Direct degradation of articular cartilage by rheumatoid synovial fluid: contribution of proteolytic enzymes.

Abstract

To test the effects of synovial fluids (SF) on human cartilage in an in vitro model. Freshly collected SF were incubated with cryostat sections of articular cartilage, and glycosaminoglycan (GAG) loss determined by microdensitometry after alcian blue staining. Of 20 rheumatoid SF, 11 induced significant GAG loss compared with only 3 out of 15 osteoarthritic SF. The effect of rheumatoid fluids appeared to be related to disease activity. GAG loss was partially prevented by a broad spectrum serine protease inhibitor and a specific elastase inhibitor. Cartilage degrading activity was lost on storage which may explain why it has not been widely reported before. Rheumatoid SF can directly degrade cartilage through the action of proteases. There is an involvement of serine proteases, elastase in particular.