OBJECTIVE: To investigate the hypothesis that a transient episode of raised-intensity phonation causes a significant increase in vocal fold inflammatory messenger RNA (mRNA) expression in vivo. STUDY DESIGN: Prospective animal study. SETTING: Laboratory. SUBJECTS AND METHODS: Ten New Zealand White breeder rabbits received 30 minutes of experimentally induced modal or raised-intensity phonation, followed by a 30-minute recovery period. A separate group of five rabbits served as sham controls. Real-time polymerase chain reaction was performed to investigate the mRNA expression of interleukin 1β (IL-1β), transforming growth factor β-1 (TGFβ1), and cyclooxygenase-2 (COX-2). Separate one-way analysis of variance (ANOVA) tests were used to investigate differences in gene expression across groups, with an appropriate alpha correction of 0.016 to control for type I error. Significant main effects were further examined using Fisher's least significant difference. RESULTS: ANOVA revealed that there were differences for IL-1β, TGFβ1, and COX-2 between sham control, modal phonation, and raised-intensity phonation (P < 0.0001). Pairwise comparisons revealed that the expression of IL-1β, COX-2, and TGFβ1 increased significantly during raised-intensity phonation, compared to modal phonation and sham control (P < 0.0001). CONCLUSION: Results provided support for the hypothesis that a transient episode of raised-intensity phonation causes a significant increase in vocal fold inflammatory mRNA expression. Future studies will investigate the signal transduction pathways and mechanisms regulating the vocal fold inflammatory response. The long-term goal of these studies is to advance understanding of the molecular and cellular events underlying phonation-related tissue alterations.
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