WDR74 facilitates TGF-β/Smad pathway activation to promote M2 macrophage polarization and diabetic foot ulcer wound healing

Abstract Diabetes is a serious global health challenge that affects millions of people worldwide. One major complication is diabetic foot ulcer (DFU), leading to decreased quality of life and increased mortality in diabetic patients. The underlying mechanism of DFU is not completely understood. The mechanism involved in wound healing in diabetes was studied in vivo and in vitro. Gain-and loss-of function studies were performed to study the roles that WDR74 and TGF-β play in DFU. M1 and M2 macrophage phenotypic marker, and extracellular matrix (ECM) components, angiogenic makers were determined by RT-qPCR and/or Western blot analysis. Localization of these proteins were determined by immunofluorescence staining and/or immunohistochemistry. Interaction between WDR74 with Smad2/3 in macrophages was detected by co-immunoprecipitation. We found that WDR74 and M2 macrophages were decreased in wound tissues from DFU mice. TGF-β upregulation increased the expression of M2 macrophage markers (arginase-1, and YM1), IL-4, while decreased expression of M1 macrophage marker (iNOS). TGF-β upregulation also increased the production of ECM and promoted the wound closure in diabetic mice. We also noticed that WDR74 overexpression increased Smad2/3 phosphorylation elevated the population of M2 macrophage ECM production, and alleviated DFU. LY2109761 treatment normalized effects of TGF-β or WDR74 overexpression. In conclusion, WDR74 promoted M2 macrophage polarization, leading to improved DFU in mice, through the activation of TGF-β/Smad pathway.