Biochemical analysis of synoviocytes from normal and arthritic rats. Evidence for an activated state associated with adjuvant polyarthritis.

Adjuvant-induced polyarthritis in rats is a common model system used for the study of the synovitis that occurs in rheumatoid arthritis. Synoviocytes A, the major cell type covering the internal surface of the joint, could be involved in the pathogenesis of rheumatoid arthritis because of their increased proliferation and the intraarticular manifestations of the disease. So far only a few molecular studies have been reported on synoviocytes upon arthritis induction. We report here changes in polypeptides, between control and arthritic synoviocytes, by using two different radiolabeling methods and two-dimensional gel electrophoresis analysis. Major differences were found using metabolic labeling on regions of tropomyosins, cyclin, tubulins and vimentin. In addition, external surface labeling of the cells with lactoperoxidase showed clear differences between control and arthritic synoviocytes in the region of 77-100-kDa proteins. Some of these differences can be reproduced by certain macrophage activators such as phorbol myristate acetate and lipopolysaccharide acting on synoviocytes in vitro and in vivo respectively. These results exclude the possibility that the changes observed were due to a possible infiltration of other cell types in the arthritic synovia and strongly support the existence of an activated state of synoviocytes associated with arthritis induction.