JAK2 and pulmonary arterial hypertension: To address this question, we generated a SMC‐specific Jak2 knockout model and demonstrated that Jak2 deficiency in SMCs protected mice from hypoxia‐induced PAH and substantially reduced right ventricular systolic pressure (RVSP), the right ventricle/left ventricle plus septum [RV/ (LV+S)] weight ratio and the median width of pulmonary arterioles.