Stem cell triumph

It's always exciting to hear about scientific breakthroughs, and the news today is truly remarkable: scientists at two different places (the Univ. of Wisconsin and Kyoto Univ.) have managed to turn human skin cells into embryonic stem (ES) cells. This has been the "holy grail" of stem cell research for the past ten years, and until today it wasn't at all clear when it would be achieved. The media is full of the news, and rightly so.

The promise of these ES cells is fantastic, almost the stuff of science fiction. With re-programmed ES cells, we should be able to grow replacement tissues for almost any organ in the human body, using a person's own cells as a source. By using your own cells, the problems with organ rejection that plague transplant patients are eliminated. I predict that, once this becomes reality, the first attempts will be to replace non-critical tissues such as cartilege (my knees could use it!), and if those are successful, we'll move on to growing replacements for things like kidneys, livers, lungs, and heart tissue. This is likely years away, but it really does seem feasible now. And of course - though none of today's news stories seem to mention this - the hope of life extension through permanently young organs seems much brighter now.

Of course, there are many caveats. This is basic research, not clinical practice, and the first problem is that both groups used retroviruses to transform skin cells into ES cells. The idea is simple: retroviruses insert themselves into the host DNA, so the two groups (Shinya Yamanaka in Kyoto, James Thomson in Wisconsin) each identified four genes that seemed to be able to turn normal cells into ES cells. Intriguingly, the two groups used four different genes - Yamanaka used oct3, sox2, klf4, and c-myc, while Thomson used oct3, sox2, nanog, and lin28. (See their papers in the journals Cell and Science for details.) They created one retrovirus for each gene, and then infected skin cells with all four retroviruses. The result is that some skin cells, about 1/10,000, got all four extra genes (of course they already had one copy of each gene), and purely by chance the genes were inserted into their genomes in such a way that they turned on. The randomness of the method is one thing that needs work - if a retrovirus inserts in the wrong place, it will disrupt normal functions, and the resulting ES cells will be defective.

I've already been asked whether this means that we can abandon research on human embryonic stem cells created from fertilized human eggs - this is the research that President Bush and other conservative Republicans have opposed, based on religious reasons. The answer is a resounding no, as Thomson already said. Among other things, we need "real" ES lines to be able to determine if the new ES cells are truly pluripotent; that is, to see if they're as good as the real thing. One should always be very skeptical when politicians - especially politicians as anti-science as Bush - make assertions about the implications of any scientific result. (An aside: I'm a member of the Maryland Stem Cell Commission, which determines how to allocate the state funding that my state has set aside to promote human ES research, but I don't do stem cell research myself and I'm not eligible to receive these funds.)

These and other caveats aside, though, today is a good day for science. What a great way to start the Thanksgiving holiday in the U.S., with real hope for the future.

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