Neuroprotective Effect Of Self-assembling Peptides Nanofiber Hydrogel After Cervical Spinal Cord Injury And Its Mechanism

BackgroundRat models of spinal cord contusion are more clinically relevant than transected spinal cord injury.As a promising artificial biomaterial,self-assembling peptides(SAPs)nanofiber hydrogels have the advantages of injectability,biocompatibility,and biodegradability for neural repair,which facilitate the attachment and differentiation of neural cells.Also,as a slow release system,it is capable of slow release of neurotrophic factor NT3,which acts in the center of spinal cord injury.However,the efficacy of SAPs hydrogel in a contusion rat model needs to be evaluated.ObjectiveThe aim of this study was to clarify whether SAPs hydrogel could promote neurological recovery and its remyelination in rats with severe cervical spinal cord inj ury,mainly from behavioral,electrophysiological,and histological perspectives,and additionally to evaluate the mechanism of action of SAPs hydrogel in it from the perspective of transcriptome sequencing of RNA-Sequencing(RNA-Seq).Research methodsThirty-six male SD rats weighting approximately 250g were randomized into four groups,including sham group(sham-operated group,n=9),C group(contusion group,n=9),C+SAPs group(contusion+SAPs hydrogel treatment group,n=9),and C+SAPs+NT3 group(contusion+SAPs+NT3 hydrogel treatment group,n=9).Minimally invasive administration to the cervical spinal cord of rats was performed by microsampler,and the improvement of neurological function and remyelination improvement in rats with hemi-contusion of the cervical spinal cord were evaluated by behavioral evaluation and electrophysiological monitoring,quantitative analysis of EC staining,and MBP/SM312 immunofluorescence staining,respectively,4 weeks after surgery.Differential genes between different groups were obtained by RNA-Seq,and the relevant targets of SAPs hydrogel on cervical spinal cord hemi-contusion were explored by raw letter analysis.ResultsThe mechanical parameters of cervical spinal cord hemi-contusion in all rats in this study were not statistically different,suggesting that the degree of injury was consistent and stable in all groups.Behavioral evaluation:Compared with group C,the C+SAPs and C+SAPs+NT3 groups had significantly higher scores in the Forelimb locomotor scores(FLS)and grooming test score,but there was no significant difference in the cylinder rearing test score.Electrophysiological monitoring:The C+SAPs and C+SAPs+NT3 groups had shorter latencies in somatosensory evoked potentials(SEPs)and motor evoked potentials(MEPs)compared to the C group;however,there were no significant differences in the wave amplitudes of SEPs and MEPs between the three groups.MBP/SM312 staining:There was a tendency for the C+SAPs and C+SAPs+NT3 groups to have higher axonal density in the peripheral gray matter of the injury center and higher density of new myelin in the central region of the injury center than the C group,but there was no statistically significant difference among the three previously.RNA-Seq revealed that the immune system processes,positive regulation of tumor necrosis factor production,and inflammatory response mainly occurred in C group relative to sham group,and SAPs hydrogel changed the regulation of ion transport across the membrane,GABAergic synapses,and chemokine signaling relative to C group,while SAPs+NT3 hydrogel changed the signaling pathways,immune system,GABAergic synapses,and GABA-A receptor activity,etc.ConclusionsIn this study,we found that SAPs hydrogel could improve the electrical signaling pathway and motor function on the injured side after spinal cord injury through a rat cervical spinal cord hemi-contusion model;and SAPs hydrogel had a tendency to promote myelin and axon regeneration through histology.Meanwhile,RNA-Seq revealed that SAPs hydrogel may improve the microenvironment of spinal cord injury through the immune system,ion channels,synaptic regulation and other targets.