MMP1 and rheumatoid arthritis: Compared to non-inflammatory OA, higher levels of IL-6, IFN-γ, IFN stimulated genes (OAS1, IFIT2, IFI27 and STAT1), chemokines including CCL2, CCL8, CCL13, CXCL9, and CXCL12, and MMP1, MMP13, MMP16 and VEGFB were observed on all cell types in RA joint (Figs. 2d and S2b), indicating a highly inflammatory microenvironment in RA.