Pulmonary endothelial cells exhibit sexual dimorphism in their response to hyperoxia.

Abnormal pulmonary vascular development is a critical factor in the pathogenesis of bronchopulmonary dysplasia (BPD). Despite the well-established sex-specific differences in the incidence of BPD, the molecular mechanism(s) behind these are not completely understood. Exposure to high concentration of oxygen (hyperoxia) contributes to BPD and creates a pro-fibrotic environment in the lung. Our objective was to elucidate the sex-specific differences in neonatal human pulmonary microvascular endothelial cells (HPMECs) in normoxic and hyperoxic conditions including propensity for endothelial to mesenchymal transition. HPMECs (18-24 weeks gestation donors; 6 male and 5 female) were subjected to hyperoxia (95% O2 and 5% CO2 ) or normoxia (air and 5% CO2) up to 72 h. We assessed cell migration and angiogenesis at baseline. Cell proliferation, viability, and expression of endothelial (CD31) and fibroblast markers (α-SMA) were measured upon exposure to hyperoxia. Female HPMECs had significantly higher cell migration when assessed by the wound healing assay (40.99 ± 4.4 %) compared to male (14.76 ± 3.7 %) and showed greater sprouting (1710 ± 962 μm in female vs 789 ± 324 in male) compared to male endothelial cells in normoxia. Hyperoxia exposure decreased cell viability (by 9.8% at 48h and 11.7% at 72h) and proliferation (by 26.7% at 72 h) markedly in male HPMECs, while viability was sustained in female endothelial cells. There was greater expression of α-SMA (2.5-fold) and decreased expression (5-fold) of CD31 in male HPMECs, upon exposure to hyperoxia. The results indicate that cellular sex affects response in HPMECs in normoxia and hyperoxia.