Alterations of inner ear morphology in experimental hypercholesterolemia

Previous clinical and experimental studies have indicated that auditory function may be compromised by hypercholesterolemia. In this investigation, inner ear tissue from chinchillas maintained on a cholesterol-supplemented diet for 3 months was examined for morphological alterations which might underlie the physiological changes observed with this condition in earlier studies. Ultrastructural analysis of cochleas from 16 hypercholesterolemic chinchillas revealed alterations in both the stria vascularis and outer hair cells. Strial marginal cells throughout the cochlea and outer hair cells of the apical turn, contained electron-lucent patches of an amorphous material. These patches had the morphological characteristics and histochemical properties of glycogen. Mild extracellular edema and increased numbers of lysosomes were also noted in the stria vascularis of experimental animals. These alterations suggest that chronic hypercholesterolemia metabolically stresses inner ear tissue. It is hypothesized that such changes could increase susceptibility of the cochlea to ototraumatic agents.