Tu and colleagues showed that BMP9-knock-out mice exposed to chronic hypoxia demonstrate decreased endothelin-1 and increased apelin and adrenomedullin mRNA levels compared to wild-type BMP9 mice, thus proposing that selective inhibition of BMP9 in mice could prevent the development of experimental pulmonary hypertension [19]. This evidence concerns the gene EDN1 and pulmonary arterial hypertension.