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.

  2. Uniform spatial distribution of collagen fibril radii within tendon implies local activation of pC-collagen at individual fibrils

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

    Collagen fibril cross-sectional radii show no systematic variation between the interior and the periphery of fibril bundles, indicating an effectively constant rate of collagen incorporation into fibrils throughout the bundle. Such spatially homogeneous incorporation constrains the extracellular diffusion of collagen precursors from sources at the bundle boundary to sinks at the growing fibrils. With a coarse-grained diffusion equation we determine stringent bounds, using parameters extracted from published experimental measurements of tendon development. From the lack of new fibril formation after birth, we further require that the concentration of diffusing precursors stays below the critical concentration for fibril nucleation. We find that the combination of the diffusive bound, which requires larger concentrations to ensure homogeneous fibril radii, and lack of nucleation, which requires lower concentrations, is only marginally consistent with fully processed collagen using conservative bounds. More realistic bounds may leave no consistent concentrations. Therefore, we propose that unprocessed pC-collagen diffuses from the bundle periphery followed by local C-proteinase activity and subsequent collagen incorporation at each fibril. We suggest that C-proteinase is localized within bundles, at fibril surfaces, during radial fibrillar growth. The much greater critical concentration of pC-collagen, as compared to fully processed collagen, then provides broad consistency between homogeneous fibril radii and the lack of fibril nucleation during fibril growth.

  3. Unraveling the role of Calcium ions in the mechanical properties of individual collagen fibrils

    PubMed Central

    Pang, Xiangchao; Lin, Lijun; Tang, Bin

    2017-01-01

    Collagen, the dominating material in the extracellular matrix, provides the strength, elasticity and mechanical stability to the organisms. The mechanical property of collagen is mainly dominated by its surrounding environments. However, the variation and origin of the mechanics of collagen fibril under different concentrations of calcium ions (χCa) remains unknown. By using the atomic force microscopy based nanoindentation, the mechanics and structure of individual type II collagen fibril were first investigated under different χCa in this study. The results demonstrate that both of the mechanical and structural properties of the collagen fibril show a prominent dependence on χCa. The mechanism of χCa-dependence of the collagen fibril was attributed to the chelation between collagen molecules and the calcium ions. Given the role of calcium in the pathology of osteoarthritis, the current study may cast new light on the understanding of osteoarthritis and other soft tissue hardening related diseases in the future. PMID:28378770

  4. Collagen fibrils: nanoscale ropes.

    PubMed

    Bozec, Laurent; van der Heijden, Gert; Horton, Michael

    2007-01-01

    The formation of collagen fibrils from staggered repeats of individual molecules has become "accepted" wisdom. However, for over thirty years now, such a model has failed to resolve several structural and functional questions. In a novel approach, it was found, using atomic force microscopy, that tendon collagen fibrils are composed of subcomponents in a spiral disposition-that is, their structure is similar to that of macroscale ropes. Consequently, this arrangement was modeled and confirmed using elastic rod theory. This work provides new insight into collagen fibril structure and will have wide application-from the design of scaffolds for tissue engineering and a better understanding of pathogenesis of diseases of bone and tendon, to the conservation of irreplaceable parchment-based museum exhibits.

  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.

  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. Nanoscale scraping and dissection of collagen fibrils.

    PubMed

    Wenger, M P E; Horton, M A; Mesquida, P

    2008-09-24

    The main function of collagen is mechanical, hence there is a fundamental scientific interest in experimentally investigating the mechanical and structural properties of collagen fibrils on the nanometre scale. Here, we present a novel atomic force microscopy (AFM) based scraping technique that can dissect the outer layer of a biological specimen. Applied to individual collagen fibrils, the technique was successfully used to expose the fibril core and reveal the presence of a D-banding-like structure. AFM nanoindentation measurements of fibril shell and core indicated no significant differences in mechanical properties such as stiffness (reduced modulus), hardness, adhesion and adhesion work. This suggests that collagen fibrils are mechanically homogeneous structures. The scraping technique can be applied to other biological specimens, as demonstrated on the example of bacteria.

  10. 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.

  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. Alginate-Collagen Fibril Composite Hydrogel

    PubMed Central

    Baniasadi, Mahmoud; Minary-Jolandan, Majid

    2015-01-01

    We report on the synthesis and the mechanical characterization of an alginate-collagen fibril composite hydrogel. Native type I collagen fibrils were used to synthesize the fibrous composite hydrogel. We characterized the mechanical properties of the fabricated fibrous hydrogel using tensile testing; rheometry and atomic force microscope (AFM)-based nanoindentation experiments. The results show that addition of type I collagen fibrils improves the rheological and indentation properties of the hydrogel. PMID:28787971

  13. Alginate-Collagen Fibril Composite Hydrogel.

    PubMed

    Baniasadi, Mahmoud; Minary-Jolandan, Majid

    2015-02-16

    We report on the synthesis and the mechanical characterization of an alginate-collagen fibril composite hydrogel. Native type I collagen fibrils were used to synthesize the fibrous composite hydrogel. We characterized the mechanical properties of the fabricated fibrous hydrogel using tensile testing; rheometry and atomic force microscope (AFM)-based nanoindentation experiments. The results show that addition of type I collagen fibrils improves the rheological and indentation properties of the hydrogel.

  14. Evidence of structurally continuous collagen fibrils in tendons.

    PubMed

    Svensson, Rene B; Herchenhan, Andreas; Starborg, Tobias; Larsen, Michael; Kadler, Karl E; Qvortrup, Klaus; Magnusson, S Peter

    2017-03-01

    Tendons transmit muscle-generated force through an extracellular matrix of aligned collagen fibrils. The force applied by the muscle at one end of a microscopic fibril has to be transmitted through the macroscopic length of the tendon by mechanisms that are poorly understood. A key element in this structure-function relationship is the collagen fibril length. During embryogenesis short fibrils are produced but they grow rapidly with maturation. There is some controversy regarding fibril length in adult tendon, with mechanical data generally supporting discontinuity while structural investigations favor continuity. This study initially set out to trace the full length of individual fibrils in adult human tendons, using serial block face-scanning electron microscopy. But even with this advanced technique the required length could not be covered. Instead a statistical approach was used on a large volume of fibrils in shorter image stacks. Only a single end was observed after tracking 67.5mm of combined fibril lengths, in support of fibril continuity. To shed more light on this observation, the full length of a short tendon (mouse stapedius, 125μm) was investigated and continuity of individual fibrils was confirmed. In light of these results, possible mechanisms that could reconcile the opposing findings on fibril continuity are discussed. Connective tissues hold all parts of the body together and are mostly constructed from thin threads of the protein collagen (called fibrils). Connective tissues provide mechanical strength and one of the most demanding tissues in this regard are tendons, which transmit the forces generated by muscles. The length of the collagen fibrils is essential to the mechanical strength and to the type of damage the tissue may experience (slippage of short fibrils or breakage of longer ones). This in turn is important for understanding the repair processes after such damage occurs. Currently the issue of fibril length is contentious, but this

  15. Molecular mechanics of mineralized collagen fibrils in bone

    NASA Astrophysics Data System (ADS)

    Nair, Arun K.; Gautieri, Alfonso; Chang, Shu-Wei; Buehler, Markus J.

    2013-04-01

    Bone is a natural composite of collagen protein and the mineral hydroxyapatite. The structure of bone is known to be important to its load-bearing characteristics, but relatively little is known about this structure or the mechanism that govern deformation at the molecular scale. Here we perform full-atomistic calculations of the three-dimensional molecular structure of a mineralized collagen protein matrix to try to better understand its mechanical characteristics under tensile loading at various mineral densities. We find that as the mineral density increases, the tensile modulus of the network increases monotonically and well beyond that of pure collagen fibrils. Our results suggest that the mineral crystals within this network bears up to four times the stress of the collagen fibrils, whereas the collagen is predominantly responsible for the material’s deformation response. These findings reveal the mechanism by which bone is able to achieve superior energy dissipation and fracture resistance characteristics beyond its individual constituents.

  16. Molecular mechanics of mineralized collagen fibrils in bone

    PubMed Central

    Nair, Arun K.; Gautieri, Alfonso; Chang, Shu-Wei; Buehler, Markus J.

    2013-01-01

    Bone is a natural composite of collagen protein and the mineral hydroxyapatite. The structure of bone is known to be important to its load-bearing characteristics, but relatively little is known about this structure or the mechanism that govern deformation at the molecular scale. Here we perform full-atomistic calculations of the three-dimensional molecular structure of a mineralized collagen protein matrix to try to better understand its mechanical characteristics under tensile loading at various mineral densities. We find that as the mineral density increases, the tensile modulus of the network increases monotonically and well beyond that of pure collagen fibrils. Our results suggest that the mineral crystals within this network bears up to four times the stress of the collagen fibrils, whereas the collagen is predominantly responsible for the material’s deformation response. These findings reveal the mechanism by which bone is able to achieve superior energy dissipation and fracture resistance characteristics beyond its individual constituents. PMID:23591891

  17. Mechanical properties of mineralized collagen fibrils as influenced by demineralization

    PubMed Central

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

    2009-01-01

    Dentin and bone derive their mechanical properties from a complex arrangement of collagen type I fibrils reinforced with nanocrystaline 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. PMID:18467127

  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. Bending rigidity of type I collagen homotrimer fibrils

    NASA Astrophysics Data System (ADS)

    Han, Sejin; Leikin, Sergey; Losert, Wolfgang

    2009-03-01

    Normal type I collagen is an α1(I)2α2(I) heterotrimeric triple helix, but α1(I)3 homotrimers are also found in fetal tissues and various pathological conditions, e.g., causing bone fragility and reducing tendon tensile strength. It remains unclear whether homotrimers alter mechanical properties of individual fibrils or affect tissues by altering their organization at a higher level. To address this question, we investigated how homotrimers affect fibril bending rigidity. Homotrimer fibrils have been shown to be more loosely packed so that we expected them to be more susceptible to bending. However, homotrimer fibrils were more rigid despite being thinner and more hydrated. To quantify fibril rigidity, we analyzed their shape by Fourier decomposition, determined the correlation function for the direction along each fibril, and calculated the distribution of local fibril curvature. The estimated persistence length of homotrimer fibrils was 3 ˜ 10 times longer than for heterotrimer fibrils, indicating much higher bending rigidity of homotrimer fibrils.

  20. [Fibril formation in solutions of solubilized collagen].

    PubMed

    Istranov, L P; Belova, L A; Shekhter, A B; Sychenikov, I A

    1975-01-01

    Influence of the preparations of bacterial proteinases, protorisine and prototerrisine, was studied on the stability of the mature collagen of beef skin. The chemical composition of the tissue has been shown to be changed by these enzymes inconsiderably. The tissue treated by orisine and terrisine is completely dissolved in 0.5 M acetic acid (solubilized collagen). When the solutions of such collagen are heated to 37 degrees within the pH range from 4 to 10 at the ionic strength of 0.25 fibrils are formed. Under electron microscope fibres are cross-striated that is typical of native collagen fibres with periodicity of about 640 A. After chilling to 4 degrees, a part of fibrils is dissolved again. Nephlometry was used to study the rate of fibril formation as a function of pH and temperature values. A conclusion has been drawn that the mature collagne dissolved after incubation with bacterial proteinases is close to the acid-soluble collagen fraction in the ability to produce fibres upon heating.

  1. 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

  2. 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

    2015-10-06

    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.

  3. 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.

  4. 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.

  5. 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

  6. Collagen fibril arrangement and size distribution in monkey oral mucosa

    PubMed Central

    OTTANI, V.; FRANCHI, M.; DE PASQUALE, V.; LEONARDI, L.; MOROCUTTI, M.; RUGGERI, A.

    1998-01-01

    Collagen fibre organisation and fibril size were studied in the buccal gingival and hard palate mucosa of Macacus rhesus monkey. Light and electron microscopy analysis showed connective papillae exhibiting a similar inner structure in the different areas examined, but varying in distribution, shape and size. Moving from the deep to surface layers of the buccal gingival mucosa (free and attached portions), large collagen fibril bundles became smaller and progressively more wavy with decreasing collagen fibril diameter. This gradual diameter decrease did not occur in the hard palate mucosa (free portion, rugae and interrugal regions) where the fibril diameter remained constant. A link between collagen fibril diameter and mechanical function is discussed. PMID:9688498

  7. Collagen Fibril Ultrastructure in Mice Lacking Discoidin Domain Receptor 1.

    PubMed

    Tonniges, Jeffrey R; Albert, Benjamin; Calomeni, Edward P; Roy, Shuvro; Lee, Joan; Mo, Xiaokui; Cole, Susan E; Agarwal, Gunjan

    2016-06-01

    The quantity and quality of collagen fibrils in the extracellular matrix (ECM) have a pivotal role in dictating biological processes. Several collagen-binding proteins (CBPs) are known to modulate collagen deposition and fibril diameter. However, limited studies exist on alterations in the fibril ultrastructure by CBPs. In this study, we elucidate how the collagen receptor, discoidin domain receptor 1 (DDR1) regulates the collagen content and ultrastructure in the adventitia of DDR1 knock-out (KO) mice. DDR1 KO mice exhibit increased collagen deposition as observed using Masson's trichrome. Collagen ultrastructure was evaluated in situ using transmission electron microscopy, scanning electron microscopy, and atomic force microscopy. Although the mean fibril diameter was not significantly different, DDR1 KO mice had a higher percentage of fibrils with larger diameter compared with their wild-type littermates. No significant differences were observed in the length of D-periods. In addition, collagen fibrils from DDR1 KO mice exhibited a small, but statistically significant, increase in the depth of the fibril D-periods. Consistent with these observations, a reduction in the depth of D-periods was observed in collagen fibrils reconstituted with recombinant DDR1-Fc. Our results elucidate how DDR1 modulates collagen fibril ultrastructure in vivo, which may have important consequences in the functional role(s) of the underlying ECM.

  8. Collagen Fibril Ultrastructure in Mice Lacking Discoidin Domain Receptor 1

    PubMed Central

    Tonniges, Jeffrey R.; Albert, Benjamin; Calomeni, Edward P.; Roy, Shuvro; Lee, Joan; Mo, Xiaokui; Cole, Susan E.; Agarwal, Gunjan

    2016-01-01

    The quantity and quality of collagen fibrils in the extracellular matrix (ECM) have a pivotal role in dictating biological processes. Several collagen-binding proteins (CBPs) are known to modulate collagen deposition and fibril diameter. However, limited studies exist on alterations in the fibril ultrastructure by CBPs. In this study, we elucidate how the collagen receptor, discoidin domain receptor 1 (DDR1) regulates the collagen content and ultrastructure in the adventitia of DDR1 knock-out (KO) mice. DDR1 KO mice exhibit increased collagen deposition as observed using Masson’s trichrome. Collagen ultrastructure was evaluated in situ using transmission electron microscopy, scanning electron microscopy, and atomic force microscopy. Although the mean fibril diameter was not significantly different, DDR1 KO mice had a higher percentage of fibrils with larger diameter compared with their wild-type littermates. No significant differences were observed in the length of D-periods. In addition, collagen fibrils from DDR1 KO mice exhibited a small, but statistically significant, increase in the depth of the fibril D-periods. Consistent with these observations, a reduction in the depth of D-periods was observed in collagen fibrils reconstituted with recombinant DDR1-Fc. Our results elucidate how DDR1 modulates collagen fibril ultrastructure in vivo, which may have important consequences in the functional role(s) of the underlying ECM. PMID:27329311

  9. 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

  10. 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.

  11. Glassy state of native collagen fibril?

    NASA Astrophysics Data System (ADS)

    Gevorkian, S. G.; Allahverdyan, A. E.; Gevorgyan, D. S.; Hu, C.-K.

    2011-07-01

    Our micromechanical experiments show that viscoelastic features of type-I collagen fibril at physiological temperatures display essential dependence on the frequency and speed of heating. For temperatures of 20-30 °C the internal friction has a sharp maximum for a frequency less than 2 kHz. Upon heating the internal friction displays a peak at a temperature Tsoft(v) that essentially depends on the speed of heating v: Tsoft≈70°C for v=1°C/min, and Tsoft≈25°C for v=0.1°C/min. At the same temperature Tsoft(v) Young's modulus passes through a minimum. All these effects are specific for the native state of the fibril and disappear after heat-denaturation. Taken together with the known facts that the fibril is axially ordered as quasicrystal, but disordered laterally, we interpret our findings as indications of a glassy state, where Tsoft is the softening transition.

  12. Mechanical properties of a collagen fibril under simulated degradation.

    PubMed

    Malaspina, David C; Szleifer, Igal; Dhaher, Yasin

    2017-11-01

    Collagen fibrils are a very important component in most of the connective tissue in humans. An important process associated with several physiological and pathological states is the degradation of collagen. Collagen degradation is usually mediated by enzymatic and non-enzymatic processes. In this work we use molecular dynamics simulations to study the influence of simulated degradation on the mechanical properties of the collagen fibril. We applied tensile stress to the collagen fiber at different stages of degradation. We compared the difference in the fibril mechanical priorities due the removal of enzymatic crosslink, surface degradation and volumetric degradation. As anticipated, our results indicated that, regardless of the degradation scenario, fibril mechanical properties is reduced. The type of degradation mechanism (crosslink, surface or volumetric) expressed differential effect on the change in the fibril stiffness. Our simulation results showed dramatic change in the fibril stiffness with a small amount of degradation. This suggests that the hierarchical structure of the fibril is a key component for the toughness and is very sensitive to changes in the organization of the fibril. The overall results are intended to provide a theoretical framework for the understanding the mechanical behavior of collagen fibrils under degradation. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Microscale Mechanical Testing of Individual Collagen Fibers

    NASA Astrophysics Data System (ADS)

    Poissant, Jeffrey

    Collagen is a key constituent for a large number of biological materials including bone, tendon, cartilage, skin and fish scales. Understanding the mechanical behavior of collagen's microscale structural components (fibers and fibrils) is therefore of utmost importance for fields such as biomimetics and biomedical engineering. However, the mechanics of collagen fibers and fibrils remain largely unexplored. The main research challenges are the small sample sizes (diameters less than 1 im) and the need to maintain physiologically relevant conditions. In this work, a microscale mechanical testing device (MMTD) capable of measuring the stress-strain response of individual collagen fibers and fibrils was developed. The MMTD consists of: (i) a transducer from a commercial nanoindenter to measure load and displacement, (ii) an optical microscope to observe the deformation of the sample in-situ and (iii) micromanipulators to isolate, position and fix samples. Collagen fibers and fibrils were extracted from fish scales using a novel dissection procedure and tested using the MMTD. A variety of tensile tests were performed including monotonic loading and cyclic tests with increasing loading rate or maximum displacement. The monotonic test results found that the elastic modulus, ultimate tensile strength and strain at failure range from 0.5 to 1.3 GPa, 100 to 200 MPa and 20% to 60%, respectively. The cyclic tests revealed that the largest increase in damage accumulation occurs at strains between 10% and 20%, when hydrogen bonds at the molecular level are ruptured. Further straining the fibril causes little additional damage accumulation and signals the approach of failure. The addition of water is shown to increase damage tolerance and strain to failure.

  14. Deformation micromechanisms of collagen fibrils under uniaxial tension.

    PubMed

    Tang, Yuye; Ballarini, Roberto; Buehler, Markus J; Eppell, Steven J

    2010-05-06

    Collagen, an essential building block of connective tissues, possesses useful mechanical properties due to its hierarchical structure. However, little is known about the mechanical properties of collagen fibril, an intermediate structure between the collagen molecule and connective tissue. Here, we report the results of systematic molecular dynamics simulations to probe the mechanical response of initially unflawed finite size collagen fibrils subjected to uniaxial tension. The observed deformation mechanisms, associated with rupture and sliding of tropocollagen molecules, are strongly influenced by fibril length, width and cross-linking density. Fibrils containing more than approximately 10 molecules along their length and across their width behave as representative volume elements and exhibit brittle fracture. Shorter fibrils experience a more graceful ductile-like failure. An analytical model is constructed and the results of the molecular modelling are used to find curve-fitted expressions for yield stress, yield strain and fracture strain as functions of fibril structural parameters. Our results for the first time elucidate the size dependence of mechanical failure properties of collagen fibrils. The associated molecular deformation mechanisms allow the full power of traditional material and structural engineering theory to be applied to our understanding of the normal and pathological mechanical behaviours of collagenous tissues under load.

  15. Mechanical Properties of Single Collagen Fibrils Revealed by Force Spectroscopy

    NASA Astrophysics Data System (ADS)

    Graham, John; Phillips, Charlotte; Grandbois, Michel

    2004-03-01

    In the field of biomechanics, collagen fibrils are believed to be robust mechanical structures characterized by a low extensibility. Until very recently, information on the mechanical properties of collagen fibrils could only be derived from ensemble measurements performed on complete tissues such as bone, skin and tendon. Here we measure force-elongation/relaxation profiles of single collagen fibrils using atomic force microscopy-based force spectroscopy. The elongation profiles indicate that in vitro assembled heterotrimeric type I collagen fibrils are characterized by a large extensibility. Numerous discontinuities and a plateau in the force profile indicate major reorganization occurs within the fibrils in the 1.5 -- 4.5 nN range. Our study demonstrates that newly assembled collagen fibrils are robust structures with a significant reserve of elasticity that could play a determinant role in cellular motion in the context of tissue growth and morphogenesis. In contrast, homotrimeric collagen fibrils corresponding to osteogenesis imperfecta pathology exhibit a marked difference in their elasticity profile.

  16. 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.

  17. 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.

  18. 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.

  19. Fracture mechanics of collagen fibrils: influence of natural cross-links.

    PubMed

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

    2013-06-04

    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.

  20. Effect of hydroxypropyl methylcellulose on collagen fibril formation in vitro.

    PubMed

    Ding, Cuicui; Zhang, Min; Tian, Huilin; Li, Guoying

    2013-01-01

    Collagen and hydroxypropyl methylcellulose (HPMC) were mixed to obtain blends and the effect of HPMC on collagen self-assembly was studied. As deduced from atomic force microscopy (AFM), the amount of nuclei in collagen-HPMC solutions was changed with the addition of HPMC. Under physiological conditions, the kinetics curves of fibril formation showed that the turbidity of blends at 313 nm was higher than that of native collagen. More HPMC was involved in the hydrogel network for blends with higher HPMC/collagen. However, both the thermal stability and the storage moduli of hydrogels, which was evaluated by UV and rheological measurements respectively, reached the maximum just when HPMC/collagen=0.25. Furthermore, it was showed by AFM that denser fibrils with smaller diameter would be obtained as HPMC/collagen<0.25, while more addition of HPMC (HPMC/collagen>0.25) would bring about fibrils with larger diameter. However, HPMC did not significantly affect the characteristic D-periods of the fibrils for all blends.

  1. 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

  2. Collagen fibril formation in the presence of sodium dodecyl sulphate.

    PubMed Central

    Dombi, G W; Halsall, H B

    1985-01-01

    Sodium dodecyl sulphate (SDS) was used to weaken both the electrostatic and the hydrophobic interactions during collagen fibrillogenesis in vitro. The rate and extent of fibril formation as well as fibril morphology were affected by SDS concentration. Both the formation of large fibrils at 0.3 mM-SDS and the complete cessation of fibril formation at 0.5 mM-SDS were considered to be the result of SDS-induced conformational changes in the non-helical telopeptides. A possible mechanism of SDS interaction with the N-terminal and the distal region of the C-terminal telopeptides is offered. Images Fig. 5. PMID:4026797

  3. Does the genetic type of collagen determine fibril structure

    SciTech Connect

    Eikenberry, E.; Brodsky, B.; Cassidy, K.

    1980-10-01

    A number of genetic types of collagen, all triple-helical but with significant variations in their amino acid sequences, have been found and the distribution of these genetic types is tissue specific. For example, tendon is composed only of type I collagen, while cartilage contains largely type II collagen. Skin contains a large amount of type I, but has a significant fraction, approx. 15%, of type III. Each of these types can form fibrils, but it is not known whether they form distinctive fibril structures that are important in determining tissue organization. We are using x-ray diffraction to analyze a variety of tissues with different collagen genetic types to compare the fibril structures and thus investigate whether genetic type is an important determinant of this structure.

  4. Graded arrangement of collagen fibrils in the equine superficial digital flexor tendon.

    PubMed

    Watanabe, Takafumi; Imamura, Yasutada; Hosaka, Yoshinao; Ueda, Hiromi; Takehana, Kazushige

    2007-01-01

    By using ultramorphological and biochemical methods, we analyzed the regional differences between the three parts of the equine superficial digital flexor tendon (SDFT), namely, the myotendinous junction (MTJ), middle metacarpal (mM), and osteotendinous junction (OTJ). Cross-sectional images showed unique distributions of collagen fibrils of varying diameters in each region. Small collagen fibrils (diameter <100 nm) were distributed predominantly in the MTJ region, and the OTJ region was relatively rich in large collagen fibrils (diameter >200 nm). In the mM region, the collagen fibrils were intermediately distributed between the MTJ and OTJ. The results indicate a graded arrangement of collagen fibrils in the tendon. Type V collagen was detected preferentially in the MTJ region. Since type V collagen is believed to be one of the collagens regulating collagen fibril formation, its possible functionality in the MTJ region in terms of fibril formation and fibril arrangement in the tendon has been discussed here.

  5. Nanomechanical mapping of hydrated rat tail tendon collagen I fibrils.

    PubMed

    Baldwin, Samuel J; Quigley, Andrew S; Clegg, Charlotte; Kreplak, Laurent

    2014-10-21

    Collagen fibrils play an important role in the human body, providing tensile strength to connective tissues. These fibrils are characterized by a banding pattern with a D-period of 67 nm. The proposed origin of the D-period is the internal staggering of tropocollagen molecules within the fibril, leading to gap and overlap regions and a corresponding periodic density fluctuation. Using an atomic force microscope high-resolution modulus maps of collagen fibril segments, up to 80 μm in length, were acquired at indentation speeds around 10(5) nm/s. The maps revealed a periodic modulation corresponding to the D-period as well as previously undocumented micrometer scale fluctuations. Further analysis revealed a 4/5, gap/overlap, ratio in the measured modulus providing further support for the quarter-staggered model of collagen fibril axial structure. The modulus values obtained at indentation speeds around 10(5) nm/s are significantly larger than those previously reported. Probing the effect of indentation speed over four decades reveals two distinct logarithmic regimes of the measured modulus and point to the existence of a characteristic molecular relaxation time around 0.1 ms. Furthermore, collagen fibrils exposed to temperatures between 50 and 62°C and cooled back to room temperature show a sharp decrease in modulus and a sharp increase in fibril diameter. This is also associated with a disappearance of the D-period and the appearance of twisted subfibrils with a pitch in the micrometer range. Based on all these data and a similar behavior observed for cross-linked polymer networks below the glass transition temperature, we propose that collagen I fibrils may be in a glassy state while hydrated.

  6. 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.

  7. 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

  8. Mechanical model for a collagen fibril pair in extracellular matrix.

    PubMed

    Chan, Yue; Cox, Grant M; Haverkamp, Richard G; Hill, James M

    2009-04-01

    In this paper, we model the mechanics of a collagen pair in the connective tissue extracellular matrix that exists in abundance throughout animals, including the human body. This connective tissue comprises repeated units of two main structures, namely collagens as well as axial, parallel and regular anionic glycosaminoglycan between collagens. The collagen fibril can be modeled by Hooke's law whereas anionic glycosaminoglycan behaves more like a rubber-band rod and as such can be better modeled by the worm-like chain model. While both computer simulations and continuum mechanics models have been investigated for the behavior of this connective tissue typically, authors either assume a simple form of the molecular potential energy or entirely ignore the microscopic structure of the connective tissue. Here, we apply basic physical methodologies and simple applied mathematical modeling techniques to describe the collagen pair quantitatively. We found that the growth of fibrils was intimately related to the maximum length of the anionic glycosaminoglycan and the relative displacement of two adjacent fibrils, which in return was closely related to the effectiveness of anionic glycosaminoglycan in transmitting forces between fibrils. These reveal the importance of the anionic glycosaminoglycan in maintaining the structural shape of the connective tissue extracellular matrix and eventually the shape modulus of human tissues. We also found that some macroscopic properties, like the maximum molecular energy and the breaking fraction of the collagen, were also related to the microscopic characteristics of the anionic glycosaminoglycan.

  9. 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.

  10. Piezoelectricity in collagen type II fibrils measured by scanning probe microscopy

    NASA Astrophysics Data System (ADS)

    Denning, D.; Kilpatrick, J. I.; Hsu, T.; Habelitz, S.; Fertala, A.; Rodriguez, B. J.

    2014-08-01

    The converse piezoelectric effect in collagen type II fibrils, the main collagen constituent in cartilage, was investigated using piezoresponse force microscopy. The fibrils exhibited shear piezoelectric behavior similar to that previously reported in collagen type I fibrils and followed the same cantilever-fibril angle dependence present for type I. A uniform polarization directed from the amine to carboxyl termini, as seen for collagen type I, was observed in all type II fibrils studied. The shear piezoelectric coefficient, d15, however, for type II was roughly 28-32% of the value measured for type I fibrils. Possible explanations for the reduced piezoelectric coefficient of type II collagen are provided.

  11. 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.

  12. Tensile Properties of Human Collagen Fibrils and Fascicles Are Insensitive to Environmental Salts

    PubMed Central

    Svensson, René B.; Hassenkam, Tue; Grant, Colin A.; Magnusson, S. Peter

    2010-01-01

    To carry out realistic in vitro mechanical testing on anatomical tissue, a choice has to be made regarding the buffering environment. Therefore, it is important to understand how the environment may influence the measurement to ensure the highest level of accuracy. The most physiologically relevant loading direction of tendon is along its longitudinal axis. Thus, in this study, we focus on the tensile mechanical properties of two hierarchical levels from human patellar tendon, namely: individual collagen fibrils and fascicles. Investigations on collagen fibrils and fascicles were made at pH 7.4 in solutions of phosphate-buffered saline at three different concentrations as well as two HEPES buffered solutions containing NaCl or NaCl + CaCl2. An atomic force microscope technique was used for tensile testing of individual collagen fibrils. Only a slight increase in relative energy dissipation was observed at the highest phosphate-buffered saline concentration for both the fibrils and fascicles, indicating a stabilizing effect of ionic screening, but changes were much less than reported for radial compression. Due to the small magnitude of the effects, the tensile mechanical properties of collagen fibrils and fascicles from the patellar tendon of mature humans are essentially insensitive to environmental salt concentration and composition at physiological pH. PMID:21156145

  13. Papain-gel degrades intact nonmineralized type I collagen fibrils.

    PubMed

    Bertassoni, L E; Marshall, G W

    2009-01-01

    Papain-gel has been utilized as a chemo-mechanical material for caries removal due to its ability to preserve underlying sound dentin. However, little is known about the effect of the papain enzyme on intact type I collagen fibrils that compose the dentin matrix. Here we sought to define structural changes that occur in intact type I collagen fibrils after an enzymatic treatment with a papain-gel. Intact and nonmineralized type I collagen fibrils from rat tail were obtained and treated with a papain-gel (Papacarie) for 30 s, rinsed with water and imaged using an atomic force microscope (AFM). Additionally, polished healthy dentin specimens were also treated using the same protocol described above and had their elastic modulus (E) and hardness (H) measured by means of AFM-based nanoindentation. AFM images showed that the papain-gel induced partial degradation of the fibrils surface, yet no rupture of fibrils was noticed. The distinction between gap and overlap zones of fibrils vanished in most regions after treatment, and overlap zones appeared to be generally more affected. Mechanical data suggested a gradual decrease in E and H after treatments. A significant two-fold drop from the values of normal dentin (E=20+/-1.9, H=0.8+/-0.08 GPa) was found after four applications (E=9.7+/-3.2, H=0.24+/-0.1 GPa) (P<0.001), which may be attributed to the degradation of proteoglycans of the matrix. In summary, this study provided novel evidence that intact nonmineralized type I collagen fibrils are partially degraded by a papain-gel. (c) 2010 Wiley Periodicals, Inc.

  14. Papain-gel Degrades Intact Nonmineralized Type I Collagen Fibrils

    PubMed Central

    BERTASSONI, L. E.; MARSHALL, G. W.

    2010-01-01

    Summary Papain-gel has been utilized as a chemomechanical material for caries removal due to its ability to preserve underlying sound dentin. However, little is known about the effect of the papain enzyme on intact type I collagen fibrils that compose the dentin matrix. Here we sought to define structural changes that occur in intact type I collagen fibrils after an enzymatic treatment with a papaingel. Intact and nonmineralized type I collagen fibrils from rat tail were obtained and treated with a papain-gel (Papacarie) for 30 s, rinsed with water and imaged using an atomic force microscope (AFM). Additionally, polished healthy dentin specimens were also treated using the same protocol described above and had their elastic modulus (E) and hardness (H) measured by means of AFM-based nanoindentation. AFM images showed that the papain-gel induced partial degradation of the fibrils surface, yet no rupture of fibrils was noticed. The distinction between gap and overlap zones of fibrils vanished in most regions after treatment, and overlap zones appeared to be generally more affected. Mechanical data suggested a gradual decrease in E and H after treatments. A significant two-fold drop from the values of normal dentin (E= 20 +/− 1.9, H = 0.8 +/− 0.08 GPa) was found after four applications (E = 9.7 +/− 3.2, H = 0.24 +/− 0.1 GPa) ( P<0.001), which may be attributed to the degradation of proteoglycans of the matrix. In summary, this study provided novel evidence that intact nonmineralized type I collagen fibrils are partially degraded by a papain-gel. PMID:20205185

  15. Targeted Disruption of Decorin Leads to Abnormal Collagen Fibril Morphology and Skin Fragility

    PubMed Central

    Danielson, Keith G.; Baribault, Helene; Holmes, David F.; Graham, Helen; Kadler, Karl E.; Iozzo, Renato V.

    1997-01-01

    Decorin is a member of the expanding group of widely distributed small leucine-rich proteoglycans that are expected to play important functions in tissue assembly. We report that mice harboring a targeted disruption of the decorin gene are viable but have fragile skin with markedly reduced tensile strength. Ultrastructural analysis revealed abnormal collagen morphology in skin and tendon, with coarser and irregular fiber outlines. Quantitative scanning transmission EM of individual collagen fibrils showed abrupt increases and decreases in mass along their axes, thereby accounting for the irregular outlines and size variability observed in cross-sections. The data indicate uncontrolled lateral fusion of collagen fibrils in the decorindeficient mice and provide an explanation for the reduced tensile strength of the skin. These findings demonstrate a fundamental role for decorin in regulating collagen fiber formation in vivo. PMID:9024701

  16. Cartilage Fibrils of Mammals are Biochemically Heterogeneous: Differential Distribution of Decorin and Collagen IX

    PubMed Central

    Hagg, Rupert; Bruckner, Peter; Hedbom, Erik

    1998-01-01

    Cartilage fibrils contain collagen II as the major constituent, but the presence of additional components, minor collagens, and noncollagenous glycoproteins is thought to be crucial for modulating several fibril properties. We have examined the distribution of two fibril constituents—decorin and collagen IX—in samples of fibril fragments obtained after bovine cartilage homogenization. Decorin was preferentially associated with a population of thicker fibril fragments from adult articular cartilage, but was not present on the thinnest fibrils. The binding was specific for the gap regions of the fibrils, and depended on the decorin core protein. Collagen IX, by contrast, predominated in the population with the thinnest fibrils, and was scarce on wider fibrils. Double-labeling experiments demonstrated the coexistence of decorin and collagen IX in some fibrils of intermediate diameter, although most fibril fragments from adult cartilage were strongly positive for one component and lacked the other. Fibril fragments from fetal epiphyseal cartilage showed a different pattern, with decorin and collagen IX frequently colocalized on fragments of intermediate and large diameters. Hence, the presence of collagen IX was not exclusive for fibrils of small diameter. These results establish that articular cartilage fibrils are biochemically heterogeneous. Different populations of fibrils share collagen II, but have distinct compositions with respect to macromolecules defining their surface properties. PMID:9660881

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

    USDA-ARS?s Scientific Manuscript database

    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...

  18. 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.

  19. Ultrastructure features of camel cornea--collagen fibril and proteoglycans.

    PubMed

    Almubrad, Turki; Akhtar, Saeed

    2012-01-01

      The uniform distribution of collagen fibrils and proteoglycans maintain the transparency of normal cornea. We describe the ultrastructural features of camel cornea including collagen fibrils and proteoglycans (PGs).   Camel corneas (of 6-, 8-, and 10-month-old animals) were fixed in 2.5% glutaraldehyde containing cuprolinic blue in sodium acetate buffer and processed for electron microscopy. The 'AnalySIS LS Professional' program was used to analyze the collagen fibril diameter.   The camel cornea consists of four layers: the epithelium (227 μm), stroma (388 μm), Descemet's membrane (DM), and endothelium. The epithelium constituted 36% of the camel cornea, whereas corneal stroma constituted 62% of the corneal thickness (629 μm). The PGs in the posterior stroma were significantly larger in number and size compared with the anterior and middle stroma. The collagen fibril diameter was 25 nm and interfibrillar spacing 40 nm. Fibrillar structures are present throughout the DM.   The structure of the camel cornea is very different from human and other animals. The unique structure of the cornea might be an adaptation to help the camel to survive in a hot and dry climate. The camel cornea may also be a good model to study the effect of hot and dry climates on the cornea. © 2011 American College of Veterinary Ophthalmologists.

  20. Collagen fibril diameter and alignment promote the quiescent keratocyte phenotype

    PubMed Central

    Muthusubramaniam, Lalitha; Peng, Lily; Zaitseva, Tatiana; Paukshto, Michael; Martin, George R.; Desai, Tejal

    2011-01-01

    In this study, we investigated how matrix nanotopography affects corneal fibroblast phenotype and matrix synthesis. To this end, corneal fibroblasts isolated from bovine corneas were grown on collagen nanofiber scaffolds of different diameters and alignment – 30 nm aligned fibrils (30A), 300 nm or larger aligned fibrils (300A), and 30 nm nonaligned fibrils (30NA) in comparison to collagen coated flat glass substrates (FC). Cell morphology was visualized using confocal microscopy. Quantitative PCR was used to measure expression levels of six target genes: the corneal crystallin - transketolase (TKT), the myofibroblast marker - α-smooth muscle actin (SMA), and four matrix proteins - collagen 1 (COL1), collagen 3 (COL3), fibronectin (FN) and biglycan. It was found that SMA expression was down-regulated and TKT expression was increased on all three collagen nanofiber substrates, compared to the FC control substrates. However, COL3 and biglycan expression was also significantly increased on 300A, compared to the FC substrates. Thus matrix nanotopography down-regulates the fibrotic phenotype, promotes formation of the quiescent keratocyte phenotype and influences matrix synthesis. These results have significant implications for the engineering of corneal replacements and for promoting regenerative healing of the cornea after disease and/or injury. PMID:22213336

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

    PubMed

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

    2011-02-01

    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.

  2. 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.

  3. Mechanically overloading collagen fibrils uncoils collagen molecules, placing them in a stable, denatured state.

    PubMed

    Veres, Samuel P; Harrison, Julia M; Lee, J Michael

    2014-01-01

    Due to the high occurrence rate of overextension injuries to tendons and ligaments, it is important to understand the fundamental mechanisms of damage to these tissues' primary load-bearing elements: collagen fibrils and their constituent molecules. Based on our recent observations of a new subrupture, overload-induced mode of fibril disruption that we call discrete plasticity, we have sought in the current study to re-explore whether the tensile overload of collagen fibrils can alter the helical conformation of collagen molecules. In order to accomplish this, we have analyzed the conformation of collagen molecules within repeatedly overloaded tendons in relation to their undamaged matched-pair controls using both differential scanning calorimetry and variable temperature trypsin digestion susceptibility. We find that tensile overload reduces the specific enthalpy of denaturation of tendons, and increases their susceptibility to trypsin digestion, even when the digestion is carried out at temperatures as low as 4 °C. Our results indicate that the tensile overload of collagen fibrils can uncoil the helix of collagen molecules, placing them in a stable, denatured state.

  4. Epidermolysis Bullosa Acquisita: Autoimmunity to Anchoring Fibril Collagen

    PubMed Central

    Chen, Mei; Kim, Gene H.; Prakash, Lori; Woodley, David T.

    2012-01-01

    Epidermolysis bullosa acquisita (EBA) is a rare and acquired autoimmune subepidermal bullous disease of the skin and mucosa. EBA includes various distinct clinical manifestations resembling Bullous Pemphigus, Brunsting-Perry pemphigoid, or cicatricial pemphigoid. These patients have autoantibodies against type VII collagen, an integral component of anchoring fibrils, which are responsible for attaching the dermis to the epidermis. Destruction or perturbation of the normally functioning anchoring fibrils clinically results in skin fragility, blisters, erosions, scars, milia and nail loss, all features reminiscent of genetic dystrophic epidermolysis bullosa. These anti-type VII collagen antibodies are “pathogenic” because when injected into a mouse, the mouse develops an EBA-like blistering disease. Currently treatment is often unsatisfactory, however some success has been achieved with colchichine, dapsone, photopheresis, plasmaphresis, infliximab, rituximab and IVIG. PMID:21955050

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

    USDA-ARS?s Scientific Manuscript database

    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...

  6. Collagen assembly from acid solution to networks on solid surfaces and to fibrils

    NASA Astrophysics Data System (ADS)

    Bradt, Jens-Hilmar; Mertig, Michael; Winzer, Bettina; Thiele, Uwe; Pompe, Wolfgang

    1996-04-01

    Two different kinds of collagen assembly have been studied: the reconstitution of type I collagen to fibrils and the formation of 2D networks on surfaces. The kinetics of fibril assembly are influenced by polyaspartate, as measured turbidimetrically. Addition of polyaspartate increases the fibril diameter. The reconstituted fibrils are imaged by atomic force microscopy and scanning electron microscopy. The preparation of thin collagen films on highly oriented pyrolytic graphite leads to networks or tree like structures depending on the collagen concentration in the precursor. The results presented are of interest for the development of new bone-like implant materials and the covering of bone grafts with a biocompatible layer.

  7. 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.

  8. Surface coupling of long-chain hyaluronan to the fibrils of reconstituted type II collagen.

    PubMed

    Chen, Yong G; Lee, Ming W; Tu, Yi H; Hung, Shih C; Wang, Yng J

    2009-01-01

    The aim of this study was to fabricate type II collagen fibrils with surface modified by long-chain hyaluronic acid. Monomeric type II collagen was isolated from bovine articular cartilage and reconstituted into collagen fibrils followed by a reaction with EDC (1-Ethyl-3-[3-dimethylaminopropyl] carbodiimide)-activated long-chain hyaluronic acid. The existence of the hyaluronan molecules on the fibrillar surface was confirmed by the specific bindings of gold nanoparticles labeled with wheat germ agglutinin. The topographic pattern of type II collagen fibrils revealed by AFM scanning changed significantly after the surface coupling of hyaluronic acid. Beneath the hyaluronan, the characteristic D-bandings of the reconstituted collagen fibrils remained intact as shown by the results of TEM observation. The collagen fibrils became more resistant to collagenase digestion after surface coupling of hyaluronic acid as compared with that without hyaluronic acid immobilization. In addition, human mesenchymal stem cells encapsulated and cultured within the matrix of HA-collagen fibrils have a higher proliferation rate than cells grown within the unmodified type II collagen fibrils. The newly synthesized material of HA-collagen II fibrils has a great potential for use in constructing scaffold for tissue repair.

  9. The effect of collagen fibril orientation on the biphasic mechanics of articular cartilage.

    PubMed

    Meng, Qingen; An, Shuqiang; Damion, Robin A; Jin, Zhongmin; Wilcox, Ruth; Fisher, John; Jones, Alison

    2017-01-01

    The highly inhomogeneous distribution of collagen fibrils may have important effects on the biphasic mechanics of articular cartilage. However, the effect of the inhomogeneity of collagen fibrils has mainly been investigated using simplified three-layered models, which may have underestimated the effect of collagen fibrils by neglecting their realistic orientation. The aim of this study was to investigate the effect of the realistic orientation of collagen fibrils on the biphasic mechanics of articular cartilage. Five biphasic material models, each of which included a different level of complexity of fibril reinforcement, were solved using two different finite element software packages (Abaqus and FEBio). Model 1 considered the realistic orientation of fibrils, which was derived from diffusion tensor magnetic resonance images. The simplified three-layered orientation was used for Model 2. Models 3-5 were three control models. The realistic collagen orientations obtained in this study were consistent with the literature. Results from the two finite element implementations were in agreement for each of the conditions modelled. The comparison between the control models confirmed some functions of collagen fibrils. The comparison between Models 1 and 2 showed that the widely-used three-layered inhomogeneous model can produce similar fluid load support to the model including the realistic fibril orientation; however, an accurate prediction of the other mechanical parameters requires the inclusion of the realistic orientation of collagen fibrils.

  10. 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

  11. Abnormality of dermal collagen fibrils in Ehlers Danlos syndrome. Anticipation of the abnormality for the inherited hypermobile disorders.

