To determine whether PDE9A attenuates protective cGMP signaling and promotes PH development in the murine CH model, we compared RVH, hemodynamics, VASP phosphorylation, and PDE expression between Pde9a−/− mice and Pde9a+/+ littermates subjected to 3 weeks of CH‐PH. This evidence concerns the gene PDE9A and cyclic hematopoiesis.