MicroRNA and Embryo Implantation

Problem: In mammals, implantation involves interactions between an activated blastocyst and a receptive endometrium. There are controversies on the role of microRNAs in preimplantation embryo development. The actions of endometrial microRNAs on implantation are beginning to be understood. Method of Study: Review of literature on microRNAs in preimplantation embryos and endometrium. Results: Emerging evidence suggests a role of microRNAs in blastocyst activation and implantation. Differential expression of microRNAs is found between receptive and non-receptive endometria. Members of the let-7, miR-200, miR-30 families, and the miR-17-92 clusters are more commonly found to be associated with endometrial receptivity. Experimental studies show that the targets of the differentially expressed microRNAs affect endometrial receptivity, decidualization, and embryo implantation. Free and exosome/microvesicle containing microRNAs have been detected in human and ovine uterine luminal fluid (ULF). They may serve as mediators of embryo–endometrium dialog. Some observations suggest that the microRNAs in ULF may be used as biomarkers in infertility treatment. Conclusion: MicroRNAs in endometrium and blastocysts are involved in the implantation process.