A silk-based hydrogel containing dexamethasone and lipoic acid microcrystals for local delivery to the inner ear

Local drug delivery has been exploited recently to treat hearing loss, as this method can both bypass the blood-labyrinth barrier and provide sustained drug release. Combined drug microcrystals (MCs) offer additional advantages for sensorineural hearing loss treatment via intratympanic (IT) injection due to their shape effect and combination strategy. In this study, to endow viscous effects of hydrogels, nonspherical dexamethasone (DEX) and lipoic acid (LA) MCs were incorporated into silk fibroin (SF) hydrogels, which were subsequently administered to the tympanic cavity to investigate their pharmaceutical properties. First, we prepared DEX and LA MCs by a traditional precipitation technique followed by SF hydrogel incorporation (SF+DEX+LA). After characterization of the physicochemical features, including morphology, rheology, and dissolution, both a suspension of combined DEX and LA MCs (DEX+LA) and SF+DEX+LA were administered to guinea pigs by IT injection, after which the pharmacokinetics, biodegradation and biocompatibility were evaluated. To our surprise, compared to the DEX+LA group, the pharmacokinetics of the SF+DEX+LA hydrogel group did not improve significantly, which may be ascribed to their nonspherical shape and deposition effects of the drugs MCs. The cochlear tissue in each group displayed good morphology, with no obvious inflammatory reactions. This combined MC suspension has the clear advantages of no vehicle, easy scale-up preparation, and good biocompatibility and outcomes, which paves the way for practical treatment of hearing loss via local drug delivery.

Biochemical changes to the inner ear contributing to diabetes-induced hearing loss: possible pharmacological targets for therapy

OBJECTIVES

Biochemical alterations due to diabetes development and progress are complex and diabetes-associated injury to various tissues has been well reported. Nevertheless, a close investigation of the literature demonstrates limited coverage regarding these biochemical and molecular alterations within the inner ear and their impact on the vestibulocochlear environment. A closer look at these may reveal pharmacological targets that could alleviate the severity of disease in patients.

KEY FINDINGS

Tight control of glucose levels within the highly metabolic inner ear structures is crucial for their physiology and function. Impaired glucose homeostasis is well known to occur in vestibulocochlear malfunctioning. Moreover, the involvement of insulin signalling, and glucose transporters were recently confirmed in vestibulocochlear structures and are believed to play a crucial role in auditory and vestibular functions.

CONCLUSION

Oxidative overload, glucolipotoxicity, perturbed blood rheology, endothelial dysfunction, compromised microvascular supply, and neurotoxicity are reported in many diabetic complications such as nephropathy, retinopathy, and diabetic neuropathy and are incriminated in the disruption of blood labyrinth barrier as well as vestibulocochlear neuritis. Dysfunctional insulin signalling was recently reported in the Organ of Corti. Insulin resistance in the inner ear niche warrants further studies to verify and uncover new pharmacological targets to manage this debilitating condition better.

Disease Manifestations and Complications in Dutch X-Linked Hypophosphatemia Patients

X-linked hypophosphatemia (XLH) is the most common monogenetic cause of chronic hypophosphatemia, characterized by rickets and osteomalacia. Disease manifestations and treatment of XLH patients in the Netherlands are currently unknown. Characteristics of XLH patients participating in the Dutch observational registry for genetic hypophosphatemia and acquired renal phosphate wasting were analyzed. Eighty XLH patients, including 29 children, were included. Genetic testing, performed in 78.8% of patients, showed a PHEX mutation in 96.8%. Median (range) Z-score for height was - 2.5 (- 5.5; 1.0) in adults and - 1.4 (- 3.7; 1.0) in children. Many patients were overweight or obese: 64.3% of adults and 37.0% of children. All children received XLH-related medication e.g., active vitamin D, phosphate supplementation or burosumab, while 8 adults used no medication. Lower age at start of XLH-related treatment was associated with higher height at inclusion. Hearing loss was reported in 6.9% of children and 31.4% of adults. Knee deformities were observed in 75.0% of all patients and osteoarthritis in 51.0% of adult patients. Nephrocalcinosis was observed in 62.1% of children and 33.3% of adults. Earlier start of XLH-related treatment was associated with higher risk of nephrocalcinosis and detection at younger age. Hyperparathyroidism longer than six months was reported in 37.9% of children and 35.3% of adults. This nationwide study confirms the high prevalence of adiposity, hearing loss, bone deformities, osteoarthritis, nephrocalcinosis and hyperparathyroidism in Dutch XLH patients. Early start of XLH-related treatment appears to be beneficial for longitudinal growth but may increase development of nephrocalcinosis.

Can Ganciclovir and Quercetin-P188 Ameliorate Cytomegalovirus Induced Hearing Loss?

OBJECTIVE

Determine whether combination therapy with ganciclovir (GCV) and a Quercetin-P188 solution improves hearing outcomes in a murine cytomegalovirus (CMV) model.

METHODS

BALB/c mice were infected with murine CMV on postnatal day 3 (p3). Quercetin was solubilized in saline using P188 (QP188). Treatment groups received either GCV, QP188, GCV and QP188, or P188 delivery vehicle BID at 12-hour intervals via intraperitoneal injection. All treatment groups were treated for 14 days starting at p3. Uninfected controls were treated with the combined regimen, saline or P188 delivery vehicle. Auditory thresholds were assessed using distortion product otoacoustic emission (DPOAE) and auditory brainstem response (ABR) testing at 4, 6, and 8 weeks of age. Temporal bones from separate CMV-infected groups were harvested at p10, and viral load was determined by quantitative polymerase chain reaction.

RESULTS

CMV-infected mice receiving combination therapy GCV+QP188 demonstrated statistically significant lower ABR (p < 0.001) and DPOAE thresholds (p < 0.001) compared with mice treated with GCV monotherapy, QP188 monotherapy, and P188 delivery vehicle at 4, 6, and 8 weeks of age. GCV+QP188 combination therapy, GCV monotherapy, and QP188 monotherapy resulted in a nonsignificant reduction in mean viral titers compared to P188 monotherapy (p = 0.08).

CONCLUSION

Combining GCV with the excipients quercetin and P188 effectively ameliorated CMV-induced sensorineural hearing loss in a murine model. This result may be partially explained by a reduction in viral titers in mouse temporal bones that correlate with in vitro studies demonstrating additive antiviral effect in cell culture.

LEVEL OF EVIDENCE

NA Laryngoscope, 134:1457-1463, 2024.

Discovery of a Novel Missense Variant in NLRP3 Causing Atypical Cryopyrin-Associated Periodic Syndromes With Hearing Loss as the Primary Presentation, Responsive to Anti-Interleukin-1 Therapy

OBJECTIVE

Cryopyrin-associated periodic syndromes (CAPS), also known as NLRP3-associated autoinflammatory diseases, are a spectrum of rare autoinflammatory diseases caused by gain-of-function variants in the NLRP3 gene, resulting in inflammasome hyperactivation and dysregulated release of interleukin-1β (IL-1β). Many patients with CAPS develop progressive sensorineural hearing loss (SNHL) because of cochlear autoinflammation, which may be the sole manifestation in rare cases. This study was undertaken to establish the suspected diagnosis of CAPS in a family presenting with autosomal-dominant progressive/acute SNHL and a novel missense variant in the NLRP3 gene of unknown significance (NM_001079821.3:c.1784G>A p.Ser595Asn).

METHODS

We conducted an ex vivo functional assessment of the NLRP3 inflammasome in heterozygous individuals (n = 10) and healthy family members (n = 5).

RESULTS

The assay revealed hyperactivation of the inflammasome among heterozygous individuals, supporting the hypothesis that this missense variant is a pathogenic gain-of-function variant. Administration of IL-1 receptor antagonist resulted in a substantial clinical improvement among pediatric patients, who exhibited near resolution of hearing impairment within 1 to 3 months of treatment.

CONCLUSION

Our findings highlight the crucial role of early diagnosis and treatment with an anti-IL-1 agent in reversing cochlear damage. Furthermore, our results suggest that high- and ultrahigh-frequency ranges need to be included in the auditory assessment to enable early detection of subclinical SNHL. Finally, incorporating functional inflammasome assessment as part of the clinical evaluation could establish the diagnosis in inconclusive cases.

