Damage to cochlear hair cells results in permanent loss of hearing and effects 10% of the population. But, what if you could regrow these hair cells and restore lost hearing?
It has been established that hair cell regeneration in the auditory and vestibular systems does occur in chickens and other non-mammals, though not in humans. This spontaneous regeneration leads to restoration of hearing and balance, and may also prove to be essential in future cures for hearing loss in humans.
A new paper, published today in the journal Development, by Dr. Cheng, of the Stanford Initiative to Cure Hearing Loss, and Jian Zuo and colleagues from St. Jude Children’s Research Hospital, shows that spontaneous hair cell regeneration does in fact occur in the immature mammalian cochlea.
The findings in today’s paper are significant; as until now, though it has been possible to coax postnatal mammalian inner ear cells in culture to differentiate into hair cells, it was not believed that this process occurred spontaneously in vivo. Also, while prior research has shown the rare regeneration of hair cells in embryonic mice, until this point spontaneous regeneration had not been observed in the mammalian postnatal cochlea.
Hair cell regeneration occurs by two methods: direct transdifferentiation, where supporting cells directly become hair cells; and mitotic regeneration, in which supporting hair cells divide and one or both of the resulting cells develops into a hair cell. When hair cell loss was induced in mice at birth, the authors were able to observe spontaneous regeneration. They were further able to observe both methods of hair cell regeneration of hair cells and also the formation of hair cell bundles, necessary for the hearing process. Further, they were able to determine that spontaneous regeneration of hair cells did not occur after the first post natal week.
Many of the resulting hair cells did not survive, so the next step will be to further understand factors that can enhance hair cell survival, in addition to those that initiate this spontaneous regeneration. All of which are pieces in the puzzle of eventually restoring lost hearing in humans.
