Direct Delivery of Antisense Oligonucleotides to the Middle and Inner Ear Improves Hearing and Balance in Usher Mice

Abstract

Usher syndrome is a syndromic form of hereditary hearing impairment that includes sensorineural hearing loss and delayed-onset retinitis pigmentosa (RP). Type 1 Usher syndrome (USH1) is characterized by congenital profound sensorineural hearing impairment and vestibular areflexia, with adolescent-onset RP. Systemic treatment with antisense oligonucleotides (ASOs) targeting the human USH1C c.216G>A splicing mutation in a knockin mouse model of USH1 restores hearing and balance. Herein, we explore the effect of delivering ASOs locally to the ear to treat hearing and vestibular dysfunction associated with Usher syndrome. Three localized delivery strategies were investigated in USH1C mice: inner ear injection, trans-tympanic membrane injection, and topical tympanic membrane application. We demonstrate, for the first time, that ASOs delivered directly to the ear correct Ush1c expression in inner ear tissue, improve cochlear hair cell transduction currents, restore vestibular afferent irregularity, spontaneous firing rate, and sensitivity to head rotation, and successfully recover hearing thresholds and balance behaviors in USH1C mice. We conclude that local delivery of ASOs to the middle and inner ear reach hair cells and can rescue both hearing and balance. These results also demonstrate the therapeutic potential of ASOs to treat hearing and balance deficits associated with Usher syndrome and other ear diseases.

Characterizing the Access of Cholinergic Antagonists to Efferent Synapses in the Inner Ear

“…Another interesting outcome of this study was the observation that the contralateral middle ear application of glycopyrrolate and methscopolamine eventually reached the ipsilateral ear. A number of inner ear studies have reported similar observations with a number of different substances (Bath et al, 1999;Stöver et al, 2000;Landegger et al, 2017;Salt et al, 2018a;Lee et al, 2020;Lentz et al, 2020), but the current study, for the first time, tried to monitor the time course of drug communication between ears in mice. While the mechanism by which mAChR antagonists gain access to the ipsilateral ear in our preparation is unknown, possible routes from the contralateral to the ipsilateral ear include a perilymph to vascular route, perilymph to CSF route via the cochlear aqueduct, lymphatic pathways, and/or the eustachian tube (Salt and Hirose, 2018;Talaei et al, 2019;Lee et al, 2020).…”

Vestibular Deficits in Deafness: Clinical Presentation, Animal Modeling, and Treatment Solutions

“…Alternative approaches involving dual AAVs, or RNA-based therapies have also been explored to overcome this AAV limitation ( 49 , 240 , 243 ). Splice-switching antisense oligonucleotides (ASO) have been successfully used to target the USH1C messenger RNA (mRNA) transcribed in mice homozygous for the Ush1c c.216G > A mutation ( 135 , 137 ). Recent studies include direct assessments of vestibular function based on vestibular sensory evoked potentials (VsEPs).…”

Progress in Gene Editing Tools and Their Potential for Correcting Mutations Underlying Hearing and Vision Loss

“…Alongside gene replacement strategies, RNA-based therapies [e.g., antisense oligonucleotides (ASOs), RNA interference (RNAi), or read through agents] have been developed to silence the messenger RNA (mRNA) transcribed from the mutant allele by Watson-Crick base pairing (Maeda et al, 2009). For instance, the ASO approach has been successfully used to bypass or correct blindness/deafness causal mutations, leading to recovery of normal hearing and balance function (e.g., USH1C, Lentz et al, 2020) or retinal function (e.g., USH2A, Dulla et al, 2021). A phase 1/2 clinical trial (NCT03780257) uses an ASO designed to trigger skipping of exon 13 in USH2A, enabling expression of a functional protein.…”