Increased risk of hearing loss associated with macrolide use: a systematic review and meta-analysis

The increased risk of hearing loss with macrolides remains controversial. We aimed to systematically review and meta-analyze data on the clinical risk of hearing loss, tinnitus, and ototoxicity following macrolide use. A systematic search was conducted across PubMed, MEDLINE, Cochrane, and Embase databases from database inception to May 2023. Medical Subject Heading (MeSH) terms and text keywords were utilized, without any language restrictions. In addition to the electronic databases, two authors manually and independently searched for relevant studies in the US and European clinical trial registries and Google Scholar. Studies that involved (1) patients who had hearing loss, tinnitus, or ototoxicity after macrolide use, (2) intervention of use of macrolides such as azithromycin, clarithromycin, erythromycin, fidaxomicin, roxithromycin, spiramycin, and/or telithromycin, (3) comparisons with specified placebos or other antibiotics, (4) outcomes measured as odds ratio (OR), relative risk (RR), hazard ratio (HR), and mean difference for ototoxicity symptoms using randomized control trial (RCT)s and observational studies (case-control, cross-section, and cohort studies) were included. Data extraction was performed independently by two extractors, and a crosscheck was performed to identify any errors. ORs along with their corresponding 95% confidence intervals (CIs) were estimated using random-effects models. The Preferred Reporting Items for Systematic Reviews and Meta-analyses reporting guidelines for RCTs and Meta-Analysis of Observational Studies in Epidemiology guidelines for observational studies were followed. We assessed the hearing loss risk after macrolide use versus controls (placebos and other antibiotics). Based on data from 13 studies including 1,142,021 patients (n = 267,546 for macrolide and n = 875,089 for controls), the overall pooled OR was 1.25 (95% CI 1.07-1.47). In subgroup analysis by study design, the ORs were 1.37 (95% CI 1.08-1.73) for RCTs and 1.33 (95% CI 1.24-1.43) for case-control studies, indicating that RCT and case-control study designs showed a statistically significant higher risk of hearing loss. The group with underlying diseases such as multiple infectious etiologies (OR, 1.16 [95% CI 0.96-1.41]) had a statistically significant lower risk than the group without (OR, 1.53 [95% CI 1.38-1.70] P = .013). The findings from this systematic review and meta-analysis suggest that macrolide antibiotics increase the risk of hearing loss and that healthcare professionals should carefully consider this factor while prescribing macrolides.

Repurposing AZD5438 and Dabrafenib for Cisplatin-Induced AKI

SIGNIFICANCE STATEMENT

To combat both untoward effects of nephrotoxicity and ototoxicity in cisplatin-treated patients, two potential therapeutic oral anticancer drugs AZD5438 and dabrafenib, a phase-2 clinical trial protein kinase CDK2 inhibitor and an US Food and Drug Administration-approved drug BRAF inhibitor, respectively, were tested in an established mouse AKI model. Both drugs have previously been shown to protect significantly against cisplatin-induced hearing loss in mice. Each drug ameliorated cisplatin-induced increases in the serum biomarkers BUN, creatinine, and neutrophil gelatinase-associated lipocalin. Drugs also improved renal histopathology and inflammation, mitigated cell death by pyroptosis and necroptosis, and significantly enhanced overall survival of cisplatin-treated mice.

BACKGROUND

Cisplatin is an effective chemotherapy agent for a wide variety of solid tumors, but its use is dose-limited by serious side effects, including AKI and hearing loss. There are no US Food and Drug Administration-approved drugs to treat both side effects. Recently, two anticancer oral drugs, AZD5438 and dabrafenib, were identified as protective against cisplatin-induced hearing loss in mice. We hypothesize that similar cell stress and death pathways are activated in kidney and inner ear cells when exposed to cisplatin and tested whether these drugs alleviate cisplatin-induced AKI.

METHODS

The HK-2 cell line and adult FVB mice were used to measure the protection from cisplatin-induced cell death and AKI by these drugs. Serum markers of kidney injury, BUN, creatinine, and neutrophil gelatinase-associated lipocalin as well as histology of kidneys were analyzed. The levels of markers of kidney cell death, including necroptosis and pyroptosis, pERK, and proliferating cell nuclear antigen, were also examined by Western blotting and immunofluorescence. In addition, CDK2 knockout (KO) mice were used to confirm AZD5438 protective effect is through CDK2 inhibition.

RESULTS

The drugs reduced cisplatin-induced cell death in the HK-2 cell line and attenuated cisplatin-induced AKI in mice. The drugs reduced serum kidney injury markers, inhibited cell death, and reduced the levels of pERK and proliferating cell nuclear antigen, all of which correlated with prolonged animal survival. CDK2 KO mice were resistant to cisplatin-induced AKI, and AZD5438 conferred no additional protection in the KO mice.

CONCLUSIONS

Cisplatin-induced damage to the inner ear and kidneys shares similar cellular beneficial responses to AZD5438 and dabrafenib, highlighting the potential therapeutic use of these agents to treat both cisplatin-mediated kidney damage and hearing loss.

Prevention and treatment of cisplatin-induced ototoxicity in adults: A systematic review

OBJECTIVES

Ototoxicity is a common disabling side effect of platinum-based chemotherapy. This study aimed to assess the evidence on the management of platinum-induced ototoxicity in adult cancer patients.

METHODS

Four databases were searched up to 1 November 2022. Original studies were included if they reported on a pharmacologic or non-pharmacologic intervention to prevent or treat platinum ototoxicity in adults. The articles' quality was assessed via two grading scales.

RESULTS

Nineteen randomised controlled trials and five quasi-experimental studies with 1673 patients were analysed. Eleven interventions were identified, nine pharmacological and two non-pharmacological. Six of the interventions (sodium thiosulphate, corticoids, sertraline, statins, multivitamins and D-methionine) showed mild benefits in preventing cisplatin-induced ototoxicity. Only one trial assessed corticoids as a potential treatment. Overall, only six trials were deemed with a low risk of bias. The majority of studies inadequately documented intervention-related adverse effects, thereby limiting safety conclusions.

CONCLUSIONS

Current interventions have mild benefits in preventing cisplatin-induced ototoxicity in adult cancer patients. Sodium thiosulphate is the most promising intervention as a preventive strategy. Rigorous, high-quality research is warranted, encompassing an evaluation of all potential symptoms and innovative treatment modalities.

Dabrafenib protects from cisplatin-induced hearing loss in a clinically relevant mouse model

The widely used chemotherapy cisplatin causes permanent hearing loss in 40%-60% of patients with cancer. One drug, sodium thiosulfate, is approved by the FDA for use in pediatric patients with localized solid tumors for preventing cisplatin-induced hearing loss, but more drugs are desperately needed. Here, we tested dabrafenib, an FDA-approved BRAF kinase inhibitor and anticancer drug, in a clinically relevant multidose cisplatin mouse model. The protective effects of dabrafenib, given orally twice daily with cisplatin, were determined by functional hearing tests and cochlear outer hair cell counts. Toxicity of the drug cotreatment was evaluated, and levels of phosphorylated ERK were measured. A dabrafenib dose of 3 mg/kg BW, twice daily, in mice, was determined to be the minimum effective dose, and it is equivalent to one-tenth of the daily FDA-approved dose for human cancer treatment. The levels of hearing protection acquired, 20-25 dB at the 3 frequencies tested, in both female and male mice, persisted for 4 months after completion of treatments. Moreover, dabrafenib exhibited a good in vivo therapeutic index (> 25), protected hearing in 2 mouse strains, and diminished cisplatin-induced weight loss. This study demonstrates that dabrafenib is a promising candidate drug for protection from cisplatin-induced hearing loss.

Molecular Characteristics of Cisplatin-Induced Ototoxicity and Therapeutic Interventions

Cisplatin is a commonly used chemotherapeutic agent with proven efficacy in treating various malignancies, including testicular, ovarian, cervical, breast, bladder, head and neck, and lung cancer. Cisplatin is also used to treat tumors in children, such as neuroblastoma, osteosarcoma, and hepatoblastoma. However, its clinical use is limited by severe side effects, including ototoxicity, nephrotoxicity, neurotoxicity, hepatotoxicity, gastrointestinal toxicity, and retinal toxicity. Cisplatin-induced ototoxicity manifests as irreversible, bilateral, high-frequency sensorineural hearing loss in 40-60% of adults and in up to 60% of children. Hearing loss can lead to social isolation, depression, and cognitive decline in adults, and speech and language developmental delays in children. Cisplatin causes hair cell death by forming DNA adducts, mitochondrial dysfunction, oxidative stress, and inflammation, culminating in programmed cell death by apoptosis, necroptosis, pyroptosis, or ferroptosis. Contemporary medical interventions for cisplatin ototoxicity are limited to prosthetic devices, such as hearing aids, but these have significant limitations because the cochlea remains damaged. Recently, the U.S. Food and Drug Administration (FDA) approved the first therapy, sodium thiosulfate, to prevent cisplatin-induced hearing loss in pediatric patients with localized, non-metastatic solid tumors. Other pharmacological treatments for cisplatin ototoxicity are in various stages of preclinical and clinical development. This narrative review aims to highlight the molecular mechanisms involved in cisplatin-induced ototoxicity, focusing on cochlear inflammation, and shed light on potential antioxidant and anti-inflammatory therapeutic interventions to prevent or mitigate the ototoxic effects of cisplatin. We conducted a comprehensive literature search (Google Scholar, PubMed) focusing on publications in the last five years.

