Experimental Study Of Collagen's Changes In Osteoarthritic Cartilage In Rabbits

Objective To observe the change of collagen in osteoarthritis and study the pathogenesis of osteoarthritis.Methods The right hind limb of twenty-four adult New Zealand White rabbits was immobilized by plaster cast in extension position for 10, 20, 30 and 40 days. Six animals without immobilization were served as control. The articular cartilage of the medial femoral condyle was harvested for transmission electron microscopy, in-situ hybridization of collagen â…¡, and immunohistochemistry of collagen â… ,â…¡,â…¢.Results In adult articular cartilage tangential zones consist of three layer: muciferous layer, fine collagen fibers network, and the collegen layer containning cell. In earlier period of osteoarthritis, the muciferous layer disappeared and the fine collagen fibers network was damaged, then inferior layers were gradually damaged. In osteoarthritis collagen fibers increased in diameter, or break, or lysis. The chondrocytes largely proliferated when structure of collagen fibers was complete, but degenerated and die when structure of collagen fibers was damaged. In earlier period of osteoarthritis, chondrocytes enhanced expressing andsynthesizing of type â…¡ collagen mainly in transition zone and upper deep zone, In articular cartilage of osteoarthritis there was type â…¢ collagen, but not type I collagen.Conclusion Chondrocytes enhanced expressing and synthesizing of collagen in response to injury mainly in transition zone and upper deep zone. Cartilage was destructed from the fine collagen fibers network of tangential zone in the beginning of osteoarthritis. The fine collagen fibers network does not contain chondrocyte, and can not be repaired in response to injury. It is speculated that these may contribute to the pathogenesis of osteoarthritis.