Human Stem Cells Made From Cloned Embryos

Scientists have made a long-sought—and controversial—breakthrough: They created stem cells from cloned human embryos for the first time, reports AP. In theory, the development by researchers at Oregon Health & Science University means that doctors might someday be able to grow tissue from an ailing patient's own DNA, thus reducing the chance of rejection in a transplant. Commonly cited examples are growing brain tissue to help a patient with Parkinson's disease, or pancreatic tissue to help diabetics.

It's "one landmark step in a very long journey," says an expert at Children's Hospital Boston who wasn't involved with the work. The Oregon scientists say they don't think the embryos used in their process could develop into babies, reports NBC News, but the procedure is nonetheless controversial because it requires that the embryos be destroyed. Nature notes that competing technology in the last decade has made the push toward embryonic stem cells less intensive, but adds that the new paper in Cell is sure to reignite the debate. The scientists used eggs from donors, and it took six years to replicate the success they had with monkey embryos. They chalked it up to a series of small revisions over the years instead of a single aha! moment. (More cloning stories.)