ACTA1 and systemic sclerosis: On the contrary, PDGF-BB treatment induced a significant decrease of α-SMA when compared with UT cells, in both HC- and SSc-MSC [α-SMA mRNA levels in PDGF-BB SSc-MSC 1.84 (1.52–2.01) vs UT SSc-MSC 7.53 (6.94–7.94); p < 0.0001; α-SMA mRNA levels in PDGF-BB HC-MSC 0.54 (0.24–0.70) vs UT HC-MSC 1.05 (0.84–1.18); p < 0.0001] (Fig. 3b).