Trabecular Meshwork Cytoskeletal Signaling-Regulation of Aqueous Humor Outflow

描述（由申请人提供）：原发性开角型青光眼 (POAG) 是美国第二大失明原因，通常与眼内压 (IOP) 升高相关，眼压升高是由于房水 (AH) 通过小梁网 (TM) 和施累姆氏管 (SC) 流出的阻力增加所致。尽管 IOP 被认为是开角型青光眼的主要危险因素，但导致 AH 流出阻力增加的病因机制在很大程度上尚不清楚。该应用的长期目标是确定通过 TM 和 SC 对 AH 流出阻力增加的具体病因机制，并利用这些知识开发新颖的靶向疗法来降低青光眼患者的 IOP。 我们最近开发了一种动物模型，该模型表现出 IOP 持续增加，以响应 AH 流出途径中组成型活性 Rho GTPase (RhoAV14) 的表达。基于从该模型得出的非常重要和有希望的初步观察结果，我们提出了一个新的假设，即小梁流出途径中异常的 Rho/Rho 激酶信号传导活性引起的高眼压在机制上与 TM 和 SC 细胞向基质生成肌成纤维细胞样细胞的内皮向间质转化增强有关，其激活导致细胞外基质 (ECM) 沉积和小管旁结缔组织 (JCT) 结构的变化，从而导致眼高压阻力 AH 流出。我们的研究结果支持了这一中心假设，即 RhoAV14 诱导的高眼压大鼠眼和人 POAG 供体眼中的 JCT 疤痕、ECM 积累以及肌成纤维细胞特异性标记物的表达。 我们建议在三个具体目标下研究这一新假设： 1. 在暴露于与青光眼相关的机械应变和生理相关因子（TGF-¿、自分泌运动因子/LPA轴、结缔组织生长因子）时，确定 Rho/Rho 激酶信号传导在驱动 TM 和 SC 细胞向基质生成肌成纤维细胞样细胞的内皮间质转化 (EndMT) 中的作用； 2. 验证 RhoAV14 大鼠模型中的高眼压、TM 和 SC 细胞向肌成纤维细胞样细胞的 EndMT 增加、AH 流出途径组织内的结构改变以及对 AH 流出的抵抗力增加之间的机制联系，以及 3. 评估 Rho 激酶抑制剂增加高眼压青光眼眼中 AH 流出的功效部分与抑制 ECM 沉积和激活的纤维形成作用有关的预测的有效性。 AH 流出途径中的肌成纤维细胞，使用 RhoAV14 高眼压大鼠作为模型系统。 对这些研究的探索有望确定青光眼受试者 AH 流出阻力增加的具体病因机制，并增强我们对某些生理因素和 Rho 激酶抑制剂如何影响青光眼患者 AH 流出和 IOP 的机制理解。

DESCRIPTION (provided by applicant): Primary open-angle glaucoma (POAG) is the second leading cause of blindness in the United States and is commonly associated with elevation of intraocular pressure (IOP) resulting from increased resistance to aqueous humor (AH) outflow through the trabecular meshwork (TM) and Schlemm's canal (SC). Although IOP is considered to be a primary risk factor for open angle glaucoma, the etiological mechanisms responsible for increased resistance to AH outflow are largely unknown. The long-range goal of this application is to identify specific etiological mechanisms underlying increased resistance to AH outflow through the TM and SC, and leverage this knowledge to develop novel and targeted therapies for lowering IOP in glaucoma patients. We recently developed an animal model that exhibits a sustained increase in IOP in response to expression of a constitutively active Rho GTPase (RhoAV14) in the AH outflow pathway. Based on the highly significant and promising preliminary observations derived from this model, we propose a novel hypothesis that ocular hypertension induced by aberrant Rho/Rho kinase signaling activity in the trabecular outflow pathway is mechanistically linked to an enhanced endothelial to mesenchymal transition of TM and SC cells into matrix producing myofibroblast-like cells, the activation of which results in extracellular matrix (ECM) deposition and changes in juxtacanalicular connective tissue (JCT) architecture, leading to increased resistance to AH outflow. This central hypothesis is supported by our findings of scarring of the JCT, ECM accumulation and expression of myofibroblast-specific markers in the trabecular pathway of RhoAV14-induced ocular hypertensive rat eyes and in human POAG donor eyes. We propose to investigate this novel hypothesis under three specific aims: 1. Establish the role of Rho/Rho kinase signaling in driving the endothelial to mesenchymal transition (EndMT) of TM and SC cells into matrix-producing myofibroblast-like cells, upon exposure to mechanical strain and physiologically relevant factors (TGF-¿, autotaxin/LPA axis, connective tissue growth factor) associated with glaucoma; 2. Verify the mechanistic link between ocular hypertension in the RhoAV14 rat model, increased EndMT of TM and SC cells into myofibroblast-like cells, structural alterations within AH outflow pathway tissues, and increased resistance to AH outflow, and 3. Evaluate the validity of the prediction that the efficacy of Rho kinase inhibitors to increase AH outflow in ocular hypertensive glaucomatous eyes is linked partly to suppression of ECM deposition and fibrogenic effects of activated myofibroblasts in AH outflow pathway, using the RhoAV14 ocular hypertensive rat as a model system. Exploration of these studies is expected to identify the specific etiological mechanisms involved in increased resistance to AH outflow in glaucoma subjects and enhance our mechanistic understanding of how certain physiological factors and Rho kinase inhibitors influence AH outflow and IOP in glaucoma patients.