Endometriosis is frequently associated with infertility and it is believed that the impairment of endometrial receptivity may be one of the mechanisms involved in this condition. Pinopodes are endometrial cycle-dependent structures that seem to participate in embryo implantation, and alterations in their presence and/or morphology during the window of implantation could affect the endometrial receptivity and be involved in the disease-related infertility. However, the data on pinopodes in these women are scarce and inconclusive. This pilot study aimed to evaluate the cell pattern, including the presence and developmental stage of pinopodes, in eutopic endometrium of infertile patients with and without endometriosis during the window of implantation, using scanning electron microscopy (SEM). Endometrial biopsies were performed using a Pipelle catheter, and 12 samples classified in the window of implantation (6 infertile women with endometriosis and 6 infertile controls) were analyzed by SEM. The frequencies of cell types (microvilli, ciliated, and pinopodes) and the developmental stage of pinopodes were compared between groups using Mann-Whitney U test. Although the study was limited by its sample size, no large differences were detected between the groups regarding the presence and developmental stage of pinopodes, suggesting the absence of large structural changes in the endometrium of infertile women with endometriosis during the window of implantation.
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