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 神经节细胞变性的病理生理机制尚不清楚 清楚因此，目前的药物依赖于改变一个主要的风险因素，即眼内压。 然而，仅仅降低眼内压并不总是足够的，许多患者继续缓慢地 失去视力。识别对神经节细胞存活有害或有益的新机制， 有利于开发青光眼的替代治疗方法。 青光眼病理生理学中的一个主要假设是视神经乳头内的星形胶质细胞 (ONH)在神经节细胞变性中发挥重要作用，尽管尚不清楚这种作用是什么。星形细胞 是一个焦点，因为（1）他们填充ONH，一个早期神经节细胞轴突损伤发生的部位，和（2） ONH中的星形胶质细胞变得高度“反应性”，这是一个改变其形态、功能和 分子表型，但在中枢神经系统的白色物质是不是很清楚。尽管该领域认识到 虽然它们的重要性，但对ONH星形胶质细胞（和白色星形胶质细胞）的性质基本缺乏了解， 重要的星形胶质细胞一般），是什么使他们不同，他们在疾病中做什么。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， 更好地了解ONH星形胶质细胞，但这是一个不完整的图片。 在这里，我们将全转录组分析与一种新的核糖标签策略相结合， 从不同组织区域星形胶质细胞特异性分离mRNA。我们将比较星形胶质细胞 年轻人无髓ONH、有髓视神经和胼胝体的转录组 以及老年小鼠和经历眼内压慢性升高的小鼠。我们假设 ONH星形胶质细胞是一个分子上不同的群体相比，星形胶质细胞在更远端的髓鞘 视神经本身，并且它们具有与昏迷的事实相关的功能特化， 病理生理变化优先发生在神经头区域。年龄和眼内升高 压力诱导独特的转录谱。我们之前的形态学特征和 免疫细胞化学标记模式强烈提示ONH星形胶质细胞确实是独特的， 其他地区。我们检验这一假说的具体目标是：（1）研究 正常青年（3个月）和老年小鼠ONH、视神经本体和胼胝体中的星形胶质细胞 (12 mths），（2）研究ONH和视神经固有星形胶质细胞的转录谱， 年轻（3个月）和老年小鼠（12个月）在眼内压慢性升高后。 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.