Effect of Topical Insulin on Second-Degree Burns in Diabetic Rats

The healing process is complex in diabetic wounds, and the healing mechanism of burn wounds is different from that of incisional or excisional wounds. Data from our previous study indicated that topical insulin cream reduced wound closure time in diabetic rats. Our aim was to investigate the effect of topical insulin cream on wound healing following second-degree burns in control and diabetic rats. Rats were divided into four groups: control (nondiabetic) rats treated with placebo (CP), control (nondiabetic) rats treated with topical insulin cream (CI), diabetic rats treated with placebo (DP), and diabetic rats treated with topical insulin cream (DI). The wounds were assessed at 4 time points (1, 7, 14, and 26 days) post-wounding for morphometric analysis of wound sections stained with hematoxylin/eosin, α-smooth muscle actin, and Picrosirius red to evaluate general aspects of the wound, inflammatory infiltrate, blood vessels, and Types I and III collagen fibers. Histological analysis showed that topical insulin cream increased the inflammatory cell infiltrate in the DI group (at 7 and 14 days postburn, p < .05) and blood vessels (at 14 days postburn, p < .05) to levels similar to those of groups CP and CI. Wounds treated with topical insulin cream (CI and DI groups) showed significantly stronger staining for fibrillar collagen than wounds of the DP group. The use of topical insulin may reduce the duration of the inflammatory phase; improve wound reepithelialization, tissue granulation, and wound contraction; and increase collagen deposition in second-degree burns in healthy and diabetic animals.