Stem Cell Zoo

Scientists produce first stem cells from endangered species

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Drawing on tissues stored in an unusual “frozen zoo,” researchers have created the first stem cells from endangered species. In humans, researchers are excited about stem cells – which can become any tissue in the body – because of their potential to treat disease. Now, it is possible endangered organisms could see some benefit too.

“It’s not classical conservation and it’s not ordinary biological research,” says Jeanne Loring of The Scripps Research Institute in San Diego, California, one of the authors of the Nature Methods study. Stem cells could eventually make it possible to improve reproduction and genetic diversity for some species, or be used to bolster the health of endangered animals in captivity.

The stem cell project originated about five years ago, according to a Scripps Research press release, when Oliver Ryder, director of genetics at the San Diego Zoo Institute for Conservation Research, contacted Loring. Ryder’s team had already established the Frozen Zoo, a bank of skin cells and other materials from more than 800 species, and he wondered if the samples might be used as starting points for creating stem cells.
At the time, although researchers were working with stem cells taken from embryos, scientists had not yet developed reliable techniques for inducing normal adult cells to revert to stem cells. But they now accomplish this feat, called induced pluripotency, by inserting genes in normal cells that spark the transformation.

In 2008, the researchers realized that the emerging technique might be applied to endangered species. A Scripps postdoctoral fellow, Inbar Friedrich Ben-Nun, set out to systematically explore the possibilities.

Ryder suggested two species for initial work. The first was a highly endangered primate called a drill (see photo); he chose it because of its close genetic connection to humans, and because in captivity the animals often suffer from diabetes, which researchers are working to treat in humans using stem cell-based therapies.

The northern white rhinoceros was the second candidate. Ryder chose this animal because it is genetically far removed from primates, and because it is one of the most endangered species on the planet. There are only seven animals still in existence, two of which reside at the San Diego Zoo Safari Park.

Initially, the team thought they would have to isolate and use genes from animals closely related to the endangered species to successfully induce pluripotency. But that line of experimentation didn’t work. Instead, to their surprise, after a year of trial and error, the researchers found that the same genes that induce pluripotency in humans also worked for the drill and the rhino. “It has been just amazing,” said Ryder of the Scripps Research team’s successes.

The process is inefficient, meaning only a few stem cells are produced at a time, but that’s enough. “There are only two animals in it,” said Ben-Nun, “but we have the start of a new zoo, the stem cell zoo.”

Eventually, stem cells might help endangered animals reduced to small populations, such as the northern white rhinos. Even if these rhinos did reproduce, which hasn’t happened in many years, their genetic diversity is inevitably and dangerously low, and such inbreeding leads to unhealthy animals.

If researchers can induce stem cells to differentiate into sperm or egg cells – which should be possible — scientists could combine “homemade” sperm with a living animal’s eggs through in vitro fertilization. Genetic diversity would then be reintroduced into the population, making it healthier, larger, and more robust. Or, both eggs and sperm might be produced from the stem cells, with the resulting embryos implanted in live animals, a process that current research suggests could be much more reliable than existing cloning techniques.

In the meantime, the group is hoping to continue producing stem cells from other species to expand their fledgling stem cell “zoo.” – David Malakoff | September 5, 2011

Source: Friedrich Ben-Nun, I., Montague, S., Houck, M., Tran, H., Garitaonandia, I., Leonardo, T., Wang, Y., Charter, S., Laurent, L., Ryder, O., & Loring, J. (2011). Induced pluripotent stem cells from highly endangered species. Nature Methods DOI: 10.1038/nmeth.1706

Image: San Diego Zoo