Hearing loss due to aging, noise and certain cancer therapy drugs and antibiotics has been irreversible because scientists have not been able to reprogram existing cells to develop into the outer and inner ear sensory cells — essential for hearing — once they die.
The Northwestern Medicine scientists have now discovered a single master gene that programmes ear hair cells into either outer or inner ones, overcoming a major hurdle that had prevented the development of these cells to restore hearing ( Nature).
Currently, scientists can produce an artificial hair cell, but it does not differentiate into an inner or outer cell, which provide different essential functions to produce hearing. The discovery is a major step towards developing these specific cells.
The death of outer hair cells made by the cochlea are most often the cause of deafness and hearing loss. The cells develop in the embryo and do not reproduce. The outer hair cells expand and contract in response to the pressure of sound waves and amplify sound for the inner hair cells. The inner cells transmit those vibrations to the neurons to create the sounds we hear.
The master gene switch Northwestern scientists discovered that programmes the ear hair cells is TBX2. When the gene is expressed, the cell becomes an inner hair cell. When the gene is blocked, the cell becomes an outer hair cell. The ability to produce one of these cells will require a gene cocktail, says a press release. The goal would be to reprogramme supporting cells, which are latticed among the hair cells and provide them with structural support, into outer or inner hair cells.
