Therapeutic potential of neurotrophins for treatment of hearing loss

Degeneration of spiral ganglion neurons (SGNs) and hair cells in the cochle a induced by aging, injury, ototoxic drugs, acoustic trauma, and various di seases is the major cause of hearing loss. Discovery of growth factors that can either prevent SGN and hair-cell death or stimulate hair-cell regenera tion would be of great interest. Studies over the past several years have p rovided evidence that specific neurotrophins are potent survival factors fo r SGNs and protect these neurons from ototoxic drugs in vitro and in vivo. Current research focuses more on understanding the mechanism of hair-cell r egeneration/differentiation and identification of growth factors that can s timulate hair-cell regeneration. SGNs are required to relay the signal to t he central nervous system even when a cochlear implant is used to replace h air-cell function or in the case that cochlear sensory epithelium can be st imulated to regenerate new hair cells successfully. Therefore, neurotrophin s may have their therapeutic value in prevention and treatment of hearing i mpairment.