Tue, Aug 31, 2010 - Page 16 News List

Zoo aims to save endangered species from extinction

San Diego Zoo began collecting skin samples from rare animals in 1972 in the hope they might be used to protect these endangered species in the future. A breakthrough in stem-cell technology means that day is getting closer

By Paul Harris  /  THE GUARDIAN , LONDON

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The inside of a metal box filled with liquid nitrogen and frozen to minus 173°C is hardly the ideal habitat for a large African mammal. But, as a test tube is fished out of the container amid a billowing cloud of white gas, a note written on its side is unequivocal about its contents. “This is a northern white rhino,” says scientist Inbar Ben-Nun as she reads out the label and holds the freezing vial with thick gloves.

Ben-Nun is holding no ordinary scientific sample. For the frozen cells in that test tube could one day give rise to baby northern white rhinos and help save the species from extinction. They would be living specimens of one of the most endangered species on Earth, who after a few months would be trotting into wildlife parks, and maybe, just maybe, helping repopulate their kind on the African grasslands. No wonder that the place where the sample came from is called the Frozen Zoo.

The Frozen Zoo was founded in 1972 at San Diego Zoo’s Institute for Conservation Research as a repository for skin-cell samples from rare and endangered species. At the time that the first samples were collected and put into deep freeze it was not really known how they would be used and genetic technology was in its infancy. But there was a sense that one day some unknown scientific advance might make use of them and it was better to be safe than sorry. Now, thanks to a team at the nearby Scripps Research Institute, that day has come a lot closer.

Genetic scientists at Scripps, working from an anonymous-looking building in a business park in San Diego’s northern suburbs, have succeeded in taking samples of skin cells from the Frozen Zoo and turning them into a culture of special cells known as induced pluripotent stem cells. Stem cells are a sort of all-purpose building block of life that can then become any other sort of cell. By creating induced pluripotent stem cells from a species it is now theoretically possible to use them to create egg cells and sperm cells. Those two could then be combined via in vitro fertilization to form a viable embryo. And long-dead animals whose species are almost extinct could create new life. The breakthrough, so far, has come with creating induced pluripotent stem cells for the silver-maned drill monkey, a primate native to just a few parts of West Africa and which is the continent’s most endangered monkey. On June 1 this year, the stem cells morphed into brain cells, proving their viability.

“The Frozen Zoo was a wonderful idea. They just thought: ‘Well, something might happen, so we should preserve some samples for the future,’” says Jeanne Loring, who is leading the Scripps team of which Ben-Nun is a part. “This is the first time that there has been something that we can do.”

The implications of Loring’s breakthrough are clear for those trying to save endangered animals. If the technology is perfected and induced pluripotent stem cell cultures can be established for many of the species held in the Frozen Zoo, then conservationists will not just have to rely on preventing extinction by coaxing a few remaining individuals to breed. Instead, cell lines preserved in the Frozen Zoo can be added to the possible gene pool, increasing the chances of healthy reproduction.

“If we could use animals that were already dead ... to generate sperm and eggs then we can use those individuals to create greater genetic diversity. I see it as being possible. I see no scientific barrier,” Loring says.

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