Monkey Embryos Cloned, Scientists Report

American scientists reported Wednesday that they had cloned embryos from a nine-year-old male monkey and derived stem cells from them, reaching a long-sought goal that may pay off someday in new treatments for people.

The work was published online by the journal Nature, which took the unusual step of asking another team of researchers to verify the work before publication. That decision reflected the legacy of a spectacular fraud in stem cell research from South Korea several years ago.

The new work is important because someday researchers hope to use such a process in humans to make transplant tissue that is genetically matched to patients, thus reducing the risk of rejection.

Scientists had tried for years to produce stem cells through cloning in monkeys, because the animals are so closely related to humans. But until now, it hasn't worked.

The advance was reported by Shoukhrat Mitalipov of the Oregon National Primate Research Center and colleagues. Some media outlets, including the Associated Press (AP), had reported their success earlier this year, based on a presentation at a scientific meeting.

The scientists combined DNA from skin cells of the monkey, a rhesus macaque, with unfertilized monkey eggs that had their own DNA removed. The eggs were grown into early embryos, from which stem cells were removed.

The researchers cautioned that even if their procedure could be used to produce human stem cells, it's far too inefficient to be used in medicine.

Human unfertilized eggs are in short supply and are cumbersome to obtain. The monkey work required 304 eggs from 14 female macaques to produce just two batches of stem cells, the scientists wrote.

Still, George Daley of the Harvard Stem Cell Institute, who was familiar with the work, told the AP it was a "a very important demonstration" that the process is feasible in primates, the group that includes monkeys and humans.

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