A zebrafish model for hearing loss and regeneration induced by blast wave

Abstract

Zebrafish have the potential to regrow injured organs and tissues, but their use as a model for hearing regeneration following blast injury has never been reported. In this study, zebrafish were exposed to a blast wave produced by an underwater blast wave generator. The first peak sound pressures produced by this generator were up to 224 dB and 160kPa, measured at 25 cm away from the machine. Zebrafish hearing sensitivity was examined by analyzing auditory evoked potentials from 1 to 35 days post blast wave exposure. Cell death and cell proliferation in inner ear organs, including the saccule, lagena, and utricle, were investigated using a terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick-end labeling assay, and cell proliferation assay using 5-ethynyl-2＇-deoxyuridine, respectively. Significant differences in auditory evoked potential thresholds were observed between exposed and control groups, demonstrating both blast wave-induced hearing loss and recovery of hearing sensitivity. An apoptosis assay revealed significantly increased numbers of terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick-end labeling- positive cells in the inner ear sensory epithelia of exposed groups compared with the control group. However, numbers of 5-ethynyl- 2＇-deoxyuridine-positive cells in the inner ear of exposed groups recovered to a normal level within 10 post blast wave exposure. Furthermore, blast wave exposure caused brain injury with increased cell apoptosis and decreased neurogenesis. Compared with drug or noise-induced zebrafish models, our blast wave-induced model elicited more serious hearing loss phenotypes, which required more time to return to a normal level. Overall, this zebrafish model can provide a reliable animal model for both hearing loss and regeneration research. The study was approved by the Shanghai 6th Hospital Animal Care and Use Committee, China (approval No. 2017-0196) on February 28, 2017. Key words: blast wave; zebrafish; hearing loss; brain injury; auditory evoked potential; hair cell; apoptosis; regeneration