The astrocyte transcriptome in age and glaucoma: a comparative study of the optic nerve head, optic nerve proper and corpus callosum

项目摘要 青光眼神经节细胞变性的潜在病理生理机制尚不清楚 安全。正因为如此，目前的药物依赖于修改一个主要的危险因素，即眼压。 然而，仅仅降低眼压并不总是足够的，许多患者继续缓慢地 失去视力。识别对神经节细胞生存有害或有益的新机制将 有利于青光眼替代疗法的发展。 青光眼病理生理学的一个主要假说是视神经头内的星形胶质细胞 (ONH)在神经节细胞退行性变中起重要作用，尽管目前还不清楚这一作用是什么。星形胶质细胞 是一个焦点，因为(1)它们分布在ONH，一个发生早期神经节细胞轴突损伤的地方，以及(2) ONH中的星形胶质细胞变得高度“反应”，这一过程改变了它们的形态、功能和 分子表型，但在白质的中枢神经系统还不是很清楚。尽管该领域认识到 它们的重要性，根本上缺乏对ONH星形胶质细胞(和白色星形细胞)的特性的了解 一般的星形胶质细胞)，它们的不同之处，以及它们在疾病中的作用。迄今为止的研究 通常使用整个ONH组织和/或检查单个或一小组基因/途径来 更好地理解ONH星形胶质细胞，但这是一幅不完整的图景。 在这里，我们将整个转录组分析与一种新的核标签策略相结合，该策略允许我们 从不同组织区域的星形胶质细胞中分离特异性的mRNAs。我们会比较星形细胞 幼年无髓ONH、有髓视神经本身和胼胝体的转录组 以及衰老的小鼠，以及经历了慢性眼压升高的小鼠。我们假设 与更远端髓鞘的星形胶质细胞相比，ONH星形胶质细胞在分子上是不同的群体 视神经本身，并且它们具有与青光眼相关的功能特化 病理生理改变主要发生在神经头区。眼内高度与年龄的关系 压力会导致一种独特的转录模式。我们之前的形态特征和 免疫细胞化学标记模式强烈表明ONH星形胶质细胞确实是独一无二的 其他地区。我们检验这一假说的具体目的是：(1)研究转录图谱 正常青年(3月龄)和老年小鼠ONH、视神经本体和穹隆体内星形胶质细胞的分布 (2)ONH和视神经组织中星形胶质细胞的转录水平。 幼鼠(3个月)和老龄鼠(12个月)慢性眼压升高。 这一探索性的建议将为未来更有针对性的假设提供重要的知识基础 驱动型研究。

Project Summary The underlying pathophysiological mechanisms in glaucomatous ganglion cell degeneration are still not clear. Because of this, current medications rely on modifying a major risk factor, which is intraocular pressure. However, lowering intraocular pressure alone is not always sufficient, and many patients continue to slowly lose vision. Identifying new mechanisms that are either harmful or beneficial for ganglion cell survival will benefit the development of alternative treatments for glaucoma. A leading hypothesis in the pathophysiology of glaucoma is that astrocytes within the optic nerve head (ONH) play an important role in the ganglion cell degeneration, albeit it is not clear what this role is. Astrocytes are a focus because (1) they populate the ONH, a site where early ganglion cell axon injury occurs, and (2) astrocytes in the ONH become highly “reactive”, a process that changes their morphology, function and molecular phenotype, but in the white matter of the CNS is not well understood. Although the field recognizes their importance, there is a fundamental lack of understanding of the properties of ONH astrocytes (and white matter astrocytes in general), what makes them different and what they are doing in disease. Studies to date have typically used whole ONH tissues and/or examined either a single or a small group of genes/pathways to better understand ONH astrocytes, but this is an incomplete picture. Here, we have combined whole transcriptome profiling with a novel ribotag strategy that allows us to isolate mRNAs specifically from astrocytes from different tissue regions. We will compare the astrocyte transcriptome from the unmyelinated ONH, the myelinated optic nerve proper and corpus callosum, in young and aged mice, and mice that have undergone chronic elevations in intraocular pressure. We hypothesize that ONH astrocytes are a molecularly distinct population compared to astrocytes in the more distal myelinated optic nerve proper, and that they have functional specializations associated with the fact that glaucomatous pathophysiological changes preferentially occur in the nerve head region. Age and elevations in intraocular pressure induces a unique transcriptional profile. Our previous morphological characterization and immunocytochemical labeling patterns strongly suggest that ONH astrocytes are indeed unique from those in the other regions. Our specific aims to test the hypothesis are: (1) investigate the transcriptional profile of astrocytes in the ONH, optic nerve proper and corpus callosum in both normal young (3 mths) and aged mice (12 mths), and (2) investigate the transcriptional profile of astrocytes from the ONH and optic nerve proper in young (3 mths) and aged mice (12 mths) following a chronic elevation in intraocular pressure. This exploratory proposal will provide an important knowledge base for future more focused hypothesis driven studies.