Arg1 and Tgfb1 Identify a Partially Shared Macrophage Polarization Program in Postinfarction Cardiac Repair: A Single-Cell Transcriptomic Analysis.

Background: Postinfarction cardiac repair is orchestrated by macrophages that undergo sequential polarization from proinflammatory M1 to reparative M2 states. These macrophage subsets regulate inflammation resolution, angiogenesis, and fibrotic remodeling in the infarcted myocardium. Tumor-associated macrophages (TAMs) in breast cancer share transcriptional features with cardiac M2 macrophages, providing an opportunity for cross-disease comparison of shared immune programs. Understanding the molecular programs common to reparative macrophages across pathological contexts may identify candidate regulatory nodes for future therapeutic investigation. Methods: Single-cell RNA sequencing data were obtained from GEO: GSE136088 (murine post-AMI cardiac macrophages), GSE176078 and GSE167036 (human primary breast cancer). Analyses included quality control, UMAP/t-SNE dimensionality reduction, graph-based clustering, diffusion pseudotime trajectory reconstruction, ligand-receptor communication analysis, principal component analysis, and cross-dataset correlation analysis. All analyses were performed in Python using scanpy with cross-species ortholog mapping in R (biomaRt, 14,892 one-to-one mouse-human orthologs) with downstream analyses in Python (scanpy). Results: Post-QC datasets (GSE136088: ~14,900 cells; GSE176078: 100,064 cells; and GSE167036: 49,141 cells) were analyzed. UMAP and t-SNE resolved multiple macrophage and immune subpopulations across all three datasets. Diffusion pseudotime analysis reconstructed a sequential activation trajectory with an M1/M2 fate bifurcation. A 7-gene coexpression module (Spp1, Mif, Tgfb1, Arg1, Il10, Tnf, and Mrc1) was identified in cardiac macrophages and showed partially conserved expression patterns in breast cancer macrophage populations (GSE176078: Pearson r = 0.72; GSE167036: 6 of 7 genes detected, ARG1 not detected). Ligand-receptor communication analysis identified MIF-ACKR3, SPP1-CD44, and TGFB1-TGFBR2 as shared ligand-receptor pairs mediating macrophage-stromal communication in both cardiac and tumor microenvironments. Cross-dataset Pearson correlation of the 7-gene module between cardiac macrophages and breast cancer macrophage populations reached Conclusion: This single-cell transcriptomic analysis characterizes macrophage polarization programs in postinfarction cardiac repair and evaluates their partial conservation in breast cancer. The identified 7-gene module showed moderate cross-dataset correlation with GSE176078 (