Experimental Research Of 3D Gelatin Microspheres Scaffold For Spinal Cord Injury Repair

BackgroundSpinal cord injury(SCI)is a central nervous system disease with high disability and high mortality which could lead to sensory,motor or autonomic nerve dysfunction.SCI is difficult to be treated that causing a heavy economic burden to families and society.However,the effect of available treatment strategies was limited,and more efficient treatment measures need to be developed to promote the recovery of neurological function after SCI.The rapid development of tissue engineering has created broad prospects for the treatment of SCI.Tissue engineering materials could not only make up for the tissue defects in the lesion area and provide bridging and support,but also serve as the carrier of transplanted cells and nutritional factors to promote wound repair and functional reconstruction.Nevertheless,tissue engineering materials still have many problems to be solved,such as the selection of material sources,the regulation of performance and the design of structure,which place restrictions on clinical application.Therefore,a three-dimensional gelatin microspheres scaffold(3D GMS)with multiple voids was designed based on the simple and convenient preparation of gelatin microspheres by microfluidic device in this research,and was used to explore the advantage of 3D GMS implantation on the functional recovery of SCI.ObjectiveTo explore whether the porous solid three-dimensional structure of 3D GMS meets the requirements of scaffolds in SCI,and its impact on the functional recovery and its possible mechanism for SCI treatment.Methods3D GMS was prepared and assembled by microfluidic device and characterized.The SCI model of rats was established by semi transection of spinal cord.Rats were divided into SCI group,SCI+control gelatin scaffold group(SCI+control GS group)and SCI+3D gelatin microspheres scaffold group(SCI+3D GMS group).The recovery of motor function was evaluated by behavioral and electrophysiological tests.The repair of spinal cord tissue was evaluated by microscopy,Nissl staining and scanning electron microscopy.The expression of inflammatory factors was detected by qRT-PCR.Immunofluorescence staining was used to detect the activation and distribution of microglia and astrocytes,as well as the survival and regeneration of neurons and axons.TUNEL staining was used to evaluate the biocompatibility.The expression of protein was detected by Western blot.ResultsThe characterization showed that 3D GMS has a three-dimensional cubic close packed structure with well-connected 3D porous architecture,appropriate void size,high porosity,and appropriate Young’s modulus and degradation characteristics.Compared with SCI and SCI+control GS group,SCI+3D GMS group significantly improved BBB score,stride length and motor evoked potential amplitude,which reflect the recovery of motor function after SCI.3D GMS filled the lesion defect and promoted tissue regeneration by alleviating tissue ulceration and cystic cavitations without causing additional apoptosis.Compared with SCI and SCI+control GS group,the expression level of proinflammatory factors in the lesion area of SCI+3D GMS group was significantly reduced.The activation level of microglia was inhibited,and the number of microglia and astrocytes was also significantly reduced.In addition,the number of neurons and axons in the lesion area increased and distributed widely.MAP-2 and NF protein expression increased significantly.The Western blot result showed that 3D GMS implantation increased a higher phosphorylation level of ATK and ERK compared to other groups.Conclusion3D GMS has a porous cubic close packed three-dimensional structure,which improved the inflammatory microenvironment,reduced glial scar formation,promoted the repair and regeneration of nerve and axons after SCI,and may improve neurological function by activating Akt and ERK pathways.