Future of logopedics and phoniatrics based on regenerative medicine - Cochlear implants and regenerative medicine

Abstract

Cochlear implantation improves hearing and speech ability in patients with profound or severe sensorineural hearing loss. However, its effects are limited when there is a primary auditory neuron response deficiency because the effects of cochlear implantation are dependent on the function of the cochlear nerve. Recently, cochlear implantation indications have been expanded, and even patients with residual hearing in the low-frequency range have received cochlear implantation. In this case, the preservation or regeneration of hair cells is necessary. To overcome the limitations of cochlear implantation and to achieve more effective outcome in cases of the expanded indication, it is necessary to preserve or regenerate spiral ganglion cells, i.e. primary auditory neurons, and hair cells, both of which never regenerate naturally in mammals. Previous experiments using animals showed that these were accomplished using growth factors or stem cells, which are the important tools of regenerative medicine. Even in clinical trials on human beings to treat idiopathic sudden sensorineural hearing loss, one of the growth factors, insulin-like growth factor 1 (IGF-1), was shown to be more effective than steroid therapy, indicating that this growth factor is useful for cochlear implantation. It is necessary to apply these results to cochlear implantation in the future.