MMP1 and rheumatoid arthritis: As expected, TNF-stimulated RA-FLSs showed increased expression of genes encoding pro-inflammatory cytokines or chemokines (e.g., IL-6, IL-8, CCL20, CXCL11, and TNFSF13B), proteolytic enzymes (e.g., MMP1 and MMP3), and other key molecules involved in RA pathogenesis, such as prostaglandin-endoperoxide synthase 2 (PTGS2).