Circulating IL-17 reduces the risk of cisplatin-induced hearing loss in children: a bidirectional two-sample Mendelian randomization study

Studies have reported that cytokines and their related signaling pathways play a role in inner ear diseases. In clinical practice, approximately 50% of pediatric cancer patients experience irreversible hearing loss after cisplatin treatment. However, currently, there is a lack of systematic research on the causal relationship between circulating cytokines and cisplatin-induced hearing loss in children. Genetic variant data for 41 circulating cytokines were obtained from a meta-analysis of genome-wide association studies (GWAS) among 8293 individuals of Finnish descent. The GWAS data for Cisplatin-induced hearing loss in children were derived from a multicenter cohort of European pediatric cancer patients and survivors (N = 390), including both cases with hearing loss after cisplatin chemotherapy and controls without hearing loss. Multiple methods were employed for bidirectional Mendelian randomization (MR) estimation. Bonferroni correction was applied to adjust the original P-values, followed by a series of sensitivity analyses. In the directional Mendelian randomization (MR) analysis, it was found that IL-17 was significantly associated with a reduced risk of Cisplatin-induced hearing loss in children (OR: 0.18, CI: 0.06-0.48, P < 0.001, FDR = 0.041). In the reverse MR analysis, there were some nominal causal relationships of Cisplatin-induced hearing loss in children with certain cytokines [M-CSF: (OR: 1.04, CI: 1.01-1.08, P = 0.010, FDR = 0.41); IL-2RA: (OR: 1.03, CI: 1.00-1.05, P = 0.044, FDR = 0.447); MIP-1β: (OR: 1.02, CI: 1.00-1.04, P = 0.041, FDR = 0.447)]. leave-one-out analysis demonstrated that only M-CSF exhibited stability. These findings reveal a causal relationship between IL-17 and cisplatin-induced hearing loss in children. Further research is needed to determine the potential protective mechanisms of IL-17 in cisplatin-induced ototoxicity.

Intranasal delivery of NGF rescues hearing impairment in aged SAMP8 mice

Hearing loss impacts the quality of life and affects communication resulting in social isolation and reduced well-being. Despite its impact on society and economy, no therapies for age-related hearing loss are available so far. Loss of mechanosensory hair cells of the cochlea is a common event of hearing loss in humans. Studies performed in birds demonstrating that they can be replaced following the proliferation and transdifferentiation of supporting cells, strongly pointed out on HCs regeneration as the main focus of research aimed at hearing regeneration. Neurotrophins are growth factors involved in neuronal survival, development, differentiation, and plasticity. NGF has been involved in the interplay between auditory receptors and efferent innervation in the cochlea during development. During embryo development, both NGF and its receptors are highly expressed in the inner ears. It has been reported that NGF is implicated in the differentiation of auditory gangliar and hair cells. Thus, it has been proposed that NGF administration can decrease neuronal damage and prevent hearing loss. The main obstacle to the development of hearing impairment therapy is that efficient means of delivery for selected drugs to the cochlea are missing. Herein, in this study NGF was administered by the intranasal route. The first part of the study was focused on a biodistribution study, which showed the effective delivery in the cochlea; while the second part was focused on analyzing the potential therapeutic effect of NGF in senescence-accelerated prone strain 8 mice. Interestingly, intranasal administration of NGF resulted protective in counteracting hearing impairment in SAMP8 mice, ameliorating hearing performances (analyzed by auditory brainstem responses and distortion product otoacoustic emission) and hair cells morphology (analyzed by microscopy analysis). The results obtained were encouraging indicating that the neurotrophin NGF was efficiently delivered to the inner ear and that it was effective in counteracting hearing loss.

A prestin-targeting peptide-guided drug delivery system rearranging concentration gradient in the inner ear: An improved strategy against hearing loss

Hearing loss is mainly due to outer hair cell (OHC) damage in three cochlear turns. Local administration via the round window membrane (RWM) has considerable otological clinical potential in bypassing the blood-labyrinth barrier. However, insufficient drug distribution in the apical and middle cochlear turns results in unsatisfactory efficacy. We functionalized poly (lactic-co-glycolic acid) nanoparticles (PLGA NPs) with targeting peptide A665, which specifically bound to prestin, a protein uniquely expressed in OHCs. The modification facilitated the cellular uptake and RWM permeability of NPs. Notably, the guide of A665 towards OHCs enabled more NPs perfusion in the apical and middle cochlear turns without decreasing accumulation in the basal cochlear turn. Subsequently, curcumin (CUR), an appealing anti-ototoxic drug, was encapsulated in NPs. In aminoglycoside-treated guinea pigs with the worst hearing level, CUR/A665-PLGA NPs, with superior performance to CUR/PLGA NPs, almost completely preserved the OHCs in three cochlear turns. The lack of increased low-frequencies hearing thresholds further confirmed that the delivery system with prestin affinity mediated cochlear distribution rearrangement. Good inner ear biocompatibility and little or no embryonic zebrafish toxicity were observed throughout the treatment. Overall, A665-PLGA NPs act as desirable tools with sufficient inner ear delivery for improved efficacy against severe hearing loss.

Hydrophilic and lipophilic statin use and risk of hearing loss in hyperlipidemia using a Common Data Model: multicenter cohort study

Hearing impairment, the third largest health burden worldwide, currently lacks definitive treatments or preventive drugs. This study compared the effects of hydrophilic and lipophilic statin on hearing loss using a common database model. This retrospective multicenter study was conducted in three hospitals in South Korea (Anam, Guro, Ansan). We enrolled patients with hyperlipidemia with an initial hearing loss diagnosis. Data were collected during January 1, 2022-December 31, 2021 using the Observational Health Data Science and Informatics open-source software and Common Data Model database. The primary outcome was the occurrence of first-time hearing loss following a hyperlipidemia diagnosis, as documented in the Common Data Model cohort database. The measures of interest were hearing loss risk between hydrophilic and lipophilic statin use. Variables were compared using propensity score matching, Cox proportional regression, and meta-analysis. Among 37,322 patients with hyperlipidemia, 13,751 (7669 men and 6082 women) and 23,631 (11,390 men and 12,241 women) were treated with hydrophilic and lipophilic statins, respectively. After propensity score matching, according to the Kaplan-Meier curve, hearing loss risk did not significantly differ among the hospitals. The hazard ratio (HR) of the male patients from Anam (0.29, [95% confidence interval (CI), 0.05-1.51]), Guro (HR, 0.56, [95% CI 0.18-1.71]), and Ansan (hazard ratio, 0.29, [95% CI 0.05-1.51]) hospitals were analyzed using Cox proportional regression. Overall effect size (HR, 0.40, [95% CI 0.18-0.91]) was estimated using meta-analysis, which indicated that hearing loss risk among hydrophilic statin users was less than that among lipophilic statin users and was statistically significant. Men in the hydrophilic statin group had a lower risk of hearing impairment than those in the lipophilic statin group.

Preclinical prospects of investigational agents for hearing loss treatment

INTRODUCTION

: Hearing loss has a high prevalence, with aging, noise exposure, ototoxic drug therapies, and genetic mutations being some of the leading causes of hearing loss. Health conditions such as cardiovascular disease and diabetes are associated with hearing loss, perhaps due to shared vascular pathology in the ear and in other tissues.

AREAS COVERED

: Issues in the design of preclinical research preclude the ability to make comparisons regarding the relative efficacy of different drugs of interest for possible hearing loss prevention or hearing restoration. This has not slowed the advancement of candidate therapeutics into human clinical testing. There is a robust pipeline with drugs that have different mechanisms of action providing diverse candidate therapies and opportunities for combination therapies to be considered.

EXPERT OPINION

: Much of the preclinical research literature lacks standard study design elements such as dose response testing, and lack of standardization of test protocols significantly limits conclusions regarding relative efficacy. Nonetheless, the many positive results to date have supported translation of preclinical efforts into clinical trials assessing potential human benefits. Approval of the first hearing loss prevention therapeutic is a major success, providing a pathway for other drugs to follow.

Valproic Acid Inhibits Progressive Hereditary Hearing Loss in a KCNQ4 Variant Model through HDAC1 Suppression

Genetic or congenital hearing loss still has no definitive cure. Among genes related to genetic hearing loss, the potassium voltage-gated channel subfamily Q member 4 (KCNQ4) is known to play an essential role in maintaining ion homeostasis and regulating hair cell membrane potential. Variants of the KCNQ4 show reductions in the potassium channel activity and were responsible for non-syndromic progressive hearing loss. KCNQ4 has been known to possess a diverse variant. Among those variants, the KCNQ4 p.W276S variant produced greater hair cell loss related to an absence of potassium recycling. Valproic acid (VPA) is an important and commonly used histone deacetylase (HDAC) inhibitor for class I (HDAC1, 2, 3, and 8) and class IIa (HDAC4, 5, 7, and 9). In the current study, systemic injections of VPA attenuated hearing loss and protected the cochlear hair cells from cell death in the KCNQ4 p.W276S mouse model. VPA activated its known downstream target, the survival motor neuron gene, and increased acetylation of histone H4 in the cochlea, demonstrating that VPA treatment directly affects the cochlea. In addition, treatment with VPA increased the KCNQ4 binding with HSP90β by inhibiting HDAC1 activation in HEI-OC1 in an in vitro study. VPA is a candidate drug for inhibiting late-onset progressive hereditary hearing loss from the KCNQ4 p.W276S variant.

