon or bone, but the size and nature of this region depended strongly upon the sequence of mineralization. These models and observations have implications for engineered tissue scaffolds at the attachment of tendon to bone, bone development and graded biomimetic attachment of dissimilar hierarchical materials in general. PMID:24352669

  9. Synchrotron radiation x-ray scattering in the early stages of in vitro collagen fibril formation

    SciTech Connect

    Suarez, G.; Oronsky, A.L.; Bordas, J.; Koch, M.H.

    1985-07-01

    The time course of in vitro collagen fibril formation was monitored by synchrotron radiation x-ray scattering. Collagen polymerization was induced by a temperature jump from 4 degrees C to 32 degrees C and the solution scattering pattern was recorded continuously with a time resolution of a few seconds. The scattered intensity increased as soon as the final temperature was attained, without discernible lag phase, when the collagen concentration was about 0.56 mg/ml, whereas turbidimetric measurements revealed a lag phase of ca. 2.5 min at 1.05 mg/ml. A direct correlation was found between the temperature and both the rate of formation and the total amount of early aggregates. The formation of these aggregates was only partially reversed by lowering the temperature, except when the collagen had been prevented from forming Schiff base-mediated intermolecular crosslinks by sodium borohydride reduction. In this case, formation of aggregates was completely reversible. The authors conclude that the aggregates that appear to correspond to the subfibrils proposed on the basis of independent methods are formed and simultaneously crosslinked in the early phases of in vitro collagen self-assembly.

  10. Agent-based modeling traction force mediated compaction of cell-populated collagen gels using physically realistic fibril mechanics.

    PubMed

    Reinhardt, James W; Gooch, Keith J

    2014-02-01

    Agent-based modeling was used to model collagen fibrils, composed of a string of nodes serially connected by links that act as Hookean springs. Bending mechanics are implemented as torsional springs that act upon each set of three serially connected nodes as a linear function of angular deflection about the central node. These fibrils were evaluated under conditions that simulated axial extension, simple three-point bending and an end-loaded cantilever. The deformation of fibrils under axial loading varied <0.001% from the analytical solution for linearly elastic fibrils. For fibrils between 100 μm and 200 μm in length experiencing small deflections, differences between simulated deflections and their analytical solutions were <1% for fibrils experiencing three-point bending and <7% for fibrils experiencing cantilever bending. When these new rules for fibril mechanics were introduced into a model that allowed for cross-linking of fibrils to form a network and the application of cell traction force, the fibrous network underwent macroscopic compaction and aligned between cells. Further, fibril density increased between cells to a greater extent than that observed macroscopically and appeared similar to matrical tracks that have been observed experimentally in cell-populated collagen gels. This behavior is consistent with observations in previous versions of the model that did not allow for the physically realistic simulation of fibril mechanics. The significance of the torsional spring constant value was then explored to determine its impact on remodeling of the simulated fibrous network. Although a stronger torsional spring constant reduced the degree of quantitative remodeling that occurred, the inclusion of torsional springs in the model was not necessary for the model to reproduce key qualitative aspects of remodeling, indicating that the presence of Hookean springs is essential for this behavior. These results suggest that traction force mediated matrix

  11. Changes in collagen fibril pattern and adhesion force with collagenase-induced injury in rat Achilles tendon observed via AFM.

    PubMed

    Lee, Gi-Ja; Choi, Samjin; Chon, Jinmann; Yoo, Seungdon; Cho, Ilsung; Park, Hun-Kuk

    2011-01-01

    The Achilles tendon consists mainly of type I collagen fibers that contain collagen fibrils. When the Achilles tendon is injured, it is inflamed. The collagenase-induced model has been widely used to study tendinitis. The major advantages of atomic force microscopy (AFM) over conventional optical and electron microscopy for bio-imaging include its non-requirement of a special coating and vacuum, and its capability to perform imaging in all environments. AFM force-distance measurements have become a fundamental tool in the fields of surface chemistry, biochemistry and materials science. Therefore, the changes in the ultrastructure and adhesion force of the collagen fibrils on the Achilles tendons of rats with Achilles tendinitis were observed using AFM. The changes in the structure of the Achilles tendons were evaluated based on the diameter and D-banding of the collagen fibrils. Collagenase-induced Achilles tendinitis was induced with the injection of 30 microl crude collagenase into 7-week-old male Sprague-Dawley rats. The animals were each sacrificed on the first, second, third, fifth and seventh day after the collagenase injection. The normal and injured Achilles tendons were fixed in 4% buffered formalin and dehydrated with increasing concentrations of ethanol. AFM was performed using the non-contact mode at the resolution of 512 x 512 pixels, with a scan speed of 0.8 line/sec. The adhesion force was measured via the force-distance curve that resulted from the interactions between the AFM tip and the collagen fibril sample using the contact mode. The diameter of the collagen fibrils in the Achilles tendons significantly decreased (p < 0.05) after the collagenase injection, and the pattern of the D-banding of the collagen fibrils was similar to that of the diameter changes. The adhesion force decreased until the fifth day after the collagenase injection, but increased on the seventh day after the collagenase injection (p < 0.0001). PMID:21446543

  12. Molecular and intermolecular effects in collagen fibril mechanics: a multiscale analytical model compared with atomistic and experimental studies.

    PubMed

    Marino, Michele

    2016-02-01

    Both atomistic and experimental studies reveal the dependence of collagen fibril mechanics on biochemical and biophysical features such as, for instance, cross-link density, water content and protein sequence. In order to move toward a multiscale structural description of biological tissues, a novel analytical model for collagen fibril mechanics is herein presented. The model is based on a multiscale approach that incorporates and couples: thermal fluctuations in collagen molecules; the uncoiling of collagen triple helix; the stretching of molecular backbone; the straightening of the telopeptide in which covalent cross-links form; slip-pulse mechanisms due to the rupture of intermolecular weak bonds; molecular interstrand delamination due to the rupture of intramolecular weak bonds; the rupture of covalent bonds within molecular strands. The effectiveness of the proposed approach is verified by comparison with available atomistic results and experimental data, highlighting the importance of cross-link density in tuning collagen fibril mechanics. The typical three-region shape and hysteresis behavior of fibril constitutive response, as well as the transition from a yielding-like to a brittle-like behavior, are recovered with a special insight on the underlying nanoscale mechanisms. The model is based on parameters with a clear biophysical and biochemical meaning, resulting in a promising tool for analyzing the effect of pathological or pharmacological-induced histochemical alterations on the functional mechanical response of collagenous tissues. PMID:26220454

  13. Elemental distribution analysis of type I collagen fibrils in tilapia fish scale with energy-filtered transmission electron microscope.

    PubMed

    Okuda, Mitsuhiro; Takeguchi, Masaki; Tagaya, Motohiro; Tonegawa, Toru; Hashimoto, Ayako; Hanagata, Nobutaka; Ikoma, Toshiyuki

    2009-01-01

    Elemental distribution of calcium, phosphorus, oxygen, and carbon in a single collagen fibril obtained from tilapia fish scales was identified with an electron energy-loss spectroscopy and an energy-filtered transmission electron microscopy, for the first time. The carbon intensity profile of the single collagen fibril showed the specific D-periodic pattern at 67 nm of type I collagen fibrils. The calcium L(2,3)-edge and oxygen K-edge peak positions were detected at 347/350 eV and 137 eV, respectively, and these positions were identical to those of hydroxyapatite. Calcium, phosphorus, and oxygen were present in the hole zones as the amorphous phase, while carbon was present in the overlap zone. Our results indicated that the hole zones preferentially attract calcium and phosphate ions and thus serve as possible nucleation sites for mineralization. PMID:19419879

  14. Observations on the different substrate behavior of tropocollagen molecules in solution and intermolecularly cross-linked tropocollagen within insoluble polymeric collagen fibrils.

    PubMed Central

    Steven, F S

    1976-01-01

    Bacterial collagenase was used to compare the extent of digestion of tropocollagen monomers in solution and in reconstituted fibrils with that of tropocollagen molecules intermolecularly cross-linked within insoluble polymeric collagen fibrils obtained from mature tendons at given time-intervals. The extent of digestion of tropocollagen monomers in solution was directly proportional to the enzyme concentration (a range of enzyme substrate molar ratios 1:200 to 1:10 was used). The extent of digestion of polymeric collagen was followed by measuring the solubilization of fluorescent peptides from fluorescent-labelled insoluble polymeric collagen fibrils. The extent of digestion of tropocollagen within polymeric collagen was linear over a very small range of enzyme concentrations, when the enzyme/substrate ratio in the reaction mixture was less than 1:400 on a molecular basis. The behavior of tropocollagen in the form of reconstituted collagen fibrils, which had been matured at 37 degrees C for 8 weeks, was intermediate between the behaviour of solutions of tropocollagen and insoluble polymeric collagen fibrils. The significance of the results is discussed in terms of the structure of polymeric collagen fibrils and the protection against enzymic attack provided by tropocollagen molecules on the circumference of the fibril. The results suggest that assays of collagenase activities based on tropocollagen as substrate cannot be directly related to the ability of these enzymes to degrade mature insoluble collagen fibrils. PMID:180984

  15. Corneal Opacity in Lumican-Null Mice: Defects in Collagen Fibril Structure and Packing in the Posterior Stroma

    PubMed Central

    Chakravarti, Shukti; Petroll, W. Matthew; Hassell, John R.; Jester, James V.; Lass, Jonathan H.; Paul, Jennifer; Birk, David E.

    2015-01-01

    Purpose Gene targeted lumican-null mutants (lumtm1sc/lumtm1sc) have cloudy corneas with abnormally thick collagen fibrils. The purpose of the present study was to analyze the loss of transparency quantitatively and to define the associated corneal collagen fibril and stromal defects. Methods Backscattering of light, a function of corneal haze and opacification, was determined regionally using in vivo confocal microscopy in lumican-deficient and wild-type control mice. Fibril organization and structure were analyzed using transmission electron microscopy. Biochemical approaches were used to quantify glycosaminoglycan contents. Lumican distribution in the cornea was elucidated immunohistochemically. Results Compared with control stromas, lumican-deficient stromas displayed a threefold increase in backscattered light with maximal increase confined to the posterior stroma. Confocal microscopy through-focusing (CMTF) measurement profiles also indicated a 40% reduction in stromal thickness in the lumican-null mice. Transmission electron microscopy indicated significant collagen fibril abnormalities in the posterior stroma, with the anterior stroma remaining relatively unremarkable. The lumican-deficient posterior stroma displayed a pronounced increase in fibril diameter, large fibril aggregates, altered fibril packing, and poor lamellar organization. Immunostaining of wild-type corneas demonstrated high concentrations of lumican in the posterior stroma. Biochemical assessment of keratan sulfate (KS) content of whole eyes revealed a 25% reduction in KS content in the lumican-deficient mice. Conclusions The structural defects and maximum backscattering of light clearly localized to the posterior stroma of lumican-deficient mice. In normal mice, an enrichment of lumican was observed in the posterior stroma compared with that in the anterior stroma. Taken together, these observations indicate a key role for lumican in the posterior stroma in maintaining normal fibril

  16. A possible role of collagen fibrils in the process of calcification observed in the capsule of the pineal gland in aging rats.

    PubMed

    Humbert, W; Cuisinier, F; Voegel, J C; Pévet, P

    1997-06-01

    The relationship between collagen fibrils and calcified concretions exclusively appearing in the pineal gland of adult/aging rats has been investigated. Deposits of lanthanum, which replace calcium ions are distributed along collagen fibrils with a repeating period of about 70 nm. Calcium has been detected histochemically between collagen bundles surrounding extracellular concretions by means of the pyroantimonate method and by X-ray microanalysis. It is associated with phosphorus. The data presented here suggest that collagen fibrils are involved in the genesis and growth of extracellular concretions located in the connective tissue surrounding the pineal gland of aging rats. PMID:9134857

  17. Pseudo-hyperelastic model of tendon hysteresis from adaptive recruitment of collagen type I fibrils.

    PubMed

    Ciarletta, Pasquale; Dario, Paolo; Micera, Silvestro

    2008-02-01

    Understanding the functional relationship between the viscoelasticity and the morphology of soft collagenous tissues is fundamental for many applications in bioengineering science. This work presents a pseudo-hyperelastic constitutive theory aiming at describing the time-dependant hysteretic response of tendons subjected to uniaxial tensile loads. A macroscopic tendon is modeled as a composite homogeneous tissue with the anisotropic reinforcement of collagen type I fibrils. The tissue microstructure is considered as an adaptive network of fibrillar units connected in temporary junctions. The processes of breakage and reformation of active fibrils are thermally activated, and are occurring at random times. An internal softening variable and a dissipation energy function account for the adaptive arrangement of the fibrillar network in the pseudo-hyperelastic model. Cyclic uniaxial tensile tests have been performed in vitro on porcine flexor digital tendons. The theoretical predictions fit accurately the experimental stress-strain data both for the loading and the unloading processes. The hysteresis behavior reflects the improvement in the efficiency and performance of the motion of the muscle-tendon unit at high strain rates. The results of the model demonstrate the microstructural importance of proteoglycans in determining the functional viscoelastic adaptability of the macroscopic tendon. PMID:17997481

  18. The Impact of Collagen Fibril Polarity on Second Harmonic Generation Microscopy.

    PubMed

    Couture, Charles-André; Bancelin, Stéphane; Van der Kolk, Jarno; Popov, Konstantin; Rivard, Maxime; Légaré, Katherine; Martel, Gabrielle; Richard, Hélène; Brown, Cameron; Laverty, Sheila; Ramunno, Lora; Légaré, François

    2015-12-15

    In this work, we report the implementation of interferometric second harmonic generation (SHG) microscopy with femtosecond pulses. As a proof of concept, we imaged the phase distribution of SHG signal from the complex collagen architecture of juvenile equine growth cartilage. The results are analyzed in respect to numerical simulations to extract the relative orientation of collagen fibrils within the tissue. Our results reveal large domains of constant phase together with regions of quasi-random phase, which are correlated to respectively high- and low-intensity regions in the standard SHG images. A comparison with polarization-resolved SHG highlights the crucial role of relative fibril polarity in determining the SHG signal intensity. Indeed, it appears that even a well-organized noncentrosymmetric structure emits low SHG signal intensity if it has no predominant local polarity. This work illustrates how the complex architecture of noncentrosymmetric scatterers at the nanoscale governs the coherent building of SHG signal within the focal volume and is a key advance toward a complete understanding of the structural origin of SHG signals from tissues. PMID:26682809

  19. Rapid biomimetic mineralization of collagen fibrils and combining with human umbilical cord mesenchymal stem cells for bone defects healing.

    PubMed

    Ye, Bihua; Luo, Xueshi; Li, Zhiwen; Zhuang, Caiping; Li, Lihua; Lu, Lu; Ding, Shan; Tian, Jinhuan; Zhou, Changren

    2016-11-01

    Collagen biomineralization is regulated by complicated interactions between the collagen matrix and non-collagenous extracellular proteins. Here, the use of sodium tripolyphosphate to simulate the templating functional motif of the C-terminal fragment of non-collagenous proteins is reported, and a low molecular weight polyacrylic acid served as a sequestration agent to stabilize amorphous calcium phosphate into nanoprecursors. Self-assembled collagen fibrils served as a fixed template for achieving rapid biomimetic mineralization in vitro. Results demonstrated that, during the mineralization process, intrafibrillar and extrafibrillar hydroxyapatite mineral with collagen fibrils formed and did so via bottom-up nanoparticle assembly based on the non-classical crystallization approach in the presence of these dual biomimetic functional analogues. In vitro human umbilical cord mesenchymal stem cell (hUCMSC) culture found that the mineralized scaffolds have a better cytocompatibility in terms of cell viability, adhesion, proliferation, and differentiation into osteoblasts. A rabbit femoral condyle defect model was established to confirm the ability of the n-HA/collagen scaffolds to facilitate bone regeneration and repair. The images of gross anatomy, MRI, CT and histomorphology taken 6 and 12weeks after surgery showed that the biomimetic mineralized collagen scaffolds with hUCMSCs can promote the healing speed of bone defects in vivo, and both of the scaffolds groups performing better than the bone defect control group. As new bone tissue formed, the scaffolds degraded and were gradually absorbed. All these results demonstrated that both of the scaffolds and cells have better histocompatibility. PMID:27523994

  20. Purification, characterization and cloning of tensilin, the collagen-fibril binding and tissue-stiffening factor from Cucumaria frondosa dermis.

    PubMed

    Tipper, Jennifer P; Lyons-Levy, Gillian; Atkinson, Mark A L; Trotter, John A

    2002-12-01

    The inner dermis of the sea cucumber, Cucumaria frondosa, is a mutable collagenous tissue characterized by rapid and reversible changes in its mechanical properties regulated by one or more protein effectors that are released from neurosecretory cells. One such effector, tensilin, is a collagen-fibril binding protein, named for its ability to induce dermis stiffening. Tensilin was purified using an affinity column constructed from C. frondosa collagen-fibrils. The protein migrates as a single band on SDS-PAGE (Mr approximately 33 kDa) and has an isoelectric point of 5.8. Equilibrium sedimentation experiments suggest a molecular mass of approximately 28.5-29.4 kDa. Carbohydrate analysis of tensilin revealed no measurable sugar content. The molar amount of tensilin was determined to be 0.38% that of collagen and 47% that of stiparin, a constitutive matrix glycoprotein. A full-length cDNA clone for tensilin was obtained from a C. frondosa inner dermis cDNA expression library. Predicted properties derived from the deduced peptide sequence were in agreement with those of the native protein. A noted feature of tensilin's deduced peptide sequence, particularly in its N-terminal domain, is its homology to tissue inhibitor of metalloproteinases. Tensilin's C-terminal tail has no known homology to other proteins but contains a putative collagen-fibril binding site. PMID:12524049

  1. The organisation of collagen fibrils in the superficial zones of articular cartilage.

    PubMed Central

    Clark, J M

    1990-01-01

    The origin and structure of collagen fibres in the surface of articular cartilage were studied using SEM. Cryofracture was used to create orthogonal fracture surfaces in three planes. Fibres which originated in the radial zone could be traced into the surface where they flattened and overlapped in a common direction. Thick fibres from the periosteum ran into the surface as well, but apparently ended there and did not enter the radial zone. The tangential fibres were covered by a dense, separate layer of small fibrils. The fundamental aspects of the model proposed by Benninghoff are supported by these findings. Images Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 PMID:2081698

  2. Interleukin-4 Receptor α Signaling in Myeloid Cells Controls Collagen Fibril Assembly in Skin Repair.

    PubMed

    Knipper, Johanna A; Willenborg, Sebastian; Brinckmann, Jürgen; Bloch, Wilhelm; Maaß, Tobias; Wagener, Raimund; Krieg, Thomas; Sutherland, Tara; Munitz, Ariel; Rothenberg, Marc E; Niehoff, Anja; Richardson, Rebecca; Hammerschmidt, Matthias; Allen, Judith E; Eming, Sabine A

    2015-10-20

    Activation of the immune response during injury is a critical early event that determines whether the outcome of tissue restoration is regeneration or replacement of the damaged tissue with a scar. The mechanisms by which immune signals control these fundamentally different regenerative pathways are largely unknown. We have demonstrated that, during skin repair in mice, interleukin-4 receptor α (IL-4Rα)-dependent macrophage activation controlled collagen fibril assembly and that this process was important for effective repair while having adverse pro-fibrotic effects. We identified Relm-α as one important player in the pathway from IL-4Rα signaling in macrophages to the induction of lysyl hydroxylase 2 (LH2), an enzyme that directs persistent pro-fibrotic collagen cross-links, in fibroblasts. Notably, Relm-β induced LH2 in human fibroblasts, and expression of both factors was increased in lipodermatosclerosis, a condition of excessive human skin fibrosis. Collectively, our findings provide mechanistic insights into the link between type 2 immunity and initiation of pro-fibrotic pathways. PMID:26474656

  3. Thrombogenic collagen-mimetic peptides: Self-assembly of triple helix-based fibrils driven by hydrophobic interactions

    PubMed Central

    Cejas, Mabel A.; Kinney, William A.; Chen, Cailin; Vinter, Jeremy G.; Almond, Harold R.; Balss, Karin M.; Maryanoff, Cynthia A.; Schmidt, Ute; Breslav, Michael; Mahan, Andrew; Lacy, Eilyn; Maryanoff, Bruce E.

    2008-01-01

    Collagens are integral structural proteins in animal tissues and play key functional roles in cellular modulation. We sought to discover collagen model peptides (CMPs) that would form triple helices and self-assemble into supramolecular fibrils exhibiting collagen-like biological activity without preorganizing the peptide chains by covalent linkages. This challenging objective was accomplished by placing aromatic groups on the ends of a representative 30-mer CMP, (GPO)10, as with l-phenylalanine and l-pentafluorophenylalanine in 32-mer 1a. Computational studies on homologous 29-mers 1a′–d′ (one less GPO), as pairs of triple helices interacting head-to-tail, yielded stabilization energies in the order 1a′ > 1b′ > 1c′ > 1d′, supporting the hypothesis that hydrophobic aromatic groups can drive CMP self-assembly. Peptides 1a–d were studied comparatively relative to structural properties and ability to stimulate human platelets. Although each 32-mer formed stable triple helices (CD) spectroscopy, only 1a and 1b self-assembled into micrometer-scale fibrils. Light microscopy images for 1a depicted long collagen-like fibrils, whereas images for 1d did not. Atomic force microscopy topographical images indicated that 1a and 1b self-organize into microfibrillar species, whereas 1c and 1d do not. Peptides 1a and 1b induced the aggregation of human blood platelets with a potency similar to type I collagen, whereas 1c was much less effective, and 1d was inactive (EC50 potency: 1a/1b ≫ 1c > 1d). Thus, 1a and 1b spontaneously self-assemble into thrombogenic collagen-mimetic materials because of hydrophobic aromatic interactions provided by the special end-groups. These findings have important implications for the design of biofunctional CMPs. PMID:18559857

  4. Minerals and aligned collagen fibrils in tilapia fish scales: structural analysis using dark-field and energy-filtered transmission electron microscopy and electron tomography.

    PubMed

    Okuda, Mitsuhiro; Ogawa, Nobuhiro; Takeguchi, Masaki; Hashimoto, Ayako; Tagaya, Motohiro; Chen, Song; Hanagata, Nobutaka; Ikoma, Toshiyuki

    2011-10-01

    The mineralized structure of aligned collagen fibrils in a tilapia fish scale was investigated using transmission electron microscopy (TEM) techniques after a thin sample was prepared using aqueous techniques. Electron diffraction and electron energy loss spectroscopy data indicated that a mineralized internal layer consisting of aligned collagen fibrils contains hydroxyapatite crystals. Bright-field imaging, dark-field imaging, and energy-filtered TEM showed that the hydroxyapatite was mainly distributed in the hole zones of the aligned collagen fibrils structure, while needle-like materials composed of calcium compounds including hydroxyapatite existed in the mineralized internal layer. Dark-field imaging and three-dimensional observation using electron tomography revealed that hydroxyapatite and needle-like materials were mainly found in the matrix between the collagen fibrils. It was observed that hydroxyapatite and needle-like materials were preferentially distributed on the surface of the hole zones in the aligned collagen fibrils structure and in the matrix between the collagen fibrils in the mineralized internal layer of the scale. PMID:21899811

  5. Metastatic Bladder Cancer Cells Distinctively Sense and Respond to Physical Cues of Collagen Fibril-Mimetic Nanotopography

    PubMed Central

    Iuliano, James N.; Kutscha, Paul D.; Biderman, Norbert J.; Subbaram, Sita; J; Groves, Timothy R.; Tenenbaum, Scott A.; Hempel, Nadine

    2015-01-01

    Tumor metastasis is characterized by enhanced invasiveness and migration of tumor cells through the extracellular matrix (ECM), resulting in extravasation into the blood and lymph and colonization at secondary sites. The ECM provides a physical scaffold consisting of components such as collagen fibrils, which have distinct dimensions at the nano-scale. In addition to the interaction of peptide moieties with tumor cell integrin clusters, the ECM provides a physical guide for tumor cell migration. Using nanolithography we set out to mimic the physical dimensions of collagen fibrils using lined nanotopographical silicon surfaces and to explore whether metastatic tumor cells are uniquely able to respond to these physical dimensions. Etched silicon surfaces containing nanoscale lined-patterns with varying trench and ridge sizes (65-500 nm) were evaluated for their ability to distinguish between a non-metastatic (253J) and a highly metastatic (253-J-BV) derivative bladder cancer cell line. Enhanced alignment was distinctively observed for the metastatic cell lines on feature sizes that mimic the dimensions of collagen fibrils (65-100 nm lines, 1:1-1:1.5 pitch). Further, these sub-100 nm lines acted as guides for migration of metastatic cancer cells. Interestingly, even at this sub-cellular scale, metastatic cell migration was abrogated when cells were forced to move perpendicular to these lines. Compared to flat surfaces, 65 nm lines enhanced the formation of actin stress fibers and filopodia of metastatic cells. This was accompanied by increased formation of focal contacts, visualized by immunofluorescent staining of phospho-focal adhesion Kinase (FAK) along the protruding lamellopodia. Simple lined nanotopography appears to be an informative platform for studying the physical cues of the ECM in a pseudo-3D format and likely mimics physical aspects of collagen fibrils. Metastatic cancer cells appear distinctively well-adapted to sense these features using filopodia

  6. New method for Raman investigation of the orientation of collagen fibrils and crystallites in the Haversian system of bone.

    PubMed

    Falgayrac, Guillaume; Facq, Sébastien; Leroy, Gérard; Cortet, Bernard; Penel, Guillaume

    2010-07-01

    Knowledge of the organization of the components of bone is of primary importance in understanding how this tissue responds to stresses and provides a starting point for the design and development of biomaterials. Bone structure has been the subject of numerous studies. The mineralized fiber arrangement in cortical bone is either a twisted or orthogonal plywood structure. Both mineral models coexist in compact bone. Raman polarized spectroscopy offers definite advantages in the study of biological samples, enabling the simultaneous analysis of mineral and organic components and the determination of molecular orientation through the polarization properties of the Raman scattering. In this study, we used the Raman polarization approach to simultaneously investigate the orientation of collagen fibrils and apatite crystals in human cortical bone. Raman bands ratios were monitored as a function of sample orientation. Specific ratios were chosen--such as nu(3) PO(4)/nu(1) PO(4), amide III (1271 cm(-1))/amide III (1243 cm(-1)), and amide I/amide III (1243 cm(-1))--due to their sensitivity to apatite-crystal and collagen-fibril orientation. Based on this original approach, spatial changes were monitored as a function of distance from the Haversian canal. The results revealed simultaneous tilting in intra-lamellar collagen-fibril and mineral crystal orientations. These results are consistent with a twisted plywood organization in the Haversian bone structure at the lamellar level. But at molecular level, the co-alignment of the collagen fibrils and the apatite crystal is observed in the innermost lamellae and becomes gradually less ordered as the distance from the Haversian canal increases. This work highlights the interest of Raman spectroscopy for the multiscale investigation of bone structure. PMID:20615291

  7. The 3D structure of the collagen fibril network in human trabecular bone: relation to trabecular organization.

    PubMed

    Reznikov, Natalie; Chase, Hila; Brumfeld, Vlad; Shahar, Ron; Weiner, Steve

    2015-02-01

    Trabecular bone is morphologically and functionally different from compact bone at the tissue level, but both are composed of lamellae at the micrometer-scale level. We present a three-dimensional study of the collagenous network of human trabecular lamellar bone from the proximal femur using the FIB-SEM serial surface view method. The results are compared to human compact lamellar bone of the femoral shaft, studied by the same method. Both demineralized trabecular and compact lamellar bone display the same overall structural organization, namely the presence of ordered and disordered materials and the confinement of the canalicular network to the disordered material. However, in trabecular bone lamellae a significant proportion of the ordered collagen fibril arrays is aligned with the long axis of the trabecula and, unlike in compact bone, is not related to the anatomical axis of the whole femur. The remaining ordered collagen fibrils are offset from the axis of a trabecula either by about 30° or 70°. Interestingly, at the tissue scale of millimeters, the most abundant angles between any two connected trabeculae - the inter-trabecular angles - center around 30° and 70°. This implies that within a framework of interconnected trabeculae the same lamellar structure will always have a significant component of the fibrils aligned with the long axes of connected trabeculae. This structural complementarity at different hierarchical levels presumably reflects an adaptation of trabecular bone to function. PMID:25445457

  8. Nano measurements with micro-devices: mechanical properties of hydrated collagen fibrils

    PubMed Central

    Eppell, S.J; Smith, B.N; Kahn, H; Ballarini, R

    2005-01-01

    The mechanical response of a biological material to applied forces reflects deformation mechanisms occurring within a hierarchical architecture extending over several distinct length scales. Characterizing and in turn predicting the behaviour of such a material requires an understanding of the mechanical properties of the substructures within the hierarchy, the interaction between the substructures, and the relative influence of each substructure on the overall behaviour. While significant progress has been made in mechanical testing of micrometre to millimetre sized biological specimens, quantitative reproducible experimental techniques for making mechanical measurements on specimens with characteristic dimensions in the smaller range of 10–1000 nm are lacking. Filling this void in experimentation is a necessary step towards the development of realistic multiscale computational models useful to predict and mitigate the risk of bone fracture, design improved synthetic replacements for bones, tendons and ligaments, and engineer bioinspired efficient and environmentally friendly structures. Here, we describe a microelectromechanical systems device for directly measuring the tensile strength, stiffness and fatigue behaviour of nanoscale fibres. We used the device to obtain the first stress–strain curve of an isolated collagen fibril producing the modulus and some fatigue properties of this soft nanofibril. PMID:16849223

  9. Dependencies of multi-component T 2 and T 1 ρ relaxation on the anisotropy of collagen fibrils in bovine nasal cartilage

    NASA Astrophysics Data System (ADS)

    Wang, Nian; Xia, Yang

    2011-09-01

    Both NMR spectroscopy and MRI were used to investigate the dependencies of multi-component T2 and T1ρ relaxation on the anisotropy of bovine nasal cartilage (BNC). The non-negative least square (NNLS) method and the multi-exponential fitting method were used to analyze all experimental data. When the collagen fibrils in nasal cartilage were oriented at the magic angle (55°) to the magnetic field B 0, both T2 and T1ρ were single component, regardless of the spin-lock field strength or the echo spacing time in the pulse sequences. When the collagen fibrils in nasal cartilage were oriented at 0° to B 0, both T2 and T1ρ at a spin-lock field of 500 Hz had two components. When the spin-lock field was increased to 1000 Hz or higher, T1ρ relaxation in nasal cartilage became a single component, even when the specimen orientation was 0°. These results demonstrate that the specimen orientation must be considered for any multi-component analysis, even for nasal cartilage that is commonly considered homogenously structured. Since the rapidly and slowly relaxing components can be attributed to different portions of the water population in tissue, the ability to resolve different relaxation components could be used to quantitatively examine individual molecular components in connective tissues.

  10. Age- and diabetes-related nonenzymatic crosslinks in collagen fibrils: candidate amino acids involved in Advanced Glycation End-products.

    PubMed

    Gautieri, Alfonso; Redaelli, Alberto; Buehler, Markus J; Vesentini, Simone

    2014-02-01

    Ageing and diabetes share a common deleterious phenomenon, the formation of Advanced Glycation Endproducts (AGEs), which accumulate predominantly in collagen due to its low turnover. Though the general picture of glycation has been identified, the detailed knowledge of which collagen amino acids are involved in AGEs is still missing. In this work we use an atomistic model of a collagen fibril to pinpoint, for the first time, the precise location of amino acids involved in the most relevant AGE, glucosepane. The results show that there are 14 specific lysine-arginine pairs that, due to their relative position and configuration, are likely to form glucosepane. We find that several residues involved in AGE crosslinks are within key collagen domains, such as binding sites for integrins, proteoglycans and collagenase, hence providing molecular-level explanations of previous experimental results showing decreased collagen affinity for key molecules. Altogether, these findings reveal the molecular mechanism by which glycation affects the biological properties of collagen tissues, which in turn contribute to age- and diabetes-related pathological states. PMID:24060753

  11. COLLAGEN PROCESSING

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Collagen dispersions, produced from fibrils recovered from milled bovine collagen, have shown promise in environmental remediation in applications as settling aids, filtration aids, fractionation media, oil drop stabilizers, and water purification aids. Macroporous structures, processed by controll...

  12. Softenin, a Novel Protein That Softens the Connective Tissue of Sea Cucumbers through Inhibiting Interaction between Collagen Fibrils

    PubMed Central

    Takehana, Yasuhiro; Yamada, Akira; Tamori, Masaki; Motokawa, Tatsuo

    2014-01-01

    The dermis in the holothurian body wall is a typical catch connective tissue or mutable collagenous tissue that shows rapid changes in stiffness. Some chemical factors that change the stiffness of the tissue were found in previous studies, but the molecular mechanisms of the changes are not yet fully understood. Detection of factors that change the stiffness by working directly on the extracellular matrix was vital to clarify the mechanisms of the change. We isolated from the body wall of the sea cucumber Stichopus chloronotus a novel protein, softenin, that softened the body-wall dermis. The apparent molecular mass was 20 kDa. The N-terminal sequence of 17 amino acids had low homology to that of known proteins. We performed sequential chemical and physical dissections of the dermis and tested the effects of softenin on each dissection stage by dynamic mechanical tests. Softenin softened Triton-treated dermis whose cells had been disrupted by detergent. The Triton-treated dermis was subjected to repetitive freeze-and-thawing to make Triton-Freeze-Thaw (TFT) dermis that was softer than the Triton-treated dermis, implying that some force-bearing structure had been disrupted by this treatment. TFT dermis was stiffened by tensilin, a stiffening protein of sea cucumbers. Softenin softened the tensilin-stiffened TFT dermis while it had no effect on the TFT dermis without tensilin treatment. We isolated collagen from the dermis. When tensilin was applied to the suspending solution of collagen fibrils, they made a large compact aggregate that was dissolved by the application of softenin or by repetitive freeze-and-thawing. These results strongly suggested that softenin decreased dermal stiffness through inhibiting cross-bridge formation between collagen fibrils; the formation was augmented by tensilin and the bridges were broken by the freeze-thaw treatment. Softenin is thus the first softener of catch connective tissue shown to work on the cross-bridges between

  13. Temperature-Responsive Gelation of Type I Collagen Solutions Involving Fibril Formation and Genipin Crosslinking as a Potential Injectable Hydrogel

    PubMed Central

    Yunoki, Shunji

    2013-01-01

    We investigated the temperature-responsive gelation of collagen/genipin solutions using pepsin-solubilized collagen (PSC) and acid-solubilized collagen (ASC) as substrates. Gelation occurred in the PSC/genipin solutions at genipin concentrations 0–2 mM under moderate change in temperature from 25 to 37°C. The PSC/genipin solutions exhibited fluidity at room temperature for at least 30 min, whereas the ASC/genipin solutions rapidly reached gel points. In specific cases PSC would be preferred over ASC as an injectable gel system. The temperature-responsive gelation of PSC/genipin solutions was due to temperature responses to genipin crosslinking and collagen fibril formation. The elastic modulus of the 0.5% PSC/genipin gel system could be adjusted in a range of 2.5 to 50 kPa by the PSC and genipin concentrations, suggesting that a PSC/genipin solution is a potential injectable gel system for drug and cell carriers, with mechanical properties matching those of living tissues. PMID:24222766

  14. Investigation of the three-dimensional orientation of mineralized collagen fibrils in human lamellar bone using synchrotron X-ray phase nano-tomography.

    PubMed

    Varga, Peter; Pacureanu, Alexandra; Langer, Max; Suhonen, Heikki; Hesse, Bernhard; Grimal, Quentin; Cloetens, Peter; Raum, Kay; Peyrin, Françoise

    2013-09-01

    We investigate the three-dimensional (3-D) organization of mineralized collagen fibrils in human cortical bone based on synchrotron X-ray phase nano-tomography images. In lamellar bone the collagen fibrils are assumed to have a plywood-like arrangement, but due to experimental limitations the 3-D fibril structure has only been deduced from section surfaces so far and the findings have been controversial. Breakthroughs in synchrotron tomographic imaging have given access to direct 3-D information on the bone structure at the nanoscale level. Using an autocorrelation-based orientation measure we confirm that the fibrils are unidirectional in quasi-planes of sub-lamellae and find two specific dominant patterns, oscillating and twisted plywoods coexisting in a single osteon. Both patterns exhibit smooth orientation changes between adjacent quasi-planes. Moreover, we find that the periodic changes in collagen fibril orientation are independent of fluctuations in local mass density. These data improve our understanding of the lamellar arrangement in bone and allow more detailed investigations of structure-function relationships at this scale, providing templates for bio-inspired materials. The presented methodology can be applied to non-destructive 3-D characterization of the sub-micron scale structure of other natural and artificial mineralized biomaterials. PMID:23707503

  15. Structural constraints on the evolution of the collagen fibril: convergence on a 1014-residue COL domain

    PubMed Central

    Slatter, David Anthony; Farndale, Richard William

    2015-01-01

    Type I collagen is the fundamental component of the extracellular matrix. Its α1 gene is the direct descendant of ancestral fibrillar collagen and contains 57 exons encoding the rod-like triple-helical COL domain. We trace the evolution of the COL domain from a primordial collagen 18 residues in length to its present 1014 residues, the limit of its possible length. In order to maintain and improve the essential structural features of collagen during evolution, exons can be added or extended only in permitted, non-random increments that preserve the position of spatially sensitive cross-linkage sites. Such sites cannot be maintained unless the twist of the triple helix is close to 30 amino acids per turn. Inspection of the gene structure of other long structural proteins, fibronectin and titin, suggests that their evolution might have been subject to similar constraints. PMID:25994354

  16. Investigation of ethanol infiltration into demineralized dentin collagen fibrils using molecular dynamics simulations.

    PubMed

    Jee, Sang Eun; Zhou, Jienfeng; Tan, Jianquo; Breschi, Lorenzo; Tay, Franklin R; Grégoire, Geneviève; Pashley, David H; Jang, Seung Soon

    2016-05-01

    The purpose of this study is to investigate the interaction of neat ethanol with bound and non-bound water in completely demineralized dentin that is fully hydrated, using molecular dynamics (MD) simulation method. The key to creating ideal resin-dentin bonds is the removal of residual free water layers and its replacement by ethanol solvent in which resin monomers are soluble, using the ethanol wet-bonding technique. The test null hypotheses were that ethanol cannot remove any collagen-bound water, and that ethanol cannot infiltrate into the spacing between collagen triple helix due to narrow interlayer spacing. Collagen fibrillar structures of overlap and gap regions were constructed by aligning the collagen triple helix of infinite length in hexagonal packing. Three layers of the water molecules were specified as the layers of 0.15-0.22nm, 0.22-0.43nm and 0.43-0.63nm from collagen atoms by investigating the water distribution surrounding collagen molecules. Our simulation results show that ethanol molecules infiltrated into the intermolecular spacing in the gap region, which increased due to the lateral shrinkage of the collagen structures in contact with ethanol solution, while there was no ethanol infiltration observed in the overlap region. Infiltrated ethanol molecules in the gap region removed residual water molecules via modifying mostly the third water layer (50% decrease), which would be considered as a loosely-bound water layer. The first and second hydration layers, which would be considered as tightly bound water layers, were not removed by the ethanol molecules, thus maintaining the helical structures of the collagen molecules. PMID:26969524

  17. [Atrial fibrillation--epidemiologic, economic and individual burden of disease].

    PubMed

    Brüggenjürgen, B; Reinhold, T; McBride, D; Willich, S N

    2010-03-01

    Atrial fibrillation (AF) is the most frequent cardiac arrhythmia. AF affects especially the elderly. The incidence rises with increasing age to over 15% for those over 90 years old. AF is a risk factor for systemic embolism and ischemic stroke. Stroke with AF is more severe with regard to neurologic impairment. In the management of AF an anticoagulation is essential. However, only half of the patients benefit from anticoagulation in therapeutic target ranges. Costs associated with AF accrue to 660 to 924 Mio Euro in Germany with hospitalization being the major cost contributor. Management of stroke patients with AF is at 3000 Euro higher compared to those patients without AF. AF has an impact on patients' wellbeing and impairs patients' quality of life, particularly the symptomatic form. With an increasing ageing of the society it is suggested to ensure that care management for patients with AF will be optimized. PMID:20221974

  18. Age-associated reduction of cellular spreading/mechanical force up-regulates matrix metalloproteinase-1 expression and collagen fibril fragmentation via c-Jun/AP-1 in human dermal fibroblasts

    PubMed Central

    Qin, Zhaoping; Voorhees, John J; Fisher, Gary J; Quan, Taihao

    2014-01-01

    The dermal compartment of human skin is largely composed of dense collagen-rich fibrils, which provide structural and mechanical support. Skin dermal fibroblasts, the major collagen-producing cells, are interact with collagen fibrils to maintain cell spreading and mechanical force for function. A characteristic feature of aged human skin is fragmentation of collagen fibrils, which is initiated by matrix metalloproteinase 1 (MMP-1). Fragmentation impairs fibroblast attachment and thereby reduces spreading. Here, we investigated the relationship among fibroblast spreading, mechanical force, MMP-1 expression, and collagen fibril fragmentation. Reduced fibroblast spreading due to cytoskeletal disruption was associated with reduced cellular mechanical force, as determined by atomic force microscopy. These reductions substantially induced MMP-1 expression, which led to collagen fibril fragmentation and disorganization in three-dimensional collagen lattices. Constraining fibroblast size by culturing on slides coated with collagen micropatterns also significantly induced MMP-1 expression. Reduced spreading/mechanical force induced transcription factor c-Jun and its binding to a canonical AP-1 binding site in the MMP-1 proximal promoter. Blocking c-Jun function with dominant negative mutant c-Jun significantly reduced induction of MMP-1 expression in response to reduced spreading/mechanical force. Furthermore, restoration of fibroblast spreading/mechanical force led to decline of c-Jun and MMP-1 levels and eliminated collagen fibril fragmentation and disorganization. These data reveal a novel mechanism by which alteration of fibroblast shape/mechanical force regulates c-Jun/AP-1-dependent expression of MMP-1 and consequent collagen fibril fragmentation. This mechanism provides a foundation for understanding the cellular and molecular basis of age-related collagen fragmentation in human skin. PMID:25201474

  19. A Novel 3D Fibril Force Assay Implicates Src in Tumor Cell Force Generation in Collagen Networks

    PubMed Central

    Polackwich, Robert J.; Koch, Daniel; Arevalo, Richard; Miermont, Anne M.; Jee, Kathleen J.; Lazar, John; Urbach, Jeffrey; Mueller, Susette C.; McAllister, Ryan G.

    2013-01-01

    New insight into the biomechanics of cancer cell motility in 3D extracellular matrix (ECM) environments would significantly enhance our understanding of aggressive cancers and help identify new targets for intervention. While several methods for measuring the forces involved in cell-matrix interactions have been developed, previous to this study none have been able to measure forces in a fibrillar environment. We have developed a novel assay for simultaneously measuring cell mechanotransduction and motility in 3D fibrillar environments. The assay consists of a controlled-density fibrillar collagen gel atop a controlled-stiffness polyacrylamide (PAA) surface. Forces generated by living cells and their migration in the 3D collagen gel were measured with the 3D motion of tracer beads within the PAA layer. Here, this 3D fibril force assay is used to study the role of the invasion-associated protein kinase Src in mechanotransduction and motility. Src expression and activation are linked with proliferation, invasion, and metastasis, and have been shown to be required in 2D for invadopodia membranes to direct and mediate invasion. Breast cancer cell line MDA-MD-231 was stably transfected with GFP-tagged constitutively active Src or wild-type Src. In 3D fibrillar collagen matrices we found that, relative to wild-type Src, constitutively active Src: 1) increased the strength of cell-induced forces on the ECM, 2) did not significantly change migration speed, and 3) increased both the duration and the length, but not the number, of long membrane protrusions. Taken together, these results support the hypothesis that Src controls invasion by controlling the ability of the cell to form long lasting cellular protrusions to enable penetration through tissue barriers, in addition to its role in promoting invadopodia matrix-degrading activity. PMID:23536784

  20. A Stochastic Individual-Based Model of the Progression of Atrial Fibrillation in Individuals and Populations

    PubMed Central

    Galla, Tobias; Clayton, Richard H.

    2016-01-01

    Models that represent the mechanisms that initiate and sustain atrial fibrillation (AF) in the heart are computationally expensive to simulate and therefore only capture short time scales of a few heart beats. It is therefore difficult to embed biophysical mechanisms into both policy-level disease models, which consider populations of patients over multiple decades, and guidelines that recommend treatment strategies for patients. The aim of this study is to link these modelling paradigms using a stylised population-level model that both represents AF progression over a long time-scale and retains a description of biophysical mechanisms. We develop a non-Markovian binary switching model incorporating three different aspects of AF progression: genetic disposition, disease/age related remodelling, and AF-related remodelling. This approach allows us to simulate individual AF episodes as well as the natural progression of AF in patients over a period of decades. Model parameters are derived, where possible, from the literature, and the model development has highlighted a need for quantitative data that describe the progression of AF in population of patients. The model produces time series data of AF episodes over the lifetimes of simulated patients. These are analysed to quantitatively describe progression of AF in terms of several underlying parameters. Overall, the model has potential to link mechanisms of AF to progression, and to be used as a tool to study clinical markers of AF or as training data for AF classification algorithms. PMID:27070920

  1. Genetic linkage of type VII collagen (COL7A1) to dominant dystrophic epidermolysis bullosa in families with abnormal anchoring fibrils.

    PubMed Central

    Ryynänen, M; Ryynänen, J; Sollberg, S; Iozzo, R V; Knowlton, R G; Uitto, J

    1992-01-01

    Epidermolysis bullosa (EB) in a group of genodermatoses characterized by the fragility of skin. Previous studies on the dystrophic (scarring) forms of EB have suggested abnormalities in anchoring fibrils, morphologically recognizable attachment structures that provide stability to the association of the cutaneous basement membrane to the underlying dermis. Since type VII collagen is the major component of the anchoring fibrils, we examined the genetic linkage of dominant dystrophic EB (EBDD) and the type VII collagen gene (COL7A1) locus, which we have recently mapped to chromosome 3p, in three large kindreds with abnormal anchoring fibrils. Strong genetic linkage of EBDD and COL7A1 loci was demonstrated with the maximum logarithm of odds (LOD) score of 8.77 at theta = 0. This linkage was further confirmed with two additional markers in this region of the short arm of chromosome 3, and these analyses allowed further refinement of the map locus of COL7A1. Since there were no recombinants between the COL7A1 and EBDD loci, our findings suggest that type VII collagen is the candidate gene that may harbor the mutations responsible for the EB phenotype in these three families. Images PMID:1347297

  2. On the computation of stress in affine versus nonaffine fibril kinematics within planar collagen network models.

    PubMed

    Pence, Thomas J; Monroe, Ryan J; Wright, Neil T

    2008-08-01

    Some recent analyses modeled the response of collagenous tissues, such as epicardium, using a hypothetical network consisting of interconnected springlike fibers. The fibers in the network were organized such that internal nodes served as the connection point between three such collagen springs. The results for assumed affine and nonaffine deformations are contrasted after a homogeneous deformation at the boundary. Affine deformation provides a stiffer mechanical response than nonaffine deformation. In contrast to nonaffine deformation, affine deformation determines the displacement of internal nodes without imposing detailed force balance, thereby complicating the simplest intuitive notion of stress, one based on free body cuts, at the single node scale. The standard notion of stress may then be recovered via average field theory computations based on large micromesh realizations. An alternative and by all indications complementary viewpoint for the determination of stress in these collagen fiber networks is discussed here, one in which stress is defined using elastic energy storage, a notion which is intuitive at the single node scale. It replaces the average field theory computations by an averaging technique over randomly oriented isolated simple elements. The analytical operations do not require large micromesh realizations, but the tedious nature of the mathematical manipulation is clearly aided by symbolic algebra calculation. For the example case of linear elastic deformation, this results in material stiffnesses that relate the infinitesimal strain and stress. The result that the affine case is stiffer than the nonaffine case is recovered, as would be expected. The energy framework also lends itself to the natural inclusion of changes in mechanical response due to the chemical, electrical, or thermal environment. PMID:18601451

  3. Relationship between Prion Propensity and the Rates of Individual Molecular Steps of Fibril Assembly*

    PubMed Central

    Wang, Yi-Qian; Buell, Alexander K.; Wang, Xin-Yu; Welland, Mark E.; Dobson, Christopher M.; Knowles, Tuomas P. J.; Perrett, Sarah

    2011-01-01

    Peptides and proteins possess an inherent propensity to self-assemble into generic fibrillar nanostructures known as amyloid fibrils, some of which are involved in medical conditions such as Alzheimer disease. In certain cases, such structures can self-propagate in living systems as prions and transmit characteristic traits to the host organism. The mechanisms that allow certain amyloid species but not others to function as prions are not fully understood. Much progress in understanding the prion phenomenon has been achieved through the study of prions in yeast as this system has proved to be experimentally highly tractable; but quantitative understanding of the biophysics and kinetics of the assembly process has remained challenging. Here, we explore the assembly of two closely related homologues of the Ure2p protein from Saccharomyces cerevisiae and Saccharomyces paradoxus, and by using a combination of kinetic theory with solution and biosensor assays, we are able to compare the rates of the individual microscopic steps of prion fibril assembly. We find that for these proteins the fragmentation rate is encoded in the structure of the seed fibrils, whereas the elongation rate is principally determined by the nature of the soluble precursor protein. Our results further reveal that fibrils that elongate faster but fracture less frequently can lose their ability to propagate as prions. These findings illuminate the connections between the in vitro aggregation of proteins and the in vivo proliferation of prions, and provide a framework for the quantitative understanding of the parameters governing the behavior of amyloid fibrils in normal and aberrant biological pathways. PMID:21233211

  4. Two-way regulation between cells and aligned collagen fibrils: local 3D matrix formation and accelerated neural differentiation of human decidua parietalis placental stem cells.

    PubMed

    Li, Wen; Zhu, Bofan; Strakova, Zuzana; Wang, Rong

    2014-08-01

    It has been well established that an aligned matrix provides structural and signaling cues to guide cell polarization and cell fate decision. However, the modulation role of cells in matrix remodeling and the feedforward effect on stem cell differentiation have not been studied extensively. In this study, we report on the concerted changes of human decidua parietalis placental stem cells (hdpPSCs) and the highly ordered collagen fibril matrix in response to cell-matrix interaction. With high-resolution imaging, we found the hdpPSCs interacted with the matrix by deforming the cell shape, harvesting the nearby collagen fibrils, and reorganizing the fibrils around the cell body to transform a 2D matrix to a localized 3D matrix. Such a unique 3D matrix prompted high expression of β-1 integrin around the cell body that mediates and facilitates the stem cell differentiation toward neural cells. The study offers insights into the coordinated, dynamic changes at the cell-matrix interface and elucidates cell modulation of its matrix to establish structural and biochemical cues for effective cell growth and differentiation. PMID:25003322

  5. Liquid crystalline collagen: a self-assembled morphology for the orientation of mammalian cells.

    PubMed

    Kirkwood, John E; Fuller, Gerald G

    2009-03-01

    We report the creation of collagen films having a cholesteric banding structure with an orientation that can be systematically controlled. The action of hydrodynamic flow and rapid desiccation was used to influence the orientation of collagen fibrils, producing a film with a twisted plywood architecture. Adult human fibroblasts cultured on these substrates orient in the direction of the flow deposition, and filopodia are extended onto individual bands. Atomic force microscopy reveals the assembly of 30 nm collagen fibrils into the uniform cholesteric collagen films with a periodic surface relief. The generation of collagen with a reticular, "basket-weave" morphology when using lower concentrations is also discussed. PMID:19437784

  6. Lateral growth limitation of corneal fibrils and their lamellar stacking depend on covalent collagen cross-linking by transglutaminase-2 and lysyl oxidases, respectively.

    PubMed

    Wang, Lei; Uhlig, Philipp C; Eikenberry, Eric F; Robenek, Horst; Bruckner, Peter; Hansen, Uwe

    2014-01-10

    Corneal stroma contains an extracellular matrix of orthogonal lamellae formed by parallel and equidistant fibrils with a homogeneous diameter of ~35 nm. This is indispensable for corneal transparency and mechanical functions. However, the mechanisms controlling corneal fibrillogenesis are incompletely understood and the conditions required for lamellar stacking are essentially unknown. Under appropriate conditions, chick embryo corneal fibroblasts can produce an extracellular matrix in vitro resembling primary corneal stroma during embryonic development. Among other requirements, cross-links between fibrillar collagens, introduced by tissue transglutaminase-2, are necessary for the self-assembly of uniform, small diameter fibrils but not their lamellar stacking. By contrast, the subsequent lamellar organization into plywood-like stacks depends on lysyl aldehyde-derived cross-links introduced by lysyl oxidase activity, which, in turn, only weakly influences fibril diameters. These cross-links are introduced at early stages of fibrillogenesis. The enzymes are likely to be important for a correct matrix deposition also during repair of the cornea. PMID:24265319

  7. Investigating collagen self-assembly with optical tweezers microrheology

    NASA Astrophysics Data System (ADS)

    Forde, Nancy; Shayegan, Marjan; Altindal, Tuba

    Collagen is the fundamental structural protein in vertebrates. Assembled from individual triple-helical proteins to make strong fibres, collagen is a beautiful example of a hierarchical self-assembling system. Using optical tweezers to perform microrheology measurements, we explore the dynamics of interactions between collagens responsible for their self-assembly and examine the development of heterogeneous mechanics during assembly into fibrillar gels. Telopeptides, short non-helical regions that flank the triple helix, have long been known to facilitate fibril self-assembly. We find that their removal not only slows down fibril nucleation but also results in a significant frequency-dependent reduction in the elastic modulus of collagens in solution. We interpret these results in terms of a model in which telopeptides facilitate transient intermolecular interactions, which enhance network connectivity in solution and lead to more rapid assembly in fibril-forming conditions. Current address: Department of Physics, McGill University.

  8. Identification of novel short peptides derived from the {alpha}4, {alpha}5, and {alpha}6 fibrils of type IV collagen with anti-angiogenic properties

    SciTech Connect

    Karagiannis, Emmanouil D. . E-mail: ekaragi1@jhmi.edu; Popel, Aleksander S.

    2007-03-09

    Angiogenesis, or neovascularization, is tightly controlled by positive and negative regulators, many of which reside in the extracellular matrix. We have now identified eight novel 19- to 20-residue peptides derived from the {alpha}4, {alpha}5, and {alpha}6 fibrils of type IV collagen, which we have designated tetrastatins, pentastatins, and hexastatins, respectively. We have shown that these endogenous peptides suppress the proliferation and migration of HUVECs in vitro. By performing clustering analyses of the sequences using sequence similarity criteria and of the experimental results using a hierarchical algorithm, we report that the clusters identified by the experimental results coincide with the sequence-based clusters, indicating a tight relationship between peptide sequence and anti-angiogenic potency. These peptides may have potential as anti-angiogenic therapeutic agents.

  9. COLLAGEN STRUCTURE AND STABILITY

    PubMed Central

    Shoulders, Matthew D.; Raines, Ronald T.

    2010-01-01

    Collagen is the most abundant protein in animals. This fibrous, structural protein comprises a right-handed bundle of three parallel, left-handed polyproline II-type helices. Much progress has been made in elucidating the structure of collagen triple helices and the physicochemical basis for their stability. New evidence demonstrates that stereoelectronic effects and preorganization play a key role in that stability. The fibrillar structure of type I collagen–the prototypical collagen fibril–has been revealed in detail. Artificial collagen fibrils that display some properties of natural collagen fibrils are now accessible using chemical synthesis and self-assembly. A rapidly emerging understanding of the mechanical and structural properties of native collagen fibrils will guide further development of artificial collagenous materials for biomedicine and nanotechnology. PMID:19344236

  10. Electron microscopic stereological study of collagen fibrils in bovine articular cartilage: volume and surface densities are best obtained indirectly (from length densities and diameters) using isotropic uniform random sampling

    PubMed Central

    LÅNGSJÖ, TEEMU K.; HYTTINEN, MIKA; PELTTARI, ALPO; KIRALY, KARI; AROKOSKI, JARI; HELMINEN, HEIKKI J.

    1999-01-01

    Results obtained by the indirect zonal isotropic uniform random (IUR) estimation were compared with those obtained by the direct point and interception counting methods on vertical (VS) or IUR sections in a stereological study of bovine articular cartilage collagen fibrils at the ultrastructural level. Besides comparisons between the direct and indirect estimations (direct IUR vs indirect IUR estimations) and between different sampling methods (VS vs IUR sampling), simultaneous comparison of the 2 issues took place (direct VS vs indirect IUR estimation). Using the direct VS method, articular cartilage superficial zone collagen volume fraction (Vv 41%) was 67% and fibril surface density (Sv 0.030 nm2/nm3) 15% higher (P<0.05) than values obtained by the indirect IUR method (Vv 25% and Sv 0.026 nm2/nm3). The same was observed when the direct IUR method was used: collagen volume fraction (Vv 40%) was 63% and fibril surface density (Sv 0.032 nm2/nm3) 21% higher (P<0.05) than those obtained by the indirect IUR technique. Similarly, in the deep zone of articular cartilage direct VS and direct IUR methods gave 50 and 55% higher (P<0.05) collagen fibril volume fractions (Vv 43 and 44% vs 29%) and the direct IUR method 25% higher (P<0.05) fibril surface density values (Sv 0.025 vs 0.020 nm2/nm3) than the indirect IUR estimation. On theoretical grounds, scrutiny calculations, as well as earlier reports, it is concluded that the direct VS and direct IUR methods systematically overestimated the Vv and Sv of collagen fibrils. This bias was due to the overprojection which derives from the high section thickness in relation to collagen fibril diameter. On the other hand, factors that during estimation tend to underestimate Vv and Sv, such as profile overlapping and truncation (‘fuzzy’ profiles), seemed to cause less bias. As length density (Lv) and collagen fibril diameter are minimally biased by the high relative section thickness, the indirect IUR method, based on

  11. Viscoelastic properties of model segments of collagen molecules.

    PubMed

    Gautieri, Alfonso; Vesentini, Simone; Redaelli, Alberto; Buehler, Markus J

    2012-03-01

    Collagen is the prime construction material in vertebrate biology, determining the mechanical behavior of connective tissues such as tendon, bone and skin. Despite extensive efforts in the investigation of the origin of collagen unique mechanical properties, a deep understanding of the relationship between molecular structure and mechanical properties remains elusive, hindered by the complex hierarchical structure of collagen-based tissues. In particular, although extensive studies of viscoelastic properties have been pursued at the macroscopic (fiber/tissue) level, fewer investigations have been performed at the smaller scales, including in particular collagen molecules and fibrils. These scales are, however, important for a complete understanding of the role of collagen as an important constituent in the extracellular matrix. Here, using an atomistic modeling approach, we perform in silico creep tests of a collagen-like peptide, monitoring the strain-time response for different values of applied external load. The results show that individual collagen molecules exhibit a nonlinear viscoelastic behavior, with a Young's modulus increasing from 6 to 16GPa (for strains up to 20%), a viscosity of 3.84.±0.38Pa·s, and a relaxation time in the range of 0.24-0.64ns. The single molecule viscosity, for the first time reported here, is several orders of magnitude lower than the viscosity found for larger-scale single collagen fibrils, suggesting that the viscous behavior of collagen fibrils and fibers involves additional mechanisms, such as molecular sliding between collagen molecules within the fibril or the effect of relaxation of larger volumes of solvent. Based on our molecular modeling results we propose a simple structural model that describes collagen tissue as a hierarchical structure, providing a bottom-up description of elastic and viscous properties form the properties of the tissue basic building blocks. PMID:22204879

  12. Collagen IX is required for the integrity of collagen II fibrils and the regulation of vascular plexus formation in zebrafish caudal fins.

