Novel drug delivery systems for inner ear protection and regeneration after hearing loss

Abstract

Background: A cochlear implant, the only current treatment for restoring auditory perception after severe or profound sensorineural hearing loss (SNHL), works by electrically stimulating spiral ganglion neurons (SGNs). However, gradual degeneration of SGNs associated with SNHL can compromise the efficacy of the device. Objective: To review novel drug delivery systems for preserving and/or regenerating sensory cells in the cochlea after SNHL. Methods: The effectiveness of traditional cochlear drug delivery systems is compared to newer techniques such as cell, polymer and gene transfer technologies. Special requirements for local drug delivery to the cochlea are discussed, such as protecting residual hearing and site-specific drug delivery for cell preservation and regeneration. Results/conclusions: Drug delivery systems with the potential for immediate clinical translation, as well as those that will contribute to the future of hearing preservation or cochlear cellular regeneration, are identified.

Keywords::

• cell-based therapy
• conducting polymer
• cochlear implant
• dexamethasone
• gene transfer
• hair cell
• hearing protection
• neurotrophin
• polypyrrole
• regeneration
• sensorineural hearing loss
• spiral ganglion neuron

Acknowledgements

The authors would like to thank the funding institutions, mentioned in the declaration of interest below, which are associated with research discussed in this review. Figure 2 was prepared by H Eastwood.