Dynamics of extracellular vesicle-coupled microRNAs in equine follicular fluid associated with follicle selection and ovulation

Abstract

Innumerable similarities in reproductive cyclicity and hormonal alterations highlight the considerable utility of the mare to study aspects of follicular dynamics and reproductive function in view of the largely constricted, human research subjects. The bi-directional communication between the growing oocyte and the surrounding somatic cells embodies the hallmark of mammalian follicular development, partially mediated by extracellular vesicles (EVs) encapsulated with microRNAs (miRNAs) and present in the follicular fluid (FF). Here, we aimed to decipher the dynamics of the miRNAs in EVs from equine FF aspirated in vivo during different stages of follicular development, namely, predeviation (PreDev; 18–20 mm), deviation (Dev; 22–25 mm), postdeviation (PostDev; 26–29 mm), preovulatory (PreOV; 30–35 mm), and impending ovulation (IMP; ∼40 mm). Approximately 176 known miRNAs were found in all groups with 144 mutually detected among all groups. Cluster analysis exhibited 15 different expression patterns during follicular development. Among these patterns, a group of 22 miRNAs (including miR-146b-5p, miR-140, and miR-143) exhibited a sharp reduction in expression from the PreDev until the PreOV stage. Another cluster of 23 miRNAs (including miR-106b, miR-199a-5p, and miR-125a-5p) exhibited a stable expression pattern at the PreDev stage until the PostDev stage, with a significant increase at the PreOV stage followed by a significant decrease at the IMP stage. In conclusion, this study provides greater insights into the stage-specific expression dynamics of FF EV-miRNAs during equine follicular development, which may propose novel approaches to improve ART and provide new biomarkers to facilitate the assessment of ovarian pathophysiological conditions.

Dominant follicle growth patterns and associated endocrine dynamics in anovulatory and ovulatory waves in women

“…Greater follicle growth rates have been reported for minor waves compared to major waves ( Baerwald et al 2003 b ); minor waves were not evaluated in the present study. Future studies focused on the follicular fluid endocrine milieu, proteomics, and extracellular vesicle-coupled microRNA dynamics, as well as on granulosa cell gene expression in W1ADF and W2ADF vs W2OvF and W3OvF, as recently performed in mares during different phases of the ovulatory wave ( Wischral et al 2021 , Ishak et al 2022 , Gebremedhn et al 2023 ), would provide insight into why major anovulatory follicle waves develop prior to ovulation in women. Recently, a follicle wall biopsy (FWB) technique was developed in our lab ( Ishak et al 2018 ) to study in mares the expression pattern of growth factors and hormone receptors and gene expression in the layers (i.e., granulosa and theca) of the follicular wall ( Ishak et al 2019 , 2020 ) in association with the follicular fluid milieu.…”

MicroRNA Nano-Shuttles: Engineering Extracellular Vesicles as a Cutting-Edge Biotechnology Platform for Clinical Use in Therapeutics

“…Here we focus on miRNAs, which exert functional regulatory impacts on gene expression through post-transcriptional regulation of target mRNAs. It is well-documented that the expression level of particular miRNAs are key during development [29,30] and stress responses [31,32], and that EVs play an important role in transferring miRNA cargoes between cells [33]. Alterations in the release and uptake of EVs are associated with pathologies including cancer [34] and cellular stress [32,[35][36][37][38][39].…”