With a few strokes of genetic trickery, scientists have transformed mouse skin cells into embryonic stem cells and proved their potency by using the new cells to produce baby mice.
The experiments are seen as a major advance for regenerative medicine, which aims to custom-build tissues and cells to repair ailing and aging bodies.
Scientists caution there are serious safety issues that must be resolved before the techniques could ever be used on people, but they say the advance points to a new way of making embryonic stem cells for patients from their own cells.
There is no need to destroy embryos, and might allow researchers to sidestep many of the ethical objections now dogging stem-cell research.
Three different teams, one in Japan and two in the U.S., reported Wednesday in the journals Nature and Cell Stem Cell they have reprogrammed skin cells to an embryonic state.
"Neither eggs nor embryos are necessary," says Shinya Yamanka of Kyoto University, who pioneered the technique that's been replicated by the U.S. teams. All three groups individually used the cells to generate live mice.
The feat has the stem-cell world buzzing.
"It's pretty phenomenal," Michael Rudnicki, scientific director of Canada's Stem Cell Network and director of molecular medicine at the Ottawa Health Research Institute, said in an interview.
The skin cells reverted to embryonic stem cells, or a state that the scientists describe as nearly identical to it, after they added four genes to the skin cells. The genes triggered a process that made the cells become "pluripotent" and capable of turning into any type of cell found in the body, which is the hallmark of embryonic stem cells and what makes them so alluring.
"This is very exciting scientifically because these four genes can reprogram any cell, it would seem, to become an embryonic stem cell," says Rudnicki. The technique presents a possible "work around" that could eliminate the need to use embryos to generate cells for regenerative medicine, he says.
Until now the only way to obtain embryonic stem cells has been to take them from an embryo. Producing cells that are a genetic match for a patient would entail making a clone of that person and harvesting the cells when the cloned embryo is days old, which raises thorny ethical issues and is illegal in several countries, including Canada.
The new work promises cells free of such contentious issues.
"You could take a skin cell, or a blood cell, and reprogram it with these four genes to make embryonic stem cells," says Rudnicki. They could then be turned into any type of cell required for therapeutic use, be it neurons to treat Alzheimer's or insulin producing for diabetics.
He cautions that significant hurdles still need to be overcome.
"You wouldn't want any of these cells put into a person or they'd end up with tumours," Rudnicki says of the cell lines created for the experiments. He notes that one of the genes used to reprogram the cells is involved in cancer.
Yamanaka's team reports that 20 per cent of the mice produced from the reprogrammed cells developed cancer. He and his colleagues think the risk can be eliminated.
The three teams produced live mice from their reprogrammed cells by injecting them into days-old mouse embryos. The baby mice proved the reprogrammed cells can give rise to every kind of tissue type, including sperm and eggs, the co-called "germ line" cell that is passed on to the next generation.
"Germ line transmission is the final and definitive proof that these cells can do anything a traditionally derived embryonic stem cell can do," says Rudolf Jaenisch of the Massachusetts Institute of Technology, who led the team working at the Whitehead Institute for Biomedical Research.
Meanwhile, the scientists say cell lines taken from human embryos are still essential to researchers striving to understand their biology.
"We still need to work with embryonic stem cells, to compare them and understand them," says Rudnicki. His network has financed derivation of a few Canadian cell lines created from human embryos donated by couples who had undergone fertility treatment and no longer needed the extra embryos.
© CanWest News Service 2007
The experiments are seen as a major advance for regenerative medicine, which aims to custom-build tissues and cells to repair ailing and aging bodies.
Scientists caution there are serious safety issues that must be resolved before the techniques could ever be used on people, but they say the advance points to a new way of making embryonic stem cells for patients from their own cells.
There is no need to destroy embryos, and might allow researchers to sidestep many of the ethical objections now dogging stem-cell research.
Three different teams, one in Japan and two in the U.S., reported Wednesday in the journals Nature and Cell Stem Cell they have reprogrammed skin cells to an embryonic state.
"Neither eggs nor embryos are necessary," says Shinya Yamanka of Kyoto University, who pioneered the technique that's been replicated by the U.S. teams. All three groups individually used the cells to generate live mice.
The feat has the stem-cell world buzzing.
"It's pretty phenomenal," Michael Rudnicki, scientific director of Canada's Stem Cell Network and director of molecular medicine at the Ottawa Health Research Institute, said in an interview.
The skin cells reverted to embryonic stem cells, or a state that the scientists describe as nearly identical to it, after they added four genes to the skin cells. The genes triggered a process that made the cells become "pluripotent" and capable of turning into any type of cell found in the body, which is the hallmark of embryonic stem cells and what makes them so alluring.
"This is very exciting scientifically because these four genes can reprogram any cell, it would seem, to become an embryonic stem cell," says Rudnicki. The technique presents a possible "work around" that could eliminate the need to use embryos to generate cells for regenerative medicine, he says.
Until now the only way to obtain embryonic stem cells has been to take them from an embryo. Producing cells that are a genetic match for a patient would entail making a clone of that person and harvesting the cells when the cloned embryo is days old, which raises thorny ethical issues and is illegal in several countries, including Canada.
The new work promises cells free of such contentious issues.
"You could take a skin cell, or a blood cell, and reprogram it with these four genes to make embryonic stem cells," says Rudnicki. They could then be turned into any type of cell required for therapeutic use, be it neurons to treat Alzheimer's or insulin producing for diabetics.
He cautions that significant hurdles still need to be overcome.
"You wouldn't want any of these cells put into a person or they'd end up with tumours," Rudnicki says of the cell lines created for the experiments. He notes that one of the genes used to reprogram the cells is involved in cancer.
Yamanaka's team reports that 20 per cent of the mice produced from the reprogrammed cells developed cancer. He and his colleagues think the risk can be eliminated.
The three teams produced live mice from their reprogrammed cells by injecting them into days-old mouse embryos. The baby mice proved the reprogrammed cells can give rise to every kind of tissue type, including sperm and eggs, the co-called "germ line" cell that is passed on to the next generation.
"Germ line transmission is the final and definitive proof that these cells can do anything a traditionally derived embryonic stem cell can do," says Rudolf Jaenisch of the Massachusetts Institute of Technology, who led the team working at the Whitehead Institute for Biomedical Research.
Meanwhile, the scientists say cell lines taken from human embryos are still essential to researchers striving to understand their biology.
"We still need to work with embryonic stem cells, to compare them and understand them," says Rudnicki. His network has financed derivation of a few Canadian cell lines created from human embryos donated by couples who had undergone fertility treatment and no longer needed the extra embryos.
© CanWest News Service 2007
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