Remyelination in a mouse model of multiple sclerosis resulting from microbial metabolite sensor disruption

摘要： 多发性硬化症(MS)是一种衰弱和复杂的自身免疫性疾病，其中 中枢神经系统受到攻击。复发的频率和严重程度是高度可变的，并与 既有环境因素也有遗传因素。从MS患者和动物模型获得的令人信服的数据 表明肠道微生物群是致病过程中的关键媒介。而两国之间的关系 共生微生物群和免疫系统已经很好地建立了，其精确的机制 在多发性硬化症中看到的微生物免疫串扰仍不清楚。在这项拟议的研究中，我提出了一种机械联系 实验性自身免疫性脑脊髓炎MS小鼠模型中微生物组与髓鞘恢复之间的关系 (EAE)。一种被称为芳烃受体(AHR)的微生物代谢物传感器是一种转录因子 它调节屏障组织的免疫和代谢动态平衡，包括皮肤、肺，更重要的是， 胃肠道。T细胞中的AHR活性具有修饰肠道微生物组和修饰肠道微生物组的能力 免疫细胞健康。以前的工作主要集中在生殖系AHR基因敲除或细胞特异性基因敲除 神经系统；然而，我已经产生了一种CD4T细胞特异性AHR基因敲除小鼠，而这些动物 从EAE中表现出依赖微生物组的恢复。这些小鼠在最初的实验中增加了髓鞘覆盖率 在疾病高峰期，脊髓组织中IL-12水平下降，瘫痪。此外，我还发现IL-12减少了 少突胶质前体细胞(OPC)体外分化为髓鞘少突胶质细胞。在这下面 提议，我的目标是使用我之前描述的恢复模型，T细胞AhR基因敲除小鼠，来表征 重新髓鞘病变中的髓鞘动力学和2)确定IL-12作为中介的作用 免疫系统和髓鞘少突胶质前体细胞。我会确定髓磷脂的恢复 是OPC分化的结果，还是用透射电子显微镜观察成熟少突胶质细胞恢复的结果 和血统追踪。我将尝试了解这个模型中IL-12的来源和细胞内部信号转导 IL-12影响OPC和少突胶质细胞的级联反应。最后，我将利用IL-12受体基因敲除 了解IL-12在体内髓鞘形成过程中的作用。理解这一机制上的联系 微生物组和中枢神经系统将对早期MS患者的康复有意义 复发症状。通过建立环境传感器(AHR)对环境的直接和间接影响 脊髓微环境，我们可以更好地了解MS恢复的潜在基础，并识别 更有针对性的治疗方法，从而避免了目前的全身免疫抑制方法。

ABSTRACT: Multiple sclerosis (MS) is a debilitating and complex autoimmune disorder in which the myelin within the central nervous system is attacked. The frequency and severity of relapses are highly variable and are linked to both environmental and genetic etiologies. Compelling data obtained from patients and animal models of MS show that the gut microbiome is a critical mediator of pathogenesis. While the relationship between the commensal microbiota and the immune system is well established, the precise mechanisms underlying microbiota-immune crosstalk seen in MS remain unclear. In this proposed study, I suggest a mechanistic link between microbiome and myelin recovery in a mouse model of MS, experimental autoimmune encephalomyelitis (EAE). A sensor of microbial metabolites called the aryl hydrocarbon receptor (AHR) is a transcription factor that modulates immune and metabolic homeostasis at barrier tissues including the skin, lungs, and, importantly, the gastrointestinal tract. AHR activity in T cells has the capacity to modify the gut microbiome as well as modify immune cell fitness. Previous work has focused on germ-line AHR knockouts or cell specific knock out in the nervous system; however, I have produced a CD4 T cell specific AHR knockout mouseline, and these animals exhibit a microbiome-dependent recovery from EAE. These mice have increased myelin coverage after initial paralysis and decreased IL-12 in the spinal cord at peak of disease. Additionally, I have found that IL-12 reduces oligodendrocyte progenitor cell (OPC) differentiation into myelinating oligodendrocytes in vitro. Under this proposal, I aim to use my previously described model of recovery, T cell Ahr knockout mice, to 1) characterize the myelin dynamics in a remyelinating lesions and 2) determine the role of IL-12 as an intermediary between the immune system and myelinating oligodendrocyte progenitor cells. I will determine whether myelin recovery is the result of OPC differentiation or of mature oligodendrocyte recovery using transmission electron microscopy and lineage tracing. I will attempt to understand the source of the IL-12 in this model and the cell intrinsic signaling cascades in OPCs and oligodendrocytes affected by IL-12. Finally, I will utilize an IL-12 receptor knockout to understand the role of IL-12 during myelination in vivo. Understanding this mechanistic link between the microbiome and the central nervous system will have implications for early stage MS patients recovering from relapsing symptoms. By establishing the direct and indirect effects of an environmental sensor (AHR) on the spinal cord microenvironment, we can better understand the underlying basis of recovery in MS and identify more targeted therapeutics, thus avoiding the current approach of systemic immunosuppression.