Duan Xiuyun, Zhang Li, Liu Keyu, Guo Kaiyin, You Yingnan, Jia Hailin, Zhou Shan, Han Bo
Department of Pediatric Cardiology, Cheeloo Colledge of Medicine, Shandong Provincial Hospital, Shandong University, Jinan, Shandong, China.
Department of Pediatric Cardiology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, Shandong, China.
Biol Direct. 2025 Mar 14;20(1):30. doi: 10.1186/s13062-025-00621-2.
Viral myocarditis (VMC) is an inflammatory myocardial condition triggered by viral infections which involves pathogenic-related damage and immune-mediated damage. However, the precise immunopathogenic mechanisms underlying VMC remain elusive.
We performed single-cell RNA sequencing on mouse hearts during the acute phase of CVB3-induced VMC. After manually annotating cell types, functional analyses of macrophage were performed by cell ratio changes, customized gene set module scoring and CellPhoneDB. Utilizing indirect co-culture experiments in vitro, the effects of macrophage-derived SPP1 on cardiac fibroblasts were investigated. Depletion of macrophages and inhibition of SPP1 expression in mice were carried out to study the effects of macrophage-derived SPP1 on cardiac function, inflammation levels, and myocardial injury in mice with VMC.
Our data revealed that macrophages are the major immune cells which infiltrate the heart during the acute phase of VMC, particularly a macrophage subpopulation which highly expresses Spp1 (Spp1 macrophages) and exhibited characteristics of peripheral blood monocytes. Spp1 macrophages communicate extensively with fibroblasts during VMC, and that SPP1 promotes fibroblast conversion to an inflammatory phenotype with high Ccl2/Ccl7 expression. This in turn increases monocyte chemotaxis to the heart. Besides, a partial depletion of macrophages in the early stages of VMC attenuated myocardial inflammation and myocardial injury in mice. Inhibition of SPP1 reduced cardiac macrophage infiltration, attenuated myocardial inflammation, and improved cardiac function in VMC mice.
Our findings suggested that Spp1 macrophages could self-recruit, and macrophage-derived SPP1 exacerbated myocardial immune injury by promoting high Ccl2/Ccl7 expression in fibroblasts. Our study advances understandings of VMC pathogenesis, and provides novel insight into potential immunotherapies for VMC.
病毒性心肌炎（VMC）是一种由病毒感染引发的炎症性心肌疾病，涉及致病相关损伤和免疫介导损伤。然而，VMC潜在的精确免疫致病机制仍不清楚。
我们对柯萨奇病毒B3（CVB3）诱导的VMC急性期小鼠心脏进行了单细胞RNA测序。在手动注释细胞类型后，通过细胞比例变化、定制基因集模块评分和CellPhoneDB对巨噬细胞进行功能分析。利用体外间接共培养实验，研究巨噬细胞衍生的分泌性磷蛋白1（SPP1）对心脏成纤维细胞的影响。在小鼠中进行巨噬细胞耗竭和SPP1表达抑制，以研究巨噬细胞衍生的SPP1对VMC小鼠心脏功能、炎症水平和心肌损伤的影响。
我们的数据显示，巨噬细胞是VMC急性期浸润心脏的主要免疫细胞，特别是一个高表达Spp1的巨噬细胞亚群（Spp1巨噬细胞），表现出外周血单核细胞的特征。在VMC期间，Spp1巨噬细胞与成纤维细胞广泛交流，并且SPP1促进成纤维细胞转变为具有高Ccl2/Ccl7表达的炎症表型。这反过来增加了单核细胞向心脏的趋化作用。此外，VMC早期巨噬细胞的部分耗竭减轻了小鼠的心肌炎症和心肌损伤。抑制SPP1减少了VMC小鼠心脏巨噬细胞浸润，减轻了心肌炎症，并改善了心脏功能。
我们的研究结果表明，Spp1巨噬细胞可以自我招募，并且巨噬细胞衍生的SPP1通过促进成纤维细胞中高Ccl2/Ccl7表达加剧心肌免疫损伤。我们的研究推进了对VMC发病机制的理解，并为VMC的潜在免疫治疗提供了新见解。
