A new cloning technique has passed the ultimate scientific test showing that it is possible to generate healthy animals from single skin cells without the need for sexual reproduction.
Scientists have shown that these clones grow into healthy adults capable of producing their own offspring by normal breeding.
The technique, highlighted by The Independent last year and radically different from the cloning method used more than 10 years ago to produce Dolly the sheep, opens up the possibility of producing stem cells from a patient's skin to generate human tissue and possibly organs for transplant medicine. It also raises the prospect of it being used as a reproductive technique to help endangered species produce cloned offspring in captivity. But scientists have warned that it would be unethical – and illegal in Britain – to contemplate adapting the method to help infertile couples have their own biological children.
Two teams of Chinese scientists working independently said yesterday that they had produced live mice by genetically modifying mouse skin cells to convert them into embryonic-like cells called induced pluripotent stem cells (iPS cells). They both used a "gold standard" method to prove that the iPS cells were truly "pluripotent", meaning that they were capable of developing into complete adult animals.
Such iPS cells have already been shown to be capable of developing into the many different specialised tissues of the body but the two studies, to be published in the journals Nature and Cell Stem Cell went further by showing that the iPS cells could produce adult mice – clones of the mice that provided the original skin cells.
One of the groups, led by Professor Qi Zhou of the State Key Laboratory of Reproductive Biology in Beijing, used the technique to produce 27 cloned mice which went on to produce more than 300 second- and third-generation offspring by normal sexual reproduction.
The other group, led by Shaorong Gao of the Chinese National Institute of Biological Sciences in Beijing produced just one cloned embryo that survived to adulthood. Both groups used "tetraploid" embryos – which cannot develop on their own into viable foetuses – to prove that the iPS cells could produce healthy clones.
It would be unethical and illegal in Britain to use tetraploid human embryos to demonstrate the pluripotency of human iPS cells, says Professor Robin Lovell-Badge, a stem cell scientist at the MRC Institute for Medical Research in Mill Hill, north London.
"This work is important as it demonstrates that the reprogramming methods applied to mouse cells can give truly pluripotent cells, but it has to be stressed that it is not directly applicable to similar work with human cells," he said.
However, Robert Lanza, the chief scientific officer at the American biotechnology company Advanced Cell Technology, said that there was little doubt that the same sorts of techniques could be applied to human cells to produce cloned children or "designer" babies, created by inserting iPS cells into an IVF embryo.
"In the excitement surrounding the generation of iPS cells, a number of serious scientific and ethical ramifications have been overlooked," he said.