Inner Ear Gene Delivery: Vectors and Routes.

Objectives: Current treatments for hearing loss offer some functional improvements in hearing, but do not restore normal hearing. The aim of this review is to highlight recent advances in viral and non-viral vectors for gene therapy and to discuss approaches for overcoming barriers inherent to inner ear delivery of gene products.

Data Sources: The databases used were Medline, EMBASE, Web of Science, and Google Scholar. Search terms were [("cochlea*" or "inner ear" or "transtympanic" or "intratympanic" or "intracochlear" or "hair cells" or "spiral ganglia" or "Organ of Corti") and ("gene therapy" or "gene delivery")]. The references section of resulting articles was also used to identify relevant studies.

Results: Both viral and non-viral vectors play important roles in advancing gene delivery to the inner ear. The round window membrane is one significant barrier to gene delivery that intratympanic delivery methods attempt to overcome through diffusion and intracochlear delivery methods bypass completely.

Conclusions: Gene therapy for hearing loss is a promising treatment for restoring hearing function by addressing innate defects. Recent technological advances in inner ear drug delivery techniques pose exciting opportunities for progress in gene therapy.