Nerve Regrowth

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Nerve Regrowth
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Damaged Spinal Cord Found to Have Great Potential for Nerve Regrowth

CLEVELAND, July 15 /PRNewswire - Injury to the spinal cord can often result in dire consequences, as witnessed in actor Christopher Reeve's paralysis following a horseback riding accident.

In a study published today, neuroscientists at Case Western Reserve University (CWRU) School of Medicine show tremendous capacity for nerve fiber regeneration from transplanted adult nerve cells in adult spinal cords with large lesions. While the research was not designed to restore function in test animals, their work demonstrates an important new basic principle that the damaged spinal cord has, in fact, far greater potential for nerve regeneration than had been thought possible. Their work further points the finger at molecules in scar tissue at the direct site of injury as being the major obstacle to spinal cord regeneration.

In the Journal of Neuroscience, Stephen J.A. Davies, Ph.D., Jerry Silver, Ph.D., and colleagues at CWRU report that they transplanted sensory nerve cells from adult, green fluorescent mice into the damaged spinal cord of rats. The spinal cord, specifically the dorsal column sensory pathways, had been cut with a knife. The adult nerve cells, which carry their own fluorescent marker, were transplanted from the mice into the degenerating spinal cord tissue beyond the direct site of injury in host rats. This was accomplished by using a micro-transplantation technique developed by Davies which itself causes no further damage to the rat spinal cord.

"Nobody would have put money on these nerve cells regenerating," said Silver, a CWRU professor of neurosciences. "This paper shows the most robust and efficient regeneration of nerve cell axons in the chronically injured spinal cord to date."

Current, dominating theory holds that both normal as well as injured adult white matter tracts in the spinal cord are overtly inhibitory because they contain molecules within the myelin sheaths that signal nerve fibers not to grow. "One might suspect that the added amount of damage to the white matter pathways in our study, all that degeneration and inflammation, would produce a nerve fiber pathway potently inhibitory for nerve growth," Silver said. "But we saw scads of axons," he said. "Amazingly, after a full three months, there is still potential for regeneration, away from the injury."

When the researchers looked at the lesion site, they saw proteoglycan molecules, which Silver's laboratory has strongly correlated in past studies with the cessation of axon growth. Davies said, "Not only do the regenerating axons stop upon reaching the scar, but they change the shape of their tips and become 'dystrophic' with malformed endings. This is the hallmark of regeneration failure."

The researchers suggest that their study offers hope that removing or overcoming the molecular obstacles in the scar may unlock potential for nerve regeneration in the spinal cord.

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