Characteristics of the protease activity in synovial fluid from patients with rheumatoid arthritis and osteoarthritis.

Objective: To clarify which proteases are specifically activated in the lesions of rheumatoid arthritis (RA) and osteoarthritis (OA).

Methods: The activity levels of the serine proteases of the coagulation and fibrinolytic systems, and of elastase and collagenase as controls, in synovial fluid from 27 RA patients and 28 OA patients were measured using fluorogenic synthetic substrates which had methylcoumarylamide (MCA) at their COOH-termini. The thrombin-antithrombin III complex (TAT) content was also measured by ELISA.