Semaphorin3A抑制嗅鞘细胞迁移参与嗅球胶质屏障形成和神经再生

olfactory ensheathing cells（OECs）transplantation has emerged as a promising experimental therapy for promoting the central nervous system repair after injury.The motility of OECs is critical for neural regeneration and development of olfactory system, however, the underlying mechanisms remain unclear.Semaphorin 3A(Sema3A) is highly expressed in spinal cord injury and olfactory bulb, however, whether Sema3A guides the migration of OECs remains unclear.Our preliminary data has shown that Sema3A was expressed highly in the inner layer,lowly outer layer of olfactory bulb, and their receptors were higly experssed in OECs,furthermore,Sema3A induced the collapse,and inhibited OEC migration. Based on these preliminary data, we firstly further examined the roles and mechanisms of Sema3A in OEC migration using cellular and molecular technologies.Secondly, we examined the phenotypes of OEC migration in Sema3A knockout mice.Finally, we exmamined the effects of Sema3A expressed in injuried sites on the migration of transplanted OECs and their promoting properties of neural regeneration based on spinal cord injuried model with Sema3A knockout mice or Sema3A inhibitors. Taken together, these experiments will test our hypothesis:Sema3A gradient formed in olfactory bulb inhibits OEC migration, then they stop the olfactory neural layer, to form the glia limitations in olfactory bulb;OEC transplantation combiding with Sema3A inhibitor are more effective to treat spinal cord injuries.

嗅鞘细胞移植治疗中枢神经损伤显示潜在的临床应用前景，其迁移对促神经再生和嗅觉系统形成起关键作用，然而机制不清楚。Sema3A高表达于脊髓损伤和嗅球中，但是否对嗅鞘细胞迁移起作用不清楚。预实验发现Sema3A在嗅球呈内高外低分布，受体高表达于嗅鞘细胞；Sema3A引起嗅鞘细胞塌缩，抑制其迁移。拟在前期工作基础上，运用细胞、分子生物学等技术进一步观察Sema3A对嗅鞘细胞迁移作用和机制。其次，采用Sema3A基因敲除鼠，观察Sema3A对嗅球胶质屏障形成、维持的生理意义。最后，基于脊髓损伤模型，结合Sema3A基因敲除鼠或Sema3A抑制剂，观察脊髓损伤高表达的Sema3A对移植的嗅鞘细胞迁移作用，及其对脊髓损伤再生修复的影响。以期验证假说：嗅球形成内高外低的Sema3A浓度梯度，终止嗅鞘细胞迁移，参与嗅球胶质屏障的形成和维持；嗅鞘细胞移植联合Sema3A抑制剂对于治疗脊髓损伤具有协同作用。

嗅鞘细胞移植治疗中枢神经损伤显示潜在的临床应用前景，其迁移对促神经再生和嗅觉系统形成起关键作用，然而机制不清楚。本研究主要发现：1）Sema3A在嗅球形成从内到外的浓度梯度，其受体NP1和NP2高表达于在体和离体培养嗅鞘细胞中；Collapse Assay和单细胞迁移实验发现Sema3A通过受体NP1引起嗅鞘细胞前导突起塌缩，并抑制嗅鞘细胞迁移; Sema3A刺激引起受体内吞依赖的适应现象，但不依赖于蛋白合成；Sema3A引起前导突起黏附减少和通过Cofilin激活引起的F-actin丢失，F-actin flow后流导致前导突起塌缩；并发现脊髓损伤高表达的 Sema3A 很可能排除移植到损伤区域的嗅鞘细胞，从而影响其发挥促神经损伤再生的功能。这些结果的取得为嗅鞘细胞迁移的分子机制提供了新见解，并为嗅鞘细胞移植治疗中枢神经损伤和脱髓鞘病变的研究提供新思路和新策略。2)搭建嗅鞘细胞单细胞迁移平台，并阐明在发育过程中，嗅鞘细胞从嗅上皮方向性迁移进入嗅球的分子机制，包括 BDNF/TRPCs介导嗅鞘细胞吸引迁移、Myosin II 极性分布维持嗅鞘细胞方向性迁移，这些研究帮助我们更深入地认识嗅鞘细胞基本生物学特性和发育的分子基础。3)研究与嗅鞘细胞形态和功能类似的星形胶质细胞产生和激活机制，发现在大脑皮层发育过程中，BMP2/Neogenin/YAP 信号通路促进皮层星形胶质细胞分化和增殖，参与皮层星形胶质细胞产生;并发现 YAP/STAT3/SOCS3 信号通路抑制星形胶质细胞激活，参与神经炎症反应，这些研究是 YAP 通路新功能的阐明，也为发育过程中大脑皮层星形胶质细胞产生和激活提供新的分子机制。