Saturday science topic: Of mice and men

The debate over the ethical implications of embryonic stem cell research is raging harder than ever lately, with the research's detractors objecting to the fact that human embryos must be destroyed in order for human ES cells to be extracted. But what if there were a way to harvest ES cells from human embryos without destroying them?

Earlier this year, Dr. Robert Lanza and his team at Advanced Cell Technologies in Worcester, Massachusetts developed a method to do just that, but only 2% of the cells extracted developed into ES cell lines. Dr. Takumi Takeuchi and his colleagues at the Weill Medical College in New York have now tested a new technique on mouse embryos that has a 25% success rate—better than not only Dr. Lanza's method, but also the conventional ES cell extraction technique.

The researchers used slightly older embryos that have formed into hollow balls called blastocysts. These consist of a clump of 20-25 cells called an inner cell mass, which will give rise to the embryo, circled by cells that will form the placenta and supporting tissues. Normally, the entire inner cell mass is extracted and grown into ES cells, killing the embryo.

Takeuchi and his team extracted blastocysts from mice and used an enzyme to soften the natural glue holding the inner cell mass together. They then took one, two or three cells and tried to grow these into ES cells, before implanting the embryos back into the mice.

This technique did seem to cut down the survival rate of embryos slightly: 54% of the mouse embryos that had ES cells extracted developed into mice pups, while the survival rate for a control group was 62%. Nonetheless, Takeuchi says this is not a statistical difference, and the research group's leader, Dr. Gianpiero Palermo, says he and his colleagues are working on improving the technique.
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