The Effects of KLF4 in experimental aortic aneurysm formation

项目概述：主动脉瘤（Aortic动脉瘤，AA）是美国第13大致死原因。由于目前还没有药物治疗来改变疾病的进展，因此了解其发病机制是一项重要的工作。AAs的特征包括炎症浸润，巨噬细胞和平滑肌细胞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，SMCs经历了表型转换，其定义为SMC产生MMPs增加和SMC收缩标记基因下调。在结扎诱导的血管损伤模型中，Kruppel样因子-4 （KLF4）的缺失已被证明可以延迟表型向炎症表型的转换。此外，在该模型中，KLF4缺失导致内侧间充质干细胞过度增殖。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已经通过免疫组织化学证明KLF4在人和实验性动脉瘤中显著升高。本研究的重点是验证KLF4在实验性动脉瘤中起关键作用的假设，以及KLF4在SMCs、巨噬细胞和/或内皮细胞中的作用。目的1将确定条件KLF4敲除小鼠是否表现出动脉瘤形成的改变，以及这种影响是否通过SMCs或其他细胞类型介导。我们将利用Owens （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，允许细胞特异性删除KLF4，并使用弹性蛋白酶灌注使它们进行实验性动脉瘤形成。目的2将确定表观遗传机制是否有助于KLF4对主动脉瘤形成的影响。研究将验证KLF4通过结合这些基因的启动子，介导组蛋白修饰与转录沉默和激活相关，从而抑制SMC标记基因和激活动脉瘤内几个炎症基因的假设。最后，我们将使用KLF4敲除小鼠来确定这些AA中的表观遗传修饰是否依赖于KLF4。小灵通398/2590 （Rev. 11/07）页延续格式页

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