miRNAs and their roles in predicting length and timing of window of implantation

Abstract Study question What are the differences between results from a miRNA-based endometrial receptivity test (MIRA) and a mRNA-based one (ERA)? Summary answer There was a 74.1% concordance between MIRA’s and ERA’s results with additional implications from the select miRNAs that were indicators for window of implantation length. What is known already As more technologies become available, different types of biomarkers have been used to analyze endometrial receptivity such as microRNAs instead of mRNAs. A limitation to these existing technologies is in their ability to determine the length of window of implantation. Patients that are analyzed to be in the post-receptive stage have been seen to have varied lengths of window of implantation. The current solution is to obtain multiple biopsies from an IVF patient in order to confirm the length of their window in order to provide a suggestion on how to alter their embryo transfer time. Study design, size, duration 58 endometrial tissue biopsy samples were analyzed with MIRA. These results were compared to ERA to calculate concordance. Additional analysis was performed by comparing individual miRNA biomarkers between shortened and average window of implantation samples. 11 post-receptive samples with a successful embryo transfer were chosen. Second biopsies for these samples with a “receptive” result indicated “average” window of implantation, while a “ pre-receptive” result from the second biopsy indicated a “shortened” window of implantation. Participants/materials, setting, methods Endometrial tissue biopsy samples were collected from residual clinical samples that had previously undergone ERA testing. The residual tissue samples’ RNA was extracted and analyzed via a multiplex, quantitative qPCR-based platform called NextAmp™ to profile the expression profiles of 96 miRNA biomarkers on MIRA’s testing panel. The subsequent raw expression profiles were analyzed through a proprietary algorithm in order to determine the endometrial stage of the patient (pre-receptive, receptive, or post-receptive). Main results and the role of chance Concordance between the two tests was 74.1%. Further analysis of the individual miRNAs on MIRA’s panel identified 2 down-regulated and 7 up-regulated differentially expressed miRNAs that had potential acting as indicators for shortened window of implantation. The identified differentially expressed miRNAs were based on fold change (log2) = > 0.585 or < -0.585 and p-value = < 0.05 (t-test). Of the 9 identified differentially expressed miRNAs, KEGG analysis was performed to explore their implications in more depth. The end of the secretory phase of the endometrium is usually characterized by phenomena such as degradation of the stromal network (MMP catalysis), infiltration of the stroma by leukocytes, cessation of glandular activity, and apoptosis throughout the tissue. Through KEGG pathway analysis results, pathways that implicate these characterizations were identified such as ECM-receptor interaction, cellular senescence, necroptosis, adherens junctions, and gap junction. With these findings, we see that the 9 miRNAs identified are potential regulators of the morphological changes that occur at the end of the secretory phase in the endometrium, and by monitoring their expression levels can be early indicators of an advanced end to the secretory phase, implying a shortened window of implantation. Limitations, reasons for caution Larger studies should be performed in order to confirm these findings as the current study sample size is limited. Additionally, this only takes into account post-receptive patients; therefore, the same analysis should also be done on patients that fall in the pre-receptive and receptive stages when undergoing endometrial receptivity testing. Wider implications of the findings In this preliminary study, we see that miRNAs could act as potential future biomarkers for identifying shortened window of implantations for patients through endometrial receptivity testing, cutting out the need for multiple biopsies when identifying patients’ windows of implantation. Trial registration number not applicable