Axonal cytoskeletal changes in experimental glaucoma

描述(由申请人提供)：我们和其他人发表的证据明确表明，在实验性视网膜神经节细胞(RGC)轴索损伤(包括非人灵长类动物(NHP)单侧实验性青光眼(EG))后，扫描激光偏振仪(SLP)测量的视网膜神经纤维层(RNFL)延迟比光学相干断层扫描(OCT)测量的RNFL厚度下降更快。SLP在穿过双折射RNFL组织后，通过扫描束检测相位延迟的相对程度。正常的RNFL组织固有地表现出强烈的双折射，主要是因为它的轴突富含致密、有序的轴突细胞骨架元素，特别是微管。因此，SLP测量RNFL迟缓提供了RNFL轴突细胞骨架完整性的临床分析。我们发现，这些早期的RNFL迟缓异常伴随着RGC功能的丧失，当光谱域OCT(SDOCT)检测到RNFL厚度变化时，10-15%的眶内视神经轴突丢失。目前的提案将以两种方式扩展这一调查路线，这两种方式对于将我们的发现转化为人类青光眼患者的临床管理至关重要。首先，我们将检验这一假说，即早期RNFL迟缓异常与轴突运输缺陷有关。其次，我们将验证以下假设：早期RNFL延迟异常可以通过降低眼压来逆转，钙通道调节增强逆转，逆转将保护随后的RGC功能丧失、RNFL变薄、轴突运输中断和视神经轴突丢失。该项目的具体目标是：具体目标1：检验部门异常的RNFL迟滞(用SLP衡量)可以预测随后的部门RNFL变薄(用SDOCT衡量)和随后的部门视网膜功能障碍(用多焦视网膜电描记术衡量)。具体目的2：验证轴突运输缺陷与SLP测量的RNFL迟滞改变的开始有关的假设。具体目的3：验证以下假设：SLP测量的RNFL延迟变化在局部治疗干预下是可逆的，逆转将对随后在体内测量的进行性RGC功能丧失和RNFL变薄以及轴突运输中断和视神经轴突丢失(通过尸检组织病理学评估)具有保护作用。证明早期RNFL迟缓异常与轴突运输中断有关，并且通过普通局部治疗干预逆转其对随后进行性RGC功能改变和视神经轴突丢失具有保护作用，这将对人类青光眼患者的临床护理具有直接的翻译相关性，并为青光眼轴突变性的病理生理序列提供洞察。

DESCRIPTION (provided by applicant): Evidence we and others have published unequivocally demonstrates that retinal nerve fiber layer (RNFL) retardance measured by scanning laser polarimetry (SLP) declines prior to and faster than RNFL thickness measured by optical coherence tomography (OCT) following experimental retinal ganglion cell (RGC) axonal injury, including non-human primate (NHP) unilateral experimental glaucoma (EG). SLP detects the relative degree of phase retardance manifest by a scanning beam after it passes through the birefringent RNFL tissue. Normal RNFL tissue inherently exhibits strong birefringence primarily because its axons are enriched with a dense, orderly array of axonal cytoskeletal elements, microtubules in particular. SLP measurements of RNFL retardance thus provide a clinical assay of RNFL axonal cytoskeletal integrity. We have shown that these early RNFL retardance abnormalities are accompanied by loss of RGC function and that by the time RNFL thickness changes are detected by spectral domain OCT (SDOCT), 10-15% of the orbital optic nerve axons are lost. The current proposal will extend this line of investigation in two ways that are critical to translating our findings to the clinical management of human glaucoma patients. First, we will test the hypothesis that early-stage RNFL retardance abnormalities are associated with axonal transport deficits. Second, we will test the hypothesis that early RNFL retardance abnormalities are reversible by lowering intraocular pressure (IOP), that reversal is enhanced by calcium channel regulation, and that reversal will be protective against subsequent RGC functional loss, RNFL thinning, axonal transport disruption and optic nerve axon loss. The Specific Aims of the project are: Specific Aim 1: To test the prediction that sectoral abnormalitie of RNFL retardance (measured by SLP) are predictive of subsequent sectoral RNFL thinning (measured by SDOCT) and of subsequent sectoral retinal dysfunction (measured by multifocal electroretinography). Specific Aim 2: To test the hypothesis that axonal transport deficits exist a the onset of RNFL retardance changes measured by SLP. Specific Aim 3: To test the hypothesis that RNFL retardance changes measured by SLP are reversible upon topical therapeutic intervention and that reversal will be protective against subsequent progressive RGC functional loss and RNFL thinning measured in vivo, as well as axonal transport disruption and optic nerve axon loss (assessed by post mortem histopathological studies). Proving that early-stage RNFL retardance abnormalities are associated with axonal transport disruption and that their reversal by common topical therapeutic intervention is protective against subsequent progressive RGC functional changes and optic nerve axon loss will have direct, translational relevance to the clinical care of human glaucoma patients and provide insight into the pathophysiological sequence of glaucomatous axonal degeneration.