Serum levels of matrix metalloproteinase 3 (stromelysin 1) for monitoring synovitis in rheumatoid arthritis.

CONTEXT: Matrix metalloproteinase 3 (MMP-3) is expressed in synovial tissues and involved in cartilage destruction in rheumatoid arthritis and osteoarthritis.
OBJECTIVE: To study whether measurement of MMP-3 serum concentrations is useful to monitor the activity of rheumatoid synovitis.
DESIGN: Levels of MMP-3 in serum and synovial tissue samples obtained from 29 rheumatoid arthritis patients and 20 osteoarthritis patients were measured by the 1-step sandwich enzyme immunoassay system.
RESULTS: Levels of MMP-3 in the serum and synovial samples were significantly higher in rheumatoid arthritis than in osteoarthritis (P < .001), and the levels correlated directly with each other (r = 0.712, P < .001; N = 49). Immunohistochemistry demonstrated almost exclusive localization of MMP-3 to the lining cells in rheumatoid synovium. The immunoreactivity correlated directly with the scores of synovial inflammatory cell infiltration (r = 0.606, P < .001; n = 29) and the MMP-3 levels in the synovial tissues (r = 0.564, P = .001; n = 29) and those in the serum samples (r = 0.529, P = .003; n = 29) in rheumatoid arthritis. Levels of MMP-3 in rheumatoid serum samples dropped to low values at 1 and 2 weeks after total knee arthroplasty, while the levels of C-reactive protein increased at 1 week and the erythrocyte sedimentation rate and counts of white blood cells and platelets were unchanged at 1 and 2 weeks postoperative.
CONCLUSIONS: Our results demonstrate that MMP-3 levels in the serum of rheumatoid arthritis patients correlate with the levels produced by the synovial lining cells and suggest that the activity of rheumatoid synovitis can be monitored by measuring serum levels of MMP-3.