Specifically, combination therapy further attenuated the development of monocrotaline (MCT)- or Hypoxia/Sugen-induced pulmonary hypertension (PH) in rats as demonstrated by further reductions in the Fulton index, right ventricular systolic pressure (RVSP), pulmonary vascular wall thickness and vessel muscularization, and decreased proliferating cell nuclear antigen (PCNA) staining in PASMCs. Here, PCNA is linked to pulmonary arterial hypertension.