High relative humidity environment alleviates hypoxia-induced pulmonary arterial hypertension in mice

The environment has long been considered a crucial factor influencing the onset and progression of pulmonary diseases. Environmental therapy is also a practical treatment approach for many conditions. While research has explored the effects of factors like air pressure and oxygen concentration on pulmonary arterial hypertension (PAH), the impact of air humidity on PAH has not been investigated. In this study, we examined the role of different air humidity levels in a mouse model of PAH by controlling relative humidity. We induced PAH in mice using 10 % hypoxia, which led to significant thickening of the pulmonary vasculature, elevated right ventricular systolic pressure, and an increased right ventricular hypertrophy index (RVHI). However, when exposed to an environment with 80-95 % relative humidity, there was a marked reduction in the extent of pulmonary vascular remodeling, decreased vascular thickening, and lower RVHI, effectively preserving right heart function. Notably, changes in the Bmpr2/Tgf-β signaling pathway were significant and may play a pivotal role in this protective effect. In summary, our findings indicate that high relative humidity confers a protective effect on hypoxia-induced PAH in mice, providing novel insights into potential treatments for PAH.