CLONED embryos have been created from an adult monkey for the first time, leading scientists to speculate that cloning human embryos using stem-cell therapies is a significant possibility.
The success in the United States, which has been verified by independent scientists, provides the first proof that viable cloned embryos can be produced from primates, which many experts had feared would be so technically demanding that it would be impossible to achieve.
Though further work is required before the technique can be applied to human cells, it suggests that it will be feasible to clone embryos from the DNA of living patients, and to derive working stem cells from them. These embryonic stem (ES) cells could then be transplanted to treat diseases such as Parkinson's and diabetes without fear of rejection by the body's immune system.
Such therapeutic cloning has been a goal for medical research since the birth of Dolly the sheep was announced in 1997, but that initial hope has been tempered by the apparent complexity of primate cloning. Although some monkey embryos have been cloned before, they have always died before reaching the stage at which stem cells can be extracted.
Claims by a South Korean team to have cloned human embryos and extracted stem cells generated widespread excitement in 2005, but these were later revealed to have been fraudulent. The only human embryo to have been cloned so far, by a British team, died almost immediately. These problems had led many scientists to speculate that primate cloning was so difficult that therapeutic cloning would always remain impractical.
A group led by Prof Shoukhrat Mitalipov, of the Oregon National Primate Research Centre, has now created two colonies of ES cells from embryos cloned from the DNA of an adult male rhesus macaque monkey called Semos, named after the ape god in the film Planet of the Apes.
Nuclei from Semos' skin cells were removed and placed into 304 eggs from 14 female monkeys. The scientists attribute their success to a new technique for handling the eggs during this nuclear transfer process.
Prof Mitalipov first announced his results at a conference in Cairns, Australia, in June. The research has now been peer-reviewed, and was published online yesterday in the journal Nature.
As claims about cloning have often met extreme scepticism, since the disgrace of Woo Suk Hwang, the Korean scientist who faked supposedly pioneering human research, Nature also took the rare step of commissioning an independent assessment of Prof Mitalipov's results before publishing them.
The analysis by David Cram, Bi Song and Alan Trounson of Monash University, Melbourne, has confirmed beyond doubt that the two ES cell lines are true clones of Semos. (©The Times, London)