In vitro sex-dependent properties of male and female human umbilical vein endothelial cells (HUVECs)

Loss of normal endothelial function is a critical step in the development and clinical expression of atherosclerosis and cardiovascular diseases (CVDs). Substantial sex/gender differences have been described with a prevalence in men than women until midlife. However, the occurrence of CVD increases with age in both sexes. Despite these well-established observations, very little is known about innate gender differences existing between male and female endothelial cells (ECs). To characterize sex-dependent differences, we compared in vitro properties of male and female cells obtained from human umbilical vein ECs (HUVECs). Importantly, we always used HUVECs pooled from two or more donors to minimize the variability associated with cells derived from a single male or female newborn donor. First, we focused our attention on properties shown by male and female HUVECs grown in standard conditions i.e. in 199 medium supplemented with FBS. We demonstrated that metabolic activity was similar in cells of both sex. On the other hand, female HUVECs expressed an higher amount of endothelial Nitric Oxide Synthase (eNOS) mRNA and protein, and showed greater migratory capabilities in comparison to male cells. The female advantage in younger women has been attributed to vascular protection by estrogens, which is lost with menopause. To study the contribution of estrogens in EC physiology, male and female HUVECs were cultured in the absence of estrogens i.e. in phenol red-free 199 medium supplemented with charcoal-stripped FBS. We found that loss of estrogens induced a significant decrease in metabolic activity in comparison to growth standard conditions in cells of both sex. Very interestingly, the expression of eNOS was decreased in the absence in estrogens only in female HUVECs. These preliminary results confirm a role for estrogen in the modulation of in vitro EC physiology. Further studies should be carried out to determine whether innate gender differences between male and female cells and estrogens might play a crucial role in the vascular protection responsible for the lower prevalence of CVDs in women until menopause.