Cloning Gets Closer

(2 of 2)

Several factors helped the Koreans succeed where others had failed. To start with, they had a large supply of eggs. The researchers lined up 16 female volunteers who found the project through its website. To avoid any taint of coercion, the women weren't paid. They were fully informed about the research and its risks, however, and given several opportunities to change their mind. In the end, the 16 women furnished 242 eggs many more than in any previous cloning attempt.

The scientists' basic strategy was the same as in most post-Dolly cloning experiments: remove the nucleus of the egg, with its single set of chromosomes, and replace it with the nucleus of a mature cell, containing two sets (in this case, the mature nuclei came from cumulus cells, which surround eggs during development). With a quantity of eggs that a commentary in Science calls "whopping," the scientists were able to experiment with different techniques to find which worked best varying the time between inserting the new nucleus and zapping it with electricity to trigger cell division, for example, or testing different growth media.

The Korean team believes that two other factors may have helped them succeed. While most cloners suck out an egg's nucleus with a tiny pipette, Moon and Hwang made a pinhole in the cell wall and used a tiny glass needle to apply pressure and squeeze the nucleus out. "It's more gentle with the egg and allows you to remove only the DNA and leave some of the major components of the egg still inside," says Jose Cibelli, a professor of animal biotechnology at Michigan State University and a co-author of the Science paper. "Actually, it's pure speculation, but we can't come up with anything else, so we think that may be important." Technicians also honed their skills until they could transfer a nucleus in less than a minute, a much better time than most labs and one less likely to allow deterioration.

What makes the achievement even more significant is that it gives doctors a way to create stem cells bearing a patient's own DNA. Tissues grown from those cells could replace diseased tissue in the patient without any risk of rejection.

It could be years, however, before such replacement actually happens. "This is an important step forward," says Goldstein, "but it's just one obstacle out of the way." The Korean technique has only worked in women so far, perhaps because they alone have cumulus cells, which seem especially amenable to cloning. It should work in men too, but first, researchers will have to isolate the male equivalent of cumulus cells. Moreover, scientists are still learning how to coax stem cells into becoming particular types of tissue, and for many diseases they don't even know what kind of cells they need to end up with. "With juvenile diabetes," says Goldstein, "I think we have a sense of what cells we want to make. With ALS [Lou Gehrig's disease] we have less of a sense."

Some researchers say all the talk about replacement tissue overlooks a more immediate benefit of stem cells: if you cloned them from someone with a genetic disorder, you could perform all kinds of experiments zeroing in on the DNA that is causing the problem. "If you had that," says Dr. Irv Weissman, director of Stanford's Institute for Cancer/Stem Cell Biology and Medicine, "this would be a transforming technology as important as recombinant DNA."

The way things stand, all the benefits of stem cells will probably be developed as this latest breakthrough was outside the U.S. "I'm not really surprised it came from Korea," says Goldstein, citing the researchers' skill and experience. "I'm disappointed it didn't happen first in the U.S. But given the absolute stranglehold that federal policy has put on this field, that doesn't surprise me either."

Even with sensible laws, of course, there's always a chance that cloning technology will be misused. Plenty of useful technologies are abused every day, says Dr. William Gibbons, professor of obstetrics and gynecology at Eastern Virginia Medical School including automobiles and antibiotics. "It doesn't mean that these are inherently bad," he says. The trick is to legislate against the misuse, not against the technology.