MMP1 and rheumatoid arthritis: In this study, we also found that TSP-1, TGF-β1, CTGF and VEGF expression levels in either NH-FLS and HDMECs co-culture or RA-FLS and HDMECs co-culture increased significantly after TNF-α induction, in consistent with the report that numerous cytokines, such as IL-6 and MMP-1 from both NH-FLS and RA-FLS, were up-regulated by TNF-α treatment [26, 27].