ACTA ENDOCRINOLOGICA (BUC)

Background. Repeated implantation failure (RIF) is the most important problem in assisted reproductive technologies (ART). In the process of embryo implantation, accurate function of progesterone through progesterone receptors (PR) is crucial for establishment of a receptive endometrium. FKBP51 and FKBP52 are two co-chaperones acting as negative and positive regulators of PR function, respectively. Studies have shown that any deficiencies in expression of PR or its co-chaperones causes reproductive disorders. Materials and Methods. In this study we evaluated the PR protein expression by immunohistochemistry and expression of PR, FKBP51, FKBP52 genes by quantitative real-time PCR in endometrial tissue of normal and RIF women during the window of implantation. Results. Immunohistochemical studies showed that the PR protein expression in stromal cells is significantly higher in the endometrium of normal women than RIF women (P< 0.001). In addition, a significantly lower PR and FKBP52 gene expression was observed in endometrial tissue of RIF women compared to normal women (P< 0.001 and P< 0.001, respectively), whereas there was no significant difference in PR protein in epithelial cells (P= 0.3) and FKBP51 gene expression between the two groups (P= 0.6). Conclusion. The results indicate that altered expression of PR protein in stromal compartment and gene expression of PR and FKBP52 gene in endometrial tissue can be related to endometrial receptivity defects and occurrence of RIF.