Effect of photodynamic therapy on local muscle treatment in a rat muscle injury model: a controlled trial

BACKGROUND: Muscle injury is common and is thought to account for 10%–50% of all sports-related injuries. The use of rest, ice, compression, and elevation is common in clinical practice, but many treatments over a long period are required to produce a therapeutic effect. We evaluated the utility of photodynamic therapy as a new treatment option for the acute stage of muscle injury. METHODS: Twenty 8-week-old Sprague-Dawley male rats underwent experimental injury of the right gastrocnemius muscle with a drop-mass method. After muscle injury was induced, a liposomally formulated indocyanine green derivative (7 mg/kg) near-infrared laser irradiation was performed at 18 h after injury. Local time-dependent changes in the treatment (n = 14) and no treatment (n = 14) groups were evaluated with in vivo imaging, histologic examination, and enzyme-linked immunosorbent assay methods. RESULTS: In vivo imaging fluorescence values were significantly higher in the no treatment group, whereas interleukin-6 and tumor necrosis factor-α levels were significantly higher in the treatment group at 18 h after injury. Histologic examination results revealed that the treatment group had less bleeding and more degeneration repair processes than the no treatment group at 24 h and 1 week after muscle injury. CONCLUSIONS: These findings suggest that photodynamic therapy promotes a tissue-repairing effect during the early stage of muscle injury.