MMP9 and rheumatoid arthritis: Gallic acid has been reported to induce apoptosis of rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLS) by regulating the expression of apoptosis-related proteins and reducing the expression of pro-inflammatory mediators, such as pro-inflammatory cytokines, chemokines, COX-2 and MMP-9 [9].