Understanding how the inner ear develops and how it may regenerate after damage
30 March 2010
In humans, damage to the inner ear by factors such as loud noise and some types of drugs can lead to permanent hearing loss. However in birds, these damaged cells in the inner ear can regenerate throughout a bird's life to restore hearing. Dr Nico Daudet, the inaugural Deafness Research UK UCLEI Research Fellow, is investigating some of the signals and processes thought to be important for regeneration in chick ears, which may help researchers in the future to reverse hearing loss in humans.
Age-related hearing loss affects over 50% of people over 65. People become deafened primarily because the inner ear sensory hair cells – so called because of the tiny hair-like bundles at their tips that detect sound vibrations – die when damaged. In mammals, including humans, regeneration of these cells does not occur, so the hearing loss due to hair cell death is permanent. Aside from hearing aids and cochlear implants, developing therapies to induce regeneration by cells of the inner ear offers hope to the millions of people suffering from hearing loss.
In birds, hair cells are regenerated spontaneously and throughout adult life. The regeneration of hair cells could be used as a therapy for certain forms of human deafness, but developing efficient and safe cures relies on a better understanding of the molecular signals involved in hair cell formation and regeneration.
The aim of the research in Dr Daudet’s laboratory is to investigate development and regeneration in the chick inner ear, and in particular to study the function of a protein called Notch in the formation of hair cells. Notch is an important signalling protein that mediates communication between cells and is involved in many early processes of development in many types of organisms, including mammals and birds.
In collaboration with Dr Jennifer Stone (Seattle, USA), Dr Daudet has recently published a scientific paper showing that Notch plays an important role by regulating the number of hair cells that are produced following damage in the regenerating chick ear. This is important as, in order for the inner hair cells to work properly, so that sound vibrations are transmitted to the brain for us to hear, they must be present in an ordered pattern within the inner ear. Signalling by Notch from one cell to another stops cells becoming inner hair cells, thus preventing too many forming.
This research, funded in part by Deafness Research UK, has contributed further to our understanding of how the inner hair cells communicate and revealed a part of the complex jigsaw that is the formation of the inner ear.
Reference: Daudet et al (2009) Notch regulation of progenitor cell behaviour in quiescent and regenerating auditory epithelium of mature birds. Developmental Biology 326:86-100.
