MMP9 and rheumatoid arthritis: As shown in Figure 3, multiplex cytokine assay kits assays showed that addition of CRP dose-dependently upregulated CCL2, CXCL8, IL-6, MMP2, MMP9 in RA-FLS but not in HFLS, although expression of IL-1β and TNFα was not significantly changed (Figure 3A).