The Role of HDAC9/MITR in the Pathogenesis of Thoracic Aortic Aneurysm (TAA)

 描述(由申请人提供)：主动脉瘤很常见，在美国影响高达1%的人。主动脉瘤的危险因素包括高血压、高胆固醇血症和男性。与腹主动脉动脉瘤不同，胸主动脉(TAA)的动脉瘤样扩张受遗传易感性的影响很大，通常与孟德尔遗传模式有关。通过对马凡综合征(MFS)、Loeys-Dietz综合征(LDS)等与TAA密切相关的孟德尔疾病的临床和实验研究，已在阐明动脉瘤发病机制方面取得了相当大的进展。与TAA相关的基因通常编码转化生长因子-β(β)信号通路的成员，或者编码平滑肌收缩功能的正效应因子。这些人类疾病分别被称为转化生长因子-β血管病(TGFR-βvs)或平滑肌收缩血管病(SMCV)。尽管转化生长因子βvs和SMCV在主动脉表型上有相似之处，但这两种形式的TAA之间的机制联系仍然不清楚。为了确定转化生长因子βvs和SMCV之间的致病相似性，我们建立了遗传触发的人类血管平滑肌细胞模型，并通过微阵列图谱检查了转录特征。寻找的记录显示，这两组人之间存在类似的调控失调。有趣的是，表观遗传效应基因HDAC9在转化生长因子β和SMCV中表达上调。有趣的是，HDAC9最近被牵涉到大血管卒中和冠状动脉疾病患者的全基因组关联筛选(GWAS)中，尽管它在这些人类血管疾病中的作用机制尚不清楚。在我们的实验中，表达模拟人类突变TGFBR2G357W(转化生长因子βV)和ACTA2R179H(SMCV)的动脉瘤转基因细胞被发现降低了迁移能力，细胞骨架异常，并减少了血管平滑肌细胞特异转录的平滑蛋白、钙粘蛋白和纽蛋白的表达。重要的是，所有这些表型都可以被siRNA介导的HDAC9沉默所抑制。我们继续记录了HDAC9在Marfan(Fbn1C1039G/+)和Loeys-Dietz 4型(Tgfb2-/+)小鼠主动脉中的表达增加，并伴随着VSMC特异性蛋白表达的降低，概括了体外观察。这些初步数据表明，HDAC9是TAA血管发病的关键介质。在这项应用中，我们将广泛研究HDAC9转录诱导(AIM1)的机制，增加HDAC9对血管平滑肌细胞表型(AIM2)的影响，以及靶向HDAC9活性以治疗实验性主动脉瘤(AIM3)的可行性。

 DESCRIPTION (provided by applicant): Aortic aneurysm is common, affecting up to 1% of people in the United States. Risk factors for aortic aneurysm include hypertension, hypercholesterolemia, and male sex. In contrast to aneurysm of the abdominal aorta, aneurysmal dilation of the ascending thoracic aorta (TAA) is heavily influenced by genetic predisposition, often associated with a Mendelian inheritance pattern. Considerable progress has been made in the elucidation of aneurysm pathogenesis through the clinical and experimental study of Mendelian disorders closely associated with TAA, such as Marfan syndrome (MFS) or Loeys-Dietz syndrome (LDS). Genes involved in TAA often encode members of the canonical transforming growth factor beta (TGF-β) signaling pathway, or alternatively encode positive effectors of smooth muscle contractile function. These human diseases have been termed transforming growth factor-β vasculopathies (TGFβVs) or smooth muscle contraction vasculopathies (SMCVs), respectively. Despite the aortic phenotypic similarities between TGFβVs and SMCVs, mechanistic links between the two forms of TAA remain obscure. To identify pathogenetic similarities between TGFβVs and SMCVs we created human vascular smooth muscle cellular models of genetically-triggered TAA and examined transcriptional signatures through microarray profiling. Transcripts were sought that showed similar dysregulation across these two groups. Interestingly, the epigenetic effector HDAC9 was found to be upregulated in TGFβVs and SMCVs. Interestingly, HDAC9 has recently been implicated in genome wide association screens (GWAS) involving patients with both large vessel stroke as well as coronary artery disease, although its mechanism of action in these human vascular diseases is poorly understood. In our experiments, cells expressing aneurysm transgenes mimicking human mutations TGFBR2G357W (TGFβV) and ACTA2R179H (SMCV) were found to have reduced migratory capacity, cytoskeletal abnormalities, and reduced expression of VSMC-specific transcripts for smoothelin, calponin, and vinculin. Importantly all of these phenotypes could be suppressed by siRNA mediated silencing of HDAC9. We went on to document increased expression of HDAC9 in aortas of Marfan (Fbn1C1039G/+) and Loeys-Dietz type 4 mice (Tgfb2-/+) that was accompanied by decreased VSMC specific protein expression, recapitulating in vitro observations. These preliminary data implicate HDAC9 as a critical mediator of vascular pathogenesis in TAA. In this application we will extensively investigate the mechanism of HDAC9 transcriptional induction (AIM1), the effect of increased HDAC9 on vascular smooth muscle cell phenotype (AIM2), and the feasibility of targeting HDAC9 activity for therapeutic benefit in experimental aortic aneurysm (AIM3).