Single-cell transcriptomics reveals reduction of a population of monocyte-derived dendritic cells associated with impaired healing in diabetic wounds of mice 2656

Description Diabetes induces dysregulation of inflammatory cells, which contributes to persistent inflammation and defective tissue repair. To explore the impact of dysregulation of the spectrum of monocyte/macrophage (Mo/Ma) subsets in wound healing, we performed scRNAseq analysis on live CD45+CD11b+Ly6G- cells isolated from excisional skin wounds of non-diabetic C57Bl/6 (ND) and diabetic db/db (DB) mice. In the scRNAseq data, we identified a cluster with characteristics of antigen presenting cells (APC) that was populated primarily by cells from ND mice, with a smaller contribution from DB mice. Using markers identified from the scRNAseq data, flow cytometry analysis verified reduced cells with the APC phenotype in wounds of DB versus ND mice. Experiments with CCR2KO mice, which have severely reduced levels of circulating Mo, and Mo adoptive transfer demonstrated that these APC are derived from Mo, and the diabetic environment impairs such differentiation. To identify the mechanisms involved, we found that the transcription factor Irf4 was highly expressed in the APC cluster and that mice with deletion of Irf4 in Csf1r expressing cells showed impaired differentiation of Mo to APC in wounds along with persistent accumulation of pro-inflammatory Mo/Ma and delayed wound closure compared with controls. We also found that reduced APC in wounds of these mice led to reduced levels of activated regulatory T cells, indicating one potential mechanism by which APC could promote wound healing.