Adeno-associated virus-mediated gene delivery into the scala media of the normal and deafened adult mouse ear

Abstract

Murine models are ideal for studying cochlear gene transfer as many hearing loss-related mutations have been discovered and mapped within the mouse genome. However, due to its small size and delicate nature, the membranous labyrinth of the mouse is a challenging target for delivery of viral vectors. To minimize injection trauma, we developed a procedure for the controlled release of adeno-associated viruses (AAV) into the scala media of adult mice. This procedure poses minimal risk of injury to structures of the cochlea and middle ear and allows for near-complete preservation of low and middle frequency hearing. In the present study, transduction efficiency and cellular specificity of AAV vectors (serotypes 1, 2, 5, 6, and 8) were investigated in normal and drug-deafened ears. Using the cytomegalovirus (CMV) promoter to drive gene expression, a variety of cell types were transduced successfully, including sensory hair cells and supporting cells, as well as cells in the auditory nerve and spiral ligament. Among all five serotypes, inner hair cells (IHCs) were the most effectively transduced cochlear cell type. All five serotypes of AAV vectors transduced cells of the auditory nerve, though serotype 8 was the most efficient vector for transduction. Our findings indicate that efficient AAV inoculation (via the scala media) can be performed in adult mouse ears, with hearing preservation a realistic goal. The procedure we describe may also have applications for intra-endolymphatic drug delivery in many mouse models of human deafness.

Gene Therapy Restores Balance and Auditory Functions in a Mouse Model of Usher Syndrome

“…AAV 2/8 can infect both cochlear and vestibular hair cells with high efficiency. 18,19 In this study, AAV8-whirlin was delivered to the mouse inner ear via the posterior semicircular canal approach, which has been shown to be a safe and effective route for inner ear gene delivery. 20 When AAV8-whirlin was injected into whirler inner ears through the posterior semicircular canal, robust whirlin expression was observed at the stereocilia tips in many vestibular hair cells ( Figure 1D).…”

Identification of Adeno-Associated Viral Vectors That Target Neonatal and Adult Mammalian Inner Ear Cell Subtypes

“…In adult, the procedure of cochleostomy invariably damages most OHCs with the exception of the apex cells, leading to profound hearing loss, which is consistent with previous studies. 9 We therefore focused on transfection of AAV on other inner ear cell types.…”

“…4 By a nanoliterlevel fluid delivery system, Kilpatrick et al studied 5 AAV vectors (serotypes 1, 2, 5, 6, and 8) injected through the scala media in normal and deaf adult inner ear, and showed transduction in the sensory hair cells, supporting cells, the auditory nerve, and spiral ligament. 9 To comprehensively survey AAV vectors for their transduction capacity into mouse inner ear at different stages and assess their impact on hearing, we systematically analyzed 12 AAV vectors with different serotypes. We identified AAV subtypes that infect major inner ear cell types in neonatal and adult mice.…”

Thérapie génique des surdités humaines

“…Malheureusement, ces vecteurs ont montré une efficacité de transfert limitée et un faible taux d'expression du transgène, ce qui limite leur utilité [10,11]. Des études plus récentes ont porté sur l'utilisation de vecteurs viraux dépourvus des séquences génomiques responsables de leur réplication, afin de cibler l'expression du transgène dans un type particulier de cellules cochléaires [12][13][14]. Différents vecteurs viraux ont été testés dans la cochlée : adénovirus [11], virus adéno-associés (adeno-associated virus, AAV) [7], lentivirus [7], virus herpes simplex [15,16] [20].…”

“…Nous avons observé que la microinjection intracochléaire d'AAV à travers la membrane de la fenêtre ronde de souriceaux âgés de deux jours n'affecte pas la morphologie de la cochlée (Meyer et al, résultats non publiés). Contrairement à ce qui a été décrit chez les souris injectées au stade adulte [12], les seuils auditifs enregistrés au niveau de l'oreille au-delà de la deuxième semaine postopératoire chez les animaux injectés au stade précoce sont comparables à ceux de l'oreille témoin, suggérant que la chirurgie et l'injection du vecteur AAV n'interfèrent guère avec le processus de maturation du système auditif et la fonction cochléaire. Ces résultats sont très encourageants pour développer des approches thérapeutiques applicables en clinique, avec une bonne préservation de la fonction auditive.…”