Advances in cochlear gene therapies.

PURPOSE OF REVIEW: Hearing loss is the most common sensory deficit and in young children sensorineural hearing loss is most frequently genetic in etiology. Hearing aids and cochlear implant do not restore normal hearing. There is significant research and commercial interest in directly addressing the root cause of hearing loss through gene therapies. This article provides an overview of major barriers to cochlear gene therapy and recent advances in preclinical development of precision treatments of genetic deafness. RECENT FINDINGS: Several investigators have recently described successful gene therapies in many common forms of genetic hearing loss in animal models. Elegant strategies that do not target a specific pathogenic variant, such as mini gene replacement and mutation-agnostic RNA interference (RNAi) with engineered replacement, facilitate translation of these findings to development of human therapeutics. Clinical trials for human gene therapies are in active recruitment. SUMMARY: Gene therapies for hearing loss are expected to enter clinical trials in the immediate future. To provide referral for appropriate trials and counseling regarding benefits of genetic hearing loss evaluation, specialists serving children with hearing loss such as pediatricians, geneticists, genetic counselors, and otolaryngologists should be acquainted with ongoing developments in precision therapies.

De novo variants are a common cause of genetic hearing loss.

PURPOSE: De novo variants (DNVs) are a well-recognized cause of genetic disorders. The contribution of DNVs to hearing loss (HL) is poorly characterized. We aimed to evaluate the rate of DNVs in HL-associated genes and assess their contribution to HL. METHODS: Targeted genomic enrichment and massively parallel sequencing were used for molecular testing of all exons and flanking intronic sequences of known HL-associated genes, with no exclusions on the basis of type of HL or clinical features. Segregation analysis was performed, and previous reports of DNVs in PubMed and ClinVar were reviewed to characterize the rate, distribution, and spectrum of DNVs in HL. RESULTS: DNVs were detected in 10% (24/238) of trios for whom segregation analysis was performed. Overall, DNVs were causative in at least ∼1% of probands for whom a genetic diagnosis was resolved, with marked variability based on inheritance mode and phenotype. DNVs of MITF were most common (21% of DNVs), followed by GATA3 (13%), STRC (13%), and ACTG1 (8%). Review of reported DNVs revealed gene-specific variability in contribution of DNV to the mutational spectrum of HL-associated genes. CONCLUSION: DNVs are a relatively common cause of genetic HL and must be considered in all cases of sporadic HL.

Outcomes of Near-Total and Subtotal Resection of Sporadic Vestibular Schwannoma: A Systematic Review and Meta-Analysis.

OBJECTIVE: To evaluate tumor control and facial nerve outcomes after gross-total (GTR), near-total (NTR), and subtotal resection (STR) of sporadic vestibular schwannomas (VS). DATA SOURCES: PubMed, Cochrane Central Register of Controlled Trials, Web of Science, and Scopus databases were searched in August 2021 through inception following PRISMA guidelines. REVIEW METHODS: English language articles reporting tumor control and facial nerve outcomes of adults (≥18 years) with NTR and STR of VS were evaluated. Study characteristics, demographics data, tumor characteristics, type of surgical intervention, and outcome measures on tumor control and facial nerve function were collected. Pooled relative risk (RR) estimates for tumor recurrence and facial nerve outcomes were calculated and stratified by extent of resection. RESULTS: From an initial search of 2504 articles, 48 studies were included in the analysis. When comparing 1108 patients who underwent NTR to 3349 patients with GTR, the pooled RR of recurrence in the NTR cohort was 2.94 (95% confidence interval [CI] 1.65-5.24, P = .0002). When comparing 1016 patients who underwent STR to 6171 patients with GTR, the pooled RR of recurrence in the STR cohort was 11.50 (95% CI 6.64-19.92, P < .0001). Estimates for risk of tumor regrowth for less-than-complete resection are presented. There was no elevated risk of adverse facial nerve outcome (defined as House-Brackmann grade III and above) in each category of extent of resection compared to GTR. CONCLUSION: Extent of resection predicts risk of tumor recurrence/regrowth following microsurgical resection. Favorable facial nerve outcome should be weighed against the increased risk of regrowth and the potential need for further treatment.

Mutation-agnostic RNA interference with engineered replacement rescues Tmc1-related hearing loss.

