Axonal cytoskeletal changes in experimental glaucoma

实验性青光眼的轴突细胞骨架变化

• 批准号: 8129511
• 负责人: BRAD FORTUNE
• 金额: $ 32.72万
• 依托单位: LEGACY EMANUEL HOSPITAL AND HEALTH CENTER
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-01 至 2013-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8129511
• 关键词: Animals; Axon; Biopsy Specimen; Birefringence; Blindness; Caliber; Cell Death; Cell physiology; Chronic; Chronic Disease; Clinical; Data; Data Analyses; Data Collection; Detection; Diagnosis; Early Diagnosis; Electroretinography; Experimental Models; Eye; Functional disorder; Glaucoma; Health; Histologic; Individual; Lasers; Measurement; Measures; Microtubules; Optic Disk; Optic Nerve; Optical Coherence Tomography; Optics; Patients; Phase; Physiologic Intraocular Pressure; Property; Retina; Retinal; Retinal Ganglion Cells; Scanning; Staging; Staining method; Stains; Structure; Surface; Testing; Therapeutic; Therapeutic Intervention; Thick; Trabecular meshwork structure; Transmission Electron Microscopy; United States; base; cell injury; clinical care; design; functional loss; in vivo; laser photocoagulation; nonhuman primate; polarimetry; polarized light; prospective; research study; retinal nerve fiber layer; tomography; tool

DESCRIPTION (provided by applicant): This project proposes that prior to retinal ganglion cell (RGC) death in glaucoma, and before permanent loss of vision, there exists a stage of RGC dysfunction characterized by degradation of axonal microtubules (MTs). Emerging evidence suggests that MT degradation can occur initially without substantial changes in axonal caliber. Therefore, it is proposed that early stage RGC dysfunction involving MT degradation should be preferentially detectable by scanning laser polarimetry (SLP) of the retinal nerve fiber layer (RNFL) prior to changes in RNFL thickness. This is because the fundamental optical principle of SLP is based on detecting phase retardance of polarized light, which is due to the optical property birefringence produced in the RNFL by the long, thin cylindrical MTs. Preliminary studies demonstrate that RNFL retardance declines prior to, and faster than RNFL thickness in several different experimental models of RGC injury, including experimental glaucoma (EG). Clinical detection of axonal MT disruption by SLP, in the absence of RNFL thickness changes, might represent an early and potentially reversible phase of glaucomatous damage and provide a clinically detectable marker for therapeutic adjustment. Thus the central hypothesis of this proposal is that disruption of MTs within the axons of the peripapillary RNFL is an early indicator of glaucomatous damage, preceding both changes in axonal caliber and physical loss of those axons. Predictions arising from this hypothesis are tested in three Specific Aims using a non-human primate (NHP) model of EG. Specific Aim 1: To test the prediction that peripapillary RNFL retardance will decline prior to RNFL thickness changes measured by spectral domain optical coherence tomography (sd-OCT) and prior to optic nerve head (ONH) surface changes measured by confocal scanning laser tomography (CSLT) in NHP eyes with EG; Specific Aim 2: To test the predictions that histological evidence of peripapillary RNFL MT disruption will be more pronounced than histologically-defined RNFL thickness changes and retrobulbar optic nerve axon loss; Specific Aim 3: To test the prediction that RGC functional abnormalities are associated with the intermediate stage of RGC degeneration characterized by abnormal axonal MTs. To achieve these Aims, EG will be induced via laser photocoagulation of the trabecular meshwork to cause moderate, unilateral chronic IOP elevation in 24 NHPs. Weekly measurements of peripapillary RNFL retardance, RNFL thickness and ONH surface topography will be made in both eyes of each NHP using SLP, sd-OCT and CSLT, respectively, during a 4-week pre-laser baseline period and for up to 8 months after onset of EG (Aim 1). For each parameter, statistically significant change is defined as any change exceeding the baseline intersession variability for each individual eye, twice confirmed. Once each animal progresses to its endpoint, it is sacrificed for histological data collection and analysis (Aim 2). During each week of in vivo structural testing for Aim 1, RGC function will also be assessed in both eyes using three proven forms of electroretinography (Aim 3). PUBLIC HEALTH RELEVANCE: Glaucoma is one of the most common causes of blindness in the United States and around the world. It is a chronic disease with no known cure, but prospective longitudinal trials have found that treatment to lower intraocular pressure decreases the rate of progressive vision loss. Thus, early diagnosis enables timely therapeutic intervention and reduces the overall impact of glaucoma. However, achieving a timely diagnosis requires clinical detection of the onset and progression of glaucomatous damage to the optic nerve head (ONH) and retinal nerve fiber layer (RNFL), which remain a central challenge in the clinical care of every glaucoma patient. This project evaluates and advances clinical tools for detecting early damage and progression of glaucoma.

