NAIROBI, Oct 22 (Swara) – One of the two remaining northern white rhino females, Najin, has been officially retired as a donor of egg cells (oocytes) under a scientific project aimed at saving the species from extinction, the consortium of scientists and conservationists spearheading the effort reported.
Two females, Najin and her daughter Fatu, are the only remaining northern white rhinos in the world and are hosted in the Ol Pejeta Conservancy in Kenya.
To prevent the extinction of the northern white rhino, an international consortium of scientists and conservationists called BioRescue, led by the German research institute Leibniz-IZW, has been harvesting immature egg cells (oocytes) from the two females and artificially inseminating them using frozen sperm from deceased males in order to create viable northern white rhino embryos since 2019. In the near future, the embryos will be transferred to southern white rhino surrogate mothers to create northern white rhino offspring.
The decision to stop harvesting oocytes from 32-year-old Najin was arrived “after an in-depth ethical risk assessment, weighing up risks and opportunities for the individuals and the entire species,” BioRescue said in a statement.
“This situation will further strengthen the need for stem cell associated techniques, which are also part of the BioRescue mission as well as long-term biobanking. Najin will remain an important part of the mission as an ambassador for her kind and by transferring social knowledge to future offspring,” the statement added.
Recent ultrasound examinations had revealed multiple small, benign tumours in Najin’s cervix and uterus as well as a large cystic structure in her left ovary.
“The ethical risk assessment applied the best scientific approach aimed at safeguarding Najin’s welfare given her advanced age and the pathological signs in her uterus,” said Patrick Omondi, Director, Wildlife Research and Training Institute (Kenya). “We are pleased to have participated in this assessment which affirms the collaborative and innovative approaches by the BioRescue Consortium in saving the species from extinction,” he added.
In the face of Najin’s phase-out from the first pillar of the BioRescue programme (advanced assisted reproduction technologies, aART), its second pillar will become even more important, according to BioRescue. The aART relies on natural gametes for the creation of embryos, meaning that both the oocytes and the sperm have been collected directly from northern white rhino females and males. The stem cell associated techniques (SCAT), the second pillar of the mission, strive to create artificial gametes from stored tissue of northern white rhinos. For example, tissue such as skin cells collected from Najin could be transformed into induced pluripotent stem cells that could then be reprogrammed to develop into artificial gametes (oocytes or sperm).
Najin was born in the Safari Park Dvůr Králové zoo in the Czech Republic in 1989 and was moved to Ol Pejeta Conservancy along with three other northern white rhinos in 2009 for a natural breeding programme. Five years later, scientists established that the last chance to survive for Najin and her kind lies in advanced techniques of assisted reproduction conducted by the BioRescue consortium. This approach relies on collecting oocytes from female northern white rhinos, which involves hormone stimulation, full anaesthesia and transrectal ultrasound-guided oocyte retrieval.