Aucubin protects mouse cochlear hair cells from cisplatin-induced ototoxicity via activation of the PI3K/AKT/STAT3 pathway

Cisplatin is commonly used to treat cancers and is associated with a significant risk of irreversible sensorineural hearing loss. However, no effective preventive strategies are available for cisplatin-induced HL. Therefore, significant efforts have been made to discover new drugs protecting cochlear hair cells from cisplatin-induced damage. We found that a new phytochemical, aucubin, attenuated cisplatin-induced apoptosis, the production of reactive oxygen species, and mitochondrial dysfunction in House Ear Institute Organ of Corti 1 cells and cochlear hair cells. Moreover, aucubin attenuated cisplatin-induced sensorineural hearing loss and hair cells loss in vivo. Furthermore, RNA sequencing analysis revealed that the otoprotective effects of aucubin were mainly mediated by increased STAT3 phosphorylation via the PI3K/AKT pathway. Inhibition of the STAT3 signaling pathway with the inhibitor S3I-201 or siRNA disrupted the protective effects of aucubin on cisplatin-induced apoptosis. In conclusion, we identified an otoprotective effect of aucubin. Therefore, aucubin could be used to prevent cisplatin-induced ototoxicity.

Ototoxicity of Long-Term α-Difluoromethylornithine for Skin Cancer Prevention

OBJECTIVE

Evaluate the effects of α-difluoromethylornithine (DFMO) on hearing thresholds as part of a randomized, double-blind, placebo-controlled trial.

METHODS

Subjects were randomized and assigned to the control (placebo) or experimental (DFMO) group. DFMO or placebo were administered orally (500 mg/m2 /day) for up to 5 years.

RESULTS

Subjects taking DFMO had, on average, increased hearing thresholds from baseline across the frequency range compared to subjects in the control group. Statistical analysis revealed this was significant in the lower frequency range.

CONCLUSIONS

This randomized controlled trial revealed the presence of increased hearing thresholds associated with long-term DFMO use. As a whole, DFMO may help prevent and treat certain types of cancers; however, it can result in some degree of hearing loss even when administered at low doses. This study further highlights the importance of closely monitoring hearing thresholds in subjects taking DFMO. Laryngoscope, 133:676-682, 2023.

[Effects of E-learning on Pharmacists' Recognition and Practice in Medication Education for Patients with Hearing Loss]

Pharmacists are required to provide and collect medication information based on patients' health literacy and communication abilities to provide effective pharmaceutical care. Due to a lack of understanding of hearing loss and awareness of the inconvenience that patients with hearing loss face, appropriate actions for effective communication in medication education are not fully implemented. An e-learning system consisting of two courses, a learning course and an evaluation course, has been developed. The learning course explains hearing loss and appropriate actions in medication education and investigates pharmacists' recognition of medication education, while the evaluation course assesses the implementation of necessary actions in medication education and changes in pharmacists' recognition of medication education with patients compared to before the e-learning. From February to September 2022, 41 pharmacists completed the learning course, with 22 advancing to the evaluation course. Prior to learning, they had difficulty in communicating with patients with hearing loss. However, after the learning course, their confidence in medication education improved with a better understanding of hearing loss and practice of appropriate actions. They also felt that pharmacists who were unfamiliar with the system should understand hearing loss and take actions tailored to patients' hearing loss. Further examination may be needed of the effects of the e-learning on patients with hearing loss.

Altering gene expression using antisense oligonucleotide therapy for hearing loss

Hearing loss affects more than 430 million people, worldwide, and is the third most common chronic physical condition in the United States and Europe (GBD Hearing Loss Collaborators, 2021; NIOSH, 2021; WHO, 2021). The loss of hearing significantly impacts motor and cognitive development, communication, education, employment, and overall quality of life. The inner ear houses the sensory organs for both hearing and balance and provides an accessible target for therapeutic delivery. Antisense oligonucleotides (ASOs) use various mechanisms to manipulate gene expression and can be tailor-made to treat disorders with defined genetic targets. In this review, we discuss the preclinical advancements within the field of the highly promising ASO-based therapies for hereditary hearing loss disorders. Particular focus is on ASO mechanisms of action, preclinical studies on ASO treatments of hearing loss, timing of therapeutic intervention, and delivery routes to the inner ear.

Network pharmacology and experimental evidence reveal the protective mechanism of Yi-Qi Cong-Ming decoction on age-related hearing loss

CONTEXT

Yi-Qi Cong-Ming (YQCM) decoction has been widely used to prevent age-related hearing loss (ARHL), the most prevalent neurodegenerative disease in the elderly.

OBJECTIVE

To explore the mechanism of YQCM decoction in the treatment of ARHL.

MATERIALS AND METHODS

The chemical constituents of YQCM were screened from the Traditional Chinese Medicine Systems Pharmacology Database. Potential targets of YQCM against ARHL were predicted by DrugBank, GeneCards, and OMIM database. Protein-protein network and enrichment analysis were used for exploring possible molecular mechanisms. Molecular docking and an in vitro model of ARHL by exposing auditory cells with 100 μM H₂O₂ for 3 h were applied. Cell viability and mitochondrial membrane potential (ΔΨM) were detected by CCK-8 and high-content analysis. γH2AX and cleaved caspase-3 were detected by Western blot.

RESULTS

The main compounds have good affinities with hub targets, especially AKT1, PTGS2, and CASP3. GO and KEGG analysis showed that the main biological process and key targets were related to negative regulation of the apoptotic process. H₂O₂ treatment could reduce the cell viability by 68% and impaired ΔΨM, while 90 μg/mL YQCM pre-treatment could restore the cell viability by 97.45% and increase ΔΨM (2-fold higher). YQCM pre-treatment also reduced γH2AX and cleaved caspase-3 protein levels.

CONCLUSIONS

Our study suggested that YQCM prevents ARHL by modulating the apoptosis process in auditory hair cells. Moreover, this study proved that bioinformatics analysis combined with molecular docking and cell model is a promising method to explore other possible pharmacological interventions of ARHL.

Microfluidic Preparation of Gelatin Methacryloyl Microgels as Local Drug Delivery Vehicles for Hearing Loss Therapy

Local drug delivery has become an effective method for disease therapy in fine organs including ears, eyes, and noses. However, the multiple anatomical and physiological barriers, unique clearance pathways, and sensitive perceptions characterizing these organs have led to suboptimal drug delivery efficiency. Here, we developed dexamethasone sodium phosphate-encapsulated gelatin methacryloyl (Dexsp@GelMA) microgel particles, with finely tunable size through well-designed microfluidics, as otic drug delivery vehicles for hearing loss therapy. The release kinetics, encapsulation efficiency, drug loading efficiency, and cytotoxicity of the GelMA microgels with different degrees of methacryloyl substitution were comprehensively studied to optimize the microgel formulation. Compared to bulk hydrogels, Dexsp@GelMA microgels of certain sizes hardly cause air-conducted hearing loss in vivo. Besides, strong adhesion of the microgels on the round window membrane was demonstrated. Moreover, the Dexsp@GelMA microgels, via intratympanic administration, could ameliorate acoustic noise-induced hearing loss and attenuate hair cell loss and synaptic ribbons damage more effectively than Dexsp alone. Our results strongly support the adhesive and intricate microfluidic-derived GelMA microgels as ideal intratympanic delivery vehicles for inner ear disease therapies, which provides new inspiration for microfluidics in drug delivery to the fine organs.

Rifle Blast Exacerbating Hearing Loss in a Patient Treated With Teprotumumab for Thyroid Eye Disease

Teprotumumab is a promising new immunomodulatory therapy for thyroid eye disease. One unique adverse effect observed in clinical trials was hearing impairment; however, all adverse auditory effects in prior clinical trials resolved spontaneously after completion of teprotumumab therapy. The authors present a case of a patient on teprotumumab for thyroid eye disease who experienced sustained hearing loss secondary to shooting a rifle without ear protection. In this case, it is suspected the teprotumumab infusions resulted in increased susceptibility of the inner ear hair cells to noise-induced trauma secondary to IGF-IR inhibition. Specific ear protection protocols may need to be implemented in the future for patients on teprotumumab therapy to prevent sustained hearing loss, especially for susceptible patient populations.

