It’s the year 2286. The transmission signal of an alien space probe is wreaking havoc on Earth, knocking out the worldwide power grid and causing massive storms. It turns out the mysterious orbiting probe is trying to communicate with humpback whales through whale song and the devastation won’t stop until contact is made. But there’s a tiny problem: in that future, the humpback has long since become extinct. So the captain and crew travel back in time to snag two whales and save 23rd century civilization. Phew!
My fellow science fiction nerds will recognize that plot line from 1986’s Star Trek IV: A Voyage Home. It’s pure fantasy and yet there is a real lesson for our present day world: you shouldn’t underestimate how the extinction of a species will impact our world. For instance, the collapse and potential extinction of the bee population and other pollinators threatens to destabilize our global food supply.
Northern White Rhinos: At the Brink of Extinction
Beyond how it may affect us humans, I think there’s also a moral obligation to save endangered species that have dwindled in number directly due to human actions. It may be too late for the northern white rhino though. Because their horns are highly sought after as a status symbol and for use in traditional medicine, poachers have wiped out the population and now only three – Sudan, Najin and Fatu (grandfather, mother and daughter) – exist in the world. Sadly, none of them can breed naturally so they quietly graze in a Kenyan conservation park as their species heads towards extinction.
Jeanne Loring, a CIRM grantee and professor at The Scripps Research Institute, still sees a glimmer of hope in the form of stem cells. In an essay published yesterday in Genetic Engineering and Biotechnology News, Loring describes her research team’s efforts to apply stem cell technology toward saving the Northern White Rhino and other endangered species.
Their efforts began about ten years ago in 2007, the same year that Shinya Yamanaka’s lab first reported that human fibroblasts, collected from a skin sample, can be reprogrammed into an embryonic stem cell-like state with the capacity to indefinitely make copies of themselves and to specialize into almost every cell type of the body. The properties of these induced pluripotent stem (iPS) cells have provided an important means for studying all sorts of human diseases in a lab dish and for deriving potential cell therapies.
FrozenZoo® and iPS Cells: A Modern Day Noah’s Ark?
But it was a free tour at the San Diego Safari Park just two months after Yamanka’s discovery which inspired the Loring lab to chart this additional research path using iPS cells. In exchange for the free safari ride, the team reciprocated by chatting with Oliver Ryder, director of the San Diego Zoo Institute for Conservation Research, about using stem cells to help save endangered species. Ryder’s institute runs the FrozenZoo® a cell and tissue bank containing thousands of frozen samples from a diverse set of species. In her essay, Loring recounts what happened after the visit:
“It was obvious to us: why not try to reprogram fibroblasts from the FrozenZoo®? When my group returned to the lab from the safari, I asked them: who would like to try to reprogram fibroblasts from an endangered species? It was far from a safe bet, but a young postdoctoral researcher who had recently joined my lab from Israel said that she’d love to give it a try. Inbar Friedrich Ben-Nun spent the next couple of years trying out methods in parallel on human cells and fibroblasts from the zoo. We chose fibroblasts from the drill because it is [an endangered] primate, making it more likely that the technology used for humans would work.
Oliver [Ryder] chose the northern white rhino, a particular favorite of his, and one of the world’s most endangered mammals. Through hard work and insight, Inbar reprogrammed both species, and in 2011, we published the first report of making iPSCs from endangered species (Ben-Nun, et al., 2011). Nature Methods featured our work, with a cover illustration of an ark stuffed with endangered animals.”
So how exactly would these iPS cells be used to save the northern white rhino and other animals from the brink of extinction? Last December, Ben-Nun along with 20 other scientists and zoologists from four continents met in Vienna to map out a strategy. They published their plan on May 3rd in Zoo Biology.
The Stem Cell-Based Plan to Save the Northern White
In the first phase, an in vitro fertilization (IVF) procedure for the rhino – never before attempted – will be worked out. Frozen sperm samples from four now-deceased rhinos plus one sample from Sudan are ready for IVF. Researchers then hope to collect eggs from Najin and Fatu and implant embryos in surrogates of a related species, the southern white rhino. However, even if IVF is successful, the offspring would not represent enough genetic diversity to ultimately thrive as a species in the wild. So in the second phase, iPS cells will be generated using tissue fibroblast samples from several more northern whites that were banked in The FrozenZoo®. Those iPS cells will be specialized into sperm and eggs to provide a larger, more diverse set of embryos which again will be implanted in surrogate rhinos. Breeding animals using iPS-derived sperm and eggs has only been successful in mice so much work remains.
“Does this plan have any chance of succeeding?” Loring asks. Her response is cautiously optimistic:
“I know it will be difficult, but I think it’s not impossible. Perhaps the most important advance is that such a diverse group agreed on a plan—it wasn’t just a stem cell biologist like me imagining how the cells might be used, but rather a whole chain of experts who can imagine how to accomplish each step.”
Not all experts agree with this strategy. In a Nature News interview back in May, Michael Knight, chair of the International Union for Conservation Nature’s African Rhino Specialist Group, expressed concerns that the effort is misdirected:
“It’s Star Trek-type science. They should not be pushing this idea that they’re saving a species. If you want to save a [rhino] species, put your money into southern white conservation.”
Knight’s point is well-taken that conventional conservation approaches are critical to ensure that the southern white rhino doesn’t meet the same disastrous fate as the northern white. But if the funding is available, it seems worth the effort to also attempt this innovative iPS strategy, a technology that’s deep in development now and not awaiting Captain Kirk’s distant Star Trek future.