The Effect of Apoptosis Inducing Factor Gene on Peripheral Hearing Function During Aging

XIONG Binbin; HU Bohua; ZHAO Xiaoming; LIU Zhao; ZHAO Lidong; SUN Wei

doi:10.3969/j.issn.1672-2922.2017.009.

Abstract：Objective To study the functional role of apoptosis inducing factor gene (AIF) in cochlear homeosta-sis during aging. Methods Harlequin mice (2 and 6 months old) that were lack of the AIFM1 gene were used. Com-pound action potentials (CAP) and cochlear microphonics (CM) elicited by tone-bursts were recorded from the round window. The level of cochlear outer hair cell damage was evaluated using phalloidin staining. Results In the 2-months age group, the average compound action potentials threshold was 18.6 ± 1.6 dB SPL for wild-type (WT) mice (n=6) and 22.22.2 dB SPL for knockout (KO) mice (n=6), respectively (Student's t-test, P>0.05). However, for the 6 months age group, the average CAP threshold was 25.70 ± 1.69 dB SPL for WT mice (n=5), which was significantly lower than that for KO mice (42.10 ± 3.59 dB SPL, n=5) (Student's t-test, t=4.129, P<0.01). Comparisons of CAP amplitudes be-tween the WT and KO mice revealed a significant difference at higher frequencies (30, 35 and 40 kHz;two-way ANO-VA,P<0.05), but not at middle and low frequencies. The CM amplitude I/O functions were non-linear in both WT and KO mice at both 2 months and 6 months of age, with no significant difference between the WT and KO mice (Two-way ANOVA, P>0.05). Consistent with this functional assessment, comparison of missing OHCs revealed a significant dif-ference at basal turn of cochlea between the WT and KO groups at the age of 6 months (Student t-test, t=15.11, P<0.0001). Conclusions Loss of AIFM1 gene function accelerates age-related outer hair cell degeneration and high fre-quency hearing loss.