Effect of urinary trypsin inhibitor on osteoarthritis.

The plasminogen activator (PA) and plasminogen activator inhibitor (PAI) in synovial fluid (SF) of osteoarthritis (OA) were examined to clarify their pathophysiological roles in this disease. Three PAs with molecular weights of 90K, 55K, and 33K were found in the SF, but the 55K PA was dominant. Immunologically, both the 55K and 33K PA were u-PA, while the 90K PA was t-PA. The PAI reacted against both u-PA and t-PA, but the PAI activity against u-PA was much stronger. Urinary trypsin inhibitor (UTI) made a complex with the 55K PA and suppressed the PA activity. A clinical study in which UTI was injected into the joint space of OA (18 joints in 15 patients) revealed excellent (39%), good (16%), and fair (44%) results based on assessment of the pain, range of motion, ballottement and activity of daily living.