MMP9 and rheumatoid arthritis: For fibroblasts, transforming growth factor (TGF)-β1 or tumor necrosis factor (TNF)-α induction can enhance the expression of MMP2 and MMP9 in fibroblasts (Kobayashi et al. 2003), while the endogenous MMP2 and MMP9 contribute to the survival and proliferation of rheumatoid arthritis (RA) synovial fibroblasts (Xue et al. 2014).