Establishment of a radiation-induced vocal fold fibrosis mouse model

Post-radiation fibrosis of the vocal folds is thought to cause vocal impairment. However, the mechanism by which this occurs has been poorly documented, probably because of the lack of an appropriate experimental animal model. The purpose of this study was to establish a simple and reproducible mouse model of laryngeal radiation to investigate the development of vocal fold fibrosis over time. C57BL/6 mice individually placed in a lead shield were irradiated with a single dose of 20 Gy. At 1, 2, and 6 months after irradiation, larynges were harvested and subjected to histological examination and gene expression analysis. Irradiated vocal folds showed time-dependent tissue contraction and increased collagen deposition, with no significant difference in the changes in hyaluronic acid levels. Transcriptional analysis revealed upregulated expressions of TGF-β1 and iNOS at 6 months, but downregulated expressions of Acta2, Col1a1, Col3a1, and MMP8. Moreover, elevated TGF-β1 and reduced downstream gene expression levels indicated the existence of an inhibitory factor over the TGF-β/Smad pathway. Discrepancies in histological and transcriptional studies of collagen might suggest that radiation-induced vocal fold fibrosis could be caused by the elongated turnover of collagen. Overall, we established a mouse model of radiation-induced vocal fold fibrosis using a simple protocol. Further investigations are warranted to elucidate the pathogenesis of irradiation-induced fibrosis in vocal folds.