Role of CD44 in experimental Multiple Sclerosis

描述(由申请人提供)： 多发性硬化症(MS)是一种神经退行性自身免疫性疾病，全球约有100万人受到影响。由于MS的高患病率，目前有超过28,000名退伍军人被诊断为MS。由于MS的高患病率，2003年，退伍军人健康管理局(VHA)成立了MS卓越中心，致力于服务于MS退伍军人的医疗需求。最近的海湾战争和其他战争退伍军人的症状患病率增加，包括认知功能障碍、抑郁、慢性疲劳、肌肉骨骼抱怨、创伤后应激障碍和呼吸系统疾病。根据国家多发性硬化症协会(NMSS)最近向国防小组委员会提供的证词，越来越多的海湾战争退伍军人出现上述症状，实际上可能是多发性硬化症。实验性自身免疫性脑脊髓炎(EAE)是一种概括了MS的许多特征的动物模型，其中Th1和Th17细胞与髓鞘抗原反应，穿过血脑屏障，进入中枢神经系统，引发炎症，从而导致脱髓鞘和诱导瘫痪。我们实验室的研究表明，NAOVE T细胞表达CD44的标准型(CD44s)，并在激活后通过选择性剪接表达CD44的某些独特的变体亚型(CD44v)。具体地说，我们发现CD44v6/v7等CD44亚型在炎症部位活化的T细胞和内皮细胞(ECs)之间的相互作用中发挥着关键作用，从而导致EC损伤。有趣的是，我们还注意到，与CD44野生型(WT)小鼠相比，CD44基因敲除(KO)小鼠对EAE的抵抗力增强，神经炎症减少。此外，T细胞CD44缺乏促进了从Th1/Th17向Th2/Treg分化的转换。初步研究还发现了CD44WT和CD44KO T细胞在miRNA表达谱上的独特差异。在上述研究的基础上，我们将检验一个中心假设，即表达CD44s的NAOVE T细胞在被DC呈递的髓鞘抗原激活后，经历了microRNA表达的表观遗传调节失调，该失调调控炎性细胞因子基因的转录，从而促进Th1/Th17分化。此外，MOG反应性T细胞表达独特的CD44v亚型，通过特定的配体，如透明质酸(HA)和/或骨桥蛋白(OPN)，促进它们与血脑屏障内皮细胞的相互作用。这种相互作用会引发EC损伤和对血脑屏障的重大损害。这些事件共同促进了中枢神经系统的炎症和脱髓鞘。为此，在本研究中，我们将鉴定活化的MOG特异性T细胞上表达的CD44变异亚型，并研究它们在EAE发病机制中的作用。接下来，我们将确定CD44与HA或OPN之间的相互作用如何通过转录因子基因启动子甲基化和/或miRs的表达来触发表观遗传调控，从而导致T细胞从Th1/T17细胞向Th2/Tregs细胞的转变。将尝试进行药物和遗传干预，以逆转Th/Treg功能及其对EAE的影响。此外，还将测试在EAE过程中，抗原特异性T细胞上表达的CD44与BBB ECs上的特定配体之间的相互作用，从而导致BBB的破坏和T细胞跨EC向CNS的迁移。最后，我们将使用包括模拟的策略来确定靶向CD44s或CD44v是否会阻止EAE的发展和进展。总之，我们的研究将为理解CD44亚型在调节MS和其他影响大部分退伍军人的中枢神经系统炎症性疾病中的作用提供新的曙光，并提供有利于退伍军人健康的新治疗模式。

DESCRIPTION (provided by applicant): Multiple sclerosis (MS) is a neurodegenerative autoimmune disease that affects approximately one million people worldwide. There are over 28,000 veterans currently diagnosed with MS. Due to its high prevalence, in 2003, the Veterans Health Administration (VHA) established the MS Centers of Excellence which are committed to serving the health care needs of veterans with MS. There is increased prevalence of symptoms among recent Gulf war and other war veterans which include cognitive dysfunction, depression, chronic fatigue, musculoskeletal complaints, post-traumatic stress disorder and respiratory illness. According to recent testimony by the National Multiple Sclerosis Society (NMSS) to the Subcommittee on Defense, the increasing number of Gulf war veterans exhibiting symptoms described above may actually be suffering from multiple sclerosis. Experimental autoimmune encephalomyelitis (EAE) is an animal model that recapitulates many features of MS in which Th1 and Th17 cells reactive against myelin antigens, cross the blood-brain barrier (BBB), enter the CNS and trigger inflammation, thereby causing demyelination and induction of paralysis. Studies from our laboratory have demonstrated that naove T cells express the standard form of CD44 (CD44s) and upon activation, express certain unique variant isoforms of CD44 (CD44v) through alternative splicing. Specifically, we have shown that CD44 isoforms such as CD44v6/v7 play a critical role in the interaction between activated T cells and endothelial cells (ECs) at sites of inflammation leading to EC injury. Interestingly, we have also noted that CD44 knockout (KO) mice exhibit increased resistance to EAE and decreased neuroinflammation when compared to CD44 wild type (WT) mice. Also, CD44 deficiency on T cells promoted a switch from Th1/Th17 to Th2/Treg differentiation. Preliminary studies also identified unique differences in miRNA expression profiles between CD44 WT and CD44 KO T cells. Based on the above studies, we will test the central hypothesis that naove T cells expressing CD44s, upon activation with myelin antigens presented by the DCs, undergo epigenetic modulation dysregulation in microRNA expression that regulate the transcription of inflammatory cytokine genes leading to promotion of Th1/Th17 differentiation. Furthermore, MOG-reactive T cells express unique CD44v isoforms which promote their interactions with ECs at the BBB via specific ligands, such as hyaluronic acid (HA) and/or osteopontin (OPN). Such an interaction would trigger EC injury and significant damage to the BBB. These events together promote inflammation and demyelination in the CNS. To this end, in the current study, we will identify CD44 variant isoforms expressed on activated MOG- specific T cells and study their role in the pathogenesis of EAE. Next, we will determine how interactions between CD44 with HA or OPN trigger epigenetic regulation by transcription factor gene promoter methylation and/or expression of miRs that lead to a switch in T differentiation from Th1/T17 cells to Th2/Tregs. Pharmacological and genetic intervention will be attempted for reversal of the Th/Treg functions and its effects on EAE. In addition, the interactions between CD44 expressed on antigen-specific T cells and specific ligands on BBB ECs leading to breakdown of BBB and trans-EC migration of T cells into CNS, during EAE, will be tested. Lastly, we will determine if targeting CD44s or CD44v, using strategies that include mimetics, would prevent the development and progression of EAE. Together, our studies should shed new light in understanding the role of CD44 isoforms in the regulation of MS and other inflammatory diseases of the CNS that affect a large proportion of Veterans as well provide novel treatment modalities that would benefit Veterans' health.