    PubMed

    Kobayasi, Takasi

    2004-01-01

    The abnormality of dermal collagen fibrils is the ultrastructural criterion of Ehlers-Danlos syndrome (EDS). This study evaluates the clinical significance of the abnormality. Besides 348 lax patients presenting the stigmata of EDS, skin specimens from 12 normal members in the pedigree of EDS, 98 randomly selected normal individuals, 7 Marfan syndrome and 4 osteogenesis inperfecta type I, were studied by electron microscopy. The abnormality was defined by thickness, array and shape of collagen fibrils. Of 348 lax patients, 115 patients showed Beighton's score higher than 6 and constantly the abnormality (EDS). Variable numbers of the patients with scores 1 to 5 displayed the abnormality (forme fruste). The abnormality did not correspond with variation of laxity. Marfan syndrome and osteogenesis imperfecta were indistinguishable from EDS by the abnormality. Some of the normal persons in the EDS pedigree and some controls also showed the abnormality. The abnormality expressed the disposition for heritably defected collagen fibril formation.

  12. 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. Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. The binding capacity of α1β1-, α2β1- and α10β1-integrins depends on non-collagenous surface macromolecules rather than the collagens in cartilage fibrils.

    PubMed

    Woltersdorf, Christian; Bonk, Melanie; Leitinger, Birgit; Huhtala, Mikko; Käpylä, Jarmo; Heino, Jyrki; Gil Girol, Christian; Niland, Stephan; Eble, Johannes A; Bruckner, Peter; Dreier, Rita; Hansen, Uwe

    2017-02-10

    Interactions of cells with supramolecular aggregates of the extracellular matrix (ECM) are mediated, in part, by cell surface receptors of the integrin family. These are important molecular components of cell surface-suprastructures regulating cellular activities in general. A subfamily of β1-integrins with von Willebrand-factor A-like domains (I-domains) in their α-chains can bind to collagen molecules and, therefore, are considered as important cellular mechano-receptors. Here we show that chondrocytes strongly bind to cartilage collagens in the form of individual triple helical molecules but very weakly to fibrils formed by the same molecules. We also find that chondrocyte integrins α1β1-, α2β1- and α10β1-integrins and their I-domains have the same characteristics. Nevertheless we find integrin binding to mechanically generated cartilage fibril fragments, which also comprise peripheral non-collagenous material. We conclude that cell adhesion results from binding of integrin-containing adhesion suprastructures to the non-collagenous fibril periphery but not to the collagenous fibril cores. The biological importance of the well-investigated recognition of collagen molecules by integrins is unknown. Possible scenarios may include fibrillogenesis, fibril degradation and/or phagocytosis, recruitment of cells to remodeling sites, or molecular signaling across cytoplasmic membranes. In these circumstances, collagen molecules may lack a fibrillar organization. However, other processes requiring robust biomechanical functions, such as fibril organization in tissues, cell division, adhesion, or migration, do not involve direct integrin-collagen interactions.

  14. Advanced Glycation End-Products Reduce Collagen Molecular Sliding to Affect Collagen Fibril Damage Mechanisms but Not Stiffness

    PubMed Central

    Fessel, Gion; Li, Yufei; Diederich, Vincent; Guizar-Sicairos, Manuel; Schneider, Philipp; Sell, David R.; Monnier, Vincent M.; Snedeker, Jess G.

    2014-01-01

    Advanced glycation end-products (AGE) contribute to age-related connective tissue damage and functional deficit. The documented association between AGE formation on collagens and the correlated progressive stiffening of tissues has widely been presumed causative, despite the lack of mechanistic understanding. The present study investigates precisely how AGEs affect mechanical function of the collagen fibril – the supramolecular functional load-bearing unit within most tissues. We employed synchrotron small-angle X-ray scattering (SAXS) and carefully controlled mechanical testing after introducing AGEs in explants of rat-tail tendon using the metabolite methylglyoxal (MGO). Mass spectrometry and collagen fluorescence verified substantial formation of AGEs by the treatment. Associated mechanical changes of the tissue (increased stiffness and failure strength, decreased stress relaxation) were consistent with reports from the literature. SAXS analysis revealed clear changes in molecular deformation within MGO treated fibrils. Underlying the associated increase in tissue strength, we infer from the data that MGO modified collagen fibrils supported higher loads to failure by maintaining an intact quarter-staggered conformation to nearly twice the level of fibril strain in controls. This apparent increase in fibril failure resistance was characterized by reduced side-by-side sliding of collagen molecules within fibrils, reflecting lateral molecular interconnectivity by AGEs. Surprisingly, no change in maximum fibril modulus (2.5 GPa) accompanied the changes in fibril failure behavior, strongly contradicting the widespread assumption that tissue stiffening in ageing and diabetes is directly related to AGE increased fibril stiffness. We conclude that AGEs can alter physiologically relevant failure behavior of collagen fibrils, but that tissue level changes in stiffness likely occur at higher levels of tissue architecture. PMID:25364829

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

    PubMed

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

    2008-02-26

    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.

  16. 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.

  17. Severe disruption and disorganization of dermal collagen fibrils in early striae gravidarum.

    PubMed

    Wang, F; Calderone, K; Do, T T; Smith, N R; Helfrich, Y R; Johnson, T R B; Kang, S; Voorhees, J J; Fisher, G J

    2017-08-17

    Striae gravidarum (SG), or stretch marks of pregnancy, begin as erythematous streaks, and mature into hypopigmented atrophic bands. To investigate molecular alterations that may promote atrophy of SG, we investigated dermal type I collagen fibrils, which provide human skin with support. We obtained skin samples of recently developed, erythematous abdominal SG from pregnant women. To examine the organization of collagen fibrils, second-harmonic generation imaging was performed using multiphoton microscopy. Immunostaining was used to determine protein expression and localization of type I procollagen, the precursor of type I collagen fibrils. Real-time polymerase chain reaction was used to determine gene expression levels. In control (hip) and stretched, normal-appearing perilesional abdominal skin, dermal collagen fibrils were organized as tightly packed, interwoven bundles. In SG, collagen bundles appeared markedly separated, especially in the mid-to-deep dermis. In the spaces separating bundles, loosely packed wavy collagen fibrils lacking organization as bundles were present. These disorganized fibrils persisted into the postpartum period and failed to form densely packed bundles. Numerous large fibroblasts displaying type I procollagen expression were in close proximity to the disorganized fibrils, suggesting that the fibrils are newly synthesized. Supporting this possibility, immunostaining and gene expression of type I procollagen were increased throughout the dermis of SG. Early SG display marked separation of collagen bundles and emergence of disorganized collagen fibrils that fail to form bundles. These alterations may reflect ineffective repair of collagen bundles disrupted by intense skin stretching. Persistent disruption of the collagenous extracellular matrix likely promotes formation and atrophy of SG. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  18. Determination of extracellular matrix collagen fibril architectures and pathological remodeling by polarization dependent second harmonic microscopy.

    PubMed

    Rouède, Denis; Schaub, Emmanuel; Bellanger, Jean-Jacques; Ezan, Frédéric; Scimeca, Jean-Claude; Baffet, Georges; Tiaho, François

    2017-09-22

    Polarization dependence second harmonic generation (P-SHG) microscopy is gaining increase popularity for in situ quantification of fibrillar protein architectures. In this report, we combine P-SHG microscopy, new linear least square (LLS) fitting and modeling to determine and convert the complex second-order non-linear optical anisotropy parameter ρ of several collagen rich tissues into a simple geometric organization of collagen fibrils. Modeling integrates a priori knowledge of polyhelical organization of collagen molecule polymers forming fibrils and bundles of fibrils as well as Poisson photonic shot noise of the detection system. The results, which accurately predict the known sub-microscopic hierarchical organization of collagen fibrils in several tissues, suggest that they can be subdivided into three classes according to their microscopic and macroscopic hierarchical organization of collagen fibrils. They also show, for the first time to our knowledge, intrahepatic spatial discrimination between genuine fibrotic and non-fibrotic vessels. CCl4-treated livers are characterized by an increase in the percentage of fibrotic vessels and their remodeling involves peri-portal compaction and alignment of collagen fibrils that should contribute to portal hypertension. This integrated P-SHG image analysis method is a powerful tool that should open new avenue for the determination of pathophysiological and chemo-mechanical cues impacting collagen fibrils organization.

  19. Biphasic function of focal adhesion kinase in endothelial tube formation induced by fibril-forming collagens.

    PubMed

    Nakamura, Junko; Shigematsu, Satoshi; Yamauchi, Keishi; Takeda, Teiji; Yamazaki, Masanori; Kakizawa, Tomoko; Hashizume, Kiyoshi

    2008-10-03

    Migration and tube formation of endothelial cells are important in angiogenesis and require a coordinated response to the extra-cellular matrix (ECM) and growth factor. Since focal adhesion kinase (FAK) integrates signals from both ECM and growth factor, we investigated its role in angiogenesis. Type I and II collagens are fibril-forming collagens and stimulate human umbilical vein endothelial cells (HUVECs) to form tube structure. Although knockdown of FAK restrained cell motility and resulted in inhibition of tube formation, FAK degradation and tube formation occurred simultaneously after incubation with fibril-forming collagens. The compensation for the FAK degradation by a calpain inhibitor or transient over-expression of FAK resulted in disturbance of tube formation. These phenomena are specific to fibril-forming collagens and mediated via alpha2beta1 integrin. In conclusion, our data indicate that FAK is functioning in cell migration, but fibril-forming collagen-induced FAK degradation is necessary for endothelial tube formation.

  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.

  1. Determination of collagen fibril size via absolute measurements of second-harmonic generation signals.

    PubMed

    Bancelin, Stéphane; Aimé, Carole; Gusachenko, Ivan; Kowalczuk, Laura; Latour, Gaël; Coradin, Thibaud; Schanne-Klein, Marie-Claire

    2014-09-16

    The quantification of collagen fibril size is a major issue for the investigation of pathological disorders associated with structural defects of the extracellular matrix. Second-harmonic generation microscopy is a powerful technique to characterize the macromolecular organization of collagen in unstained biological tissues. Nevertheless, due to the complex coherent building of this nonlinear optical signal, it has never been used to measure fibril diameter so far. Here we report absolute measurements of second-harmonic signals from isolated fibrils down to 30 nm diameter, via implementation of correlative second-harmonic-electron microscopy. Moreover, using analytical and numerical calculations, we demonstrate that the high sensitivity of this technique originates from the parallel alignment of collagen triple helices within fibrils and the subsequent constructive interferences of second-harmonic radiations. Finally, we use these absolute measurements as a calibration for ex vivo quantification of fibril diameter in the Descemet's membrane of a diabetic rat cornea.

  2. Determination of collagen fibril size via absolute measurements of second-harmonic generation signals

    NASA Astrophysics Data System (ADS)

    Bancelin, Stéphane; Aimé, Carole; Gusachenko, Ivan; Kowalczuk, Laura; Latour, Gaël; Coradin, Thibaud; Schanne-Klein, Marie-Claire

    2014-09-01

    The quantification of collagen fibril size is a major issue for the investigation of pathological disorders associated with structural defects of the extracellular matrix. Second-harmonic generation microscopy is a powerful technique to characterize the macromolecular organization of collagen in unstained biological tissues. Nevertheless, due to the complex coherent building of this nonlinear optical signal, it has never been used to measure fibril diameter so far. Here we report absolute measurements of second-harmonic signals from isolated fibrils down to 30 nm diameter, via implementation of correlative second-harmonic-electron microscopy. Moreover, using analytical and numerical calculations, we demonstrate that the high sensitivity of this technique originates from the parallel alignment of collagen triple helices within fibrils and the subsequent constructive interferences of second-harmonic radiations. Finally, we use these absolute measurements as a calibration for ex vivo quantification of fibril diameter in the Descemet’s membrane of a diabetic rat cornea.

  3. New insight into the shortening of the collagen fibril D-period in human cornea.

    PubMed

    Jastrzebska, Maria; Tarnawska, Dorota; Wrzalik, Roman; Chrobak, Artur; Grelowski, Michal; Wylegala, Edward; Zygadlo, Dorota; Ratuszna, Alicja

    2017-02-01

    Collagen fibrils type I display a typical banding pattern, so-called D-periodicity, of about 67 nm, when visualized by atomic force or electron microscopy imaging. Herein we report on a significant shortening of the D-period for human corneal collagen fibrils type I (21 ± 4 nm) upon air-drying, whereas no changes in the D-period were observed for human scleral collagen fibrils type I (64 ± 4 nm) measured under the same experimental conditions as the cornea. It was also found that for the corneal stroma fixed with glutaraldehyde and air-dried, the collagen fibrils show the commonly accepted D-period of 61 ± 8 nm. We used the atomic force microscopy method to image collagen fibrils type I present in the middle layers of human cornea and sclera. The water content in the cornea and sclera samples was varying in the range of .066-.085. Calculations of the D-period using the theoretical model of the fibril and the FFT approach allowed to reveal the possible molecular mechanism of the D-period shortening in the corneal collagen fibrils upon drying. It was found that both the decrease in the shift and the simultaneous reduction in the distance between tropocollagen molecules can be responsible for the experimentally observed effect. We also hypothesize that collagen type V, which co-assembles with collagen type I into heterotypic fibrils in cornea, could be involved in the observed shortening of the corneal D-period.

  4. Nanomechanical assessment of human and murine collagen fibrils via atomic force microscopy cantilever-based nanoindentation.

    PubMed

    Andriotis, Orestis G; Manuyakorn, Wiparat; Zekonyte, Jurgita; Katsamenis, Orestis L; Fabri, Sebastien; Howarth, Peter H; Davies, Donna E; Thurner, Philipp J

    2014-11-01

    The nanomechanical assessment of collagen fibrils via atomic force microscopy (AFM) is of increasing interest within the biomedical research community. In contrast to conventional nanoindentation there exists no common standard for conducting experiments and analysis of data. Currently used analysis approaches vary between studies and validation of quantitative results is usually not performed, which makes comparison of data from different studies difficult. Also there are no recommendations with regards to the maximum indentation depth that should not be exceeded to avoid substrate effects. Here we present a methodology and analysis approach for AFM cantilever-based nanoindentation experiments that allows efficient use of captured data and relying on a reference sample for determination of tip shape. Further we show experimental evidence that maximum indentation depth on collagen fibrils should be lower than 10-15% of the height of the fibril to avoid substrate effects and we show comparisons between our and other approaches used in previous works. While our analysis approach yields similar values for indentation modulus compared to the Oliver-Pharr method we found that Hertzian analysis yielded significantly lower values. Applying our approach we successfully and efficiently indented collagen fibrils from human bronchi, which were about 30 nm in size, considerably smaller compared to collagen fibrils obtained from murine tail-tendon. In addition, derived mechanical parameters of collagen fibrils are in agreement with data previously published. To establish a quantitative validation we compared indentation results from conventional and AFM cantilever-based nanoindentation on polymeric samples with known mechanical properties. Importantly we can show that our approach yields similar results when compared to conventional nanoindentation on polymer samples. Introducing an approach that is reliable, efficient and taking into account the AFM tip shape, we anticipate

  5. 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.

  6. 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.

  7. 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.

  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. 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.

  10. Structure of type I and type III heterotypic collagen fibrils: an X-ray diffraction study.

    PubMed

    Cameron, G J; Alberts, I L; Laing, J H; Wess, T J

    2002-01-01

    The molecular packing arrangement within collagen fibrils has a significant effect on the tensile properties of tissues. To date, most studies have focused on homotypic fibrils composed of type I collagen. This study investigates the packing of type I/III collagen molecules in heterotypic fibrils of colonic submucosa using a combination of X-ray diffraction data, molecular model building, and simulated X-ray diffraction fibre diagrams. A model comprising a 70-nm-diameter D- (approximately 65 nm) axial periodic structure containing type I and type III collagen chains was constructed from amino acid scattering factors organised in a liquid-like lateral packing arrangement simulated using a classical Lennard-Jones potential. The models that gave the most accurate correspondence with diffraction data revealed that the structure of the fibril involves liquid-like lateral packing combined with a constant helical inclination angle for molecules throughout the fibril. Combinations of type I:type III scattering factors in a ratio of 4:1 gave a reasonable correspondence with the meridional diffraction series. The attenuation of the meridional intensities may be explained by a blurring of the electron density profile of the D period caused by nonspecific or random interactions between collagen types I and III in the heterotypic fibril. (c) 2002 Elsevier Science (USA).

  11. Repeated subrupture overload causes progression of nanoscaled discrete plasticity damage in tendon collagen fibrils.

    PubMed

    Veres, Samuel P; Harrison, Julia M; Lee, J Michael

    2013-05-01

    A critical feature of tendons and ligaments is their ability to resist rupture when overloaded, resulting in strains or sprains instead of ruptures. To treat these injuries more effectively, it is necessary to understand how overload affects the primary load-bearing elements of these tissues: collagen fibrils. We have investigated how repeated subrupture overload alters the collagen of tendons at the nanoscale. Using scanning electron microscopy to examine fibril morphology and hydrothermal isometric tension testing to look at molecular stability, we demonstrated that tendon collagen undergoes a progressive cascade of discrete plasticity damage when repeatedly overloaded. With successive overload cycles, fibrils develop an increasing number of kinks along their length. These kinks-discrete zones of plastic deformation known to contain denatured collagen molecules-are accompanied by a progressive and eventual total loss of D-banding along the surface of fibrils, indicating a loss of native molecular packing and further molecular denaturation. Thermal analysis of molecular stability showed that the destabilization of collagen molecules within fibrils is strongly related to the amount of strain energy dissipated by the tendon after yielding during tensile overload. These novel findings raise new questions about load transmission within tendons and their fibrils and about the interplay between crosslinking, strain-energy dissipation ability, and molecular denaturation within these structures.

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

    PubMed Central

    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; Forlino, Antonella; Cabral, Wayne A.; Barnes, Aileen M.; Marini, Joan C.; Antonio, James D. San

    2008-01-01

    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. PMID:18487200

  13. 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.

  14. Decorin core protein (decoron) shape complements collagen fibril surface structure and mediates its binding.

    PubMed

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

    2009-09-15

    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 e(1) 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(1) bands). This work helps us to understand collagen-decorin interactions and the molecular architecture of the fibrillar ECM in health and disease.

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

    PubMed Central

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

    2009-01-01

    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 e1 bands). This work helps us to understand collagen-decorin interactions and the molecular architecture of the fibrillar ECM in health and disease. PMID:19753304

  16. Collagen fibril disruption occurs early in primary guinea pig knee osteoarthritis.

    PubMed

    Huebner, J L; Williams, J M; Deberg, M; Henrotin, Y; Kraus, V B

    2010-03-01

    A major barrier inhibiting the discovery of structural modifying agents for osteoarthritis (OA) is an incomplete understanding of early disease events. Herein, we investigated the time course of collagen II cleavage and fibril disruption in the well-validated Hartley guinea pig model of spontaneous OA of the knee. Knee joints of 46 male Hartley guinea pigs were analyzed at 3 weeks, 2, 4, 7, 10, 12, and 18 months of age for histological severity of OA, cartilage collagen fibril disruption by semi-quantitative polarized light microscopy, and expression of type II collagen degradation biomarkers, 9A4 and Coll2-1, by immunohistochemistry. In addition, serum biomarkers specific for collagen II degradation, CTX-II, C2C, and Coll2-1 were quantified. Collagen fibril disruption and expression of the collagenase-generated cleavage neoepitope, 9A4, were observed as early as 2 months of age, despite the appearance of histological OA at 4 months of age. Only serum Coll2-1 increased coincident with the early disruption of the collagen fibril between 3 weeks and 7 months, in contrast to serum C2C, which did not change significantly or correlate with histological severity. Inversely, CTX-II declined dramatically from 3 weeks to 4 months and remaining low thereafter, coincident with growth plate turnover. Collagenase cleavage and disruption of the type II collagen network are early OA disease events in this model, preceding histological evidence of proteoglycan loss. The markedly different serum profiles of collagen II-related biomarkers during the early stages of disease development suggest compartmental segregation and temporal regulation of collagen degrading enzymes. Copyright 2009 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.

  17. Collagen Fibril Disruption Occurs Early in Primary Guinea Pig Knee Osteoarthritis

    PubMed Central

    Huebner, Janet L; Williams, James M; Deberg, Michelle; Henrotin, Yves; Kraus, Virginia Byers

    2009-01-01

    Objective A major barrier inhibiting the discovery of structural modifying agents for osteoarthritis (OA) is an incomplete understanding of early disease events. Herein, we investigated the time course of collagen II cleavage and fibril disruption in the well-validated Hartley guinea pig model of spontaneous osteoarthritis of the knee. Methods: Knee joints of 46 male Hartley guinea pigs were analyzed at 3 weeks, 2, 4, 7, 10, 12, and 18 months of age for histological severity of OA, cartilage collagen fibril disruption by semi-quantitative polarized light microscopy, and expression of type II collagen degradation biomarkers, 9A4 and Coll2-1, by immunohistochemistry. In addition, serum biomarkers specific for collagen II degradation, CTX-II, C2C, and Coll2-1 were quantified. Results Collagen fibril disruption and expression of the collagenase-generated cleavage neoepitope, 9A4, were observed as early as 2 months of age, despite the appearance of histological OA at 4 months of age. Only serum Coll2-1 increased coincident with the early disruption of the collagen fibril between 3 weeks and 7 months, in contrast to serum C2C, which did not change significantly or correlate with histological severity. Inversely, CTX-II declined dramatically from 3 weeks to 4 months and remaining low thereafter, coincident with growth plate turnover. Conclusions Collagenase cleavage and disruption of the type II collagen network are early OA disease events in this model, preceding histological evidence of proteoglycan loss. The markedly different serum profiles of collagen II-related biomarkers during the early stages of disease development suggest compartmental segregation and temporal regulation of collagen degrading enzymes. PMID:19825496

  18. 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

  19. 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.

  20. Characterization of the correlation between collagen fibril thickness and forward and backward second harmonic signal

    NASA Astrophysics Data System (ADS)

    Hsueh, Chiu-Mei; Hovhannisyan, Vladimir A.; Dong, Chen-Yuan

    2011-07-01

    Optical-based microscopy plays an important role in various scientific fields such as physics, chemistry and biology. Second harmonic generation (SHG) microscopy has become one of the indispensable tools for biomedical imaging for the last decade because the signal generated from SHG is sensitive to the objective structure and this amazing non-invasive method can also directly observe the objective without using extra fluorescent labels, especially for collagen molecules. As the most abundant protein in animals, collagen is responsible for a number of important structural and functional roles in vertebrates. For certain diseases, it has been shown that collagen fiber diameter has a significant variation and thus as a vital symptom for diagnosis. Moreover, collagen diameter is also a key parameter for fibrogenesis studying. Therefore, the determination of collagen fiber diameter is important for studying biophysical processes and identifying bioengineering applications. In this study, we investigated various collagen fibril thicknesses and the corresponding forward (FSHG) and backward (BSHG) second harmonic signal intensity variation. Our result exhibits that SHG intensity can quantify describe the relative collagen fibril thickness alteration, which also indicates the coherent effect difference between FSHG and BSHG. This approach demonstrates the capability of SHG imaging in providing collagen mechanical information and that may be applied in the evaluation of advancing collagen issues in vivo.

  1. Characterization of a liver organoid tissue composed of hepatocytes and fibroblasts in dense collagen fibrils.

    PubMed

    Tamai, Miho; Adachi, Eijiro; Tagawa, Yoh-ichi

    2013-11-01

    The adult liver is wrapped in a connective tissue sheet called the liver capsule, which consists of collagen fibrils and fibroblasts. In this study, we set out to construct a liver organoid tissue that would be comparable to the endogenous liver, using a bioreactor. In vitro liver organoid tissue was generated by combining collagen fibrils, fibroblasts, and primary murine hepatocytes or Hep G2 on a mesh of poly-lactic acid fabric using a bioreactor. Then, the suitability of this liver organoid tissue for transplantation was tested by implanting the constructs into partially hepatectomized BALB/cA-nu/nu mice. As determined by using scanning and transmission electron microscopes, the liver organoid tissues were composed of densely packed collagen fibrils with fibroblasts and aggregates of oval or spherical hepatocytes. Angiogenesis was induced after the transplantation, and blood vessels connected the liver organoid tissue with the surrounding tissue. Thus, a novel approach was applied to generate transplantable liver organoid tissue within a condensed collagen fibril matrix. These results suggested that a dense collagen network populated with fibroblasts can hold a layer of concentrated hepatocytes, providing a three-dimensional microenvrionment suitable for the reestablishment of cell-cell and cell-extracellular matrix (ECM) interactions, and resulting in the maintenance of their liver-specific functions. This liver organoid tissue may be useful for the study of intrahepatic functions of various cells, cytokines, and ECMs, and may fulfill the fundamental requirements of a donor tissue.

  2. Isolated posterior cruciate ligament insufficiency induces morphological changes of anterior cruciate ligament collagen fibrils.

    PubMed

    Ochi, M; Murao, T; Sumen, Y; Kobayashi, K; Adachi, N

    1999-04-01

    We studied the ultrastructural changes of the human anterior cruciate ligament (ACL) with transmission electron micrograph cross-sections following isolated posterior cruciate ligament (PCL) injury. Biopsy specimens were obtained from the proximal third and anteromedial aspect of the ACL. Fourteen patients with PCL-deficient knees at a mean of 22.1 months from injury to surgery and 5 normal knees amputated secondary to malignant tumors or traumatic injuries were used as controls. A significant difference was found in the number of collagen fibrils per 1 microm2 between the PCL-deficient knee group and the control group. There was a significant difference found in the collagen fibril diameter between the PCL-deficient knee group and the control group. The collagen packing density (the percentage of sampled area occupied by collagen fibrils) was also significantly different between the PCL-deficient knee and the control group. The current study shows that an isolated PCL insufficiency can induce morphological changes in ACL collagen fibrils, suggesting that a PCL insufficiency can have adverse effects on other ligamentous structures in the knee joint.

  3. 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.

  4. Evidence that translocation of collagen fibril segments plays a role in early intrinsic tendon repair.

    PubMed

    Gunn, J Stephen; Ehrlich, H Paul

    2012-02-01

    Severed tendon repair advances with either a scar through extrinsic repair or regeneration through intrinsic repair. The authors examined whether intrinsic tendon repair reintroduces embryonic fibrillogenesis, whereby preformed collagen fibril segments are incorporated into growing collagen fibers at wound edges. Isolated tendons from 10-day-old chicken embryos were suspended in 1 mg/ml of the antibiotic gentamicin for 90 days, which released fibril segments that were fluorescently tagged with rhodamine. Tendons isolated from 14-day-old chicken embryos were wounded to half their diameter and then maintained as explants in stationary organ culture. Fluorescent-tagged fibril segments were introduced to wounded tendon explants in the presence of high concentrations of neomycin, an antibiotic; cycloheximide, a protein synthesis inhibitor; cytochalasin D, a disruptor of microfilaments; and colchicine, a disruptor of microtubules. At 24 hours, explants were viewed by means of fluorescent microscopy. Untreated, wounded tendon explants showed the translocation of fluorescent-tagged fibril segments from the explant surface to accumulation at wound edges. In the presence of high concentrations of neomycin, cytochalasin D, or colchicine, fluorescent-tagged fibril segments failed to accumulate at wound edges and were retained on the explant surface. Inhibition of protein synthesis by cycloheximide did not alter the accumulation of fluorescent-tagged fibril segments at wound edges. Inhibiting fluorescent-tagged fibril segment accumulation by antibiotics is consistent with their role in releasing fibril segments. Experimental findings show fibril segment translocation and accumulation at wound edges involves microfilaments and microtubules, but not protein synthesis. The experiments support the hypothesis that intrinsic tendon repair advances through the incorporation of fibril segments at wound edges.

  5. 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.

  6. Fabrication of high-density collagen fibril matrix gels by renaturation of triple-helix collagen from gelatin.

    PubMed

    Ohyabu, Yoshimi; Yunoki, Shunji; Hatayama, Hirosuke; Teranishi, Yoshikazu

    2013-11-01

    Collagen-based 3-D hydrogels often lack sufficient mechanical strength for tissue engineering. We developed a method for fabrication of high-density collagen fibril matrix (CFM) gels from concentrated solutions of uncleaved gelatin (UCG). Denatured random-coil UCG exhibited more rapid and efficient renaturation into collagen triple-helix than cleaved gelatin (CG) over a broad range of setting temperatures. The UCG solution formed opaque gels with high-density reconstituted collagen fibrils at 28-32 °C and transparent gels similar to CG at <25 °C. The unique gelation properties of UCG enabled the encapsulation of cultured cells in CFM of high solid volume (>5%) and elasticity (1.28 ± 0.15 kPa at 5% and 4.82 ± 0.38 kPa at 8%) with minimal cell loss. The elastic modulus of these gels was higher than that of conventional CFM containing 0.5% collagen. High-strength CFM may provide more durable hydrogels for tissue engineering and regenerative medicine.

  7. Collagen fibrils in functionally distinct tendons have differing structural responses to tendon rupture and fatigue loading.

    PubMed

    Herod, Tyler W; Chambers, Neil C; Veres, Samuel P

    2016-09-15

    In this study we investigate relationships between the nanoscale structure of collagen fibrils and the macroscale functional response of collagenous tissues. To do so, we study two functionally distinct classes of tendons, positional tendons and energy storing tendons, using a bovine forelimb model. Molecular-level assessment using differential scanning calorimetry (DSC), functional crosslink assessment using hydrothermal isometric tension (HIT) analysis, and ultrastructural assessment using scanning electron microscopy (SEM) were used to study undamaged, ruptured, and cyclically loaded samples from the two tendon types. HIT indicated differences in both crosslink type and crosslink density, with flexor tendons having more thermally stable crosslinks than the extensor tendons (higher TFmax of >90 vs. 75.1±2.7°C), and greater total crosslink density than the extensor tendons (higher t1/2 of 11.5±1.9 vs. 3.5±1.0h after NaBH4 treatment). Despite having a lower crosslink density than flexor tendons, extensor tendons were significantly stronger (37.6±8.1 vs. 23.1±7.7MPa) and tougher (14.3±3.6 vs. 6.8±3.4MJ/m(3)). SEM showed that collagen fibrils in the tougher, stronger extensor tendons were able to undergo remarkable levels of plastic deformation in the form of discrete plasticity, while those in the flexor tendons were not able to plastically deform. When cyclically loaded, collagen fibrils in extensor tendons accumulated fatigue damage rapidly in the form of kink bands, while those in flexor tendons did not accumulate significant fatigue damage. The results demonstrate that collagen fibrils in functionally distinct tendons respond differently to mechanical loading, and suggests that fibrillar collagens may be subject to a strength vs. fatigue resistance tradeoff. Collagen fibrils-nanoscale biological cables-are the fundamental load-bearing elements of all structural human tissues. While all collagen fibrils share common features, such as being composed of a

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. 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

    2016-04-01

    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.

  14. Fibrils of different collagen types containing immobilised proteoglycans (PGs) as coatings: characterisation and influence on osteoblast behaviour.

    PubMed

    Douglas, T; Hempel, U; Mietrach, C; Heinemann, S; Scharnweber, D; Worch, H

    2007-11-01

    Collagen, the main organic component of bone, is used as a coating on titanium implants and as a scaffold material in bone tissue engineering. Surface modifications of titanium which promote osteoblast adhesion, proliferation and synthesis of collagen by osteoblasts are desirable. One biomimetic approach is the coating of titanium with collagen in fibrillar form. Other organic components of bone may be bound to fibrils and exert additional effects. In this study, the collagen types I-III were compared regarding their ability to bind the proteoglycans decorin and biglycan, which are found in bone. More collagen was bound to collagen II fibrils than to those of types I and III. Therefore, titanium surfaces were coated with fibrils of collagen type II containing biglycan or decorin or neither to investigate the effect of the proteoglycans on human primary osteoblast behaviour. In addition, the growth factor TGF-beta1 was adsorbed onto surfaces coated with fibrils of collagen type II containing biglycan or decorin or neither to investigate the influence of decorin and biglycan on the effect of TGF-beta1 on osteoblasts. Fibril-bound biglycan and decorin influence primary osteoblast behaviour by themselves. The presence of substrate-bound biglycan or decorin influences the effect of TGF-beta1. These results may be important when designing collagen-based coatings or scaffolds for tissue engineering, including those loaded with growth factors.

  15. Vertebrae length and ultra-structure measurements of collagen fibrils and mineral content in the vertebrae of lordotic gilthead seabreams (Sparus aurata).

    PubMed

    Berillis, Panagiotis; Panagiotopoulos, Nikolaos; Boursiaki, Vaia; Karapanagiotidis, Ioannis T; Mente, Eleni

    2015-08-01

    Skeletal deformities of gilthead seabream (Sparus aurata) are a major factor affecting the production cost, the external morphology and survival and growth of the fish. Adult individuals of S. aurata were collected from a commercial fish farm in Greece and were divided into two groups: one with the presence of lordosis, a skeletal deformity, and one without any skeletal deformity. Fishes were X-rayed, and cervical, abdominal and caudal vertebrae lengths were measured. Vertebrae were taken from the site of the vertebral column where lordosis occurred. One part was decalcified and prepared for collagen examination with transmission electron microscopy, and the rest were incinerated, and the Ca and P contents were measured. The stoichiometries of the samples were obtained by EDS (Energy Dispersive Spectroscopy). The same procedure was followed for fish without skeletal deformities (vertebrae were taken from the middle region of the vertebral column). The decalcified vertebrae parts were examined with TEM, collagen micrographs were taken and the fibrils' periods and diameters were measured. There were no significant differences for both Ca and P or the collagen fibrils' periods between the two fish groups. The mean lengths of the cervical, abdominal and caudal vertebrae where lordosis occurred were similar to the lengths of the respective regions of the individuals without the skeletal deformity. The TEM examination showed a significantly smaller mean vertebrae collagen fibril diameter from the fishes with lordosis compared with those from the controls, revealing the significance of collagen to bone structure.

  16. Structural variations in anchoring fibrils in dystrophic epidermolysis bullosa: correlation with type VII collagen expression.

    PubMed

    McGrath, J A; Ishida-Yamamoto, A; O'Grady, A; Leigh, I M; Eady, R A

    1993-04-01

    Dystrophic epidermolysis bullosa is characterized by various abnormalities of anchoring fibrils, which are mainly composed of type VII collagen, at the dermal-epidermal junction. To define these changes more clearly, we examined skin samples from 22 patients with different forms of dystrophic epidermolysis bullosa by pre-embedding immunoelectron microscopy using an antibody (LH 7:2) that binds to the NC-1 globular domain of type VII collagen, followed by 1 nm colloidal gold-labeled secondary antibodies and subsequent silver enhancement. In dominant dystrophic epidermolysis bullosa cases, there was only a slight but variable reduction in the immunolabeling density on anchoring fibrils and on the lamina densa, in parts similar to normal human skin. In localized recessive dystrophic epidermolysis bullosa skin, some fibrillar structures just below the lamina densa (and particularly subjacent to hemidesmosomes) had specific antibody labeling despite their lack of resemblance to definitive anchoring fibrils. Immunolabeling with LH 7:2 was also seen within basal keratinocyte endoplasmic reticulum and cytoplasmic vesicles in some dystrophic epidermolysis bullosa patients, usually with milder phenotypic features. Even in the most severe cases of generalized recessive dystrophic epidermolysis bullosa, occasional immunolabeling was found within the lamina densa and on scanty thin filamentous structures at sub-lamina densa sites usually occupied by anchoring fibrils. This study suggests that dystrophic epidermolysis bullosa patients express some type VII collagen NC-1 domain epitopes that may be variably reduced at the dermal-epidermal junction or retained within basal keratinocytes. The clinical heterogeneity in dystrophic epidermolysis bullosa is mirrored by a range of immunoelectron microscopy findings, indicating variability in completeness of anchoring fibril formation and a possible spectrum of underlying type VII collagen structural protein abnormalities.

  17. Stress shielding of patellar tendon: effect on small-diameter collagen fibrils in a rabbit model.

    PubMed

    Majima, Tokifumi; Yasuda, Kazunori; Tsuchida, Takamasa; Tanaka, Kunio; Miyakawa, Kiyoshi; Minami, Akio; Hayashi, Kozaburo

    2003-01-01

    The purpose of this study was to assess the effects of stress shielding on the microstructure and ultrastructure of the patellar tendon using 40 mature female Japanese white rabbits. The patellar tendon was completely released from stress by drawing the patella toward the tibial tubercle with a stainless steel wire installed between them. Microstructurally, stress shielding for 3 and 6 weeks increased the number of cells approximately fivefold, to that of the control tendon. Collagen bundles were less well oriented in the stress-shielded tendon than in the control. Ultrastructurally, small collagen fibrils with a diameter of less than 90 nm increased in the stress-shielded tendon. The median collagen fibril diameter in 6-week stress-shielded tendon was significantly smaller ( P < 0.05) than in the control tendon (58.8% of control). The ratio of the total area of collagen fibrils to the whole visualized area in the stress-shielded patellar tendon was significantly smaller at 3 and 6 weeks than that in the control. This study demonstrated that complete stress shielding significantly affects the microstructure and ultrastructure of the patellar tendon

  18. Blocking collagen fibril formation in injured knees reduces flexion contracture in a rabbit model.

    PubMed

    Steplewski, Andrzej; Fertala, Jolanta; Beredjiklian, Pedro K; Abboud, Joseph A; Wang, Mark L Y; Namdari, Surena; Barlow, Jonathan; Rivlin, Michael; Arnold, William V; Kostas, James; Hou, Cheryl; Fertala, Andrzej

    2017-05-01

    Post-traumatic joint contracture is a frequent orthopaedic complication that limits the movement of injured joints, thereby severely impairing affected patients. Non-surgical and surgical treatments for joint contracture often fail to improve the range of motion. In this study, we tested a hypothesis that limiting the formation of collagen-rich tissue in the capsules of injured joints would reduce the consequences of the fibrotic response and improve joint mobility. We targeted the formation of collagen fibrils, the main component of fibrotic deposits formed within the tissues of injured joints, by employing a relevant rabbit model to test the utility of a custom-engineered antibody. The antibody was delivered directly to the cavities of injured knees in order to block the formation of collagen fibrils produced in response to injury. In comparison to the non-treated control, mechanical tests of the antibody-treated knees demonstrated a significant reduction of flexion contracture. Detailed microscopic and biochemical studies verified that this reduction resulted from the antibody-mediated blocking of the assembly of collagen fibrils. These findings indicate that extracellular processes associated with excessive formation of fibrotic tissue represent a valid target for limiting post-traumatic joint stiffness. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1038-1046, 2017. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

  19. 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

  20. Nanoscale Structure of Type I Collagen Fibrils: Quantitative Measurement of D-spacing

    PubMed Central

    Erickson, Blake; Fang, Ming; Wallace, Joseph M.; Orr, Bradford G.; Les, Clifford M.; Holl, Mark M. Banaszak

    2012-01-01

    This paper details a quantitative method to measure the D-periodic spacing of Type I collagen fibrils using Atomic Force Microscopy coupled with analysis using a 2D Fast Fourier Transform approach. Instrument calibration, data sampling and data analysis are all discussed and comparisons of the data to the complementary methods of electron microscopy and X-ray scattering are made. Examples of the application of this new approach to the analysis of Type I collagen morphology in disease models of estrogen depletion and Osteogenesis Imperfecta are provided. We demonstrate that it is the D-spacing distribution, not the D-spacing mean, that showed statistically significant differences in estrogen depletion associated with early stage Osteoporosis and Osteogenesis Imperfecta. The ability to quantitatively characterize nanoscale morphological features of Type I collagen fibrils will provide important structural information regarding Type I collagen in many research areas, including tissue aging and disease, tissue engineering, and gene knock out studies. Furthermore, we also envision potential clinical applications including evaluation of tissue collagen integrity under the impact of diseases or drug treatments. PMID:23027700

  1. Reduced anchoring fibril formation and collagen VII immunoreactivity in feline dystrophic epidermolysis bullosa.

    PubMed

    Olivry, T; Dunston, S M; Marinkovich, M P

    1999-11-01

    Dystrophic epidermolysis bullosa was diagnosed in a cat with juvenile-onset epithelial sloughing of the oral mucosa, footpads, and haired skin. Dermoepidermal separation occurred in the absence of inflammation or cytolysis of basal epidermal cells. Collagen IV-specific immunostaining corroborated the fact that clefting took place below the epidermal basement membrane. Ultrastructural examination revealed that the proband's anchoring fibrils exhibited a filamentous morphology and were decreased in number compared with those in a normal cat. Finally, the attenuated immunoreactivity for collagen VII in our patient led us to suspect that its encoding gene, COL7A1, could be mutated in this case of feline dystrophic epidermolysis bullosa.

  2. A computational remodeling approach to predict the physiological architecture of the collagen fibril network in corneo-scleral shells.

    PubMed

    Grytz, Rafael; Meschke, Günther

    2010-04-01

    Organized collagen fibrils form complex networks that introduce strong anisotropic and highly nonlinear attributes into the constitutive response of human eye tissues. Physiological adaptation of the collagen network and the mechanical condition within biological tissues are complex and mutually dependent phenomena. In this contribution, a computational model is presented to investigate the interaction between the collagen fibril architecture and mechanical loading conditions in the corneo-scleral shell. The biomechanical properties of eye tissues are derived from the single crimped fibril at the micro-scale via the collagen network of distributed fibrils at the meso-scale to the incompressible and anisotropic soft tissue at the macro-scale. Biomechanically induced remodeling of the collagen network is captured on the meso-scale by allowing for a continuous re-orientation of preferred fibril orientations and a continuous adaptation of the fibril dispersion. The presented approach is applied to a numerical human eye model considering the cornea and sclera. The predicted fibril morphology correlates well with experimental observations from X-ray scattering data.

  3. Collagen fibril diameter distribution does not reflect changes in the mechanical properties of in vitro stress-deprived tendons.

    PubMed

    Lavagnino, Michael; Arnoczky, S P Steven P; Frank, Katherine; Tian, Tao

    2005-01-01

    The purpose of this study was to determine if an association exists between the tensile properties and the collagen fibril diameter distribution in in vitro stress-deprived rat tail tendons. Rat tail tendons were paired into two groups of 21 day stress-deprived and 0 time controls and compared using transmission electron microscopy (n = 6) to measure collagen fibril diameter distribution and density, and mechanical testing (n =6) to determine ultimate stress and tensile modulus. There was a statistically significant decrease in both ultimate tensile strength (control: 17.95+/-3.99 MPa, stress-deprived: 6.79+/-3.91 MPa) and tensile modulus (control: 312.8+/-89.5 MPa, stress-deprived: 176.0+/-52.7 MPa) in the in vitro stress-deprived tendons compared to controls. However, there was no significant difference between control and stress-deprived tendons in the number of fibrils per tendon counted, mean fibril diameter, mean fibril density, or fibril size distribution. The results of this study demonstrate that the decrease in mechanical properties observed in in vitro stress-deprived rat tail tendons is not correlated with the collagen fibril diameter distribution and, therefore, the collagen fibril diameter distribution does not, by itself, dictate the decrease in mechanical properties observed in in vitro stress-deprived rat tail tendons.

  4. Effect of ultrasonication on the fibril-formation and gel properties of collagen from grass carp skin.

    PubMed

    Jiang, Ying; Wang, Haibo; Deng, Mingxia; Wang, Zhongwen; Zhang, Juntao; Wang, Haiyin; Zhang, Hanjun

    2016-02-01

    Controlling the fibril-formation process of collagen in vitro to fabricate novel biomaterials is a new area in the field of collagen research. This study aimed to determine the effect of ultrasonication on collagen fibril formation and the properties of the resulting collagen gels. Native collagen, extracted from the skin of grass carp, self-assembled under ultrasonic conditions (at different ultrasonic power and duration). The self-assembly kinetics, fibrillar morphology, and physical and cell growth-promoting properties of the collagen gels were analyzed and compared. The results showed that the self-assembly rate of collagen was increased by ultrasonication at the nucleation stage. The resulting fibrils exhibited smaller diameters and D-periodicity lengths than that of the untreated collagen samples (p<0.05). The viscoelasticity and textural properties of collagen gels also changed after ultrasonication at the nucleation stage. Texture profile analysis and cell proliferation assays showed that ultrasonication produced softer collagen gel colloids, which were more suitable for cell proliferation than the untreated collagen gels.

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

    PubMed

    Szczesny, Spencer E; Elliott, Dawn M

    2014-06-01

    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. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  6. 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

  7. Gel-spinning of mimetic collagen and collagen/nano-carbon fibers: Understanding multi-scale influences on molecular ordering and fibril alignment.

    PubMed

    Green, Emily C; Zhang, Yiying; Li, Heng; Minus, Marilyn L

    2017-01-01

    Synthetic gel-spun collagen and collagen/nano-carbon fibers were found to exhibit structural mimicry comparable to native tendons. X-ray scattering and microscopy analyses are used to characterize the molecular and fibrillar alignment in the synthetic fibers, where D-banding is observed throughout the spun fibers - consistent with native collagen. For the composite collagen/nano-carbon fibers, the morphology and dispersion quality of the nano-carbons within was found to play a significant role in influencing collagen molecular ordering and fibril alignment. Fibrillar and molecular alignment was also better preserved during elongation of the composites as compared to the control collagen fibers. These results show the structural influence of a rigid inclusion on the collagen fibril structure. Both dry- and wet-state tensile testing were performed on the collagen fibers, and these results show behavior comparable to the native materials. Dry-state tests also reveal interfacial interaction between the nano-fillers and the collagen fibrils through theoretical analysis. Wet-state tensile testing indicates the structure-property behavior of the mimetic hierarchical structure within the synthetic fibers.

