Expression of reactive oxygen species during wound healing of vocal folds in a rat model

Objectives: Previous studies have indicated that although normal wound healing requires low levels of reactive oxygen species (ROS), excessive amounts of ROS impair wound healing. In injured vocal folds, this excess may result in dysphonia due to scarring that is difficult to treat. However, the expression of ROS during vocal fold wound healing has yet to be investigated. In this study, we assessed the expression and localization of ROS in injured vocal folds by immunohistochemical analysis. Methods: Vocal folds of Sprague-Dawley rats were unilaterally injured by stripping the mucosa under transoral endoscopy. The larynges were harvested at specific time points after injury and were immunohistochemically examined for 4-hydroxy-2-nonenal (4-HNE), an ROS marker, and for the presence of inflammatory cells. Results: We found that 4-HNE-immunopositive cells were significantly increased in the lamina propria of the injured vocal folds as compared to the normal vocal folds on postinjury days 1 and 3. More than half of the 4-HNE-immunopositive cells were also immunopositive for a macrophage- and granulocyte-specific antibody. Conclusions: This study suggests that a large amount of ROS is produced during early-phase wound healing, until postinjury day 3, and that this period may be crucial for regulating ROS levels. The results also suggest that inflammatory cells may contribute to ROS generation.