Global Characteristics and Dynamics of Single Immune Cells After Myocardial Infarction

Abstract

Background Myocardial infarction (MI) is characterized by the emergence of dead or dying cardiomyocytes and excessive immune cell infiltration after coronary vessel occlusion. However, the complex transcriptional profile, pathways, cellular interactome, and transcriptional regulators of immune subpopulations after MI remain elusive. Methods and Results Here, male C57BL/6 mice were subjected to MI surgery and monitored for 1 day and 7 days, or sham surgery for 7 days, then cardiac CD45‐positive immune cells were collected for single‐cell RNA sequencing to determine immune heterogeneity. A total of 30 135 CD45 + immune cells were partitioned into macrophages, monocytes, neutrophils, dendritic cells, and T or B cells for further analysis. We showed that macrophages enriched for Olr1 and differentially expressed Gpnmb represented 2 crucial ischemia‐associated macrophages with distinct proinflammatory and prophagocytic capabilities. In contrast to the proinflammatory subset of macrophages enriched for Olr1, Gpnmb‐positive macrophages exhibited higher phagocytosis and fatty acid oxidation preference, which could be abolished by etomoxir treatment. In addition to macrophages, MI triggered prompt recruitment of neutrophils into murine hearts, which constituted the sequential cell‐fate from naïve S100a4‐positive, to activated Sell‐high, to aging Icam1‐high neutrophils. In silico tools predicted that the excessively expanded neutrophils at 1 day were attributed to chemokine C‐C motif ligand/chemokine C‐X‐C motif ligand pathways, whereas CD80/inducible T‐cell costimulator (ICOS) signaling was responsible for the immunosuppressive response at day 7 after MI. Finally, the Fos/AP‐1 (activator protein 1) regulon was identified as the critical regulator of proinflammatory responses, which was significantly activated in patients with dilated cardiomyopathy and ischemic cardiomyopathy. We showed the enriched Fos/AP‐1 target gene loci in genome‐wide association study signals for coronary artery diseases and MI. Targeting Fos/AP‐1 with the selective inhibitor T5224 blunted leukocyte infiltration and alleviated cardiac dysfunction in the preclinical murine MI model. Conclusions Taken together, this single‐cell RNA sequencing data lay the groundwork for the understanding of immune cell heterogeneity and dynamics in murine ischemic hearts. Moreover, Fos/AP‐1 inhibition mitigates inflammatory responses and cardiac dysfunction, which might provide potential therapeutic benefits for heart failure intervention after MI.

Elucidating the changes in the heterogeneity and function of radiation-induced cardiac macrophages using single-cell RNA sequencing

“…In detail, Cluster 1 and 3 both expressed classic resident macrophage (RTM) markers (Lyve1, Cbr2, Folr2). Cluster 1, which expressed higher RTM markers, was similar to the previously described Timd4+ or Folr2+ cluster ( 21 , 24 ). In contrast, Cluster 3 highly expressed inflammation-related genes (Ccl2, Ccl7, Ccl12), endoplasmic reticulum stress-related genes (Phlda3 and C5ar1) ( 43 , 44 ), mitochondrial metabolism-related marker (Gdf15) ( 45 ), and cell cycle arrest and senescence biomarker (Cdkn1a) ( 46 , 47 ).…”

“…To understand the metabolic status and inflammatory status of the above four clusters of macrophages, we performed genetic scoring according to previous studies ( Figure 4E ) ( 24 , 38 ). The related genes of each score are listed in the Supplementary Table 2 .…”

“…The average expression of genes used by Zhuang Lingfang et al. was utilized to define chemotaxis, phagocytosis, oxidative phosphorylation (OXPHOS), glycolysis, fatty acid oxidation (FAO) and myeloid-derived suppressor cell (MDSC) scores for macrophage subclusters ( 24 ). Similarly, gene scores by groups were also performed according to the gene sets described above.…”

Macrophage-based therapeutic approaches for cardiovascular diseases

“…Upon ischemia injury following coronary occlusion, remarkable infiltration of macrophages was observed from day 1 and persisting through day 7 post-operation [ 64 ]. Several previous scRNA-seq analyses have unveiled distinct subpopulations of cardiac macrophage during MI progression.…”

Immune heterogeneity in cardiovascular diseases from a single-cell perspective

“…Furthermore, with the improved statistical power for large-scale single-cell datasets, it becomes possible to construct gene regulatory networks in dynamic processes by combining inferred trajectories and co-expression analyses (39). Zhuang et al (40) analyzed the global characteristics and dynamics of single immune cells after myocardial infarction (MI), demonstrating not only dynamic inward flow of immune cells under ischemic conditions, but also identifying Fos/activator protein 1regulation as a key proinflammatory regulator. Multi-omics analysis further links transcriptional data with epigenetic characteristics, combines regulatory networks with clustering and trajectory inference, and constructs a regulatory landscape of the immune system (41)(42)(43).…”