Chapter 13 - Repairing and Building New Ears

Abstract

Here we review findings in birds that regenerate hair cells after noise trauma, and how this lead to studies to help restore hair cells in mammals that cannot automatically regenerate them. In neonatal animals, there is spontaneous regeneration of hair cells after damage to the sensory epithelium, but this becomes very limited as the mammalian cochlea matures. This resulted in identifying and introducing genes into the cochlea. The Atoh1 gene that directs hair cell and supporting cell development in the cochlea, through hair cell differentiation, hair cell maturation, and stereocilia formation emerged as a potential candidate. Atoh1 gene therapy in the mature cochlea forces supporting cells to transdifferentiate into immature hair cells that express multiple hair cell markers with functional mechano-transducer channels. It still remains to be seen if supporting cells can be reprogrammed to generate new hair cells. It is currently not clear if there are options for treatment long after hair cell damage has occurred. All in all, application to these procedures to humans is likely still many years, if not decades away.