Treating the mice with sildenafil during hyperoxia effectively blocked PDE5 activity, pulmonary vascular remodeling, and development of right ventricular hypertrophy, solidifying the role for hyperoxia-induced PDE5 activity in PH and right ventricular hypertrophy (RVH) in this model [10]. The gene discussed is PDE5A; the disease is Right ventricular hypertrophy.