There are only two left on the face of the earth: two females, Najin and her daughter Fatu. It is they who are entrusted with the mission of saving the northern white rhino from extinction. “A race against time”. Only frozen sperm samples remain from the males. Alongside Najin and Fatu, an international consortium of scientists – which also includes the Italian Cesare Galli, 'father' of the first cloned bull Galileo – who for several years has been working on the task of giving the world puppies of hope. Today, experts illustrate a new step forward. This is a sort of 'dress rehearsal': researchers have managed to obtain the first rhino pregnancy in the world after the successful transfer of an embryo resulting from in vitro fertilization.
This achievement, which paves the way for saving northern white rhinos, was achieved by involving their southern 'cousins'. The team of scientists and conservationists first produced a southern white rhino embryo in vitro from collected eggs and sperm. The embryo was then transferred to a surrogate southern white rhino mother at the Ol Pejeta Conservancy in Kenya in September 2023. The BioRescue team – this is the name of the consortium – has now confirmed the 70-day pregnancy with one embryo well developed male, 6.4 centimeters long. The successful embryo transfer and pregnancy are a proof of concept and now allow the safe move to northern white rhino embryo transfer: “A milestone in the rescue mission,” the experts explain in a statement.
One of the protagonists of the operation illustrated today is the surrogate mother Curra, a female southern white rhino selected in the Kenyan reserve. On September 24, BioRescue scientists and veterinarians, led by the Leibniz Institute for Zoo and Wildlife Research (Leibniz-Izw), transferred two embryos. It is “completely new terrain in the veterinary field”, they point out. And scientific procedures, protocols, methods and equipment had to be developed from scratch. The oocytes used in the production of the embryos were recovered from Elenore, a southern white rhinoceros living in the Pairi Daiza Zoo in Belgium. As for the male component, the sperm used for fertilization is from Athos, from the Salzburg Hellbrunn Zoo, in Austria. Elenore's oocytes were fertilized with the Icsi technique and developed into blastocysts in Italy in the Avantea laboratories in Cremona, kingdom of Galli. Then the scientists flew to Kenya for the embryo transfer thanks to which a 'cosmopolitan' puppy was growing in Curra's belly.
Curra, surrogate mother, and the demonstration that it can be done
Then unfortunately the surrogate mother, who made a crucial contribution, died following an infection. From September to November 2023 she was monitored daily in the Ol Pejeta Conservancy enclosure. During this period, after the initial sterile mating on September 17 and 18, Ouwan, the sterilized male sentinel for the breeding cycle, showed no further interest in Curra. It was the first positive sign of a successful embryo transfer resulting in pregnancy. The BioRescue team had scheduled a pregnancy check for November 28, but Ouwan was found dead on November 22 and Curra on the 25th.
Extremely heavy rainfall, linked to climate change, has been reported to have caused their enclosure to flood and released spores of dormant Clostridia bacteria. Dissection of the animals revealed severe systemic clostridial infection and subsequent bacterial toxin intoxication. And it was confirmed that Curra was pregnant with a 70-day-old male fetus, measuring 6.4 cm in length. Fetal tissue samples were collected and transported to the Max Delbrück Center for Molecular Medicine and the Leibniz-Izw in Berlin. In January 2024, through analysis of the fetus's DNA, it was confirmed that the pregnancy was the result of embryo transfer. Immediately after the incident the BioRescue team, which includes the Kenya Wildlife Service, the Wildlife Training Research Institute, the Ol Pejeta Conservancy and the Dvůr Králové Safari Park, formed an on-site crisis team and established rapid and effective measures to protect all current rhinos in semi-captivity, including the last two northern white rhinos Najin and Fatu. The measures included a vaccination programme, quarantine of affected areas and new life-saving pens.
So far the BioRescue team has performed 13 embryo transfers, 4 in Kenya and 10 in Europe. The transfer, like all BioRescue procedures, is accompanied by an ethical evaluation conducted by the University of Padua, another Italian institution involved in the mission. Also in September, all embryo transfer participants filled out a questionnaire that proposed every possible scenario during the procedure and detailed the risks. With the first pregnancy obtained in the surrogate mother from the South, the time of Najin and Fatu is now approaching. Najin is now 34 years old and Fatu is technically the only natural egg donor left. Currently – in addition to these two unique living Northern specimens who always live in Kenya, in the Ol Pejeta Conservancy, monitored and cared for day and night – there are the live cells of 12 different Northern white rhinoceros individuals preserved in liquid nitrogen.
