Potential of Pluripotent Stem Cells for the Replacement of Inner Ears

The inner ear, which manages our senses of hearing and balance, has mechanosensitive hair cells, which convert vibration into electronic signal to depolarize auditory or vestibular neurons. Inner ear functions depend largely on hair cells, their associated neurons and cochlear lateral wall, and defects in these cells result in hearing loss and deafness. Although some investigations indicated hair cell regeneration in mammalian vestibular sensory epithelia, loss of mammalian auditory hair cells is currently irreversible, which is the reason why hundreds of millions of people worldwide with hearing impairment have no way of restoring their auditory function. To date, the cochlear implant, which is designed to electrically stimulate the auditory neurons, is the only available prosthesis for severe to profoundly deaf individuals. However, it depends on remaining auditory neurons, named as spiral ganglion neurons, and their loss severely compromises its efficacy. In this context, several research strategies are directed toward replacing the degenerating spiral ganglion neurons following hearing loss. Here we review recent advances in the field of inner ear regeneration using pluripotent stem cells.