Zhang et al. (2018) also determined that rats exposed to chronic hypobaric hypoxia exhibited increased TGF-β levels and phosphorylation of smad3 (a key downstream molecule in the TGF-β signaling pathway) in pulmonary arteries, contributing to pulmonary hypertension and remodeling. Importantly, that study also showed that primary pulmonary adventitial fibroblasts and macrophages contributed to the TGF-β secretion under this hypoxic condition; these mechanisms could thus play an important role in PASMC proliferation and pulmonary artery remodeling (Zhang et al., 2018). Here, TGFB1 is linked to pulmonary hypertension.