Circular RNAs and mammalian follicular development: current insights and future prospects-an updated review

Circular RNAs (circRNAs), a newly recognized category of non-coding RNA, have recently become a central point of interest in biological research. The ovaries are critical reproductive organs in female mammals, profoundly influencing fertility through their effects on endocrine functions and follicular cycle activities. Follicle development, as the fundamental functional component of the ovaries, is elaborately regulated by granulosa cells, oocytes, and endocrine signals. Recent research has progressively underscored the critical role of circRNAs in regulating follicular development and maturation in mammalian species. This review comprehensively examines the formation, molecular characteristics, and biological significance of circRNAs during mammalian follicular development, with a specific focus on their regulatory mechanisms and functional patterns in this process. We propose that future research should continue to explore the specific mechanisms by which circRNAs influence follicular development in mammals, including their interactions with other non-coding RNAs, the mechanisms of their interaction with the follicular microenvironment, and the alterations in follicular environments under pathological conditions, including polycystic ovary syndrome (PCOS) and primary ovarian insufficiency (POI). Furthermore, we analyze the potential contributions of circRNAs in follicular development in view of advances in high-throughput sequencing technologies and gene editing tools, aiming to deepen our understanding of the biological significance of circRNAs in this context. In summary, this review elucidates the specific mechanisms and critical roles of circRNAs in follicular development in female mammals, potentially providing new therapeutic targets and strategies for future reproductive medicine and fertility treatments.