The Effectiveness of Local Application of Melatonin in the Original Dermal Film in Experimental Thermal Trauma
Authors: Osikov M , Ageeva A , Ageev Yu , Fedosov A , Nikushkina K , Loginova Yu 
Published: December 2021

Background: The development and pathogenetic substantiation of the new agents used for local therapy of thermal trauma (TT) is an urgent problem in medicine. Melatonin (MT) is an endogenous factor of homeostasis regulation with pleiotropic potential. The aim of our study was to assess the morphology, expression of matrix metalloproteinase-9 (MMP-9) and vascular endothelial growth factor (VEGF), indicators of repair, oxidative destruction of lipids in the skin lesion focus in the dynamics of experimental TT under the conditions of using the original dermal film (DF) with MT.	Methods and Results: The experiment was performed on 104 male Wistar rats weighing 200-240 g. For modeling TT II degree according to ICD-10 a relative area of 3.5% of the body surface, an interscapular region isolated from the surrounding tissues, was immersed in distilled water at 98-99 °C for 12 sec. DF based on sodium carboxymethylcellulose with an area of 12 cm2 with MT at a concentration of 5 mg/g was applied daily for five days. The wound area and epithelialization rate were calculated. The content of MMP-9 and VEGF in the burn wound was assessed by an immunohistochemical method. In the homogenate of the burn wound, the content of LPO products was assessed. Morphological and biochemical studies were performed on Days 5, 10 and 20 after TT induction.	With experimental TT from Day 5 to Day 20, the absolute area of the burn wound decreases by 35%, the rate of epithelialization increases, the number of neutrophils in the focus of thermal damage decreases, while the representation of lymphocytes, histiocytes, and fibroblasts increases; the expression of MMP-9 and VEGF increases; predominantly secondary and final LPO products in the heptane phase accumulate, the final products of LPO in the isopropanol phase of the lipid extract. The use of MT in the composition of DF daily for 5 days with experimental TT leads to a decrease in the area of the wound defect (by 46% of the original area on Day 20), an increase in the rate of its epithelialization, an increase in the content of lymphocytes and fibroblasts in the burn wound on Days 5, 10 and 20 of TT, a decrease in the representation of neutrophils and macrophages on Days 5 and 10, as well as an increase in VEGF expression on Days 5 and 10, MMP-9 - on Day 5 and a decrease in MMP-9 expression on Days 10 and 20 of TT. In addition, the use of MT in the composition of DF leads to a decrease in the content of predominantly secondary and end products of LPO in the heptane and isopropanol phases of the burn wound on Days 10 and 20 of TT. Correlation analysis revealed that a decrease in the burn surface area under a local application of MT occurs with an increase in the content of VEGF in the wound area and a decrease in the content of MMP-9 and secondary and final LPO products in the heptane phase and the isopropanol phase. On Day 20, there were direct moderate correlations between the absolute burn surface area, on one hand, and secondary and final LPO products, on the other, in the heptane phase (R=0.51, R=0,68; P<0.05) and the isopropanol phase (R=0.44, R=0.46; P<0.05), respectively.	Conclusion: The results obtained expand the existing understanding of the role of changes in the expression of MMP-9 and VEGF in the pathogenesis of TT. We believe that the repair-stimulating effect of MT in the DF, which we established during TT at the preclinical stage, is associated with the LPO-limiting effect of MT and a change in the expression of MMP-9 and VEGF in the burn wound and is a prerequisite for further study of the mechanism of action and the effectiveness of MT application in clinical conditions in TT.