Fractalkine/CX3CR1调控小胶质细胞极化促进血管性认知障碍髓鞘修复的研究

Vascular cognitive impairment (VCI) is the second most common form of dementia. Pathologically VCI features noticeable white matter atrophy resulting from insufficient remyelination. Currently there are no effective treatments. The relation between VCI and inflammation has been highlighted recently. Microglia is the main inflammatory cell type in the central nervous system (CNS). Under different conditions, activated microglia are known to be polarized into M1 and M2 phenotypes and exert dual functions, that is, pro-inflammatory (M1) and tissue repairing (M2) functions. In our previous studies, we found activated microglia can release inflammatory factors resulting in demyelization; however, anti-inflammatory interventions ameliorate the damage and improve the cognitive impairment of VCI animal models. Remyelination is blocked in absence of microglia. Polarization of microglia into M2 has been shown to enhance remyelination. Fractalkine/CX3CR1 is exclusively expressed on microglia in CNS which can regulate injury/repairing respectively. Here we hypothesize that polarization of microglia into M2 is regulated through the Fractalkine/CX3CR1 pathway, and promoting M2 polarization of microglia is a therapeutic strategy for VCI. To test this hypothesis, we propose experiments to systemically determine the effects of polarization of microglia on remyelination. Specifically, we will rigorously examine the role of Fractalkine/CX3CR1 pathway in M2 polarization of microglia, determine the effects of M2 polarization on activation, migration, proliferation and differentiation of oligodendrocyte precursor cells (OPCs), and functional maturation of oligodendrocytes, and investigate behavioral outcomes of promoting remyelination through microglia polarization. Successful completion of the project will provide insights into mechanism of VCI and likely identify the Fractalkine/CX3CR1 pathway as a novel target for development of new drugs for VCI.

血管性认知障碍（Vascular Cognitive Impairment，VCI）是位列第二的常见痴呆类型。其病理改变为髓鞘再生障碍导致的脑白质损伤，至今无有效疗法。近期发现小胶质细胞可极化为促炎（M1）与促组织修复（M2）两型。我们前期工作发现，VCI动物中小胶质细胞活化释放炎症因子致髓鞘脱失，但体外实验中小胶质细胞缺失时髓鞘再生障碍。Fractalkine/CX3CR1脑内主要在小胶质细胞上表达, 激活后能活化小胶质细胞。因此我们假设，调节该信号通路促使小胶质细胞的M2型极化，促进髓鞘再生修复，可能是VCI治疗的重要靶点。本课题拟研究如何调控Fractalkine/CX3CR1信号通路，促使小胶质细胞向M2型极化，并阐明极化小胶质细胞对VCI动物模型少突胶质细胞前体细胞增殖、分化、成熟和髓鞘再生的影响，从而实现促进髓鞘修复，改善认知行为的目的，为VCI防治提供新思路和药物作用靶点。

血管性认知障碍（Vascular Cognitive Impairment，VCI）是位列第二的常见痴呆类型，至今无有效疗法，寻找其致病机制非常重要。VCI的病理改变主要为髓鞘再生障碍导致的脑白质损伤，我们前期工作证明缺血性炎症是导致髓鞘损伤与修复障碍的重要原因。近期文献表明，中枢神经系统的炎症细胞小胶质细胞活化可表现为促炎（M1型极化）与促组织修复（M2型极化）两种情况。Fractalkine/CX3CR1在中枢神经系统主要表达于小胶质细胞，因此我们假设，调节该信号通路而调节小胶质细胞极化，抑制炎症，促进髓鞘再生修复，可能是VCI治疗的重要靶点。本研究首先通过双侧颈总动脉血流阻断60min方法制备VCI小鼠模型，行为学表现具有抑郁和认知损伤；并通过脑切片免疫组化染色、脑匀浆蛋白免疫印迹、炎症因子ELISA检测等方法证明：VCI小鼠缺血后随着时间推移，小胶质细胞主要向iNOS标记的M1型促炎型方向极化，而Arg-1标记的M2型修复型极化方向逐渐下降，这个过程与海马区及胼胝体区髓鞘损伤，以及海马区少突胶质细胞成熟障碍具有相关性。另外，VCI模型小鼠缺血后海马区Fractalkine／CX3CRl通路激活，下游蛋白主要为NF-κB表达增高，IL-1β、IL-6、TNF-α，HMGB1等促炎因子增加，提示该通路激活主要引起促炎反应；进一步通过侧脑室注射Fractalkine／CX3CRl中和抗体anti-FKR来阻断该信号通路，或通过腹腔注射该信号通路下游关键分子Src和NFκB的拮抗剂PP2和PDTC来调控该信号通路，均发现可不同程度抑制小胶质细胞激活及炎症反应，保护海马区神经元，促进海马区OPCs成熟分化并修复受损髓鞘，改善缺血小鼠抑郁行为或认知功能障碍。本研究证明，VCI模型中，调控Fractalkine/CX3CR1信号通路可调节小胶质细胞极化，促进髓鞘修复，改善认知行为，为VCI防治提供新思路和药物作用靶点。本研究基础上获国家自然基金面上项目2项，上海市人才项目1项，发表SCI论文6篇，培养研究生5人。