VWF and idiopathic pulmonary arterial hypertension: Consistent with previous reports demonstrating decreased PHD2 (31) and activated AKT (43) in lung vascular ECs from patients with IPAH, costaining for PHD2 or pAKT (S473) and von Willebrand factor (vWF), an endothelial cell marker, demonstrated that PHD2 was diminished (Fig. 7E) while pAKT was increased (Fig. 7F) in lung ECs of patients with IPAH compared with FD control specimens.