The Effects Of Rapamycin On Neuronal Autophagy And Apoptosis After Spinal Cord Injury In Rat

Objective To observe the functional and pathology changes，and toexplore the protective effect and possible mechanism of rapamycin to theneuronal after SCI in rat.Methods The150SD rats were randomly divided into three groups, thatis, the sham operation group，the injury group and the rapamycin treatmentgroup. The SCI model was injured by using the Allen weight droppingtechnique. All animals were evaluated of the hind limb behavior withBasso-beattie-bresnahan(BBB) score on five different time-point (1,3,7,14and28d).After the BBB evaluation, the rats were sacrificed and thespinal cord was taken out. HE stain was done in order to observe themorphologic changes. Immunofluorescent double-labeling was done inorder to observe the LC3expression and apoptosis of neurons. We usedwestern blot to analyze the LC3and Caspase3expression. Transmissionelectronic microscope was used to examine the anatomic formation ofautophagy.Result(1) The result of BBB scales: In the sham group, the hind limbbehavior function was normal, and the BBB score reaches20point, therewere nerve functional disorder in the injury group and the FK506treatmentgroup, which BBB score less than2point at the day of1and7, and wasno statistical difference between later groups(P＞0.05). Following, thenerve functional of FK506treatment group was much better than the injurygroup, and the score increasing with time, with a significantlystatistical difference among each group.(2) HE stain result: The boundarybetween grey and white matter is clear, the structure of the neuron andthe myelinic membrane is normal. But there were changes to certain degreebetween the injury group and treatment group, that is, some hemorrhagic foci, inflammatory cells infiltration, the cell bodies of neurons atrophy,the reactivity proliferation of neuoglia cells, the white matter appearedreticulate demyelination and glial scar formation. The result suggestthat the treatment group better than the injury group.(3) Comparing withinjury group, the number of autophagy positive neurons was obviouslyenhanced in the rapamycin treatment group on the same time-point.(4) Thenumber of apoptosis positive neurons of injury group was higher thanrapamycin treatment’s.(5)We detected significantly elevated level ofLC38h after SCI, and3d in the peak. Rapamycin evidently increased LC3expression. We also detected elevated level of Caspase-38h after SCI,and declined until7d after SCI. Rapamycin decreased Caspase3expression.(6)The existence of antophagosomes and autolysosomes were confirmed inboth injury group and rapamycin treatment group.Conclusions After rats spinal cord injury, the application of rapamycincan strengthen neurons autophagy, reduce cell apoptosis neurons, to acertain extent to neurons protective, so as to promote the rat movementfunction recovery.