Animal model for studying inner ear mechanism of aging

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Mice deficient in Klotho gene expression exhibit a syndrome resembling premature human aging. To determine whether mouse homozygotes for the kl mutation (kll kl) show hearing dysfunction, histochemical study by the PAS reaction with light (LM) and electon microscopy (EM), and physiological study by measurement of the endocochleal static potential (EP) and potassium density in endolymph. The substances with PAS positive raction are found in large amounts in the stria vascularis with LM study. Especially, the endothelial cell and the basement membrane of capillaries in stria vascularis with EM study. The both of EM PAS reactions with the PA-TCH-SP method and the PA-SP method are the same reaction. The existence of PAS reactive substances might be associated with vascular endothelial dysfunction. We demonstrate that the EP of Klotho mice is significantly smaller (80.9 ± 7.2mV) than the EP of wild-type mice (96.9 ± 7.7mV), however, potassium densities in endolymph between klotho mice (209.7 ± 20.4mM) and wild-type mice (207.2 ± 26.2mM) are almost equivalent. These results suggest a decrease in EP is associated with stria vascularis dysfunction. The process of presbyacusis might be a reflection of stria vascularis dysfunction caused by aging.