Brown Adipose Tissue Improves Angiogenesis and M2 Macrophage Polarization in Burn Wounds by Activating IL-17 Signaling

Background: Burn wound healing is a complex physiological process that requires complicated regulation by different cells and tissues. Brown adipose tissue (BAT) plays a key role in the hypermetabolic response to severe burns. However, it is unclear whether BAT contributes to burn wound healing. Methods: Mice were divided into two groups: brown adipose tissue removal group (BR group) and control group. Burn wounds were created on the backs of mice (weighing 20–25g), who were exposed to 100°C hot water for 12 seconds using a homemade burn tube, resulting in a burned area measuring 10 mm in diameter. The treatments were applied once a day for 10 days. Full-thickness wound tissue was collected on days 1, 4, 7, 10, and analyzed by immunostaining of CD31，α-SMA+, F4/80 and CD206 (n = 3). Results: On days 4, 7, and 10, the wound healing rate of the control group was significantly higher than that of the BR group. In the histological analysis, evident inflammatory infiltration, severe collagen denaturation in the BR group. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that the IL-17 pathway was enriched and related genes were up-regulated in the heat map. Immunostaining and transcriptional analyses revealed that angiogenesis and fibroblast were enhanced in the control group, fewer CD206-positive M2 macrophages and higher levels of inflammatory infiltration in the BR group. Conclusions: Brown adipose tissue may reduce inflammatory signaling in burn wounds by increasing the IL-17A-HIF1α axis and driving M2 macrophage polarization.