Thus, to approach clinical CTD-PH, an experimental model of CTD that spontaneously develops pulmonary hypertension is necessary in addition to monocrotaline-administered mice and vascular endothelial growth factor (VEGF) inhibition with hypoxic exposure mice which are popular as animal models of pulmonary arterial hypertension [8, 9]. The gene discussed is VEGFA; the disease is pulmonary arterial hypertension.