    PubMed

    Huang, Cheng-chen; Wang, Tai-Chuan; Lin, Bo-Hung; Wang, Yi-Wen; Johnson, Stephen L; Yu, John

    2009-08-15

    Capillary plexuses form during both vasculogenesis and angiogenesis and are remodeled into mature vessel types and patterns which are delicately orchestrated with the sizes and shapes of other tissues and organs. We isolated a zebrafish mutation named prp (for persistent plexus) that causes persistent formation of vascular plexuses in the caudal fins and consequent mispatterning of bony fin rays and the fin shape. Detailed analyses revealed that the prp mutation causes a significant reduction in the size and dramatic structural defects in collagen II-rich extracellular matrices called actinotrichia of both embryonic finfolds and adult fins. prp was mapped to chromosome 19 and found to encode the zebrafish collagen9alpha1 (col9alpha1) gene which is abundantly expressed in developing finfolds. A point mutation resulting in a leucine-to-histidine change was detected in the thrombospondin domain of the col9alpha1 gene in prp. Morpholino-mediated knockdown of col9alpha1 phenocopied the prp small-finfold phenotype in wild-type embryos, and an injection of plasmids containing the col9alpha1 cDNA into prp embryos locally restored the finfold size. Furthermore, we found that osteoblasts in prp mutants were mispatterned apparently following the abnormal vascular plexus pattern, demonstrating that blood vessels play an important role in the patterning of bony rays in zebrafish caudal fins. PMID:19501583

  13. Epitaxially guided assembly of collagen layers on mica surfaces.

    PubMed

    Leow, Wee Wen; Hwang, Wonmuk

    2011-09-01

    Ordered assembly of collagen molecules on flat substrates has potential for various applications and serves as a model system for studying the assembly process. While previous studies demonstrated self-assembly of collagen on muscovite mica into highly ordered layers, the mechanism by which different conditions affect the resulting morphology remains to be elucidated. Using atomic force microscopy, we follow the assembly of collagen on muscovite mica at a concentration lower than the critical fibrillogenesis concentration in bulk. Initially, individual collagen molecules adsorb to mica and subsequently nucleate into fibrils possessing the 67 nm D-periodic bands. Emergence of fibrils aligned in parallel despite large interfibril distances agrees with an alignment mechanism guided by the underlying mica. The epitaxial growth was further confirmed by the formation of novel triangular networks of collagen fibrils on phlogopite mica, whose surface lattice is known to have a hexagonal symmetry, whereas the more widely used muscovite does not. Comparing collagen assembly on the two types of mica at different potassium concentrations revealed that potassium binds to the negatively charged mica surface and neutralizes it, thereby reducing the binding affinity of collagen and enhancing surface diffusion. These results suggest that collagen assembly on mica follows the surface adsorption, diffusion, nucleation, and growth pathway, where the growth direction is determined at the nucleation step. Comparison with other molecules that assemble similarly on mica supports generality of the proposed assembly mechanism, the knowledge of which will be useful for controlling the resulting surface morphologies. PMID:21740026

  14. Fibulin-4 E57K Knock-in Mice Recapitulate Cutaneous, Vascular and Skeletal Defects of Recessive Cutis Laxa 1B with both Elastic Fiber and Collagen Fibril Abnormalities.

    PubMed

    Igoucheva, Olga; Alexeev, Vitali; Halabi, Carmen M; Adams, Sheila M; Stoilov, Ivan; Sasaki, Takako; Arita, Machiko; Donahue, Adele; Mecham, Robert P; Birk, David E; Chu, Mon-Li

    2015-08-28

    Fibulin-4 is an extracellular matrix protein essential for elastic fiber formation. Frameshift and missense mutations in the fibulin-4 gene (EFEMP2/FBLN4) cause autosomal recessive cutis laxa (ARCL) 1B, characterized by loose skin, aortic aneurysm, arterial tortuosity, lung emphysema, and skeletal abnormalities. Homozygous missense mutations in FBLN4 are a prevalent cause of ARCL 1B. Here we generated a knock-in mouse strain bearing a recurrent fibulin-4 E57K homozygous missense mutation. The mutant mice survived into adulthood and displayed abnormalities in multiple organ systems, including loose skin, bent forelimb, aortic aneurysm, tortuous artery, and pulmonary emphysema. Biochemical studies of dermal fibroblasts showed that fibulin-4 E57K mutant protein was produced but was prone to dimer formation and inefficiently secreted, thereby triggering an endoplasmic reticulum stress response. Immunohistochemistry detected a low level of fibulin-4 E57K protein in the knock-in skin along with altered expression of selected elastic fiber components. Processing of a precursor to mature lysyl oxidase, an enzyme involved in cross-linking of elastin and collagen, was compromised. The knock-in skin had a reduced level of desmosine, an elastin-specific cross-link compound, and ultrastructurally abnormal elastic fibers. Surprisingly, structurally aberrant collagen fibrils and altered organization into fibers were characteristics of the knock-in dermis and forelimb tendons. Type I collagen extracted from the knock-in skin had decreased amounts of covalent intermolecular cross-links, which could contribute to the collagen fibril abnormalities. Our studies provide the first evidence that fibulin-4 plays a role in regulating collagen fibril assembly and offer a preclinical platform for developing treatments for ARCL 1B. PMID:26178373

  15. Molecular crowding of collagen: a pathway to produce highly-organized collagenous structures.

    PubMed

    Saeidi, Nima; Karmelek, Kathryn P; Paten, Jeffrey A; Zareian, Ramin; DiMasi, Elaine; Ruberti, Jeffrey W

    2012-10-01

    Collagen in vertebrate animals is often arranged in alternating lamellae or in bundles of aligned fibrils which are designed to withstand in vivo mechanical loads. The formation of these organized structures is thought to result from a complex, large-area integration of individual cell motion and locally-controlled synthesis of fibrillar arrays via cell-surface fibripositors (direct matrix printing). The difficulty of reproducing such a process in vitro has prevented tissue engineers from constructing clinically useful load-bearing connective tissue directly from collagen. However, we and others have taken the view that long-range organizational information is potentially encoded into the structure of the collagen molecule itself, allowing the control of fibril organization to extend far from cell (or bounding) surfaces. We here demonstrate a simple, fast, cell-free method capable of producing highly-organized, anistropic collagen fibrillar lamellae de novo which persist over relatively long-distances (tens to hundreds of microns). Our approach to nanoscale organizational control takes advantage of the intrinsic physiochemical properties of collagen molecules by inducing collagen association through molecular crowding and geometric confinement. To mimic biological tissues which comprise planar, aligned collagen lamellae (e.g. cornea, lamellar bone or annulus fibrosus), type I collagen was confined to a thin, planar geometry, concentrated through molecular crowding and polymerized. The resulting fibrillar lamellae show a striking resemblance to native load-bearing lamellae in that the fibrils are small, generally aligned in the plane of the confining space and change direction en masse throughout the thickness of the construct. The process of organizational control is consistent with embryonic development where the bounded planar cell sheets produced by fibroblasts suggest a similar confinement/concentration strategy. Such a simple approach to nanoscale

  16. The novel cuticular collagen Ovcol-1 of Onchocerca volvulus is preferentially recognized by immunoglobulin G3 from putatively immune individuals.

    PubMed Central

    Stewart, G R; Zhu, Y; Parredes, W; Tree, T I; Guderian, R; Bradley, J E

    1997-01-01

    The cDNA sequence encoding an Onchocerca volvulus collagen, Ovcol-1, has been isolated and the corresponding native antigen has been identified. The cDNA encodes an open reading frame of 96 amino acid residues containing an uninterrupted 66-residue Gly-X-Y repeat triple-helical (TH) domain (where X and Y may be any amino acids) flanked by a 26-residue amino non-TH domain and a 4-residue carboxyl non-TH domain. The size (9.7 kDa) and structure of the deduced molecule are unique among previously identified collagen chains. This novel collagen type has been designated "mini-chain collagen." Native Ovcol-1 is aqueous soluble and resolves by sodium dodecyl sulfate-polyacrylamide gel electrophoresis at 14.2 kDa under reducing conditions. Immunoelectron microscopy of adult female O. volvulus localized Ovcol-1 to the cuticles of both the adult worm and uterine microfilaria. A group of individuals from an area in Ecuador where O. volvulus is hyperendemic have been classified as putatively immune (PI) to O. volvulus infection. Analysis of the humoral immune responses to Ovcol-1 demonstrated that immunoglobulin G3 (IgG3) of PI individuals preferentially recognized this antigen in comparison to IgG3 of infected individuals. PMID:8975907

  17. Information contained in the amino acid sequence of the alpha1(I)-chain of collagen and its consequences upon the formation of the triple helix, of fibrils and crosslinks.

    PubMed

    Fietzek, P P; Kühn, K

    1975-09-30

    The molecule of type I collagen from skin consists of two alpha1(I)-chains and one alpha2-chain. The sequence of the entire alpha1-chain comprising 1052 residues is summarily presented and discussed. Apart from the 279 residues of alpha1(I)-CB8 whose sequence has been established for rat skin collagen, all sequences have been determined for calf skin collagen. In order to facilitate sequence analysis, the alpha1-chain was cleaved into defined fragments by cyanogen bromide or hydroxylamine or limited collagenase digestion. Most of the sequence was established by automated stepwise Edman degradation. The alpha1-chain contains two basically different types of sequences: the triple helical region of 1011 amino acid residues in which every third position is occupied by glycine and the N- and C-terminal regions not displaying this type of regularity. Both of these non-triple helical regions carry oxidizable lysine or hydroxylysine residues as functional sites for the intermolecular crosslink formation. Implications of the amino acid sequence for the stability of the triple helix and the fibril as well as for formation of crosslinks are discussed. Evaluation of the sequence in connection with electron microscopical investigations yielded the parameters of the axial arrangement of the molecules within the fibrils. Axial stagger of the molecules by a distance D = 670 angstrom = 233 amino acid residues results in maximal interaction of polar sequence regions of adjacent molecules and similarly of regions of hydrophobic residues. Ordered aggregation of molecules into fibrils is, therefore, regulated by electrostatic and electrophobic forces. Possible loci of intermolecular crosslinks between the alpha1-chains of adjacent molecules may be deduced from the dimensions of the axial aggregation of molecules. PMID:171554

  18. Tenascin-X deficiency mimics Ehlers-Danlos syndrome in mice through alteration of collagen deposition.

    PubMed

    Mao, Jau Ren; Taylor, Glen; Dean, Willow B; Wagner, Diane R; Afzal, Veena; Lotz, Jeffrey C; Rubin, Edward M; Bristow, James

    2002-04-01

    Tenascin-X is a large extracellular matrix protein of unknown function. Tenascin-X deficiency in humans is associated with Ehlers-Danlos syndrome, a generalized connective tissue disorder resulting from altered metabolism of the fibrillar collagens. Because TNXB is the first Ehlers-Danlos syndrome gene that does not encode a fibrillar collagen or collagen-modifying enzyme, we suggested that tenascin-X might regulate collagen synthesis or deposition. To test this hypothesis, we inactivated Tnxb in mice. Tnxb-/- mice showed progressive skin hyperextensibility, similar to individuals with Ehlers-Danlos syndrome. Biomechanical testing confirmed increased deformability and reduced tensile strength of their skin. The skin of Tnxb-/- mice was histologically normal, but its collagen content was significantly reduced. At the ultrastructural level, collagen fibrils of Tnxb-/- mice were of normal size and shape, but the density of fibrils in their skin was reduced, commensurate with the reduction in collagen content. Studies of cultured dermal fibroblasts showed that although synthesis of collagen I by Tnxb-/- and wildtype cells was similar, Tnxb-/- fibroblasts failed to deposit collagen I into cell-associated matrix. This study confirms a causative role for TNXB in human Ehlers-Danlos syndrome and suggests that tenascin-X is an essential regulator of collagen deposition by dermal fibroblasts. PMID:11925569

  19. Tenascin-x deficiency mimics ehlers-danlos syndrome in mice through alteration of collagen deposition

    SciTech Connect

    Mao, J.R.; Taylor, G.; Dean, W.B.; Wagner, D.R.; Afzal, V.; Lotz, J.C.; Rubin, E.M.; Bristow, J.

    2002-03-01

    Tenascin-X is a large extracellular matrix protein of unknown function1-3. Tenascin-X deficiency in humans is associated with Ehlers-Danlos syndrome4,5, a generalized connective tissue disorder resulting from altered metabolism of the fibrillar collagens6. Because TNXB is the first Ehlers-Danlos syndrome gene that does not encode a fibrillar collagen or collagen-modifying enzyme7-14, we suggested that tenascin-X might regulate collagen synthesis or deposition15. To test this hypothesis, we inactivated Tnxb in mice. Tnxb-/- mice showed progressive skin hyperextensibility, similar to individuals with Ehlers-Danlos syndrome. Biomechanical testing confirmed increased deformability and reduced tensile strength of their skin. The skin of Tnxb-/- mice was histologically normal, but its collagen content was significantly reduced. At the ultrastructural level, collagen fibrils of Tnxb-/- mice were of normal size and shape, but the density of fibrils in their skin was reduced, commensurate with the reduction in collagen content. Studies of cultured dermal fibroblasts showed that although synthesis of collagen I by Tnxb-/- and wildtype cells was similar, Tnxb-/- fibroblasts failed to deposit collagen I into cell-associated matrix. This study confirms a causative role for TNXB in human Ehlers-Danlos syndrome and suggests that tenascin-X is an essential regulator of collagen deposition by dermal fibroblasts.

  20. Collagen fibrillogenesis: fibronectin, integrins, and minor collagens as organizers and nucleators

    PubMed Central

    Kadler, Karl E; Hill, Adele; Canty-Laird, Elizabeth G

    2008-01-01

    Collagens are triple helical proteins that occur in the extracellular matrix (ECM) and at the cell–ECM interface. There are more than 30 collagens and collagen-related proteins but the most abundant are collagens I and II that exist as D-periodic (where D = 67 nm) fibrils. The fibrils are of broad biomedical importance and have central roles in embryogenesis, arthritis, tissue repair, fibrosis, tumor invasion, and cardiovascular disease. Collagens I and II spontaneously form fibrils in vitro, which shows that collagen fibrillogenesis is a selfassembly process. However, the situation in vivo is not that simple; collagen I-containing fibrils do not form in the absence of fibronectin, fibronectin-binding and collagen-binding integrins, and collagen V. Likewise, the thin collagen II-containing fibrils in cartilage do not form in the absence of collagen XI. Thus, in vivo, cellular mechanisms are in place to control what is otherwise a protein self-assembly process. This review puts forward a working hypothesis for how fibronectin and integrins (the organizers) determine the site of fibril assembly, and collagens V and XI (the nucleators) initiate collagen fibrillogenesis. PMID:18640274

  1. A collagen and elastic network in the wing of the bat.

    PubMed Central

    Holbrook, K A; Odland, G F

    1978-01-01

    Bundles of collagen fibrils, elastic fibres and fibroblasts are organized into a network that lies in the plane of a large portion of the bat wing. By ultrastructural (TEM and SEM) and biochemical analyses it was found that individual bundles of the net are similar to elastic ligaments. Although elastic fibres predominate, they are integrated and aligned in parallel with small bundles of collagen. A reticulum of fibroblasts, joined by focal junctions, forms a cellular framework throughout each bundle. Because of the unique features of the fibre bundles of the bat's wing, in particular their accessibility, and the parallel alignment of the collagen fibrils and elastic fibres in each easily isolatable fibre bundle, they should prove a most valuable model for connective tissue studies, particularly for the study of collagen-elastin interactions. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 9 Fig. 10 Fig. 11 Fig. 12 PMID:649500

  2. Structural relations between collagen and mineral in bone as determined by high voltage electron microscopic tomography

    NASA Technical Reports Server (NTRS)

    Landis, W. J.; Hodgens, K. J.; Arena, J.; Song, M. J.; McEwen, B. F.

    1996-01-01

    Aspects of the ultrastructural interaction between collagen and mineral crystals in embryonic chick bone have been examined by the novel technique of high voltage electron microscopic tomography to obtain three-dimensional information concerning extracellular calcification in this tissue. Newly mineralizing osteoid along periosteal surfaces of mid-diaphyseal regions from normal chick tibiae was embedded, cut into 0.25 microns thick sections, and documented at 1.0 MV in the Albany AEI-EM7 high voltage electron microscope. The areas of the tissue studied contained electron dense mineral crystals associated with collagen fibrils, some marked by crystals disposed along their cylindrically shaped lengths. Tomographic reconstructions of one site with two mineralizing fibrils were computed from a 5 degrees tilt series of micrographs over a +/- 60 degrees range. Reconstructions showed that the mineral crystals were platelets of irregular shape. Their sizes were variable, measured here up to 80 x 30 x 8 nm in length, width, and thickness, respectively. The longest crystal dimension, corresponding to the c-axis crystallographically, was generally parallel to the collagen fibril long axis. Individual crystals were oriented parallel to one another in each fibril examined. They were also parallel in the neighboring but apparently spatially separate fibrils. Crystals were periodically (approximately 67 nm repeat distance) arranged along the fibrils and their location appeared to correspond to collagen hole and overlap zones defined by geometrical imaging techniques. The crystals appeared to be continuously distributed along a fibril, their size and number increasing in a tapered fashion from a relatively narrow tip containing smaller and infrequent crystals to wider regions having more densely packed and larger crystals. Defined for the first time by direct visual 3D imaging, these data describe the size, shape, location, orientation, and development of early crystals in normal

  3. Nanoscale Heterogeneity of the Molecular Structure of Individual hIAPP Amyloid Fibrils Revealed with Tip-Enhanced Raman Spectroscopy.

    PubMed

    vandenAkker, Corianne C; Deckert-Gaudig, Tanja; Schleeger, Michael; Velikov, Krassimir P; Deckert, Volker; Bonn, Mischa; Koenderink, Gijsje H

    2015-09-01

    Type 2 diabetes mellitus is characterized by the pathological deposition of fibrillized protein, known as amyloids. It is thought that oligomers and/or amyloid fibrils formed from human islet amyloid polypeptide (hIAPP or amylin) cause cell death by membrane damage. The molecular structure of hIAPP amyloid fibrils is dominated by β-sheet structure, as probed with conventional infrared and Raman vibrational spectroscopy. However, with these techniques it is not possible to distinguish between the core and the surface structure of the fibrils. Since the fibril surface crucially affects amyloid toxicity, it is essential to know its structure. Here the surface molecular structure and amino acid residue composition of hIAPP fibrils are specifically probed with nanoscale resolution using tip-enhanced Raman spectroscopy (TERS). The fibril surface mainly contains unordered or α-helical structures, in contrast to the β-sheet-rich core. This experimentally validates recent models of hIAPP amyloids based on NMR measurements. Spatial mapping of the surface structure reveals a highly heterogeneous surface structure. Finally, TERS can probe fibrils formed on a lipid interface, which is more representative of amyloids in vivo. PMID:25952953

  4. Ventricular fibrillation

    MedlinePlus

    ... Fibrillation is an uncontrolled twitching or quivering of muscle fibers (fibrils). When it occurs in the lower chambers of the heart, it is called ventricular fibrillation. During ... the heart muscle does not get enough oxygen for any reason. ...

  5. Can We Predict Individual Combined Benefit and Harm of Therapy? Warfarin Therapy for Atrial Fibrillation as a Test Case

    PubMed Central

    Li, Guowei; Thabane, Lehana; Delate, Thomas; Witt, Daniel M.; Levine, Mitchell A. H.; Cheng, Ji; Holbrook, Anne

    2016-01-01

    Objectives To construct and validate a prediction model for individual combined benefit and harm outcomes (stroke with no major bleeding, major bleeding with no stroke, neither event, or both) in patients with atrial fibrillation (AF) with and without warfarin therapy. Methods Using the Kaiser Permanente Colorado databases, we included patients newly diagnosed with AF between January 1, 2005 and December 31, 2012 for model construction and validation. The primary outcome was a prediction model of composite of stroke or major bleeding using polytomous logistic regression (PLR) modelling. The secondary outcome was a prediction model of all-cause mortality using the Cox regression modelling. Results We included 9074 patients with 4537 and 4537 warfarin users and non-users, respectively. In the derivation cohort (n = 4632), there were 136 strokes (2.94%), 280 major bleedings (6.04%) and 1194 deaths (25.78%) occurred. In the prediction models, warfarin use was not significantly associated with risk of stroke, but increased the risk of major bleeding and decreased the risk of death. Both the PLR and Cox models were robust, internally and externally validated, and with acceptable model performances. Conclusions In this study, we introduce a new methodology for predicting individual combined benefit and harm outcomes associated with warfarin therapy for patients with AF. Should this approach be validated in other patient populations, it has potential advantages over existing risk stratification approaches as a patient-physician aid for shared decision-making PMID:27513986

  6. Ecological niche of Neanderthals from Spy Cave revealed by nitrogen isotopes of individual amino acids in collagen.

    PubMed

    Naito, Yuichi I; Chikaraishi, Yoshito; Drucker, Dorothée G; Ohkouchi, Naohiko; Semal, Patrick; Wißing, Christoph; Bocherens, Hervé

    2016-04-01

    This study provides a refined view on the diet and ecological niche of Neanderthals. The traditional view is that Neanderthals obtained most of their dietary protein from terrestrial animals, especially from large herbivores that roamed the open landscapes. Evidence based on the conventional carbon and nitrogen isotopic composition of bulk collagen has supported this view, although recent findings based on plant remains in the tooth calculus, microwear analyses, and small game and marine animal remains from archaeological sites have raised some questions regarding this assumption. However, the lack of a protein source other than meat in the Neanderthal diet may be due to methodological difficulties in defining the isotopic composition of plants. Based on the nitrogen isotopic composition of glutamic acid and phenylalanine in collagen for Neanderthals from Spy Cave (Belgium), we show that i) there was an inter-individual dietary heterogeneity even within one archaeological site that has not been evident in bulk collagen isotopic compositions, ii) they occupied an ecological niche different from those of hyenas, and iii) they could rely on plants for up to ∼20% of their protein source. These results are consistent with the evidence found of plant consumption by the Spy Neanderthals, suggesting a broader subsistence strategy than previously considered. PMID:27086057

  7. Prediction of individual combined benefit and harm for patients with atrial fibrillation considering warfarin therapy: a study protocol

    PubMed Central

    Li, Guowei; Holbrook, Anne; Delate, Thomas; Witt, Daniel M; Levine, Mitchell AH; Thabane, Lehana

    2015-01-01

    Introduction Clinical prediction rules have been validated and widely used in patients with atrial fibrillation (AF) to predict stroke and major bleeding. However, these prediction rules were not developed in the same population, and do not provide the key information that patients and prescribers need at the time anticoagulants are being considered—what is the individual patient-specific risk of both benefit (decreased stroke) and harm (increased major bleeding). In this study, our primary objective is to develop and validate a prediction model for patients’ individual combined benefit and harm outcomes (stroke, major bleeding and neither event) with and without warfarin therapy. Our secondary outcome is all-cause mortality. Methods and analysis We will use data from the Kaiser Permanente Colorado (KPCO) anticoagulation management databases and electronic medical records. Patients with a primary or secondary diagnosis during an ambulatory KPCO medical office visit, emergency department visit, or inpatient stay between 1 January 2005 and 31 December 2012 with no AF diagnosis in the previous 180 days will be included. Patients’ demographic characteristics, laboratory data, comorbidities, warfarin medication data and concurrent use of medication will be used to construct the prediction model. For primary outcomes (stroke with no major bleeding, and major bleeding with no stroke), we will perform polytomous logistic regression to develop a prediction model for patients’ individual combined benefit and harm outcomes, taking neither event group as the reference group. As regards death, we will use Cox proportional hazards regression analysis to build a prediction model for all-cause mortality. Ethics and dissemination This study has been approved by the KPCO Institutional Review Board and the Hamilton Integrated Research Ethics Board. Results from this study will be published in a peer-reviewed journal electronically and in print. The prediction models may aid

  8. A Twelve-SNP Genetic Risk Score Identifies Individuals at Increased Risk for Future Atrial Fibrillation and Stroke

    PubMed Central

    Smith, J. Gustav; Sjögren, Marketa; Lubitz, Steven A.; Ellinor, Patrick T.; Louie, Judy Z.; Catanese, Joseph J.; Engström, Gunnar; Devlin, James J.

    2015-01-01

    Background and Purpose Atrial fibrillation (AF) is prevalent and there is a clinical need for biomarkers to identify individuals at higher risk for AF. Fixed throughout a life course and assayable early in life, genetic biomarkers may meet this need. Here, we investigate whether multiple single nucleotide polymorphisms (SNPs) together as an AF genetic risk score (AF-GRS) can improve prediction of one's risk for AF. Methods In 27,471 participants of the Malmö Diet and Cancer Study, a prospective, community-based cohort, we used Cox models that adjusted for established AF risk factors to assess the association of AF-GRS with incident AF and ischemic stroke. Median follow-up was 14.4 years for incident AF and 14.5 years for ischemic stroke. The AF-GRS comprised 12 SNPs that had been previously shown to be associated with AF at genome-wide significance. Results During follow-up, 2,160 participants experienced a first AF event and 1,495 had a first ischemic stroke event. Participants in the top AF-GRS quintile were at increased risk for incident AF (HR = 2.00; 95%CI = 1.73 to 2.31; P=2.7×10−21) and ischemic stroke (HR = 1.23; 95%CI = 1.04 to 1.46; P=0.02) when compared with the bottom quintile. Addition of the AF-GRS to established AF risk factors modestly improved both discrimination and reclassification (P<0.0001 for both). Conclusions An AF-GRS can identify 20% of individuals who are at approximately two-fold increased risk for incident AF and at 23% increased risk for ischemic stroke. Targeting diagnostic or therapeutic interventions to this subset may prove clinically useful. PMID:25123217

  9. VLDL from Metabolic Syndrome Individuals Enhanced Lipid Accumulation in Atria with Association of Susceptibility to Atrial Fibrillation

    PubMed Central

    Lee, Hsiang-Chun; Lin, Hsin-Ting; Ke, Liang-Yin; Wei, Chi; Hsiao, Yi-Lin; Chu, Chih-Sheng; Lai, Wen-Ter; Shin, Shyi-Jang; Chen, Chu-Huang; Sheu, Sheng-Hsiung; Wu, Bin-Nan

    2016-01-01

    Metabolic syndrome (MetS) represents a cluster of metabolic derangements. Dyslipidemia is an important factor in MetS and is related to atrial fibrillation (AF). We hypothesized that very low density lipoproteins (VLDL) in MetS (MetS-VLDL) may induce atrial dilatation and vulnerability to AF. VLDL was therefore separated from normal (normal-VLDL) and MetS individuals. Wild type C57BL/6 male mice were divided into control, normal-VLDL (nVLDL), and MetS-VLDL (msVLDL) groups. VLDL (15 µg/g) and equivalent volumes of saline were injected via tail vein three times a week for six consecutive weeks. Cardiac chamber size and function were measured by echocardiography. MetS-VLDL significantly caused left atrial dilation (control, n = 10, 1.64 ± 0.23 mm; nVLDL, n = 7, 1.84 ± 0.13 mm; msVLDL, n = 10, 2.18 ± 0.24 mm; p < 0.0001) at week 6, associated with decreased ejection fraction (control, n = 10, 62.5% ± 7.7%, vs. msVLDL, n = 10, 52.9% ± 9.6%; p < 0.05). Isoproterenol-challenge experiment resulted in AF in young msVLDL mice. Unprovoked AF occurred only in elderly msVLDL mice. Immunohistochemistry showed excess lipid accumulation and apoptosis in msVLDL mice atria. These findings suggest a pivotal role of VLDL in AF pathogenesis for MetS individuals. PMID:26805814

  10. Collagen: Biochemistry, biomechanics, biotechnology

    SciTech Connect

    Nimni, M.E.

    1988-01-01

    This book is an up-to-date reference for new ideas, information, and concepts in collagen research. The first volume emphasizes the relationship between the molecular structure and function of collagen, including descriptions of collagen types which exist in tissues as well as how these molecules organize into fibrils and the nature of the chemical crosslinks which stabilize them. In Volume II the biomechanical behavior of various specialized tissues, abnormal accumulation of collagen in the form of scars of fibrous infiltration are examined/and wound healing, tissue regulation and repair are covered in detail. Volume III explores the increasing application of collagen technology to the field of bioprosthesis, including the production of heart valve bioprosthesis, blood vessels, ligament substitutes, and bone substitutes.

  11. Frequency Analysis of Atrial Action Potential Alternans: A Sensitive Clinical Index of Individual Propensity to Atrial Fibrillation

    PubMed Central

    Lalani, Gautam G.; Schricker, Amir A.; Clopton, Paul; Krummen, David E.; Narayan, Sanjiv M.

    2013-01-01

    Background Few clinical indices identify the propensity of patients to atrial fibrillation (AF) when not in AF. Repolarization alternans has been shown to indicate AF vulnerability, but is limited in its sensitivity to detect changes in action potential duration (APD), that may be subtle. We hypothesized that spectral analysis would be a more sensitive and robust marker of action potential (AP) alternans and thus a better clinical index of individual propensity to AF than APD alternans. Methods and Results In 31 patients (12 persistent AF, 15 paroxysmal AF, 4 controls with no AF), we recorded left (n=27) and right (n=6) atrial monophasic APs during incremental pacing from cycle length (CL) 500 ms (120 bpm) to AF onset. Alternans was measured by APD and spectral analysis. At baseline pacing [median CL 500 (IQR 500,500) ms], APD alternans was detected in only 7/27 AF patients (no controls), while spectral AP alternans was detected in 18/27 AF patients (no controls; p=0.003); AP alternans was more prevalent in persistent than paroxysmal AF, and absent in controls (p=0.018 APD, p=0.042 spectral). Spectral AP alternans magnitude at baseline was highest in persistent AF, with modest rate-dependent amplification, then in paroxysmal AF, with marked rate-dependence, and was undetectable in controls until just before induced AF. Conclusions Spectral AP alternans near baseline rates can identify patients with, versus those without, clinical histories and pathophysiological substrates for AF. Future studies should examine whether the presence of spectral AP alternans during sinus rhythm may obviate the need to actually demonstrate AF, such as on ambulatory ECG monitoring. PMID:23995250

  12. Nanoscale Mechanics of Type I Collagen

    NASA Astrophysics Data System (ADS)

    Harper, H.; Cropper, E.; Bulger, A.; Choksi, U.; Koob, T. J.; Pandit, S.; Matthews, W. G.

    2009-03-01

    Collagen is the most abundant protein in the body by mass. Type I collagen fibrils provide mechanical strength and cellular housing within tissues exhibiting a broad range of mechanical properties. This diversity in the mechanics of tissues with similar underlying components warrants detailed study of the process by which structure and mechanics develop. While collagen mechanics have been studied at the tissue level for decades, surprising little is known about collagen mechanics at the fibril and molecular level. Presented herein is a multi-scale experimental and computational investigation of collagen I mechanics, bridging the single molecule and fibril hierarchal forms. The mechanics of single collagen molecules are explored using AFM and force spectroscopy. Moreover, atomistic molecular-dynamics simulations are performed to provide structural information not accessible to the experimental system. Fibrils then are grown from molecular collagen, and the mechanics of these fibrils are investigated using AFM. Based upon the single molecule and fibril results, a coarse-grain computational model is being developed. The outcomes include a better understanding of how the mechanics of filamentous self-organizing systems are derived and how their hierarchical forms are established.

  13. Teleost fish scales amongst the toughest collagenous materials.

    PubMed

    Khayer Dastjerdi, A; Barthelat, F

    2015-12-01

    Fish scales from modern teleost fish are high-performance materials made of cross-plies of collagen type I fibrils reinforced with hydroxyapatite. Recent studies on this material have demonstrated the remarkable performance of this material in tension and against sharp puncture. Although it is known that teleost fish scales are extremely tough, actual measurements of fracture toughness have so far not been reported because it is simply not possible to propagate a crack in this material using standard fracture testing configurations. Here we present a new fracture test setup where the scale is clamped between two pairs of miniature steel plates. The plates transmit the load uniformly, prevent warping of the scale and ensure a controlled crack propagation. We report a toughness of 15 to 18kJm(-2) (depending on the direction of crack propagation), which confirms teleost fish scales as one of the toughest biological material known. We also tested the individual bony layers, which we found was about four times less tough than the collagen layer because of its higher mineralization. The mechanical response of the scales also depends on the cohesion between fibrils and plies. Delamination tests show that the interface between the collagen fibrils is three orders of magnitude weaker than the scale, which explains the massive delamination and defibrillation observed experimentally. Finally, simple fracture mechanics models showed that process zone toughening is the principal source of toughening for the scales, followed by bridging by delaminated fibrils. These findings can guide the design of cross-ply composites and engineering textiles for high-end applications. This study also hints on the fracture mechanics and performance of collagenous materials with similar microstructures: fish skin, lamellar bone or tendons. PMID:25457170

  14. Dermal ultrastructure in collagen VI myopathy.

    PubMed

    Hermanns-Lê, Trinh; Piérard, Gérald E; Piérard-Franchimont, Claudine; Delvenne, Philippe

    2014-04-01

    The COL VI mutations are responsible for a spectrum of myopathies. The authors report cutaneous ultrastructural alterations in a patient with COL6A2 myopathy. The changes include variations in size of collagen fibrils, flower-like sections of collagen fibrils, as well as thickening of vessel and nerve basement membranes. Electron microscopy of a skin biopsy contributes to the diagnosis of COL VI myopathies. PMID:24134684

  15. Collagen type I and III synthesis by Tenon's capsule fibroblasts in culture: individual patient characteristics and response to mitomycin C, 5-fluorouracil, and ascorbic acid.

    PubMed Central

    Gross, R L

    1999-01-01

    PURPOSE: This study was performed to better understand the differences between patients in specific components of wound healing as it may pertain to glaucoma filtration surgery, including the use of antimetabolites. METHODS: Human Tenon's capsule fibroblasts were obtained at the time of glaucoma filtering surgery and established in individual cell cultures from 35 glaucoma patients. The dose-response to 5-fluorouracil (5FU) and mitomycin C (MMC) was determined. The individual cell lines were exposed to the antimetabolites and ascorbic acid with measurement of collagen type I and III production by an ELISA-type dot blot assay. These results were then statistically compared to the individual patient characteristics including age, race, previous surgery and medications, and type of glaucoma. RESULTS: 5-FU had little effect on collagen type I and III production or protein synthesis. MMC had an inhibitory effect on collagen secretion and total protein synthesis with increasing concentration. Photomicrographs of the cells after each treatment condition revealed characteristic morphologic changes when compared to controls. There was a large range of collagen type I and III production with correlation between the amounts of each collagen type secreted in response to the antimetabolites. However, there was no correlation with accepted risk factors for filtration failure. CONCLUSION: These antimetabolites act similarly on different cell lines in a nonspecific manner. The results suggest that the increased risk of filtration failure due to age, race, diagnosis, and previous conjunctival surgery is not due to differences in secretion of collagen types I and III by Tenon's capsule fibroblasts. Images FIGURE 3 PMID:10703140

  16. Enhanced stabilization of collagen by furfural.

    PubMed

    Lakra, Rachita; Kiran, Manikantan Syamala; Usha, Ramamoorthy; Mohan, Ranganathan; Sundaresan, Raja; Korrapati, Purna Sai

    2014-04-01

    Furfural (2-furancarboxaldehyde), a product derived from plant pentosans, has been investigated for its interaction with collagen. Introduction of furfural during fibril formation enhanced the thermal and mechanical stability of collagen. Collagen films treated with furfural exhibited higher denaturation temperature (Td) (p<0.04) and showed a 3-fold increase in Young's modulus (p<0.04) at higher concentration. Furfural and furfural treated collagen films did not have any cytotoxic effect. Rheological characterization showed an increase in shear stress and shear viscosity with increasing shear rate for treated collagen. Circular dichroism (CD) studies indicated that the furfural did not have any impact on triple helical structure of collagen. Scanning electron microscopy (SEM) of furfural treated collagen exhibited small sized porous structure in comparison with untreated collagen. Thus this study provides an alternate ecologically safe crosslinking agent for improving the stability of collagen for biomedical and industrial applications. PMID:24468046

  17. The evolution of fibrillar collagens: a sea-pen collagen shares common features with vertebrate type V collagen.

    PubMed

    Tillet, E; Franc, J M; Franc, S; Garrone, R

    1996-02-01

    The extracellular matrix of marine primitive invertebrates (sponges, polyps and jellyfishes) contains collagen fibrils with narrow diameters. From various data, it has been hypothesized that these primitive collagens could represent ancestral forms of the vertebrate minor collagens, i.e., types V or XI. Recently we have isolated a primitive collagen from the soft tissues of the sea-pen Veretillum cynomorium. This report examines whether the sea-pen collagen shares some features with vertebrate type V collagen. Rotary shadowed images of acid-soluble collagen molecules extracted from beta-APN treated animals, positive staining of segment-long-spacing crystallites precipitated from pepsinized collagen, Western blots of the pepsinized alpha1 and alpha2 chains with antibodies to vertebrate types I, III and V collagens, and in situ gold immunolabeling of ECM collagen fibrils were examined. Our results showed that the tissue form of the sea-pen collagen is a 340-nm threadlike molecule, which is close to the vertebrate type V collagen with its voluminous terminal globular domain, the distribution of most of its polar amino-acid residues, and its antigenic properties. PMID:8653581

  18. Atrial Fibrillation

    MedlinePlus

    ... cause the atria to fibrillate. The faulty signals flood the AV node with electrical impulses. As a ... people who have permanent AF, treatment can help control symptoms and prevent complications. Treatment may include medicines, ...

  19. Ventricular fibrillation

    MedlinePlus

    ... seconds, it can lead to fainting (syncope) or cardiac arrest. Fibrillation is an uncontrolled twitching or quivering of ... pubmed/23801105 . Myerburg RJ, Castellanos A. Approach to cardiac arrest and life-threatening arrhythmias. In: Goldman L, Schafer ...

  20. Eumelanin fibrils

    NASA Astrophysics Data System (ADS)

    McQueenie, Ross; Sutter, Jens; Karolin, Jan; Birch, David J. S.

    2012-07-01

    We describe the auto-oxidation of 3, 4-dihydroxy-L-phenylalanine (L-DOPA) in the synthesis of eumelanin to spontaneously produce fibrils upon drying. The self-assembled fibrils are of characteristic diameter ~1 to 2 μm, composed of filaments, and are unidirectional, apart from branches that are formed at typically an angle of 20 to 22 deg. The fibrils are characterized using fluorescence spectroscopy, fluorescence decay times, scanning electron microscopy, atomic force microscopy, and fluorescence lifetime imaging microscopy. The fibrils mimic natural melanin in consisting of core eumelanin with efficient nonradiative properties, but they also display pockets of electronically isolated species with higher radiative rates on the nanosecond timescale. Eumelanin fibrils formed occasionally in solution are tentatively attributed to a scaffold of bacteria or fungus. Fabricating and characterizing novel synthetic eumelanin structures such as fibrils are of interest in helping to reveal a functional structure for eumelanin, in understanding its photophysics, in learning more about L-DOPA as it is used in the treatment of Parkinson's disease, and in producing novel materials which might embody some of the diverse properties of eumelanin.

  1. Acid phosphatase activity and intracellular collagen degradation by fibroblasts in vitro.

    PubMed

    Yajima, T

    1986-01-01

    Human gingival fibroblasts were cultured with collagen fibrils. The precise process of collagen phagocytosis and the relationship between acid phosphatase activity and intracellular degradation of collagen were investigated by cytochemical methods at the ultrastructural level. The collagen fibrils were first engulfed at one end by cellular processes, or the cell membrane wrapped itself around the middle of the fibrils. Collagen phagocytosis induced acid phosphatase activity in the fibroblast Golgi-endoplasmic reticulum-lysosome system. By application of the tracer lanthanum, deposits were observed in the intercellular spaces and along the fibrils being phagocytosed. At this stage, primary lysosomes were seen in close proximity to the collagen being engulfed, but no signs of fusion were observed. When the fibrils had been interiorized in whole or in part, they ultimately became enclosed within phagosomes, and no tracer was observed along the interiorized portion of the fibrils. Primary lysosomes then fused with these collagen-containing phagosomes to form phagolysosomes. Collagen degradation occurred within these bodies even though the end of a fibril might have protruded outside of the cell. These results suggest that selective and controlled phagocytosis of collagen and intracellular digestion of it may play a central role in the physiological remodeling and metabolic breakdown of the collagen of connective tissues. PMID:3742560

  2. Type I Collagen and Collagen Mimetics as Angiogenesis Promoting Superpolymers

    SciTech Connect

    Twardowski, T.; Fertala, A.; Orgel, J.P.R.O.; San Antonio, J.D.

    2008-07-18

    Angiogenesis, the development of blood vessels from the pre-existing vasculature, is a key component of embryogenesis and tissue regeneration. Angiogenesis also drives pathologies such as tumor growth and metastasis, and hemangioma development in newborns. On the other hand, promotion of angiogenesis is needed in tissues with vascular insufficiencies, and in bioengineering, to endow tissue substitutes with appropriate microvasculatures. Therefore, much research has focused on defining mechanisms of angiogenesis, and identifying pro- and anti-angiogenic molecules. Type I collagen, the most abundant protein in humans, potently stimulates angiogenesis in vitro and in vivo. Crucial to its angiogenic activity appears to be ligation and possibly clustering of endothelial cell (EC) surface {alpha}1{beta}1/{alpha}2{beta}1 integrin receptors by the GFPGER502-507 sequence of the collagen fibril. However, additional aspects of collagen structure and function that may modulate its angiogenic properties are discussed. Moreover, type I collagen and fibrin, another angiogenic polymer, share several structural features. These observations suggest strategies for creating 'angiogenic superpolymers', including: modifying type I collagen to influence its biological half-life, immunogenicity, and integrin binding capacity; genetically engineering fibrillar collagens to include additional integrin binding sites or angiogenic determinants, and remove unnecessary or deleterious sequences without compromising fibril integrity; and exploring the suitability of poly(ortho ester), PEG-lysine copolymer, tubulin, and cholesteric cuticle as collagen mimetics, and suggesting means of modifying them to display ideal angiogenic properties. The collagenous and collagen mimetic angiogenic superpolymers described here may someday prove useful for many applications in tissue engineering and human medicine.

  3. Ultrastructural quantification of collagen in human chordae tendineae.

    PubMed Central

    Berkovitz, B K; Rollinson, C

    1993-01-01

    OBJECTIVE--To determine collagen fibril diameter distributions in the chordae tendineae and to see whether there are any differences between right and left sides of the human heart. DESIGN--Collagen fibril diameters and the percentage volume occupied by collagen fibrils (as opposed to ground substance) were determined by means of a planimeter with a digitising tablet from electron micrographs printed at a magnification of 136; 000. MATERIAL--Human chordae tendineae were obtained at postmortem examination from seven subjects aged 50-75 years. MEASUREMENTS AND MAIN RESULTS--Histograms of collagen fibril diameter distributions showed a sharp, unimodal distribution. The mean collagen fibril diameters associated with the tricuspid and mitral valves were 41.1 nm and 40.5 nm respectively. The percentage volume occupied by collagen was about 39% for each valve. There were no significant differences for any of these values between the right and left sides of the heart. CONCLUSIONS--The greater pressures present on the left side of the heart are not reflected in any difference in collagen fibril diameters within the chordae tendineae compared with the right side. Images PMID:8461224

  4. Collagen coated tantalum substrate for cell proliferation.

    PubMed

    Li, Yinli; Zhang, Shuai; Guo, Lijun; Dong, Mingdong; Liu, Bo; Mamdouh, Wael

    2012-06-15

    The extracellular matrix (ECM) plays a key role in cell culture in various physiological and pathological processes in the field of tissue engineering. Recently, the type I collagen ECM has been widely utilized in vitro model systems for the attachment of many different cell lines since it has multi-functions in human tissues. For example it accounts for 6% of the weight of strong, tendinous muscles. In this paper, we reported a new material by coating tantalum (Ta), one highly biocompatible metal, with type I collagen fibrils. The morphology of the new material was studied by high resolution atomic force microscope. It was shown that the adhesion force between type I collagen fibrils network and Ta was strong enough to overcome surface defects. A possible way to explain the phenomenon is that the longitudinal periodicity of collagen fibrils matches the grain size of the Ta domains, which results in increase of the physical adsorption contact area, thereby inducing the dramatic adhesion enhancement between collagen fibrils and Ta. The obtained material was then employed as a template for cell proliferation. Although the surface of this template is more hydrophobic by comparison with the bare Ta surface, the cells on this material were successfully incubated, indicating that the collagen coated Ta might be used as the buffer layer for proliferating cells in hydrophobic biomaterials. PMID:22494669

  5. A continuum model for hierarchical fibril assembly

    NASA Astrophysics Data System (ADS)

    van Lith, B. S.; Muntean, A.; Storm, C.

    2014-06-01

    Most of the biological polymers that make up our cells and tissues are hierarchically structured. For biopolymers ranging from collagen, to actin, to fibrin and amyloid fibrils this hierarchy provides vitally important versatility. The structural hierarchy must be encoded in the self-assembly process, from the earliest stages onward, in order to produce the appropriate substructures. In this letter, we explore the kinetics of multistage self-assembly processes in a model system which allows comparison to bulk probes such as light scattering. We apply our model to recent turbidimetry data on the self-assembly of collagen fibrils. Our analysis suggests a connection between diffusion-limited aggregation kinetics and fibril growth, supported by slow, power-law growth at very long time scales.

  6. Magnetic Resonance Microscopy of Collagen Mineralization

    PubMed Central

    Chesnick, Ingrid E.; Mason, Jeffrey T.; Giuseppetti, Anthony A.; Eidelman, Naomi; Potter, Kimberlee

    2008-01-01

    A model mineralizing system was subjected to magnetic resonance microscopy to investigate how water proton transverse (T2) relaxation times and magnetization transfer ratios can be applied to monitor collagen mineralization. In our model system, a collagen sponge was mineralized with polymer-stabilized amorphous calcium carbonate. The lower hydration and water proton T2 values of collagen sponges during the initial mineralization phase were attributed to the replacement of the water within the collagen fibrils by amorphous calcium carbonate. The significant reduction in T2 values by day 6 (p < 0.001) was attributed to the appearance of mineral crystallites, which were also detected by x-ray diffraction and scanning electron microscopy. In the second phase, between days 6 and 13, magnetic resonance microscopy properties appear to plateau as amorphous calcium carbonate droplets began to coalesce within the intrafibrillar space of collagen. In the third phase, after day 15, the amorphous mineral phase crystallized, resulting in a reduction in the absolute intensity of the collagen diffraction pattern. We speculate that magnetization transfer ratio values for collagen sponges, with similar collagen contents, increased from 0.25 ± 0.02 for control strips to a maximum value of 0.31 ± 0.04 at day 15 (p = 0.03) because mineral crystals greatly reduce the mobility of the collagen fibrils. PMID:18487295

  7. Cytoskeletal organization and collagen orientation in the fish scales.

    PubMed

    Zylberberg, L; Bereiter-Hahn, J; Sire, J Y

    1988-09-01

    Immunofluorescence and electron microscopy were used to analyze the relationships between the organization of collagen fibrils in elasmoid scales, and the orientation of microtubules and actin microfilaments in the scleroblasts producing this collagenous stroma. Attention was focused on the basal plate of the scales because of the highly ordered three-dimensional arrangement of the collagen fibrils in superimposed plies forming an acellular plywood-like structure. The collagen fibrils are synthesized by the scleroblasts forming a monolayered pseudo-epithelium, the hyposquama, at the lowest surface of the scale. Fully developed scales with a low collagen deposition rate were compared with regenerating scales active in fibrillogenesis. When an ordered array of the collagen fibrils is found, the innermost collagen fibrils are coaligned with microtubules and actin microfilaments. Thus, because of this coalignment, microtubules and actin microfilaments of the hyposquamal scleroblasts are subjected to consecutive alterations during the formation of the plies of the basal plate. The sequence of events when the collagen fibrils change their direction from one ply to the other in the basal plate is deduced from immunofluorescence and phase-contrast-microscopic observations. During the formation of the orthogonal plywood-like structure in the regenerating scales, first microtubules may change their curse with a rotating angle of about 90 degrees; then, actin microfilaments are disorganized and reorganized by interacting mechanically with the microtubules with which they are coaligned. Collagen fibrils are synthesized in a direction that is roughly perpendicular to that of the preceding ply. The unknown signals inducing the change in direction of the cytoskeleton may be transmitted throughout the hyposquama via gap junctions. PMID:3052849

  8. The effect of gamma irradiation on injectable human amnion collagen

    SciTech Connect

    Liu, B.C.; Harrell, R.; Davis, R.H.; Dresden, M.H.; Spira, M. )

    1989-08-01

    The effect of gamma irradiation on the physicochemical properties of injectable human amnion collagen was investigated. Pepsin-extracted human amnion collagen was purified, reconstituted, and irradiated with varying doses of gamma irradiation (0.25 Mrads to 2.5 Mrads). Gamma irradiation had a significant impact on the physical characteristics of the collagen. The neutral solubility of collagen in PBS at 45{degrees}C was decreased from 100% for the nonirradiated control sample to 16% for the 2.5 Mrads irradiated sample. SDS polyacrylamide gel electrophoresis also demonstrated the dose-dependent effect of gamma irradiation on collagen cross-links. Electron microscopic observation revealed that even at low irradiation dose (0.25 Mrads), collagen fibril diameter increased. The average diameter was 50 nm for nonirradiated control fibrils, while 4.4% of the irradiated collagen fibrils had a diameter greater than 100 nm. Irradiated collagen showed little evidence of damage. Well-preserved cross-striations were found in collagen fibrils at all doses of irradiation. Native amnion collagen irradiated with gamma rays demonstrated a slight increase in resistance to collagenase degradation compared with nonirradiated native collagen samples. Increased resistance to collagenase did not correlate with increasing irradiation dose. After 30 min of incubation at 37{degrees}C, both irradiated and nonirradiated collagen was completely digested by collagenase. However, gamma-irradiated collagen did become more sensitive to hydrolysis by trypsin. The higher the irradiation doses used, the greater sensitivity to trypsin was observed. At 0.25 Mrads irradiation only a slight increase was found. No marked differences in amino acid composition were noted among the high dose irradiated, low dose irradiated and control amnion collagen.

  9. Fluid pressure driven fibril reinforcement in creep and relaxation tests of articular cartilage.

    PubMed

    Li, L P; Korhonen, R K; Iivarinen, J; Jurvelin, J S; Herzog, W

    2008-03-01

    Biological tissues exhibit diverse mechanical behaviors because of complex material properties. As has been shown for ligaments and intervertebral discs, mathematical models often appear to well predict load responses individually by adjusting model parameters, but likely fail to describe several different load responses simultaneously using the same model parameters. In the present study, we attempted to describe and explain both creep and relaxation responses of articular cartilage using a fibril-reinforced model, which has been successfully used to account for the load response of the relaxation tests of articular cartilage. Experiments were performed on bovine articular cartilage disks (n=8) using multi-step loading protocols, involving both creep and relaxation in each protocol. The experimental results indicated that mechanical changes, such as fiber recruitment in collagen network during stretch, recovered fully upon unloading. Creep loading did not affect relaxation properties, and vice versa. Relaxation proceeded much faster than creep, because of different fluid pressure profiles. The load sharing among the proteoglycan matrix, collagen network and fluid pressurization was predicted to differ for the creep and relaxation testing. The experimentally observed strong creep and relaxation responses in unconfined compression could not be predicted if either fibril reinforcement or fluid pressurization were neglected. It was essential to consider the interplay between nonlinear fibril reinforcement and fluid pressurization for the transient response (this interplay may be best termed as fluid pressure driven fibril reinforcement). Fibril reinforcement played a relatively insignificant role in the compressive load response at equilibrium, in agreement with previous findings for cartilage stress relaxation testing. PMID:17524700

  10. The collagen type I segment long spacing (SLS) and fibrillar forms: Formation by ATP and sulphonated diazo dyes.

    PubMed

    Harris, J Robin; Lewis, Richard J

    2016-07-01

    The collagen type I segment long spacing (SLS) crystallite is a well-ordered rod-like molecular aggregate, ∼300nm in length, which is produced in vitro under mildly acidic conditions (pH 2.5-3.5) in the presence of 1mM ATP. The formation of the SLS crystallite amplifies the inherent linear structural features of individual collagen heterotrimers, due to the punctate linear distribution and summation of the bulkier amino acid side chains along the length of individual collagen heterotrimers. This can be correlated structurally with the 67nm D-banded collagen fibril that is found in vivo, and formed in vitro. Although first described many years ago, the range of conditions required for ATP-induced SLS crystallite formation from acid-soluble collagen have not been explored extensively. Consequently, we have addressed biochemical parameters such as the ATP concentration, pH, speed of formation and stability so as to provide a more complete structural understanding of the SLS crystallite. Treatment of collagen type I with 1mM ATP at neutral and higher pH (6.0-9.0) also induced the formation of D-banded fibrils. Contrary to previous studies, we have shown that the polysulphonated diazo dyes Direct red (Sirius red) and Evans blue, but not Congo red and Methyl blue, can also induce the formation of SLS-like aggregates of collagen, but under markedly different ionic conditions to those employed in the presence of ATP. Specifically, pre-formed D-banded collagen fibrils, prepared in a higher than the usual physiological NaCl concentration (e.g. 500mM NaCl, 20mM Tris-HCl pH7.4 or x3 PBS), readily form SLS aggregates when treated with 0.1mM Direct red and Evans blue, but this did not occur at lower NaCl concentrations. These new data are discussed in relation to the anion (Cl(-)) and polyanion (phosphate and sulphonate) binding by the collagen heterotrimer and their likely role in collagen fibrillogenesis and SLS formation. PMID:27162200

  11. Quantification of Collagen Organization in the Peripheral Human Cornea at Micron-Scale Resolution

    PubMed Central

    Boote, Craig; Kamma-Lorger, Christina S.; Hayes, Sally; Harris, Jonathan; Burghammer, Manfred; Hiller, Jennifer; Terrill, Nicholas J.; Meek, Keith M.

    2011-01-01

    The collagen microstructure of the peripheral cornea is important in stabilizing corneal curvature and refractive status. However, the manner in which the predominantly orthogonal collagen fibrils of the central cornea integrate with the circumferential limbal collagen is unknown. We used microfocus wide-angle x-ray scattering to quantify the relative proportion and orientation of collagen fibrils over the human corneolimbal interface at intervals of 50 μm. Orthogonal fibrils changed direction 1–1.5 mm before the limbus to integrate with the circumferential limbal fibrils. Outside the central 6 mm, additional preferentially aligned collagen was found to reinforce the cornea and limbus. The manner of integration and degree of reinforcement varied significantly depending on the direction along which the limbus was approached. We also employed small-angle x-ray scattering to measure the average collagen fibril diameter from central cornea to limbus at 0.5 mm intervals. Fibril diameter was constant across the central 6 mm. More peripherally, fibril diameter increased, indicative of a merging of corneal and scleral collagen. The point of increase varied with direction, consistent with a scheme in which the oblique corneal periphery is reinforced by chords of scleral collagen. The results have implications for the cornea's biomechanical response to ocular surgeries involving peripheral incision. PMID:21723812

  12. Anisotropic collagen fibrillogenesis within microfabricated scaffolds: implications for biomimetic tissue engineering.

    PubMed

    Jean, Aurélie; Engelmayr, George C

    2012-01-11

    Anisotropic collagen fibrillogenesis is demonstrated within the pores of an accordion-like honeycomb poly(glycerol sebacate) tissue engineering scaffold. Confocal reflectance microscopy and image analysis demonstrate increased fibril distribution order, fibril density, and alignment in accordion-like honeycomb pores compared with collagen gelled unconstrained. Finite element modeling predicts how collagen gel and scaffold mechanics couple in matching native heart muscle stiffness and anisotropy. PMID:23184695

  13. Fibrillar assembly and stability of collagen coating on titanium for improved osteoblast responses.

    PubMed

    Kim, Hae-Won; Li, Long-Hao; Lee, Eun-Jung; Lee, Su-Hee; Kim, Hyoun-Ee

    2005-12-01

    Collagen, as a major constituent of human connective tissues, has been regarded as one of the most important biomaterials. As a coating moiety on Ti hard-tissue implants, the collagen has recently attracted a great deal of attention. This article reports the effects of fibrillar assembly and crosslinking of collagen on its chemical stability and the subsequent osteoblastic responses. The fibrillar self-assembly of collagen was carried out by incubating acid-dissolved collagen in an ionic-buffered medium at 37 degrees C. The degree of assembly was varied with the incubation time and monitored by the turbidity change. The differently assembled collagen was coated on the Ti and crosslinked with a carbodiimide derivative. The partially assembled collagen contained fibrils with varying diameters as well as nonfibrillar aggregates. On the other hand, the fully assembled collagen showed the complete formation of fibrils with uniform diameters of approximately 100-200 nm with periodic stain patterns within the fibrils, which are typical of native collagen fibers. Through this fibrillar assembly, the collagen coating had significantly improved chemical stability in both the saline and collagenase media. The subsequent crosslinking step also improved the stability of the collagen coating, particularly in the unassembled collagen. The fibrillar assembly and the crosslinking of collagen significantly influenced the osteoblastic cell responses. Without the assembly, the collagen layer on Ti adversely affected the cell attachment and proliferation. However, those cellular responses were improved significantly when the collagen was assembled to fibrils and the assembly degree was increased. After crosslinking the collagen coating, these cellular responses were significantly enhanced in the case of the unassembled collagen but were not altered much in the assembled collagen. Based on these observations, it is suggested that the fibrillar assembly and the crosslinking of collagen

  14. Surgical Therapy by Sandwich Transplantation using a Dermal Collagen-Elastin Matrix and Full Thickness Split Grafts and Gait Rehabilitation with Individualized Orthesis

    PubMed Central

    Wollina, Uwe; Heinig, Birgit

    2012-01-01

    Painful callosities of the feet (PCOF) are a rare complaint in children with severe impairment of mobility and quality of life. There is no medical treatment available. We investigated the usefulness of a recently developed combined transplant technique-the sandwich transplantation with dermal collagen-elastin template in this rare condition. A 14-year-old boy suffered from PCOF for several years without any improvement by topical therapy, dermabrasion, and oral retinoids. He was unable to walk normally and suffered from severe pain. We performed a complete deep excision of the hyperkeratotic plantar tissue in general anaesthesia in combination with sandwich transplantation in the same setting. Dry sheets of collagen-elastin matrix (1 mm thickness) were placed on the soft tissue defects and covered by full-thickness mesh graft transplants from the upper leg. An individualized orthosis was produced for gait rehabilitation. Two weeks after surgery the gait-related pain was reduced remarkably. Using the orthosis, the boy was able to walk pain-free even on staircase. Surgery of PCOF with sandwich transplantation and gait rehabilitation appears to be a promising strategy for this rare condition. PMID:23378711

  15. Surgical Therapy by Sandwich Transplantation using a Dermal Collagen-Elastin Matrix and Full Thickness Split Grafts and Gait Rehabilitation with Individualized Orthesis.