Outcomes of transtympanic dexamethasone perfusion using the MicroWickTM in patients with Ménière's disease: A cross-sectional study

PURPOSE

To assess the efficacy of a 4-week transtympanic dexamethasone perfusion using the Silverstein MicroWick^TM in patients with Ménière's disease.

MATERIALS AND METHODS

A self-reported questionnaire was designed and sent to patients who underwent transtympanic dexamethasone perfusion using the Silverstein MicroWick^TM from January 2017 to December 2020. A retrospective chart review was conducted to gather demographic and audiological data of those who responded.

RESULTS

Forty respondents were separated into Group 1 (n = 34), who required no further procedure, and Group 2 (n = 6), who required additional procedure for Ménière's disease. In Group 1, 50% reported subjective improvement in tinnitus, 59% in aural fullness, 79% in vertigo, and 21% in hearing loss after the MicroWick^TM treatment. A statistical analysis of the scores revealed that the improvement in aural fullness and vertigo met significance (p = 0.03 and p = 0.002, respectively). In Group 2, no significant change was seen in their symptoms. Audiological data showed no significant change in the pure tone average or the word recognition score after the treatment.

CONCLUSION

Transtympanic dexamethasone perfusion using the Silverstein MicroWick^TM is a well-tolerated treatment option for patients with Ménière's disease. Our survey data suggest its significant efficacy in reducing aural fullness and vertigo attacks in these patients. Prospective studies will be conducted to further establish its potential role in successfully managing patients with Ménière's disease.

mTOR Signaling in the Inner Ear as Potential Target to Treat Hearing Loss

Hearing loss affects many people worldwide and occurs often as a result of age, ototoxic drugs and/or excessive noise exposure. With a growing number of elderly people, the number of people suffering from hearing loss will also increase in the future. Despite the high number of affected people, for most patients there is no curative therapy for hearing loss and hearing aids or cochlea implants remain the only option. Important treatment approaches for hearing loss include the development of regenerative therapies or the inhibition of cell death/promotion of cell survival pathways. The mammalian target of rapamycin (mTOR) pathway is a central regulator of cell growth, is involved in cell survival, and has been shown to be implicated in many age-related diseases. In the inner ear, mTOR signaling has also started to gain attention recently. In this review, we will emphasize recent discoveries of mTOR signaling in the inner ear and discuss implications for possible treatments for hearing restoration.

Gap Junction-Mediated Intercellular Communication of cAMP Prevents CDDP-Induced Ototoxicity via cAMP/PKA/CREB Pathway

In the cochlea, non-sensory supporting cells are directly connected to adjacent supporting cells via gap junctions that allow the exchange of small molecules. We have previously shown that the pharmacological regulation of gap junctions alleviates cisplatin (CDDP)-induced ototoxicity in animal models. In this study, we aimed to identify specific small molecules that pass through gap junctions in the process of CDDP-induced auditory cell death and suggest new mechanisms to prevent hearing loss. We found that the cyclic adenosine monophosphate (cAMP) inducer forskolin (FSK) significantly attenuated CDDP-induced auditory cell death in vitro and ex vivo. The activation of cAMP/PKA/CREB signaling was observed in organ of Corti primary cells treated with FSK, especially in supporting cells. Co-treatment with gap junction enhancers such as all-trans retinoic acid (ATRA) and quinoline showed potentiating effects with FSK on cell survival via activation of cAMP/PKA/CREB. In vivo, the combination of FSK and ATRA was more effective for preventing ototoxicity compared to either single treatment. Our study provides the new insight that gap junction-mediated intercellular communication of cAMP may prevent CDDP-induced ototoxicity.

Characterization of quinoxaline derivatives for protection against iatrogenically induced hearing loss

Hair cell loss is the leading cause of hearing and balance disorders in humans. It can be caused by many factors, including noise, aging, and therapeutic agents. Previous studies have shown the therapeutic potential of quinoxaline against drug-induced ototoxicity. Here, we screened a library of 68 quinoxaline derivatives for protection against aminoglycoside-induced damage of hair cells from the zebrafish lateral line. We identified quinoxaline-5-carboxylic acid (Qx28) as the best quinoxaline derivative that provides robust protection against both aminoglycosides and cisplatin in zebrafish and mouse cochlear explants. FM1-43 and aminoglycoside uptake, as well as antibiotic efficacy studies, revealed that Qx28 is neither blocking the mechanotransduction channels nor interfering with aminoglycoside antibacterial activity, suggesting that it may be protecting the hair cells by directly counteracting the ototoxin’s mechanism of action. Only when animals were incubated with higher doses of Qx28 did we observe a partial blockage of the mechanotransduction channels. Finally, we assessed the regulation of the NF-κB pathway in vitro in mouse embryonic fibroblasts and in vivo in zebrafish larvae. Those studies showed that Qx28 protects hair cells by blocking NF-κB canonical pathway activation. Thus, Qx28 is a promising and versatile otoprotectant that can act across different species and toxins.

Cool OtOprotective Ear Lumen (COOL) Therapy for Cisplatin-induced Hearing Loss

HYPOTHESIS

Localized cooling of the external ear has a protective effect on the susceptibility to cisplatin-induced hearing loss.

BACKGROUND

We previously demonstrated significant protection from cisplatin-induced hearing loss using cool water ear canal irrigation. However, the study was limited to a single bolus injection of cisplatin and an acute time period. Here, we examined the application of localized cooling of the ear canal with repeated doses of cisplatin, over an expanded period of time, and using two methods of cooling.

METHODS

Twenty-four guinea pigs (12 male and 12 female) underwent auditory physiological testing (auditory brainstem response and distortion product otoacoustic emissions at 8-32 kHz) and pre/postadministration of cisplatin. Cisplatin (4 mg/kg i.p.) was administered in 3 weekly single injections for a total of 12 mg/kg. While anesthetized, the left ears of the guinea pigs were exposed to either cool water (22°C; ICS Water Caloric Irrigator), a cool ear bar (15°C, cooled by a Peltier device; TNM, Scion NeuroStim), or left uncooled as a sham control. The animals were tested 3 days post each dosage and 1 month post the final dose. At the end of the experiment the animals were euthanized for histological evaluation.

RESULTS

We found that hearing loss was significantly reduced, and hair cell survival greatly improved, in animals that received cooling treatments compared to cisplatin-only control animals. No significant difference was observed between the two methods of cooling.

CONCLUSION

Localized cooling of the ear canal during administration of cisplatin mitigated loss of auditory function and loss of hair cells.

Intratympanic administration of alpha-lipoic acid-loaded pluronic F-127 nanoparticles ameliorates acute hearing loss

We used antioxidant-containing nanoparticles (NPs) to treat acute hearing loss. Alpha-lipoic acid (ALA) served as the antioxidant; we employed Pluronic F127 to fabricate NPs. In vitro, ALA-NPs protected cells of the organ of Corti in HEI-OC1 mice, triggering nuclear translocation of NRF2 and increases in the levels of antioxidant proteins, including Nrf2, HO-1, SOD-1, and SOD-2. In vivo, the hearing of mice that received ALA-NP injections into the middle ear cavity was better preserved after induction of ototoxicity than in control animals. The cochlear Nrf2 level increased in test mice, indicating that the ALA-NPs protected hearing via the antioxidant mechanism observed in vitro. ALA-NPs effectively protected against acute hearing loss by activating the Nrf2/HO-1 pathway.

Generation of Cochlear Hair Cells from Sox2 Positive Supporting Cells via DNA Demethylation

Regeneration of auditory hair cells in adult mammals is challenging. It is also difficult to track the sources of regenerated hair cells, especially in vivo. Previous paper found newly generated hair cells in deafened mouse by injecting a DNA methyltransferase inhibitor 5-azacytidine into the inner ear. This paper aims to investigate the cell sources of new hair cells. Transgenic mice with enhanced green fluorescent protein (EGFP) expression controlled by the Sox2 gene were used in the study. A combination of kanamycin and furosemide was applied to deafen adult mice, which received 4 mM 5-azacytidine injection into the inner ear three days later. Mice were followed for 3, 5, 7 and 14 days after surgery to track hair cell regeneration. Immunostaining of Myosin VIIa and EGFP signals were used to track the fate of Sox2-expressing supporting cells. The results show that (i) expression of EGFP in the transgenic mice colocalized the supporting cells in the organ of Corti, and (ii) the cell source of regenerated hair cells following 5-azacytidine treatment may be supporting cells during 5-7 days post 5-azacytidine injection. In conclusion, 5-azacytidine may promote the conversion of supporting cells to hair cells in chemically deafened adult mice.

