Structure and Biomechanics of the Human Optic Nerve Head

描述（由申请人提供）：原发性开角型青光眼（POAG）是一种严重且日益严重的健康问题，约占全球失明人数的12%。研究已经确定年龄、祖先群体（种族背景）和眼内压（IOP）是POAG发生和进展的重要风险因素。我们的长期目标是了解这些既定的危险因素和视网膜神经节细胞的反应性丧失之间的关系，这是这种疾病的特征。目前的观点认为，视神经乳头（ONH）和筛板（LC）的生物力学特性在定义POAG的病理学中起着关键作用。在初步研究中，我们已经确定LC易受压迫性变化影响的区域（下、上级）比LC其他区域（鼻和颞）含有更少的胶原蛋白，并显示出更多的压力诱导变形（更顺应性）。在这些发现的基础上，本提案的目的是通过在微米尺度上显微重建LC的结构组件和生物力学特性来定义ONH的三维生物力学特性，并将这些特性与POAG风险因素联系起来。 根据我们的初步研究，我们提出了以下可验证的假设：1）LC的结构和压力诱导的变形存在区域差异，易发生早期青光眼改变的区域胶原减少，变形增加; 2）LC结构和压致变形的区域差异随年龄的增长而增大，并随祖先群体的不同而变化;使得年龄较大的个体和具有对POAG更敏感的祖先的那些个体将具有更大的结构变化并显示出更大的压力诱导的变形; 3）LC结构和压力诱导变形的区域差异与三维微观弹性模量的差异直接相关，使得LC最易受昏迷损伤（并且与年龄和血统相关）的区域与其他区域相比将具有显著的弹性模量差异。 为了验证这些假设，我们开发了创新的、最先进的技术，以高分辨率全面评估人类ONH的三维（3D）结构和生物力学特性。这些技术利用了已知的非线性光学效应，当超快激光器产生的高强度光子与组织相互作用时，会发生这种效应。 使用这些新技术，我们建议通过以下具体目标来研究不同年龄的正常个体和不同祖先的离体人眼：1）在4个维度上动态映射（时间和空间）使用人工压力室和超快激光在离体人ONH中IOP诱导的胶原纤维和弹性纤维结构的变化; 2）以高分辨率（0.9mm横向和2 mm轴向）三维重建ONH，以体积测量结构的区域变化，并将这些变化与同一只眼睛中测量的压力诱导变形相关;体外人ONH的生物力学性质，以将结构与生物力学性质和对POAG的敏感性相关联。 我们希望这些研究将提供新的，至关重要的，有关人类ONH的生物力学特性的信息，并提供一个更清楚的了解POAG的危险因素。 公共卫生相关性：在这个建议中，我们将阐明胶原蛋白和弹性成分的筛板（LC）在轴突损伤的病理生理学中的作用，随着年龄的增长，以及它如何可能会加速增加眼压。我们完全期望这些数据能够为人类视神经乳头（ONH）的生物力学特性提供至关重要的信息，并为原发性开角型青光眼（POAG）的危险因素提供更清晰的理解。为了实现我们的目标，我们将使用基于超快激光的最先进的创新技术，该技术可以产生用于识别弹性蛋白的双光子激发荧光，用于识别胶原蛋白的二次谐波产生的信号和激光诱导的光学击穿，以使用声辐射力弹性显微镜来探测微观生物力学特性，从而全面评估ONH的三维结构和生物力学特性。

DESCRIPTION (provided by applicant): Primary open angle glaucoma (POAG) represents a serious and growing health problem accounting for ~12% of global blindness. Studies have identified age, ancestral group (racial background), and intra- ocular pressure (IOP) as significant risk factors for the development and progression of POAG. Our long- range goal is to understand the relationship between these established risk factors and the responsive loss of retinal ganglia cells that characterizes this disease. Current wisdom proposes that the biomechanical properties of the optic nerve head (ONH) and lamina cribrosa (LC) play a critical role in defining the pathology of POAG. In preliminary studies, we have identified that regions of the LC susceptible to glaucomatous change (inferior, superior) contain less collagen and show more pressure-induced deformation (more compliant) than other regions of the LC (nasal and temporal). Building on these findings, the objective of this proposal is to define the 3 dimensional biomechanical properties of the ONH by microscopically reconstructing the structural components and biomechanical properties across the LC at a micron scale and relate these properties to POAG risk factors. Based on our preliminary studies we propose the following testable hypotheses:1) That there are regional differences in both the structure and pressure-induced deformation of the LC such that regions susceptible to early glaucomatous change have decreased collagen and increased deformation; 2) That the regional differences in LC structure and pressure-induced deformation increase with age and vary with ancestral group, such that older individuals and those with ancestries more susceptible to POAG will have greater structural changes and show greater pressure induced deformation; 3) That the regional differences in LC structure and pressure-induced deformation are directly related to differences in the 3 dimensional, microscopic elastic modulus such that regions of the LC most susceptible to glaucomatous damage (and related to age and ancestry) will have significant differences in the elastic modulus compared to other regions. To test these hypotheses, we have developed innovative, state of the art technologies to globally assess the three dimensional (3D) structure and biomechanical properties of the human ONH with high resolution. These technologies take advantage of known non-linear optical affects that occur when high intensity photons generated by ultrafast lasers interact with tissue. Using these novel technologies we propose to study ex vivo human eyes from normal individuals and different ancestries at varying ages by the following Specific Aims: 1) Dynamically map in 4 dimensions (time and space) IOP induced changes in collagen fibril and elastic fiber structure in ex vivo human ONH using an artificial pressure chamber and an ultrafast laser; 2) Three dimensionally reconstruct the ONH at high resolution (0.9 mm lateral and 2 mm axial) to volumetrically measure the regional changes in structure and relate these to the measured pressure induce deformations in the same eye; 3) Measure the regional (superior vs. inferior etc.) biomechanical properties of ex vivo human ONH to relate structure to the biomechanical properties and susceptibility to POAG. We expect that these investigations will provide new, and critically important, information concerning the biomechanical properties of the human ONH and provide a clearer understanding of the risk factors for POAG. PUBLIC HEALTH RELEVANCE: In this proposal, we will clarify the role of collagen and elastic components of the lamina cribrosa (LC) in the pathophysiology of axonal injury that occurs with aging and how it may be accelerated by increased IOP. We fully expect these data to lead to critically important information concerning the biomechanical properties of the human optic nerve head (ONH) and provide a clearer understanding of the risk factors for primary open angle glaucoma (POAG). To achieve our goal, we will use innovative, state of the art technologies based on ultrafast lasers that can produce two photon excited fluorescence for identifying elastin, second harmonic generated signals for identifying collagen and laser induced optical breakdown to probe the microscopic biomechanical properties using Acoustic Radiation Force Elastic Microscopy to globally assess the three dimensional structure and biomechanical properties of the ONH.