Portland scientists report cloning monkey embryos

American scientists reported Wednesday that they had cloned embryos from a 9-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 new work is important because someday researchers hope to use such a process in humans to make transplant tissue that’s genetically matched to patients, thus avoiding 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 and provide a good way to study the process. But until now, it hasn’t worked.

The advance is reported by Shoukhrat Mitalipov of the Oregon National Primate Research Center in Portland with colleagues there and elsewhere. Some media outlets, including The Associated Press, had reported their success earlier, 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, they wrote.