Previous research found that apoptotic vascular cells are present and play important roles in both medial and intimal lesions of the pulmonary arteries in the pathogenesis of a Sugen PAH rat model.17,19,20 Therefore, apoptosis was analyzed by the number of cleaved caspase-3-positive apoptotic cells. The gene discussed is CASP3; the disease is pulmonary arterial hypertension.