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Scientists claim embryonic stem cell advance 
Reprogrammed mouse cells avoid controversial destruction of embryos
The Associated Press
Updated: 2:42 p.m. ET June 6, 2007
NEW YORK - In a big step toward a long-sought goal, three teams of scientists
say they've produced the equivalent of embryonic stem cells, at least in mice,
without taking the controversial step of destroying embryos.

Their procedure makes ordinary skin cells behave like stem cells. If the same
can be done with human cells - a big if - the procedure could lead to
breakthrough medical treatments without the contentious ethical and political
debates surrounding the use of embryos.

Embryonic stem cells can give rise to all types of tissue, so experts believe
they might be used to create transplant therapies for people who are paralyzed
or have ilnesses ranging from diabetes to Parkinson's disease.

To harvest human embryonic stem cells, human embryos have to be destroyed, an
action opposed by many people. The new studies are the latest to attempt to
avoid embryo destruction.

'A long way to go'
Scientists have long hoped to find a way to reprogram ordinary body cells to act
like stem cells, avoiding the use of embryos altogether. The new mouse studies
seem to have accomplished that.

"I think it's one of the most exciting things that has come out about embryonic
stem cells, period," said stem cell researcher Dr. Asa Abeliovich of Columbia
University in New York, who didn't participate in the work. "It's very
convincing that it's real."

But he and others cautioned that it will take further study to see whether this
scientific advance can be harnessed for new human therapies.

"We have a long way to go," said John Gearhart of Johns Hopkins University, a
stem cell researcher who also wasn't involved in the new work.

In any case, it is crucial that scientists continue research with standard
embryonic stem cells, said researcher Konrad Hochedlinger of the Harvard Stem
Cell Institute, who led one of the three teams.

He and his colleagues present their work in the inaugural issue of the journal
Cell Stem Cell. (The first word in the journal's name refers to its publisher,
Cell Press).

The other two teams reported their results Wednesday on the web site of the
journal Nature. Rudolf Jaenisch of the Whitehead Institute in Cambridge, Mass.,
is the senior author of one paper, and the work behind the other paper was led
by Shinya Yamanaka of Kyoto University in Japan.


Will it work with human cells?
The new work builds on a landmark paper Yamanaka published last August. He found
that by slipping four genes into mouse skin cells called fibroblasts, he could
make the altered cells behave much like embryonic stem cells in lab tests.

But these so-called "iPS" cells still showed significant differences from
embryonic stem cells. The three new papers report on creating iPS cells that
proved virtually identical to stem cells in a variety of lab tests.

The four inserted genes regulate the activity of other genes, which is why they
can dramatically affect the cell's behavior.

Scientists caution that the experimental procedure followed in the studies
wouldn't be suitable for use in treating disease, and that it's not yet clear
whether a modified version would work with human cells.


One of the inserted genes is known to promote cancer, and Yamanaka reports that
mice carrying descendants of iPS cells showed tumors as a result. He and other
researchers said a new approach will be needed that avoids a cancer hazard.

Gearhart called that a major issue to be resolved. In addition, he said,
scientists still must show that these cells can give rise to many cell types in
the lab, as embryonic stem cells can.

And all this must be accomplished in human cells - a difficult task, he said,
because introducing genes into human cells is a major challenge.

If the technique can be harnessed for people, the iPS cells and the tissue they
develop into would provide a genetic match to the person who donated the skin
cells. That would make them suitable for transplant to that person,
theoretically without fear of rejection.


C 2007 The Associated Press. All rights reserved. This material may not be
published, broadcast, rewritten or redistributed.
URL: http://www.msnbc.msn.com/id/19067616/


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