Role of LMO7 in atherosclerosis

LMO 7在动脉粥样硬化中的作用动脉粥样硬化是心血管疾病发病率的主要原因， 死亡率，包括心肌梗死（MI）、卒中和外周血管疾病。由于斑块破裂是一种 作为动脉粥样硬化血栓事件的关键因素，了解斑块稳定性的决定因素至关重要。的 其潜在的分子机制知之甚少，但薄帽纤维粥样硬化，其特征在于 炎症、基质金属蛋白酶（MMP）活性、大的坏死核心和薄的纤维帽也被考虑在内 更容易破裂血管平滑肌细胞（SMC）在斑块稳定中起关键作用， 形成纤维帽，覆盖脂质斑块和坏死核心。最近的研究表明， 改变范式的发现，即SMC占斑块内部的比例比以前更大 通过转分化到缺乏SMC标记的表型来欣赏，并且对SMC的投资是通过对SMC的标记来实现的。 SMC衍生细胞的斑块似乎具有动脉粥样硬化保护作用。因此，SMC在调节 斑块大小和稳定性。 多种证据支持TGF β 1信号在斑块中的保护作用。我们最近 鉴定了蛋白质LIM结构域仅7（LMO 7）作为SMC中TGF β 1信号传导的关键负反馈调节剂 促进伤口愈合解决（Xie et al，Circulation，2019）。具有全局或诱导性光滑的小鼠 肌肉特异性敲除LMO 7（SM-LMO 7-/-）表现出增强的TGF β信号传导和细胞外基质 (ECM)合成相比，对照血管损伤后。我们发现LMO 7抑制TGF β通路， 在多个层面上。在新的研究中，我们证明了SM-LMO 7-/-小鼠产生类似大小的斑块， 在ApoE-/-高脂饮食（HFD）模型中，与对照相比具有增加的稳定性的特征。SM- LMO 7-/-斑块具有减少的坏死核心尺寸、减少的CD 68+细胞、增加的ACTA 2和胶原蛋白 染色和较厚的纤维帽。这些小鼠中的初步谱系追踪数据显示，SM-LMO 7-/- 增加病变中转分化SMC衍生细胞的数量，这是一种可能具有保护作用的表型。 人颈动脉标本的初步数据显示，斑块中LMO 7 mRNA表达增加5.6倍， 相对于正常动脉，并且在破裂相对于非破裂病变中富集。我们假设LMO 7功能丧失 在SMC中促进小鼠和人类中更稳定的斑块。在目标1中，我们将确定SMC LMO 7的作用 在噬菌斑组成和基因表达中使用综合染色和单细胞RNA测序 分析。在目标2中，我们将剖析潜在的机制，在目标3中，我们直接测试SMC LMO 7的作用 通过评估小鼠中斑块破裂以及人中LMO 7表达和定位， 破裂vs稳定病变。这些研究将提供深入了解动脉粥样硬化斑块的病理生理学 具有潜在治疗意义的重塑。

Role of LMO7 in atherosclerosis Atherosclerosis is a major cause of cardiovascular disease morbidity and mortality, including myocardial infarction (MI), stroke, and peripheral vascular disease. As plaque rupture is a key factor in atherothrombotic events, understanding the determinants of plaque stability is critical. The underlying molecular mechanisms are poorly understood, but thin cap fibroatheromas, characterized by inflammation, matrix metalloprotease (MMP) activity, large necrotic cores, and thin fibrous caps, are considered more vulnerable to rupture. Vascular smooth muscle cells (SMC) play a critical role in plaque stabilization by forming the fibrous cap that covers the lipid-laden plaque and necrotic core. Recent studies have revealed the paradigm-changing findings that SMC comprise a greater portion of the plaque interior than previously appreciated by transdifferentiating to phenotypes that lack SMC markers, and that investment of the plaque by SMC-derived cells appears to be atheroprotective. Thus, SMC play a central role in regulating both plaque size and stability. Multiple lines of evidence support a protective role for TGF signaling in plaques. We have recently identified the protein LIM Domain Only 7 (LMO7) as a key negative feedback regulator of TGF signaling in SMC that promotes wound healing resolution (Xie et al, Circulation, 2019). Mice with global or inducible smooth muscle-specific knockout of LMO7 (SM-LMO7-/-) exhibit enhanced TGF signaling and extracellular matrix (ECM) synthesis compared to controls following vascular injury. We find that LMO7 represses the TGF pathway at multiple levels. In new studies, we demonstrate that SM-LMO7-/- mice develop plaques of similar size but with features of increased stability compared to controls in the ApoE-/- high fat diet (HFD) model. The SM- LMO7-/- plaques have reduced necrotic core size, decreased CD68+ cells, increased ACTA2 and collagen staining, and thicker fibrous caps. Preliminary lineage tracing data in these mice reveals that SM-LMO7-/- increases the number of transdifferentiated SMC-derived cells in lesions, a phenotype that may be protective. Preliminary data in human carotid specimens reveals that LMO7 mRNA expression is increased 5.6X in plaque vs normal artery, and is enriched in ruptured vs non-ruptured lesions. We hypothesize that LMO7 loss of function in SMC promotes more stable plaques in mice and humans. In Aim 1, we will determine the role of SMC LMO7 in plaque composition and gene expression using comprehensive staining and single cell RNA-sequencing analyses. In Aim 2, we will dissect underlying mechanisms, and in Aim 3, we directly test the role of SMC LMO7 in lesion stability by assessing plaque rupture in mice, as well as LMO7 expression and localization in human ruptured vs stable lesions. These studies will provide insights into the pathophysiology of atherosclerotic plaque remodeling with potential therapeutic implications.