Aldh inhibitor restores auditory function in a mouse model of human deafness

Genetic hearing loss is a common health problem with no effective therapy currently available. DFNA15, caused by mutations of the transcription factor POU4F3, is one of the most common forms of autosomal dominant non-syndromic deafness. In this study, we established a novel mouse model of the human DFNA15 deafness, with a Pou4f3 gene mutation (Pou4f3Δ) identical to that found in a familial case of DFNA15. The Pou4f3(Δ/+) mice suffered progressive deafness in a similar manner to the DFNA15 patients. Hair cells in the Pou4f3(Δ/+) cochlea displayed significant stereociliary and mitochondrial pathologies, with apparent loss of outer hair cells. Progression of hearing and outer hair cell loss of the Pou4f3(Δ/+) mice was significantly modified by other genetic and environmental factors. Using Pou4f3(-/+) heterozygous knockout mice, we also showed that DFNA15 is likely caused by haploinsufficiency of the Pou4f3 gene. Importantly, inhibition of retinoic acid signaling by the aldehyde dehydrogenase (Aldh) and retinoic acid receptor inhibitors promoted Pou4f3 expression in the cochlear tissue and suppressed the progression of hearing loss in the mutant mice. These data demonstrate Pou4f3 haploinsufficiency as the main underlying cause of human DFNA15 deafness and highlight the therapeutic potential of Aldh inhibitors for treatment of progressive hearing loss.

More than 50% of deafness cases are due to genetic defects with no treatment available. DFNA15, caused by mutations of the transcription factor POU4F3, is one of the most common types of autosomal dominant non-syndromic deafness. Here, we established a novel mouse model with the exact Pou4f3 mutation identified in human patients. The mutant mouse display similar auditory pathophysiology as human patients and exhibit multiple hair cell abnormalities. The onset and severity of hearing loss in the mouse model is highly modifiable to environmental factors, such as aging, noise exposure or genetic backgrounds. Using a new knockout mouse model, we found Pou4f3 haploinsufficiency as the underlying mechanism of human DFNA15. Importantly, we identified Aldh inhibitor as a potent small molecule for upregulation of Pou4f3 and treatment of hearing loss in the mutant mouse. The identification of Aldh inhibitor for treatment of DFNA15 deafness represents a major advance in the unmet medical need for this common form of progressive hearing loss.

Prevention of cisplatin-induced ototoxicity in children and adolescents with cancer: a clinical practice guideline

Despite ototoxicity being a prevalent consequence of cisplatin chemotherapy, little guidance exists on interventions to prevent this permanent and progressive adverse event. To develop a clinical practice guideline for the prevention of cisplatin-induced ototoxicity in children and adolescents with cancer, we convened an international, multidisciplinary panel of experts and patient advocates to update a systematic review of randomised trials for the prevention of cisplatin-induced ototoxicity. The systematic review identified 27 eligible adult and paediatric trials that evaluated amifostine, sodium diethyldithiocarbamate or disulfiram, systemic sodium thiosulfate, intratympanic therapies, and cisplatin infusion duration. Regarding systemic sodium thiosulfate, the panel made a strong recommendation for administration in non-metastatic hepatoblastoma, a weak recommendation for administration in other non-metastatic cancers, and a weak recommendation against its routine use in metastatic cancers. Amifostine, sodium diethyldithiocarbamate, and intratympanic therapy should not be routinely used. Cisplatin infusion duration should not be altered as a means to reduce ototoxicity. Further research to determine the safety of sodium thiosulfate in patients with metastatic cancer is encouraged.

Mid-term evaluation of perioperative i.v. corticosteroid treatment efficacy on overall and audiological outcome following CO2 laser stapedotomy: a retrospective study of 84 cases

Purpose

Our aim was to determine whether perioperatively administered corticosteroid treatment has any beneficial effect on the outcome of stapes surgery, with special regard to the audiological results and early postoperative morbidity.

Methods

84 CO₂ laser stapedotomies performed in our institute between 2013 and 2018 were included in our investigation. All cases underwent preoperative and mid-term postoperative pure-tone audiometric evaluation. Vestibular complications were also evaluated. The cases were subdivided into two groups, 23 patients received perioperative i.v. methylprednisolone treatment (“S”) while the other 61 patients (“nS”) did not receive any adjuvant pharmacological therapy. The data were analyzed retrospectively using IBM SPSS Statistics.

Results

CO₂ laser stapedotomy proved to be a successful intervention with a significant improvement in ABG and AC thresholds as well. Long-term BC levels were significantly better compared to preoperative ones in the S group; however, in the nS group, no difference could be shown. Hearing and ABG gain were significantly superior in group S [28.1 dB (SD11.2) vs. 18.1 dB (SD 10.9) and 23.9 dB(SD 9.8) vs. 17.2 dB (SD 9.5), respectively].

Conclusion

No significant inner ear damage was detectable in the results of our CO₂ laser stapedotomy method; however, the positive effect of corticosteroid treatment could be demonstrated through the postoperative hearing levels. We found no statistical difference in early postoperative morbidity. According to our data, the routine administration of corticosteroids during stapes surgery could be an issue worthy of consideration. The effects of perioperative treatment vs that on the first day after surgery, and topical vs. systemic treatment could be the subject of further investigation in a prospective manner.

Medicines discovery for auditory disorders: Challenges for industry

Currently, no approved medicines are available for the prevention or treatment of hearing loss. Pharmaceutical industry productivity across all therapeutic indications has historically been disappointing, with a 90% chance of failure in delivering a marketed drug after entering clinical evaluation. To address these failings, initiatives have been applied in the three cornerstones of medicine discovery: target selection, clinical candidate selection, and clinical studies. These changes aimed to enable data-informed decisions on the translation of preclinical observations into a safe, clinically effective medicine by ensuring the best biological target is selected, the most appropriate chemical entity is advanced, and that the clinical studies enroll the correct patients. The specific underlying pathologies need to be known to allow appropriate patient selection, so improved diagnostics are required, as are methodologies for measuring in the inner ear target engagement, drug delivery and pharmacokinetics. The different therapeutic strategies of protecting hearing or preventing hearing loss versus restoring hearing are reviewed along with potential treatments for tinnitus. Examples of current investigational drugs are discussed to highlight key challenges in drug discovery and the learnings being applied to improve the probability of success of launching a marketed medicine.

Mouse methods and models for studies in hearing

Laboratory mice have become the dominant animal model for hearing research. The mouse cochlea operates according to standard "mammalian" principles, uses the same cochlear cell types, and exhibits the same types of injury as found in other mammals. The typical mouse lifespan is less than 3 years, yet the age-associated pathologies that may be found are quite similar to longer-lived mammals. All Schuknecht's types of presbycusis have been identified in existing mouse lines, some favoring hair cell loss while others favor strial degeneration. Although noise exposure generally affects the mouse cochlea in a manner similar to other mammals, mice appear more prone to permanent alterations to hair cells or the organ of Corti than to hair cell loss. Therapeutic compounds may be applied systemically or locally through the tympanic membrane or onto (or through) the round window membrane. The thinness of the mouse cochlear capsule and annular ligament may promote drug entry from the middle ear, although an extremely active middle ear lining may quickly remove most drugs. Preclinical testing of any therapeutic will always require tests in multiple animal models. Mice constitute one model providing supporting evidence for any therapeutic, while genetically engineered mice can test hypotheses about mechanisms.

Generation of new hair cells by DNA methyltransferase (Dnmt) inhibitor 5-azacytidine in a chemically-deafened mouse model

Regeneration of mature mammalian inner ear hair cells remains to be a challenge. This study aims to evaluate the ability of DNA methyltransferase (Dnmt) inhibitor 5-azacytidine (5-aza) to generate outer hair cells (OHCs) in a chemically-deafened adult mouse model. 5-aza was administrated into the mouse inner ear via the round window. Immunofluorescence was used to examine the expression of hair cell specific proteins following 5-aza treatment. The results showed that in the chemically-deafened mouse cochlea, new OHCs were found post 5-aza treatment, whereas OHCs were completely lost in saline-treated mice. New hair cells expressed multiple hair cell markers included Myosin VIIa, Pou4f3 and Myosin VI. Newly-generated hair cells presented in three cochlear turns and were able to survive for at least six weeks. The effects of new hair cells generation by 5-aza were concentration dependent. Quantitative PCR study indicates that 5-aza may function through Dnmt1 inhibition. The results of this report suggest that the Dnmt inhibitor 5-aza may promote hair cell regeneration in a chemically-deafened mouse model.

