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Stem Cell Advances Bring Therapy Closer

INTRO: Massachusetts scientists are announcing two sets of discoveries that might one day make stem cell therapy feasible. The two new techniques, published Wednesday, both concern new ways to make embryonic stem cells. WBUR's health and science reporter Allan Coukell explains.ALLAN COUKELL: Say you want to create a line of stem cells. You might want to do this for research or eventually to create new therapies. You would take the DNA-containing nucleus from a cell, a cell from your arm, for example, and pop it into an unfertilized egg.

The magic of the egg is that it seems to "reset" the cell's genes. Instead of just skin, it can now grow into any kind of tissue in the body. This is a so-called embryonic stem cell.
Conventional wisdom among scientists has long been that the unfertilized egg is essential.

Here's the problem for researchers: human eggs are really, really hard to get.

KEVIN EGGAN: Over the last year, we've spent many tens of thousands of dollars on advertising to try to recruit egg donors. And more than a year later now, we have yet to recruit a single donor.

COUKELL: Kevin Eggan from the Harvard Stem Cell Institute says attempts by him and his colleagues to create new human stem cell lines have been stalled, because Massachusetts law won't let him pay women to donate eggs.

So a year ago, Eggan and one of his post-doc researchers decided to try an alternate strategy. They began working in mice, this time using fertilized eggs, also called very early embryos.

This had been tried before, without success. But Eggan reasoned that the mistake everyone had always made was to removed the nucleus from the fertilized egg, and with it, whatever mysterious factors were required to reset the genes of the new cell.

EGGAN: And so it was sort of like taking all the gas out of the embryo. And what we realized is that if you waited until the right phase of the cell cycle, you take out the chromosomes by themselves without depleting this early embryonic fuel, and replace them with a set of chromosomes from an adult cell.

COUKELL: Eggan's paper this week in the journal Nature shows that the resulting new cell can be used to make new mouse embryonic stem cells. He is already trying the same approach with human cells. Eggan points to an estimated half-million fertilized eggs frozen in in-vitro fertilization clinics around the country as a potential source of cells for research.

This approach won't satisfy those with moral objections to the destruction of very early embyos, but other scientists praised its potential to break the scientific log jam caused by a shortage of eggs. George Daley is a stem cell scientist at Children's Hospital:

DALEY: If in fact this can work in human cells, there are so many more early human embryos available than there are eggs, that it could make nuclear transfer research practical.

COUKELL: Three other studies this week in Nature and the journal Cell Stem Cell outline a different way to create stem cells.

Alex Meissner of the Whitehead Institute in Cambridge was part of a team that showed that an adult cell could be turned into a stem cell with the injection of just four genes.

ALEX MEISSNER: Now, you can take this cell, and return it to a state that is a little bit like an embryonic state. Now at this point, the cell can form all kinds of different cell types.

COUKELL: The work builds on a Japanese study published last year. George Daley calls that study and this new work "the most exciting in years."

DALEY: What they've really shown is that this mysterious process of nuclear reprogramming can be reduced to a defined set of four genes.

COUKELL: It could eventually pave the way for individualized stem cell therapy. But Daley notes that there are major hurdles before this approach could be used therapeutically. First, human genes for reprogramming may be different from those in mice. Secondly, the current strategies cause cancer in some of the mice.

Nevertheless, in more ways than one, science is unraveling the mystery of the egg.
For WBUR, I'm Allan Coukell.

This program aired on June 7, 2007. The audio for this program is not available.

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