The fibrous cap of atherosclerotic lesions arise from multiple cellular origins by PDGFRB- and bioenergetic mechanisms

Stable atherosclerotic plaques are characterized by a thick extracellular matrix (ECM)-rich fibrous cap populated by protective ACTA2+ myofibroblast (MF)-like cells, assumed to be almost exclusively derived from smooth muscle cells (SMC). Herein, we show that in murine and human lesions, ~20-40% of ACTA2+ fibrous caps cells, respectively, are derived from non-SMC sources, including endothelial cells (EC) or macrophages that have undergone Endothelial-to-Mesenchymal (EndoMT) or Macrophage-to-Mesenchymal (MMT) transitions. In addition, weshow that SMC-specific knockout of the platelet-derived growth factor receptor beta (PDGFRB) in Apoe-/- mice fed a Western diet (WD) for 18 weeks results in brachiocephalic artery (BCA) lesions nearly devoid of SMC. While absence of SMCs does not affect lesion size, remodeling, or ACTA2+ fibrous cap cell content, prolonged WD feeding results in reduced indices of stability, indicating that EndoMT and MMT-derived MFs cannot compensate indefinitely for loss of SMC-derived MFs. Using RNA-seq analysis of the BCA region and in vitro models, we demonstrate that SMC to MF transitions (SMC-MFT) is induced by PDGF and TFGβ and is dependent on aerobic glycolysis, while EndoMT is induced by IL1β and TGFβ. Together, we provide the first quantitative evidence that the ACTA2+ fibrous cap originates from a tapestry of cell types, which transition to an MF state through distinct signaling pathways that are either dependent on or associated with extensive metabolic reprogramming. scRNA-seq of atherosclerotic plaques of Apoe-/- mouse (with or without specific SMC KO of PDGFRB)

稳定性动脉粥样硬化斑块以富含厚细胞外基质（extracellular matrix, ECM）的纤维帽为特征，该纤维帽内充斥具有保护作用的ACTA2+成纤维细胞样（myofibroblast, MF）细胞，此前认为这类细胞几乎完全来源于平滑肌细胞（smooth muscle cell, SMC）。本研究表明，在小鼠和人类的动脉粥样硬化病灶中，ACTA2+纤维帽细胞分别有约20%~40%来源于非平滑肌细胞谱系，包括经历了内皮-间充质转化（Endothelial-to-Mesenchymal, EndoMT）的内皮细胞（endothelial cell, EC），以及经历了巨噬细胞-间充质转化（Macrophage-to-Mesenchymal, MMT）的巨噬细胞。此外，本研究发现，在喂食西方饮食（Western diet, WD）18周的载脂蛋白E基因敲除（Apoe-/-）小鼠中，特异性敲除平滑肌细胞的血小板衍生生长因子受体β（platelet-derived growth factor receptor beta, PDGFRB），会导致头臂动脉（brachiocephalic artery, BCA）病灶内几乎完全缺失平滑肌细胞。尽管平滑肌细胞的缺失不会影响病灶大小、重塑过程或ACTA2+纤维帽细胞总量，但长期喂食西方饮食会导致斑块稳定性指标下降，这表明内皮-间充质转化和巨噬细胞-间充质转化来源的成纤维细胞样细胞无法永久补偿平滑肌细胞来源的成纤维细胞样细胞的缺失。通过对头臂动脉区域进行RNA测序（RNA-seq）分析并结合体外模型，本研究证实：平滑肌细胞向成纤维细胞样细胞的转化（SMC-MFT）由血小板衍生生长因子（PDGF）和转化生长因子β（TGFβ）诱导，且依赖于有氧糖酵解；而内皮-间充质转化则由白细胞介素1β（IL1β）和转化生长因子β诱导。综上，本研究首次提供了定量证据，证明ACTA2+纤维帽起源于多种细胞谱系的组合，这些细胞通过不同的信号通路转化为成纤维细胞样细胞状态，这些信号通路依赖于或伴随广泛的代谢重编程。本数据集包含载脂蛋白E基因敲除小鼠（无论是否存在平滑肌细胞特异性血小板衍生生长因子受体β敲除）的动脉粥样硬化斑块的单细胞RNA测序（single-cell RNA-sequencing, scRNA-seq）数据。