Single-cell transcriptomic analysis of peripheral blood mononuclear cells reveals key immune responses in ST-segment elevation myocardial infarction

Inflammation plays a crucial role in the pathogenesis of ST-segment elevation myocardial infarction (STEMI). However, the precise immunological mechanisms remain incompletely understood. Single-cell RNA sequencing (scRNA-seq) provides a powerful approach to dissect immune cell heterogeneity and dynamic changes at single-cell resolution. Peripheral blood mononuclear cells (PBMCs) were collected from 7 STEMI patients (within 6h after primary percutaneous coronary intervention) and 3 healthy controls. Single-cell suspensions were prepared and subjected to scRNA-seq using the 10x Genomics Chromium platform and Illumina NovaSeq 6000. Data were processed using Cell Ranger and analyzed with Seurat for quality control, clustering, and annotation. Differentially expressed genes (DEGs) were identified and analyzed through Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), gene set variation analysis (GSVA), and gene set enrichment analysis (GSEA). Cell-cell communication was inferred using CellChat. And protein–protein interaction (PPI) network analysis was performed via STRING and Cytoscape. Key genes were validated using quantitative real-time PCR (qRT-PCR). A total of 71,288 PBMCs were analyzed. Significant differences in immune cell composition were observed between groups, especially in monocytes and T cells. Monocytes were divided into 10 subclusters; subclusters 0, 1, and 6 showed marked expansion and were functionally associated with inflammation, antigen presentation, and cytokine regulation. PPI network analysis identified JUN as a key hub gene, which was confirmed by qRT-PCR. T cells were divided into 7 subtypes, and GSEA revealed enrichment of IL-2/STAT5 and TNF-α/NF-κB signaling in STEMI. CD69 and ICOS were significantly upregulated in T cells. CellChat analysis revealed enhanced intercellular communication in STEMI, with the CXCL signaling pathway (notably PF4–CXCR3 interaction) being highly upregulated. This study reveals key inflammatory and immune characteristics of PBMCs in STEMI patients. JUN and the CXCL signaling axis represent potential targets for immunomodulatory therapy in acute myocardial infarction.