  8. 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.

  9. Supramolecular Organization of Collagen Fibrils in Healthy and Osteoarthritic Human Knee and Hip Joint Cartilage.

    PubMed

    Gottardi, Riccardo; Hansen, Uwe; Raiteri, Roberto; Loparic, Marko; Düggelin, Marcel; Mathys, Daniel; Friederich, Niklaus F; Bruckner, Peter; Stolz, Martin

    2016-01-01

    Cartilage matrix is a composite of discrete, but interacting suprastructures, i.e. cartilage fibers with microfibrillar or network-like aggregates and penetrating extrafibrillar proteoglycan matrix. The biomechanical function of the proteoglycan matrix and the collagen fibers are to absorb compressive and tensional loads, respectively. Here, we are focusing on the suprastructural organization of collagen fibrils and the degradation process of their hierarchical organized fiber architecture studied at high resolution at the authentic location within cartilage. We present electron micrographs of the collagenous cores of such fibers obtained by an improved protocol for scanning electron microscopy (SEM). Articular cartilages are permeated by small prototypic fibrils with a homogeneous diameter of 18 ± 5 nm that can align in their D-periodic pattern and merge into larger fibers by lateral association. Interestingly, these fibers have tissue-specific organizations in cartilage. They are twisted ropes in superficial regions of knee joints or assemble into parallel aligned cable-like structures in deeper regions of knee joint- or throughout hip joints articular cartilage. These novel observations contribute to an improved understanding of collagen fiber biogenesis, function, and homeostasis in hyaline cartilage.

  10. Supramolecular Organization of Collagen Fibrils in Healthy and Osteoarthritic Human Knee and Hip Joint Cartilage

    PubMed Central

    Raiteri, Roberto; Loparic, Marko; Düggelin, Marcel; Mathys, Daniel; Friederich, Niklaus F.; Bruckner, Peter

    2016-01-01

    Cartilage matrix is a composite of discrete, but interacting suprastructures, i.e. cartilage fibers with microfibrillar or network-like aggregates and penetrating extrafibrillar proteoglycan matrix. The biomechanical function of the proteoglycan matrix and the collagen fibers are to absorb compressive and tensional loads, respectively. Here, we are focusing on the suprastructural organization of collagen fibrils and the degradation process of their hierarchical organized fiber architecture studied at high resolution at the authentic location within cartilage. We present electron micrographs of the collagenous cores of such fibers obtained by an improved protocol for scanning electron microscopy (SEM). Articular cartilages are permeated by small prototypic fibrils with a homogeneous diameter of 18 ± 5 nm that can align in their D-periodic pattern and merge into larger fibers by lateral association. Interestingly, these fibers have tissue-specific organizations in cartilage. They are twisted ropes in superficial regions of knee joints or assemble into parallel aligned cable-like structures in deeper regions of knee joint- or throughout hip joints articular cartilage. These novel observations contribute to an improved understanding of collagen fiber biogenesis, function, and homeostasis in hyaline cartilage. PMID:27780246

  11. 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. Copyright © 2016 Elsevier Inc. All rights reserved.

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

    PubMed

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

    2015-12-01

    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.

  13. 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

  14. 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.

  15. 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.

  16. Fibrillar, fibril-associated and basement membrane collagens of the arterial wall: architecture, elasticity and remodeling under stress.

    PubMed

    Osidak, M S; Osidak, E O; Akhmanova, M A; Domogatsky, S P; Domogatskaya, A S

    2015-01-01

    The ability of a human artery to pass through 150 million liters of blood sustaining 2 billion pulsations of blood pressure with minor deterioration depends on unique construction of the arterial wall. Viscoelastic properties of this construction enable to re-seal the occuring damages apparently without direct immediate participance of the constituent cells. Collagen structures are considered to be the elements that determine the mechanoelastic properties of the wall in parallel with elastin responsible for elasticity and resilience. Collagen scaffold architecture is the function-dependent dynamic arrangement of a dozen different collagen types composing three distinct interacting forms inside the extracellular matrix of the wall. Tightly packed molecules of collagen types I, III, V provide high tensile strength along collagen fibrils but toughness of the collagen scaffold as a whole depends on molecular bonds between distinct fibrils. Apart of other macromolecules in the extracellular matrix (ECM), collagen-specific interlinks involve microfilaments of collagen type VI, meshwork-organized collagen type VIII, and FACIT collagen type XIV. Basement membrane collagen types IV, XV, XVIII and cell-associated collagen XIII enable transmission of mechanical signals between cells and whole artery matrix. Collagen scaffold undergoes continuous remodeling by decomposition promoted with MMPs and reconstitution from newly produced collagen molecules. Pulsatile stress-strain load modulates both collagen synthesis and MMP-dependent collagen degradation. In this way the ECM structure becomes adoptive to mechanical challenges. The mechanoelastic properties of the arterial wall are changed in atherosclerosis concomitantly with collagen turnover both type-specific and dependent on the structure. Improving the feedback could be another approach to restore sufficient blood circulation.

  17. 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.

  18. 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

  19. 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

  20. 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.

  1. 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.

  2. Intrafibrillar mineralization of polyacrylic acid-bound collagen fibrils using a two-dimensional collagen model and Portland cement-based resins.

    PubMed

    Wu, Shiyu; Gu, Lisha; Huang, Zihua; Sun, Qiurong; Chen, Huimin; Ling, Junqi; Mai, Sui

    2017-02-01

    The biomimetic remineralization of apatite-depleted dentin is a potential method for enhancing the durability of resin-dentin bonding. To advance this strategy from its initial proof-of-concept design, we sought to investigate the characteristics of polyacrylic acid (PAA) adsorption to desorption from type I collagen and to test the mineralization ability of PAA-bound collagen. Portland cement and β-tricalcium phosphate (β-TCP) were homogenized with a hydrophilic resin blend to produce experimental resins. The collagen fibrils reconstituted on nickel (Ni) grids were mineralized using different methods: (i) group I consisted of collagen treated with Portland cement-based resin in simulated body fluid (SBF); (ii) group II consisted of PAA-bound collagen treated with Portland cement-based resin in SBF; and (iii) group III consisted of PAA-bound collagen treated with β-TCP-doped Portland cement-based resin in deionized water. Intrafibrillar mineralization was evaluated using transmission electron microscopy. We found that a carbonyl-associated peak at pH 3.0 increased as adsorption time increased, whereas a hydrogen bond-associated peak increased as desorption time increased. The experimental resins maintained an alkaline pH and the continuous release of calcium ions. Apatite was detected within PAA-bound collagen in groups II and III. Our results suggest that PAA-bound type I collagen fibrils can be mineralized using Portland cement-based resins.

  3. Molecular properties and fibril ultrastructure of types II and XI collagens in cartilage of mice expressing exclusively the α1(IIA) collagen isoform.

    PubMed

    McAlinden, Audrey; Traeger, Geoffrey; Hansen, Uwe; Weis, Mary Ann; Ravindran, Soumya; Wirthlin, Louisa; Eyre, David R; Fernandes, Russell J

    2014-02-01

    Until now, no biological tools have been available to determine if a cross-linked collagen fibrillar network derived entirely from type IIA procollagen isoforms, can form in the extracellular matrix (ECM) of cartilage. Recently, homozygous knock-in transgenic mice (Col2a1(+ex2), ki/ki) were generated that exclusively express the IIA procollagen isoform during post-natal development while type IIB procollagen, normally present in the ECM of wild type mice, is absent. The difference between these Col2a1 isoforms is the inclusion (IIA) or exclusion (IIB) of exon 2 that is alternatively spliced in a developmentally regulated manner. Specifically, chondroprogenitor cells synthesize predominantly IIA mRNA isoforms while differentiated chondrocytes produce mainly IIB mRNA isoforms. Recent characterization of the Col2a1(+ex2) mice has surprisingly shown that disruption of alternative splicing does not affect overt cartilage formation. In the present study, biochemical analyses showed that type IIA collagen extracted from ki/ki mouse rib cartilage can form homopolymers that are stabilized predominantly by hydroxylysyl pyridinoline (HP) cross-links at levels that differed from wild type rib cartilage. The findings indicate that mature type II collagen derived exclusively from type IIA procollagen molecules can form hetero-fibrils with type XI collagen and contribute to cartilage structure and function. Heteropolymers with type XI collagen also formed. Electron microscopy revealed mainly thin type IIA collagen fibrils in ki/ki mouse rib cartilage. Immunoprecipitation and mass spectrometry of purified type XI collagen revealed a heterotrimeric molecular composition of α1(XI)α2(XI)α1(IIA) chains where the α1(IIA) chain is the IIA form of the α3(XI) chain. Since the N-propeptide of type XI collagen regulates type II collagen fibril diameter in cartilage, the retention of the exon 2-encoded IIA globular domain would structurally alter the N-propeptide of type XI collagen

  4. Molecular properties and fibril ultrastructure of types II and XI collagens in cartilage of mice expressing exclusively the α1(IIA) collagen isoform

    PubMed Central

    McAlinden, Audrey; Traeger, Geoffrey; Hansen, Uwe; Weis, Mary Ann; Ravindran, Soumya; Wirthlin, Louisa; Eyre, David R.; Fernandes, Russell J.

    2013-01-01

    Until now, no biological tools have been available to determine if a cross-linked collagen fibrillar network derived entirely from type IIA procollagen isoforms, can form in the extracellular matrix (ECM) of cartilage. Recently, homozygous knock-in transgenic mice (Col2a1+ex2, ki/ki) were generated that exclusively express the IIA procollagen isoform during post-natal development while type IIB procollagen, normally present in the ECM of wild type mice, is absent. The difference between these Col2a1 isoforms is the inclusion (IIA) or exclusion (IIB) of exon 2 that is alternatively spliced in a developmentally regulated manner. Specifically, chondroprogenitor cells synthesize predominantly IIA mRNA isoforms while differentiated chondrocytes produce mainly IIB mRNA isoforms. Recent characterization of the Col2a1+ex2 mice has surprisingly shown that disruption of alternative splicing does not affect overt cartilage formation. In the present study, biochemical analyses showed that type IIA collagen extracted from ki/ki mouse rib cartilage can form homopolymers that are stabilized predominantly by hydroxylysyl pyridinoline (HP) cross-links at levels that differed from wild type rib cartilage. The findings indicate that mature type II collagen derived exclusively from type IIA procollagen molecules can form hetero-fibrils with type XI collagen and contribute to cartilage structure and function. Heteropolymers with type XI collagen also formed. Electron microscopy revealed mainly thin type IIA collagen fibrils in ki/ki mouse rib cartilage. Immunoprecipitation and mass spectrometry of purified type XI collagen revealed a heterotrimeric molecular composition of α1(XI)α2(XI)α1(IIA) chains where the α1(IIA) chain is the IIA form of the α3(XI) chain. Since the N-propeptide of type XI collagen regulates type II collagen fibril diameter in cartilage, the retention of the exon 2-encoded IIA globular domain would structurally alter the N-propeptide of type XI collagen. This

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

    PubMed Central

    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

    2015-01-01

    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

  6. 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.

  7. Collagen Fibril Diameter Distributions in Rabbit Anterior Cruciate and Medial Collateral Ligaments

    PubMed Central

    Hart, Robert A; Akeson, Wayne H; Spratt, Kevin; Amiel, David

    1999-01-01

    This study presents morphometric analyses of the collagen fibril diameters of rabbit anterior cruciate and medial collateral knee ligaments of New Zealand White rabbits (young, age two months and adult, age thirty-six to forty months). Measurements were made from transmission electron micrographs of transverse ligament sections of approximately 50,000x magnification. Statistically significant differences in the mean fibril diameters were found between the anterior cruciate and medial collateral ligaments of the thirty-six to forty month old animals (.069 ± .005, .092 ± .016 mm, p < .1); however, no statistical significance was found for differences between these ligaments in two month old animals (.077 ± .006, .082 ± .009, p > .1). These data support the idea that known differences in fibril distributions of adult rabbit anterior cruciate and medial collateral ligaments develop with maturation, and may reflect both the cellular environment in which the fibrocytes of these ligaments are subject to, as well as the developmental genetic program of these cell populations. PMID:10847518

  8. Development of human corneal epithelium on organized fibrillated transparent collagen matrices synthesized at high concentration.

    PubMed

    Tidu, Aurélien; Ghoubay-Benallaoua, Djida; Lynch, Barbara; Haye, Bernard; Illoul, Corinne; Allain, Jean-Marc; Borderie, Vincent M; Mosser, Gervaise

    2015-08-01

    Several diseases can lead to opacification of cornea requiring transplantation of donor tissue to restore vision. In this context, transparent collagen I fibrillated matrices have been synthesized at 15, 30, 60 and 90 mg/mL. The matrices were evaluated for fibril organizations, transparency, mechanical properties and ability to support corneal epithelial cell culture. The best results were obtained with 90 mg/mL scaffolds. At this concentration, the fibril organization presented some similarities to that found in corneal stroma. Matrices had a mean Young's modulus of 570 kPa and acellular scaffolds had a transparency of 87% in the 380-780 nm wavelength range. Human corneal epithelial cells successfully colonized the surface of the scaffolds and generated an epithelium with characteristics of corneal epithelial cells (i.e. expression of cytokeratin 3 and presence of desmosomes) and maintenance of stemness during culture (i.e. expression of ΔNp63α and formation of holoclones in colony formation assay). Presence of cultured epithelium on the matrices was associated with increased transparency (89%).

  9. 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.

  10. Substitutions of aspartic acid for glycine-220 and of arginine for glycine-664 in the triple helix of the pro alpha 1(I) chain of type I procollagen produce lethal osteogenesis imperfecta and disrupt the ability of collagen fibrils to incorporate crystalline hydroxyapatite.

    PubMed Central

    Culbert, A A; Lowe, M P; Atkinson, M; Byers, P H; Wallis, G A; Kadler, K E

    1995-01-01

    We identified two infants with lethal (type II) osteogenesis imperfecta (OI) who were heterozygous for mutations in the COL1A1 gene that resulted in substitutions of aspartic acid for glycine at position 220 and arginine for glycine at position 664 in the product of one COL1A1 allele in each individual. In normal age- and site-matched bone, approximately 70% (by number) of the collagen fibrils were encrusted with plate-like crystallites of hydroxyapatite. In contrast, approximately 5% (by number) of the collagen fibrils in the probands' bone contained crystallites. In contrast with normal bone, the c-axes of hydroxyapatite crystallites were sometimes poorly aligned with the long axis of fibrils obtained from OI bone. Chemical analysis showed that the OI samples contained normal amounts of calcium. The probands' bone samples contained type I collagen, overmodified type I collagen and elevated levels of type III and V collagens. On the basis of biochemical and morphological data, the fibrils in the OI samples were co-polymers of normal and mutant collagen. The results are consistent with a model of fibril mineralization in which the presence of abnormal type I collagen prevents normal collagen in the same fibril from incorporating hydroxyapatite crystallites. Images Figure 1 Figure 2 Figure 3 PMID:7487936

  11. Surface located procollagen N-propeptides on dermatosparactic collagen fibrils are not cleaved by procollagen N-proteinase and do not inhibit binding of decorin to the fibril surface.

    PubMed

    Watson, R B; Holmes, D F; Graham, H K; Nusgens, B V; Kadler, K E

    1998-04-24

    Dermatosparaxis is a recessive disorder of animals (including man) which is caused by mutations in the gene for the enzyme procollagen N-proteinase and is characterised by extreme skin fragility. Partial loss of enzyme activity results in accumulation of pNcollagen (collagen with N-propeptides) and abnormal collagen fibrils in the fragile skin. How the N-propeptides persist in the tissue and how abnormal fibril morphology results in fragile skin is poorly understood. Using biochemical and quantitative mass mapping electron microscopy we showed that the collagen fibrils in the skin of a dermatosparactic calf contained 57% type I pNcollagen and 43% type I collagen and the fibrils were irregularly arranged in bundles and hieroglyphic in cross-section. Image analysis of the fibril cross-sections suggested that the deviation from circularity of dermatosparactic fibrils was caused by N-propeptides of pNcollagen being located at the fibril surface. Comparison of experimental and theoretical axial mass distributions of the fibrils showed that the N-propeptides were located to the overlap zone of the fibril D-period (where D=67 nm, the characteristic axial periodicity of collagen fibrils). Treatment of the dermatosparactic fibrils with N-proteinase did not remove the N-propeptides from the fibrils, although the N-propeptides were efficiently removed by trypsin and chymotrypsin. However, the N-propeptides were efficiently cleaved by the N-proteinase when the pNcollagen molecules were extracted from the fibrils. These results are consistent with close packing of N-propeptides at the fibril surface which prevented cleavage by the N-proteinase. Long-range axial mass determination along the fibril length showed gross non-uniformity with multiple mass bulges. Of note is the skin fragility in dermatosparaxis, and also the appearance of mass bulges along the fibril long axis symptomatic of the fragile skin of mice which lack decorin. Western blot analysis showed that the

  12. The Self-assembly of a Mini-fibril with Axial Periodicity from a Designed Collagen-mimetic Triple Helix*

    PubMed Central

    Kaur, Parminder Jeet; Strawn, Rebecca; Bai, Hanying; Xu, Ke; Ordas, Gabriel; Matsui, Hiroshi; Xu, Yujia

    2015-01-01

    In this work we describe the self-assembly of a collagen-like periodic mini-fibril from a recombinant triple helix. The triple helix, designated Col108, is expressed in Escherichia coli using an artificial gene and consists of a 378-residue triple helix domain organized into three pseudo-repeating sequence units. The peptide forms a stable triple helix with a melting temperature of 41 °C. Upon increases of pH and temperature, Col108 self-assembles in solution into smooth mini-fibrils with the cross-striated banding pattern typical of fibrillar collagens. The banding pattern is characterized by an axially repeating feature of ∼35 nm as observed by transmission electron microscopy and atomic force microscopy. Both the negatively stained and the positively stained transmission electron microscopy patterns of the Col108 mini-fibrils are consistent with a staggered arrangement of triple helices having a staggering value of 123 residues, a value closely connected to the size of one repeat sequence unit. A mechanism is proposed for the mini-fibril formation of Col108 in which the axial periodicity is instigated by the built-in sequence periodicity and stabilized by the optimized interactions between the triple helices in a 1-unit staggered arrangement. Lacking hydroxyproline residues and telopeptides, two factors implicated in the fibrillogenesis of native collagen, the Col108 mini-fibrils demonstrate that sequence features of the triple helical domain alone are sufficient to “code” for axially repeating periodicity of fibrils. To our knowledge, Col108 is the first designed triple helix to self-assemble into periodic fibrils and offers a unique opportunity to unravel the specific molecular interactions of collagen fibrillogenesis. PMID:25673694

  13. The self-assembly of a mini-fibril with axial periodicity from a designed collagen-mimetic triple helix.

    PubMed

    Kaur, Parminder Jeet; Strawn, Rebecca; Bai, Hanying; Xu, Ke; Ordas, Gabriel; Matsui, Hiroshi; Xu, Yujia

    2015-04-03

    In this work we describe the self-assembly of a collagen-like periodic mini-fibril from a recombinant triple helix. The triple helix, designated Col108, is expressed in Escherichia coli using an artificial gene and consists of a 378-residue triple helix domain organized into three pseudo-repeating sequence units. The peptide forms a stable triple helix with a melting temperature of 41 °C. Upon increases of pH and temperature, Col108 self-assembles in solution into smooth mini-fibrils with the cross-striated banding pattern typical of fibrillar collagens. The banding pattern is characterized by an axially repeating feature of ∼35 nm as observed by transmission electron microscopy and atomic force microscopy. Both the negatively stained and the positively stained transmission electron microscopy patterns of the Col108 mini-fibrils are consistent with a staggered arrangement of triple helices having a staggering value of 123 residues, a value closely connected to the size of one repeat sequence unit. A mechanism is proposed for the mini-fibril formation of Col108 in which the axial periodicity is instigated by the built-in sequence periodicity and stabilized by the optimized interactions between the triple helices in a 1-unit staggered arrangement. Lacking hydroxyproline residues and telopeptides, two factors implicated in the fibrillogenesis of native collagen, the Col108 mini-fibrils demonstrate that sequence features of the triple helical domain alone are sufficient to "code" for axially repeating periodicity of fibrils. To our knowledge, Col108 is the first designed triple helix to self-assemble into periodic fibrils and offers a unique opportunity to unravel the specific molecular interactions of collagen fibrillogenesis.

  14. Analysis of the contraction of fibroblast-collagen gels and the traction force of individual cells by a novel elementary structural model.

    PubMed

    Feng, Z; Wagatsuma, Y; Kobayashi, S; Kosawada, T; Sato, D; Nakamura, T; Kitajima, T; Umezu, M

    2013-01-01

    Based on the experimental data of the contraction ratio of fibroblast-collagen gels with different initial collagen concentrations and cell numbers, we analyzed the traction force exerted by individual cells through a novel elementary structural model. We postulate that the mechanical mechanism of the gel contraction is mainly because that populated cells apply traction force to some of the surrounding collagen fibrils with such proper length potential to be pulled straight so as to be able to sustain the traction force; this traction induce the cells moving closely to each other and consequently compact the fibrillar network; the bending force of the fibrils in turn resists the movement. By employing fiber packing theory for random fibrillar networks and network alteration theory, the bending force of collagen fibrils was deduced. The traction force exerted by individual fibroblasts in the gels was balanced by the bending force and the resistance from interstitial fluid since inertial force can be neglected. The maximum traction force per cell under free floating condition is in the range of 0.27-9.02 nN depending on the initial collagen concentration and populated cell number. The most important outcome of this study is that the traction force of individual cells dynamically varies under different gel conditions, whereas the adhesion force between cell and individual fibrils is relatively converging and stable.

  15. 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. Copyright © 2014 Elsevier Ltd. All rights reserved.

  16. The collagen fibril architecture in the lamina cribrosa and peripapillary sclera predicted by a computational remodeling approach.

    PubMed

    Grytz, Rafael; Meschke, Günther; Jonas, Jost B

    2011-06-01

    The biomechanics of the optic nerve head is assumed to play an important role in ganglion cell loss in glaucoma. Organized collagen fibrils form complex networks that introduce strong anisotropic and nonlinear attributes into the constitutive response of the peripapillary sclera (PPS) and lamina cribrosa (LC) dominating the biomechanics of the optic nerve head. The recently presented computational remodeling approach (Grytz and Meschke in Biomech Model Mechanobiol 9:225-235, 2010) was used to predict the micro-architecture in the LC and PPS, and to investigate its impact on intraocular pressure-related deformations. The mechanical properties of the LC and PPS were derived from a microstructure-oriented constitutive model that included the stretch-dependent stiffening and the statistically distributed orientations of the collagen fibrils. Biomechanically induced adaptation of the local micro-architecture was captured by allowing collagen fibrils to be reoriented in response to the intraocular pressure-related loading conditions. In agreement with experimental observations, the remodeling algorithm predicted the existence of an annulus of fibrils around the scleral canal in the PPS, and a predominant radial orientation of fibrils in the periphery of the LC. The peripapillary annulus significantly reduced the intraocular pressure-related expansion of the scleral canal and shielded the LC from high tensile stresses. The radial oriented fibrils in the LC periphery reinforced the LC against transversal shear stresses and reduced LC bending deformations. The numerical approach presents a novel and reasonable biomechanical explanation of the spatial orientation of fibrillar collagen in the optic nerve head.

  17. Fibril reinforced poroelastic model predicts specifically mechanical behavior of normal, proteoglycan depleted and collagen degraded articular cartilage.

    PubMed

    Korhonen, Rami K; Laasanen, Mikko S; Töyräs, Juha; Lappalainen, Reijo; Helminen, Heikki J; Jurvelin, Jukka S

    2003-09-01

    Degradation of collagen network and proteoglycan (PG) macromolecules are signs of articular cartilage degeneration. These changes impair cartilage mechanical function. Effects of collagen degradation and PG depletion on the time-dependent mechanical behavior of cartilage are different. In this study, numerical analyses, which take the compression-tension nonlinearity of the tissue into account, were carried out using a fibril reinforced poroelastic finite element model. The study aimed at improving our understanding of the stress-relaxation behavior of normal and degenerated cartilage in unconfined compression. PG and collagen degradations were simulated by decreasing the Young's modulus of the drained porous (nonfibrillar) matrix and the fibril network, respectively. Numerical analyses were compared to results from experimental tests with chondroitinase ABC (PG depletion) or collagenase (collagen degradation) digested samples. Fibril reinforced poroelastic model predicted the experimental behavior of cartilage after chondroitinase ABC digestion by a major decrease of the drained porous matrix modulus (-64+/-28%) and a minor decrease of the fibril network modulus (-11+/-9%). After collagenase digestion, in contrast, the numerical analyses predicted the experimental behavior of cartilage by a major decrease of the fibril network modulus (-69+/-5%) and a decrease of the drained porous matrix modulus (-44+/-18%). The reduction of the drained porous matrix modulus after collagenase digestion was consistent with the microscopically observed secondary PG loss from the tissue. The present results indicate that the fibril reinforced poroelastic model is able to predict specifically characteristic alterations in the stress-relaxation behavior of cartilage after enzymatic modifications of the tissue. We conclude that the compression-tension nonlinearity of the tissue is needed to capture realistically the mechanical behavior of normal and degenerated articular cartilage.

  18. Microstructures and rheological properties of tilapia fish-scale collagen hydrogels with aligned fibrils fabricated under magnetic fields.

    PubMed

    Chen, S; Hirota, N; Okuda, M; Takeguchi, M; Kobayashi, H; Hanagata, N; Ikoma, T

    2011-02-01

    Tilapia fish-scale type I atelocollagen hydrogels with aligned fibril structures were fabricated under a strong magnetic field of 6 or 12 T using two different methods. In the first method, a solution of acid-soluble collagen was neutralized with phosphate buffer saline and maintained in the magnetic field at 28°C for 3h. Under these conditions fibrogenesis occurs, and a hydrogel is formed. The hydrogel was subsequently crosslinked with ethyl-dimethylcarbodiimide (EDC). In the second method, the hydrogels were formed as described above, but in the absence of an applied magnetic field. Only after being crosslinked with EDC were these gels exposed to the magnetic field (28°C for 3h). Both methods led to alignment of the collagen fibrils perpendicular to the magnetic direction, the extent of which depended on the duration of magnetic treatment. Even after EDC treatment, collagen fibrils can align, indicating that crosslinking has taken place within fibrils. Both sorts of aligned hydrogels exhibited similar rheological properties with higher storage and loss moduli than were observed with unoriented gels. The hydrogels treated at 6 T had the best rheological properties. The decrease in tangent angle phase delta indicated that the ratio of elasticity to viscosity was greater in the crosslinked than in the non-crosslinked hydrogels. Atomic force microscopy images showed that magnetic treatment had no effect on the nanostructure of collagen fibrils. Differential scanning calorimetry measurements indicated that collagen hydrogels with and without magnetic treatment had the same denaturation temperature, 48°C, while EDC crosslinking increased the denaturation temperature to 62°C. Copyright © 2010. Published by Elsevier Ltd.

  19. 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. Copyright © 2015 Elsevier Inc. All rights reserved.

  20. The phenotype of cancer cell invasion controlled by fibril diameter and pore size of 3D collagen networks.

    PubMed

    Sapudom, Jiranuwat; Rubner, Stefan; Martin, Steve; Kurth, Tony; Riedel, Stefanie; Mierke, Claudia T; Pompe, Tilo

    2015-06-01

    The behavior of cancer cells is strongly influenced by the properties of extracellular microenvironments, including topology, mechanics and composition. As topological and mechanical properties of the extracellular matrix are hard to access and control for in-depth studies of underlying mechanisms in vivo, defined biomimetic in vitro models are needed. Herein we show, how pore size and fibril diameter of collagen I networks distinctively regulate cancer cell morphology and invasion. Three-dimensional collagen I matrices with a tight control of pore size, fibril diameter and stiffness were reconstituted by adjustment of concentration and pH value during matrix reconstitution. At first, a detailed analysis of topology and mechanics of matrices using confocal laser scanning microscopy, image analysis tools and force spectroscopy indicate pore size and not fibril diameter as the major determinant of matrix elasticity. Secondly, by using two different breast cancer cell lines (MDA-MB-231 and MCF-7), we demonstrate collagen fibril diameter--and not pore size--to primarily regulate cell morphology, cluster formation and invasion. Invasiveness increased and clustering decreased with increasing fibril diameter for both, the highly invasive MDA-MB-231 cells with mesenchymal migratory phenotype and the MCF-7 cells with amoeboid migratory phenotype. As this behavior was independent of overall pore size, matrix elasticity is shown to be not the major determinant of the cell characteristics. Our work emphasizes the complex relationship between structural-mechanical properties of the extracellular matrix and invasive behavior of cancer cells. It suggests a correlation of migratory and invasive phenotype of cancer cells in dependence on topological and mechanical features of the length scale of single fibrils and not on coarse-grained network properties.

  1. Collagen Fibrils in Skin Orient in the Direction of Applied Uniaxial Load in Proportion to Stress while Exhibiting Differential Strains around Hair Follicles

    PubMed Central

    Nesbitt, Sterling; Scott, Wentzell; Macione, James; Kotha, Shiva

    2015-01-01

    We determined inhomogeneity of strains around discontinuities as well as changes in orientation of collagen fibrils under applied load in skin. Second Harmonic Generation (SHG) images of collagen fibrils were obtained at different strain magnitudes. Changes in collagen orientation were analyzed using Fast Fourier Transforms (FFT) while strain inhomogeneity was determined at different distances from hair follicles using Digital Image Correlation (DIC). A parameter, defined as the Collagen Orientation Index (COI), is introduced that accounts for the increasingly ellipsoidal nature of the FFT amplitude images upon loading. We show that the COI demonstrates two distinct mechanical regimes, one at low strains (0%, 2.5%, 5% strain) in which randomly oriented collagen fibrils align in the direction of applied deformation. In the second regime, beginning at 5% strain, collagen fibrils elongate in response to applied deformation. Furthermore, the COI is also found to be linearly correlated with the applied stress indicating that collagen fibrils orient to take the applied load. DIC results indicated that major principal strains were found to increase with increased load at all locations. In contrast, minimum principal strain was dependent on distance from hair follicles. These findings are significant because global and local changes in collagen deformations are expected to be changed by disease, and could affect stem cell populations surrounding hair follicles, including mesenchymal stem cells within the outer root sheath. PMID:28788035

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

    PubMed

    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

    2008-06-24

    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 (EC(50) 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.

  3. 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. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Collagen fibril orientation in ovine and bovine leather affects strength: a small angle X-ray scattering (SAXS) study.

    PubMed

    Basil-Jones, Melissa M; Edmonds, Richard L; Cooper, Sue M; Haverkamp, Richard G

    2011-09-28

    There is a large difference in strength between ovine and bovine leather. The structure and arrangement of fibrous collagen in leather and the relationship between collagen structure and leather strength has until now been poorly understood. Synchrotron based SAXS is used to characterize the fibrous collagen structure in a series of ovine and bovine leathers and to relate it to tear strength. SAXS gives quantitative information on the amount of fibrous collagen, the orientation (direction and spread) of the collagen microfibrils, and the d-spacing of the collagen. The amount of collagen varies through the thickness of the leather from the grain to the corium, with a greater concentration of crystalline collagen measured toward the corium side. The orientation index (OI) is correlated strongly with strength in ovine leather and between ovine and bovine leathers. Stronger leather has the fibrils arranged mostly parallel to the plane of the leather surface (high OI), while weaker leather has more out-of-plane fibrils (low OI). With the measurement taken parallel to the animal's backbone, weak (19.9 N/mm) ovine leather has an OI of 0.422 (0.033), stronger (39.5 N/mm) ovine leather has an OI of 0.452 (0.033), and bovine leather with a strength of (61.5 N/mm) has an OI of 0.493 (0.016). The d-spacing profile through leather thickness also varies according to leather strength, with little variation being detected in weak ovine leather (average=64.3 (0.5) nm), but with strong ovine leather and bovine leather (which is even stronger) exhibiting a dip in d-spacing (from 64.5 nm at the edges dropping to 62 nm in the center). This work provides a clear understanding of a nanostructural characteristic of ovine and bovine leather that leads to differences in strength.

  5. 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.

  6. Regional stiffening with aging in tibialis anterior tendons of mice occurs independent of changes in collagen fibril morphology

    PubMed Central

    Wood, Lauren K.; Arruda, Ellen M.

    2011-01-01

    The incidence of tendon degeneration and rupture increases with advancing age. The mechanisms underlying this increased risk remain unknown but may arise because of age-related changes in tendon mechanical properties and structure. Our purpose was to determine the effect of aging on tendon mechanical properties and collagen fibril morphology. Regional mechanical properties and collagen fibril characteristics were determined along the length of tibialis anterior (TA) tendons from adult (8- to 12-mo-old) and old (28- to 30-mo-old) mice. Tangent modulus of all regions along the tendons increased in old age, but the increase was substantially greater in the proximal region adjacent to the muscle than in the rest of the tendon. Overall end-to-end modulus increased with old age at maximum tendon strain (799 ± 157 vs. 1,419 ± 91 MPa) and at physiologically relevant strain (377 ± 137 vs. 798 ± 104 MPa). Despite the dramatic changes in tendon mechanical properties from adulthood to old age, collagen fibril morphology and packing fraction remained relatively constant in all tendon regions examined. Since tendon properties are influenced by their external loading environment, we also examined the effect of aging on TA muscle contractile properties. Maximum isometric force did not differ between the age groups. We conclude that TA tendons stiffen in a region-dependent manner throughout the life span, but the changes in mechanical properties are not accompanied by corresponding changes in collagen fibril morphology or force-generating capacity of the TA muscle. PMID:21737825

  7. Lower strength of the human posterior patellar tendon seems unrelated to mature collagen cross-linking and fibril morphology.

    PubMed

    Hansen, Philip; Haraldsson, Bjarki Thor; Aagaard, Per; Kovanen, Vuokko; Avery, Nicholas C; Qvortrup, Klaus; Larsen, Jytte Overgaard; Krogsgaard, Michael; Kjaer, Michael; Peter Magnusson, S

    2010-01-01

    The human patellar tendon is frequently affected by tendinopathy, but the etiology of the condition is not established, although differential loading of the anterior and posterior tendon may be associated with the condition. We hypothesized that changes in fibril morphology and collagen cross-linking would parallel differences in material strength between the anterior and posterior tendon. Tendon fascicles were obtained from elective ACL surgery patients and tested micromechanically. Transmission electron microscopy was used to assess fibril morphology, and collagen cross-linking was determined by HPLC and calorimetry. Anterior fascicles were markedly stronger (peak stress: 54.3 +/- 21.2 vs. 39.7 +/- 21.3 MPa; P < 0.05) and stiffer (624 +/- 232 vs. 362 +/- 170 MPa; P < 0.01) than posterior fascicles. Notably, mature pyridinium type cross-links were less abundant in anterior fascicles (hydroxylysylpyridinoline: 0.859 +/- 0.197 vs. 1.416 +/- 0.250 mol/mol, P = 0.001; lysylpyridinoline: 0.023 +/- 0.006 vs. 0.035 +/- 0.006 mol/mol, P < 0.01), whereas pentosidine and pyrrole concentrations showed no regional differences. Fibril diameters tended to be larger in anterior fascicles (7.819 +/- 2.168 vs. 4.897 +/- 1.434 nm(2); P = 0.10). Material properties did not appear closely related to cross-linking or fibril morphology. These findings suggest region-specific differences in mechanical, structural, and biochemical properties of the human patellar tendon.

  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. Evidence against proteoglycan mediated collagen fibril load transmission and dynamic viscoelasticity in tendon.

    PubMed

    Fessel, Gion; Snedeker, Jess G

    2009-10-01

    The glycosaminoglycan (GAG) dermatan sulfate and chondroitin sulfate side-chains of small leucine-rich proteoglycans have been increasingly posited to act as molecular cross links between adjacent collagen fibrils and to directly contribute to tendon elasticity. GAGs have also been implicated in tendon viscoelasticity, supposedly affecting frictional loss during elongation or fluid flow through the extra cellular matrix. The current study sought to systematically test these theories of tendon structure-function by investigating the mechanical repercussions of enzymatic depletion of GAG complexes by chondroitinase ABC in a reproducible tendon structure-function model (rat tail tendon fascicles). The extent of GAG removal (at least 93%) was verified by relevant spectrophotometric assays and transmission electron microscopy. Dynamic viscoelastic tensile tests on GAG depleted rat tail tendon fascicle were not mechanically different from controls in storage modulus (elastic behavior) over a wide range of strain-rates (0.05, 0.5, and 5% change in length per second) in either the linear or nonlinear regions of the material curve. Loss modulus (viscoelastic behavior) was only affected in the nonlinear region at the highest strain-rate, and even this effect was marginal (19% increased loss modulus, p=0.035). Thus glycosaminoglycan chains of small leucine-rich proteoglycans do not appear to mediate dynamic elastic behavior nor do they appear to regulate the dynamic viscoelastic properties in rat tail tendon fascicles.

  10. Ultrastructure Organization of Collagen Fibrils and Proteoglycans of Stingray and Shark Corneal Stroma

    PubMed Central

    Alanazi, Saud A.; Almubrad, Turki; AlIbrahim, Ahmad I. A.; Khan, Adnan A.; Akhtar, Saeed

    2015-01-01

    We report here the ultrastructural organization of collagen fibrils (CF) and proteoglycans (PGs) of the corneal stroma of both the stingray and the shark. Three corneas from three stingrays and three corneas from three sharks were processed for electron microscopy. Tissues were embedded in TAAB 031 resin. The corneal stroma of both the stingray and shark consisted of parallel running lamellae of CFs which were decorated with PGs. In the stingray, the mean area of PGs in the posterior stroma was significantly larger than the PGs of the anterior and middle stroma, whereas, in the shark, the mean area of PGs was similar throughout the stroma. The mean area of PGs of the stingray was significantly larger compared to the PGs, mean area of the shark corneal stroma. The CF diameter of the stingray was significantly smaller compared to the CF diameter in the shark. The ultrastructural features of the corneal stroma of both the stingray and the shark were similar to each other except for the CFs and PGs. The PGs in the stingray and shark might be composed of chondroitin sulfate (CS)/dermatan sulfate (DS) PGs and these PGs with sutures might contribute to the nonswelling properties of the cornea of the stingray and shark. PMID:26167294

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

    PubMed

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

    2006-02-22

    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.

  12. Ultrastructure Organization of Collagen Fibrils and Proteoglycans of Stingray and Shark Corneal Stroma.

    PubMed

    Alanazi, Saud A; Almubrad, Turki; AlIbrahim, Ahmad I A; Khan, Adnan A; Akhtar, Saeed

    2015-01-01

    We report here the ultrastructural organization of collagen fibrils (CF) and proteoglycans (PGs) of the corneal stroma of both the stingray and the shark. Three corneas from three stingrays and three corneas from three sharks were processed for electron microscopy. Tissues were embedded in TAAB 031 resin. The corneal stroma of both the stingray and shark consisted of parallel running lamellae of CFs which were decorated with PGs. In the stingray, the mean area of PGs in the posterior stroma was significantly larger than the PGs of the anterior and middle stroma, whereas, in the shark, the mean area of PGs was similar throughout the stroma. The mean area of PGs of the stingray was significantly larger compared to the PGs, mean area of the shark corneal stroma. The CF diameter of the stingray was significantly smaller compared to the CF diameter in the shark. The ultrastructural features of the corneal stroma of both the stingray and the shark were similar to each other except for the CFs and PGs. The PGs in the stingray and shark might be composed of chondroitin sulfate (CS)/dermatan sulfate (DS) PGs and these PGs with sutures might contribute to the nonswelling properties of the cornea of the stingray and shark.

  13. Changes in collagen fibril network organization and proteoglycan distribution in equine articular cartilage during maturation and growth.

    PubMed

    Hyttinen, Mika M; Holopainen, Jaakko; van Weeren, P René; Firth, Elwyn C; Helminen, Heikki J; Brama, Pieter A J

    2009-11-01

    The aim of this study was to record growth-related changes in collagen network organization and proteoglycan distribution in intermittently peak-loaded and continuously lower-level-loaded articular cartilage. Cartilage from the proximal phalangeal bone of the equine metacarpophalangeal joint at birth, at 5, 11 and 18 months, and at 6-10 years of age was collected from two sites. Site 1, at the joint margin, is unloaded at slow gaits but is subjected to high-intensity loading during athletic activity; site 2 is a continuously but less intensively loaded site in the centre of the joint. The degree of collagen parallelism was determined with quantitative polarized light microscopy and the parallelism index for collagen fibrils was computed from the cartilage surface to the osteochondral junction. Concurrent changes in the proteoglycan distribution were quantified with digital densitometry. We found that the parallelism index increased significantly with age (up to 90%). At birth, site 2 exhibited a more organized collagen network than site 1. In adult horses this situation was reversed. The superficial and intermediate zones exhibited the greatest reorganization of collagen. Site 1 had a higher proteoglycan content than site 2 at birth but here too the situation was reversed in adult horses. We conclude that large changes in joint loading during growth and maturation in the period from birth to adulthood profoundly affect the architecture of the collagen network in equine cartilage. In addition, the distribution and content of proteoglycans are modified significantly by altered joint use. Intermittent peak-loading with shear seems to induce higher collagen parallelism and a lower proteoglycan content in cartilage than more constant weight-bearing. Therefore, we hypothesize that the formation of mature articular cartilage with a highly parallel collagen network and relatively low proteoglycan content in the peak-loaded area of a joint is needed to withstand

  14. In vitro tendon tissue development from human fibroblasts demonstrates collagen fibril diameter growth associated with a rise in mechanical strength.

    PubMed

    Herchenhan, Andreas; Bayer, Monika L; Svensson, René B; Magnusson, S Peter; Kjaer, Michael

    2013-01-01

    Collagen-rich tendons and ligaments are important for joint stability and force transmission, but the capacity to form new tendon is poorly understood. In the present study, we investigated mechanical strength, fibril size, and structure during development of tendon-like tissue from adult human tenocytes (termed tendon constructs) in vitro over 5 weeks in 3D tissue culture. The constructs displayed large elongated tendon cells aligned along the tendon axis together with collagen fibrils that increased in diameter by 50% from day 14 to 35, which approaches that observed in adult human tendon in vivo. The increase in diameter was accompanied by a 5-fold increase in mechanical strength (0.9±0.1 MPa to 4.9±0.6 MPa) and Young's modulus (5.8±0.9 MPa to 32.3±4.2 MPa), while the maximal strain at failure (16%) remained constant throughout the 5-week culture period. The present study demonstrates that 3D tendon constructs can be formed by isolated human tendon fibroblasts, and when these constructs are subjected to static self-generated tension, the fibrils will grow in size and strength approaching that of adult human tendon in vivo. Copyright © 2012 Wiley Periodicals, Inc.

  15. Concerted and adaptive alignment of decorin dermatan sulfate filaments in the graded organization of collagen fibrils in the equine superficial digital flexor tendon.

    PubMed

    Watanabe, Takafumi; Imamura, Yasutada; Suzuki, Daisuke; Hosaka, Yoshinao; Ueda, Hiromi; Hiramatsu, Kohzy; Takehana, Kazushige

    2012-02-01

    The equine superficial digital flexor tendon (SDFT) has a graded distribution of collagen fibril diameters, with predominantly small-diameter fibrils in the region of the myotendinous junction (MTJ), a gradual increase in large-diameter fibrils toward the osteotendinous junction (OTJ), and a mixture of small- and large-diameter fibrils in the middle metacarpal (MM) region. In this study, we investigated the ultrastructure of the SDFT, to correlate the spatial relationship of the collagen fibrils with the graded distribution. The surface-to-surface distances of pairs of fibrils were found to be almost constant over the entire tendon. However, the center-to-center distances varied according to fibril diameter. Decorin is the predominant proteoglycan in normal mature tendons, and has one dermatan sulfate (DS) or chondroitin sulfate (CS) filament as a side chain which is associated with the surfaces of the collagen fibrils via its core protein. We identified a coordinated arrangement of decorin DS filaments in the equine SDFT. The sizes of the decorin DS filaments detected by Cupromeronic blue staining showed a unique regional variation; they were shortest in the MM region and longer in the MTJ and OTJ regions, and a considerable number of filaments were arranged obliquely to adjacent collagen fibrils in the MTJ region. This regional variation of the filaments may be an adaptation to lubricate the interfibrillar space in response to local mechanical requirements. The results of this study suggest that the MTJ region, which receives the muscular contractile force first, acts as a buffer for mechanical forces in the equine SDFT. © 2011 The Authors. Journal of Anatomy © 2011 Anatomical Society.

