Reduced Connexin26 in the Mature Cochlea Increases Susceptibility to Noise-Induced Hearing Loss in Mice
<p>Connexin26 deletion in conditional connexin26 (Cx26) Knockdown (KD) mice after noise exposure. Summary of Cx26 expression in control and experimental groups. (<b>A</b>,<b>B</b>) Western blot and histogram detecting Cx26 in the cochleae of control, KD, noise and knockdown+noise groups (KN groups) at P30 (<span class="html-italic">n</span> = 4 in each group); (<b>C</b>) Immunolabeling of Cx26 (<b>red</b>) in the cochlear sections of control and different experimental groups at P30; (<b>D</b>) Immunolabeling of Cx26 (<b>red</b>) and phalloidin (<b>green</b>) in flattened cochlear preparations of control and experimental groups at P30. There was an obvious Cx26 reduction in Deiter and Pillar cells of KD and KN mouse groups. Abbreviations: PC: Pillar cell; DC: Deiter cell. * <span class="html-italic">p</span> < 0.05 when compared with the control group.</p> "> Figure 2
<p>Hearing thresholds shift after Cx26 reduction and noise exposure. Auditory thresholds were measured in control, KD, noise and KN group at P30 (<b>A</b>) and P45 (<b>B</b>). * Significantly different from the control group (<span class="html-italic">p</span> < 0.01); <sup>#</sup> Significantly different from the noise group (<span class="html-italic">p</span> < 0.01). Plot legends for different groups are given in the panel.</p> "> Figure 3
<p>Hair cell loss patterns in control, KD, noise and KN groups. Patterns and time courses of OHC loss in control and experimental groups (<span class="html-italic">n</span> = 3–4 in each group). Panels (<b>A</b>,<b>B</b>) show the examples of the HC nucleus (<b>blue</b>) and <span class="html-italic">F</span>-actin (<b>red</b>) in control, KD, noise and KN groups; Three rows of OHCs are at the bottom; Panels (<b>C</b>,<b>D</b>) show quantifications of OHC loss at specific cochlear locations in control and different experimental groups. The inset in panel C shows a dissected surface preparation and the red frames represent different check points.* Significantly different from the control group (<span class="html-italic">p</span> < 0.05); <sup>#</sup> Significantly different from the noise group (<span class="html-italic">p</span> < 0.05). Plot legends for different groups are given in the panels.</p> "> Figure 4
<p>Cochlear morphology of the basal turn in control, KD, noise and KN groups. A full view of a cochlea obtained from noise (<b>A</b>) and KN groups (<b>B</b>); Panels <b>C</b>, <b>F</b>, <b>I</b> and <b>L</b> show the morphology of the cochleae at the basal turn in control and experimental groups; Panels <b>D</b>, <b>G</b>, <b>J</b> and <b>M</b> show the morphology of the magnified OC in panels <b>C</b>, <b>F</b>, <b>I</b> and <b>L</b>, respectively; Panels <b>E</b>, <b>H</b>, <b>K</b> and <b>N</b> show the SGN at the basal turn in the different groups. Abbreviations: SV: stria vascularis; OC: organ of Corti; SG: spiral ganglia. The scale in panel represents 200 μm, and scales in panel <b>C</b>, <b>D</b> and <b>E</b> represent approximately 40 μm.</p> "> Figure 5
