Monkey embryo cloned in major breakthrough

After years of false starts and an international scientific scandal, researchers said Wednesday they have achieved a feat some scientists believed was impossible: cloning a monkey embryo from a skin cell of an adult and using it to harvest embryonic stem cells.

Scientists previously have cloned embryos and animals from a variety of species, including rats, dogs and cattle. But primates — the family that includes monkeys and humans — have proved remarkably resistant to the most sophisticated techniques in the cloner's arsenal.

Reproductive biologist Shoukhrat Mitalipov, of the Oregon Health & Science University, and his colleagues reported in the online version of the journal Nature that they have cloned rhesus macaque embryos using DNA from skin cells taken from the ear of a 9-year-old male. The resulting stem cells grew into viable heart and nerve cells, among others.

"This is a giant step toward showing that human therapeutic cloning is possible," said Dr. Robert Lanza, who is trying to produce human embryonic stem cells at Advanced Cell Technology in Worcester, Mass., and was not involved in the research. "It proves once and for all that primate cloning is not impossible ... as many people had thought."

Work has begun to use the new technique to clone human embryos, although the process remains very inefficient. Even so, Mitalipov said, "I am quite sure that it will work in humans."

That fact alone could reinvigorate a stalled congressional battle over whether restrictions on human embryo cloning should be tightened or loosened. Such work is legal with private funds but off-limits to federally funded scientists.

The Oregon researchers' feat is a breakthrough in efforts to use cloned human embryos for the purpose of creating stem-cell lines that are genetically matched to sick patients so the cells will not be rejected.

Although clinical applications of the technology are years away, some preliminary studies suggest the cells, which have the potential to grow into any type of cell in the body, could be used to treat a range of diseases, including Parkinson's, Alzheimer's, diabetes and a variety of others.

Cloning pioneer Ian Wilmut, who created Dolly the sheep more than a decade ago, said that in the more immediate future, Mitalipov's technique could be used to produce monkeys with diseases that more closely mimic human ailments. That would lead to a better understanding of disease and the identification of drugs to treat them, Wilmut and Jane Taylor of the University of Edinburgh wrote in an editorial accompanying the paper.

Mitalipov said his lab is working toward those goals, particularly for type 1 diabetes.

While other scientists hailed the achievement, the Rev. Thomas Berg, executive director of the Westchester Institute, a Catholic ethics think tank, called it "a two-edged sword."

He praised the possibility of gaining a better understanding of diseases in primates but said applying the technology to humans "would be one of humanity's darkest endeavors."

Social conservatives object to human embryonic stem-cell research because it involves the destruction of embryos. President Bush has made such research off-limits to federally funded labs.

Creating stem cells through therapeutic cloning is particularly controversial because the technology theoretically could lead to the birth of a cloned baby. None of the researchers said they were planning to clone children.

Mitalipov's team used a technique called somatic-cell nuclear transfer, in which genetic material from a somatic cell — any cell other than a sperm or egg — is transferred into the nucleus of an unfertilized egg.

The problem is that the nuclear material from the donor is not at the same stage of life as the cytoplasmic material in the egg, and getting the two materials into rhythm can be exceptionally difficult.

The team was able to produce only two stem-cell lines from 304 eggs, a success rate of only 0.7 percent.

Other scientists were not concerned with the inefficiency. When any technology is developed, "it will be inefficient and not terribly practical," said molecular biologist Larry Goldstein, of the University of California, San Diego.

The team did not try to bring the monkey embryos to term by implanting them in surrogate mothers, Mitalipov said.

James Byrne, lead author of the study, moved to Stanford University over the summer and is trying to replicate the work using human eggs and cells, said Renee Reijo Pera, director of human embryonic stem-cell research at the Stanford Institute for Stem Cell Biology and Regenerative Medicine.

Wednesday's report was not the first of a success at cloning a primate embryo. Korean researcher Hwang Woo-suk reported in two papers in the journal Science in 2004 and 2005 that he had cloned a human embryo.

The papers were later withdrawn when Hwang was accused of fabricating data, and other researchers were unable to replicate his results.

Hwang lost his position at Seoul National University and faces criminal charges for fraud and misusing research funds.

To prevent a repetition of the episode, the editors of Nature took the unusual step of submitting biological samples from Mitalipov's lab to Australian researchers.

In a paper accompanying Mitalipov's, geneticist David Cram and his colleagues at Monash University analyzed DNA from the male macaque that served as a skin-cell donor, the two females that donated the eggs and the stem cells.

They concluded that "beyond any doubt" the stem cells came from cloned embryos.

The Washington Post contributed to this report.