  16. Connective Tissue Polarity Unraveled by a Markov-Chain Mechanism of Collagen Fibril Segment Self-Assembly

    PubMed Central

    Hulliger, Jürg

    2003-01-01

    The well-established occurrence of pyroelectricity (Lang, 1966) in tissues of living organisms has found a first explanation by a Markov-chain mechanism taking place during collagen fibril self-assembly in extracytoplasmic channels. Recently reported biochemical findings on the longitudinal fusion reactivity of small fibril segments (which undergo C-, N- and C-, C- but not N-, N-terminal fusions; see Graham et al., 2000; Kadler et al., 1996) may provide a mechanism by which a difference in the fusion probabilities PCC, PNN drives the self-assembly into partial macroscopic polar order. In principle, a Markov-chain growth process can lower the noncentrosymmetric ∞2 symmetry describing dielectric properties of a growing limb (as managed by fibroblasts) into the polar ∞ group. It is proposed that macroscopically polar properties enter the biological world by a stochastic mechanism of unidirectional growth. Polarity formation in organisms shows similarity to effects reported for molecular crystals (Hulliger et al., 2002). PMID:12770863

  17. Decorin and biglycan are necessary for maintaining collagen fibril structure, fiber realignment, and mechanical properties of mature tendons.

    PubMed

    Robinson, Kelsey A; Sun, Mei; Barnum, Carrie E; Weiss, Stephanie N; Huegel, Julianne; Shetye, Snehal S; Lin, Linda; Saez, Daniel; Adams, Sheila M; Iozzo, Renato V; Soslowsky, Louis J; Birk, David E

    2017-09-04

    The small leucine-rich proteoglycans (SLRPs), decorin and biglycan, are key regulators of collagen fibril and matrix assembly. The goal of this work was to elucidate the roles of decorin and biglycan in tendon homeostasis. Our central hypothesis is that decorin and biglycan expression in the mature tendon would be critical for the maintenance of the structural and mechanical properties of healthy tendons. Defining the function(s) of these SLRPs in tendon homeostasis requires that effects in the mature tendon be isolated from their influence on development. Thus, we generated an inducible knockout mouse model that permits genetic ablation of decorin and biglycan expression in the mature tendon, while maintaining normal expression during development. Decorin and biglycan expression were knocked out in the mature patellar tendon with the subsequent turnover of endogenous SLRPs deposited prior to induction. The acute absence of SLRP expression was associated with changes in fibril structure with a general shift to larger diameter fibrils in the compound knockout tendons, together with fibril diameter heterogeneity. In addition, tendon mechanical properties were altered. Compared to wild-type controls, acute ablation of both genes resulted in failure of the tendon at lower loads, decreased stiffness, a trend towards decreased dynamic modulus, as well as a significant increase in percent relaxation and tissue viscosity. Collagen fiber realignment was also increased with a delayed and slower in response to load in the absence of expression. These structural and functional changes in response to an acute loss of decorin and biglycan expression in the mature tendon demonstrate a significant role for these SLRPs in adult tendon homeostasis. Copyright © 2017. Published by Elsevier B.V.

  18. Some observations on the subfibrillar structure of collagen fibrils as noted during treatment with NKISK and cathepsin G with mechanical agitation.

    PubMed

    Zhao, Tailun; Weinhold, Paul S; Lee, Nicole Y; Dahners, Laurence E

    2011-01-01

    We observed the structure of collagen fibrils in rat tail tendons after treatment with NKISK and cathepsin G. NKISK is a pentapeptide that has been previously shown to bind fibronectin, while cathepsin G is a serine protease that cleaves fibronectin but not type I collagen. In tendons treated with NKISK, fibrils were seen to extensively dissociate into smaller-diameter subfibrils. These subfibrils were homogeneous in diameter with an average diameter of 26.3 ± 5.8 nm. Similar, although less extensive, dissociation into subfibrils was found in tendons treated with cathepsin G. The average diameter of these subfibrils was 24.8 ± 4.9 nm. The ability of NKISK and cathepsin G to release subfibrils at physiological pH without harsh denaturants may enhance the study of the subfibrillar structure of collagen fibrils.

  19. 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

  20. Dynamics of Structural Parameters and Accumulation of Collagen Fibrils in Rat Lung after Inhalations of Surfactant-BL at Various Terms of Bleomycin-Induced Alveolitis.

    PubMed

    Volchkov, V A; Dubrovskaya, V F; Valkovich, A A; Klestova, O V; Serzhanina, V A; Zhuikov, A G; Seiliev, A A; Rosenberg, O A

    2016-08-01

    Rats were subjected to surfactant-BL inhalations at the early and late phases of bleomycininduced alveolitis. In both regimens, the drug reduced the severity of inflammation. In the acute phase of alveolitis, the therapeutic effect of inhalation was accompanied by activation of the synthesis of fine lose collagen fibrils. In the late phase of alveolitis, inhalation of surfactant-BL thickened the fibrils and diminished their population in alveolar walls.

  1. Loss of fibulin-4 results in abnormal collagen fibril assembly in bone, caused by impaired lysyl oxidase processing and collagen cross-linking.

    PubMed

    Sasaki, Takako; Stoop, Reinout; Sakai, Takao; Hess, Andreas; Deutzmann, Rainer; Schlötzer-Schrehardt, Ursula; Chu, Mon-Li; von der Mark, Klaus

    2016-03-01

    The extracellular matrix protein fibulin-4 has been shown to be indispensable for elastic fiber assembly, but there is also evidence from human mutations that it is involved in controlling skeletal development and bone stability. Fibulin-4 mutations were identified in patients suffering from vascular abnormality and/or cutis laxa, and some of these patients exhibited bone fragility, arachnodactyly and joint laxity. In order to elucidate the role of fibulin-4 in bone structure and skeletal development, we analyzed structural changes in skeletal tissues of Fbln4(-/-) mice. Immunostaining confirmed that fibulin-4 is highly expressed in cartilage, bone, ligaments and tendons. No morphological abnormalities were found in the skeleton of Fbln4(-/-) mice as compared to wild type littermates except forelimb contractures as well as unusually thick collagen fibrils. Furthermore, fibulin-4 deficiency caused enhanced susceptibility of bone collagen for acid extraction, consistent with significantly reduced lysylpyridinoline and hydroxylysylpyridinoline cross-links in bone. In accordance with that, the amount of lysyl oxidase in long bones and calvaria was strongly decreased and proteolytic activation of lysyl oxidase was reduced in fibulin-4 deficient osteoblasts, while addition of recombinant fibulin-4 rescued the activation. The finding suggested that fibulin-4 is important for the proteolytic activation of lysyl oxidase which has a pivotal role in cross-linking of collagen and elastin. Copyright © 2015 International Society of Matrix Biology. Published by Elsevier B.V. All rights reserved.

  2. 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

  3. Ehlers-Danlos syndrome type VIIB. Morphology of type I collagen fibrils formed in vivo and in vitro is determined by the conformation of the retained N-propeptide.

    PubMed

    Holmes, D F; Watson, R B; Steinmann, B; Kadler, K E

    1993-07-25

    Previously we showed that fibrils generated from collagen and pNcollagen-ex6 from fibroblasts of an individual with Ehlers-Danlos syndrome (EDS) type VIIB were hieroglyphic in cross-section and all N-propeptides were located at the fibril surface. Hieroglyphs were resolved to near-cylindrical fibrils (that were similar in appearance to the fibrils seen in the tissues of individuals with EDS type VIIB) by treatment with N-proteinase which cleaved the pN alpha 1(I) chains but not the pN alpha 2(I)-ex6 chains (Watson, R. B., Wallis, G. A., Holmes, D. F., Viljoen, D., Byers, P. H., and Kadler, K. E. (1992) J. Biol. Chem. 267, 9093-9100). Here, quantitative scanning transmission electron microscopy (STEM) showed that N-propeptides in hieroglyphs were in a "bent-back" conformation and thus located exclusively in the overlap zone of the fibril D-period (D = 67 nm). In contrast, STEM of fibrils from the dermis of an individual with EDS type VIIB showed that partially cleaved N-propeptides (in which cleaved pN alpha 1(I) remained in noncovalent association with pN alpha 2(I)-ex6 chains) were distributed equally between the gap and overlap zones of the fibrils. Comparison of experimental data with theoretical mass distributions of the fibril based on amino acid sequence data gave a consistent value of 33 nm for the total axial extent for the N-propeptides in hieroglyphic and tissue fibrils irrespective of the location of N-propeptides to the gap or overlap zone. These data exclude the possibility that N-propeptides adopt a random configuration, but rather, that they locate to specific sites in the gap and overlap zones. The results demonstrated that cleavage of pN alpha 1(I) chains in vivo releases the N-propeptides from the constraints of the bent-back conformation. Co-distribution of partially cleaved N-propeptides between gap and overlap zones allows a higher surface packing density of N-propeptides and explains how circularity of large diameter fibrils can be achieved

  4. Changes in collagen fibril network organization and proteoglycan distribution in equine articular cartilage during maturation and growth

    PubMed Central

    Hyttinen, Mika M; Holopainen, Jaakko; René van Weeren, P; Firth, Elwyn C; Helminen, Heikki J; Brama, Pieter A J

    2009-01-01

    The aim of this study was to record growth-related changes in collagen network organization and proteoglycan distribution in intermittently peak-loaded and continuously lower-level-loaded articular cartilage. Cartilage from the proximal phalangeal bone of the equine metacarpophalangeal joint at birth, at 5, 11 and 18 months, and at 6–10 years of age was collected from two sites. Site 1, at the joint margin, is unloaded at slow gaits but is subjected to high-intensity loading during athletic activity; site 2 is a continuously but less intensively loaded site in the centre of the joint. The degree of collagen parallelism was determined with quantitative polarized light microscopy and the parallelism index for collagen fibrils was computed from the cartilage surface to the osteochondral junction. Concurrent changes in the proteoglycan distribution were quantified with digital densitometry. We found that the parallelism index increased significantly with age (up to 90%). At birth, site 2 exhibited a more organized collagen network than site 1. In adult horses this situation was reversed. The superficial and intermediate zones exhibited the greatest reorganization of collagen. Site 1 had a higher proteoglycan content than site 2 at birth but here too the situation was reversed in adult horses. We conclude that large changes in joint loading during growth and maturation in the period from birth to adulthood profoundly affect the architecture of the collagen network in equine cartilage. In addition, the distribution and content of proteoglycans are modified significantly by altered joint use. Intermittent peak-loading with shear seems to induce higher collagen parallelism and a lower proteoglycan content in cartilage than more constant weight-bearing. Therefore, we hypothesize that the formation of mature articular cartilage with a highly parallel collagen network and relatively low proteoglycan content in the peak-loaded area of a joint is needed to withstand

  5. Kniest dysplasia is characterized by an apparent abnormal processing of the C-propeptide of type II cartilage collagen resulting in imperfect fibril assembly.

    PubMed Central

    Poole, A R; Pidoux, I; Reiner, A; Rosenberg, L; Hollister, D; Murray, L; Rimoin, D

    1988-01-01

    Epiphyseal and growth plate cartilages from four cases of Kniest dysplasia have been studied. In each case collagen fibril organization appeared abnormal by electron microscopy compared with age-matched normal cartilages: fibrils were much thinner, of irregular shape and did not exhibit the characteristic banding pattern. This was associated with the absence (compared with normal cartilage) of the C-propeptide of type II collagen (chondrocalcin) from the extracellular matrix of epiphyseal cartilages, although it was detected (as in normal cartilages) in the lower hypertrophic zone of the growth plate in association with calcifying cartilage. The C-propeptide was abnormally concentrated in intracellular vacuolar sites in Kniest cartilages and its total content was reduced in all cases but not in all cartilages. Moreover, it was not a part of the procollagen molecule. In contrast, type II collagen alpha-chain size was normal, indicating the formation of a triple helix. Also type II collagen content was normal and it was present in extracellular sites and only occasionally detected intracellularly. These observations suggest that the defect in Kniest dysplasia may result from the secretion of type II procollagen lacking the C-propeptide and abnormal fibril formation, and that the C-propeptide is normally required for fibril formation. Images PMID:3276736

  6. Spatially resolved spectroscopic differentiation of hydrophilic and hydrophobic domains on individual insulin amyloid fibrils

    PubMed Central

    Deckert-Gaudig, Tanja; Kurouski, Dmitry; Hedegaard, Martin A. B.; Singh, Pushkar; Lednev, Igor K.; Deckert, Volker

    2016-01-01

    The formation of insoluble β-sheet-rich protein structures known as amyloid fibrils is associated with numerous neurodegenerative diseases, such as Alzheimer’s and Parkinson’s disease. A detailed understanding of the molecular structure of the fibril surface is of interest as the first contact with the physiological environment in vivo and plays a decisive role in biological activity and associated toxicity. Recent studies reveal that the inherent sensitivity and specificity of tip-enhanced Raman scattering (TERS) renders this technique a compelling method for fibril surface analysis at the single-particle level. Here, the reproducibility of TERS is demonstrated, indicating its relevance for detecting molecular variations. Consequently, individual fibrils are systematically investigated at nanometer spatial resolution. Spectral parameters were obtained by band-fitting, particularly focusing on the identification of the secondary structure via the amide III band and the differentiation of hydrophobic and hydrophilic domains on the surface. In addition multivariate data analysis, specifically the N-FINDR procedure, was employed to generate structure-specific maps. The ability of TERS to localize specific structural domains on fibril surfaces shows promise to the development of new fibril dissection strategies and can be generally applied to any (bio)chemical surface when structural variations at the nanometer level are of interest. PMID:27650589

  7. Spatially resolved spectroscopic differentiation of hydrophilic and hydrophobic domains on individual insulin amyloid fibrils

    NASA Astrophysics Data System (ADS)

    Deckert-Gaudig, Tanja; Kurouski, Dmitry; Hedegaard, Martin A. B.; Singh, Pushkar; Lednev, Igor K.; Deckert, Volker

    2016-09-01

    The formation of insoluble β-sheet-rich protein structures known as amyloid fibrils is associated with numerous neurodegenerative diseases, such as Alzheimer’s and Parkinson’s disease. A detailed understanding of the molecular structure of the fibril surface is of interest as the first contact with the physiological environment in vivo and plays a decisive role in biological activity and associated toxicity. Recent studies reveal that the inherent sensitivity and specificity of tip-enhanced Raman scattering (TERS) renders this technique a compelling method for fibril surface analysis at the single-particle level. Here, the reproducibility of TERS is demonstrated, indicating its relevance for detecting molecular variations. Consequently, individual fibrils are systematically investigated at nanometer spatial resolution. Spectral parameters were obtained by band-fitting, particularly focusing on the identification of the secondary structure via the amide III band and the differentiation of hydrophobic and hydrophilic domains on the surface. In addition multivariate data analysis, specifically the N-FINDR procedure, was employed to generate structure-specific maps. The ability of TERS to localize specific structural domains on fibril surfaces shows promise to the development of new fibril dissection strategies and can be generally applied to any (bio)chemical surface when structural variations at the nanometer level are of interest.

  8. 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

  9. 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.

  10. Reduction of collagen VII anchoring fibrils in the airway basement membrane zone of infant rhesus monkeys exposed to house dust mite

    PubMed Central

    Fanucchi, Michelle V.; Miller, Lisa A.; Carlson, Melinda A.; Nishio, Susan J.; Hyde, Dallas M.

    2010-01-01

    Collagen VII anchoring fibrils in the basement membrane zone (BMZ) are part of a supracellular anchoring network that attaches the epithelium to the BMZ. Sloughing of airway epithelium in asthmatics (creola bodies) is a pathology associated with the supracellular anchoring network. In a rhesus monkey model of house dust mite (HDM)-induced allergic asthma, we found increased deposition of collagen I in the BMZ. In this study, we determine whether HDM also affected deposition of collagen VII in the BMZ. In the developing airway of rhesus monkeys, the width of collagen VII anchoring fibrils in the BMZ was 0.02 ± 0.04 μm at 1 mo of age. At 6 mo the width had increased to 1.28 ± 0.34 μm and at 12 mo 2.15 ± 0.13 μm. In animals treated with HDM, we found a 42.2% reduction in the width of collagen VII layer in the BMZ at 6 mo (0.74 ± 0.15 μm; P < 0.05). During recovery, the rate of collagen VII deposition returned to normal. However, the amount of collagen VII lost was not recovered after 6 mo. We concluded that normal development of the collagen VII attachment between the epithelium and BMZ occurs in coordination with development of the BMZ. However, in HDM-treated animals, the collagen VII attachment with the epithelium was significantly reduced. Such a reduction in collagen VII may weaken the supracellular anchoring network and be associated with sloughing of the epithelium and formation of creola bodies in asthmatics. PMID:20139177

  11. Some properties of the reactive hydroxylysyl residues in collagen: their possible role in nucleation during fibril formation.

    PubMed

    Gonzalez, E; Hamabata, A; Rojkind, M

    1984-10-01

    Native or heat-denatured collagens were incubated under controlled conditions of temperature and pH with variable molar ratios of KCNO or 2,4,6-trinitrobenzene sulphonic acid. The results obtained suggest that a small number of free amino groups are available for reaction on the native protein, while all the free amino groups react on the denatured protein. The highly reactive free amino groups in the native protein are hydroxylysine residues and have an abnormally low pK of 8.5 which is conformation dependent; this pK becomes normalized upon denaturation of the protein. The reactive hydroxylysines appear to be located in basic regions that could be the nucleation sites needed for fiber formation in the heat-gelation assay; the modified protein does not form stable fibrils upon heating at 37 degrees C and the few fibers formed are not stabilized after reduction with NaBH4. Our results also suggest that the triple helix in collagen is heterogeneous with respect to the reactivity of free amino groups and that several discrete transition temperatures are observed with two main breaks at 30 degrees C and at 37 degrees C, respectively.

  12. Collagen biogenesis and assembly into fibrils as shown by ultrastructural and 3H-proline radioautographic studies on the fibroblasts of the rat food pad

    SciTech Connect

    Marchi, F.; Leblond, C.P.

    1983-10-01

    To examine whether collagen is assembled into fibrils within or outside fibroblasts, the connective tissue of the rat foot pad was investigated by electron microscopy and by radioautography at times varying from 4 min to 3 days after an intravenous injection of 3H-proline. The fibroblasts of the rat food pad are long polarized cells with the nucleus at one end, the Golgi apparatus in the center, and a region with long processes at the other end. This region contains secretory granules and is considered to be the secretory pole of the cell. In the Golgi apparatus the stacks of saccules are separated from rough endoplasmic reticulum (rER) by groups of ''intermediate vesicles'' including similarly structured tubules which may be over 300 nm long and are referred to as ''intermediate tubules.'' The Golgi saccules exhibit distended portions which differ at the various levels of the stack. Finally, the fibroblasts are associated with two types of collagen fibrils: extracellular ones arranged into large groups between the cells and intracellular ones located within long intracytoplasmic channels. Quantitative radioautography after 3H-proline injection reveals that the number of silver grains per unit area reaches a peak over the rER at 4-10 min, Golgi apparatus at 40 min, secretory granules at 60 min, and extracellular collagen fibrils at 3 h. At no time are intracellular collagen fibrils labeled. Qualitative observations further indicate that spherical Golgi distentions are mainly labeled at 40 min, and cylindrical distentions, at 60 min. In addition, from 20 min to 3 hr, some lysosomal elements are labeled.

  13. 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.

  14. A comparison of glycosaminoglycan distributions, keratan sulphate sulphation patterns and collagen fibril architecture from central to peripheral regions of the bovine cornea.

    PubMed

    Ho, Leona T Y; Harris, Anthony M; Tanioka, Hidetoshi; Yagi, Naoto; Kinoshita, Shigeru; Caterson, Bruce; Quantock, Andrew J; Young, Robert D; Meek, Keith M

    2014-09-01

    This study investigated changes in collagen fibril architecture and the sulphation status of keratan sulphate (KS) glycosaminoglycan (GAG) epitopes from central to peripheral corneal regions. Freshly excised adult bovine corneal tissue was examined as a function of radial position from the centre of the cornea outwards. Corneal thickness, tissue hydration, hydroxyproline content, and the total amount of sulphated GAG were all measured. High and low-sulphated epitopes of keratan sulphate were studied by immunohistochemistry and quantified by ELISA. Chondroitin sulphate (CS) and dermatan sulphate (DS) distributions were observed by immunohistochemistry following specific enzyme digestions. Electron microscopy and X-ray fibre diffraction were used to ascertain collagen fibril architecture. The bovine cornea was 1021±5.42 μm thick at its outer periphery, defined as 9-12 mm from the corneal centre, compared to 844±8.10 μm at the centre. The outer periphery of the cornea was marginally, but not significantly, more hydrated than the centre (H=4.3 vs. H=3.7), and was more abundant in hydroxyproline (0.12 vs. 0.06 mg/mg dry weight of cornea). DMMB assays indicated no change in the total amount of sulphated GAG across the cornea. Immunohistochemistry revealed the presence of both high- and low-sulphated epitopes of KS, as well as DS, throughout the cornea, and CS only in the peripheral cornea before the limbus. Quantification by ELISA, disclosed that although both high- and low-sulphated KS remained constant throughout stromal depth at different radial positions, high-sulphated epitopes remained constant from the corneal centre to outer-periphery, whereas low-sulphated epitopes increased significantly. Both small angle X-ray diffraction and TEM analysis revealed that collagen fibril diameter remained relatively constant until the outer periphery was reached, after which fibrils became more widely spaced (from small angle x-ray diffraction analysis) and of larger diameter

  15. Fast determination of three-dimensional fibril orientation of type-I collagen via macroscopic chirality

    NASA Astrophysics Data System (ADS)

    Zhuo, Guan-Yu; Chen, Mei-Yu; Yeh, Chao-Yuan; Guo, Chin-Lin; Kao, Fu-Jen

    2017-01-01

    Polarization-resolved second harmonic generation (SHG) microscopy is appealing for studying structural proteins and well-organized biophotonic nanostructures, due to its highly sensitized structural specificity. In recent years, it has been used to investigate the chiroptical effect, particularly SHG circular dichroism (SHG-CD) in biological tissues. Although SHG-CD attributed to macromolecular structures has been demonstrated, the corresponding quantitative analysis and interpretation on how SHG correlates with second-order susceptibility χ(2) under circularly polarized excitations remains unclear. In this study, we demonstrate a method based on macroscopic chirality to elucidate the correlation between SHG-CD and the orientation angle of the molecular structure. By exploiting this approach, three-dimensional (3D) molecular orientation of type-I collagen is revealed with only two cross polarized SHG images (i.e., interactions of left and right circular polarizations) without acquiring an image stack of varying polarization.

  16. Dental adhesives and strategies for displacement of water/solvents from collagen fibrils.

    PubMed

    Matuda, Larissa Sgarbosa de Araújo; Marchi, Giselle Maria; Aguiar, Thaiane Rodrigues; Leme, Ariene Arcas; Ambrosano, Gláucia M B; Bedran-Russo, Ana Karina

    2016-06-01

    To evaluate the influence of temperature of evaporation in adhesive systems with different solvents on the apparent modulus of elasticity and mass change of macro-hybrid layers modified by proanthocyanidins (PACs). Adhesive resin beams (A) from Single Bond Plus (SB), Excite (EX) and One Step Plus (OS) were prepared after solvent evaporation at 23°C or 40°C (n=12). Macro-hybrid layers (M) (n=12) were prepared using demineralized dentin beams sectioned from extracted human third molars. The demineralized dentin specimens were infiltrated with each one of the three adhesive systems at 23°C or 40°C; with or without prior dentin treatment with PACs for 10min. The apparent modulus of elasticity (E) and mass change (Wmc, %) of adhesives beams and resin-infiltrated specimens were assessed in dry and wet conditions after immersion in water (24h, 1, 3 and 6 months). The E was statistically analyzed by Tukey-Kramer test and the Wmc, % by Kruskal Wallis, and Dunn (α=0.05). Solvent evaporation at 40°C resulted in higher E values for adhesive resin beams at all storage conditions, regardless of the adhesive system (p<0.05). Increased mass loss (3 months: -0.01%; 6 months: -0.05%) was observed in One Step resin beams (p≤0.05). In the macro-hybrid layer models the pretreatment with PACs along with solvent evaporation at 40°C increased E and decreased the Wmc, % (3 months: -2.5; 6 months: 2.75%) for adhesives evaluated over time (p<0.05). No significant differences in ratio (resin/dentin) were found for the macro-hybrid layers (p>0.05). Improved solvent evaporation at higher temperature, and increased collagen cross-linking induced by PACs, enhanced the mechanical properties resulting in highly stable macro-hybrid layers over 6 months storage. Copyright © 2016 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  17. Fibronectin antibody labels corneal stromal collagen fibrils in situ along their length and circumference and demonstrates distinct staining along the cell and stromal interfaces of Descemet's membrane.

    PubMed

    Gordon, Sheldon R

    2014-03-01

    An immunoperoxidase cytochemical study of fibronectin localization in the rat corneal stroma and Descemet's membrane was conducted following organ culture to determine whether stromal swelling allowed better primary antibody penetration into the normally tough fibrous corneal stroma. Following 24 h organ culture, corneas were fixed in 4% paraformaldehyde, washed and stained overnight at 4 °C in anti-fibronectin followed by washing and incubation in an appropriate secondary antibody and exposure to protein A-HRP. Cytochemical processing was carried out in a DAB-containing medium followed by dehydration and Epon embedding. Observations of the stromal lamellae revealed the presence of a novel punctate staining pattern along the length of the collagen fibrils that extended around the fibril's circumference. Measurements on the peroxidase reaction product spacing indicated a periodicity of approximately 20.69 ± 3.57 nm along the fibril's length. Light microscopic immunocytochemistry revealed the presence of fibronectin staining occurred within the endothelial cell layer but only along the DM/stromal interface. Electron microscopic observations however, revealed that fibronectin staining occurred in distinct linear patterns along the length of both the endothelial and stromal DM interfaces. Results indicate that organ culture mediated swelling helps facilitate the penetration of primary antibody into the corneal stroma. Observations suggest a novel association exists between fibronectin and stromal collagen fibrils that helps to mediate the arrangement and organization of the stromal extracellular matrix. Results also definitively indicate that fibronectin is deposited along both DM interfaces suggesting that it plays a role in the adhesion of both the endothelial cell layer and stroma to Descemet's membrane to help maintain the tissue architecture within this region of the cornea.

  18. Lateral Growth Limitation of Corneal Fibrils and Their Lamellar Stacking Depend on Covalent Collagen Cross-linking by Transglutaminase-2 and Lysyl Oxidases, Respectively*

    PubMed Central

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

    2014-01-01

    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

  19. Keratinocyte apoptosis on type I collagen fibrils is prevented by Erk1/2 activation under high calcium condition.

    PubMed

    Fujisaki, Hitomi; Ebihara, Tetsuya; Irie, Shinkichi; Kobayashi, Takashi; Adachi, Eijiro; Mochitate, Katumi; Hattori, Shunji

    2007-01-01

    Keratinocytes adhere and proliferate well on collagen-coated surfaces, but they undergo apoptosis without differentiation on collagen gels according to our past research. In the current studies, we investigated the necessary conditions for keratinocyte survival on fibrous collagen gels. We found that keratinocytes survived on collagen gels when the medium contains elevated levels (1.8 mM) of calcium. Under this high calcium condition, cells formed multicellular colonies and differentiated. Akt was not activated in cells cultured on collagen gels regardless of the calcium concentration, whereas it was activated in cells cultured on nonfibrous collagen. On the other hand, Erk1/2, key kinases of MAPK pathway, were phosphorylated in cells cultured under high calcium condition but not in cells cultured on collagen gels under low calcium condition. The necessity of Erk1/2 activation for keratinocyte survival on collagen gel was confirmed with experiment using U0126, an inhibitor for Erk1/2. These studies show that activation of Akt depends on collagen assembly, whereas activation of Erk1/2 is induced by increased extracellular calcium concentration. Thus, activation of the Erk1/2 by increasing calcium concentration in the incubation medium may compensate for the loss of Akt activation, allowing keratinocyte survival on collagen gels.

  20. Increase in dermal collagen fibril diameter and elastogenesis with UVB exposure: an optical and ultrastructural study in albino Balb/c mice.

    PubMed

    Carneiro, Sueli Coelho; Cassia, Flavia de Freire; Pascarelli, Bernardo Miguel; Souza, Sonia Oliveira; Ramos-e-Silva, Marcia; Filgueira, Absalom Lima; Japiassu, Maria Augusta; Takiya, Christina Maeda

    2007-01-01

    Cutaneous aging is a complex biological phenomenon, dependent not only on the innate or intrinsic process ("biological clock"), but also on extrinsic elements, primarily chronic sun exposure (photoaging). In order to verify dermal morphological changes in the elastic fiber system and collagen associated with aged skin, we performed a light and electron microscopic study on exposed-shaved albino mice, which were exposed to UVB radiation. The experimental group consisted of 48 exposed animals, randomly distributed in three groups and submitted to different radiation doses (A, 28800 J/m2; B, 57600 J/m2; and C, 86400 J/m2) and studied 0, 30, 60 and 90 days of exposure discontinuation. Nonexposed-shaved and nonexposed-nonshaved animals were included as controls. From the day of exposure discontinuation and subsequently, the elastic system and collagen network were progressively modified. The increase in collagen fibril diameter was prominent in the 60 and 90 day groups (p<0.05), as noticed on electron microscopy. Elastic fiber density also increased after irradiation (p<0.05). On electron microscopy, elastogenesis was seen in the deep dermis. The comparative study among the groups disclosed clear relationship between doses and "elastotic changes". It also showed that chronological aging of mice skin was apparently intensified after UVB exposure. Skin elastogenesis seems to be a major consequence of UVB exposure, apart from elastolysis, and occurs not only in humans but also in hairless mice submitted to continuous, long-term UVB exposure.

  1. 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.

  2. 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.

  3. Risk assessment for incident heart failure in individuals with atrial fibrillation

    PubMed Central

    Schnabel, Renate B.; Rienstra, Michiel; Sullivan, Lisa M.; Sun, Jenny X.; Moser, Carlee B.; Levy, Daniel; Pencina, Michael J.; Fontes, João D.; Magnani, Jared W.; McManus, David D.; Lubitz, Steven A.; Tadros, Thomas M.; Wang, Thomas J.; Ellinor, Patrick T.; Vasan, Ramachandran S.; Benjamin, Emelia J.

    2013-01-01

    Background Atrial fibrillation (AF) is a strong risk factor for heart failure (HF); HF onset in patients with AF is associated with increased morbidity and mortality. Risk factors that predict HF in individuals with AF in the community are not well established. Methods and results We examined clinical variables related to the 10-year incidence of HF in 725 individuals (mean 73.3 years, 45% women) with documented AF in the Framingham Heart Study. Event rates for incident HF (n = 161, 48% in women) were comparable in women (4.30 per 100 person-years) and men (3.34 per 100 person-years). Age, body mass index, ECG LV hypertrophy, diabetes, significant murmur, and history of myocardial infarction were positively associated with incident HF in multivariable models (C-statistic 0.71; 95% confidence interval 0.67–0.75). We developed a risk algorithm for estimating absolute risk of HF in AF patients with good model fit and calibration (adjusted calibration χ2 statistic 7.29; Pχ2 = 0.61). Applying the algorithm, 47.6% of HF events occurred in the top tertile in men compared with 13.1% in the bottom tertile, and 58.4% in women in the upper tertile compared with 18.2% in the lowest category. For HF type, women had a non-significantly higher incidence of HF with preserved EF compared with men. Conclusions We describe advancing age, LV hypertrophy, body mass index, diabetes, significant heart murmur, and history of myocardial infarction as clinical predictors of incident HF in individuals with AF. A risk algorithm may help identify individuals with AF at high risk of developing HF. PMID:23594831

  4. A fibril-based structural constitutive theory reveals the dominant role of network characteristics on the mechanical behavior of fibroblast-compacted collagen gels.

    PubMed

    Feng, Zhonggang; Ishiguro, Yuki; Fujita, Kyohei; Kosawada, Tadashi; Nakamura, Takao; Sato, Daisuke; Kitajima, Tatsuo; Umezu, Mitsuo

    2015-10-01

    In this paper, we present a general, fibril-based structural constitutive theory which accounts for three material aspects of crosslinked filamentous materials: the single fibrillar force response, the fibrillar network model, and the effects of alterations to the fibrillar network. In the case of the single fibrillar response, we develop a formula that covers the entropic and enthalpic deformation regions, and introduce the relaxation phase to explain the observed force decay after crosslink breakage. For the filamentous network model, we characterize the constituent element of the fibrillar network in terms its end-to-end distance vector and its contour length, then decompose the vector orientation into an isotropic random term and a specific alignment, paving the way for an expanded formalism from principal deformation to general 3D deformation; and, more important, we define a critical core quantity over which macroscale mechanical characteristics can be integrated: the ratio of the initial end-to-end distance to the contour length (and its probability function). For network alterations, we quantitatively treat changes in constituent elements and relate these changes to the alteration of network characteristics. Singular in its physical rigor and clarity, this constitutive theory can reproduce and predict a wide range of nonlinear mechanical behavior in materials composed of a crosslinked filamentous network, including: stress relaxation (with dual relaxation coefficients as typically observed in soft tissues); hysteresis with decreasing maximum stress under serial cyclic loading; strain-stiffening under uniaxial tension; the rupture point of the structure as a whole; various effects of biaxial tensile loading; strain-stiffening under simple shearing; the so-called "negative normal stress" phenomenon; and enthalpic elastic behaviors of the constituent element. Applied to compacted collagen gels, the theory demonstrates that collagen fibrils behave as enthalpic

  5. [Atrial fibrillation].

    PubMed

    Cárdenas, Manuel

    2007-01-01

    Atrial fibrillation is an arrhythmia characterized by no-coordinated atrial contraction that results in an inefficient atrial systole. The clinical classification of atrial fibrillation includes: ocassional, paroxysmal, persistent, and permanent. Multiple mechanisms have been described and accounts for a single ECG manifestation. Treatment should be individualized and has to considered several aspects including age, associated heart disease, and symptoms. Treatment strategies are: rhythm control, rate control, and thromboprophylaxis.

  6. Three-dimensional energy-minimized model of human type II "Smith" collagen microfibril.

    PubMed

    Chen, J M; Sheldon, A; Pincus, M R

    1995-06-01

    A procedure is described for constructing a three-dimensional model of fibril-forming human type II collagen based on the "Smith" microfibril model. This model is a complex of five individual collagen triple-helical molecules, and is based on known structural parameters for collagen. Both experimental and theoretical data were used as constraints to guide the modeling. The resulting fibril model for type II collagen is in agreement with both physical and chemical characteristics produced by experimental staining patterns of type II fibrils. Some advantages of the type II model are that the stereochemistry of all the sidechain groups is accounted for, and specific atomic interactions can now be studied. This model is useful for: development of therapeutics for collagen related diseases; development of synthetic collagen tissues; design of chemical reagents (i.e., tanning agents) to treat collagen-related products; and study of the structural and functional aspects of type II collagen. Described is the procedure by which the Smith microfibril of type II collagen was developed using molecular modeling tools, validation of the model by comparison to electron-microscopic images of fibril staining patterns, and some applications of this microfibril model.

  7. 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 Central

    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

    2015-01-01

    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

  8. 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. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

  9. Characterization of whole fibril-forming collagen proteins of types I, III, and V from fetal calf skin by infrared matrix-assisted laser desorption ionization mass spectrometry.

    PubMed

    Dreisewerd, Klaus; Rohlfing, Andreas; Spottke, Beatrice; Urbanke, Claus; Henkel, Werner

    2004-07-01

    Fibril-forming collagen proteins of the types I, III, and V were extracted from fetal calf skin, purified by differential salt precipitation, and analyzed by infrared matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (IR-MALDI-TOF-MS). Glycerol was used as liquid IR-MALDI matrix. Noncovalently bound triple helices of the types I and V were detected from the NaCl precipitate. After heating at 43 degrees C for 10 min, resulting in the dissociation of the triple helix, the single alpha-chain subunits were detected. For type I, mass spectra acquired from molecular sieve chromatography fractions revealed the presence of further substructures of dimeric type and of supramolecular complexes up to the tetramer. Triple helices of type III, stabilized by covalent disulfide bonds, were detected from the total protein precipitate also after heat treatment. For type III, even hexamer and nonamer structures with molecular weights close to 600 and 900 kDa were recorded. For comparison, ultraviolet (UV-)MALDI-MS measurements with 2,5-dihydroxybenzoic acid as matrix were carried out with some of the samples. Here, only the single alpha-chains were detected with significantly reduced sensitivity.

  10. The Role of Collagen Organization on the Properties of Bone.

    PubMed

    Garnero, Patrick

    2015-09-01

    Bone is a complex tissue constituted by a collagen matrix filled in with crystal of hydroxyapatite (HAP). Bone mechanical properties are influenced by the collagen matrix which is organized into hierarchical structures from the individual type I collagen heterotrimer flanked by linear telopeptides at each end to the collagen fibrils that are interconnected by enzymatic and non-enzymatic cross-links. Although most studies focused on the role of collagen cross-links in bone strength, other organizational features may also play a role. At the molecular level it has been shown that homotrimer of type I collagen found in bone tissue of some patients with osteogenesis imperfecta (OI) is characterized by decreased mechanical competence compared to the regular heterotrimer. The state of C-telopeptide isomerization-which can be estimated by the measurement in body fluids of the native and isomerized isoforms-has also been shown to be associated with bone strength, particularly the post-yield properties independent of bone size and bone mineral density. Other higher hierarchical features of collagen organization have shown to be associated with changes in bone mechanical behavior in ex vivo models and may also be relevant to explain bone fragility in diseases characterized by collagen abnormalities e.g., OI and Paget's disease. These include the orientation of collagen fibrils in a regular longitudinal direction, the D-spacing period between collagen fibrils and the collagen-HAP interfacial bonding. Preliminary data indicate that some of these organizational features can change during treatment with bisphosphonate, raloxifene, and PTH suggesting that they may contribute to their anti-fracture efficacy. It remains however to be determined which of these parameters play a specific and independent role in bone matrix properties, what is the magnitude of mechanical strength explained by collagen organization, whether they are relevant to explain osteoporosis-induced bone

  11. Combining nano-physical and computational investigations to understand the nature of "aging" in dermal collagen.

    PubMed

    Ahmed, Tarek; Nash, Anthony; Clark, Kristina En; Ghibaudo, Marion; de Leeuw, Nora H; Potter, Anne; Stratton, Richard; Birch, Helen L; Enea Casse, Ramona; Bozec, Laurent

    2017-01-01

    The extracellular matrix of the dermis is a complex, dynamic system with the various dermal components undergoing individual physiologic changes as we age. Age-related changes in the physical properties of collagen were investigated in particular by measuring the effect of aging, most likely due to the accumulation of advanced glycation end product (AGE) cross-links, on the nanomechanical properties of the collagen fibril using atomic force microscope nano-indentation. An age-related decrease in the Young's modulus of the transverse fibril was observed (from 8.11 to 4.19 GPa in young to old volunteers, respectively, P<0.001). It is proposed that this is due to a change in the fibril density caused by age-related differences in water retention within the fibrils. The new collagen-water interaction mechanism was verified by electronic structure calculations, showing it to be energetically feasible.

  12. Mechanical properties of human patellar tendon at the hierarchical levels of tendon and fibril.

    PubMed

    Svensson, René B; Hansen, Philip; Hassenkam, Tue; Haraldsson, Bjarki T; Aagaard, Per; Kovanen, Vuokko; Krogsgaard, Michael; Kjaer, Michael; Magnusson, S Peter

    2012-02-01

    Tendons are strong hierarchical structures, but how tensile forces are transmitted between different levels remains incompletely understood. Collagen fibrils are thought to be primary determinants of whole tendon properties, and therefore we hypothesized that the whole human patellar tendon and its distinct collagen fibrils would display similar mechanical properties. Human patellar tendons (n = 5) were mechanically tested in vivo by ultrasonography. Biopsies were obtained from each tendon, and individual collagen fibrils were dissected and tested mechanically by atomic force microscopy. The Young's modulus was 2.0 ± 0.5 GPa, and the toe region reached 3.3 ± 1.9% strain in whole patellar tendons. Based on dry cross-sectional area, the Young's modulus of isolated collagen fibrils was 2.8 ± 0.3 GPa, and the toe region reached 0.86 ± 0.08% strain. The measured fibril modulus was insufficient to account for the modulus of the tendon in vivo when fibril content in the tendon was accounted for. Thus, our original hypothesis was not supported, although the in vitro fibril modulus corresponded well with reported in vitro tendon values. This correspondence together with the fibril modulus not being greater than that of tendon supports that fibrillar rather than interfibrillar properties govern the subfailure tendon response, making the fibrillar level a meaningful target of intervention. The lower modulus found in vitro suggests a possible adverse effect of removing the tissue from its natural environment. In addition to the primary work comparing the two hierarchical levels, we also verified the existence of viscoelastic behavior in isolated human collagen fibrils.

  13. Variants in ZFHX3 are associated with atrial fibrillation in individuals of European ancestry.

    PubMed

    Benjamin, Emelia J; Rice, Kenneth M; Arking, Dan E; Pfeufer, Arne; van Noord, Charlotte; Smith, Albert V; Schnabel, Renate B; Bis, Joshua C; Boerwinkle, Eric; Sinner, Moritz F; Dehghan, Abbas; Lubitz, Steven A; D'Agostino, Ralph B; Lumley, Thomas; Ehret, Georg B; Heeringa, Jan; Aspelund, Thor; Newton-Cheh, Christopher; Larson, Martin G; Marciante, Kristin D; Soliman, Elsayed Z; Rivadeneira, Fernando; Wang, Thomas J; Eiríksdottir, Gudny; Levy, Daniel; Psaty, Bruce M; Li, Man; Chamberlain, Alanna M; Hofman, Albert; Vasan, Ramachandran S; Harris, Tamara B; Rotter, Jerome I; Kao, W H Linda; Agarwal, Sunil K; Stricker, Bruno H Ch; Wang, Ke; Launer, Lenore J; Smith, Nicholas L; Chakravarti, Aravinda; Uitterlinden, André G; Wolf, Philip A; Sotoodehnia, Nona; Köttgen, Anna; van Duijn, Cornelia M; Meitinger, Thomas; Mueller, Martina; Perz, Siegfried; Steinbeck, Gerhard; Wichmann, H-Erich; Lunetta, Kathryn L; Heckbert, Susan R; Gudnason, Vilmundur; Alonso, Alvaro; Kääb, Stefan; Ellinor, Patrick T; Witteman, Jacqueline C M

    2009-08-01

    We conducted meta-analyses of genome-wide association studies for atrial fibrillation (AF) in participants from five community-based cohorts. Meta-analyses of 896 prevalent (15,768 referents) and 2,517 incident (21,337 referents) AF cases identified a new locus for AF (ZFHX3, rs2106261, risk ratio RR = 1.19; P = 2.3 x 10(-7)). We replicated this association in an independent cohort from the German AF Network (odds ratio = 1.44; P = 1.6 x 10(-11); combined RR = 1.25; combined P = 1.8 x 10(-15)).

  14. 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

  15. Greater Mechanical Loading During Walking Is Associated With Less Collagen Turnover in Individuals With Anterior Cruciate Ligament Reconstruction.

    PubMed

    Pietrosimone, Brian; Blackburn, J Troy; Harkey, Matthew S; Luc, Brittney A; Hackney, Anthony C; Padua, Darin A; Driban, Jeffrey B; Spang, Jeffrey T; Jordan, Joanne M

    2016-02-01

    Individuals who have sustained an anterior cruciate ligament (ACL) injury and undergo ACL reconstruction (ACLR) are at higher risk of developing knee osteoarthritis. It is hypothesized that altered knee loading may influence the underlying joint metabolism and hasten development of posttraumatic knee osteoarthritis. To explore the associations between serum biomarkers of cartilage metabolism and peak vertical ground-reaction force (vGRF) and vGRF loading rate in the injured and uninjured limbs of individuals with ACLR. Descriptive laboratory study. Patients with a history of a primary unilateral ACLR who had returned to unrestricted physical activity (N = 19) participated in the study. Resting blood was collected from each participant before completing 5 walking gait trials at a self-selected comfortable speed. Peak vGRF was extracted for both limbs during the first 50% of the stance phase of gait, and the linear vGRF loading rate was determined between heel strike and peak vGRF. Sera were assessed for collagen breakdown (collagen type II cleavage product [C2C]) and synthesis (collagen type II C-propeptide [CPII]), as well as aggrecan concentrations, via commercially available specific enzyme-linked immunosorbent assays. Pearson product-moment correlations (r) and Spearman rank-order correlations (ρ) were used to evaluate associations between loading characteristics and biomarkers of cartilage metabolism. Lower C2C:CPII ratios were associated with higher peak vGRF in the injured limb (ρ = -0.59, uncorrected P = .007). There were no significant associations between peak vGRF or linear vGRF loading rate and CPII, C2C, or aggrecan serum concentrations. Lower C2C:CPII ratios were associated with higher peak vGRF in the ACLR limb during gait, suggesting that higher peak loading in the ACLR limb is related to lower type II collagen breakdown relative to type II collagen synthesis. These data suggest that type II collagen synthesis may be higher relative to the amount

  16. 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.

