KDR and pulmonary arterial hypertension: Interestingly, Vegfr2 expression in lung EC was reduced in this model, similar to the Sugen/Hypoxia rat model, the most common preclinical model of Group 1 PAH, where Sugen suppresses vascular endothelial growth factor receptors (VEGFR2; FLK1/KDR) and causes endothelial cell dysfunction.