Matrix metalloproteinase-3 (MMP-3) is produced by fibroblasts, synovial cells, and chondrocytes in response to cytokines like interleukin-1 and tumor necrosis factor-α [1,2]. In rheumatoid arthritis (RA), MMP-3 is abundantly expressed in the rheumatoid synovium of the affected joint; MMP-3 is not expressed in normal synovium. In RA, MMP-3 levels in synovial fluid are several-hundredfold higher than those in serum [3]. MMP-3 in synovial fluid is thought to diffuse into the circulation mainly via the lymphatic system and then excreted through the kidney [4].
