Single-cell RNA sequencing reveals cell–cell communication and potential biomarker in sepsis and septic shock patients

•The RETN-CAP1 ligand-receptor pair, which mediated Resistin signaling, was enhanced in monocytes of septic patients when compared to healthy controls.•The signaling of IL-16, mediated by the IL16-CD4 ligand-receptor pair, was enhanced in monocytes of septic shock patients when compared to sepsis patients.•Single-cell transcriptome data revealed monocyte heterogeneity in sepsis progression. Sepsis is a disease characterized by infection-induced multiorgan dysfunction, which can progress to septic shock if not promptly treated. Early identification of sepsis is crucial for its treatment. However, there are currently limited specific biomarkers for sepsis or septic shock. This study aims to identify potential biomarkers for sepsis and septic shock. We analyzed single-cell transcriptomic data of peripheral blood mononuclear cells (PBMCs) from healthy individuals, sepsis and septic shock patients, identified differences in gene expression and cell–cell communication between different cell types during disease progression. Moreover, our analyses were further validated with flow cytometry and bulk RNA-seq data. Our study elucidates the alterations in cellular proportions and cell–cell communication among healthy controls, sepsis, and septic shock patients. We identified a specific augmentation in the Resistin signaling within sepsis monocytes, mediated via RETN-CAP1 ligand-receptor pairs. Additionally, we observed enhanced IL16 signaling within monocytes from septic shock patients, mediated through IL16-CD4 ligand-receptor pairs. Subsequently, we confirmed our findings by validating the increase in CAP-1+ monocytes in sepsis and IL16+ monocytes in septic shock in mouse models. And a significant upregulation of CAP-1 and IL16 was also observed in the bulk RNA-seq data from patients with sepsis and septic shock. Furthermore, we identified four distinct clusters of CD14+ monocytes, highlighting the heterogeneity of monocytes in the progress of sepsis. In summary, our work demonstrates changes in cell–cell communication of healthy controls, sepsis and septic shock, confirming that the molecules CAP-1 and IL16 on monocytes may serve as potential diagnostic markers for sepsis and septic shock, respectively. These findings provide new insights for early diagnosis and stratified treatment of the disease.