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NEWS New Orleans, Louisiana, US, November 2000 Single shot The ability of stem cells to migrate may mean one injection could repair widespread nerve damage Neurobiologists have helped paralysed mice regain the partial use of their legs. Researchers at John Hopkins University in Baltimore gave the mice an injection of neural stem cells into the spine. Stem cells can develop into every type of cell in the nervous system. Some of the stem cells matured into neurons and replaced nerve cells that had died off, the researchers found. Within a few weeks more than half the mice were able to place both pads of their feet on the floor. Although the mice never fully regained the ability to walk, the study shows for the first time that it may be possible to use stem cells to repair wide spread nerve damage in people. Right on target John Gearhart and his colleagues Jeffrey Rothstein and Douglas Kerr infected mice with a Sindbis virus which destroys nerve cells in the spinal cord. "The animal is left completely and permanently paralysed," says Kerr. The effect mimics an inherited neurological disorder in humans known as spinal motor atrophy, which affects more than 1 in 20,000 infants. Next, the researchers harvested neural stem cells from mouse embryos and injected them into the base of the spines of the paralysed mice. The team then tracked the progress of the cells, which are distinguished by a particular genetic marker. Neurons killed off by disease or injury are seldom replaced naturally. But the stem cells travelled the length of the spine in the spinal fluid, replacing the damaged nerves on the way. "They preferentially go to the right site as if the death of motor neurons attracts them," Kerr says. Since the spinal fluid bathes the brain as well as the spine, a single injection could work on the entire nervous system. Choosing a vintage Kerr hopes that future tests will restore even more leg movement. One way to do this may be to allow the stem cells to mature further before injecting them. But the researchers will have to be careful. If the cells differentiate too much before injection, they will lose the ability to migrate along the spinal cord. If the cells are too undifferentiated, they could grow into other cell types or even become cancerous. These problems must be worked out before trying the technique in humans, Kerr says. Scientists have already injected neural stem cells into the brains of patients with Parkinson's, hoping that the cells would replace a type of neuron missing in the disease. But they had limited success. This research was presented at a conference in New Orleans, organised by the US-based Society for Neuroscience. New Scientist's full coverage of the conference is here: http://www.newscientist.com/conferences/ Correspondence about this story should be directed to [log in to unmask] 1337 GMT, 6 November 2000 Jonathan Knight, New Orleans http://www.newscientist.com/conferences/confarticle.jsp?conf=soneu200011&id=ns9999136 [log in to unmask]