Abstract
The antiprogestin mifepristone has been used for more than 20 years as a medical alternative for early pregnancy termination. After mifepristone administration, significant changes have been observed in the endometrial vessels, with cell injury and cell death in capillary endothelial cells. In this study, the effect of mifepristone on human endometrial endothelial cells (HEECs) in vitro was evaluated using proliferation and viability assays, quantitative polymerase chain reaction of markers important for the regulation of angiogenesis, and by tube formation assay. There were no detectable effects of mifepristone on HEECs messenger RNA expression of the studied markers. Exposure to mifepristone did not alter tube formation. However, mifepristone exposure to HEECs cocultured with endometrial stromal cells significantly reduced the activity in the tube formation assay compared with mifepristone exposure of HEECs in monoculture. This implies that mifepristone causes changes in HEEC-associated angiogenic activity and that this effect is mediated through stromal cells via paracrine mechanisms.