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ORIGINAL RESEARCH article

Front. Neurosci.
Sec. Auditory Cognitive Neuroscience
Volume 18 - 2024 | doi: 10.3389/fnins.2024.1466514

Effects of Aging on Otolith Morphology and Functions in Mice

Provisionally accepted
Keita Ueda Keita Ueda 1*Takao Imai Takao Imai 1Taeko Ito Taeko Ito 1Tadao Okayasu Tadao Okayasu 1Shotaro Harada Shotaro Harada 2Takefumi Kamakura Takefumi Kamakura 2Kazuya Ono Kazuya Ono 3Tatsuya Katsuno Tatsuya Katsuno 4Tatsuhide Tanaka Tatsuhide Tanaka 5Kouko Tatsumi Kouko Tatsumi 5Hiroshi Hibino Hiroshi Hibino 3,6Akio Wanaka Akio Wanaka 7Tadashi Kitahara Tadashi Kitahara 8
  • 1 Department of Otolaryngology-Head and Neck Surgery, Nara Medical University,, nara, Japan
  • 2 Department of Otorhinolaryngology-Head and Neck Surgery, Osaka University Graduate School of Medicine, Japan, osaka, Japan
  • 3 Division of Glocal Pharmacology, Department of Pharmacology, Graduate School of Medicine, Osaka University, Japan, osaka, Japan
  • 4 Electron Microscopy Facility, Center for Anatomical Studies, Graduate School of Medicine, Kyoto University, Japan, kyoto, Japan
  • 5 Department of Anatomy and Neuroscience, Faculty of Medicine, Nara Medical University, Japan, nara, Japan
  • 6 AMED-CREST, AMED, Osaka, Japan
  • 7 Department of Anatomy and Neuroscience, Faculty of Medicine, Nara Medical University, Japanna, nara, Japan
  • 8 Department of Otolaryngology-Head and Neck Surgery, Nara Medical University, Japan, nara, Japan

The final, formatted version of the article will be published soon.

    Background: Increased fall risk caused by vestibular system impairment is a significant problem associated with aging. A vestibule is composed of linear acceleration-sensing otoliths and rotationsensing semicircular canals. Otoliths, composed of utricle and saccule, detect linear accelerations. Otolithic organs partially play a role in falls due to aging. Aging possibly changes the morphology and functions of otoliths. However, the specific associations between aging and otolith changes remain unknown. Therefore, this study aimed to clarify these associations in mice.Methods: Young C56BL/6N (8-week-old) and old (108-117 weeks old) mice were used in a microcomputed tomography (μCT) experiment for morphological analysis and a linear acceleration experiment for functional analysis. Young C56BL/6N (8-week-old) and middle-aged (50-week-old) mice were used in electron microscopy experiments for morphological analysis. Results: μCT revealed no significant differences in the otolith volume (p=0.11) but significant differences in the otolith density (p=0.001) between young and old mice. μCT and electron microscopy revealed significant differences in the structure of striola at the center of the otolith (μCT; p=0.029, electron microscopy; p=0.017). Significant differences were also observed in the amplitude of the eye movement during the vestibulo-ocular reflex induced by linear acceleration (maximum amplitude of stimulation = 1.3G [p=0.014]; maximum amplitude of stimulation = 0.7G [p=0.015]), indicating that the otolith function was worse in old mice than in young mice.Discussion: This study demonstrated the decline in otolith function with age caused by age-related morphological changes. Specifically, when otolith density decreased, inertial force acting on the hair cells decreased, and when the structure of striola collapsed, the function of cross-striolar inhibition decreased, thereby causing a decline in the overall otolith function.

    Keywords: otolith, otoconia, Micro-computed tomography, Linear vestibulo-ocular reflex, Mice

    Received: 18 Jul 2024; Accepted: 03 Oct 2024.

    Copyright: © 2024 Ueda, Imai, Ito, Okayasu, Harada, Kamakura, Ono, Katsuno, Tanaka, Tatsumi, Hibino, Wanaka and Kitahara. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence: Keita Ueda, Department of Otolaryngology-Head and Neck Surgery, Nara Medical University,, nara, Japan

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