Modulation of macrophages by a phillyrin-loaded thermosensitive hydrogel promotes skin wound healing in mice

Background   Impaired wound healing in traumatic skin injuries remains a severe clinical challenge due to impaired re-vascularization, harmful bacteria infection, and inflammation dysregulation. Macrophages are recognized as prominent immune cells in tissue regeneration and wound healing. Consequently, the modulation of macrophages provides a promising therapeutic target for wound healing disorders. Here, we aimed to explore whether a novel constructed combination of thermosensitive hydrogel Pluronic F-127 (PF-127) and phillyrin (PH, the main active compound of forsythia suspensa) could improve skin wound healing. Methods   Firstly, the biological effects of pH on the phenotype and inflammation of macrophages were assessed by flow cytometry and ELISA. The biocompatibility of the PF-127 plus PH combination was investigated on keratinocytes and red blood cells. The biological effect of PF-127/PH hydrogel on the migratory ability of keratinocytes in vitro was evaluated using the scratch and transwell migration assays. In addition,   S. aureus   and   E. coli   were employed to test the antibacterial properties of the PF-127 plus PH combination. Finally, PF-127 plus PH scaffold was applied   to the full-thickness skin defect in mice. Histomorphological evaluation and immunochemistry were performed to explore the wound-healing activity of PF-127/PH hydrogel. Results   PH can promote the polarization of macrophages from the M1 (pro-inflammatory) phenotype to the M2 (anti-inflammatory) phenotype. The PF-127/PH hydrogel was highly biocompatible and showed a potent stimulative effect on the migration of keratinocytes   in vitro. The combination of PF-127 and PH exerted a pronounced antibacterial activity on   S. aureus   and   E. coli in vitro.   PF-127/PH hydrogel potently accelerates the healing of full-thickness skin defects by promoting skin cell proliferation, accelerating angiogenesis, and inhibiting inflammation. Conclusions Our study suggests that PF-127/PH hydrogel has excellent potential for treating traumatic skin defects.