For the first time ever, scientists have successfully used IVF techniques to combine sperm from the near-extinct northern white rhino with eggs from the more abundant southern white rhino to create viable hybrid embryos.

The researchers hope to implant the embryos into surrogate female southern white rhinos to produce hybrid baby rhinos that can then ensure that at least some of the northern white rhino DNA is preserved.

Such IVF techniques can also be used to rescue populations of other endangered rhino species, such as the Sumatran rhino, researchers say.

But other experts say that while the science is promising, the underlying threat to the survival of all rhino species remains the insatiable demand for the animals’ horns.

In March this year, Sudan, the last known male northern white rhino, died at Kenya’s Ol Pejeta Conservancy at the age of 45. He left behind a daughter, Najin, and granddaughter, Fatu, neither capable of reproducing naturally.

With no other confirmed northern white rhinos (Ceratotherium simum cottoni) remaining in the wild — although there are speculations of some unconfirmed individuals in South Sudan — the subspecies is thought to be as good as extinct. But there might be a glimmer of hope.

For the first time ever, scientists have successfully used IVF (in vitro fertilization) techniques to combine previously frozen sperm from the near-extinct northern white rhino with eggs from the more abundant southern white rhino (Ceratotherium simum simum) to create viable hybrid embryos. The researchers hope to implant the embryos into surrogate female southern white rhinos to produce baby rhinos that are a mix of both subspecies. The hybrid babies can then ensure that at least some of the northern white rhino DNA is preserved, according to a new study published in Nature Communications.

“The only two remaining females of the northern white rhino are in Kenya and not accessible to us for a number of reasons I am not going to discuss here, so the best we could do was to make a hybrid embryo that technically has 50 percent of the genome coming from the northern white rhino,” Cesare Galli, a veterinarian and embryologist at Avantea, a biotechnology laboratory in Cremona, Italy, told Mongabay.

The team’s goal is to have the first northern white rhino calf born in three years, according to study co-author Thomas Hildebrandt, a professor at the Leibniz Institute for Zoo and Wildlife Research in Germany.

“Taking into account 16 months of pregnancy, we have a little more than a year to have a successful implantation,” he said.

The journey to create these hybrid embryos has taken a long time.

Since northern white rhino females are rare, the researchers had to depend on their close relative, the southern white rhinos, for eggs. Even so, it took more than five years, from 2005 to 2010, to develop a technique that would allow the researchers to recover eggs from anesthetized female southern white rhinos living in European zoos. It took several more years to turn the eggs into viable embryos, Galli said.

Eventually, the team hopes to create a small population of hybrid white rhinos as a backup to preserve some of the northern white rhino’s genetic information.

However, the ultimate aim is to use their “optimized” techniques to recover eggs from Najin and Fatu, if they get the required permits, and use them to create “pure” northern white rhino embryos. The procedure is risky though because it involves putting the aged rhinos under general anesthesia. Moreover, the researchers have old, low-quality frozen semen samples from just four male northern white rhinos, which means that the offsprings would not have the genetic diversity needed for a healthy wild population.

To circumvent this problem, the researchers hope to create embryonic stem cells — cells that are capable of turning into any type of cell of the body — from frozen tissues collected from northern white rhinos in the past, and turn them into eggs and sperm.

“This is one of the objective of our future work,” Galli said. “Once we have gametes [eggs and sperm] we know how to make embryos from them now.”

The successful use of IVF to create rhino embryos inspires hope for the revival of a subspecies that’s been virtually wiped off the face of the Earth, some conservationists say.

“It’s a brave effort to save some of the genetic information of a spectacular species, now gone from the wild,” Stuart Pimm, Doris Duke chair of conservation ecology at the Nicholas School of the Environment at Duke University, North Carolina, U.S., who was not involved in the study, told Mongabay. “Would I want to see northern rhinos, or even part northern rhinos in the wild? The answer is ‘you bet!’. The rhinos need to be back where they belong, having as much of their original DNA. It is as much as we can hope for and may improve their chances of survival. Rhinos need to be back on that landscape.”

Such assisted reproductive technologies (ART) can also be used to rescue populations of other endangered rhino species, such as the Sumatran rhino (Dicerorhinus sumatrensis), Galli said, “if there is international cooperation between politicians and above all between scientists that as usual are always divided.”

Some critics argue that ART is expensive, and the money would be better spent trying to protect the remaining rhino species.

But Galli thinks that in some cases ART is the only option. “Clearly the critics have to accept that they have failed first,” he said. “Regarding the millions of dollar spent, we have done this work without spending public money, using mainly our own internal funding and some donations.”

Hildebrandt agreed that sometimes biotechnology might be the only option for salvation.

“The northern white rhino didn’t fail in evolution, it failed because it was not bulletproof,” Hildebrandt said.

Once ranging across Uganda, the Central African Republic, Sudan, Chad and the Democratic Republic of Congo, the northern white rhino today is believed to be extinct in the wild mainly because of intense poaching to meet rhino horn demand in China and other Asian countries.

However, viable rhino embryos do not translate to viable rhino populations.

“This is only a very tiny piece of the problem,” Pimm said. “It’s a long way from baby rhinos. And, even if we had baby rhinos, where would we put them? They belong in South Sudan and the DRC [Democratic Republic of the Congo]. They were hunted to extinction in short order for their horn. The overarching problem with rhinos of all kinds is our inability to protect them against determined poachers.”

Pimm said there was a moral hazard to resurrecting an extinct subspecies or species.

“If people believe we can rescue a species from extinction — or even from very low numbers — then it encourages reckless actions that harm our world,” he said. “So, yes, well done the Galli team, but let’s not miss the larger picture.”

Citation:

Thomas B. Hildebrandt et al., (2018) Embryos and embryonic stem cells from the white rhinoceros, Nature Communications. DOI: 10.1038/s41467-018-04959-2.