神经干细胞携载PEG-PLGA-BDNF/bFGF纳米基因靶向治疗大鼠缺血性脑卒中的作用及机制研究

Ischemic stroke induced nerve tissue necrosis occurs shortly after brain ischemia and hypoxia, which has a poor prognosis, high mortality and morbidity. The current therapies are limited, due to their insufficient repairment of the injured neural tissue. The therapeutic outcomes depend on the improvement of wicked extracellular environment, and rapid reconstruction of the neuro-vascular network. Neural stem cells (NSCs) are promising natural resources for treating neurological diseases, which have the potential to differentiate into neuron, astrocyte and oligodendrocyte, and when given by ex vivo, NSCs can cross the blood brain barrier (BBB) and migrate to the ischemic sites. Our previous study has demonstrated that transplanted NSCs in brain-ischemia rats improved the neurological functions. However, the transplanted NSCs are limited by their shorter survived time and lower grafting efficiency. In addition, a majority of endogenous NSCs remain inactivated. In this study, we use the exogenous NSCs (as carrier and seed cells) loaded with PEG-PLGA-BDNF/bFGF nanoparticle gene drugs treat brain ischemic stroke. We will evaluate the transportation and delivery efficiency of NSCs, and investigate the exocytosis of nanoparticles from NSCs, as well as the activation of endogenous NSCs. Finally, we will determine the therapeutical effects and also the molecular mechanisms of NSCs loaded with nano-gene drugs. In conclusion, our study will provide an experimental basis for developing novel approach using NSCs for ischemic stroke.

缺血性脑卒中主要表现为短时间内脑组织缺血缺氧后坏死，临床预后差，现有的治疗措施和手段有限。其根本解决途径是尽早修复损伤的脑组织、改善细胞周围内环境及重建神经血管网络。神经干细胞（NSCs）可分化为神经元、星形胶质和少突胶质细胞，外源性NSCs可穿过血脑屏障趋向迁移到病理部位，被认为是修复损伤脑组织最具希望的天然资源。我们前期研究已证实外源性NSCs移植治疗对于大鼠脑缺血后神经功能恢复具有一定的促进作用。然而单纯的外源性NSCs移植后存活时间有限、嫁接效率不高，而内源性NSCs又难以被大量激活，致使疗效有限。因此我们拟用外源性NSCs同时作为载体和种子细胞，装载PEG-PLGA-BDNF/bFGF纳米基因颗粒，评价该NSCs载体的运载和递送效能，研究纳米基因在体内外的胞排、分泌及内源性NSCs的活化。探索NSCs在携载纳米基因治疗缺血性脑卒中的作用及分子机制，为治疗脑缺血提供新的思路和方法。

缺血性脑卒中主要表现为短时间内脑组织缺血缺氧后坏死，现有的治疗手段有限。其根本解决途径是尽早修复损伤的脑组织、改善细胞周围内环境及重建神经血管网络。本项目在神经干细胞（NSCs）移植的研究基础上，进一步探索了载PEG-PLGA-BDNF纳米微球基因的外源性NSCs对缺血性脑卒中的治疗潜能。研究结果发现：载纳米微球基因的NSCs组大鼠的神经功能恢复速度和程度优于单NSCs组和PBS组、脑梗体积少于单NSCs治疗组和PBS组；载纳米微球基因的NSCs组在体内分化为神经元的比例更多，且对受损区域的神经元的保护能力更强，以及脑内激活的内源性神经干细胞比例优于单NSCs组和PBS组。另外，在研究中我们发现旁分泌效应（外泌体）是干细胞移植后发挥作用的最主要方式。因此，本研究主要证实载PEG-PLGA-BDNF纳米微球基因的外源性NSCs通过减轻局部炎性反应、修复损伤部位神经组织、重建神经血管网络以最终恢复神经功能，同时也为发展一种基于神经干细胞的无细胞治疗方法（外泌体治疗方法）奠定了一定的研究基础。