The last two northern white rhinos in the world, Fatu and Najin, are females. This means that critically endangered subspecies can no longer reproduce naturally, so rhino extinction looms with each passing day.
However, international teams of scientists are now racing to harness the benefits of modern science and help rhinos have a chance of survival through cutting-edge laboratory advances.
In one approach being explored, scientists are looking to use animal skin cells to create induced pluripotent stem (iPS) cells in the lab and convert these cells into immature eggs called oocytes.
an important step
Scientists from Germany, the Netherlands and Japan have managed to thoroughly examine rhinoceros pluripotent stem cells. These cells, like stem cells, have the ability to grow into any cell in the body, so rhinoceros oocytes may soon be artificially generated from them.
The BioRescue project, a German initiative of which the research is part, builds on the work of Professor Katsuhiko Hayashi, a Japanese stem cell researcher at Kyushu University who succeeded in 2016 in generating eggs from the mouse skin, artificially fertilize these cells. , and implant them into females.
Mice engineered in this way are born healthy and fertile with historic success. However, despite these promising results with mice, scientists encountered a few obstacles with rhinoceros cells.
“The iPS cells that we cultured contain persistent foreign genetic material, ie the reprogramming factors and the gene that prevents cell death. This means that we cannot use them to produce germ cells, because there is a risk that they will be pathologically altered, ”explains Vera Zywitza, researcher at the Max Delbrück Center for Molecular Medicine of the Helmholtz Association and lead author of an article on the results.
However, studying these cells helps scientists better understand the molecular mechanisms within stem cells. “For example, we can study why the gestation period of a rhinoceros is 16 months while that of a mouse is only 21 days, or how organs develop in different species. It tells us a lot about evolution,” says Zywitza.
In another development, scientists working to produce iPS primordial germ cells successfully grew ovarian tissue from mouse stem cells last year. Since primordial germ cells only become egg cells when surrounded by ovarian tissue, this was a significant breakthrough.
At the same time…
Other teams of scientists are working on assisted reproduction techniques for white rhinos and progress has been made on this front as well. Scientists have just harvested oocytes, or immature eggs, in Fatu, Kenya. These cells were matured in laboratories in Italy and inseminated with thawed sperm from a dead male rhino.
As a result, there are now 14 northern white rhino embryos stored in liquid nitrogen at extremely low temperatures. The plan is to soon implant these embryos into Southern White Rhino surrogate mothers in hopes that healthy Northern White Rhino calves will emerge.
“Najin and Fatu are also closely related and their genetic makeup is largely identical. Due to age and reproductive system issues, we were unable to collect any oocytes from Najin that could develop into embryos, so the 14 embryos are from Fatu,” explains Professor Thomas Hildebrandt, who leads the BioRescue research consortium.
Not just white rhinos
These advances in the race to save northern white rhinos from extinction could one day be used to revitalize populations of other critically endangered species. Moreover, once reproduction from stem cells has been achieved, the technique could be used to revive many already extinct species.
“Generating functional eggs from the northern white rhinoceros would be the greatest achievement of our research,” says project lead researcher Sebastian Diecke.
More than 10,000 live cell cultures from more than 1,000 endangered species are stored at the frozen zoo at the Arnold and Mabel Beckman Center for Conservation Research in San Diego and at a biobank in Berlin, and “this invaluable resource could be used to bring back species from the edge of the abyss”. extinction,” observes Diecke.
However, adds the scientist, “I would prefer that we never had to use our technique and that we did more to preserve the species before it is too late”.
By Daniel T. Cross. Articles in English