神经保护和再生是脊髓损伤修复的关键。骨髓间充质干细胞（BMSCs）是脊髓损伤移植治疗的理想“种子细胞”，但其分泌的神经营养因子有限，同时极易受损伤区域富含活性氧（ROS）微环境影响；基因治疗可将神经营养因子基因导入靶细胞，在局部产生神经营养因子，但缺乏高效的非病毒载体是困扰其应用的瓶颈。本项目针对脊髓损伤区域富含ROS的特点，构建一种氧化响应的电荷反转型阳离子基因载体，克服非病毒载体难以高效转染干细胞的难题，搭载睫状神经营养因子（CNTF）基因，对BMSCs进行基因修饰，通过静脉注射定植于脊髓损伤区域，高效表达CNTF，同时消耗ROS，有助于BMSCs存活，两者协同促进神经功能恢复。本项目旨在阐明ROS与干细胞转染的关系、基因修饰对BMSCs结构和功能的影响以及联合治疗系统对脊髓损伤微环境的调节，通过多种技术手段评价其对模型动物的修复效果和作用机制，为脊髓损伤后的神经再生修复提供新思路。

Axon regeneration and functional recovery are critical for successful treatment of spinal cord injury (SCI). Bone Marrow Stem Cells (BMSCs) are ideal "seed cells" for stem cell transplantation therapy of spinal cord injury. Howerver, the secretion of neurotrophic factor is poor and the hostile microenvironment of the SCI region resulting from the high levels of reactive oxygen species (ROS) increase the difficulty of transplanted cell survival, thereby limiting the overall efficacy of stem cell transplantation therapy. Gene therapy has emerged as a new approach treating SCI by delivering neurotrophic factor genes to targeted SCI region and make stem cells overexpress neurotrophic factors locally for a long time. However, its application is bottlenecked by the low transfection efficiency of nonviral gene vectors. In this project, we plan to synthesis a ROS-labile charge-reversal cationic polymer which can be oxidized by the harsh microenvironment of SCI region rich in ROS, successfully overcoming these difficulty of efficient gene transfection of BMSCs. Gene transfection to make BMSCs overexpress ciliary neurotrophic factor (CNTF) can enhance their therapeutic efficacy. After i.v. injection in SCI rat, the transfected BMSCs can home to SCI region and produce BDNF efficiently, simultaneously consumed some ROS and, thus, relieved ROS stress, ultimately contributing to microenvironment of the SCI region and the survival of BMSCs. The combined therapy system enables more rapid and superior functional reconstruction. This project aims to study the relationship between ROS and stem cell gene transfection, explore the ability of the combined therapy system to regulate the microenvironment of SCI region, clarify the effect of gene modification on the structure and function of BMSCs, and evaluate the repair effect and mechanism with multiple comprehensive evaluation system in SCI models. so as to provide a new idea for nerve regeneration and repair after spinal cord injury. By this project, we expect to develop a promising gene delivery system for neural regeneration after spinal cord injury.