Cell Biology of Astrocytes in the Optic Nerve Head

描述(申请人提供)：在青光眼中观察到的神经节细胞变性(在人类和小鼠中)不是扩散到整个视网膜，而是发生在指向视神经头的部分。第一次对轴突造成这种几何形状的明显定位是位于巩膜正后方的视神经头部分，因为在那里轴突被组织成与视网膜具有地形关系的束状结构。可能是个别轴突束单独受损或幸免于难，导致同一视网膜中出现部分变性或正常的神经节细胞。在人类，视神经头包含一个坚硬的胶原层筛板，由星形胶质细胞排列。相比之下，小鼠的视神经只包含一个星形细胞网络(“胶质层”)，它在青光眼神经中是杂乱无章的。由于星形胶质细胞不是刚性的，这表明轴突束的损伤可能不是机械性的。相反，它增加了胶质层星形胶质细胞可能直接参与青光眼病理生理学的可能性。我们提出了四项关于胶质板层星形胶质细胞生物学的单细胞水平的研究，使用的是一只在分散的单个星形胶质细胞中表达GFP的小鼠。(1)我们将描述正常星形细胞构筑的胶质细胞板层。(2)在视网膜表面引入整体视神经损伤(视神经挤压)或节细胞轴突局灶性损伤(激光)，研究单个星形胶质细胞在病理条件下的行为。(3)我们将在转基因小鼠中观察这些轴突损伤的后果，这些转基因小鼠的星形胶质细胞因中间丝或连接蛋白43的敲除而受损。(4)我们将观察GFP标记的星形胶质细胞在一种新品系的GFP-DBA/2J青光眼小鼠身上的行为，作为一种现实的、缓慢的青光眼模型。公共卫生相关性：青光眼导致视网膜神经节细胞进行性和不可逆转的丧失，其轴突形成视神经，从而切断原本具有功能的视网膜与大脑的连接。最近的实验证据表明，视神经中的一种非神经细胞类型(星形胶质细胞)可能在该病中发挥了积极作用。我们的目标是比以往更详细地研究单个星形胶质细胞对损伤和青光眼变性的反应。

DESCRIPTION (provided by applicant): The ganglion cell degeneration observed in glaucoma (in humans and mice) is not spread diffusely over the whole retina but occurs in sectors that point towards the optic nerve head. The obvious localization for a first insult to the axons that would cause this geometry is the portion of the optic nerve head that lies directly behind the sclera, because there the axons are organized into bundles with a topographic relationship to the retina. It is possible that individual axon bundles are separately damaged or spared, leading to sectors of degenerated or normal ganglion cells in the same retina. In humans, the optic nerve head contains a rigid, collagenous lamina cribrosa, lined by astrocytes. In contrast, the murine optic nerve contains only a meshwork of astrocyes (the "glial lamina"), which is disorganized in glaucomatous nerves. Because astrocytes are not rigid, this suggests that the damage to axon bundles may not be mechanical. Instead it raises the possibility that astrocytes of the glial lamina may be directly involved in the pathophysiology of glaucoma. We propose four studies on the single-cell level of the cell biology of glial lamina astrocytes using a mouse that expresses GFP in sporadic, individual astrocytes. (1) We will describe the normal astrocytic architecture of the glial lamina. (2) We will introduce global optic nerve lesions (optic nerve crush) or focal lesions of ganglion cell axons on the retinal surface (by laser) to study the behavior of individual astrocytes under pathological conditions. (3) We will observe the consequences of these axonal lesions in transgenic mice whose astrocytes are compromised by knock-out of intermediate filaments or connexin43. (4) We will observe the behavior of GFP-labeled astrocyes in a new strain of GFP-DBA/2J glaucomatous mice as a realistic, slow model of glaucoma. PUBLIC HEALTH RELEVANCE: Glaucoma leads to a progressive and irreversible loss of retinal ganglion cells, whose axons form the optic nerve, and thereby severs the connection of an otherwise functional retina with the brain. Recent experimental evidence suggests that a non-neuronal cell type (astrocytes) in the optic nerve might play an active role in the disease. Our goal is to study the reaction of individual astrocytes to injury and glaucomatous degeneration in more detail than has been possible before.