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- Title
Microglia impact on hearing preservation.
- Authors
Liu, W.; Li, H.; Garnham, C.; Benav, H.; Helge Rask-Andersen, H.
- Abstract
Objectives: Atraumatic CI-surgery may not only be a requisite for preservation of residual hearing but also for long term hearing.The human inner ear, which is segregated by a blood/labyrinth barrier, contains resident macrophages/ microglia (CD163, IBA1-, and CD68-positive cells) within the connective tissue, neurons and supporting cells. In the lateral wall of the cochlea, these cells frequently lie close to blood vessels as perivascular macrophages. Macrophages are also shown to be recruited from bloodborne monocytes to damaged and dying hair cells induced by noise, ototoxic drugs, aging and diphtheria toxin-induced hair cell degeneration. Precise monitoring may be crucial to avoid self-targeting. Macrophage biology has recently shown that populations of resident tissue macrophages may be fundamentally different from circulating macrophages. These cells may be detrimental and their priming should be avoided during and after CI surgery. Material and Methods: We removed uniquely preserved human cochleae during surgery for treating petro-clival meningioma compressing the brain stem, after ethical consent. Molecular and cellular characterization using antibodies against IBA1, TUJ1, CX3CL1 and type IV collagen, and super-resolution structured illumination microscopy (SR-SIM) were made together with transmission electron microscopy. Results and Conclusions: High resolution microscopy disclosed remarkable phenotypic variants of IBA1 cells closely associated with the spiral ganglion cells. Monitoring cells adhered to neurons with "synapse-like" specializations and protrusions. Active macrophages migrated occasionally nearby damaged hair cells. Results suggest that the human auditory nerve is under the surveillance and possible neurotrophic stimulation of a well-developed resident macrophage system. It may be alleviated by the non-myelinated nerve soma partly explaining why, in contrary to most mammals, the human's auditory nerve is conserved following deafferentiation. It makes cochlear implantation possible, for the advantage of the profoundly deaf. The IBA1 cells may serve additional purposes such as immune modulation, waste disposal and nerve regeneration. Their role in future stem cell-based therapy needs further exploration. The cells can be drug-influenced and corticosteroids may play an essential role to arrest their immune reactivity in connections with CI surgery. Results from experimental cochlear electrode studies will also be presented.
- Subjects
BELGIUM; CONFERENCES &; conventions; COCHLEAR implants; HEARING disorders; NEUROPHYSIOLOGY
- Publication
Journal of Hearing Science, 2018, Vol 8, Issue 2, p275
- ISSN
2083-389X
- Publication type
Article