On the opposite site, BMP9 caused a significant drop in PAH MVECs resistance after 24 h (2212 ± 92 vs. 1844 ± 105 Ω, p = 0.004) that continued to regress until a complete loss of barrier integrity at 72 h (1904 ± 160 vs. 269 ± 3 Ω, p < 0.001). This evidence concerns the gene GDF2 and pulmonary arterial hypertension.