NT-3Chitosan Scaffolds Induced Hippocampal Neural Network Formation After Traumatic Brain Injury In Adult Rat

Background: Neuronal death or loss cause a variety of neurological deficits.Hippocampal damages lead to cognitive function defects which affect the spatiallearning and memory function of patient. Previous view argued that central nervouspathways was stable and lost neural cells were only placed by glial cells. Recentstudies indicate that endogenous neural progenitor cells resided in adult rathippocampus could consistently proliferate and regenerate new neurons in response toischemia brain injury. These findings provide a theoretical basis for repairing centralnervous system damage.Purpose: Implanted NT-3chitosan scaffolds into damaged area after traumatic braininjury, investigated glial scars surrounding damaged area and observed neuralregeneration process and formation of new synapses involved in neural circuitryreconstruction.Methods:In this study, using self-made biological suction device hippocampal CA1area and cerebral cortex were aspired to cause mechanical brain injury. Experimentalanimals were randomly divided into three groups: lesioned groups, blank chitosanscaffolds groups and NT-3chitosan scaffolds groups. On3,7,14,28and60daysafter the operation, four rats from each group were killed and brain frozen sectionswere prepared for the following immunohistochemical staining. Regenerationneurons and nerve fibers in damaged area were observed using NF staining. Matureand immature neurons were, observed by β-tubulinⅢ and MAP2staining. Glial scarformation surrounding damaged areas was detected by GFAP staining. Activation andproliferation of neural progenitor cells were detected by nestin staining. On30and60 days after operation, regenerated synaptic ultrastructure in damaged area wasobserved by immune electron microscope and immunohistochemistry staining. On60days after the operation, BDA-FITC neural tracer was stereotactically injected intocontralateral CA3area of the injury with a glass micropipette and regenerated neuralpathway was observed under fluorescence microscope.Results: Immunohistochemical staining showed that each group has differentnumbers of neural regeneration on60days after operation. Statistics found thatresults of NT-3chitosan scaffolds group had significantly differences compared withother groups. Staining of glial scar on the damage edge indicated that the number ofGFAP positive cells in the NT-3chitosan scaffolds group was significantly less thanthat in other groups. These results indicated that implanting NT-3chitosan scaffoldsinto the injury area could promote neural regeneration and inhibit formation of glialscar after traumatic brain injury. Further studies found that nestin positive cells wereactivated after operation3days and the number of these cells peaked on7days anddeclined on14days. The number of β-tubulinⅢ positive cells began to increase on14days but decreased after28days. MAP2positive cells increased gradually on28days after operation and keep stable until60days. The number of nestin, βtubulinⅢand MAP2positive cells in NT-3chitosan scaffolds group was significantly morethan that in other groups. BrdU+/MAP2+double-positive neurons and synapticconnections between newborn neurons could be observed in damaged hippocampalarea in NT-3chitosan scaffolds group using immune electron microscopy. The studyalso found BDA positive neurons in the injury area and some of them expressedMAP2.Conclusion: NT-3chitosan scaffolds could promote neural regeneration in damagedarea, and inhibited glial scar formation surrounding damaged tissue. Neuralprogenitor cells could proliferate, differentiate into mature neurons and formfunctional synapses involved in neural circuitry reconstruction in respond to traumatic brain injury.