Two teams of scientists reported yesterday that they had 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 need to destroy embryos has made stem cell research one of the most divisive issues in American politics, pitting President Bush against prominent Republicans like Nancy Reagan, and patient advocates who hoped that stem cells could cure diseases like Alzheimer’s. The new studies could defuse the issue as a presidential election nears. 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 today’s drawbacks will prove to be temporary. Researchers and ethicists not involved in the findings say the work, conducted by independent teams from Japan and Wisconsin, 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 White House said that Mr. Bush was “very pleased” about the new findings, adding that “By avoiding techniques that destroy life, while vigorously supporting alternative approaches, President Bush is encouraging scientific advancement within ethical boundaries.” The new method sidesteps other ethical quandaries, creating stem cells that genetically match the donor without having to resort to cloning or the requisite donation of women’s eggs. Genetically matched cells would not be rejected by the immune system if used as replacement tissues for patients. Even more important, scientists say, is that genetically matched cells from patients would enable them to study complex diseases, like Alzheimer’s, in the laboratory. Until now, the only way most scientists thought such patient-specific stem cells could be made 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. The new cells in theory might be turned into an embryo, but not by simply implanting them in a womb. “It really is amazing,” said Dr. Leonard Zon, director of the stem cell program at Children’s Hospital Boston at Harvard Medical School. And, said Dr. Douglas A. Melton, co-director of the Stem Cell Institute at Harvard University, it is “ethically uncomplicated.” For all the hopes invested in it over the last decade, embryonic stem cell research has moved slowly, with no cures or major therapeutic discoveries in sight. The new work could allow the field to vault significant problems, including the shortage of human embryonic stem cells and restrictions on federal financing for such research. Even when scientists have other sources of financing, 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 today in Cell, in a paper by Shinya Yamanaka of Kyoto University and the Gladstone Institute of Cardiovascular Disease in San Francisco, and in Science, in a paper by James A. Thomson and his colleagues at the University of Wisconsin. Dr. Thomson’s work received some federal money. While both groups used just four genes to reprogram human skin cells, two of the genes used differed from group to 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 very much like human embryonic stem cells but were called “induced pluripotent stem cells,” meaning cells that can change into many different types. “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 under way, Dr. Thomson and others say, it would be premature to abandon research with stem cells taken from human embryos.