Artificial eggs may save critically endangered animals

In order to save the northern white rhinoceros from extinction, a team of researchers from BioRescue – an association coordinated by the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) – has struggled for years to create lab-grown egg and sperm cells of this critically endangered species. Now, the experts reported a major milestone in these efforts: the generation of primordial egg cells from stem cells.

Thirty-three-year-old Najin and her daughter Fatu are the last northern white rhinoceros on Earth, living together in a wildlife conservancy in Kenya. With only two females left, this species is unable to reproduce on its own. However, the fact that scientists have finally managed to cultivate primordial germ cells (PGCs) – the precursors of rhino eggs and sperm – from embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) is a crucial step forward for saving northern white rhinos from extinction.

Although this amazing scientific feat has previously been achieved in rodents and primates, this is the first time that primordial germ cells of a large, endangered mammalian species have been successfully generated from stem cells. 

“Developing a culture system that delivers robust results has been extremely challenging since the precise orchestration of the specific signals required to induce the desired cellular differentiation is unique to every species. It was also necessary to confirm that the primordial germ cell-like cells were genetically identical to the cells from which they originated – this can be a daunting task,” explained study senior author Katsuhiko Hayashi, a professor of Stem Cell Biology and Medicine at Kyushu University.

In a next step, the scientists plan to implant the resulting embryos into closely related southern white rhino females, who will then carry the surrogate offspring. Before this though, the PGCs will need to be matured in the laboratory in order to turn them into functional egg and sperm cells.  

“The primordial cells are relatively small compared to matured germ cells and, most importantly, still have a double set of chromosomes,” said study co-author Vera Zywitza, a postdoctoral fellow at the Max-Delbrück Center for Molecular Medicine in Berlin. “We therefore have to find suitable conditions under which the cells will grow and divide their chromosome set in half.”

The study is published in the journal Science Advances.

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By Andrei Ionescu, Earth.com Staff Writer

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