Expression of cyclooxygenase-1 and-2 in rheumatoid arthritis synovium

The aim of this study was to investigate the expression and localization of cyclooxygenase-1 and -2 (COX-1 and COX-2) in synovial tissues from patient s with rheumatoid arthritis (RA), Synovial tissues from 9 patients with RA and 5 patients with osteoarthritis (OA) were examined for COX-1 and COX-2 e xpressions by immunohistochemical staining using 2 polyclonal COX-1 and COX -2 antibodies. In RA synovia, synovial lining cells showed intense immunost aining for COX-1, whereas slight to moderate staining was observed in infla mmatory cells, stromal fibroblast-like cells and vascular endothelial cells . There was no significant difference in COX-1 expression between RA and OA synovia. The localization of COX-2 expression clearly differed from that o f COX-1 expression, being most intense in inflammatory cells, However, ther e was no difference in COX-1 and COX-2 expressions between RA and OA synovi al tissues. Our observations support that inflammatory mechanisms modulated by COX-1 and COX-2 in chronic RA synovium might be similar to those in chr onic OA synovium.