Enhanced viral-mediated cochlear gene delivery in adult mice by combining canal fenestration with round window membrane inoculation

Abstract

Cochlear gene therapy holds promise for the treatment of genetic deafness. Assessing its impact in adult murine models of hearing loss, however, has been hampered by technical challenges that have made it difficult to establish a robust method to deliver transgenes to the mature murine inner ear. Here in we demonstrate the feasibility of a combined round window membrane injection and semi-circular canal fenestration technique in the adult cochlea. Injection of both AAV2/9 and AAV2/Anc80L65 via this approach in P15–16 and P56–60 mice permits robust eGFP transduction of virtually all inner hair cells throughout the cochlea with variable transduction of vestibular hair cells. Auditory thresholds are not compromised. Transduction rate and cell tropism is primarily influenced by viral titer and AAV serotype but not age at injection. This approach is safe, versatile and efficient. Its use will facilitate studies using cochlear gene therapy in murine models of hearing loss over a wide range of time points.

Therapeutic AAV Gene Transfer to the Nervous System: A Clinical Reality

“…Like the eye, the ear presents an opportunity to deliver a vector bolus in the proximity of the neural target tissue in the cochlea at high concentration and minimal biodistribution. No clinical AAV programs have been pursued to date, in part due to the lack of precedent for intra-cochlear drug delivery; however, experimentally, Figure 2 describes the various routes that have been explored for AAV gene transfer preclinical studies (Holt and Vandenberghe, 2012;Tao et al, 2018;Yoshimura et al, 2018). In the only cochlear gene transfer study to date that has been performed in humans (NCT02132130), human adenoviral vector was injected via an oval window procedure.…”

A dual‐AAV approach restores fast exocytosis and partially rescues auditory function in deaf otoferlin knock‐out mice

“…Even though we did not observe an apparent HC loss in our immunohistochemical analyses and click ABR thresholds were unaffected, a minor elevation of the 24 kHz ABR threshold () might point to potential damage of HCs by the injection. The sensory cells of the inner ear are particularly sensitive to pressure and volume changes that might occur while injecting the virus solution into the cochlea (Yoshimura et al , ). In addition, we found a reduction in ABR wave II‐V amplitudes in injected compared to non‐injected ears (), the origin of which is unclear.…”

Development of the Mouse and Human Cochlea at Single Cell Resolution

“…Furthermore, the distinct cellular tropism of hearing loss gene expression needs to be accounted for when selecting viral vectors and appropriate promoters for gene therapy. Although some currently available viral vectors appear relatively efficient at transducing hair cells (György et al, 2019; Landegger et al, 2017; Yoshimura et al, 2018), we will likely need to identify additional viral vectors capable of efficiently transducing other distinct cell types within the cochlea for those genes expressed within other cell populations.…”