c-Jun Expression in Adult Rat Dorsal Root Ganglion Neurons: Differential Response after Central or Peripheral Axotomy

Dec 17, 1997Experimental neurology

c-Jun protein levels in adult rat sensory neurons after injury to central or peripheral nerve fibers

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Abstract

Following peripheral axotomy, c-Jun expression was upregulated substantially in 63% of dorsal root ganglion neurons after dorsal rhizotomy and fetal spinal cord transplant.

CNS neurons typically do not regenerate after injury, while PNS neurons generally do.
The role of specific genes in the regenerative response of injured neurons is not fully understood.
Increased expression of the immediate early gene c-jun may be associated with successful axonal regeneration.
Only 18% of DRG neurons expressed c-Jun after a central axotomy, compared to 63% after a central lesion combined with transplant.
These findings suggest that c-Jun expression may influence the regenerative capacity of neurons following both PNS and CNS injuries.

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The response of the mature central nervous system (CNS) to injury differs significantly from the response of the peripheral nervous system (PNS). Axotomized PNS neurons generally regenerate following injury, while CNS neurons do not. The mechanisms that are responsible for these differences are not completely known, but both intrinsic neuronal and extrinsic environmental influences are likely to contribute to regenerative success or failure. One intrinsic factor that may contribute to successful axonal regeneration is the induction of specific genes in the injured neurons. In the present study, we have evaluated the hypothesis that expression of the immediate early gene c-jun is involved in a successful regenerative response. We have compared c-Jun expression in dorsal root ganglion (DRG) neurons following central or peripheral axotomy. We prepared animals that received either a sciatic nerve (peripheral) lesion or a dorsal rhizotomy in combination with spinal cord hemisection (central lesion). In a third group of animals, several dorsal roots were placed into the hemisection site along with a fetal spinal cord transplant. This intervention has been demonstrated to promote regrowth of severed axons and provides a model to examine DRG neurons during regenerative growth after central lesion. Our results indicated that c-Jun was upregulated substantially in DRG neurons following a peripheral axotomy, but following a central axotomy, only 18% of the neurons expressed c-Jun. Following dorsal rhizotomy and transplantation, however, c-Jun expression was upregulated dramatically; under those experimental conditions, 63% of the DRG neurons were c-Jun-positive. These data indicate that c-Jun expression may be related to successful regenerative growth following both PNS and CNS lesions.

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c-Jun Expression in Adult Rat Dorsal Root Ganglion Neurons: Differential Response after Central or Peripheral Axotomy

Abstract

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