OBJECTIVETo investigate the value of metalloproteinase-3 (MMP-3) levels in assessing efficacy of etanercept treatment in patients with ankylosing spondylitis (AS).

METHODSThe serum and synovial fluid levels of MMP-3 were measured by enzyme linked immunosorbent assay (ELISA) in 48 patients with AS in week 0, 6 and 12; and also measured in 30 serum samples and 10 synovial fluid samples from healthy controls.

RESULTSThe serum levels of MMP-3 in AS patients were significantly higher than those in controls. In AS patients, the MMP-3 levels in synovial fluid were significantly higher than those in serum levels. The serum MMP-3 levels in AS patients with peripheral arthritis were higher than those with exclusively axial involvement; while C-reactive protein (CRP) levels and erythrocyte sedimentation rate (ESR) did not differ between these 2 groups of AS. At week 6 and week 12 of etanercept treatment, the serum MMP-3 levels were significantly decreased (p<0.01) with the declining trend of ESR, CRP, Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and Bath Ankylosing Spondylitis Functional Index (BASFI) (all p<0.01). Before the etanercept treatment (week 0), serum levels of MMP-3 were correlated with ESR, CRP, BASDAI and BASFI (p<0.05). ESR was also correlated with CRP and BASFI, but not with BASDAI (r=0.361, P=0.071). At weeks 12, serum MMP-3 levels were still correlated with ESR, CRP and BASDAI (P<0.05), but not with BASFI (P=0.339); ESR was correlated with CRP, but not with BASDAI and BASFI. There was a significant correlation between BASDAI and BASFI (r=0.818,P=0.001).

CONCLUSIONSerum MMP-3 levels are closely related to disease activity and may serve as an useful indicator for efficacy of etanercept treatment in AS patients.