Effect And Mechanism Of IL-33 On Skin Wound Healing In Diabetic Mice

BackgroundImpaired wound healing is one of the most prevalent complications that develop from diabetes.Refractory wound often accompany with repeated infection of wound,leading to ischemic necrosis of local tissues,which lack effective treatments.There is a variety of studies that IL-33,known as an inducer of Th2-type immune response,exhibits a central role in the treatment of situations such as stroke,transplantation,experimental autoimmune uveitis and Alzheimer’s disease.Recently,emerging evidence imply that IL-33 represents a crucial mediator of epithelial repair in cutaneous wound defect,and that IL-33 may act as an alarm to alert the immune system when released by epithelial barrier tissues during trauma or infection.Studies have shown that IL-33 can promote the healing of skin infections.In early experiments,we observed that the level of IL-33 in the skin wound tissue of the non-diabetic mice was obviously increased.Meanwhile,the exogenous IL-33 can promote the skin wound healing of the non-diabetic mice.On the contrary,cutaneous wound closure was significantly delayed in IL-33-/-mice.Nevertheless,whether IL-33 can promote wound healing of diabetic wound and its related mechanism still remains unclear.In view of these,this study intends to establish a model of wound healing in diabetic mice to explore the mechanism of IL-33 promoting skin wound healing and provide a new idea on the treatment of clinical wound tissues.Objectives1.To observe the effect of IL-33 on wound healing in diabetic mice model,and to study the role of IL-33 in the wound healing of skin wound;2.In vitro,the effects of IL-33 on the proliferation and chemotaxis of mouse fibroblast(NIH3T3)and macrophage polarization were studied to explore the possible mechanism of IL-33 promoting wound healing in diabetic mice.MethodsThe skin wound model of diabetic mice was established.The wound tissue was treated with IL-33,and the effect of IL-33 on the area change of wound healing and the healing rate were observed at different time points.ECM formation,neovascularization and granulation tissue generation on local wound tissues were detected by histopathological examination.In vitro,the effect of IL-33 on the proliferation,chemotaxis and secretion function of NIH3T3 cells was studied,and the induction effect of IL-33 on macrophage polarization and the effect of macrophage polarization on NIH3T3 cells were explored.Results1.IL-33 can promote the healing of skin wound in diabetic miceWe successfully established the diabetic mice model and made the skin wound in its back.Compared with the control group,the skin wound scab area of experimental group diabetic mice(after treatment with IL-33)was smaller and wound healing time was significantly shorter.The tissue pathology showed that the formation rate of wound granulation tissue,neovascularization and ECM were significantly higher than that of the control group,and immunofluorescence showed that the level of M2 macrophages was increased in the wound tissues.2.Effect of IL-33 on the function of NIH3T3 cellsIL-33 can upregulate the chemotaxis,proliferation and secretion of NIH3T3 cells,and synergy with TGF-β can increase the biological function of NIH3T3 cells more obviously.3.Effect of IL-33 on macrophage polarization in diabetic miceIn vitro,IL-33 alone could not induce macrophages to M2 polarization,but IL-33 could significantly enhance the effect of IL-13 on M2 polarization induced by IL-13.Experiments show M2 macrophage supernatant promoted the expression of TGF-β,which displayed a positive role on NIH3T3 cells via TGF-β signaling pathway.The expression of IL-6 was decreased which weaken its effect on the function of NIH3T3 cells.4.Effect of IL-33 on the biological activity of NIH3T3 cells via M2 macrophagesAfter culture with supernatant of M2 macrophages,the chemotaxis,proliferation and secretion function of NIH3T3 cells were significantly increased.ConclusionsIL-33 treatment accelerates the skin wound healing in diabetic mice.IL-33 can directly and indirectly affect the biological functions of fibroblasts,such as chemotaxis,proliferation and secretion,and then accelerates the generation of ECM,new vessels and granulation tissue.These results strongly suggest manipulation of IL-33-mediated signal might be a potential therapeutic approach for diabetic skin wounds.