Stem cell based therapy in the inner ear: appropriate donor cell types and routes for transplantation.

Losing one of our main sensory systems such as hearing can have devastating consequences in the way we interact with the world. The main problem lies in the fact that the critical sensory cells, the auditory neurons and hair cells located in the cochlea are only generated during development and, when damaged, cannot be replaced. The options currently available to treat this condition are very limited, and are mostly represented by prosthetic devices such as hearing aids and cochlear implants. There is a clear need for a therapeutic breakthrough that will help the millions of people affected, and the advances in stem cell technologies are offering a glimmer of hope for this affliction. Although still at a very early stage, a growing bulk of literature is being produced attempting to pave the path for a stem cell-based therapy for deafness. From the many variables to bear in mind when developing this approach, two appear to be of paramount importance. First, different cell types are potentially to be used, all of them having advantages and disadvantages. Second, in order to target such a small and secluded organ as the cochlea, difficult surgical techniques are to be used, some of which still need to be developed. The present article will aim to present the most recent advances of the field, focussing on these two critical issues.