A PH model associated with more severe pulmonary vascular remodeling and RV loading (e.g., rat model of SU5416 and CH or pulmonary artery banding) may be required to sufficiently stimulate important protective NP‐dependent signaling pathways in lung and/or heart and evaluate the role of PDE9A. The gene discussed is PDE9A; the disease is cyclic hematopoiesis.