Dual AAV gene therapy achieves recovery of hearing and auditory processing in a DFNB16 mouse model.

Abstract

BACKGROUND: DFNB16, the second most common genetic cause of hearing loss, is caused by mutations of the STRC gene encoding stereocilin, a protein essential for the effective functioning of outer hair cells (OHCs) as cochlear amplifiers. Strcmice, which lack stereocilin, display severe to profound deafness and constitute a relevant preclinical model for DFNB16. METHODS: Using Strc/mice, we developed a gene therapy strategy based on the use of dual AAV9-PHP.eB vectors to deliver the full-length Strc cDNA. Therapeutic efficacy was assessed by evaluating stereocilin expression, OHC bundle architecture, and their attachment to the tectorial membrane, together with functional recovery using distortion product otoacoustic emissions (DPOAEs), auditory brainstem responses (ABR) measurements and Go/No-Go behavioral testing with psychometric analysis. RESULTS: Dual-AAV-mediated Strc gene delivery restored stereocilin expression, OHC bundle architecture and their attachment to the tectorial membrane, leading to the recovery of cochlear amplification and hearing to near normal thresholds, as confirmed by distortion product otoacoustic emission (DPOAE) and auditory brainstem response measurements. Behavioural assessment showed that treated Strcmice regained normal frequency discrimination, indicating a restoration of higher-order auditory processing, up to 100 days post-treatment. CONCLUSION: These findings provide the first proof-of-principle that peripheral gene therapy can restore OHC function, cochlear amplification and central auditory perception in a DFNB16 model. KEY POINTS: Dual AAV-mediated gene delivery restored peripheral hearing in a DFNB16 preclinical mouse model. The same treatment also restored central auditory processing. AAV-mediated gene therapy represents a promising curative strategy for DFNB16. These results reinforce the translational potential for treating human genetic deafness.