PARIS: In work that could spur cloning of human cells for medical research, scientists confirm their creation of the first cloned monkey embryos.
In a paper published online by the British journal Nature, a team in the U.S. said they had created cloned embryos of rhesus macaques, using the same method that famously led to Dolly the Sheep and other genetically duplicated animals.
Cosmos Online first reported the discovery in June 2007, when lead researcher Shoukhrat Mitalipov announced it at a conference in Cairns, Australia (see, Human cloning closer than ever before, Cosmos Online).
Path to human clones
It represented the first time that this technique has been successfully used to create cloned primate embryos. Mitalipov’s team of the Oregon National Primate Research Centre in Beaverton, U.S., subsequently generated two lines of embryonic stem cells from the embryos.
Dolly, the world’s first cloned animal, was created in 1996, by using so-called somatic cell nuclear transfer (SCNT) in which the genetic core of an egg is removed and replaced with the nucleus of an adult cell. The egg is then stimulated with chemicals or a jolt of electricity to prompt its division. The list of other cloned creatures using SCNT includes mice, pigs, cats, cows and dogs.
Until now, though, there has been no cloned primate, for researchers have encountered obstacles that cause cell development to be catastrophically flawed.
Work on primate cloning has also stirred controversy among ethicists, who say it could open the door to cloning human beings, not just cells.
Researchers distinguish between “reproductive cloning” of humans, in which a putative cloned baby would be born and “therapeutic cloning,” in which only cloned cells would be used for medical reasons and no baby would result.
Helen Wallace of Genewatch U.K., a group that monitors cloning and other activities in biotechnology, said the breakthrough would cause “a real worry” in some quarters that it would tempt a renegade scientist to create a cloned baby.
“The clear risk of an experiment [in human reproductive cloning] is of a deformed baby and maternal suffering,” she said. “In Britain, we don’t think that the technology is going to go that far because there are laws against reproductive cloning… However, in most countries around the world, there are no legal safeguards.”
Stem cells are immature cells that develop into the specific tissues of the body. Embryonic stem cells have the highest capability of all, because they can differentiate into any tissue. Scientists hope to be able to coax these cells into one day becoming replacement tissue for organs that are damaged or diseased.
Transplanted cells from a donor, though, run the risk of being attacked as intruders by the patient’s immune system. By creating stem cells that are programmed with the patient’s own DNA the risk of rejection would be skirted.
Clues to inherited disorders
Mitalipov’s team now say they collected 304 eggs, also known as oocytes, from 14 female rhesus macaques. The donor nucleus came from skin cells taken from an adult male monkey housed at the Oregon National Primate Research Centre.
The claim that the stem cells were an exact DNA copy of the donor monkey’s genetic code has been validated independently by a team led by David Cram of Monash University in Melbourne, Australia.
In a commentary published in the same issue of Nature, British scientist Ian Wilmut (the creator of Dolly) and colleague Jane Taylor of the Centre for Regenerative Medicine in Edinburgh, Scotland, said the new advance’s brightest benefits may lie not in creating replacement tissue from stem cells but in unlocking basic knowledge about inherited disorders.
By making patient-specific cells, doctors could obtain cells whose genome would provide tell-tale clues of disease. These cells could be compared with healthy counterparts to see what is wrong, and a library of drugs could then be screened to see if a treatment is available.
“Ultimately, this approach might lead to treatments for neurodegenerative diseases, some cancers and psychiatric disorders,” the pair said.