Cell Replacement Therapy in the Inner Ear: Implications for Cochlear Implantation

This article provides an overview of recent advances in inner ear cell replacement therapy. Current strategies designed both to initiate hair cell regeneration and maintain or regenerate neural cells are reviewed. Using animal models, investigators have shown that hearing loss from hair cell and neural degeneration can be reversed through molecular and genetic manipulation. Successful strategies in animal models have included the use of growth factors, stem cells, and gene therapy. One significant challenge for the use of these strategies in humans is the development of safe, efficient, and targeted drug delivery systems. Using animal models investigators have shown that cochlear implants can be used to deliver growth factors, such as neurotrophins to the inner ear. Targeting the appropriate neural elements will be important for future application of this technique in humans. Finally, the prognosis for hearing restoration through cell replacement or maintenance therapy will certainly be influenced by the underlying etiology of the hearing loss. Audiologists will play a critical role in the future determination of candidacy for these therapeutic approaches.