News that Chinese researchers have succeeded in growing healthy living mice from mouse skin cells takes scientists a significant step closer to human cloning, and reopens the debate about the ethics of such reproductive techniques. The new feat — in which animals were grown from cells that had been reverted to their embryonic state — is technically different from cloning. But the outcome is the same in both cases: a genetically identical copy of the donor animal.

“We are fast-forwarding to the era of designer babies,” said Dr Robert Lanza, chief scientific officer at the Advanced Cell Technology Inc. in Worcester, Massachusetts, who was not involved in the studies. “We have gone from science fiction to reality.” Cloning, in which the nucleus is removed from a cell and implanted in a fertilised egg, has never been achieved in humans. Nor has the new technique — using what is known as induced pluripotent stem, or iPS, cells — been tested in them. Because that process works in mice, however, it should work in humans, Lanza added.

“We now have the technology to create iPS cells from skin or hair follicles,” he said. “There are a dozen approaches that could be used. What’s troubling is that if you have a piece of skin from anybody — Albert Einstein, Marilyn Monroe, Michael Jackson — you could create a child.”

Said biologist Kathrin Plath of the University of California, Los Angeles’ Broad Center of Regenerative Medicine and Stem Cell Research, who was not involved in the research: “That is an experiment that shouldn’t be done. If you look back at the mouse cloning experiments,” she noted, many died shortly after birth or suffered from genetic abnormalities.

The researchers involved in the new research agreed. “It would not be ethical to attempt to use iPS cells in human reproduction,” said Fanyi Zeng of the Shanghai Jiao Tong University. “It is important for science to have ethical boundaries.”

Her study, she added, was “in no way meant as a first step in that direction”.

But even as the finding revives the cloning issue, it should relieve much of the debate about the morality of using embryonic cells in research on curing diseases like diabetes and Parkinson’s disease because it provides a source of tissue that can be obtained without destroying foetuses.

Researchers first produced iPS cells two years ago, but there have been lingering doubts about whether the cells are truly identical to embryonic cells or instead are capable of producing only some types of body cells.

The new results appear to erase those doubts. The results also open the door to applications beyond producing stem cells for medicinal purposes, including the production of endangered species and the reproduction of prized farm and other animals.

The reports “show that iPS cells are identical to embryonic stem cells,” Plath said. “It hadn’t worked before, so it wasn’t clear that it would ever work.”

The results are “comforting, because there has been a lingering concern that iPS cells had failed in this particular assay,” said biologist Robert Blelloch of UC San Francisco’s Broad Center for Regeneration Medicine and Stem Cell Research, who was not involved in the research.

But he cautioned that the teams were successful in only a few out of many attempts.

In the new studies, “the method of producing iPS cells didn’t change,” Blelloch said. “They used the same methods and materials everybody else is using.”

He characterised their research as a “brute force effort” in which enough attempts yielded success.

The more successful of the studies, by Zeng and colleagues at the Chinese Academy of Sciences in Beijing, created 37 iPS cell lines that could be grown in the laboratory. Three of those lines produced 27 live offspring by tetraploid complementation. Some of the mice have mated and have produced more than 100 healthy second- and 100 third-generation mice.

Zeng cautioned that some of the first-generation living mice had abnormalities, although she did not say how many and what those abnormalities were. That, she said, will be the subject of a future paper.

The second team, from the National Institute of Biological Sciences in Beijing, achieved only four births, with only one mouse making it to adulthood.