To evaluate the significance of serum matrix metalloproteinase-3 (MMP-3) levels in relation to the development of radiological damage (X-ray damage) in early rheumatoid arthritis (RA).
Serum MMP-3 levels were measured in 46 healthy controls (CTRL), 19 osteoarthritis (OA) and 78 RA patients with joint symptoms for <1 yr at presentation (T0): 48 patients without and 30 with X-ray damage at T0. Serum MMP-3, measured by ELISA, and X-ray damage, scored according to Sharp's method, were assessed at 0, 6, 12 and 24 months.
MMP-3 levels in CTRL and OA were low or undetectable with no differences between the groups (P=0.19). Levels in RA were higher than in CTRL (P<0.01). Initial MMP-3 levels in patients with X-ray damage at T0 (n=30) were higher than the levels in patients without any X-ray damage during follow-up (n=19) (P<0.01), but were not different from those in patients who developed X-ray damage during the study (n=29) (P=0.11). In the patients without X-ray damage at T0, there was a significant correlation between MMP-3 at T0 and the total X-ray damage after 6 months (r=0.34, P=0.02) and 12 months (r=0.32, P=0.03). This correlation was almost exclusively determined by joint space narrowing in the Sharp score.
The serum MMP-3 level seems to be an indicator for the development of radiological damage in patients with early RA and appears to be particularly indicative of cartilage degradation.