Testing the Central Gain Model: Loudness Growth Correlates with Central Auditory Gain Enhancement in a Rodent Model of Hyperacusis

The central gain model of hyperacusis proposes that loss of auditory input can result in maladaptive neuronal gain increases in the central auditory system, leading to the over-amplification of sound-evoked activity and excessive loudness perception. Despite the attractiveness of this model, and supporting evidence for it, a critical test of the central gain theory requires that changes in sound-evoked activity be explicitly linked to perceptual alterations of loudness. Here we combined an operant conditioning task that uses a subject's reaction time to auditory stimuli to produce reliable measures of loudness growth with chronic electrophysiological recordings from the auditory cortex and inferior colliculus of awake, behaviorally-phenotyped animals. In this manner, we could directly correlate daily assessments of loudness perception with neurophysiological measures of sound encoding within the same animal. We validated this novel psychophysical-electrophysiological paradigm with a salicylate-induced model of hearing loss and hyperacusis, as high doses of sodium salicylate reliably induce temporary hearing loss, neural hyperactivity, and auditory perceptual disruptions like tinnitus and hyperacusis. Salicylate induced parallel changes to loudness growth and evoked response-intensity functions consistent with temporary hearing loss and hyperacusis. Most importantly, we found that salicylate-mediated changes in loudness growth and sound-evoked activity were correlated within individual animals. These results provide strong support for the central gain model of hyperacusis and demonstrate the utility of using an experimental design that allows for within-subject comparison of behavioral and electrophysiological measures, thereby making inter-subject variability a strength rather than a limitation.

A review of magnet systems for targeted drug delivery

Magnetic drug targeting is a method by which magnetic drug carriers in the body are manipulated by external magnetic fields to reach the target area. This method is potentially promising in applications for treatment of diseases like cancers, nervous system diseases, sudden sensorineural hearing loss, and so on, due to the advantages in that it can improve efficacy, reduce drug dosage and side effects. Therefore, it has received extensive attention in recent years. Successful magnetic drug targeting requires a good magnet system to guide the drug carriers to the target site. Up to date there have been many efforts to design the magnet systems for targeted drug delivery. However, there are few comprehensive reviews on these systems. Here we review the progresses made in this field. We summarized the systems already developed or proposed, and categorized them into two groups: static field magnet systems and varying field magnet systems. Based on the requirements for more powerful targeting performance, the prospects and the future research directions in this field are anticipated.

Animal model studies yield translational solutions for cochlear drug delivery

The field of hearing and deafness research is about to enter an era where new cochlear drug delivery methodologies will become more innovative and plentiful. The present report provides a representative review of previous studies where efficacious results have been obtained with animal models, primarily rodents, for protection against acute hearing loss such as acoustic trauma due to noise overexposure, antibiotic use and cancer chemotherapies. These approaches were initiated using systemic injections or oral administrations of otoprotectants. Now, exciting new options for local drug delivery, which opens up the possibilities for utilization of novel otoprotective drugs or compounds that might not be suitable for systemic use, or might interfere with the efficacious actions of chemotherapeutic agents or antibiotics, are being developed. These include interesting use of nanoparticles (with or without magnetic field supplementation), hydrogels, cochlear micropumps, and new transtympanic injectable compounds, sometimes in combination with cochlear implants.

Anatomical basis of drug delivery to the inner ear

The isolated anatomical position and blood-labyrinth barrier hampers systemic drug delivery to the mammalian inner ear. Intratympanic placement of drugs and permeation via the round- and oval window are established methods for local pharmaceutical treatment. Mechanisms of drug uptake and pathways for distribution within the inner ear are hard to predict. The complex microanatomy with fluid-filled spaces separated by tight- and leaky barriers compose various compartments that connect via active and passive transport mechanisms. Here we provide a review on the inner ear architecture at light- and electron microscopy level, relevant for drug delivery. Focus is laid on the human inner ear architecture. Some new data add information on the human inner ear fluid spaces generated with high resolution microcomputed tomography at 15 μm resolution. Perilymphatic spaces are connected with the central modiolus by active transport mechanisms of mesothelial cells that provide access to spiral ganglion neurons. Reports on leaky barriers between scala tympani and the so-called cortilymph compartment likely open the best path for hair cell targeting. The complex barrier system of tight junction proteins such as occludins, claudins and tricellulin isolates the endolymphatic space for most drugs. Comparison of relevant differences of barriers, target cells and cell types involved in drug spread between main animal models and humans shall provide some translational aspects for inner ear drug applications.

Improvement in Patient-reported Hearing After Treatment With Bevacizumab in People With Neurofibromatosis Type 2

OBJECTIVE

Assess patient-reported outcomes (PRO) for hearing and tinnitus relative to clinical hearing assessment in people with neurofibromatosis 2 (NF2) associated hearing loss.

STUDY DESIGN

Prospective, open label, phase-II clinical trial with PRO administered pre-, post-, and after treatment.

SETTING

Three tertiary referral centers.

PATIENTS

Fourteen patients with NF2, median age of 30 years (range, 14-79 yr) and progressive hearing loss (median baseline word recognition score, 60%; range, 13-82%). Half of these patients achieved objective hearing response (word recognition score improved beyond the 95% critical difference versus baseline).

INTERVENTION

Bevacizumab 7.5 mg/kg was administered every 3 weeks for 48 weeks, followed by surveillance for 24 weeks off-drug.

MAIN OUTCOME MEASURES

Speech, spatial, and qualities of hearing scale (SSQ) and tinnitus reaction questionnaire (TRQ) to assess hearing difficulties in life situations and tinnitus related distress.

RESULTS

Patient-reported speech understanding and auditory quality improved with bevacizumab treatment and were significantly correlated with word recognition scores, but not pure tone threshold average. There was no change in spatial perception after treatment. Reduction in tinnitus distress after treatment with bevacizumab did not reach statistical significance.

CONCLUSION

Participants had reductions in hearing difficulty during treatment with bevacizumab, suggesting that patients subjectively experience hearing-related benefit mirroring clinical hearing assessments. We suspect the lack of significant reduction in tinnitus distress is related to small sample size and low intensity of distress in our sample. These data highlight the usefulness of PRO measures to assess benefits of treatment in the setting of NF2-associated hearing loss.

Counseling our aging population: A training program for pharmacy students on hearing loss

BACKGROUND AND PURPOSE

Hearing loss affects approximately one-third of adults age 61-70 and >80% of those older than 85 years. This can impede the ability to hear medication administration instructions, leading to poor adherence and unnecessary disease progression and complications. The study purpose was to educate students on hearing loss and identify program impact.

EDUCATIONAL ACTIVITY AND SETTING

An online program for advanced pharmacy practice experience (APPE) students was developed to train students how to counsel patients with hearing loss to improve medication understanding and adherence. The purpose of the training program was to provide background on hearing loss, increase understanding of the impact hearing loss, and to prepare students to counsel this population. A link from SurveyMonkey was provided upon training program completion.

FINDINGS

Ninety-two students completed the survey. Prior to training, < 20% (18.5%) were comfortable interacting with patients with hearing impairment, despite ∼50% of these students completing more than three APPEs with direct patient care. The majority (88%) recognized that hearing loss contributes to poor medication adherence. More than 80% believed that the training program improved their understanding of the psychological consequences of hearing loss and ability to counsel patients with hearing loss. Over 70% agreed that the training program made them feel more prepared to counsel patients with hearing loss.

DISCUSSION AND SUMMARY

It is crucial to prepare students to better understand this population in order to meet their needs. This program enhanced students' knowledge of hearing loss and increased their understanding of communication barriers.

Clinical trials for inner ear drugs: Design and execution challenges

The development of therapies for the inner ear presents unique opportunities and challenges. On the one hand, the ear presents an opportunity for localized drug delivery to avoid systemic side effects. However, we do not understand the pathobiology of many common ear disorders clearly enough to develop rational therapeutic solutions. Further, identification of biomarkers beyond conventional audiometry and balance testing to track disease progress and recovery remain elusive. Because of the comparatively low incidence and prevalence of many inner ear disorders, as well as issues with respect to timing of drug delivery for certain diseases, multi-center, multi-investigator collaborative networks are required to promote effective clinical trial design.

Pantoprazole, an Inhibitor of the Organic Cation Transporter 2, Does Not Ameliorate Cisplatin-Related Ototoxicity or Nephrotoxicity in Children and Adolescents with Newly Diagnosed Osteosarcoma Treated with Methotrexate, Doxorubicin, and Cisplatin

Lessons Learned.

Using a randomized crossover design and continuous variables such as change in hearing threshold and biomarkers of acute renal injury as short‐term endpoints, it was determined that pantoprazole, an organic cation transporter 2 inhibitor, did not ameliorate cisplatin‐associated nephrotoxicity or ototoxicity.

Cystatin C is a robust method to estimate glomerular filtration rate in patients with cancer. Using a patient‐reported outcome survey, all patients identified tinnitus and subjective hearing loss occurring “at least rarely” after cycle 1, prior to objective high‐frequency hearing loss measured by audiograms.

New therapies that improve outcome with less acute and long‐term toxicity are needed.

Background.

Organic cation transporter 2 (OCT2), which is a cisplatin uptake transporter expressed on renal tubules and cochlear hair cells but not on osteosarcoma cells, mediates cisplatin uptake. Pantoprazole inhibits OCT2 and could ameliorate cisplatin ototoxicity and nephrotoxicity. Using a randomized crossover design, we evaluated audiograms, urinary acute kidney injury (AKI) biomarkers, and glomerular filtration rate (GFR) estimated from cystatin C (GFR_cysC) in patients receiving cisplatin with and without pantoprazole.

