Vascular endothelial growth factor expression up-regulated by endometrial ischemia in secretory phase plays an important role in endometriosis.

Primary human endometrial cells were exposed to hypoxia preconditioning (HPC), HPC-hypoxia, and hypoxia conditions, and then endometrial tissue treated with ischemia preconditioning (IPC) was transplanted onto the chick embryo chorioallantoic membrane to investigate the role of slight ischemia of endometrium in the pathologic process of endometriosis. IPC up-regulated vascular endothelial growth factor expression and decreased apoptosis of endometrial cells, thus facilitating the endometrial fragments' ectopic implantation.