The objective of the proposed research is to discover the enzymatic mechanisms by which the extracellular matrix of human articular cartilage is broken down. Proteolytic enzymes will be studied with respect to the digestion of collagen and proteoglycan complexes. These proteases will be characterized and quantitated in normal cartilage and in cartilage from patients with osteoarthritis and rheumatoid arthritis. We have shown that human and bovine cartilages contain a new family of neutral metalloproteases that degrade the proteoglycan subunit. These enzymes will be further characterized with respect to specificity and inhibition properties. Their implication in arthritis will be studied by tissue quantitation, immunofluorescent localization, and the use of animal models of osteoarthritis. Collagenase will be studied by a direct tissue assay to follow its change with disease. PZ-Peptidase and collagenolytic cathepsin are postulated to play a role in the further degradation of collagen after initial attack by collagenase. These proteases will be characterized and quantitated. Other proteases have been detected, including a chymotrypsin-like protease of low molecular weight from bovine cartilage and one or more metal-dependent acid cathepsins of human cartilage. These will be studied in more detail along the lines pursued with the neutral metalloproteases and using proteoglycan subunit as substrate. This work on cartilage proteases will be of considerable importance in understanding the pathogenesis of joint diseases, since it will elucidate the nature of the proteases arising from within the cartilage. The knowledge of enzyme properties and specificities may open the way to rational treatment of joint disease. This information may also be of value in understanding cartilage remodeling, calcification, fracture healing, bone remodeling and osteoporosis.