Susceptibility of interstitial rabbit collagens to rabbit articular chondrocyte collagenase

Conditioned culture media from confluent rabbit articular chondrocytes maintained in serum-free monolayer culture contained metal-dependent neutral pH collagenolytic activity degrading Type I, II and III rabbit [125I]-labeled collagens. This collagenolytic activity degraded Type II collagen more slowly than Type I collagen and Type III collagen at 37 degrees C. By contrast, collagenolysis by chondrocyte cytosolic protein, lysosomal granule protein and residual lysosomal membrane protein was highly specific for Type II collagen. Although collagenolytic activity against all the collagen isotypes tested was predominantly in a latent form after 24 h of culture, increasing levels of constitutive collagenolytic activity was measured with increasing culture time. These results are consistent with a differential degradation of rabbit interstitial collagens by rabbit chondrocyte collagenase. The data suggest a cellular compartmentalization of collagenolytic activity with specificity toward Type II collagen.