From ScienceDaily: "scientists have successfully produced functional auditory hair cells in the cochlea of the mouse inner ear. ... researchers specifically focused on the tiny hair cells located in a portion of the ear's cochlea called the organ of Corti. It has long been understood that as these hair cells die, hearing loss occurs. Throughout a person's life, a certain number of these cells malfunction or die naturally leading to gradual hearing loss often witnessed in aging persons. Those who are exposed to loud noises for a prolonged period or suffer from certain diseases lose more sensory hair cells than average and therefore suffer from more pronounced hearing loss. ... One approach to restore auditory function is to replace defective cells with healthy new cells. Our work shows that it is possible to produce functional auditory hair cells in the mammalian cochlea. ... It remains to be determined whether gene transfer into a deaf mouse will lead to the production of healthy cells that enable hearing."