Role of IL1b in Regulating SMC and Macrophage Differentiation in Atherosclerosis

描述(申请人提供)：动脉粥样硬化是一种慢性炎症性疾病，是发达国家发病率和死亡率的主要原因。然而，我们对其发生的潜在机制以及包括斑块破裂和可能的心肌梗死或中风在内的终末期临床事件的了解仍然存在根本差距。尽管该领域的教条是病变内平滑肌细胞(SMC)与巨噬细胞的比率增加有助于斑块稳定性，但该模型的实验证据存在重大局限性，包括关于病变内哪些细胞是SMC还是单核巨噬细胞起源以及控制SMC和巨噬细胞数量和表型的机制。具有重要意义的是，使用欧文斯实验室开发的独特的SMC谱系追踪载脂蛋白E-/-小鼠的研究表明，在MAC2+但包括SMα-肌动蛋白(SMαA)在内的SMC标志物阴性的晚期病变中，约25%的细胞来自SMC-而不是巨噬细胞。相反，很大一部分SMαA+纤维帽细胞被认为是由SMC来源的，但事实并非如此。此外，我们有证据表明，很大一部分巨噬细胞来源的细胞显示巨噬细胞标志物表达减少，但却是SMαA+。综上所述，结果表明巨噬细胞可以转化为SMC样细胞，SMC可以转化为巨噬细胞样细胞。此外，结果表明，很可能有许多 在以前的研究中，病变细胞被错误地识别，从而极大地混淆了我们对调节这些细胞表型转换的机制和因素的理解。这项资助的中心焦点是确定IL1β和IL1R1信号的遗传或药物抑制对平滑肌细胞和巨噬细胞表型转变的影响，以及对晚期动脉粥样硬化病变的整体大小和稳定性的影响。然而，有很好的证据表明，干扰IL-1β信号可以抑制脂肪条纹的形成和早期 IL-1在晚期皮损中的作用尚不清楚。目的1a将利用我们实验室建立的新的SMC和髓系特异性谱系追踪IL1R1基因敲除小鼠来验证这一假说，即晚期动脉粥样硬化病变中SMC和巨噬细胞表型依赖于IL1R1的转变在决定整体斑块和管腔大小以及包括多个斑块稳定性指标的病变成分中起关键作用。目的1b将根据我们实验室最近开发的一种非常新颖的表观遗传学SMC谱系追踪方法(Gomez等人，自然方法)对尸检标本进行分析，确定在我们的小鼠研究中观察到的表型转换是否发生在人类动脉粥样硬化病变中。目的2将确定用诺华公司小鼠抗白细胞介素1β抗体治疗载脂蛋白E基因缺失小鼠是否会导致病变大小、细胞成分或斑块稳定性指数的变化，以及平滑肌细胞和/或巨噬细胞表型的转变。

DESCRIPTION (provided by applicant): Atherosclerosis is a chronic inflammatory disease and is the leading cause of morbidity and death in developed countries. However, there are still fundamental gaps in our knowledge of the underlying mechanisms that contribute to its development, and end-stage clinical events including plaque rupture with possible myocardial infarction or stroke. Although the dogma in the field is that an increased ratio of smooth muscle cells (SMC) to macrophages within lesions promotes plaque stability, there are major limitations in the experimental evidence for this model including major ambiguities regarding which cells within lesions are of SMC versus monocyte-macrophage origin and the mechanisms that control SMC and macrophage number and phenotype. Of major significance, studies employing unique SMC lineage tracing ApoE-/- mice developed by the Owens lab provide evidence that ~25% of cells within advanced lesions that are Mac2+ but negative for SMC markers including SM α-actin (SMαA), are SMC- rather than macrophage-derived. Conversely, a significant fraction of SMαA+ fibrous cap cells, presumed to be SMC-derived, are not. Moreover, we have evidence in that a significant fraction of macrophage- derived cells show reduced macrophage marker expression but are SMαA+. Collectively, results show that macrophages may convert to SMC-like cells and SMC to macrophage-like cells. Moreover, results indicate that it is likely that many lesion cells have been mis-identified in previous studies in the field, thus greatly confounding our understanding of the mechanisms and factors that regulate phenotypic transitions of these cells. The central focus of this grant is to determine the effects of genetic or pharmacological inhibition of IL1β and IL1R1 signaling on phenotypic transitions of SMC and macrophages, as well as on the overall size and stability of late stage atherosclerotic lesions. Whereas there is good evidence that disruption of IL1β signaling inhibits formation of fatty streaks and early stage lesions, the role of IL1 in late stage lesions is unclear. Aim 1a will use novel utilize SMC and myeloid specific lineage tracing IL1R1 knockout mouse lines generated by our lab to test the hypothesis that IL1R1-dependent transitions in phenotype of SMC and macrophages within advanced atherosclerotic lesions play a critical role in determining overall plaque and lumen size, as well as lesion composition including multiple indices of plaque stability. Aim 1b will be o determine if phenotypic transitions observed in our mouse studies occur in human atherosclerotic lesions based on analysis of autopsy specimens using a highly novel epigenetic SMC lineage tracing method recently developed by our laboratory (Gomez et al., Nature Methods). Aim 2 will determine if treatment of ApoE null mice with a Novartis mouse anti-IL1β antibody induces changes in lesion size, cellular composition, or indices of plaque stability, as well as transitions in SMC and/or macrophage phenotype.