Endometriosis and human infertility: a new investigation into the role of eutopic endometrium

BACKGROUND Endometriosis is related to infertility even in the absence of mechanical alterations of the reproductive tract. Even though the pathogenesis of this phenomenon is still unclear, an impaired endometrial receptivity has been recently suggested. The aim of the present study was to investigate if endometriotic peritoneal fluids (EPF) could interfere with endometrial stromal cell (ESC) decidualization and if tumor necrosis factor (TNF)-alpha could be involved in the EPF effect. METHODS Eutopic ESC were isolated from patients with or without endometriosis. ESC were treated with 17beta-estradiol 10(-8) M and 6alpha-methyl-17alpha-hydroxyprogesteroneacetate 2x10(-7) M for 16 days. In vitro decidualization was morphologically and biochemically assessed. We analysed whether ESC decidualization could be affected by EPF or peritoneal fluids from control patients (CPF), with or without soluble TNF-alpha receptor 1 (sTNFR-1). RESULTS Compared with ESC from control patients, eutopic ESC from patients with endometriosis showed an impaired decidualization. Decidualization of normal ESC was morphologically normal but biochemically abnormal in the presence of EPF, which was able to decrease the secretion of decidualization markers. sTNFR-1 was able to partially counteract this effect. CONCLUSIONS In endometriosis, the milieu surrounding the uterine cavity may be involved in impaired eutopic ESC decidualization, partially due to increased peritoneal levels of TNF-alpha.