Aim: To investigate the effect of endogenous matrix metalloproteinase (MMP)-2 and MMP-9 on the invasive characteristics of rheumatoid synovial fibroblasts (SF).
Methods: SF isolated from patients with rheumatoid arthritis (RA) or osteoarthritis (OA) were treated with MMP siRNAs, inhibitors and recombinant (r) proteins or TNF-a, with or without cartilage explants. Cell viability and proliferation were measured by MTT and BrdU proliferation assays, respectively; apoptosis by an in situ cell death detection kit; migration and invasion by CytoSelectTM invasion assay, scratch migration and collagen gel assays; cartilage degradation by 1,9-dimethylmethylene blue assay; inflammatory mediators and MMPs by ELISA, western blot and zymography.
Results: MMP-2 was expressed by both OASF and RASF, whereas only RASF expressed MMP-9. Suppressing MMP-2 or MMP-9 reduced RASF proliferation equally. However, MMP-9 siRNA had greater effects, compared to MMP-2 siRNA, on promoting apoptosis and suppressing RASF viability, migration and invasion. Suppression/inhibition of MMP-9 also decreased the production of IL-1β, IL-6, IL-8 and TNF-α, inactivated nuclear factor (NF)-κB, ERK and JNK and suppressed RASF-mediated cartilage degradation. In contrast, Suppression/inhibition of MMP-2 stimulated TNF-a and IL-17 secretion and activated NF-κB, while rMMP-2 inactivated NF-κB and suppressed RASF-mediated cartilage degradation. Results using specific inhibitors and rMMPs provided supportive evidence for the siRNA results.
Conclusions: Endogenous MMP-2 or MMP-9 contribute to RASF survival, proliferation, migration and invasion, with MMP-9 having more potent effects. Additionally, MMP-9 stimulates RASF-mediated inflammation and degradation of cartilage, whereas MMP-2 inhibits these parameters. Overall, our data indicate that MMP-9 derived from RASF may directly contribute to joint destruction in RA.