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New Study Gives Hope for Nerve Regeneration A study by a Packard Center scientist and his colleagues at Johns Hopkins makes an important step toward repair of nerves after they've been long damaged. The work, which involved rat models and stem cells from mice, is the first to show that nerve regeneration is possible, as long as six months after injury. The repaired nerves recovered about a quarter of their lost function. For some time, Center investigator Ahmet Höke has studied the changes that occur in nerve cells after injury. He's primarily focused on the peripheral nervous system (PNS)--nerves extending from the spinal cord out to skin, muscles and organs--where nerve repair is more likely to occur than in the spinal cord proper or the brain. "But even in the PNS, getting a piece of long-damaged nerve to regrow would be highly unusual," says Höke. The results of the current study, which was presented at the San Francisco meetings of the American Neurological Association in October, should help understand principles of regrowth that apply to all types of nerves. "Of course our goal down the line is therapy," he says. In this study, Höke's team used a model system of chronic nerve injury. The researchers severed a nerve in the leg, letting the free piece deteriorate for six months. Then, they connected a new, freshly-cut nerve to that segment to see if repair and regrowth through it was still possible. Most important, they injected neural stem cells from mice to the nerve area. The happy result was that, in models using the stem cells, nerve fibers grew from the healthy nerve through the formerly injured section. And though it wasn't 100 percent, electrical activity was restored. Recordings of nerve activity in the foot showed messages were getting through the previously injured leg nerve. Höke believes the success was due, in part, from stem cell secretion of a potent growth factor called GDNF. The team also had strong signs that natural systems that suppress nerve growth--nature's way of preventing nerve overgrowth--were damped down as a result of having stem cells at the injury site. "There's still work to do," says Höke. "We'd like to improve the recovery of nerve function so it's higher than 25 percent. We also need to identify more precisely what combination of growth factors and other agents are missing in chronically denervated nerves." "Dr. Höke's team has provided solid work that shows nerve repair
is a worthwhile direction for ALS research to take," says Jeffrey
Rothstein, director of the Packard Center for ALS Research at Johns Hopkins.
"We intend to help him continue." |
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