Role of reactive astrocytes in prion diseases

摘要 Prion病是一种无法治疗且100%致命的遗传性神经退行性疾病家族。星形胶质细胞和小胶质细胞向反应性状态的转变被认为是包括Pron、阿尔茨海默病和帕金森病在内的神经退行性疾病的主要特征之一。以往的研究主要集中在反应性小胶质细胞，而对反应性星形胶质细胞在疾病发病机制中的作用知之甚少。近年来，越来越多的人认识到，反应性星形胶质细胞与小胶质细胞一样，与慢性神经变性密切相关。然而，与Pron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，并首次对反应性星形胶质细胞在普恩病毒疾病中的作用进行了批判性研究。我们对感染病毒的动物的初步研究揭示了多种生理功能的全球失调，包括反应性星形胶质细胞中神经元支持功能的丧失。此外，从普恩病毒感染的小鼠分离的反应性星形胶质细胞被发现对初级神经元显示出有害的影响。星形胶质细胞的反应程度被发现可以预测病毒病的潜伏期，这表明星形胶质细胞的表型变化有助于更快的疾病进展。与目前认为星形胶质细胞的反应性是由STAT3转录因子驱动的知识一致，我们观察到在感染普恩病毒的动物中，STAT3在反应性星形胶质细胞中被激活。目前的应用将使用一种新的小鼠模型，ALDH1L1-CreERT-STAT3-FLOXP，用于条件敲除星形胶质细胞中的STAT3，以检查反应性星形胶质细胞在普恩疾病中的作用。具体目标1将检测星形胶质细胞中STAT3转录因子的条件性敲除对小鼠Pron病发病机制的影响。特定目标2将使用从感染普恩病毒的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的STAT3基因敲除在多大程度上挽救了它们的体内平衡功能，并影响了小胶质细胞的反应状态。具体目标3将使用单核RNAseq来表征与普里恩病相关的反应性星形胶质细胞的表型异质性。在该提案完成后，我们希望了解反应性星形胶质细胞是否推动疾病的发病机制，以及有条件地敲除STAT3是否拯救了重要的星形胶质细胞内稳功能和/或延迟或改善了疾病。因此，这项研究的结果将提供关键信息，即星形胶质细胞的反应性是否应该被作为治疗普恩病毒疾病的潜在治疗策略。

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.