COL1A1 and systemic sclerosis: After co-culture with HC-ECs, the SSc-MSCs displayed significant downregulation of α-SMA and collagen gene expression when compared to basal levels (α-SMA, P = 0.0028; Col1A1, P = 0.0002; Col1A2, P = 0.0002), as shown in Figure 5a-c.