By Rivka Borochov
As sure as you’re born, you may never see another unicorn –– goes the famous song of the Irish Rovers, but in this lifetime we may see the rise of seriously endangered species, thanks to the work of an Israeli scientist.
Working in a post-doctoral fellowship position at the Scripps Research Institute in California, Inbar Friedrich Ben-Nun put herself on a course to do what no scientist had done before – create stem cells from the skin cells of endangered animals.
She did her research under the auspices of Jeanne Loring, a professor of developmental neurobiology at Scripps, with the counsel of Oliver Ryder, head of genetic research at the San Diego Zoo. About five years ago, Ryder contacted Loring to discuss the possibility of creating stem cells from endangered animals. Ryder oversees the Frozen Zoo, a cryogenic bank containing skin cells and other material from more than 800 different kinds of animals.
This unusual zoo was established in the 1970s with the vision that the technology would one day be available to make use of the genetic samples of deceased animals. The time has come, and Ben-Nun has taken the first major step in a new kind of laboratory conservation work.
“We can use this method to save species from extinction,” she says.
The drill is an endangered primate species
The research was funded by the Esther O'Keefe Foundation, the Millipore Foundation and the California Institute for Regenerative Medicine. And it’s important to note, says Ben-Nun, that funding in this area is badly needed. With a half million dollars, stem cells could be created from any endangered animal, she believes.
The artificial stem cells created from a rhino and a primate in the lab headed by Loring now provide a basis for new genetic material, via preserved samples of dead animals, to enter into the gene pool of endangered animals at severe risk of extinction. This project was a top-100 story for Discover magazine in 2011.
Rhino test-tube babies
The stem cells developed by Ben-Nun from genetic material preserved at the Frozen Zoo are pluripotent, meaning they are capable of differentiating into one of many cell types. Scientists can create any kind of cell from them, potentially including sperm and eggs that could be “mated” and implanted in a living animal to create new, genetically diverse babies.
Rhino nerve cells originated from stem cells made from rhino skin cells.
Nerve cells are stained in red, cell nucleus in blue.
The essential aim of the research was to demonstrate scientifically that stem cells can be created from high-level animals -- such as the primate drill species, which does not fare well in captivity, and the northern white rhinoceros, of which only seven exist in the world today.
Stem cells have already been created in mice and are often used as an animal model for testing treatments for human diseases. Little funding and interest has been given to other animals that don’t have medical use to humans. This could change, thanks to the new research.
The next step will be finding donor dollars to develop the stem cells into eggs or sperm. This could take as long as a rhino gestation period –– 15 months –– assuming that rhino in-vitro fertilization actually works, Ben-Nun says.
New hope for dinosaurs and the woolly mammoth?
While it’s possible that the melting arctic icecaps may give rise to previously extinct animals like the woolly mammoth, she does not believe scientists will be able to restore dinosaurs the way they were created in the Jurassic Park movie.
“I won’t say no, but it seems far-fetched. There is a small chance. You need to have preserved cells,” she explains.
The key for successful stem cell research, she notes, is access to some basic and well-preserved skin or body cells. Since the dinosaurs are so long gone, it is not likely that good genetic material is out there. But in the case of recent extinctions, “the sky’s the limit,” she says.
If Ben-Nun could pick one animal to conserve, it would be the northern white rhino. Of the five species of rhinos, this native of Africa was thriving in the Sixties, but became decimated from over-poaching and is in danger of total extinction if solutions aren’t found to preserve it. The last birth of a northern white rhinoceros was in 2000.
Only seven individual specimens of this rhino are alive today, two at the San Diego Zoo Safari Park and four others in a monitored reserve, where they were released in a last-ditch attempt to preserve the species. But time is running out.
Having met the rhinos at the San Diego Zoo before she started her project, Ben-Nun and her lab staff went back to the zoo to celebrate and see the rhinos after their paper was published in a September issue of Nature Methods
, a prestigious science journal. The lab’s accomplishments are outlined in the paper to inspire labs around the world to try doing the same.
Since the paper was published, Ben-Nun has been contacted by several labs offering to sequence the genomes of the drill and the rhino, another step to ensuring their survival.
"The best way to manage extinctions is to preserve species and their habitats," says Ryder, "but that's not working all the time.”
Stem cell research can improve reproductive success and increase the gene pool. Ben-Nun, a mother of two, started on the groundbreaking project in 2008.
After one year of trial and error, the team found that the genes that create pluripotency in humans worked for the drill and the rhino. Only a few stem cells are produced each time, but this is enough: “We have the start of a new zoo, the stem-cell zoo,” says Ben-Nun.