In a Kenyan wildlife conservancy near the equator, armed guards protect two northern white rhinoceroses, Najin and Fatu. They are the last two northern white rhinos alive—both non-reproductive females—making the species functionally extinct.

For several years, Jeanne Loring, a stem cell biologist at Scripps Research Institute, along with other scientists, has explored ways to rescue these animals from eventual extinction. In 2011, Loring and her team created the first induced pluripotent stem cells (iPSCs) from the skin cells of northern white rhinos.

A Genomic Milestone

This ambitious goal took a major leap forward with the recent full sequencing of the northern white rhino genome, enabling scientists to compare lab-cultured stem cells to healthy genetic baselines. This step is crucial for selecting high-integrity stem cell lines for generating germ cells (sperm and egg), avoiding mutations that may have arisen during the reprogramming process.

Scientists can now screen for harmful genetic mutations and optimize the reproductive success of any embryos produced. The genome was assembled using cells from Angalifu, a male rhino who died in 2014, whose skin cells had been preserved in the San Diego Zoo Wildlife Alliance’s Frozen Zoo.

From Cells to Life

To achieve true resurrection of the subspecies, researchers must create fertilized embryos and implant them into surrogate southern white rhino females, a closely related and more populous species. While several northern white rhino embryos have already been created using egg cells from southern white rhinos and stored sperm from deceased northern males, the creation of fully lab-derived gametes (from iPSCs) would provide a more sustainable and diverse approach.

This project involves collaboration across institutions—Scripps Research, the Max Planck Institute, the Leibniz Institute for Zoo and Wildlife Research, and Kenya Wildlife Service, among others—illustrating the global scale of this conservation endeavor.

Hope Beyond Rhinos

The techniques developed in this project have wider implications. If successful, they could become a model for reviving other critically endangered species—from the Sumatran rhino to vanished amphibians—by combining genetic engineering, cryopreservation, and advanced reproductive technologies.

But time is critical. Najin and Fatu are aging, and ethical discussions also loom over how far humans should go in manipulating life to correct past ecological damage. Still, for Dr. Loring and her colleagues, the mission is clear.