A priori implantation potential does not differ in eutopic endometrium of patients with and without endometriosis

In endometriosis, angiogenesis is a crucial step for implantation of the exfoliates. A priori potential to induce angiogenesis by vascular endothelial growth factor (VEGF) expression was compared in eutopic endometrium of patients with and without endometriosis to discriminate the pivotal pathogenic step that differs in endometriosis.

In an experimental prospective study, endometrium samples were obtained from endometriosis patients (n=10) and from healthy, ovulating women as controls (n=6) undergoing curettage and laparoscopy for benign gynaecological conditions at the Aachen University Hospital, Aachen, Germany. Endometrial fragments were transplanted to the chicken chorioallantoic membrane (CAM) and re-explanted after 0, 24, 48, 72 and 96 h of cultivation for analysis. The main outcome measure was VEGF mRNA expression and protein localisation in endometrial fragments as parameters of angiogenic induction that was quantified by the vessel index.

VEGF mRNA expression increased significantly in endometrial fragments of endometriosis and control patients (p<0.05). Protein is expressed in the glands and endometrial stroma. The vessel index is significantly elevated compared with native CAM controls. Endometrial fragments of endometriosis and control patients showed no significant differences in VEGF expression or angiogenic induction.

Eutopic endometrial fragments of patients with and without endometriosis do not differ in their VEGF expression or angiogenic activity in the CAM assay. Implantation is obviously decided by external regulating influences on the exfoliates.