Breakthrough in stem cell research could ease ethical concerns
Two teams of scientists are reporting Tuesday that they turned human skin cells into what appear to be embryonic stem cells without having to make or destroy an embryo — a feat that could quell the ethical debate troubling the field.
All they had to do, the scientists said, was add four genes. The genes reprogrammed the chromosomes of the skin cells, making the cells into blank slates that should be able to turn into any of the 220 cell types of the human body, be it heart, brain, blood or bone. Until now, the only way to get such human universal cells was to pluck them from a human embryo several days after fertilization, destroying the embryo in the process.
The reprogrammed skin cells may yet prove to have subtle differences from embryonic stem cells that come directly from human embryos, and the new method includes potentially risky steps, like introducing a cancer gene. But stem cell researchers say they are confident that it will not take long to perfect the method and that Tuesday's drawbacks will prove to be temporary.
Researchers and ethicists not involved in the findings say the work should reshape the stem cell field. At some time in the near future, they said, today's debate over whether it is morally acceptable to create and destroy human embryos to obtain stem cells should be moot.
“Everyone was waiting for this day to come,” said the Rev. Tadeusz Pacholczyk, director of education at the National Catholic Bioethics Center. “You should have a solution here that will address the moral objections that have been percolating for years,” he added.
The two independent teams, from Japan and Wisconsin, note that their method also creates stem cells that genetically match the donor without having to resort to the controversial step of cloning. If stem cells are used to make replacement cells and tissues for patients, it would be invaluable to have genetically matched cells because they would not be rejected by the immune system. Even more important, scientists say, is that genetically matched cells from patients will enable them to study complex diseases, like Alzheimer's, in the lab.
Until now, the only way to get embryonic stem cells that genetically matched an individual would be to create embryos that were clones of that person and extract their stem cells. Just last week, scientists in Oregon reported that they did this with monkeys, but the prospect of doing such experiments in humans has been ethically fraught.
But with the new method, human cloning for stem cell research, like the creation of human embryos to extract stem cells, may be unnecessary.
“It really is amazing,” said Dr. Leonard Zon, director of the stem cell program at Harvard Medical School's Children's Hospital.
And, said Dr. Douglas Melton, co-director of the Stem Cell Institute at Harvard University, it is “ethically uncomplicated.”
For all the hopes invested in it over the past decade, embryonic stem cell research has not yet produced any cures or major therapeutic discoveries. Stem cells are so malleable that they may pose risk of cancer, and the new method of obtaining stem cells includes steps that raise their own safety concerns.
Still, the new work could allow the field to vault significant problems, including the shortage of human embryonic stem cells and restrictions on U.S. funding for such research. Even when scientists have other sources of funding, they report that it is expensive and difficult to find women who will provide eggs for such research.
The new discovery is being published online Tuesday in Cell, in a paper by Shinya Yamanaka of Kyoto University and the Gladstone Institute for Cardiovascular Disease in San Francisco, and in Science, in a paper by James Thomson and his colleagues at the University of Wisconsin.
While both groups used just four genes to reprogram human skin cells, two of the four genes used by the Japanese scientists were different from two of the four used by the American group. All the genes in question, though, act in a similar way – they are master regulator genes whose role is to turn other genes on or off.
The reprogrammed cells, the scientists report, appear to behave exactly like human embryonic stem cells.
“By any means we test them they are the same as embryonic stem cells,” Dr. Thomson says.
He and Dr. Yamanaka caution, though, that they still must confirm that the reprogrammed human skin cells really are the same as stem cells they get from embryos. And while those studies are underway, Dr. Thomson and others say, it would be premature to abandon research with stem cells taken from human embryos.