The Effects of KLF4 in experimental aortic aneurysm formation

描述(申请人提供)：Ailawadi，Gorav项目摘要：主动脉瘤(AA)是美国第13大致死原因。由于目前还没有改变疾病进展的药物治疗，了解AA的发病机制是一项重要的工作。腹主动脉硬化的特点是炎症浸润，巨噬细胞和平滑肌细胞(SMC)产生基质金属蛋白酶(MMP)，导致主动脉壁胶原和弹性蛋白的破坏和血管扩张。我们的初步数据表明，在实验性动脉瘤形成之前，SMC经历了表型转换，其特征是SMC产生MMPs的增加和SMC收缩标记基因的下调。在结扎诱导的血管损伤模型中，Kruppel样因子-4(KLF4)的丢失已被证明延迟了表型向炎性表型的转换。此外，在该模型中，KLF4丢失导致了中膜SMC的过度增殖。KLF4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证明，通过免疫组织化学方法，KLF4在人和实验性动脉瘤中显著升高。这项建议的重点是验证KLF4在实验性动脉瘤中起关键作用的假设，以及KLF4通过作用于SMC、巨噬细胞和/或内皮细胞而发挥作用的假设。目的1将确定条件性KLF4基因敲除小鼠是否表现出动脉瘤形成的改变，以及影响是否通过SMC或其他细胞类型的影响而介导。我们将利用欧文斯(Mentor‘s)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删除KLF4，并使用弹性蛋白酶灌流使它们形成实验性动脉瘤。目的2将确定表观遗传机制是否有助于KLF4在主动脉瘤形成中的作用。研究将验证这一假设，即KLF4通过与这些基因中的每个基因中的启动子结合，介导组蛋白修饰与转录沉默和激活相关，从而有助于抑制SMC标记基因和激活动脉瘤中的几个炎症基因。最后，我们将使用KLF4基因敲除小鼠来确定AA中的这些表观遗传修饰是否依赖于KLF4。PHS 398/2590(11/07版)页面续格式页面 公共卫生相关性：项目主任/首席调查员(最后、第一、中间)：Ailawadi，Gorav项目叙述/相关性目前还没有证实的药物治疗可以改变动脉瘤疾病的进展。KLF4延缓血管损伤模型中SMC向炎症状态的表型转换。此外，KLF4在再生障碍性贫血中高度上调。KLF4研究的缺失将使我们能够确定KLF4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.