Death modes of cochlea hair cells in aged rats / 解放军医学杂志

ABSTRACT

Objective To examine the age-related morphological changes in hair cell nuclei,and explore the death modes of cochlea hair cells in aged rats.Methods Thirty-two Wistar rats were used in present experiment.The animals were assigned to one of the two groups,rats in aged group(n=20)were 22-23 months of age,and those in young group(n=12)were 2-3 months of age.The auditory brainstem response(ABR)thresholds of both ears elicited with tone bursts at 4,10 and 20 kHz were measured in both young and aged Wistar rats.Upon completion of the auditory test,animals were decapitated and both left and right bullae were exposed.Following fixation,whole specimens comprising the basilar membrane with Corti's organ were separated from the modiolus.Propidium iodide(PI),a popular DNA intercalating fluorescent probe,was used to trace the morphological changes in cochlea hair cell nuclei in the aged rats.Each Corti's organ was thoroughly inspected from the apical to the basal turns of cochlea with fluorescence microscopy.According to the morphological changes in the nuclei,the death modes of cochlea hair cell were determined.Results There were significant differences on ABR thresholds(P=0.001)at all tested frequencies between the young and aged rats.Three types of cochlea hair cell pathology appeared in the aged rats,including karyopyknosis,nuclear swelling and denucleation.A large number of loss or degenerated hair cells were present in the apical and basal end of cochlea in aged rats.Conclusion The present study indicates that apoptosis and necrosis are the death modes of cochlea hair cells in aged Wistar rats.