Collagenase-induced experimental arthritis

Rabbits were injected intraarticularly three times with 0.5 ml of 10, 50 or 100 mg% purified rheumatoid synovial collagenase or with identical amounts of trypsin. 18 hours after the last injection the collagenase-injected animals showed distinct cellular exudation into the synovial fluid and acute arthritis; one week later there was a decrease of the cell count in the synovial fluid and appearance of proliferative synovitis, while 3 weeks later there was no exudation and less chronic inflammation but distinct fibrosis of the synovium. A direct action of collagenase on the connective tissue components would seem to be responsible for these changes. No pathologic alteration of the cartilage was observed. Trypsin-injected control animals showed negligible cellular exudation and no pathologic alteration of the synovium.