Researchers from Japan and Wisconsin reported Tuesday that they had reprogrammed mature human cells to behave almost exactly like embryonic stem cells, a biological breakthrough that instantly recasts the field's ethical, scientific and economic landscape.
By activating a handful of dormant genes, the researchers were able to coax the cells back in time to a point in embryonic development before they had committed to becoming a particular type of tissue.
The rejuvenated cells were able to grow into all the main tissue types in the body, including muscle, gut, cartilage, neurons and heart cells.
The discovery provides a clear road map for creating genetically matched replacement cells that could be used to treat patients for a variety of diseases -- the personalized biological repair kits that are the ultimate goal of regenerative medicine.
For scientists, the method offers a straightforward alternative to the tricky and still unsuccessful cloning process in which a patient's DNA is inserted into a human egg to create a cloned embryo whose stem cells theoretically could be harvested.
The technique also bypasses the thorny debate over the morality of destroying embryos in the cause of alleviating human suffering.
"It's a win-win," said Richard Doerflinger, secretariat for pro-life activities at the U.S. Conference of Catholic Bishops in Washington. "The scientists can get all the benefits they think they might get from embryonic stem cells, and the rest of us can applaud and support it."
Several key hurdles remain before the technique is ready for clinical use. The viruses employed to turn on the genes cause mutations that can lead to cancer, and one of the genes itself also has a tendency to cause tumors.
But scientists said solutions to these problems were in the works.
"This is a tremendous scientific milestone -- the biological equivalent of the Wright brothers' first airplane," said Dr. Robert Lanza, a stem cell researcher at Advanced Cell Technology in Worcester, Mass., who wasn't involved in the research.
The White House praised the work as an example of cutting-edge research that was conducted "within ethical boundaries."
"The president believes medical problems can be solved without compromising either the high aims of science or the sanctity of human life," Press Secretary Dana Perino said.
