MMP13 and rheumatoid arthritis: The production of chemokines (such as MCP-1, IL-8) is also increased in endothelial cells, rheumatoid arthritis fibroblast-like synoviocytes (RA-FLS) and mononuclear cells [35, 36], as is the synthesis of RANK-L by RA-FLS, and that of MMP-1, MMP-3 and MMP-13 in chondrocytes [37].