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扩散到整个视网膜，而是发生在指向视神经乳头的部分。对轴突的第一次损伤将导致这种几何形状的明显定位是直接位于巩膜后面的视神经乳头的部分，因为在那里轴突被组织成与视网膜具有拓扑关系的束。有可能个别轴突束分别受损或幸免，导致同一视网膜中的节细胞退化或正常。在人类，视神经乳头包含一个刚性的胶原筛板，内衬星形胶质细胞。相比之下，鼠视神经仅包含星形胶质细胞的网状结构（“胶质层”），其在胶质瘤神经中是紊乱的。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，它提出了胶质层的星形胶质细胞可能直接参与青光眼的病理生理学的可能性。我们提出了四项研究的单细胞水平的胶质层星形胶质细胞的细胞生物学使用的小鼠，表达GFP在零星的，个别的星形胶质细胞。(1)我们将描述正常的星形胶质细胞结构的胶质层。(2)我们将介绍全球视神经病变（视神经挤压）或视网膜表面神经节细胞轴突的局灶性病变（通过激光），以研究病理条件下单个星形胶质细胞的行为。(3)我们将观察这些轴突病变的后果，在转基因小鼠的星形胶质细胞受到损害敲除中间丝或连接蛋白43。(4)我们将观察GFP标记的星形胶质细胞在新品系的GFP-DBA/2 J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的进行性和不可逆的损失，其轴突形成视神经，从而切断了功能性视网膜与大脑的连接。最近的实验证据表明，视神经中的非神经元细胞类型（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胶质瘤变性的反应，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.