2.1. Human PAH PAVSMC (Pulmonary Arterial Hypertension Pulmonary Arterial Vascular Smooth Muscle Cells) Have Increased Secretion of TGF-β1 and Reduced Smad2 and Smad3 Phosphorylation Compared to Controls. Here, TGFB1 is linked to pulmonary arterial hypertension.