Further analysis of a selection of these differentially regulated genes with TaqMan PCR validated several genes previously described as important in the pathogenesis of PH/PAH, specifically TRAIL, PDGFRA, tenascin-C, VEGFA, and caveolin-1, as all being significantly up-regulated by OPG, and the VIP receptor as being significantly down-regulated by OPG (Fig. 3c). This evidence concerns the gene PDGFRA and pulmonary arterial hypertension.