Impact of Systemic versus Intratympanic Dexamethasone Administration on the Perilymph Proteome.

Glucocorticoids are the first-line treatment for sensorineural hearing loss, but little is known about the mechanism of their protective effect or the impact of route of administration. The recent development of hollow microneedles enables safe and reliable sampling of perilymph for proteomic analysis. Using these microneedles, we investigate the effect of intratympanic (IT) versus intraperitoneal (IP) dexamethasone administration on guinea pig perilymph proteome. Guinea pigs were treated with IT dexamethasone (n = 6), IP dexamethasone (n = 8), or untreated for control (n = 8) 6 h prior to aspiration. The round window membrane (RWM) was accessed via a postauricular approach, and hollow microneedles were used to perforate the RWM and aspirate 1 µL of perilymph. Perilymph samples were analyzed by liquid chromatography-mass spectrometry-based label-free quantitative proteomics. Mass spectrometry raw data files have been deposited in an international public repository (MassIVE proteomics repository at https://massive.ucsd.edu/) under data set # MSV000086887. In the 22 samples of perilymph analyzed, 632 proteins were detected, including the inner ear protein cochlin, a perilymph marker. Of these, 14 proteins were modulated by IP, and three proteins were modulated by IT dexamethasone. In both IP and IT dexamethasone groups, VGF nerve growth factor inducible was significantly upregulated compared to control. The remaining adjusted proteins modulate neurons, inflammation, or protein synthesis. Proteome analysis facilitated by the use of hollow microneedles shows that route of dexamethasone administration impacts changes seen in perilymph proteome. Compared to IT administration, the IP route was associated with greater changes in protein expression, including proteins involved in neuroprotection, inflammatory pathway, and protein synthesis. Our findings show that microneedles can mediate safe and effective intracochlear sampling and hold promise for inner ear diagnostics.

A Novel 3D-Printed Head Holder for Guinea Pig Ear Surgery.

BACKGROUND: Otologic surgery in guinea pig requires head immobilization for microscopic manipulation. Existing commercially available stereotaxic frames are expensive and impede access to the ear as they rely on ear bars or mouthpieces to secure the head. METHOD: Prototype head holders were designed using the Solidworks 2019 software and 3D-printed using Formlabs Form 2 Printers with photopolymer resin. The head holder consists of a C-shaped brace with adjustable radial inserts of 1/4-20 UNC standard screws with cone point tips providing head fixation for animals of various sizes. The C-shaped brace is attached to a rod that can be secured to a commercially available micromanipulator. The head holder design was tested during in vivo guinea pig experiments where their head motion with (n = 22) and without the head holder (n = 2) was evaluated visually through a stereotaxic microscope at 24× magnification during surgery. RESULTS: The head holder design was easy to use and allowed for both nose cone administration of anesthesia and access to the ear for intraoperative auditory testing and manipulation. Functionally, the head holder successfully minimized head movement. Furthermore, harvested round window membranes evaluated at 72 hours following surgery showed precise perforations with the use of head holder. CONCLUSION: The novel 3D-printed head holder enables simultaneous access for nose cone administration of anesthesia and surgical manipulation of the ear and brain. Moreover, it provides a modular, intuitive, and economical alternative to commercial stereotaxic devices for minimizing head motion during small animal surgery.

Price Differences Between Otic and Ophthalmic Drops.

OBJECTIVE: Otic drops are one of the most frequently prescribed medications in otolaryngology. However, some forms of these drops can be very expensive, and ophthalmic formulations are sometimes used by practitioners to decrease the cost for their patients. The goal of this study is to determine the cost differential between otic and ophthalmic drops. METHODS: Pharmacies in New York City, Chicago, and Portland were surveyed in the span of 6 weeks by telephone to evaluate the current prices of various otic and ophthalmic drops commonly prescribed by otolaryngologists. RESULTS: A total of 83 pharmacies were surveyed. Surveyed drugs included ciprofloxacin/dexamethasone (cip/dex) otic, neomycin/polymyxin B sulfates/hydrocortisone (neo/poly/HC) otic, acetic acid (AA) otic, acetic acid/hydrocortisone (AA/HC) otic, ofloxacin otic, ofloxacin ophthalmic, and tobramycin/dexamethasone (tob/dex) ophthalmic. Per milliliter, cip/dex otic was consistently the most expensive, with a median price of $38.00 per milliliter. Among the antibiotic drops, neo/poly/HC otic was the least expensive formulation with a median price of $11.60 per milliliter. Ofloxacin ophthalmic was significantly less expensive than the otic formulation, at $11.00 and $31.00 per milliliter, respectively (adjusted p < 0.001). In general, otic and ophthalmic formulations were not significantly different according to manufacturing information, although ophthalmic drops were more often packaged in a sterile fashion and with less abrasive ingredients for use in the more sensitive tissue of the eye. CONCLUSION: Significant and meaningful price differences exist between otic and ophthalmic drops. Given the safety of ophthalmic drops used in the ears, they may be a more cost-effective alternative to traditionally prescribed otic drops when clinically appropriate.

Novel 3D-printed hollow microneedles facilitate safe, reliable, and informative sampling of perilymph from guinea pigs.

