NEUTRAL PROTEINASES FROM ARTICULAR CHONDROCYTES IN CULTURE .1. A LATENT COLLAGENASE THAT DEGRADES HUMAN CARTILAGE TYPE-II COLLAGEN

Culture media collected from secondary monolayer and spinner cultures of rabbit articular chondrocytes showed evidence of collagenolytic activity by th following criteria: Amicon PM-10 concentrates of culture medium released [14C]glycine from reconstituted rabbit skin collagen fibrils at 37.degree. C; medium concentrated by lyophilization decreased the relative viscosity of human cartilage collagen in solution; The loss in viscosity was partially inhibited if medium was preincubated with o-phenathroline; degradation of human cartilage collagen after 60 h incubation at 24.degree. C was characterized primarily by the appearance of 75,000 dalton (TCA) and 25,000 dalton (TCB) products. The majority of the collagenase (EC 3.4.24.3) from cultured chondrocytes was secreted in latent form, since preincubation with trypsin or p-aminophenylmercuric acetate significantly increased activity against human cartilage collagen. Chondrocyte collagenase may be important in mediating the normal slow turnover of cartilage collagen and may be particulary active in collagen destruction associated with early stages of synovial joint arthritides, before attack by non-cartilage cells or extra articular soft tissues.