The purpose of this grant is to characterize the biochemical basis for articular cartilage autocatabolism. Specifically, we intend to determine what enzymatic activities are responsible for the onset of cartilage destruction. We have shown that bacteria stimulate proteoglycan loss from cartilage if living cartilage cells are present. The initiation of proteoglycan loss is clearly the first step in cartilage destruction. We have established this in animal models of infectious and inflammatory arthritis. Other laboratories have shown that cartilage proteoglycan loss can be triggered by the presence of a low molecular weight protein, catabolin, and that living cartilage is required. The question which remains is what biochemical mechanism supports the proteoglycan degradation. Is it proteolytic? Is it extremely labile or is it present only after some inductive signal for protein synthesis? Are a number of enzymatic activities involved? To answer these questions we are proposing to trigger cartilage degradation by bacteria, Staphylococcus aureus, and after specific times, 12, 24 and 48 hours, to homogenize the cartilage and assay for enzymatic activities. The enzymes to be studied are glucuronidase, hexosaminidase, alkaline phosphatase, cathespin D, neutral proteinases and hyaluronidase. Metabolic inhibitors will be used to study turnover rates and synthesis patterns of enzymatic cartilage degrading enzymes. The significance of this investigation will be to characterize the extent to which cartilage cells alone contribute to arthritis in response to extracellular signals. A cartilage specific response to any foreign stimulus, in conjunction with immune system reactions, may then be additive in cartilage destruction in all forms of arthritis. To effectively control the arthritic reaction, the biochemical characteristics of chondrocyte behavior must first be determined.
