The Histological Changes of Photodynamic Therapy Using 635 nm Diode Laser on Normal Tissues of C57BL/6 Mouse Model

ABSTRACT

PURPOSE: Photodynamic therapy, with photosensitizer and non-thermal laser, produces selective destruction of cancer without affecting the adjacent normal tissues. The aim of our study was to evaluate the pathological changes to the normal tissues when photodynamic therapy, with non-thermal laser irradiation, after the administration of a photosensitizer. MATERIALS AND METHODS: Studies were performed on four C57BL/6 mouse models using a photosensitizer (Photogem(R), Moscow Institute of High Chemical Technologies). The mice received Photogem, 3 mg/kg i.v., 24 hours prior to the exposure of normal tissues to 180 J/cm2 laser light, at a wavelength and power density of 635 nm and 600 mW/cm2, respectively, with the light source being a 635 nm Diode Laser (Laxcell 2004, Bio-Optics. co.) Histological staining and analysis were used to determine the nature and extent of injury at the first, third, fifth, and seventh days after the photodynamic therapy. RESULTS: Histologically, there were losses of endothelium from small vessels in the skin and muscle, with focal necrosis and diffuse inflammatory changes in the adjacent tissues. Between the fifth and seventh days following the photodynamic therapy, generation of granulation tissue, composed of fibroblasts and endothelial cells was observed surrounding the necrotic area. CONCLUSION: Photodynamic therapy using Photogem and a 635 nm Diode Laser, with a power density of 600 mW/cm2, develops non-selective necrosis and has a thermal effect on normal tissue