“That raises questions of where we would want to go,” he added.
Still, the techniques used to make those clones are not new, and other researchers previously had initiated the process in primates.
An initial step was reported in 2007 by Shoukhrat Mitalipov at Oregon Health and Science University. He and his colleagues removed skin cells from a 9-year-old macaque and inserted them into eggs from which the original DNA had been removed.
The eggs adopted genes from the inserted cells, and the resulting clones were grown to an early embryo stage. Dr. Mitalipov and his colleagues did similar work with human embryos in 2013.
The researchers, led by Qiang Sun, director of the primate research facility at the Chinese Academy of Sciences Institute of Neuroscience, began with cells taken from an aborted female monkey fetus.
From those, he and his colleagues created 149 early embryos, clones whose DNA was entirely derived from the fetal cells. Seventy-nine embryos survived in the lab, apparently healthy enough to transfer into the uteruses of surrogate monkey mothers.
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Four of those surrogates remained pregnant, but two soon miscarried. In the end, there were two live births.
The investigators say they followed international guidelines for animal research set by the National Institutes of Health. They anticipate that the method could be used to produce monkeys for research. (The United States, however, is backing away from the use of primates in medical research.)
The genes of cloned monkeys could be manipulated before the process begins, yielding animals that have edited genes in every cell of their bodies, the researchers suggested. This might allow scientists to probe the genes’ functions and to test experimental drugs on monkeys custom-made to have various genetic conditions.
The scientists tried cloning adult cells, but those attempts failed. The older a starting cell, the more difficult it is to clone and the more likely the resulting embryo or fetus will be miscarried in a surrogate female.
If scientists wanted to create a monkey identical to an adult, or even an adolescent, this method so far would not succeed. And the technique used by the Chinese scientists is still a long way from producing human babies, even if that were ethically permissible.
“It is unlikely it can be applied to humans,” Dr. Mitalipov said.