The Role of the Unfolded Protein Response in the Pathogenesis of Fuchs Endothelial Corneal Dystrophy

富氏内皮性角膜营养不良（FECD）是一种常见的角膜内皮疾病，可导致疼痛和视力丧失。由于缺乏有效的医学治疗和对潜在病理生理的不完全了解，FECD是角膜移植的主要指征。先前的实验表明，基因异种人FECD标本的角膜内皮中未折叠蛋白反应（UPR）上调。UPR是内质网（ER）内错误折叠蛋白积累时激活的主要细胞应激途径。在内质网应激未解决的情况下，它可能最终启动细胞凋亡。家族性FECD与α - 2胶原VIII （COL8A2）基因突变有关。含有人类FECD COL8A2 Q455K突变的转基因小鼠模型可在宿主机构获得。最近对其角膜表型的表征显示出与人类FECD疾病模式惊人的相似性。该小鼠模型提供了独特的机会，可以在遗传定义的体内系统中专门研究FECD的细胞病理生理学。本文提出的总体假设是，角膜内皮细胞表达COL8A2 Q455K FECD突变激活UPR，导致内皮细胞凋亡诱导。为了验证这一假设，我们将在不同年龄的COL8A2 Q455K突变小鼠中评估UPR相关基因的mRNA和蛋白水平。此外，我们还将研究COL8A2 FECD突变小鼠的内皮细胞是否对药物诱导的UPR激活具有更高的敏感性。这些拟议的研究应该为FECD的分子机制提供更深入的理解，并作为未来发展保守治疗方法的基础。

Fuchs endothelial corneal dystrophy (FECD) is a common disorder of the corneal endothelium leading to pain and loss of vision. FECD is a leading indication for corneal transplantations due to lack of curative medical treatments and an incomplete understanding of the underlying pathophysiology. Previous experiments indicate upregulation of the unfolded protein response (UPR) in the corneal endothelium of genetically heterogeneous human FECD specimens. The UPR is a major cell stress pathway activated in response to accumulation of misfolded proteins within the endoplasmic reticulum (ER). In the case of unresolved ER stress, it may eventually initiate apoptosis. Familial FECD has been associated with mutations in the alpha 2 collagen VIII (COL8A2) gene. A transgenic mouse model containing the human FECD COL8A2 Q455K mutation is available at the host institution. The recently conducted characterization of its corneal phenotype showed a striking similarity to the human FECD disease pattern. This mouse model provides the unique opportunity to specifically study the cellular pathophysiology of FECD in a genetically defined, in vivo system. The overall hypothesis of the proposal presented here is that corneal endothelial cell expression of the COL8A2 Q455K FECD mutation activates the UPR, resulting in endothelial apoptosis induction. To test this hypothesis the mRNA and protein levels of UPR associated genes will be assessed in COL8A2 Q455K mutant mice at different ages. Furthermore, it will be investigated if cultured endothelial cells from COL8A2 FECD mutant mice have increased sensitivity to pharmacologically induced UPR activation. These proposed studies should provide a deeper understanding of the molecular mechanisms implicated in FECD and should serve as a basis for the future development of conservative therapeutic approaches.