Two or three years for the most important goal
And then there is the greatest 'treasure': since 2019 the scientific conservation program BioRescue has produced and cryopreserved 30 northern white rhino embryos. These are currently preserved in liquid nitrogen at -196 °C between Germany (in Berlin) and Italy (Cremona), awaiting the transfer of the embryos into surrogate mothers of southern white rhinos who will once again lend themselves to the cause of saving the cousins of the North, carrying the future 'heir' of the species. Now, experts point out, for the first time it will be possible to take this crucial step: the transfer of a northern white rhino embryo.
The next steps of the BioRescue research program include the selection and preparation of a new sentinel male. This will allow scientists to know when a possible surrogate female is ready to receive an embryo implantation. The team must also select the next surrogate mothers. After these stages, which will take several months, an embryo transfer will follow with a northern white rhino embryo. The BioRescue research program has several partners, including those outside the world of science, and is supported by the German Federal Ministry of Education and Research for a period of 6 years. The grant will end in 2025. For this reason, the consortium members are looking for new sources of funding. “It's a race against time. Humanity has put this magnificent species at risk. Now it is our responsibility to save it,” say the researchers. “We must save this keystone species not only for its intrinsic value to humanity – they add – but also for its crucial ecological importance.”
“It is bitter that this milestone is confirmed in such tragic circumstances, with the death of Curra and her baby – comments Thomas Hildebrandt, head of the BioRescue project, Leibniz-Izw – but I am sure that this proof of concept represents a turning point for the survival of the northern white rhino and for the health of Central African ecosystems. It arrives just in time to achieve a pregnancy for the northern white rhinos: we want the offspring to live for years together with Najin and Fatu to learn the social behavior of the species. Also If embryos can be stored in liquid nitrogen for a long time, we are in a hurry to bring a baby northern white rhino into the world: with this proof of concept it can become a reality in two to three years.”
Next step use northern white rhino embryos
“All businesses have setbacks and we have had them too, but today we are here to proclaim that we have done something never done before, today we can confirm that the DNA test proves that the embryo we transferred into the uterus of the female southern white rhino, Curra”, who later died of an infection in the Kenyan reserve where she lived, “developed into a healthy and well-developed male fetus. Thanks to this development, we believe that the embryo transfer work can move without hesitation to the use of genetically pure northern white rhino embryos, a year earlier than expected”, declares Galli, who is CEO of the Avantea Laboratories in Cremona.
This step forward illustrated today by the experts “demonstrates that the process of in vitro maturation of oocytes, ICSI, embryo culture and cryopreservation, carried out by Avantea in Cremona, is successful in producing embryos that will successfully mature in surrogate females. This data not only testifies the feasibility of the process, but shortens the time to verify success and no longer requires the birth of a calf. In the horse, the closest domestic relative of the rhinoceros, fetal losses are more frequent in the first 50 days than in any other period of the pregnancy”. Curra's pregnancy had been going on for 70 days when the tragic accident caused by bacterial contamination ended her life. “The development of this fetus indicates that the chances of a successful birth would have been greater than 95%.”
The project is also carried out with attention to the ethical aspect, which is also handled by Italian experts. “BioRescue has established a model for the ethical monitoring of international conservation research projects – explains Barbara De Mori, director of the Ethics Laboratory for Veterinary Medicine, Conservation and Animal Welfare, in the Department of Comparative Biomedicine and Food Science of the University of Padua – All phases of the project are constantly monitored to verify compliance with animal welfare standards, scientific quality and safety of the people involved”.
“There are things we cannot control – concludes the expert – but with BioRescue we have established the highest possible ethical standards in conservation research projects. Continuous ethical monitoring is carried out routinely to avoid risks for both people and animals animals, while the opinions and perceptions of the public and stakeholders are included in the evaluation process. The continued development of BioRescue's ethical monitoring procedures can be of great benefit to other conservation research projects that save species at risk.”
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