ECM Regulation of Ocular Surface Disease

摘要 细菌性角膜炎是一种严重的公共健康威胁，与严重的眼部疾病有关，是 世界范围内致盲的主要原因。据估计，细菌性角膜炎的年发病率为 全球约有500,000名患者。即使使用现代的治疗方法，角膜感染也可能导致 50%的患者视力不佳，12%的患者接受手术治疗。几种革兰氏阳性和革兰氏阴性 细菌病原体可以感染角膜并导致角膜炎。细菌病原体使用所有可用的资源 在充满敌意的寄主环境中生存。宿主细胞外基质(ECM)成分的颠覆及其 受体作为附着部位被认为是许多细菌共有的一种常见的毒力机制。 然而，在活体内几乎没有数据明确支持这一想法。我们在初步研究中发现，删除 Syndecan-1(Sdc1)是上皮细胞的一种主要细胞表面硫酸乙酰肝素蛋白多糖(HSPG)，可引起 在Sdc1-/-角膜明显较少的划痕性角膜感染小鼠模型中获得功能 易受肺炎链球菌感染。局部给药过量的Sdc1胞外结构域或 硫酸乙酰肝素(HS)对肺炎链球菌角膜感染有明显的抑制作用，提示HS链是Sdc1 作为细胞表面附着受体促进感染。然而，肺炎链球菌不与Sdc1相互作用 而Sdc1在肺炎链球菌感染后脱落，表明Sdc1不直接支持肺炎链球菌。 粘附力。相反，Sdc1通过驱动纤维连接蛋白(FN)纤维的组装来促进肺炎链球菌的粘连 在感染受损角膜时肺炎链球菌附着的角膜基底膜中。过剩 Sdc1胞外结构域通过与FN中的肝素结合结构域结合来抑制肺炎链球菌的角膜感染，以及 干扰肺炎链球菌与Fn的结合。根据这些数据，这项提案将审查总体 假设特定的ECM相互作用协调角膜基底膜的组装，并且 眼表的某些细菌病原体利用这些正常的生物过程来促进其 发病机制。这一假设将在三个具体目标上得到检验。目标1将定义HS的结构基础 抑制细菌性角膜感染。目标2将确定细菌诱导的 Sdc1在角膜感染中的脱落，目标3将阐明Sdc1调节的潜在机制。 角膜基底膜中纤维连接蛋白的形成。这些研究有望揭开之前 角膜细胞外基质的未知功能及细菌毒力整合途径的建立 角膜炎。

ABSTRACT Bacterial keratitis is a serious public health threat associated with significant ocular morbidity and is one of the major causes of blindness worldwide. By one estimate, the annual incidence of bacterial keratitis is approximately 500,000 patients worldwide. Even with modern day treatment, corneal infections can result in poor vision in 50% and surgical intervention in 12% of patients. Several Gram-positive and Gram-negative bacterial pathogens can infect the cornea and cause keratitis. Bacterial pathogens use all resources available to survive in the hostile host environment. Subversion of host extracellular matrix (ECM) components and their receptors as attachment sites is thought to be a common virulence mechanism shared by many bacteria. However, there are few data that clearly support this idea in vivo. We found in preliminary studies that deletion of syndecan-1 (Sdc1), a major cell surface heparan sulfate proteoglycan (HSPG) of epithelial cells, causes a gain of function in a mouse model of scarified corneal infection, where Sdc1-/- corneas are significantly less susceptible to Streptococcus pneumoniae infection. Topical administration of excess Sdc1 ectodomains or heparan sulfate (HS) significantly inhibits S. pneumoniae corneal infection, suggesting that HS chains of Sdc1 promote infection as a cell surface attachment receptor. However, S. pneumoniae does not interact with Sdc1 and Sdc1 is shed upon S. pneumoniae infection, indicating that Sdc1 does not directly support S. pneumoniae adhesion. Instead, Sdc1 promotes S. pneumoniae adhesion by driving the assembly of fibronectin (FN) fibrils in the corneal basement membrane to which S. pneumoniae attaches when infecting injured corneas. Excess Sdc1 ectodomains inhibit S. pneumoniae corneal infection by binding to the heparin-binding domain in FN, and interfering with S. pneumoniae binding to FN. Based on these data, this proposal will examine the overall hypothesis that specific ECM interactions coordinate the assembly of corneal basement membranes, and that certain bacterial pathogens of the ocular surface exploit these normal biological processes to promote their pathogenesis. This hypothesis will be tested in 3 Specific Aims. Aim 1 will define the structural basis of how HS inhibits bacterial corneal infection. Aim 2 will determine the significance and relevance of bacteria-induced Sdc1 shedding in corneal infection, and Aim 3 will elucidate the underlying mechanisms of how Sdc1 regulates FN fibrillogenesis in the corneal basement membrane. These studies are expected to uncover previously unknown functions of the ECM in the cornea and to establish a new integrated virulence pathway in bacterial keratitis.