Project description: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.
Project description:Mapping the follicle-specific regulation of extracellular vesicle-mediated microRNA transport in the southern white rhinoceros (Ceratotherium simum simum)
Project description:All species in the extant Rhinocerotidae family are experiencing increased threats in the wild, making captive populations essential genetic reservoirs for species survival. However, managed species face distinct challenges in captivity, resulting in populations that are not self-sustaining. Captive southern white rhinoceros (Ceratotherium simum simum) have low reproductive rates and presumed acyclicity is common among females. Although many females fail to ovulate, follicle growth may occur and ovulation can be hormonally induced. Female southern white rhino (n = 6), housed as a bachelorette group, were determined to be ovulatory (n = 1) or anovulatory (n = 5) by serial ultrasound and fecal progestagen analysis. When follicles reached pre-ovulatory size (~35 mm), females (n = 4) were induced to ovulate in 11 trials with a GnRH analog (4.5 mg, SucroMate™) via single intramuscular injection. Nine trials resulted in ovulation (81.8%), all between 36 and 48 hours post-treatment. Ovulations were confirmed by progestagen elevation above baseline coincident with visualization of a corpus luteum (CL). Luteal phases were characterized as short (<50 days) or long (≥50 days). Between short and long cycles, only the number of days of progestagen above baseline was significantly different (P < 0.05), while days with visible luteal structures was not significant (P = 0.11). Both cycle types were observed following both spontaneous and induced ovulations. Furthermore, we showed that longer cycle lengths do not necessarily indicate early pregnancy loss as none of the females were bred or inseminated during the study. While anovulation is common in the southern white rhino captive population, ovulation induction can be achieved efficiently and predictably for use in conjunction with artificial insemination or to facilitate natural breeding. This information will lead to more efficient use of assisted reproductive technologies to overcome reproductive challenges in this species and to generate genetically healthy captive populations as a hedge against extinction.