Rationale; Vascular smooth muscle cell (VSMC) dysregulation is a hallmark of vascular disease, including atherosclerosis. In particular, the majority of cells within atherosclerotic lesions are generated from pre-existing VSMCs and a clonal nature has been documented for VSMC-derived cells in multiple disease models. However, the mechanisms underlying the generation of oligoclonal lesions and the phenotype of proliferating VSMCs are unknown. Objective; To understand the cellular mechanisms underlying clonal VSMC expansion in disease. Methods and Results; Here we analyse clonal dynamics in multi-color lineage-traced animals over time after vessel injury. We demonstrate that VSMC proliferation is initiated in a small fraction of VSMCs that initially expand clonally in the medial layer and then migrate to form the oligoclonal neointima. Selective activation of VSMC proliferation also occurs in vitro, suggesting that this is a cell-autonomous feature. Mapping of VSMC trajectories using single-cell RNA-sequencing reveals a continuum of cellular states after injury and suggests that VSMC proliferation initiates in cells that have downregulated the contractile phenotype and show evidence of pronounced phenotypic switching. We show that proliferation is associated with induced expression of stem cell antigen 1 (SCA1) and the expression signature previously identified in SCA1+ VSMCs in healthy arteries. A remarkably increased proliferation of SCA1+ VSMCs, directly validated in functional assays, indicates that SCA1+ VSMCs act as "first responders" in vascular injury. Early atherosclerotic lesions also had clonal VSMC contribution and we show that the proliferation-associated injury response is conserved in plaque VSMCs, extending these findings to atherosclerosis. Finally, we identify VSMCs in healthy human arteries that correspond to the SCA1+ state in mouse VSMCs and show that genes identified as differentially expressed in this human VSMC subpopulation are enriched for genes showing genetic association with cardiovascular disease. Conclusions; We show that cell-intrinsic, selective VSMC activation drives clonal proliferation after injury and in atherosclerosis. Our study suggests that healthy mouse and human arteries contain VSMCs characterised by expression of disease-associated genes that are predisposed for proliferation. Targeting such "first responder" cells in patients undergoing vascular surgery could effectively prevent injury-associated VSMC activation and neoatherosclerosis.

中文翻译：

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引发的平滑肌细胞在疾病中充当第一反应细胞

理由；血管平滑肌细胞（VSMC）失调是包括动脉粥样硬化在内的血管疾病的标志。特别是，动脉粥样硬化病变内的大多数细胞是由预先存在的VSMC产生的，并且在多种疾病模型中已证明VSMC衍生的细胞具有克隆性质。但是，尚不清楚寡克隆病变的产生和增生VSMC表型的潜在机制。目的; 了解疾病中克隆性VSMC扩展的细胞机制。方法和结果；在这里，我们分析了血管损伤后随时间变化的多色谱系追踪动物的克隆动力学。我们证明，VSMC增殖是在一小部分VSMC中引发的，该VSMC最初在中间层克隆扩展，然后迁移以形成寡克隆新内膜。VSMC增殖的选择性激活也发生在体外，这表明这是一种细胞自主功能。使用单细胞RNA测序的VSMC轨迹图揭示了损伤后细胞状态的连续性，并表明VSMC增殖在下调收缩表型并显示明显表型转换证据的细胞中开始。我们表明增殖与干细胞抗原1（SCA1）的诱导表达和先前在健康动脉中的SCA1 + VSMCs中鉴定的表达特征有关。在功能测定中直接验证的SCA1 + VSMC增殖显着增加，表明SCA1 + VSMC在血管损伤中充当“第一反应者”。早期的动脉粥样硬化病变也具有克隆的VSMC贡献，我们显示斑块VSMC中与增殖相关的损伤反应得以保留，从而将这些发现扩展至动脉粥样硬化。最后，我们在健康的人动脉中识别出与小鼠VSMC中的SCA1 +状态相对应的VSMC，并表明在该人VSMC亚群中差异表达的基因被丰富了显示与心血管疾病遗传相关的基因。结论；我们表明，细胞内在的，选择性的VSMC激活在损伤后和动脉粥样硬化中驱动克隆增殖。我们的研究表明，健康的小鼠和人类动脉中含有以表达与疾病相关的基因为特征的VSMC，这些基因容易扩散。针对这样的“第一响应者”