    PubMed

    Wollina, Uwe; Heinig, Birgit

    2012-10-01

    Painful callosities of the feet (PCOF) are a rare complaint in children with severe impairment of mobility and quality of life. There is no medical treatment available. We investigated the usefulness of a recently developed combined transplant technique-the sandwich transplantation with dermal collagen-elastin template in this rare condition. A 14-year-old boy suffered from PCOF for several years without any improvement by topical therapy, dermabrasion, and oral retinoids. He was unable to walk normally and suffered from severe pain. We performed a complete deep excision of the hyperkeratotic plantar tissue in general anaesthesia in combination with sandwich transplantation in the same setting. Dry sheets of collagen-elastin matrix (1 mm thickness) were placed on the soft tissue defects and covered by full-thickness mesh graft transplants from the upper leg. An individualized orthosis was produced for gait rehabilitation. Two weeks after surgery the gait-related pain was reduced remarkably. Using the orthosis, the boy was able to walk pain-free even on staircase. Surgery of PCOF with sandwich transplantation and gait rehabilitation appears to be a promising strategy for this rare condition. PMID:23378711

  16. Atrial Fibrillation and Stroke

    MedlinePlus

    ... Find People About NINDS NINDS Atrial Fibrillation and Stroke Information Page Table of Contents (click to jump ... done? Clinical Trials What is Atrial Fibrillation and Stroke? Atrial fibrillation (AF) describes the rapid, irregular beating ...

  17. Living with Atrial Fibrillation

    MedlinePlus

    ... Topics » Atrial Fibrillation » Living With Atrial Fibrillation Explore Atrial Fibrillation What Is... Types Other Names Causes Who Is at Risk Signs & Symptoms Diagnosis Treatments Prevention Living With Clinical Trials Links Related Topics Arrhythmia ...

  18. Anisotropy of Chemical Bonds in Collagen Molecules Studied by X-ray Absorption Near-Edge Structure (XANES) Spectroscopy

    PubMed Central

    Lam, Raymond S.K.; Metzler, Rebecca A.; Gilbert, Pupa U.P.A.; Beniash, Elia

    2012-01-01

    Collagen type I fibrils are the major building blocks of connective tissues. Collagen fibrils are anisotropic supra-molecular structures, and their orientation can be revealed by polarized light microscopy and vibrational microspectroscopy. We hypothesized that the anisotropy of chemical bonds in the collagen molecules, and hence their orientation, might also be detected by X-ray photoemission electron spectromicroscopy (X-PEEM) and X-ray absorption near-edge structure (XANES) spectroscopy, which use linearly polarized synchrotron light. To test this hypothesis, we analyzed sections of rat-tail tendon, composed of parallel arrays of collagen fibrils. The results clearly indicate that XANES-PEEM is sensitive to collagen fibril orientation and, more specifically, to the orientations of carbonyl and amide bonds in collagen molecules. These data suggest that XANES-PEEM is a promising technique for characterizing the chemical composition and structural organization at the nanoscale of collagen-based connective tissues, including tendons, cartilage, and bone. PMID:22148847

  19. Collagen interactions: Drug design and delivery.

    PubMed

    An, Bo; Lin, Yu-Shan; Brodsky, Barbara

    2016-02-01

    Collagen is a major component in a wide range of drug delivery systems and biomaterial applications. Its basic physical and structural properties, together with its low immunogenicity and natural turnover, are keys to its biocompatibility and effectiveness. In addition to its material properties, the collagen triple-helix interacts with a large number of molecules that trigger biological events. Collagen interactions with cell surface receptors regulate many cellular processes, while interactions with other ECM components are critical for matrix structure and remodeling. Collagen also interacts with enzymes involved in its biosynthesis and degradation, including matrix metalloproteinases. Over the past decade, much information has been gained about the nature and specificity of collagen interactions with its partners. These studies have defined collagen sequences responsible for binding and the high-resolution structures of triple-helical peptides bound to its natural binding partners. Strategies to target collagen interactions are already being developed, including the use of monoclonal antibodies to interfere with collagen fibril formation and the use of triple-helical peptides to direct liposomes to melanoma cells. The molecular information about collagen interactions will further serve as a foundation for computational studies to design small molecules that can interfere with specific interactions or target tumor cells. Intelligent control of collagen biological interactions within a material context will expand the effectiveness of collagen-based drug delivery. PMID:26631222

  20. Collagen telopeptides (cross-linking sites) play a role in collagen gel lattice contraction

    NASA Technical Reports Server (NTRS)

    Woodley, D. T.; Yamauchi, M.; Wynn, K. C.; Mechanic, G.; Briggaman, R. A.

    1991-01-01

    Solubilized interstitial collagens will form a fibrillar, gel-like lattice when brought to physiologic conditions. In the presence of human dermal fibroblasts the collagen lattice will contract. The rate of contraction can be determined by computer-assisted planemetry. The mechanisms involved in contraction are as yet unknown. Using this system it was found that the rate of contraction was markedly decreased when collagen lacking telopeptides was substituted for native collagen. Histidinohydroxylysinonorleucine (HHL) is a major stable trifunctional collagen cross-link in mature skin that involves a carboxyl terminal, telopeptide site 16c, the sixteenth amino acid residue from the carboxy terminal of the telopeptide region of alpha 1 (I) in type I collagen. Little, if any, HHL was present in native, purified, reconstituted, soluble collagen fibrils from 1% acetic acid-extracted 2-year-old bovine skin. In contrast, HHL cross-links were present (0.22 moles of cross-link per mole of collagen) in lattices of the same collagen contracted by fibroblasts. However, rat tail tendon does not contain HHL cross-links, and collagen lattices made of rat tail tendon collagen are capable of contraction. This suggests that telopeptide sites, and not mature HHL cross-links per se, are essential for fibroblasts to contract collagen lattices. Beta-aminopropionitrile fumarate (BAPN), a potent lathyrogen that perturbs collagen cross-linking by inhibition of lysyl oxidase, also inhibited the rate of lattice cell contraction in lattices composed of native collagen. However, the concentrations of BAPN that were necessary to inhibit the contraction of collagen lattices also inhibited fibroblast growth suggestive of cellular toxicity. In accordance with other studies, we found no inhibition of the rate of lattice contraction when fibronectin-depleted serum was used. Electron microscopy of contracted gels revealed typical collagen fibers with a characteristic axial periodicity. The data

  1. Polymorphism of Amyloid Fibrils In Vivo.

    PubMed

    Annamalai, Karthikeyan; Gührs, Karl-Heinz; Koehler, Rolf; Schmidt, Matthias; Michel, Henri; Loos, Cornelia; Gaffney, Patricia M; Sigurdson, Christina J; Hegenbart, Ute; Schönland, Stefan; Fändrich, Marcus

    2016-04-01

    Polymorphism is a wide-spread feature of amyloid-like fibrils formed in vitro, but it has so far remained unclear whether the fibrils formed within a patient are also affected by this phenomenon. In this study we show that the amyloid fibrils within a diseased individual can vary considerably in their three-dimensional architecture. We demonstrate this heterogeneity with amyloid fibrils deposited within different organs, formed from sequentially non-homologous polypeptide chains and affecting human or animals. Irrespective of amyloid type or source, we found in vivo fibrils to be polymorphic. These data imply that the chemical principles of fibril assembly that lead to such polymorphism are fundamentally conserved in vivo and in vitro. PMID:26954430

  2. Atrial fibrillation or flutter

    MedlinePlus

    ... causes of atrial fibrillation include: Alcohol use (especially binge drinking) Coronary artery disease Heart attack or heart ... conditions that cause atrial fibrillation and flutter. Avoid binge drinking.

  3. Manipulation of in vitro collagen matrix architecture for scaffolds of improved physiological relevance

    NASA Astrophysics Data System (ADS)

    Hapach, Lauren A.; VanderBurgh, Jacob A.; Miller, Joseph P.; Reinhart-King, Cynthia A.

    2015-12-01

    Type I collagen is a versatile biomaterial that is widely used in medical applications due to its weak antigenicity, robust biocompatibility, and its ability to be modified for a wide array of applications. As such, collagen has become a major component of many tissue engineering scaffolds, drug delivery platforms, and substrates for in vitro cell culture. In these applications, collagen constructs are fabricated to recapitulate a diverse set of conditions. Collagen fibrils can be aligned during or post-fabrication, cross-linked via numerous techniques, polymerized to create various fibril sizes and densities, and copolymerized into a wide array of composite scaffolds. Here, we review approaches that have been used to tune collagen to better recapitulate physiological environments for use in tissue engineering applications and studies of basic cell behavior. We discuss techniques to control fibril alignment, methods for cross-linking collagen constructs to modulate stiffness, and composite collagen constructs to better mimic physiological extracellular matrix.

  4. Manipulation of in vitro collagen matrix architecture for scaffolds of improved physiological relevance.

    PubMed

    Hapach, Lauren A; VanderBurgh, Jacob A; Miller, Joseph P; Reinhart-King, Cynthia A

    2015-01-01

    Type I collagen is a versatile biomaterial that is widely used in medical applications due to its weak antigenicity, robust biocompatibility, and its ability to be modified for a wide array of applications. As such, collagen has become a major component of many tissue engineering scaffolds, drug delivery platforms, and substrates for in vitro cell culture. In these applications, collagen constructs are fabricated to recapitulate a diverse set of conditions. Collagen fibrils can be aligned during or post-fabrication, cross-linked via numerous techniques, polymerized to create various fibril sizes and densities, and copolymerized into a wide array of composite scaffolds. Here, we review approaches that have been used to tune collagen to better recapitulate physiological environments for use in tissue engineering applications and studies of basic cell behavior. We discuss techniques to control fibril alignment, methods for cross-linking collagen constructs to modulate stiffness, and composite collagen constructs to better mimic physiological extracellular matrix. PMID:26689380

  5. Collagen network strengthening following cyclic tensile loading.

    PubMed

    Susilo, Monica E; Paten, Jeffrey A; Sander, Edward A; Nguyen, Thao D; Ruberti, Jeffrey W

    2016-02-01

    The bulk mechanical properties of tissues are highly tuned to the physiological loads they experience and reflect the hierarchical structure and mechanical properties of their constituent parts. A thorough understanding of the processes involved in tissue adaptation is required to develop multi-scale computational models of tissue remodelling. While extracellular matrix (ECM) remodelling is partly due to the changing cellular metabolic activity, there may also be mechanically directed changes in ECM nano/microscale organization which lead to mechanical tuning. The thermal and enzymatic stability of collagen, which is the principal load-bearing biopolymer in vertebrates, have been shown to be enhanced by force suggesting that collagen has an active role in ECM mechanical properties. Here, we ask how changes in the mechanical properties of a collagen-based material are reflected by alterations in the micro/nanoscale collagen network following cyclic loading. Surprisingly, we observed significantly higher tensile stiffness and ultimate tensile strength, roughly analogous to the effect of work hardening, in the absence of network realignment and alterations to the fibril area fraction. The data suggest that mechanical loading induces stabilizing changes internal to the fibrils themselves or in the fibril-fibril interactions. If such a cell-independent strengthening effect is operational in vivo, then it would be an important consideration in any multiscale computational approach to ECM growth and remodelling. PMID:26855760

  6. Microstructural characterization of vocal folds toward a strain-energy model of collagen remodeling.

    PubMed

    Miri, Amir K; Heris, Hossein K; Tripathy, Umakanta; Wiseman, Paul W; Mongeau, Luc

    2013-08-01

    Collagen fibrils are believed to control the immediate deformation of soft tissues under mechanical load. Most extracellular matrix proteins remain intact during frozen sectioning, which allows them to be scanned using atomic force microscopy (AFM). Collagen fibrils are distinguishable because of their periodic roughness wavelength. In the present study, the shape and organization of collagen fibrils in dissected porcine vocal folds were quantified using nonlinear laser scanning microscopy data at the micrometer scale and AFM data at the nanometer scale. Rope-shaped collagen fibrils were observed. The geometric characteristics for the fibrils were fed into a hyperelastic model to predict the biomechanical response of the tissue. The model simulates the micrometer-scale unlocking behavior of collagen bundles when extended from their unloaded configuration. Force spectroscopy using AFM was used to estimate the stiffness of collagen fibrils (1±0.5MPa). The presence of rope-shaped fibrils is postulated to change the slope of the force-deflection response near the onset of nonlinearity. The proposed model could ultimately be used to evaluate changes in elasticity of soft tissues that result from the collagen remodeling. PMID:23643604

  7. Microstructural Characterization of Vocal Folds toward a Strain-Energy Model of Collagen Remodeling

    PubMed Central

    Miri, Amir K.; Heris, Hossein K.; Tripathy, Umakanta; Wiseman, Paul W.; Mongeau, Luc

    2013-01-01

    Collagen fibrils are believed to control the immediate deformation of soft tissues under biomechanical load. Most extracellular matrix proteins remain intact during frozen sectioning, which allows them to be scanned using atomic force microscopy (AFM). Collagen fibrils are distinguishable because of their helical shape. In the present study, the shape and organization of collagen fibrils in dissected porcine vocal folds were quantified using nonlinear laser scanning microscopy data at the micrometer scale and AFM data at the nanometer scale. Rope-shape collagen fibrils were observed. Geometric characteristics for the fibrils were fed to a hyperelastic model to predict the biomechanical response of the tissue. The model simulates the micrometer-scale unlocking behavior of collagen bundles when extended from their unloaded configuration. Force spectroscopy using AFM was used to estimate the stiffness of collagen fibrils (1 ± 0.5 MPa). The presence of rope-shape fibrils is postulated to change the slope of the force-deflection response near the onset of nonlinearity. The proposed model could ultimately be used to evaluate changes in elasticity of soft tissues that result from the collagen remodeling. PMID:23643604

  8. Nonlinear microscopy of collagen fibers

    NASA Astrophysics Data System (ADS)

    Strupler, M.; Pena, A.-M.; Hernest, M.; Tharaux, P.-L.; Fabre, A.; Marchal-Somme, J.; Crestani, B.; Débarre, D.; Martin, J.-L.; Beaurepaire, E.; Schanne-Klein, M.-C.

    2007-02-01

    We used intrinsic Second Harmonic Generation (SHG) by fibrillar collagen to visualize the three-dimensional architecture of collagen fibrosis at the micrometer scale using laser scanning nonlinear microscopy. We showed that SHG signals are highly specific to fibrillar collagen and provide a sensitive probe of the micrometer-scale structural organization of collagen in tissues. Moreover, recording simultaneously other nonlinear optical signals in a multimodal setup, we visualized the tissue morphology using Two-Photon Excited Fluorescence (2PEF) signals from endogenous chromophores such as NADH or elastin. We then compared different methods to determine accurate indexes of collagen fibrosis using nonlinear microscopy, given that most collagen fibrils are smaller than the microscope resolution and that second harmonic generation is a coherent process. In order to define a robust method to process our three-dimensional images, we either calculated the fraction of the images occupied by a significant SHG signal, or averaged SHG signal intensities. We showed that these scores provide an estimation of the extension of renal and pulmonary fibrosis in murine models, and that they clearly sort out the fibrotic mice.

  9. Human collagen produced in plants

    PubMed Central

    Shoseyov, Oded; Posen, Yehudit; Grynspan, Frida

    2014-01-01

    Consequential to its essential role as a mechanical support and affinity regulator in extracellular matrices, collagen constitutes a highly sought after scaffolding material for regeneration and healing applications. However, substantiated concerns have been raised with regard to quality and safety of animal tissue-extracted collagen, particularly in relation to its immunogenicity, risk of disease transmission and overall quality and consistency. In parallel, contamination with undesirable cellular factors can significantly impair its bioactivity, vis-a-vis its impact on cell recruitment, proliferation and differentiation. High-scale production of recombinant human collagen Type I (rhCOL1) in the tobacco plant provides a source of an homogenic, heterotrimeric, thermally stable “virgin” collagen which self assembles to fine homogenous fibrils displaying intact binding sites and has been applied to form numerous functional scaffolds for tissue engineering and regenerative medicine. In addition, rhCOL1 can form liquid crystal structures, yielding a well-organized and mechanically strong membrane, two properties indispensable to extracellular matrix (ECM) mimicry. Overall, the shortcomings of animal- and cadaver-derived collagens arising from their source diversity and recycled nature are fully overcome in the plant setting, constituting a collagen source ideal for tissue engineering and regenerative medicine applications. PMID:23941988

  10. Chondrogenic differentiation of human mesenchymal stem cells on fish scale collagen.

    PubMed

    Hsu, Han-Hsiu; Uemura, Toshimasa; Yamaguchi, Isamu; Ikoma, Toshiyuki; Tanaka, Junzo

    2016-08-01

    Fish collagen has recently been reported to be a novel biomaterial for cell and tissue culture as an alternative to conventional mammalian collagens such as bovine and porcine collagens. Fish collagen could overcome the risk of zoonosis, such as from bovine spongiform encephalopathy. Among fish collagens, tilapia collagen, the denaturing temperature of which is near 37°C, is appropriate for cell and tissue culture. In this study, we investigated chondrogenic differentiation of human mesenchymal stem cells (hMSCs) cultured on tilapia scale collagen fibrils compared with porcine collagen and non-coated dishes. The collagen fibrils were observed using a scanning electronic microscope. Safranin O staining, glycosaminoglycans (GAG) expression, and real-time PCR were examined to evaluate chondrogenesis of hMSCs on each type of collagen fibril. The results showed that hMSCs cultured on tilapia scale collagen showed stronger Safranin O staining and higher GAG expression at day 6. Results of real-time PCR indicated that hMSCs cultured on tilapia collagen showed earlier SOX9 expression on day 4 and higher AGGRECAN and COLLAGEN II expression on day 6 compared with on porcine collagen and non-coated dishes. Furthermore, low mRNA levels of bone gamma-carboxyglutamate, a specific marker of osteogenesis, showed that tilapia collagen fibrils specifically enhanced chondrogenic differentiation of hMSCs in chondrogenic medium, as well as porcine collagen. Accordingly, tilapia scale collagen may provide an appropriate collagen source for hMSC chondrogenesis in vitro. PMID:26829997

  11. Atrial fibrillation

    PubMed Central

    Munger, Thomas M.; Wu, Li-Qun; Shen, Win K.

    2014-01-01

    Atrial fibrillation is the most common arrhythmia affecting patients today. Disease prevalence is increasing at an alarming rate worldwide, and is associated with often catastrophic and costly consequences, including heart failure, syncope, dementia, and stroke. Therapies including anticoagulants, anti-arrhythmic medications, devices, and non-pharmacologic procedures in the last 30 years have improved patients' functionality with the disease. Nonetheless, it remains imperative that further research into AF epidemiology, genetics, detection, and treatments continues to push forward rapidly as the worldwide population ages dramatically over the next 20 years. PMID:24474959

  12. Multiple risk factors and ischaemic stroke in the elderly Asian population with and without atrial fibrillation. An analysis of 425,600 Chinese individuals without prior stroke.

    PubMed

    Guo, Yutao; Wang, Hao; Tian, Yingchun; Wang, Yutang; Lip, Gregory Y H

    2016-01-01

    Ischaemic stroke risk rises with the increasing cardiovascular risk factors. How atrial fibrillation (AF) incrementally contributes to the risk for ischaemic stroke with increasing age and multiple cardiovascular risk factors is unclear. In an individual patient with AF the mechanism of ischaemic stroke may be related directly to AF itself or to risk factors associated with AF. It was this study's objective to investigate incident ischaemic stroke in relation to age and increasing cardiovascular risk factor(s), and the incremental impact of AF on stroke rates. We studied a 5% random sampling from Chinese medical insurance data covering more than 10 million individuals, for the years 2001 to 2012. The rate of ischaemic stroke was calculated amongst the individuals with no prior history of ischaemic stroke, in relation to age groups (aged < 65, 65-74, ≥ 75 years old; n = 348,431, n = 56,952, n = 20,217, respectively), and increasing risk factors using the CHA2DS2-VASc score. Among the randomly sampled 425,600 individuals with total follow-up of 1,864,232 patient-years [63.8% male, mean age 60 years; 880 with AF, vs 424,720 non-AF], there were 13,242 (3.1%) ischaemic strokes after 64,834 person-years follow-up. Overall, ischaemic stroke incidence (per 100 person-years) was 0.35 (95%CI 0.34-0.35) in the non-AF population and 1.11 (0.84-1.45) with AF. The AF population age < 65 and 65-74 had higher CHA2DS2-VASc scores than the non-AF population (p< 0.001), but this was non-significant between the non-AF and AF population age ≥ 75 (p=0.086). For the population age ≥ 75 years, incident stroke rates were 2.07 (0.86-4.76) and 4.29 (4.08-4.51) in non-AF and AF populations, respectively. The non-AF population age ≥ 65 years with ≥ 2 additional comorbidities (hypertension, vascular disease, diabetic, or heart failure) had ischaemic stroke rates similar to an AF population with CHA2DS2-VASc ≥ 4. In both non-AF and AF populations, those with CHA2DS2

  13. Bioengineered collagens

    PubMed Central

    Ramshaw, John AM; Werkmeister, Jerome A; Dumsday, Geoff J

    2014-01-01

    Mammalian collagen has been widely used as a biomedical material. Nevertheless, there are still concerns about the variability between preparations, particularly with the possibility that the products may transmit animal-based diseases. Many groups have examined the possible application of bioengineered mammalian collagens. However, translating laboratory studies into large-scale manufacturing has often proved difficult, although certain yeast and plant systems seem effective. Production of full-length mammalian collagens, with the required secondary modification to give proline hydroxylation, has proved difficult in E. coli. However, recently, a new group of collagens, which have the characteristic triple helical structure of collagen, has been identified in bacteria. These proteins are stable without the need for hydroxyproline and are able to be produced and purified from E. coli in high yield. Initial studies indicate that they would be suitable for biomedical applications. PMID:24717980

  14. Dynamic shear-influenced collagen self-assembly.

    PubMed

    Saeidi, Nima; Sander, Edward A; Ruberti, Jeffrey W

    2009-12-01

    The ability to influence the direction of polymerization of a self-assembling biomolecular system has the potential to generate materials with extremely high anisotropy. In biological systems where highly-oriented cellular populations give rise to aligned and often load-bearing tissue such organized molecular scaffolds could aid in the contact guidance of cells for engineered tissue constructs (e.g. cornea and tendon). In this investigation we examine the detailed dynamics of pepsin-extracted type I bovine collagen assembly on a glass surface under the influence of flow between two plates. Differential Interference Contrast (DIC) imaging (60x-1.4NA) with focal plane stabilization was used to resolve and track the growth of collagen aggregates on borosilicate glass for 4 different shear rates (500, 80, 20, and 9s(-1)). The detailed morphology of the collagen fibrils/aggregates was examined using Quick Freeze Deep Etch (QFDE) electron microscopy. Nucleation of fibrils on the glass was observed to occur rapidly (approximately 2 min) followed by continued growth of the fibrils. The growth rates were dependent on flow in a complex manner with the highest rate of axial growth (0.1 micro/s) occurring at a shear rate of 9s(-1). The lowest growth rate occurred at the highest shear. Fibrils were observed to both branch and join during the experiments. The best alignment of fibrils was observed at intermediate shear rates of 20 and 80s(-1). However, the investigation revealed that fibril directional growth was not stable. At high shear rates, fibrils would often turn downstream forming what we term "hooks" which are likely the combined result of monomer interaction with the initial collagen layer or "mat" and the high shear rate. Further, QFDE examination of fibril morphology demonstrated that the assembled fibrillar structure did not possess native D-periodicity. Instead, fibrils comprised a collection of generally aligned, monomers which were self-assembled to form a fibril

  15. Lysyl Oxidase Activity Is Required for Ordered Collagen Fibrillogenesis by Tendon Cells*

    PubMed Central

    Herchenhan, Andreas; Uhlenbrock, Franziska; Eliasson, Pernilla; Weis, MaryAnn; Eyre, David; Kadler, Karl E.; Magnusson, S. Peter; Kjaer, Michael

    2015-01-01

    Lysyl oxidases (LOXs) are a family of copper-dependent oxido-deaminases that can modify the side chain of lysyl residues in collagen and elastin, thereby leading to the spontaneous formation of non-reducible aldehyde-derived interpolypeptide chain cross-links. The consequences of LOX inhibition in producing lathyrism are well documented, but the consequences on collagen fibril formation are less clear. Here we used β-aminoproprionitrile (BAPN) to inhibit LOX in tendon-like constructs (prepared from human tenocytes), which are an experimental model of cell-mediated collagen fibril formation. The improvement in structure and strength seen with time in control constructs was absent in constructs treated with BAPN. As expected, BAPN inhibited the formation of aldimine-derived cross-links in collagen, and the constructs were mechanically weak. However, an unexpected finding was that BAPN treatment led to structurally abnormal collagen fibrils with irregular profiles and widely dispersed diameters. Of special interest, the abnormal fibril profiles resembled those seen in some Ehlers-Danlos Syndrome phenotypes. Importantly, the total collagen content developed normally, and there was no difference in COL1A1 gene expression. Collagen type V, decorin, fibromodulin, and tenascin-X proteins were unaffected by the cross-link inhibition, suggesting that LOX regulates fibrillogenesis independently of these molecules. Collectively, the data show the importance of LOX for the mechanical development of early collagenous tissues and that LOX is essential for correct collagen fibril shape formation. PMID:25979340

  16. Lysyl Oxidase Activity Is Required for Ordered Collagen Fibrillogenesis by Tendon Cells.

    PubMed

    Herchenhan, Andreas; Uhlenbrock, Franziska; Eliasson, Pernilla; Weis, MaryAnn; Eyre, David; Kadler, Karl E; Magnusson, S Peter; Kjaer, Michael

    2015-06-26

    Lysyl oxidases (LOXs) are a family of copper-dependent oxido-deaminases that can modify the side chain of lysyl residues in collagen and elastin, thereby leading to the spontaneous formation of non-reducible aldehyde-derived interpolypeptide chain cross-links. The consequences of LOX inhibition in producing lathyrism are well documented, but the consequences on collagen fibril formation are less clear. Here we used β-aminoproprionitrile (BAPN) to inhibit LOX in tendon-like constructs (prepared from human tenocytes), which are an experimental model of cell-mediated collagen fibril formation. The improvement in structure and strength seen with time in control constructs was absent in constructs treated with BAPN. As expected, BAPN inhibited the formation of aldimine-derived cross-links in collagen, and the constructs were mechanically weak. However, an unexpected finding was that BAPN treatment led to structurally abnormal collagen fibrils with irregular profiles and widely dispersed diameters. Of special interest, the abnormal fibril profiles resembled those seen in some Ehlers-Danlos Syndrome phenotypes. Importantly, the total collagen content developed normally, and there was no difference in COL1A1 gene expression. Collagen type V, decorin, fibromodulin, and tenascin-X proteins were unaffected by the cross-link inhibition, suggesting that LOX regulates fibrillogenesis independently of these molecules. Collectively, the data show the importance of LOX for the mechanical development of early collagenous tissues and that LOX is essential for correct collagen fibril shape formation. PMID:25979340

  17. Role of Decorin Core Protein in Collagen Organisation in Congenital Stromal Corneal Dystrophy (CSCD)

    PubMed Central

    Kamma-Lorger, Christina S.; Pinali, Christian; Martínez, Juan Carlos; Harris, Jon; Young, Robert D.; Bredrup, Cecilie; Crosas, Eva; Malfois, Marc; Rødahl, Eyvind

    2016-01-01

    The role of Decorin in organising the extracellular matrix was examined in normal human corneas and in corneas from patients with Congenital Stromal Corneal Dystrophy (CSCD). In CSCD, corneal clouding occurs due to a truncating mutation (c.967delT) in the decorin (DCN) gene. Normal human Decorin protein and the truncated one were reconstructed in silico using homology modelling techniques to explore structural changes in the diseased protein. Corneal CSCD specimens were also examined using 3-D electron tomography and Small Angle X-ray diffraction (SAXS), to image the collagen-proteoglycan arrangement and to quantify fibrillar diameters, respectively. Homology modelling showed that truncated Decorin had a different spatial geometry to the normal one, with the truncation removing a major part of the site that interacts with collagen, compromising its ability to bind effectively. Electron tomography showed regions of abnormal stroma, where collagen fibrils came together to form thicker fibrillar structures, showing that Decorin plays a key role in the maintenance of the order in the normal corneal extracellular matrix. Average diameter of individual fibrils throughout the thickness of the cornea however remained normal. PMID:26828927

  18. Atrial fibrillation.

    PubMed

    Lip, Gregory Y H; Fauchier, Laurent; Freedman, Saul B; Van Gelder, Isabelle; Natale, Andrea; Gianni, Carola; Nattel, Stanley; Potpara, Tatjana; Rienstra, Michiel; Tse, Hung-Fat; Lane, Deirdre A

    2016-01-01

    Atrial fibrillation (AF) is the most common sustained cardiac rhythm disorder, and increases in prevalence with increasing age and the number of cardiovascular comorbidities. AF is characterized by a rapid and irregular heartbeat that can be asymptomatic or lead to symptoms such as palpitations, dyspnoea and dizziness. The condition can also be associated with serious complications, including an increased risk of stroke. Important recent developments in the clinical epidemiology and management of AF have informed our approach to this arrhythmia. This Primer provides a comprehensive overview of AF, including its epidemiology, mechanisms and pathophysiology, diagnosis, screening, prevention and management. Management strategies, including stroke prevention, rate control and rhythm control, are considered. We also address quality of life issues and provide an outlook on future developments and ongoing clinical trials in managing this common arrhythmia. PMID:27159789

  19. Amyloid fibrils

    PubMed Central

    Rambaran, Roma N

    2008-01-01

    Amyloid refers to the abnormal fibrous, extracellular, proteinaceous deposits found in organs and tissues. Amyloid is insoluble and is structurally dominated by β-sheet structure. Unlike other fibrous proteins it does not commonly have a structural, supportive or motility role but is associated with the pathology seen in a range of diseases known as the amyloidoses. These diseases include Alzheimer's, the spongiform encephalopathies and type II diabetes, all of which are progressive disorders with associated high morbidity and mortality. Not surprisingly, research into the physicochemical properties of amyloid and its formation is currently intensely pursued. In this chapter we will highlight the key scientific findings and discuss how the stability of amyloid fibrils impacts on bionanotechnology. PMID:19158505

  20. Generation of 3D Collagen Gels with Controlled Diverse Architectures.

    PubMed

    Doyle, Andrew D

    2016-01-01

    Rat tail collagen solutions have been used as polymerizable in vitro three dimensional (3D) extracellular matrix (ECM) gels for single and collective cell migration assays as well as spheroid formation. Factors such as ECM concentration, pH, ionic concentration, and temperature can alter collagen polymerization and ECM architecture. This unit describes how to generate 3D collagen gels that have distinct architectures ranging from a highly reticular meshwork of short thin fibrils with small pores to a loose matrix consisting of stiff, parallel-bundled long fibrils by changing collagen polymerization temperature. This permits analysis of 3D cell migration in different ECM architectures found in vivo while maintaining a similar ECM concentration. Also included are collagen labeling techniques helpful for ECM visualization during live fluorescence imaging. © 2016 by John Wiley & Sons, Inc. PMID:27580704

  1. Three-dimensional collagen architecture in bovine articular cartilage.

    PubMed

    Jeffery, A K; Blunn, G W; Archer, C W; Bentley, G

    1991-09-01

    The three-dimensional architecture of bovine articular cartilage collagen and its relationship to split lines has been studied with scanning electron microscopy. In the middle and superficial zones, collagen was organised in a layered or leaf-like manner. The orientation was vertical in the intermediate zone, curving to become horizontal and parallel to the articular surface in the superficial zone. Each leaf consisted of a fine network of collagen fibrils. Adjacent leaves merged or were closely linked by bridging fibrils and were arranged according to the split-line pattern. The surface layer (lamina splendens) was morphologically distinct. Although ordered, the overall collagen structure was different in each plane (anisotropic) a property described in previous morphological and biophysical studies. As all components of the articular cartilage matrix interact closely, the three-dimensional organisation of collagen is important when considering cartilage function and the processes of cartilage growth, injury and repair. PMID:1894669

  2. The size exclusion characteristics of type I collagen: implications for the role of noncollagenous bone constituents in mineralization.

    PubMed

    Toroian, Damon; Lim, Joo Eun; Price, Paul A

    2007-08-01

    The mineral in bone is located primarily within the collagen fibril, and during mineralization the fibril is formed first and then water within the fibril is replaced with mineral. The collagen fibril therefore provides the aqueous compartment in which mineral grows. Although knowledge of the size of molecules that can diffuse into the fibril to affect crystal growth is critical to understanding the mechanism of bone mineralization, there have been as yet no studies on the size exclusion properties of the collagen fibril. To determine the size exclusion characteristics of collagen, we developed a gel filtration-like procedure that uses columns containing collagen from tendon and bone. The elution volumes of test molecules show the volume within the packed column that is accessible to the test molecules, and therefore reveal the size exclusion characteristics of the collagen within the column. These experiments show that molecules smaller than a 6-kDa protein diffuse into all of the water within the collagen fibril, whereas molecules larger than a 40-kDa protein are excluded from this water. These studies provide an insight into the mechanism of bone mineralization. Molecules and apatite crystals smaller than a 6-kDa protein can diffuse into all water within the fibril and so can directly impact mineralization. Although molecules larger than a 40-kDa protein are excluded from the fibril, they can initiate mineralization by forming small apatite crystal nuclei that diffuse into the fibril, or can favor fibril mineralization by inhibiting apatite growth everywhere but within the fibril. PMID:17562713

  3. Changes in Scleral Collagen Organization in Murine Chronic Experimental Glaucoma

    PubMed Central

    Pijanka, Jacek K.; Kimball, Elizabeth C.; Pease, Mary E.; Abass, Ahmed; Sorensen, Thomas; Nguyen, Thao D.; Quigley, Harry A.; Boote, Craig

    2014-01-01

    Purpose. The organization of scleral collagen helps to determine the eye's biomechanical response to intraocular pressure (IOP), and may therefore be important in glaucoma. This study provides a quantitative assessment of changes in scleral collagen fibril organization in bead-induced murine experimental glaucoma. Methods. Wide-angle X-ray scattering was used to study the effect of bead-induced glaucoma on posterior scleral collagen organization in one eye of 12 CD1 mice, with untreated fellow eyes serving as controls. Three collagen parameters were measured: the local preferred fibril directions, the degree of collagen anisotropy, and the total fibrillar collagen content. Results. The mouse sclera featured a largely circumferential orientation of fibrillar collagen with respect to the optic nerve head canal. Localized alteration to fibril orientations was evident in the inferior peripapillary sclera of bead-treated eyes. Collagen anisotropy was significantly (P < 0.05) reduced in bead-treated eyes in the superior peripapillary (Treated: 43 ± 8%; Control: 49 ± 6%) and midposterior (Treated: 39 ± 4%; Control: 43 ± 4%) sclera, and in the peripapillary region overall (Treated: 43 ± 6%; Control: 47 ± 3%). No significant differences in total collagen content were found between groups. Conclusions. Spatial changes in collagen fibril anisotropy occur in the posterior sclera of mice with bead-induced chronic IOP elevation and axonal damage. These results support the idea that dynamic changes in scleral form and structure play a role in the development of experimental glaucoma in mice, and potentially in human glaucoma. PMID:25228540

  4. A monomer-trimer model supports intermittent glucagon fibril growth

    NASA Astrophysics Data System (ADS)

    Košmrlj, Andrej; Cordsen, Pia; Kyrsting, Anders; Otzen, Daniel E.; Oddershede, Lene B.; Jensen, Mogens H.

    2015-03-01

    We investigate in vitro fibrillation kinetics of the hormone peptide glucagon at various concentrations using confocal microscopy and determine the glucagon fibril persistence length 60μm. At all concentrations we observe that periods of individual fibril growth are interrupted by periods of stasis. The growth probability is large at high and low concentrations and is reduced for intermediate glucagon concentrations. To explain this behavior we propose a simple model, where fibrils come in two forms, one built entirely from glucagon monomers and one entirely from glucagon trimers. The opposite building blocks act as fibril growth blockers, and this generic model reproduces experimental behavior well.

  5. Collagen in Human Tissues: Structure, Function, and Biomedical Implications from a Tissue Engineering Perspective

    NASA Astrophysics Data System (ADS)

    Balasubramanian, Preethi; Prabhakaran, Molamma P.; Sireesha, Merum; Ramakrishna, Seeram

    The extracellular matrix is a complex biological structure encoded with various proteins, among which the collagen family is the most significant and abundant of all, contributing 30-35% of the whole-body protein. "Collagen" is a generic term for proteins that forms a triple-helical structure with three polypeptide chains, and around 29 types of collagen have been identified up to now. Although most of the members of the collagen family form such supramolecular structures, extensive diversity exists between each type of collagen. The diversity is not only based on the molecular assembly and supramolecular structures of collagen types but is also observed within its tissue distribution, function, and pathology. Collagens possess complex hierarchical structures and are present in various forms such as collagen fibrils (1.5-3.5 nm wide), collagen fibers (50-70 nm wide), and collagen bundles (150-250 nm wide), with distinct properties characteristic of each tissue providing elasticity to skin, softness of the cartilage, stiffness of the bone and tendon, transparency of the cornea, opaqueness of the sclera, etc. There exists an exclusive relation between the structural features of collagen in human tissues (such as the collagen composition, collagen fibril length and diameter, collagen distribution, and collagen fiber orientation) and its tissue-specific mechanical properties. In bone, a transverse collagen fiber orientation prevails in regions of higher compressive stress whereas longitudinally oriented collagen fibers correlate to higher tensile stress. The immense versatility of collagen compels a thorough understanding of the collagen types and this review discusses the major types of collagen found in different human tissues, highlighting their tissue-specific uniqueness based on their structure and mechanical function. The changes in collagen during a specific tissue damage or injury are discussed further, focusing on the many tissue engineering applications for

  6. Collagen Self-Assembly on Orthopedic Magnesium Biomaterials Surface and Subsequent Bone Cell Attachment

    PubMed Central

    Zhao, Nan; Zhu, Donghui

    2014-01-01

    Magnesium (Mg) biomaterials are a new generation of biodegradable materials and have promising potential for orthopedic applications. After implantation in bone tissues, these materials will directly interact with extracellular matrix (ECM) biomolecules and bone cells. Type I collagen, the major component of bone ECM, forms the architecture scaffold that provides physical support for bone cell attachment. However, it is still unknown how Mg substrate affects collagen assembly on top of it as well as subsequent cell attachment and growth. Here, we studied the effects of collagen monomer concentration, pH, assembly time, and surface roughness of two Mg materials (pure Mg and AZ31) on collagen fibril formation. Results showed that formation of fibrils would not initiate until the monomer concentration reached a certain level depending on the type of Mg material. The thickness of collagen fibril increased with the increase of assembly time. The structures of collagen fibrils formed on semi-rough surfaces of Mg materials have a high similarity to that of native bone collagen. Next, cell attachment and growth after collagen assembly were examined. Materials with rough surface showed higher collagen adsorption but compromised bone cell attachment. Interestingly, surface roughness and collagen structure did not affect cell growth on AZ31 for up to a week. Findings from this work provide some insightful information on Mg-tissue interaction at the interface and guidance for future surface modifications of Mg biomaterials. PMID:25303459

  7. Quantitative Assessment of Local Collagen Matrix Remodeling in 3-D Culture: The Role of Rho Kinase

    PubMed Central

    Kim, Areum; Lakshman, Neema; Petroll, W.Matthew

    2007-01-01

    The purpose of this study was to quantitatively assess the role of Rho kinase in modulating the pattern and amount of local cell-induced collagen matrix remodeling. Human corneal fibroblasts were plated inside 100 μm thick fibrillar collagen matrices and cultured for 24 hours in media with or without the Rho kinase inhibitor Y-27632. Cells were then fixed and stained with phalloidin. Fluorescent (for f-actin) and reflected light (for collagen fibrils) 3-D optical section images were acquired using laser confocal microscopy. Fourier transform analysis was used to assess collagen fibril alignment, and 3-D cell morphology and local collagen density were measured using MetaMorph. Culture in serum-containing media induced significant global matrix contraction, which was inhibited by blocking Rho kinase (p < 0.001). Fibroblasts generally had a bipolar morphology and intracellular stress fibers. Collagen fibrils were compacted and aligned parallel to stress fibers and pseudopodia. When Rho kinase was inhibited, cells had a more cortical f-actin distribution and dendritic morphology. Both local collagen fibril density and alignment were significantly reduced (p<0.01). Overall, the data suggests that Rho kinase dependent contractile force generation leads to co-alignment of cells and collagen fibrils along the plane of greatest resistance, and that this process contributes to global matrix contraction. PMID:16978606

  8. [Atrial fibrillation].

    PubMed

    Colín Lizalde, L J

    2001-01-01

    Atrial fibrillation (AF) is the most common sustained arrhythmia. AF has now been exhaustively studied: more is known about its mechanism and research is moving towards new forms of treatment. For chronic AF, basically the control of ventricular rate and the brain protection are the main issues. It is well known that with the identification of high risk group for embolism, oral anticoagulation should be administered. Ventricular rate control can be achieved by using betablockers or calcium channel blockers, unless these are contraindicated for the elderly. Oral anticoagulation prevents the stroke. The main mechanism of AF is the re-entry of multiple wavelets, but now it is more frequently found on patients with focal AF. Therapies are employed to bring the patient to a sinusal rhythm as soon as possible with antiarryhthmics or electric cardioversion externally or internally. The internal procedure includes 1 to 15 J and the success rate is of 91% vs 67% in relation to the external one. The introduction of the catheter ablation has opened new frontiers for the treatment of AF, first as the ablate-and-pace technique and now trying to mimic the maze procedure or with the ablation of the focal tachycardia. The stimulation for prevention of AF under research, as well as the implantable dysfibrillation for selected patients. On going studies will show the possible benefit of this type of benefits. PMID:11565343

  9. Atrial Fibrillation Medications

    MedlinePlus

    ... think you are pregnant If you notice red, dark brown or black urine or stools If you ... Fibrillation • Introduction • What is Atrial Fibrillation? • Why AFib Matters • Understand your Risk for AFib Children • Symptoms of ...

  10. Amyloid Fibril Solubility.

    PubMed

    Rizzi, L G; Auer, S

    2015-11-19

    It is well established that amyloid fibril solubility is protein specific, but how solubility depends on the interactions between the fibril building blocks is not clear. Here we use a simple protein model and perform Monte Carlo simulations to directly measure the solubility of amyloid fibrils as a function of the interaction between the fibril building blocks. Our simulations confirms that the fibril solubility depends on the fibril thickness and that the relationship between the interactions and the solubility can be described by a simple analytical formula. The results presented in this study reveal general rules how side-chain-side-chain interactions, backbone hydrogen bonding, and temperature affect amyloid fibril solubility, which might prove to be a powerful tool to design protein fibrils with desired solubility and aggregation properties in general. PMID:26496385

  11. Collagen Gel Contraction by Fibroblasts: The Role of Myosin 2 and Gravity Effects

    NASA Technical Reports Server (NTRS)

    Johnson-Wint, Barbara P.; Malouvier, Alexandre; Holton, Emily

    1996-01-01

    Several lines of evidence suggest that collagen organization by connective tissue cells is sensitive to force. For instance, in flight experiments on rats the collagen fibrils which were produced under weightlessness and which were immediately next to the tendon fibroblasts were shown to be oriented randomly around the cells while the older fibrils right next to these and which were produced under 1 G, were highly organized.

  12. A substitution at a non-glycine position in the triple-helical domain of pro alpha 2(I) collagen chains present in an individual with a variant of the Marfan syndrome.

    PubMed Central

    Phillips, C L; Shrago-Howe, A W; Pinnell, S R; Wenstrup, R J

    1990-01-01

    A substitution for a highly conserved non-glycine residue in the triple-helical domain of the pro alpha 2(I) collagen molecule was found in an individual with a variant of the Marfan syndrome. A single base change resulted in substitution of arginine618 by glutamine at the Y position of a Gly-X-Y repeat, and is responsible for the decreased migration in SDS-polyacrylamide gels of some pro alpha 2(I) chains of type I collagen synthesized by dermal fibroblasts from this individual. Family studies suggest that this substitution was inherited from the individual's father who also produces abnormally migrating pro alpha 2(I) collagen chains and shares some of the abnormal skeletal features. This single base change creates a new Bsu36 I (Sau I, Mst II) restriction site detectable in genomic DNA by Southern blot analysis when probed with a COL1A2 fragment. The analysis of 52 control individuals (103 chromosomes) was negative for the new Bsu36 I site, suggesting that the substitution is not a common polymorphism. Images PMID:1978725

  13. Atrial Fibrillation in Children

    MedlinePlus

    ... Pressure High Blood Pressure Tools & Resources Stroke More Atrial Fibrillation in Children Updated:Jul 18,2016 Does your ... content was last reviewed on 04/16/14. Atrial Fibrillation • Introduction • What is Atrial Fibrillation? • Why AFib Matters • ...

  14. Fibromodulin Interacts with Collagen Cross-linking Sites and Activates Lysyl Oxidase*

    PubMed Central

    Bihan, Dominique; Bonna, Arkadiusz; Rubin, Kristofer; Farndale, Richard W.

    2016-01-01

    The hallmark of fibrotic disorders is a highly cross-linked and dense collagen matrix, a property driven by the oxidative action of lysyl oxidase. Other fibrosis-associated proteins also contribute to the final collagen matrix properties, one of which is fibromodulin. Its interactions with collagen affect collagen cross-linking, packing, and fibril diameter. We investigated the possibility that a specific relationship exists between fibromodulin and lysyl oxidase, potentially imparting a specific collagen matrix phenotype. We mapped the fibromodulin-collagen interaction sites using the collagen II and III Toolkit peptide libraries. Fibromodulin interacted with the peptides containing the known collagen cross-linking sites and the MMP-1 cleavage site in collagens I and II. Interestingly, the interaction sites are closely aligned within the quarter-staggered collagen fibril, suggesting a multivalent interaction between fibromodulin and several collagen helices. Furthermore, we detected an interaction between fibromodulin and lysyl oxidase (a major collagen cross-linking enzyme) and mapped the interaction site to 12 N-terminal amino acids on fibromodulin. This interaction also increases the activity of lysyl oxidase. Together, the data suggest a fibromodulin-modulated collagen cross-linking mechanism where fibromodulin binds to a specific part of the collagen domain and also forms a complex with lysyl oxidase, targeting the enzyme toward specific cross-linking sites. PMID:26893379

  15. Type VII Collagen is Enriched in the Enamel Organic Matrix Associated with the Dentin-Enamel Junction of Mature Human Teeth

    PubMed Central

    McGuire, Jacob D.; Walker, Mary P.; Mousa, Ahmad; Wang, Yong; Gorski, Jeff P.

    2014-01-01

    The inner enamel region of erupted teeth is known to exhibit higher fracture toughness and crack growth resistance than bulk phase enamel. However, an explanation for this behavior has been hampered by the lack of compositional information for the residual enamel organic matrix. Since enamel-forming ameloblasts are known to express type VII collagen and type VII collagen null mice display abnormal amelogenesis, the aim of this study was to determine whether type VII collagen is a component of the enamel organic matrix at the dentin-enamel junction (DEJ) of mature human teeth. Immunofluorescent confocal microscopy of demineralized tooth sections localized type VII collagen to the organic matrix surrounding individual enamel rods near the DEJ. Morphologically, immunoreactive type VII collagen helical-bundles resembled the gnarled-pattern of enamel rods detected by Coomassie Blue staining. Western blotting of whole crown or enamel matrix extracts also identified characteristic Mr=280 and 230 kDa type VII dimeric forms, which resolved into 75 and 25 kDa bands upon reduction. As expected, the collagenous domain of type VII collagen was resistant to pepsin digestion, but was susceptible to purified bacterial collagenase. These results demonstrate the inner enamel organic matrix in mature teeth contains macromolecular type VII collagen. Based on its physical association with the DEJ and its well-appreciated capacity to complex with other collagens, we hypothesize that enamel embedded type VII collagen fibrils may contribute not only to the structural resilience of enamel, but may also play a role in bonding enamel to dentin. PMID:24594343

  16. [Anticoagulation in atrial fibrillation].

    PubMed

    Schwarz, M; Bode, Ch

    2008-10-01

    In this overview the actual guideline-recommendations for anticoagulation in atrial fibrillation and the problems of the currently available therapy are discussed. Furthermore an outlook over future developments in this field is given. Effective anticoagulation can prohibit thrombembolic events and is thus essential for the prognosis of patients suffering from atrial fibrillation. Until now vitamin-K-antagonists (VKAs) and acetylsalicylic acid (ASA) are available for oral anticoagulation in these patients. VKAs demonstrate a satisfying efficiency combined with rather high bleeding hazard. ASA on the other hand allows only moderate risk reduction with minimal side effects. Thus the guidelines recommend anticoagulation tailored to the individual risk, which can be evaluated by the CHADS2-Score. New therapeutic strategies, like the factor Xa inhibitor rivaroxaban or the factor II inhibitor dabigatran, are actually evaluated in phase III studies. These drugs bear the hope of higher efficiency combined with improved safety and much more comfortable use in the daily practice (e. g. no need for INR measurement, no dose adaptation). PMID:18836647

  17. Biomimetic Analogs for Collagen Biomineralization

    PubMed Central

    Gu, L.; Kim, Y.K.; Liu, Y.; Ryou, H.; Wimmer, C.E.; Dai, L.; Arola, D.D.; Looney, S.W.; Pashley, D.H.; Tay, F.R.

    2011-01-01

    Inability of chemical phosphorylation of sodium trimetaphosphate to induce intrafibrillar mineralization of type I collagen may be due to the failure to incorporate a biomimetic analog to stabilize amorphous calcium phosphates (ACP) as nanoprecursors. This study investigated adsorption/desorption characteristics of hydrolyzed and pH-adjusted sodium trimetaphosphate (HPA-Na3P3O9) to collagen. Based on those results, a 5-minute treatment time with 2.8 wt% HPA-Na3P3O9 was used in a single-layer reconstituted collagen model to confirm that both the ACP-stabilization analog and matrix phosphoprotein analog must be present for intrafibrillar mineralization. The results of that model were further validated by complete remineralization of phosphoric-acid-etched dentin treated with the matrix phosphoprotein analog and lined with a remineralizing lining composite, and with the ACP-stabilization analog supplied in simulated body fluid. An understanding of the basic processes involved in intrafibrillar mineralization of reconstituted collagen fibrils facilitates the design of novel tissue engineering materials for hard tissue repair and regeneration. PMID:20940362

  18. Treatment of photoaged skin with topical tretinoin increases epidermal-dermal anchoring fibrils

    SciTech Connect

    Woodley, D.T.; Briggaman, R.A. ); Zelickson, A.S. ); Hamilton, T.A.; Weiss, J.S.; Ellis, C.N.; Voorhees, J.J. )

    1990-06-13

    Topical 0.1% tretinoin or vehicle control was applied daily to the forearm skin of six caucasian adults for 4 months. Two-millimeter punch biopsy specimens were obtained from treatment sites at the beginning and end of the study period for electron microscopy. Anchoring fibrils within the epidermal-dermal junction of skin treatment sites were quantitated by blinded, standardized, computer-assisted morphometry. After 4 months of continual daily treatment, skin sites that received topical tretinoin showed double the anchoring fibril density compared with vehicle control sites. The possible mechanism by which topical tretinoin increases anchoring fibrils in skin include the drug's property of inhibiting collagenase, a dermal enzyme that degrades anchoring fibril collagen. The authors speculate that increased numbers of collagenous anchoring fibrils within the papillary dermis of human skin is one of the connective-tissue correlates of the clinical improvement observed in photoaged skin after treatment with topical tretinoin.

  19. Atrial fibrillation.

    PubMed

    Bang, Casper N

    2013-10-01

    Atrial fibrillation (AF) is a common complication after myocardial infarction (MI) and new-onset AF has been demonstrated to be associated with adverse outcome and a large excess risk of death in both MI and aortic stenosis (AS) patients. Prevention of new-onset AF is therefore a potential therapeutic target in AS and MI patients. Lipid-lowering drugs, particularly statins, have anti-inflammatory and antioxidant properties that may prevent AF. Accordingly, statins are recommended as a class IIa recommendation for prevention of new-onset AF after coronary artery bypass grafting (CABG). However, this preventive effect has not been investigated on new-onset AF in asymptomatic patients with AS or a large scale first-time MI patient sample and data in patients not undergoing invasive cardiac interventions are limited. This PhD thesis was conducted at the Heart Centre, Rigshospitalet, Denmark, with the aim to investigate the three aforementioned questions and to add to the existing evidence of AF prevention with statins. This was done using three different settings: 1) a randomized patients sample of 1,873 from the Simvastatin and Ezetimibe in Aortic Stenosis (SEAS) study, 2) a register patient sample of 97,499 with first-time MI, and 3) all published studies until beginning of June 2011 examining statin treatment on new-onset and recurrent AF in patients not undergoing cardiac surgery. This thesis revealed that statins did not lower the incidence or the time to new-onset AF in patients with asymptomatic AS. However, statin treatment showed an independently preventive effect on new-onset AF, including type-dependent effect and a trend to dosage-dependent effect. In addition, this thesis showed that good compliance to statin treatment was important to prevent new-onset AF. Finally, the meta-analysis in this PhD thesis showed a preventive effect in the observational studies although this effect was absent in the randomized controlled trials. Based on this PhD thesis

  20. Quantification of Collagen Ultrastructure after Penetrating Keratoplasty – Implications for Corneal Biomechanics

    PubMed Central

    Gardner, Steven J.; Kamma-Lorger, Christina S.; Hayes, Sally; Nielsen, Kim; Hjortdal, Jesper; Sorensen, Thomas; Terrill, Nicholas J.; Meek, Keith M.

    2013-01-01

    Purpose To quantify long-term changes in stromal collagen ultrastructure following penetrating keratoplasty (PK), and evaluate their possible implications for corneal biomechanics. Methods A pair of 16 mm post-mortem corneo-scleral buttons was obtained from a patient receiving bilateral penetrating keratoplasty 12 (left)/28 (right) years previously. Small-angle x-ray scattering quantified collagen fibril spacing, diameter and spatial order at 0.5 mm or 0.25 mm intervals along linear scans across the graft margin. Corresponding control data was collected from two corneo-scleral buttons with no history of refractive surgery. Wide-angle x-ray scattering quantified collagen fibril orientation at 0.25 mm (horizontal)×0.25 mm (vertical) intervals across both PK specimens. Quantification of orientation changes in the graft margin were verified by equivalent analysis of data from a 13 year post-operative right PK specimen obtained from a second patient in a previous study, and comparison made with new and published data from normal corneas. Results Marked changes to normal fibril alignment, in favour of tangentially oriented collagen, were observed around the entire graft margin in all PK specimens. The total number of meridional fibrils in the wound margin was observed to decrease by up to 40%, with the number of tangentially oriented fibrils increasing by up to 46%. As a result, in some locations the number of fibrils aligned parallel to the wound outnumbered those spanning it by up to five times. Localised increases in fibril spacing and diameter, with an accompanying reduction in matrix order, were also evident. Conclusions Abnormal collagen fibril size and spatial order within the PK graft margin are indicative of incomplete stromal wound remodelling and the long term persistence of fibrotic scar tissue. Lasting changes in collagen fibril orientation in and around PK wounds may alter corneal biomechanics and compromise the integrity of the graft-host interface in the

  1. The streptococcal collagen-binding protein CNE specifically interferes with alphaVbeta3-mediated cellular interactions with triple helical collagen.

    PubMed

    van Wieringen, Tijs; Kalamajski, Sebastian; Lidén, Asa; Bihan, Dominique; Guss, Bengt; Heinegård, Dick; Farndale, Richard W; Rubin, Kristofer

    2010-11-12

    Collagen fibers expose distinct domains allowing for specific interactions with other extracellular matrix proteins and cells. To investigate putative collagen domains that govern integrin α(V)β(3)-mediated cellular interactions with native collagen fibers we took advantage of the streptococcal protein CNE that bound native fibrillar collagens. CNE specifically inhibited α(V)β(3)-dependent cell-mediated collagen gel contraction, PDGF BB-induced and α(V)β(3)-mediated adhesion of cells, and binding of fibronectin to native collagen. Using a Toolkit composed of overlapping, 27-residue triple helical segments of collagen type II, two CNE-binding sites present in peptides II-1 and II-44 were identified. These peptides lack the major binding site for collagen-binding β(1) integrins, defined by the peptide GFOGER. Peptide II-44 corresponds to a region of collagen known to bind collagenases, discoidin domain receptor 2, SPARC (osteonectin), and fibronectin. In addition to binding fibronectin, peptide II-44 but not II-1 inhibited α(V)β(3)-mediated collagen gel contraction and, when immobilized on plastic, supported adhesion of cells. Reduction of fibronectin expression by siRNA reduced PDGF BB-induced α(V)β(3)-mediated contraction. Reconstitution of collagen types I and II gels in the presence of CNE reduced collagen fibril diameters and fibril melting temperatures. Our data indicate that contraction proceeded through an indirect mechanism involving binding of cell-produced fibronectin to the collagen fibers. Furthermore, our data show that cell-mediated collagen gel contraction does not directly depend on the process of fibril formation. PMID:20837478

  2. Development and utilization of a bovine type I collagen microfibril model

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The structure of fibrous collagen, a long triple helix that self-associates in a staggered array to form a matrix of fibrils, fibers and fiber bundles, makes it uniquely suitable as a scaffold for biomaterial engineering. A major challenge for this application is to stabilize collagen structure by m...

