The role of COX-2 produced by cartilage in arthritis

The development of selective COX-2 inhibitors has renewed interest in the treatment of osteoarthritis with prostaglandin synthesis inhibitors. The therapeutic effects of COX inhibitors in OA may be due to their analgesic properties. However, it is now apparent that stable prostaglandins are produced by chondrocytes in OA cartilage where they may act to alter matrix synthesis and degradation. In vitro, PGEs activate metalloproteinases, but also enhance proteoglycan and type II collagen synthesis. Their net effect on matrix homeostasis in vivo remains to be determined.