For the first time, researchers in the BioRescue consortium successfully converted rhino skin cells to stem cells, which with more research could develop into viable egg cells. The team behind the breakthrough, published in Scientific Reports, hopes that this could be the key to saving the species.
There are sadly only two northern white rhinoceros in the world: Fatu and Najin. Since the last remaining male died in 2018, both are female. Fortunately, scientists had the good sense to freeze sperm from the final males, providing a lifeline for the species through IVF.
This, of course, requires an egg – which, after this latest advancement, could one day be created from skin cells.
“Our paper sheds new light on pluripotency – the ability of stem cells to differentiate into all cells of the body,” lead author Dr. Vera Zywitza said in a statement.
“It therefore represents an important milestone on the road to artificially generated rhino oocytes.”
Having had previous success in mice, the team reprogrammed rhino skin cells to become induced pluripotent stem cells (iPS) by introducing foreign DNA. iPS cells can differentiate into any type of cell in the body, including germ cells, which then divide to become egg or sperm cells.
But first, they must be in a “naive” state. When researchers initially tried to convert the cells from a more advanced state, they died. To remedy this, the researchers added a gene that prevents cell death, and were able to create naive iPS cells, “a promising starting point for generating germline cells,” Zywitza said.
Before any rhino iPS cells can be triggered to develop into germ cells, however, there are a few changes to be made to the protocol.
“The iPS cells we have cultivated contain persistent foreign genetic material – namely, the reprogramming factors and the gene that prevents cell death,” Zywitza explained. “There is a risk [germ cells] would be pathologically altered.”
One way to bypass this could be by using RNA viruses, instead of foreign DNA, to reprogram the skin cells, which the team is experimenting with now.
They also need to create ovarian tissue – which can’t be obtained naturally – to surround the germ cells so they develop into egg cells.
Artificial eggs may be some way off, so thankfully they are not the only option for saving the rhinos. The team has already attempted assisted reproduction using eggs from Fatu and deceased male sperm, bringing the number of frozen northern white rhino embryos up to 14.
With any luck, one or both of these strategies could save the northern white rhino from extinction – and, the team hope, could help bring thousands of other endangered species back from the brink as well.