Effects of the Diabetes-Induced MicroRNA-155 on Wound Healing and Fibroblast Growth Factor 7 Expression

Abstract

Impaired wound healing is a serious late-diabetic complication resulting in significant morbidity. MicroRNAs (miRNAs), post-transcriptional gene-regulators, are differentially expressed in several conditions, such as diabetes. To assess the mechanistic action of miRNAs in diabetic wound healing streptozotocin (STZ)-induced diabetic and control mice (n=6/group, 6 weeks of diabetes) were subjected to 6-mm full-thickness excisional wounds. Biopsies were obtained at days 3 and 10 post-wounding. Wound healing was delayed in diabetic mice (p<0.05). The skin miRNA profile was determined for up to 561 unique miRNAs using Taqman MicroRNA array cards. We identified 288 different robustly expressed miRNA in skin. While half of them were decreased more than 1.5 fold, 41 were increased more than 1.5 fold, during wound healing. MiR-155-5p was increased in diabetic skin (15.8 fold (95% CI: 3.5-28.1), however, it was 9.7 fold (95% CI: 4.2-15.2) decreased at day 10 post wounding, as compared to nondiabetic mouse skin. Scratch assays in HaCaT cells showed increased scratch closure after 24 hours, when miR-155 was inhibited (Ctrl: 31%, miR-155 inhibitor: 8.1% of scratch remaining, P<0.001). In vivo, topical treatment of diabetic mouse wounds with miR-155 inhibitor dose-dependently accelerated wound closure with maximal effect at 2.5pmol (P<0.03). Interestingly, reporter-gene analysis identified fibroblast growth factor (FGF) 7 mRNA as a target of miR-155-5p. Moreover, miR-155 inhibitor treated mouse wounds showed significant increase in FGF7 protein expression by immunofluorescence. We present evidence that miR-155-5p expression is altered in diabetic mouse skin and its suppression significantly improves wound healing under diabetic conditions, indicating its potential as a novel chronic diabetic foot ulcer treatment. Disclosure L.T. Dalgaard: Employee; Spouse/Partner; Novo Nordisk A/S. Stock/Shareholder; Spouse/Partner; Novo Nordisk A/S. Stock/Shareholder; Self; Novo Nordisk A/S. E.C. Leal: None. R. Svendsen: None. J. Moura: None. A.E. Sørensen: Research Support; Self; Danish Diabetes Academy, Merck Serono. P.T. Jørgensen: None.