Collagenase and collagenolytic activity in human osteoarthritic cartilage.

Forty-nine specimens of human cartilage were taken from 3 sites on the tibial plateau (center of osteoarthritic lesion, edge of lesion, and remote site) and graded histologically by the scale of Mankin. The tissue was homogenized and centrifuged to obtain an insoluble pellet. This was resuspended in buffer and incubated at 37 degrees C, pH 7.5. Collagen digestion was quantitated by the release of hydroxyproline-containing peptides. The highest collagenolytic activity (4.6%) was found in the center of lesions, declining in remote sites to 2.4% and in controls to 1.1%. Moderately severe disease of grade 6--9 had the highest collagenolytic activity. Approximately 55% of the metal-dependent collagenolytic activity was in a latent form, activatable by amino-phenylmercuric acetate; the remainder was self-active. A method was developed for the extraction of collagenase from cartilage; the extracted enzyme produced the typical 75:25 cleavage products of type I collagen.