Hearing loss is the most common sensory deficit, of which genetic etiologies are a frequent cause. Dominant and recessive mutations in TMC1, a gene encoding the pore-forming subunit of the hair cell mechanotransduction channel, cause DFNA36 and DFNB7/11, respectively, accounting for ∼2% of genetic hearing loss. Previous work has established the efficacy of mutation-targeted RNAi in treatment of murine models of autosomal dominant non-syndromic deafness. However, application of such approaches is limited by the infeasibility of development and validation of novel constructs for each variant. We developed an allele-non-specific approach consisting of mutation-agnostic RNAi suppression of both mutant and WT alleles, co-delivered with a knockdown-resistant engineered WT allele with or without the use of woodchuck hepatitis virus post-transcriptional regulatory element (WPRE) to augment transgene expression. This therapeutic construct was delivered into the mature murine model of DFNA36 with an AAV vector and achieved robust hair cell and auditory brainstem response preservation. However, WPRE-enhanced Tmc1 expression resulted in inferior outcomes, suggesting a role for gene dosage optimization in future TMC1 gene therapy development.

Proximal reflux: biochemical mediators, markers, therapeutic targets, and clinical correlations.

Airway reflux is implicated in the pathophysiology of a wide range of adult and pediatric upper and lower airway diseases. However, the diagnosis of proximal reflux-associated disease remains challenging due to evolving clinical criteria and institutional and regional variances in diagnostic practices. Evidence suggests that nonacidic contents of reflux may serve as both pathologic mediators of and biomarkers for reflux in the upper airway. Furthermore, they offer potential pharmaceutical and surgical intervention targets and are the focus of novel clinical diagnostic tools currently under investigation.

Detection of Pepsin in Oral Secretions of Infants with and without Laryngomalacia.

OBJECTIVES: Laryngomalacia is a common cause of stridor in infants and is associated with laryngopharyngeal reflux (LPR). Although pepsin in operative supraglottic lavage specimens is associated with severe laryngomalacia, detection of pepsin in oral secretions has not been demonstrated in an outpatient setting. METHODS: Children <2 years old with laryngomalacia diagnosed by flexible laryngoscopy and children without stridor were selected. Oral secretion samples were obtained in clinic from all subjects. Pepsin, IL-1ß, and IL-8 enzyme-linked immunosorbent assays were performed to determine presence of LPR. RESULTS: Sixteen laryngomalacia and sixteen controls were enrolled. Pepsin was detected more frequently in oral secretions of patients with laryngomalacia (13/16) than in controls (2/16; P < .001). Four patients with laryngomalacia developed symptoms requiring supraglottoplasty. Presence and level of salivary pepsin was not significantly associated with need for surgical management, nor were the levels or presence of IL-1ß or IL-8 significantly associated with presence or level of pepsin, diagnosis of laryngomalacia, or need for operative management. CONCLUSION: Pepsin in saliva appears to be associated with laryngomalacia, suggesting a role for salivary pepsin as a noninvasive marker of LPR in patients with laryngomalacia. Future studies will determine the utility of this test in laryngomalacia.

Correlation of salivary and nasal lavage pepsin with MII-pH testing.

OBJECTIVES: Laryngopharyngeal reflux (LPR) is a common upper airway disease. Salivary pepsin is a proposed marker for LPR; however, the optimal time for collection of specimens for pepsin detection and pepsin's presence in the oral and nasal secretions relative to concurrent multichannel intraluminal impedance-pH (MII-pH) monitoring are unknown. STUDY DESIGN: Prospective case-control study with an experimental design. METHODS: Patients undergoing MII-pH testing for evaluation of LPR and asymptomatic control subjects were selected. Nasal lavage and saliva samples were collected in the clinic prior to MII-pH probe placement. Additional saliva samples were obtained an hour after each meal and upon waking the following morning. Nasal lavage and salivary pepsin were measured by ELISA. RESULTS: Twenty-six patients undergoing MII-pH testing and 13 reflux-free control patients were enrolled. Salivary pepsin was detected in 11 of 26 patients with suspected LPR and 0 of 13 controls. Pepsin was most frequently detected in the specimen provided upon waking at an average concentration of 186.9 ng/mL. A significant correlation was observed between salivary pepsin in waking samples to MII-pH measurements, including reflux bolus duration, and proximal and distal recumbent reflux episodes (P < 0.05). A significant correlation was also observed between salivary pepsin upon waking or sinus lavage and reflux symptom index (P < 0.05). CONCLUSION: Pepsin in salivary and nasal lavage samples demonstrated an association with MII-pH-documented LPR. Pepsin detection was most frequent in morning samples, supporting use of morning salivary pepsin levels as a potential noninvasive technique for LPR diagnosis. LEVEL OF EVIDENCE: 2 Laryngoscope, 130:961-966, 2020.