GDF2 and pulmonary arterial hypertension: Long et al. injected recombinant BMP-9 into mice to enhance the biological effects of BMPR II in the vascular endothelium, and they found that BMP-9 treatment successfully reversed PAH by preventing endothelial cell apoptosis and permeability in a transgenic mouse model and in a monocrotaline-induced rat model (Long et al., 2015).