  17. 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

  18. 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

  19. 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

  20. 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

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

    PubMed

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

    1996-02-01

    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

  2. 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.

  3. 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

  4. Microstructural and mechanical differences between digested collagen-fibrin co-gels and pure collagen and fibrin gels.

    PubMed

    Lai, Victor K; Frey, Christina R; Kerandi, Allan M; Lake, Spencer P; Tranquillo, Robert T; Barocas, Victor H

    2012-11-01

    Collagen and fibrin are important extracellular matrix (ECM) components in the body, providing structural integrity to various tissues. These biopolymers are also common scaffolds used in tissue engineering. This study investigated how co-gelation of collagen and fibrin affected the properties of each individual protein network. Collagen-fibrin co-gels were cast and subsequently digested using either plasmin or collagenase; the microstructure and mechanical behavior of the resulting networks were then compared with the respective pure collagen or fibrin gels of the same protein concentration. The morphologies of the collagen networks were further analyzed via three-dimensional network reconstruction from confocal image z-stacks. Both collagen and fibrin exhibited a decrease in mean fiber diameter when formed in co-gels compared with the pure gels. This microstructural change was accompanied by an increased failure strain and decreased tangent modulus for both collagen and fibrin following selective digestion of the co-gels. In addition, analysis of the reconstructed collagen networks indicated the presence of very long fibers and the clustering of fibrils, resulting in very high connectivities for collagen networks formed in co-gels.

  5. Microstructural and Mechanical Differences Between Digested Collagen-Fibrin Co-Gels and Pure Collagen and Fibrin Gels

    PubMed Central

    Lai, Victor K.; Frey, Christina R.; Kerandi, Allan M.; Lake, Spencer P.; Tranquillo, Robert T.; Barocas, Victor H.

    2012-01-01

    Collagen and fibrin are important extra-cellular matrix (ECM) components in the body, providing structural integrity to various tissues. These biopolymers are also common scaffolds used in tissue engineering. This study investigated how co-gelation of collagen and fibrin affected the properties of each individual protein network. Collagen-fibrin co-gels were cast and subsequently digested using either plasmin or collagenase; the microstructure and mechanical behavior of the resulting networks were then compared with respective pure collagen or fibrin gels of the same protein concentration. The morphologies of the collagen networks were further analyzed via 3-D network reconstruction from confocal image z-stacks. Both collagen and fibrin exhibited a decrease in mean fiber diameter when formed in the co-gels compared to the pure gels; this microstructural change was accompanied by increased failure strain and decreased tangent modulus for both collagen and fibrin following selected digestion of the co-gels. In addition, analysis of the reconstructed collagen networks indicated presence of very long fibers and clustering of fibrils, resulting in very high connectivities for collagen networks formed in co-gels. PMID:22828381

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

    PubMed

    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

    2016-01-20

    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.

  7. Twelve-single nucleotide polymorphism genetic risk score identifies individuals at increased risk for future atrial fibrillation and stroke.

    PubMed

    Tada, Hayato; Shiffman, Dov; Smith, J Gustav; Sjögren, Marketa; Lubitz, Steven A; Ellinor, Patrick T; Louie, Judy Z; Catanese, Joseph J; Engström, Gunnar; Devlin, James J; Kathiresan, Sekar; Melander, Olle

    2014-10-01

    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 together as an AF genetic risk score (AF-GRS) can improve prediction of one's risk for AF. 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 single nucleotide polymorphisms that had been previously shown to be associated with AF at genome-wide significance. During follow-up, 2160 participants experienced a first AF event and 1495 had a first ischemic stroke event. Participants in the top AF-GRS quintile were at increased risk for incident AF (hazard ratio, 2.00; 95% confidence interval, 1.73-2.31; P=2.7×10(-21)) and ischemic stroke (hazard ratio, 1.23; 95% confidence interval, 1.04-1.46; 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). An AF-GRS can identify 20% of individuals who are at ≈2-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. © 2014 American Heart Association, Inc.

  8. Is orthostatic hypotension more common in individuals with atrial fibrillation?-Findings from The Irish Longitudinal Study on Ageing (TILDA).

    PubMed

    McNicholas, T; Tobin, K; O'Callaghan, S; Kenny, R A

    2017-06-15

    atrial fibrillation (AF) and orthostatic hypotension (OH) share common risk factors such as age, hypertension and cardiovascular (CV) disease. The autonomic nervous system (ANS) also plays a role in the pathogenesis of both AF and OH. The aim of this study is to assess whether individuals with AF are more likely to have OH than those without AF. data from wave 1 of The Irish Longitudinal Study on Ageing were used. Beat-to-beat blood pressure was measured during active stand lasting 110 s. OH, defined as a drop in systolic blood pressure (SBP) ≥20 mmHg or a drop in diastolic blood pressure ≥10 mmHg at 30, 60 and 90 s was assessed. Initial OH (IOH) was assessed as a drop in SBP ≥40 mmHg or a drop in diastolic BP≥20 mmHg. in total 4,408 participants aged ≥50 had active stand and electrocardiogram data suitable for analysis. AF was identified in 101 of these. Logistic regression found participants with AF were more likely to have OH at 30 (odds ratio (OR) 1.95, 95% confidence interval (CI) 1.24-3.06) and 60 (OR 2.13, 95% CI 1.18-3.87) seconds, and IOH (OR 1.81, 95% CI 1.21-2.70). The association between IOH and OH at 30 s remained significant following adjustment for confounders (age, sex, baseline HR, education, BP, smoking, frailty, beta blocker (BB) use, anti-hypertensive use (excluding BBs) and number of CV conditions). OH is more common in individuals with AF, this may reflect the role of the ANS in both AF and OH.

  9. Ultrastructure of the rat periodontal ligament as observed with quick-freeze, deep-etch and replica methods: arrangement of collagen and related structures.

    PubMed

    Kuroiwa, M; Tachikawa, T; Izumiyama, N; Takubo, K; Yoshiki, S; Higashi, S

    1996-01-01

    The ultrastructure of the periodontal ligament of rat molars was examined with the quick-freeze, deep-etch replica methods. It was mainly composed of elongated fibroblast-like cells and 40- to 50-nm-wide collagen fibrils that are arranged parallel to one another to form fibers approximately 1 micron in width. Collagen fibrils are composed of 10-nm-wide substructures that may run helically against the long axis of the fibril. Numerous rod-like structures ('rods') approximately 10 nm in width are present around the collagen fibrils. Individual or groups of rods span spaces between neighboring collagen fibrils to interconnect them. The surfaces of the fibroblast-like cells are also connected to the nearest collagen fibrils through the rods. In place, strands with a thickness similar to that of the rods were seen self-assembled into irregular meshwork structures. The treatment of the tissue with 10% sodium hydroxide for up to 5 days removed most of these rods and strands, thus exposing a three-dimensional arrangement of collagen fibrils that is often not fully visualized in untreated tissues. With histochemical staining of thinly sectioned tissues using Alcian blue, these rods and strands were positively stained, and thus they were demonstrated to be composed of proteoglycans. The ultrastructural arrangement of the periodontal ligament, observed in this study as a delicate interaction of collagen and proteoglycan components, is likely to play a significant role in the transmission of occlusal forces applied to the tissue and in the dissipation of mechanical shock.

  10. Cluster Individuals Based on Phenotype and Determine the Risk for Atrial Fibrillation in the PREVEND and Framingham Heart Study Populations

    PubMed Central

    Rienstra, Michiel; Geelhoed, Bastiaan; Yin, Xiaoyan; Siland, Joylene E.; Vermond, Rob A.; Mulder, Bart A.; Van Der Harst, Pim; Hillege, Hans L.; Van Gelder, Isabelle C.

    2016-01-01

    Background Risk prediction of atrial fibrillation (AF) is of importance to improve the early diagnosis and treatment of AF. Latent class analysis takes into account the possible existence of classes of individuals each with shared risk factors, and maybe a better method of incorporating the phenotypic heterogeneity underlying AF. Methods and findings Two prospective community-based cohort studies from Netherlands and United States were used. Prevention of Renal and Vascular End-stage Disease (PREVEND) study, started in 1997, and the Framingham Heart Study (FHS) Offspring cohort started in 1971, both with 10-years follow-up. The main objective was to determine the risk of AF using a latent class analysis, and compare the discrimination and reclassification performance with traditional regression analysis. Mean age in PREVEND was 49±13 years, 49.8% were men. During follow-up, 250(3%) individuals developed AF. We built a latent class model based on 18 risk factors. A model with 7 distinct classes (ranging from 341 to 1517 individuals) gave the optimum tradeoff between a high statistical model-likelihood and a low number of model parameters. All classes had a specific profile. The incidence of AF varied; class 1 0.0%, class 2 0.3%, class 3 7.5%, class 4 0.2%, class 5 1.3%, class 6 4.2%, class 7 21.7% (p<0.001). The discrimination (C-statistic 0.830 vs. 0.842, delta-C -0.013, p = 0.22) and reclassification (IDI -0.028, p<0.001, NRI -0.090, p = 0.049, and category-less-NRI -0.049, p = 0.495) performance of both models was comparable. The results were successfully replicated in a sample of the FHS study (n = 3162; mean age 58±9 years, 46.3% men). Conclusions Latent class analysis to build an AF risk model is feasible. Despite the heterogeneity in number and severity of risk factors between individuals at risk for AF, latent class analysis produces distinguishable groups. PMID:27832125

  11. Net clinical benefit of warfarin in individuals with atrial fibrillation across stroke risk and across primary and secondary care

    PubMed Central

    Banerjee, Amitava; Shah, Anoop Dinesh; Patel, Riyaz; Denaxas, Spiros; Casas, Juan-Pablo; Hemingway, Harry

    2017-01-01

    Objective To investigate net clinical benefit (NCB) of warfarin in individuals with atrial fibrillation (AF) across stroke risk and across primary and secondary care. Methods We conducted a linked electronic health record cohort study of 70 206 individuals with initial record of diagnosis of AF in primary (n=29 568) or secondary care (n=40 638) in England (1998–2010). We defined stroke risk according to the CHA2DS2-VASc score, and followed individuals over a median 2.2 years for 7005 ischaemic strokes (IS) and for 906 haemorrhagic strokes (HS). We calculated incidence rates (IRs) and 95% CIs per 100 person-years (PYs) (IR (95% CI)/100 PY) of IS and HS, with and without use of warfarin, and the NCB (ie, number of IS avoided) per 100 PYs of warfarin use (NCB (95% CI)/100 PY). Results Compared with individuals with initial record of diagnosis in secondary care, those in primary care had lower scores of IS risk (CHA2DS2-VASc≤2: 30.8% vs 20.6%), and lower overall incidence of IS (IR (95% CI)/100 PY: 2.3 (2.2 to 2.4) vs 4.3 (4.2 to 4.4), p value=0.00); however among individuals with CHA2DS2-VASc=0, 1 or 2 there were no differences in IS rate between those with initial record of diagnosis in primary care or secondary care (IR (95% CI)/100 PY: 0.2 (0.1 to 0.3) vs 0.3 (0.2 to 0.5), p value=0.16), (IR (95% CI)/100 PY: 0.6 (0.4 to 0.7) vs 0.7 (0.6 to 0.9), p value=0.08) and (IR (95% CI)/100 PY: 1.1 (1.00 to 1.3) vs 1.4 (1.2 to 1.6), p value=0.05), respectively. For CHA2DS2-VASc=0, 1 and 2, IRs of IS with versus without warfarin were (IR (95% CI)/100 PY: 0.4 (0.2 to 0.8) vs 0.2 (0.1 to 0.3), p value=0.16), (IR (95% CI)/100 PY: 0.4 (0.3 to 0.7) vs 0.7 (0.6 to 0.8), p value=0.03) and (IR (95% CI)/100 PY: 0.8 (0.7 to 1.0) vs 1.4 (1.3 to 1.6), p value=0.00), respectively. We found a significant positive NCB of warfarin from CHA2DS2-VASc≥2 in men (NCB (95% CI)/100 PY: 0.5 (0.1 to 0.9)) and from CHA2DS2-VASc≥3 in women (NCB (95% CI)/100 PY: 1.5 (1

  12. Net clinical benefit of warfarin in individuals with atrial fibrillation across stroke risk and across primary and secondary care.

    PubMed

    Allan, Victoria; Banerjee, Amitava; Shah, Anoop Dinesh; Patel, Riyaz; Denaxas, Spiros; Casas, Juan-Pablo; Hemingway, Harry

    2017-02-01

    To investigate net clinical benefit (NCB) of warfarin in individuals with atrial fibrillation (AF) across stroke risk and across primary and secondary care. We conducted a linked electronic health record cohort study of 70 206 individuals with initial record of diagnosis of AF in primary (n=29 568) or secondary care (n=40 638) in England (1998-2010). We defined stroke risk according to the CHA2DS2-VASc score, and followed individuals over a median 2.2 years for 7005 ischaemic strokes (IS) and for 906 haemorrhagic strokes (HS). We calculated incidence rates (IRs) and 95% CIs per 100 person-years (PYs) (IR (95% CI)/100 PY) of IS and HS, with and without use of warfarin, and the NCB (ie, number of IS avoided) per 100 PYs of warfarin use (NCB (95% CI)/100 PY). Compared with individuals with initial record of diagnosis in secondary care, those in primary care had lower scores of IS risk (CHA2DS2-VASc≤2: 30.8% vs 20.6%), and lower overall incidence of IS (IR (95% CI)/100 PY: 2.3 (2.2 to 2.4) vs 4.3 (4.2 to 4.4), p value=0.00); however among individuals with CHA2DS2-VASc=0, 1 or 2 there were no differences in IS rate between those with initial record of diagnosis in primary care or secondary care (IR (95% CI)/100 PY: 0.2 (0.1 to 0.3) vs 0.3 (0.2 to 0.5), p value=0.16), (IR (95% CI)/100 PY: 0.6 (0.4 to 0.7) vs 0.7 (0.6 to 0.9), p value=0.08) and (IR (95% CI)/100 PY: 1.1 (1.00 to 1.3) vs 1.4 (1.2 to 1.6), p value=0.05), respectively. For CHA2DS2-VASc=0, 1 and 2, IRs of IS with versus without warfarin were (IR (95% CI)/100 PY: 0.4 (0.2 to 0.8) vs 0.2 (0.1 to 0.3), p value=0.16), (IR (95% CI)/100 PY: 0.4 (0.3 to 0.7) vs 0.7 (0.6 to 0.8), p value=0.03) and (IR (95% CI)/100 PY: 0.8 (0.7 to 1.0) vs 1.4 (1.3 to 1.6), p value=0.00), respectively. We found a significant positive NCB of warfarin from CHA2DS2-VASc≥2 in men (NCB (95% CI)/100 PY: 0.5 (0.1 to 0.9)) and from CHA2DS2-VASc≥3 in women (NCB (95% CI)/100 PY: 1.5 (1.1 to 1.9)). CHA2DS2-VASc

  13. Jellyfish collagen scaffolds for cartilage tissue engineering.

    PubMed

    Hoyer, Birgit; Bernhardt, Anne; Lode, Anja; Heinemann, Sascha; Sewing, Judith; Klinger, Matthias; Notbohm, Holger; Gelinsky, Michael

    2014-02-01

    Porous scaffolds were engineered from refibrillized collagen of the jellyfish Rhopilema esculentum for potential application in cartilage regeneration. The influence of collagen concentration, salinity and temperature on fibril formation was evaluated by turbidity measurements and quantification of fibrillized collagen. The formation of collagen fibrils with a typical banding pattern was confirmed by atomic force microscopy and transmission electron microscopy analysis. Porous scaffolds from jellyfish collagen, refibrillized under optimized conditions, were fabricated by freeze-drying and subsequent chemical cross-linking. Scaffolds possessed an open porosity of 98.2%. The samples were stable under cyclic compression and displayed an elastic behavior. Cytotoxicity tests with human mesenchymal stem cells (hMSCs) did not reveal any cytotoxic effects of the material. Chondrogenic markers SOX9, collagen II and aggrecan were upregulated in direct cultures of hMSCs upon chondrogenic stimulation. The formation of typical extracellular matrix components was further confirmed by quantification of sulfated glycosaminoglycans.

  14. Early stiffening and softening of collagen: interplay of deformation mechanisms in biopolymer networks.

    PubMed

    Kurniawan, Nicholas A; Wong, Long Hui; Rajagopalan, Raj

    2012-03-12

    Collagen networks, the main structural/mechanical elements in biological tissues, increasingly serve as biomimetic scaffolds for cell behavioral studies, assays, and tissue engineering, and yet their full spectrum of nonlinear behavior remains unclear. Here, with self-assembled type-I collagen as model, we use metrics beyond those in standard single-harmonic analysis of rheological measurements to reveal strain-softening and strain-stiffening of collagen networks both in instantaneous responses and at steady state. The results show how different deformation mechanisms, such as deformation-induced increase in the elastically active fibrils, nonlinear extension of individual fibrils, and slips in the physical cross-links in the network, can lead to the observed complex nonlinearity. We demonstrate how comprehensive rheological analyses can uncover the rich mechanical properties of biopolymer networks, including the above-mentioned softening as well as an early strain-stiffening, which are important for understanding physiological response of biological materials to mechanical loading.

  15. Microfluidic assay of platelet deposition on collagen by perfusion of whole blood from healthy individuals taking aspirin.

    PubMed

    Li, Ruizhi; Fries, Susanne; Li, Xuanwen; Grosser, Tilo; Diamond, Scott L

    2013-08-01

    Microfluidic devices can create hemodynamic conditions for platelet assays. We validated an 8-channel device in a study of interdonor response to acetylsalicylic acid (ASA, aspirin) with whole blood from 28 healthy individuals. Platelet deposition was assessed before treatment or 24 h after ingestion of 325 mg ASA. Whole blood (plus 100 μmol/L H-d-Phe-Pro-Arg-chloromethylketone to inhibit thrombin) was further treated ex vivo with ASA (0-500 μmol/L) and perfused over fibrillar collagen for 300 s at a venous wall shear rate (200 s(-1)). Ex vivo ASA addition to blood drawn before aspirin ingestion caused a reduction in platelet deposition [half-maximal inhibitory concentration (IC50) approximately 10-20 μmol/L], especially between 150 and 300 s of perfusion, when secondary aggregation mediated by thromboxane was expected. Twenty-seven of 28 individuals displayed smaller deposits (45% mean reduction; range 10%-90%; P < 0.001) from blood obtained 24 h after ASA ingestion (no ASA added ex vivo). In replicate tests, an R value to score secondary aggregation [deposition rate from 150 to 300 s normalized by rate from 60 to 150 s] showed R < 1 in only 2 of 28 individuals without ASA ingestion, with R > 1 in only 3 of 28 individuals after 500 μmol/L ASA addition ex vivo. At 24 h after ASA ingestion, 21 of 28 individuals displayed poor secondary aggregation (R < 1) without ex vivo ASA addition, whereas the 7 individuals with residual secondary aggregation (R > 1) displayed insensitivity to ex vivo ASA addition. Platelet deposition was not correlated with platelet count. Ex vivo ASA addition caused similar inhibition at venous and arterial wall shear rates. Microfluidic devices quantified platelet deposition after ingestion or ex vivo addition of aspirin.

  16. Self-association of collagen triple helic peptides into higher order structures.

    PubMed

    Kar, Karunakar; Amin, Priyal; Bryan, Michael A; Persikov, Anton V; Mohs, Angela; Wang, Yuh-Hwa; Brodsky, Barbara

    2006-11-03

    Interest in self-association of peptides and proteins is motivated by an interest in the mechanism of physiologically higher order assembly of proteins such as collagen as well as the mechanism of pathological aggregation such as beta-amyloid formation. The triple helical form of (Pro-Hyp-Gly)(10), a peptide that has proved a useful model for molecular features of collagen, was found to self-associate, and its association properties are reported here. Turbidity experiments indicate that the triple helical peptide self-assembles at neutral pH via a nucleation-growth mechanism, with a critical concentration near 1 mM. The associated form is more stable than individual molecules by about 25 degrees C, and the association is reversible. The rate of self-association increases with temperature, supporting an entropically favored process. After self-association, (Pro-Hyp-Gly)(10) forms branched filamentous structures, in contrast with the highly ordered axially periodic structure of collagen fibrils. Yet a number of characteristics of triple helix assembly for the peptide resemble those of collagen fibril formation. These include promotion of fibril formation by neutral pH and increasing temperature; inhibition by sugars; and a requirement for hydroxyproline. It is suggested that these similar features for peptide and collagen self-association are based on common lateral underlying interactions between triple helical molecules mediated by hydrogen-bonded hydration networks involving hydroxyproline.

  17. Calcium concentration dependent collagen mineralization.

    PubMed

    Niu, Xufeng; Fan, Rui; Tian, Feng; Guo, Xiaolin; Li, Ping; Feng, Qingling; Fan, Yubo

    2017-04-01

    Mineralization of collagen fibrils is a regular combination process of organic and mineral components mainly involving calcium, phosphate and collagen. We report the influence of calcium to the self-assembly of collagen by changing the concentration of calcium ion in the process of mineralization. Low concentration of calcium results in the well collagen self-assembly while poor mineral crystallization. Relatively, high concentration of calcium can hinder collagen self-assembly, whereas it is benefited to mineral crystallization. We also reveal that collagen self-assembly happens in advance of the formation of better mineral crystals. These results interpret the mechanism of collagen mineralization further. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. 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. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. β-Aminopropionitrile-Induced Reduction in Enzymatic Crosslinking Causes In Vitro Changes in Collagen Morphology and Molecular Composition

    PubMed Central

    Canelón, Silvia P.

    2016-01-01

    Type I collagen morphology can be characterized using fibril D-spacing, a metric which describes the periodicity of repeating bands of gap and overlap regions of collagen molecules arranged into collagen fibrils. This fibrillar structure is stabilized by enzymatic crosslinks initiated by lysyl oxidase (LOX), a step which can be disrupted using β-aminopropionitrile (BAPN). Murine in vivo studies have confirmed effects of BAPN on collagen nanostructure and the objective of this study was to evaluate the mechanism of these effects in vitro by measuring D-spacing, evaluating the ratio of mature to immature crosslinks, and quantifying gene expression of type I collagen and LOX. Osteoblasts were cultured in complete media, and differentiated using ascorbic acid, in the presence or absence of 0.25mM BAPN-fumarate. The matrix produced was imaged using atomic force microscopy (AFM) and 2D Fast Fourier transforms were performed to extract D-spacing from individual fibrils. The experiment was repeated for quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Fourier Transform infrared spectroscopy (FTIR) analyses. The D-spacing distribution of collagen produced in the presence of BAPN was shifted toward higher D-spacing values, indicating BAPN affects the morphology of collagen produced in vitro, supporting aforementioned in vivo experiments. In contrast, no difference in gene expression was found for any target gene, suggesting LOX inhibition does not upregulate the LOX gene to compensate for the reduction in aldehyde formation, or regulate expression of genes encoding type I collagen. Finally, the mature to immature crosslink ratio decreased with BAPN treatment and was linked to a reduction in peak percent area of mature crosslink hydroxylysylpyridinoline (HP). In conclusion, in vitro treatment of osteoblasts with low levels of BAPN did not induce changes in genes encoding LOX or type I collagen, but led to an increase in collagen D-spacing as well as

  20. Mandibular Cartilage Collagen Network Nanostructure

    PubMed Central

    Vanden Berg-Foels, Wendy S.

    2015-01-01

    Background Mandibular condyle cartilage (MCC) has a unique structure among articular cartilages; however, little is known about its nanoscale collagen network architecture, hampering design of regeneration therapies and rigorous evaluation of regeneration experiment outcomes in preclinical research. Helium ion microscopy is a novel technology with a long depth of field that is uniquely suited to imaging open 3D collagen networks at multiple scales without obscuring conductive coatings. Objective The objective of this research was to image, at the micro- and nanoscales, the depth-dependent MCC collagen network architecture. Design MCC was collected from New Zealand white rabbits. Images of MCC zones were acquired using helium ion, transmission electron, and light microscopy. Network fibril and canal diameters were measured. Results For the first time, the MCC was visualized as a 3D collagen fibril structure at the nanoscale, the length scale of network assembly. Fibril diameters ranged from 7 to 110 nm and varied by zone. The articular surface was composed of a fine mesh that was woven through thin layers of larger fibrils. The fibrous zone was composed of approximately orthogonal lamellae of aligned fibrils. Fibrocyte processes surrounded collagen bundles forming extracellular compartments. The proliferative, mature, and hypertrophic zones were composed of a branched network that was progressively remodeled to accommodate chondrocyte hypertrophy. Osteoid fibrils were woven around osteoblast cytoplasmic processes to create numerous canals similar in size to canaliculi of mature bone. Conclusion This multiscale investigation advances our foundational understanding of the complex, layered 3D architecture of the MCC collagen network. PMID:27375843

  1. 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

  2. Genetic linkage to the type VII collagen gene (COL7A1) in 26 families with generalised recessive dystrophic epidermolysis bullosa and anchoring fibril abnormalities.

    PubMed Central

    Dunnill, M G; Richards, A J; Milana, G; Mollica, F; Atherton, D; Winship, I; Farrall, M; al-Imara, L; Eady, R A; Pope, F M

    1994-01-01

    To strengthen the evidence for genetic linkage to COL7A1, we have studied 26 generalised recessive dystrophic epidermolysis bullosa (EB) families of British, Italian, Irish, and South African origin. We chose two linkage markers, a COL7A1 PvuII intragenic polymorphism and a highly informative anonymous microsatellite marker, D3S1100, which maps close to the COL7A1 locus at 3p21.1-3. Diagnosis was established by family history, clinical examination, immunofluorescence, and ultrastructural studies. The PvuII marker was informative in 16 families with a maximum lod score (Zmax) of 3.51 at recombination fraction (theta) = 0. The D3S1100 microsatellite was informative in 24 out of 25 families with Zmax = 6.8 at theta = 0.05 (Z = 4.94 at theta = 0) and no obligatory recombination events. These data strongly suggest that COL7A1 mutations cause EB in these families and, combined with previous studies, indicate locus homogeneity. The importance of anchoring fibrils for dermal-epidermal adhesion is further underlined. D3S1100 may later prove useful in prenatal diagnosis of this disease, if used in combination with other markers. Images PMID:7837248

  3. Amino acid delta13C analysis of hair proteins and bone collagen using liquid chromatography/isotope ratio mass spectrometry: paleodietary implications from intra-individual comparisons.

    PubMed

    Raghavan, Maanasa; McCullagh, James S O; Lynnerup, Niels; Hedges, Robert E M

    2010-03-15

    We report a novel method for the chromatographic separation and measurement of stable carbon isotope ratios (delta(13)C) of individual amino acids in hair proteins and bone collagen using the LC-IsoLink system, which interfaces liquid chromatography (LC) with isotope ratio mass spectrometry (IRMS). This paper provides baseline separation of 15 and 13 of the 18 amino acids in bone collagen and hair proteins, respectively. We also describe an approach to analysing small hair samples for compound-specific analysis of segmental hair sections. The LC/IRMS method is applied in a historical context by the delta(13)C analysis of hair proteins and bone collagen recovered from six individuals from Uummannaq in Greenland. The analysis of hair and bone amino acids from the same individual, compared for the first time in this study, is of importance in palaeodietary reconstruction. If hair proteins can be used as a proxy for bone collagen at the amino acid level, this validates compound-specific isotope studies using hair as a model for palaeodietary reconstruction. Our results suggest that a small offset observed in the bulk delta(13)C values of the hair and bone samples may be attributed to two factors: (i) amino acid compositional differences between hair and bone proteins, and (ii) differential turnover rates of the tissues and the amino acid pools contributing to their synthesis. This application proposes that hair may be a useful complementary or alternative source of compound-specific paleodietary information.

  4. Structure of collagen-glycosaminoglycan matrix and the influence to its integrity and stability.

    PubMed

    Bi, Yuying; Patra, Prabir; Faezipour, Miad

    2014-01-01

    Glycosaminoglycan (GAG) is a chain-like disaccharide that is linked to polypeptide core to connect two collagen fibrils/fibers and provide the intermolecular force in Collagen-GAG matrix (C-G matrix). Thus, the distribution of GAG in C-G matrix contributes to the integrity and mechanical properties of the matrix and related tissue. This paper analyzes the transverse isotropic distribution of GAG in C-G matrix. The angle of GAGs related to collagen fibrils is used as parameters to qualify the GAGs isotropic characteristic in both 3D and 2D rendering. Statistical results included that over one third of GAGs were perpendicular directed to collagen fibril with symmetrical distribution for both 3D matrix and 2D plane cross through collagen fibrils. The three factors tested in this paper: collagen radius, collagen distribution, and GAGs density, were not statistically significant for the strength of Collagen-GAG matrix in 3D rendering. However in 2D rendering, a significant factor found was the radius of collagen in matrix for the GAGs directed to orthogonal plane of Collagen-GAG matrix. Between two cross-section selected from Collagen-GAG matrix model, the plane cross through collagen fibrils was symmetrically distributed but the total percentage of perpendicular directed GAG was deducted by decreasing collagen radius. There were some symmetry features of GAGs angle distribution in selected 2D plane that passed through space between collagen fibrils, but most models showed multiple peaks in GAGs angle distribution. With less GAGs directed to perpendicular of collagen fibril, strength in collagen cross-section weakened. Collagen distribution was also a factor that influences GAGs angle distribution in 2D rendering. True hexagonal collagen packaging is reported in this paper to have less strength at collagen cross-section compared to quasi-hexagonal collagen arrangement. In this work focus is on GAGs matrix within the collagen and its relevance to anisotropy.

  5. 3-D ultrastructure and collagen composition of healthy and overloaded human tendon: evidence of tenocyte and matrix buckling

    PubMed Central

    Pingel, Jessica; Lu, Yinhui; Starborg, Tobias; Fredberg, Ulrich; Langberg, Henning; Nedergaard, Anders; Weis, MaryAnn; Eyre, David; Kjaer, Michael; Kadler, Karl E

    2014-01-01

    Achilles tendinopathies display focal tissue thickening with pain and ultrasonography changes. Whilst complete rupture might be expected to induce changes in tissue organization and protein composition, little is known about the consequences of non-rupture-associated tendinopathies, especially with regards to changes in the content of collagen type I and III (the major collagens in tendon), and changes in tendon fibroblast (tenocyte) shape and organization of the extracellular matrix (ECM). To gain new insights, we took biopsies from the tendinopathic region and flanking healthy region of Achilles tendons of six individuals with clinically diagnosed tendinopathy who had no evidence of cholesterol, uric acid and amyloid accumulation. Biochemical analyses of collagen III/I ratio were performed on all six individuals, and electron microscope analysis using transmission electron microscopy and serial block face-scanning electron microscopy were made on two individuals. In the tendinopathic regions, compared with the flanking healthy tissue, we observed: (i) an increase in the ratio of collagen III : I proteins; (ii) buckling of the collagen fascicles in the ECM; (iii) buckling of tenocytes and their nuclei; and (iv) an increase in the ratio of small-diameter : large-diameter collagen fibrils. In summary, load-induced non-rupture tendinopathy in humans is associated with localized biochemical changes, a shift from large-to small-diameter fibrils, buckling of the tendon ECM, and buckling of the cells and their nuclei. PMID:24571576

  6. 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.

  7. Collagen model peptides: Sequence dependence of triple-helix stability.

    PubMed

    Persikov, A V; Ramshaw, J A; Brodsky, B

    2000-01-01

    The triple helix is a specialized protein motif, found in all collagens as well as in noncollagenous proteins involved in host defense. Peptides will adopt a triple-helical conformation if the sequence contains its characteristic features of Gly as every third residue and a high content of Pro and Hyp residues. Such model peptides have proved amenable to structural studies by x-ray crystallography and NMR spectroscopy, suitable for thermodynamic and kinetic analysis, and a valuable tool in characterizing the binding activities of the collagen triple helix. A systematic approach to understanding the amino acid sequence dependence of the collagen triple helix has been initiated, based on a set of host-guest peptides of the form, (Gly-Pro-Hyp)(3)-Gly-X-Y-(Gly-Pro-Hyp)(4). Comparison of their thermal stabilities has led to a propensity scale for the X and Y positions, and the additivity of contributions of individual residues is now under investigation. The local and global stability of the collagen triple helix is normally modulated by the residues in the X and Y positions, with every third position occupied by Gly in fibril-forming collagens. However, in collagen diseases, such as osteogenesis imperfecta, a single Gly may be substituted by another residue. Host-guest studies where the Gly is replaced by various amino acids suggest that the identity of the residue in the Gly position affects the degree of destabilization and the clinical severity of the disease.

  8. Subfibrillar architecture and functional properties of collagen: a comparative study in rat tendons.

    PubMed Central

    Raspanti, M; Ottani, V; Ruggeri, A

    1990-01-01

    Collagen fibrils from different rat tendons have been investigated by freeze-fracture and transmission electron microscopy. In all cases, marked differences in both fibril morphology and subfibrillar organisation have been consistently found between the tendon core (composed of large and heterogeneous fibrils comprising tightly-packed, straight, parallel molecules) and sheath (showing small, uniform collagen fibrils with a helical arrangement of the molecules). The bio-mechanical requirements to which these tissues are subjected suggest, as do previous observations on other tissues, that a causal correlation exists between substructure and collagen fibril function. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 PMID:2272900

  9. 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.

  10. Structural and functional features of a collagen-binding matrix protein from the mussel byssus.

    PubMed

    Suhre, Michael H; Gertz, Melanie; Steegborn, Clemens; Scheibel, Thomas

    2014-02-26

    Blue mussels adhere to surfaces by the byssus, a holdfast structure composed of individual threads representing a collagen fibre reinforced composite. Here, we present the crystal structure and function of one of its matrix proteins, the proximal thread matrix protein 1, which is present in the proximal section of the byssus. The structure reveals two von Willebrand factor type A domains linked by a two-β-stranded linker yielding a novel structural arrangement. In vitro, the protein binds heterologous collagens with high affinity and affects collagen assembly, morphology and arrangement of its fibrils. By providing charged surface clusters as well as insufficiently coordinated metal ions, the proximal thread matrix protein 1 might interconnect other byssal proteins and thereby contribute to the integrity of the byssal threads in vivo. Moreover, the protein could be used for adjusting the mechanical properties of collagen materials, a function likely important in the natural byssus.

  11. Ventricular Fibrillation

    MedlinePlus

    ... machine that produces a magnetic field that aligns atomic particles in some of your cells. Radio waves ... fibrillation is caused by a change in the structure of your heart, such as scarred tissue from ...

  12. Atrial Fibrillation

    MedlinePlus

    ... information about the heart's electrical system and detailed animations, go to the Diseases and Conditions Index How ... can't restore a normal heart rhythm. The animation below shows atrial fibrillation. Click the "start" button ...

  13. 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.

  14. Differential anion effects on thermal stability of collagen in the dispersed and aggregated states.

    PubMed

    Russell, A E

    1974-03-01

    The effects of KCNS and KI on thermal transition temperatures of calf skin collagen molecules in dilute acid solution and precipitated collagen fibrils from the same source were compared as a function of salt concentration and pH. The two salts produced qualitatively similar effects on each collagen form, but the response shown by single collagen molecules in dilute solution differed from that observed for molecular aggregates present in native-type fibrils.

  15. UV damage of collagen: insights from model collagen peptides.

    PubMed

    Jariashvili, Ketevan; Madhan, Balaraman; Brodsky, Barbara; Kuchava, Ana; Namicheishvili, Louisa; Metreveli, Nunu

    2012-03-01

    Fibrils of Type I collagen in the skin are exposed to ultraviolet (UV) light and there have been claims that collagen photo-degradation leads to wrinkles and may contribute to skin cancers. To understand the effects of UV radiation on collagen, Type I collagen solutions were exposed to the UV-C wavelength of 254 nm for defined lengths of time at 4°C. Circular dichroism (CD) experiments show that irradiation of collagen leads to high loss of triple helical content with a new lower thermal stability peak and SDS-gel electrophoresis indicates breakdown of collagen chains. To better define the effects of UV radiation on the collagen triple-helix, the studies were extended to peptides which model the collagen sequence and conformation. CD studies showed irradiation for days led to lower magnitudes of the triple-helix maximum at 225 nm and lower thermal stabilities for two peptides containing multiple Gly-Pro-Hyp triplets. In contrast, the highest radiation exposure led to little change in the T(m) values of (Gly-Pro-Pro)(10) and (Ala-Hyp-Gly)(10) , although (Gly-Pro-Pro)(10) did show a significant decrease in triple helix intensity. Mass spectroscopy indicated preferential cleavage sites within the peptides, and identification of some of the most susceptible sites of cleavage. The effect of radiation on these well defined peptides gives insight into the sequence and conformational specificity of photo-degradation of collagen.

  16. The Role of Collagen Quaternary Structure in the Platelet:Collagen Interaction

    PubMed Central

    Brass, Lawrence F.; Bensusan, Howard B.

    1974-01-01

    We have investigated whether collagen queternary structure is required for the platelet: collagen interaction. Quaternary structure refers to the assembly of collagen monomers (tropocollagen) into polymers (native-type fibrils). Purified monomeric collagen was prepared from acetic acid extracts of fetal calfskin. Polymeric collagen was prepared by dispersion of bovine Achilles tendon collagen and by incubation of monomeric collagen at 37°C and pH 7.4. The state of polymerization was confirmed by electron microscopy. Release of platelet serotonin in the absence of platelet aggregation was used to determine the effectiveness of the platelet: collagen interaction. All forms of collagen produced serotonin release only after a lag period, but polymeric collagen gave a shorter lag period than did monomeric collagen. Monomeric collagen was also quanidinated selectively to convert collagen lysine groups to homoarginine, while leaving the arrangement of polar groups intact. Guanidination of monomeric collagen increased the rate of polymerization and reduced the lag time in serotonin release. Glucosamine (17 mM) retarded polymerization and inhibited the release of platelet serotonin by monomeric collagen but had little effect on release produced by thrombin or polymeric collagen. At the same concentration, glucosamine did not reduce the sensitivity of platelets to stimulation by collagen or block the platelet: collagen interaction. The only effect of glucosamine was on the collagen: collagen interaction. Galactosamine had a similar effect, but glucose, galactose, and N-acetylglycosamine had no effect. We conclude from this data that collagen monomers cannot effectively interact with platelets and that, therefore, collagen quaternary structure has a role in the recognition of collagen by platelets. PMID:4215825

  17. 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.

  18. Spiroplasma fibrils.

    PubMed

    Williamson, D L; Brink, P R; Zieve, G W

    1984-09-01

    A fundamental question in biology concerns the morphology of spiroplasmas: How does a wall-less microorganism maintain its characteristic morphology as a helical filament? An answer to this question began to form when it was discovered that spiroplasmas treated with any of a number of detergents (sodium deoxycholate, Triton X-100, Nonidet P-40) release their cytoplasmic contents. If this procedure is performed on a formvar-coated electron microscope grid and the resultant preparation negatively stained and observed by transmission electron microscopy, numerous striated microfibrils can be seen where spiroplasmas once were. The fibrils are of varying lengths, 4 nm in width, and show a striation repeat at 9 nm along their length. It is not possible to discern from the pattern of the released fibrils just how they are organized within the intact spiroplasma; nor is it yet possible to identify a fibrillar substructure in thin sections or in freeze-fractured organisms. Townsend and his colleagues at the John Innes Institute in Norwich, UK, purified fibrils by density gradient centrifugation. SDS-PAGE showed the fibrils to consist of a 55,000-dalton protein recognizable in the four serogroups tested by protein blotting with an antiserum made against the PAGE-separated protein. The presence of fibrils is a feature common to all spiroplasma, regardless of whether they are helical or nonhelical, as in the Ixodes tick-derived spiroplasma or Townsend's ASP-1 strain of Spiroplasma citri. We have employed gentle demembranation treatments that preserve filamentous substructure in an effort to elucidate the organization of the fibrils within the spiroplasma cell.

  19. WOUND HEALING AND COLLAGEN FORMATION

    PubMed Central

    Ross, Russell; Benditt, Earl P.

    1961-01-01

    The regular sequence encountered in healing guinea pig skin wounds has been examined by methods of light and electron microscopy. Observations on cell populations, their fine structure, and fibril formation in the connective tissue have been made. Linear incisions in the skin of normal female guinea pigs weighing 300 to 350 grams were allowed to heal. The wounds were then excised, fixed with buffered 2 per cent osmium tetroxide, and postfixed in neutral buffered formalin, at 16 and 24 hours and at 3, 5, 9, and 14 days after wounding. They were then embedded in epoxy resin. In the inflammatory phase the exudate observed in the early wounds consists largely of polymorphonuclear neutrophilic leukocytes, macrophages, fibrin, and free extracellular organelles from the disrupted inflammatory cells. These organelles later appear in vacuoles in the cytoplasm of the macrophages. Fibroblasts first appear at 24 hours, and show extensive development and dilatation of the endoplasmic reticulum, which sometimes contains moderately dense flocculent material. In addition, these fibroblasts have enlarged mitochondria and condensations of filamentous material within the cytoplasm near the cell surface. Occasional myelin figures and moderately dense, 0.5 to 1.0 micron bodies are found within the cytoplasm of the early fibroblasts. Collagen fibrils are first seen at 3 days extracellularly near the cell surfaces. They appear at the later times in two populations of sizes. With increasing wound age the fibroblasts retain their morphology and the wounds decrease in cellularity concomitantly with the formation of increasing amounts of collagen. Several proposed mechanisms of collagen fibril formation are discussed in relation to the observed phenomena. The problem of correlating fibril diameter with the appearance of the periodic structure of collagen in relation to the minimal size fibril which would be anticipated to display this appearance is discussed. PMID:14494202

  20. Second harmonic generation in collagen

    NASA Astrophysics Data System (ADS)

    Reiser, Karen M.; Stoller, Patrick; Celliers, Peter; Rubenchik, Alexander; Bratton, Clay; Yankelevich, Diego

    2003-11-01

    Collagen possesses a strong second order nonlinear susceptibility; when it is irradiated with intense laser light, some of the reflected and transmitted light will have twice the frequency of the incident beam, a phenomenon known as second harmonic generation (SHG). Polarization modulation of an ultra-short pulse laser beam can be used to simultaneously measure collagen fiber orientation, SHG intensity, and a parameter related to the second order non-linear susceptibility. This technique has made it possible to discriminate among patterns of fibrillar orientation in many tissues. In the present study the role that organizational complexity plays in the relationship between nonlinear optical properties and collagen structure is investigated. As a component of tissues and organs, collagen"s structure and function is inextricably intertwined with that of the many other matrix components; to what extent do these noncollagenous components affect its nonlinear properties? To answer this, we investigated SHG in two different collagenous tissues, liver and cartilage; in addition we looked at the effect of progressive pathological changes in these tissues on SHG. At the other end of the spectrum, we studied collagen organized at the minimal level of complexity necessary for SHG detection: fibrils generated from solutions containing only a single type of collagen. Data obtained from these studies suggest that collagen"s strong nonlinear susceptibility, a property no other biologically significant macromolecule shares to the same degree, may serve as more than the basis of a novel imaging device for soft tissue. Collagen"s nonlinear optical properties in conjunction with its vast capacity for self-initiated conformational change--through self-assembly, site recognition, post-translational modification, and the like -make it an attractive candidate molecule for any of several demanding engineering applications, such as nanopatterning.

  1. Collagen cross-linking: insights on the evolution of metazoan extracellular matrix

    PubMed Central

    Rodriguez-Pascual, Fernando; Slatter, David Anthony

    2016-01-01

    Collagens constitute a large family of extracellular matrix (ECM) proteins that play a fundamental role in supporting the structure of various tissues in multicellular animals. The mechanical strength of fibrillar collagens is highly dependent on the formation of covalent cross-links between individual fibrils, a process initiated by the enzymatic action of members of the lysyl oxidase (LOX) family. Fibrillar collagens are present in a wide variety of animals, therefore often being associated with metazoan evolution, where the emergence of an ancestral collagen chain has been proposed to lead to the formation of different clades. While LOX-generated collagen cross-linking metabolites have been detected in different metazoan families, there is limited information about when and how collagen acquired this particular modification. By analyzing telopeptide and helical sequences, we identified highly conserved, potential cross-linking sites throughout the metazoan tree of life. Based on this analysis, we propose that they have importantly contributed to the formation and further expansion of fibrillar collagens. PMID:27876853

  2. Influence of collagen source on fibrillar architecture and properties of vitrified collagen membranes.

    PubMed

    Majumdar, Shoumyo; Guo, Qiongyu; Garza-Madrid, Marcos; Calderon-Colon, Xiomara; Duan, Derek; Carbajal, Priscilla; Schein, Oliver; Trexler, Morgana; Elisseeff, Jennifer

    2016-02-01

    Collagen vitrigel membranes are transparent biomaterials characterized by a densely organized, fibrillar nanostructure that show promise in the treatment of corneal injury and disease. In this study, the influence of different type I collagen sources and processing techniques, including acid-solubilized collagen from bovine dermis (Bov), pepsin-solubilized collagen from human fibroblast cell culture (HuCC), and ficin-solubilized collagen from recombinant human collagen expressed in tobacco leaves (rH), on the properties of the vitrigel membranes was evaluated. Postvitrification carbodiimide crosslinking (CX) was also carried out on the vitrigels from each collagen source, forming crosslinked counterparts BovXL, HuCCXL, and rHXL, respectively. Collagen membrane ultrastructure and biomaterial properties were found to rely heavily on both collagen source and crosslinking. Bov and HuCC samples showed a random fibrillar organization of collagen, whereas rH vitrigels showed remarkable regional fibril alignment. After CX, light transmission was enhanced in all groups. Denaturation temperatures after CX increased in all membranes, of which the highest increase was seen in rH (14.71°C), suggesting improved thermal stability of the collagen fibrils in the membranes. Noncrosslinked rH vitrigels may be reinforced through CX to reach levels of mechanical strength and thermal stability comparable to Bov.

