PTGS2 and pulmonary arterial hypertension: Under the gene ontology term ‘response to hypoxia’ (Figure 1c), vascular remodeling BOECs expressed genes such as VEGF-induced PTGS2 (cyclooxygenase-2), an early response gene that leads to downstream proangiogenic effects [42,43], THBS1 (thrombospondin-1), a hypoxia-induced modulator of vascular remodeling in pulmonary arterial hypertension [44,45], and EDN1 (endothelin-1), a potent growth factor that induces the migration, proliferation and invasion of endothelial cells during angiogenesis [46].