Cell Biology of Astrocytes in the Optic Nerve Head

描述（由申请人提供）：在青光眼（人类和小鼠）中观察到的神经节细胞变性不是弥漫性地分布在整个视网膜上，而是发生在指向视神经头的部分。轴突的第一个损伤会导致这种几何形状的明显定位是视神经头部直接位于巩膜后面的部分，因为轴突在那里被组织成束，与视网膜有地形关系。可能单个轴突束单独受损或幸免，导致同一视网膜上的神经节细胞部分退化或正常。在人类中，视神经头包含一个坚硬的，胶原的网层，由星形胶质细胞排列。相比之下，小鼠视神经只包含星形胶质细胞（“胶质层”）的网状结构，在青光眼神经中是无序的。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，它提出了胶质层星形胶质细胞可能直接参与青光眼的病理生理的可能性。我们提出在单细胞水平上对胶质层星形胶质细胞的细胞生物学进行四项研究，使用在散发性单个星形胶质细胞中表达GFP的小鼠。(1)我们将描述正常的胶质层星形细胞结构。(2)引入视神经全局性病变（视神经挤压）或视网膜表面神经节细胞轴突局灶性病变（激光），研究病理条件下单个星形胶质细胞的行为。(3)我们将在星形胶质细胞因敲除中间细丝或连接蛋白而受损的转基因小鼠中观察这些轴突损伤的后果。(4)我们将观察gfp标记星形胶质细胞在新型GFP-DBA/2J青光眼小鼠中的行为，作为青光眼的真实、缓慢模型。公共卫生相关性：青光眼导致视网膜神经节细胞（其轴突形成视神经）的进行性和不可逆丧失，从而切断了原本功能正常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元细胞（星形胶质细胞）可能在该疾病中发挥积极作用。我们的目标是研究单个星形胶质细胞对损伤和青光眼变性的反应，比以前更详细。

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.