Background This study is designed to investigate whether vitamin D promotes diabetic wound healing and explore the potential mechanism which may be involved in the healing process. Material and Methods Human umbilical vein endothelial cells (HUVECs) were treated with 200 μg/ml of advanced glycation end product-modified human serum albumin (AGE-HSA) and 250 mg/dl of glucose with vitamin D. Cell viability was analyzed using the CCK-8 assay, and the apoptosis rate was measured using flow cytometry. Endogenous markers of ER stress were quantified using Western blot and a real-time polymerase chain reaction. Diabetic mice were treated with vitamin D (100 ng/kg per day) for 14 days. The ulcer area and ulcerative histology were detected dynamically. Results Vitamin D administration not only decreased the apoptosis rate but also increased cell viability. Furthermore, the expression of endogenous markers of ER stress was downregulated as a result of vitamin D treatment. Vitamin D supplementation significantly accelerated wound healing of diabetic mice and improved the healing quality. Further studies showed that reduced ER stress was associated with the positive outcome. Conclusion These results suggest that vitamin D may ameliorate impaired wound healing in diabetic mice by suppressing ER stress.

To explore whether or not inhibition of protein kinase C βII (PKC βII) stimulates angiogenesis as well as prevents excessive NETosis in diabetics thus accelerating wound healing. Streptozotocin (STZ, 60 mg/kg/day for 5 days, i.p.) was injected to induce type I diabetes in male ICR mice. Mice were treated with ruboxistaurin (30 mg/kg/day, orally) for 14 consecutive days. Wound closure was evaluated by wound area and number of CD31-stained capillaries. Peripheral blood flow cytometry was done to evaluate number of circulating endothelial progenitor cells (EPCs). NETosis assay and wound tissue immunofluorescence imaging were done to evaluate the percentage of neutrophils undergoing NETosis. Furthermore, the expression of PKC βII, protein kinase B (Akt), endothelial nitric oxide synthase (eNOS), vascular endothelial growth factor (VEGF), and histone citrullation (H3Cit) were determined in the wound by Western blot analysis. Ruboxistaurin accelerated wound closure and stimulated angiogenesis in diabetic mice. The number of circulating EPCs was increased significantly in ruboxistaurin-treated diabetic mice. Moreover, ruboxistaurin treatment significantly decreases the percentages of H3Cit+ cells in both peripheral blood and wound areas. This prevented excess activated neutrophils forming an extracellular trap (NETs) formation. The expressions of phospho-Akt (p-Akt), phospho-eNOS (p-eNOS), and VEGF increased significantly in diabetic mice on ruboxistaurin treatment. The expressions of PKC βII and H3Cit+, on the other hand, decreased with ruboxistaurin treatment. The results of the present study suggest that ruboxistaurin by inhibiting PKC βII activation, reverses EPCs dysfunction as well as prevents exaggerated NETs formation in a diabetic mouse model; thereby accelerating the wound healing process.

The general status of the patient and the target limb's condition are important predictors of wound nonhealing. Regarding the limb's condition, information on wound depth and duration in addition to wound extent and infection would further enable the selection of suitable CLI patients for EVT. Such information would also enable optimal wound management, leading to successful wound healing and improved limb salvage and survival rates.