Abstract

The influx of cells into the synovial intima in rheumatoid joints may include osteoclasts and their precursors. The distribution of osteoclast markers--namely, tartrate resistant acid phosphatase activity and the expression of vitronectin receptor (shown with monoclonal antibodies 13C2 and 23C6)--was therefore examined in synovium obtained from patients with rheumatoid (RA) or degenerative (OA) arthritis. Tartrate resistant acid phosphatase positive cells were found in frozen sections of 60% (n = 30) of RA and 69% (n = 29) of OA synovial membranes. Whereas all synovia tested (four RA, four OA) showed diffuse staining of the lining cells with 13C2, 55% (n = 11) of RA and 57% (n = 14) of OA synovial membranes contained isolated cells stained with 23C6 scattered throughout the tissue. In cultures of synovial cells, tartrate resistant acid phosphatase positive, multinuclear, and 23C6 positive cells were found; these cells did not, however, form resorption pits on bone slices. The results show that fully differentiated osteoclasts are uncommon in synovium from patients with either degenerative or inflammatory arthropathies.