  3. Choosing a particular oral anticoagulant and dose for stroke prevention in individual patients with non-valvular atrial fibrillation: part 2.

    PubMed

    Diener, Hans-Christoph; Aisenberg, James; Ansell, Jack; Atar, Dan; Breithardt, Günter; Eikelboom, John; Ezekowitz, Michael D; Granger, Christopher B; Halperin, Jonathan L; Hohnloser, Stefan H; Hylek, Elaine M; Kirchhof, Paulus; Lane, Deirdre A; Verheugt, Freek W A; Veltkamp, Roland; Lip, Gregory Y H

    2016-02-04

    The choice of oral anticoagulant (OAC) for patients with atrial fibrillation (AF) may be influenced by individual clinical features or by patterns of risk factors and comorbidities. We reviewed analyses of subgroups of patients from trials of vitamin K antagonists vs. non-vitamin K oral anticoagulants (NOACs) for stroke prevention in AF with the aim to identify patient groups who might benefit from a particular OAC more than from another. In addition, we discuss the timing of initiation of anticoagulation. In the second of a two-part review, we discuss the use of NOAC for stroke prevention in the following subgroups of patients with AF: (vii) secondary stroke prevention in patients after stroke or transient ischaemic attack (TIA), (viii) patients with acute stroke requiring thrombolysis or thrombectomy, (ix) those initiating or restarting OAC treatment after stroke or TIA, (x) those with renal impairment on dialysis, (xi) the elderly, (xii) those at high risk of gastrointestinal bleeding, and (xiii) those with hypertension. In addition, we discuss adherence and compliance. Finally, we present a summary of treatment suggestions. In specific subgroups of patients with AF, evidence supports the use of particular NOACs and/or particular doses of anticoagulant. The appropriate choice of treatment for these subgroups will help to promote optimal clinical outcomes.

  4. 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.

  5. Atrial Fibrillation.

    PubMed

    Zimetbaum, Peter

    2017-03-07

    This issue provides a clinical overview of atrial fibrillation, focusing on diagnosis, treatment, and practice improvement. The content of In the Clinic is drawn from the clinical information and education resources of the American College of Physicians (ACP), including MKSAP (Medical Knowledge and Self-Assessment Program). Annals of Internal Medicine editors develop In the Clinic in collaboration with the ACP's Medical Education and Publishing divisions and with the assistance of additional science writers and physician writers.

  6. Atrial Fibrillation: Complications

    MedlinePlus

    ... this page please turn JavaScript on. Feature: Atrial Fibrillation Atrial Fibrillation: Complications Past Issues / Winter 2015 Table of Contents ... two major complications—stroke and heart failure. Atrial Fibrillation and Stroke Click to enlarge image This illustration ...

  7. Atrial Fibrillation: Treatment

    MedlinePlus

    ... this page please turn JavaScript on. Feature: Atrial Fibrillation Atrial Fibrillation: Treatment Past Issues / Winter 2015 Table of Contents Treatment for atrial fibrillation depends on how often you have symptoms, how ...

  8. Individual isomers of conjugated linoleic acid reduce inflammation associated with established collagen-induced arthritis in DBA/1 mice.

    PubMed

    Huebner, Shane M; Campbell, James P; Butz, Daniel E; Fulmer, Tyler G; Gendron-Fitzpatrick, Annette; Cook, Mark E

    2010-08-01

    Previously, dietary conjugated linoleic acid [(CLA), an equal mixture of cis-9, trans-11 (c9t11) and trans-10, cis-12 (t10c12) CLA isomers], was found to reduce inflammation in the murine collagen antibody-induced arthritis model, but less so in the murine collagen-induced arthritis (CIA) model, an arthritic model dependent upon acquired immunity. Because CLA is known to alter the acquired immune response, it was hypothesized that feeding CLA after the establishment of arthritis would reduce paw swelling in the CIA model. In this study, upon the establishment of arthritic symptoms, mice were randomized to the following dietary treatments: corn oil (CO) control (n = 6), 0.5% c9t11-CLA (n = 8), 0.5% t10c12-CLA (n = 6), or 1% combined CLA (1:1 c9t11:t10c12-CLA, n = 6). Paws were scored for severity of arthritis and measured for changes in thickness during an 84-d study period. Dietary c9t11- and combined-CLA similarly decreased the arthritic score (29%, P = 0.036, P = 0.049, respectively, when normalized to initial score) and paw thickness (0.11 mm, P = 0.027, P = 0.035, respectively) compared with CO. Dietary t10c12-CLA reduced the arthritic score (41%, P = 0.007 when normalized) and paw thickness (0.12 mm, P = 0.013) relative to CO. Reduced interleukin-1beta on d 7 and 21 for all CLA treatments (n = 3) relative to CO suggested that antiinflammatory effects of CLA isomers might work by common mechanisms of known pathways involved in chronic inflammation. In conclusion, dietary CLA reduced inflammation associated with CIA, and both c9t11-CLA and t10c12-CLA exhibited antiinflammatory effects.

  9. Collagen-type specificity of glycoprotein VI as a determinant of platelet adhesion.

    PubMed

    Jung, Stephanie M; Takemura, Yukitoshi; Imamura, Yasutada; Hayashi, Toshihiko; Adachi, Eijiro; Moroi, Masaaki

    2008-02-01

    Of the two physiologically important platelet collagen receptors, glycoprotein (GP) VI is the receptor responsible for platelet activation. However, its reactivities towards different types of vascular collagen have not been directly and quantitatively analysed with collagen preparations of defined composition, although the other major platelet collagen receptor integrin alpha(2)beta(1) was shown to react with collagen types I-VI and VIII under either static or flow conditions. We analysed the collagen type specificity of GPVI binding to identify the physiological contribution of the various vascular collagens and how platelet reactivity towards the various collagens may be affected by fibril size. We used two methods to analyse the binding of recombinant GPVI (GPVI-Fc(2)) to different types of bovine collagen: binding to collagen microparticles in suspension and binding to immobilized collagen. GPVI-Fc(2) bound to type I-III collagens that can form large fibrils, but not to type V that only forms small fibrils. The apparent GPVI binding to types IV and V could be ascribed to type I collagen that was a contaminant in each of these preparations. Kinetic analyses of the binding data showed that type III collagen fibrils have both a higher Kd and Bmax than types I and II. Flow adhesion studies demonstrated that type III collagen supports the formation of larger platelet aggregates than type I. Our present results suggest that the physiological importance of type III collagen is to induce thrombus formation. Furthermore, these studies indicate that GPVI mainly binds to collagen types that can form large collagen fibrils.

  10. Atrial fibrillation - discharge

    MedlinePlus

    Auricular fibrillation - discharge; A-fib - discharge; AF - discharge; Afib - discharge ... been in the hospital because you have atrial fibrillation . This condition occurs when your heart beats faster ...

  11. Discoidin domain receptor 2 inhibits fibrillogenesis of collagen type 1.

    PubMed

    Mihai, Cosmin; Iscru, Daniel F; Druhan, Lawrence J; Elton, Terry S; Agarwal, Gunjan

    2006-09-01

    Discoidin domain receptors (DDR1 and DDR2) are widely expressed cell-surface receptors, which bind to and are activated by collagens, including collagen type 1. Activation of DDRs and the resulting downstream signaling is known to regulate the extracellular matrix. However, little is known about how DDRs interact with collagen and its direct impact on collagen regulation. Here, we have established that by binding to collagen, the extracellular domain (ECD) of DDR2 inhibits collagen fibrillogenesis and alters the morphology of collagen type 1 fibers. Our in vitro assays utilized DDR2-Fc fusion proteins, which contain only the ECD of DDR2. Using surface plasmon resonance, we confirmed that further oligomerization of DDR2-Fc (by means of anti-Fc antibody) greatly enhances its binding to immobilized collagen type 1. Collagen turbidity measurements and biochemical assays indicated that DDR2 delays the formation of collagen fibrils. Atomic force microscopy of soluble collagen revealed that a predominately monomeric state of collagen was present with DDR2, while control solutions had an abundance of polymeric collagen. Transmission electron microscopy of collagen fibers, showed that the native periodic banded structure of collagen fibers was weakened and nearly absent in the presence of DDR2. Further, using a cell-based assay we demonstrate that overexpression of full length DDR2 inhibits fibrillogenesis of collagen type 1. Our results demonstrate a novel and important functional role of the DDR2 ECD that may contribute to collagen regulation via modulation of fibrillogenesis.

  12. Post-discharge electrocardiogram Holter monitoring in recently hospitalised individuals with chronic atrial fibrillation to enhance therapeutic monitoring and identify potentially predictive phenotypes.

    PubMed

    Ball, Jocasta; Carrington, Melinda J; Thompson, David R; Horowitz, John D; Stewart, Simon

    2015-10-01

    Atrial fibrillation (AF) is the most common cardiac arrhythmia managed in clinical practice. Maintenance of intended rate or rhythm control following hospitalisation is a key therapeutic goal. The purpose of this study was to assess post-discharge maintenance of intended AF control and classify potentially predictive heart rate (HR) phenotypes via electrocardiogram (ECG) Holter monitoring. In a sub-study of a multicentre randomised controlled trial comparing AF-specific management with usual care, 24-hour ECG Holter monitoring was undertaken in 133 patients 7-14 days post-discharge. Intended rate and rhythm control were compared to Holter data. Analysis of the frequency distribution of mean hour-to-hour differences identified those with labile HRs. Mean age was 71 ± 10 years, 67 (50%) were male and mean HR was 72 ± 14 bpm. Most (89%) had persistent AF (median time in AF=39% (IQR 0-100%)). Uncontrolled HR (>90 bpm for >10% of recording) occurred in 35 (26%) patients and 49 (37%) patients did not achieve their intended rate (n=26) or rhythm control (n=23). Patients in the upper quartile of mean hour-to-hour HR variability were identified as persistently labile (n=33). A further group (n=22) with periodically labile HRs was identified. Those with coronary artery disease (OR 0.34; 95% CI 0.13-0.91, p=0.033) or renal disease/dysfunction (OR 0.24; 95% CI 0.06-0.98, p=0.047) were less likely to demonstrate HR stability (n=78). Post-discharge ECG Holter monitoring of AF patients represents a valuable tool to identify deviations in intended rhythm/rate control and adjust therapeutic management accordingly. It may also identify individuals who demonstrate labile HRs. © The European Society of Cardiology 2014.

  13. In vitro crystal growth of octacalcium phosphate on type 1 collagen fiber

    NASA Astrophysics Data System (ADS)

    Iijima, Mayumi; Moriwaki, Yutaka; Kuboki, Yoshinori

    1994-04-01

    Octacalcium phosphate crystals grew on tendon collagen, which was sliced into a disk, in an experimental system where Ca2(+) and PO3(-)(sub 4) ions diffused into the collagen disk from mutually opposite sides. Crystal growth on collagen fibrils reflected the intrinsic property of the collagenous matrix. The results indicate that the collagenous matrix modulates the ionic diffusion and therefore regulates the crystal growth.

  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. Collagen organization in canine myxomatous mitral valve disease: an x-ray diffraction study.

    PubMed

    Hadian, Mojtaba; Corcoran, Brendan M; Han, Richard I; Grossmann, J Günter; Bradshaw, Jeremy P

    2007-10-01

    Collagen fibrils, a major component of mitral valve leaflets, play an important role in defining shape and providing mechanical strength and flexibility. Histopathological studies show that collagen fibrils undergo dramatic changes in the course of myxomatous mitral valve disease in both dogs and humans. However, little is known about the detailed organization of collagen in this disease. This study was designed to analyze and compare collagen fibril organization in healthy and lesional areas of myxomatous mitral valves of dogs, using synchrotron small-angle x-ray diffraction. The orientation, density, and alignment of collagen fibrils were mapped across six different valves. The findings reveal a preferred collagen alignment in the main body of the leaflets between two commissures. Qualitative and quantitative analysis of the data showed significant differences between affected and lesion-free areas in terms of collagen content, fibril alignment, and total tissue volume. Regression analysis of the amount of collagen compared to the total tissue content at each point revealed a significant relationship between these two parameters in lesion-free but not in affected areas. This is the first time this technique has been used to map collagen fibrils in cardiac tissue; the findings have important applications to human cardiology.

  16. Anisotropy of chemical bonds in collagen molecules studied by X-ray absorption near-edge structure (XANES) spectroscopy.

    PubMed

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

    2012-03-16

    Collagen type I fibrils are the major building blocks of connective tissues. Collagen fibrils are anisotropic supramolecular 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.

  17. 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.

  18. Characterization of collagenous matrix assembly in a chondrocyte model system

    PubMed Central

    Yingst, Sorcha; Bloxham, Kaci; Warner, Lisa R.; Brown, Raquel J.; Cole, Jennifer; Kenoyer, Linda; Knowlton, William B.; Oxford, Julia Thom

    2010-01-01

    Collagen is a major component of the newly synthesized pericellular microenvironment of chondrocytes. Collagen types II, IX, and XI are synthesized and assembled into higher ordered complexes by a mechanism in which type XI collagen plays a role in nucleation of new fibrils, and in limiting fibril diameter. This study utilizes a cell line derived from the Swarm rat chondrosarcoma that allows the accumulation and assembly of pericellular matrix. Immunofluorescence and atomic force microscopy were used to assess early intermediates of fibril formation. Results indicate that this cell line synthesizes and secretes chondrocyte-specific pericellular matrix molecules including types II, IX, and XI collagen and is suitable for the study of newly synthesized collagen matrix under the experimental conditions used. AFM data indicate that small fibrils or assemblies of microfibrils are detectable and may represent precursors of the ~20 nm thin fibrils reported in cartilage. Treatment with hyaluronidase indicates that the dimensions of the small fibrils may be dependent upon the presence of hyaluronan within the matrix. This study provides information on the composition and organization of the newly synthesized extracellular matrix that plays a role in establishing the material properties and performance of biological materials such as cartilage. PMID:18496861

  19. 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

  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. 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

  2. Defining the hierarchical organisation of collagen VI microfibrils at nanometre to micrometre length scales.

    PubMed

    Godwin, Alan R F; Starborg, Tobias; Sherratt, Michael J; Roseman, Alan M; Baldock, Clair

    2017-04-01

    Extracellular matrix microfibrils are critical components of connective tissues with a wide range of mechanical and cellular signalling functions. Collagen VI is a heteromeric network-forming collagen which is expressed in tissues such as skin, lung, blood vessels and articular cartilage where it anchors cells into the matrix allowing for transduction of biochemical and mechanical signals. It is not understood how collagen VI is arranged into microfibrils or how these microfibrils are arranged into tissues. Therefore we have characterised the hierarchical organisation of collagen VI across multiple length scales. The frozen hydrated nanostructure of purified collagen VI microfibrils was reconstructed using cryo-TEM. The bead region has a compact hollow head and flexible tail regions linked by the collagenous interbead region. Serial block face SEM imaging coupled with electron tomography of the pericellular matrix (PCM) of murine articular cartilage revealed that the PCM has a meshwork-like organisation formed from globular densities ∼30nm in diameter. These approaches can characterise structures spanning nanometer to millimeter length scales to define the nanostructure of individual collagen VI microfibrils and the micro-structural organisation of these fibrils within tissues to help in the future design of better mimetics for tissue engineering. Cartilage is a connective tissue rich in extracellular matrix molecules and is tough and compressive to cushion the bones of joints. However, in adults cartilage is poorly repaired after injury and so this is an important target for tissue engineering. Many connective tissues contain collagen VI, which forms microfibrils and networks but we understand very little about these assemblies or the tissue structures they form. Therefore, we have use complementary imaging techniques to image collagen VI microfibrils from the nano-scale to the micro-scale in order to understand the structure and the assemblies it forms. These

  3. Molecular dynamics simulations on networks of heparin and collagen.

    PubMed

    Kulke, Martin; Geist, Norman; Friedrichs, Wenke; Langel, Walter

    2017-06-01

    Synthetic scaffolds containing collagen (Type I) are of increasing interest for bone tissue engineering, especially for highly porous biomaterials in combination with glycosaminoglycans. In experiments the integration of heparin during the fibrillogenesis resulted in different types of collagen fibrils, but models for this aggregation on a molecular scale were only tentative. We conducted molecular dynamic simulations investigating the binding of heparin to collagen and the influence of the telopeptides during collagen aggregation. This aims at explaining experimental findings on a molecular level. Novel structures for N- and C-telopeptides were developed with the TIGER2 replica exchange algorithm and dihedral principle component analysis. We present an extended statistical analysis of the mainly electrostatic interaction between heparin and collagen and identify several binding sites. Finally, we propose a molecular mechanism for the influence of glycosaminoglycans on the morphology of collagen fibrils. Proteins 2017; 85:1119-1130. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  4. 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.

  5. 96-Well plate assays for measuring collagenase activity using (3)H-acetylated collagen.

    PubMed

    Koshy, P J; Rowan, A D; Life, P F; Cawston, T E

    1999-11-15

    We describe two alternative assays for measuring collagenolytic activity using (3)H-acetylated collagen. Both assays have been developed for the 96-well plate format and measure the amount of radiolabeled collagen fragments released into the supernatant from an insoluble (3)H-acetylated collagen fibril preparation. The first method separates digested solubilized fragments from the intact fibril by sedimentation of the undigested collagen by centrifugation. The second method achieves this separation by filtration of the supernatant through the membrane of a 96-well filtration plate which retains the undigested collagen fibril. Both methods give linear dose- and time-dependent responses of collagenase activity > or = 70% of total collagen lysis. In addition, both assays can be simply modified to measure tissue inhibitors of metalloproteinases (TIMPs) inhibitory activity, which is also linear between 20 and 75% of total collagen lysis with the amount of TIMP added.

  6. Collagen network strengthening following cyclic tensile loading.

    PubMed

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

    2016-02-06

    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.

  7. Bacterial collagen-binding domain targets undertwisted regions of collagen

    PubMed Central

    Philominathan, Sagaya Theresa Leena; Koide, Takaki; Matsushita, Osamu; Sakon, Joshua

    2012-01-01

    Clostridium histolyticum collagenase causes extensive degradation of collagen in connective tissue that results in gas gangrene. The C-terminal collagen-binding domain (CBD) of these enzymes is the minimal segment required to bind to a collagen fibril. CBD binds unidirectionally to the undertwisted C-terminus of triple helical collagen. Here, we examine whether CBD could also target undertwisted regions even in the middle of the triple helix. Collageneous peptides with an additional undertwisted region were synthesized by introducing a Gly → Ala substitution [(POG)xPOA(POG)y]3, where x + y = 9 and x > 3). 1H–15N heteronuclear single quantum coherence nuclear magnetic resonance (HSQC NMR) titration studies with 15N-labeled CBD demonstrated that the minicollagen binds to a 10 Å wide 25 Å long cleft. Six collagenous peptides each labeled with a nitroxide radical were then titrated with 15N-labeled CBD. CBD binds to either the Gly → Ala substitution site or to the C-terminus of each minicollagen. Small-angle X-ray scattering measurements revealed that CBD prefers to bind the Gly → Ala site to the C-terminus. The HSQC NMR spectra of 15N-labeled minicollagen and minicollagen with undertwisted regions were unaffected by the titration of unlabeled CBD. The results imply that CBD binds to the undertwisted region of the minicollagen but does not actively unwind the triple helix. PMID:22898990

  8. An Agent-Based Discrete Collagen Fiber Network Model of Dynamic Traction Force-Induced Remodeling.

    PubMed

    Reinhardt, James W; Gooch, Keith

    2017-09-21

    We developed an agent-based model that incorporates repetitively applied traction force within a discrete fiber network to understand how microstructural properties of the network influence mechanical properties and traction force-induced remodeling. An important difference between our model and similar finite-element models is that by implementing more biologically-realistic dynamic traction, we can explore a greater range of matrix remodeling. Here, we validated our model by reproducing qualitative trends observed in three sets of experimental data reported by others: tensile and shear testing of cell-free collagen gels, collagen remodeling around a single isolated cell, and collagen remodeling between pairs of cells. In response to tensile and shear strain, simulated acellular networks exhibited biphasic stress-strain curves indicative of strain-stiffening. Our data support the notion that strain-stiffening might occur as individual fibrils successively align along the axis of strain and become engaged in tension. In simulations with a single, contractile cell, peak collagen displacement occurred closest to the cell and decreased with increasing distance. In simulations with two cells, compaction of collagen between cells appeared inversely related to the initial distance between cells. Further analysis revealed strain energy was relatively uniform around the outer surface of cells separated by 250 microns, but became increasingly non-uniform as the distance between cells decreased. This pattern was partly attributable to the pattern of collagen compaction. These findings are of interest because fibril alignment, density, and strain energy may each contribute to contact guidance during tissue morphogenesis.

  9. Effect of oxy radicals on several types of collagen.

    PubMed

    Monboisse, J C; Poulin, G; Braquet, P; Randoux, A; Ferradini, C; Borel, J P

    1984-01-01

    Fibrils of collagen reconstituted in vitro by dialysis against sodium formate are exposed to free oxy radicals generated by three different systems: (i) xanthine oxidase + hypoxanthine, (ii) gamma-rays originating from a cobalt bomb; (iii) pulse radiolysis in a particle accelerator. A degradation of the collagen fibres is demonstrated by determination of the amount of hydroxyproline-containing peptides in the supernatant after incubation. Types I and III collagen are sensitive to the effect, whereas type V collagen is not. The effect persists when collagen is specially delipidated.

  10. Feasibility study of the natural derived chitosan dialdehyde for chemical modification of collagen.

    PubMed

    Liu, Xinhua; Dan, Nianhua; Dan, Weihua; Gong, Juxia

    2016-01-01

    The aim of this study is to evaluate the chemical crosslinking effects of the natural derived chitosan dialdehyde (OCS) on collagen. Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC) and circular dichroism (CD) measurements suggest that introducing OCS might not destroy the natural triple helix conformation of collagen but enhance the thermal-stability of collagen. Meanwhile, a denser fibrous network of cross-linked collagen is observed by atomic force microscopy. Further, scanning electron microscopy (SEM) and aggregation kinetics analysis confirm that the fibrillation process of collagen advances successfully and OCS could lengthen the completion time of collagen fibrillogenesis but raise the reconstitution rate of collagen fibrils or microfibrils. Besides, the cytocompatibility analysis implies that when the dosage of OCS is less than 15%, introducing OCS into collagen might be favorable for the cell's adhesion, growth and proliferation. Taken as a whole, the present study demonstrates that OCS might be an ideal crosslinker for the chemical fixation of collagen.

  11. The synergic role of collagen and citrate in stabilizing amorphous calcium phosphate precursors with platy morphology.

    PubMed

    Delgado-López, José Manuel; Bertolotti, Federica; Lyngsø, Jeppe; Pedersen, Jan Skov; Cervellino, Antonio; Masciocchi, Norberto; Guagliardi, Antonietta

    2017-02-01

    Bioinspired in vitro collagen mineralization experiments have been performed in the presence of citrate and the combined role of the two bone organic matrix components in controlling mineral formation was investigated for the first time. Mineralized and non-mineralized collagen fibrils have been in depth characterized by combining small- and wide-angle X-ray scattering (SAXS/WAXS) techniques with Atomic Force Microscopy (AFM) imaging. A synergic effect of collagen and citrate in driving the formation of long-term stable amorphous calcium phosphate (ACP) nanoparticles with platy morphology was found. AFM images on mineralized collagen fibrils revealed that some of the ACP nanoparticles were deposited on the intramolecular nanoscopic holes of collagen fibrils. Citrate is an important component of the bone organic matrix but its specific role in bone mineralization is presently unclear. In this work, bioinspired in vitro collagen mineralization experiments in the presence of citrate have been carried out and the combined role of collagen and citrate in controlling mineral formation has been addressed for the first time. Through X-ray scattering and Atomic Force Microscopy characterizations on mineralized and non-mineralized collagen fibrils, we have found that citrate in synergy with collagen stabilizes an amorphous calcium phosphate (ACP) phase with platy morphology over one week and controls its deposition on collagen fibrils. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  12. 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

  13. 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.

  14. 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

  15. 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

  16. 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.

  17. In vitro, interaction of homotrimers with heterotrimers of type I collagen

    NASA Astrophysics Data System (ADS)

    Han, Sejin; Losert, Wolfgang; Leikin, Sergey

    2007-03-01

    The dominant mutations in type I collagen cause a group of diseases, often termed collagen, or connective tissue, diseases: for example, Osteogenesis Imperfecta (OI) characterized by bone fragility and skeletal deformity. The mechanism in which collagen mutations affect on the diseases is still unknown. To understand the fibril assembly and their interactions might provide a key to approaching the cause of the collagen diseases. This study demonstrates that the self-assembly, termed fibrillogenesis, of type I collagen homozygous mutations revealed substantial differences in the kinetics with the absence of lag time and in the morphology of 3D fibril network structure. The heterotrimers (normal) and homotrimers (mutant) in mixtures were segregated within the same fibrils during fibrillogenesis, in correspondence between confocal microscopy and thermodynamic measurements. The efficiency for self-assembly of the homotrimers into fibrils was markedly reduced, while that of the heterotrimers was not affected by the presence of homotrimers with no change in solubility.

  18. 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. Copyright © 2016 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

  19. The essential role of fetuin in the serum-induced calcification of collagen.

    PubMed

    Toroian, Damon; Price, Paul A

    2008-02-01

    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. Our goal is to understand the mechanism of fibril mineralization, and as a first step we recently determined the size exclusion characteristics of the fibril. This study indicates that apatite crystals up to 12 unit cells in size can access the water within the fibril while molecules larger than a 40-kDa protein are excluded. We proposed a novel mechanism for fibril mineralization based on these observations, one that relies exclusively on agents excluded from the fibril. One agent generates crystals outside the fibril, some of which diffuse into the fibril and grow, and the other selectively inhibits crystal growth outside of the fibril. We have tested this mechanism by examining the impact of removing the major serum inhibitor of apatite growth, fetuin, on the serum-induced calcification of collagen. The results of this test show that fetuin determines the location of serum-driven mineralization: in fetuin's presence, mineral forms only within collagen fibrils; in fetuin's absence, mineral forms only in solution outside the fibrils. The X-ray diffraction spectrum of serum-induced mineral is comparable to the spectrum of bone crystals. These observations show that serum calcification activity consists of an as yet unidentified agent that generates crystal nuclei, some of which diffuse into the fibril, and fetuin, which favors fibril mineralization by selectively inhibiting the growth of crystals outside the fibril.

  20. 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

  1. Matrix metalloproteinase interactions with collagen and elastin

    PubMed Central

    Van Doren, Steven R.

    2015-01-01

    Most abundant in the extracellular matrix are collagens, joined by elastin that confers elastic recoil to the lung, aorta, and skin. These fibrils are highly resistant to proteolysis but can succumb to a minority of the matrix metalloproteinases (MMPs). Considerable inroads to understanding how such MMPs move to the susceptible sites in collagen and then unwind the triple helix of collagen monomers have been gained. The essential role in unwinding of the hemopexin-like domain of interstitial collagenases or the collagen binding domain of gelatinases is highlighted. Elastolysis is also facilitated by the collagen binding domain in the cases of MMP-2 and MMP-9, and remote exosites of the catalytic domain in the case of MMP-12. PMID:25599938

  2. Loss of Type I Collagen Telopeptide Lysyl Hydroxylation Causes Musculoskeletal Abnormalities in a Zebrafish Model of Bruck Syndrome

    PubMed Central

    Gistelinck, Charlotte; Witten, Paul Eckhard; Huysseune, Ann; Symoens, Sofie; Malfait, Fransiska; Larionova, Daria; Simoens, Pascal; Dierick, Manuel; Van Hoorebeke, Luc; De Paepe, Anne; Kwon, Ronald Y; Weis, MaryAnn; Eyre, David R; Willaert, Andy; Coucke, Paul J

    2017-01-01

    Bruck syndrome (BS) is a disorder characterized by joint flexion contractures and skeletal dysplasia that shows strong clinical overlap with the brittle bone disease Osteogenesis Imperfecta (OI). BS is caused by bi-allelic mutations in either the FKBP10 or the PLOD2 gene. PLOD2 encodes the lysyl hydroxylase 2 (LH2) enzyme, which is responsible for the hydroxylation of lysine residues in fibrillar collagen telopeptides. This hydroxylation directs cross-linking of collagen fibrils in the extracellular matrix, which is necessary to provide stability and tensile integrity to the collagen fibrils. To further elucidate the function of LH2 in vertebrate skeletal development, we created a zebrafish model harboring a homozygous plod2 nonsense mutation resulting in reduced telopeptide hydroxylation and cross-linking of bone type I collagen. Adult plod2 mutants present with a shortened body axis and severe skeletal abnormalities with evidence of bone fragility and fractures. The vertebral column of plod2 mutants is short and scoliotic with compressed vertebrae that show excessive bone formation at the vertebral end plates, and increased tissue mineral density in the vertebral centra. The muscle fibers of mutant zebrafish have a reduced diameter near the horizontal myoseptum. The endomysium, a layer of connective tissue ensheathing the individual muscle fibers, is enlarged. Transmission electron microscopy of mutant vertebral bone shows type I collagen fibrils that are less organized with loss of the typical plywood-like structure. In conclusion, plod2 mutant zebrafish show molecular and tissue abnormalities in the musculoskeletal system that are concordant with clinical findings in BS patients. Therefore, the plod2 zebrafish mutant is a promising model for the elucidation of the underlying pathogenetic mechanisms leading to BS and the development of novel therapeutic avenues in this syndrome. PMID:27541483

  3. Probing multiscale mechanics of collagen with optical tweezers

    NASA Astrophysics Data System (ADS)

    Shayegan, Marjan; Rezaei, Naghmeh; Lam, Norman H.; Altindal, Tuba; Wieczorek, Andrew; Forde, Nancy R.

    2013-09-01

    How the molecular structure of the structural, extracellular matrix protein collagen correlates with its mechanical properties at different hierarchical structural levels is not known. We demonstrate the utility of optical tweezers to probe collagen's mechanical response throughout its assembly hierarchy, from single molecule force-extension measurements through microrheology measurements on solutions of collagen molecules, collagen fibrillar gels and gelatin. These experiments enable the determination of collagen's flexibility, mechanics, and timescales and strengths of interaction at different levels of hierarchy, information critical to developing models of how collagen's physiological function and stability are influenced by its chemical composition. By investigating how the viscoelastic properties of collagen are affected by the presence of telopeptides, protein domains that strongly influence fibril formation, we demonstrate that these play a role in conferring transient elasticity to collagen solutions.

  4. DYNAMIC SHEAR-INFLUENCED COLLAGEN SELF-ASSEMBLY

    PubMed Central

    Saeidi, Nima; Sander, Edward A.

    2011-01-01

    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 9 s-1). The detailed morphology of the collagen fibrils/aggregates was examined using Quick Freeze Deep Etch electron microscopy. Nucleation of fibrils on the glass was observed to occur rapidly (~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 microns/sec) occurring at a shear rate of 9 s-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

  5. 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

  6. Heterogeneous nanomechanical properties of type I collagen in longitudinal direction.

    PubMed

    Tang, Ming; Li, Tong; Gandhi, Neha S; Burrage, Kevin; Gu, YuanTong

    2017-01-07

    Collagen is an abundant structural biopolymer in mammal vertebrates, providing structural support as well as mechanical integrity for connective tissues such as bone, ligament, and tendon. The mechanical behaviours of these tissues are determined by the nanomechanics of their structures at different hierarchies and the role of collagen structures in the extracellular matrix. Some studies revealed that there is significant microstructural difference in the longitudinal direction of the collagen fibril, which challenges the conventional rod-like assumption prevalently adopted in the existing studies. Motivated by this discrepancy, in this study, we investigated the longitudinal heterogeneous nanomechanical properties of type I collagen molecule to probe the origin of the longitudinal heterogeneity of the collagen fibril at the molecular level. A full length type I collagen molecule structure was built based on the experimentally calibrated nanostructure. Then, a suitable strain rate was determined for stretching the three intact 'gap' regions and three intact 'overlap' regions of the collagen molecule. Further, the nanomechanical properties of the six collagen molecule segments were characterized by performing steered molecular dynamics simulations, using the obtained suitable strain rate in modelling. The results indicate that this computational model can be used to capture the mechanical behaviour of the collagen molecule under physiological stress conditions. Moreover, the 'gap' regions show a lower stiffness and undergo a slightly lager strain in the unwinding process, compared to the 'overlap' regions of the collagen molecule. This investigation provides insights into the origin of the longitudinal heterogeneity of collagen fibrils at the molecular level and suggests that it is of significant importance to consider the longitudinal heterogeneous mechanical properties of the collagen molecule in the development of coarse-grained models of collagen-related tissues.

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

    PubMed Central

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

    2015-01-01

    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. PMID:25758791

  8. 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.

  9. 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

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

    PubMed

    Doyle, Andrew D

    2016-09-01

    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. Copyright © 2016 John Wiley & Sons, Inc.

  11. [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.

  12. Second Harmonic Light Scattering from Macromolecules: Collagen.

    NASA Astrophysics Data System (ADS)

    Roth, Shmuel

    In this work we present the theory and practice of optical second harmonic generation (SHG) as applied to rat-tail tendon collagen. Our work is the first quantitative application of SHG to biological systems. The angular dependence of SHG is found to display a sharp, intense, forward peak superimposed on a broad background. The sharp peak is shown to imply long-range polar order, while the broad background corresponds to that predicted for the random "up"/"down" array of collagen fibrils seen with the electron microscope. The dependence of fibril diameter distribution on age and state of hydration is measured. Our experiments also reveal information concerning the structure of the fibrils and their arrangement in the tendon. The degree of polar order, the coherence length of tendon for harmonic generation and the absolute magnitude of the nonlinear susceptibility of the collagen fibril are also determined. The biological significance of these findings and the many advantages of SHG for the structural study of biological macromolecules and tissues are discussed.

  13. Estrogen-induced collagen reorientation correlates with sympathetic denervation of the rat myometrium.

    PubMed

    Martínez, G F; Bianchimano, P; Brauer, M M

    2016-12-01

    Estrogen inhibits the growth and causes the degeneration (pruning) of sympathetic nerves supplying the rat myometrium. Previous cryoculture studies evidenced that substrate-bound signals contribute to diminish the ability of the estrogenized myometrium to support sympathetic nerve growth. Using electron microscopy, here we examined neurite-substrate interactions in myometrial cryocultures, observing that neurites grew associated to collagen fibrils present in the surface of the underlying cryosection. In addition, we assessed quantitatively the effects of estrogen on myometrial collagen organization in situ, using ovariectomized rats treated with estrogen and immature females undergoing puberty. Under low estrogen levels, most collagen fibrils were oriented in parallel to the muscle long axis (83% and 85%, respectively). Following estrogen treatment, 89% of fibrils was oriented perpendicularly to the muscle main axis; while after puberty, 57% of fibrils acquired this orientation. Immunohistochemistry combined with histology revealed that the vast majority of fine sympathetic nerve fibers supplying the myometrium courses within the areas where collagen realignment was observed. Finally, to assess whether depending on their orientation collagen fibrils can promote or inhibit neurite outgrowth, we employed cryocultures, now using as substrate tissue sections of rat-tail tendon. We observed that neurites grew extensively in the direction of the parallel-aligned collagen fibrils in the tendon main axis but were inhibited to grow perpendicularly to this axis. Collectively, these findings support the hypothesis that collagen reorientation may be one of the factors contributing to diminish the neuritogenic capacity of the estrogen-primed myometrial substrate.

  14. Changes induced by ozone and ultraviolet light in type I collagen. Bovine Achilles tendon collagen versus rat tail tendon collagen.

    PubMed

    Fujimori, E

    1985-10-15

    High-molecular-mass aggregates were made soluble from insoluble collagens of bovine Achilles tendon and rat tail tendon by limited thermal hydrolysis. These polymeric collagen aggregates were cross-linked by 390-nm-fluorescent 3-hydroxy-pyridinium residues (excited at 325 nm) in the former tendon and by unknown non-fluorescent residues in the latter. With the solubilized insoluble-collagens from both tendons, as well as with acid-soluble collagen from rat tail tendon, other 350-385-nm fluorescence intensities (excited at 300 nm) were found to be higher in monomeric chains than in dimeric and polymeric chains. Low levels of ozone inhibited fibril formation of acid-soluble collagen particularly from young rat tail tendon, reacting with tyrosine residues and the 350-385-nm fluorophores. Aldehyde groups, involved in cross-linking, were not effectively modified by ozone. beta-Components (alpha-chain dimers) were not efficiently dissociated even by higher doses of ozone compared to gamma-components (alpha-chain trimers). Polymeric chain aggregates from bovine Achilles tendon collagen, whose 3-hydroxy-pyridinium cross-links are cleaved by ozone, were more readily dissociated by ozone than those from rat tail tendon collagen. Ultraviolet (300-nm) light, which destroyed the 350-385-nm fluorophores, inhibited fibril formation less effectively than ultraviolet (275-nm) light, which is absorbed by tyrosine residues, and did not dissociate collagen polymers from rat tail tendon. On the other hand, ultraviolet (320-nm) light, absorbed by 3-hydroxy-pyridinium cross-links which were rapidly photolyzed, partially dissociated polymeric collagen aggregates from bovine Achilles tendon after subsequent heating.

  15. 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 ...

  16. 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.

  17. What Is Atrial Fibrillation?

    MedlinePlus

    ANSWERS by heart Cardiovascular Conditions What Is Atrial Fibrillation? Your heart has a natural pacemaker, called the “ ... if the electric signals are normal. In atrial fibrillation (AFib), the heart’s two small upper chambers (atria) ...

  18. Atrial fibrillation or flutter

    MedlinePlus

    ... atrial fibrillation include: Alcohol use (especially binge drinking) Coronary artery disease Heart attack or heart bypass surgery Heart failure ... low. An ECG (a test that records the electrical activity of the heart) may show atrial fibrillation ...

  19. Mineralization by inhibitor exclusion: the calcification of collagen with fetuin.

    PubMed

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

    2009-06-19

    One of our goals is to understand the mechanisms that deposit mineral within collagen fibrils, and as a first step we recently determined the size exclusion characteristics of the fibril. This study revealed that apatite crystals up to 12 unit cells in size can access the water within the fibril, whereas molecules larger than a 40-kDa protein are excluded. Based on these observations, we proposed a novel mechanism for fibril mineralization: that macromolecular inhibitors of apatite growth favor fibril mineralization by selectively inhibiting crystal growth in the solution outside of the fibril. To test this mechanism, we developed a system in which crystal formation is driven by homogeneous nucleation at high calcium phosphate concentration and the only macromolecule in solution is fetuin, a 48-kDa inhibitor of apatite growth. Our experiments with this system demonstrated that fetuin determines the location of mineral growth; in the presence of fetuin mineral grows exclusively within the fibril, whereas in its absence mineral grows in solution outside the fibril. Additional experiments showed that fetuin is also able to localize calcification to the interior of synthetic matrices that have size exclusion characteristics similar to those of collagen and that it does so by selectively inhibiting mineral growth outside of these matrices. We termed this new calcification mechanism "mineralization by inhibitor exclusion," the selective mineralization of a matrix using a macromolecular inhibitor of mineral growth that is excluded from that matrix. Future studies will be needed to evaluate the possible role of this mechanism in bone mineralization.

  20. Collagen crosslink status analysed in vitro using second-harmonic generation (SHG) and fluorescence lifetime imaging (FLIM)

    NASA Astrophysics Data System (ADS)

    Lutz, Vivien; Puschmann, Stefan; Gallinat, Stefan; Wenck, Horst; Wittern, Klaus-Peter; Fischer, Frank

    2012-02-01

    One of the major structural proteins in human skin is collagen. Collagen and its crosslinks are essential for the mechanical stability of the skin. Looking at extrinsically aged human skin (photo damaged skin) we find a decrease of mature collagen crosslinks. Immature crosslinks an indicator of the collagen turnover are decreasing as well in extrinsically aged skin. Hence, we assume that a certain range of mature and immature crosslinks reflect a 'good quality' of collagen in terms of photoaging. In this study we established in vitro models of reduced crosslinking. We found that reduced collagen crosslinking resulted in a higher Second Harmonic Generation (SHG) intensity. Furthermore, we found a higher fibril diameter after crosslink reduction without an increase in collagen concentration. SHG is generated by a non-linear effect of femtosecond laser irradiation on collagen molecules. This effect might be influenced by the interspaces of the collagen molecules within the collagen fibril. From these findings the following hypothesis was introduced: reduced collagen crosslinking changes the interspace of single collagen molecules within the collagen fibril resulting in an enhanced SHG signal. Furthermore, in this study the fluorescence lifetime (FLIM) of collagen fluorescence was found to decrease in the in vitro models of reduced crosslinking. We speculate on possible mechanisms being responsible for the decrease in lifetime. Future in vivo measurements of the two parameters (SHG and FLIM) could lead to information about the collagen crosslink status, and therefore the status of photoaging of the skin.

  1. The importance of size-exclusion characteristics of type I collagen in bonding to dentin matrices

    PubMed Central

    M, Takahashi; M, Nakajima; J, Tagami; DLS, Scheffel; RM, Carvalho; A, Mazzoni; M, Carrilho; A, Tezvergil-Mutluay; L, Breschi; L, Tjäderhane; SS, Jang; FR, Tay; KA, Agee; DH, Pashley

    2013-01-01

    The mineral phase of dentin is located primarily within collagen fibrils. During development, bone or dentin collagen fibrils are formed first and then water within the fibril is replaced with apatite crystallites. Mineralized collagen contains very little water. During dentin bonding, acid-etching of mineralized dentin solubilizes the mineral crystallites and replaces them with water. During the infiltration phase of dentin bonding, adhesive comonomers are supposed to replace all of the collagen water with adhesive monomers that are then polymerized into copolymers. The authors of a recently published review suggested that dental monomers were too large to enter and displace water from collagen fibrils. If that were true, the endogenous proteases bound to dentin collagen could be responsible for unimpeded collagen degradation that is responsible for the poor durability of resin-dentin bonds. The current work studied the size-exclusion characteristics of dentin collagen, using a gel-filtration-like column chromatography technique, using dentin powder instead of Sephadex. The elution volumes of test molecules, including adhesive monomers, revealed that adhesive monomers smaller than about 1000 Da can freely diffuse into collagen water, while molecules of 10,000 Da begin to be excluded, and bovine serum albumin (66,000 Da) was fully excluded. These results validate the concept that dental monomers can permeate between collagen molecules during infiltration by etch-and-rinse adhesives. PMID:23928333

  2. Understanding the viscoelastic behavior of collagen matrices through relaxation time distribution spectrum.

    PubMed

    Xu, Bin; Li, Haiyue; Zhang, Yanhang

    2013-01-01

    This study aims to provide understanding of the macroscopic viscoelastic behavior of collagen matrices through studying the relaxation time distribution spectrum obtained from stress relaxation tests. Hydrated collagen gel and dehydrated collagen thin film was exploited as two different hydration levels of collagen matrices. Genipin solution was used to induce crosslinking in collagen matrices. Biaxial stress relaxation tests were performed to characterize the viscoelastic behavior of collagen matrices. The rate of stress relaxation of both hydrated and dehydrated collagen matrices shows a linear initial stress level dependency. Increased crosslinking reduces viscosity in collagen gel, but the effect is negligible for thin film. Relaxation time distribution spectrum was obtained from the stress relaxation data by inverse Laplace transform. For most of the collagen matrices, three peaks at the short (0.3s ~1 s), medium (3s ~90 s), and long relaxation time (> 200 s) were observed in the continuous spectrum, which likely corresponds to relaxation mechanisms involve fiber, inter-fibril, and fibril sliding. Splitting of the middle peak was observed at higher initial stress levels suggesting increased structural heterogeneity at the fibril level with mechanical loading. The intensity of the long-term peaks increases with higher initial stress levels indicating the engagement of collagen fibrils at higher levels of tissue strain.

