GREM1 and pulmonary arterial hypertension: Indeed, recent studies from Pagano group show that Gremlin 1 modulates proliferation of PAECs in PAH [46], and Ciuclan and colleagues reported beneficial effects of antibodies against Gremlin 1 to reduce pulmonary vascular remodeling and RV pressures in mice with SU5416/hypoxia-induced PH [15], suggesting that more studies are needed to determine whether PAEC-secreted Gremlin 1 affects PAVSMC growth and proliferation in human PAH.