title: Tenocyte contraction induces crimp formation in tendon-like tissue.
abstract: Tendons are composed of longitudinally aligned collagen fibrils arranged in bundles with an undulating pattern, called crimp. The crimp structure is established during embryonic development and plays a vital role in the mechanical behaviour of tendon, acting as a shock-absorber during loading. However, the mechanism of crimp formation is unknown, partly because of the difficulties of studying tendon development in vivo. Here, we used a 3D cell culture system in which embryonic tendon fibroblasts synthesise a tendon-like construct comprised of collagen fibrils arranged in parallel bundles. Investigations using polarised light microscopy, scanning electron microscopy and fluorescence microscopy showed that tendon constructs contained a regular pattern of wavy collagen fibrils. Tensile testing indicated that this superstructure was a form of embryonic crimp producing a characteristic toe region in the stress-strain curves. Furthermore, contraction of tendon fibroblasts was the critical factor in the buckling of collagen fibrils during the formation of the crimp structure. Using these biological data, a finite element model was built that mimics the contraction of the tendon fibroblasts and monitors the response of the Extracellular matrix. The results show that the contraction of the fibroblasts is a sufficient mechanical impulse to build a planar wavy pattern. Furthermore, the value of crimp wavelength was determined by the mechanical properties of the collagen fibrils and inter-fibrillar matrix. Increasing fibril stiffness combined with constant matrix stiffness led to an increase in crimp wavelength. The data suggest a novel mechanism of crimp formation, and the finite element model indicates the minimum requirements to generate a crimp structure in embryonic tendon.
authors: Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, Michael Smith Building, University of Manchester, Oxford Road, Manchester M13 9PT UK.
authors: Andreas
authors: A
authors: Herchenhan
authors: Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, Michael Smith Building, University of Manchester, Oxford Road, Manchester M13 9PT UK.
authors: Nicholas S
authors: NS
authors: Kalson
authors: Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, Michael Smith Building, University of Manchester, Oxford Road, Manchester M13 9PT UK.
authors: David F
authors: DF
authors: Holmes
authors: School of Chemical Engineering and Analytical Science, University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom.
authors: Patrick
authors: P
authors: Hill
authors: Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, Michael Smith Building, University of Manchester, Oxford Road, Manchester M13 9PT UK.
authors: Karl E
authors: KE
authors: Kadler
authors: High Performance Computing, Research Computing Services, University of Manchester, Devonshire House, Oxford Road, Manchester M13 9PL UK.
authors: Lee
authors: L
authors: Margetts
mesh_terms: D001696:Biomechanical Phenomena; D018929:Cell Culture Techniques; D003094:Collagen / Q000737:chemistry; D003902:Detergents / Q000494:pharmacology; D005109:Extracellular Matrix / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D020342:Finite Element Analysis; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008855:Microscopy, Electron, Scanning / Q000379:methods; D008856:Microscopy, Fluorescence / Q000379:methods; D009068:Movement; D017830:Octoxynol / Q000494:pharmacology; D011312:Pressure; D013710:Tendons / Q000166:cytology* / Q000473:pathology*; D013718:Tensile Strength
chemical_list: D003902:Detergents; D017830:Octoxynol; D003094:Collagen