New Stem-Cell Source Sought

Moral and ethical issues aside, getting an adequate supply of human eggs for research is a major logistical hurdle. Deriving stem cells from an adult cell requires that an egg be "reprogrammed" so the adult cell nucleus behaves like an embryonic cell. But several groups around the world are trying to find an alternative to the egg for reprogramming.

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Scientists may have solved a political and moral problem facing embryonic stem cell research. They think that they found a way to make embryonic stem cells without destroying embryos. Initial results are promising, but as Joe Palca reports, it'll be a while before the technique is perfected.

JOE PALCA reporting:

Nearly every cell in our bodies has a complete set of the DNA we were born with. But as we grow from an embryo to an adult, the DNA changes according to a set program. As cells take on particular roles, some of their genes get permanently switched off. That makes sense; you don't need genes for skin cells switched on in a brain cell.

But what if you could reverse the program? What if you could take the genes in adults cells--also called somatic cells--and make them behave like they did when they were all-purpose embryonic cells? Right now the only way to reprogram the DNA in a human somatic cell is to put it into a human egg. But Kevin Eggan's experiments may have revealed another way.

Mr. KEVIN EGGAN (Harvard University): The point of these experiments is to determine whether or not human embryonic stem cells themselves can be used as a source of material--really, a replacement for eggs--to reprogram adult somatic cells.

PALCA: Eggan is at Harvard University. Using eggs to reprogram somatic cells has been a problem. Once the egg starts dividing, it becomes an embryo, and you have to destroy the embryo to get the stem cells. Some people find that morally unacceptable. Kevin Eggan thinks there's a way to get stem cells without using eggs at all.

Mr. EGGAN: We reasoned that human embryonic stem cells themselves might have--harbor reprogramming activities, like the egg, and could be used to sort of set back the developmental clock of adult, say, skin cells.

PALCA: In his experiments, Eggan takes a human skin cell and fuses it with a human embryonic stem cell. Once joined with the stem cell, the genes in the adult skin cell do start behaving as they would in an embryonic cell. That's the good news. The bad news is that the fused cells have twice as much DNA as normal cells; all the DNA from the skin cell, plus the DNA from the embryonic stem cell. Cells with too much DNA tend to behave strangely after a while and probably would not be useful for therapy.

But Alan Trounson may have found a way around that problem. Trounson is a stem cell researcher at Monash University in Melbourne, Australia. He uses embryonic stem cells with extra-heavy DNA. He then puts the fused cells in a centrifuge, the heavy DNA from the embryonic stem cells is spun off, leaving behind the reprogrammed DNA from the skin cell. But Trounson says there's still a problem.

Mr. ALAN TROUNSON (Monash University): We really don't have evidence that would totally define that they've got the same capacity as embryonic stem cells at this stage.

PALCA: In other words, Trounson is not yet sure his reprogrammed cells behave the way stem cells should behave. But Trounson is optimistic enough to continue tinkering with the technique.

Mr. TROUNSON: It would be a much more robust and sustainable method for reprogramming somatic cells for patients into cells which will be more capable of regeneration.

PALCA: And using stem cells to regenerate cells damaged by disease is the great hope of stem cell research. Joe Palca, NPR News, Washington.

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