Synovial fluid matrix metalloproteinase‐3 levels are increased in inflammatory arthritides whether erosive or not

Objective. To study the levels of matrix metalloproteinase-3 (MMP-3) in the knee synovial fluid (SF) of inflammatory arthropathies (rheumatoid arthritis whether erosive or not, reactive arthritis, acute crystal arthritis) and degenerative arthropathies [chronic crystal disease, osteoarthritis and (control) meniscus pathology] and to correlate them with the degree of joint destruction, local inflammatory and immune parameters and systemic markers of inflammation. Methods. SF levels of MMP-3 (precursor, active and tissue inhibitor of MMP-bound forms), tumour necrosis factor (TNF) a, soluble TNF receptors I and II, interleukin (IL)-6 and soluble IL-6 receptor were measured by ELISA in 107 inflammatory and 53 degenerative arthropathies. Results. MMP-3 levels in SF were (i) significantly higher in inflammatory than in degenerative arthropathies; (ii) not related to the degree of joint destruction; (iii) significantly correlated with the levels of all SF markers tested and with erythrocyte sedimentation rate and serum levels of C-reactive protein and fibrinogen. Conclusion. Increased MMP-3 levels in SF are found in inflammatory arthropathies and are not specific for erosive joint diseases. MMP-3 in SF is therefore a potential candidate for the assessment of the inflammatory process in joints. However, the exclusive determination of the active form could indicate the degree of joint destruction.