Efeito da fotobiomodulação laser sobre a língua de camundongos em um modelo de carcinogênese oral

Abstract

Photobiomodulation (PBM) has been widely used for the management of adverse effects of oncological therapies such as oral mucositis, hyposalivation, xerostomia, radiation-induced dermatitis and lymphedema. Due to limited knowledge and inconclusive results on the effects of this therapy on epithelial dysplasia or oral squamous cell carcinomas (SCC), the present study aimed to evaluate the effect of laser PBM, with different irradiation parameters, in a model of nitroquinoline oxide (4-NQO)-induced oral carcinogenesis on the tongue of mice. The sample consisted of 48 C57Bl/6 female mice, divided into four groups: (1) control, (2) 4-NQO, (3) 1.5 J laser and (4) 9 J laser. Oral carcinogenesis was induced with 4-NQO dissolved in propylene glycol (4 mg/ml), diluted in drinking water at a concentration of 50 μg/ml and administered for 16 weeks. In the control group, propylene glycol was used. In the 18th and 19th weeks of the study, laser PBM was applied to the 1.5 and 9 J laser groups and to the control group for two weeks, on alternate days, totaling seven sessions. In the group laser 1.5 J the continuous emission mode was used, 660 nm wavelength, 30 mW power, 1.5 J energy per point, 1071.42 mW/cm² power density, 53.57 J/cm² energy density for 50 seconds. In the laser 9 J group the continuous emission mode was used, 660 nm wavelength, 100 mW power, 9 J energy per point, 3571.42 mW/cm² power density, 321.42 J/cm² energy density for 90 seconds. In the 20th week the animals were euthanized, and the clinical analysis was performed. We performed standardized photographs to measure the area of leukoplakia and carcinomas using a software. The tongue was collected for histological analysis of the lesions, evaluation of the incidence of carcinomas, and its grade of differentiation. In addition, the thickness of the epithelial tissue and keratin layer of the dorsum of the tongue was evaluated. All animals exposed to the oral carcinogen developed clinical and histological changes on the tongue. Laser PBM did not cause significant changes in the area of leukoplakia and carcinomas, since there was no difference in this parameter between the laser groups and the 4-NQO group (p>0.05). Furthermore, there was no association between laser PBM and histological classification of lesions (p=0.87), incidence of tumors detectable through clinical exam or in the histological analysis (p=0.45, p=0.57, respectively), and grade of tumor differentiation (p=0.88). The thickness of the epithelium and keratin was increased in the groups that received the carcinogen compared to the control (p<0.001), however, there was also no difference among 4-NQO, 1.5 laser and 9 J laser groups (p=0.89). It is concluded that the PBM, in the parameters used in the present study, has no influence on the clinical and histological characteristics of leukoplakia and squamous cell carcinomas of the oral mucosa.