<p>The Importance of Small Non-Coding RNAs in Human Reproduction: A Review Article</p>

Abstract

Background: MicroRNAs (miRNA) play a key role in the regulation of gene expression through the translational suppression and control of post-transcriptional modifications. Aim: Previous studies demonstrated that miRNAs conduct the pathways involved in human reproduction including maintenance of primordial germ cells (PGCs), spermatogenesis, oocyte maturation, folliculogenesis and corpus luteum function. The association of miRNA expression with infertility, polycystic ovary syndrome (PCOS), premature ovarian failure (POF), and repeated implantation failure (RIF) was previously revealed. Furthermore, there are evidences of the importance of miRNAs in embryonic development and implantation. Piwi-interacting RNAs (piRNAs) and miRNAs play an important role in the posttranscriptional regulatory processes of germ cells. Indeed, the investigation of small RNAs including miRNAs and piRNAs increase our understanding of the mechanisms involved in fertility. In this review, the current knowledge of microRNAs in embryogenesis and fertility is discussed. Conclusion: Further research is necessary to provide new insights into the application of small RNAs in the diagnosis and therapeutic approaches to infertility.

miRNAs as a novel clinical biomarker and therapeutic targets in polycystic ovary syndrome (PCOS): A review

“…Maternal age is another major factor for infertility. In a study, various differentially expressed miRNAs were expressed in women above the age of 40s compared to women in their 20s and miR-93 was exceptionally expressed only in blastocytes with chromosomal abnormalities in older women (57), this is a clear indication that maternal ageing is not only a risk factor for infertility but also associated with modification of miRNAs profiles (58).…”

The current perspective on genetic and epigenetic factors in sperm maturation in the epididymis

“…The pre‐miRNA is exported from the nucleus to the cytoplasm via Exportin 5, and it is cleaved by Dicer1, a cytoplasmic RNase III. Dicer1 and Argonaute proteins make the RNA‐induced silencing complex (RISC), which is responsible for mature miRNA formation, and the guided strand of miRNA is loaded on RISC (Kamalidehghan et al., 2020; Ni et al., 2011; Sharma et al., 2018).…”

“…miRNAs can control their target gene expression by antisense base‐paring with mRNAs, a result of which is suppression of mRNA translation and mRNA degradation (Kamalidehghan et al., 2020; Ni et al., 2011; Sharma et al., 2018). miRNAs participate in male reproductive functions at several stages, including gametogenesis, sperm maturation and fertilisation.…”

“…Even though the mechanism is not well understood, it has been suggested that piRNAs play a role in the maintenance of germline stem cells, epigenetic inheritance and gene silencing via heterochromatin assembly or via co‐transcriptional or post‐transcriptional destruction of transcripts (Klattenhoff & Theurkauf, 2008). piRNA‐associated protein mutations cause sexual developmental arrest or male infertility in different organisms; for humans, piRNA expression is limited to the testis, and an effect on sperm maturation is unlikely (Kamalidehghan et al., 2020; Klattenhoff & Theurkauf, 2008), but mouse spermatozoa are enriched with piRNAs during epididymal transit. In addition to the increase in the amount of piRNA in maturing spermatozoa, the detection of PIWIL1 in the epididymal spermatozoa of mice raises questions about the understanding that spermatozoa are transcriptionally and translationally quiescent cells (Hutcheon et al., 2017).…”

Morphological and Molecular Biological Determinants of Repeated Implantation Failure

“…Thirteen different miRNAs have already been identified in endometrial samples of patients, with repeated implantation failures that presumably regulate the expression of 3800 genes and which were not found in the group of healthy women. It was also shown that ten miRNAs are overexpressed in endometrial samples in women with repeated implantation failures, including miR-23b, miR -199a, and miR-145 [37].…”