描述（由申请人提供）：本项目提出在青光眼患者视网膜神经节细胞（RGC）死亡之前和永久性视力丧失之前，存在一个以轴突微管（MTs）降解为特征的RGC功能障碍阶段。新出现的证据表明，在轴突直径没有实质性变化的情况下，轴突退化最初可能发生。因此，我们建议在视网膜神经纤维层（RNFL）厚度变化之前，通过扫描激光偏振法（SLP）优先检测涉及MT降解的早期RGC功能障碍。这是因为SLP的基本光学原理是基于检测偏振光的相位延迟，这是由于长而薄的圆柱形mt在RNFL中产生的光学特性双折射。初步研究表明，在几种不同的RGC损伤实验模型中，包括实验性青光眼（EG）， RNFL延迟先于RNFL厚度下降，并且下降速度快于RNFL厚度。在没有RNFL厚度变化的情况下，SLP检测轴突MT破坏可能代表青光眼损害的早期和潜在可逆阶段，并为治疗调整提供临床可检测的标记。因此，本研究的核心假设是，乳头周围RNFL轴突内mt的破坏是青光眼损伤的早期指标，它先于轴突直径的改变和这些轴突的物理损失。从这一假设中产生的预测在三个特定目标中使用非人类灵长类动物（NHP） EG模型进行了测试。具体目的1：验证NHP伴EG眼在光谱域光学相干断层扫描（sd-OCT）测量RNFL厚度变化和共聚焦扫描激光断层扫描（CSLT）测量视神经头（ONH）表面变化之前乳头周围RNFL延迟下降的预测；具体目的2：验证预测乳头周围RNFL MT破坏的组织学证据将比组织学定义的RNFL厚度变化和球后视神经轴突损失更明显；具体目标3：为了验证RGC功能异常与以轴突MTs异常为特征的RGC退行性变中期相关的预测。为了实现这些目标，我们将通过激光光凝小梁网诱导EG，在24个NHPs中引起中度、单侧慢性IOP升高。在4周的激光前基线期和EG发作后长达8个月的时间内，将分别使用SLP、sd-OCT和CSLT对每个NHP的双眼进行乳头周围RNFL延迟、RNFL厚度和ONH表面形貌的每周测量（Aim 1）。对于每个参数，统计上显著的变化被定义为任何超过每只眼睛的基线间歇变异性的变化，两次确认。一旦每只动物进展到终点，就会被处死以收集和分析组织学数据（目的2）。在每周一周的Aim 1体内结构测试期间，还将使用三种已证实的视网膜电图（Aim 3）对双眼进行RGC功能评估。公共卫生相关性：青光眼是美国乃至全世界最常见的致盲原因之一。这是一种慢性疾病，没有已知的治愈方法，但前瞻性纵向试验发现，降低眼压的治疗可以降低进行性视力丧失的速度。因此，早期诊断可以使治疗干预及时，减少青光眼的整体影响。然而，及时诊断青光眼需要临床检测视神经头（ONH）和视网膜神经纤维层（RNFL）损伤的发生和进展，这仍然是每个青光眼患者临床护理的核心挑战。本项目评估和发展用于检测青光眼早期损伤和进展的临床工具。