South Korean scientists said today that they had cloned a human cell from an infertile woman, creating a four-cell embryo that theoretically could have grown into a genetically identical replica of the woman. But they said that because of the legal and ethical implications of their work, they stopped the experiment and did not try to create a human clone.
The scientists, at a major hospital here, are believed to be the first to publicly claim that they taken steps to clone a human being. Their research has not been confirmed or reviewed by other scientists, but experts in the United States said that although they did not know of the scientists' work, the requisite techniques had been demonstrated in animals and that there was no theoretical reason they could not be applied to people.
The South Korean researchers said they let the embryo reach only four cells before halting the experiment and did not take the critical step of implanting the embryo in a woman, so there is no guarantee that it would have developed into a fetus. Still, the research shows how quickly cloning, dismissed as science fiction a decade ago, has crossed into uncharted ethical territory.
''They need some genetic proof that this really happened,'' said Dr. Alan DeCherney, chairman of the obstetrics and gynecology department at University of California, Los Angeles.
In Scotland, researchers at the institute that produced the first clone, Dolly the sheep, also expressed skepticism about the Korean claim.Continue reading the main story
''By stopping the experiment when they did, the Korean researchers are unable to provide any evidence that the transferred nucleus had been successfully 'reprogrammed,' '' said Dr. Harry Griffin, assistant director of the Roslin Institute in Edinburgh.
In the experiment, conducted by a three-man research team at the Kyunghee University Hospital in Seoul, scientists at an infertility clinic said they cultivated a human embryo by using an unfertilized egg and an ordinary, or somatic, cell donated by a woman in her 30's. They used a technique similar to the one used by researchers at the University of Hawaii who announced in July that they had cloned mice.
The Korean Government restricts the cloning of humans, though it does not ban it outright. There is a significant amount of cloning experimentation in South Korea, and some experts say that it is about as advanced as that in Japan, where scientists recently cloned eight calves from a single adult cow.
Yukio Tsunoda, a scientist at Kinki University who led the recent cloning of the eight calves in Japan, said that he had little information on the research work by the Korean team. But he said that since cloning of animals could be done, he did not see any scientific reason why cloning humans could not. Moreover, he said it is possible that human cloning to the same stage reached by the Korean team may have been done secretly in other countries.
Rather than admiration, however, the work in Korea inspired outrage and was immediately denounced by lawmakers and civics groups.
''We oppose the cloning of human cells,'' said Jung Myoung-hee, director of Green Korea United, a group concerned with ethics in biology and environmental pollution. ''This is not an advancement for medical technology and now we have to be prepared to accept international criticism. The result of this experiment is not something Koreans should be proud of.''
''The only reason other countries have not developed this technology is because they feared the ethical repercussions, not because they lacked the technology,'' Mr. Jung said.
Rhee Shang-hi, a legislator, along with 35 other lawmakers introduced a proposal in Parliament last month that would strictly limit experimentation on areas that ''may damage the integrity of human life,'' according to a statement released by Mr. Rhee's office.
Kim Sung-bo, who supervised the research team, said he was very aware of the ethical issues surrounding his experiment. He added that while he was worried that such concerns could sometimes stand in the way of medical advances, his team had no plans to disregard ethical standards.
''We have no intention of developing our technology while disobeying the rule of ethics,'' said Dr. Kim by telephone. ''But if conditions are ripe and if we can reach a point of agreement with medical experts around the world, we are willing to continue our experiment within limited boundaries, but not involving the implantation of an egg into a uterus.''
Implantation was the key step that the team did not take. If they had taken the embryo and implanted it in the woman's uterus, they said, it perhaps would have developed as a fetus and been born regularly, but they chose not to do so.
The team said it plans to publish its results in a major scientific journal, which would lend the work credibility.
''I think they wanted to experiment on the early stage of human embryo growth, which is potentially a technology of making clones,'' said Shohei Yonemoto, senior researcher at Mitsubishi Kasei Institute of Life Sciences in Japan. He noted that even if the embryo had been implanted, the success rate of in vitro fertilization is only about 10 percent.
Dr. Kim's colleague in cloning the human cell, Lee Bo-yon, said today that ''cloning humans was not so hi-tech.'' He also stressed, however, that the experiment was not related to solving infertility problems for patients at the clinic, and that they had received permission from the donor to use three of her eggs for experimentation.
Altogether, the team cultured six eggs on two different occasions from two different women. But only one developed into an embryo. In the successful round, Dr. Lee said that on Dec. 8 he took an egg from a healthy woman and removed its nucleus, which contains its genetic material. In its place, he put the nucleus from a somatic cell, a typical body cell, which was taken from near the ovum of the same woman. By Dec. 10, the cell had divided into four cells, a stage at which the embryo can be implanted into the wall of the uterus. However, as they did not plant the embryo, it died.
Though it may appear relatively simple, the experiment could be looked upon someday as a milestone. ''It might be said that this experiment was a trigger,'' said Mr. Yonemoto, at Mitsubishi. ''It showed proof that human cloning is possible.''Continue reading the main story