  3. 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

  4. Insulin-like growth factor I enhances collagen synthesis in engineered human tendon tissue.

    PubMed

    Herchenhan, Andreas; Bayer, Monika L; Eliasson, Pernilla; Magnusson, S Peter; Kjaer, Michael

    2015-02-01

    Isolated human tendon cells form 3D tendon constructs that demonstrate collagen fibrillogenesis and feature structural similarities to tendon when cultured under tensile load. The exact role of circulating growth factors for collagen formation in tendon is sparsely examined. We investigated the influence of insulin-like growth factor I (IGF-I) on tendon construct formation in 3D cell culture. Tendon constructs were grown in 0.5 or 10% FBS with or without IGF-I (250 mg/ml) supplementation. Collagen content (fluorometric), mRNA levels (PCR) and fibril diameter (transmission electron microscopy) were determined at 7, 10, 14, 21 and 28 days. IGF-I revealed a stimulating effect on fibril diameter (up to day 21), mRNA for collagen (to day 28), tenomodulin (to day 28) and scleraxis (at days 10 and 14), and on overall collagen content. 10% FBS diminished the development of fibril diameter (day 14), collagen content (at days 21 and 28) and mRNA expression for collagen, tenomodulin and scleraxis. IGF-I supplementation promotes early onset of tensile load induced collagen formation and tendon structural arrangement, whereas the FBS concentration routinely used in cultures diminishes collagen expression, collagen content and fibril formation. Copyright © 2014 Elsevier Ltd. All rights reserved.

  5. Collagen immobilization on 316L stainless steel surface with cathodic deposition of calcium phosphate

    NASA Astrophysics Data System (ADS)

    Roguska, Agata; Hiromoto, Sachiko; Yamamoto, Akiko; Woźniak, Michał Jerzy; Pisarek, Marcin; Lewandowska, Małgorzata

    2011-03-01

    Collagen fibril/(calcium phosphate and carbonate) composite coatings on 316L stainless steel were developed with a cathodic deposition technique. The response of SaOS-2 osteoblast-like cells to the collagen/calcium salt-coated 316L steel was investigated. The collagen fibrils were self-assembled on the 316L steel surface and immobilized by their partial incorporation into a calcium salt layer electrodeposited cathodically in Hanks' solution. The amount of calcium salt depended on the applied cathodic potential. The mineralization of collagen fibrils was observed. The collagen coverage localized and the composition of calcium salts varied on the same specimen. Such non-uniform surfaces affected the cell response. The observed outlines of cell bodies and nuclei on the thin collagen coating were clearer than those on the thick collagen coating in most cases. The collagen coating did not significantly influence the mean viability of cells on the whole specimen surface. Interestingly, the alkaline phosphatase activity per cell on the collagen/calcium salt-coated specimens was higher than that on the as-received specimen. It was revealed that cathodic deposition is an effective technique to immobilize collagen fibrils on a 316L steel surface.

  6. Fine structure of the dogfish egg case: a unique collagenous material.

    PubMed

    Knight, D P; Hunt, S

    1976-01-01

    The fine structure of the dogfish egg case is described with special reference to the highly ordered, unique, collagen-containing fibrils. The outer layer of the case wall contains densely packed, amorphous granules, rich in tyrosine while approximately 98% of the thickness of the case is built up from orthogonally stacked laminae of closely packed, collagen-containing fibrils. These fibrils show a paracrystalline three-dimensional construction. A model for the structure of the B band of the fibril is proposed, based on appearances in transverse sections of different thickness and on two projection seen in longitudinal sections. The transverse projection of the unit cell appears to be a square lattice with sides approximately 110 A possibly containing a pseudocell with sides (see article). The structure of these fibrils is discussed in relation to those of rat tail tendon collagen.

  7. 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

  8. Similarity between the major collagens of cuttlefish cranial cartilage and cornea.

    PubMed

    Sivakumar, Pitchumani; Suguna, Lonchin; Chandrakasan, Gowri

    2003-01-01

    Invertebrates possess unique collagen-containing connective tissue elements, the biochemistry of which is not clearly understood. We previously reported the occurrence of a novel heterotrimeric type V/XI like collagen in the cranial cartilage of the cuttlefish Sepia officinalis. We report here the purification of the three chains by ion exchange chromatography and the physicochemical characteristics of this collagen. This collagen shared substantial similarity to the collagen purified from the cornea of S. officinalis, with respect to chain composition, cyanogen bromide peptide profile and amino acid composition. The mobility of the C3 chain was retarded in the corneal collagen, which also had an increased glycine content and a smaller ratio of hydroxylysine to lysine, together with a reduction in bound carbohydrates. The cartilage collagen had a higher denaturation temperature than corneal collagen. As observed by transmission electron microscopy of reconstituted fibrils, the heterotrimeric invertebrate collagen formed fibrils of no apparent periodicities as opposed to the regular 64-nm banding pattern of milk shark (Rhizoprionodon acutus) cartilage collagen. This is also the first report on the molecular species of collagen in an invertebrate cornea. Our results strongly support the functioning of minor vertebrate collagens as major collagens in some invertebrates, close similarity of collagens in two tissues with different functions and would hold significance to our understanding of collagen polymorphism and the evolution of the extracellular matrix.

  9. Decrimping: The first stage of collagen thermal denaturation unraveled by in situ second-harmonic-generation imaging

    NASA Astrophysics Data System (ADS)

    Liao, Chien-Sheng; Zhuo, Zong-Yan; Yu, Jiun-Yann; Tzeng, Yu-Yi; Chu, Shi-Wei; Yu, Shih-Fan; Chao, Pen-Hsiu Grace

    2011-04-01

    With polarized and time-lapsed second-harmonic-generation (SHG) imaging, three distinct thermodynamic stages are revealed during heating of collagenous tissue. In the first "decrimping" stage, SHG intensity remains unchanged while the characteristic crimp pattern of collagen fiber disappears. The intactness of underlying fibrils is confirmed by unaffected second-order susceptibility, suggesting decrimping is related to the breakage of cross-linking between collagen fibrils. In the latter stages, significant SHG decrease is observed, providing quantification to collagen thermal denaturation. This study manifests the benefits of adopting SHG for understanding the thermal response of collagen, and will be useful toward better thermal therapy design.

  10. Collagen Formation by Fibroblasts of the Chick Embryo Dermis

    PubMed Central

    Porter, Keith R.; Pappas, George D.

    1959-01-01

    This investigation has sought to determine the relation between collagen fiber and fibroblast during fibrogenesis. Toward this end the surfaces of chick fibroblasts grown under in vitro conditions have been examined with the electron microscope after fixation in OsO4. Supplementary information has been obtained from thin sections of fibroblasts fixed in situ during phases of fiber production. The evidence provided by these studies and by various conditions of the experiments indicates that the unit fibrils of collagen form in close association with the cell surface. They were never observed within the cell. When these unit fibrils form in bundles it appears as though templates of some nature, possibly coinciding with stress fibers within the cell cortex, influence the polymerization of the fibrils out of material available at the cell surface. From here the fibrils and bundles of them are shed into the intercellular spaces and there grow to limited diameters by accretion of materials from the general milieu. PMID:13630947

  11. Collagen self-assembly and the development of tendon mechanical properties.

    PubMed

    Silver, Frederick H; Freeman, Joseph W; Seehra, Gurinder P

    2003-10-01

    The development of the musculoskeleton and the ability to locomote requires controlled cell division as well as spatial control over deposition of extracellular matrix. Self-assembly of procollagen and its final processing into collagen fibrils occurs extracellularly. The formation of crosslinked collagen fibers results in the conversion of weak liquid-like embryonic tissues to tough elastic solids that can store energy and do work. Collagen fibers in the form of fascicles are the major structural units found in tendon. The purpose of this paper is to review the literature on collagen self-assembly and tendon development and to relate this information to the development of elastic energy storage in non-mineralizing and mineralizing tendons. Of particular interest is the mechanism by which energy is stored in tendons during locomotion. In vivo, collagen self-assembly occurs by the deposition of thin fibrils in recesses within the cell membrane. These thin fibrils later grow in length and width by lateral fusion of intermediates. In vitro, collagen self-assembly occurs by both linear and lateral growth steps with parallel events seen in vivo; however, in the absence of cellular control and enzymatic cleavage of the propeptides, the growth mechanism is altered, and the fibrils are irregular in cross section. Results of mechanical studies suggest that prior to locomotion the mechanical response of tendon to loading is dominated by the viscous sliding of collagen fibrils. In contrast, after birth when locomotion begins, the mechanical response is dominated by elastic stretching of crosslinked collagen molecules.

  12. Management of atrial fibrillation.

    PubMed

    Moukabary, Talal; Gonzalez, Mario D

    2015-07-01

    Atrial fibrillation is a very common clinical problem with a high prevalence that is expected to rise over time because of increasing risk factors (eg, age, obesity, hypertension). This high prevalence is also associated with high cost, because atrial fibrillation represents about 1% of overall health care spending. The management of atrial fibrillation involves multiple facets: (1) management of underlying disease if present and the management of atrial fibrillation risk factors, (2) prevention of thromboembolism, (3) control of the ventricular rate during atrial fibrillation, and (4) restoration and maintenance of normal sinus rhythm.

  13. 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.

  14. 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.

  15. Immunohistochemical localization of collagen VI in arthrofibrosis.

    PubMed

    Zeichen, J; van Griensven, M; Albers, I; Lobenhoffer, P; Bosch, U

    1999-01-01

    Arthrofibrosis is a disabling complication after knee trauma and surgery. Clinically, it is characterized by pain and joint stiffness due to massive connective tissue proliferation. In similar pathological conditions with fibrotic transformation such as lung fibrosis or superficial fibromatoses, an increased expression of collagen type VI has been reported. Collagen VI, which forms a filamentous network, is thought to serve as an anchoring element between collagen I/III fibrils and basement membranes and as a cell binding structure. Collagen VI may also play a contributing role in the pathogenesis of arthrofibrosis. The aim of the present study was therefore to demonstrate the localization and distribution of type VI collagen in arthrofibrotic tissue. Tissue samples from the infrapatellar fat pad and intercondylar synovia of 13 patients suffering from arthrofibrosis were taken at surgery. The expression of type VI collagen was studied immunohistochemically using an immunoperoxidase method for light microscopic visualization. Histologic analysis showed a synovial hyperplasia with inflammatory cell infiltration and vascular proliferation. Compared with normal synovial tissue, type VI collagen was widely distributed as a network subsynovially and around the capillary walls. The results of the present study suggest that dysregulation of collagen VI synthesis could be an important contributing factor in the complex mechanisms of disordered matrix protein deposition leading to arthrofibrosis.

  16. 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.

  17. 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

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

    PubMed

    Kalamajski, Sebastian; Bihan, Dominique; Bonna, Arkadiusz; Rubin, Kristofer; Farndale, Richard W

    2016-04-08

    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.

  20. Collagen V expression is crucial in regional development of the supraspinatus tendon.

    PubMed

    Connizzo, Brianne K; Adams, Sheila M; Adams, Thomas H; Birk, David E; Soslowsky, Louis J

    2016-12-01

    Manipulations in cell culture and mouse models have demonstrated that reduction of collagen V results in altered fibril structure and matrix assembly. A tissue-dependent role for collagen V in determining mechanical function was recently established, but its role in determining regional properties has not been addressed. The objective of this study was to define the role(s) of collagen V expression in establishing the site-specific properties of the supraspinatus tendon. The insertion and midsubstance of tendons from wild type, heterozygous and tendon/ligament-specific null mice were assessed for crimp morphology, fibril morphology, cell morphology, as well as total collagen and pyridinoline cross-link (PYD) content. Fibril morphology was altered at the midsubstance of both groups with larger, but fewer, fibrils and no change in cell morphology or collagen compared to the wild type controls. In contrast, a significant disruption of fibril assembly was observed at the insertion site of the null group with the presence of structurally aberrant fibrils. Alterations were also present in cell density and PYD content. Altogether, these results demonstrate that collagen V plays a crucial role in determining region-specific differences in mouse supraspinatus tendon structure. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:2154-2161, 2016.

  1. Tendon Creep Is Potentiated by NKISK and Relaxin Which Produce Collagen Fiber Sliding

    PubMed Central

    Wood, Mark L; Luthin, William N; Lester, Gayle E; Dahners, Laurence E

    2003-01-01

    The pentapeptide NKISK has been reported to inhibit the binding of decorin, a proteoglycan on the surface of collagen fibrils, to fibronectin, a tissue adhesion molecule. Relaxin has been shown to be effective in relaxing ligaments and other connective tissues. Through collagen staining studies, we have previously demonstrated that collagen fiber sliding is important during changes in ligament length. Because of our interest in fibril-fibril binding as it relates to changes in length of tendon or ligament, we investigated the potential of NKISK, relaxin, or both in combination to potentiate creep. We suspended stained rat tail tendons in test solutions under a constant stress and observed length changes and subsequent collagen fiber sliding. Both NKISK and relaxin potentiated rat tail tendon creep with changes in length most likely occurring as a result of collagen fiber sliding as evidenced by photomicrography. PMID:14575254

  2. Tendon creep is potentiated by NKISK and relaxin which produce collagen fiber sliding.

    PubMed

    Wood, Mark L; Luthin, William N; Lester, Gayle E; Dahners, Laurence E

    2003-01-01

    The pentapeptide NKISK has been reported to inhibit the binding of decorin, a proteoglycan on the surface of collagen fibrils, to fibronectin, a tissue adhesion molecule. Relaxin has been shown to be effective in relaxing ligaments and other connective tissues. Through collagen staining studies, we have previously demonstrated that collagen fiber sliding is important during changes in ligament length. Because of our interest in fibril-fibril binding as it relates to changes in length of tendon or ligament, we investigated the potential of NKISK, relaxin, or both in combination to potentiate creep. We suspended stained rat tail tendons in test solutions under a constant stress and observed length changes and subsequent collagen fiber sliding. Both NKISK and relaxin potentiated rat tail tendon creep with changes in length most likely occurring as a result of collagen fiber sliding as evidenced by photomicrography.

  3. Acceleration of bone formation during fracture healing by injectable collagen powder and human basic fibroblast growth factor containing a collagen-binding domain from Clostridium histolyticum collagenase.

    PubMed

    Saito, Wataru; Uchida, Kentaro; Ueno, Masaki; Matsushita, Osamu; Inoue, Gen; Nishi, Nozomu; Ogura, Takayuki; Hattori, Shunji; Fujimaki, Hisako; Tanaka, Keisuke; Takaso, Masashi

    2014-09-01

    Growth factor delivered with implantable biomaterials has been used to both accelerate and ensure healing of open fractures in human patients. However, a major limitation of implantable biomaterials is the requirement for open surgical placement. Here, we developed an injectable collagen material-based bone formation system consisting of injectable collagen powder with fibril morphology and collagen triple helix conformation, and basic fibroblast growth factor (bFGF) fused to the collagen-binding domain (CBD) of Clostridium histolyticum collagenase. The affinity of the CBD towards collagen was confirmed by the results of collagen-binding assays. Moreover, the combination of the collagen binding-bFGF fusion protein (CB-bFGF) with injectable collagen powder induced bone formation at protein concentrations lower than those required for bFGF alone in mice fracture models. Taken together, these properties suggest that the CB-bFGF/collagen powder composite is a promising injectable material for bone repair in the clinical setting.

  4. Elevated expression of type VII collagen in the skin of patients with systemic sclerosis. Regulation by transforming growth factor-beta.

    PubMed Central

    Rudnicka, L; Varga, J; Christiano, A M; Iozzo, R V; Jimenez, S A; Uitto, J

    1994-01-01

    A hallmark of systemic sclerosis (SSc) is the development of tissue fibrosis. Excessive production of several connective tissue components normally present in the dermis, including type I, III, V, and VI collagens as well as fibronectin and proteoglycans, is a consistent finding in the skin of SSc patients. Type VII collagen is a major constituent of anchoring fibrils, present in the skin at the dermal-epidermal basement membrane zone. TGF-beta has been shown to upregulate the expression of the type VII collagen gene. In this study, we assessed the expression of type VII collagen and TGF-beta in the skin of patients with SSc. Indirect immunofluorescence showed an abundance of type VII collagen in the patients' skin, including the dermis. Ultrastructural analysis of SSc skin revealed an abundance of fibrillar material, possibly representing type VII collagen. The increased expression of type VII collagen epitopes was accompanied by the elevated expression of immunodetectable TGF-beta 1 and TGF-beta 2. Dermal fibroblasts cultured from the affected individuals showed a statistically significant (P < 0.02) increase in the expression of type VII collagen at the mRNA level, as detected by reverse transcription-PCR with a mutated cDNA as an internal standard, and increased deposition of the protein as assessed by indirect immunofluorescence. Thus, type VII collagen is abundantly present in SSc patients' dermis, a location not characteristic of its normal distribution, and its aberrant expression may relate to the presence of TGF-beta in the same topographic distribution. The presence of type VII collagen in the dermis may contribute to the tightly bound and indurated appearance of the affected skin in SSc patients. Images PMID:7512991

  5. 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

  6. Type VII collagen is enriched in the enamel organic matrix associated with the dentin-enamel junction of mature human teeth.

    PubMed

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

    2014-06-01

    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. Copyright © 2014 Elsevier Inc. All rights reserved.

  7. Impacts of fullerene derivatives on regulating the structure and assembly of collagen molecules.

    PubMed

    Yin, Xiaohui; Zhao, Lina; Kang, Seung-gu; Pan, Jun; Song, Yan; Zhang, Mingyi; Xing, Gengmei; Wang, Fei; Li, Jingyuan; Zhou, Ruhong; Zhao, Yuliang

    2013-08-21

    During cancer development, the fibrous layers surrounding the tumor surface get thin and stiff which facilitates the tumor metastasis. After the treatment of metallofullerene derivatives Gd@C82(OH)22, the fibrous layers become thicker and softer, the metastasis of tumor is then largely suppressed. The effect of Gd@C82(OH)22 was found to be related to their direct interaction with collagen and the resulting impact on the structure of collagen fibrils, the major component of extracellular matrices. In this work we study the interaction of Gd@C82(OH)22 with collagen by molecular dynamics simulations. We find that Gd@C82(OH)22 can enhance the rigidity of the native structure of collagen molecules and promote the formation of an oligomer or a microfibril. The interaction with Gd@C82(OH)22 may regulate further the assembly of collagen fibrils and change the biophysical properties of collagen. The control run with fullerene derivatives C60(OH)24 also indicates that C60(OH)24 can influence the structure and assembly of collagen molecules as well, but to a lesser degree. Both fullerene derivatives can form hydrogen bonds with multiple collagen molecules acting as a "fullerenol-mediated bridge" that enhance the interaction within or among collagen molecules. Compared to C60(OH)24, the interaction of Gd@C82(OH)22 with collagen is stronger, resulting in particular biomedical effects for regulating the biophysical properties of collagen fibrils.

  8. 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

  9. Evidence that interfibrillar load transfer in tendon is supported by small diameter fibrils and not extrafibrillar tissue components.

    PubMed

    Szczesny, Spencer E; Fetchko, Kristen L; Dodge, George R; Elliott, Dawn M

    2017-10-01

    Collagen fibrils in tendon are believed to be discontinuous and transfer tensile loads through shear forces generated during interfibrillar sliding. However, the structures that transmit these interfibrillar forces are unknown. Various extrafibrillar tissue components (e.g., glycosaminoglycans, collagens XII and XIV) have been suggested to transmit interfibrillar loads by bridging collagen fibrils. Alternatively, collagen fibrils may interact directly through physical fusions and interfibrillar branching. The objective of this study was to test whether extrafibrillar proteins are necessary to transmit load between collagen fibrils or if interfibrillar load transfer is accomplished directly by the fibrils themselves. Trypsin digestions were used to remove a broad spectrum of extrafibrillar proteins and measure their contribution to the multiscale mechanics of rat tail tendon fascicles. Additionally, images obtained from serial block-face scanning electron microscopy were used to determine the three-dimensional fibrillar organization in tendon fascicles and identify any potential interfibrillar interactions. While trypsin successfully removed several extrafibrillar tissue components, there was no change in the macroscale fascicle mechanics or fibril:tissue strain ratio. Furthermore, the imaging data suggested that a network of smaller diameter fibrils (<150 nm) wind around and fuse with their neighboring larger diameter fibrils. These findings demonstrate that interfibrillar load transfer is not supported by extrafibrillar tissue components and support the hypothesis that collagen fibrils are capable of transmitting loads themselves. Conclusively determining how fibrils bear load within tendon is critical for identifying the mechanisms that impair tissue function with degeneration and for restoring tissue properties via cell-mediated regeneration or engineered tissue replacements. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop

  10. Collagenous gastritis.

    PubMed

    Jin, Xiaoyi; Koike, Tomoyuki; Chiba, Takashi; Kondo, Yutaka; Ara, Nobuyuki; Uno, Kaname; Asano, Naoki; Iijima, Katsunori; Imatani, Akira; Watanabe, Mika; Shirane, Akio; Shimosegawa, Tooru

    2013-09-01

    In the present paper, we report a case of rare collagenous gastritis. The patient was a 25-year-old man who had experienced nausea, abdominal distention and epigastralgia since 2005. Esophagogastroduodenoscopy (EGD) carried out at initial examination by the patient's local doctor revealed an extensively discolored depression from the upper gastric body to the lower gastric body, mainly including the greater curvature, accompanied by residual mucosa with multiple islands and nodularity with a cobblestone appearance. Initial biopsies sampled from the nodules and accompanying atrophic mucosa were diagnosed as chronic gastritis. In August, 2011, the patient was referred to Tohoku University Hospital for observation and treatment. EGD at our hospital showed the same findings as those by the patient's local doctor. Pathological findings included a membranous collagen band in the superficial layer area of the gastric mucosa, which led to a diagnosis of collagenous gastritis. Collagenous gastritis is an extremely rare disease, but it is important to recognize its characteristic endoscopic findings to make a diagnosis.

  11. Collagenous colitis.

    PubMed Central

    Kingham, J G; Levison, D A; Morson, B C; Dawson, A M

    1986-01-01

    Clinical and pathological aspects of six patients with collagenous colitis are presented. These patients have been observed for between four and 15 years and the evolution of the condition is documented in three (cases 1, 3 and 5). Management and possible pathogenetic mechanisms of this enigmatic condition are discussed. Images Fig. 1 Fig. 2 PMID:3699567

  12. A peptide study of the relationship between the collagen triple-helix and amyloid.

    PubMed

    Parmar, Avanish S; Nunes, Ana Monica; Baum, Jean; Brodsky, Barbara

    2012-10-01

    Type XXV collagen, or collagen-like amyloidogenic component, is a component of amyloid plaques, and recent studies suggest this collagen affects amyloid fibril elongation and has a genetic association with Alzheimer's disease. The relationship between the collagen triple helix and amyloid fibrils was investigated by studying peptide models, including a very stable triple helical peptide (Pro-Hyp-Gly)₁₀ , an amyloidogenic peptide GNNQQNY, and a hybrid peptide where the GNNQQNY sequence was incorporated between (GPO)(n) domains. Circular dichroism and nuclear magnetic resonance (NMR) spectroscopy showed the GNNQQNY peptide formed a random coil structure, whereas the hybrid peptide contained a central disordered GNNQQNY region transitioning to triple-helical ends. Light scattering confirmed the GNNQQNY peptide had a high propensity to form amyloid fibrils, whereas amyloidogenesis was delayed in the hybrid peptide. NMR data suggested the triple-helix constraints on the GNNQQNY sequence within the hybrid peptide may disfavor the conformational change necessary for aggregation. Independent addition of a triple-helical peptide to the GNNQQNY peptide under aggregating conditions delayed nucleation and amyloid fibril growth. The inhibition of amyloid nucleation depended on the Gly-Xaa-Yaa sequence and required the triple-helix conformation. The inhibitory effect of the collagen triple-helix on an amyloidogenic sequence, when in the same molecule or when added separately, suggests Type XXV collagen, and possibly other collagens, may play a role in regulating amyloid fibril formation.

  13. The tooth attachment mechanism defined by structure, chemical composition and mechanical properties of collagen fibers in the periodontium.

    PubMed

    Ho, Sunita P; Marshall, Sally J; Ryder, Mark I; Marshall, Grayson W

    2007-12-01

    In this study, a comparison between structure, chemical composition and mechanical properties of collagen fibers at three regions within a human periodontium, has enabled us to define a novel tooth attachment mechanism. The three regions include, (1) the enthesis region: insertion site of periodontal ligament (PDL) fibers (collagen fibers) into cementum at the root surface, (2) bulk cementum, and (3) the cementum-dentin junction (CDJ). Structurally, continuity in collagen fibers was observed from the enthesis, through bulk cementum and CDJ. At the CDJ the collagen fibers split into individual collagen fibrils and intermingled with the extracellular matrix of mantle dentin. Under wet conditions, the collagen fibers at the three regions exhibited significant swelling suggesting a composition rich in polyanionic molecules such as glycosaminoglycans. Additionally, site-specific indentation illustrated a comparable elastic modulus between collagen fibers at the enthesis (1-3 GPa) and the CDJ (2-4 GPa). However, the elastic modulus of collagen fibers within bulk cementum was higher (4-7 GPa) suggesting presence of extrafibrillar mineral. It is known that the tooth forms a fibrous joint with the alveolar bone, which is termed a gomphosis. Although narrower in width than the PDL space, the hygroscopic CDJ can also be termed as a gomphosis; a fibrous joint between cementum and root dentin capable of accommodating functional loads similar to that between cementum and alveolar bone. From an engineering perspective, it is proposed that a tooth contains two fibrous joints that accommodate the masticatory cyclic loads. These joints are defined by the attachment of dissimilar materials via graded stiffness interfaces, such as: (1) alveolar bone attached to cementum with the PDL; and (2) cementum to root dentin with the CDJ. Thus, through variations in concentrations of basic constituents, distinct regions with characteristic structures and graded properties allow for attachment

  14. How Is Atrial Fibrillation Treated?

    MedlinePlus

    ... from the NHLBI on Twitter. How Is Atrial Fibrillation Treated? Treatment for atrial fibrillation (AF) depends on ... much thyroid hormone). Who Needs Treatment for Atrial Fibrillation? People who have AF but don't have ...

  15. Molecular assessment of collagen denaturation in decellularized tissues using a collagen hybridizing peptide.

    PubMed

    Hwang, Jeongmin; San, Boi Hoa; Turner, Neill J; White, Lisa J; Faulk, Denver M; Badylak, Stephen F; Li, Yang; Yu, S Michael

    2017-04-15

    Decellularized extracellular matrix (ECM) derived from tissues and organs are emerging as important scaffold materials for regenerative medicine. Many believe that preservation of the native ECM structure during decellularization is highly desirable. However, because effective techniques to assess the structural damage in ECM are lacking, the disruptive effects of a decellularization method and the impact of the associated structural damage upon the scaffold's regenerative capacity are often debated. Using a novel collagen hybridizing peptide (CHP) that specifically binds to unfolded collagen chains, we investigated the molecular denaturation of collagen in the ECM decellularized by four commonly used cell-removing detergents: sodium dodecyl sulfate (SDS), 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS), sodium deoxycholate (SD), and Triton X-100. Staining of the detergent-treated porcine ligament and urinary bladder matrix with carboxyfluorescein-labeled CHP demonstrated that SDS and Triton X-100 denature the triple helical collagen molecule while CHAPS and SD do not, although second harmonic generation imaging and transmission electron microscopy (TEM) revealed that all four detergents disrupt collagen fibrils. Our findings from the CHP staining were further confirmed by the circular dichroism spectra of intact triple helical collagen molecules in CHAPS and SD solutions, and the TEM images of CHP-conjugated gold nanoparticles binding only to the SDS and Triton X-100 treated collagen fibrils. CHP is a powerful new tool for direct and reliable measurement of denatured collagen molecules in decellularized tissues. It is expected to have wide applications in the development and standardization of the tissue/organ decellularization technology. Preservation of the native ECM structure in decellularized tissues is highly desirable, since denaturation of ECM molecules (e.g., collagen) during decellularization can strongly influence the cellular response

  16. Molecular assessment of collagen denaturation in decellularized tissues using a collagen hybridizing peptide

    PubMed Central

    Hwang, Jeongmin; San, Boi Hoa; Turner, Neill J.; White, Lisa J.; Faulk, Denver M.; Badylak, Stephen F.; Li, Yang; Yu, S. Michael

    2017-01-01

    Decellularized extracellular matrix (ECM) derived from tissues and organs are emerging as important scaffold materials for regenerative medicine. Many believe that preservation of the native ECM structure during decellularization is highly desirable. However, because effective techniques to assess the structural damage in ECM are lacking, the disruptive effects of a decellularization method and the impact of the associated structural damage upon the scaffold’s regenerative capacity are often debated. Using a novel collagen hybridizing peptide (CHP) that specifically binds to unfolded collagen chains, we investigated the molecular denaturation of collagen in the ECM decellularized by four commonly used cellremoving detergents: sodium dodecyl sulfate (SDS), 3-[(3-cholamidopropyl)dimethylammonio]-1-propa nesulfonate (CHAPS), sodium deoxycholate (SD), and Triton X-100. Staining of the detergent-treated porcine ligament and urinary bladder matrix with carboxyfluorescein-labeled CHP demonstrated that SDS and Triton X-100 denature the triple helical collagen molecule while CHAPS and SD do not, although second harmonic generation imaging and transmission electron microscopy (TEM) revealed that all four detergents disrupt collagen fibrils. Our findings from the CHP staining were further confirmed by the circular dichroism spectra of intact triple helical collagen molecules in CHAPS and SD solutions, and the TEM images of CHP-conjugated gold nanoparticles binding only to the SDS and Triton X-100 treated collagen fibrils. CHP is a powerful new tool for direct and reliable measurement of denatured collagen molecules in decellularized tissues. It is expected to have wide applications in the development and standardization of the tissue/organ decellularization technology. Statement of Significance Preservation of the native ECM structure in decellularized tissues is highly desirable, since denaturation of ECM molecules (e.g., collagen) during decellularization can strongly

  17. Choosing a particular oral anticoagulant and dose for stroke prevention in individual patients with non-valvular atrial fibrillation: part 1.

    PubMed

    Diener, Hans-Christoph; Aisenberg, James; Ansell, Jack; Atar, Dan; Breithardt, Günter; Eikelboom, John; Ezekowitz, Michael D; Granger, Christopher B; Halperin, Jonathan L; Hohnloser, Stefan H; Hylek, Elaine M; Kirchhof, Paulus; Lane, Deirdre A; Verheugt, Freek W A; Veltkamp, Roland; Lip, Gregory Y H

    2016-02-04

    Patients with atrial fibrillation (AF) have a high risk of stroke and mortality, which can be considerably reduced by oral anticoagulants (OAC). Recently, four non-vitamin-K oral anticoagulants (NOACs) were compared with warfarin in large randomized trials for the prevention of stroke and systemic embolism. Today's clinician is faced with the difficult task of selecting a suitable OAC for a patient with a particular clinical profile or a particular pattern of risk factors and concomitant diseases. We reviewed analyses of subgroups of patients from trials of vitamin K antagonists vs. NOACs for stroke prevention in AF with the aim to identify patient groups who might benefit from a particular OAC more than from another. In the first of a two-part review, we discuss the choice of NOAC for stroke prevention in the following subgroups of patients with AF: (i) stable coronary artery disease or peripheral artery disease, including percutaneous coronary intervention with stenting and triple therapy; (ii) cardioversion, ablation and anti-arrhythmic drug therapy; (iii) mechanical valves and rheumatic valve disease, (iv) patients with time in therapeutic range of >70% on warfarin; (v) patients with a single stroke risk factor (CHA2DS2VASc score of 1 in males, 2 in females); and (vi) patients with a single first episode of paroxysmal AF. Although there are no major differences in terms of efficacy and safety between the NOACs for some clinical scenarios, in others we are able to suggest that particular drugs and/or doses be prioritized for anticoagulation.

  18. Stroke as the First Manifestation of Atrial Fibrillation

    PubMed Central

    Jaakkola, Jussi; Mustonen, Pirjo; Kiviniemi, Tuomas; Hartikainen, Juha E. K.; Palomäki, Antti; Hartikainen, Päivi; Nuotio, Ilpo; Ylitalo, Antti; Airaksinen, K. E. Juhani

    2016-01-01

    Atrial fibrillation may remain undiagnosed until an ischemic stroke occurs. In this retrospective cohort study we assessed the prevalence of ischemic stroke or transient ischemic attack as the first manifestation of atrial fibrillation in 3,623 patients treated for their first ever stroke or transient ischemic attack during 2003–2012. Two groups were formed: patients with a history of atrial fibrillation and patients with new atrial fibrillation diagnosed during hospitalization for stroke or transient ischemic attack. A control group of 781 patients with intracranial hemorrhage was compiled similarly to explore causality between new atrial fibrillation and stroke. The median age of the patients was 78.3 [13.0] years and 2,009 (55.5%) were women. New atrial fibrillation was diagnosed in 753 (20.8%) patients with stroke or transient ischemic attack, compared to 15 (1.9%) with intracranial hemorrhage. Younger age and no history of coronary artery disease or other vascular diseases, heart failure, or hypertension were the independent predictors of new atrial fibrillation detected concomitantly with an ischemic event. Thus, ischemic stroke was the first clinical manifestation of atrial fibrillation in 37% of younger (<75 years) patients with no history of cardiovascular diseases. In conclusion, atrial fibrillation is too often diagnosed only after an ischemic stroke has occurred, especially in middle-aged healthy individuals. New atrial fibrillation seems to be predominantly the cause of the ischemic stroke and not triggered by the acute cerebrovascular event. PMID:27936187

  19. Directing collagen fibers using counter-rotating cone extrusion.

    PubMed

    Hoogenkamp, Henk R; Bakker, Gert-Jan; Wolf, Louis; Suurs, Patricia; Dunnewind, Bertus; Barbut, Shai; Friedl, Peter; van Kuppevelt, Toin H; Daamen, Willeke F

    2015-01-01

    The bio-inspired engineering of tissue equivalents should take into account anisotropic morphology and the mechanical properties of the extracellular matrix. This especially applies to collagen fibrils, which have various, but highly defined, orientations throughout tissues and organs. There are several methods available to control the alignment of soluble collagen monomers, but the options to direct native insoluble collagen fibers are limited. Here we apply a controlled counter-rotating cone extrusion technology to engineer tubular collagen constructs with defined anisotropy. Driven by diverging inner and outer cone rotation speeds, collagen fibrils from bovine skin were extruded and precipitated onto mandrels as tubes with oriented fibers and bundles, as examined by second harmonic generation microscopy and quantitative image analysis. A clear correlation was found whereby the direction and extent of collagen fiber alignment during extrusion were a function of the shear forces caused by a combination of the cone rotation and flow direction. A gradual change in the fiber direction, spanning +50 to -40°, was observed throughout the sections of the sample, with an average decrease ranging from 2.3 to 2.6° every 10μm. By varying the cone speeds, the collagen constructs showed differences in elasticity and toughness, spanning 900-2000kPa and 19-35mJ, respectively. Rotational extrusion presents an enabling technology to create and control the (an)isotropic architecture of collagen constructs for application in tissue engineering and regenerative medicine.

  20. SPARC regulates collagen interaction with cardiac fibroblast cell surfaces.

    PubMed

    Harris, Brett S; Zhang, Yuhua; Card, Lauren; Rivera, Lee B; Brekken, Rolf A; Bradshaw, Amy D

    2011-09-01

    Cardiac tissue from mice that do not express secreted protein acidic and rich in cysteine (SPARC) have reduced amounts of insoluble collagen content at baseline and in response to pressure overload hypertrophy compared with wild-type (WT) mice. However, the cellular mechanism by which SPARC affects myocardial collagen is not clearly defined. Although expression of SPARC by cardiac myocytes has been detected in vitro, immunohistochemistry of hearts demonstrated SPARC staining primarily associated with interstitial fibroblastic cells. Primary cardiac fibroblasts isolated from SPARC-null and WT mice were assayed for collagen I synthesis by [(3)H]proline incorporation into procollagen and by immunoblot analysis of procollagen processing. Bacterial collagenase was used to discern intracellular from extracellular forms of collagen I. Increased amounts of collagen I were found associated with SPARC-null versus WT cells, and the proportion of total collagen I detected on SPARC-null fibroblasts without propeptides [collagen-α(1)(I)] was higher than in WT cells. In addition, the amount of total collagen sensitive to collagenase digestion (extracellular) was greater in SPARC-null cells than in WT cells, indicating an increase in cell surface-associated collagen in the absence of SPARC. Furthermore, higher levels of collagen type V, a fibrillar collagen implicated in collagen fibril initiation, were found in SPARC-null fibroblasts. The absence of SPARC did not result in significant differences in proliferation or in decreased production of procollagen I by cardiac fibroblasts. We conclude that SPARC regulates collagen in the heart by modulating procollagen processing and interactions with fibroblast cell surfaces. These results are consistent with decreased levels of interstitial collagen in the hearts of SPARC-null mice being due primarily to inefficient collagen deposition into the extracellular matrix rather than to differences in collagen production.

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

    USDA-ARS?s Scientific Manuscript database

    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...

  2. Characterization of ultrastructure and collagen composition of the teratoma membrane: comparison to the amniotic membrane.

    PubMed

    Kim, Kyung Sook; Cho, Chang-Hoon; Kim, Young-Sun; Yoon, Kyung-Sik; Jung, Min-Hyung; Park, Hun-Kuk

    2013-04-01

    The structural and morphological properties of the teratoma membrane were investigated to better understand the pathogenesis of ovarian teratomas. A mature cystic teratoma and amnion were obtained from patients who underwent laparoscopic cystectomy and uncomplicated delivery, respectively. The teratoma membrane was divided into three layers according to the results of the histological analysis. Each layer showed distinct morphological properties, including an outer layer that was uniformly arranged, a middle layer with an irregular pattern of fibers, and an inner layer that was structurally dense with a wavy pattern of fibers. The morphology of the layers of the amniotic membrane was the reverse that of the teratoma membrane. In the teratoma membrane, the outer layer was primarily composed of type III collagen and the inner layer had a large amount of type III and IV collagen. The amniotic membrane showed a small amount of type III collagen in the outer layer, whereas the inner layer had large amounts of type I, III, and IV collagen. In the teratoma membrane, the collagen fibrils were arranged regularly in the outer layer, but irregularly in the inner layer. In the amniotic membrane, the arrangement of collagen fibrils was the reverse that of the teratoma membrane. Additionally, the collagen fibrils in the teratoma membrane were thinner than those of the amniotic membrane and had slightly shorter d-spacing. Two membranes showed the differences in collagen fibril arrangement, which may caused by the different functional roles.

  3. Analysis of mineral deposition in turkey tendons and self-assembled collagen fibers using mechanical techniques.

    PubMed

    Freeman, Joseph W; Silver, Frederick H

    2004-01-01

    During limb movement and locomotion, animals store elastic energy in the tendons of the feet, legs, and other limbs. In the turkey, much of the force generated by the gastrocnemius muscle during locomotion is stored as elastic energy through deformation of the tendon. During growth and development, the leg tendons in some avians, including turkeys, mineralize and result in an increase in tensile strength and modulus. The purpose of our study was to evaluate the effects of mineralization on elastic energy storage and transmission in turkey tendons. Elastic and viscous stress-strain curves and elastic energy storage behavior were used to compare the behavior of mineralized turkey gastrocnemius tendons and mineralized self-assembled type I collagen fibers. Based on analysis of these two systems, we concluded that a simple mineralized fibrillar collagenous substrate can mimic the behavior of a more complex fibrillar collagenous substrate such as mineralized turkey tendon; however, the exact mechanism of mineralization may be different between the two substrates. Changes in mechanical properties of turkey tendon were consistent with a model in which mineralization appears to increase the effective collagen fibril length by efficiently transferring stress between neighboring collagen fibrils. Mineralization in self-assembled collagen fibers increased elastic energy storage less efficiently as compared with turkey tendon suggesting that the noncollagenous components of mineralizing tissue may act to promote collagen fibril to collagen fibril interactions.

  4. Effect of chromium(III) gallate complex on stabilization of collagen.

    PubMed

    Jaikumar, Dhanya; Baskaran, Babu; Vaidyanathan, V G

    2017-03-01

    To improve the stability of the collagen, here we studied the interaction of chromium(III) polyphenolic complex, [Cr(GA)2] (GA: Gallic acid) with collagen using various spectroscopic techniques. Circular dichroism studies show that the [Cr(GA)2] and gallic acid did not induce any structural perturbations on the triple helix of the collagen. Both differential scanning calorimetric(DSC) data and micro-shrinkage temperature studies showed that [Cr(GA)2] stabilized the collagen by 6±1°C compared to gallic acid. Hydrodynamic studies revealed that the viscosity of collagen drastically reduced in the presence of [Cr(GA)2] while gallic acid did not. Fibrillation assay displayed a significant delay in fibril formation with Cr(III) complex compared to gallic acid treated collagen. The inhibition of fibril formation was further confirmed by microscopic data in which collagen fibres are seen with GA while [Cr(GA)2] treated collagen exhibit a thin microfibrils. From AFM studies, the d-periodicity of collagen was found to be decreased with [Cr(GA)2] while increased with gallic acid. The present study deliberate the advantage of metal complex containing polyphenolic ligand as crosslinking agent due to its synergistic effect of both metal center as well as polyphenolic groups in the stabilization of collagen structure. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. Hierarchical model of fibrillar collagen distribution for polarization-resolved SHG microscopy

    NASA Astrophysics Data System (ADS)

    Tuer, Adam E.; Akens, Margarete K.; Krouglov, Serguei; Sandkuijl, Daaf; Wilson, Brian C.; Whyne, Cari M.; Barzda, Virginijus

    2013-02-01

    A hierarchical model of the organization of fibrillar collagen is developed and its implications on polarization-resolved second harmonic generation (SHG) microscopy are investigated. A "ground-up" approach is employed to develop the theory for understanding of the origin of SHG from fibrillar collagen. The effects of fibril ultrastructure and fibril macroscopic organization on the second-order polarization properties of fibrillar collagen are presented in conjunction with recent ab initio results performed on a collagen triple-helix model (-GLY-PRO-HYP-)n. Various tissues containing fibrillar collagen are quantified using a polarization-resolved SHG technique, termed polarization-in, polarization-out (PIPO) and interpreted in light of the aforementioned theory. The method involves varying the incident laser polarization, while monitoring the SHG intensity through an analyzer. From the SHG polarization data the orientation of the fibers, in biological tissue, can be deduced. Unique PIPO signatures are observed for different rat tissues and interpreted in terms of the collagen composition, fibril ultrastructure, and macroscopic organization. Similarities and discrepancies in the second-order polarization properties of different collagen types and ultrastructures will be presented. PIPO SHG microscopy shows promise in its ability to quantify the organization of collagen in various tissues. The ability to characterize the structure of collagen in various tissue microenvironments will aid in the study of numerous collagen related biological process, including tissue diseases, wound repair, and tumor development and progression.

  6. 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

  7. 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.

  8. Collagen-Binding Peptidoglycans Inhibit MMP Mediated Collagen Degradation and Reduce Dermal Scarring

    PubMed Central

    Snyder, Paul W.; Freeman, Lynetta; Panitch, Alyssa

    2011-01-01

    Scarring of the skin is a large unmet clinical problem that is of high patient concern and impact. Wound healing is complex and involves numerous pathways that are highly orchestrated, leaving the skin sealed, but with abnormal organization and composition of tissue components, namely collagen and proteoglycans, that are then remodeled over time. To improve healing and reduce or eliminate scarring, more rapid restoration of healthy tissue composition and organization offers a unique approach for development of new therapeutics. A synthetic collagen-binding peptidoglycan has been developed that inhibits matrix metalloproteinase-1 and 13 (MMP-1 and MMP-13) mediated collagen degradation. We investigated the synthetic peptidoglycan in a rat incisional model in which a single dose was delivered in a hyaluronic acid (HA) vehicle at the time of surgery prior to wound closure. The peptidoglycan treatment resulted in a significant reduction in scar tissue at 21 days as measured by histology and visual analysis. Improved collagen architecture of the treated wounds was demonstrated by increased tensile strength and transmission electron microscopy (TEM) analysis of collagen fibril diameters compared to untreated and HA controls. The peptidoglycan's mechanism of action includes masking existing collagen and inhibiting MMP-mediated collagen degradation while modulating collagen organization. The peptidoglycan can be synthesized at low cost with unique design control, and together with demonstrated preclinical efficacy in reducing scarring, warrants further investigation for dermal wound healing. PMID:21779387

  9. Age-associated increase of skin fibroblast-derived prostaglandin E2 contributes to reduced collagen levels in elderly human skin

    PubMed Central

    Li, Yong; Lei, Dan; Swindell, William R; Xia, Wei; Weng, Shinuo; Fu, Jianping; Worthen, Christal A; Okubo, Toru; Johnston, Andrew; Gudjonsson, Johann E; Voorhees, John J; Fisher, Gary J

    2015-01-01

    Production of type I collagen declines during aging, leading to skin thinning and impaired function. Prostaglandin E2 (PGE2) is a pleiotropic lipid mediator that is synthesized from arachidonic acid by the sequential actions of cyclooxygenases (COX) and PGE synthases (PTGES). PGE2 inhibits collagen production by fibroblasts in vitro. We report that PTGES1 and COX2 progressively increase with aging in sun-protected human skin. PTGES1 and COX2 mRNA was increased 3.4-fold and 2.7-fold, respectively, in the dermis of elderly (>80 years) versus young (21-30 years) individuals. Fibroblasts were the major cell source of both enzymes. PGE2 levels were increased 70% in elderly skin. Fibroblasts in aged skin display reduced spreading due to collagen fibril fragmentation. To investigate the relationship between spreading and PGE2 synthesis, fibroblasts were cultured on micropost arrays or hydrogels of varying mechanical compliance. Reduced spreading/mechanical force resulted in increased expression of both PTGES1 and COX2 and elevated levels of PGE2. Inhibition of PGE2 synthesis by diclofenac enhanced collagen production in skin organ cultures. These data suggest that reduced spreading/mechanical force of fibroblasts in aged skin elevates PGE2 production, contributing to reduced collagen production. Inhibition of PGE2 production may be therapeutically beneficial for combating age-associated collagen deficit in human skin. PMID:25905589

  10. 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.

