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Hope for white rhinos

Female northern white rhinos Najin and Fatu (left) in Kenya

Tony Karumba / AFP via Getty Images

Researchers from Japan and Europe are hoping laboratory production of eggs and spermatozoa can prevent total disappearance of the northern white rhinoceros (Ceratotherium simum cottoni). Since 2018, there have been just two specimens of this subspecies living in the wild: a mother and daughter call Najin and Fatu, who live in a wildlife reserve in Kenya. It would be possible to attempt assisted reproduction via in vitro fertilization (IVF), but Fatu is the only female able to donate eggs and the frozen sperm are from just a few males, some related to Fatu. To increase the chance of success, a team of scientists led by biologist Katsuhiko Hayashi of Osaka University in Japan are attempting to generate reproductive cells in the lab from the preserved skin samples of rhinos that have already died. They recently took an important step forward: they identified the conditions necessary to transform stem cells generated from skin cells into egg and sperm precursors, and they produced these precursors in the lab (Science Advances, December 9). The next step is to try to obtain mature and functional reproductive cells.