Alterations of circulating endothelial cell and endothelial progenitor cell counts around the ovulation.

Context: Circulating endothelial cells (CECs) and progenitor cells (CEPs) have been intensively studied as a promising tool for treating ischemic diseases and monitoring cancer treatments, but how the menstrual cycle affects the variation in their counts remains unclear.
Objective: The aims of the study were to determine the influence of the menstrual cycle on the number of CECs and CEPs and to investigate the association of their counts with circulating hormones and angiogenesis-associated factors.
Design: CEP and CEC counts by flow cytometry and the CellSearch system and circulating factor levels were measured eight times during the menstrual cycle in 18 volunteers. The menstrual cycle was divided into six phases based on hormone concentrations.
Results: CEP counts peaked in the periovulatory and middle luteal phases with a drop in the early luteal phase. CEC counts showed no significant variation. There were significant correlations between the CEP counts and the serum concentrations of estradiol (E2), LH, and granulocyte colony-stimulating factor (G-CSF) (P < 0.0001, P < 0.0001, and P = 0.01, respectively). The difference in CEP counts between two adjacent phases was significantly correlated with that in E2, LH, G-CSF, and serum vascular endothelial growth factor (P < 0.0001, P < 0.0001, P = 0.02, and P = 0.006, respectively).
Conclusion: CEP counts peaked in the periovulatory and middle luteal phases, with a drop in the early luteal phase, and were correlated with serum E2, LH, and G-CSF concentrations. Consideration of the variation in CEP counts would be important for the clinical application of CEPs.