Sex Differences In Circulating Angiogenic Cells And Circulating Endothelial Cells In Response To Acute Exercise

Abstract

Acute exercise provides a stimulus for improving the function and health of the endothelium by initiating release of circulating angiogenic cells (CACs). However, this may also result in endothelial stress through the shedding of endothelial cells into circulation (CECs). The ratio of CACs/CECs may serve as a unique indicator of vascular health but sex differences in the ratio of CACs/CECs in response to acute aerobic exercise are unknown. PURPOSE: To determine whether there are sex differences in the CAC and CEC response to a single bout of submaximal treadmill exercise. METHODS: Subjects were healthy physically active men (n=15) and women (n=10) between the ages of 18-29 years. Maximal oxygen consumption (VO2max) was assessed and 48 hours later, participants performed 30 minutes of treadmill running at 70% VO2max. Fasted blood was obtained before and 30-minutes after the treadmill exercise. Peripheral blood mononuclear cells were isolated, FcR blocked and immunostained with antibodies specific to CD34-FITC, KDR-PE, CD31-FITC, CD3-APC, CD146-PECy7 and CD45-PerCP, and fixed in paraformaldehyde. The forward-side-scatter plot was used to identify the lymphocyte and monocyte gates from a total of 5,000 events/sample using a flow cytometer. CACs (CD34+/KDR+, CD31dim, and CD31dim/CD3+) and CECs (CD146+/CD45-) were quantified. RESULTS: There was no main effect for exercise or sex, or a sex*exercise interaction in the number of CD34+/KDR+ and CD31dim cells (P>0.05 for both). There was no main effect of exercise in CD31dim/CD3+ cells but there was a significant main effect of sex (P=0.038) and a trend for a sex*exercise interaction (P=0.069) in with men exhibiting 8% and 3% fewer CD31dim/CD3+ cells vs. women before and after exercise, respectively. Regardless of sex, CECs increased from 45.2 ± 9.7 events to 66.7 ± 18.7 events after the acute exercise bout (P=0.027). There was no main effect for exercise or sex, or a sex*exercise interaction in CAC/CEC ratios (P>0.05 for all). CONCLUSIONS: Regardless of sex, the lack of mobilization of CACs in response to submaximal treadmill exercise suggests that other repair mechanisms may play a stronger role in maintaining the balance between endothelial repair and disturbance in younger physically active adults.