适时调控Notch1信号对脑卒中后内源性神经再生放大作用及机制的影像学研究

Notch1 signaling plays pivotal roles in endogenous neurogenesis after stroke. The applicant has demonstrated that inhibition of Notch1 signaling in the subacute phase of ischemia could promote neuronal regeneration and functional recovery, but its mechanism remains unexplored. In our preliminary study, we found that the activated Notch1 signaling was in temporal and spatial correlation with the proliferated astrocytes, neural stem cells and neuroblasts. So we hypothesized that inhibition of Notch1 signaling in the subacute phase of ischemia could able to produce large proliferative pools of astrocytes and neural stem cells and then promote their differentiation to neuroblasts. To confirm this hypothesis，we dynamically observe the proliferation and differentiation of astrocytes and neural stem cells after ischemia in pathology, and then analyze the multiple roles of Notch1 signaling. At the same time, we in vivo evaluate the structural and functional changes of cerebral axonal bundles with morphological and functional magnetic resonance imaging method. Finally, we aim to illuminate the underlying mechanism of amplified neuronal regeneration and remodeling with timely control of Notch1 signaling, and to develop the systematic treatment mode and the corresponding evaluation method. Our study could provide theoretical reference to achieve endogenous neurogenesis within the effective therapeutic time window.

Notch1信号对脑卒中后内源性神经再生起到关键性调控作用。本申请者发现，脑卒中后亚急性期阻断Notch1信号能促进神经元再生及大鼠行为功能恢复，但其机理尚待阐明。结合前期研究，Notch1信号激活与星形胶质细胞、神经干细胞、成神经细胞增生变化之间有一定时间和空间相关性，我们推测，亚急性期阻断Notch1信号能在诱导星形胶质细胞和神经干细胞充分增殖后，最大化地促进其向成神经细胞分化。为证实这一假说，我们应用病理学方法，动态观察脑缺血后星形胶质细胞和神经干细胞增殖、分化，分析Notch1信号的多向、多环节调节作用，并结合形态学和功能学磁共振成像技术，活体动态评估脑内神经传导束结构和功能改变，阐明适时调控Notch1信号促进神经元再生、脑组织神经重塑的发生机制，发展以Notch1信号为靶点的整体调节、综合治疗模式及相应的活体评价手段，为实现脑卒中后有效时间窗内的神经再生治疗奠定理论基础。

脑缺血后脑组织修复与Notch1信号调控的内源性神经再生及炎性反应、类淋巴通路、是否存在出血转归密切相关。本研究团队发现，脑卒中后亚急性期阻断Notch1信号能够促进神经元再生、脑组织结构修复，此外，星形胶质细胞足突水通道蛋白4（quaroin4,AQP4）介导的类淋巴通路功能下降可导致脑组织退行性改变，脑出血转归也与卒中病人预后密切相关。为进一步阐明其机理，首先，我们利用病毒脑内注射追踪星形胶质细胞，动态观察脑缺血后星形胶质细胞向神经元的转化过程，分析Notch1信号在此过程的调节作用及其激活与星形胶质细胞向神经元逆转化之间的时间相关性；同时，分析星形胶质细胞形态及相应的细胞足突AQP4极化率变化引起的类淋巴通路清除功能改变，以及小胶质细胞亚型转化，并结合形态学和功能学磁共振成像技术，活体动态评估缺血脑组织结构、脑内神经传导束结构和功能改变，阐明适时调控Notch1信号促进星形胶质细胞来源的神经元再生、星形胶质细胞及小胶质细胞介导的抗炎性反应的发生机制及与脑修复之间的关联。此外，我们还通过分析脑缺血病人影像学指标，阐明侧支循环及表面通透性可以独立预测脑缺血患者的出血转归。我们将动物学实验与临床试验相结合，共同探索促进卒中患者机体恢复的有效时间窗、干预靶点、相应的影像学在体评估手段及预测指标，为发展脑卒中后有效时间窗内治疗及评估模式奠定理论基础。