Trabecular Meshwork Cytoskeletal Signaling-Regulation of Aqueous Humor Outflow

描述(申请人提供)：原发性开角型青光眼(POAG)是美国第二大致盲原因，通常与眼内压(IOP)升高有关，这是由于小梁网(TM)和Schlemm管(SC)对房水(AH)流出的阻力增加所致。虽然眼压被认为是开角型青光眼的主要危险因素，但导致青光眼排出阻力增加的病因机制尚不清楚。这项应用的长期目标是确定通过TM和SC对AH流出阻力增加的特定病因机制，并利用这一知识开发新的、有针对性的治疗方法来降低青光眼患者的眼压。我们最近开发了一个动物模型，该模型显示了在AH流出通路中结构性活性Rho GTP酶(RhoAV14)的表达导致眼压持续升高。基于这一模型的重要和有希望的初步观察，我们提出了一个新的假说，即小梁流出通路中异常的Rho/Rho激酶信号活性导致的高眼压与TM和SC细胞向基质产生肌成纤维样细胞的内皮-间充质转化增强有关，这种转化导致细胞外基质(ECM)沉积和跟侧结缔组织(JCT)结构改变，从而增加对AH流出的阻力。在RhoAV14诱导的高眼压大鼠和人类POAG供体眼的小梁通路中，JCT的瘢痕形成、ECM积聚和肌成纤维细胞特异性标记物的表达支持了这一中心假说。我们建议在三个特定的目标下研究这一新的假说：1.在机械应变和青光眼相关的生理因素(转化生长因子β、自体趋化蛋白/LPA轴、结缔组织生长因子)的作用下，确定Rho/Rho激酶信号在驱动TM和SC细胞内皮细胞向间充质转化(EndMT)向产生基质的肌成纤维样细胞转变中的作用；2.以RhoAV14大鼠为模型系统，验证了RhoAV14模型大鼠高眼压、TM细胞和SC细胞向肌成纤维细胞样细胞的EndMT增加、AH流出通路组织结构改变和AH流出阻力增加之间的机制联系；3.以RhoAV14高眼压大鼠为模型系统，评价Rho激酶抑制剂增加AH流出的有效性部分与抑制ECM沉积和AH流出通路中激活的肌成纤维细胞的纤维化作用有关。对这些研究的探索有望确定青光眼患者对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流出和眼压的机制理解。

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.