Axonal cytoskeletal changes in experimental glaucoma

实验性青光眼的轴突细胞骨架变化

• 批准号: 7921993
• 负责人: BRAD FORTUNE
• 金额: $ 34.08万
• 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/7921993
• 关键词: Animals; Axon; Biopsy Specimen; Birefringence; Blindness; Caliber; Cell Death; Cell physiology; Chronic; Chronic Disease; Clinical; Data; Data Collection; Detection; Diagnosis; Early Diagnosis; Electroretinography; Experimental Models; Eye; Functional disorder; Glaucoma; 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; public health relevance; 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）：该项目提出，在视网膜神经节细胞（RGC）死亡之前以及视力永久丧失之前，存在一个RGC功能障碍的阶段，其特征是轴突微管（MTS）降解。新兴的证据表明，MT降解最初可以发生，而没有轴突口径的实质性变化。因此，建议在RNFL厚度变化之前，应通过扫描视网膜神经纤维层（RNFL）的扫描激光极化（SLP）来优先检测涉及MT降解的早期RGC功能障碍。这是因为SLP的基本光学原理基于检测偏振光的相位延迟，这是由于长圆柱MTS在RNFL中产生的光学性质双折射所致。初步研究表明，在几种不同的RGC损伤模型（包括实验性青光眼（EG））中，RNFL延迟在下降之前下降，并且比RNFL厚度快于RNFL厚度。在没有RNFL厚度变化的情况下，SLP对轴突MT破坏的临床检测可能代表青光眼损伤的早期且可能可逆的相位，并为治疗调整提供了可检测到的临床检测标记。因此，该提案的中心假设是，围绕乳头乳腺癌轴突内MT的破坏是青光眼损伤的早期指标，在轴突能力的变化和这些轴突的物理损失之前。使用非人类灵长类动物（NHP）模型在三个特定目标中测试了这一假设产生的预测。具体目的1：测试围绕乳腺胞周围RNFL延迟的预测将在通过光谱域光学相干断层扫描（SD-OCT）和前视神经头（ONH）表面变化测量的RNFL厚度变化之前下降。具体目的2：测试预测，与组织学定义的RNFL厚度变化和腹膜后视神经轴突丢失相比，乳腺周围RNFL MT中断的组织学证据将更为明显。特定目的3：测试RGC功能异常与以异常轴突MT为特征的RGC变性相关的预测。为了实现这些目标，例如，将通过小梁网络的激光光凝诱导例如，在24 NHP中引起中度的单侧慢性IOP升高。每周使用SLP，SD-OCT和CSLT，在每种NHP的双眼中，每周测量每周的RNFL延迟，RNFL厚度和ONH表面地形，在4周的激光前基线期间，并在EG发作后长达8个月（AIM 1）。对于每个参数，统计学上的显着变化被定义为超过每只眼睛基线间隔变异性的任何变化，两次证实。一旦每只动物发展到其终点，就会为组织学数据收集和分析牺牲（AIM 2）。在AIM 1的体内结构测试的每个星期，RGC功能还将在两只眼睛中使用三种经过验证的电视模拟形式进行评估（AIM 3）。公共卫生相关性：青光眼是美国和世界各地最常见的失明原因之一。这是一种慢性疾病，没有已知的治愈方法，但是前瞻性纵向试验发现，降低眼内压力的治疗可降低渐进视力丧失率。因此，早期诊断可以及时进行治疗干预，并减少青光眼的总体影响。但是，实现及时的诊断需要临床检测到视神经头（ONH）和视网膜神经纤维层（RNFL）（RNFL）的青光眼损伤的发作和进展，这在每位青光眼患者的临床护理中仍然是核心挑战。该项目评估和进步，用于检测青光眼的早期损害和进展。