The world nudged closer to an era of Frankenstein science after an animal killed and frozen 16 years ago was cloned.
Ethical watchdogs branded the experiment disturbing and warned it could lead to people being ‘brought back to life’ after decades or centuries in deep freeze.
In a pioneering experiment, researchers took tissue from a laboratory mouse frozen in the early 1990s and used it to create a healthy, fully formed clone.
It is the first time scientists have been able to clone a frozen animal.
The scientists say their work will benefit mankind – and could be used to bring back extinct animals such as the woolly mammoth or sabre tooth tiger.
But critics say the experiment brings the world closer to the day when people attempt to clone long dead relatives stored in cryopreservation clinics.
It could also lead to a macabre new industry – where people leave behind ‘relics’ of their bodies in freezers in the hope that they could one day be cloned.
The latest experiment comes more than 11 years after British scientists stunned the world with Dolly, the first sheep to be cloned from an adult.
Cloning is the creation of life with just one parent. It involves taking a single cell from an animal or human, using the cell to create an embryo and implanting that embryo in a surrogate mother.
The resulting clone is a genetic copy of the original animal or person.
Although scientists have been able to clone a host of animals – including sheep, mice, cattle, goats, pigs, cats and dogs – they have never before been able to clone a frozen animal.
Previously it was thought that ice crystals from the freezing process would shred and destroy the DNA in cells, making them unusable.
Josephine Quintavalle, an expert on the ethics of fertility and reproduction, said the experiment pushed the boundaries of acceptable science even further.
‘This kind of research raises disturbing questions about what happens to our bodies – and any tissue we leave for medical science – after we die,’ she said.
‘It means that tissue donated for medical research, or stored in laboratories, could be used many years later for cloning research.
‘It has never been more important that when people leave tissue for research, the consent should be very specific given the potential for all kinds of scientific developments in the future.’
But British scientists welcomed the breakthrough.
Prof Malcolm Alison, biologist at Barts and The London School of Medicine and Dentistry, said: ‘It is absolutely fascinating.
‘The researchers obtained cell nuclei from mice that had been deep frozen for 16 years and then generated new mice by the same technology that created Dolly.
‘While 16 years is not a long time for cells to be frozen – IVF clinics often have viable sperm frozen for longer periods – there are no scientific reasons why extinct animals like mammoths could not be similarly generated.’
The research was carried out by Dr Teruhiko Wakayama and colleagues at the Centre for Developmental Biology in Kobe, Japan.
He took brain cells from ordinary dead male mice stored in a freezer for up to 16 years and removed their nuclei – the blobs in the centre of cells that contain DNA.
Each cell’s nucleus was injected into a hollowed-out egg cell from a female mouse. When the egg was fused with electricity, it began to divide and grow just like a newly conceived embryo.
After a few days, the embryo clone was implanted into the womb of a surrogate mouse and three weeks later, the clone was born.
‘These cloned mice did not show any abnormalities and grew to adulthood,’ the researchers report in the journal Proceedings of the National Academy of Sciences.
The researchers tried to clone mice from other parts of the body, but found that brain cells were the most successful.
They believe the high fat content of brains – and the extra protection that brains get from the skull – could reduce the damage to brain cells when bodies freeze.
Even using brain cells, the success rate was low.
In total, more than 1,100 attempts using frozen tissue, produced just seven healthy clones. More than 500 embryo clones died after being implanted into the wombs of a surrogate mother.
Helen Wallace of Genewatch UK said: ‘Cloning produces high failure rates because many eggs and fetuses do not develop normally. It would therefore be extremely dangerous for both mothers and their babies to attempt this kind of experiment in humans.’
Dr Robin Lovell-Badge of the Medical Research Council’s National Institute for Medical Research in London said the breakthrough could help scientists researching disease.
‘It could be a valuable practical tool – not just for work on animals but on humans as well,’ he said.
‘There might be human material stored by laboratories that you could work on. If it came from people with genetic diseases, it could help explore the causes of those disease.’
However, he suspects it will have most use in the research on extinct animals, such as mammoths, whose bodies are preserved for thousands of year in ice. It could also be used on frozen cavemen recovered from glaciers.