Deletion of Klf4 in smooth muscle surrounding arterioles led to reduced distal pulmonary arteriole muscularization, prevention of right ventricular hypertrophy and prevention of hypertension [162], yet endothelial cell deletion (following hypoxia) led to increased right ventricular and pulmonary artery pressures and increased right ventricular hypertrophy [149,150]. Here, KLF4 is linked to Right ventricular hypertrophy.