Expression of endothelin-1 is induced by TGF-β, and its signaling via the endothelin receptors A and B results in fibroblast migration, myofibroblast differentiation, and proliferation of smooth muscle cells [163], while its induction of vasoconstriction mainly occurs via the endothelin receptor type A. Therefore, in SSc it is established that endothelin-1 plays a critical role in proliferative vasculopathies such as PAH [164]. Here, TGFB1 is linked to systemic sclerosis.