Survival of fetal rat otocyst cells grafted into the damaged inner ear

Hair cell loss induced by aging, ototoxic drugs and noise leads to irreversible hearing loss and balance disorders in mammals due to the failure of hair cells to regenerate. To investigate the possibility of transplantation therapy to repair damaged inner ear, we have examined whether grafted fetal otocyst cells could survive and migrate into injured sensory organs. We obtained otocyst cells from green fluorescein protein (GFP)-transgenic rats on embryonic day 12.5, then transplanted these cells into the inner ears of young rats previously exposed to intense sound. One month after transplantation, the grafted inner ear sensory organs were examined immunohistochemically. Grafted otocyst cells had survived and demonstrated special morphological features in the host organs; cells that migrated into the organ of Corti were similar to supporting cells. These results indicate that injured sensory organs express some kind of scaffolding that plays important roles in the survival and differentiation of the grafted otocyst cells.