Chinese researchers report that they have transformed mouse skin cells into fully grown fertile mice which are now great grandparents. Researchers have known for a couple of years that these induced pluripotent stem (iPS) cells are very similiar to embryonic stem cells in that they can be manipulated into becoming nearly any kind of cell or tissue. The test of true pluripotency is to see if they could be grown into adult animals.
As The Scientist reports:
"This ability to make a mouse from the cells of a Petri dish is the most stringent standard that mouse embryonic cells are held to, and iPS cells now meet that standard, which has been a lingering doubt," said stem cell biologist George Daley of the Harvard Stem Cell Institute and Children's Hospital Boston, who was not involved in the work. "It assures us that iPS cells can do all the things that ES cells can do."
In one study, published in Nature, researchers created 37 iPS cell lines from mouse embryonic fibroblasts (MEFs) by exposing them to the four 'Yamanaka factors'—the cocktail of transcription factors that most robustly induce pluripotency. They then subjected six of these cells lines to tetraploid complementation, a technique involving the creation of a four-cell blastocyst. These four-cell blastocysts can only contribute to extraembryonic tissues such as the placenta and thus fail to develop, but injected stem cells can develop into young if the stem cells are truly pluripotent. It's "the gold standard of pluripotency," said Fanyi Zeng of Shanghai Jiao Tong University, a coauthor on the study, in a telephone press briefing.
Using this technique with their iPS cell lines, the researchers succeeded in producing 27 live mice composed entirely from iPS cells. The first generation mice are now more than 9 months old. The researchers said they have some abnormalities (not described in the paper), but declined to specify what they were in the briefing. They did say they had also produced more than 200 second generation iPS mice and 100 third generation offspring, which seem normal and healthy so far. "[This is the] first time to confirm [that] iPS cells have full potency," said study coauthor Qi Zhou of the Chinese Academy of Sciences in the briefing.
Whole article on the research at The Scientist here.
In my column "Do Skin Cells Have Souls?" I analyzed how iPS cell research affects the ethical debate over human embryonic stem cell research.
Hat tip to Jonathan Moreno.