MMP3 and rheumatoid arthritis: RA patients exhibited increased baseline plasma levels MMP3 (29.93 ± 18.57 ng/ml), which is a molecule responsible for degradation of the extracellular matrix, compared with the healthy controls (12.79 ± 8.17 ng/ml, P = 0.007) and the OA group (5.25 ± 1.95 ng/ml, P < 0.001).