ALTERATION AND RECOVERY OF THE SPATIAL ORIENTATION OF THE COLLAGEN NETWORK OF ARTICULAR-CARTILAGE IN ADOLESCENT RABBITS FOLLOWING INTRAARTICULAR CHYMOPAPAIN INJECTION

We have used polarized light (POL) to monitor changes in the organizat ion of the articular cartilage collagen network and matrix proteoglyca ns (PGs) after intra-articular injection of chymopapain (CP), POL view ing of sirius red stained sections revealed a loss of normal birefring ence suggesting an apparent collapse of the collagen network following intra-articular CP, After 21 days, knees injected with 2.0 mg CP show ed no return of normal birefringence, however, normal birefringence wa s noted in knees injected with only 0.2 mg CP, POL viewing of toluidin e blue stained sections revealed a severe loss of matrix PGs followed by PG restoration in animals injected with 0.2 mg CP, The most importa nt inference from the data is that articular cartilage can recover fro m enzyme-induced alterations in the spatial collapse of its fibrillar network, This is an important finding since it has often been inferred that damage to the collagen network leads invariably to progressive a rticular cartilage destruction.