MicroRNAs as Regulators of Reproductive Function: From Gametogenesis to Pregnancy

The regulation of transcriptional activity constitutes a primary layer of control over cellular function across diverse tissues and cell types. This regulatory transcriptional landscape is largely governed by epigenetic mechanisms, including DNA and histone modifications, the dynamic activity of epigenetic "writers" and "erasers," and the influence of small regulatory molecules such as microRNAs (miRNAs). miRNAs are small non-coding RNA molecules that play critical roles in transcriptional and post-transcriptional gene regulation. By modulating the expression of transcription factors, kinases, and other regulatory proteins, miRNAs exert tight control over cellular processes and maintain homeostasis. Given the essential requirement for precise cellular coordination in reproductive biology, miRNAs have emerged as key regulators of reproductive function. They participate in multiple stages of reproductive processes, ranging from ovarian function to the establishment and maintenance of pregnancy, thereby influencing fertility outcomes across species. In this review, we summarize recent advances in understanding the roles of miRNAs in key reproductive events, including gametogenesis, oocyte maturation, embryonic genome activation, early embryonic development, implantation and pregnancy. We aim to highlight the principal miRNAs involved in the maintenance of reproductive function and fertility, and their molecular targets and the regulatory networks when known. Based on our review, we conclude that although their potential in clinical and/or agricultural applications still remains uncertain, their role in regulating fundamental aspects of cellular biology, particularly reproductive processes, is becoming increasingly clear.