Scientists at the Scripps Research Institute in La Jolla have produced the first artificial embryonic stem cells from the highly endangered mammals, marking the initial steps towards ensuring the survival of endangered species.
Using frozen cells stored at the San Diego Zoo, Jeanne Loring PhD, professor of developmental neurobiology at Scripps Research and her collaborators have created stem cells from frozen skin cells of two such endangered species-- the silver-maned drill monkey and the northern white rhinoceros.
The study, which was published in an advance online edition of the journal Nature Methods on Sunday, states that induced pluripotent stem cells, or IPS cells, could be used to preserve - or even revive - these endangered species and others like them.
The best way to manage extinction is to preserve species and habitats but that is not always working, Oliver Ryder, director of genetics at the San Diego Zoo and co-leader of the study, said in a statement.
Stem cell technology provides some level of hope that they won't have to become extinct even though they have been completely eliminated from their habitat.
Induced pluripotent stem cells are created by reprogramming somatic cells. In this case, researchers generated the IPS cells from skin cells stored in the Frozen Zoo at the San Diego Zoo Institute for Conservation Research. San Diego's Frozen Zoo has skin cells and other tissue samples from more than 800 species.
Almost four decades ago, in 1972, conservationists in San Diego began freezing skin samples from endangered species in the hopes that science would come up with a way to utilize the cells to pull these species from the brink of extinction, according to a MIT Technology Review report.
In 2006, Ryder contacted Loring about the possibility of using the samples from the Frozen Zoo to generate and store stem cells, according to the Scripps Research Institute press release.
Just as is hoped with humans, Ryder thought stem cells from endangered species might enable lifesaving medical therapies or offer the potential to preserve or expand genetic diversity by offering new reproduction possibilities.
At the time, although researchers had been working with stem cells from embryos, scientists had not yet developed techniques for reliably inducing normal adult cells to become stem cells. But the technology arrived soon after, and scientists now accomplish this feat, called induced pluripotency, by inserting genes in normal cells that spark the transformation.
While Loring's team met with Ryder in early 2008, they realized that these newly emerging techniques might be applied to endangered species. Post-doctoral fellow, Inbar Friedrich Ben-Nun, PhD, set out to systematically explore the possibilities.
Ryder suggested two species for initial work. The first was a highly endangered primate - the drill. The second candidate was the northern white rhinoceros.
Initially members of 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.
The process is inefficient since only a few stem cells are produced at a time, but that’s enough, says Ben-Nun.“There are only two animals in it. But we have the start of a new zoo, the stem cell zoo.”
Studies using the stem cell approach are in progress to cure human diseases. However, scientists hope to be able to use stem cells to create eggs and sperm, which could be then used for breeding and boosting the genetic diversity of endangered species.
Either induced sperm cells could be combined with the eggs from living animals through in vitro fertilization or both eggs and sperms might be generated from stem cells and the resulting embryos could be planted in live host animals.
Scientists believe that this technique would be much more reliable than cloning techniques where the frequency of success is very low, Loring said.
I think that work would be a lot easier ethically with endangered species than with humans, Loring said.
Moving forward, Loring said the group is hoping to continue producing stem cells from other species to expand their fledgling stem cell zoo.