Konishi Hiroyuki, Ohgami Nobutaka, Matsushita Aika, Kondo Yuki, Aoyama Yuki, Kobayashi Masaaki, Nagai Taku, Ugawa Shinya, Yamada Kiyofumi, Kato Masashi, Kiyama Hiroshi
Department of Functional Anatomy and Neuroscience, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan.
Department of Occupational and Environmental Health, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan; Nutritional Health Science Research Center, Chubu University, Kasugai 487-8501, Japan.
Neuroscience. 2017 May 20;351:15-23. doi: 10.1016/j.neuroscience.2017.03.028. Epub 2017 Mar 24.
Diphtheria toxin (DT) administration into transgenic mice that express the DT receptor (DTR) under control of specific promoters is often used for cell ablation studies in vivo. Because DTR is not expressed in mice, DT injection has been assumed to be nontoxic to cells in vivo. In this study, we demonstrated that DT application during the juvenile stage leads to hearing loss in wild-type mice. Auditory brainstem response measurement showed severe hearing loss in C57BL/6 mice administered DT during the juvenile period, and the hearing loss persisted into adulthood. However, ototoxicity did not occur when DT was applied on postnatal day 28 or later. Histological studies demonstrated that hearing loss was accompanied by significant degeneration of inner and outer hair cells (HCs), as well as spiral ganglion neurons. Scanning electron microscopy showed quick degeneration of inner HCs within 3days and gradual degeneration of outer HCs within 1week. These results demonstrated that DT has ototoxic action on C57BL/6 mice during the juvenile period, but not thereafter, and the hearing loss was due to degeneration of inner and outer HCs by unknown DT-related mechanisms.
将白喉毒素（DT）注射到在特定启动子控制下表达白喉毒素受体（DTR）的转基因小鼠体内，常用于体内细胞消融研究。由于DTR在小鼠体内不表达，因此DT注射被认为对体内细胞无毒。在本研究中，我们证明了在幼年阶段应用DT会导致野生型小鼠听力丧失。听觉脑干反应测量显示，在幼年时期接受DT注射的C57BL/6小鼠出现严重听力丧失，且听力丧失持续至成年期。然而，在出生后第28天或之后应用DT时未发生耳毒性。组织学研究表明，听力丧失伴随着内、外毛细胞（HCs）以及螺旋神经节神经元的显著退化。扫描电子显微镜显示，内毛细胞在3天内迅速退化，外毛细胞在1周内逐渐退化。这些结果表明，DT在幼年时期对C57BL/6小鼠具有耳毒性作用，而在此之后则无此作用，且听力丧失是由于内、外毛细胞通过未知的与DT相关的机制退化所致。
