Cloned monkeys, a first, spur inevitable questions of when human clones will follow

Elizabeth Weise | USA TODAY

Show Caption Hide Caption Move over, Dolly: Scientists clone two monkeys For the first time, researchers have used the cloning method that produced Dolly the sheep to create two healthy monkeys, bringing science an important step closer to being able to do the same with humans. (Jan. 24)

SAN FRANCISCO — In a feat that raises questions about how close the cloning of humans may be, scientists in China announced on Wednesday they have successfully cloned two long-tailed macaque monkeys.

The cloning of primates was long thought to be fundamentally more difficult than horses, sheep and other mammals and therefore much further away.

"It’s a significant advance. Nobody has previously been able to create a cloned non-human primate,” said Arnold Kriegstein, director of the stem cell center at the University of California at San Francisco.

The monkeys were born to surrogate macaque monkey mothers by caesarian section ten days apart, in a lab in Shanghai. They are the first primates to be cloned using tissue cells. The cloning was reported in the prestigious scientific journal Cell.

Named Zhong Zhong and Hua Hua, the monkeys were produced using some of the same cloning techniques that created Dolly the sheep 22 years ago. Their names are alliterations on a Chinese word for China, 中华 or Zhonghua.

In a news conference in China, one of the paper’s authors, Muming Poo, said the work was done to produce primates that could be used as models to understand human medical issues.

The team has no intention of using their techniques to clone humans, said Poo, who directs the Institute of Neuroscience at the Chinese Academy of Sciences Center for Excellence in Brain Science and Intelligence Technology.

How it was done

The Chinese researchers used a cloning technique called somatic cell nuclear transfer to create the monkeys. The same technique has been used to clone 23 different mammal species so far, including sheep, mice, cattle, pigs, cats and dogs.

In this technique, the DNA from a single cell is inserted into a egg that has had its DNA removed. Using chemicals and other treatments, the scientists coax the DNA and egg to fuse together. A tiny amount of electricity is applied to make the egg begin dividing.

The resulting embryo is implanted into a surrogate mother of the same or a similar species. The baby is an exact genetic replicate of the animal from which the original cell was taken.

That said, the process developed by the team at the Chinese Academy of Sciences Institute of Neuroscience in Shanghai is far from perfect.

They started with 127 eggs, created 79 long-tailed macaque monkey embryos using cells from fetal connective tissue, which they implanted into 21 surrogate long-tailed macaque monkey mothers.

Only six of those became pregnant and only Zhong Zhong and Hua Hua survived.They are in good health and continue to grow normally, the scientists reported.

Cloning humans next?

Kriegstein notes the Chinese team attempted to clone macaques using cells from an adult monkey but were unable to do so. They only succeeded using cells from aborted macaque fetuses.

That’s important because it’s a sign that cloning humans isn’t necessarily just around the corner, said Hank Greely, director of the Center for Law and the Biosciences at Stanford University.

“If anybody ever wants to do human reproductive cloning, they’re not going to want to clone a fetus,” he said.

Cloning macaque monkeys is also by no means proof humans can be cloned, said Greely. If you've cloned one primate, you haven't cloned them all, he said.

The numbers are also gruesome. For the adult cell experiment, the Chinese researchers began with 290 macaque eggs, created 192 embryos and attempted to transplant 181 of those to 42 surrogate monkey mothers. That resulted in 22 pregnancies and just two baby monkeys born alive by caesarian section, but both died of respiratory failure within 30 hours.

“It’s very inefficient and unsafe — and if you tried that with humans you’d be criminally reckless,” Greely said.

Not likely in the United States

The Chinese team was clear that its work is meant to better allow diseases to be studied in primates, a common technique for medical researchers.

“You could create many cloned monkeys that all have the same genetic defect, then you would have a very powerful approach to study that disease” and something that can’t be done in humans, said UCSF's Kriegstein.

But it's not a surprise the breakthrough happened in China, he said.

That’s in part because China has invested heavily in basic research in recent years but also because European and U.S. scientists have moved away from doing research using monkeys and apes due to ethical concerns.

“The trend in recent years has been to do less and less non-human primate research, largely because of the sensitivity surrounding using primates for research purposes. Many of the primate colonies in the United States have been closed down and the number of researchers working on non-human primates has dropped,” he said.