In a somewhat poetic twist of events, human stem cell research could one day save endangered species and maybe even revive extinct ones.
This week, researchers have produced stem cells from the silver-maned drill monkey and the northern white rhinoceros that could help create more genetically diverse breeding populations.
The story begins with Oliver Ryder of the San Diego Zoo Institute for Conservation Research, who spent years amassing thousands of skin cells from more than 800 species for his Frozen Zoo. About 5 years ago, he contacted Jeanne Loring from Scripps Research Institute to discuss the possibility of collecting stem cells from endangered species.
And by 2007, a new technique called 'induced pluripotent stem cell reprogramming' had emerged that allowed scientists to transform adult cells into stem cells. But first, a little more info on the first endangered animals to have this done:
- The drill (Mandrillus leucophaeus) is only found in tiny pockets of western Africa now; between 3000 and 8000 remain in the wild. They have a close genetic connection to humans, and in captivity, they often suffer from diabetes (which we’re trying to treat in humans using stem cell-based therapies). The team was given cells from a male named Loon.
- The northern white rhinoceros (Ceratotherium simum cottoni) is one of the most endangered species on the planet, with only 7 animals still in existence. The team used cells from a female named Fatu.
"There are only two animals in it," says coauthor Inbar Friedrich Ben-Nun of Scripps, "but we have the start of a new zoo, the stem cell zoo."
In particular, these are induced pluripotent stem (iPS) cells – which are embryonic-like stem cells. The pluripotent stage is when the fate of undifferentiated cells are decided – when they can be coaxed to become new cell types. And in these cases, adult skin cells are reprogrammed, or induced, to become stem cells.
These cells have played huge roles in recent research on heart failure, blindness, stroke, and spinal injuries in humans, BBC reports.
Fertility scientists are avidly searching for ways to develop sperm and eggs from stem cells in order to treat human infertility, and Loring tells Technology Review that those technologies could be applied to these animals.
In fact, a clever combo of retroviruses and human genes were used to transform both animals' cells into iPS cells. These can be stored and multiplied in culture, and are theoretically capable of making any tissue in the body, Nature News explains, including sperm cells that could be used in assisted captive breeding programs.
One of the greatest concerns with small surviving populations is that even if they did have sex and reproduce, their genetic diversity is dangerously low, and such inbreeding leads to unhealthy animals.
1. If scientists could make the stem cells into sperm or egg cells, then they could: take skin cells in the Frozen Zoo from long dead animals, induce pluripotency, trigger differentiation into sperm cells, and then combine these with a living animal's eggs through in vitro fertilization, according to a news release.
With these test tube babies, otherwise-lost genetic diversity would be reintroduced into the population, making it healthier and more robust.
2. Or, both eggs and sperm could be produced from stem cells, and the resulting embryos implanted in live animals. And a living drill or northern white rhino wouldn't have to carry the pregnancy, according to New Scientist – another animal could be a surrogate mother for the embryo.
Also, this process could be much more reliable than existing cloning techniques: “Here, you have the possibility to make new genetic combinations,” Loring says, “rather than cloning which simply reproduces existing animals."
But she concedes that there are technological gaps to fill in: "I don't know how you could super-ovulate a rhino.” And sadly, there were 8 rhinos when she started the project. As she tells The Scientist: “One of them died between the time we submitted and the time we were accepted.”
The study was published on Sunday in Nature Methods.
Images: San Diego Zoo
This post was originally published on Smartplanet.com