Early joint erosions and serum levels of matrix metalloproteinase 1, matrix metalloproteinase 3, and tissue inhibitor of metalloproteinases 1 in rheumatoid arthritis

Objective. To further evaluate the roles of matrix metalloproteinase I (MMP -1), MMP-3, and tissue inhibitor of metalloproteinases 1 (TIMP-1) in the pa thogenesis of joint inflammation and articular erosions in early inflammato ry arthritis. Methods. Untreated patients with joint symptoms for <2 years were evaluated at presentation and followed up prospectively for 18 months. Swollen joint count and serum levels of C-reactive protein (CRP) were determined every 6 months. Serum levels of MMP-1, MMP-3, and TIMP-1 were measured by double-a ntibody sandwich enzyme-linked immunosorbent assay at the same time interva ls. The number of joint erosions in serial radiographs of the hands and fee t was also recorded. Analysis of synovial fluid levels of MMPs and TIMP-1 a t presentation was completed in some patients. Results. Of 175 patients evaluated at baseline, 85 had rheumatoid arthritis (RA), 39 had seronegative spondylarthropathy, 38 had undifferentiated arth ritis, and 13 had self-limiting arthritis. Of 164 patients with available r adiographs of the hands and feet at presentation, 33 (20.1%) had joint eros ions. Baseline levels of MMP-1, MMP-3, and TIMP-1 were significantly higher (P = 0.0001, P = 0.013, and P = 0.0001, respectively) and ratios of TIMP-1 :MMP-1 and TIMP-1:MMP-3 were significantly lower (P = 0.0001 and P = 0.013, respectively) in RA versus non-RA patients. In RA, patients, serum levels of CRP correlated with MMP-3 and TIMP-1 levels, but not with MMP-1 levels. The number of erosions at presentation correlated with baseline levels of b oth MMP-1 and MMP-3, but not with levels of TIMP-1. One hundred one patient s were followed up for the next 18 months. The number of patients with eros ions and the number of erosions per patient increased significantly during this period. Area under the curve (AUC) measurements of MMP-1 and TIMP-1 le vels, but not of MMP-3 levels, yielded significantly higher values in RA th an in non-RA patients. In RA patients, only the AUC level of MMP-3 correlat ed with the AUC CRP level (r = 0.67, P = 0.0001), while only the AUC level of MMP-1 correlated with the number of new joint erosions (r = 0.28, P = 0. 034). Conclusion. These data suggest an uncoupling of the pathophysiologic mechan isms associated with joint inflammation and articular erosion. Treatments t hat inhibit the production and activity of MMP-1 may preferentially limit t he formation of new joint erosions and improve the long-term functional out come of some patients with inflammatory arthritis.