ACTA1 and systemic sclerosis: The main studies on the anti-fibrotic effect of ETR antagonists on SSc FBs were reported by Shi-Wen et al. [32–35], showing that bosentan may suppress the expression of α-SMA, type I collagen, fibronectin, and CCN2 in SSc lung FBs and that ET-1 acts as a downstream mediator of TGF-β in human lung FBs.