Role of reactive astrocytes in prion diseases

总结 朊病毒疾病是一种无法治疗的可传播神经退行性疾病，并且是100%致命的。星形胶质细胞和小胶质细胞转化为反应性状态被认为是神经退行性疾病（包括朊病毒、阿尔茨海默病和帕金森病）的主要标志之一。绝大多数以前的工作与朊病毒疾病相关的神经炎症集中在反应性小胶质细胞，而很少有人知道反应性星形胶质细胞在疾病发病机制中的作用。近年来，越来越多的人认识到，像小胶质细胞一样，反应性星形胶质细胞与慢性神经退行性变密切相关。然而，与朊病毒疾病相关的反应性星形胶质细胞是有益的还是有害的尚不清楚。目前的项目旨在填补这一空白，是第一个严格审查反应性星形胶质细胞在朊病毒疾病中的作用。我们在感染朊病毒的动物中的初步研究揭示了多种生理功能的整体失调，包括反应性星形胶质细胞中神经元支持功能的丧失。此外，发现从朊病毒感染小鼠中分离的反应性星形胶质细胞对原代神经元表现出有害作用。发现星形胶质细胞反应性的程度可预测朊病毒疾病的潜伏期，表明星形胶质细胞的表型变化有助于更快的疾病进展。与目前的知识，星形胶质细胞的反应性是由Stat 3转录因子驱动的一致，我们观察到活化的Stat 3在朊病毒感染的动物的反应性星形胶质细胞。本申请将采用一种新的小鼠模型Aldh 1 l1-CreERT-Stat 3-BMP 3，用于条件性敲除星形胶质细胞中的Stat 3，以检查反应性星形胶质细胞在朊病毒疾病中的作用。具体目标1将检查星形胶质细胞中Stat 3转录因子的条件性敲除对小鼠朊病毒病发病机制的影响。具体目标2将采用从朊病毒感染动物中急性分离的星形胶质细胞和小胶质细胞来测试星形胶质细胞中Stat 3敲除拯救其稳态功能的程度;并影响小胶质细胞的反应状态。具体目标3将采用单核RNAseq来表征与朊病毒疾病相关的反应性星形胶质细胞的表型异质性。在完成该提案后，我们希望了解反应性星形胶质细胞是否驱动疾病的发病机制，以及Stat 3的条件性敲除是否挽救了星形胶质细胞的重要稳态功能和/或延迟或改善疾病。因此，这项研究的结果将提供关键信息，星形胶质细胞的反应性是否应作为一个潜在的治疗策略治疗朊病毒疾病的目标。

Summary Prion diseases are a family of transmissible neurodegenerative maladies that have no treatment and are 100% lethal. Transformation of astrocytes and microglia into reactive states is recognized as one of the major hallmarks of neurodegenerative disease including prion, Alzheimer’s, and Parkinson’s diseases. The vast majority of previous work on neuroinflammation associated with prion diseases has focused on reactive microglia, whereas very little is known about the role of reactive astrocytes in disease pathogenesis. Recent years witnessed a growing appreciation of the view that, like microglia, reactive astrocytes are intimately involved in chronic neurodegeneration. However, whether the reactive astrocytes associated with prion diseases are beneficial or detrimental is not known. The current project is designed to fill this gap and is the first to critically examine the role of reactive astrocytes in prion disease. Our preliminary studies in animals infected with prions reveal global dysregulation across multiple physiological functions including the loss of neuronal support function in reactive astrocytes. Moreover, reactive astrocytes isolated from prion-infected mice were found to exhibit deleterious effects on primary neurons. The degree of astrocyte reactivity was found to be predictive of the incubation time to prion disease, suggesting that phenotypic changes in astrocytes contribute to faster disease progression. Consistent with current knowledge that astrocyte reactivity is driven by the Stat3 transcription factor, we observed activation of Stat3 in reactive astrocytes in prion-infected animals. The current application will employ a novel mouse model, Aldh1l1-CreERT-Stat3-floxP, for conditional knockout of Stat3 in astrocytes to examine the role of reactive astrocytes in prion disease. Specific Aim 1 will examine the effects of conditional knockout of the Stat3 transcription factor in astrocytes on the pathogenesis of prion disease in mice. Specific Aim 2 will employ astrocytes and microglia acutely isolated from prion-infected animals to test the extent to which Stat3 knockout in astrocytes rescues their homeostatic functions; and impacts the reactive state of microglia. Specific Aim 3 will employ single-nuclei RNAseq to characterize the phenotypic heterogeneity of reactive astrocytes associated with prion disease. Upon completion of the proposal we expect to learn whether reactive astrocytes drive disease pathogenesis, and whether conditional knockout of Stat3 rescues important homeostatic functions of astrocytes and/or delays or ameliorates the disease. Thus, the results of this study will provide critical information as to whether astrocyte reactivity should be targeted as a potential therapeutic strategy for treating prion disease.