RATIONALE Monocytes are key effectors of the mononuclear phagocyte system, playing critical roles in regulating tissue homeostasis and coordinating inflammatory reactions, including those involved in chronic inflammatory diseases such as atherosclerosis. Monocytes have traditionally been divided into 2 major subsets termed conventional monocytes and patrolling monocytes (pMo) but recent systems immunology approaches have identified marked heterogeneity within these cells, and much of what regulates monocyte population homeostasis remains unknown. We and others have previously identified LYN tyrosine kinase as a key negative regulator of myeloid cell biology; however, LYN's role in regulating specific monocyte subset homeostasis has not been investigated. OBJECTIVE We sought to comprehensively profile monocytes to elucidate the underlying heterogeneity within monocytes and dissect how Lyn deficiency affects monocyte subset composition, signaling, and gene expression. We further tested the biological significance of these findings in a model of atherosclerosis. METHODS AND RESULTS Mass cytometric analysis of monocyte subsets and signaling pathway activation patterns in conventional monocytes and pMos revealed distinct baseline signaling profiles and far greater heterogeneity than previously described. Lyn deficiency led to a selective expansion of pMos and alterations in specific signaling pathways within these cells, revealing a critical role for LYN in pMo physiology. LYN's role in regulating pMos was cell-intrinsic and correlated with an increased circulating half-life of Lyn-deficient pMos. Furthermore, single-cell RNA sequencing revealed marked perturbations in the gene expression profiles of Lyn-/- monocytes with upregulation of genes involved in pMo development, survival, and function. Lyn deficiency also led to a significant increase in aorta-associated pMos and protected Ldlr-/- mice from high-fat diet-induced atherosclerosis. CONCLUSIONS Together our data identify LYN as a key regulator of pMo development and a potential therapeutic target in inflammatory diseases regulated by pMos.

中文翻译：

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质谱分析和单细胞RNA测序的深表型揭示了单核细胞亚群异质性和寿命背后的LYN调控信号图谱。

RATIONALE单核细胞是单核吞噬细胞系统的关键效应物，在调节组织稳态和协调炎症反应（包括与慢性炎性疾病（如动脉粥样硬化）有关的炎症反应）中发挥关键作用。传统上，单核细胞被分为2个主要子集，分别称为常规单核细胞和巡逻单核细胞（pMo），但是最近的系统免疫学方法已经确定了这些细胞内明显的异质性，而调节单核细胞种群稳态的许多因素仍然未知。我们和其他人先前已将LYN酪氨酸激酶鉴定为髓样细胞生物学的关键负调控因子。然而，尚未研究LYN在调节特定单核细胞亚稳态中的作用。目的我们试图对单核细胞进行全面的分析，以阐明单核细胞内潜在的异质性，并剖析Lyn缺陷如何影响单核细胞亚群的组成，信号传导和基因表达。我们在动脉粥样硬化模型中进一步测试了这些发现的生物学意义。方法和结果对传统单核细胞和pMos中单核细胞亚群和信号通路激活模式的大规模细胞计数分析揭示了不同的基线信号特征，并且异质性比以前描述的要大得多。Lyn缺乏症导致pMos的选择性扩增和这些细胞内特定信号通路的改变，揭示了LYN在pMo生理中的关键作用。林恩 调节pMos的作用是细胞内在的，并且与Lyn缺陷pMos的循环半衰期增加有关。此外，单细胞RNA测序显示Lyn-/-单核细胞的基因表达谱中存在明显的扰动，而与pMo发育，存活和功能有关的基因上调。Lyn缺乏症还导致与主动脉相关的pMos显着增加，并保护Ldlr-/-小鼠免受高脂饮食诱导的动脉粥样硬化。结论我们的数据一起确定LYN是pMo发育的关键调节剂，并且是pMos调节的炎性疾病的潜在治疗靶标。Lyn缺乏症还导致与主动脉相关的pMos显着增加，并保护Ldlr-/-小鼠免受高脂饮食诱导的动脉粥样硬化。结论我们的数据一起确定LYN是pMo发育的关键调节剂，并且是pMos调节的炎性疾病的潜在治疗靶标。Lyn缺乏症还导致与主动脉相关的pMos显着增加，并保护Ldlr-/-小鼠免受高脂饮食诱导的动脉粥样硬化。结论我们的数据一起确定LYN是pMo发育的关键调节剂，并且是pMos调节的炎性疾病的潜在治疗靶标。