Wnt/β-catenin信号调控不同分化状态间充质干细胞定向迁移的机制研究

Intracranially or intravenously injected mesenchymal stem cells (MSCs) migrate toward neural pathologies in murine models of nervous injury. This innate chemotropism has been exploited for cell replacement therapies to offer hope for functional neurological diseases. A thorough understanding of the molecular events that regulate MSC migration is necessary to optimize the use of MSCs as therapeutic delivery vehicles. Our previous study indicated that the chemotactic response of the differentiating MSCs correlates closely with their differentiation states: the migration ability of MSCs in different neural differentiation status is dramatically different. PI3K/AKT and MAPKs pathways are involved in the regulation of HGF-induced migration of the differentiating MSCs. Moreover, HGF stimulated the activation of Wnt/β-catenin signaling including nuclear accumulation of β-catenin and β-catenin/TCF transcription activity. In addition, Wnt 3a and LiCl treatment significantly increased the migration of MSCs, suggesting that Wnt/β-catenin signaling is involved in the regulation of the directed migration of MSCs. In this study, we will investigate the role of Wnt/β-catenin signaling and the underlying mechanisms in regulating the directed migration of MSCs in different neural differentiation states. First, the relationship between the differentiation states and the activation of Wnt/β-catenin signaling will be analyzed. Next,Wnt/β-catenin signaling will be altered at different levels and the effects of changes in Wnt/β-catenin signaling on the directed migration of differentiating MSCs as well as the interactions with PI3K/AKT and MAPKs pathways will be studied. Third, the expression of migration-related Wnt/β-catenin downstream effectors including Tiam1、RUNX2 and HEF1, and their regulatory roles and interactions with PI3K/AKT and MAPKs pathways during the directed migration of MSCs in different neural differentiation status will be analyzed. Meanwhile,the migration behavior including migration speed and migration effeciency, and the focal adhesion turnover of MSCs will be thoroughly examined. Our study is of great importance for optimization of the therapeutic strategies of MSCs to be employed for neural regeneration after injury.

增强间充质干细胞（MSCs）向病变部位的趋化性迁移对细胞移植治疗至关重要，然而MSCs的定向迁移机理不明。我们的前期工作发现，MSCs对趋化因子的应答、PI3K/AKT和MAPKs信号对该过程的调控与MSCs的分化状态密切相关；进一步研究发现，趋化因子如HGF促进β-catenin入核，上调β-catenin/TCF转录活性；而Wnt/β-catenin信号的改变影响MSCs的定向迁移。在此基础上，本项目将从配体与受体、β-catenin、Dvl和TCF四个水平改变Wnt/β-catenin信号，探讨对不同分化状态MSCs定向迁移的作用及与PI3K/AKT、MAPKs的相互关系，分析与迁移细胞极化方向的稳定直接相关的下游靶基因对MSCs定向迁移的作用，联系迁移轨迹、迁移速度、迁移效率及片状伪足形成、粘着斑周转等，最终阐明Wnt/β-catenin信号调控不同分化状态MSCs定向迁移的机制。

增强间充质干细胞（MSCs）向病变部位的趋化性迁移对细胞移植治疗至关重要，然而MSCs的定向迁移机理不明。我们的前期工作发现，MSCs对趋化因子的应答、PI3K/AKT和MAPKs信号对该过程的调控与MSCs的分化状态密切相关；进一步研究发现，趋化因子如HGF促进β-catenin入核，上调β-catenin/TCF转录活性；而Wnt/β-catenin信号的改变影响MSCs的定向迁移。在此基础上，本项目从配体与受体、β-catenin、Dvl和TCF四个水平改变Wnt/β-catenin信号，探讨对不同分化状态MSCs定向迁移的作用及与PI3K/AKT、MAPKs的相互关系，分析与迁移细胞极化方向的稳定直接相关的下游靶基因对MSCs定向迁移的作用，联系迁移轨迹、迁移速度、迁移效率及片状伪足形成、粘着斑周转等，最终阐明Wnt/β-catenin信号调控不同分化状态MSCs定向迁移的机制。结果证明，Wnt/β-catenin信号激活促进MSCs的定向迁移，HGF通过激活β-catenin信号诱导MSCs的趋化性迁移，包括迁移速度、迁移效率或迁移持续性的提高以及对粘着斑的形成、周转、分布、大小等的影响。PI3K/AKT、MAPKs信号不同程度地参与了Wnt/β-catenin信号对MSCs定向迁移的调控；在HGF诱导的定向迁移过程中，β-catenin信号主要通过p38MAPK通路发挥作用。进一步的研究发现，抑制Nedd9的表达阻断了MSCs向HGF或Wnt3a的定向迁移，而高表达Nedd9可以恢复干扰β-catenin信号通路引起的细胞迁移的抑制，证明Wnt/β-catenin信号通路靶基因Nedd9直接参与了MSCs的趋化性迁移调控。本项目的研究结果为今后细胞移植MSCs治疗神经系统疾病提供实验与理论基础。