cxcr2/gas6修饰MSC在病毒性脑炎模型中保护效应及免疫调控机制

Viral encephalitis is inflammation of the brain parenchyma caused by a variety of viruses with high mortality rate and the survivors often accompanied by severe neurological sequelae. So far, there are no effective treatments for many viruses available. The damaged permeability of blood-brain barrier and the excessive inflammation in the brain is common and important mechanism of neuronal damage and encephalitis. Alleviation of inflammatory response and enhancement of neuronal repair is an important strategy in the treatment of viral encephalitis. Recently, the immunomodulatory activity of mesenchymal stem cells (MSC) has attracted much attention. There are many promising clinical trials for central nervous system disorders using MSC. Activation of Gas6/TAM signaling pathway can decrease the production of inflammatory cytokines and promote the myelination of axons and protect the blood-brain barrier..Our data from mouse encephalitis model infected with JEV showed that MSC can effectively reduce the level of inflammation in the brain although the efficiency still needs to be improved.Due to the upregulation of chemokine CCL2 in most encephalitis tissues, CXCR2 and Gas6 modified MSC cells would be prepared. In the encephalitis model infected with JEV or EV71, it would define the enhancement of homing and anti-inflammatory effect of cxcr2/gas6 gene modified MSC, and then study the mechanism of Gas6/TAM signal axis enhanced inhibition of encephalitis, and finally find the novel molecule targeting inflammation. This study will provide the novel strategy against viral encephalitis.

病毒性脑炎是多种病毒直接侵犯中枢神经系统引起脑实质的炎症，死亡率高、存活者常伴有严重神经后遗症，迄今许多病毒尚无有效的治疗药物。血脑屏障通透性破坏、脑内过度炎症反应是神经元损伤并形成脑炎的重要共同机制，抑制炎症反应和促进神经元存活是治疗病毒性脑炎的重要方向。最近，间充质干细胞（MSC）的免疫调控活性备受关注，其在多种中枢神经系统疾病的治疗方面已进入临床试验阶段。我们在JEV脑炎模型中发现：MSC可以有效减少脑组织的炎性损伤，但靶向性和抗炎能力仍需提高。Gas6/TAM信号通路活化可抑制炎症、改善血脑屏障，从而减少神经元损伤。CCL2在脑炎组织内呈高表达，可趋化CXCR2+细胞归巢至脑内。本项目拟以JEV和EV71建立脑炎动物模型，明确cxcr2/gas6修饰MSC细胞增强其归巢与抗炎效应，并研究Gas6/TAM信号轴增强对脑炎抑制的机制和发现新的有效分子，为病毒性脑炎的治疗提供新策略。

血脑屏障的破坏和大量炎性细胞浸润是病毒性脑炎发生的共同特征，故减少血脑屏障破坏和过度炎症反应是降低神经元损伤并促进修复的重要策略。近年来，间充质干细胞（MSC）是应用最为广泛的干细胞之一，其显著的免疫调节作用在多种疾病模型中显示了良好的治疗效果。Gas6/TAM 通路参与炎症反应调控、血脑屏障完整性等。本项目主要完成了ccr2/gas6 基因修饰 MSC 的构建及生物学特性鉴定；体外实验测定 ccr2/gas6 基因修饰 MSC 的生物学效应；病毒性脑炎模型中测定 ccr2/gas6 基因修饰 MSC 的生物学效应；Gas/TAM 轴分子参与 ccr2/gas6 基因修饰 MSC 治疗效应的确定及分子调控机制。细胞和动物层面的实验结果发现：gas6/ccr2修饰可提高MSCs的增殖活性和趋化功能，缓解JE进展；gas6/TAM通路提高BBB完整性，缓解JEV致脑组织炎症损伤；进一步发现AXL和MerTK分子在神经元中通过与干扰素信号通路协同作用参与抗病毒免疫反应，而且AXL和MerTK分子参与JEV进入巨噬细胞、神经元。本项目为利用gas6/TAM通路联合趋化因子受体分子CCR2双重修饰间充质干细胞进行病毒性脑炎的治疗提供了实验支撑。