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Giese D, Li H, Liu W, Staxäng K, Hodik M, Ladak HM, Agrawal S, Schrott-Fischer A, Glueckert R, Rask-Andersen H. Microanatomy of the human tunnel of Corti structures and cochlear partition-tonotopic variations and transcellular signaling. J Anat 2024. [PMID: 38613211 DOI: 10.1111/joa.14045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Revised: 03/22/2024] [Accepted: 03/23/2024] [Indexed: 04/14/2024] Open
Abstract
Auditory sensitivity and frequency resolution depend on the optimal transfer of sound-induced vibrations from the basilar membrane (BM) to the inner hair cells (IHCs), the principal auditory receptors. There remains a paucity of information on how this is accomplished along the frequency range in the human cochlea. Most of the current knowledge is derived either from animal experiments or human tissue processed after death, offering limited structural preservation and optical resolution. In our study, we analyzed the cytoarchitecture of the human cochlear partition at different frequency locations using high-resolution microscopy of uniquely preserved normal human tissue. The results may have clinical implications and increase our understanding of how frequency-dependent acoustic vibrations are carried to human IHCs. A 1-micron-thick plastic-embedded section (mid-modiolar) from a normal human cochlea uniquely preserved at lateral skull base surgery was analyzed using light and transmission electron microscopy (LM, TEM). Frequency locations were estimated using synchrotron radiation phase-contrast imaging (SR-PCI). Archival human tissue prepared for scanning electron microscopy (SEM) and super-resolution structured illumination microscopy (SR-SIM) were also used and compared in this study. Microscopy demonstrated great variations in the dimension and architecture of the human cochlear partition along the frequency range. Pillar cell geometry was closely regulated and depended on the reticular lamina slope and tympanic lip angle. A type II collagen-expressing lamina extended medially from the tympanic lip under the inner sulcus, here named "accessory basilar membrane." It was linked to the tympanic lip and inner pillar foot, and it may contribute to the overall compliance of the cochlear partition. Based on the findings, we speculate on the remarkable microanatomic inflections and geometric relationships which relay different sound-induced vibrations to the IHCs, including their relevance for the evolution of human speech reception and electric stimulation with auditory implants. The inner pillar transcellular microtubule/actin system's role of directly converting vibration energy to the IHC cuticular plate and ciliary bundle is highlighted.
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Affiliation(s)
- Dina Giese
- Department of Surgical Sciences, Otorhinolaryngology and Head and Neck Surgery, Uppsala University, Uppsala, Sweden
| | - Hao Li
- Department of Surgical Sciences, Otorhinolaryngology and Head and Neck Surgery, Uppsala University, Uppsala, Sweden
| | - Wei Liu
- Department of Surgical Sciences, Otorhinolaryngology and Head and Neck Surgery, Uppsala University, Uppsala, Sweden
| | - Karin Staxäng
- The Rudbeck TEM Laboratory, BioVis Platform, Uppsala University, Uppsala, Sweden
| | - Monika Hodik
- The Rudbeck TEM Laboratory, BioVis Platform, Uppsala University, Uppsala, Sweden
| | - Hanif M Ladak
- Department of Medical Biophysics, Western University, London, Ontario, Canada
- Department of Electrical and Computer Engineering, Western University, London, Ontario, Canada
| | - Sumit Agrawal
- Department of Otolaryngology-Head and Neck Surgery, Western University, London, Ontario, Canada
| | - Anneliese Schrott-Fischer
- Inner Ear Laboratory, Department of Otorhinolaryngology, Medical University Innsbruck, Innsbruck, Austria
| | - Rudolf Glueckert
- Inner Ear Laboratory, Department of Otorhinolaryngology, Medical University Innsbruck, Innsbruck, Austria
| | - Helge Rask-Andersen
- Department of Surgical Sciences, Otorhinolaryngology and Head and Neck Surgery, Uppsala University, Uppsala, Sweden
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Zhao Z, Yao W, Wang M, Wang J, Zhang T. Radial Flow Field of Spiral Cochlea and Its Effect On Stereocilia. J Biomech Eng 2022; 144:1143034. [PMID: 35789250 DOI: 10.1115/1.4054930] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Indexed: 11/08/2022]
Abstract
The opening of the ion channels ultimately depends on the movement and energy conversion of the microstructural organization. It has not been clear how active sound amplification is generated by the microstructure of the cochlea's characteristic spiral shape. In this paper, an analytical model of the spiral cochlea is developed to investigate the radial flow field generated by the spiral shape of the cochlea and its effect on the outer hair cell stereocilia, and to analyze the effect of the spiral shape on the micromechanics of the cochlea. The results show that the spiral shape of the cochlea exerts a radial shear force on the hair cell stereocilia by generating a radial flow field. This causes the stereocilia to deflect in the radial flow field, with the maximum deflection occurring at the apex of the cochlea. This finding explains the microscopic mechanism that causes the cochlea's spiral shape to enhance low-frequency hearing in humans, and it provides a basis for further studies on the contribution of the movement of stereocilia in the radial flow field of the lymphatic fluid to activate ion channels for auditory production.
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Affiliation(s)
- Zhengshan Zhao
- School of Mechanics and Engineering Science, Shanghai University, Shanghai Institute of Applied Mathematics and Mechanics, Shanghai, 200072, PRC
| | - Wenjuan Yao
- School of Mechanics and Engineering Science, Shanghai University, Shanghai Institute of Applied Mathematics and Mechanics, Shanghai, 200072, PRC
| | - Mianzhi Wang
- School of Mechanics and Engineering Science, Shanghai University, Shanghai Institute of Applied Mathematics and Mechanics, Shanghai, 200072, PRC
| | - Jiakun Wang
- School of Mechanics and Engineering Science, Shanghai University, Shanghai Institute of Applied Mathematics and Mechanics, Shanghai, 200072, PRC
| | - Tianyu Zhang
- ENT Institute, Eye & ENT Hospital of Fudan University, Hearing Medicine Key Laboratory, National Health Commission of China; Department of Facial Plastic Reconstruction Surgery, Eye & ENT Hospital of Fudan University, Shanghai 200031, PRC
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