Breakthrough renders stem cell debate over?
By Eryn Brown
New turn in science v. religion controversy
OS ANGELES (MCT) 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 study 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, in itself, was new. But when the scientists examined the stem cells more closely, 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 another novel development, and a sign that the stem cells in the mice were more flexible than other types of pluripotent stem cells.
Serrano said it wouldn't make sense to use this exact technique to treat human disease: Rewinding cells to such an early state of development isn't considered safe because it can cause cancer. But it may make sense to partially rewind cells in particular parts of the body before redirecting them to regenerate desired tissues, he said.
Researchers who were not involved in the study had mixed reactions.
Dr. Deepak Srivastava, director for cardiovascular disease at the Gladstone Institutes in San Francisco, said that the work was fascinating "from a biological standpoint" because it showed it was possible to take a mature cell all the way back to its primitive state immediately after conception a "baseline state," he called it. (Human embryonic stem cells are like cells in a 5-day-old embryo.) He said he expected researchers to try to figure out why these cells rewound more fully in vivo than they did in vitro, and to figure out how to reproduce those conditions in a lab dish.
McMahon also mentioned a controversial possibility posed by the experiment: If you have stem cells that could produce the cells that make up an embryo, as well as the tissues that support that embryo, you could "make a new individual."
Asked about the possibility of such an outcome, Serrano and Abad emphasized that the cysts they saw in their mice were not, in fact, embryos.
"That would be a major surprise," they said.
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© 2013, Los Angeles Times Distributed by MCT Information Services