Structural and functional features of the endometrium in chronic endometritis and implantation failure in IVF cycles

BACKGROUND: Implantation failure of the endometrium in women with chronic endometritis remains a subject of discussion, despite certain progress in the diagnosis and treatment of this pathology. It has been proven that chronic endometritis is a predictor of endometrial dysfunction, which contributes to the disruption of the morphogenesis of the endometrium necessary for its implantation capacity. Implantation disorders associated with chronic endometritis are related to pathology of the receptor profile and vascular bed, as well as dysregulation of proliferative and apoptotic mechanisms. AIM: The aim of this study was to evaluate the expression of estrogen and progesterone receptors, endothelial marker and apoptosis-inducing factor in the endometrium of patients with chronic endometritis and ineffective embryo transfer in IVF protocols. MATERIALS AND METHODS: This study enrolled 50 patients with ineffective embryo transfers in IVF protocols and 25 women in the control group with positive reproductive outcomes. All patients underwent a comprehensive morphological study of the endometrium including histological examination, immunohistochemical study with assessment of the receptor profile [estrogen (ERα) and progesterone (PR) receptor expression], chronic endometritis (CD8+, CD4+, CD20+, CD138+), apoptosis [antibodies to apoptosis-inducing factor (anti-AIF [E20])], and angiogenesis (CD34+), with microscopic, morphometric and statistical methods used as well. RESULTS: Endometrial implantation failure is associated with a history of urogenital infection, benign cervical diseases, high incidence of endometrial pathology and reproductive loss. It is characterized by the presence of follicle-like mononuclear infiltrates in the endometrium, fibroplastic changes in the stromal component, vascular sclerosis, abnormal increase in the pro-inflammatory cell count, multifocal decrease in estrogen (ERα) and progesterone (PR) receptor expression, as well as activation of pathological neoangiogenesis and apoptosis in the stroma. CONCLUSIONS: Chronic endometritis leads to disruption of the structural and functional characteristics of the endometrium, stimulates pathological neoangiogenesis and dysregulates proliferative and apoptotic mechanisms, which forms a vicious circle of endometrial implantation failure and inefficiency of embryo transfer in IVF protocols.