IVF and stem cells as the last hope

Artificial propagation is the last straw for the northern white rhinoceros to hang on. If that does not work, it will soon be over for this subspecies. Two other females live on the Ol Pejeta Reserve in Kenya; the last male left on March 19th.

But now, an international team of researchers led by Thomas Hildebrandt of the Leibnitz Institute for Zoological and Wildlife Research in Berlin reports that they took the first steps to save the subspecies with the technology of modern propagation of destruction. Their results appeared Wednesday, Nature Communications .

This is a curious survey, in which everything came out of the closet to revive the northern white rhino with advanced lab techniques. The goal, new growth of this subspecies, has not yet been reached. Four hybrid embryos (northern half, southern half white rhino) is the best result up here. But researchers now think that they have mastered the trick enough to make the next step.

"In a few months we want to place these hybrid embryos in a surrogate mother," says Hildebrandt at a telephone press conference. "If it goes well, the first hybrid calves will be born in a year and a half – the rhinos have a gestation period of 16 months." A southern white rhino that has already calved will be the surrogate mother. "Hybrids become a reserve of reserves, a genetic reserve from which one can then produce a line of pure white rhinos."

The team tried to breed a pure embryo of the northern white rhinoceros, but this failed. . From an ovary of a female deceased in 2015, they managed to isolate four eggs. They could fertilize two, but no embryo came out. "Unfortunately, this opportunity came too early for us, at a time when we were not so good at working with oocytes of this species," says the Italian expert in team fertility. , Cesare Galli.

19659007] Researchers are now waiting for permission from the Kenyan authorities to harvest the eggs of the last two live females, Najin (28) and Fatu (18). They have gained experience with southern white rhinos in European zoos. With a specially developed lance of a meter and a half long, they can use the anus of huge animals to push follicles into the ovaries to harvest eggs. "It's risky," says Hildebrandt, "because the animals have to undergo anesthesia for two hours. It's dangerous for the heart, and it worries me. Nevertheless, he expects to travel to Kenya before the end of the year to collect the oocytes. "We will have calves in three years," he says.

It's a little optimistic because on the male side of fertilization there are also hordes. According to Hildebrandt, 300 milliliters of sperm from the northern white rhino were harvested. It sounds a lot, but in practice it is enormously disappointing. The semen comes only from three bulls and is also of average quality. Once thawed, the sperm does not move or little, so the ICSI (injection of a sperm into the egg) is the only way to get fertilization.

Researchers also hope for stem cell technology. . "Twelve Northern White Rhinoceros cell lines are available," says Hildebrandt. Stem cells can be made from these skin cells. "From this we can produce sexual cells," says Galli. "It will be a big challenge to do it, but in Japan, he has already managed to make himself a mouse."

Bart Gadella, Reproductive Expert of the Faculty of Veterinary Medicine of the University of Utrecht thinks that means the genes of an almost extinct animal species can be preserved. "I have some reservations," says Gadella. "Only hybrids have been made, and it is uncertain whether the two still-living females can still produce fertile eggs, so the offspring must of course be fertile for a successful breeding program. there are enough genetic variations to save the species. "

The environmentalist Herbert Prins of the University of Wageningen welcomes the initiative, but for quite a different reason than the ## 147 ## 39, Hildebrandt team. "The fact that they will now make hybrids is a great idea! After all, if you look at this project with a cool look, the northern white rhino can save the southern region instead of the other way around. "

The northern white rhino is genetically much more diverse than the south," says Prins. "The southern population passed through a bottleneck at the beginning of the nineteenth century, with a size of only a few tens of thousands. 39; animals. This has considerably lowered the genetic base. The northern white rhinoceros has only been threatened for sixty years, but it retains its genetic diversity. It can thus stimulate the total genetic base of all white rhinos. "

According to Prins, there is" all the space "to reintroduce white rhinos into their native habitat in East Africa." The whole ecosystem will benefit because there are no grazers more efficient than rhinos and hippos, and I am doing research in a private park in South Africa where we recently introduced rhinos, and in a few years we have completely changed the landscape. All sorts of other species such as wildebeest and zebra benefit. "