Impaired Stria Vascularis in the Inner Ear of Apolipoprotein E Gene Knockout Mice

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Purpose: To study apoptotic cell death, the expression of endothelial nitric oxide synthase (eNOS) and the capillary density in the cochleae of apolipoprotein E gene knockout (ApoE KO) mice. Methods: Cochleae of ApoE KO mice were stained by HE, anti-caspase-3 and anti-eNOS antibodies and TUNEL (in situ terminal deoxynucleotidyl transferase-mediated dUTP-biotin end labeling). Capillary density was measured in the stria vascularis and in the modiolus. Results: Apoptotic cell death was found in the stria vascularis of ApoE KO mice, but not in the organ of Corti. The expression of eNOS and the capillary density were decreased in the stria vascularis and in the modiolus of ApoE KO mice. Conclusion: These results suggest that cells in the inner ear of ApoE KO mice take different pathways to undergo cell death, and apoptotic cell death is only involved in the stria vascularis. These pathological changes may play a role in the hearing loss that has been found in ApoE KO mice.