ACTA1 and rheumatoid arthritis: Upon stimulation with SF from two different RA patients, expression of collagen I remained stable, while expression of α-sma was modestly increased (1.8 ± 0.5-fold with SF16 and 1.4 ± 0.3-fold with SF17 (mean ± standard deviation), n = 10, p < 0.001 for both SFs) (Figure 5).