title: Prestrain decreases cartilage susceptibility to injury by ramp compression in vitro.
abstract: BACKGROUND
  Injurious mechanical loading of articular cartilage can be an initiating factor in the development of degenerative joint disease. The tissue response to compression depends on the loading conditions and matrix mechanical properties. The short-term loading history of cartilage can affect its water content and microstructural organization, and may thereby modify its susceptibility to injury. We therefore examined the role of prestrain on the response of articular cartilage to injurious compression.
  
  
  METHODS
  The full-thickness cartilage of bovine osteochondral explants was subjected to prestrains of 0, 5, 10, 25 or 50% before application of injurious ramp compression characterized by a strain rate of 7x10(-2) or 7x10(-3)s-1 and peak stress of 3.5 or 14 MPa. Effects of prestrain were evaluated in terms of fluid exudation, tissue mechanical stiffening, and the tissue response to injurious compression as characterized by macroscopic crack formation, cell viability and glycosaminoglycan release to culture media.
  
  
  RESULTS
  Macroscopic crack formation due to injurious compression decreased with increasing prestrain in association with lower cell mortality. Significantly decreased susceptibility to injury was already evident for 10% prestrain. In contrast, explant mechanical stiffness was unchanged up to 25% prestrain.
  
  
  CONCLUSIONS
  Findings demonstrate that compressive strains due to the short-term loading history of cartilage may strongly reduce its susceptibility to mechanical injury. Conversely, matrix swelling may render cartilage more vulnerable to injury. The cartilage response to injurious compression is therefore strongly influenced by matrix fluid content, and possibly also by other structural parameters such as collagen fiber orientation.
authors.affiliation: Cartilage Biomechanics Group, Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland.
authors.forename: V
authors.initials: V
authors.lastname: Morel
authors.forename: A
authors.initials: A
authors.lastname: Merçay
authors.forename: T M
authors.initials: TM
authors.lastname: Quinn
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000293:injuries* / Q000473:pathology / Q000503:physiopathology; D002417:Cattle; D002470:Cell Survival / Q000502:physiology; D003470:Culture Media; D004548:Elasticity; D006025:Glycosaminoglycans / Q000032:analysis; D018613:Microscopy, Confocal / Q000379:methods; D013314:Stress, Mechanical; D046509:Tissue Culture Techniques
chemical_list: D003470:Culture Media; D006025:Glycosaminoglycans