  3. Mineralisation of reconstituted collagen using polyvinylphosphonic acid/polyacrylic acid templating matrix protein analogues in the presence of calcium, phosphate and hydroxyl ions

    PubMed Central

    Kim, Young Kyung; Gu, Li-sha; Bryan, Thomas E.; Kim, Jong Ryul; Chen, Liang; Liu, Yan; Yoon, James C.; Breschi, Lorenzo; Pashley, David H.; Tay, Franklin R.

    2010-01-01

    The complex morphologies of mineralised collagen fibrils are regulated through interactions between the collagen matrix and non-collagenous extracellular proteins. In the present study, polyvinylphosphonic acid, a biomimetic analogue of matrix phosphoproteins, was synthesised and confirmed with FTIR and NMR. Biomimetic mineralisation of reconstituted collagen fibrils devoid of natural non-collagenous proteins was demonstrated with TEM using a Portland cement-containing resin composite and a phosphate-containing fluid in the presence of polyacrylic acid as sequestration, and polyvinylphosphonic acid as templating matrix protein analogues. In the presence of these dual biomimetic analogues in the mineralisation medium, intrafibrillar and extrafibrillar mineralisation via bottom-up nanoparticle assembly based on the nonclassical crystallisation pathway could be identified. Conversely, only large mineral spheres with no preferred association with collagen fibrils were observed in the absence of biomimetic analogues in the medium. Mineral phases were evident within the collagen fibrils as early as 4 hours after the initially-formed amorphous calcium phosphate nanoprecursors were transformed into apatite nanocrystals. Selected area electron diffraction patterns of highly mineralised collagen fibrils were nearly identical to those of natural bone, with apatite crystallites preferentially aligned along the collagen fibril axes. PMID:20621767

  4. Mineralisation of reconstituted collagen using polyvinylphosphonic acid/polyacrylic acid templating matrix protein analogues in the presence of calcium, phosphate and hydroxyl ions.

    PubMed

    Kim, Young Kyung; Gu, Li-sha; Bryan, Thomas E; Kim, Jong R; Chen, Liang; Liu, Yan; Yoon, James C; Breschi, Lorenzo; Pashley, David H; Tay, Franklin R

    2010-09-01

    The complex morphologies of mineralised collagen fibrils are regulated through interactions between the collagen matrix and non-collagenous extracellular proteins. In the present study, polyvinylphosphonic acid, a biomimetic analogue of matrix phosphoproteins, was synthesised and confirmed with FTIR and NMR. Biomimetic mineralisation of reconstituted collagen fibrils devoid of natural non-collagenous proteins was demonstrated with TEM using a Portland cement-containing resin composite and a phosphate-containing fluid in the presence of polyacrylic acid as sequestration, and polyvinylphosphonic acid as templating matrix protein analogues. In the presence of these dual biomimetic analogues in the mineralisation medium, intrafibrillar and extrafibrillar mineralisation via bottom-up nanoparticle assembly based on the non-classical crystallisation pathway could be identified. Conversely, only large mineral spheres with no preferred association with collagen fibrils were observed in the absence of biomimetic analogues in the medium. Mineral phases were evident within the collagen fibrils as early as 4 h after the initially-formed amorphous calcium phosphate nanoprecursors were transformed into apatite nanocrystals. Selected area electron diffraction patterns of highly mineralised collagen fibrils were nearly identical to those of natural bone, with apatite crystallites preferentially aligned along the collagen fibril axes. PMID:20621767

  5. Structural basis of sequence-specific collagen recognition by SPARC

    PubMed Central

    Hohenester, Erhard; Sasaki, Takako; Giudici, Camilla; Farndale, Richard W.; Bächinger, Hans Peter

    2008-01-01

    Protein interactions with the collagen triple helix play a critical role in collagen fibril formation, cell adhesion, and signaling. However, structural insight into sequence-specific collagen recognition is limited to an integrin-peptide complex. A GVMGFO motif in fibrillar collagens (O denotes 4-hydroxyproline) binds 3 unrelated proteins: von Willebrand factor (VWF), discoidin domain receptor 2 (DDR2), and the extracellular matrix protein SPARC/osteonectin/BM-40. We report the crystal structure at 3.2 Å resolution of human SPARC bound to a triple-helical 33-residue peptide harboring the promiscuous GVMGFO motif. SPARC recognizes the GVMGFO motifs of the middle and trailing collagen chains, burying a total of 720 Å2 of solvent-accessible collagen surface. SPARC binding does not distort the canonical triple helix of the collagen peptide. In contrast, a critical loop in SPARC is substantially remodelled upon collagen binding, creating a deep pocket that accommodates the phenylalanine residue of the trailing collagen chain (“Phe pocket”). This highly restrictive specificity pocket is shared with the collagen-binding integrin I-domains but differs strikingly from the shallow collagen-binding grooves of the platelet receptor glycoprotein VI and microbial adhesins. We speculate that binding of the GVMGFO motif to VWF and DDR2 also results in structural changes and the formation of a Phe pocket. PMID:19011090

  6. Northern pike (Esox lucius) collagen: Extraction, characterization and potential application.

    PubMed

    Kozlowska, J; Sionkowska, A; Skopinska-Wisniewska, J; Piechowicz, K

    2015-11-01

    Acid soluble collagen (ASC) and pepsin soluble collagen (PSC) from the scales of northern pike (Esox lucius) were extracted and characterized. It was the first time that this species was used as sources of collagen. FT-IR and amino acid analysis results revealed the presence of collagen. Glycine accounts for one-third of its amino acid residues and specific for collagen amino acid - hydroxyproline - is present in isolated protein. The content of imino acid: proline and hydroxyproline in ASC and PSC was similar (12.5% Pro and 6.5% Hyp). Both ASC and PSC were type I collagen. The denaturation temperature of ASC and PSC were 28.5 and 27°C, respectively. Thin collagen films were obtained by casting of collagen solution onto glass plates. The surface properties of ASC and PSC films were different - the surface of ASC collagen film was more polar and less rough than PSC and we can observe the formation of collagen fibrils after solvent evaporation. ASC films showed much higher tensile properties than PSC. The obtained results suggest that northern pike scales have potential as an alternative source of collagen for use in various fields. PMID:26254247

  7. Highly nonlinear stress-relaxation response of articular cartilage in indentation: Importance of collagen nonlinearity.

    PubMed

    Mäkelä, J T A; Korhonen, R K

    2016-06-14

    Modern fibril-reinforced computational models of articular cartilage can include inhomogeneous tissue composition and structure, and nonlinear mechanical behavior of collagen, proteoglycans and fluid. These models can capture well experimental single step creep and stress-relaxation tests or measurements under small strains in unconfined and confined compression. Yet, it is known that in indentation, especially at high strain velocities, cartilage can express highly nonlinear response. Different fibril reinforced poroelastic and poroviscoelastic models were used to assess measured highly nonlinear stress-relaxation response of rabbit articular cartilage in indentation. Experimentally measured depth-dependent volume fractions of different tissue constituents and their mechanical nonlinearities were taken into account in the models. In particular, the collagen fibril network was modeled using eight separate models that implemented five different constitutive equations to describe the nonlinearity. These consisted of linear elastic, nonlinear viscoelastic and multiple nonlinear elastic representations. The model incorporating the most nonlinearly increasing Young׳s modulus of collagen fibrils as a function of strain captured best the experimental data. Relative difference between the model and experiment was ~3%. Surprisingly, the difference in the peak forces between the experiment and the model with viscoelastic collagen fibrils was almost 20%. Implementation of the measured volume fractions did not improve the ability of the model to capture the measured mechanical data. These results suggest that a highly nonlinear formulation for collagen fibrils is needed to replicate multi-step stress-relaxation response of rabbit articular cartilage in indentation with high strain rates. PMID:27130474

  8. Nucleation of amyloid fibrils

    NASA Astrophysics Data System (ADS)

    Kashchiev, Dimo; Auer, Stefan

    2010-06-01

    We consider nucleation of amyloid fibrils in the case when the process occurs by the mechanism of direct polymerization of practically fully extended protein segments, i.e., β-strands, into β-sheets. Applying the classical nucleation theory, we derive a general expression for the work to form a nanosized amyloid fibril (protofilament) constituted of successively layered β-sheets. Analysis of this expression reveals that with increasing its size, the fibril transforms from one-dimensional to two-dimensional aggregate in order to preserve the equilibrium shape corresponding to minimal formation work. We determine the size of the fibril nucleus, the fibril nucleation work, and the fibril nucleation rate as explicit functions of the concentration and temperature of the protein solution. The results obtained are applicable to homogeneous nucleation, which occurs when the solution is sufficiently pure and/or strongly supersaturated.

  9. Internal strain drives spontaneous periodic buckling in collagen and regulates remodeling

    PubMed Central

    Dittmore, Andrew; Silver, Jonathan; Sarkar, Susanta K.; Marmer, Barry; Goldberg, Gregory I.; Neuman, Keir C.

    2016-01-01

    Fibrillar collagen, an essential structural component of the extracellular matrix, is remarkably resistant to proteolysis, requiring specialized matrix metalloproteinases (MMPs) to initiate its remodeling. In the context of native fibrils, remodeling is poorly understood; MMPs have limited access to cleavage sites and are inhibited by tension on the fibril. Here, single-molecule recordings of fluorescently labeled MMPs reveal cleavage-vulnerable binding regions arrayed periodically at ∼1-µm intervals along collagen fibrils. Binding regions remain periodic even as they migrate on the fibril, indicating a collective process of thermally activated and self-healing defect formation. An internal strain relief model involving reversible structural rearrangements quantitatively reproduces the observed spatial patterning and fluctuations of defects and provides a mechanism for tension-dependent stabilization of fibrillar collagen. This work identifies internal–strain-driven defects that may have general and widespread regulatory functions in self-assembled biological filaments. PMID:27402741

  10. Pathways of tau fibrillization.

    PubMed

    Kuret, Jeff; Chirita, Carmen N; Congdon, Erin E; Kannanayakal, Theresa; Li, Guibin; Necula, Mihaela; Yin, Haishan; Zhong, Qi

    2005-01-01

    New methods for analyzing tau fibrillization have yielded insights into the biochemical transitions involved in the process. Here we review the parallels between the sequential progression of tau fibrillization observed macroscopically in Alzheimer's disease (AD) lesions and the pathway of tau aggregation observed in vitro with purified tau preparations. In addition, pharmacological agents for further dissection of fibrillization mechanism and lesion formation are discussed. PMID:15615636

  11. Biomimetic silicification of demineralized hierarchical collagenous tissues

    PubMed Central

    Ryou, Heonjune; Diogenes, Anibal; Yiu, Cynthia K.Y.; Mazzoni, Annalisa; Chen, Ji-hua; Arola, Dwayne D.; Hargreaves, Kenneth M.; Pashley, David H.; Tay, Franklin R.

    2013-01-01

    Unlike man-made composite materials, natural biominerals containing composites usually demonstrate different levels of sophisticated hierarchical structures which are responsible for their mechanical properties and other metabolic functions. However, the complex spatial organizations of the organic-inorganic phases are far beyond what they be achieved by contemporary engineering techniques. Here, we demonstrate that carbonated apatite present in collagen matrices derived from fish scale and bovine bone may be replaced by amorphous silica, using an approach that simulates what is utilized by phylogenetically ancient glass sponges. The structural hierarchy of these collagen-based biomaterials is replicated by the infiltration and condensation of fluidic polymer-stabilized silicic acid precursors within the intrafibrillar milieu of type I collagen fibrils. This facile biomimetic silicification strategy may be used for fabricating silica-based, three-dimensional functional materials with specific morphological and hierarchical requirements. PMID:23586938

  12. Individual and Combined Risk Factors for Incident Atrial Fibrillation and Incident Stroke: An Analysis of 3 Million At-Risk US Patients

    PubMed Central

    Chyou, Janice Y; Hunter, Tina D; Mollenkopf, Sarah A; Turakhia, Mintu P; Reynolds, Matthew R

    2015-01-01

    Background The incremental effects of risk factor combinations for atrial fibrillation (AF) and stroke are incompletely understood. We sought to quantify the risks of incident AF and stroke for combinations of established risk factors in a large US sample. Methods and Results Patients with no evidence of AF or stroke in 2007 were stratified by combinations of the following risk factors: heart failure, hypertension, diabetes, age 65 to 74, age ≥75, coronary artery disease, and chronic kidney disease. Patients with ≥2 of the first 5 or ≥3 of the first 7, classified as “high-risk,” and an age-matched sample of patients with fewer risk factors, classified as “low-risk,” were followed over 2008–2010 for incident AF and stroke. Annualized incidence rates and risks were quantified for each combination of factors by using Cox regression. Annualized incidence rates for AF, stroke, and both were 3.59%, 3.27%, and 0.62% in 1 851 653 high-risk patients and 1.32%, 1.48%, and 0.18% in 1 156 221 low-risk patients, respectively. Among patients with 1 risk factor, those with age ≥75 had the highest hazards of incident AF and stroke (HR 9.2, 6.9). Among patients with 2 risk factors, those with age ≥75 and heart failure had the highest annualized incidence rates of AF and stroke (10.2%, 5.9%). The combination of age ≥75 and hypertension was prevalent and had the highest incidences of AF and stroke. Conclusions Adults with combinations of known risk factors are at increased risk of incident AF and stroke, but combinations of risk factors are not always additive. PMID:26206736

  13. Post-translational control of collagen fibrillogenesis in mineralizing cultures of chick osteoblasts

    NASA Technical Reports Server (NTRS)

    Gerstenfeld, L. C.; Riva, A.; Hodgens, K.; Eyre, D. R.; Landis, W. J.

    1993-01-01

    Cultured osteoblasts from chick embryo calvaria were used as a model system to investigate the post-translational extracellular mechanisms controlling the macroassembly of collagen fibrils. The results of these studies demonstrated that cultured osteoblasts secreted a collagenous extracellular matrix that assembled and mineralized in a defined temporal and spatial sequence. The assembly of collagen occurred in a polarized fashion, such that successive orthogonal arrays of fibrils formed between successive cell layers proceeding from the culture surface toward the media. Mineralization followed in the same manner, being observed first in the deepest and oldest fibril layers. Collagen fibrillogenesis, the kinetics of cross-link formation, and collagen stability in the extracellular matrix of the cultures were examined over a 30 day culture period. Between days 8 and 12 in culture, collagen fibril diameters increased from < 30 nm to an average of 30-45 nm. Thereafter, diameters ranged in size from 20 to 200 nm. Quantitation of the collagen cross-linking residues, hydroxylysyl pyridinoline (HP) and lysyl pyridinoline (LP), showed that these mature cross-links increased from undetectable levels to concentrations found in normal chick bone. Analysis of the kinetics of their formation by pulse-chase labeling the cultures with [3H]lysine showed a doubling time of approximately 5 days. The relationships between cross-link formation, fibrillogenesis, and collagen stability were examined in cultures treated with beta-aminopropionitrile (beta-APN), a potent inhibitor of lysyl oxidase and cross-link formation. In beta-APN-treated cultures, total collagen synthesis was increased twofold, with no change in mRNA levels for type I collagen, whereas the amount of collagen accumulated in the cell layer was decreased by 50% and mineral deposition was reduced. The rate of collagen retention in the matrix was assessed by pulse-chase analysis of [3H]proline over a 16 day period in

  14. Quantitative Raman characterization of cross-linked collagen thin films as a model system for diagnosing early osteoarthritis

    NASA Astrophysics Data System (ADS)

    Wang, Chao; Durney, Krista M.; Fomovsky, Gregory; Ateshian, Gerard A.; Vukelic, Sinisa

    2016-03-01

    The onset of osteoarthritis (OA)in articular cartilage is characterized by degradation of extracellular matrix (ECM). Specifically, breakage of cross-links between collagen fibrils in the articular cartilage leads to loss of structural integrity of the bulk tissue. Since there are no broadly accepted, non-invasive, label-free tools for diagnosing OA at its early stage, Raman spectroscopyis therefore proposed in this work as a novel, non-destructive diagnostic tool. In this study, collagen thin films were employed to act as a simplified model system of the cartilage collagen extracellular matrix. Cross-link formation was controlled via exposure to glutaraldehyde (GA), by varying exposure time and concentration levels, and Raman spectral information was collected to quantitatively characterize the cross-link assignments imparted to the collagen thin films during treatment. A novel, quantitative method was developed to analyze the Raman signal obtained from collagen thin films. Segments of Raman signal were decomposed and modeled as the sum of individual bands, providing an optimization function for subsequent curve fitting against experimental findings. Relative changes in the concentration of the GA-induced pyridinium cross-links were extracted from the model, as a function of the exposure to GA. Spatially resolved characterization enabled construction of spectral maps of the collagen thin films, which provided detailed information about the variation of cross-link formation at various locations on the specimen. Results showed that Raman spectral data correlate with glutaraldehyde treatment and therefore may be used as a proxy by which to measure loss of collagen cross-links in vivo. This study proposes a promising system of identifying onset of OA and may enable early intervention treatments that may serve to slow or prevent osteoarthritis progression.

  15. Nanostructure and mechanics of mummified type I collagen from the 5300-year-old Tyrolean Iceman

    PubMed Central

    Janko, Marek; Zink, Albert; Gigler, Alexander M.; Heckl, Wolfgang M.; Stark, Robert W.

    2010-01-01

    Skin protects the body from pathogens and degradation. Mummified skin in particular is extremely resistant to decomposition. External influences or the action of micro-organisms, however, can degrade the connective tissue and lay the subjacent tissue open. To determine the degree of tissue preservation in mummified human skin and, in particular, the reason for its durability, we investigated the structural integrity of its main protein, type I collagen. We extracted samples from the Neolithic glacier mummy known as ‘the Iceman’. Atomic force microscopy (AFM) revealed collagen fibrils that had characteristic banding patterns of 69 ± 5 nm periodicity. Both the microstructure and the ultrastructure of dermal collagen bundles and fibrils were largely unaltered and extremely well preserved by the natural conservation process. Raman spectra of the ancient collagen indicated that there were no significant modifications in the molecular structure. However, AFM nanoindentation measurements showed slight changes in the mechanical behaviour of the fibrils. Young's modulus of single mummified fibrils was 4.1 ± 1.1 GPa, whereas the elasticity of recent collagen averages 3.2 ± 1.0 GPa. The excellent preservation of the collagen indicates that dehydration owing to freeze-drying of the collagen is the main process in mummification and that the influence of the degradation processes can be addressed, even after 5300 years. PMID:20356896

  16. Thermal Destabilization of Collagen Matrix Hierarchical Structure by Freeze/Thaw

    PubMed Central

    Ozcelikkale, Altug; Han, Bumsoo

    2016-01-01

    This study aims to characterize and understand the effects of freezing on collagen structures and functionality. Specifically, thermodynamic destabilization of collagen at molecular- and fibril-levels by combination of low temperatures and freezing were experimentally characterized using modulated differential scanning calorimetry. In order to delineate the effects of sub-zero temperature and water-ice phase change, we hypothesized that the extent of destabilization can be determined based on post-thaw heat induced thermal denaturation of collagen. It is found that thermal denaturation temperature of collagen in hydrogel decreases by 1.4–1.6°C after freeze/thaw while no such decrease is observed in the case of molecular solution. The destabilization is predominantly due to ice formation. Exposure to low temperatures in the absence of ice has only minimal effect. Calorimetry measurements combined with morphological examination of collagen matrices by scanning electron microscopy suggest that freezing results in destabilization of collagen fibrils due to expansion of intrafibrillar space by ice formation. This fibril-level damage can be alleviated by use of cryoprotectant DMSO at concentrations as low as 0.5 M. A theoretical model explaining the change in collagen post-thaw thermal stability by freezing-induced fibril expansion is also proposed. PMID:26765741

  17. Collagen type IX from human cartilage: a structural profile of intermolecular cross-linking sites.

    PubMed Central

    Diab, M; Wu, J J; Eyre, D R

    1996-01-01

    Type IX collagen, a quantitatively minor collagenous component of cartilage, is known to be associated with and covalently cross-linked to type II collagen fibrils in chick and bovine cartilage. Type IX collagen molecules have also been shown to form covalent cross-links with each other in bovine cartilage. In the present study we demonstrate by structural analysis and location of cross-linking sites that, in human cartilage, type IX collagen is covalently cross-linked to type II collagen and to other molecules of type IX collagen. We also present evidence that, if the proteoglycan form of type IX collagen is present in human cartilage, it can only be a minor component of the matrix, similar to findings with bovine cartilage. PMID:8660302

  18. In vitro phagocytosis of exogenous collagen by fibroblasts from the periodontal ligament: an electron microscopic study.

    PubMed Central

    Svoboda, E L; Brunette, D M; Melcher, A H

    1979-01-01

    There have been numerous electron microscopic reports of apparent phagocytosis of collagen by fibroblasts and other cells in vivo. We have developed an in vitro system which, to the best of our knowledge, will permit for the first time the study of regulatory mechanisms governing phagocytosis and digestion of collagen fibres. Cells were cultured from explants of monkey periodontal ligament, subcultured, and grown to confluence in alpha-MEM plus 15% fetal calf serum plus antibiotics. The confluent cells were then cultured together with minced rat tail tendon collagen in alpha-MEM lacking proline, lysine, glycine and fetal calf serum for up to 7 days, after which they were processed for electron microscopy. Intracellular collagen profiles could be seen in cultured cells that were associated with exogenous collagen fibrils as early as 24 hours after addition of the collagen. Through electron microscopic examination of serial sections of the culture, we have demonstrated: (1) that fibroblasts can phagocytose collagen; (2) that the observed intracellular collagen is not the result of aggregation of endogenous synthesized collagen; (3) that it is not possible to base a decision as to whether a collagen fibril has been phagocytosed in whole or in part by the type of vesicle with which it is associated; (4) that cleavage of collagen into small pieces may not be a necessary prelude to its phagocytosis. Images Fig. 1 Fig. 2 Fig. 4 (cont.) Fig. 4 Fig. 6 (cont.) Fig. 6 Fig. 7 Fig. 8 Fig. 9 PMID:108237

  19. Controlling collagen fiber microstructure in three-dimensional hydrogels using ultrasound

    PubMed Central

    Garvin, Kelley A.; VanderBurgh, Jacob; Hocking, Denise C.; Dalecki, Diane

    2013-01-01

    Type I collagen is the primary fibrillar component of the extracellular matrix, and functional properties of collagen arise from variations in fiber structure. This study investigated the ability of ultrasound to control collagen microstructure during hydrogel fabrication. Under appropriate conditions, ultrasound exposure of type I collagen during polymerization altered fiber microstructure. Scanning electron microscopy and second-harmonic generation microscopy revealed decreased collagen fiber diameters in response to ultrasound compared to sham-exposed samples. Results of mechanistic investigations were consistent with a thermal mechanism for the effects of ultrasound on collagen fiber structure. To control collagen microstructure site-specifically, a high frequency, 8.3-MHz, ultrasound beam was directed within the center of a large collagen sample producing dense networks of short, thin collagen fibrils within the central core of the gel and longer, thicker fibers outside the beam area. Fibroblasts seeded onto these gels migrated rapidly into small, circularly arranged aggregates only within the beam area, and clustered fibroblasts remodeled the central, ultrasound-exposed collagen fibrils into dense sheets. These investigations demonstrate the capability of ultrasound to spatially pattern various collagen microstructures within an engineered tissue noninvasively, thus enhancing the level of complexity of extracellular matrix microenvironments and cellular functions achievable within three-dimensional engineered tissues. PMID:23927189

  20. Expression of type I and type V collagen mRNAs in the elasmoid scales of a teleost fish as revealed by in situ hybridization.

    PubMed

    Le Guellec, D; Zylberberg, L

    1998-01-01

    The ability of scale-forming cells to produce both type I and type V collagens was investigated by in situ hybridization at the light and electron microscope levels. Biochemical analyses reported that type I collagen, the predominant component, was associated with the minor type V collagen in the collagenous matrix of the teleost scales where, thin and thick collagen fibrils formed distinct layers. Thin collagen fibrils of the external layer were produced by the episquamal scleroblasts scattered on the outer scale surface, while thick collagen fibrils forming the compact basal plate were produced by the hyposquamal scleroblasts lining the inner surface of the scale. We demonstrated that episquamal and hyposquamal scleroblasts contained mRNAs for alpha1(I) and alpha1(V) collagens. Quantification by image analysis of the relative amount of alpha1(I) and alpha1(V) mRNAs in episquamal and hyposquamal scleroblasts suggests that the gene expression of type V collagen was proportionally higher in episquamal scleroblasts. These results support our hypothesis that the diameter of the thin fibrils of the external layer is regulated by the significant amount of type V collagen that interacts with type I collagen. PMID:11063006

  1. Type V Collagen in Health, Disease, and Fibrosis.

    PubMed

    Mak, Ki M; Png, Chien Yi M; Lee, Danielle J

    2016-05-01

    Type V collagen (COLV) is a regulatory fibril-forming collagen. It has at least three different molecular isoforms-α1(V)2 α2(V), α1(V)3, and α1(V)α2(V)α3(V)-formed by combinations of three different polypeptide α chains-α1(V), α2(V), and α3(V). COL V is a relatively minor collagen of the extracellular matrix (ECM). Morphologically, COLV occurs as heterotypic fibrils with type I collagen (COLI), microfilaments, or 12-nm-thick fibrils. COLV is synthesized in various mesenchymal cells and its gene expression is modulated by TGF-β and growth factors. While resistant to digestion by interstitial collagenases, native and denatured COLV are degraded by metalloproteinases and gelatinases, thereby promoting ECM remodeling. COLV interacts with matrix collagens and structural proteins, conferring structural integrity to tissue scaffolds. It binds matrix macromolecules, modulating cellular behavior, and functions. COLV co-assembles with COLI into heterotypic fibrils in the cornea and skin dermis, acting as a dominant regulator of collagen fibrillogenesis. COLV deficiency is associated with loss of corneal transparency and classic Ehlers-Danlos syndrome, while COLV overexpression is found in cancer, granulation tissue, inflammation, atherosclerosis, and fibrosis of lungs, skin, kidneys, adipose tissue, and liver. COLV isoform containing the α3(V) chain is involved in mediating pancreatic islet cell functions. In the liver, COLV is a minor but regular component of the ECM. Increases in COLV are associated with both early and advanced hepatic fibrosis. The neoepitopes of COLV have been shown to be a useful noninvasive serum biomarker for assessing fibrotic progression and resolution in experimental hepatic fibrosis. COLV is multifunctional in health, disease, and fibrosis. PMID:26910848

  2. Sodium hypochlorite alterations of dentin and dentin collagen

    NASA Astrophysics Data System (ADS)

    Marshall, G. W.; Yücel, N.; Balooch, M.; Kinney, J. H.; Habelitz, S.; Marshall, S. J.

    2001-10-01

    NaOCl aq is used as a cleansing and non-specific deproteinizing agent in endodontic treatment, as a component of new chemomechanical caries treatment, and is under study for its alterations of dentin bonding characteristics. We sought to determine the microstructural and nanomechanical changes with such treatments and to test if NaOCl aq removed dentin collagen without microstructural or nanomechanical alteration of underlying mineralized dentin. Polished human dentin disks were prepared with a double reference technique that allowed changes to be determined following 10% citric acid etching for 15 s and subsequent treatment of the etched and unetched portions of the sample with 6.5% NaOCl aq, using atomic force microscopy (AFM) (Nanoscope III, Digital Instruments, Santa Barbara, CA). Images and measurements were made at intervals up to 1800 s. A Triboscope (Hysitron, Minneapolis, MN) on the AFM was used to measure nanohardness and the reduced elastic modulus. The double reference method allowed measurements immediately following etching and at intervals during deproteinization. Etching caused deep peritubular dentin removal and a small depth change of hydrated intertubular dentin as mineral was removed and left a remnant collagen matrix. NaOCl aq removed collagen over time, during which individual fibrils could be resolved; the underlying mineralized dentin was left with a unique porous surface containing numerous channels that are not normally observed in etched or fractured dentin. This could provide an attractive bonding substrate because of the increased surface area and high mineral content, if toughness is not reduced too much. Nanomechanical measurements showed that the reduced elastic modulus and hardness were 75% of original values after removal of the exposed collagen. Current dentin bonding systems rely on hybrid layer formation in which hydrophilic primers/polymers penetrate the opened collagen matrix exposed by etching. However some research suggests

  3. Atrial fibrillation ablation.

    PubMed

    Pappone, Carlo; Santinelli, Vincenzo

    2012-06-01

    Atrial fibrillation is the commonest cardiac arrhythmia, with significant morbidity related to symptoms, heart failure, and thromboembolism, which is associated with excess mortality. Over the past 10 years, many centers worldwide have reported high success rates and few complications after a single ablation procedure in patients with paroxysmal atrial fibrillation. Recent studies indicate a short-term and long-term superiority of catheter ablation as compared with conventional antiarrhythmic drug therapy in terms of arrhythmia recurrence, quality of life, and arrhythmia progression. As a result, catheter ablation is evolving to a front-line therapy in many patients with atrial fibrillation. However, in patients with persistent long-standing atrial fibrillation catheter ablation strategy is more complex and time-consuming, frequently requiring repeat procedures to achieve success rates as high as in paroxysmal atrial fibrillation. In the near future, however, with growing experience and evolving technology, catheter ablation of atrial fibrillation may be extended also to patients with long-standing atrial fibrillation. PMID:22541284

  4. Mutations in the collagen XII gene define a new form of extracellular matrix-related myopathy.

    PubMed

    Hicks, Debbie; Farsani, Golara Torabi; Laval, Steven; Collins, James; Sarkozy, Anna; Martoni, Elena; Shah, Ashoke; Zou, Yaqun; Koch, Manuel; Bönnemann, Carsten G; Roberts, Mark; Lochmüller, Hanns; Bushby, Kate; Straub, Volker

    2014-05-01

    Bethlem myopathy (BM) [MIM 158810] is a slowly progressive muscle disease characterized by contractures and proximal weakness, which can be caused by mutations in one of the collagen VI genes (COL6A1, COL6A2 and COL6A3). However, there may be additional causal genes to identify as in ∼50% of BM cases no mutations in the COL6 genes are identified. In a cohort of -24 patients with a BM-like phenotype, we first sequenced 12 candidate genes based on their function, including genes for known binding partners of collagen VI, and those enzymes involved in its correct post-translational modification, assembly and secretion. Proceeding to whole-exome sequencing (WES), we identified mutations in the COL12A1 gene, a member of the FACIT collagens (fibril-associated collagens with interrupted triple helices) in five individuals from two families. Both families showed dominant inheritance with a clinical phenotype resembling classical BM. Family 1 had a single-base substitution that led to the replacement of one glycine residue in the triple-helical domain, breaking the Gly-X-Y repeating pattern, and Family 2 had a missense mutation, which created a mutant protein with an unpaired cysteine residue. Abnormality at the protein level was confirmed in both families by the intracellular retention of collagen XII in patient dermal fibroblasts. The mutation in Family 2 leads to the up-regulation of genes associated with the unfolded protein response (UPR) pathway and swollen, dysmorphic rough-ER. We conclude that the spectrum of causative genes in extracellular matrix (ECM)-related myopathies be extended to include COL12A1. PMID:24334769

  5. Intrinsic Structural Heterogeneity and Long-Term Maturation of Amyloid β Peptide Fibrils

    PubMed Central

    2013-01-01

    Amyloid β peptides form fibrils that are commonly assumed to have a dry, homogeneous, and static internal structure. To examine these assumptions, fibrils under various conditions and different ages have been examined with multidimensional infrared spectroscopy. Each peptide in the fibril had a 13C=18O label in the backbone of one residue to disinguish the amide I′ absorption due to that residue from the amide I′ absorption of other residues. Fibrils examined soon after they formed, and reexamined after 1 year in the dry state, exhibited spectral changes confirming that structurally significant water molecules were present in the freshly formed fibrils. Results from fibrils incubated in solution for 4 years indicate that water molecules remained trapped within fibrils and mobile over the 4 year time span. These water molecules are structurally significant because they perturb the parallel β-sheet hydrogen bonding pattern at frequent intervals and at multiple points within individual fibrils, creating structural heterogeneity along the length of a fibril. These results show that the interface between β-sheets in an amyloid fibril is not a “dry zipper”, and that the internal structure of a fibril evolves while it remains in a fibrillar state. These features, water trapping, structural heterogeneity, and structural evolution within a fibril over time, must be accommodated in models of amyloid fibril structure and formation. PMID:23701594

  6. Development of collagen-hydroxyapatite nanostructured composites via a calcium phosphate precursor mechanism

    NASA Astrophysics Data System (ADS)

    Jee, Sang Soo

    Bone is an interpenetrating inorganic/organic composite that consists of mineralized collagen fibrils, which is hierarchically organized into various structures. The structure of mineralized collagen fibril, in which nano-crystals of hydroxyapatite are embedded within the collagen fibrils, provides remarkable mechanical and bio-resorptive properties. Therefore, there have been many attempts to produce collagen-hydroxyapatite composites having a bone-like structure. However, duplication of even the most fundamental level of bone structure has not been easily achieved by conventional nucleation and growth techniques, which are based on the most widely accepted hypothesis of bone mineralization. In nature, the collagen fibril is mineralized via intrafibrillar mineralization, which produces preferentially oriented hydroxyapatite nano-crystals occupying the interstices in collagen fibrils. Our group has demonstrated that intrafibrillar mineralization can be achieved by using a new method based on the Polymer-Induced Liquid-Precursor (PILP) mineralization process. In the PILP process, a poly-anionic additive can produce an amorphous calcium phosphate precursor which enables us to achieve intrafibrillar mineralization of collagen. It is thought that the precursor is pulled into the interstices of the collagen fibrils via capillary forces, and upon solidification and crystallization of the precursor produces an interpenetrating composite with the nanostructured architecture of bone. In this dissertation, to demonstrate the effectiveness of the PILP process on the intrafibrillar mineralization of collagen fibril, various collagen scaffolds, such as turkey tendon, bovine tendon and synthetic collagen sponge, were mineralized by the PILP process. Various poly-aspartates with different molecular weight were also used for the optimization of the PILP process for the mineralization of the collagen scaffolds. With the systematic researches, we discovered that the molecular weight

  7. Cell Alignment Driven by Mechanically Induced Collagen Fiber Alignment in Collagen/Alginate Coatings.

    PubMed

    Chaubaroux, Christophe; Perrin-Schmitt, Fabienne; Senger, Bernard; Vidal, Loïc; Voegel, Jean-Claude; Schaaf, Pierre; Haikel, Youssef; Boulmedais, Fouzia; Lavalle, Philippe; Hemmerlé, Joseph

    2015-09-01

    For many years it has been a major challenge to regenerate damaged tissues using synthetic or natural materials. To favor the healing processes after tendon, cornea, muscle, or brain injuries, aligned collagen-based architectures are of utmost interest. In this study, we define a novel aligned coating based on a collagen/alginate (COL/ALG) multilayer film. The coating exhibiting a nanofibrillar structure is cross-linked with genipin for stability in physiological conditions. By stretching COL/ALG-coated polydimethylsiloxane substrates, we developed a versatile method to align the collagen fibrils of the polymeric coating. Assays on cell morphology and alignment were performed to investigate the properties of these films. Microscopic assessments revealed that cells align with the stretched collagen fibrils of the coating. The degree of alignment is tuned by the stretching rate (i.e., the strain) of the COL/ALG-coated elastic substrate. Such coatings are of great interest for strategies that require aligned nanofibrillar biological material as a substrate for tissue engineering. PMID:25658028

  8. A mathematical model of collagen lattice contraction

    PubMed Central

    Dallon, J. C.; Evans, E. J.; Ehrlich, H. Paul

    2014-01-01

    Two mathematical models for fibroblast–collagen interaction are proposed which reproduce qualitative features of fibroblast-populated collagen lattice contraction. Both models are force based and model the cells as individual entities with discrete attachment sites; however, the collagen lattice is modelled differently in each model. In the collagen lattice model, the lattice is more interconnected and formed by triangulating nodes to form the fibrous structure. In the collagen fibre model, the nodes are not triangulated, are less interconnected, and the collagen fibres are modelled as a string of nodes. Both models suggest that the overall increase in stress of the lattice as it contracts is not the cause of the reduced rate of contraction, but that the reduced rate of contraction is due to inactivation of the fibroblasts. PMID:25142520

  9. Fibroblast cluster formation on 3D collagen matrices requires cell contraction dependent fibronectin matrix organization.

    PubMed

    da Rocha-Azevedo, Bruno; Ho, Chin-Han; Grinnell, Frederick

    2013-02-15

    Fibroblasts incubated on 3D collagen matrices in serum or lysophosphatidic acid (LPA)-containing medium self-organize into clusters through a mechanism that requires cell contraction. However, in platelet-derived growth factor (PDGF)-containing medium, cells migrate as individuals and do not form clusters even though they constantly encounter each other. Here, we present evidence that a required function of cell contraction in clustering is formation of fibronectin (FN) fibrillar matrix. We found that in serum or LPA but not in PDGF or basal medium, cells organized FN (both serum and cellular) into a fibrillar, detergent-insoluble matrix. Cell clusters developed concomitant with FN matrix formation. FN fibrils accumulated beneath cells and along the borders of cell clusters in regions of cell-matrix tension. Blocking Rho kinase or myosin II activity prevented FN matrix assembly and cell clustering. Using siRNA silencing and function-blocking antibodies and peptides, we found that cell clustering and FN matrix assembly required α5β1 integrins and fibronectin. Cells were still able to exert contractile force and compact the collagen matrix under the latter conditions, which showed that contraction was not sufficient for cell clustering to occur. Our findings provide new insights into how procontractile (serum/LPA) and promigratory (PDGF) growth factor environments can differentially regulate FN matrix assembly by fibroblasts interacting with collagen matrices and thereby influence mesenchymal cell morphogenetic behavior under physiologic circumstances such as wound repair, morphogenesis and malignancy. PMID:23117111

  10. Probing electromechanical coupling in collagen at the nanoscale via scanning probe microscopy

    NASA Astrophysics Data System (ADS)

    Denning, Denise

    Electromechanical coupling is ubiquitous in nature and is a functional characteristic in a large range of inorganic and organic materials, including collagen type I -- a fibrous protein abundant in mammals. Understanding the biofunctionality of electromechanical coupling in its linear form -- piezoelectricity, has been a topic of research spanning over seven decades and yet many questions still remain unanswered. Piezoelectricity in bone and connective tissues such as tendon has been investigated at the macroscopic scale since the discovery of piezoelectricity in bone in 1957 and induced currents via the piezoelectric effect have been shown to activate the healing process in tissues under tension. Biological systems consist of complex hierarchical structures which results from a high degree of organization from the macroscale down to the nanoscale. These complex structures, however, make quantitative piezoelectric measurements difficult. Therefore, there exists a need to understand these processes at the individual protein level -- i.e. at the nanoscale. In this thesis, a voltage-modulated form of atomic force microscopy called piezoresponse force microscopy is utilized to investigate the counterpart which is responsible for piezoelectricity in bone and connective tissues -- collagen. The polar properties of collagen were revealed at the nanoscale and were shown to result in a highly complex polar architecture in natural tissue, which is important for understanding tissue development. Shear piezoelectricity was discovered to persist in engineered collagen hydrogels, a study intended to highlight the importance of replicating both structural and functional properties in replacement tissues. The electromechanical properties of collagen type II were investigated which were previously unknown. Collagen type II was shown to be a shear piezoelectric, exhibiting an angle dependence of the piezoelectric signal with cantilever-fibril angle. In addition, the piezoelectric

  11. Kinetics of protein fibrillation controlled by fibril elongation.

    PubMed

    Kashchiev, Dimo

    2014-09-01

    Numerous proteins have the ability to assemble into fibrillar aggregates which are of great interest, because they feature in scores of human diseases and many technological products. In the present work, we analyze the kinetics of protein fibrillation when the process is governed solely by elongation of initially appeared fibrils in the protein solution. We derive exact expressions for the time dependences of the fibrillation degree, the concentration of monomeric protein in the solution, and the average fibril size. Furthermore, we present formulas for the initial fibrillation rate and the half-fibrillation time in terms of experimentally controllable quantities. The results obtained provide a mechanistic insight into the kinetics of protein fibrillation mediated by fibril elongation. We confront theory with experiment and find that it allows a good description of available experimental data for fibrillation of the Alzheimer's disease-associated protein Aβ(1-40) and the yeast prion protein Sup35. PMID:24753319

  12. Three dimensional patient-specific collagen architecture modulates cartilage responses in the knee joint during gait.

    PubMed

    Räsänen, Lasse P; Mononen, Mika E; Lammentausta, Eveliina; Nieminen, Miika T; Jurvelin, Jukka S; Korhonen, Rami K

    2016-08-01

    Site-specific variation of collagen fibril orientations can affect cartilage stresses in knee joints. However, this has not been confirmed by 3-D analyses. Therefore, we present a novel method for evaluation of the effect of patient-specific collagen architecture on time-dependent mechanical responses of knee joint cartilage during gait. 3-D finite element (FE) models of a human knee joint were created with the collagen architectures obtained from T2 mapped MRI (patient-specific model) and from literature (literature model). The effect of accuracy of the implementation of collagen fibril architecture into the model was examined by using a submodel with denser FE mesh. Compared to the literature model, fibril strains and maximum principal stresses were reduced especially in the superficial/middle regions of medial tibial cartilage in the patient-specific model after the loading response of gait (up to -413 and -26%, respectively). Compared to the more coarsely meshed joint model, the patient-specific submodel demonstrated similar strain and stress distributions but increased values particularly in the superficial cartilage regions (especially stresses increased >60%). The results demonstrate that implementation of subject-specific collagen architecture of cartilage in 3-D modulates location- and time-dependent mechanical responses of human knee joint cartilage. Submodeling with more accurate implementation of collagen fibril architecture alters cartilage stresses particularly in the superficial/middle tissue. PMID:26714834

  13. What Is Atrial Fibrillation?

    MedlinePlus

    ... regular beat. Certain cells in your heart make electric signals that cause the heart to contract and ... read your ECG to find out if the electric signals are normal. In atrial fibrillation (AFib), the ...

  14. Structural response of human corneal and scleral tissues to collagen cross-linking treatment with riboflavin and ultraviolet A light.

    PubMed

    Choi, Samjin; Lee, Seung-Chan; Lee, Hui-Jae; Cheong, Youjin; Jung, Gyeong-Bok; Jin, Kyung-Hyun; Park, Hun-Kuk

    2013-09-01

    High success rates in clinical trials on keratoconic corneas suggest the possibility of efficient treatment against myopic progression. This study quantitatively investigated the in vitro ultrastructural effects of a photooxidative collagen cross-linking treatment with photosensitizer riboflavin and UVA light in human corneo-scleral collagen fibrils. A total of 30.8 × 2 mm corneo-scleral strips from donor tissue were sagittally dissected using a scalpel. The five analytic parameters namely fibril density, fibril area, corneo-scleral thickness, fibril diameter, and fibril arrangement were investigated before and after riboflavin-UVA-catalyzed collagen cross-linking treatment. Collagen cross-linking effects were measured at the corneo-scleral stroma and were based on clinical corneal cross-linking procedures. The structural response levels were assessed by histology, digital mechanical caliper measurement, scanning electron microscopy, and atomic force microscopy. Riboflavin-UVA-catalyzed collagen cross-linking treatment led to an increase in the area, density, and diameters of both corneal (110, 112, and 103 %) and scleral (133, 133, and 127 %) stromal collagens. It also led to increases in corneal (107 %) and scleral (105 %) thickness. Collagen cross-linking treatment through riboflavin-sensitized photoreaction may cause structural property changes in the collagen fibril network of the cornea and sclera due to stromal edema and interfibrillar spacing narrowing. These changes were particularly prominent in the sclera. This technique can be used to treat progressive keratoconus in the cornea as well as progressive myopia in the sclera. Long-term collagen cross-linking treatment of keratoconic and myopic progression dramatically improves weakened corneo-scleral tissues. PMID:23179311

  15. Measurement of Elastic Modulus of Collagen Type I Single Fiber.

    PubMed

    Dutov, Pavel; Antipova, Olga; Varma, Sameer; Orgel, Joseph P R O; Schieber, Jay D

    2016-01-01

    Collagen fibers are the main components of the extra cellular matrix and the primary contributors to the mechanical properties of tissues. Here we report a novel approach to measure the longitudinal component of the elastic moduli of biological fibers under conditions close to those found in vivo and apply it to type I collagen from rat tail tendon. This approach combines optical tweezers, atomic force microscopy, and exploits Euler-Bernoulli elasticity theory for data analysis. This approach also avoids drying for measurements or visualization, since samples are freshly extracted. Importantly, strains are kept below 0.5%, which appear consistent with the linear elastic regime. We find, surprisingly, that the longitudinal elastic modulus of type I collagen cannot be represented by a single quantity but rather is a distribution that is broader than the uncertainty of our experimental technique. The longitudinal component of the single-fiber elastic modulus is between 100 MPa and 360 MPa for samples extracted from different rats and/or different parts of a single tail. Variations are also observed in the fibril-bundle/fibril diameter with an average of 325±40 nm. Since bending forces depend on the diameter to the fourth power, this variation in diameter is important for estimating the range of elastic moduli. The remaining variations in the modulus may be due to differences in composition of the fibril-bundles, or the extent of the proteoglycans constituting fibril-bundles, or that some single fibrils may be of fibril-bundle size. PMID:26800120

  16. Measurement of Elastic Modulus of Collagen Type I Single Fiber

    PubMed Central

    Dutov, Pavel; Antipova, Olga; Varma, Sameer; Orgel, Joseph P. R. O.; Schieber, Jay D.

    2016-01-01

    Collagen fibers are the main components of the extra cellular matrix and the primary contributors to the mechanical properties of tissues. Here we report a novel approach to measure the longitudinal component of the elastic moduli of biological fibers under conditions close to those found in vivo and apply it to type I collagen from rat tail tendon. This approach combines optical tweezers, atomic force microscopy, and exploits Euler-Bernoulli elasticity theory for data analysis. This approach also avoids drying for measurements or visualization, since samples are freshly extracted. Importantly, strains are kept below 0.5%, which appear consistent with the linear elastic regime. We find, surprisingly, that the longitudinal elastic modulus of type I collagen cannot be represented by a single quantity but rather is a distribution that is broader than the uncertainty of our experimental technique. The longitudinal component of the single-fiber elastic modulus is between 100 MPa and 360 MPa for samples extracted from different rats and/or different parts of a single tail. Variations are also observed in the fibril-bundle / fibril diameter with an average of 325±40 nm. Since bending forces depend on the diameter to the fourth power, this variation in diameter is important for estimating the range of elastic moduli. The remaining variations in the modulus may be due to differences in composition of the fibril-bundles, or the extent of the proteoglycans constituting fibril-bundles, or that some single fibrils may be of fibril-bundle size. PMID:26800120

  17. Effect of alcohols and neutral salt on the thermal stability of soluble and precipitated acid-soluble collagen

    PubMed Central

    Russell, Allan E.

    1973-01-01

    The effects of mono- and poly-hydric alcohols in the presence of KCl on the intrinsic stability of collagen molecules in dilute acid solution were compared with corresponding solvent and salt effects on the increased stability of the aggregated molecules in salt-precipitated fibrils. Salt addition decreased solubility and increased the thermal stability of fibrils, but progressively decreased the stability of collagen molecules in solution. In contrast, the alcohols enhanced solubility and decreased fibril stability, the effects increasing with solvent hydrocarbon chain length and with decreasing hydroxyl/methylene-group ratio. Molar destabilization of dissolved collagen by alcohols was lower than for fibrils, and at low salt concentration, both ethylene glycol and glycerol were structural stabilizers. Electron-micrograph studies indicated that salt-precipitated fibrils tended to adopt the native aggregation mode, and qualitatively similar solvent effects were observed in insoluble collagens. Implications of the experimental findings are discussed in terms of a model in which electrostatic and apolar interactions mainly govern the excess of stability in collagen fibrils whereas intrinsic stability of single molecules is a function of polar interactions and polypeptide-chain rigidity. PMID:4737319

  18. Collagen Cross-linking Increases Its Biodegradation Resistance in Wet Dentin Bonding

    PubMed Central

    Xu, Changqi; Wang, Yong

    2014-01-01

    Purpose The biodegradation of exposed dentin collagen within the adhesive/dentin (a/d) interface is one of main reasons leading to composite restoration failures and seriously affects the durability of dental restorations. In the present study, the objective was to investigate whether the inclusion of the crosslinking reagent (glutaraldehyde, GA) in the adhesive would increase collagen biodegradation resistance within the a/d interface. Materials and methods The model adhesive consisted of ~60 % monomers (HEMA/BisGMA, 45/55 wt/wt) and ~ 40 % ethanol as a solvent. 5% GA was added to the above formulation. After the dentin surfaces were etched for 15 s with 35% phosphoric acid, rinsed with water and blotted dry, adhesives both with and without GA were applied and polymerized by visible light for 20 s. These a/d specimens were immersed in the biodegradation solution (prepared by adding 160 mg collagenase in 1 liter of TESCA buffer solution) for up to 30 days after proceeding with the sectioning/fracture to expose the a/d interfaces. The specimens were analyzed using SEM and micro-Raman. Results SEM results indicated that for the adhesive without GA, there were many voids and was a loss of collagen fibrils in the a/d interface after being challenged by the biodegradation solution. The Raman spectra collected from the interface showed that the amide I of collagen at 1667 cm−1 obviously decreased, indicating a removal of collagen fibrils during the degradation process. For the adhesive containing GA, the collagen fibrils within the interface did not degrade at all, which was also confirmed by the Raman results. Conclusion The results corroborate the previous findings that by using the current adhesive system and wet bonding, the collagen fibrils in the a/d interface are largely unprotected and easily undergo biodegradation. Directly including crosslinking agents in the adhesive could protect collagen fibrils from degradation in situ within the a/d interface. PMID

  19. Microstructural modeling of collagen network mechanics and interactions with the proteoglycan gel in articular cartilage.

    PubMed

    Quinn, T M; Morel, V

    2007-01-01

    Cartilage matrix mechanical function is largely determined by interactions between the collagen fibrillar network and the proteoglycan gel. Although the molecular physics of these matrix constituents have been characterized and modern imaging methods are capable of localized measurement of molecular densities and orientation distributions, theoretical tools for using this information for prediction of cartilage mechanical behavior are lacking. We introduce a means to model collagen network contributions to cartilage mechanics based upon accessible microstructural information (fibril density and orientation distributions) and which self-consistently follows changes in microstructural geometry with matrix deformations. The interplay between the molecular physics of the collagen network and the proteoglycan gel is scaled up to determine matrix material properties, with features such as collagen fibril pre-stress in free-swelling cartilage emerging naturally and without introduction of ad hoc parameters. Methods are developed for theoretical treatment of the collagen network as a continuum-like distribution of fibrils, such that mechanical analysis of the network may be simplified by consideration of the spherical harmonic components of functions of the fibril orientation, strain, and stress distributions. Expressions for the collagen network contributions to matrix stress and stiffness tensors are derived, illustrating that only spherical harmonic components of orders 0 and 2 contribute to the stress, while orders 0, 2, and 4 contribute to the stiffness. Depth- and compression-dependent equilibrium mechanical properties of cartilage matrix are modeled, and advantages of the approach are illustrated by exploration of orientation and strain distributions of collagen fibrils in compressed cartilage. Results highlight collagen-proteoglycan interactions, especially for very small physiological strains where experimental data are relatively sparse. These methods for

  20. Shear flow promotes amyloid-{beta} fibrilization.

    PubMed

    Dunstan, Dave E; Hamilton-Brown, Paul; Asimakis, Peter; Ducker, William; Bertolini, Joseph

    2009-12-01

    The rate of formation of amyloid fibrils in an aqueous solution of amyloid-beta (Abeta) is greatly increased when the solution is sheared. When Abeta solution is stirred with a magnetic stirrer bar at 37 degrees C, a rapid increase in thioflavin T fluorescence is observed. Atomic Force Microscopy (AFM) images show the formation of aggregates, the growth of fibrils and the intertwining of the fibrils with time. Circular dichroism (CD) spectroscopy of samples taken after stirring shows a transition from random coil to alpha-helix to beta-sheet secondary structure over 20 h at 37 degrees C. The fluorescence, AFM and CD measurements are all consistent with the formation of amyloid fibrils. Quiescent, non-stirred solutions incubated at 37 degrees C showed no evidence of amyloid formation over a period of 3 days. Couette flow was found to accelerate the formation of amyloid fibrils demonstrating that the primary effect of stirring is not mixing but shearing. Only very small shear forces are applied to individual molecules in our experiments. Simple calculation suggests that the force is too small to support a hypothesis that shearing promotes partial unfolding of the protein as is observed. PMID:19850675

  1. Fibril structure of human islet amyloid polypeptide.

    PubMed

    Bedrood, Sahar; Li, Yiyu; Isas, J Mario; Hegde, Balachandra G; Baxa, Ulrich; Haworth, Ian S; Langen, Ralf

    2012-02-17

    Misfolding and amyloid fibril formation by human islet amyloid polypeptide (hIAPP) are thought to be important in the pathogenesis of type 2 diabetes, but the structures of the misfolded forms remain poorly understood. Here we developed an approach that combines site-directed spin labeling with continuous wave and pulsed EPR to investigate local secondary structure and to determine the relative orientation of the secondary structure elements with respect to each other. These data indicated that individual hIAPP molecules take up a hairpin fold within the fibril. This fold contains two β-strands that are much farther apart than expected from previous models. Atomistic structural models were obtained using computational refinement with EPR data as constraints. The resulting family of structures exhibited a left-handed helical twist, in agreement with the twisted morphology observed by electron microscopy. The fibril protofilaments contain stacked hIAPP monomers that form opposing β-sheets that twist around each other. The two β-strands of the monomer adopt out-of-plane positions and are staggered by about three peptide layers (∼15 Å). These results provide a mechanism for hIAPP fibril formation and could explain the remarkable stability of the fibrils. Thus, the structural model serves as a starting point for understanding and preventing hIAPP misfolding. PMID:22187437

  2. Cross-linking and the molecular packing of corneal collagen

    NASA Technical Reports Server (NTRS)

    Yamauchi, M.; Chandler, G. S.; Tanzawa, H.; Katz, E. P.

    1996-01-01

    We have quantitatively characterized, for the first time, the cross-linking in bovine cornea collagen as a function of age. The major iminium reducible cross-links were dehydro-hydroxylysinonorleucine (deH-HLNL) and dehydro-histidinohydroxymerodesmosine (deH-HHMD). The former rapidly diminished after birth; however, the latter persisted in mature animals at a level of 0.3 - 0.4 moles/mole of collagen. A nonreducible cross-link, histidinohydroxylysinonorleucine (HHL), previously found only in skin, was also found to be a major mature cross-link in cornea. The presence of HHL indicates that cornea fibrils have a molecular packing similar to skin collagen. However, like deH-HHMD, the HHL content in corneal fibrils only reaches a maximum value with time about half that of skin. These data suggest that the corneal fibrils are comprised of discrete filaments that are internally stabilized by HHL and deH-HHMD cross-links. This pattern of intermolecular cross-linking would facilitate the special collagen swelling property required for corneal transparency.

  3. Enhancing collagen stability through nanostructures containing chromium(III) oxide.

    PubMed

    Sangeetha, Selvam; Ramamoorthy, Usha; Sreeram, Kalarical Janardhanan; Nair, Balachandran Unni

    2012-12-01

    Stabilization of collagen for various applications employs chemicals such as aldehydes, metal ions, polyphenols, etc. Stability against enzymatic, thermal and mechanical degradation is required for a range of biomedical applications. The premise of this research is to explore the use of nanoparticles with suitable functionalization/encapsulation to crosslink with collagen, such that the three dimensional architecture had the desired stability. Collagen solution prepared as per standard protocols is treated with chromium(III) oxide nanoparticules encapsulated within a polymeric matrix (polystyrene-block-polyacrylic acid copolymer). Selectivity towards encapsulation was ensured by the reaction in dimethyl sulfoxide, where the PS groups popped out and encapsulated the Cr(2)O(3). Subsequently when immersed in aqueous solution, PAA units popped up to react with functional groups of collagen. The interaction with collagen was monitored through techniques such as CD, FTIR, viscosity measurements, stress analysis. CD studies and FTIR showed no degradation of collagen. Thermal stability was enhanced upon interaction of nanostructures with collagen. Self-assembly of collagen was delayed but not inhibited, indicating a compete binding of the metal oxide encapsulated polymer to collagen. Metal oxide nanoparticles encapsulated within a polymeric matrix could provide thermal and mechanical stability to collagen. The formed fibrils of collagen could serve as ideal material for various smart applications such as slow/sustained drug release. The study is also relevant to the leather industry in that the nanostructures can diffuse through the highly networked collagen fibre bundles in skin matrix easily, thus overcoming the rate limiting step of diffusion. PMID:22766281

  4. Myeloperoxidase acts as a profibrotic mediator of atrial fibrillation

    PubMed Central

    Rudolph, Volker; Andrié, René P; Rudolph, Tanja K; Friedrichs, Kai; Klinke, Anna; Hirsch-Hoffmann, Birgit; Schwoerer, Alexander P; Lau, Denise; Fu, XiaoMing; Klingel, Karin; Sydow, Karsten; Didié, Michael; Seniuk, Anika; von Leitner, Eike-Christin; Szoecs, Katalin; Schrickel, Jan W; Treede, Hendrik; Wenzel, Ulrich; Lewalter, Thorsten; Nickenig, Georg; Zimmermann, Wolfram-Hubertus; Meinertz, Thomas; Böger, Rainer H; Reichenspurner, Hermann; Freeman, Bruce A; Eschenhagen, Thomas; Ehmke, Heimo; Hazen, Stanley L; Willems, Stephan; Baldus, Stephan

    2010-01-01

    Observational clinical and ex vivo studies have established a strong association between atrial fibrillation and inflammation1. However, whether inflammation is the cause or the consequence of atrial fibrillation and which specific inflammatory mediators may increase the atria's susceptibility to fibrillation remain elusive. Here we provide experimental and clinical evidence for the mechanistic involvement of myeloperoxidase (MPO), a heme enzyme abundantly expressed by neutrophils, in the pathophysiology of atrial fibrillation. MPO-deficient mice pretreated with angiotensin II (AngII) to provoke leukocyte activation showed lower atrial tissue abundance of the MPO product 3-chlorotyrosine, reduced activity of matrix metalloproteinases and blunted atrial fibrosis as compared to wild-type mice. Upon right atrial electrophysiological stimulation, MPO-deficient mice were protected from atrial fibrillation, which was reversed when MPO was restored. Humans with atrial fibrillation had higher plasma concentrations of MPO and a larger MPO burden in right atrial tissue as compared to individuals devoid of atrial fibrillation. In the atria, MPO colocalized with markedly increased formation of 3-chlorotyrosine. Our data demonstrate that MPO is a crucial prerequisite for structural remodeling of the myocardium, leading to an increased vulnerability to atrial fibrillation. PMID:20305660

  5. Segmentation and measurement of collagen fibers for shoulder and joint therapy studies

    SciTech Connect

    Mascio, L.

