Up-regulation of CD44 in rheumatoid chondrocytes.

The adhesion molecule CD44 is thought to play an important role in the inflammatory process. To identify the expression of CD44 in articular chondrocytes in rheumatoid arthritis (RA), monoclonal anti-CD44 antibodies were immunohistochemically used to react with articular cartilage specimens of 15 patients with RA, 9 with osteoarthritis (OA), and 6 with femoral neck fracture (FF). The proportion of CD44-positive chondrocytes in RA was 93 +/- 2% (N=16), which was significantly higher than that in OA (59 +/- 7%, N=9, p<0.001) and FF (46 +/- 5%, N=6, p<0.001). Among CD44 isoforms examined, the hemopoietic form was dominant in chondrocytes in RA. Therefore, up-regulation of CD44 on chondrocytes may play a significant role in cartilage degeneration in RA.