Topical application of butyrate improves skin wound healing in diabetic mice

Chronic wounds are characterized by a persistent, hyper-inflammatory microenvironment that impairs wound healing progression and is one of the most prominent troublesome complications for diabetic patients worldwide. SCFA are bacterial metabolites produced by microbiota that play essential roles in maintaining homeostasis and have several positive effects on the skin through canonical and epigenetic mechanisms. In this work, we aimed to explore the effect of local applications of SCFA butyrate on the wound healing process using a full-thickness excisional skin wound model in type 1 diabetic C57BL/6 mice. Since we did not observe differences in wound closure rate using 1 mM of butyrate, we conducted experiments based on a dose-response curve at 10, 30, and 100 mM, which were applied once a day during the first 14 days after wounding. Topical butyrate improved the wound closure rate at 100 mM (p<0.05). On day 7 after wounding, the butyrate-treated group presented a reduced infiltrate of macrophages on the wound compared to the untreated group (p<0.05), while no differences were observed for neutrophils. Moreover, butyrate treatment at 100 mM accelerates the wound closure rate in euglycemic C57BL/6 mice (p<0.05). To determine if FFAR2, a canonical receptor for SCFA, is essential to diabetic wound healing, we performed an experiment using FFAR2^-/- mice, and we found no differences in skin wound closure rate between WT and FFAR2^-/- mice. Topical butyrate treatment did not accelerate wound closure in FFAR2^-/- mice, suggesting that this receptor plays a role in the mechanisms through which butyrate influences skin wound healing. In our in vitro approaches, butyrate increased fibroblast migration in a scratch test and did not reduce cell viability at high micromolar to low millimolar concentrations. In conclusion, these preliminary results show the therapeutic potential of butyrate in diabetic wound management.