Multipotent stem cells from the young rat inner ear

The terminal mitosis of hair cells (HCs) and supporting cells (SCs) in mammalian cochlea occurred during middle embryonic development. Most hearing loss results from the incapacity of the cochlear sensory epithelium to replace lost hear cells. Deafness due to hair cells loss is normally irreversible. The present study showed that cells acutely dissociated from the cochlea of young rat, cultured with EGF and FGF2, developed into otospheres that showed expression of nestin and incorporation of 5′-Bromo-2-deoxyuridine (BrdU). The subcultured otospheres maintained for up to 10 passages. In addition, the cochlea sphere-derivatives contributed to a variety of cell types. They were found to differentiate to neuron, glia, hair cell and supporting cell phenotypes. The results suggest that the young rat inner ear cells have self-renewal capability and multipotent differentiation potential. This work raises the possibility that inner ear cells in the early post-natal rat have the character of pluripotent stem cells and might be a source for cell replacement therapy in the inner ear.