IL-27 accelerates diabetic wound healing by modulating macrophage polarization.

Diabetic foot ulcer (DFU), a serious complication of diabetes, is a life-threatening disease that often leads to lower limb amputation and a shortened lifespan. Interleukin-27 (IL-27) is a member of the IL-12 family and has the potential to exert dual effects on the immune response. The role of IL-27 in diabetic skin wound healing is unknown. The aim of this study was to investigate whether there is abnormal expression of IL-27 in diabetic skin and whether supplementation with IL-27 can promote diabetic wound healing by modulating macrophage polarization. We established a streptozotocin (STZ)-induced diabetic mouse model and constructed diabetic wounds. We assessed protein expression by western blotting (WB) and immunohistochemical (IHC) staining. We also performed hematoxylin-eosin (H&E) staining and Masson's trichrome staining. In the presence of lipopolysaccharide (LPS) and high glucose (HG), we treated the mononuclear macrophage line RAW264.7 and bone marrow-derived macrophages (BMDMs) with IL-27. To assess macrophage polarization, we examined the expression of inducible nitric oxide synthase (iNOS), IL-1β and arginase-1 (Arg-1). To understand the underlying mechanisms, we used macrophage IL-27ra knockout mice to knockout macrophage IL-27 receptors. Our in vivo experiments revealed that the expression of IL-27 in the skin of diabetic mice was significantly decreased and that supplementation with IL-27 promoted diabetic wound healing. In vitro, compared with the LPS group, supplementation with IL-27 alleviated the suppression of multiple cellular functions, such as iNOS and IL-1β expression, cell migration, and phagocytosis, in macrophages after HG exposure. Mechanistically, we found that IL-27 expression was decreased and that the activation of signal transducer and activator of transcription 3 (STAT3) by phosphorylation was inhibited in diabetic skin, leading to an inability of wound macrophages to polarize to an M1 phenotype effectively, which in turn blocked M1-to-M2 polarization of wound macrophages and ultimately delayed wound healing. The present study revealed that supplementation with IL-27 promoted M1-to-M2 polarization of wound macrophages and diabetic wound healing through the IL-27-IL-27Rα-p-STAT3 axis. These findings suggest that IL-27 may be a potential therapeutic target for DFU.