Epigenetic control of vascular smooth muscle in cardiovascular disease

描述（由申请人提供）：血管平滑肌细胞（VSMC）表现出显著的可塑性，允许可逆分化和去分化。这一特性与骨骼肌或心肌细胞不同，后者经历终末分化。平滑肌可塑性在正常发育、生长和伤口愈合中是重要的，但也有助于病理学，包括动脉粥样硬化、内膜增生、高血压和移植动脉硬化。由于VSMC表现出这种独特的可塑性，我们假设在其他类型的干细胞中发现的调节机制也可能参与VSMC的表型调节。事实上，我们的初步数据表明，去分化的VSMC表达多种干细胞基因，包括Oct 4，Nanog和KLF 4。由于染色质修饰蛋白的泰特（ten-eleven translocation）家族最近被认为是胚胎和造血干细胞多能性的重要调节因子，我们研究了泰特蛋白在VSMC中的作用。我们的初步数据显示，TET 2在VSMC中以高水平表达，并且被分化剂诱导，但被PDGF-BB抑制。我们发现，TET 2是必要的和足够的SMC分化，其中TET 2协会与收缩基因启动子，并增加可及性，但抑制染色质在干细胞基因启动子。我们进一步发现，TET 2在正常血管中以高水平表达，但在疾病状态下显著下调，包括人类动脉粥样硬化和小鼠内膜增生。重要的是，TET 2过表达挽救动脉损伤后内膜增生。我们假设TET 2是一种新的VSMC表型的表观遗传主调节因子。我们相信我们已经发现了一个基本的新机制，这是平滑肌可塑性的基础。因此，这项工作对多种血管疾病具有重要意义。在以下具体目标中，我们提出了TET 2的作用机制，并确定TET 2在血管疾病模型中的作用。在具体目标1中，我们将使用最先进的方法来确定TET 2调节收缩和干细胞启动子甲基化和基因表达的表观遗传机制。在具体目标2中，我们将使用小鼠模型来确定TET 2在心血管疾病发病机制中的作用，包括动脉粥样硬化、内膜增生和移植物动脉硬化。因为我们已经发现TET 2的表观遗传调节位于VSMC表型调节的顶点，控制其他已知的介质，如心肌蛋白，SRF和KLF 4，我们建议理解TET 2在细胞和疾病水平的作用机制将产生新的治疗方法用于治疗和预防心血管疾病。

DESCRIPTION (provided by applicant): Vascular smooth muscle cells (VSMC) exhibit a remarkable plasticity that allows for reversible differentiation and de-differentiation. This propety is distinct from skeletal or cardiac myocytes, which undergo terminal differentiation. Smooth muscle plasticity is important in normal development, growth, and wound healing, but also contributes to pathologies including atherosclerosis, intimal hyperplasia, hypertension, and transplant arteriosclerosis. Because VSMC exhibit this unique plasticity, we hypothesized that regulatory mechanisms found in other types of stem cells might also be involved in VSMC phenotypic modulation. Indeed, our preliminary data demonstrate that de-differentiated VSMC express multiple stem cell genes, including Oct4, Nanog, and KLF4. As the TET (ten-eleven translocation) family of chromatin-modifying proteins has recently been implicated as essential regulators of pluripotency in embryonic and hematopoietic stem cells, we investigated the roles of TET proteins in VSMC. Our preliminary data reveal that TET2 is expressed at high levels in VSMC, and is induced by differentiating agents but repressed by PDGF-BB. We find that TET2 is necessary and sufficient for SMC differentiation, where TET2 associates with contractile gene promoters and increases accessibility, but represses chromatin at stem cell gene promoters. We further found that TET2 is expressed at high levels in normal vessels, but markedly downregulated in disease states, including human atherosclerosis and intimal hyperplasia in mice. Importantly, TET2 overexpression rescues intimal hyperplasia post-arterial injury. We hypothesize that TET2 is a novel epigenetic master regulator of VSMC phenotype. We believe we have uncovered a fundamental new mechanism that is the basis for smooth muscle plasticity. As such, this work has important implications for multiple vascular diseases. In the following specific aims, we propose to address mechanisms of action of TET2, and determine the role of TET2 in vascular disease models. In Specific Aim 1, we will use cutting edge methods to determine the epigenetic mechanisms by which TET2 regulates methylation and gene expression at contractile and stem cell promoters. In Specific Aim 2, we will use mouse models to determine the role of TET2 in the pathogenesis of cardiovascular diseases, including atherosclerosis, intimal hyperplasia, and graft arteriosclerosis. Because we have found that epigenetic regulation by TET2 lies at the apex of VSMC phenotypic modulation, controlling other known mediators such as myocardin, SRF, and KLF4, we propose that understanding the mechanisms of TET2 action at the cellular and disease level will generate new therapeutic approaches for treatment and prevention of cardiovascular disease.