Materials and Methods.

Cisplatin (60 mg/m² × 2 days per cycle) was administered concurrently with pantoprazole (intravenous [IV], 1.6 mg/kg over 4 hours) on cycles 1 and 2 or cycles 3 and 4 in 12 patients with osteosarcoma (OS) with a median (range) age of 12.8 (5.6–19) years. Audiograms, urinary AKI biomarkers, and serum cystatin C were monitored during each cycle.

Results.

Pantoprazole had no impact on decrements in hearing threshold at 4–8 kHz, post‐treatment elevation of urinary AKI biomarkers, or GFR_cysC (Fig. 1, Table 1). Histological response (percent necrosis) after two cycles was similar with or without pantoprazole. All eight patients with localized OS at diagnosis are alive and in remission; three of four patients with metastases at diagnosis have died.

Conclusion.

Pantoprazole did not ameliorate cisplatin ototoxicity or nephrotoxicity. The decrease in GFR_cysC and increase in N‐acetyl‐ß‐glucosaminidase (NAG) and creatinine demonstrate that these biomarkers can quantify cisplatin glomerular and proximal tubular toxicity. OCT2 inhibition by pantoprazole did not appear to alter antitumor response or survival.

Neurological Complications of Acute and Chronic Otitis Media

PURPOSE OF REVIEW

The aim of this study is to discuss the symptoms, diagnosis, and management of the neurologic complications of acute and chronic otitis media.

RECENT FINDINGS

Antibiotic therapy has greatly reduced the frequency of complications of otitis media. However, it is of vital importance to remain aware of the possible development of neurologic complications. There is a trend toward less severe presenting symptoms including otorrhea, headache, nausea, and fever, with altered mental status and focal neurologic deficits presenting later. In order to reduce morbidity, early deployment of a multidisciplinary approach with prompt imaging and laboratory studies is imperative to guide appropriate management. Complications of acute and chronic otitis media may present with neurologic signs and symptoms. It is important to recognize the possible otitic origin of such complications to ensure proper management and to decrease overall morbidity and mortality.

Effects of salso-bromo-iodine thermal water in children suffering from otitis media with effusion: a randomized controlled pilot study

BACKGROUND

Otitis media with effusion (OME) is an ear disorder defined by the presence of fluid in the middle ear without signs or symptoms of acute infection. The aim of this randomised and controlled pilot study was to evaluate whether the treatment with a watery salsobromo- iodine solution, administered by nasal douche, could induce ear healing better than isotonic saline in children with OME.

METHODS

The study was randomized, single-blind, and controlled. Study group (40 children) was treated with salso-bromo-iodine thermal water solution and Control group (40 children) was treated with isotonic saline; both compounds were administered by nasal nebulization with Rinowash nasal douche twice/day for 10 days a month for 3 consecutive months. Tympanogram and audiometry were performed at baseline and after treatment.

RESULTS

Salso-bromo-iodine therapy shows better and statistically significant trend after treatment when compared to control group both for tympanogram results with greater improvement (represented by type C tympanogram; p = 0.031) and healing (represented by type A tympanogram; p < 0.001) and audiometric results, with higher presence of patients with normal hearing (p = 0.029) and lower among patients with moderate hypoacusis (p = 0.014).

CONCLUSIONS

The current randomized-controlled pilot study demonstrated that watery salso-bromo-iodine solution was effective in the treatment of children with OME.

Protective role of intratympanic nigella sativa oil against gentamicin induced hearing loss

OBJECTIVE

Aminoglycosides, used to combat with life-threatening infections, have a substantial risk of hearing loss. Nigella sativa is an annual herbaceous plant and used for treatment of many diseases for ages. We aimed to investigate the protective role of intratympanic nigella sativa oil against gentamicin induced hearing loss in an animal model.

METHODS AND MATERIALS

Twenty eight guinea pigs were randomly divided into four groups: i-control, ii- Intratympanic nigella sativa oil (IT-NSO), iii- Intraperitoneal gentamicin (IP-G) and iv- Intraperitoneal gentamicin and intratympanic nigella sativa oil (IP-G + IT-NSO). Preoperative and postoperative hearing thresholds were determined with auditory brainstem response with click and 8 kHz tone-burst stimuli. Histological analysis of the cochlea specimens were performed under light microscope. Semiquantitative grading of the histological findings was carried out and compared between the groups.

RESULTS

Highest posttreatment hearing thresholds were detected in IP-G group. Posttreatment mean hearing threshold of the IP-G group with click stimulus was significantly higher than the IP-G + IT-NSO group (p = 0.004). whereas the difference was not significant with 8 kHz tone-burst stimulus (p = 0.137). Both IP-G and IP-G + IT-NSO groups had significantly higher hearing thresholds compared to control and IT-NSO groups (p > 0.05). Histological examination of the control and IT-NSO groups demonstrated normal appearance of cochlear nerve, stria vascularis and organ of Corti. IP-G group showed the most severe histological alterations including hydropic and vacuolar degenerations, hair cell damage and deformation of the basilar mambrane. Histological evidence of damage was significantly reduced in IP-G + IT-NSO group compared to IP-G group.

CONCLUSION

Addition of intratympanic NSO to systemic gentamicin was demonstrated to have beneficial effects in hearing thresholds which was supported by histological findings.

Sympathetic neural hyperalgesia edema syndrome as a cause of autoimmune hearing loss

PURPOSE

To describe another previous unreported manifestation of the sympathetic neural hyperalgesia edema syndrome - autoimmune hearing loss.

MATERIALS AND METHODS

Dextroamphetamine sulfate 30 mg extended release capsules was given to a woman to try to help her conceive since, with her pelvic pain, chronic fatigue syndrome, and diarrhea, it was thought that an inflammatory condition related to permeation of unwanted chemicals into endometrial tissue related to the sympathetic neural hyperalgesia edema syndrome could be inhibiting her failure from conceiving despite three cycles of embryo transfer.

RESULTS

Not only did the symptoms mentioned above disappear, but she also noted marked improvement of hearing loss that had been present for several years. The improvement in hearing was documented by audiology tests and had not responded to many months of 15 mg/day prednisone.

CONCLUSIONS

Autoimmune hearing loss (diagnosis established by her ear nose and throat specialist) should be added to the long list of manifestation of the sympathetic neural hyperalgesia edema syndrome.

Hearing function after betahistine therapy in patients with Ménière's disease

Introduction

Objective

Methods

Results

Conclusion

Hearing Loss in HIV-Infected Children in Lilongwe, Malawi

INTRODUCTION

With improved access to antiretroviral therapy (ART), HIV infection is becoming a chronic illness. Preliminary data suggest that HIV-infected children have a higher risk of disabilities, including hearing impairment, although data are sparse. This study aimed to estimate the prevalence and types of hearing loss in HIV-infected children in Lilongwe, Malawi.

METHODS

This was a cross-sectional survey of 380 HIV-infected children aged 4-14 years attending ART clinic in Lilongwe between December 2013-March 2014. Data was collected through pediatric quality of life and sociodemographic questionnaires, electronic medical record review, and detailed audiologic testing. Hearing loss was defined as >20 decibels hearing level (dBHL) in either ear. Predictors of hearing loss were explored by regression analysis generating age- and sex-adjusted odds ratios. Children with significant hearing loss were fitted with hearing aids.

RESULTS

Of 380 patients, 24% had hearing loss: 82% conductive, 14% sensorineural, and 4% mixed. Twenty-one patients (23% of those with hearing loss) were referred for hearing aid fitting. There was a higher prevalence of hearing loss in children with history of frequent ear infections (OR 7.4, 4.2-13.0) and ear drainage (OR 6.4, 3.6-11.6). Hearing loss was linked to history of WHO Stage 3 (OR 2.4, 1.2-4.5) or Stage 4 (OR 6.4, 2.7-15.2) and history of malnutrition (OR 2.1, 1.3-3.5), but not to duration of ART or CD4. Only 40% of caregivers accurately perceived their child's hearing loss. Children with hearing impairment were less likely to attend school and had poorer emotional (p = 0.02) and school functioning (p = 0.04).

CONCLUSIONS

There is an urgent need for improved screening tools, identification and treatment of hearing problems in HIV-infected children, as hearing loss was common in this group and affected school functioning and quality of life. Clear strategies were identified for prevention and treatment, since most hearing loss was conductive in nature, likely due to frequent ear infections, and many children with hearing loss qualified for hearing aids. Screening strategies need to be developed and tested since caregivers were not reliable at identifying hearing loss, and often mis-identified children with normal hearing as having hearing loss. Children with frequent ear infections, ear drainage, TB, severe HIV disease, or low BMI should receive more frequent ear assessments and hearing evaluations.