Impact of Irradiation on laryngeal hydration and lubrication in rat larynx

OBJECTIVES: The larynx is susceptible to irradiation, which causes significant vocal fold (VF) edema and dehydration shortly after radiotherapy for head and neck cancers. However little is known about radiation-induced damage to VF liquid homeostasis. To evaluate the effects of irradiation on VF hydration and lubrication, we investigated changes in water transporters (aquaporins [AQPs]) and mucin production in vivo and ex vivo, as well as morphometric changes in the laryngeal mucosa and glands of irradiated rat larynges. STUDY DESIGN: Animal study. MATERIALS AND METHODS: Local irradiation at 18 Gy was delivered to rat larynges. Histologic changes in laryngeal mucosa and glands were observed by light microscopy, and the distributions of AQPs and mucin were investigated by immunofluorescence staining 3 months after irradiation. Early effects on gene regulation of AQPs and mucin were evaluated by quantitative real-time polymerase chain reaction of the extirpated VFs and subglottic laryngeal mucosa at 12, 24, and 72 hours after irradiation. RESULTS: Laryngeal glands exhibited severe atrophic changes and showed decreased density throughout the irradiated larynx. The expression of AQP1, 4, 5, and mucin in VFs, as well as AQP5 and mucin in submucosal laryngeal glands, decreased significantly 3 months after irradiation. An ex vivo study revealed that the gene expression of AQP5 in VF tissues was significantly downregulated at 12 hours postirradiation. CONCLUSION: Laryngeal irradiation induces damage in laryngeal mucosal barriers and alters laryngeal liquid homeostasis, which may be one reason for vocal dysfunction following irradiation.restrictio