IL-17/miR-126-3p/PEX5通路在OPCs分化与再髓鞘化中的作用和机制研究

Multiple sclerosis (MS) is a classic autoimmune demyelinating disease. Most of MS patients initially have a relapsing-remitting disease then later developed into a secondary progressive phase. However the effective treatment for progressive MS is very limited. Oligodendrocyte progenitor cells (OPCs) are the cell source of myelin repair (remyelination). The impairment of OPCs maturation and remyelination in chronic MS lesions has been strongly suggested to be a major reason for MS progression. Thus, a thorough understanding of the molecular mechanisms that control the differentiation of OPCs in MS lesions would be of great significances to develop new therapies for progressive MS. IL-17 is a pro-inflammatory molecule that plays a key role in the pathogenesis of MS and it animal model- experimental autoimmune encephalomyelitis (EAE). However, the precise mechanism by which IL-17 participates in EAE development and pathogenesis remains unclear. Our preliminary results showed that IL-17 inhibited OPCs differentiation though up-regulating miR-126-3p and down-regulating PEX5. On this basis of the present studies, we plan to verify the role of IL-17/miR-126-3p/PEX5 pathway on OPCs differentiation and myelination/remyelination both in vitro and in vivo, and then further screen small molecular drugs to promote OPCs differentiation and myelination through IL-17/miR-126-3p/PEX5 pathway. Our findings not only provide a new molecular mechanism of neuroimmunomodulation, but also provide new molecular targets for the treatment of progressive MS.

进展型MS目前缺乏确切有效的治疗手段，迫切需要寻找新的治疗策略和靶点。慢性脱髓鞘病灶OPCs分化障碍和再髓鞘化延迟是MS转变为继发进展型的重要原因。IL-17是在MS发病中起关键作用的重要炎症因子，其在脱髓鞘病灶中显著上调，但IL-17对中枢神经系统细胞尤其是OPCs的分化和再髓鞘化的影响及机制远未完全阐明。我们的初步研究表明，IL-17可抑制OPCs的分化，这种作用是通过上调miR-126-3p的表达并进一步抑制PEX5实现的，IL-17/miR-126-3p/PEX5通路可能是导致MS脱髓鞘病灶再髓鞘化失败的全新、重要的分子调控通路。本项目拟在已有工作基础上，结合条件性基因敲除小鼠和人类MS标本，深入揭示该通路在体内外OPCs分化和再髓鞘化中的作用。进一步采用高通量技术，筛选通过此通路促进OPCs分化和再髓鞘化的小分子药物，以期为进展性MS的治疗提供新的分子靶标和治疗手段。

目前研究表明，多种微小RNA（microRNAs，miRNAs）对少突胶质前体细胞（Oligodendrocyte Progenitor Cells，OPCs）增殖、分化和髓鞘化具有调控作用。但在中枢神经系统脱髓鞘疾病中miRNAs是否参与了对慢性脱髓鞘病灶髓鞘再生的抑制，目前还不清楚。我们通过芯片筛选发现miR-126-3p在分化成熟的少突胶质细胞（Oligodendrocyte，OLs）中表达明显下调，而且在小鼠中枢神经系统炎症性脱髓鞘模型及多发性硬化（Multiple Sclerosis，MS）患者脑片中，miR-126-3p在脱髓鞘病灶周围表达明显上调。体外实验发现miR-126-3p可以明显下调MBP等相关髓鞘蛋白的表达，而且在OLs谱系中特异性敲除miR-126-3p的小鼠来源的OPCs分化能力较对照组来源的OPCs有较大的提高。此外，我们还发现miR-126-3p可以抑制人源OPCs的分化成熟。miR-126-3p条件性敲除可以显著加快实验性自身免疫性脑脊髓膜炎（Experimental autoimmune encephalomyelitis，EAE）病程的恢复和LPC模型的再髓鞘化进程。我们的工作进一步发现，IL-17可以明显上调miR-126-3p的表达，干扰OPCs内miR-126-3p的表达可以显著削弱IL-17对OPCs分化的抑制，这也提示了IL-17对OPCs分化的抑制作用至少部分是通过miR-126-3p实现的。深入研究发现miR-126-3p 是通过调控PEX5水平来发挥其对OPCs分化的调节作用。总之，我们的研究结果表明，IL-17/miR-126-3p/PEX5 轴在OPCs的分化成熟中发挥重要的调控作用，影响了炎症性脱髓鞘疾病的进程。据我们所知，本工作首次证实miRNA可以通过调控OPCs分化来阻遏脱慢性髓鞘病灶的髓鞘再生过程。