Experimental Study Of AMPK In Peripheral Nerve Regeneration In Mouse Spinal Motor Neurons

Objective: Peripheral nerve injury is common and may result in limb weakness and loss of sensory function.After injury,axons distal to the lesion are disconnected from the neuronal body and degenerate,which eventually leading to the loss of innervation of the peripheral organs.A microenvironment distal to the lesion created in Wallerian degeneration can support axonal regrowth,while the neurons changes in phenotype to promote nerve regeneration.Key factors for successful axonal regeneration include the inherent changes that neurons suffer to switch their transmitter state to a pro-regenerative.Therefore,the exploration of changes in neurons after nerve injury becomes a new target for the treatment of nerve injury.AMPK is a heterotrimeric serine/threonine kinase that exists in all eukaryotic cells.The role of AMP-activated protein kinase(AMPK)in the regulation of energy metabolism and the control of skeletal muscle regeneration post injury has been described previously.However,it remains unknown whether this metabolic sensor plays a role in the mechanism of axonal regeneration post injury.In this study,using a sciatic nerve crush(SNC)mouse model,we explored the dynamic expression of AMPK in spinal motor neurons during the nerve regeneration process.Methods: mice were randomly assigned to four groups(n=6 per group):(1)normal control group,(2)SNC 7d group,(3)SNC 14 d group and(4)SNC 21 d group.All the mice in the experimental group were then anaesthetized with the left sciatic nerve crushed.Electrophysiological and histopathological studies were used to confirm the nerve injury and regeneration.After the crush model was successfully constructed,the spinal cord and sciatic nerve removed from each group mouse were used to make frozen section.The dynamic expression of AMPK in spinal motor neurons the sciatic nerve was observed by immunofluorescence.Results: The electrophysiological study and electron microscopic analysis confirmed the dynamic changes of sciatic nerve after injury.There was typical nerve regeneration at 3 weeks after injury.The frequency of AMPK-positive spinal motor neurons in the SNC 7d group and SNC 14 d group was higher than in the normal group.The frequency of AMPK-positive spinal motor neurons in the SNC 7d group and SNC14 d group was also significantly higher than in the SNC 21 d group.No significant difference of the frequency was found between the SNC 21 d group and normal group(P> 0.05).No expression of AMPK was detected in axons of normal and injured sciatic nerve.Conclusion: 1.Expression of AMPK can be changed dynamically in the spinal motor neurons.2.The dynamic expression of AMPK in the spinal motor neurons after sciatic nerve injury is consistent with theprocess of nerve regeneration.3.AMPK may play a role in the process of nerve regeneration after injury.