Expression analysis of genes and MicroRNAs involved in recurrent implantation failure: New noninvasive biomarkers of implantation

Background: Recurrent implantation failure (RIF) is defined as three or more failed in vitro fertilization attempts and is due to several factors such as oocyte and embryo quality. Methods: Fifty-one RIF patients and 19 controls were selected based on the inclusion criteria. EFNB2, CAMK1D, AREG, and PTGS2 as well as miR-34, miR-145, miR-204-5p, and miR-26-5p were selected since the microRNAs (miRNAs) targeted the genes based on bioinformatic predictions and literature review. Total RNA was extracted from cumulus cells (CCs) and follicular fluid (FF) of the oocytes. We performed real-time polymerase chain reaction to evaluate the expression of the genes and the miRNAs in CC and FF of pregnant and nonpregnant RIF patients. The expression of CAMK1D, AREG, miR-34-5p, and miR-26-5p was higher in CC than FF. Results: The expression of CAMK1D, PTGS2, and miR-26-5p in CC of the pregnant group was higher than FF. The expression of EFNB2, PTGS2, miR-145, and miR-204-5p was lower in the CC, and the expression of EFNB2, AREG, miR-34-5p, mR-145, and miR-204-5p was lower in the FF of the pregnant group. The expression of CAMK1D, AREG, PTGS2, miR-34-5p, and miR-26-5p was higher in the CC and FF of the high quality (HQ) embryos than non-HQ (NHQ) embryos. The expression of EFNB2, miR-145, and miR-204-5p was higher in the CC and FF of the NHQ embryos. The difference was statistically significant for EFNB2 in CC and FF as well as miR-145 in CC. The level of progesterone and prostaglandin E2 in the FF of the pregnant group was higher than their level in the nonpregnant group. Conclusion: CAMK1D expression and overexpression of miR-34-5p and miR-26-5p could be considered as markers of successful pregnancy. In addition, the results show that normal FF treatment of RIF patients may result in the production of high-quality embryos.