Chondromucoprotein-degrading neutral protease activity in rheumatoid synovial fluid.

Erosion of articular cartilage, which is characteristic of inflammatory joint diseases, including rheumatoid arthritis (RA), is due in part to enzymic breakdown of the components of the cartilage matrix (Bollet, 1963), particularly collagen and chondromucoprotein (CMP). It has been suggested that lysozomal hydrolases, possibly derived from cells of the synovial membrane or from leucocytes present in synovial fluid, are involved in this process (Dingle, 1962; Weissmann, 1966). In this communication we report the existence, in the synovial fluids of patients with rheumatoid arthritis, of protease activity which degrades CMP optimally near neutral pH. It thus differs from the majority of lysozomal enzymes, which are optimally active at pH values lower than those (Goldie and Nachemson, 1969) likely to appertain at the cartilage surface.