The Role of Embryo Secreted MicroRNAs in Implantation

The process of implantation, a critical phenomenon in early development of embryo, is result of regulated reciprocal interaction between receptive endometrium and competent embryo. This dialogue is mediated by cell surface molecules, components of extracellular matrix and both embryo and endometrium secreted substances such as cytokines, growth factors, hormones and extracellular vesicles. Intensive recent studies introduce secreted microRNAs (miRNAs) as novel mediators in intercellular communication. MiRNAs are endogenous small single-stranded non-coding RNAs which involved in regulating post-transcriptionally target genes and influencing various intracellular processes. These molecules can be secreted and delivered into recipient cells where they affect host cellular events through target gene suppressing. Inthis regard, we reviewed the role of miRNAs in trophoblast cell differentiation, blastocyst secreted miRNAs in interaction with endometrium and regulation of implantation. In infertility treatment through assisted reproductive techniques, clinician needs to non-invasive strategies for exploring the criteria to select the best in vitro-produced embryo for transfer into uterine and achieving pregnancy. Here, we also reviewed potential role of miRNAs as biomarkers for selecting of competent embryos to transfer into uterine during infertility treatment such as in vitro fertilization and intracytoplasmic sperm injection.