Endogenous MMP-9 and not MMP-2 promotes rheumatoid synovial fibroblast survival, inflammation and cartilage degradation

Rheumatology (Oxford). 2014 Dec;53(12):2270-9. doi: 10.1093/rheumatology/keu254. Epub 2014 Jun 29.


Objective: The aim of this study was to investigate the effect of endogenous matrix metalloproteinases 2 and 9 (MMP-2 and MMP-9) on the invasive characteristics of RA synovial fibroblasts.

Methods: Synovial fibroblasts isolated from patients with RA or OA were treated with MMP small interfering RNA (siRNA), inhibitors and recombinant proteins or TNF-α, with or without cartilage explants. Cell viability and proliferation were measured by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide and 5-bromo-2-deoxyuridine (BrdU) proliferation assays, respectively; apoptosis by an in situ cell death detection kit; migration and invasion by CytoSelect invasion assay, scratch migration and collagen gel assays; cartilage degradation by 1,9-dimethylmethylene blue assay; and inflammatory mediators and MMPs by ELISA, western blot and zymography.

Results: MMP-2 was expressed by both OA and RA synovial fibroblasts, whereas only RA synovial fibroblasts expressed MMP-9. Suppressing MMP-2 or MMP-9 reduced RA synovial fibroblast proliferation equally. However, MMP-9 siRNA had greater effects compared with MMP-2 siRNA on promoting apoptosis and suppressing RA synovial fibroblast 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 κB (NF-κB), extracellular signal-regulated kinase (ERK) and c-Jun NH2-terminal kinase (JNK) and suppressed RA synovial fibroblast-mediated cartilage degradation. In contrast, suppression/inhibition of MMP-2 stimulated TNF-α and IL-17 secretion and activated NF-κB, while recombinant MMP-2 (rMMP-2) inactivated NF-κB and suppressed RA synovial fibroblast-mediated cartilage degradation. Results using specific inhibitors and rMMPs provided supportive evidence for the siRNA results.

Conclusion: Endogenous MMP-2 or MMP-9 contribute to RA synovial fibroblast survival, proliferation, migration and invasion, with MMP-9 having more potent effects. Additionally, MMP-9 stimulates RA synovial fibroblast-mediated inflammation and degradation of cartilage, whereas MMP-2 inhibits these parameters. Overall, our data indicate that MMP-9 derived from RA synovial fibroblasts may directly contribute to joint destruction in RA.

Keywords: cartilage degradation; inflammation; invasion; matrix metalloproteinase 2 and 9; migration; proliferation; rheumatoid arthritis; survival; synovial fibroblasts.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Apoptosis / physiology
  • Arthritis, Rheumatoid / enzymology
  • Arthritis, Rheumatoid / pathology*
  • Cartilage, Articular / metabolism*
  • Cell Movement / physiology
  • Cell Proliferation
  • Cell Survival / physiology
  • Cells, Cultured
  • Cytokines / biosynthesis
  • Female
  • Fibroblasts / enzymology
  • Fibroblasts / pathology
  • Fibroblasts / physiology*
  • Humans
  • Inflammation Mediators / metabolism
  • Male
  • Matrix Metalloproteinase 2 / physiology
  • Matrix Metalloproteinase 9 / genetics
  • Matrix Metalloproteinase 9 / physiology*
  • Middle Aged
  • Osteoarthritis, Knee / enzymology
  • Osteoarthritis, Knee / pathology
  • RNA Interference
  • RNA, Small Interfering / genetics
  • Synovial Membrane / enzymology
  • Synovial Membrane / pathology*


  • Cytokines
  • Inflammation Mediators
  • RNA, Small Interfering
  • Matrix Metalloproteinase 2
  • Matrix Metalloproteinase 9