BACKGROUND: Inner ear diagnostics is limited by the inability to atraumatically obtain samples of inner ear fluid. The round window membrane (RWM) is an attractive portal for accessing perilymph samples as it has been shown to heal within one week after the introduction of microperforations. A 1 µL volume of perilymph is adequate for proteome analysis, yet the total volume of perilymph within the scala tympani of the guinea pig is limited to less than 5 µL. This study investigates the safety and reliability of a novel hollow microneedle device to aspirate perilymph samples adequate for proteomic analysis. METHODS: The guinea pig RWM was accessed via a postauricular surgical approach. 3D-printed hollow microneedles with an outer diameter of 100 µm and an inner diameter of 35 µm were used to perforate the RWM and aspirate 1 µL of perilymph. Two perilymph samples were analyzed by liquid chromatography-mass spectrometry-based quantitative proteomics as part of a preliminary study. Hearing was assessed before and after aspiration using compound action potential (CAP) and distortion product otoacoustic emissions (DPOAE). RWMs were harvested 72 h after aspiration and evaluated for healing using confocal microscopy. RESULTS: There was no permanent damage to hearing at 72 h after perforation as assessed by CAP (n = 7) and DPOAE (n = 8), and all perforations healed completely within 72 h (n = 8). In the two samples of perilymph analyzed, 620 proteins were detected, including the inner ear protein cochlin, widely recognized as a perilymph marker. CONCLUSION: Hollow microneedles can facilitate aspiration of perilymph across the RWM at a quality and volume adequate for proteomic analysis without causing permanent anatomic or physiologic dysfunction. Microneedles can mediate safe and effective intracochlear sampling and show great promise for inner ear diagnostics.

Low vitamin D status is associated with hearing loss in the elderly: a cross-sectional study.

BACKGROUND: The elderly are at increased risk of both hearing loss (HL) and osteoporosis. Bone mineral density (BMD) has been putatively linked to HL. However, the roles of serum calcium concentrations and vitamin D status have yet to be elucidated. OBJECTIVES: The purpose of this study was to examine the relation between vitamin D status, parathyroid hormone (PTH), total calcium, BMD, and HL in a nationally representative sample of elderly adults. METHODS: Using the NHANES (2005-2010), audiometry and BMD data of 1123 participants aged ≥70 y were analyzed in a cross-sectional manner. HL was defined as pure tone averages >25 dB HL at 500, 1000, and 2000 Hz (low frequency); 500, 1000, 2000, and 4000 Hz (speech frequency); and 3000, 4000, 6000, and 8000 Hz (high frequency) in either ear. Multivariable logistic regression was used to examine the relation between HL and total 25-hydroxyvitamin D [25(OH)D], PTH, total calcium, and BMD, adjusting for covariates. RESULTS: In multivariable analyses, total 25(OH)D < 20 ng/mL was found to be associated with greater odds of low-frequency HL (OR: 2.02; 95% CI: 1.28, 3.19) and speech-frequency HL (OR: 1.96; 95% CI: 1.12, 3.44). A 1-unit decrease in femoral neck BMD (OR: 4.55; 95% CI: 1.28, 16.67) and a 1-unit decrease in total spine BMD (OR: 6.25; 95% CI: 1.33, 33.33) were found to be associated with greater odds of low-frequency HL. Serum PTH and total calcium were not found to be associated with HL. CONCLUSIONS: In the elderly, low vitamin D status was associated with low-frequency and speech-frequency HL. Low vitamin D status may be a potential risk factor for age-related HL.

Inner ear delivery: Challenges and opportunities.

OBJECTIVES: The treatment of inner ear disorders remains challenging due to anatomic barriers intrinsic to the bony labyrinth. The purpose of this review is to highlight recent advances and strategies for overcoming these barriers and to discuss promising future avenues for investigation. DATA SOURCES: The databases used were PubMed, EMBASE, and Web of Science. RESULTS: Although some studies aimed to improve systemic delivery using nanoparticle systems, the majority enhanced local delivery using hydrogels, nanoparticles, and microneedles. Developments in direct intracochlear delivery include intracochlear injection and intracochlear implants. CONCLUSIONS: In the absence of a systemic drug that targets only the inner ear, the best alternative is local delivery that harnesses a combination of new strategies to overcome anatomic barriers. The combination of microneedle technology with hydrogel and nanoparticle delivery is a promising area for future investigation. LEVEL OF EVIDENCE: NA.

Inner Ear Gene Delivery: Vectors and Routes.

OBJECTIVES: Current treatments for hearing loss offer some functional improvements in hearing, but do not restore normal hearing. The aim of this review is to highlight recent advances in viral and non-viral vectors for gene therapy and to discuss approaches for overcoming barriers inherent to inner ear delivery of gene products. DATA SOURCES: The databases used were Medline, EMBASE, Web of Science, and Google Scholar. Search terms were [("cochlea*" or "inner ear" or "transtympanic" or "intratympanic" or "intracochlear" or "hair cells" or "spiral ganglia" or "Organ of Corti") and ("gene therapy" or "gene delivery")]. The references section of resulting articles was also used to identify relevant studies. RESULTS: Both viral and non-viral vectors play important roles in advancing gene delivery to the inner ear. The round window membrane is one significant barrier to gene delivery that intratympanic delivery methods attempt to overcome through diffusion and intracochlear delivery methods bypass completely. CONCLUSIONS: Gene therapy for hearing loss is a promising treatment for restoring hearing function by addressing innate defects. Recent technological advances in inner ear drug delivery techniques pose exciting opportunities for progress in gene therapy.