Rapid cochlear gene therapy in adult deaf mice: Vglut3 rescue via AAV8 achieves day-1 hearing restoration.

Genetic hearing loss, caused by mutations in critical auditory genes, has seen promising advances through gene therapy, yet the temporal dynamics of early-stage auditory functional recovery and therapeutic transgene expression patterns following intervention remain uncharacterized in preclinical deafness models. This study systematically investigates the post-treatment progression of cochlear functional restoration and spatially resolved transgene expression kinetics in adult Vglut3 knockout (Vglut3 KO ) mice following adeno-associated virus (AAV)-mediated inner ear gene therapy. AAV8 vectors delivering Vglut3 were injected via the posterior semicircular canal (PSCC), with auditory brainstem response (ABR) thresholds and cochlear transgene expression assessed at days 1-14 post-injection. VGLUT3 expression in Vglut3 KO mice revealed rapid transduction, detectable in inner hair cells (IHCs) by day 1, peaking at day 14. Remarkably, hearing recovery commenced as early as day 1 post-injection, and plateaued near wild-type (WT) levels by day 5. Functional correlation analysis demonstrated a robust inverse relationship between FLAG expression and hearing thresholds. This study provides critical insights into the dynamic processes underlying cochlear gene therapy and challenges the conventional paradigm that 1-2 weeks are required for functional recovery.