|Photo by Stemagen|
Scientists at a California company reported yesterday that they had created the first mature cloned human embryos from single skin cells taken from adults, a significant advance toward the goal of growing personalized stem cells for patients suffering from various diseases.
Creation of the embryos -- grown from cells taken from the company's chief executive and one of its investors -- also offered sobering evidence that few, if any, technical barriers may remain to the creation of cloned babies. That reality could prompt renewed controversy on Capitol Hill, where the debate over human cloning has died down of late.
Five of the new embryos grew in laboratory dishes to the stage that fertility doctors consider ready for transfer to a woman's womb: a degree of development that clones of adult humans have never achieved before.
No one knows whether those embryos were healthy enough to grow into babies. But the study leader, who is also the medical director of a fertility clinic, said they looked robust, even as he emphasized that he has no interest in cloning people.
"It's unethical and it's illegal, and we hope no one else does it either," said Samuel H. Wood, chief executive of Stemagen in La Jolla, whose skin cells were cloned and who led the study with Andrew J. French, the firm's chief scientific officer.
The closely held company hopes to make embryos that are clones, or genetic twins, of patients, then harvest stem cells from those embryos and grow them into replacement tissues. When transplanted into patients, the tissues would not be rejected because the immune system would see them as "self."
"All our efforts are being directed toward personalized medicine and diseases," said Wood, adding that the scientists did not try to extract stem cells from the first embryos they made because they were focused on proving they could make the clones.
Other stem cell scientists expressed optimism but said they want to see the work repeated and more details presented.
"I'd really like to believe it, but I'm not sold yet," said Robert Lanza of Advanced Cell Technology (ACT) in Worcester, Mass. He said the report did not show the results of molecular tests that scientists typically do to prove that the cloning process was complete. He and George Daley, a stem cell scientist at Children's Hospital Boston, said the embryos look only marginally healthy in photos.
The work is the latest evidence, however, that the field is recovering from the scientific and public relations debacle of 2005, when similar claims by South Korean scientists proved to have been fabricated.
Nevertheless, opponents of research on human embryos lashed out at the approach.
"This study seems to confirm that human cloning . . . is technically possible," said Richard Doerflinger of the U.S. Conference of Catholic Bishops. "It does not show that a viable or normal embryonic stem cell line can be derived this way, or that any such cell has 'therapeutic' value. It does not answer the ethical or social questions about the mass-production of developing human lives in order to destroy them. . . . It only tells us that these questions are more urgent than ever."
Other critics noted that scientists in Japan and Wisconsin recently discovered a way to "reprogram" stem cells directly from skin cells, without having to make embryos as a middle step.
"In light of the recent cell reprogramming developments, cloning-based stem cell research is less justified than ever," said Marcy Darnovsky of the Center for Genetics and Society in Oakland, Calif.
Wood and others countered that, for now, those approaches require the use of gene-altered viruses, which can trigger tumor growth.
"It's hard to believe the FDA would approve the use of those cells," Wood said.
Criticism also arose on Capitol Hill, where enthusiasm has grown for the newer stem cell methods that do not involve embryos.
"Human cloning is now less about the science and more about the novelty, which makes it all the more nefarious," said Rep. Dave Weldon (R-Fla.), who has sought to ban all kinds of human cloning.
He said he hopes to revive the legislation this year. Previous bills have failed because Congress, though willing to ban the creation of cloned babies, is divided on the issue of banning human embryo cloning for research.
No law bans cloned-baby-making, but the Food and Drug Administration has said that such experiments would require its approval.
Cloning involves fusing an ordinary body cell with a female's egg cell whose DNA has been removed. Chemical factors inside the egg reprogram the body cell's DNA so that the newly created cell develops into an embryo that is a genetic twin of the person or animal that donated the body cell.
The technology has developed rapidly in animals, and scientists have been trying to apply it to human cells. In 2001, scientists at ACT said that they had made cloned human embryos but that they grew for only a day or two.
In 2005, scientists in Britain grew human embryo clones to the fully mature "blastocyst" stage that the California team described yesterday. But the body cells they used were taken from other human embryos, not from adults.
That approach offers no help to patients who are already born.
In the new work, the team took skin cells -- some from Wood's arm and some from an anonymous Stemagen investor -- and fused them to eggs from women who were donating their eggs to help infertile women. About one-quarter of the resulting clones, or five in all, developed into five-day-old blastocysts.
Wood said the key was that his lab is directly adjacent to a fertility clinic with which the company has an arrangement, so his team obtained the eggs within an hour or so of when they were retrieved from the women's ovaries.
And although researchers are typically given the poorest quality "leftover" eggs from fertility patients, donors in this experiment -- and the women for whom those eggs were intended -- agreed to give away several of the best eggs because, in each case, they had far more than were needed.
"They are the heroes in this," Wood said. "Think about it. You're spending $25,000 [trying to get pregnant], and you're giving some of those eggs away."
Under California law, egg donors cannot be paid for their service.
DNA tests proved definitively in one case, and less clearly in two others, that the embryos were indeed clones. Results could not be obtained from two of the embryos.
R. Alta Charo, a professor of law and bioethics at the University of Wisconsin, said the approach is attractive because the egg donors were not subjected to the medical risks of ovarian stimulation and egg retrieval just for research.
"The protocol entailed no marginal increased health risks to the egg donors, as they were already undergoing hormonal stimulation for non-research purposes," Charo said.
Asked what it was like to look at embryos that were replicas of himself, Wood said: "I have to admit, it's a very strange feeling. It is very difficult to look at an embryo and realize it is what you were a few decades ago. It is you, in a way."
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