Cytokine regulation of glial reactivity

描述(申请人提供)：虽然多发性硬化症(MS)的中枢神经系统(CNS)髓鞘再分化有很好的文献记载，但其发生和程度并不普遍，这一点多年来一直困扰着研究人员。现在公认的是，多发性硬化症病变含有相当数量的早髓鞘少突胶质细胞，这表明重新髓鞘形成的可能性不受这些细胞的丧失的限制。这些数据表明，少突胶质细胞与其周围环境之间的相互作用可能决定重新髓鞘形成的成败。 反应性星形胶质细胞是多发性硬化症的一个突出的病理特征，已被证明在病变中与非髓鞘少突胶质细胞相互作用。我们利用原代培养的人类星形胶质细胞探索了星形胶质细胞反应和损伤修复之间的联系，并发现用TGFBeta1处理这些细胞培养物，一种在MS病变中上调的细胞因子，诱导Jagged1的表达，Jagged1是锯齿状/Notch/Hes发育信号通路的配体。Notch信号的激活被认为是中枢神经系统发育过程中维持迁移的少突胶质细胞处于未成熟状态的机制之一。在缺乏再髓鞘形成的活性MS斑块内部和周围，我们发现Jagged1由肥大的星形胶质细胞表达，而其受体Notch 1和下游效应因子Hes5定位于未成熟少突胶质细胞表型的细胞，TGFBeta1与血管周围细胞外基质相关。相比之下，Jagged1在再髓鞘病变中的表达可以忽略不计。此外，我们还发现，在Jagged1转基因的3T3细胞或TGFBeta1处理的星形胶质细胞上培养未成熟的原代人类少突胶质细胞，可以显著减少这些细胞的突起生长。 在这一应用中，我们将测试TGFBeta1在星形胶质细胞中触发的事件最终导致Notch介导的抑制少突胶质细胞成熟的假设。提出了三个具体目标。在第一个具体目标中，我们将确定TGFBeta1在原代人脑星形胶质细胞中诱导Jagged1的主要信号通路。在第二个特定目标中，我们将确定TGFBeta1处理的星形胶质细胞是否通过Notch信号抑制少突胶质细胞的成熟。在第三个特定目标中，我们将TGFBeta1、Jagged1及其下游Notch效应器的表达与多发性硬化症病变活动相关联。本申请中提出的实验是对我们实验室使用动物模型正在进行的工作的补充和平行，我们的长期目标将是寻找新的治疗途径，旨在鼓励多发性硬化症病变中的髓鞘再分化。

DESCRIPTION (provided by applicant): Although central nervous system (CNS) remyelination in multiple sclerosis (MS) is well documented, that its occurrence and extent are not more widespread has perplexed investigators for many years. It is now accepted that MS lesions contain appreciable numbers of premyelinating oligodendrocytes, indicating that the potential for remyelination is not limited by the loss of these cells. These data would suggest that interactions between oligodendrocytes and their surrounding environment may determine the success or failure of remyelination. Reactive astrocytes are a prominent pathological feature of MS, and have been shown to interact with nonmyelinating oligodendrocytes in lesions. We have explored links between astrocyte reactivity and lesion repair using primary cultures of human astrocytes, and have found that treatment of these cultures with TGFBeta1, a cytokine upregulated in MS lesions, induces expression of Jagged1, a ligand for the Jagged/Notch/Hes developmental signaling pathway. Activation of Notch signaling is considered to be one of the mechanisms used in the developing CNS to maintain migrating oligodendrocytes in an immature state. Within and around active MS plaques lacking remyelination, we have found that Jagged1 is expressed by hypertrophic astrocytes, while its receptor Notch 1 and the downstream effector Hes5 localize to cells with an immature oligodendrocyte phenotype, and TGFBeta1 is associated with perivascular extracellular matrix. In contrast, there is negligible Jagged1 expression in remyelinated lesions. In addition, we have found that culturing immature primary human oligodendrocytes on either Jagged1-transfected 3T3 cells or TGFBeta1-treated astrocytes leads to a significant reduction in process outgrowth from these cells. In this application, we will test the hypothesis that events triggered by TGFBeta1 in the astrocyte culminate in Notch-mediated inhibition of oligodendrocyte maturation. Three specific aims are proposed. In the first specific aim, we will define the major signaling pathways used by TGFBeta1 to induce Jagged1 in primary human astrocytes. In the second specific aim, we will determine whether TGFBeta1-treated astrocytes inhibit oligodendrocyte maturation via Notch signaling. In the third specific aim, we will correlate expression of TGFBeta1, Jagged1, and downstream Notch effectors with multiple sclerosis lesion activity. The experiments proposed in this application complement and parallel ongoing work in our laboratory using animal models, and our long-term goal will be to identify novel therapeutic avenues designed to encourage remyelination in the multiple sclerosis lesion.