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，影响全球约100万人。目前有超过28，000名退伍军人被诊断患有MS。由于其高患病率，2003年，退伍军人健康管理局（VHA）建立了MS卓越中心，致力于为退伍军人的医疗保健需求提供服务。肌肉骨骼疾病、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表现出上述症状，实际上可能患有多发性硬化症。实验性自身免疫性脑脊髓炎（EAE）是一种动物模型，其重现了MS的许多特征，其中Th 1和Th 17细胞对髓鞘抗原反应，穿过血脑屏障（BBB），进入CNS并触发炎症，从而引起脱髓鞘和诱导瘫痪。我们实验室的研究表明，幼稚T细胞表达标准形式的CD 44（CD 44 s），并在活化后，通过选择性剪接表达某些独特的CD 44（CD 44 v）变体同种型。具体地说，我们已经表明，CD 44亚型，如CD 44 v6/v7在活化的T细胞和内皮细胞（EC）之间的相互作用中发挥关键作用，在炎症部位导致EC损伤。有趣的是，我们还注意到，与CD 44野生型（WT）小鼠相比，CD 44敲除（KO）小鼠表现出对EAE的抵抗力增加和神经炎症减少。此外，T细胞上的CD 44缺陷促进了从Th 1/Th 17向Th 2/Treg分化的转变。初步研究还确定了CD 44 WT和CD 44 KO T细胞之间miRNA表达谱的独特差异。 基于上述研究，我们将检验中心假设，即表达CD 44 s的幼稚T细胞在被DC呈递的髓磷脂抗原激活后，经历microRNA表达的表观遗传调节失调，所述microRNA表达调节炎性细胞因子基因的转录，导致促进Th 1/Th 17分化。此外，MOG反应性T细胞表达独特的CD 44 v同种型，其通过特异性配体如透明质酸（HA）和/或骨桥蛋白（OPN）促进它们与BBB处的EC的相互作用。这种相互作用会引发EC损伤和对BBB的显著损害。这些事件共同促进CNS中的炎症和脱髓鞘。为此，在本研究中，我们将鉴定在活化的MOG特异性T细胞上表达的CD 44变体同种型，并研究它们在EAE发病机制中的作用。接下来，我们将确定CD 44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miR表达触发表观遗传调控，从而导致T细胞从Th 1/T17细胞分化为Th 2/T17细胞。将尝试药物和遗传干预来逆转Th/Treg功能及其对EAE的影响。此外，将测试抗原特异性T细胞上表达的CD 44与BBB EC上的特异性配体之间的相互作用，导致EAE期间BBB的破坏和T细胞向CNS的跨EC迁移。最后，我们将确定使用包括模拟物在内的策略靶向CD 44 s或CD 44 v是否会预防EAE的发生和进展。总之，我们的研究应该为理解CD 44亚型在MS和其他影响大部分退伍军人的CNS炎性疾病的调节中的作用提供新的思路，并提供有利于退伍军人健康的新治疗方式。

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.