HEARING IN THE MRL LPR MOUSE AS A POSSIBLE MODEL OF IMMUNE-MEDIATED SENSORINEURAL HEARING-LOSS/

In order to clarify the possible mechanism of hearing loss in immune-m ediated sensorineural hearing loss, basic research needed includes ani mal model studies. In the present investigation, we examined hearing t hresholds and cochlear histologies of the MRL/lpr mouse which is now w ell-known as a model for pathology consistent with systemic lupus eryt hematosis (SLE). Present findings demonstrated that there were no stat istically significant differences in auditory brainstem response (ABR) thresholds between 4- to 6-week-old ''young'' and 20- to 25-week-old ''old'' MRL mice. These differences were not sex-dependent. Under ligh t microscopy, there were no abnormal morphological findings in the coc hleas of either young or old MRL mice. With immunohistochemistry, mous e IgG was detected around the capillary walls in the stria vascularis in both young and old MRL mice. Serum IgG level of the MRL mice signif icantly decreased after predonisolone (PSL) administration. However, e xpression of mouse IgG in the stria vascularis was not observed in the MRL mice after PSL administration. From these results, we speculate t hat the hearing of the MRL mouse does not always deteriorate, and the deposition of mouse IgG on the capillary wall in the stria vascularis is not a sufficient factor to induce hearing loss. At this point, we c onclude that the MRL mouse should not be considered a useful model for immune-mediated sensorineural hearing loss.