    1994-11-15

    Various shoulder instabilities are debilitating, especially in individuals who perform overhead activities. Thermal modification of soft tissues in joints may allow precise alteration of these tissues` mechanical and/or structural properties to enhance joint function without inducing cell death or an inflammatory response. Several studies have evaluated laser energy for tissue welding. The collective findings are promising, and the next step is to identify the mechanisms responsible for laser-induced capsular tissue alternation, and the short- and long-term effects of non-ablative laser energy on joint capsular tissue. One step toward this goal is to compare the effect of three laser energy densities on the histologic properties of the tissue evaluating the architecture of the collagen (including density, fibril diameter distribution, and interfibrillar space) in sheep at various time intervals after surgery. The specific computer algorithms that are being used to make these measurements will be described.

  6. Collagen deposition and mechanical strength of colon anastomoses and skin incisional wounds of rats.

    PubMed

    Oxlund, H; Christensen, H; Seyer-Hansen, M; Andreassen, T T

    1996-11-01

    The mechanical strength development of healing wounds depends on the formation of collagen fibrils bridging the wound cleft. A considerable deposition, degradation, and remodeling of these fibrils takes place influencing the mechanical strength of the healing wounds. A method for studies of wound collagen metabolism in vivo is delineated, enabling determination of collagen deposition per hour in rat colon anastomoses and skin incisional wounds. Labeled proline was incorporated into wound collagen with a flooding dose of unlabeled proline, reducing errors introduced by proline recycling and proline de novo synthesis. The mechanical strength was determined by a materials testing machine. In both colon anastomoses and skin wounds a substantial increase in collagen deposition was observed at Day 2, reached a maximum at Day 6, and was still relatively high at Day 12 during the remodeling of collagen fibers in the wound cleft. The collagen deposition in colon anastomoses at Day 6, however, was 10-fold higher compared with that of the skin incisional wounds. The time course of the collagen deposition was much alike in colon anastomoses and skin incisional wounds reaching a maximum at Day 6. The mechanical strength of these two rather different types of wounds was increased correspondingly and to the same level during the 1st week of healing. The measurements of collagen deposition, collagen content, and biomechanical strength indicated a substantial turnover of newly synthesized and deposited collagen during the early phases of wound healing. On the basis of this, it seems obvious that even small disturbances to the balance between collagen synthesis, deposition, collagen cross-linking, and collagen degradation/remodeling may result in defective wound healing. PMID:8954827

  7. Human recombinant type I collagen produced in plants.

    PubMed

    Shoseyov, Oded; Posen, Yehudit; Grynspan, Frida

    2013-07-01

    As a central element of the extracellular matrix, collagen is intimately involved in tissue development, remodeling, and repair and confers high tensile strength to tissues. Numerous medical applications, particularly, wound healing, cell therapy, bone reconstruction, and cosmetic technologies, rely on its supportive and healing qualities. Its synthesis and assembly require a multitude of genes and post-translational modifications, where even minor deviations can be deleterious or even fatal. Historically, collagen was always extracted from animal and human cadaver sources, but bare risk of contamination and allergenicity and was subjected to harsh purification conditions resulting in irreversible modifications impeding its biofunctionality. In parallel, the highly complex and stringent post-translational processing of collagen, prerequisite of its viability and proper functioning, sets significant limitations on recombinant expression systems. A tobacco plant expression platform has been recruited to effectively express human collagen, along with three modifying enzymes, critical to collagen maturation. The plant extracted recombinant human collagen type I forms thermally stable helical structures, fibrillates, and demonstrates bioactivity resembling that of native collagen. Deployment of the highly versatile plant-based biofactory can be leveraged toward mass, rapid, and low-cost production of a wide variety of recombinant proteins. As in the case of collagen, proper planning can bypass plant-related limitations, to yield products structurally and functionally identical to their native counterparts. PMID:23252967

  8. Depth-Dependent Changes in Collagen Organization in the Human Peripapillary Sclera

    PubMed Central

    Pijanka, Jacek K.; Spang, Martin T.; Sorensen, Thomas; Liu, Jun; Nguyen, Thao D.; Quigley, Harry A.; Boote, Craig

    2015-01-01

    Purpose The collagen structure of the human peripapillary sclera plays a significant role in determining optic nerve head (ONH) biomechanics, and is therefore of interest in the study of glaucoma. The aim of the current work was to map the anisotropic collagen structure of the normal human peripapillary sclera as a function of tissue depth. Methods Wide-angle x-ray scattering was used to quantify collagen fibril orientation at 0.5mm intervals across six 150μm-thick serial sections through the peripapillary sclera of eight normal European-derived human eyes. Two structural parameters were measured: 1) the relative number of fibrils preferentially aligned at a given angle within the tissue plane, 2) the degree of collagen alignment (anisotropy). Results The inner-most one-third of the peripapillary scleral stroma (nearest to the choroid) was characterised by collagen fibrils either randomly arranged or preferentially aligned radially with respect to the ONH. In contrast, the outer two-thirds of the tissue was dominated by a circumferential arrangement of collagen encircling the ONH. In all tissue regions the degree of collagen anisotropy peaked in the mid-stroma and progressively decreased towards the tissue surfaces, with the largest depth variations occurring in the inferior-nasal quadrant, and the smallest occurring in the superior-nasal quadrant. Conclusions Significant, region-specific variations in collagen structure are present in the human peripapillary sclera as a function of depth. In normal eyes, the circumferential collagen fibril architecture is most prominent in the outer two-thirds of the stroma, possibly as a mechanical adaption to more effectively support the lamina cribrosa at the level of its insertion into the scleral canal wall. PMID:25714753

  9. The role of collagen in bone apatite formation in the presence of hydroxyapatite nucleation inhibitors

    PubMed Central

    Nudelman, Fabio; Pieterse, Koen; George, Anne; Bomans, Paul H. H.; Friedrich, Heiner; Brylka, Laura J.; Hilbers, Peter A. J.; de With, Gijsbertus; Sommerdijk, Nico A. J. M.

    2011-01-01

    Bone is a composite material, in which collagen fibrils form a scaffold for a highly organized arrangement of uniaxially oriented apatite crystals1,2. In the periodic 67 nm cross-striated pattern of the collagen fibril3–5, the less dense 40-nm-long gap zone has been implicated as the place where apatite crystals nucleate from an amorphous phase, and subsequently grow6–9. This process is believed to be directed by highly acidic non-collagenous proteins6,7,9–11; however, the role of the collagen matrix12–14 during bone apatite mineralization remains unknown. Here, combining nanometre-scale resolution cryogenic transmission electron microscopy and cryogenic electron tomography15 with molecular modelling, we show that collagen functions in synergy with inhibitors of hydroxyapatite nucleation to actively control mineralization. The positive net charge close to the C-terminal end of the collagen molecules promotes the infiltration of the fibrils with amorphous calcium phosphate (ACP). Furthermore, the clusters of charged amino acids, both in gap and overlap regions, form nucleation sites controlling the conversion of ACP into a parallel array of oriented apatite crystals. We developed a model describing the mechanisms through which the structure, supramolecular assembly and charge distribution of collagen can control mineralization in the presence of inhibitors of hydroxyapatite nucleation. PMID:20972429

  10. Thermal Denaturation Studies of Collagen by Microthermal Analysis and Atomic Force Microscopy

    PubMed Central

    Bozec, Laurent; Odlyha, Marianne

    2011-01-01

    The structural properties of collagen have been the subject of numerous studies over past decades, but with the arrival of new technologies, such as the atomic force microscope and related techniques, a new era of research has emerged. Using microthermal analysis, it is now possible to image samples as well as performing localized thermal measurements without damaging or destroying the sample itself. This technique was successfully applied to characterize the thermal response between native collagen fibrils and their denatured form, gelatin. Thermal transitions identified at (150 ± 10)°C and (220 ± 10)°C can be related to the process of gelatinization of the collagen fibrils, whereas at higher temperatures, both the gelatin and collagen samples underwent two-stage transitions with a common initial degradation temperature at (300 ± 10)°C and a secondary degradation temperature of (340 ± 10)°C for the collagen and of (420 ± 10)°C for the gelatin, respectively. The broadening and shift in the secondary degradation temperature was linked to the spread of thermal degradation within the gelatin and collagen fibrils matrix further away from the point of contact between probe and sample. Finally, similar measurements were performed inside a bone resorption lacuna, suggesting that microthermal analysis is a viable technique for investigating the thermomechanical response of collagen for in situ samples that would be, otherwise, too challenging or not possible using bulk techniques. PMID:21723833

  11. Modification by UV radiation of the surface of thin films based on collagen extracted from fish scales.

    PubMed

    Sionkowska, Alina; Kozłowska, Justyna; Lazare, Sylvain

    2014-06-01

    Collagen was extracted from fish scales (Esox lucius) through demineralization process. Thin films by solvent evaporation from collagen extracted from fish scales were prepared. The surface of thin films made of fish scales collagen was modified by ultraviolet (UV)-irradiation with the wavelength λ = 254 nm. The amino acid composition of the Esox lucius scale collagen was analyzed before and after UV-irradiation by means of high-pressure liquid chromatography. The surface properties of films were investigated using the technique of atomic force microscopy (AFM) and by means of contact angle measurements allowing the calculation of surface free energy. Measurements of the contact angle for diiodomethane (D) and glycerol (G) on the surface of fish collagen films were made and surface free energy was calculated. The structure of collagen before and after UV-irradiation was studied using Fourier-transform infrared spectroscopy. It was found that after UV-irradiation the amount of all amino acids present in collagen molecule decreased. It was found also that the contact angle and the surface free energy were altered by UV-irradiation of collagen film. AFM showed that the surface roughness of collagen films was also altered by UV-irradiation. UV-irradiation caused the decrease of surface roughness due to photochemical processes, which occurred in the top layer of collagen film. The formation of collagen fibrils after solvent evaporation was observed using AFM. The diameter of collagen fibrils was bigger for irradiated collagen film than the diameter of collagen fibrils before UV-irradiation. PMID:24985207

  12. Strain stiffening in collagen I networks.

    PubMed

    Motte, Stéphanie; Kaufman, Laura J

    2013-01-01

    Biopolymer gels exhibit strain stiffening that is generally not seen in synthetic gels. Here, we investigate the strain-stiffening behavior in collagen I gels that demonstrate elasticity derived from a variety of sources including crosslinking through telopeptides, bundling through low-temperature gelation, and exogenous crosslinking with genipin. In all cases, it is found that these gels exhibit strain stiffening; in general, onset of strain stiffening occurs earlier, yield strain is lower, and degree of strain stiffening is smaller in higher concentration gels and in those displaying thick fibril bundles. Recovery after exposure to high strains is substantial and similar in all gels, suggesting that much of the stiffening comes from reversible network deformations. A key finding of this study is that collagen I gels of identical storage and loss moduli may display different nonlinear responses and different capacities to recover from high strain. PMID:23097228

  13. The Collagen Family

    PubMed Central

    Ricard-Blum, Sylvie

    2011-01-01

    Collagens are the most abundant proteins in mammals. The collagen family comprises 28 members that contain at least one triple-helical domain. Collagens are deposited in the extracellular matrix where most of them form supramolecular assemblies. Four collagens are type II membrane proteins that also exist in a soluble form released from the cell surface by shedding. Collagens play structural roles and contribute to mechanical properties, organization, and shape of tissues. They interact with cells via several receptor families and regulate their proliferation, migration, and differentiation. Some collagens have a restricted tissue distribution and hence specific biological functions. PMID:21421911

  14. Targeted Deletion of Collagen V in Tendons and Ligaments Results in a Classic Ehlers-Danlos Syndrome Joint Phenotype

    PubMed Central

    Sun, Mei; Connizzo, Brianne K.; Adams, Sheila M.; Freedman, Benjamin R.; Wenstrup, Richard J.; Soslowsky, Louis J.; Birk, David E.

    2016-01-01

    Collagen V mutations underlie classic Ehlers-Danlos syndrome, and joint hypermobility is an important clinical manifestation. We define the function of collagen V in tendons and ligaments, as well as the role of alterations in collagen V expression in the pathobiology in classic Ehlers-Danlos syndrome. A conditional Col5a1flox/flox mouse model was bred with Scleraxis-Cre mice to create a targeted tendon and ligament Col5a1-null mouse model, Col5a1Δten/Δten. Targeting was specific, resulting in collagen V–null tendons and ligaments. Col5a1Δten/Δten mice demonstrated decreased body size, grip weakness, abnormal gait, joint laxity, and early-onset osteoarthritis. These gross changes were associated with abnormal fiber organization, as well as altered collagen fibril structure with increased fibril diameters and decreased fibril number that was more severe in a major joint stabilizing ligament, the anterior cruciate ligament (ACL), than in the flexor digitorum longus tendon. The ACL also had a higher collagen V content than did the flexor digitorum longus tendon. The collagen V–null ACL and flexor digitorum longus tendon both had significant alterations in mechanical properties, with ACL exhibiting more severe changes. The data demonstrate critical differential regulatory roles for collagen V in tendon and ligament structure and function and suggest that collagen V regulatory dysfunction is associated with an abnormal joint phenotype, similar to the hypermobility phenotype in classic Ehlers-Danlos syndrome. PMID:25797646

  15. Targeted deletion of collagen V in tendons and ligaments results in a classic Ehlers-Danlos syndrome joint phenotype.

    PubMed

    Sun, Mei; Connizzo, Brianne K; Adams, Sheila M; Freedman, Benjamin R; Wenstrup, Richard J; Soslowsky, Louis J; Birk, David E

    2015-05-01

    Collagen V mutations underlie classic Ehlers-Danlos syndrome, and joint hypermobility is an important clinical manifestation. We define the function of collagen V in tendons and ligaments, as well as the role of alterations in collagen V expression in the pathobiology in classic Ehlers-Danlos syndrome. A conditional Col5a1(flox/flox) mouse model was bred with Scleraxis-Cre mice to create a targeted tendon and ligament Col5a1-null mouse model, Col5a1(Δten/Δten). Targeting was specific, resulting in collagen V-null tendons and ligaments. Col5a1(Δten/Δten) mice demonstrated decreased body size, grip weakness, abnormal gait, joint laxity, and early-onset osteoarthritis. These gross changes were associated with abnormal fiber organization, as well as altered collagen fibril structure with increased fibril diameters and decreased fibril number that was more severe in a major joint stabilizing ligament, the anterior cruciate ligament (ACL), than in the flexor digitorum longus tendon. The ACL also had a higher collagen V content than did the flexor digitorum longus tendon. The collagen V-null ACL and flexor digitorum longus tendon both had significant alterations in mechanical properties, with ACL exhibiting more severe changes. The data demonstrate critical differential regulatory roles for collagen V in tendon and ligament structure and function and suggest that collagen V regulatory dysfunction is associated with an abnormal joint phenotype, similar to the hypermobility phenotype in classic Ehlers-Danlos syndrome. PMID:25797646

  16. Anticoagulation in atrial fibrillation

    PubMed Central

    Piccini, Jonathan P

    2014-01-01

    Atrial fibrillation increases the risk of stroke, which is a leading cause of death and disability worldwide. The use of oral anticoagulation in patients with atrial fibrillation at moderate or high risk of stroke, estimated by established criteria, improves outcomes. However, to ensure that the benefits exceed the risks of bleeding, appropriate patient selection is essential. Vitamin K antagonism has been the mainstay of treatment; however, newer drugs with novel mechanisms are also available. These novel oral anticoagulants (direct thrombin inhibitors and factor Xa inhibitors) obviate many of warfarin’s shortcomings, and they have demonstrated safety and efficacy in large randomized trials of patients with non-valvular atrial fibrillation. However, the management of patients taking warfarin or novel agents remains a clinical challenge. There are several important considerations when selecting anticoagulant therapy for patients with atrial fibrillation. This review will discuss the rationale for anticoagulation in patients with atrial fibrillation; risk stratification for treatment; available agents; the appropriate implementation of these agents; and additional, specific clinical considerations for treatment. PMID:24733535

  17. Anticoagulation in atrial fibrillation.

    PubMed

    Steinberg, Benjamin A; Piccini, Jonathan P

    2014-01-01

    Atrial fibrillation increases the risk of stroke, which is a leading cause of death and disability worldwide. The use of oral anticoagulation in patients with atrial fibrillation at moderate or high risk of stroke, estimated by established criteria, improves outcomes. However, to ensure that the benefits exceed the risks of bleeding, appropriate patient selection is essential. Vitamin K antagonism has been the mainstay of treatment; however, newer drugs with novel mechanisms are also available. These novel oral anticoagulants (direct thrombin inhibitors and factor Xa inhibitors) obviate many of warfarin's shortcomings, and they have demonstrated safety and efficacy in large randomized trials of patients with non-valvular atrial fibrillation. However, the management of patients taking warfarin or novel agents remains a clinical challenge. There are several important considerations when selecting anticoagulant therapy for patients with atrial fibrillation. This review will discuss the rationale for anticoagulation in patients with atrial fibrillation; risk stratification for treatment; available agents; the appropriate implementation of these agents; and additional, specific clinical considerations for treatment. PMID:24733535

  18. Protein Fibrils Induce Emulsion Stabilization.

    PubMed

    Peng, Jinfeng; Simon, Joana Ralfas; Venema, Paul; van der Linden, Erik

    2016-03-01

    The behavior of an oil-in-water emulsion was studied in the presence of protein fibrils for a wide range of fibril concentrations by using rheology, diffusing wave spectroscopy, and confocal laser scanning microscopy. Results showed that above a minimum fibril concentration depletion flocculation occurred, leading to oil droplet aggregation and enhanced creaming of the emulsion. Upon further increasing the concentration of the protein fibrils, the emulsions were stabilized. In this stable regime both aggregates of droplets and single droplets are present, and these aggregates are smaller than the aggregates in the flocculated emulsion samples at the lower fibril concentrations. The size of the droplet aggregates in the stabilized emulsions is independent of fibril concentration. In addition, the droplet aggregation was reversible upon dilution both by a pH 2 HCl solution and by a fibril solution at the same concentration. The viscosity of the emulsions containing fibrils was comparable to that of the pure fibril solution. Neither fibril networks nor droplet gel networks were observed in our study. The stabilization mechanism of emulsions containing long protein fibrils at high protein fibril concentrations points toward the mechanism of a kinetic stabilization. PMID:26882086

  19. Atrial Fibrillation (AF or AFib)

    MedlinePlus

    ... Pressure High Blood Pressure Tools & Resources Stroke More Atrial Fibrillation (AF or AFib) Updated:Feb 10,2016 What ... to the Terms and Conditions and Privacy Policy Atrial Fibrillation • Introduction • What is Atrial Fibrillation? • Why AFib Matters • ...

  20. Biomedical applications of collagens.

    PubMed

    Ramshaw, John A M

    2016-05-01

    Collagen-based biomedical materials have developed into important, clinically effective materials used in a range of devices that have gained wide acceptance. These devices come with collagen in various formats, including those based on stabilized natural tissues, those that are based on extracted and purified collagens, and designed composite, biosynthetic materials. Further knowledge on the structure and function of collagens has led to on-going developments and improvements. Among these developments has been the production of recombinant collagen materials that are well defined and are disease free. Most recently, a group of bacterial, non-animal collagens has emerged that may provide an excellent, novel source of collagen for use in biomaterials and other applications. These newer collagens are discussed in detail. They can be modified to direct their function, and they can be fabricated into various formats, including films and sponges, while solutions can also be adapted for use in surface coating technologies. PMID:26448097

  1. Collagen vascular disease

    MedlinePlus

    ... this page: //medlineplus.gov/ency/article/001223.htm Collagen vascular disease To use the sharing features on ... were previously said to have "connective tissue" or "collagen vascular" disease. We now have names for many ...

  2. Evaluation of bioprosthetic heart valve failure using a matrix-fibril shear stress transfer approach.

    PubMed

    Anssari-Benam, Afshin; Barber, Asa H; Bucchi, Andrea

    2016-02-01

    A matrix-fibril shear stress transfer approach is devised and developed in this paper to analyse the primary biomechanical factors which initiate the structural degeneration of the bioprosthetic heart valves (BHVs). Using this approach, the critical length of the collagen fibrils l c and the interface shear acting on the fibrils in both BHV and natural aortic valve (AV) tissues under physiological loading conditions are calculated and presented. It is shown that the required critical fibril length to provide effective reinforcement to the natural AV and the BHV tissue is l c  = 25.36 µm and l c  = 66.81 µm, respectively. Furthermore, the magnitude of the required shear force acting on fibril interface to break a cross-linked fibril in the BHV tissue is shown to be 38 µN, while the required interfacial force to break the bonds between the fibril and the surrounding extracellular matrix is 31 µN. Direct correlations are underpinned between these values and the ultimate failure strength and the failure mode of the BHV tissue compared with the natural AV, and are verified against the existing experimental data. The analyses presented in this paper explain the role of fibril interface shear and critical length in regulating the biomechanics of the structural failure of the BHVs, for the first time. This insight facilitates further understanding into the underlying causes of the structural degeneration of the BHVs in vivo. PMID:26715134

  3. Biochemical and biophysical characterization of collagens of marine sponge, Ircinia fusca (Porifera: Demospongiae: Irciniidae).

    PubMed

    Pallela, Ramjee; Bojja, Sreedhar; Janapala, Venkateswara Rao

    2011-07-01

    Collagens were isolated and partially characterized from the marine demosponge, Ircinia fusca from Gulf of Mannar (GoM), India, with an aim to develop potentially applicable collagens from unused and under-used resources. The yield of insoluble, salt soluble and acid soluble forms of collagens was 31.71 ± 1.59, 20.69 ± 1.03, and 17.38 ± 0.87 mg/g dry weight, respectively. Trichrome staining, Scanning & Transmission Electron microscopic (SEM & TEM) studies confirmed the presence of collagen in the isolated, terminally globular irciniid filaments. The partially purified (gel filtration chromatography), non-fibrillar collagens appeared as basement type collagenous sheets under light microscopy whereas the purified fibrillar collagens appeared as fibrils with a repeated band periodicity of 67 nm under Atomic Force Microscope (AFM). The non-fibrillar and fibrillar collagens were seen to have affinity for anti-collagen type IV and type I antibodies raised against human collagens, respectively. The macromolecules, i.e., total protein, carbohydrate and lipid contents within the tissues were also quantified. The present information on the three characteristic irciniid collagens (filamentous, fibrillar and non-fibrillar) could assist the future attempts to unravel the therapeutically important, safer collagens from marine sponges for their use in pharmaceutical and cosmeceutical industries. PMID:21501629

  4. Rapid Fabrication of Living Tissue Models by Collagen Plastic Compression: Understanding Three-Dimensional Cell Matrix Repair In Vitro

    PubMed Central

    Cheema, Umber; Brown, Robert A.

    2013-01-01

    Objective To produce biomimetic collagen scaffolds for tissue modeling and as tissue-engineered implants. Approach Control of collagen fibril material parameters in collagen hydrogel scaffolds by using plastic compression (PC), resulting in direct control of cell proliferation, cell migration, and cell–cell interaction. Results We were able to control the density of collagen in such scaffolds from between 0.2% and 30%, and controllably layer the fibrils in the Z-plane. Cell migration was observed in gels where a gradient of collagen density was present. In these gels, cells preferentially migrated toward the collagen-dense areas. Cell proliferation rates were measurably higher in dense collagen gels. Innovation The use of PC to control material properties of collagen hydrogels results in collagen scaffolds that are biomimetic. These collagen gels reproduce the relevant matrix-mechanical environment in which behavior is more representative of that found in vivo. Conclusion The material properties of native collagen type I gels can be engineered to match those found in tissues in vivo to elicit more biomimetic cell behavior. PMID:24527341

  5. Fish collagen is an important panallergen in the Japanese population.

    PubMed

    Kobayashi, Y; Akiyama, H; Huge, J; Kubota, H; Chikazawa, S; Satoh, T; Miyake, T; Uhara, H; Okuyama, R; Nakagawara, R; Aihara, M; Hamada-Sato, N

    2016-05-01

    Collagen was identified as a fish allergen in early 2000s. Although its allergenic potential has been suggested to be low, risks associated with collagen as a fish allergen have not been evaluated to a greater extent. In this study, we aimed to clarify the importance of collagen as a fish allergen. Our results showed that 50% of Japanese patients with fish allergy had immunoglobulin E (IgE) against mackerel collagen, whereas 44% had IgE against mackerel parvalbumin. IgE inhibition assay revealed high cross-reactivity of mackerel collagen to 22 fish species (inhibition rates: 87-98%). Furthermore, a recently developed allergy test demonstrated that collagen triggered IgE cross-linking on mast cells. These data indicate that fish collagen is an important and very common panallergen in fish consumed in Japan. The high rate of individuals' collagen allergy may be attributable to the traditional Japanese custom of raw fish consumption. PMID:26785247

  6. Contribution of Long Fibrils and Peptides to Surface and Foaming Behavior of Soy Protein Fibril System.

    PubMed

    Wan, Zhili; Yang, Xiaoquan; Sagis, Leonard M C

    2016-08-16

    When soy glycinin (11S) is heated for a prolonged time at pH 2 (20 h at 85 °C), a mixture is formed consisting of long semiflexible 11S fibrils and small peptides. The surface and foaming properties of this mixture were investigated at different pHs, and compared to the behavior of pure fibrils and pure peptides, to determine the individual contributions of these two factions to the behavior of the mixture. The adsorption of these three systems at air-water interfaces and the resulting surface rheological properties were studied by combining drop shape analysis tensiometry, ellipsometry, and surface large amplitude oscillatory dilatational (LAOD) rheology. Lissajous plots of surface pressure versus deformation were used to analyze the surface rheological response in terms of interfacial microstructure. Our results show that the adsorption kinetics, dilatational rheological properties, and the foaming behavior of the mixture were mainly dominated by the small peptides in the fibril system. Compared to pH 2, the fibril mixture at pH 5 and 7 provides much better foam stability and appears to be a very promising protein material to make stable foams, even at low protein concentration (0.1 wt %). The presence of fibril clusters and peptide aggregates at pH 5 and 7 contributed to foam stability of the mixture. In contrast, pure fibril formed an interface with a highly pH-responsive adsorption and rheological behavior, and the foamability and foam stability of the pure fibrils were very poor. PMID:27452662

  7. Are amyloid fibrils molecular spandrels?

    PubMed

    Hane, Francis

    2013-11-15

    Amyloid-β, the protein implicated in Alzheimer's disease, along with a number of other proteins, has been shown to form amyloid fibrils. Fibril forming proteins share no common primary structure and have little known function. Furthermore, all proteins have the ability to form amyloid fibrils under certain conditions as the fibrillar structure lies at the global free energy minimum of proteins. This raises the question of the mechanism of the evolution of the amyloid fibril structure. Experimental evidence supports the hypothesis that the fibril structure is a by-product of the forces of protein folding and lies outside the bounds of evolutionary pressures. PMID:24140343

  8. Nucleation of polymorphic amyloid fibrils.

    PubMed

    Auer, Stefan

    2015-03-10

    One and the same protein can self-assemble into amyloid fibrils with different morphologies. The phenomenon of fibril polymorphism is relevant biologically because different fibril polymorphs can have different toxicity, but there is no tool for predicting which polymorph forms and under what conditions. Here, we consider the nucleation of polymorphic amyloid fibrils occurring by direct polymerization of monomeric proteins into fibrils. We treat this process within the framework of our newly developed nonstandard nucleation theory, which allows prediction of the concentration dependence of the nucleation rate for different fibril polymorphs. The results highlight that the concentration dependence of the nucleation rate is closely linked with the protein solubility and a threshold monomer concentration below which fibril formation becomes biologically irrelevant. The relation between the nucleation rate, the fibril solubility, the threshold concentration, and the binding energies of the fibril building blocks within fibrils might prove a valuable tool for designing new experiments to control the formation of particular fibril polymorphs. PMID:25762329

  9. Glycine substitutions in the triple-helical region of type VII collagen result in a spectrum of dystrophic epidermolysis bullosa phenotypes and patterns of inheritance

    SciTech Connect

    Christiano, A.M.; McGrath, J.A.; Uitto, J.; Kong Chong Tan

    1996-04-01

    The dystrophic forms of epidermolysis bullosa (DEB) are characterized by fragility of the skin and mucous membranes. DEB can be inherited in either an autosomal dominant or autosomal recessive pattern, and the spectrum of clinical severity is highly variable. The unifying diagnostic hallmark of DEB is abnormalities in the anchoring fibrils, which consist of type VII collagen, and recently, mutations in the corresponding gene, COL7A1, have been disclosed in a number of families. In this study, we report six families with glycine substitution mutations in the triple-helical region of type VII collagen. Among the six families, two demonstrated a mild phenotype, and the inheritance of the mutation was consistent with the dominantly inherited form of DEB. In the four other families, the mutation was silent in the heterozygous state but, when present in the homozygous state, or combined with a second mutation, resulted in a recessively inherited DEB phenotype. Type VII collagen is, therefore, unique among the collagen genes, in that different glycine substitutions can be either silent in heterozygous individuals or result in a dominantly inherited DEB. Inspection of the locations of the glycine substitutions along the COL7A1 polypeptide suggests that the consequences of these mutations, in terms of phenotype and pattern of inheritance, are position independent. 29 refs., 4 figs., 2 tabs.

  10. Prolyl hydroxylation of collagen type I is required for efficient binding to integrin alpha 1 beta 1 and platelet glycoprotein VI but not to alpha 2 beta 1.

    PubMed

    Perret, Stéephanie; Eble, Johannes A; Siljander, Pia R-M; Merle, Christine; Farndale, Richard W; Theisen, Manfred; Ruggiero, Florence

    2003-08-01

    Collagen is a potent adhesive substrate for cells, an event essentially mediated by the integrins alpha 1 beta 1 and alpha 2 beta 1. Collagen fibrils also bind to the integrin alpha 2 beta 1 and the platelet receptor glycoprotein VI to activate and aggregate platelets. The distinct triple helical recognition motifs for these receptors, GXOGER and (GPO)n, respectively, all contain hydroxyproline. Using unhydroxylated collagen I produced in transgenic plants, we investigated the role of hydroxyproline in the receptor-binding properties of collagen. We show that alpha 2 beta 1 but not alpha 1 beta 1 mediates cell adhesion to unhydroxylated collagen. Soluble recombinant alpha 1 beta 1 binding to unhydroxylated collagen is considerably reduced compared with bovine collagens, but binding can be restored by prolyl hydroxylation of recombinant collagen. We also show that platelets use alpha 2 beta 1 to adhere to the unhydroxylated recombinant molecules, but the adhesion is weaker than on fully hydroxylated collagen, and the unhydroxylated collagen fibrils fail to aggregate platelets. Prolyl hydroxylation is thus required for binding of collagen to platelet glycoprotein VI and to cells by alpha 1 beta 1. These observations give new insights into the molecular basis of collagen-receptor interactions and offer new selective applications for the recombinant unhydroxylated collagen I. PMID:12771137

  11. A Mouse Model for Dominant Collagen VI Disorders

    PubMed Central

    Pan, Te-Cheng; Zhang, Rui-Zhu; Arita, Machiko; Bogdanovich, Sasha; Adams, Sheila M.; Gara, Sudheer Kumar; Wagener, Raimund; Khurana, Tejvior S.; Birk, David E.; Chu, Mon-Li

    2014-01-01

    Dominant and recessive mutations in collagen VI genes, COL6A1, COL6A2, and COL6A3, cause a continuous spectrum of disorders characterized by muscle weakness and connective tissue abnormalities ranging from the severe Ullrich congenital muscular dystrophy to the mild Bethlem myopathy. Herein, we report the development of a mouse model for dominant collagen VI disorders by deleting exon 16 in the Col6a3 gene. The resulting heterozygous mouse, Col6a3+/d16, produced comparable amounts of normal Col6a3 mRNA and a mutant transcript with an in-frame deletion of 54 bp of triple-helical coding sequences, thus mimicking the most common molecular defect found in dominant Ullrich congenital muscular dystrophy patients. Biosynthetic studies of mutant fibroblasts indicated that the mutant α3(VI) collagen protein was produced and exerted a dominant-negative effect on collagen VI microfibrillar assembly. The distribution of the α3(VI)-like chains of collagen VI was not altered in mutant mice during development. The Col6a3+/d16 mice developed histopathologic signs of myopathy and showed ultrastructural alterations of mitochondria and sarcoplasmic reticulum in muscle and abnormal collagen fibrils in tendons. The Col6a3+/d16 mice displayed compromised muscle contractile functions and thereby provide an essential preclinical platform for developing treatment strategies for dominant collagen VI disorders. PMID:24563484

  12. Variation in the helical structure of native collagen.

    PubMed

    Orgel, Joseph P R O; Persikov, Anton V; Antipova, Olga

    2014-01-01

    The structure of collagen has been a matter of curiosity, investigation, and debate for the better part of a century. There has been a particularly productive period recently, during which much progress has been made in better describing all aspects of collagen structure. However, there remain some questions regarding its helical symmetry and its persistence within the triple-helix. Previous considerations of this symmetry have sometimes confused the picture by not fully recognizing that collagen structure is a highly complex and large hierarchical entity, and this affects and is effected by the super-coiled molecules that make it. Nevertheless, the symmetry question is not trite, but of some significance as it relates to extracellular matrix organization and cellular integration. The correlation between helical structure in the context of the molecular packing arrangement determines which parts of the amino acid sequence of the collagen fibril are buried or accessible to the extracellular matrix or the cell. In this study, we concentrate primarily on the triple-helical structure of fibrillar collagens I and II, the two most predominant types. By comparing X-ray diffraction data collected from type I and type II containing tissues, we point to evidence for a range of triple-helical symmetries being extant in the molecules native environment. The possible significance of helical instability, local helix dissociation and molecular packing of the triple-helices is discussed in the context of collagen's supramolecular organization, all of which must affect the symmetry of the collagen triple-helix. PMID:24586843

  13. X-ray scattering used to map the preferred collagen orientation in the human cornea and limbus.

    PubMed

    Aghamohammadzadeh, Hossein; Newton, Richard H; Meek, Keith M

    2004-02-01

    Many properties of connective tissues are governed by the organization of the constituent collagen. For example, the organization of collagen in the cornea and the limbus, where the cornea and sclera meet, is an important determinant of corneal curvature and hence of the eye's focusing power. We have used synchrotron X-ray scattering to map the orientation of the collagen fibrils throughout the human cornea, limbus, and adjacent sclera. We demonstrate a preferred orientation of collagen in the vertical and horizontal directions that is maintained to within about 1 mm from the limbus, where a circular or tangential disposition of fibrils occurs. The data are also used to map the relative distribution of both the total and the preferentially aligned collagen in different parts of the tissue, revealing considerable anisotropy. The detailed structural information provided is an important step toward understanding the shape and the mechanical properties of the tissue. PMID:14962385

  14. Meta-analysis identifies six new susceptibility loci for atrial fibrillation

    PubMed Central

    Ellinor, Patrick T; Lunetta, Kathryn L; Albert, Christine M; Glazer, Nicole L; Ritchie, Marylyn D; Smith, Albert V; Arking, Dan E; Müller-Nurasyid, Martina; Krijthe, Bouwe P; Lubitz, Steven A; Bis, Joshua C; Chung, Mina K; Dörr, Marcus; Ozaki, Kouichi; Roberts, Jason D; Smith, J Gustav; Pfeufer, Arne; Sinner, Moritz F; Lohman, Kurt; Ding, Jingzhong; Smith, Nicholas L; Smith, Jonathan D; Rienstra, Michiel; Rice, Kenneth M; Van Wagoner, David R; Magnani, Jared W; Wakili, Reza; Clauss, Sebastian; Rotter, Jerome I; Steinbeck, Gerhard; Launer, Lenore J; Davies, Robert W; Borkovich, Matthew; Harris, Tamara B; Lin, Honghuang; Völker, Uwe; Völzke, Henry; Milan, David J; Hofman, Albert; Boerwinkle, Eric; Chen, Lin Y; Soliman, Elsayed Z; Voight, Benjamin F; Li, Guo; Chakravarti, Aravinda; Kubo, Michiaki; Tedrow, Usha B; Rose, Lynda M; Ridker, Paul M; Conen, David; Tsunoda, Tatsuhiko; Furukawa, Tetsushi; Sotoodehnia, Nona; Xu, Siyan; Kamatani, Naoyuki; Levy, Daniel; Nakamura, Yusuke; Parvez, Babar; Mahida, Saagar; Furie, Karen L; Rosand, Jonathan; Muhammad, Raafia; Psaty, Bruce M; Meitinger, Thomas; Perz, Siegfried; Wichmann, H-Erich; Witteman, Jacqueline C M; Kao, W H Linda; Kathiresan, Sekar; Roden, Dan M; Uitterlinden, Andre G; Rivadeneira, Fernando; McKnight, Barbara; Sjögren, Marketa; Newman, Anne B; Liu, Yongmei; Gollob, Michael H; Melander, Olle; Tanaka, Toshihiro; Ch Stricker, Bruno H; Felix, Stephan B; Alonso, Alvaro; Darbar, Dawood; Barnard, John; Chasman, Daniel I; Heckbert, Susan R; Benjamin, Emelia J; Gudnason, Vilmundur; Kääb, Stefan

    2012-01-01

    Atrial fibrillation is a highly prevalent arrhythmia and a major risk factor for stroke, heart failure and death1. We conducted a genome-wide association study (GWAS) in individuals of European ancestry, including 6,707 with and 52,426 without atrial fibrillation. Six new atrial fibrillation susceptibility loci were identified and replicated in an additional sample of individuals of European ancestry, including 5,381 subjects with and 1 0,030 subjects without atrial fibrillation (P < 5 × 10−8). Four of the loci identified in Europeans were further replicated in silico in a GWAS of Japanese individuals, including 843 individuals with and 3,350 individuals without atrial fibrillation. The identified loci implicate candidate genes that encode transcription factors related to cardiopulmonary development, cardiac-expressed ion channels and cell signaling molecules. PMID:22544366

  15. Micro-mechanical model for the tension-stabilized enzymatic degradation of collagen tissues

    NASA Astrophysics Data System (ADS)

    Nguyen, Thao; Ruberti, Jeffery

    We present a study of how the collagen fiber structure influences the enzymatic degradation of collagen tissues. Experiments of collagen fibrils and tissues show that mechanical tension can slow and halt enzymatic degradation. Tissue-level experiments also show that degradation rate is minimum at a stretch level coincident with the onset of strain-stiffening in the stress response. To understand these phenomena, we developed a micro-mechanical model of a fibrous collagen tissue undergoing enzymatic degradation. Collagen fibers are described as sinusoidal elastica beams, and the tissue is described as a distribution of fibers. We assumed that the degradation reaction is inhibited by the axial strain energy of the crimped collagen fibers. The degradation rate law was calibrated to experiments on isolated single fibrils from bovine sclera. The fiber crimp and properties were fit to uniaxial tension tests of tissue strips. The fibril-level kinetic and tissue-level structural parameters were used to predict tissue-level degradation-induced creep rate under a constant applied force. We showed that we could accurately predict the degradation-induce creep rate of the pericardium and cornea once we accounted for differences in the fiber crimp structure and properties.

  16. Lumican deficiency results in cardiomyocyte hypertrophy with altered collagen assembly.

    PubMed

    Dupuis, Loren E; Berger, Matthew G; Feldman, Samuel; Doucette, Lorna; Fowlkes, Vennece; Chakravarti, Shukti; Thibaudeau, Sarah; Alcala, Nicolas E; Bradshaw, Amy D; Kern, Christine B

    2015-07-01

    The ability of the heart to adapt to increased stress is dependent on the modification of its extracellular matrix (ECM) architecture that is established during postnatal development as cardiomyocytes differentiate, a process that is poorly understood. We hypothesized that the small leucine-rich proteoglycan (SLRP) lumican (LUM), which binds collagen and facilitates collagen assembly in other tissues, may play a critical role in establishing the postnatal murine myocardial ECM. Although previous studies suggest that LUM deficient mice (lum(-/-)) exhibit skin anomalies consistent with Ehlers-Danlos syndrome, lum(-/-) hearts have not been evaluated. These studies show that LUM was immunolocalized to non-cardiomyocytes of the cardiac ventricles and its expression increased throughout development. Lumican deficiency resulted in significant (50%) perinatal death and further examination of the lum(-/-) neonatal hearts revealed an increase in myocardial tissue without a significant increase in cell proliferation. However cardiomyocytes from surviving postnatal day 0 (P0), 1 month (1 mo) and adult (4 mo) lum(-/-) hearts were significantly larger than their wild type (WT) littermates. Immunohistochemistry revealed that the increased cardiomyocyte size in the lum(-/-) hearts correlated with alteration of the cardiomyocyte pericellular ECM components collagenα1(I) and the class I SLRP decorin (DCN). Western blot analysis demonstrated that the ratio of glycosaminoglycan (GAG) decorated DCN to core DCN was reduced in P0 and 1 mo lum(-/-) hearts. There was also a reduction in the β and γ forms of collagenα1(I) in lum(-/-) hearts. While the total insoluble collagen content was significantly reduced, the fibril size was increased in lum(-/-) hearts, indicating that LUM may play a role in collagen fiber stability and lateral fibril assembly. These results suggest that LUM controls cardiomyocyte growth by regulating the pericellular ECM and also indicates that LUM may coordinate

  17. Developmental Stage-dependent Regulation of Prolyl 3-Hydroxylation in Tendon Type I Collagen.

    PubMed

    Taga, Yuki; Kusubata, Masashi; Ogawa-Goto, Kiyoko; Hattori, Shunji

    2016-01-01

    3-Hydroxyproline (3-Hyp), which is unique to collagen, is a fairly rare post-translational modification. Recent studies have suggested a function of prolyl 3-hydroxylation in fibril assembly and its relationships with certain disorders, including recessive osteogenesis imperfecta and high myopia. However, no direct evidence for the physiological and pathological roles of 3-Hyp has been presented. In this study, we first estimated the overall alterations in prolyl hydroxylation in collagens purified from skin, bone, and tail tendon of 0.5-18-month-old rats by LC-MS analysis with stable isotope-labeled collagen, which was recently developed as an internal standard for highly accurate collagen analyses. 3-Hyp was found to significantly increase in tendon collagen until 3 months after birth and then remain constant, whereas increased prolyl 3-hydroxylation was not observed in skin and bone collagen. Site-specific analysis further revealed that 3-Hyp was increased in tendon type I collagen in a specific sequence region, including a previously known modification site at Pro(707) and newly identified sites at Pro(716) and Pro(719), at the early ages. The site-specific alterations in prolyl 3-hydroxylation with aging were also observed in bovine Achilles tendon. We postulate that significant increases in 3-Hyp at the consecutive modification sites are correlated with tissue development in tendon. The present findings suggest that prolyl 3-hydroxylation incrementally regulates collagen fibril diameter in tendon. PMID:26567337

  18. COMP-assisted collagen secretion--a novel intracellular function required for fibrosis.

    PubMed

    Schulz, Jan-Niklas; Nüchel, Julian; Niehoff, Anja; Bloch, Wilhelm; Schönborn, Katrin; Hayashi, Shujiro; Kamper, Matthias; Brinckmann, Jürgen; Plomann, Markus; Paulsson, Mats; Krieg, Thomas; Zaucke, Frank; Eckes, Beate

    2016-02-15

    Cartilage oligomeric matrix protein (COMP) is an abundant component in the extracellular matrix (ECM) of load-bearing tissues such as tendons and cartilage. It provides adaptor functions by bridging different ECM structures. We have previously shown that COMP is also a constitutive component of healthy human skin and is strongly induced in fibrosis. It binds directly and with high affinity to collagen I and to collagen XII that decorates the surface of collagen I fibrils. We demonstrate here that lack of COMP-collagen interaction in the extracellular space leads to changes in collagen fibril morphology and density, resulting in altered skin biomechanical properties. Surprisingly, COMP also fulfills an important intracellular function in assisting efficient secretion of collagens, which were retained in the endoplasmic reticulum of COMP-null fibroblasts. Accordingly, COMP-null mice showed severely attenuated fibrotic responses in skin. Collagen secretion was fully restored by introducing wild-type COMP. Hence, our work unravels a new, non-structural and intracellular function of the ECM protein COMP in controlling collagen secretion. PMID:26746240

  19. On the Presence of Affine Fibril and Fiber Kinematics in the Mitral Valve Anterior Leaflet

    PubMed Central

    Lee, Chung-Hao; Zhang, Will; Liao, Jun; Carruthers, Christopher A.; Sacks, Jacob I.; Sacks, Michael S.

    2015-01-01

    In this study, we evaluated the hypothesis that the constituent fibers follow an affine deformation kinematic model for planar collagenous tissues. Results from two experimental datasets were utilized, taken at two scales (nanometer and micrometer), using mitral valve anterior leaflet (MVAL) tissues as the representative tissue. We simulated MVAL collagen fiber network as an ensemble of undulated fibers under a generalized two-dimensional deformation state, by representing the collagen fibrils based on a planar sinusoidally shaped geometric model. The proposed approach accounted for collagen fibril amplitude, crimp period, and rotation with applied macroscopic tissue-level deformation. When compared to the small angle x-ray scattering measurements, the model fit the data well, with an r2 = 0.976. This important finding suggests that, at the homogenized tissue-level scale of ∼1 mm, the collagen fiber network in the MVAL deforms according to an affine kinematics model. Moreover, with respect to understanding its function, affine kinematics suggests that the constituent fibers are largely noninteracting and deform in accordance with the bulk tissue. It also suggests that the collagen fibrils are tightly bounded and deform as a single fiber-level unit. This greatly simplifies the modeling efforts at the tissue and organ levels, because affine kinematics allows a straightforward connection between the macroscopic and local fiber strains. It also suggests that the collagen and elastin fiber networks act independently of each other, with the collagen and elastin forming long fiber networks that allow for free rotations. Such freedom of rotation can greatly facilitate the observed high degree of mechanical anisotropy in the MVAL and other heart valves, which is essential to heart valve function. These apparently novel findings support modeling efforts directed toward improving our fundamental understanding of tissue biomechanics in healthy and diseased conditions

  20. Collagen Accumulation in Osteosarcoma Cells lacking GLT25D1 Collagen Galactosyltransferase.

    PubMed

    Baumann, Stephan; Hennet, Thierry

    2016-08-26

    Collagen is post-translationally modified by prolyl and lysyl hydroxylation and subsequently by glycosylation of hydroxylysine. Despite the widespread occurrence of the glycan structure Glc(α1-2)Gal linked to hydroxylysine in animals, the functional significance of collagen glycosylation remains elusive. To address the role of glycosylation in collagen expression, folding, and secretion, we used the CRISPR/Cas9 system to inactivate the collagen galactosyltransferase GLT25D1 and GLT25D2 genes in osteosarcoma cells. Loss of GLT25D1 led to increased expression and intracellular accumulation of collagen type I, whereas loss of GLT25D2 had no effect on collagen secretion. Inactivation of the GLT25D1 gene resulted in a compensatory induction of GLT25D2 expression. Loss of GLT25D1 decreased collagen glycosylation by up to 60% but did not alter collagen folding and thermal stability. Whereas cells harboring individually inactivated GLT25D1 and GLT25D2 genes could be recovered and maintained in culture, cell clones with simultaneously inactive GLT25D1 and GLT25D2 genes could be not grown and studied, suggesting that a complete loss of collagen glycosylation impairs osteosarcoma cell proliferation and viability. PMID:27402836

  1. Polyvinyl alcohol-graft-polyethylene glycol hydrogels improve utility and biofunctionality of injectable collagen biomaterials.

    PubMed

    Hartwell, Ryan; Chan, Ben; Elliott, Keenan; Alnojeidi, Hatem; Ghahary, Aziz

    2016-01-01

    Collagen-based materials have become a staple in both research and the clinic. In wound care, collagen-based materials comprise a core gamut of biological dressings and therapeutic strategies. In research, collagen-based materials are employed in everything from 3D cultures to bioprinting. Soluble collagen is well characterized to undergo fibrillation at neutral pH and 37 °C. To remain stable, a neutralized collagen solution must be maintained at 4 °C. These physical characteristics of collagen impose limitations on its utility. In our previous work, we identified that the incorporation of a simple polyvinyl alcohol:borate hydrogel could improve the rate of collagen gel fibrillation. In this work we sought to further investigate the interactions of polyvinyl alcohol blend variants, as surfactant-like polymers, in comparison with known non-polymer surfactants. To conduct our investigations scaffold variants were created using increasing concentrations of polyvinyl alcohol, differing combinations of polymers, and non-polymer surfactants Tweens 20 and 80, and TritonX-100. Activation energy for collagen fibrillation was found to significantly decrease in the presence of polyvinyl alcohols (p  <  0.01) at and above 0.4%w/v concentration. Further, addition of polyvinyl alcohol-graft-polyethylene glycol had the greatest enhancement (2.02 fold) on the fibrillation kinetics (p  <  0.01), wetting properties and the stability of the collagen scaffolds post-freeze drying. Our results demonstrated that the addition of polyvinyl alcohol hydrogels to a collagen solution could stabilize collagen solution such that the solution could easily be lyophilized (at pH 7) and then reconstituted with water. Cells cultured in polyvinyl alcohol scaffolds also exhibited more organized F-actin, as well as a reduced abundance of pro-collagen and α-smooth actin. In conclusion, our results demonstrate for the first time that polyvinyl alcohol, preferably polyvinyl alcohol

  2. Impact of temperature and electrical potentials on the stability and structure of collagen adsorbed on the gold electrode

    NASA Astrophysics Data System (ADS)

    Meiners, Frank; Ahlers, Michael; Brand, Izabella; Wittstock, Gunther

    2015-01-01

    The morphology and structure of collagen type I adsorbed on gold electrodes were studied as a function of electrode potential and temperature by means of capacitance measurements, polarization modulation infrared reflection-absorption spectroscopy and scanning force microscopy at temperatures of 37 °C, 43 °C and 50 °C. The selected temperatures corresponded to the normal body temperature, temperature of denaturation of collagen molecules and denaturation of collagen fibrils, respectively. Independently of the solution temperature, collagen was adsorbed on gold electrodes in the potential range - 0.7 V < E < 0.4 V vs. Ag/AgCl, where the protein film was very stable. Fragments of collagen molecules made a direct contact to the gold surface and water was present in the film. Protein molecules were oriented preferentially with their long axis towards the gold surface. Collagen molecules in the adsorbed state preserved their native triple helical structure even at temperatures corresponding to collagen denaturation in aqueous solutions. Application of E < - 0.75 V vs. Ag/AgCl leads to the swelling of the protein film by water and desorption from the electrode surface. IR spectra provided no evidence of the thermal denaturation of adsorbed collagen molecules. A temperature increase to 50 °C leads to a distortion of the collagen film. The processes of aggregation and fibrilization were preferred over thermal denaturation for collagen adsorbed on the electrode surface and exposed to changing potentials.

  3. Lung response to ultrafine Kevlar aramid synthetic fibrils following 2-year inhalation exposure in rats.

    PubMed

    Lee, K P; Kelly, D P; O'Neal, F O; Stadler, J C; Kennedy, G L

    1988-07-01

    Four groups of 100 male and 100 female rats were exposed to ultrafine Kevlar fibrils at concentrations of 0, 2.5, 25, and 100 fibrils/cc for 6 hr/day, 5 days/week for 2 years. One group was exposed to 400 fibrils/cc for 1 year and allowed to recover for 1 year. At 2.5 fibrils/cc, the lungs had normal alveolar architecture with a few dust-laden macrophages (dust cell response) in the alveolar airspaces. At 25 fibrils/cc, the lungs showed a dust cell response, slight Type II pneumocyte hyperplasia, alveolar bronchiolarization, and a negligible amount of collagenized fibrosis in the alveolar duct region. At 100 fibrils/cc, the same pulmonary responses were seen as at 25 fibrils/cc. In addition, cystic keratinizing squamous cell carcinoma (CKSCC) was found in 4 female rats, but not in male rats. Female rats had more prominent foamy alveolar macrophages, cholesterol granulomas, and alveolar bronchiolarization. These pulmonary lesions were related to the development of CKSCC. The lung tumors were derived from metaplastic squamous cells in areas of alveolar bronchiolarization. At 400 fibrils/cc following 1 year of recovery, the lung dust content, average fiber length, and the pulmonary lesions were markedly reduced, but slight centriacinar emphysema and minimal collagenized fibrosis were found in the alveolar duct region. One male and 6 female rats developed CKSCC. The lung tumors were a unique type of experimentally induced tumors in the rats and have not been seen as spontaneous tumors in man or animals. Therefore, the relevance of this type of lung tumor to the human situation is minimal. PMID:3209007

  4. Ovine tendon collagen: Extraction, characterisation and fabrication of thin films for tissue engineering applications.

    PubMed

    Fauzi, M B; Lokanathan, Y; Aminuddin, B S; Ruszymah, B H I; Chowdhury, S R

    2016-11-01

    Collagen is the most abundant extracellular matrix (ECM) protein in the human body, thus widely used in tissue engineering and subsequent clinical applications. This study aimed to extract collagen from ovine (Ovis aries) Achilles tendon (OTC), and to evaluate its physicochemical properties and its potential to fabricate thin film with collagen fibrils in a random or aligned orientation. Acid-solubilized protein was extracted from ovine Achilles tendon using 0.35M acetic acid, and 80% of extracted protein was measured as collagen. SDS-PAGE and mass spectrometry analysis revealed the presence of alpha 1 and alpha 2 chain of collagen type I (col I). Further analysis with Fourier transform infrared spectrometry (FTIR), X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS) confirms the presence of triple helix structure of col I, similar to commercially available rat tail col I. Drying the OTC solution at 37°C resulted in formation of a thin film with randomly orientated collagen fibrils (random collagen film; RCF). Introduction of unidirectional mechanical intervention using a platform rocker prior to drying facilitated the fabrication of a film with aligned orientation of collagen fibril (aligned collagen film; ACF). It was shown that both RCF and ACF significantly enhanced human dermal fibroblast (HDF) attachment and proliferation than that on plastic surface. Moreover, cells were distributed randomly on RCF, but aligned with the direction of mechanical intervention on ACF. In conclusion, ovine tendon could be an alternative source of col I to fabricate scaffold for tissue engineering applications. PMID:27524008

  5. Structural aspects of the calcification process of lower vertebrate collagen.

    PubMed

    Bigi, A; Koch, M H; Panzavolta, S; Roveri, N; Rubini, K

    2000-01-01

    In order to investigate the structural relationship between inorganic phase and collagen fibrils in the calcified tissues of lower vertebrates we have carried out a wide and small angle X-ray diffraction investigation on carp scales and bone samples. The small angle patterns from decalcified bone and scales, as well as uncalcified tendon samples from carp are very similar to that of type I collagen from higher vertebrates. The D-axial period, 67 nm, is the same as that of higher vertebrate type I collagen, while the most significant difference is the relatively low intensity of the first order reflection, which is, however, the most intense. The relative intensity distributions of the meridional reflections recorded from fish bone and scales are in agreement with an electron density distribution according to a step function. The calculated step length is very close to the values previously reported for calcified tissues from higher vertebrates. The small angle reflections from calcified, as well as decalcified, scales display different directions of orientation, which could be in agreement with a plywood arrangement of collagen fibrils in successive sheets parallel to the plane of the scale. PMID:10826707

  6. Phase matching of backward second harmonic generation assisted by lattice structure in collagen tissues.

    PubMed

    Shen, Mengzhe; Zeng, Haishan; Tang, Shuo

    2015-10-01

    Phase matching of backward second harmonic generation (SHG) in a periodic structure of collagen fibrils is investigated through theoretical modeling, simulation, and experiments. The lattice structure of collagen fibrils is considered to provide a virtual momentum for assisting the phase matching of backward SHG. Phase matching over a relatively wide excitation wavelength range is achieved by tilting the angle of the fundamental excitation and SHG wave vectors. The SHG intensity in the periodic structure is simulated to quantify the phase matching effect. The effect of the fundamental excitation and the SHG emission angles on the peak excitation wavelength of the SHG excitation spectrum is further validated in experiments, where the excitation and emission angles are controlled by spatial filtering. It is found that an optimized excitation wavelength exists for a certain collagen fibril structure, which shifts toward a shorter wavelength when the excitation and emission angles are increased. Our results show that the lattice structure of collagen fibrils can assist the phase matching, providing a mechanism for generating backward SHG in multiphoton microscopy. PMID:26502229

  7. Phase matching of backward second harmonic generation assisted by lattice structure in collagen tissues

    NASA Astrophysics Data System (ADS)

    Shen, Mengzhe; Zeng, Haishan; Tang, Shuo

    2015-10-01

    Phase matching of backward second harmonic generation (SHG) in a periodic structure of collagen fibrils is investigated through theoretical modeling, simulation, and experiments. The lattice structure of collagen fibrils is considered to provide a virtual momentum for assisting the phase matching of backward SHG. Phase matching over a relatively wide excitation wavelength range is achieved by tilting the angle of the fundamental excitation and SHG wave vectors. The SHG intensity in the periodic structure is simulated to quantify the phase matching effect. The effect of the fundamental excitation and the SHG emission angles on the peak excitation wavelength of the SHG excitation spectrum is further validated in experiments, where the excitation and emission angles are controlled by spatial filtering. It is found that an optimized excitation wavelength exists for a certain collagen fibril structure, which shifts toward a shorter wavelength when the excitation and emission angles are increased. Our results show that the lattice structure of collagen fibrils can assist the phase matching, providing a mechanism for generating backward SHG in multiphoton microscopy.

