The effects of aging on axon regeneration currently remain unclear. In addition, the up-regulated expression of neurotrophic factors that occurs within one week of peripheral nerve injury has been shown to play an important role in the axon regeneration. To investigate the effects of aging on axon regeneration, the expression of nerve-specific proteins immediately after peripheral nerve injury were compared between young and aged mice. A mouse peripheral nerve injury model was prepared using the sciatic nerve compression method. In each group, Luxol fast blue staining and immunofluorescence staining were performed to assess the degree of Wallerian degeneration in the sciatic nerve, and to evaluate the expression of repressor element 1-silencing transcription factor (REST)/neuron-restrictive silencer factor (NRSF), brain-derived neurotrophic factor (BDNF), neurotrophin 3 (NT3), nerve growth factor (NGF), and semaphorin 3A (Sema3A) in the dorsal root ganglion, respectively. Wallerian degeneration was observed in both young and aged mice after peripheral nerve injury. Significant increases were observed in the expression of REST/NRSF (P<0.0001), NT3 (P=0.0279), and Sema3A (P=0.0175) following peripheral nerve injury in young mice, while that of BDNF (P=0.5583) and NGF (P=0.9769) remained unchanged. On the other hand, no significant differences were noted in the expression of these nerve-specific proteins in aged mice. Based on the results of the present study, compensatory changes induced by peripheral nerve injury were initiated by the up-regulated expression of REST/NRSF in young mice, but not in aged mice.
Keywords: Wallerian degeneration; aging; nerve-specific proteins; neurotrophic factor; peripheral nerve injury; repressor element 1-silencing transcription factor/neuron-restrictive silencer factor.
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