A freeze-fracture study of afferent and efferent synapses of hair cells in the sensory epithelium of the organ of Corti in the guinea pig

AbstractSound evokes sub-nanoscale vibration within the sensory epithelium. The epithelium contains not only immotile cells but also contractile outer hair cells (OHCs) that actively shrink and elongate synchronously with the sound. However, the in vivo motion of OHCs has remained undetermined. The aim of this work is to perform high-resolution and -accuracy vibrometry in live guinea pigs with an SC-introduced spectral-domain optical coherence tomography system (SD-OCT). In this study, to reveal the effective contribution of SC source in the recording of the low reflective materials with the short total acquisition time, we compare the performances of the SC-introduced SD-OCT (SCSD-OCT) to that of the conventional SD-OCT. As inanimate comparison objects, we record a mirror, a piezo actuator, and glass windows. For the measurements in biological materials, we use in/ex vivo guinea pig cochleae. Our study achieved the optimization of a SD-OCT system for high-resolution in vivo vibrometry in the cochlear sensory epithelium, termed the organ of Corti, in mammalian cochlea. By introducing a supercontinuum (SC) light source and reducing the total acquisition time, we improve the axial resolution and overcome the difficulty in recording the low reflective material in the presence of biological noise. The high power of the SC source enables the system to achieve a spatial resolution of 1.72 ± 0.00 μm on a mirror and reducing the total acquisition time contributes to the high spatial accuracy of sub-nanoscale vibrometry. Our findings reveal the vibrations at the apical/basal region of OHCs and the extracellular matrix, basilar membrane.

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Early appearance of key transcription factors influence the spatiotemporal development of the human inner ear

Cell and Tissue Research ◽

10.1007/s00441-019-03115-6 ◽

2019 ◽

Vol 379 (3) ◽

pp. 459-471 ◽

Cited By ~ 1

Author(s):

Lejo Johnson Chacko ◽

Consolato Sergi ◽

Theresa Eberharter ◽

Jozsef Dudas ◽

Helge Rask-Andersen ◽

...

Keyword(s):

Transcription Factors ◽

Inner Ear ◽

Hair Cells ◽

Transforming Growth Factor ◽

Expression Patterns ◽

Organ Of Corti ◽

Sensory Epithelium ◽

Receptor Expression ◽

Cell Phenotype ◽

Type I

AbstractExpression patterns of transcription factors leucine-rich repeat-containing G protein-coupled receptor 5 (LGR5), transforming growth factor-β-activated kinase-1 (TAK1), SRY (sex-determining region Y)-box 2 (SOX2), and GATA binding protein 3 (GATA3) in the developing human fetal inner ear were studied between the gestation weeks 9 and 12. Further development of cochlear apex between gestational weeks 11 and 16 (GW11 and GW16) was examined using transmission electron microscopy. LGR5 was evident in the apical poles of the sensory epithelium of the cochlear duct and the vestibular end organs at GW11. Immunostaining was limited to hair cells of the organ of Corti by GW12. TAK1 was immune positive in inner hair cells of the organ of Corti by GW12 and colocalized with p75 neurotrophic receptor expression. Expression for SOX2 was confined primarily to the supporting cells of utricle at the earliest stage examined at GW9. Intense expression for GATA3 was presented in the cochlear sensory epithelium and spiral ganglia at GW9. Expression of GATA3 was present along the midline of both the utricle and saccule in the zone corresponding to the striolar reversal zone where the hair cell phenotype switches from type I to type II. The spatiotemporal gradient of the development of the organ of Corti was also evident with the apex of the cochlea forming by GW16. It seems that highly specific staining patterns of several transcriptions factors are critical in guiding the genesis of the inner ear over development. Our findings suggest that the spatiotemporal gradient in cochlear development extends at least until gestational week 16.

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Cochlear progenitor number is controlled through mesenchymal FGF receptor signaling

eLife ◽

10.7554/elife.05921 ◽

2015 ◽

Vol 4 ◽

Cited By ~ 39

Author(s):

Sung-Ho Huh ◽

Mark E Warchol ◽

David M Ornitz

Keyword(s):

Growth Factors ◽

Hair Cells ◽

Fibroblast Growth Factors ◽

Organ Of Corti ◽

Sensory Epithelium ◽

Feedback Mechanism ◽

Outer Hair Cells ◽

Fibroblast Growth ◽

Supporting Cells ◽

Fgf Receptor

The sensory and supporting cells (SCs) of the organ of Corti are derived from a limited number of progenitors. The mechanisms that regulate the number of sensory progenitors are not known. Here, we show that Fibroblast Growth Factors (FGF) 9 and 20, which are expressed in the non-sensory (Fgf9) and sensory (Fgf20) epithelium during otic development, regulate the number of cochlear progenitors. We further demonstrate that Fgf receptor (Fgfr) 1 signaling within the developing sensory epithelium is required for the differentiation of outer hair cells and SCs, while mesenchymal FGFRs regulate the size of the sensory progenitor population and the overall cochlear length. In addition, ectopic FGFR activation in mesenchyme was sufficient to increase sensory progenitor proliferation and cochlear length. These data define a feedback mechanism, originating from epithelial FGF ligands and mediated through periotic mesenchyme that controls the number of sensory progenitors and the length of the cochlea.

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Aquaporin-6 Expression in the Cochlear Sensory Epithelium Is Downregulated by Salicylates

Journal of Biomedicine and Biotechnology ◽

10.1155/2010/264704 ◽

2010 ◽

Vol 2010 ◽

pp. 1-8 ◽

Cited By ~ 2

Author(s):

Paola Perin ◽

Simona Tritto ◽

Laura Botta ◽

Jacopo Maria Fontana ◽

Giulia Gastaldi ◽

...

Keyword(s):

Inner Ear ◽

Expression Pattern ◽

Hair Cells ◽

Organ Of Corti ◽

Sensory Epithelium ◽

Outer Hair Cells ◽

Rt Pcr ◽

Supporting Cells ◽

Sensory Epithelia ◽

Mechanical Compliance

We characterize the expression pattern of aquaporin-6 in the mouse inner ear by RT-PCR and immunohistochemistry. Our data show that in the inner ear aquaporin-6 is expressed, in both vestibular and acoustic sensory epithelia, by the supporting cells directly contacting hair cells. In particular, in the Organ of Corti, expression was strongest in Deiters' cells, which provide both a mechanical link between outer hair cells (OHCs) and the Organ of Corti, and an entry point for ion recycle pathways. Since aquaporin-6 is permeable to both water and anions, these results suggest its possible involvement in regulating OHC motility, directly through modulation of water and chloride flow or by changing mechanical compliance in Deiters' cells. In further support of this role, treating mice with salicylates, which impair OHC electromotility, dramatically reduced aquaporin-6 expression in the inner ear epithelia but not in control tissues, suggesting a role for this protein in modulating OHCs' responses.

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