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First cloning of monkey embryo raises hope of a great leap in medical science
« on: 2007-11-17 15:21:07 » |
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First cloning of monkey embryo raises hope of a great leap in medical science
Source: The Times Online
Authors: Mark Henderson (Science Editor)
Dated: 2007-11-17
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. The cells could also be used to study these conditions in the laboratory and to develop new treatments.
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 and attempts to implant them into the womb have also failed.
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 Professor 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’s 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.
Professor 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 Professor Mitalipov’s results before agreeing to publish 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. “Proof of concept for creating somatic cell nuclear transfer primate stem cells is firmly established,” they concluded.
The low success rate of 0.7 per cent means that it is still too early to use the new technique to attempt to clone human embryos, especially given the shortage of human eggs available for such research, scientists say. It also means that the method would not yet be a practical way of cloning human embryos for reproductive purposes.
The achievement, however, does suggest that human therapeutic cloning is a possibility. It is also likely to strengthen calls for an international ban on reproductive cloning, as was recently made by an expert panel of the United Nations.
Professor Ian Wilmut, of the University of Edinburgh, who led the team that cloned Dolly the sheep, said: “The group in Oregon are to be congratulated on this achievement. The ability to produce embryo stem cells from cloned human embryos would create entirely new opportunities to study inherited diseases.”
Anna Krassowska, research manager of the UK Stem Cell Foundation, said: “This puts us one important step closer to developing patient-specific ES cell lines, not only for possible therapies in the future but for drug discovery and research into serious diseases. Publishing the independent verification simultaneously was a judicious move, which will put to rest the doubts that would otherwise exist postHwang.”
Professor Robin Lovell-Badge, of the National Institute for Medical Research, who described the work as “very exciting”, said: “The paper is not only the best but also by far the most useful work to date showing that it is possible to carry out the cloning procedure and to obtain ES cell lines in primates.”
From Dolly to Semos
1996 Birth of Dolly the sheep, above, the first mammal cloned with somatic cell nuclear transfer technique. The achievement was announced in 1997
2002 First cloned cat, Cc or Copy Cat, born. Other animals to be cloned include rats, mice and cows
2002 Raelian cult claims birth of first cloned human baby. Story discounted as fantasy
2004 South Korean team led by Woo Suk Hwang announces first cloned human embryo
2005 Hwang’s team announces further human clones, from which stem cells have been extracted
2005 Scientists at Newcastle University produce cloned human embryo, but it dies before stem cells can be removed
2005 Hwang’s human research shown to have been faked. His papers are withdrawn by the journals that published them
2007 Announcement that US scientists have cloned monkey embryos and extracted stem cells
Source: Times database
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