CCN1 and rheumatoid arthritis: Levels of Cyr61 secretion in culture media were consistent with the status of Cyr61 expression; the level of secreted Cyr61 was elevated in normal FLS cells transfected with Cyr61 cDNA, whilst it was significantly decreased in RA-FLS cells transfected with Cyr61-siRNA (P<0.0001 and P<0.05, respectively; Fig. 2C).