203: Endogenous matrix metalloproteinase (MMP)-9, and not MMP-2, promotes rheumatoid synovial fibroblast survival, inflammation and cartilage degradation

Abstract

To investigate the effect of endogenous matrix metalloproteinase (MMP)-2 and MMP-9 on the invasive characteristics of rheumatoid synovial fibroblasts (SF). 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. 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. 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.