With only seven northern white rhinos left in the world, creating eggs and sperm from stem cells offers the possibility of salvaging some of the species.
What's the News: In an effort to help preserve endangered rhinos and primates, biologists have converted skin cells taken from the animals into pluripotent stem cells, which can grow into nearly anything, given the right conditions. They might even grow into egg and sperm cells, eventually, the researchers think, suggesting a cell biological route to conservation. How the Heck:
The samples came from a repository at the San Diego Zoo Institute for Conservation Research called the Frozen Zoo, where cells from 8600 animals of 800 species have been preserved.
Using lab-grown viruses, the team inserted four genes that have been shown to make human cells revert to their pluripotent state into skin cells from the northern white rhino and the drill, a primate that's one of the most endangered mammals in Africa.
Over the course of a few weeks, a small fraction of the cells morphed into pluripotent stem cells, displaying markers on their surfaces that let researcher identify them.
What's the Context:
When attempts to preserve an animal's habitat in the wild fail, conservationists try to keep the species alive through captive breeding programs. But many animals fail to thrive in captivity and either do not mate or do not care for their offspring. When even captive breeding fails, scientists begin projects like this one, exploring whether stem cells or genetic technologies can help salvage what's left of the species.
There are only seven northern white rhinos---two female, five male---left in the world; all are in captivity and none have had offspring since 2000. The drill is hunted for bush meat in the small region of Africa where it lives and attempts at captive breeding are hampered by pervasive diabetes in the captive population, perhaps because it was founded with just a few individuals. For these species, the authors write, "extraordinary measures are required to prevent extinction."
The Future Holds:
Biologists would like to be able to make sperm and egg cells, or gametes, from such stem cells, with the aim of creating embryos that can be implanted into the wombs of surrogate mothers of the same or another species. Making gametes from stem cells is an active area of research---recently, Japanese scientists announced the first animal born from such cells, a mouse---but there is a still long way before such procedures are established.
Stem cells could also help alleviate the diabetes of the captive drill population, if they could be grown into pancreatic cells to replace the drills' malfunctioning versions.
Even if this technique turns out to be helpful in making new baby rhinos and drills, though, it will never be able to erase the fact that the vast majority of these species have died due to habitat loss and hunting. Much of the genetic diversity that once existed is lost, as well as whatever cultural heritage these animals once had, and captive breeding programs will continue to suffer from that loss. The best approach to conservation will continue to be preserving habitat.
Reference: Ben-Nun et al. Induced pluripotent stem cells from highly endangered species. Nature Methods (4 September 2011), doi:10.1038/nmeth.1706
(via New Scientist
Image courtesy of Ikiwaner / Wikimedia Commons