Objective. To test the hypothesis that local proliferation contributes significantly to the hyperplasia of rheumatoid synovium.
Methods. Immunohistologic and chemical staining was used to identify 3 markers of cell proliferation: proliferating cell nuclear antigen, c-myc proto-oncogene, and nucleolar organizer regions. Synovium from 21 patients with rheumatoid arthritis, 34 with degenerative joint disease, and 7 with joint trauma was examined.
Results. All 3 markers indicated substantial, active proliferation of synovial lining cells in synovium with hyperplasia. Proliferating cells showed type I procollagen immunoreactivity but were negative for CD68, a monocyte/macrophage marker. Proliferation was greater in rheumatoid arthritis than in the other conditions evaluated.
Conclusion. In situ proliferation of fibroblast-like synoviocytes in the synovium lining contributes considerably to the increase in cell numbers in rheumatoid synovium.