Stem cells—highly adaptable cells that can regenerate themselves almost without limit—could lead to cures for ailments ranging from paralysis to Parkinson's to Alzheimer's. Or they could lead to an ethical dead end, as Congress gears up to ban research on stem cells derived from human embryos. Two recent reports emphasize a possible compromise, adding new evidence that stem cells extracted from adults might be able to perform some of the same medical marvels as those taken from embryos.
In one study, researchers at the New York University School of Medicine extracted bone marrow cells from mice and then implanted them in a second group of mice that had been irradiated, killing the cells that produce insulin. The new cells incorporated themselves into the pancreas and took over for the dead cells, allowing the irradiated mice to manufacture their own insulin again. Meanwhile, an independent team at Argonne National Laboratory in Illinois applied a cellular growth factor to various cell lines and managed to transform one kind of human white blood cell into many other cell forms, including neurons and skin cells.
These findings show how much scientists have yet to learn about the workings of stem cells. "These are really early days in this field," says Ronald McKay, a molecular biologist at the National Institutes of Health who studies embryonic and adult stem cells. He argues that the best path to progress is to experiment with both cell types simultaneously. "They're completely linked. We need to understand how cells change through life, and how these stem cell populations change," he says. Politics might prohibit that approach. The House of Representatives voted overwhelmingly in February to ban research on stem cells from cloned embryos. A Senate vote on this issue is pending.