BMP4 and pulmonary arterial hypertension: There is growing evidence that abnormalities of the BMP signaling pathway are linked to the pathogenesis of PAH [4,10,15], and BMP4 has been found to be up-regulated by hypoxia in murine lung tissue and to promote the growth and migration of PASMCs, and thus to promote pulmonary arterial remodeling during the development of chronic hypoxic pulmonary hypertension (CHPH) [12,13,14].