The role of the serum exosomal and endometrium MicroRNAs in recurrent implantation failure

Recurrent implantation failure (RIF) refers to the failure to achieve a clinical pregnancy after transfer of at least three good-quality embryos in in-vitro fertilization (IVF). RIF is a major problem encountered in IVF. An important factor in the development and function of the RIF disorder is epigenetic regulation of gene expression, in which one of the most noteworthy molecules are microRNAs (miRNAs). In the menstrual cycle, it has been identified that endometrium specific miRNAs have different expression levels in endometrial tissues and maternal serum. Quantitative miRNAs expression level can be measured in a biological sample by different methods which the most important method is quantitative real-time PCR (qRT-PCR) technique. This technology quantitatively measures the expression of targeted miRNA in a biological sample with high sensitivity. The significant feature of this study is that this is the first study to analyse of miRNA expression level in two different types of samples in same cases. The first aim in the study is revealing the factors involved in the biological process of disease by targeted expression of miRNAs. Second aim is to create a basis for developing a new theory for the potential treatment of RIF patients and the last aim of study is that significantly different expressed miRNAs can be used for non-invasive molecular biomarkers in early diagnosis of RIF disorder. In this study, it was studied on 12 RIF samples and 8 samples from normal and fertile individuals which are collected as two peripheral venipunctures (5 mL) and two endometrial biopsies; one in the proliferative phase (CD 7-10) and one in the implantation phase (CD 20-24). In first step RNA was isolated from endometrium tissue and sera exosomes, Expression levels and bioinformatics analysis of candidate miRNAs (hsa-miR-31, hsa-miR-30b, hsa-miR-145 and hsa-miR-23b) which we think are related to implantation were performed. The statistical analysis showed that four selected miRNAs (hsa-miR-145, hsa-miR-23b, hsa-miR-31and hsa-miR-30b) were significant (P<0.05) up-regulated in proliferative phase and down-regulated in secretory phase of endometrium samples. In serum samples, only two miRNAs (hsa-miR-145 and hsa-miR-23b) were significantly down-regulated in both of proliferative phase and secretory phase. Target analysis for dysregulated miRNAs in different and updated target scan databases (Target Scan, Miranda and Pictar) identified important target genes. Pathway analysis of targeted genes showed critical pathways which are related to important cell functions such as proliferation, apoptosis, invasion, adhesion, and differentiation which are hypothesized to be related to the embryo implantation process. Keywords: Recurrent implantation failure, microRNA, epigenetics, exosome, serum, endometrium