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From NPR NEWS, this is ALL THINGS CONSIDERED. I'm Robert Siegel.


And I'm Rebecca Roberts.

Today, scientists said they've come up with two new ways to make embryonic stem cells that do not involve starting with an unfertilized egg. Right now, a woman's eggs are considered a necessary ingredient for one of the most promising directions for stem cell therapy: creating stem cells tailored to an individual patient. But human eggs are in short supply and using them is ethically contentious.

NPR's Joe Palca reports.

JOE PALCA: Dolly the cloned sheep proved that an egg could do something truly remarkable: it could transform the DNA in an adult cell into the DNA of an embryonic cell. And once you get these so-called embryonic stem cells, you can, in theory, use them to make any cell you might need to treat a patient's disease.

Rudolf Jaenisch is a stem-cell biologist at the Whitehead Institute in Cambridge, Massachusetts. He spent the last several years trying to accomplish the same transformation in the laboratory without an egg.

Dr. RUDOLPH JAENISCH (Stem Cell Biologist, Whitehead Institute): Because if you could do that, you could take a skin cell from a patient, expose it to something and get an embryonic stem cell. If you could do that, then all the problems would go away.

PALCA: By problems, Jaenisch means getting enough human eggs. But he also means the problem of destroying a human embryo because right now, making an embryonic stem cell requires destroying an embryo. That's made the work very controversial.

So working with mice, Jaenisch has been searching for alternatives. Jaenisch's latest approach was first tried last year by a Japanese scientist Shinya Yamanaka. He found four genes appear to be crucial for transforming an adult cell into the embryonic cell.

Now, Jaenisch and several other scientists, including Yamanaka himself, have confirmed that if you take a mouse skin cell, switch on those four genes, you get a new kind of cell.

Dr. JAENISCH: When we analyzed them, they were indistinguishable from normal embryonic stem cells.

PALCA: Jaenisch reports the findings in the journal "Nature." He is now trying to adapt the approach to human cells.

Harvard University stem cell biologist Kevin Eggan has tried another avenue around the egg problem. He spoke earlier at a teleconference organized by Harvard.

Mr. KEVIN EGGAN (Assistant Professor, Molecular and Cellular Biology, Harvard University): You can use cells from very early fertilized embryos to do the same things that we thought only unfertilized eggs would do in the past.

PALCA: Again, working in mice, Eggan showed that an unfertilized egg can make adult DNA behave like embryonic DNA. And it doesn't even have to be a healthy fertilized egg. Even an egg that has the wrong number of chromosomes will work. And that could help solve the problem of getting human eggs, because fertility clinics often have eggs with abnormal chromosomes.

Mr. EGGAN: Those are always set aside or discarded because they can never make a child. They would only make an abnormal fetus that would fail.

PALCA: Eggan's work also appears in this week's "Nature." He says his lab has already begun experimenting with these damaged human eggs to see if they could transform human adult cells.

Stanford University medical ethicist William Hurlbut says Eggan's approach is scientifically intriguing.

Dr. WILLIAM B. HURLBUT (Associate Professor Of Social And Medical Ethics, Stanford University): But I suspect this will not meet the moral objections -which are not to the research with embryonic stem cells themselves, it's just to the way they're procured - because they're procured by the destruction of a human embryos, and here again this would involve the destruction of a human embryo.

PALCA: Hurlbut is a member of the President's Council on Bioethics, a body that has wrestled with the moral dimensions of stem cell research. He also says Jaenisch's work that dispenses with eggs and embryos altogether could change the moral dimensions of the stem cell debate.

Dr. HURLBUT: And it just shows that there are alternative ways to get these cells without overriding the moral objections of a large, large number of Americans.

PALCA: Perfecting those ways will take some time, and many scientists are content to work with embryonic stem cells that exist today, whether or not some object to the way they were procured.

Joe Palca, NPR News, Washington.

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