AP SCIENCE WRITER
NEW YORK (AP) – For the first time, researchers used the cloning method that produced Dolly the sheep to create healthy monkeys, which brought science one step closer to be able to do the same with humans.
Since the birth of Dolly in 1996, scientists have cloned nearly two dozen types of mammals, including dogs, cats, pigs, cows and polo ponies, and have also created human embryos with this method. But so far, they have not been able to raise babies this way in primates, the category that includes monkeys, apes and people.
"The barrier of cloning of primate species is now over," said Muming Poo of the Chinese Academy of Sciences. in Shanghai.
In a document published Wednesday by Cell magazine, he and his colleagues announced that they successfully created two macaques. The baby monkeys, about 7 and 8 weeks old, are called Zhong Zhong and Hua Hua.
"It's been a long road," said a scientist who tried and did not make monkeys and did not participate in the new research. Shoukhrat Mitalipov of the Oregon University of Health and Science. "Finally, they did it."
In principle, said Poo, the feat means that humans can be cloned. But he said his team does not intend to do it. Conventional scientists generally oppose making human babies by cloning, and Poo said society would forbid it for ethical reasons.
Instead, he said, the goal is to create lots of genetically identical monkeys for use in medical research, where they would be particularly valuable because they resemble humans more than other laboratory animals, such as mice or rats.
The process is still very inefficient (it took 127 eggs to get the two babies) and so far has only succeeded in starting with a monkey fetus. Scientists failed to produce healthy babies from an adult monkey, although they still try and expect the outcome of some pregnancies. Dolly caused a sensation because it was the first adult cloned mammal.
The procedure was technically challenging. Essentially, the Chinese scientists removed the nucleus that contains DNA from monkey eggs and replaced it with DNA from the fetus of the monkey. These reconstituted eggs grew and divided, and eventually they became early embryos, which were then placed in female monkeys to be born.
The scientists implanted 79 embryos to produce the two babies. Even so, the approach succeeded where others had failed. Poo said that was due to improvements in laboratory techniques and because the researchers added two substances that helped reprogram the fetus' DNA. That allowed the DNA to abandon its work on the fetus, which involves things like helping make collagen, and taking on the new task of creating a complete monkey.
Chinese researchers said that the cloning of fetal cells could be combined with gene-editing techniques to produce large amounts of monkeys with certain genetic defects that cause diseases in people. The animals could be used to study such diseases and try treatments. The researchers said their initial targets would be Alzheimer's and Parkinson's.
Mitalipov, noting that the Chinese could not produce healthy babies from adult cells, said he suspects that attempts to clone babies from a human adult would also fail. "I do not think it's advisable for someone to even think about it," he said.
Jose Cibelli, a scientist at Michigan State University, said it might be technically possible someday, but "criminal" to try now because of the suffering caused by the many lost pregnancies that the process implies.
If the procedure became efficient enough in monkeys, he said, society could face "a great ethical dilemma" about whether to adapt it for humans. The key step of transferring DNA could be combined with genetic editing to correct genetic disorders in embryos, allowing the birth of healthy babies.
Of course, the familiar image of human cloning involves making a copy of someone who was already born. That may be possible someday, but "I do not think it should be pursued," said researcher Dieter Egli of Columbia University. "I can not think of a big benefit."
Henry Greely, a law professor at Stanford University specializing in the implications of biomedical technologies, said the strongest argument that comes to mind would be the grieving parents' desire to produce a genetic duplicate of a dead child . But he doubts that it is a sufficiently convincing reason to undertake the extensive and costly effort necessary to achieve the approval of said procedure, at least for "decades and decades".
Marcy Darnovsky, executive director of the Center for Genetics and Society in Berkeley, Calif., Described it as unethical to subject this new child to "the psychological and emotional risks of living in the shadow of his genetic predecessor." Human cloning may also require many women to donate eggs and serve as substitutes, he said.
For the time being, due to security concerns, federal regulators in the United States would not allow a human baby to be cloned, and international scientific groups are also opposed, said biomedical ethicist Insoo Hyun of Case Western University. Book in Cleveland.
People for the Ethical Treatment of Animals condemned monkeys cloning experiments.
"Cloning is a spectacle of terror: a loss of life, time and money, and the suffering that is caused by the experiments is unimaginable," said PETA Senior Vice President Kathy Guillermo in a statement.
The Associated Press journalist Dake Kang in Beijing contributed to this story.
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