In vivo delivery of Atoh1 gene to rat cochlea using a dendrimer-based nanocarrier

Gene therapy is a promising clinical solution to hearing loss. However suitable gene carriers for the auditory system are currently unavailable. Given the unique structure of the inner ear, the route of delivery and gene transfer efficiency are still not optimal at present. This study presented a non-viral delivery system of in vivo delivery of Atoh1 gene (a potentially therapeutic gene for hearing loss) to rat cochlea. We treated polyamidoamine (PAMAM) dendrimers by activating and modifying with Na-carboxymethyl-beta-cyclodextrins (CM-beta-CD) in sequence. A novel gene carrier (CM-beta-CD modified activated PAMAM dendrimers, CMAP) was then constructed. CMAP nanoparticles could bind pRK5-Atoh1-EGFP plasmids to form vector-DNA complexes (dendriplexes) with a mean particle size of 132 +/- 20 nm and zeta potential of 31 +/- 3 mV. These dendriplexes were locally applied on the round window membrane and delivered to the inner ear by passive gradient permeation. Results showed that the Atoh1 gene was successfully transferred into the cells as indicated by the green fluorescence detected in the inner ear. A relatively selective gene transfer with high efficiency was achieved in the auditory hair cells but not much in other cell types in the cochlea. Auditory brainstem response was determined seven days after inoculation, indicating good tolerance. This approach may provide a novel tool for inner ear gene therapy and initiate the applications of biomaterials to treat auditory disorders.