  8. Genetics Home Reference: familial atrial fibrillation

    MedlinePlus

    ... fibrillation also increases the risk of stroke and sudden death. Complications of familial atrial fibrillation can occur at ... beats , increasing the risk of syncope, stroke, and sudden death. Most cases of atrial fibrillation are not caused ...

  9. Reinforcement of polymeric structures with asbestos fibrils

    NASA Technical Reports Server (NTRS)

    Rader, C. A.; Schwartz, A. M.

    1970-01-01

    Investigation determines structural potential of asbestos fibrils. Methods are developed for dispersing macrofibers of the asbestos into colloidal-sized ultimate fibrils and incorporating these fibrils in matrices without causing reagglomeration.

  10. Forward versus backward polarization-resolved SHG imaging of collagen structure in tissues

    NASA Astrophysics Data System (ADS)

    Teulon, Claire; Gusachenko, Ivan; Latour, Gaël.; Schanne-Klein, Marie-Claire

    2016-03-01

    Second harmonic generation (SHG) is a powerful technique to observe fibrillar collagen without any staining and with a good contrast. More information about the molecular structure of collagen fibrils in tissues and their 3D distribution can be gained with polarization-resolved SHG imaging. Nevertheless, strong focusing is required for effective imaging and light propagation in tissues is complex and not thoroughly understood yet, preventing accurate and reproducible measurements. Theoretical analysis, vectorial numerical simulations and experiments were implemented to understand how the SHG signal builds up and how geometrical parameters affect polarization-resolved measurements in homogeneous collagen-rich tissues.

  11. Atrial fibrillation and inflammation

    PubMed Central

    Ozaydin, Mehmet

    2010-01-01

    Atrial fibrillation (AF) is the most common clinical arrhythmia. Recent investigations have suggested that inflammation might have a role in the pathophysiology of AF. In this review, the association between inflammation and AF, and the effects of several agents that have anti-inflammatory actions, such as statins, polyunsaturated fatty acids, corticosteroids and angiotensin-converting enzyme inhibitors and angiotensin receptor blockers, have been investigated. PMID:21160591

  12. Atrial fibrillation case study.

    PubMed

    Johnson, Sarah; Wilson, Tracey

    2016-03-01

    This article discusses the irregular heart rhythm caused by atrial fibrillation (AF). A brief overview of the pathophysiology will be provided. A case study is discussed to highlight the treatment and management of AF. The care provision describes common signs and symptoms and also the treatment and management of AF within the maternity care setting. The importance of maintaining the mother-baby dyad is highlighted. For the purpose of maintaining confidentiality the woman will be referred to as Shama. PMID:27044188

  13. Intrafibrillar plasticity through mineral/collagen sliding is the dominant mechanism for the extreme toughness of antler bone.

    PubMed

    Gupta, H S; Krauss, S; Kerschnitzki, M; Karunaratne, A; Dunlop, J W C; Barber, A H; Boesecke, P; Funari, S S; Fratzl, P

    2013-12-01

    The inelastic deformability of the mineralised matrix in bones is critical to their high toughness, but the nanoscale mechanisms are incompletely understood. Antler is a tough bone type, with a nanostructure composed of mineralised collagen fibrils ∼100nm diameter. We track the fibrillar deformation of antler tissue during cyclic loading using in situ synchrotron small-angle X-ray diffraction (SAXD), finding that residual strain remains in the fibrils after the load was removed. During repeated unloading/reloading cycles, the fibril strain shows minimal hysteresis when plotted as a function of tissue strain, indicating that permanent plastic strain accumulates inside the fibril. We model the tensile response of the mineralised collagen fibril by a two - level staggered model - including both elastic - and inelastic regimes - with debonding between mineral and collagen within fibrils triggering macroscopic inelasticity. In the model, the subsequent frictional sliding at intrafibrillar mineral/collagen interfaces accounts for subsequent inelastic deformation of the tissue in tension. The model is compared to experimental measurements of fibrillar and mineral platelet strain during tensile deformation, measured by in situ synchrotron SAXD and wide-angle X-ray diffraction (WAXD) respectively, as well as macroscopic tissue stress and strain. By fitting the model predictions to experimentally observed parameters like the yield point, elastic modulus and post-yield slope, extremely good agreement is found between the model and experimental data at both the macro- and at the nanoscale. Our results provide strong evidence that intrafibrillar sliding between mineral and collagen leads to permanent plastic strain at both the fibril and the tissue level, and that the energy thus dissipated is a significant factor behind the high toughness of antler bone. PMID:23707600

  14. Identification of cooked bone using TEM imaging of bone collagen.

    PubMed

    Koon, Hannah E C

    2012-01-01

    Mild heating (≤100° C, 1 h)-typical of cooking-does not lead to detectable changes in any biochemical parameter yet measured; consequently bones that have been cooked, but which have not reached a temperature that will induce charring go undetected. We have used a microscopy based approach to investigate changes in the organization of the bone protein, collagen, as it is heated, using bone from heating experiments, short term burials, and archaeological sites. The work has revealed that the presence of a mineral matrix stabilizes the collagen enabling the damage to accumulate, but preventing it from causing immediate gelatinization. Once the mineral is removed, the damage can be observed using appropriate visualization methods. This chapter describes the transmission electron microscopy (TEM) technique that has been used to detect cooked bone by visualizing minor heat-induced damage at the level of the collagen fibril. PMID:22907413

  15. Lysyl Hydroxylase 3-mediated Glucosylation in Type I Collagen

    PubMed Central

    Sricholpech, Marnisa; Perdivara, Irina; Yokoyama, Megumi; Nagaoka, Hideaki; Terajima, Masahiko; Tomer, Kenneth B.; Yamauchi, Mitsuo

    2012-01-01

    Recently, by employing the short hairpin RNA technology, we have generated MC3T3-E1 (MC)-derived clones stably suppressing lysyl hydroxylase 3 (LH3) (short hairpin (Sh) clones) and demonstrated the LH3 function as glucosyltransferase in type I collagen (Sricholpech, M., Perdivara, I., Nagaoka, H., Yokoyama, M., Tomer, K. B., and Yamauchi, M. (2011) Lysyl hydroxylase 3 glucosylates galactosylhydroxylysine residues in type I collagen in osteoblast culture. J. Biol. Chem. 286, 8846–8856). To further elucidate the biological significance of this modification, we characterized and compared type I collagen phenotypes produced by Sh clones and two control groups, MC and those transfected with empty vector. Mass spectrometric analysis identified five glycosylation sites in type I collagen (i.e. α1,2-87, α1,2-174, and α2-219. Of these, the predominant glycosylation site was α1-87, one of the major helical cross-linking sites. In Sh collagen, the abundance of glucosylgalactosylhydroxylysine was significantly decreased at all of the five sites with a concomitant increase in galactosylhydroxylysine at four of these sites. The collagen cross-links were significantly diminished in Sh clones, and, for the major cross-link, dihydroxylysinonorleucine (DHLNL), glucosylgalactosyl-DHLNL was diminished with a concomitant increase in galactosyl-DHLNL. When subjected to in vitro incubation, in Sh clones, the rate of decrease in DHLNL was lower, whereas the rate of increase in its maturational cross-link, pyridinoline, was comparable with controls. Furthermore, in Sh clones, the mean diameters of collagen fibrils were significantly larger, and the onset of mineralized nodule formation was delayed when compared with those of controls. These results indicate that the LH3-mediated glucosylation occurs at the specific molecular loci in the type I collagen molecule and plays critical roles in controlling collagen cross-linking, fibrillogenesis, and mineralization. PMID:22573318

  16. Enigmatic insight into collagen.

    PubMed

    Deshmukh, Shrutal Narendra; Dive, Alka M; Moharil, Rohit; Munde, Prashant

    2016-01-01

    Collagen is a unique, triple helical molecule which forms the major part of extracellular matrix. It is the most abundant protein in the human body, representing 30% of its dry weight. It is the fibrous structural protein that makes up the white fibers (collagen fibers) of skin, tendons, bones, cartilage and all other connective tissues. Collagens are not only essential for the mechanical resistance and resilience of multicellular organisms, but are also signaling molecules defining cellular shape and behavior. The human body has at least 16 types of collagen, but the most prominent types are I, II and III. Collagens are produced by several cell types and are distinguishable by their molecular compositions, morphologic characteristics, distribution, functions and pathogenesis. This is the major fibrous glycoprotein present in the extracellular matrix and in connective tissue and helps in maintaining the structural integrity of these tissues. It has a triple helical structure. Various studies have proved that mutations that modify folding of the triple helix result in identifiable genetic disorders. Collagen diseases share certain similarities with autoimmune diseases, because autoantibodies specific to each collagen disease are produced. Therefore, this review highlights the role of collagen in normal health and also the disorders associated with structural and functional defects in collagen. PMID:27601823

  17. Collagen and gelatin.

    PubMed

    Liu, Dasong; Nikoo, Mehdi; Boran, Gökhan; Zhou, Peng; Regenstein, Joe M

    2015-01-01

    Collagen and gelatin have been widely used in the food, pharmaceutical, and cosmetic industries due to their excellent biocompatibility, easy biodegradability, and weak antigenicity. Fish collagen and gelatin are of renewed interest, owing to the safety and religious concerns of their mammalian counterparts. The structure of collagen has been studied using various modern technologies, and interpretation of the raw data should be done with caution. The structure of collagen may vary with sources and seasons, which may affect its applications and optimal extraction conditions. Numerous studies have investigated the bioactivities and biological effects of collagen, gelatin, and their hydrolysis peptides, using both in vitro and in vivo assay models. In addition to their established nutritional value as a protein source, collagen and collagen-derived products may exert various potential biological activities on cells in the extracellular matrix through the corresponding food-derived peptides after ingestion, and this might justify their applications in dietary supplements and pharmaceutical preparations. Moreover, an increasing number of novel applications have been found for collagen and gelatin. Therefore, this review covers the current understanding of the structure, bioactivities, and biological effects of collagen, gelatin, and gelatin hydrolysates as well as their most recent applications. PMID:25884286

  18. Enigmatic insight into collagen

    PubMed Central

    Deshmukh, Shrutal Narendra; Dive, Alka M; Moharil, Rohit; Munde, Prashant

    2016-01-01

    Collagen is a unique, triple helical molecule which forms the major part of extracellular matrix. It is the most abundant protein in the human body, representing 30% of its dry weight. It is the fibrous structural protein that makes up the white fibers (collagen fibers) of skin, tendons, bones, cartilage and all other connective tissues. Collagens are not only essential for the mechanical resistance and resilience of multicellular organisms, but are also signaling molecules defining cellular shape and behavior. The human body has at least 16 types of collagen, but the most prominent types are I, II and III. Collagens are produced by several cell types and are distinguishable by their molecular compositions, morphologic characteristics, distribution, functions and pathogenesis. This is the major fibrous glycoprotein present in the extracellular matrix and in connective tissue and helps in maintaining the structural integrity of these tissues. It has a triple helical structure. Various studies have proved that mutations that modify folding of the triple helix result in identifiable genetic disorders. Collagen diseases share certain similarities with autoimmune diseases, because autoantibodies specific to each collagen disease are produced. Therefore, this review highlights the role of collagen in normal health and also the disorders associated with structural and functional defects in collagen. PMID:27601823

  19. Cell Adhesion on Amyloid Fibrils Lacking Integrin Recognition Motif.

    PubMed

    Jacob, Reeba S; George, Edna; Singh, Pradeep K; Salot, Shimul; Anoop, Arunagiri; Jha, Narendra Nath; Sen, Shamik; Maji, Samir K

    2016-03-01

    Amyloids are highly ordered, cross-β-sheet-rich protein/peptide aggregates associated with both human diseases and native functions. Given the well established ability of amyloids in interacting with cell membranes, we hypothesize that amyloids can serve as universal cell-adhesive substrates. Here, we show that, similar to the extracellular matrix protein collagen, amyloids of various proteins/peptides support attachment and spreading of cells via robust stimulation of integrin expression and formation of integrin-based focal adhesions. Additionally, amyloid fibrils are also capable of immobilizing non-adherent red blood cells through charge-based interactions. Together, our results indicate that both active and passive mechanisms contribute to adhesion on amyloid fibrils. The present data may delineate the functional aspect of cell adhesion on amyloids by various organisms and its involvement in human diseases. Our results also raise the exciting possibility that cell adhesivity might be a generic property of amyloids. PMID:26742841

  20. Electroactive biomimetic collagen-silver nanowire composite scaffolds

    NASA Astrophysics Data System (ADS)

    Wickham, Abeni; Vagin, Mikhail; Khalaf, Hazem; Bertazzo, Sergio; Hodder, Peter; Dånmark, Staffan; Bengtsson, Torbjörn; Altimiras, Jordi; Aili, Daniel

    2016-07-01

    Electroactive biomaterials are widely explored as bioelectrodes and as scaffolds for neural and cardiac regeneration. Most electrodes and conductive scaffolds for tissue regeneration are based on synthetic materials that have limited biocompatibility and often display large discrepancies in mechanical properties with the surrounding tissue causing problems during tissue integration and regeneration. This work shows the development of a biomimetic nanocomposite material prepared from self-assembled collagen fibrils and silver nanowires (AgNW). Despite consisting of mostly type I collagen fibrils, the homogeneously embedded AgNWs provide these materials with a charge storage capacity of about 2.3 mC cm-2 and a charge injection capacity of 0.3 mC cm-2, which is on par with bioelectrodes used in the clinic. The mechanical properties of the materials are similar to soft tissues with a dynamic elastic modulus within the lower kPa range. The nanocomposites also support proliferation of embryonic cardiomyocytes while inhibiting the growth of both Gram-negative Escherichia coli and Gram-positive Staphylococcus epidermidis. The developed collagen/AgNW composites thus represent a highly attractive bioelectrode and scaffold material for a wide range of biomedical applications.Electroactive biomaterials are widely explored as bioelectrodes and as scaffolds for neural and cardiac regeneration. Most electrodes and conductive scaffolds for tissue regeneration are based on synthetic materials that have limited biocompatibility and often display large discrepancies in mechanical properties with the surrounding tissue causing problems during tissue integration and regeneration. This work shows the development of a biomimetic nanocomposite material prepared from self-assembled collagen fibrils and silver nanowires (AgNW). Despite consisting of mostly type I collagen fibrils, the homogeneously embedded AgNWs provide these materials with a charge storage capacity of about 2.3 mC cm-2

  1. Mechano-regulation of Collagen Biosynthesis in Periodontal Ligament

    PubMed Central

    Kaku, Masaru; Yamauchi, Mitsuo

    2014-01-01

    Purpose Periodontal ligament (PDL) plays critical roles in the development and maintenance of periodontium such as tooth eruption and dissipation of masticatory force. The mechanical properties of PDL are mainly derived from fibrillar type I collagen, the most abundant extracellular component. Study selection The biosynthesis of type I collagen is a long, complex process including a number of intra- and extracellular post-translational modifications. The final modification step is the formation of covalent intra- and intermolecular cross-links that provide collagen fibrils with stability and connectivity. Results It is now clear that collagen post-translational modifications are regulated by groups of specific enzymes and associated molecules in a tissue-specific manner; and these modifications appear to change in response to mechanical force. Conclusions This review focuses on the effect of mechanical loading on collagen biosynthesis and fibrillogenesis in PDL with emphasis on the post-translational modifications of collagens, which is an important molecular aspect to understand in the field of prosthetic dentistry. PMID:25311991

  2. Structural basis for collagen recognition by the immune receptor OSCAR

    PubMed Central

    Zhou, Long; Hinerman, Jennifer M.; Blaszczyk, Michal; Miller, Jeanette L. C.; Conrady, Deborah G.; Barrow, Alexander D.; Chirgadze, Dimitri Y.; Bihan, Dominique; Farndale, Richard W.

    2016-01-01

    The osteoclast-associated receptor (OSCAR) is a collagen-binding immune receptor with important roles in dendritic cell maturation and activation of inflammatory monocytes as well as in osteoclastogenesis. The crystal structure of the OSCAR ectodomain is presented, both free and in complex with a consensus triple-helical peptide (THP). The structures revealed a collagen-binding site in each immunoglobulin-like domain (D1 and D2). The THP binds near a predicted collagen-binding groove in D1, but a more extensive interaction with D2 is facilitated by the unusually wide D1-D2 interdomain angle in OSCAR. Direct binding assays, combined with site-directed mutagenesis, confirm that the primary collagen-binding site in OSCAR resides in D2, in marked contrast to the related collagen receptors, glycoprotein VI (GPVI) and leukocyte-associated immunoglobulin-like receptor-1 (LAIR-1). Monomeric OSCAR D1D2 binds to the consensus THP with a KD of 28 µM measured in solution, but shows a higher affinity (KD 1.5 μM) when binding to a solid-phase THP, most likely due to an avidity effect. These data suggest a 2-stage model for the interaction of OSCAR with a collagen fibril, with transient, low-affinity interactions initiated by the membrane-distal D1, followed by firm adhesion to the primary binding site in D2. PMID:26552697

  3. Tumor matrix protein collagen XIα1 in cancer

    PubMed Central

    Raglow, Zoe; Thomas, Sufi M

    2015-01-01

    The extracellular matrix is increasingly recognized as an essential player in cancer development and progression. Collagens are one of the most important components of the extracellular matrix, and have themselves been implicated in many aspects of neoplastic transformation. Collagen XI is a minor collagen whose main physiologic function is to regulate the diameter of major collagen fibrils. The α1 chain of collagen XI (colXIα1), has known pathogenic roles in several musculoskeletal disorders. Recent research has highlighted the importance of colXIα1 in many types of cancer, including its roles in metastasis, angiogenesis, and drug resistance, as well as its potential utility in screening tests and as a therapeutic target. High levels of colXIα1 overexpression have been reported in multiple expression profile studies examining differences between cancerous and normal tissue, and between beginning and advanced stage cancer. Its expression has been linked to poor progression-free and overall survival. The consistency of this data across cancer types is particularly striking, including colorectal, ovarian, breast, head and neck, lung, and brain cancers. This review discusses the role of collagen XIα1 in cancer and its potential as a target for cancer therapy. PMID:25511741

  4. Structural basis for collagen recognition by the immune receptor OSCAR.

    PubMed

    Zhou, Long; Hinerman, Jennifer M; Blaszczyk, Michal; Miller, Jeanette L C; Conrady, Deborah G; Barrow, Alexander D; Chirgadze, Dimitri Y; Bihan, Dominique; Farndale, Richard W; Herr, Andrew B

    2016-02-01

    The osteoclast-associated receptor (OSCAR) is a collagen-binding immune receptor with important roles in dendritic cell maturation and activation of inflammatory monocytes as well as in osteoclastogenesis. The crystal structure of the OSCAR ectodomain is presented, both free and in complex with a consensus triple-helical peptide (THP). The structures revealed a collagen-binding site in each immunoglobulin-like domain (D1 and D2). The THP binds near a predicted collagen-binding groove in D1, but a more extensive interaction with D2 is facilitated by the unusually wide D1-D2 interdomain angle in OSCAR. Direct binding assays, combined with site-directed mutagenesis, confirm that the primary collagen-binding site in OSCAR resides in D2, in marked contrast to the related collagen receptors, glycoprotein VI (GPVI) and leukocyte-associated immunoglobulin-like receptor-1 (LAIR-1). Monomeric OSCAR D1D2 binds to the consensus THP with a KD of 28 µM measured in solution, but shows a higher affinity (KD 1.5 μM) when binding to a solid-phase THP, most likely due to an avidity effect. These data suggest a 2-stage model for the interaction of OSCAR with a collagen fibril, with transient, low-affinity interactions initiated by the membrane-distal D1, followed by firm adhesion to the primary binding site in D2. PMID:26552697

  5. Human collagen produced in plants: more than just another molecule.

    PubMed

    Shoseyov, Oded; Posen, Yehudit; Grynspan, Frida

    2014-01-01

    Consequential to its essential role as a mechanical support and affinity regulator in extracellular matrices, collagen constitutes a highly sought after scaffolding material for regeneration and healing applications. However, substantiated concerns have been raised with regard to quality and safety of animal tissue-extracted collagen, particularly in relation to its immunogenicity, risk of disease transmission and overall quality and consistency. In parallel, contamination with undesirable cellular factors can significantly impair its bioactivity, vis-a-vis its impact on cell recruitment, proliferation and differentiation. High-scale production of recombinant human collagen Type I (rhCOL1) in the tobacco plant provides a source of an homogenic, heterotrimeric, thermally stable "virgin" collagen which self assembles to fine homogenous fibrils displaying intact binding sites and has been applied to form numerous functional scaffolds for tissue engineering and regenerative medicine. In addition, rhCOL1 can form liquid crystal structures, yielding a well-organized and mechanically strong membrane, two properties indispensable to extracellular matrix (ECM) mimicry. Overall, the shortcomings of animal- and cadaver-derived collagens arising from their source diversity and recycled nature are fully overcome in the plant setting, constituting a collagen source ideal for tissue engineering and regenerative medicine applications. PMID:23941988

  6. Cervical Softening During Pregnancy: Regulated Changes in Collagen Cross-Linking and Composition of Matricellular Proteins in the Mouse1

    PubMed Central

    Akins, Meredith L.; Luby-Phelps, Katherine; Bank, Ruud A.; Mahendroo, Mala

    2011-01-01

    A greater understanding of the parturition process is essential in the prevention of preterm birth, which occurs in 12.7% of infants born in the United States annually. Cervical remodeling is a critical component of this process. Beginning early in pregnancy, remodeling requires cumulative, progressive changes in the cervical extracellular matrix (ECM) that result in reorganization of collagen fibril structure with a gradual loss of tensile strength. In the current study, we undertook a detailed biochemical analysis of factors in the cervix that modulate collagen structure during early mouse pregnancy, including expression of proteins involved in processing of procollagen, assembly of collagen fibrils, cross-link formation, and deposition of collagen in the ECM. Changes in these factors correlated with changes in the types of collagen cross-links formed and packing of collagen fibrils as measured by electron microscopy. Early in pregnancy there is a decline in expression of two matricellular proteins, thrombospondin 2 and tenascin C, as well as a decline in expression of lysyl hydroxylase, which is involved in cross-link formation. These changes are accompanied by a decline in both HP and LP cross-links by gestation Days 12 and 14, respectively, as well as a progressive increase in collagen fibril diameter. In contrast, collagen abundance remains constant over the course of pregnancy. We conclude that early changes in tensile strength during cervical softening result in part from changes in the number and type of collagen cross-links and are associated with a decline in expression of two matricellular proteins thrombospondin 2 and tenascin C. PMID:21248285

  7. Polarization-Modulated Second Harmonic Generation Microscopy in Collagen

    SciTech Connect

    Stoller, P C

    2002-09-30

    Collagen is a key structural protein in the body; several pathological conditions lead to changes in collagen. Among imaging modalities that can be used in vivo, second harmonic generation (SHG) microscopy has a key advantage: it provides {approx}1 {micro}m resolution information about collagen structure as a function of depth. A new technique--polarization-modulated SHG--is presented: it permits simultaneous measurement of collagen orientation, of a lower bound on the magnitude of the second order nonlinear susceptibility tensor, and of the ratio of the two independent elements in this tensor. It is applied to characterizing SHG in collagen and to determining effects of biologically relevant changes in collagen structure. The magnitude of the second harmonic signal in two dimensional images varies with position even in structurally homogeneous tissue; this phenomenon is due to interference between second harmonic light generated by neighboring fibrils, which are randomly oriented parallel or anti-parallel to each other. Studies in which focal spot size was varied indicated that regions where fibrils are co-oriented are less than {approx}1.5 {micro}m in diameter. A quartz reference was used to determine the spot size as well as a lower limit (d{sub xxx} > 0.3 pm/V) for the magnitude of the second order nonlinear susceptibility. The ratio of the two independent tensor elements ranged between d{sub XYY}/d{sub XXX} = 0.60 and 0.75. SHG magnitude alone was not useful for identifying structural anomalies in collagenous tissue. Instead, changes in the polarization dependence of SHG were used to analyze biologically relevant perturbations in collagen structure. Changes in polarization dependence were observed in dehydrated samples, but not in highly crosslinked samples, despite significant alterations in packing structure. Complete thermal denaturation and collagenase digestion produced samples with no detectable SHG signal. Collagen orientation was measured in thin

  8. Experimental and Modeling Study of Collagen Scaffolds with the Effects of Crosslinking and Fiber Alignment

    PubMed Central

    Xu, Bin; Chow, Ming-Jay; Zhang, Yanhang

    2011-01-01

    Collagen type I scaffolds are commonly used due to its abundance, biocompatibility, and ubiquity. Most applications require the scaffolds to operate under mechanical stresses. Therefore understanding and being able to control the structural-functional integrity of collagen scaffolds becomes crucial. Using a combined experimental and modeling approach, we studied the structure and function of Type I collagen gel with the effects of spatial fiber alignment and crosslinking. Aligned collagen scaffolds were created through the flow of magnetic particles enmeshed in collagen fibrils to mimic the anisotropy seen in native tissue. Inter- and intra- molecular crosslinking was modified chemically with Genipin to further improve the stiffness of collagen scaffolds. The anisotropic mechanical properties of collagen scaffolds were characterized using a planar biaxial tensile tester and parallel plate rheometer. The tangent stiffness from biaxial tensile test is two to three orders of magnitude higher than the storage moduli from rheological measurements. The biphasic nature of collagen gel was discussed and used to explain the mechanical behavior of collagen scaffolds under different types of mechanical tests. An anisotropic hyperelastic constitutive model was used to capture the characteristics of the stress-strain behavior exhibited by collagen scaffolds. PMID:21876695

  9. FTIR spectro-imaging of collagen scaffold formation during glioma tumor development.

    PubMed

    Noreen, Razia; Chien, Chia-Chi; Chen, Hsiang-Hsin; Bobroff, Vladimir; Moenner, Michel; Javerzat, Sophie; Hwu, Yeukuang; Petibois, Cyril

    2013-11-01

    Evidence has recently emerged that solid and diffuse tumors produce a specific extracellular matrix (ECM) for division and diffusion, also developing a specific interface with microvasculature. This ECM is mainly composed of collagens and their scaffolding appears to drive tumor growth. Although collagens are not easily analyzable by UV-fluorescence means, FTIR imaging has appeared as a valuable tool to characterize collagen contents in tissues, specially the brain, where ECM is normally devoid of collagen proteins. Here, we used FTIR imaging to characterize collagen content changes in growing glioma tumors. We could determine that C6-derived solid tumors presented high content of triple helix after 8-11 days of growth (typical of collagen fibrils formation; 8/8 tumor samples; 91 % of total variance), and further turned to larger α-helix (days 12-15; 9/10 of tumors; 94 % of variance) and β-turns (day 18-21; 7/8 tumors; 97 % of variance) contents, which suggest the incorporation of non-fibrillar collagen types in ECM, a sign of more and more organized collagen scaffold along tumor progression. The growth of tumors was also associated to the level of collagen produced (P < 0.05). This study thus confirms that collagen scaffolding is a major event accompanying the angiogenic shift and faster tumor growth in solid glioma phenotypes. PMID:24068168

  10. Alterations of Dermal Connective Tissue Collagen in Diabetes: Molecular Basis of Aged-Appearing Skin

    PubMed Central

    Argyropoulos, Angela J.; Robichaud, Patrick; Balimunkwe, Rebecca Mutesi; Fisher, Gary J.; Hammerberg, Craig; Yan, Yan

    2016-01-01

    Alterations of the collagen, the major structural protein in skin, contribute significantly to human skin connective tissue aging. As aged-appearing skin is more common in diabetes, here we investigated the molecular basis of aged-appearing skin in diabetes. Among all known human matrix metalloproteinases (MMPs), diabetic skin shows elevated levels of MMP-1 and MMP-2. Laser capture microdissection (LCM) coupled real-time PCR indicated that elevated MMPs in diabetic skin were primarily expressed in the dermis. Furthermore, diabetic skin shows increased lysyl oxidase (LOX) expression and higher cross-linked collagens. Atomic force microscopy (AFM) further indicated that collagen fibrils were fragmented/disorganized, and key mechanical properties of traction force and tensile strength were increased in diabetic skin, compared to intact/well-organized collagen fibrils in non-diabetic skin. In in vitro tissue culture system, multiple MMPs including MMP-1 and MM-2 were induced by high glucose (25 mM) exposure to isolated primary human skin dermal fibroblasts, the major cells responsible for collagen homeostasis in skin. The elevation of MMPs and LOX over the years is thought to result in the accumulation of fragmented and cross-linked collagen, and thus impairs dermal collagen structural integrity and mechanical properties in diabetes. Our data partially explain why old-looking skin is more common in diabetic patients. PMID:27104752

  11. Engineering and Characterization of Collagen Networks Using Wet Atomic Force Microscopy and Environmental Scanning Electron Microscopy

    NASA Astrophysics Data System (ADS)

    Osborn, Jenna; Coffey, Tonya; Conrad, Brad; Burris, Jennifer; Hester, Brooke

    2014-03-01

    Collagen is an abundant protein and its monomers covalently crosslink to form fibrils which form fibers which contribute to forming macrostructures like tendon or bone. While the contribution is well understood at the macroscopic level, it is not well known at the fibril level. We wish to study the mechanical properties of collagen for networks of collagen fibers that vary in size and density. We present here a method to synthesize collagen networks from monomers and that allows us to vary the density of the networks. By using biotynilated collagen and a surface that is functionalized with avidin, we generate two-dimensional collagen networks across the surface of a silicon wafer. During network synthesis, the incubation time is varied from 30 minutes to 3 hours or temperature is varied from 25°C to 45°C. The two-dimensional collagen network created in the process is characterized using environmental atomic force microscopy (AFM) and scanning electron microscopy (SEM). The network density is measured by the number of strands in one frame using SPIP software. We expect that at body temperature (37°C) and with longer incubation times, the network density should increase.

  12. Second-harmonic generation scattering directionality predicts tumor cell motility in collagen gels

    NASA Astrophysics Data System (ADS)

    Burke, Kathleen A.; Dawes, Ryan P.; Cheema, Mehar K.; Van Hove, Amy; Benoit, Danielle S. W.; Perry, Seth W.; Brown, Edward

    2015-05-01

    Second-harmonic generation (SHG) allows for the analysis of tumor collagen structural changes throughout metastatic progression. SHG directionality, measured through the ratio of the forward-propagating to backward-propagating signal (F/B ratio), is affected by collagen fibril diameter, spacing, and disorder of fibril packing within a fiber. As tumors progress, these parameters evolve, producing concurrent changes in F/B. It has been recently shown that the F/B of highly metastatic invasive ductal carcinoma (IDC) breast tumors is significantly different from less metastatic tumors. This suggests a possible relationship between the microstructure of collagen, as measured by the F/B, and the ability of tumor cells to locomote through that collagen. Utilizing in vitro collagen gels of different F/B ratios, we explored the relationship between collagen microstructure and motility of tumor cells in a "clean" environment, free of the myriad cells, and signals found in in vivo. We found a significant relationship between F/B and the total distance traveled by the tumor cell, as well as both the average and maximum velocities of the cells. Consequently, one possible mechanism underlying the observed relationship between tumor F/B and metastatic output in IDC patient samples is a direct influence of collagen structure on tumor cell motility.

  13. Second-harmonic generation scattering directionality predicts tumor cell motility in collagen gels.

    PubMed

    Burke, Kathleen A; Dawes, Ryan P; Cheema, Mehar K; Van Hove, Amy; Benoit, Danielle S W; Perry, Seth W; Brown, Edward

    2015-05-01

    Second-harmonic generation (SHG) allows for the analysis of tumor collagen structural changes throughout metastatic progression. SHG directionality, measured through the ratio of the forward-propagating to backward-propagating signal (F/B ratio), is affected by collagen fibril diameter, spacing, and disorder of fibril packing within a fiber. As tumors progress, these parameters evolve, producing concurrent changes in F/B. It has been recently shown that the F/B of highly metastatic invasive ductal carcinoma (IDC) breast tumors is significantly different from less metastatic tumors. This suggests a possible relationship between the microstructure of collagen, as measured by the F/B, and the ability of tumor cells to locomote through that collagen. Utilizing in vitro collagen gels of different F/B ratios, we explored the relationship between collagen microstructure and motility of tumor cells in a “clean” environment, free of the myriad cells, and signals found in in vivo. We found a significant relationship between F/B and the total distance traveled by the tumor cell, as well as both the average and maximum velocities of the cells. Consequently, one possible mechanism underlying the observed relationship between tumor F/B and metastatic output in IDC patient samples is a direct influence of collagen structure on tumor cell motility. PMID:25625899

  14. Nano-imaging collagen by atomic force, near-field and nonlinear microscope

    NASA Astrophysics Data System (ADS)

    Lim, Ken Choong; Tang, Jinkai; Li, Hao; Ng, Boon Ping; Kok, Shaw Wei; Wang, Qijie; Zhang, Ying

    2015-03-01

    As the most abundant protein in the human body, collagen has a very important role in vast numbers of bio-medical applications. The unique second order nonlinear properties of fibrillar collagen make it a very important index in nonlinear optical imaging based disease diagnosis of the brain, skin, liver, colon, kidney, bone, heart and other organs in the human body. The second-order nonlinear susceptibility of collagen has been explored at the macroscopic level and was explained as a volume-averaged molecular hyperpolarizability. However, details about the origin of optical second harmonic signals from collagen fibrils at the molecular level are still not clear. Such information is necessary for accurate interpolation of bio-information from nonlinear optical imaging techniques. The later has shown great potential in collagen based disease diagnosis methodologies. In this paper, we report our work using an atomic force microscope (AFM), near field (SNOM) and nonlinear laser scanning microscope (NLSM) to study the structure of collagen fibrils and other pro-collagen structures.

  15. Collagen V-heterozygous and -null supraspinatus tendons exhibit altered dynamic mechanical behaviour at multiple hierarchical scales.

    PubMed

    Connizzo, Brianne K; Han, Lin; Birk, David E; Soslowsky, Louis J

    2016-02-01

    Tendons function using a unique set of mechanical properties governed by the extracellular matrix and its ability to respond to varied multi-axial loads. Reduction of collagen V expression, such as in classic Ehlers-Danlos syndrome, results in altered fibril morphology and altered macroscale mechanical function in both clinical and animal studies, yet the mechanism by which changes at the fibril level lead to macroscale functional changes has not yet been investigated. This study addresses this by defining the multiscale mechanical response of wild-type, collagen V-heterozygous and -null supraspinatus tendons. Tendons were subjected to mechanical testing and analysed for macroscale properties, as well as microscale (fibre re-alignment) and nanoscale (fibril deformation and sliding) responses. In many macroscale parameters, results showed a dose-dependent response with severely decreased properties in the null group. In addition, both heterozygous and null groups responded to load faster than in wild-type tendons via earlier fibre re-alignment and fibril stretch. However, the heterozygous group exhibited increased fibril sliding, while the null group exhibited no fibril sliding. These studies demonstrate that dynamic responses play an important role in determining overall function and that collagen V is a critical regulator in the development of these relationships. PMID:26855746

  16. Effect of Collagen Nanotopography on Keloid Fibroblast Proliferation and Matrix Synthesis: Implications for Dermal Wound Healing

    PubMed Central

    Muthusubramaniam, Lalitha; Zaitseva, Tatiana; Paukshto, Michael; Martin, George

    2014-01-01

    Keloids are locally exuberant dermal scars characterized by excessive fibroblast proliferation and matrix accumulation. Although treatment strategies include surgical removal and intralesional steroid injections, an effective regimen is yet to be established due to a high rate of recurrence. The regressing center and growing margin of the keloid have different collagen architecture and also differ in the rate of proliferation. To investigate whether proliferation is responsive to collagen topography, keloid, scar, and dermal fibroblasts were cultured on nanopatterned scaffolds varying in collagen fibril diameter and alignment-small and large diameter, aligned and random fibrils, and compared to cells grown on flat collagen-coated substrates, respectively. Cell morphology, proliferation, and expression of six genes related to proliferation (cyclin D1), phenotype (α-smooth muscle actin), and matrix synthesis (collagens I and III, and matrix metalloproteinase-1 and -2) were measured to evaluate cell response. Fibril alignment was shown to reduce proliferation and matrix synthesis in all three types of fibroblasts. Further, keloid cells were found to be most responsive to nanotopography. PMID:24724556

  17. Type VII Collagen Replacement Therapy in Recessive Dystrophic Epidermolysis Bullosa-How Much, How Often?

    PubMed

    South, Andrew P; Uitto, Jouni

    2016-06-01

    Recessive dystrophic epidermolysis bullosa is a devastating blistering disease caused by mutations in the COL7A1 gene, which encodes type VII collagen, the major component of anchoring fibrils. The anchoring fibrils in patients with recessive dystrophic epidermolysis bullosa can be morphologically altered, reduced in number, or absent entirely. There is no specific treatment for this disease, but recent advances in gene, protein replacement, or cell-based therapies, with the purpose of delivering functional type VII collagen to the skin, have shown encouraging results in both preclinical and clinical settings. One critical issue is the stability of type VII collagen in anchoring fibrils, which will ultimately determine the dose and frequency of administration of the missing protein. Kühl et al. attempted to determine the half-life of type VII collagen in the skin, tongue, and esophagus of genetically altered mice that express type VII collagen constitutively, but with its expression abrogated by genetic manipulation. Their results revealed a half-life much shorter than previously anticipated, some 30 days. These findings have implications for strategies to be used for protein replacement therapy, and they also suggest that the basement membrane components at the dermal-epidermal junction are subject to ongoing remodeling and turnover. PMID:27212645

  18. Dynamic mechanical behavior of human dentin and collagen: Methods and properties

    NASA Astrophysics Data System (ADS)

    Ryou, Heonjune

    Experimental evaluations of human coronal dentin and its collagen fibrils were performed by Dynamic Mechanical Analysis (DMA) using nanoindentation and Atomic Force Microscopy (AFM). The primary objectives were to quantify the changes in mechanical behavior of intertubular and peritubular dentin with age, and to evaluate the nanostructure and mechanical behavior of the collagen fibrils. Specimens of coronal dentin were evaluated by nanoDMA using single indents and in scanning mode via scanning probe microscopy. Collagen fibrils from coronal dentin were evaluated using Pulse-Force Mode (PFM) AFM (Peakforce QNM). Nanoindentation results showed that there were no significant differences in the storage modulus or complex modulus between the two age groups (18-25 versus 54-83 yrs) for either the intertubular or peritubular dentin. However, there were significant differences in the dampening behavior between the young and old tissues, as represented in the loss modulus and tanϕ responses. For both the intertubular and peritubular components, the capacity for dampening was significantly lower in the old group. Scanning based nanoDMA showed that the tubules of old dentin exhibit a gradient in elastic behavior, with decrease in elastic modulus from the cuff to the center of tubules filled with newly deposited mineral. AFM results showed that the stiffness of the old dentin fibrils in the peak and trough regions were greater than the young dentin fibrils. In addition, there were significant differences in the dampening behavior between the young and old dentin fibrils, as represented in the energy dissipation, phase angle and loss modulus responses. For both the peak and trough regions, the dissipative capacity was significantly lower in the old dentin fibrils.

  19. He I VECTOR MAGNETOMETRY OF FIELD-ALIGNED SUPERPENUMBRAL FIBRILS

    SciTech Connect

    Schad, T. A.; Penn, M. J.; Lin, H.

    2013-05-10

    Atomic-level polarization and Zeeman effect diagnostics in the neutral helium triplet at 10830 A in principle allow full vector magnetometry of fine-scaled chromospheric fibrils. We present high-resolution spectropolarimetric observations of superpenumbral fibrils in the He I triplet with sufficient polarimetric sensitivity to infer their full magnetic field geometry. He I observations from the Facility Infrared Spectropolarimeter are paired with high-resolution observations of the H{alpha} 6563 A and Ca II 8542 A spectral lines from the Interferometric Bidimensional Spectrometer from the Dunn Solar Telescope in New Mexico. Linear and circular polarization signatures in the He I triplet are measured and described, as well as analyzed with the advanced inversion capability of the ''Hanle and Zeeman Light'' modeling code. Our analysis provides direct evidence for the often assumed field alignment of fibril structures. The projected angle of the fibrils and the inferred magnetic field geometry align within an error of {+-}10 Degree-Sign . We describe changes in the inclination angle of these features that reflect their connectivity with the photospheric magnetic field. Evidence for an accelerated flow ({approx}40 m s{sup -2}) along an individual fibril anchored at its endpoints in the strong sunspot and weaker plage in part supports the magnetic siphon flow mechanism's role in the inverse Evershed effect. However, the connectivity of the outer endpoint of many of the fibrils cannot be established.

  20. The role of polymorphisms of genes encoding collagen IX and XI in lumbar disc disease.

    PubMed

    Janeczko, Łukasz; Janeczko, Magdalena; Chrzanowski, Robert; Zieliński, Grzegorz

    2014-01-01

    The intervertebral disc disease (IDD) is one of the most common musculoskeletal disorders. A number of environment and anthropometric risk factors may contribute to it. The recent reports have suggested the importance of genetic factors, especially these which encode collagen types IX and XI. The allelic variants in the collagen IX genes - COL9A2 (Trp2) and COL9A3 (Trp3) have been identified as genetic risk factors for IDD, because they interfere the cross-linking between collagen types II, IX and XI and result in decreased stability of intervertebral discs. Type XI collagen is a minor component of cartilage collagen fibrils, but it is present in the annulus fibrosus and nucleus pulposus of intervertebral discs. Some studies have shown the association between gene COL11A1 polymorphism c.4603C>T and IDD. The frequency of 4603T allele was significantly higher in the patients with IDD than in the healthy controls. PMID:24636772

  1. Interactions between collagen IX and biglycan measured by atomic force microscopy

    SciTech Connect

    Chen, C.-H.; Yeh, M.-L.; Geyer, Mark; Wang, Gwo-Jaw; Huang, M.-H.; Heggeness, Michael H.; Hoeoek, Magnus; Luo, Z.-P. . E-mail: luo@bcm.tmc.edu

    2006-01-06

    The stability of the lattice-like type II collagen architecture of articular cartilage is paramount to its optimal function. Such stability not only depends on the rigidity of collagen fibrils themselves, but more importantly, on their interconnections. One known interconnection is through type IX and biglycan molecules. However, the mechanical properties of this interaction and its role in the overall stability remain unrevealed. Using atomic force microscopy, this study directly measured the mechanical strength (or the rupture force) of a single bond between collagen IX and biglycan. The results demonstrated that the rupture force of this single bond was 15 pN, which was significantly smaller than those of other known molecule interactions to date. This result suggested that type IX collagen and biglycan interaction may be the weak link in the cartilage collagen architecture, vulnerable to abnormal joint force and associated with disorders such as osteoarthritis.

  2. Oxidative damage to collagen.

    PubMed

    Monboisse, J C; Borel, J P

    1992-01-01

    Extracellular matrix molecules, such as collagens, are good targets for oxygen free radicals. Collagen is the only protein susceptible to fragmentation by superoxide anion as demonstrated by the liberation of small 4-hydroxyproline-containing-peptides. It seems likely that hydroxyl radicals in the presence of oxygen cleave collagen into small peptides, and the cleavage seems to be specific to proline or 4-hydroxyproline residues. Hydroxyl radicals in the absence of oxygen or hypochlorous acid do not induce fragmentation of collagen molecules, but they trigger a polymerization of collagen through the formation of new cross-links such as dityrosine or disulfure bridges. Moreover, these cross-links can not explain the totality of high molecular weight components generated under these experimental conditions, and the nature of new cross-links induced by hydroxyl radicals or hypochlorous acid remains unclear. PMID:1333311

  3. Controlling the nano-bio interface to build collagen-silica self-assembled networks

    NASA Astrophysics Data System (ADS)

    Aimé, Carole; Mosser, Gervaise; Pembouong, Gaëlle; Bouteiller, Laurent; Coradin, Thibaud

    2012-10-01

    Bio-hybrid networks are designed based on the self-assembly of surface-engineered collagen-silica nanoparticles. Collagen triple helices can be confined on the surface of sulfonate-modified silica particles in a controlled manner. This gives rise to hybrid building blocks with well-defined diameters and surface potentials. Taking advantage of the self-assembling properties of collagen, collagen-silica networks are further built-up in solution. The structural and specific recognition properties of the collagen fibrils are well-preserved within the hybrid assembly. A combination of calorimetry, dynamic light scattering, zetametry and microscopy studies indicates that network formation occurs via a surface-mediated mechanism where pre-organization of the protein chains on the particle surface favors the fibrillogenesis process. These results enlighten the importance of the nano-bio interface on the formation and properties of self-assembled bionanocomposites.Bio-hybrid networks are designed based on the self-assembly of surface-engineered collagen-silica nanoparticles. Collagen triple helices can be confined on the surface of sulfonate-modified silica particles in a controlled manner. This gives rise to hybrid building blocks with well-defined diameters and surface potentials. Taking advantage of the self-assembling properties of collagen, collagen-silica networks are further built-up in solution. The structural and specific recognition properties of the collagen fibrils are well-preserved within the hybrid assembly. A combination of calorimetry, dynamic light scattering, zetametry and microscopy studies indicates that network formation occurs via a surface-mediated mechanism where pre-organization of the protein chains on the particle surface favors the fibrillogenesis process. These results enlighten the importance of the nano-bio interface on the formation and properties of self-assembled bionanocomposites. Electronic supplementary information (ESI) available: XPS

  4. Newly identified interfibrillar collagen crosslinking suppresses cell proliferation and remodelling.

    PubMed

    Marelli, Benedetto; Le Nihouannen, Damien; Hacking, S Adam; Tran, Simon; Li, Jingjing; Murshed, Monzur; Doillon, Charles J; Ghezzi, Chiara E; Zhang, Yu Ling; Nazhat, Showan N; Barralet, Jake E

    2015-06-01

    Copper is becoming recognised as a key cation in a variety of biological processes. Copper chelation has been studied as a potential anti-angiogenic strategy for arresting tumour growth. Conversely the delivery of copper ions and complexes in vivo can elicit a pro-angiogenic effect. Previously we unexpectedly found that copper-stimulated intraperitoneal angiogenesis was accompanied by collagen deposition. Here, in hard tissue, not only was healing accelerated by copper, but again enhanced deposition of collagen was detected at 2 weeks. Experiments with reconstituted collagen showed that addition of copper ions post-fibrillogenesis rendered plastically-compressed gels resistant to collagenases, enhanced their mechanical properties and increased the denaturation temperature of the protein. Unexpectedly, this apparently interfibrillar crosslinking was not affected by addition of glucose or ascorbic acid, which are required for crosslinking by advanced glycation end products (AGEs). Fibroblasts cultured on copper-crosslinked gels did not proliferate, whereas those cultured with an equivalent quantity of copper on either tissue culture plastic or collagen showed no effect compared with controls. Although non-proliferative, fibroblasts grown on copper-cross-linked collagen could migrate, remained metabolically active for at least 14 days and displayed a 6-fold increase in Mmps 1 and 3 mRNA expression compared with copper-free controls. The ability of copper ions to crosslink collagen fibrils during densification and independently of AGEs or Fenton type reactions is previously unreported. The effect on MMP susceptibility of collagen and the dramatic change in cell behaviour on this crosslinked ECM may contribute to shedding some light on unexplained phenomena as the apparent benefit of copper complexation in fibrotic disorders or the enhanced collagen deposition in response to localised copper delivery. PMID:25907046

  5. Characterizing matrix remodeling in collagen gels using optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Levitz, David; Hinds, Monica T.; Hanson, Stephen R.; Jacques, Steven L.

    2010-02-01

    Optical coherence tomography (OCT) has shown promise at non-destructively characterizing engineered tissues such as collagen gels. However, as the collagen gels develop, the OCT images lose contrast of structures as the gels develop, making visual assessment difficult. Our group proposed quantitatively characterizing these gels by fitting the optical properties from the OCT signals. In this paper, we imaged collagen gels seeded with smooth muscle cells (SMCs) over a 5-day period and used the data to measure their optical properties. Our results showed that over time, the reflectivity of the samples increased 10-fold, corresponding to a decrease in anisotropy factor g, without much change in the scattering coefficient μs. Overall, the optical properties appeared to be dominated by scattering from the collagen matrix, not the cells. However, SMCs remodeled the collagen matrix, and this collagen remodeling by the cells is what causes the observed changes in optical properties. Moreover, the data showed that the optical properties were sensitive to the activity of matrix metalloproteinases (MMPs), enzymes that break down local collagen fibrils into smaller fragments. Blocking MMPs in the SMC gels greatly impeded both the remodeling process and change in optical properties at day 5. Treating day 1 acellular gels with MMP-8 for 3 hr managed to partially reproduce the remodeling observed in SMC gels at day 5. Altogether, we conclude that matrix remodeling in general, and MMPs specifically, greatly affect the local optical properties of the sample, and OCT is a unique tool that can assess MMP activity in collagen gels both non-destructively and label free.

  6. Hyperuricemia and Atrial Fibrillation.

    PubMed

    Maharani, Nani; Kuwabara, Masanari; Hisatome, Ichiro

    2016-07-27

    The importance of atrial fibrillation (AF) as a cause of mortality and morbidity has prompted research on its pathogenesis and treatment. Recognition of AF risk factors is essential to prevent it and reduce the risk of death. Hyperuricemia has been widely accepted to be associated with the incidence of paroxysmal or persistent AF, as well as to the risk of AF in post cardiovascular surgery patients. The possible explanations for this association have been based on their relation with either oxidative stress or inflammation. To investigate the link between hyperuricemia and AF, it is necessary to refer to hyperuricemia-induced atrial remodeling. So far, both ionic channel and structural remodeling caused by hyperuricemia might be plausible explanations for the occurrence of AF. Inhibition of xanthine oxidase and nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase, or the use of antioxidants, along with serum uric acid (SUA) level reduction to prevent inflammation, might be useful. Uric acid transporters (UATs) play a key role in the regulation of intracellular uric acid concentration. Intracellular rather than serum uric acid level is considered more important for the pathogenesis of AF. Identification of UATs expressed in cells is thus important, and targeting UATs might become a potential strategy to reduce the risk of hyperuricemia-induced atrial fibrillation. PMID:27396561

  7. Type VII Collagen Expression in the Human Vitreoretinal Interface, Corpora Amylacea and Inner Retinal Layers

    PubMed Central

    Wullink, Bart; Pas, Hendri H.; Van der Worp, Roelofje J.; Kuijer, Roel; Los, Leonoor I.

    2015-01-01

    Type VII collagen, as a major component of anchoring fibrils found at basement membrane zones, is crucial in anchoring epithelial tissue layers to their underlying stroma. Recently, type VII collagen was discovered in the inner human retina by means of immunohistochemistry, while proteomic investigations demonstrated type VII collagen at the vitreoretinal interface of chicken. Because of its potential anchoring function at the vitreoretinal interface, we further assessed the presence of type VII collagen at this site. We evaluated the vitreoretinal interface of human donor eyes by means of immunohistochemistry, confocal microscopy, immunoelectron microscopy, and Western blotting. Firstly, type VII collagen was detected alongside vitreous fibers6 at the vitreoretinal interface. Because of its known anchoring function, it is likely that type VII collagen is involved in vitreoretinal attachment. Secondly, type VII collagen was found within cytoplasmic vesicles of inner retinal cells. These cells resided most frequently in the ganglion cell layer and inner plexiform layer. Thirdly, type VII collagen was found in astrocytic cytoplasmic inclusions, known as corpora amylacea. The intraretinal presence of type VII collagen was confirmed by Western blotting of homogenized retinal preparations. These data add to the understanding of vitreoretinal attachment, which is important for a better comprehension of common vitreoretinal attachment pathologies. PMID:26709927

  8. Collagenous Colitis and Spondylarthropathy

    PubMed Central

    Ben Abdelghani, Kaouther; Sahli, Hana; Souabni, Leila; Chekili, Selma; Belhadj, Salwa; Kassab, Selma; Laatar, Ahmed; Zakraoui, Leith

    2012-01-01

    Collagenous colitis is a recent cause of chronic diarrhea. Cooccurrence with spondylarthropathy is rare. We describe two cases: one man and one woman of 33 and 20 years old were suffering from spondylarthropathy. They then developed collagenous colitis, 4 and 14 years after the onset of spondylarthropathy. The diagnosis was based on histological features. A sicca syndrome and vitiligo were observed with the female case. The presence of colitis leads to therapeutic problems. This association suggests a systemic kind of rheumatic disease of collagenous colitis. PMID:22701491

  9. Y-position cysteine substitution in type I collagen (alpha1(I) R888C/p.R1066C) is associated with osteogenesis imperfecta/Ehlers-Danlos syndrome phenotype.

    PubMed

    Cabral, Wayne A; Makareeva, Elena; Letocha, Anne D; Scribanu, Nina; Fertala, Andrzej; Steplewski, Andrzej; Keene, Douglas R; Persikov, Anton V; Leikin, Sergey; Marini, Joan C

    2007-04-01

    The most common mutations in type I collagen causing types II-IV osteogenesis imperfecta (OI) result in substitution for glycine in a Gly-Xaa-Yaa triplet by another amino acid. We delineated a Y-position substitution in a small pedigree with a combined OI/Ehlers-Danlos Syndrome (EDS) phenotype, characterized by moderately decreased DEXA z-score (-1.3 to -2.6), long bone fractures, and large-joint hyperextensibility. Affected individuals have an alpha1(I)R888C (p.R1066C) substitution in one COL1A1 allele. Polyacrylamide gel electrophoresis (PAGE) of [(3)H]-proline labeled steady-state collagen reveals slight overmodification of the alpha1(I) monomer band, much less than expected for a substitution of a neighboring glycine residue, and a faint alpha1(I) dimer. Dimers form in about 10% of proband type I collagen. Dimer formation is inefficient compared to a possible 25%, probably because the SH-side chains have less proximity in this Y-position than when substituting for a glycine. Theoretical stability calculations, differential scanning calorimetry (DSC) thermograms, and thermal denaturation curves showed only weak local destabilization from the Y-position substitution in one or two chains of a collagen helix, but greater destabilization is seen in collagen containing dimers. Y-position collagen dimers cause kinking of the helix, resulting in a register shift that is propagated the full length of the helix and causes resistance to procollagen processing by N-proteinase. Collagen containing the Y-position substitution is incorporated into matrix deposited in culture, including immaturely and maturely cross-linked fractions. In vivo, proband dermal fibrils have decreased density and increased diameter compared to controls, with occasional aggregate formation. This report on Y-position substitutions in type I collagen extends the range of phenotypes caused by nonglycine substitutions and shows that, similar to X- and Y-position substitutions in types II and III

  10. Distinct roles of GPVI and integrin α2β1 in platelet shape change and aggregation induced by different collagens

    PubMed Central

    Jarvis, Gavin E; Atkinson, Ben T; Snell, Daniel C; Watson, Steve P

    2002-01-01

    Various platelet membrane glycoproteins have been proposed as receptors for collagen, in some cases as receptors for specific collagen types. In this study we have compared the ability of a range of collagen types to activate platelets. Bovine collagen types I–V, native equine tendon collagen fibrils and collagen-related peptide (CRP) all induced platelet aggregation and shape change. Responses were abolished in FcRγ chain-deficient platelets, which also lack GPVI, indicating a critical dependence on the GPVI/FcRγ chain complex. Responses to all collagens were unaffected in CD36-deficient platelets. A monoclonal antibody (6F1) which binds to the α2 integrin subunit of human platelets had a minimal effect on the rate and extent of aggregation induced by the collagens; however, it delayed the onset of aggregation following addition of all collagens. For shape change, 6F1 abolished the response induced by collagen types I and IV, substantially attenuated that to collagen types II, III and V, but only partially inhibited Horm collagen. Simultaneous blockade of the P2Y1 and P2Y12 receptors, and inhibition of cyclo-oxygenase demonstrated that CRP can activate platelets independently of ADP and TxA2; however, responses to the collagens were dependent on these mediators. This study confirms the importance of the GPVI/FcRγ chain complex in platelet responses induced by a range of collagen agonists, while providing no evidence for collagen type-specific receptors. It also provides evidence for a modulatory role of α2β1, the significance of which depends on the collagen preparation. PMID:12183336

  11. Electroactive biomimetic collagen-silver nanowire composite scaffolds.

    PubMed

    Wickham, Abeni; Vagin, Mikhail; Khalaf, Hazem; Bertazzo, Sergio; Hodder, Peter; Dånmark, Staffan; Bengtsson, Torbjörn; Altimiras, Jordi; Aili, Daniel

    2016-08-01

    Electroactive biomaterials are widely explored as bioelectrodes and as scaffolds for neural and cardiac regeneration. Most electrodes and conductive scaffolds for tissue regeneration are based on synthetic materials that have limited biocompatibility and often display large discrepancies in mechanical properties with the surrounding tissue causing problems during tissue integration and regeneration. This work shows the development of a biomimetic nanocomposite material prepared from self-assembled collagen fibrils and silver nanowires (AgNW). Despite consisting of mostly type I collagen fibrils, the homogeneously embedded AgNWs provide these materials with a charge storage capacity of about 2.3 mC cm(-2) and a charge injection capacity of 0.3 mC cm(-2), which is on par with bioelectrodes used in the clinic. The mechanical properties of the materials are similar to soft tissues with a dynamic elastic modulus within the lower kPa range. The nanocomposites also support proliferation of embryonic cardiomyocytes while inhibiting the growth of both Gram-negative Escherichia coli and Gram-positive Staphylococcus epidermidis. The developed collagen/AgNW composites thus represent a highly attractive bioelectrode and scaffold material for a wide range of biomedical applications. PMID:27385421

  12. Regulation of immune reactivity to collagen in human beings

    SciTech Connect

    Solinger, A.M.; Stobo, J.D.

    1981-08-01

    Denaturated beef collagen was tested for its ability to induce the production of leukocyte inhibition factor among the peripheral blood mononuclear cells from patients with rheumatoid arthritis and normal individuals. Responsiveness, defined as the production of leukocyte inhibition factor sufficient to cause greater than 20% inhibition of leukocyte migration, was significantly (P less than 0.001, X2 . 31.1) associated with HLA-DR4. All HLA-DR4 positive individuals, including subjects without any evidence of synovitis, were collagen responders. There was no significant (P . 0.3) difference in the absolute reactivity of HLA-DR4+ versus HLA-DR4- individuals to respond to another antigen, Candida albicans. Collagen reactivity required interactions between macrophages and T cells and was directed against determinants inherent in the linear polypeptide, (Gly-Pro)n. In 5 normal HLA-DR4- nonresponders tested, absence of discernable reactivity to collagen was associated with the presence of antigen-specific, radiosensitive suppressive T cells. These studies suggest that during the physiologic metabolism of collagen all individuals are exposed to Gly-Pro determinants normally buried in the interstices of the collagen triple helix. In individuals whose major histocompatibility complex contains genes linked to those coding for HLA-DR4, this results in the activation of reactive T cells. Conversely, in individuals lacking these genes, collagen-specific suppressive cells predominate.