<p>Ultrastructure of cochleae at the basal turn in control, KD, noise and KN groups. The ultrastructure of the basal turn of the cochlea was observed in control and different experimental groups at P45 (<span class="html-italic">n</span> = 3 in each group). Panels <b>A</b>, <b>B</b>, <b>C</b> and <b>D</b> show the basal OC in control, KD, noise and KN groups. Distinct OHC loss was observed in noise group (C) and the basal OC was collapsed in KN group (D). The inset (panel <b>C</b>) in the left bottom show the inner hair cell; Panels <b>E</b>, <b>F</b>, <b>G</b> and <b>H</b> show the SV at the basal turn in different groups; Panels <b>I</b>, <b>J</b>, <b>K</b> and <b>L</b> show the ultrastructure of IC at the basal turn in control and experimental groups. The insets (panels <b>I</b>, <b>J</b>, <b>K</b> and <b>L</b>) on the left bottom show mitochondria and the myelinbody was magnified in the upper right boxes (Panel <b>K</b> and <b>L</b>). Panels <b>M</b>, <b>N</b>, <b>O</b> and <b>P</b> show the ultrastructure of BC in stria vascularis. Abbreviations: SV: striavascularis; OC: organ of Corti; IC: intermediate cell; BC: basal cell; MC: marginal cell; C: capillary. The scales in panel <b>A</b>, <b>E</b>, <b>I</b> and <b>M</b> represent 10, 5, 1 and 1 μm, respectively. The arrow in <b>L</b> is pointing out a mitochondria and the arrowhead indicates a myelinbody.</p> ">
Abstract
:1. Introduction
2. Results
2.1. Connexin26 Deletion in Conditional Cx26 Knocked down Mice
2.2. Hearing Thresholds Shift after Cx26 Reduction and Noise Exposure
2.3. Cx26 Reduction Exacerbates Hair Cell Loss in the Knockdown + Noise Groups (KN Groups)
2.4. Cell Degeneration Pattern after Cx26 Reduction and Noise Exposure
2.5. Ultrastructural Changes after Cx26 Reduction and Noise Exposure
3. Discussions
4. Materials and Methods
4.1. Generation of the Connexin26 (Cx26) Conditional Knockdown (KD) Mouse Model and Genotyping
4.2. Animal Treatment and Noise Exposure Procedure
4.3. Auditory Brainstem Recordings
4.4. Protein Extraction and Western Blot Analysis
4.5. Cochlear Tissue Preparation and Immunofluorescent Labeling
4.6. Quantification of Cochlear Hair Cells
4.7. Resin Sections and Transmission Electron Microscopy
4.8. Statistical Analysis
5. Conclusions
Supplementary Materials
Acknowledgments
Author Contributions
Abbreviations
Cx26 | connexin26 |
NIHL | noise-induced hearing loss |
KD | knocked down |
GJ | gap junction |
SNPs | single nucleotide polymorphisms |
SPF | specific-pathogen free |
KN | knocked down + noise |
HC | hair cell |
OHC | outer hair cell |
SV | stria vascularis |
TC | tunnel of Corti |
MC | marginal cells |
OC | organ of Corti |
BC | basal cell |
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Zhou, X.-X.; Chen, S.; Xie, L.; Ji, Y.-Z.; Wu, X.; Wang, W.-W.; Yang, Q.; Yu, J.-T.; Sun, Y.; Lin, X.; et al. Reduced Connexin26 in the Mature Cochlea Increases Susceptibility to Noise-Induced Hearing Loss in Mice. Int. J. Mol. Sci. 2016, 17, 301. https://doi.org/10.3390/ijms17030301
Zhou X-X, Chen S, Xie L, Ji Y-Z, Wu X, Wang W-W, Yang Q, Yu J-T, Sun Y, Lin X, et al. Reduced Connexin26 in the Mature Cochlea Increases Susceptibility to Noise-Induced Hearing Loss in Mice. International Journal of Molecular Sciences. 2016; 17(3):301. https://doi.org/10.3390/ijms17030301
Chicago/Turabian StyleZhou, Xing-Xing, Sen Chen, Le Xie, Yu-Zi Ji, Xia Wu, Wen-Wen Wang, Qi Yang, Jin-Tao Yu, Yu Sun, Xi Lin, and et al. 2016. "Reduced Connexin26 in the Mature Cochlea Increases Susceptibility to Noise-Induced Hearing Loss in Mice" International Journal of Molecular Sciences 17, no. 3: 301. https://doi.org/10.3390/ijms17030301