Mapping the follicle-specific regulation of extracellular vesicle-mediated microRNA transport in the southern white rhinoceros (Ceratotherium simum simum)

Efforts to implement effective assisted reproductive technologies (ART) to extricate the northern white rhinoceros (NWR; Ceratotherium simum cottoni) from extinction, could be unconventionally offset from studies carried out using the southern white rhinoceros (Ceratotherium simum simum) as a relative model species. The bi-directional communication and critical transport of regulatory molecules controlling follicular growth and oocyte development are in part mediated through extracellular vesicles (EVs), which encompass a highly conserved and advanced paracrine signaling mechanism important in shuttling unique cargo such as microRNAs (miRNAs). In this study, critical miRNAs for follicular development were identified, proposing novel approaches using EV-mediated miRNA to possibly improve the in vitro technologies outcome in a multitude of species. Overall design: Two southern white rhinoceros females (n=2) were stimulated and utilized for transrectal OPU, facilitating the in vivo collections of follicular fluid aspirate from follicles of distinct size. Prior to ultrasound-guided ablation of follicles, follicles were assigned to predetermined categories based on their established diameter: growing (G; 11-17mm), dominant (D; 18-29mm), and pre-ovulatory (P; 30-34mm). Follicular fluids were used for EV isolation from which total RNA were isolated and smallRNA sequencing were performed.