The Study On Type I Collagen Expression Of Osteoarthritis Cartilage Initiated By Local Tensile Stress On Animal Experiment

Objective: To examine whether or not intra-articular injury can generate local tensile stress, causing phenotype changes of chondrocytes characterized by synthesis of type I collagen rather than type II collagen and proteoglycan aggregates.Methods: Finite element was used to analyze the stress distribution around the injury of cartilage. The intra-articular trauma model was created using 15 four-month old New Zealand white rabbits. The cartilage was evaluated at 2, 6 and 20 weeks grossly, immunohistochemically(type I and II collagen) and histologically(proteoglycans).Results: When the crack occurred, the tensile stress formed around the crack, and varied with the crack angle; the maximum principal tensile stress at 45 o from the cartilage surface was 0.59 MPa, and no tensile stress was found at 90 o. Type I collagen was 0.13±0.07(the mean optical density) around the crack at 2 weeks, increased progressively to 0.18±0.05 at 6 weeks and 0.19±0.09 at 20 weeks,P>0.05. Type II collagen and proteoglycans remained unchanged.Conclusions: A new mechanism of OA was demonstrated in which the local tensile stress around the cartilage cracks could lead to and rise type I collagen formation, triggering the development of degeneration. The association of tensile stress with cartilage degeneration suggests that OA may be manageable by avoiding tensile stress, offering an insight toward developing new strategies in prevention and treatment of this joint disorder.