Immunohistological analysis of eotaxin and RANTES in the model animal of eosinophilic otitis media.

BACKGROUND: The most crucial clinical problem of Eosinophilic Otitis Media (EOM) is sensorineural hearing loss. A previous report revealed that repeated antigen stimulation of middle ear causes eosinophilic inflammation not only in the middle ear but also in the inner ear.

OBJECTIVE: The purpose of the present study was to elucidate the mechanism of eosinophil infiltration to the inner ear in the animal model of EOM.

METHODS: Continuous OVA stimulation to the middle ear of guinea pigs was performed for 7 days, 14 days, and 28 days. Histological observation was made for eosinophil infiltration and morphological change of the inner ear. Immunostaining for eotaxin and RANTES was performed to study immunoreactivity of those chemokines.

RESULTS: In the 7-day stimulation side, a few eosinophils were found in the scala tympani, without obvious morphological damage of the inner ear. Moreover, immunoreactivity of both eotaxin and RANTES was significantly higher in the OVA stimulation sides than control sides. For both eotaxin and RANTES, the number of immunopositive cells was significantly increased in the 14-day stimulation side over the 7-day stimulation side.

CONCLUSIONS: Eotaxin and RANTES seem to play some important roles for the eosinophil infiltration in the middle and inner ear of model animal of EOM.