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Age-related changes of the globular substance in the otoconial membrane of mice
H Suzuki1, K Ikeda, T Takasaka
1Department of Otolaryngology, Tohoku University School of Medicine, Aoba-ku, Sendai, Japan.
Abstract:
The globular substance, which occurs in the vestibular macula as a precursor of otoconia, was examined in aged mice in comparison with young adult mice. Dissected otoconial membrane from the utricular macula of C57BL/6J mice was loaded with fluo-3-AM, and directly observed under a confocal laser scanning microscope. Internal free Ca2+ concentration ([Ca2+]i) of the globular substance was determined through in situ calibration performed by superfusion with ionomycin and Mn2+. Total area of the otoconial membrane, average diameter of the globular substance, and [Ca2+]i showed no significant differences between young adult and aged groups. However, the number of globular substances in young adult mice was significantly larger than those of aged mice. These results suggest a reduced rate of otoconial formation in the aged vestibule, which would result in the sparseness of otoconia in the aged vestibule and lead to balance disorders commonly seen in elderly persons.
Insights
Aging reduces the number of otoconial precursors in the inner ear, potentially explaining age-related balance issues. This study examined globular substances in young versus aged mice.
Area of Science:
- Vestibular system research
- Gerontology
- Otolaryngology
Background:
- Otoconia are crucial for balance and hearing.
- The globular substance is a precursor to otoconia.
- Age-related changes in otoconia may cause balance disorders.
Purpose of the Study:
- To compare the globular substance in young adult and aged mice.
- To investigate potential causes of age-related balance dysfunction.
Main Methods:
- Otoconial membrane from C57BL/6J mice utricle was dissected.
- Fluo-3-AM loading and confocal laser scanning microscopy were used.
- In situ calibration determined internal free Ca2+ concentration ([Ca2+]i).
Main Results:
- No significant differences in membrane area, globular substance diameter, or [Ca2+]i were found between age groups.
- A significantly lower number of globular substances was observed in aged mice compared to young adult mice.
Conclusions:
- A reduced rate of otoconial formation occurs in the aged vestibule.
- This reduction may lead to otoconial sparseness and age-related balance disorders.