Transcriptomics and proteomics revealed sex differences in human pulmonary microvascular endothelial cells

Marked sexual dimorphism is displayed in the onset and progression of pulmonary hypertension (PH). Females more commonly develop pulmonary arterial hypertension (PAH), yet females with PAH and other types of PH have better survival than males. Pulmonary microvascular endothelial cells play a crucial role in the pulmonary vascular remodelling and increased pulmonary vascular resistance in PH. Given this background, we hypothesized that there are sex differences in the pulmonary microvascular endothelium basally and in response to hypoxia that are independent of the sex hormone environment. Human pulmonary microvascular endothelial cells (HPMECs) from healthy male and female donors, cultured under physiological shear stress, were analysed using RNA sequencing and label-free quantitative proteomics. Gene set enrichment analysis identified a number of sex different pathways both in normoxia and hypoxia, including pathways that regulate cell proliferation. In vitro, rate of proliferation in female HPMECs was lower than in male HPMECs, a finding that supports the omics results. Interestingly, thrombospondin1, an inhibitor of proliferation, was more highly expressed in female than in male cells. These results demonstrate for the first time important differences between female and male HPMECs that persist in the absence of sex hormone differences and identify novel pathways for further investigation that may contribute to sexual dimorphism in pulmonary hypertensive diseases.