The Effects of KLF4 in experimental aortic aneurysm formation

描述（由申请人提供）：Ailawadi，Gorav项目总结主动脉瘤（AA）是美国第13大死亡原因。由于不存在改变疾病进展的药物治疗，因此了解AA的发病机制是一项重要任务。动脉瘤的标志包括炎症浸润、巨噬细胞和平滑肌细胞（SMC）产生基质金属蛋白酶（MMP），导致主动脉壁胶原蛋白和弹性蛋白破坏以及血管扩张。我们的初步数据表明，SMC经历表型转换定义为增加SMC生产的基质金属蛋白酶和下调SMC收缩标记基因实验性动脉瘤形成之前。在结扎诱导的血管损伤模型中，Kruppel样因子-4（KLF 4）的缺失已显示延迟表型转换为炎性表型。此外，在该模型中，KLF 4缺失导致中膜SMC过度增殖。KLF 4似乎在巨噬细胞和内皮细胞中具有相反的作用。我们实验室的初步研究已经通过免疫组织化学证明KLF 4在人类和实验性动脉瘤中显著升高。该提案的重点是检验KLF 4在实验性动脉瘤中起关键作用以及通过SMC、巨噬细胞和/或内皮细胞中KLF 4的作用介导效应的假设。目的1将确定条件性KLF 4基因敲除小鼠是否显示动脉瘤形成的改变，以及是否通过SMC或其他细胞类型的效应介导效应。我们将利用Owens（Mentor）实验室开发的几种独特的转基因敲除小鼠以及骨髓重建研究，这些研究将允许细胞特异性缺失KLF 4，并使用弹性蛋白酶灌注使它们经历实验性动脉瘤形成。目的2将确定表观遗传机制是否有助于KLF 4对主动脉瘤形成的影响。研究将检验以下假设：KLF 4通过与每个基因的启动子结合，介导与转录沉默和激活相关的组蛋白修饰，从而抑制动脉瘤内的SMC标记基因和激活几种炎症基因。最后，我们将使用KLF 4敲除小鼠确定AA中的这些表观遗传修饰是否依赖于KLF 4。PHS 398/2590（Rev. 11/07） 公共卫生相关性：项目负责人/主要研究者（最后一名、第一名、中间名）：Ailawadi、Gorav项目叙述/相关性没有经证实的药物治疗可以改变动脉瘤疾病的进展。在血管损伤模型中，KLF 4延迟SMC表型转换为炎症状态。此外，KLF 4在AA中高度上调。KLF 4缺失研究将使我们能够确定KLF 4和SMC表型在疾病进展中的作用，并确定这是否是减缓AA进展的潜在治疗靶点。

DESCRIPTION (provided by applicant): Ailawadi, Gorav Project Summary Aortic aneurysms (AA) are the 13th leading cause of death in the U.S. Since no medical therapy exists to alter the progression of disease, understanding the pathogenesis of AA is an important undertaking. The hallmark of AAs includes inflammatory infiltration, matrix metalloproteinase (MMP) production by macrophages and smooth muscle cells (SMCs) leading to destruction of collagen and elastin in the aortic wall and vessel dilation. Our preliminary data suggests that SMCs undergo phenotypic switching defined by increased SMC production of MMPs and downregulation of SMC contractile marker genes prior to experimental aneurysm formation. The loss of Kruppel like factor-4 (KLF4) has been shown to delay phenotypic switching to an inflammatory phenotype in a ligation-induced model of vascular injury. Moreover, in this model, KLF4 loss resulted in hyperproliferation of medial SMCs. KLF4 appears to have opposing effects in macrophages and endothelial cells. Preliminary studies in our lab have documented KLF4 is profoundly elevated in human and experimental aneurysms by immunohistochemistry. The focus of this proposal is to test the hypothesis that KLF4 plays a key role in experimental aneurysms and that effects are mediated through actions of KLF4 in SMCs, macrophages, and/ or endothelial cells. Aim 1 will determine if conditional KLF4 knockout mice show altered formation of aneurysms and if effects are mediated through effects in SMCs or in other cell types. We will utilize several unique transgenic knockout mice developed in the Owens (mentor's) lab as well as bone marrow reconstitution studies that will allow cell specific deletion of KLF4 and subject them to an experimental aneurysm formation using elastase perfusion. Aim 2 will determine if epigenetic mechanisms contribute to the effects of KLF4 on aortic aneurysm formation. Studies will test the hypothesis that KLF4 contributes to suppression of SMC marker genes and activation of several inflammatory genes within aneurysms, by binding to promoters in each of these genes, mediating histone modifications association with transcriptional silencing and activation. Finally, we will determine if these epigenetic modifications in AA are KLF4 dependent using KLF4 knockout mice. PHS 398/2590 (Rev. 11/07) Page Continuation Format Page PUBLIC HEALTH RELEVANCE: Program Director/Principal Investigator (Last, First, Middle): Ailawadi, Gorav Project Narrative/ Relevance There are no proven medical treatments to alter progression of aneurysm disease. KLF4 delays SMC phenotypic switching to an inflammatory state in models of vascular injury. Furthermore, KLF4 is highly upregulated in AA. Loss of KLF4 studies will allow us to determine the effect of KLF4 and SMC phenotype in the progression of disease and determine if this is a potential therapeutic target to slow AA progression.