Experimental arthritis induced by granulocyte collagenase.

Purified human granulocyte collagenase (1 mg %, 10 mg % or 50 mg %) was injected into rabbit knee joints (three groups of 6 animals each) three times within one week. Synovium and synovial fluid were investigated 18 hours, 1 week and 3 weeks after the last injection. After 18 hours, synovial fluids showed distinct cellular exudation, its size depending on the amount of collagenase applied. A smaller number of cells was seen after one week, while normal cell counts were observed 3 weeks after the last injection. Histologically, synovium showed an acute arthritis after 18 hours, whereas after 1 and 3 weeks a chronic proliferative form of arthritis with predominant activation of fibroblasts was diagnosed. As compared with an experimental arthritis induced with rheumatoid synovial collagenase, granulocyte collagenase was less arthritogenic. Neither trypsin nor saline injections induced distinct cellular exudation into synovial fluids nor histologic signs of arthritis.