The Role of Vascular Endothelial Growth Factor in Pulmonary Arterial Hypertension The Angiogenesis Paradox

Pulmonary arterial hypertension (PAH) is characterized by dysfunctional angiogenesis leading to lung vessel obliteration. PAH is widely considered a proangiogenic disease; however, the role of angiogenic factors, such as the vascular endothelial growth factor (VEGF) and its receptors, in the pathobiology of PAH remains incompletely understood. This Review attempts to untangle some of the complex multilayered actions of VEGF to provide a VEGF-centered perspective of PAH. Furthermore, we provide a cogent explanation for the paradox of VEGF receptor blockade-induced pulmonary hypertension that characterizes the SU5416-hypoxia rat model of PAH, and attempt to translate the knowledge gained from the experimental model to the human disease by postulating the potential role of endogenous (SU5416-like) VEGF inhibitors. The main objective of this Review is to promote discussion and investigation of the opposing and complementary actions of VEGF in PAH. Understanding the balance between angiogenic and antiangiogenic factors and their role in the pathogenesis of PAH will be necessary before antiangiogenic drugs can be considered for the treatment of PAH.