Friday, July 24, 2009

Two teams of Chinese scientists have made a major advance using mice in the development of a new kind of stem cell that doesn’t involve destroying embryos.

Those cells are derived from ordinary skin cells, and when they were created two years ago from human skin and genetically reprogrammed, it was hailed as a breakthrough. But questions remained as to whether they could act as chameleon-like as embryonic stem cells and morph into any cell type in the body.

One way to show that versatility is if the new reprogrammed stem cells could be used to produce an entire new life. And now researchers have shown they can - in mice.

For the first time, scientists were able to produce live mice from stem cells that were coaxed from the skin tissue of adult mice and then reprogrammed. And while there were abnormalities and unusual deaths with some of the first generation of mice, one team produced enough normal mice using this method to create hundreds of second and third generation mice.

Studies on this type of stem cell, called “iPS” for induced pluripotent stem cells, were released Thursday by two competing scientific journals, Nature and Cell Stem Cell.

“We demonstrated the practicality of using iPS cells,” said Fanyi Zeng, associate director of the Shanghai Institute of Medical Genetics and co-author of the larger, more successful study, which appears in Nature.

A leading U.S. stem cell researcher who wasn’t part of either study, Dr. George Daley of the Harvard Stem Cell Institute and Children’s Hospital Boston, hailed the work as important because it shows that the new type of stem cells “satisfy the most stringent criteria of embryonic stem cells - the ability to make a mouse entirely from cells in a petri dish.”

These type of stem cells generate less controversy than embryonic stem cells, which scientists have been studying for more than a decade. Embryonic stem cell research involves the destruction of embryos, usually ones created at fertility clinics but which are not implanted into women seeking to give birth.

The new type of stem cells use a virus to reprogram the genetic information of the skin cell to make it a stem cell. Because it can’t create a placenta, the Chinese researchers had to then combine the new stem cell with cells that provide a placenta.

Dr. Zeng said all types of stem cell research should continue, not just the new type. Her study produced 27 live mice. Some of the mice, she said, had “abnormalities,” but she declined to say what those were or how extensive the problems were. That will be in a future report, she said.

Those 27 mice produced second and third generations that included hundreds of mice with no noticeable abnormalities.

The other team got only four births; three died quickly and only one made it into normal adulthood.

“We are confident that tremendous good can come from demonstrating the versatility of reprogrammed cells in mice,” Dr. Zeng wrote in an e-mail. She said while this is just in mice it could help doctors “understand the root causes of disease and lead to viable treatments and cures of human afflictions.”

This work is still only in mice.

“There’s a lot more [to do] before we can even mention humans,” Dr. Zeng said, adding that it would be unethical to try to use these stem cells to produce live human beings.

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