LOS ANGELES — Researchers have reprogrammed cells inside living mice — and have discovered that the stem cells created in the process are even more flexible than those derived from embryos or grown in laboratory dishes.
Someday the achievement might help scientists devise ways to treat human disease by directly regenerating tissues within patients, said Manuel Serrano, senior author of a report detailing the research that was published online Wednesday by the journal Nature.
But that won't happen immediately, he added.
The pluripotent stem cells Serrano and his colleagues created are highly flexible and have the potential to develop into nearly any cell type in the body.
Researchers hope to take advantage of them to rebuild tissues that don't regenerate on their own, such as neurons, the insulin-producing islet cells that are destroyed in patients with Type I diabetes, or heart muscle killed during a heart attack.
Interest in stem cells pushed scientists first to figure out ways to isolate them from embryos and to rewind mature cells to a more flexible state. The team from the Spanish National Cancer Research Center in Madrid set out to see if it was also possible to create pluripotent stem cells inside a living organism.
They created genetically altered mice whose bodies could produce the same four ingredients researchers use to rewind cells in a lab dish. When the scientists activated genes that produced the factors, the mice grew a type of tumor known as a teratoma — a sign that there were pluripotent cells in their bodies. The mice also produced actual stem cells the team could isolate.
That was new. But when the scientists examined the stem cells, they found that they could pull off a trick that no other stem cells could: They produced placental tissues.
The researchers also found that some mice grew cysts that had embryo-like qualities. But they emphasized that the cysts were not embryos.