SMAD2 and pulmonary arterial hypertension: Our findings regarding the necessity for pathologic TGF-β activation tie into our previous observations of increased canonical TGF-β signalling in the pulmonary vasculature of mice with experimental Schistosoma-PH and autopsy specimens from subjects who died of Schistosoma-PAH as assessed by immunostaining for phospho-Smad2/3, relative to control specimens3.