Characterization of macrophages in ischemia-reperfusion injury-induced acute kidney injury based on single-cell RNA-Seq and bulk RNA-Seq analysis.

Acute kidney injury (AKI) is a complex disease, with macrophages playing a vital role in its progression. However, the mechanism of macrophage function remains unclear and strategies targeting macrophages in AKI are controversial. To address this issue, we used single-cell RNA-seq analysis to identify macrophage sub-types involved in ischemia-reperfusion-induced AKI, and then screened for associated hub genes using intersecting bulk RNA-seq data. The single-cell and bulk RNA-seq datasets were obtained from the Gene Expression Omnibus (GEO) database. Screening of differentially-expressed genes (DEGs) and pseudo-bulk DEG analyses were used to identify common hub genes. Pseudotime and trajectory analyses were performed to investigate the progression of cell differentiation. CellChat analysis was performed to reveal the crosstalk between cell clusters. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses were used to identify enriched pathways in the cell clusters. Immunofluorescence and RT-PCR were preformed to validate the expression of the identified hub genes. Four hub genes, Vim, S100a6, Ier3, and Ccr1, were identified in the infiltrated macrophages between normal samples and those 3 days after ischemia-reperfusion renal injury (IRI); all were associated with the progression of IRI-induced AKI. Increased expression of Vim, S100a6, Ier3, and Ccr1 in infiltrated macrophages may be associated with inflammatory responses and may mediate crosstalk between macrophages and renal tubular epithelial cells under IRI conditions. Our results reveal that Ier3 may be critical in AKI, and that Vim, S100a6, Ier3, and Ccr1 may act as novel biomarkers and potential therapeutic targets for IRI-induced AKI.