  13. Mechanical properties of single electrospun collagen type I fibers.

    PubMed

    Yang, Lanti; Fitié, Carel F C; van der Werf, Kees O; Bennink, Martin L; Dijkstra, Pieter J; Feijen, Jan

    2008-03-01

    The mechanical properties of single electrospun collagen fibers were investigated using scanning mode bending tests performed with an AFM. Electrospun collagen fibers with diameters ranging from 100 to 600 nm were successfully produced by electrospinning of an 8% w/v solution of acid soluble collagen in 1,1,1,3,3,3-hexafluoro-2-propanol (HFP). Circular dichroism (CD) spectroscopy showed that 45% of the triple helical structure of collagen molecules was denatured in the electrospun fibers. The electrospun fibers were water soluble and became insoluble after cross-linking with glutaraldehyde vapor for 24h. The bending moduli and shear moduli of both non- and cross-linked single electrospun collagen fibers were determined by scanning mode bending tests after depositing the fibers on glass substrates containing micro-channels. The bending moduli of the electrospun fibers ranged from 1.3 to 7.8 GPa at ambient conditions and ranged from 0.07 to 0.26 MPa when immersed in PBS buffer. As the diameter of the fibrils increased, a decrease in bending modulus was measured clearly indicating mechanical anisotropy of the fiber. Cross-linking of the electrospun fibers with glutaraldehyde vapor increased the shear modulus of the fiber from approximately 30 to approximately 50 MPa at ambient conditions. PMID:18082253

  14. Mechanical forces regulate the interactions of fibronectin and collagen I in extracellular matrix

    PubMed Central

    Kubow, Kristopher E.; Vukmirovic, Radmila; Zhe, Lin; Klotzsch, Enrico; Smith, Michael L.; Gourdon, Delphine; Luna, Sheila; Vogel, Viola

    2015-01-01

    Despite the crucial role of extracellular matrix (ECM) in directing cell fate in healthy and diseased tissues—particularly in development, wound healing, tissue regeneration and cancer—the mechanisms that direct the assembly and regulate hierarchical architectures of ECM are poorly understood. Collagen I matrix assembly in vivo requires active fibronectin (Fn) fibrillogenesis by cells. Here we exploit Fn-FRET probes as mechanical strain sensors and demonstrate that collagen I fibres preferentially co-localize with more-relaxed Fn fibrils in the ECM of fibroblasts in cell culture. Fibre stretch-assay studies reveal that collagen I's Fn-binding domain is responsible for the mechano-regulated interaction. Furthermore, we show that Fn-collagen interactions are reciprocal: relaxed Fn fibrils act as multivalent templates for collagen assembly, but once assembled, collagen fibres shield Fn fibres from being stretched by cellular traction forces. Thus, in addition to the well-recognized, force-regulated, cell-matrix interactions, forces also tune the interactions between different structural ECM components. PMID:26272817

  15. Changes in corneal collagen induced by holmium:YAG laser irradiation

    NASA Astrophysics Data System (ADS)

    Timberlake, George T.; Reinke, Martin H.; Miller, Alvin

    1996-05-01

    Holmium:YAG laser thermokeratoplasty corrects hyperopia (farsightedness) by producing small areas of corneal collagen shrinkage that cause the central cornea to bulge outward, increasing optical power. Collagen shrinkage is probably caused by laser-heated corneal water, but details of the shrinkage mechanism are not known. We investigated the shrinkage mechanism by measuring changes in corneal ultrastructure, surface shrinkage, water content, and strength following Ho:YAG laser exposures. Morphological changes in collagen were documented by measurements from electron micrographs. Corneal adhesive strength was determined by measuring tearing force in a plane parallel to the corneal surface. Laser-induced water loss was measured by weighing corneal samples before and after exposure. Corneal surface shrinkage was assessed by photographing the movement of particles on the cornea. Lasered collagen fibrils increased in diameter, lost their orderly arrangement, and appeared `frayed.' The corneal surface contracted toward lasered areas with a maximal shift of approximately 190 micrometers , more than could be explained by a model based on collagen fibril changes. Water loss plays a minor role in corneal shrinkage since corneal samples lost about only about 1.4% of their weight after massive laser exposure. Despite marked changes in collagen structure, corneal adhesive force was unchanged.

  16. Chiral imaging of collagen by second-harmonic generation circular dichroism

    PubMed Central

    Lee, H.; Huttunen, M. J.; Hsu, K.-J.; Partanen, M.; Zhuo, G.-Y.; Kauranen, M.; Chu, S.-W.

    2013-01-01

    We provide evidence that the chirality of collagen can give rise to strong second-harmonic generation circular dichroism (SHG-CD) responses in nonlinear microscopy. Although chirality is an intrinsic structural property of collagen, most of the previous studies ignore that property. We demonstrate chiral imaging of individual collagen fibers by using a laser scanning microscope and type-I collagen from pig ligaments. 100% contrast level of SHG-CD is achieved with sub-micrometer spatial resolution. As a new contrast mechanism for imaging chiral structures in bio-tissues, this technique provides information about collagen morphology and three-dimensional orientation of collagen molecules. PMID:23761852

  17. Fibrin binds to collagen and provides a bridge for αVβ3 integrin-dependent contraction of collagen gels

    PubMed Central

    Reyhani, Vahid; Seddigh, Pegah; Guss, Bengt; Gustafsson, Renata; Rask, Lars; Rubin, Kristofer

    2014-01-01

    The functional significance of fibrin deposits typically seen in inflammatory lesions, carcinomas and in healing wounds is not fully understood. In the present study, we demonstrate that fibrinogen/fibrin specifically bound to native Col I (collagen type I) and used the Col I fibre network as a base to provide a functional interface matrix that connects cells to the Col I fibres through αVβ3 integrins. This allowed murine myoblast C2C12 cells to contract the collagenous composite gel via αVβ3 integrin. We show that fibrinogen specifically bound to immobilized native Col I at the site known to bind matrix metalloproteinase-1, discoidin domain receptor-2 and fibronectin, and that binding had no effect on Col I fibrillation. A specific competitive inhibitor blocking the Col-I-binding site for fibrinogen abolished the organization of fibrin into discernable fibrils, as well as the C2C12-mediated contraction of Col I gels. Our data show that fibrin can function as a linkage protein between Col I fibres and cells, and suggest that fibrin at inflammatory sites indirectly connects αVβ3 integrins to Col I fibres and thereby promotes cell-mediated contraction of collagenous tissue structures. PMID:24840544

  18. Nanomechanics of collagen microfibrils

    PubMed Central

    Vesentini, Simone; Redaelli, Alberto; Gautieri, Alfonso

    2013-01-01

    Summary Collagen constitutes one third of the human proteome, providing mechanical stability, elasticity and strength to organisms and is thus the prime construction material in biology. Collagen is also the dominating material in the extracellular matrix where its stiffness controls cell differentiation, growth and pathology. We use atomistic-based hierarchical multiscale modeling to describe this complex biological material from the bottom up. This includes the use and development of large-scale computational modeling tools to investigate several aspects related to collagen-based tissues, including source of visco-elasticity and deformation mechanisms at the nanoscale level. The key innovation of this research is that until now, collagen materials have primarily been described at macroscopic scales, without explicitly understanding the mechanical contributions at the molecular and fibrillar levels. The major impact of this research will be the development of fundamental models of collagenous tissues, important to the design of new scaffolding biomaterials for regenerative medicine as well as for the understanding of collagen-related diseases. PMID:23885342

  19. Thermal and infrared-diode laser effects on indocyanine-green-treated corneal collagen

    NASA Astrophysics Data System (ADS)

    Timberlake, George T.; Patmore, Ann; Shallal, Assaad; McHugh, Dominic; Marshall, John

    1993-07-01

    It has been suggested that laser welds of collagenous tissues form by interdigitation and chemical bonding of thermally 'unraveled' collagen fibrils. We investigated this proposal by attempting to weld highly collagenous, avascular corneal tissue with an infrared (IR) diode laser as follows. First, the temperature at which corneal collagen shrinks and collagen fibrils 'split' into subfibrillary components was determined. Second, since use of a near-IR laser wavelength necessitated addition of an absorbing dye (indocyanine green (ICG) to the cornea, we measured absorption spectra of ICG-treated tissue to ensure that peak ICG absorbance did not change markedly when ICG was present in the cornea. Third, using gel electrophoresis of thermally altered corneal collagen, we searched for covalently crosslinked compounds predicted by the proposed welding mechanism. Finally, we attempted to weld partial thickness corneal incisions infused with ICG. Principal experimental findings were as follows: (1) Human corneal (type I) collagen splits into subfibrillary components at approximately 63 degree(s)C, the same temperature that produces collagen shrinkage. (2) Peak ICG absorption does not change significantly in corneal stroma or with laser heating. (3) No evidence was found for the formation of novel compounds or the loss of proteins as a result of tissue heating. All tissue treated with ICG, however, exhibited a novel 244 kD protein band indicating chemical activity between collagen and corneal stromal components. (4) Laser welding corneal incisions was unsuccessful possibly due to shrinkage of the sides of the incision, lack of incision compression during heating, or a less than optimal combination of ICG concentration and radiant exposure. In summary, these experiments demonstrate the biochemical and morphological complexity of ICG-enhanced IR laser-tissue welding and the need for further investigation of laser welding mechanisms.

  20. Antithrombotic and Anticoagulant Therapy for Atrial Fibrillation.

    PubMed

    Dzeshka, Mikhail S; Lip, Gregory Y H

    2016-04-01

    As atrial fibrillation (AF) substantially increases the risk of stroke and other thromboembolic events, most AF patients require appropriate antithrombotic prophylaxis. Oral anticoagulation (OAC) with either dose-adjusted vitamin K antagonists (VKAs) (eg, warfarin) or non-VKA oral anticoagulants (eg, dabigatran, apixaban, rivaroxaban) can be used for this purpose unless contraindicated. Therefore, risk assessment of stroke and bleeding is an obligatory part of AF management, and risk has to be weighed individually. Antiplatelet drugs (eg, aspirin and clopidogrel) are inferior to OAC, both alone and in combination, with a comparable risk of bleeding events. PMID:26968670

  1. Genomics of Atrial Fibrillation.

    PubMed

    Gutierrez, Alejandra; Chung, Mina K

    2016-06-01

    Atrial fibrillation (AF) is a common clinical arrhythmia that appears to be highly heritable, despite representing a complex interplay of several disease processes that generally do not manifest until later in life. In this manuscript, we will review the genetic basis of this complex trait established through studies of familial AF, linkage and candidate gene studies of common AF, genome wide association studies (GWAS) of common AF, and transcriptomic studies of AF. Since AF is associated with a five-fold increase in the risk of stroke, we also review the intersection of common genetic factors associated with both of these conditions. Similarly, we highlight the intersection of common genetic markers associated with some risk factors for AF, such as hypertension and obesity, and AF. Lastly, we describe a paradigm where genetic factors predispose to the risk of AF, but which may require additional stress and trigger factors in older age to allow for the clinical manifestation of AF. PMID:27139902

  2. pH-responsive collagen fibrillogenesis in confined droplets induced by vapour diffusion.

    PubMed

    Ramírez-Rodríguez, Gloria Belén; Iafisco, Michele; Tampieri, Anna; Gómez-Morales, Jaime; Delgado-López, José Manuel

    2014-10-01

    A novel methodology for the assembly of collagen fibrils in microliter drops is proposed. It consists in the gradual increase of pH by means of vapour diffusion coming from the decomposition of NH4HCO3 solutions. The pH increase rate as well as the final steady pH of solutions containing collagen can be adjusted by varying the concentration of NH4HCO3. Both parameters are of predominant importance in collagen fibrillogenesis. The effect of these parameters on the kinetic of the fibrillogenesis process and on the fibrils morphology was studied. We found that both the kinetic and the morphology are mainly driven by electrostatic interactions. A gradual increase of pH slows down the formation of collagen fibres and favours the lateral interaction between fibrils producing broader fibres. On the other hand, a rapid increase of pH reduces the lateral electrostatic interactions favouring the formation of thinner fibres. The formation of the D-band periodicity is also a pH-dependent process that occurs after fibrillogenesis when the most stable state of fibres formation has been reached. PMID:24652593

  3. Distribution of type I collagen morphologies in bone: relation to estrogen depletion.

    PubMed

    Wallace, Joseph M; Erickson, Blake; Les, Clifford M; Orr, Bradford G; Banaszak Holl, Mark M

    2010-05-01

    Bone is an amazing material evolved by nature to elegantly balance structural and metabolic needs in the body. Bone health is an integral part of overall health, but our lack of understanding of the ultrastructure of healthy bone precludes us from knowing how disease may impact nanoscale properties in this biological material. Here, we show that quantitative assessments of a distribution of Type I collagen fibril morphologies can be made using atomic force microscopy (AFM). We demonstrate that normal bone contains a distribution of collagen fibril morphologies and that changes in this distribution can be directly related to disease state. Specifically, by monitoring changes in the collagen fibril distribution of sham-operated and estrogen-depleted sheep, we have shown the ability to detect estrogen-deficiency-induced changes in Type I collagen in bone. This discovery provides new insight into the ultrastructure of bone as a tissue and the role of material structure in bone disease. The observation offers the possibility of a much-needed in vitro procedure to complement the current methods used to diagnose osteoporosis and other bone disease. PMID:19932773

  4. OPTIMIZING COLLAGEN TRANSPORT THROUGH TRACK-ETCHED NANOPORES

    PubMed Central

    Bueno, Ericka M.; Ruberti, Jeffrey W.

    2008-01-01

    Polymer transport through nanopores is a potentially powerful tool for separation and organization of molecules in biotechnology applications. Our goal is to produce aligned collagen fibrils by mimicking cell-mediated collagen assembly: driving collagen monomers in solution through the aligned nanopores in track-etched membranes followed by fibrillogenesis at the pore exit. We examined type I atelo-collagen monomer transport in neutral, cold solution through polycarbonate track-etched membranes comprising 80-nm-diameter, 6-μm-long pores at 2% areal fraction. Source concentrations of 1.0, 2.8 and 7.0 mg/ml and pressure differentials of 0, 10 and 20 inH2O were used. Membrane surfaces were hydrophilized via covalent poly(ethylene-glycol) binding to limit solute-membrane interaction. Collagen transport through the nanopores was a non-intuitive process due to the complex behavior of this associating molecule in semi-dilute solution. Nonetheless, a modified open pore model provided reasonable predictions of transport parameters. Transport rates were concentration- and pressure-dependent, with diffusivities across the membrane in semi-dilute solution two-fold those in dilute solution, possibly via cooperative diffusion or polymer entrainment. The most significant enhancement of collagen transport was accomplished by membrane hydrophilization. The highest concentration transported (5.99±2.58 mg/ml) with the highest monomer flux (2.60±0.49 ×103 molecules s-1 pore-1) was observed using 2.8 mg collagen/ml, 10 inH2O and hydrophilic membranes. PMID:21394216

  5. Ameloblasts express type I collagen during amelogenesis.

    PubMed

    Assaraf-Weill, N; Gasse, B; Silvent, J; Bardet, C; Sire, J Y; Davit-Béal, T

    2014-05-01

    Enamel and enameloid, the highly mineralized tooth-covering tissues in living vertebrates, are different in their matrix composition. Enamel, a unique product of ameloblasts, principally contains enamel matrix proteins (EMPs), while enameloid possesses collagen fibrils and probably receives contributions from both odontoblasts and ameloblasts. Here we focused on type I collagen (COL1A1) and amelogenin (AMEL) gene expression during enameloid and enamel formation throughout ontogeny in the caudate amphibian, Pleurodeles waltl. In this model, pre-metamorphic teeth possess enameloid and enamel, while post-metamorphic teeth possess enamel only. In first-generation teeth, qPCR and in situ hybridization (ISH) on sections revealed that ameloblasts weakly expressed AMEL during late-stage enameloid formation, while expression strongly increased during enamel deposition. Using ISH, we identified COL1A1 transcripts in ameloblasts and odontoblasts during enameloid formation. COL1A1 expression in ameloblasts gradually decreased and was no longer detected after metamorphosis. The transition from enameloid-rich to enamel-rich teeth could be related to a switch in ameloblast activity from COL1A1 to AMEL synthesis. P. waltl therefore appears to be an appropriate animal model for the study of the processes involved during enameloid-to-enamel transition, especially because similar events probably occurred in various lineages during vertebrate evolution. PMID:24570147

  6. Flow-Induced Crystallization of Collagen: A Potentially Critical Mechanism in Early Tissue Formation.

    PubMed

    Paten, Jeffrey A; Siadat, Seyed Mohammad; Susilo, Monica E; Ismail, Ebraheim N; Stoner, Jayson L; Rothstein, Jonathan P; Ruberti, Jeffrey W

    2016-05-24

    The type I collagen monomer is one of nature's most exquisite and prevalent structural tools. Its 300 nm triple-helical motifs assemble into tough extracellular fibers that transition seamlessly across tissue boundaries and exceed cell dimensions by up to 4 orders of magnitude. In spite of extensive investigation, no existing model satisfactorily explains how such continuous structures are generated and grown precisely where they are needed (aligned in the path of force) by discrete, microscale cells using materials with nanoscale dimensions. We present a simple fiber drawing experiment, which demonstrates that slightly concentrated type I collagen monomers can be "flow-crystallized" to form highly oriented, continuous, hierarchical fibers at cell-achievable strain rates (<1 s(-1)) and physiologically relevant concentrations (∼50 μM). We also show that application of tension following the drawing process maintains the structural integrity of the fibers. While mechanical tension has been shown to be a critical factor driving collagen fibril formation during tissue morphogenesis in developing animals, the precise role of force in the process of building tissue is not well understood. Our data directly couple mechanical tension, specifically the extensional strain rate, to collagen fibril assembly. We further derive a "growth equation" which predicts that application of extensional strains, either globally by developing muscles or locally by fibroblasts, can rapidly drive the fusion of already formed short fibrils to produce long-range, continuous fibers. The results provide a pathway to scalable connective tissue manufacturing and support a mechano-biological model of collagen fibril deposition and growth in vivo. PMID:27070851

  7. Posttranslational Modifications in Type I Collagen from Different Tissues Extracted from Wild Type and Prolyl 3-Hydroxylase 1 Null Mice*

    PubMed Central

    Pokidysheva, Elena; Zientek, Keith D.; Ishikawa, Yoshihiro; Mizuno, Kazunori; Vranka, Janice A.; Montgomery, Nathan T.; Keene, Douglas R.; Kawaguchi, Tatsuya; Okuyama, Kenji; Bächinger, Hans Peter

    2013-01-01

    Type I collagen extracted from tendon, skin, and bone of wild type and prolyl 3-hydroxylase 1 (P3H1) null mice shows distinct patterns of 3-hydroxylation and glycosylation of hydroxylysine residues. The A1 site (Pro-986) in the α1-chain of type I collagen is almost completely 3-hydroxylated in every tissue of the wild type mice. In contrast, no 3-hydroxylation of this proline residue was found in P3H1 null mice. Partial 3-hydroxylation of the A3 site (Pro-707) was present in tendon and bone, but absent in skin in both α-chains of the wild type animals. Type I collagen extracted from bone of P3H1 null mice shows a large reduction in 3-hydroxylation of the A3 site in both α-chains, whereas type I collagen extracted from tendon of P3H1 null mice shows little difference as compared with wild type. These results demonstrate that the A1 site in type I collagen is exclusively 3-hydroxylated by P3H1, and presumably, this enzyme is required for the 3-hydroxylation of the A3 site of both α-chains in bone but not in tendon. The increase in glycosylation of hydroxylysine in P3H1 null mice in bone was found to be due to an increased occupancy of normally glycosylated sites. Despite the severe disorganization of collagen fibrils in adult tissues, the D-period of the fibrils is unchanged. Tendon fibrils of newborn P3H1 null mice are well organized with only a slight increase in diameter. The absence of 3-hydroxyproline and/or the increased glycosylation of hydroxylysine in type I collagen disturbs the lateral growth of the fibrils. PMID:23861401

  8. Modification of Ti6Al4V surfaces using collagen I, III, and fibronectin. I. Biochemical and morphological characteristics of the adsorbed matrix.

    PubMed

    Bierbaum, Susanne; Beutner, René; Hanke, Thomas; Scharnweber, Dieter; Hempel, Ute; Worch, Hartmut

    2003-11-01

    Studies in developmental and cell biology have established the fact that responses of cells are influenced to a large degree by morphology and composition of the extracellular matrix. Goal of this work is to use this basic principle to improve the biological acceptance of implants by modifying the surfaces with components of the extracellular matrix (ECM). Aiming at load-bearing applications in bone contact, in this study the modification of titanium surfaces with the collagen types I and III in combination with fibronectin was undertaken; fibrillogenesis, fibril morphology and adsorption of type I, III and I/III-cofibrils onto titanium were assessed. Increasing the collagen type III amount resulted in a decrease of fibril diameter, while no significant changes in adsorption could be detected. The amount of fibronectin bound to the heterotypic fibrils depended on fibrillogenesis parameters such as ionic strength or concentration of phosphate, and varied with the percentage of integrated type III collagen. PMID:14566782

  9. Small-Angle X-ray Study of the Three-Dimensional Collagen/Mineral Superstructure in Intramuscular Fish Bone

    SciTech Connect

    Zhou,H.; Burger, C.; Sics, I.; Hsiao, B.; Chu, B.; Graham, L.; Glimcher, M.

    2007-01-01

    Synchrotron small-angle X-ray scattering (SAXS) was conducted on native intramuscular shad/herring bone samples. Two-dimensional SAXS patterns were quantitatively analyzed with special consideration for preferred orientation effects, leading to new insights into the three-dimensional superstructure of mineralized collagen fibrils in shad/herring bone.

  10. Rhythm control in atrial fibrillation.

    PubMed

    Piccini, Jonathan P; Fauchier, Laurent

    2016-08-20

    Many patients with atrial fibrillation have substantial symptoms despite ventricular rate control and require restoration of sinus rhythm to improve their quality of life. Acute restoration (ie, cardioversion) and maintenance of sinus rhythm in patients with atrial fibrillation are referred to as rhythm control. The decision to pursue rhythm control is based on symptoms, the type of atrial fibrillation (paroxysmal, persistent, or long-standing persistent), patient comorbidities, general health status, and anticoagulation status. Many patients have recurrent atrial fibrillation and require further intervention to maintain long term sinus rhythm. Antiarrhythmic drug therapy is generally recommended as a first-line therapy and drug selection is on the basis of the presence or absence of structural heart disease or heart failure, electrocardiographical variables, renal function, and other comorbidities. In patients who continue to have recurrent atrial fibrillation despite medical therapy, catheter ablation has been shown to substantially reduce recurrent atrial fibrillation, decrease symptoms, and improve quality of life, although recurrence is common despite continued advancement in ablation techniques. PMID:27560278

  11. Rate control in atrial fibrillation.

    PubMed

    Van Gelder, Isabelle C; Rienstra, Michiel; Crijns, Harry J G M; Olshansky, Brian

    2016-08-20

    Control of the heart rate (rate control) is central to atrial fibrillation management, even for patients who ultimately require control of the rhythm. We review heart rate control in patients with atrial fibrillation, including the rationale for the intervention, patient selection, and the treatments available. The choice of rate control depends on the symptoms and clinical characteristics of the patient, but for all patients with atrial fibrillation, rate control is part of the management. Choice of drugs is patient-dependent. β blockers, alone or in combination with digoxin, or non-dihydropyridine calcium-channel blockers (not in heart failure) effectively lower the heart rate. Digoxin is least effective, but a reasonable choice for physically inactive patients aged 80 years or older, in whom other treatments are ineffective or are contraindicated, and as an additional drug to other rate-controlling drugs, especially in heart failure when instituted cautiously. Atrioventricular node ablation with pacemaker insertion for rate control should be used as an approach of last resort but is also an option early in the management of patients with atrial fibrillation treated with cardiac resynchronisation therapy. However, catheter ablation of atrial fibrillation should be considered before atrioventricular node ablation. Although rate control is a top priority and one of the first management issues for all patients with atrial fibrillation, many issues remain. PMID:27560277

  12. Cross-Linked Conjugated Polymer Fibrils: Robust Nanowires from Functional Polythiophene Diblock Copolymers

    SciTech Connect

    Hammer, Brenton A. G.; Bokel, Felicia A.; Hayward, Ryan C.; Emrick, Todd

    2011-09-27

    A series of poly(3-hexyl thiophene) (P3HT)-based diblock copolymers were prepared and examined in solution for their assembly into fibrils, and post-assembly cross-linking into robust nanowire structures. P3HT-b-poly(3-methanol thiophene) (P3MT), and P3HT-b-poly(3-aminopropyloxymethyl thiophene) (P3AmT) diblock copolymers were synthesized using Grignard metathesis (GRIM) polymerization. Fibrils formed from solution assembly of these copolymers are thus decorated with hydroxyl and amine functionality, and cross-linking is achieved by reaction of diisocyanates with the hydroxyl and amine groups. A variety of cross-linked structures, characterized by transmission electron microscopy (TEM), were produced by this method, including dense fibrillar sheets, fibril bundles, or predominately individual fibrils, depending on the chosen reaction conditions. In solution, the cross-linked fibrils maintained their characteristic vibronic structure in solvents that would normally disrupt (dissolve) the structures.

  13. AFM-based force spectroscopy measurements of mature amyloid fibrils of the peptide glucagon

    NASA Astrophysics Data System (ADS)

    Dong, Mingdong; Bruun Hovgaard, Mads; Mamdouh, Wael; Xu, Sailong; Otzen, Daniel Erik; Besenbacher, Flemming

    2008-09-01

    We report on the mechanical characterization of individual mature amyloid fibrils by atomic force microscopy (AFM) and AFM-based single-molecule force spectroscopy (SMFS). These self-assembling materials, formed from the 29-residue amphiphatic peptide hormone glucagon, were found to display a reversible elastic behaviour. Based on AFM morphology and SMFS studies, we suggest that the observed elasticity is due to a force-induced conformational transition which is reversible due to the β-helical conformation of protofibrils, allowing a high degree of extension. The elastic properties of such mature fibrils contribute to their high stability, suggesting that the internal hydrophobic interactions of amyloid fibrils are likely to be of fundamental importance in the assembly of amyloid fibrils and therefore for the understanding of the progression of their associated pathogenic disorders. In addition, such biological amyloid fibril structures with highly stable mechanical properties can potentially be used to produce nanofibres (nanowires) that may be suitable for nanotechnological applications.

  14. In Situ D-periodic Molecular Structure of Type II Collagen

    SciTech Connect

    Antipova, Olga; Orgel, Joseph P.R.O.

    2010-05-06

    Collagens are essential components of extracellular matrices in multicellular animals. Fibrillar type II collagen is the most prominent component of articular cartilage and other cartilage-like tissues such as notochord. Its in situ macromolecular and packing structures have not been fully characterized, but an understanding of these attributes may help reveal mechanisms of tissue assembly and degradation (as in osteo- and rheumatoid arthritis). In some tissues such as lamprey notochord, the collagen fibrillar organization is naturally crystalline and may be studied by x-ray diffraction. We used diffraction data from native and derivative notochord tissue samples to solve the axial, D-periodic structure of type II collagen via multiple isomorphous replacement. The electron density maps and heavy atom data revealed the conformation of the nonhelical telopeptides and the overall D-periodic structure of collagen type II in native tissues, data that were further supported by structure prediction and transmission electron microscopy. These results help to explain the observed differences in collagen type I and type II fibrillar architecture and indicate the collagen type II cross-link organization, which is crucial for fibrillogenesis. Transmission electron microscopy data show the close relationship between lamprey and mammalian collagen fibrils, even though the respective larger scale tissue architecture differs.

  15. Collagen based polyurethanes—A review of recent advances and perspective.

    PubMed

    Zuber, Mohammad; Zia, Fatima; Zia, Khalid Mahmood; Tabasum, Shazia; Salman, Mahwish; Sultan, Neelam

    2015-09-01

    Collagen is mostly found in fibrous tissues such as tendons, ligaments and skin. Collagen makes up approximately 30% of the proteins within the body. These are tough and strong structures found all over the body: in bones, tendons and ligaments. Collagen being the most abundant protein provides tensile strength via cell matrix interactions to tissue architecture. Biomimetic materials of collagen origin gained wide spread acceptance in clinical applications. Vitamin C deficiency causes scurvy a serious and painful disease in which defective collagen prevents the formation of strong connective tissue, gums deteriorate and bleed, with loss of teeth; skin discolors, and wounds do not heal. Effective collagens prevent the manifestation of such disorders. Polyurethanes on the other hand are frequently used for various applications as they offered in wide-ranging of compositions, properties and complex structures. Collagen/PU bio-composites have potential array for biomedical applications. Considering versatile properties of the elongated fibrils and wide industrial and biomedical applications including biocompatibility of polyurethane, this review shed a light on collagen based polyurethane materials with their potential applications especially focusing the bio-medical field. PMID:26144910

  16. Rapid and reversible regulation of collagen XII expression by changes in tensile stress.

    PubMed

    Trächslin, J; Koch, M; Chiquet, M

    1999-03-15

    We studied the expression of the fibril-associated collagen XII by fibroblasts cultured on attached (stretched) or floating (relaxed) collagen I gels. Accumulation of collagen XII in the medium as determined by semiquantitative immunoblotting was 8-16 times higher under stretched compared to relaxed conditions. Northern blot experiments showed that tensile stress controls collagen XII expression at the mRNA level. Tenascin-C mRNA levels were also influenced, whereas relative amounts of fibronectin and matrix metalloproteinase-2 mRNA were barely affected. The response to a change in tensile stress is rapid, since de novo biosynthesis of collagen XII was fully down-regulated 12 h after relaxation of a stretched culture. To demonstrate that the effect is also reversible, we mounted collagen gels with attached cells to movable polyethylene plugs. The cultures were relaxed or stretched at intervals of 24 and 48 h, and media samples were analyzed every 24 h. By ELISA, the amount of collagen XII secreted into the medium was found to increase or decrease in accordance with the tensile stress applied. This is evidence that the mechanical stimulus per se, rather than an indirect secondary effect, was responsible for the observed changes in collagen XII production. PMID:10066359

  17. Fibroblast-Derived MMP-14 Regulates Collagen Homeostasis in Adult Skin.

    PubMed

    Zigrino, Paola; Brinckmann, Jürgen; Niehoff, Anja; Lu, Yinhui; Giebeler, Nives; Eckes, Beate; Kadler, Karl E; Mauch, Cornelia

    2016-08-01

    Proteolytic activities in the extracellular matrix by the matrix metalloproteinase (MMP)-14 have been implicated in the remodeling of collagenous proteins during development. To analyze the function of fibroblast-derived MMP-14 in adult skin homeostasis, we generated mice with inducible deletion of MMP-14 in the dermal fibroblast (MMP-14(Sf-/-)). These mice are smaller and display a fibrosis-like phenotype in the skin. The skin of these mice showed increased stiffness and tensile strength but no altered collagen cross-links. In vivo, we measured a significantly increased amount of collagen type I accumulated in the skin of MMP-14(Sf-/-) mice without an increase in collagen fibril diameters. However, bleomycin-induced fibrosis in skin proceeded in a comparable manner in MMP-14(Sf+/+) and MMP-14(Sf-/-) mice, but resolution over time was impaired in MMP-14(Sf-/-) mice. Increased accumulation of collagen type I was detected in MMP-14(Sf-/-) fibroblasts in culture without significant enhancement of collagen de novo synthesis. This points to a degradative but not synthetic phenotype. In support of this, MMP-14(Sf-/-) fibroblasts lost their ability to process fibrillar collagen type I and to activate proMMP-2. Taken together, these data indicate that MMP-14 expression in fibroblasts plays a crucial role in collagen remodeling in adult skin and largely contributes to dermal homeostasis underlying its pathogenic role in fibrotic skin disease. PMID:27066886

  18. Characterization of a variety of standard collagen substrates: ultrastructure, uniformity, and capacity to bind and promote growth of neurons

    SciTech Connect

    Iversen, P.L.; Partlow, L.M.; Stensaas, L.J.; Moatamed, F.

    1981-06-01

    Collagen substrates were characterized after preparation by the four methods most commonly used for tissue culture (saline precipitation, exposure to ammonium hydroxide vapor, exposure to ultraviolet light, and air drying). Although roughly equivalent percentages of collagen were precipitated by each technique (87 to 97%), marked differences were found in surface uniformity and ultrastructure. Substrates were quite uniform if precipitated by exposure to ammonium hydroxide or ultraviolet light, of intermediate uniformity if saline precipitated, and not at all uniform if air dried. Scanning electron microscopy revealed that (a) ammonium hydroxide and saline precipitation primarily resulted in formation of collagen fibrils, (b) air drying produced a small number of fibrils plus a large amount of amorphous material, and (c) exposure to ultraviolet light only resulted in the formation of globular, nonfibrillar collagen aggregates. The capacity of collagen substrates to bind and grow neurons differed markedly with the method of preparation and the amount of collagen plated per unit area. Quantifications of binding and growth of both cerebral and sympathetic neurons revealed that these are separate measures of the biocompatibility of a surface and that growth was uniformly inferior on globular collagen that had been precipitated by ultraviolet light. Long-term (greater than or equal to 2 wk) growth of sympathetic neurons was optimal on thick beds of saline-precipitated collagen, whereas short-term growth was best on thin layers of either saline or ammonium hydroxide-precipitated collagen. Cerebral neurons bound and grew optimally on thick collagen beds after both short- and long-term culture. In addition, cerebral neurons were found to be more dependent on the method of precipitation of the thin collagen substrates than were sympathetic neurons.

  19. Collagen type VI myopathies.

    PubMed

    Bushby, Kate M D; Collins, James; Hicks, Debbie

    2014-01-01

    Mutations in each of the three collagen VI genes COL6A1, COL6A2 and COL6A3 cause two main types of muscle disorders: Ullrich congenital muscular dystrophy, a severe phenotype, and a mild to moderate phenotype Bethlem myopathy. Recently, two additional phenotypes, including a limb-girdle muscular dystrophy phenotype and an autosomal recessive myosclerosis reported in one family with mutations in COL6A2 have been reported. Collagen VI is an important component of the extracellular matrix which forms a microfibrillar network that is found in close association with the cell and surrounding basement membrane. Collagen VI is also found in the interstitial space of many tissues including muscle, tendon, skin, cartilage, and intervertebral discs. Thus, collagen VI mutations result in disorders with combined muscle and connective tissue involvement, including weakness, joint laxity and contractures, and abnormal skin findings.In this review we highlight the four recognized clinical phenotypes of collagen VI related - myopathies; Ullrich congenital muscular dystrophy (UCMD), Bethlem myopathy (BM), autosomal dominant limb-girdle muscular dystrophy phenotype and autosomal recessive myosclerosis. We discuss the diagnostic criteria of these disorders, the molecular pathogenesis, genetics, treatment, and related disorders. PMID:24443028

  20. Micromechanical Modeling Study of Mechanical Inhibition of Enzymatic Degradation of Collagen Tissues.

    PubMed

    Tonge, Theresa K; Ruberti, Jeffrey W; Nguyen, Thao D

    2015-12-15

    This study investigates how the collagen fiber structure influences the enzymatic degradation of collagen tissues. We developed a micromechanical model of a fibrous collagen tissue undergoing enzymatic degradation based on two central hypotheses. The collagen fibers are crimped in the undeformed configuration. Enzymatic degradation is an energy activated process and the activation energy is increased by the axial strain energy density of the fiber. We determined the intrinsic degradation rate and characteristic energy for mechanical inhibition from fibril-level degradation experiments and applied the parameters to predict the effect of the crimped fiber structure and fiber properties on the degradation of bovine cornea and pericardium tissues under controlled tension. We then applied the model to examine the effect of the tissue stress state on the rate of tissue degradation and the anisotropic fiber structures that developed from enzymatic degradation. PMID:26682825

  1. Collagen Cross Linking Agents: Design and Development of a Multifunctional Cross Linker

    PubMed Central

    Givens, Richard S.; Yousef, Abraham L.; Yang, Shaorong; Timberlake, George T.

    2013-01-01

    A new cross linking reagent based on the first-generation polyamidoamine dendrimer (G.1 PAMAM) has been synthesized by reaction of the PAMAM with eight equivalents of p-nitrophenyl diazopyruvate. The resulting water-soluble octadiazopyruvoyl PAMAM (8G.1 DAP, 1.3) was shown to undergo Wolff rearrangements upon photolysis in methanol at λ > 300 nm to yield the methyl esters of the ketenes formed from the loss of nitrogen. 8G.1 DAP also forms strong bonds with dehydrated collagen with glass as high as 36 N cm−2. Collagen to collagen bonds with tensile strengths as high as 92 N cm−2 were observed with fully dehydrated tissues. The bonding decreased rapidly with increasingly hydrated tissue possibly due to the increased distance between the collagen fibrils and the competition of H2O for the free ketene functions. PMID:18173719

  2. Pulsed electromagnetic field (PEMF) promotes collagen fibre deposition associated with increased myofibroblast population in the early healing phase of diabetic wound.

    PubMed

    Choi, Ming-Chun; Cheung, Kwok-Kuen; Li, Xiaohui; Cheing, Gladys Lai-Ying

    2016-01-01

    The present study evaluated the effects of PEMF on collagen fibre deposition, collagen fibril alignment and collagen fibre orientation. The potential relationships between collagen fibre deposition and myofibroblast population in diabetic wound healing were also examined. Forty young male streptozotocin-induced diabetic Sprague-Dawley rats were randomly assigned to PEMF group or control group. 2 cm × 2 cm square wounds were made at their back. The PEMF group received daily exposure of PEMF to the wounds, while control group was handled in the same manner except that the PEMF device was not activated. Wound tissues harvested on post-wounding day 7, 10 and 14 were fixed, processed and sectioned. The abundance, fibril alignment and fibre orientation of type I collagen were quantified with picro-sirius polarization method and image analysis software (Nikon NIS Element AR). Myofibroblast population data were adopted from our previous study. Correlation between myofibroblast population and collagen fibre deposition was examined. There was significantly greater abundance of type I collagen fibre in the PEMF group than in the control on day 7 (P = .013), but not on day 10 or 14. No significant between-group differences were found in collagen fibril alignment and collagen fibre orientation at any measured time points. Positive correlation was found between collagen fibre deposition and myofibroblast population only on day 7 (r = .729, P = .007). In conclusion, PEMF can significantly increase collagen fibre in the early phase of diabetic wound healing, which is associated with the enhancement of myofibroblast population. PMID:26511857

  3. Lumican Deficiency Results In Cardiomyocyte Hypertrophy With Altered Collagen Assembly

    PubMed Central

    Dupuis, Loren E.; Berger, Matthew G.; Feldman, Samuel; Doucette, Lorna; Fowlkes, Vennece; Chakravarti, Shukti; Thibaudeau, Sarah; Alcala, Nicolas E.; Bradshaw, Amy D.; Kern, Christine B.

    2015-01-01

    The ability of the heart to adapt to increased stress is dependent on modification of its extracellular matrix (ECM) architecture that is established during postnatal development as cardiomyocytes differentiate, a process that is poorly understood. We hypothesized that the small leucine-rich proteoglycan (SLRP) lumican (LUM), which binds collagen and facilitates collagen assembly in other tissues, may play a critical role in establishing the postnatal murine myocardial ECM. Although previous studies suggest LUM deficient mice (lum−/−) exhibit skin anomalies consistent with Ehlers-Danlos syndrome, lum−/− hearts have not been evaluated. These studies show LUM was immunolocalized to non-cardiomyocytes of the cardiac ventricles and its expression increased throughout development. Lumican deficiency resulted in significant (50%) perinatal death and further examination of the lum−/− neonatal hearts revealed an increase in myocardial tissue without a significant increase in cell proliferation. However cardiomyocytes from surviving postnatal day 0 (P0), 1 month (1 mo) and adult (4 mo) lum−/− hearts were significantly larger than their wild type (WT) littermates. Immunohistochemistry revealed that the increased cardiomyocyte size in the lum−/− hearts correlated with alteration of the cardiomyocyte pericellular ECM components collagenα1(I) and the class I SLRP decorin (DCN). Western blot analysis demonstrated that the ratio of glycosaminoglycan (GAG) decorated DCN to core DCN was reduced in P0 and 1 mo lum−/− hearts. There was also a reduction in the β and γ forms of collagenα1(I) in lum−/− hearts. While the total insoluble collagen content was significantly reduced, the fibril size was increased in lum−/− hearts, indicating LUM may play a role in collagen fiber stability and lateral fibril assembly. These results suggest that LUM controls cardiomyocyte growth by regulating the pericellular ECM and also indicates that LUM may coordinate

  4. Production, Characterization and Biocompatibility of Marine Collagen Matrices from an Alternative and Sustainable Source: The Sea Urchin Paracentrotus lividus

    PubMed Central

    Di Benedetto, Cristiano; Barbaglio, Alice; Martinello, Tiziana; Alongi, Valentina; Fassini, Dario; Cullorà, Emanuele; Patruno, Marco; Bonasoro, Francesco; Barbosa, Mario Adolfo; Candia Carnevali, Maria Daniela; Sugni, Michela

    2014-01-01

    Collagen has become a key-molecule in cell culture studies and in the tissue engineering field. Industrially, the principal sources of collagen are calf skin and bones which, however, could be associated to risks of serious disease transmission. In fact, collagen derived from alternative and riskless sources is required, and marine organisms are among the safest and recently exploited ones. Sea urchins possess a circular area of soft tissue surrounding the mouth, the peristomial membrane (PM), mainly composed by mammalian-like collagen. The PM of the edible sea urchin Paracentrotus lividus therefore represents a potential unexploited collagen source, easily obtainable as a food industry waste product. Our results demonstrate that it is possible to extract native collagen fibrils from the PM and produce suitable substrates for in vitro system. The obtained matrices appear as a homogeneous fibrillar network (mean fibril diameter 30–400 nm and mesh < 2 μm) and display remarkable mechanical properties in term of stiffness (146 ± 48 MPa) and viscosity (60.98 ± 52.07 GPa·s). In vitro tests with horse pbMSC show a good biocompatibility in terms of overall cell growth. The obtained results indicate that the sea urchin P. lividus can be a valuable low-cost collagen source for mechanically resistant biomedical devices. PMID:25255130

  5. Production, characterization and biocompatibility of marine collagen matrices from an alternative and sustainable source: the sea urchin Paracentrotus lividus.

    PubMed

    Benedetto, Cristiano Di; Barbaglio, Alice; Martinello, Tiziana; Alongi, Valentina; Fassini, Dario; Cullorà, Emanuele; Patruno, Marco; Bonasoro, Francesco; Barbosa, Mario Adolfo; Carnevali, Maria Daniela Candia; Sugni, Michela

    2014-09-01

    Collagen has become a key-molecule in cell culture studies and in the tissue engineering field. Industrially, the principal sources of collagen are calf skin and bones which, however, could be associated to risks of serious disease transmission. In fact, collagen derived from alternative and riskless sources is required, and marine organisms are among the safest and recently exploited ones. Sea urchins possess a circular area of soft tissue surrounding the mouth, the peristomial membrane (PM), mainly composed by mammalian-like collagen. The PM of the edible sea urchin Paracentrotus lividus therefore represents a potential unexploited collagen source, easily obtainable as a food industry waste product. Our results demonstrate that it is possible to extract native collagen fibrils from the PM and produce suitable substrates for in vitro system. The obtained matrices appear as a homogeneous fibrillar network (mean fibril diameter 30-400 nm and mesh < 2 μm) and display remarkable mechanical properties in term of stiffness (146 ± 48 MPa) and viscosity (60.98 ± 52.07 GPa·s). In vitro tests with horse pbMSC show a good biocompatibility in terms of overall cell growth. The obtained results indicate that the sea urchin P. lividus can be a valuable low-cost collagen source for mechanically resistant biomedical devices. PMID:25255130

  6. Ventricular fibrillation and atrial fibrillation are two different beasts

    NASA Astrophysics Data System (ADS)

    Gray, R. A.; Jalife, J.

    1998-03-01

    Although the mechanisms of fibrillation are no doubt multi-faceted, the geometry of the heart may play a major role in the dynamics of wave propagation during fibrillation [A. T. Winfree, Science 266, 1003-1006 (1994)]. The ventricles are thick chambers made up of sheets of parallel muscle fibers with the direction of fibers rotating across the ventricular walls (rotational anisotropy). The thick walls of the ventricles allow reentry to develop transmurally, provided the wavelength is sufficiently small. Depending on the kinetics of heart cells, the dynamics of rotating waves in three dimensions may be fundamentally different than in two dimensions, leading to destabilization of reentry and ventricular fibrillation (VF) in thick ventricles. The atria have an intricate geometry comprised of a thin sheet of cardiac tissue attached to a very complex network of pectinate muscles. The branching geometry of the pectinate muscles may lead to destabilization of two-dimensional reentry via "long-distance" electrical connections giving rise to atrial fibrillation (AF). Therefore, although fibrillation occurs via complex three-dimensional wave propagation in the ventricles and the atria, the underlying mechanisms and factors that sustain VF and AF are probably different.

  7. Surface Chemistry of Nanoscale Mineralized Collagen Regulates Periodontal Ligament Stem Cell Fate.

    PubMed

    Fu, Yu; Liu, Shuai; Cui, Sheng-Jie; Kou, Xiao-Xing; Wang, Xue-Dong; Liu, Xiao-Mo; Sun, Yue; Wang, Gao-Nan; Liu, Yan; Zhou, Yan-Heng

    2016-06-29

    The interplay between stem cells and their extracellular microenvironment is of critical importance to the stem cell-based therapeutics in regenerative medicine. Mineralized collagen is the main component of bone extracellular matrix, but the effect of interfacial properties of mineralized collagen on subsequent cellular behaviors is unclear. This study examined the role of surface chemistry of nanoscale mineralized collagen on human periodontal ligament stem cell (hPDLSC) fate decisions. The intrafibrillarly mineralized collagen (IMC), fabricated by a biomimetic bottom-up approach, showed a bonelike hierarchy with nanohydroxyapatites (HAs) periodically embedded within fibrils. The infrared spectrum of the IMC showed the presence of phosphate, carbonate, amide I and II bands; and infrared mapping displayed uniform and higher spatial distribution of mineralization in the IMC. However, the distribution of the phosphate group differed far from that of the amide I group in the extrafibrillarly mineralized collagen (EMC), in which flowerlike HA clusters randomly depositing around the surface of the fibrils. Moreover, a large quantity of extrafibrillar HAs covered up the C═O stretch and N-H in-plane bend, resulting in substantial reduction of amide I and II bands. Cell experiments demonstrated that the hPDLSCs seeded on the IMC exhibited a highly branched, osteoblast-like polygonal shape with extended pseudopodia and thick stress fiber formation; while cells on the EMC displayed a spindle shape with less branch points and thin actin fibril formation. Furthermore, the biocompatibility of EMC was much lower than that of IMC. Interestingly, even without osteogenic induction, mRNA levels of major osteogenic differentiation genes were highly expressed in the IMC during cultivation time. These data suggest that the IMC with a similar nanotopography and surface chemistry to natural mineralized collagen directs hPDLSCs toward osteoblast differentiation, providing a promising

  8. Fabrication and evaluation of a biodegradable cohesive plug based on reconstituted collagen/γ-polyglutamic acid.

    PubMed

    Hsu, Fu-Yin; Cheng, Ya-Yun; Tsai, Shiao-Wen; Tsai, Wei-Bor

    2010-10-01

    In the past decade, numerous studies have been devoted to developing natural bioadhesives that have the notable capacity to adhere to wet surfaces. Collagen and γ-polyglutamic acid (γ-PGA) are well-known natural hydrophilic polymers that have both been utilized for their versatility in a wide range of biomedical applications. The aim of this study was the construction and characterization of a cohesive plug composed of γ-PGA and reconstituted collagen fibrils crosslinked with water-soluble carbodiimide. Transmission electron microscopy examinations confirmed that the collagen fibrils in the reconstituted collagen/γ-PGA gel retained their native specific D-period structure. This unique D-pattern structure of collagen plays a major role in hemostasis and is also related to several cellular behaviors. The bonding strength of the reconstituted collagen/γ-PGA adhesive was approximately 42.9 ± 4.0 KPa after 5 min of application and increased to 76.5 ± 15.1 KPa after 24 h. This was much stronger than the fibrin adhesive, whose bonding strength was 30.9 ± 0.2 KPa. Furthermore, the reconstituted collagen/γ-PGA gel degraded gradually after subcutaneous implantation in the backs of rats over a period of 8 weeks, without any severe inflammatory response. On the basis of the histological analysis, fibroblasts migrated into the gel while it degraded, which indicates that the gel is not harmful to cellular activity. Together, these findings demonstrate that using reconstituted collagen with retained D-periodicity as a component of the bioadhesive is a possibly better option to formulate effective adhesiveness and is promising as a scaffold for tissue repair. PMID:20665682

  9. Variability in platelet responses to collagen--comparison between whole blood perfusions, traditional platelet function tests and PFA-100.

    PubMed

    Lepäntalo, A; Beer, J H; Siljander, P; Syrjälä, M; Lassila, R

    2001-07-15

    The purpose of this study was to determine if the results obtained in platelet function tests and whole blood perfusions are associated with those in platelet function analyser (PFA)-100. We used collagen type I monomers and fibrils to analyse the distinct roles of glycoprotein (GP) Ia/IIa and other collagen receptors in flowing blood under a high shear rate (1600/s) and in aggregation studies. Also, anticoagulation [citrate vs. D-phenylalanyl-1-prolyl-1 arginine chloromethyl ketone (PPACK)] was varied to enhance the functions of GP Ia/IIa, since it has been shown that the cation-poor environment of citrated blood impairs GP Ia/IIa-dependent platelet recruitment. Large interindividual variability (45-fold) was detected in deposition of platelets in whole blood perfusions over collagen monomers, whereas this variation was only fourfold in fibrils. In PFA, this variation was reduced to 2.5-fold. However, platelet deposition on monomers is associated with epinephrine-enhanced PFA (r=-.49, P<.03), whereas platelet deposition on fibrils is correlated with adenosine diphosphate (ADP)-enhanced PFA (r=-.47, P<.05), suggesting a distinct synergism between epinephrine and monomers (GP Ia/IIa) as well as ADP with fibrils (other collagen receptors). Donors with 807 C/C polymorphism of GP Ia (n=14) had longer lag phase in aggregation experiments compared with C/T (n=7) both by monomers and fibrils (P<.04), but these polymorphisms with their mild impact on GP Ia/IIa activity did not markedly differ in other tests. In conclusion, the results obtained in perfusion studies and PFA experiments correlated, but PFA fails to reveal the large-scale variability related to collagen-induced platelet responses. PMID:11457470

  10. Collagen in organ development

    NASA Technical Reports Server (NTRS)

    Hardman, P.; Spooner, B. S.

    1992-01-01

    It is important to know whether microgravity will adversely affect developmental processes. Collagens are macromolecular structural components of the extracellular matrix (ECM) which may be altered by perturbations in gravity. Interstitial collagens have been shown to be necessary for normal growth and morphogenesis in some embryonic organs, and in the mouse salivary gland, the biosynthetic pattern of these molecules changes during development. Determination of the effects of microgravity on epithelial organ development must be preceded by crucial ground-based studies. These will define control of normal synthesis, secretion, and deposition of ECM macromolecules and the relationship of these processes to morphogenesis.

  11. Interstitial Collagen Catabolism*

    PubMed Central

    Fields, Gregg B.

    2013-01-01

    Interstitial collagen mechanical and biological properties are altered by proteases that catalyze the hydrolysis of the collagen triple-helical structure. Collagenolysis is critical in development and homeostasis but also contributes to numerous pathologies. Mammalian collagenolytic enzymes include matrix metalloproteinases, cathepsin K, and neutrophil elastase, and a variety of invertebrates and pathogens possess collagenolytic enzymes. Components of the mechanism of action for the collagenolytic enzyme MMP-1 have been defined experimentally, and insights into other collagenolytic mechanisms have been provided. Ancillary biomolecules may modulate the action of collagenolytic enzymes. PMID:23430258

  12. Assessment of atherosclerotic plaque collagen content and architecture using polarization-sensitive optical coherence tomography (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Doradla, Pallavi; Villiger, Martin; Tshikudi, Diane M.; Bouma, Brett E.; Nadkarni, Seemantini K.

    2016-02-01

    Acute myocardial infarction, caused by the rupture of vulnerable coronary plaques, is the leading cause of death worldwide. Collagen is the primary extracellular matrix macromolecule that imparts the mechanical stability to a plaque and its reduction causes plaque instability. Intracoronary polarization sensitive optical coherence tomography (PS-OCT) measures the polarization states of the backscattered light from the tissue to evaluate plaque birefringence, a material property that is elevated in proteins such as collagen with an ordered structure. Here we investigate the dependence of the PS-OCT parameters on the quantity of the plaque collagen and fiber architecture. In this study, coronary arterial segments from human cadaveric hearts were evaluated with intracoronary PS-OCT and compared with Histopathological assessment of collagen content and architecture from picrosirius-red (PSR) stained sections. PSR sections were visualized with circularly-polarized light microscopy to quantify collagen birefringence, and the additional assessment of color hue indicated fibril thickness. Due to the ordered architecture of thick collagen fibers, a positive correlation between PS-OCT retardation and quantity of thick collagen fibers (r=0.54, p=0.04), and similarly with the total collagen content (r=0.51, p=0.03) was observed. In contrast, there was no perceivable relationship between PS-OCT retardation and the presence of thin collagen fibers (r=0.08, p=0.07), suggesting that thin and disorganized collagen fiber architecture did not significantly contribute to the PS-OCT retardation. Further analysis will be performed to assess the relationship between PS-OCT retardation and collagen architecture based on immunohistochemical analysis of collagen type. These results suggest that intracoronary PS-OCT may open the opportunity to assess collagen architecture in addition total collagen content, potentially enabling an improved understanding of coronary plaque rupture.

  13. Craniofacial abnormalities in mice carrying a dominant interference mutation in type X collagen.

    PubMed

    Chung, K S; Jacenko, O; Boyle, P; Olsen, B R; Nishimura, I

    1997-04-01

    Type X collagen is a short, non-fibril forming collagen restricted to hypertrophic cartilage, and has been hypothesized to play a role in endochondral ossification. The purpose of the study was to investigate the consequences resulting from the interference of type X collagen function on the growth and development of the craniofacial skeleton through analysis of transgenic mice with a dominant interference mutation for type X collagen. The craniofacial tissues of 21-day-old transgenic mice were examined by: cephalometric and radiographic densitometry analyses, conventional histology, and immunohistochemistry using antibodies specific for either endogenous mouse type X collagen or the transgene product. Genotypically positive mutant mice showed moderate but statistically significant craniofacial skeletal abnormalities, including the underdevelopment of the chondrocranium and mandible, but no cleft palate. Mean radiographic optical densities of the mutant condylar cartilage and the subchondylar areas were 32% less than the corresponding areas of normal mandibles, while mean radiographic optical density measured at the incisor tooth point remained constant. Histologically, transgene-positive mice revealed compressed hypertrophic cartilage zones and reduced trabeculae in both the mandibular condyle and the synchondroses of the chondrocranium. In the normal condyle, mouse type X collagen was localized by the monospecific antibody against a synthetic rat type X collagen NC1 peptide throughout the hypertrophic cartilage layer; in the mutant condyle, immunoreactivity to endogenous type X collagen was only seen sporadically. The truncated type X collagen transgene product, identified with the monoclonal antibody against an epitope within the chick type X collagen NC2 domain, persisted in the lower hypertrophic cartilage layer and the primary spongiosa, rather than being removed by subsequent endochondral ossification. The data suggested that the expression of the chick type

  14. Bone Collagen: New Clues to its Mineralization Mechanism From Recessive Osteogenesis Imperfecta

    PubMed Central

    Eyre, David R.; Ann Weis, Mary

    2013-01-01

    Until 2006 the only mutations known to cause osteogenesis imperfecta (OI) were in the two genes coding for type I collagen chains. These dominant mutations affecting the expression or primary sequence of collagen α1(I) and α2(I) chains account for over 90% of OI cases. Since then a growing list of mutant genes causing the 5–10% of recessive cases has rapidly emerged. They include CRTAP, LEPRE1 and PPIB, which encode three proteins forming the prolyl 3-hydroxylase complex; PLOD2 and FKBP10, which encode respectively lysyl hydroxylase 2 and a foldase required for its activity in forming mature cross-links in bone collagen; SERPIN H1, which encodes the collagen chaperone HSP47; SERPIN F1, which encodes pigment epithelium-derived factor required for osteoid mineralization; and BMP1, which encodes the type I procollagen C-propeptidase. All cause fragile bone in infancy, which can include over-mineralization or under-mineralization defects as well as abnormal collagen post-translational modifications. Consistently both dominant and recessive variants lead to abnormal cross-linking chemistry in bone collagen. These recent discoveries strengthen the potential for a common pathogenic mechanism of misassembled collagen fibrils. Of the new genes identified, eight encode proteins required for collagen post-translational modification, chaperoning of newly synthesized collagen chains into native molecules or transport through the endoplasmic reticulum and Golgi for polymerization, cross-linking and mineralization. In reviewing these findings, we conclude that a common theme is emerging in the pathogenesis of brittle bone disease of mishandled collagen assembly with important insights on post-translational features of bone collagen that have evolved to optimize it as a biomineral template. PMID:23508630

  15. Utility of an optically-based, micromechanical system for printing collagen fibers

    PubMed Central

    Paten, Jeffrey A.; Tilburey, Graham E.; Molloy, Eileen A.; Zareian, Ramin; Trainor, Christopher V.

