Collagenase and collagenase inhibitors in osteoarthritic and normal human cartilage

Abstract

In advanced osteoarthritis, all of the cartilaginous components are lost from the joint surface. Although mechanisms exist for proteoglycan degradation, there is not known to be any system for removal of the collagen. This study suggests that the loss of the collagen components may be a function of articular cartilage collagenase. The enzyme in normal human cartilage is bound to an inhibitor and appears to be present in very small amounts. Attempts to demonstrate collagenase activity in ground human articular cartilage or in its lysosomal fraction were unsuccessful. 7 Day cartilage tissue cultures also failed to demonstrate the presence of the enzyme; but the same culture fluid, incubated with trypsin, showed significant degradation of collagen, suggesting that trypsin destroyed the inhibitor. 7 Day culture fluids were then chromatographed on a heparin charged Sepharose 4B affinity column that had been activated with cyanogen bromide. This removed the inhibitor, and the chromatographed fluid from osteoarthritic cartilage released 42% of the incorporated counts of the collagen substrate, whereas normal cartilage released 10.1% and a trypsin control, 6.4%. Electrophoresis of the degradation products of the enzyme collagen complex incubated at 37°C revealed breakdown was complete to small dialyzable fragments, while at 25°C larger fragments were split off.