PROTEOGLYCAN-DEGRADING ACTIVITY ASSOCIATED WITH THE 40 KDA COLLAGEN-BINDING FRAGMENT OF FIBRONECTIN

The osteoarthritis (OA) process is characterized by the progressive de struction of articular cartilage. There is a loss of cartilage proteog lycan content and disorganization of the collagen network, as well as an increase in other non-collagenous protein such as fibronectin (Fn). Increased proteolytic activity may lead to the degradation of native Fn and generation of Fn proteolytic fragments. Among them, the 45 kDa collagen-binding Fn fragment can be autoactivated in vitro into a 40 k Da fragment. This 40 kDa fragment induces an average of 30% of proteog lycan release per day from human OA cartilage explants and can degrade proteoglycan using dead cartilage sections. Proteoglycan-degrading ac tivity related to the 40 kDa Fn fragment was decreased up to 66% by fe tal calf serum (10%), but was not prevented by protein synthesis inhib itors (cycloheximide or actinomycin D). The action of this 40 kDa Fn f ragment was greater on OA than on normal cartilage. This study suggest s that enzymatic activity induced by the 40 kDa collagen-binding fragm ent of Fn might be involved in cartilage matrix turnover.