Expression of collagenase and potential transcriptional factors in the MRL/l mouse arthropathy

Typical erosions of articular joint structures in rheumatoid arthritis and in the spontaneous destructive hind-limb arthropathy of autoimmune MRL-lpr/lpr (MRL/l) mice occur predominantly in areas contiguous with proliferating synovial lining cells, suggesting release of proteolytic enzymes from these cells. Synovial lining cells were isolated from arthritic MRL/l mice, and the spontaneous expression of the interstitial procollagenase and its potential transcriptional factors, egr-1 and c-fos, was examined in vitro. The data indicate that basal collagenase RNA expression was stronger in MRL/l cells than in virus-transformed cells. Moreover, elevated RNA levels of the c-fos gene could be detected in the collagenase-expressing synovial lining cells in vitro. In a related immunohistochemical study, collagenase was detected in situ in proliferating synovial lining cells as well as in chondrocytes of the first stage of pathological changes in the MRL/l mouse arthropathy.