目的:嗅觉受体2(Olfr2)已在至少30%的血管巨噬细胞中被鉴定,并且它的消耗被证明可以减少动脉粥样硬化的进展。单核吞噬细胞,包括血管壁内的单核细胞和巨噬细胞,是动脉粥样硬化的主要参与者。单细胞RNA测序研究表明,动脉粥样硬化动脉壁包含几个单核细胞和血管巨噬细胞,定义至少9个可能在疾病进展中发挥不同功能的不同子集。这项研究调查了表达Olfr2的血管巨噬细胞在动脉粥样硬化中的功能表型和个体发育。
结果:当喂食西方饮食(WD)时,Apoe-/-小鼠的主动脉中Olfr2+巨噬细胞迅速增加。质量细胞计数显示Olfr2+细胞聚集在CD64高群体内并富集CD11c和Ccr2标志物。Olfr2+巨噬细胞表达许多促炎细胞因子,包括Il1b,Il6、Il12和Il23,以及趋化因子,包括Ccl5、Cx3cl1、Cxcl9和Ccl22。通过从Olfr2+的批量RNA测序(RNA-seq)中提取差异表达的基因Olfr-巨噬细胞,我们定义了一个显著映射到斑块状骨髓细胞的单细胞数据的签名,包括单核细胞,内皮下MacAir,和Trem2Gpnmb泡沫巨噬细胞。通过过继转移实验,我们发现来自CD45.1Apoe-/-Olfr2+/+小鼠的Olfr2感受态单核细胞转移到CD45.2Apoe-/-Olfr2-/-受体小鼠中12周,积聚在动脉粥样硬化主动脉壁已经在72小时,并在巨噬细胞中分化。与Olfr2-巨噬细胞相比,Olfr2+巨噬细胞显示显著增加的BrdU掺入。流式细胞术证实,与Olfr2-巨噬细胞相比,至少50%的主动脉Olfr2巨噬细胞对BODIPY染色呈阳性,并且肿瘤坏死因子和白介素6的表达均增加。Olfr2+巨噬细胞标记的基因集富集分析揭示了人类动脉粥样硬化斑块中相似的富集模式,特别是在泡沫/TREM2hi-Mφ和单核细胞内。
结论:总之,我们得出的结论是,主动脉中的Olfr2+巨噬细胞起源于单核细胞,并且可以在疾病进展的早期阶段积累。这些细胞可以分化为MacAir和Trem2Gpnmb泡沫巨噬细胞,表现出增殖和促炎潜力。这种动态行为将它们定位为塑造动脉粥样硬化斑块内的骨髓景观的关键影响者。
OBJECTIVE: Olfactory receptor 2 (Olfr2) has been identified in a minimum of 30% of vascular macrophages, and its depletion was shown to reduce atherosclerosis progression. Mononuclear phagocytes, including monocytes and macrophages within the vessel wall, are major players in atherosclerosis. Single-cell RNA sequencing studies revealed that atherosclerotic artery walls encompass several monocytes and vascular macrophages, defining at least nine distinct subsets potentially serving diverse functions in disease progression. This study investigates the functional phenotype and ontogeny of Olfr2-expressing vascular macrophages in atherosclerosis.
RESULTS: Olfr2+ macrophages rapidly increase in Apoe-/- mice\'s aorta when fed a Western diet (WD). Mass cytometry showed that Olfr2+ cells are clustered within the CD64 high population and enriched for CD11c and Ccr2 markers. Olfr2+ macrophages express many pro-inflammatory cytokines, including Il1b, Il6, Il12, and Il23, and chemokines, including Ccl5, Cx3cl1, Cxcl9, and Ccl22. By extracting differentially expressed genes from bulk RNA sequencing (RNA-seq) of Olfr2+ vs. Olfr2- macrophages, we defined a signature that significantly mapped to single-cell data of plaque myeloid cells, including monocytes, subendothelial MacAir, and Trem2Gpnmb foamy macrophages. By adoptive transfer experiments, we identified that Olfr2 competent monocytes from CD45.1Apoe-/-Olfr2+/+ mice transferred into CD45.2Apoe-/-Olfr2-/- recipient mice fed WD for 12 weeks, accumulate in the atherosclerotic aorta wall already at 72 h, and differentiate in macrophages. Olfr2+ macrophages showed significantly increased BrdU incorporation compared to Olfr2- macrophages. Flow cytometry confirmed that at least 50% of aortic Olfr2+ macrophages are positive for BODIPY staining and have increased expression of both tumour necrosis factor and interleukin 6 compared to Olfr2- macrophages. Gene set enrichment analysis of the Olfr2+ macrophage signature revealed a similar enrichment pattern in human atherosclerotic plaques, particularly within foamy/TREM2hi-Mφ and monocytes.
CONCLUSIONS: In summary, we conclude that Olfr2+ macrophages in the aorta originate from monocytes and can accumulate at the early stages of disease progression. These cells can undergo differentiation into MacAir and Trem2Gpnmb foamy macrophages, exhibiting proliferative and pro-inflammatory potentials. This dynamic behaviour positions them as key influencers in shaping the myeloid landscape within the atherosclerotic plaque.