Autoimmune Saccitis and Cochlear Change

Abstract

Objectives: Injury to the endolymphatic sac may play an important role in the pathogenesis of Ménière’s disease. The purpose of this study was to) investigate the effect of an autoimmune stimulation of the endolymphatic sac in rats. Methods: Nineteen inbred male Lewis rats in an animal laboratory at the University of Copenhagen were studied. Outcome measurements: Distortion product oto-acoustic emissions (DPOAE) and transmission electron microscopy (TEM). Independent variables: autoimmunization. Preliminary analyses: Endolymphatic hydrops. Results: At day 21 the immunized group showed no significant differences in hearing assessment, on full range of frequencies, compared to the controls ( P >0.05; Welsh t-test). At day 183, the hearing assessment showed a 1.5 dB (6,35%) drop in CDP in the immunized group compared to the controls from 2-16kHz ( P < 0.05; Welsh t-test) and a 2.5 dB (11.1%) decrease in the low frequency area, from 2-5kHz ( P < 0.01; Welsh t-test). TEM investigation indicated stimulation of the endolymphatic sacs in all immunized rats: The ribosome-rich cells appeared hyperactive, and a focal inflammation of immunologically active cells and phagocytosis of ribosome-rich cells were observed. Conclusions: An autoantigen, capable of inducing an endolymphatic saccitis with concomitant cochlear change, exists in the rat. A possible relationship between these observations and Ménière’s disease is proposed.