Single-Cell RNA Sequencing Reveals That Ccr2+ Macrophages Can Promote Myocardial Fibrosis After Myocardial Ischemia-Reperfusion Injury by Recruiting Fibroblasts

Coronary reperfusion following myocardial ischemia can lead to myocardial ischemia-reperfusion injury (MIRI).Ccr2 + macrophages play a pivotal role in MIRI, engaging not only in acute inflammatory responses but also in the formation of cardiac fibrosis. The mechanisms underlying the latter are not yet fully elucidated.This study aims to explore the mechanism by which this macrophage subgroup promotes myocardial fibrosis after MIRI through bioinformatics analysis of Ccr2 + macrophages in MIRI, and to identify more molecular markers for this subgroup in MIRI. We sourced scRNA-seq and bulk RNA-seq data corresponding to mice models of MIRI from the GEO database and executed detailed bioinformatics analyses.The results revealed that after MIRI, Ccr2 + macrophages underwent M2 phenotype polarization and engaged in extensive signal interactions with fibroblasts and immune cells via the Spp1 signaling pathway. Spp1, likely by binding to the integrin receptors of fibroblasts, activates the PI3K-Akt pathway, whose activation can promote the adhesion and migration of fibroblasts, thereby facilitating myocardial fibrosis. Furthermore, we identified Spp1 as a molecular marker for Ccr2 + macrophages in MIRI and externally validated the tissue-level differences of Spp1 through additional bulk RNAseq. This study provides potential therapeutic targets for acute inflammation and chronic myocardial fibrosis occurring after MIRI.