cAMP induces axonal regeneration in spinal cord injury of rats / 中华骨科杂志

ABSTRACT

Objective cAMP promotes neurite outgrowth in vitro. The study is aimed to understand whether cAMP can repair spinal cord injury of rats. Methods 56 rats models of spinal cord hemisection were adopted and randomly distributed into six groups. Dibutyryl-cAMP or physiological saline was injected either once in the motor cortex with an amount of 6 ml of 50 mmol/L cAMP, or continuously infused through a polyethylene tube connecting with a micro-pump in the spinal lesion area or in the subarachnoid space with a total amount of 72 ml of 10 mmol/L cAMP for 72 h. The distribution of neurofilament (NF) in the lesion area was observed by immunohistochemistry. Corticospinal tracts (CST) and spinal axons regeneration were investigated by CST and spinal axons anterograde tracing with biotinylated dextran amine (BDA). The function of hindlimb movements were evaluated by BBB scales and as a reference to assess the repairing effect of treating strategy. Results NF were densely distributed and extended in the lesion area in the cAMP groups, but no connection could be found with the NF in the caudal. No axonal regeneration could be achieved when cAMP was input into the subarachnoid space. Many regenerated axons, including some CST axonal regeneration were presented in the lesion areas in cAMP groups though no continuous long regenerated axons traversed the lesion area, while there was no regenerated axon in the lesion areas in the control groups. All the rats restored to normally walk 4 to 5 weeks after operations, BBB scale exceed 20, and no significant difference between cAMP groups and control groups by comparing the BBB scales of hindlimb movements. Conclusion cAMP injected in the brain cortex or continuously infused in the spinal lesion area can induce the axonal regeneration and is beneficial to repair the spinal cord injury, but could not directly promote hindlimb movements recovering.