Gene Replacement Therapy Can Generate New Hair Cells

Background: The sensory hair cells of the inner ear play an important role in detecting sound, and people who lose hair cells due to diseases, infections, or accidents often lose some or all of their ability to hear. Scientists have determined that many forms of inherited deafness are also due to problems with hair cells. The hair cells of the inner ear act like miniature amplifiers. Sound waves that enter the inner ear are converted into a series of chemical and electrical signals within the cells.These signals are ultimately transmitted to the brain via the auditory nerve and interpreted as sound.

Advance: In the past, only birds or reptiles were thought to be capable of generating new hair cells. Now, NIDCD-supported scientists have discovered a way to use gene therapy to generate new hair cells in the ears of adult mammals. Scientists used a virus to transfer a gene called Math1 into the ears of guinea pigs. Math1 is expressed in developing hair cells, and its expression is thought to cause the cells to become hair cells, rather than becoming another cell type within the ear. The virus infects cells of the ear and causes them to produce the Math1 protein. Early experiments suggest that when the virus infects cells that do not normally express Math1, some of these cells become hair cells. In addition, the new hair cells also attract fibers of the auditory nerve, suggesting that the new cells may also be able to establish a link to the part of the brain that interprets sound – the auditory cortex.

Implications: If this work can be duplicated in human beings, it may one day enable scientists to use gene therapy to restore hearing to those who have lost it, or to enable deaf individuals to hear.

Kawamoto K, Ishimoto S, Minoda R, Brough DE, Raphael Y. Math1 Gene Transfer Generates New Cochlear Hair Cells in Mature Guinea Pigs in vivo . J Neurosci 23:4395-4400, 2003.

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