    2013-01-01

    Collagen's success as the principal structural element in load-bearing, connective tissue has motivated the development of numerous engineering approaches designed to recapitulate native fibril morphology and strength. It has been shown recently that collagen fibers can be drawn from monomeric solution through a fiber forming buffer (FFB), followed by numerous additional treatments in a complex serial process. However, internal fibril alignment, packing and resultant mechanical behavior of the fibers have not been optimized and remain inferior to native tissue. Further, no system has been developed which permits simultaneous application of molecular crowding, measurement of applied load, and direct observation of polymerization dynamics during fiber printing. The ability to perform well-controlled investigations early in the process of fiber formation, which vary single input parameters (i.e. collagen concentration, crowding agent concentration, draw rate, flow rate, temperature, pH, etc.) should substantially improve fiber morphology and strength. We have thus designed, built, and tested a versatile, in situ, optically-based, micromechanical assay and fiber printing system which permits the correlation of parameter changes with mechanical properties of fibers immediately after deposition into an FFB. We demonstrate the sensitivity of the assay by detecting changes in the fiber mechanics in response to draw rate, collagen type, small changes in the molecular crowding agent concentration and to variations in pH. In addition we found the ability to observe fiber polymerization dynamics leads to intriguing new insights into collagen assembly behavior. PMID:23352045

  16. Fibrillar structure and elasticity of hydrating collagen: a quantitative multiscale approach.

    PubMed

    Morin, Claire; Hellmich, Christian; Henits, Peter

    2013-01-21

    It is well known that hydration of collagenous tissues leads to their swelling, as well as to softening of their elastic behavior. However, it is much less clear which microstructural and micromechanical "rules" are involved in this process. Here, we develop a theoretical approach cast in analytical mathematical formulations, which is experimentally validated by a wealth of independent tests on collagenous tissues, such as X-ray diffraction, vacuum drying, mass measurements, and Brillouin light scattering. The overall emerging picture is the following: air-drying leaves water only in the gap zones between the triple-helical collagen molecules; upon re-hydration, the extrafibrillar space is established at volumes directly proportional to the hydration-induced swelling of the (micro) fibrils, until the maximum equatorial distance between the long collagen molecules is reached. Thereafter, the volume of the fibrils stays constant, and only the extrafibrillar volume continues to grow. At all these hydration stages, the elastic behavior is governed by the same, hydration-invariant mechanical interaction pattern of only two, interpenetrating mechanical phases: transversely isotropic molecular collagen and isotropic water (or empty pores in the vacuum-dried case). PMID:23032219

  17. Effects of Decorin Proteoglycan on Fibrillogenesis, Ultrastructure, and Mechanics of Type I Collagen Gels

    PubMed Central

    Reese, Shawn P.; Underwood, Clayton J.; Weiss, Jeffrey A.

    2013-01-01

    The proteoglycan decorin is known to affect both the fibrillogenesis and the resulting ultrastructure of in vitro polymerized collagen gels. However, little is known about its effects on mechanical properties. In this study, 3D collagen gels were polymerized into tensile test specimens in the presence of decorin proteoglycan, decorin core protein, or dermatan sulfate (DS). Collagen fibrillogenesis, ultrastructure, and mechanical properties were then quantified using a turbidity assay, 2 forms of microscopy (SEM and confocal), and tensile testing. The presence of decorin proteoglycan or core protein decreased the rate and ultimate turbidity during fibrillogenesis and decreased the number of fibril aggregates (fibers) compared to control gels. The addition of decorin and core protein increased the linear modulus by a factor of 2 compared to controls, while the addition of DS reduced the linear modulus by a factor of 3. Adding decorin after fibrillogenesis had no effect, suggesting that decorin must be present during fibrillogenesis to increase the mechanical properties of the resulting gels. These results show that the inclusion of decorin proteoglycan during fibrillogenesis of Type I collagen increases the modulus and tensile strength of resulting collagen gels. The increase in mechanical properties when polymerization occurs in the presence of the decorin proteoglycan is due to a reduction in the aggregation of fibrils into larger order structures such as fibers and fiber bundles. PMID:23608680

  18. Characterization of a type II collagen gene (COL2A1) mutation identified in cultured chondrocytes from human hypochondrogenesis.

    PubMed Central

    Horton, W A; Machado, M A; Ellard, J; Campbell, D; Bartley, J; Ramirez, F; Vitale, E; Lee, B

    1992-01-01

    A subtle mutation in the type II collagen gene COL2A1 was detected in a case of human hypochondrogenesis by using a chondrocyte culture system and PCR-cDNA scanning analysis. Chondrocytes obtained from cartilage biopsies were dedifferentiated and expanded in monolayer culture and then redifferentiated by culture over agarose. Single-strand conformation polymorphism and direct sequencing analysis identified a G----A transition, resulting in a glycine substitution at amino acid 574 of the pro alpha 1(II) collagen triple-helical domain. Morphologic assessment of cartilage-like structures produced in culture and electrophoretic analysis of collagens synthesized by the cultured chondrocytes suggested that the glycine substitution interferes with conversion of type II procollagen to collagen, impairs intracellular transport and secretion of the molecule, and disrupts collagen fibril assembly. This experimental approach has broad implications for the investigation of human chondrodysplasias as well as human chondrocyte biology. Images PMID:1374906

  19. Who Is at Risk for Atrial Fibrillation?

    MedlinePlus

    ... from the NHLBI on Twitter. Who Is at Risk for Atrial Fibrillation? Atrial fibrillation (AF) affects millions ... than 75. AF is uncommon in children. Major Risk Factors AF is more common in people who ...

  20. Lentiviral Engineered Fibroblasts Expressing Codon-Optimized COL7A1 Restore Anchoring Fibrils in RDEB

    PubMed Central

    Georgiadis, Christos; Syed, Farhatullah; Petrova, Anastasia; Abdul-Wahab, Alya; Lwin, Su M.; Farzaneh, Farzin; Chan, Lucas; Ghani, Sumera; Fleck, Roland A.; Glover, Leanne; McMillan, James R.; Chen, Mei; Thrasher, Adrian J.; McGrath, John A.; Di, Wei-Li; Qasim, Waseem

    2016-01-01

    Cells therapies, engineered to secrete replacement proteins, are being developed to ameliorate otherwise debilitating diseases. Recessive dystrophic epidermolysis bullosa (RDEB) is caused by defects of type VII collagen, a protein essential for anchoring fibril formation at the dermal-epidermal junction. Whereas allogeneic fibroblasts injected directly into the dermis can mediate transient disease modulation, autologous gene-modified fibroblasts should evade immunological rejection and support sustained delivery of type VII collagen at the dermal-epidermal junction. We demonstrate the feasibility of such an approach using a therapeutic grade, self-inactivating-lentiviral vector, encoding codon-optimized COL7A1, to transduce RDEB fibroblasts under conditions suitable for clinical application. Expression and secretion of type VII collagen was confirmed with transduced cells exhibiting supranormal levels of protein expression, and ex vivo migration of fibroblasts was restored in functional assays. Gene-modified RDEB fibroblasts also deposited type VII collagen at the dermal-epidermal junction of human RDEB skin xenografts placed on NOD-scid IL2Rgammanull recipients, with reconstruction of human epidermal structure and regeneration of anchoring fibrils at the dermal-epidermal junction. Fibroblast-mediated restoration of protein and structural defects in this RDEB model strongly supports proposed therapeutic applications in man. PMID:26763448

  1. Lentiviral Engineered Fibroblasts Expressing Codon-Optimized COL7A1 Restore Anchoring Fibrils in RDEB.

    PubMed

    Georgiadis, Christos; Syed, Farhatullah; Petrova, Anastasia; Abdul-Wahab, Alya; Lwin, Su M; Farzaneh, Farzin; Chan, Lucas; Ghani, Sumera; Fleck, Roland A; Glover, Leanne; McMillan, James R; Chen, Mei; Thrasher, Adrian J; McGrath, John A; Di, Wei-Li; Qasim, Waseem

    2016-01-01

    Cells therapies, engineered to secrete replacement proteins, are being developed to ameliorate otherwise debilitating diseases. Recessive dystrophic epidermolysis bullosa (RDEB) is caused by defects of type VII collagen, a protein essential for anchoring fibril formation at the dermal-epidermal junction. Whereas allogeneic fibroblasts injected directly into the dermis can mediate transient disease modulation, autologous gene-modified fibroblasts should evade immunological rejection and support sustained delivery of type VII collagen at the dermal-epidermal junction. We demonstrate the feasibility of such an approach using a therapeutic grade, self-inactivating-lentiviral vector, encoding codon-optimized COL7A1, to transduce RDEB fibroblasts under conditions suitable for clinical application. Expression and secretion of type VII collagen was confirmed with transduced cells exhibiting supranormal levels of protein expression, and ex vivo migration of fibroblasts was restored in functional assays. Gene-modified RDEB fibroblasts also deposited type VII collagen at the dermal-epidermal junction of human RDEB skin xenografts placed on NOD-scid IL2Rgamma(null) recipients, with reconstruction of human epidermal structure and regeneration of anchoring fibrils at the dermal-epidermal junction. Fibroblast-mediated restoration of protein and structural defects in this RDEB model strongly supports proposed therapeutic applications in man. PMID:26763448

  2. Antithrombotic Therapy for Atrial Fibrillation

    PubMed Central

    You, John J.; Singer, Daniel E.; Howard, Patricia A.; Lane, Deirdre A.; Eckman, Mark H.; Fang, Margaret C.; Hylek, Elaine M.; Schulman, Sam; Go, Alan S.; Hughes, Michael; Spencer, Frederick A.; Manning, Warren J.; Halperin, Jonathan L.

    2012-01-01

    Background: The risk of stroke varies considerably across different groups of patients with atrial fibrillation (AF). Antithrombotic prophylaxis for stroke is associated with an increased risk of bleeding. We provide recommendations for antithrombotic treatment based on net clinical benefit for patients with AF at varying levels of stroke risk and in a number of common clinical scenarios. Methods: We used the methods described in the Methodology for the Development of Antithrombotic Therapy and Prevention of Thrombosis Guidelines: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines article of this supplement. Results: For patients with nonrheumatic AF, including those with paroxysmal AF, who are (1) at low risk of stroke (eg, CHADS2 [congestive heart failure, hypertension, age ≥ 75 years, diabetes mellitus, prior stroke or transient ischemic attack] score of 0), we suggest no therapy rather than antithrombotic therapy, and for patients choosing antithrombotic therapy, we suggest aspirin rather than oral anticoagulation or combination therapy with aspirin and clopidogrel; (2) at intermediate risk of stroke (eg, CHADS2 score of 1), we recommend oral anticoagulation rather than no therapy, and we suggest oral anticoagulation rather than aspirin or combination therapy with aspirin and clopidogrel; and (3) at high risk of stroke (eg, CHADS2 score of ≥ 2), we recommend oral anticoagulation rather than no therapy, aspirin, or combination therapy with aspirin and clopidogrel. Where we recommend or suggest in favor of oral anticoagulation, we suggest dabigatran 150 mg bid rather than adjusted-dose vitamin K antagonist therapy. Conclusions: Oral anticoagulation is the optimal choice of antithrombotic therapy for patients with AF at high risk of stroke (CHADS2 score of ≥ 2). At lower levels of stroke risk, antithrombotic treatment decisions will require a more individualized

  3. Preparation and characterization of two types of separate collagen nanofibers with different widths using aqueous counter collision as a gentle top-down process

    NASA Astrophysics Data System (ADS)

    Kondo, Tetsuo; Kumon, Daisuke; Mieno, Akiko; Tsujita, Yutaro; Kose, Ryota

    2014-12-01

    Two types of single collagen nanofibers with different widths were successfully prepared from native collagen fibrils using aqueous counter collision (ACC) as a top-down process. A mild collision of an aqueous suspension at a 100 MPa ejection pressure yielded nanofibers, termed CNF100, which have an inherent axial periodicity and are ˜100 nm in width and ˜10 μm in length. In contrast, ACC treatment at 200 MPa provided a non-periodic, shorter and thinner nanofiber, termed CNF10, that was ˜10 nm in width and ˜5 μm in length. Both nanofibers exhibited the inherent triple helix conformation of native collagen supramolecules. Even a medial collision that exceeded the above ACC pressures provided solely a mixture of the two nanofiber products. The two nanofiber types were well characterized, and their tensile strengths were estimated based on their sonication-induced fragmentation behaviors that related to their individual fiber morphologies. As a result, CNF10, which was found to be a critical minimum nanofibril unit, and CNF10 exhibited totally different features in sizes, morphology, tensile strength and viscoelastic properties. In particular, as the mechanical strength of the molecular scaffold affects cell differentiation, the two collagen nanofibers prepared here by ACC have the potential for controlling cell differentiation in possibly different ways, as they have different mechanical properties. This encourages the consideration of the application of CNF100 and CNF10 in the fabrication of new functional materials with unique properties such as a scaffold for tissue engineering.

  4. Genetic disorders of collagen.

    PubMed Central

    Tsipouras, P; Ramirez, F

    1987-01-01

    Osteogenesis imperfecta, Ehlers-Danlos syndrome, and Marfan syndrome form a group of genetic disorders of connective tissue. These disorders exhibit remarkable clinical heterogeneity which reflects their underlying biochemical and molecular differences. Defects in collagen types I and III have been found in all three syndromes. PMID:3543367

  5. Collagen and injectable fillers.

    PubMed

    Cheng, Jacqueline T; Perkins, Stephen W; Hamilton, Mark M

    2002-02-01

    Soft tissue augmentation of facial rhytids, scars, and deformities is a frequently performed office procedure. This article reviews the available biologic (collagen, Dermalogen, Autologen, Isolagen, autologous fat, Fibrel, hyaluronic acid derivatives, particulate fascia lata, micronized Alloderm) and alloplastic (silicone, Bioplastique, and Artecoll) soft tissue injectable fillers. PMID:11781208

  6. Collagen hydrolysate based collagen/hydroxyapatite composite materials

    NASA Astrophysics Data System (ADS)

    Ficai, Anton; Albu, Madalina Georgiana; Birsan, Mihaela; Sonmez, Maria; Ficai, Denisa; Trandafir, Viorica; Andronescu, Ecaterina

    2013-04-01

    The aim of this study was to study the influence of collagen hydrolysate (HAS) on the formation of ternary collagen-hydrolysate/hydroxyapatite composite materials (COLL-HAS/HA). During the precipitation process of HA, a large amount of brushite is resulted at pH = 7 but, practically pure HA is obtained at pH ⩾ 8. The FTIR data reveal the duplication of the most important collagen absorption bands due to the presence of the collagen hydrolysate. The presence of collagen hydrolysate is beneficial for the management of bone and joint disorders such as osteoarthritis and osteoporosis.

  7. Radial organization of interstitial exchange pathway and influence of collagen in synovium.

    PubMed Central

    Price, F M; Mason, R M; Levick, J R

    1995-01-01

    The synovial intercellular space is the path by which water, nutrients, cytokines, and macromolecules enter and leave the joint cavity. In this study two structural factors influencing synovial permeability were quantified by morphometry (Delesse's principle) of synovial electronmicrographs (rabbit knee), namely interstitial volume fraction Vv.1 and the fraction of the interstitium obstructed by collagen fibrils. Mean Vv.1 across the full thickness was 0.66 +/- 0.03 SEM (n = 11); but Vv.1 actually varied systematically with depth normal to the surface, increasing nonlinearly from 0.40 +/- 0.04 (n = 5 joints) near the free surface to 0.92 +/- 0.02 near the subsynovial interface. Tending to offset this increase in transport space, however, the space "blocked" by collagen fibrils also increased nonlinearly with depth. Bundles of collagen fibrils occupied 13.6 +/- 2.4% of interstitial volume close to the free surface but 49 +/- 4.8% near the subsynovial surface (full-thickness average, 40.5 +/- 3.5%), with fibrils accounting for 48.6-57.1% of the bundle space. Because of the two counteracting compositional gradients, the space available for fibril-excluded transport (hydraulic flow and macromolecular diffusion) was relatively constant > 4 microns below the surface but constricted at the synovium-cavity interface. The space available to extracellular polymers was only 51-53% of tissue volume, raising their effective concentration and hence the lining's resistance to flow and ability to confine the synovial fluid. Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 7 PMID:8534813

  8. Obstructive sleep apnea in atrial fibrillation patients.

    PubMed

    Arias, Miguel A; Alonso-Fernández, Alberto; García-Río, Francisco; Sánchez, Ana; López, Juana M; Pagola, Carlos

    2006-06-28

    A high prevalence of obstructive sleep apnea has been demonstrated in patients with atrial fibrillation. Our comments want to emphasize the importance of identifying and treating a large proportion of patients with atrial fibrillation who have undiagnosed obstructive sleep apnea as an additional preventive strategy for atrial fibrillation patients. PMID:16309764

  9. Cryoballoon Ablation for Atrial Fibrillation

    PubMed Central

    Andrade, Jason G; Dubuc, Marc; Guerra, Peter G; Macle, Laurent; Rivard, Lena; Roy, Denis; Talajic, Mario; Thibault, Bernard; Khairy, Paul

    2012-01-01

    Focal point-by-point radiofrequency catheter ablation has shown considerable success in the treatment of paroxysmal atrial fibrillation. However, it is not without limitations. Recent clinical and preclinical studies have demonstrated that cryothermal ablation using a balloon catheter (Artic Front©, Medtronic CryoCath LP) provides an effective alternative strategy to treating atrial fibrillation. The objective of this article is to review efficacy and safety data surrounding cryoballoon ablation for paroxysmal and persistent atrial fibrillation. In addition, a practical step-by-step approach to cryoballoon ablation is presented, while highlighting relevant literature regarding: 1) the rationale for adjunctive imaging, 2) selection of an appropriate cryoballoon size, 3) predictors of efficacy, 4) advanced trouble-shooting techniques, and 5) strategies to reduce procedural complications, such as phrenic nerve palsy. PMID:22557842

  10. [Electrocardiographic aspects of atrial fibrillations].

    PubMed

    Motté, G; Dinanian, S; Sebag, C

    1995-01-01

    The electrocardiographic analysis of atrial fibrillation is usually easy. However, some cases may be difficult to interpret: the organisation and voltage of the fibrillation waves can be very variable leading to appearances of atypical flutter in cases with large "f" waves or, conversely, in cases with low voltage fibrillation, to those of sinus mode dysfunction. The ventricular response may be slow: the conduction is usually delayed in the atrioventricular node where concealed conduction plays an important role in determining the ventricular response. Regular ventriculogrammes correspond to a junctional or ventricular escape rhythms. Aberrant conduction in the His-Purkinje system may sometimes be observed after long diastoles (phase 4 block) but often terminates short, preceded by long cycles (phase 3 block). It is usually easy to differentiate them from ventricular ectopics or preexcitation by careful examination and application of classical diagnostic criteria. PMID:7786147

  11. Fibrinolytic function and atrial fibrillation.

    PubMed

    Marín, Francisco; Roldán, Vanessa; Lip, Gregory Y H

    2003-03-15

    Atrial fibrillation (AF) is the commonest sustained cardiac arrhythmia, which is associated with a substantial risk of stroke and thromboembolism. A prothrombotic or hypercoagulable state has been observed in these patients, although previous studies have mainly focused on various clotting factors, endothelial damage or dysfunction markers and platelet activation. However, fibrinolytic function has been less frequently studied, despite the fibrinolytic system playing an important role in preventing intravascular thrombosis. Indeed, increasing evidence suggests that an imbalance between the fibrinolytic function is of great importance in cardiovascular disease. This review will begin by providing a brief approach to fibrinolytic function and examine previous studies about fibrinolytic activity and atrial fibrillation. PMID:12818244

  12. [Atrial fibrillation and physical activity].

    PubMed

    Apor, Péter

    2013-03-31

    Atrial fibrillation is the most frequent arrhythmia. Its "lone" form (when underlying pathology is not discovered) can be detected in a small percentage of endurance sports participants, and in growing numbers among veterans, probably as a result of some cardiac or other irregularities. Enhanced vagal tone and sudden sympathetic impulse, repetitive oxidative stress, inflammatory processes, enlarged atria, electric instabilization can explain the higher occurrence. Treatment of atrial fibrillation enables the affected persons to participate in regular medium-intensity exercise, 3-5 hours a week, which offers a protective role against cardiovascular, metabolic and mental illnesses. PMID:23524234

  13. Atrial Fibrillation in Ten Cows

    PubMed Central

    Brightling, P.; Townsend, H. G. G.

    1983-01-01

    An irregular cardiac rhythm was identified in ten adult cows during auscultation of the heart and was subsequently characterized as atrial fibrillation by electrocardiography. The occurrence of the arrhythmia was associated with primary, organic disease of the heart in two animals which had valvular endocarditis. In seven of the other cows secondary or “functional” atrial fibrillation occurred in association with disorders of abdominal origin, six gastrointestinal disorders and one uterine torsion. Spontaneous conversion to normal sinus rhythm occurred in six cows after elimination of the primary disease. ImagesFigure 1b.Figure 3a.Figure 3b. PMID:17422324

  14. Deficiency of CRTAP in non-lethal recessive osteogenesis imperfecta reduces collagen deposition into matrix

    PubMed Central

    Valli, M; Barnes, AM; Gallanti, A; Cabral, WA; Viglio, S; Weis, MA; Makareeva, E; Eyre, D; Leikin, S; Antoniazzi, F; Marini, JC; Mottes, M

    2013-01-01

    Deficiency of any component of the ER-resident collagen prolyl 3-hydroxylation complex causes recessive osteogenesis imperfecta (OI). The complex modifies the α1(I)Pro986 residue and contains cartilage-associated protein (CRTAP), prolyl 3-hydroxylase 1 (P3H1) and cyclophilin B (CyPB). Fibroblasts normally secrete about 10% of CRTAP. Most CRTAP mutations cause a null allele and lethal type VII OI. We identified a 7-year-old Egyptian boy with non-lethal type VII OI and investigated the effects of his null CRTAP mutation on collagen biochemistry, the prolyl 3-hydroxylation complex, and collagen in extracellular matrix. The proband is homozygous for an insertion/deletion in CRTAP (c.118_133del16insTACCC). His dermal fibroblasts synthesize fully overmodified type I collagen, and 3-hydroxylate only 5% of α1(I)Pro986. CRTAP transcripts are 10% of control. CRTAP protein is absent from proband cells, with residual P3H1 and normal CyPB levels. Dermal collagen fibril diameters are significantly increased. By immunofluorescence of long-term cultures, we identified a severe deficiency (10–15% of control) of collagen deposited in extracellular matrix, with disorganization of the minimal fibrillar network. Quantitative pulse-chase experiments corroborate deficiency of matrix deposition, rather than increased matrix turnover. We conclude that defects of extracellular matrix, as well as intracellular defects in collagen modification, contribute to the pathology of type VII OI. PMID:21955071

  15. Induction of mesenchymal stem cell differentiation and cartilage formation by cross-linker-free collagen microspheres.

    PubMed

    Mathieu, M; Vigier, S; Labour, M N; Jorgensen, C; Belamie, E; Noël, D

    2014-01-01

    Because of poor self-healing ability, joint cartilage can undergo irreversible degradation in the course of various diseases or after injury. A promising approach for cartilage engineering consists of using of mesenchymal stem cells (MSC) and a differentiation factor combined with an injectable carrier biomaterial. We describe here a novel synthesis route for native collagen microspheres that does not involve the use of potentially toxic crosslinking agents. An emulsion was formed between a type I collagen solution and perfluorinated oil, stabilised by a biocompatible triblock perfluorinated copolymer surfactant. Spherical microparticles of fibrillar collagen were formed through a sol-gel transition induced by ammonia vapours. Electron microscopy observations showed that these self-cross-linked microspheres were constituted by a gel of striated collagen fibrils. Microspheres that were loaded with transforming growth factor beta (TGF-β)3 progressively released this differentiation factor over a four weeks period. Human MSC rapidly adhered to TGF-β3-loaded microspheres and, after 21 d of culture, exhibited typical chondrocyte morphology and produced an uncalcified matrix made of the predominant cartilage components, aggrecan and type II collagen, but devoid of the hypertrophic marker type X collagen. Subcutaneous co-injection of MSC and TGF-β3-loaded microspheres in mice consistently led to the formation of a cartilage-like tissue, which was however hypertrophic, calcified and vascularised. In conclusion, we developed cross-linker free collagen microspheres that allowed chondrogenic differentiation of MSC in vitro and in vivo. PMID:25179212

  16. Laser-induced collagen remodeling and deposition within the basilar membrane of the mouse cochlea

    PubMed Central

    Wenzel, Gentiana I.; Anvari, Bahman; Mazhar, Amaan; Pikkula, Brian; Oghalai, John S.

    2013-01-01

    The cochlea is the mammalian organ of hearing. Its predominant vibratory element, the basilar membrane, is tonotopically tuned, based on the spatial variation of its mass and stiffness. The constituent collagen fibers of the basilar membrane affect its stiffness. Laser irradiation can induce collagen remodeling and deposition in various tissues. We tested whether similar effects could be induced within the basilar membrane. Trypan blue was perfused into the scala tympani of anesthetized mice to stain the basilar membrane. We then irradiated the cochleas with a 694-nm pulsed ruby laser at 15 or 180 J /cm2. The mice were sacrificed 14 to 16 days later and collagen organization was studied. Polarization microscopy revealed that laser irradiation increased the birefringence within the basilar membrane in a dose-dependent manner. Electron microscopy demonstrated an increase in the density of collagen fibers and the deposition of new fibrils between collagen fibers after laser irradiation. As an assessment of hearing, auditory brainstem response (ABR) thresholds were found to increase moderately after 15 J/cm2 and substantially after 180 J /cm2. Our results demonstrate that collagen remodeling and new collagen deposition occurs within the basilar membrane after laser irradiation in a similar fashion to that found in other tissues. PMID:17477714

  17. Recognition molecules myelin-associated glycoprotein and tenascin-C inhibit integrin-mediated adhesion of neural cells to collagen.

    PubMed

    Bachmann, M; Conscience, J F; Probstmeier, R; Carbonetto, S; Schachner, M

    1995-03-01

    Because of the importance of collagens in mediating cell-substrate interactions and the association of collagens with neural recognition molecules in the peripheral nervous system, the ability of neural recognition molecules to modify the substrate properties of collagens, in particular collagen type I, for cell adhesion was determined. Two cell lines, the N2A neuroblastoma and PC12 pheochromocytoma, were investigated for their capacity to adhere to different collagen types in the absence or presence of several neural recognition molecules. Adhesion of N2A or PC12 cells and membrane vesicles from PC12 cells to collagen type I was reduced when the collagen had been preincubated prior to its application as substrate with the extracellular domain of myelin-associated glycoprotein (s-MAG) or, as control, fibroblast tenascin-C (F-tenascin). In mixture with other collagen types, s-MAG was only able to reduce the adhesiveness of collagen types III and V, but not of collagen types II and IV. F-tenascin reduced the adhesiveness of all collagen types tested. In contrast to F-tenascin, s-MAG had to be present during fibrillogenesis to exert its effect, indicating that it must be coassembled into the collagen fibril to block the binding site. Cell adhesion to collagen type I was dependent on Mg2+ or Mn2+ and inhibited by a monoclonal antibody to the alpha 1 integrin subunit. The combined observations indicate that s-MAG and F-tenascin interfere with cell binding, most probably by modifying the integrin binding site, and that the two molecules act by different mechanisms, both leading to reduction of adhesion. PMID:7542351

  18. The Surgical Treatment of Atrial Fibrillation

    PubMed Central

    Shen, Jeanne; Bailey, Marci S.; Damiano, Ralph J.

    2009-01-01

    Summary For two decades, the cut-and-sew Cox-Maze III procedure was the gold standard for the surgical treatment of atrial fibrillation (AF), and proved to be effective at eliminating AF. The incidence of late stroke was also very low. However, this procedure was not widely adopted due to its complexity and technical difficulty. Over the last 5-10 years, the introduction of new ablation technology has led to the development of the Cox-Maze IV procedure, as well as, more limited lesion sets, with the ultimate goal of performing a minimally-invasive lesion set on the beating heart, without the need for cardiopulmonary bypass. This review summarizes the current state of the art and future directions in the stand-alone surgical treatment of atrial fibrillation. The hope is that as more is learned about the mechanisms of AF and with better preoperative diagnostic technologies capable of precisely locating the areas responsible for AF, it will become possible to tailor specific lesion sets and ablation modalities to individual patients, making the surgical treatment of AF available to a larger population of patients. PMID:19631907

  19. Modeling the coupled mechanics, transport, and growth processes in collagen tissues.

    SciTech Connect

    Holdych, David J.; Nguyen, Thao D.; Klein, Patrick A.; in't Veld, Pieter J.; Stevens, Mark Jackson

    2006-11-01

    The purpose of this project is to develop tools to model and simulate the processes of self-assembly and growth in biological systems from the molecular to the continuum length scales. The model biological system chosen for the study is the tendon fiber which is composed mainly of Type I collagen fibrils. The macroscopic processes of self-assembly and growth at the fiber scale arise from microscopic processes at the fibrillar and molecular length scales. At these nano-scopic length scales, we employed molecular modeling and simulation method to characterize the mechanical behavior and stability of the collagen triple helix and the collagen fibril. To obtain the physical parameters governing mass transport in the tendon fiber we performed direct numerical simulations of fluid flow and solute transport through an idealized fibrillar microstructure. At the continuum scale, we developed a mixture theory approach for modeling the coupled processes of mechanical deformation, transport, and species inter-conversion involved in growth. In the mixture theory approach, the microstructure of the tissue is represented by the species concentration and transport and material parameters, obtained from fibril and molecular scale calculations, while the mechanical deformation, transport, and growth processes are governed by balance laws and constitutive relations developed within a thermodynamically consistent framework.

  20. X-ray diffraction study into the effects of liming on the structure of collagen.

    PubMed

    Maxwell, Clark A; Wess, Tim J; Kennedy, Craig J

    2006-08-01

    The manufacture of parchment from animal skin involves processes that remove hair, fats, and other macromolecules. Although it is well understood that the collagen fibers "open up" during processing, this study uses small and wide-angle X-ray diffraction to measure quantitatively the changes induced at the nanoscopic and microscopic levels. The axial rise per residue distance within the collagen molecules is unaffected by salt and lime treatments. Salting of the hides appears to remove noncollagenous materials. The intermolecular lateral packing distance between the hydrated collagen molecules (1.4 nm) increases after salting ( approximately 1.5 nm) and liming ( approximately 1.55 nm); drying is responsible for a reduction to approximately 1.2 nm in all samples. The axial staggered array (d spacing) is reduced by 1 nm after liming and is unaffected by drying. The average fibril diameter increases from 103.2 to 114.5 nm following liming, and the fibril-to-fibril distance increases from 122.6 to 136.1 nm. PMID:16903677

  1. Characterization of mutations of the type VII collagen gene (COL7A1) in recessive dystrophic epidermolysis bullosa mitis (M-RDEB) from three Korean patients.

    PubMed

    Ryoo, Y W; Kim, B C; Lee, K S

    2001-06-01

    In recent years, the molecular basis for the main subtypes of epidermolysis bullosa (EB) has been elucidated with pathogenetic mutations delineated in ten different genes encoding structural components of the dermal-epidermal junction. Both the autosomal dominant and recessive forms of dystrophic EB (DEB) is caused by mutations in the COL7A1 gene. Type VII collagen is a major component of anchoring fibrils, structural elements that stabilize the attachment of the basement membrane to underlying dermis. Recent delineation of the exon-intron organization of the COL7A1 gene provided the basis for the comprehensive design of PCR primer pairs that amplified exons in genomic DNA by placing the primers on the flanking introns. A number of COL7A1 mutations have been reported and some genotype-phenotype correlations are starting to emerge. In this study, we examined mutational analyses from three Korean patients with recessive dystrophic EB (RDEB) mitis. We designed and optimized primers according to the previously reported sequences. Such PCR amplification products can be examined by electrophoretic scanning technique, CSGE heteroduplex analyses. Utilizing heteroduplex analyses, we have identified a number of sequence variants in COL7A1 both in unaffected individuals and in patients with M-RDEB. Mutation detection of the COL7A1 gene revealed six allelic mutations (V6677E, P6685S, Y3749S, P6084S, P6695R and G6697C). We suggest that the full length of type VII collagen polypeptide are synthesized, but those missense mutations, that may affect a critical amino acid, can alter the conformation of the protein and interferes with the assembly and packing of type VII collagen molecules into anchoring fibrils. Immunohistochemical study of skin biopsies by use of anti-type VII collagen antibody showed markedly reduced staining and presence of a dermo/epidermal cleavage. This is the first report of a COL7A1 mutation study in DEB from Korean patients. We hope that these data

  2. Histological characteristics of collagen denaturation and injuries in bipolar radiofrequency-induced colonic anastomoses.

    PubMed

    Zhao, Lingxi; Zhuo, Changhua; Song, Chengli; Li, Xinxiang; Zhou, Yu; Shi, Debing

    2015-03-01

    Bipolar radiofrequency-induced thermo-fusion has been explored as an advanced surgical method for intestinal anastomoses; however, the histological characteristics of collagen denaturation and injuries arising from this process remain unclear. The aim of this study was to investigate the microcosmic changes and tissue damage of fusion regions with various parameters of injury. Ex vivo colons of pigs were fused serosa-serosa on two carrier rings, which were installed on a homemade anastomotic device. Five levels of compressive pressure from 171 to 313 kPa were applied for 5s to fuse the colons under radiofrequency power of 160 W, and then the collagen denaturation of the fused region was examined by transmission electron microscopy. Light microscopy was utilized to observe histological slices that were stained with picrosirius red in order to visualize the tissue injuries under two levels of radiofrequency power (120 vs. 140 W) and operation time (5 vs. 10s). Transmission electron micrographs showed that increased compressive pressure led to thicker denatured collagen fibrils and wider gaps between each collagen fibril. Serosa adhesion regions appeared abundant in collagen. No histological differences were observed when 120 W of power was applied for 5 and 10s. Significant muscle cracking occurred when colons were fused using 140 W for 5s. When the operation time was extended to 10s, 140 W led to tight fusion and less splitting on muscles. These results suggest that higher compressive pressure results in more severe collagen unfolding and also reduces collagen crosslinking in fused colons. Improved radiofrequency power along with operation time could avoid tissue injury upon radiofrequency-induced colonic anastomoses. PMID:25434604

  3. Second-harmonic generation reveals a relationship between metastatic potential and collagen fiber structure

    NASA Astrophysics Data System (ADS)

    Burke, Kathleen A.; Dawes, Ryan P.; Cheema, Mehar K.; Perry, Seth; Brown, Edward

    2014-02-01

    Second Harmonic Generation (SHG) of collagen signals allows for the analysis of collagen structural changes throughout metastatic progression. The directionality of coherent SHG signals, measured through the ratio of the forward-propagating to backward propagating signal (F/B ratio), is affected by fibril diameter, spacing, and order versus disorder of fibril packing within a fiber. As tumors interact with their microenvironment and metastasize, it causes changes in these parameters, and concurrent changes in the F/B ratio. Specifically, the F/B ratio of breast tumors that are highly metastatic to the lymph nodes is significantly higher than those in tumors with restricted lymph node involvement. We utilized in vitro analysis of tumor cell motility through collagen gels of different microstructures, and hence different F/B ratios, to explore the relationship between collagen microstructures and metastatic capabilities of the tumor. By manipulating environmental factors of fibrillogenesis and biochemical factors of fiber composition we created methods of varying the average F/B ratio of the gel, with significant changes in fiber structure occurring as a result of alterations in incubation temperature and increasing type III collagen presence. A migration assay was performed using simultaneous SHG and fluorescent imaging to measure average penetration depth of human tumor cells into the gels of significantly different F/B ratios, with preliminary data demonstrating that cells penetrate deeper into gels of higher F/B ratio caused by lower type III collagen concentration. Determining the role of collagen structure in tumor cell motility will aid in the future prediction metastatic capabilities of a primary tumor.

  4. Computational and experimental methodology for site-matched investigations of the influence of mineral mass fraction and collagen orientation on the axial indentation modulus of lamellar bone☆

    PubMed Central

    Spiesz, Ewa M.; Reisinger, Andreas G.; Kaminsky, Werner; Roschger, Paul; Pahr, Dieter H.; Zysset, Philippe K.

    2013-01-01

    Relationships between mineralization, collagen orientation and indentation modulus were investigated in bone structural units from the mid-shaft of human femora using a site-matched design. Mineral mass fraction, collagen fibril angle and indentation moduli were measured in registered anatomical sites using backscattered electron imaging, polarized light microscopy and nano-indentation, respectively. Theoretical indentation moduli were calculated with a homogenization model from the quantified mineral densities and mean collagen fibril orientations. The average indentation moduli predicted based on local mineralization and collagen fibers arrangement were not significantly different from the average measured experimentally with nanoindentation (p=0.9). Surprisingly, no substantial correlation of the measured indentation moduli with tissue mineralization and/or collagen fiber arrangement was found. Nano-porosity, micro-damage, collagen cross-links, non-collagenous proteins or other parameters affect the indentation measurements. Additional testing/simulation methods need to be considered to properly understand the variability of indentation moduli, beyond the mineralization and collagen arrangement in bone structural units. PMID:23994944

  5. Nanomechanical properties of single amyloid fibrils

    NASA Astrophysics Data System (ADS)

    Sweers, K. K. M.; Bennink, M. L.; Subramaniam, V.

    2012-06-01

    Amyloid fibrils are traditionally associated with neurodegenerative diseases like Alzheimer’s disease, Parkinson’s disease or Creutzfeldt-Jakob disease. However, the ability to form amyloid fibrils appears to be a more generic property of proteins. While disease-related, or pathological, amyloid fibrils are relevant for understanding the pathology and course of the disease, functional amyloids are involved, for example, in the exceptionally strong adhesive properties of natural adhesives. Amyloid fibrils are thus becoming increasingly interesting as versatile nanobiomaterials for applications in biotechnology. In the last decade a number of studies have reported on the intriguing mechanical characteristics of amyloid fibrils. In most of these studies atomic force microscopy (AFM) and atomic force spectroscopy play a central role. AFM techniques make it possible to probe, at nanometer length scales, and with exquisite control over the applied forces, biological samples in different environmental conditions. In this review we describe the different AFM techniques used for probing mechanical properties of single amyloid fibrils on the nanoscale. An overview is given of the existing mechanical studies on amyloid. We discuss the difficulties encountered with respect to the small fibril sizes and polymorphic behavior of amyloid fibrils. In particular, the different conformational packing of monomers within the fibrils leads to a heterogeneity in mechanical properties. We conclude with a brief outlook on how our knowledge of these mechanical properties of the amyloid fibrils can be exploited in the construction of nanomaterials from amyloid fibrils.

  6. Metalloproteases meprin α and meprin β are C- and N-procollagen proteinases important for collagen assembly and tensile strength

    PubMed Central

    Broder, Claudia; Arnold, Philipp; Vadon-Le Goff, Sandrine; Konerding, Moritz A.; Bahr, Kerstin; Müller, Stefan; Overall, Christopher M.; Bond, Judith S.; Koudelka, Tomas; Tholey, Andreas; Hulmes, David J. S.; Moali, Catherine; Becker-Pauly, Christoph

    2013-01-01

    Type I fibrillar collagen is the most abundant protein in the human body, crucial for the formation and strength of bones, skin, and tendon. Proteolytic enzymes are essential for initiation of the assembly of collagen fibrils by cleaving off the propeptides. We report that Mep1a−/− and Mep1b−/− mice revealed lower amounts of mature collagen I compared with WT mice and exhibited significantly reduced collagen deposition in skin, along with markedly decreased tissue tensile strength. While exploring the mechanism of this phenotype, we found that cleavage of full-length human procollagen I heterotrimers by either meprin α or meprin β led to the generation of mature collagen molecules that spontaneously assembled into collagen fibrils. Thus, meprin α and meprin β are unique in their ability to process and release both C- and N-propeptides from type I procollagen in vitro and in vivo and contribute to the integrity of connective tissue in skin, with consequent implications for inherited connective tissue disorders. PMID:23940311

  7. Collagen Homeostasis and Metabolism.

    PubMed

    Magnusson, S Peter; Heinemeier, Katja M; Kjaer, Michael

    2016-01-01

    The musculoskeletal system and its collagen rich tissue is important for ensuring architecture of skeletal muscle, energy storage in tendon and ligaments, joint surface protection, and for ensuring the transfer of muscular forces into resulting limb movement. Structure of tendon is stable and the metabolic activity is low, but mechanical loading and subsequent mechanotransduction and molecular anabolic signaling can result in some adaptation of the tendon especially during youth and adolescence. Within short time, tendon will get stiffer with training and lack of mechanical tissue loading through inactivity or immobilization of the human body will conversely result in a dramatic loss in tendon stiffness and collagen synthesis. This illustrates the importance of regular mechanical load in order to preserve the stabilizing role of the connective tissue for the overall function of the musculoskeletal system in both daily activity and exercise. Adaptive responses may vary along the tendon, and differ between mid-substance and insertional areas of the tendon. PMID:27535245

  8. Nonlinear Dynamical Analysis of Fibrillation

    NASA Astrophysics Data System (ADS)

    Kerin, John A.; Sporrer, Justin M.; Egolf, David A.

    2013-03-01

    The development of spatiotemporal chaotic behavior in heart tissue, termed fibrillation, is a devastating, life-threatening condition. The chaotic behavior of electrochemical signals, in the form of spiral waves, causes the muscles of the heart to contract in an incoherent manner, hindering the heart's ability to pump blood. We have applied the mathematical tools of nonlinear dynamics to large-scale simulations of a model of fibrillating heart tissue to uncover the dynamical modes driving this chaos. By studying the evolution of Lyapunov vectors and exponents over short times, we have found that the fibrillating tissue is sensitive to electrical perturbations only in narrow regions immediately in front of the leading edges of spiral waves, especially when these waves collide, break apart, or hit the edges of the tissue sample. Using this knowledge, we have applied small stimuli to areas of varying sensitivity. By studying the evolution of the effects of these perturbations, we have made progress toward controlling the electrochemical patterns associated with heart fibrillation. This work was supported by the U.S. National Science Foundation (DMR-0094178) and Research Corporation.

  9. Mechanical response of collagen molecule under hydrostatic compression.

    PubMed

    Saini, Karanvir; Kumar, Navin

    2015-04-01

    Proteins like collagen are the basic building blocks of various body tissues (soft and hard). Collagen molecules find their presence in the skeletal system of the body where they bear mechanical loads from different directions, either individually or along with hydroxy-apatite crystals. Therefore, it is very important to understand the mechanical behavior of the collagen molecule which is subjected to multi-axial state of loading. The estimation of strains of collagen molecule along different directions resulting from the changes in hydrostatic pressure magnitude, can provide us new insights into its mechanical behavior. In the present work, full atomistic simulations have been used to study global (volumetric) as well as local (along different directions) mechanical properties of the hydrated collagen molecule which is subjected to different hydrostatic pressure magnitudes. To estimate the local mechanical properties, the strains of collagen molecule along its longitudinal and transverse directions have been acquired at different hydrostatic pressure magnitudes. In spite of non-homogeneous distribution of atoms within the collagen molecule, the calculated values of local mechanical properties have been found to carry the same order of magnitude along the longitudinal and transverse directions. It has been demonstrated that the values of global mechanical properties like compressibility, bulk modulus, etc. as well as local mechanical properties like linear compressibility, linear elastic modulus, etc. are functions of magnitudes of applied hydrostatic pressures. The mechanical characteristics of collagen molecule based on the atomistic model have also been compared with that of the continuum model in the present work. The comparison showed up orthotropic material behavior for the collagen molecule. The information on collagen molecule provided in the present study can be very helpful in designing the future bio-materials. PMID:25687001

  10. Development of a Commercial Process for the Production of Silicon Carbide Fibrils

    SciTech Connect

    Nixdorf, R.D.

    1999-04-01

    A patent was issued on ''VLS'' silicon carbide fibrils to North American Phillips Corporation in 1975. Various laboratories and companies have been attempting to improve this process and scale it to larger quantities since that time. All of these efforts met with minimal success because they were using the original technology while attempting to improve the equipment. The principal impediments have been: (1) Slow crystal growth during fibril production; (2) Sensitive stoichiometry factors in the crystal growth chamber; and (3) Precise control of a high temperature process. The principal investigator has scaled silicon carbide whisker production at American Matrix and the SiC fiber process at Advanced Composite Materials Corporation from grams in the laboratory to tons per year production. This project is a proof-of-concept effort to apply some of the recent technology to the problems listed above in the fibril growth process. Two different technology approaches were investigated. A major problem with fibril growth has been generating a consistent supply of the required SiO gas reactant, which is a product of reducing SiO{sub 2}. The first approach, in this project addresses the SiO gas production, involved mixing silica and carbon fibrous raw materials in the immediate proximity of the graphite fibril growth plates to generate SiO nearer to individual sites of fibril growth. Iron bearing catalyst was painted on the graphite plates and the SiO generator mix was placed above the plate. This system was then heated to 1600/1650 C in a graphite resistance furnace. Some fibrils were started but the growth rate and fibril quality were unacceptably low. A second approach, which uses MTS + H{sub 2} gases to address stoichiometry control, was investigated to improve fibril growth rates while reducing the previous high temperature requirements for the process. A partial vacuum chamber was construct inside a commercial microwave furnace. The fibril growth container was coated

  11. Aspartic Acid Racemization and Collagen Degradation Markers Reveal an Accumulation of Damage in Tendon Collagen That Is Enhanced with Aging*

    PubMed Central

    Thorpe, Chavaunne T.; Streeter, Ian; Pinchbeck, Gina L.; Goodship, Allen E.; Clegg, Peter D.; Birch, Helen L.

    2010-01-01

    Little is known about the rate at which protein turnover occurs in living tendon and whether the rate differs between tendons with different physiological roles. In this study, we have quantified the racemization of aspartic acid to calculate the age of the collagenous and non-collagenous components of the high strain injury-prone superficial digital flexor tendon (SDFT) and low strain rarely injured common digital extensor tendon (CDET) in a group of horses with a wide age range. In addition, the turnover of collagen was assessed indirectly by measuring the levels of collagen degradation markers (collagenase-generated neoepitope and cross-linked telopeptide of type I collagen). The fractional increase in d-Asp was similar (p = 0.7) in the SDFT (5.87 × 10−4/year) and CDET (5.82 × 10−4/year) tissue, and d/l-Asp ratios showed a good correlation with pentosidine levels. We calculated a mean (±S.E.) collagen half-life of 197.53 (±18.23) years for the SDFT, which increased significantly with horse age (p = 0.03) and was significantly (p < 0.001) higher than that for the CDET (34.03 (±3.39) years). Using similar calculations, the half-life of non-collagenous protein was 2.18 (±0.41) years in the SDFT and was significantly (p = 0.04) lower than the value of 3.51 (±0.51) years for the CDET. Collagen degradation markers were higher in the CDET and suggested an accumulation of partially degraded collagen within the matrix with aging in the SDFT. We propose that increased susceptibility to injury in older individuals results from an inability to remove partially degraded collagen from the matrix leading to reduced mechanical competence. PMID:20308077

  12. Heterogeneity of collagens in rabbit cornea: type VI collagen

    SciTech Connect

    Cintron, C.; Hong, B.S.

    1988-05-01

    Normal adult rabbit corneas were digested with 5% pepsin and their collagens extracted with acetic acid. Collagen extracts were fractionated by differential salt precipitation. The 2.5 M NaCl fraction was then redissolved with tris buffer and precipitated with sodium acetate. The precipitate contained a high-molecular-weight disulfide-bonded aggregate which, upon reduction with mercaptoethanol, was converted into three distinct polypeptides having molecular weights between 45 and 66 Kd. These physical characteristics, together with the susceptibility of these polypeptides to collagenase and their amino acid composition, identified the high molecular weight aggregate as type VI collagen. Corneas from neonate rabbits and adult corneas containing 2-week-old scars were organ cultured in the presence of (/sup 14/C) glycine to incorporate radiolabel into collagen. Tissues were digested with 0.02% pepsin and their collagens extracted with formic acid. The total radioactivity of the extracts and tissue residues was determined before the collagens were separated by SDS-polyacrylamide slab gel electrophoresis. Radioactive collagen polypeptides bands were then stained with Coomassie blue, processed for fluorography, and analyzed by densitometry. The results show that: (1) type VI collagen is synthesized by neonate corneas and healing adult corneas; (2) it is not readily solubilized from either corneal tissue by 0.02% pepsin digestion and formic acid extraction; and (3) the proportion of type VI collagen deposited in scar tissue is markedly lower than that found in neonate corneas.

  13. Heterogeneity of collagens in rabbit cornea: type III collagen

    SciTech Connect

    Cintron, C.; Hong, B.S.; Covington, H.I.; Macarak, E.J.

    1988-05-01

    Whole neonate rabbit corneas and adult corneas containing 2-week-old scars were incubated in the presence of (/sup 14/C) glycine. Radiolabeled collagen extracted from the corneas and scar tissue were analyzed by sodium dodecylsulfate/polyacrylamide gel electrophoresis and fluorography to determine the types and relative quantity of collagen polypeptides present and synthesized by these tissues. In addition to other collagen types, type III was found in both neonate cornea and scar tissue from adult cornea, albeit in relatively small quantities. Type III collagen in normal cornea was associated with the residue after pepsin digestion and formic acid extraction of the tissue, and the same type of collagen was extracted from scar tissue after similar treatment. Type III collagen-specific monoclonal antibody bound to developing normal corneas and healing adult tissue sections, as determined by immunofluorescence. Antibody binding was localized to the endothelium and growing Descemet's membrane in fetal and neonate corneas, and restricted to the most posterior region of the corneal scar tissue. Although monoclonal antibody to keratan sulfate, used as a marker for stromal fibroblasts, bound to most of the scar tissue, the antibody failed to bind to the posterior scar tissue positive for type III collagen. We conclude that endothelial cells from fetal and neonate rabbit cornea and endothelium-derived fibroblasts from healing wounds of adult cornea synthesize and deposit type III collagen. Moreover, this collagen appears to be incorporated into the growing Descemet's membrane of normal corneas and narrow posterior portion of the scar tissue.

  14. Quantification of Interfibrillar Shear Stress in Aligned Soft Collagenous Tissues via Notch Tension Testing

    NASA Astrophysics Data System (ADS)

    Szczesny, Spencer E.; Caplan, Jeffrey L.; Pedersen, Pal; Elliott, Dawn M.

    2015-10-01

    The mechanical function of soft collagenous tissues is largely determined by their hierarchical organization of collagen molecules. While collagen fibrils are believed to be discontinuous and transfer load through shearing of the interfibrillar matrix, interfibrillar shear stresses have never been quantified. Scaling traditional shear testing procedures down to the fibrillar length scale is impractical and would introduce substantial artifacts. Here, through the use of a novel microscopic variation of notch tension testing, we explicitly demonstrate the existence of interfibrillar shear stresses within tendon fascicles and provide the first measurement of their magnitude. Axial stress gradients along the sample length generated by notch tension testing were measured and used to calculate a value of 32 kPa for the interfibrillar shear stress. This estimate is comparable to the interfibrillar shear stress predicted by previous multiscale modeling of tendon fascicles, which supports the hypothesis that fibrils are discontinuous and transmit load through interfibrillar shear. This information regarding the structure-function relationships of tendon and other soft collagenous tissues is necessary to identify potential causes for tissue impairment with degeneration and provide the foundation for developing regenerative repair strategies or engineering biomaterials for tissue replacement.

  15. 99mTc-DPD uptake reflects amyloid fibril composition in hereditary transthyretin amyloidosis

    PubMed Central

    Pilebro, Björn; Suhr, Ole B.; Näslund, Ulf; Westermark, Per; Lindqvist, Per; Sundström, Torbjörn

    2016-01-01

    Aims In transthyretin amyloid (ATTR) amyloidosis various principal phenotypes have been described: cardiac, neuropathic, or a mixed cardiac and neuropathic. In addition, two different types of amyloid fibrils have been identified (type A and type B). Type B fibrils have thus far only been found in predominantly early-onset V30M and in patients carrying the Y114C mutation, whereas type A is noted in all other mutations currently examined as well as in wild-type ATTR amyloidosis. The fibril type is a determinant of the ATTR V30M disease phenotype. 99mTc-DPD scintigraphy is a highly sensitive method for diagnosing heart involvement in ATTR amyloidosis. The objective of this study was to determine the relationship between ATTR fibril composition and 99mTc-DPD scintigraphy outcome in patients with biopsy-proven ATTR amyloidosis. Methods Altogether 55 patients with biopsy-proven diagnosis of ATTR amyloidosis and amyloid fibril composition determined were examined by 99mTc-DPD scintigraphy. The patients were grouped and compared according to their type of amyloid fibrils. Cardiovascular evaluation included ECG, echocardiography, and cardiac biomarkers. The medical records were scrutinized to identify subjects with hypertension or other diseases that have an impact on cardiac dimensions. Results A total of 97% with type A and none of the patients with type B fibrils displayed 99mTc-DPD uptake at scintigraphy (p < 0.001). Findings from analyses of cardiac biomarkers, ECG, and echocardiography, though significantly different, could not differentiate between type A and B fibrils in individual patients. Conclusion In ATTR amyloidosis, the outcome of 99mTc-DPD scintigraphy is strongly related to the patients’ transthyretin amyloid fibril composition. PMID:26849806

  16. (99m)Tc-DPD uptake reflects amyloid fibril composition in hereditary transthyretin amyloidosis.

    PubMed

    Pilebro, Björn; Suhr, Ole B; Näslund, Ulf; Westermark, Per; Lindqvist, Per; Sundström, Torbjörn

    2016-01-01

    Aims In transthyretin amyloid (ATTR) amyloidosis various principal phenotypes have been described: cardiac, neuropathic, or a mixed cardiac and neuropathic. In addition, two different types of amyloid fibrils have been identified (type A and type B). Type B fibrils have thus far only been found in predominantly early-onset V30M and in patients carrying the Y114C mutation, whereas type A is noted in all other mutations currently examined as well as in wild-type ATTR amyloidosis. The fibril type is a determinant of the ATTR V30M disease phenotype. (99m)Tc-DPD scintigraphy is a highly sensitive method for diagnosing heart involvement in ATTR amyloidosis. The objective of this study was to determine the relationship between ATTR fibril composition and (99m)Tc-DPD scintigraphy outcome in patients with biopsy-proven ATTR amyloidosis. Methods Altogether 55 patients with biopsy-proven diagnosis of ATTR amyloidosis and amyloid fibril composition determined were examined by (99m)Tc-DPD scintigraphy. The patients were grouped and compared according to their type of amyloid fibrils. Cardiovascular evaluation included ECG, echocardiography, and cardiac biomarkers. The medical records were scrutinized to identify subjects with hypertension or other diseases that have an impact on cardiac dimensions. Results A total of 97% with type A and none of the patients with type B fibrils displayed (99m)Tc-DPD uptake at scintigraphy (p < 0.001). Findings from analyses of cardiac biomarkers, ECG, and echocardiography, though significantly different, could not differentiate between type A and B fibrils in individual patients. Conclusion In ATTR amyloidosis, the outcome of (99m)Tc-DPD scintigraphy is strongly related to the patients' transthyretin amyloid fibril composition. PMID:26849806

  17. Col6a1 Null Mice as a Model to Study Skin Phenotypes in Patients with Collagen VI Related Myopathies: Expression of Classical and Novel Collagen VI Variants during Wound Healing

    PubMed Central

    Lettmann, Sandra; Bloch, Wilhelm; Maaß, Tobias; Niehoff, Anja; Schulz, Jan-Niklas; Eckes, Beate; Eming, Sabine A.; Bonaldo, Paolo; Paulsson, Mats; Wagener, Raimund

    2014-01-01

    Patients suffering from collagen VI related myopathies caused by mutations in COL6A1, COL6A2 and COL6A3 often also display skin abnormalities, like formation of keloids or “cigarette paper” scars, dry skin, striae rubrae and keratosis pilaris (follicular keratosis). Here we evaluated if Col6a1 null mice, an established animal model for the muscle changes in collagen VI related myopathies, are also suitable for the study of mechanisms leading to the skin pathology. We performed a comprehensive study of the expression of all six collagen VI chains in unwounded and challenged skin of wild type and Col6a1 null mice. Expression of collagen VI chains is regulated in both skin wounds and bleomycin-induced fibrosis and the collagen VI α3 chain is proteolytically processed in both wild type and Col6a1 null mice. Interestingly, we detected a decreased tensile strength of the skin and an altered collagen fibril and basement membrane architecture in Col6a1 null mice, the latter being features that are also found in collagen VI myopathy patients. Although Col6a1 null mice do not display an overt wound healing defect, these mice are a relevant animal model to study the skin pathology in collagen VI related disease. PMID:25158062

  18. Developments in purification methods for obtaining and evaluation of collagen derived endogenous angioinhibitors

    PubMed Central

    Gunda, Venugopal; Verma, Raj K.; Pawar, Smita C.; Sudhakar, Yakkanti A.

    2013-01-01

    Collagen constitutes one of the vital components of the basement membrane scaffolds. Non-collagenous domains (NC1) derived from collagens exhibit potent anti-angiogenic properties, thus attaining significance in regulation of angiogenesis promoted diseases. Individual NC1 domains essential for anti-angiogenic evaluations are generally obtained through purification of individual non-collagenous domains, which have undergone steady developments for enhancing the yields, purpose of biological evaluations and solubility based on the nature of different NC1 domains. This review focuses on the method developments in obtaining biologically active NC1 domains and for specific evaluations in different scenarios. PMID:24215863

  19. Incident atrial fibrillation hazard in hypertensive population: a risk function from and for clinical practice.

    PubMed

    Alves-Cabratosa, Lia; García-Gil, Maria; Comas-Cufí, Marc; Ponjoan, Anna; Martí, Ruth; Parramon, Dídac; Blanch, Jordi; Ramos, Rafel

    2015-06-01

    Determining the risk of atrial fibrillation within the hypertensive population without ischemic vascular disease would aid in decision making on preventive approaches. Accordingly, we aimed to estimate the risk of incident atrial fibrillation in this population. We conducted an historical cohort study between July 1, 2006, and December 31, 2011, using anonymized longitudinal patient information from primary care and hospital discharge records contained in the System for the Development of Research in Primary Care database. We included 255 440 hypertensive patients, aged ≥55 years at the time of study entry. Individuals with previous atrial fibrillation, ischemic heart disease, stroke, and peripheral artery disease were excluded. To build the incident atrial fibrillation risk function, a derivation and a validation cohort were defined, representing 60% and 40% of the entire database, respectively, and a Cox proportional hazards model was fitted. Atrial fibrillation incidence was 7.24 per 1000 person-years (95% confidence interval, 7.08-7.40). The final model included age, weight, total cholesterol, heart failure, valvular heart disease, and antihypertensive treatment. Its concordance index (standard error) was 0.769 (0.004) and 0.768 (0.005) in the derivation and validation datasets, respectively. This research provides a tool, built with variables from daily clinical practice, that can be readily used in the primary care setting to predict atrial fibrillation incidence in the hypertensive population without ischemic vascular disease. The tool may help tailor individualized diagnostic and preventive care decisions. PMID:25847950

  20. Arterial calcification: Conscripted by collagen

    NASA Astrophysics Data System (ADS)