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

    PubMed

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

    2016-07-26

    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.

  12. 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

  13. 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

  14. Association of genetic variants with atrial fibrillation.

    PubMed

    Yamase, Yuichiro; Kato, Kimihiko; Horibe, Hideki; Ueyama, Chikara; Fujimaki, Tetsuo; Oguri, Mitsutoshi; Arai, Masazumi; Watanabe, Sachiro; Murohara, Toyoaki; Yamada, Yoshiji

    2016-02-01

    Recent genome-wide association studies (GWASs) identified various genes and loci that confer susceptibility to coronary artery disease or myocardial infarction among Caucasian populations. As myocardial ischemia is an important risk factor for atrial fibrillation, we hypothesized that certain polymorphisms may contribute to the genetic susceptibility to atrial fibrillation through affecting the susceptibility to coronary artery disease. The aim of the present study was to examine the possible association of atrial fibrillation in Japanese individuals with 29 polymorphisms identified as susceptibility loci for coronary artery disease or myocardial infarction in the meta-analyses of GWASs in Caucasian populations. The study subjects comprised 5,470 Japanese individuals (305 subjects with atrial fibrillation and 5,165 controls). Genotypes for 29 polymorphisms were determined by a method that combines the polymerase chain reaction and sequence-specific oligonucleotide probes with suspension array technology. Comparisons of the allele frequencies by the χ(2) test revealed that rs599839 (G→A) of the proline/serine-rich coiled-coil 1 gene (PSRC1, P=0.0084) and rs11556924 (C→T, Arg363His) of the zinc finger, C3HC-type containing 1 gene (ZC3HC1, P=0.0076) were significantly (P<0.01) associated with atrial fibrillation. Multivariable logistic regression analysis with adjustment for age, gender, body mass index, estimated glomerular filtration rate, and the prevalence of smoking, hypertension, diabetes mellitus, and dyslipidemia revealed that rs599839 (P=0.0043; odds ratio, 1.56; dominant model) and rs11556924 (P=0.0043; odds ratio, 1.93; dominant model) were significantly associated with atrial fibrillation, with the minor G and T alleles, respectively, representing risk factors for this condition. PSRC1 and ZC3HC1 may thus be susceptibility loci for atrial fibrillation in Japanese individuals.

  15. The initiation of embryonic-like collagen fibrillogenesis by adult human tendon fibroblasts when cultured under tension.

    PubMed

    Bayer, Monika L; Yeung, Chin-Yan C; Kadler, Karl E; Qvortrup, Klaus; Baar, Keith; Svensson, René B; Magnusson, S Peter; Krogsgaard, Michael; Koch, Manuel; Kjaer, Michael

    2010-06-01

    Tendon fibroblasts synthesize collagen and form fibrils during embryonic development, but to what extent mature fibroblasts are able to recapitulate embryonic development and develop normal tendon structure is unknown. The present study examined the capability of mature human tendon fibroblasts to initiate collagen fibrillogenesis when cultured in fixed-length fibrin gels. Fibroblasts were dissected from semitendinosus and gracilis tendons from healthy humans and cultured in 3D linear fibrin gels. The fibroblasts synthesized an extracellular matrix of parallel collagen fibrils that were aligned along the axis of tension. The fibrils had a homogeneous narrow diameter that was similar to collagen fibrils occurring in embryonic tendon. Immunostaining showed colocalization of collagen type I with collagen III, XII and XIV. A fibronectin network was formed in parallel with the collagen, and fibroblasts stained positive for integrin alpha(5). Finally, the presence of cell extensions into the extracellular space with membrane-enclosed fibrils in fibripositors indicated characteristics of embryonic tendon. We conclude that mature human tendon fibroblasts retain an intrinsic capability to perform collagen fibrillogenesis similar to that of developing tendon, which implies that the hormonal/mechanical milieu, rather than intrinsic cellular function, inhibits regenerative potential in mature tendon. (c) 2010 Elsevier Ltd. All rights reserved.

  16. Amyloid Fibrils from Hemoglobin

    PubMed Central

    Jayawardena, Nadishka; Kaur, Manmeet; Nair, Smitha; Malmstrom, Jenny; Goldstone, David; Negron, Leonardo; Gerrard, Juliet A.; Domigan, Laura J.

    2017-01-01

    Amyloid fibrils are a class of insoluble protein nanofibers that are formed via the self-assembly of a wide range of peptides and proteins. They are increasingly exploited for a broad range of applications in bionanotechnology, such as biosensing and drug delivery, as nanowires, hydrogels, and thin films. Amyloid fibrils have been prepared from many proteins, but there has been no definitive characterization of amyloid fibrils from hemoglobin to date. Here, nanofiber formation was carried out under denaturing conditions using solutions of apo-hemoglobin extracted from bovine waste blood. A characteristic amyloid fibril morphology was confirmed by transmission electron microscopy (TEM) and atomic force microscopy (AFM), with mean fibril dimensions of approximately 5 nm diameter and up to several microns in length. The thioflavin T assay confirmed the presence of β-sheet structures in apo-hemoglobin fibrils, and X-ray fiber diffraction showed the characteristic amyloid cross-β quaternary structure. Apo-hemoglobin nanofibers demonstrated high stability over a range of temperatures (−20 to 80 °C) and pHs (2–10), and were stable in the presence of organic solvents and trypsin, confirming their potential as nanomaterials with versatile applications. This study conclusively demonstrates the formation of amyloid fibrils from hemoglobin for the first time, and also introduces a cost-effective method for amyloid fibril manufacture using meat industry by-products. PMID:28398221

  17. Vulnerability to ventricular fibrillation

    NASA Astrophysics Data System (ADS)

    Janse, Michiel J.

    1998-03-01

    One of the factors that favors the development of ventricular fibrillation is an increase in the dispersion of refractoriness. Experiments will be described in which an increase in dispersion in the recovery of excitability was determined during brief episodes of enhanced sympathetic nerve activity, known to increase the risk of fibrillation. Whereas in the normal heart ventricular fibrillation can be induced by a strong electrical shock, a premature stimulus of moderate intensity only induces fibrillation in the presence of regional ischemia, which greatly increases the dispersion of refractoriness. One factor that is of importance for the transition of reentrant ventricular tachycardia to ventricular fibrillation during acute regional ischemia is the subendocardial Purkinje system. After selective destruction of the Purkinje network by lugol, reentrant tachycardias still develop in the ischemic region, but they do not degenerate into fibrillation. Finally, attempts were made to determine the minimal mass of thin ventricular myocardium required to sustain fibrillation induced by burst pacing. This was done by freezing of subendocardial and midmural layers. The rim of surviving epicardial muscle had to be larger than 20 g. Extracellular electrograms during fibrillation in both the intact and the "frozen" left ventricle were indistinguishable, but activation patterns were markedly different. In the intact ventricle epicardial activation was compatible with multiple wavelet reentry, in the "frozen" heart a single, or at most two wandering reentrant waves were seen.

  18. Dynamics of Focal Fibrillation Waves during Persistent Atrial Fibrillation.

    PubMed

    Lanters, Eva A H; Allessie, Maurits A; DE Groot, Natasja M S

    2016-04-01

    The incidence and appearance of focal fibrillation waves on the right and left atrial epicardial surface were visualized during 10 seconds of persistent atrial fibrillation in a 71-year-old woman with valvular heart disease. The frequent, nonrepetitive, widespread, and capricious distribution of focal waves suggests that transmural conduction of fibrillation waves is most likely the mechanism underlying focal fibrillation waves.

  19. Collagen-Binding Peptidoglycans: A Biomimetic Approach to Modulate Collagen Fibrillogenesis for Tissue Engineering Applications

    PubMed Central

    Paderi, John E.; Sistiabudi, Rizaldi; Ivanisevic, Albena

    2009-01-01

    The small leucine-rich proteoglycans (SLRPs), prevalent in collagenous tissues, regulate collagen fibrillogenesis and provide a host of biochemical cues critical to tissue function and homeostasis. Incorporating SLRPs may enhance tissue engineering designs that mimic the native extracellular matrix, although SLRPs purified from animal sources bear low yields and lack design control. Consequently, we have designed synthetic peptidoglycans, inspired by the native SLRP decorin, that contain a collagen-binding peptide attached to a glycosaminoglycan (GAG) chain. These peptidoglycans modulate collagen fibrillogenesis and decrease fibril diameter in vitro, similarly to decorin, while maintaining the characteristic D-banded fibrils. Application for tissue engineering is demonstrated as these peptidoglycans are incorporated into collagen gels seeded with smooth muscle cells. Gels formed with peptidoglycans and decorin show a faster rate of gel compaction, and one peptidoglycan uniquely increases elastin production. The peptidoglycan design can be tailored with respect to the peptide sequence and GAG identity and is expected to have versatile application in tissue engineering. PMID:19323607

  20. Estrogen Depletion Results in Nanoscale Morphology Changes in Dermal Collagen

    PubMed Central

    Fang, Ming; Liroff, Kaitlin G.; Turner, A. Simon; Les, Clifford M.; Orr, Bradford G.; Holl, Mark M. Banaszak

    2012-01-01

    Tissue cryo-sectioning combined with Atomic Force Microscopy (AFM) imaging reveals that the nanoscale morphology of dermis collagen fibrils, quantified using the metric of D-periodic spacing, changes under the condition of estrogen depletion. Specifically, a new subpopulation of fibrils with D-spacings in the region between 56 and 59 nm is present two years following ovariectomy in ovine dermal samples. In addition, the overall width of the distribution, both values above and below the mean, has increased. The change in width due to an increase in lower values of D-spacings was previously reported for ovine bone; however, this report demonstrates that the effect is also present in non-mineralized collagen fibrils. A non-parametric Kolmogrov-Smirnov test of the cumulative density function indicates a statistical difference in the sham and OVX D-spacing distributions (p < 0.01). PMID:22437310

  1. Collagen and myosin characterization by orientation field second harmonic microscopy.

    PubMed

    Odin, Christophe; Guilbert, Thomas; Alkilani, Alia; Boryskina, Olena P; Fleury, Vincent; Le Grand, Yann

    2008-09-29

    Collagen and myosin fibrils are endogenous harmonophores that both give rise to Second Harmonic Generation (SHG). By combining four polarization SHG images provided by a scanning microscope, we show that the orientation of the principal axis of the nonlinear susceptibility tensor chi(2) can be determined for each pixel of the image. The ratio rho = chi33/chi15 of the principal components of chi(2) of collagen and myosin was obtained with the same method, and found within the range 1.6-1.8 and 0.5-0.6 respectively. The orientation of the principal axis of chi(2) is shown to be correlated to the orientation of the fibrils themselves. This provides a straightforward method, which we call Orientation Field-Second Harmonic Microscopy (OF-SHM), to reconstruct orientation fields of fibrils at various scales and resolutions in different biological systems (from muscle sarcomere to the whole embryo).

  2. Fullerene-C60/liposome complex: Defensive effects against UVA-induced damages in skin structure, nucleus and collagen type I/IV fibrils, and the permeability into human skin tissue.

    PubMed

    Kato, Shinya; Aoshima, Hisae; Saitoh, Yasukazu; Miwa, Nobuhiko

    2010-01-21

    We previously reported biological safety of fullerene-C60 (C60) incorporated in liposome consisting of hydrogenated lecithin and glycine soja sterol, as Liposome-Fullerene (0.5% aqueous phase; a particle size, 76nm; Lpsm-Flln), and its cytoprotective activity against UVA. In the present study, Lpsm-Flln was administered on the surface of three-dimensional human skin tissue model, rinsed out before each UVA-irradiation at 4 J/cm(2), and thereafter added again, followed by 19-cycle-repetition for 4 days (sum: 76 J/cm(2)). UVA-caused corneum scaling and disruption of epidermis layer were detected by scanning electron microscopy. Breakdown of collagen type I/IV, DNA strand cleavage and pycnosis/karyorrhexis were observed in vertical cross-sections of UVA-irradiated skin models visualized with fluorescent immunostain or Hoechst 33342 stain. These skin damages were scarcely repressed by liposome alone, but appreciably repressed by Lpsm-Flln of 250 ppm, containing 0.75 ppm of C60-equivalent to a 1/3300-weight amount vs. the whole liposome. Upon administration with Lpsm-Flln [16.7 microM (12 ppm): C60-equivalent] on human abdomen skin biopsies mounted in Franz diffusion cells, C60 permeated after 24h into the epidermis at 1.86 nmol/g tissue (1.34 ppm), corresponding to 0.3% of the applied amount and a 9.0-fold dilution rate, but C60 was not detected in the dermis by HPLC, suggesting no necessity for considering a toxicity of C60 due to systemic circulation via dermal veins. Thus Lpsm-Flln has a potential to be safely utilized as a cosmetic anti-oxidative ingredient for UVA-protection.

  3. 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

  4. 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

  5. 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

  6. Advanced glycation end-products diminish tendon collagen fiber sliding.

    PubMed

    Li, Yufei; Fessel, Gion; Georgiadis, Marios; Snedeker, Jess G

    2013-04-24

    Connective tissue aging and diabetes related comorbidity are associated with compromised tissue function, increased susceptibility to injury, and reduced healing capacity. This has been partly attributed to collagen cross-linking by advanced glycation end-products (AGEs) that accumulate with both age and disease. While such cross-links are believed to alter the physical properties of collagen structures and tissue behavior, existing data relating AGEs to tendon mechanics is contradictory. In this study, we utilized a rat tail tendon model to quantify the micro-mechanical repercussion of AGEs at the collagen fiber-level. Individual tendon fascicles were incubated with methylglyoxal (MGO), a naturally occurring metabolite known to form AGEs. After incubation in MGO solution or buffer only, tendons were stretched on the stage of a multiphoton confocal microscope and individual collagen fiber stretch and relative fiber sliding were quantified. Treatment by MGO yielded increased fluorescence and elevated denaturation temperatures as found in normally aged tissue, confirming formation of AGEs and related cross-links. No apparent ultrastructural changes were noted in transmission electron micrographs of cross-linked fibrils. MGO treatment strongly reduced tissue stress relaxation (p<0.01), with concomitantly increased tissue yield stress (p<0.01) and ultimate failure stress (p=0.036). MGO did not affect tangential modulus in the linear part of the stress-strain curve (p=0.46). Microscopic analysis of collagen fiber kinematics yielded striking results, with MGO treatment drastically reducing fiber-sliding (p<0.01) with a compensatory increase in fiber-stretch (p<0.01). We thus conclude that the main mechanical effect of AGEs is a loss of tissue viscoelasticity driven by matrix-level loss of fiber-fiber sliding. This has potentially important implications to tissue damage accumulation, mechanically regulated cell signaling, and matrix remodeling. It further highlights the

  7. 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.

  8. Dense tissue-like collagen matrices formed in cell-free conditions.

    PubMed

    Mosser, Gervaise; Anglo, Anny; Helary, Christophe; Bouligand, Yves; Giraud-Guille, Marie-Madeleine

    2006-01-01

    A new protocol was developed to produce dense organized collagen matrices hierarchically ordered on a large scale. It consists of a two stage process: (1) the organization of a collagen solution and (2) the stabilization of the organizations by a sol-gel transition that leads to the formation of collagen fibrils. This new protocol relies on the continuous injection of an acid-soluble collagen solution into glass microchambers. It leads to extended concentration gradients of collagen, ranging from 5 to 1000 mg/ml. The self-organization of collagen solutions into a wide array of spatial organizations was investigated. The final matrices obtained by this procedure varied in concentration, structure and density. Changes in the liquid state of the samples were followed by polarized light microscopy, and the final stabilized gel states obtained after fibrillogenesis were analyzed by both light and electron microscopy. Typical organizations extended homogeneously by up to three centimetres in one direction and several hundreds of micrometers in other directions. Fibrillogenesis of collagen solutions of high and low concentrations led to fibrils spatially arranged as has been described in bone and derm, respectively. Moreover, a relationship was revealed between the collagen concentration and the aggregation of and rotational angles between lateral fibrils. These results constitute a strong base from which to further develop highly enriched collagen matrices that could lead to substitutes that mimic connective tissues. The matrices thus obtained may also be good candidates for the study of the three-dimensional migration of cells.

  9. Collagen-Gold Nanoparticle Conjugates for Versatile Biosensing

    PubMed Central

    Unser, Sarah; Holcomb, Samuel; Cary, ReJeana; Sagle, Laura

    2017-01-01

    Integration of noble metal nanoparticles with proteins offers promising potential to create a wide variety of biosensors that possess both improved selectivity and versatility. The multitude of functionalities that proteins offer coupled with the unique optical properties of noble metal nanoparticles can allow for the realization of simple, colorimetric sensors for a significantly larger range of targets. Herein, we integrate the structural protein collagen with 10 nm gold nanoparticles to develop a protein-nanoparticle conjugate which possess the functionality of the protein with the desired colorimetric properties of the nanoparticles. Applying the many interactions that collagen undergoes in the extracellular matrix, we are able to selectively detect both glucose and heparin with the same collagen-nanoparticle conjugate. Glucose is directly detected through the cross-linking of the collagen fibrils, which brings the attached nanoparticles into closer proximity, leading to a red-shift in the LSPR frequency. Conversely, heparin is detected through a competition assay in which heparin-gold nanoparticles are added to solution and compete with heparin in the solution for the binding sites on the collagen fibrils. The collagen-nanoparticle conjugates are shown to detect both glucose and heparin in the physiological range. Lastly, glucose is selectively detected in 50% mouse serum with the collagen-nanoparticle devices possessing a linear range of 3–25 mM, which is also within the physiologically relevant range. PMID:28212282

  10. Collagen-Gold Nanoparticle Conjugates for Versatile Biosensing.

    PubMed

    Unser, Sarah; Holcomb, Samuel; Cary, ReJeana; Sagle, Laura

    2017-02-15

    Integration of noble metal nanoparticles with proteins offers promising potential to create a wide variety of biosensors that possess both improved selectivity and versatility. The multitude of functionalities that proteins offer coupled with the unique optical properties of noble metal nanoparticles can allow for the realization of simple, colorimetric sensors for a significantly larger range of targets. Herein, we integrate the structural protein collagen with 10 nm gold nanoparticles to develop a protein-nanoparticle conjugate which possess the functionality of the protein with the desired colorimetric properties of the nanoparticles. Applying the many interactions that collagen undergoes in the extracellular matrix, we are able to selectively detect both glucose and heparin with the same collagen-nanoparticle conjugate. Glucose is directly detected through the cross-linking of the collagen fibrils, which brings the attached nanoparticles into closer proximity, leading to a red-shift in the LSPR frequency. Conversely, heparin is detected through a competition assay in which heparin-gold nanoparticles are added to solution and compete with heparin in the solution for the binding sites on the collagen fibrils. The collagen-nanoparticle conjugates are shown to detect both glucose and heparin in the physiological range. Lastly, glucose is selectively detected in 50% mouse serum with the collagen-nanoparticle devices possessing a linear range of 3-25 mM, which is also within the physiologically relevant range.

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

    PubMed

    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.

  12. 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

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

    PubMed

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

    2010-08-07

    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.

  14. 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

  15. Rotor mapping and ablation to treat atrial fibrillation.

    PubMed

    Zaman, Junaid A B; Peters, Nicholas S; Narayan, Sanjiv M

    2015-01-01

    Rotors have long been postulated to drive atrial fibrillation, but evidence has been limited to animal models. This changed recently with the demonstration using focal impulse and rotor modulation (FIRM) mapping that rotors act as human atrial fibrillation sources. This mechanistic approach to diagnosing the causes of atrial fibrillation in individual patients has been supported by substantially improved outcomes from FIRM-guided ablation, resulting in increased attention to rotors as therapeutic targets. In this review, we outline the pathophysiology of rotors in animal and in-silico studies of fibrillation, and how this motivated FIRM mapping in humans. We highlight the characteristics of rotors in human atrial fibrillation, now validated by several techniques, with discussion on similar and discrepant findings between techniques. The interventional approaches to eliminate atrial fibrillation rotors are explained and the ablation results in latest studies using FIRM are discussed. We propose that mapping localized sources for human atrial fibrillation, specifically rotors, is moving the field towards a unifying hypothesis that explains several otherwise contradictory observations in atrial fibrillation management. We conclude by suggesting areas of potential research that may reveal more about these critical sites and how these may lead to better and novel treatments for atrial fibrillation.

  16. Electromechanical properties of dried tendon and isoelectrically focused collagen hydrogels.

    PubMed

    Denning, D; Abu-Rub, M T; Zeugolis, D I; Habelitz, S; Pandit, A; Fertala, A; Rodriguez, B J

    2012-08-01

    Assembling artificial collagenous tissues with structural, functional, and mechanical properties which mimic natural tissues is of vital importance for many tissue engineering applications. While the electro-mechanical properties of collagen are thought to play a role in, for example, bone formation and remodeling, this functional property has not been adequately addressed in engineered tissues. Here the electro-mechanical properties of rat tail tendon are compared with those of dried isoelectrically focused collagen hydrogels using piezoresponse force microscopy under ambient conditions. In both the natural tissue and the engineered hydrogel D-periodic type I collagen fibrils are observed, which exhibit shear piezoelectricity. While both tissues also exhibit fibrils with parallel orientations, Fourier transform analysis has revealed that the degree of parallel alignment of the fibrils in the tendon is three times that of the dried hydrogel. The results obtained demonstrate that isoelectrically focused collagen has similar structural and electro-mechanical properties to that of tendon, which is relevant for tissue engineering applications.

  17. Development of a high-throughput screening system for the compounds that inhibit collagen-protein interactions.

    PubMed

    Okano-Kosugi, Hitomi; Matsushita, Osamu; Asada, Shinichi; Herr, Andrew B; Kitagawa, Kouki; Koide, Takaki

    2009-11-01

    Collagen-binding proteins (CBPs) play important roles in various physiological events. Some CBPs are regarded as targets for drug development; for example, platelet glycoprotein VI (GPVI) and heat shock protein 47 (HSP47) are promising targets for the development of novel antiplatelet and antifibrotic drugs, respectively. However, no systematic screening method to search compounds that inhibit collagen-CBP interactions have been developed, and only a few CBP inhibitors have been reported to date. In this study, a facile turbidimetric multiwell plate assay was developed to evaluate inhibitors of CBPs. The assay is based on the finding that CBPs retard spontaneous collagen fibril formation in vitro and that fibril formation is restored in the presence of compounds that interfere with the collagen-CBP interactions. Using the same platform, the assay was performed in various combinations of fibril-forming collagen types and CBPs. This homogeneous assay is simple, convenient, and suitable as an automated high-throughput screening system.

  18. Surgery for Atrial Fibrillation.

    PubMed

    Lawrance, Christopher P; Henn, Matthew C; Damiano, Ralph J

    2016-04-01

    Atrial fibrillation is the most common cardiac arrhythmia, and its treatment options include drug therapy or catheter-based or surgical interventions. The surgical treatment of atrial fibrillation has undergone multiple evolutions over the last several decades. The Cox-Maze procedure went on to become the gold standard for the surgical treatment of atrial fibrillation and is currently in its fourth iteration (Cox-Maze IV). This article reviews the indications and preoperative planning for performing a Cox-Maze IV procedure. This article also reviews the literature describing the surgical results for both approaches including comparisons of the Cox-Maze IV to the previous cut-and-sew method.

  19. Surgery for atrial fibrillation.

    PubMed

    Lawrance, Christopher P; Henn, Matthew C; Damiano, Ralph J

    2014-11-01

    Atrial fibrillation is the most common cardiac arrhythmia, and its treatment options include drug therapy or catheter-based or surgical interventions. The surgical treatment of atrial fibrillation has undergone multiple evolutions over the last several decades. The Cox-Maze procedure went on to become the gold standard for the surgical treatment of atrial fibrillation and is currently in its fourth iteration (Cox-Maze IV). This article reviews the indications and preoperative planning for performing a Cox-Maze IV procedure. This article also reviews the literature describing the surgical results for both approaches including comparisons of the Cox-Maze IV to the previous cut-and-sew method.

  20. 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

  1. 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

  2. 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

  3. 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.

  4. Atrial Fibrillation in Children

    MedlinePlus

    ... attribute childhood AF to congenital heart abnormalities or post-surgical complications. Learn more about children and arrhythmia. This content was last reviewed July 2016. Atrial Fibrillation • Introduction • What is ...

  5. Structures for amyloid fibrils.

    PubMed

    Makin, O Sumner; Serpell, Louise C

    2005-12-01

    Alzheimer's disease and Creutzfeldt-Jakob disease are the best-known examples of a group of diseases known as the amyloidoses. They are characterized by the extracellular deposition of toxic, insoluble amyloid fibrils. Knowledge of the structure of these fibrils is essential for understanding the process of pathology of the amyloidoses and for the rational design of drugs to inhibit or reverse amyloid formation. Structural models have been built using information from a wide variety of techniques, including X-ray diffraction, electron microscopy, solid state NMR and EPR. Recent advances have been made in understanding the architecture of the amyloid fibril. Here, we describe and compare postulated structural models for the mature amyloid fibril and discuss how the ordered structure of amyloid contributes to its stability.

  6. Atrial Fibrillation - Multiple Languages

    MedlinePlus

    ... Supplements Videos & Tools You Are Here: Home → Multiple Languages → All Health Topics → Atrial Fibrillation URL of this page: https://medlineplus.gov/languages/atrialfibrillation.html Other topics A-Z Expand Section ...

  7. 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

  8. 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

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

    PubMed Central

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

    2015-01-01

    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

  10. Fabrication of homobifunctional crosslinker stabilized collagen for biomedical application.

    PubMed

    Lakra, Rachita; Kiran, Manikantan Syamala; Sai, Korrapati Purna

    2015-11-27

    Collagen biopolymer has found widespread application in the field of tissue engineering owing to its excellent tissue compatibility and negligible immunogenicity. Mechanical strength and enzymatic degradation of the collagen necessitates the physical and chemical strength enhancement. One such attempt deals with the understanding of crosslinking behaviour of EGS (ethylene glycol-bis (succinic acid N-hydroxysuccinimide ester)) with collagen to improve the physico-chemical properties. The incorporation of a crosslinker during fibril formation enhanced the thermal and mechanical stability of collagen. EGS crosslinked collagen films exhibited higher denaturation temperature (T d) and the residue left after thermogravimetric analysis was about 16 ± 5.2%. Mechanical properties determined by uniaxial tensile tests showed a threefold increase in tensile strength and Young's modulus at higher concentration (100 μM). Water uptake capacity reduced up to a moderate extent upon crosslinking which is essential for the transport of nutrients to the cells. Cell viability was found to be 100% upon treatment with 100 μM EGS whereas only 30% viability could be observed with glutaraldehyde. Rheological studies of crosslinked collagen showed an increase in shear stress and shear viscosity at 37 °C. Crosslinking with EGS resulted in the formation of a uniform fibrillar network. Trinitrobenzene sulfonate (TNBS) assay confirmed that EGS crosslinked collagen by forming a covalent interaction with ε-amino acids of collagen. The homobifunctional crosslinker used in this study enhanced the effectiveness of collagen as a biomaterial for biomedical application.

  11. Changes to collagen structure during leather processing.

    PubMed

    Sizeland, Katie H; Edmonds, Richard L; Basil-Jones, Melissa M; Kirby, Nigel; Hawley, Adrian; Mudie, Stephen; Haverkamp, Richard G

    2015-03-11

    As hides and skins are processed to produce leather, chemical and physical changes take place that affect the strength and other physical properties of the material. The structural basis of these changes at the level of the collagen fibrils is not fully understood and forms the basis of this investigation. Synchrotron-based small-angle X-ray scattering (SAXS) is used to quantify fibril orientation and D-spacing through eight stages of processing from fresh green ovine skins to staked dry crust leather. Both the D-spacing and fibril orientation change with processing. The changes in thickness of the leather during processing affect the fibril orientation index (OI) and account for much of the OI differences between process stages. After thickness is accounted for, the main difference in OI is due to the hydration state of the material, with dry materials being less oriented than wet. Similarly significant differences in D-spacing are found at different process stages. These are due also to the moisture content, with dry samples having a smaller D-spacing. This understanding is useful for relating structural changes that occur during different stages of processing to the development of the final physical characteristics of leather.

  12. Scanning tunneling microscopy reveals single-molecule insights into the self-assembly of amyloid fibrils.

    PubMed

    Kalashnyk, Nataliya; Nielsen, Jakob T; Nielsen, Erik H; Skrydstrup, Troels; Otzen, Daniel E; Lægsgaard, Erik; Wang, Chen; Besenbacher, Flemming; Nielsen, Niels Chr; Linderoth, Trolle R

    2012-08-28

    Many severe diseases are associated with amyloid fibril deposits in the body caused by protein misfolding. Structural information on amyloid fibrils is accumulating rapidly, but little is known about the assembly of peptides into fibrils at the level of individual molecules. Here we investigate self-assembly of the fibril-forming tetrapeptides KFFE and KVVE on a gold surface under ultraclean vacuum conditions using scanning tunneling microscopy. Combined with restrained molecular dynamics modeling, we identify peptide arrangements with interesting similarities to fibril structures. By resolving individual peptide residues and revealing conformational heterogeneities and dynamics, we demonstrate how conformational correlations may be involved in cooperative fibril growth. Most interestingly, intermolecular interactions prevail over intramolecular interactions, and assembly of the phenyl-rich KFFE peptide appears not to be dominated by π-π interactions. This study offers interesting perspectives for obtaining fundamental single-molecule insights into fibril formation using a surface science approach to study idealized model systems.

  13. Chloride Channels are Involved in the Development of Atrial Fibrillation - A Transcriptomic and proteomic Study.

    PubMed

    Jiang, Yi-Yao; Hou, Hai-Tao; Yang, Qin; Liu, Xiao-Cheng; He, Guo-Wei

    2017-08-31

    Electrical and structural remodeling processes are contributors to the self-perpetuating nature of atrial fibrillation (AF). However, their correlation has not been clarified. In this study, human atrial tissues from the patients with rheumatic mitral valve disease in either sinus rhythm or persistent AF were analyzed using a combined transcriptomic and proteomic approach. An up-regulation in chloride intracellular channel (CLIC) 1, 4, 5 and a rise in type IV collagen were revealed. Combined with the results from immunohistochemistry and electron microscope analysis, the distribution of type IV collagen and effects of fibrosis on myocyte membrane indicated the possible interaction between CLIC and type IV collagen, confirmed by protein structure prediction and co-immunoprecipitation. These results indicate that CLICs play an important role in the development of atrial fibrillation and that CLICs and structural type IV collagen may interact on each other to promote the development of AF in rheumatic mitral valve disease.

  14. 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

  15. Expression, in cartilage, of a 7-amino-acid deletion in type II collagen from two unrelated individuals with Kniest dysplasia.

    PubMed Central

    Bogaert, R.; Wilkin, D.; Wilcox, W. R.; Lachman, R.; Rimoin, D.; Cohn, D. H.; Eyre, D. R.

    1994-01-01

    Kniest dysplasia is a heritable chondrodysplasia that severely affects skeletal growth. Recent evidence suggests that the etiology is based on mutations in COL2A1, the gene for collagen type II. We report the detection and partial characterization of an identical defect in type II collagen in two unrelated patients with Kniest dysplasia. Analysis of cyanogen bromide (CB)-digested cartilage samples from both probands by SDS-PAGE revealed an abnormal band for peptide alpha 1(II)CB12. The peptide was purified and digested with endoproteinase Asp-N. Fragments unique to the Kniest tissues were identified by reverse-phase high-pressure liquid chromatography and by sequence analysis. The results established a deletion of amino acids 102-108 of the alpha 1(II) triple-helical domain, which disrupted the (gly-X-Y)n repeat needed for helix formation. This was confirmed by sequence analysis of DNA amplified from both probands, revealing the molecular basis to be a single nucleotide mutation at a CpG dinucleotide (GCG-->GTG) in the codon for alanine 102. The mutation created a new splice donor site, which would account for the absence of the last seven amino acids from the 3' end of exon 12 in alpha 1(II)CB12. Light and electron micrographs of the probands' cartilage showed the perilacunar foamy matrix ("Swiss cheese") characteristic of Kniest dysplasia and chondrocytes containing dilated rough endoplasmic reticulum, which earlier studies had shown were filled with type II procollagen. These two cases strengthen the concept that Kniest dysplasia is based on mutations of COL2A1 and belongs within the broad spectrum of chondrodysplasias caused by type II collagenopathies. Images Figure 1 Figure 2 Figure 3 Figure 6 Figure 7 Figure 8 PMID:7977371

  16. PRODUCTION OF HIGHLY-ALIGNED COLLAGEN LAMELLAE BY COMBINING SHEAR FORCE AND THIN-FILM CONFINEMENT

    PubMed Central

    Saeidi, Nima; Sander, Edward A.; Zareian, Ramin

    2012-01-01

    Load-bearing tissues owe their mechanical strength to their highly-anisotropic collagenous structure. To date, attempts to engineer mechanically strong connective tissue have failed mainly due to the lack of the ability to reproduce native collagen organization in constructs synthesized by cultured cells in vitro. The ability to influence the direction of the self-assembling collagen molecules and produce highly anisotropic structures has applications ranging from de novo engineering of complex tissues to the production of organized scaffolds for cell culture contact guidance. In this investigation we have used the simple technique of spin coating to produce highly-aligned arrays of collagen fibrils. By a simple modification of the method we have also successfully produced orthogonal collagen lamellae. Alternating collagen lamellae are frequently seen in load-bearing tissues such as cornea, annulus fibrosus, and cortical bone. Culturing of corneal fibroblasts onto aligned collagen shows that the cells adopt the organization of the fibrils. In this investigation, we observed the reversal of fibrillar growth direction or “hook” formation similar to those seen previously in a microfluidic shear-flow chamber. Although the results of this investigation clearly show that it is possible to produce small areas (O) 1 cm2 of collagen fibrils with enough alignment to guide fibroblasts, there is evidence that thin film instabilities are likely to be a significant barrier to producing organized collagen fibrils over larger areas. Successful application of this method to produce highly-controlled and organized collagenous structures will require the development of techniques to control thin film instability and will be the subject of the future work. PMID:21362500

  17. 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

    2016-01-01

    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.

  18. Octocoral Sarcophyton auritum Verseveldt & Benayahu, 1978: Microanatomy and Presence of Collagen Fibers.

    PubMed

    Mandelberg, Yael; Benayahu, Dafna; Benayahu, Yehuda

    2016-02-01

    The study presents the microanatomy of the polyps of the reef-dwelling octocoral Sarcophyton auritum. We demonstrate the presence of its unique collagen fibers in the colony by means of Masson Trichrome histological staining. Based on peptide profiling, mass spectroscopy analysis confirmed that the fiber proteins were homologous with those of mammalian collagen. Histological and electron microscopy results showed that six of the eight mesenterial filaments of the polyps possess an internal, coiled, spring-like collagen fiber. High-resolution electron microscopy revealed for the first time in cnidarian collagen the interwoven, three-dimensional arrangement of the fibrils that comprise the fibers. Some fibrils feature free ends, while others are bifurcated, the latter being attributed to collagen undergoing fibrogenesis. Along with the mass spectroscopy finding, the coiled nature of the fibers and the fibril microanatomy show a resemblance to those of vertebrates, demonstrating the conserved nature of collagen fibers at both the biochemical and ultrastructural levels. The location, arrangement, and small diameter of the fibers and fibrils of S. auritum may provide a highly protective factor against occasional rupture and injury during the bending of the octocoral's extended polyps under strong current conditions; that is, providing the octocoral with a hydromechanical support. The findings from the microanatomical features of these unique fibers in S. auritum, as well as their suggested function, raise the potential for translation to biomedical applications.

  19. Ultrastructural changes of collagen and elastin in human gingiva during orthodontic tooth movement.

    PubMed

    Franchi, M; D'Aloya, U; De Pasquale, V; Caldini, E; Graziani, E; Borea, G; Ruggeri, A

    1989-12-01

    After 15 days of mesializing or distalizing orthodontic treatment, 10 permanent premolars of young patients were extracted with the interdental gingiva. The connective tissues of the compressed or stretched interdental papillae were compared to that of untreated samples by light and transmission electron microscope. Large collagen fibres bundles represented by fibrils with a banding pattern of 64 nm and a mean diameter of 75 nm were observed in compressed interdental gingiva. Several elastic fibres with a mean diameter of 950 nm were also present. In some central areas of compressed gingiva collagen fibrils longitudinally split into widely spaced microfibrils were often observed in proximity to the elastic fibres. In stretched and untreated interdental papillae the collagen fibrils presented a mean diameter of 66 nm and 57 nm respectively. In both groups, few elastic fibres ranging in diameter 600 nm were seen. The increased size of the gingival collagen fibrils undergoing pressure and tension is indicative of remodelling of the fibrous collagen system. The fair increase in number and size of elastic fibres in compressed gingiva suggests that the elastic fibre system takes over the place whenever a collapse of the collagenous framework occurs.

  20. STRUCTURAL MECHANISM FOR ALTERATION OF COLLAGEN GEL MECHANICS BY GLUTARALDEHYDE CROSSLINKING

    PubMed Central

    Chandran, Preethi L.; Paik, David C.; Holmes, Jeffrey W.

    2013-01-01

    Soft collagenous tissues that are loaded in vivo undergo crosslinking during aging and wound healing. Bio-prosthetic tissues implanted in vivo are also commonly crosslinked with glutaraldehyde. While crosslinking changes the mechanical properties of the tissue, the nature of the mechanical changes and the underlying microstructural mechanism is poorly understood. In this study, a combined mechanical, biochemical and simulation approach was employed to identify the microstructural mechanism by which crosslinking alters mechanical properties. The model collagenous tissue used was an anisotropic cell-compacted collagen gel, and the model crosslinking agent was monomeric glutaraldehyde. The collagen gels were incrementally crosslinked by either increasing the glutaraldehyde concentration or by increasing the crosslinking time. In biaxial loading experiments, increased crosslinking produced: (1) decreased strain response to a small equibiaxial preload, with little change in response to subsequent loading, and (2) decreased coupling between the fiber and cross-fiber direction. The mechanical trend was found to be better described by the lysine consumption data than by the shrinkage temperature. The biaxial loading of incrementally-crosslinked collagen gels was simulated computationally with a previously published network model. Crosslinking was represented by increased fibril stiffness or by increased resistance to fibril rotation. Only the latter produced mechanical trends similar to that observed experimentally. Representing crosslinking as increased fibril stiffness did not reproduce the decreased coupling between the fiber and cross-fiber directions. The study concludes that the mechanical changes in crosslinked collagen gels are caused by the microstructural mechanism of increased resistance to fibril rotation. PMID:22775003

  1. Effects of endogenous cysteine proteinases on structures of collagen fibres from dermis of sea cucumber (Stichopus japonicus).

    PubMed

    Liu, Yu-Xin; Zhou, Da-Yong; Ma, Dong-Dong; Liu, Zi-Qiang; Liu, Yan-Fei; Song, Liang; Dong, Xiu-Ping; Li, Dong-Mei; Zhu, Bei-Wei; Konno, Kunihiko; Shahidi, Fereidoon

    2017-10-01

    Autolysis of sea cucumber, caused by endogenous enzymes, leads to postharvest quality deterioration of sea cucumber. However, the effects of endogenous proteinases on structures of collagen fibres, the major biologically relevant substrates in the body wall of sea cucumber, are less clear. Collagen fibres were prepared from the dermis of sea cucumber (Stichopus japonicus), and the structural consequences of degradation of the collagen fibres caused by endogenous cysteine proteinases (ECP) from Stichopus japonicus were examined. Scanning electron microscopic images showed that ECP caused partial disaggregation of collagen fibres into collagen fibrils by disrupting interfibrillar proteoglycan bridges. Differential scanning calorimetry and Fourier transform infrared analysis revealed increased structural disorder of fibrillar collagen caused by ECP. SDS-PAGE and chemical analysis indicated that ECP can liberate glycosaminoglycan, hydroxyproline and collagen fragments from collagen fibres. Thus ECP can cause disintegration of collagen fibres by degrading interfibrillar proteoglycan bridges. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Development of a three-dimensional unit cell to model the micromechanical response of a collagen-based extracellular matrix.

    PubMed

    Susilo, Monica E; Roeder, Blayne A; Voytik-Harbin, Sherry L; Kokini, Klod; Nauman, Eric A

    2010-04-01

    The three-dimensional microstructure and mechanical properties of the collagen fibrils within the extracellular matrix (ECM) is now being recognized as a primary factor in regulating cell proliferation and differentiation. Therefore, an appreciation of the mechanical aspects by which a cell interacts with its ECM is required for the development of engineered tissues. Ultimately, using these interactions to design tissue equivalents requires mathematical models with three-dimensional architecture. In this study, a three-dimensional model of a collagen fibril matrix undergoing uniaxial tensile stress was developed by making use of cellular solids. A structure consisting of thin struts was chosen to represent the arrangement of collagen fibrils within an engineered ECM. To account for the large deformation of tissues, the collagen fibrils were modeled as hyperelastic neo-Hookean or Mooney-Rivlin materials. The use of cellular solids allowed the fibril properties to be related to the ECM properties in closed form, which, in turn, allowed the estimation of fibril properties using ECM experimental data. A set of previously obtained experimental data consisting of simultaneous measures of the fibril microstructure and mechanical tests was used to evaluate the model's capability to estimate collagen fibril mechanical property when given tissue-scale data and to predict the tissue-scale mechanical properties when given estimated fibril stiffness. The fibril tangent modulus was found to be 1.26 + or - 0.70 and 1.62 + or - 0.88 MPa when the fibril was modeled as neo-Hookean and Mooney-Rivlin material, respectively. There was no statistical significance of the estimated fibril tangent modulus among the different groups. Sensitivity analysis showed that the fibril mechanical properties and volume fraction were the two input parameters which required accurate values. While the volume fraction was easily obtained from the initial image of the gel, the fibril mechanical properties

  3. 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.

  4. Expression of catalytically active Matrix Metalloproteinase-1 in dermal fibroblasts induces collagen fragmentation and functional alterations that resemble aged human skin

    PubMed Central

    Xia, Wei; Hammerberg, Craig; Li, Yong; He, Tianyuan; Quan, Taihao; Voorhees, John J; Fisher, Gary J

    2013-01-01

    Summary Increased expression of matrix metalloproteinase-1 (MMP-1) and reduced production of type I collagen by dermal fibroblasts are prominent features of aged human skin. We have proposed that MMP-1-mediated collagen fibril fragmentation is a key driver of age-related decline of skin function. To investigate this hypothesis, we constructed, characterized, and expressed constitutively active MMP-1 mutant (MMP-1 V94G) in adult human skin in organ culture and fibroblasts in three dimensional collagen lattice cultures. Expression of MMP-1 V94G in young skin in organ culture caused fragmentation and ultrastructural alterations of collagen fibrils similar to those observed in aged human skin in vivo. Expression of MMP-1 V94G in dermal fibroblasts cultured in three-dimensional collagen lattices caused substantial collagen fragmentation, which was markedly reduced by MMP-1 siRNA-mediated knockdown or MMP inhibitor MMI270. Importantly, fibroblasts cultured in MMP-1 V94G-fragmented collagen lattices displayed many alterations observed in fibroblasts in aged human skin, including reduced cytoplasmic area, disassembled actin cytoskeleton, impaired TGF-β pathway, and reduced collagen production. These results support the concept that MMP-1-mediated fragmentation of dermal collagen fibrils alters the morphology and function of dermal fibroblasts, and provide a foundation for understanding specific mechanisms that link collagen fibril fragmentation to age-related decline of fibroblast function. PMID:23601157

  5. 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

  6. 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.

  7. Mechanical Response Study of Collagen by means of Molecular Simulation

    NASA Astrophysics Data System (ADS)

    in't Veld, Pieter J.

    2005-03-01

    We developed a coarse-grained model to study mechanical behavior of collagen fibrils as a function of their degree of cross-linking. A collagen molecule is represented by Lennard-Jones beads, which intra-molecularly are connected through harmonic springs on both bond length and angle. In this model each bead represents a helical turn in a collagen molecule. Triple-helical collagen molecules, which are 300 nm long, are packed within fibrils in a staggered fashion with an axial spacing of 67 nm in the absence of a load on the tendon. We treat the outer layer or shell different from the core by assuming the shell has the maximum amount of available cross-links. The core has a variable amount of cross-links by allowing cross-link formation and breakage depending on a reaction-type criterion. We study the stress-strain behavior of a single fibril through tensile deformation along the principal axis and a three-point bend perpendicular to the principal axis.

  8. 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