Ly6C Hi Blood Monocyte/Macrophage Drive Chronic Inflammation and Impair Wound Healing in Diabetes Mellitus

Abstract

Objective— Wound monocyte-derived macrophage plasticity controls the initiation and resolution of inflammation that is critical for proper healing, however, in diabetes mellitus, the resolution of inflammation fails to occur. In diabetic wounds, the kinetics of blood monocyte recruitment and the mechanisms that control in vivo monocyte/macrophage differentiation remain unknown. Approach and Results— Here, we characterized the kinetics and function of Ly6C Hi [Lin − (CD3 − CD19 − NK1.1 − Ter-119 − ) Ly6G − CD11b + ] and Ly6C Lo [Lin − (CD3 − CD19 − NK1.1 − Ter-119 − ) Ly6G − CD11b + ] monocyte/macrophage subsets in normal and diabetic wounds. Using flow-sorted tdTomato -labeled Ly6C Hi monocyte/macrophages, we show Ly6C Hi cells transition to a Ly6C Lo phenotype in normal wounds, whereas in diabetic wounds, there is a late, second influx of Ly6C Hi cells that fail transition to Ly6C Lo . The second wave of Ly6C Hi cells in diabetic wounds corresponded to a spike in MCP-1 (monocyte chemoattractant protein-1) and selective administration of anti-MCP-1 reversed the second Ly6C Hi influx and improved wound healing. To examine the in vivo phenotype of wound monocyte/macrophages, RNA-seq–based transcriptome profiling was performed on flow-sorted Ly6C Hi [Lin − Ly6G − CD11b + ] and Ly6C Lo [Lin − Ly6G − CD11b + ] cells from normal and diabetic wounds. Gene transcriptome profiling of diabetic wound Ly6C Hi cells demonstrated differences in proinflammatory and profibrotic genes compared with controls. Conclusions— Collectively, these data identify kinetic and functional differences in diabetic wound monocyte/macrophages and demonstrate that selective targeting of CD11b + Ly6C Hi monocyte/macrophages is a viable therapeutic strategy for inflammation in diabetic wounds.