Expression Of Connexin26and Connexin31in Cochlea Lateral Wall Of Mice After Noise Exposure

Part one：Procedures for the model of noiseinduced hearing damageObjective To establish the animal model of noise induced hearingdamage.Methods twenty-six mice were randomly divided into2groups, there arethirteen mice in noise group and control group respectively. The mice of controlgroup were non-noise exposed. The mice of noise group were exposed to wideband noise. The duration of sound exposure was12hours over2days at115dBSPL. After noise exposure, auditory brainstem response (ABR) of mice on noiseexposure and control group were tested; Four mice’ cochleas of every group were taken to frozen section and observed by transmission electronmicroscope(TEM).Results According to HE staining and observation by TEM, there arechanges in morphology in lateral wall cells after noise exposure; ABR thresholdof noise group mice were increased remarkably.Conclusions The animal model of noise induced hearing damage wasestablished after treatment of noise described in this paper.Part two: Expression of Connexin26incochlea lateral wall of mice after noiseexposureObjective To investigate the expression of Connexin26in cochlea lateralwall of mice after noise exposure.Methods Forty mice were randomly divided into2groups, there aretwenty mice in noise group and control group respectively. The mice of controlgroup were non-noise exposed. The mice of noise group were exposed to wideband noise. The duration of sound exposure was12hours over2days at115dB SPL. After noise exposure, auditory brainstem response (ABR) of mice onnoise exposure and control group were tested. All mice’ cochleas of every groupwere extracted the total RNA of mice cochlea lateral wall. Expression of Cx26protein was observed by Immunohistochemistry. Expression of Cx26mRNAwas tested by real-time PCR. Expression of β-Tubulin protein was observed byconfocal microscopy after immunofluorescence.Results (1) Special immunoreactive Cx26was observed in spiralligament (SPL) and stria vascularis.(2) Decreased Cx26immunoreaction was observed in noise group compared to control mice.(3) The level of GJB2codingfor Cx26was reduced in noise group compared to control mice.(4)microtubules were disordered after niose exposure by the β-tubulin staining, butno shatter.Conclusions Cx26was present in mice cochlea lateral wall and was downregulated when ABR threshold shifted after noise exposure. Cx26was involvedin the pathogenesis of acoustic trauma.Part three: Expression of Connexin31in cochlealateral wall of mice after noise exposureobjective To investigate the expression of Connexin31in cochlea lateralwall of mice after noise exposure.Methods Forty mice were randomly divided into2groups, and there aretwenty-two mice in every group. The mice of control group were non-noiseexposed. The mice of noise group were exposed to wide band noise. Theduration of sound exposure was12hours over2days at115dB SPL. Afternoise exposure, auditory brainstem response (ABR) of mice on noise exposureand control group were tested. All mice’ cochlea of every group were extractedthe total RNA of mice cochlea lateral wall. Expression of Cx31protein wasobserved by immunofluorescence. Expression of Cx31mRNA was tested byreal-time PCR.Result (1) Special fluorescence of Cx31was observed in spiral ligament(SPL), but not in stria vascularis.(2) Decreased Cx31immunofluorescence wasobserved in noise group compared to control mice.(3) The level of GJB3codingfor Cx31was reduced in noise group compared to control mice. Conclusion Cx31was present in mice cochlea lateral wall and downregulated when ABR threshold shifted after noise exposure. Cx31was involvedin the pathogenesis of acoustic trauma.