Donated Eggs Don't Come Cheap

NOVEMBER was an astonishing month for embryonic stem cell research. First, Shoukhrat Mitalipov at the Oregon National Primate Research Center reported producing cloned embryonic stem cells from a rhesus macaque monkey - the first from an adult primate. The decade-long dream of using cloned human stem cells to cure intractable diseases seemed on the verge of being fulfilled.

Just a week later, two research teams stunned the world by announcing they had generated genetically matched human pluripotent stem cells - which seem to be as versatile as embryonic stem cells - without cloning. Using viruses to introduce new genes into human skin cells, Shinya Yamanaka at Kyoto University in Japan and Jamie Thomson at the University of Wisconsin, Madison, "reprogrammed" them to revert to an quasi-embryonic state.

"Cloning is not the only route to versatile stem cells that are a genetic match to adult donors"

So just as human therapeutic cloning seems achievable, a rival technique is challenging the idea that cloning is the only way to produce pluripotent stem cells that are genetically identical to their adult donors. Ian...