Expression of caspase-activated deoxyribonuclease (CAD) and caspase 3 (CPP32) in the hydropic cochlea of guinea pigs - second report.

Apoptosis was induced in the cochlea by the injection of keyhole limpet hemocyanin (KLH) into the endolymphatic sac of guinea pigs and immunohistochemically examined. Keyhole limpet hemocyanin was injected into the right endolymphatic sac. The temporal bones were fixed via cardiac infusion of fixative and immunohistochemically stained for caspase-activated deoxyribonuclease or caspase 3. Endolymphatic hydrops became evident in the cochlea 1 day after the injection of keyhole limpet hemocyanin (n=6). The temporal bones in the control group did not show any caspase-activated deoxyribonuclease or caspase 3 immunoreactivity (n=6). Immunoreactivity for caspase 3 was detected in the supporting cells of the organ of Corti, the stria vascularis and the spiral ganglion cells. Caspase-activated deoxyribonuclease was also detected in the same areas. These findings suggest that apoptosis is involved in the pathogenesis of endolymphatic hydrops. This phenomenon could lead to cochlear dysfunction, as seen in endolymphatic hydrops.