PDGFRB and systemic sclerosis: Moreover, when stimulated with agonistic anti-PDGFR autoantibodies isolated from SSc sera, healthy pulmonary VSMCs were shown to acquire a “synthetic” phenotype consisting of higher proliferation and migration activities, type I collagen production and reduced expression of the typical “contractile” markers, thus contributing to hyperplasia of the tunica media as well as intimal thickening [106].