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Spinal Motor Nerves Can Regenerate After Injury

Regeneration occurs after overexpression of neurotrophin receptors

FRIDAY, April 10 (HealthDay News) -- Adult corticospinal motor neurons, which are critical for motor function in higher species but are particularly resistant to regeneration after injury, can be induced to regenerate if growth-inducing neurotrophin receptors are overproduced, according to the results of a study published online April 9 in the Proceedings of the National Academy of Sciences.

To see whether enhancing intrinsic neuronal growth mechanisms could promote the regeneration of adult corticospinal axons after injury, Edmund R. Hollis II, Ph.D., and colleagues from the University of California San Diego in La Jolla overexpressed trkB in layer V corticospinal motor neurons in rats. They note that trkB is the receptor for BDNF, a growth factor that can promote neurite outgrowth.

The researchers found that after subcortical axotomy, corticospinal axons regenerated into lesion sites expressing BDNF, but only when trkB was overexpressed. Mutation of part of trkB necessary to activate downstream signaling pathways eliminated regeneration, according to the study.

"These findings demonstrate that regeneration of adult corticospinal axons can be induced by modulation of the intrinsic neuronal growth state," Hollis and colleagues conclude. "By overexpressing growth-inducing neurotrophin receptors and the trafficking of these receptors to the axonal compartment, regeneration of this refractory neuronal system, which is critical for motor function in higher species, can be achieved."

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