title: In vitro tendon tissue development from human fibroblasts demonstrates collagen fibril diameter growth associated with a rise in mechanical strength.
abstract: BACKGROUND
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Institute of Sports Medicine, Department of Orthopedic Surgery M, Bispebjerg Hospital and Center for Healthy Aging, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark. andreashe@sund.ku.dk
authors.forename: Andreas
authors.initials: A
authors.lastname: Herchenhan
authors.forename: Monika L
authors.initials: ML
authors.lastname: Bayer
authors.forename: René B
authors.initials: RB
authors.lastname: Svensson
authors.forename: S Peter
authors.initials: SP
authors.lastname: Magnusson
authors.forename: Michael
authors.initials: M
authors.lastname: Kjaer
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D024022:Fibrillar Collagens / Q000502:physiology* / Q000648:ultrastructure; D005347:Fibroblasts / Q000166:cytology*; D006801:Humans; D008854:Microscopy, Electron; D009024:Morphogenesis / Q000502:physiology*; D013710:Tendons / Q000254:growth & development*; D046509:Tissue Culture Techniques / Q000379:methods*; D023822:Tissue Engineering / Q000379:methods*
chemical_list: D024022:Fibrillar Collagens