Relationship between Survival of Organ of Corti and Stria Vascularis

LI Yi; LIU Huizhan; GONG Shusheng; HE David Z

doi:10.3969/j.issn.1672-2922.2014.03.032

Abstract：Objective To determine whether hair cells and stria vascularis depend on each other for functioning and survival. The atoh1 conditional knockout (Atoh1-CKO) mice and Mitf mutant mice were used for our study. The Atoh1-CKO mouse itself terminates the expression of Atoh1 in hair cells around birth. We used this model to determine whether absence of hair cells would affect development, functioning and survival of the stria vascularis. The other mouse model has a mutation of the microphthalmia-associated transcription factor (Mitf) gene expressed in melanocytes. Loss of melanocytes in the stria vascularis due to Mitf mutation causes abnormality of the stria morphology and functions, leading to hearing loss. We used this model to determine whether change of the electrochemical environment in the endolymph maintained by the stria vascu-laris would affect the functioning and survival of hair cells. Methods We used auditory brainstem response (ABR) to measure hearing thresholds and round window electrode to measure cochlear microphonics (CM) and compound action potential (CAP). Sharp electrode technique was used to measure endocochlear potential (EP). Hair cell and supporting cell morphology was ex-amined by immunocytochemistry and confocal microscopy. Thin sections of the cochlea were used to examine the morphology of strial vascularis and organ of Corti. Results showed that EP and stria morphology were unaffected when the organ of Corti had completely degenerated. However, stria defects led to progressive loss of outer hair cells (OHCs). Conclusion The surviv-al and normal operation of the stria vascularis do not depend on a functional organ of Corti. However, normal functioning of the stria vascularis is necessary for auditory functions and survival of adult OHCs.