5-Aminolevulinic acid-mediated photodynamic therapy improves scar healing of laryngeal wounds in rats.

To evaluated the efficacy of photodynamic therapy (PDT) in improving laryngeal mucosal wound scar healing in vivo and investigated its underlying mechanisms. Laryngeal mucosal wounds were induced in Sprague-Dawley rats. Two weeks post-injury, PDT was administered via intraperitoneal injection of 100 mg/kg 5-aminolevulinic acid (5-ALA) and 635-nm red laser irradiation at varying energy doses (15, 30, and 45 J/cm²). The wounds' histological assessment was performed one month after two PDTs (one/week), including hematoxylin-eosin, Masson staining, Immunohistochemical staining for collagen I and III, and Alcian Blue staining for the detection of hyaluronic acid. In vitro, the viability of human skin fibroblasts (HFF-1) exposed to different light energy (0.3, 0.6, and 1.2 J/cm²) was assessed using CCK-8. Sublethal-dose PDT (SL-PDT; 5-ALA: 0.125 mmol/L, light: 0.6 J/cm²) was used in subsequent experiments. The effect of PDT on fibroblast differentiation into myofibroblasts was evaluated by measuring α-SMA expression in fibroblasts through RT-qPCR and Western blotting. Histological evaluation revealed that following PDT, the trauma site thickness increased, collagen density decreased, and hyaluronic acid deposition was elevated. Immunohistochemical analysis showed improved distribution of type I and type III collagen, coupled with a reduction in density. The most prominent change was observed in the 45 J/cm² PDT group. PDT had a dose-dependent effect on fibroblast viability, and significantly reduced fibroblast differentiation into myofibroblasts by upregulating urokinase plasminogen activator receptor (uPAR) protein expression in fibroblast. PDT can alleviate scar healing of laryngeal tissue wounds by suppressing excessive myofibroblast activation, effectively preserving laryngeal function.