Prestin binding peptides as ligands for targeted polymersome mediated drug delivery to outer hair cells in the inner ear

Targeted delivery of treatment agents to the inner ear using nanoparticles is an advanced therapeutic approach to cure or alleviate hearing loss. Designed to target the outer hair cells of the cochlea, two 12-mer peptides (A(665) and A(666)) with affinity to prestin were identified following 3 rounds of sequential phage display. Two-round display with immobilized prestin protein was used to enrich the library for full-length prestin. The last round was performed using Cos-7 cells transiently transfected with a cCFP-prestin plasmid to display phages expressing peptides restrictive to the extracellular loops of prestin. The binding properties of A(665) and A(666) shown by flow cytometry demonstrated selectivity to prestin-expressing Chinese hamster ovary cells. PEG6K-b-PCL19K polymersomes covalently labelled with these peptides demonstrated effective targeting to outer hair cells in a rat cochlear explant study.

The consequences of tinnitus in long-standing Ménière's disease

OBJECTIVE

To explore the perceived consequences of tinnitus in patients with long-standing Ménière's disease (MD).

METHOD

A questionnaire-based cross-sectional investigation of 183 randomly selected members of the Finnish Ménière's Federation. It assessed general health related quality of life (EQ-5D), a participation restriction scale, self-listed consequences and a rating of effects of MD on life.

RESULTS

When the effects of the other cardinal symptoms of Ménière's disease were partialled out, the main reported impacts of tinnitus related to anxiety, sleep and depression. It also contributed to some difficult listening situations and to interactions with significant others. Tinnitus explained a significant component of disease-specific quality of life (QoL), but did not relate significantly to the generic measures used. However, the measure 'mood' in the QoL scale was significantly associated with severe tinnitus.

CONCLUSION

The most important specific impacts of tinnitus in chronic Ménière's disease relate to broadly psychological factors and mood.

Dynamic enhancement of the rat inner ear after ultra-small-volume administration of Gd-DOTA to the medial wall of the middle ear cavity

OBJECTIVE

To investigate minimally invasive administration of contrast agent to the middle ear and the enhancement efficacy on the inner ear compartments.

MATERIALS AND METHODS

An ultra-small volume of gadolinium-tetraazacyclododecane tetraacetic acid (Gd-DOTA) was injected onto the medial wall of the rat middle ear with a high-performance polyimide tube. The dynamic Gd-DOTA distribution in the inner ear was visualized in vivo by MRI.

RESULTS

After injection of 2.5 μl of 0.5MGd-DOTA, uptake first occurred in the vestibulum, then in the scala vestibuli, and finally in the scala tympani (ST). A significant difference in signal intensities among these compartments was demonstrated with an intensity gradient, indicating that the vestibulum was the highest and the ST was the lowest. After 24 h, Gd-DOTA remained in the inner ear and the vestibule remained higher compared to the cochlea. The signal/noise ratio was significantly improved by a fluid-attenuated inversion recovery sequence.

CONCLUSIONS

This novel minimally invasive technique can be applied to both animal studies and clinical evaluations of inner ear barrier function and fluid spaces with gadolinium-enhanced MRI. This technique might also be exploited for use as a minimally invasive drug delivery means for inner ear treatment.

Visualization of intracellular trafficking of Math1 protein in different cell types with a newly-constructed nonviral gene delivery plasmid

BACKGROUND

In recent years, Math1 gene therapy was indicated to be the future therapy for deafness in combination with other growth factors. However, Math1 delivery using adenovirus-mediated gene delivery or electroporation was impractical. The contribution of Math1 in the combined procedure was not clearly elucidated using the existing plasmids. Nonviral gene delivery vectors are expected to be extremely safe and convenient. The present study aimed to construct the pCDNA6.2/C-EmGFP-Math1 plasmid and evaluate its transfection efficiency and intracellular trafficking of Math1 protein corresponding to transcription regulation function.

METHODS

After constructing the pCDNA6.2/C-EmGFP-Math1 expression plasmid, the plasmid was transfected into different cell lines and primary cochlear cells using Lipofectamine 2000. Transfection efficiencies of the plasmid were evaluated. Transfection efficiencies using liposome nanoparticles containing Math1 plasmid were also assessed. Intracellular trafficking of Math1 was monitored using confocal microscopy.

RESULTS

Different cell types can be transfected with high transfection efficiencies by the pcDNA6.2/C-EmGFP-Math1 plasmid using Lipofectamine 2000. Liposome nanoparticles containing the Math1 plasmid expressed the gene with variable efficiencies, depending on the particle size, surface charge and PEGylation status. Unique intracellular trafficking of Math1 was demonstrated in different cell types.

CONCLUSIONS

The newly-constructed plasmid pcDNA6.2/C-EmGFP-Math1 was suitable for nonviral gene delivery of Math1. Unique intracellular trafficking of Math1 with dynamics from the cytoplasm to the nucleus was demonstrated. The modification of mesenchymal stem cells by Math1 gene delivery and by brain-derived neurotrophic factor and glial cell line-derived neurotrophic factor treatments can potentially be applied to cell replacement for the treatment of cochlear spiral ganglion cell loss in deafness.

Hearing loss among classical-orchestra musicians

This study intended to evaluate classical musicians' risk of hearing loss. We studied 63 musicians from four Helsinki classical orchestras. We measured their hearing loss with an audiometer, found their prior amount of exposure to sound and some individual susceptibility factors with a questionnaire, measured their present sound exposure with dosimeters, and tested their blood pressure and cholesterol levels, then compared their hearing loss to ISO 1999-1990's predictions. The musicians' hearing loss distribution corresponded to that of the general population, but highly exposed musicians had greater hearing loss at frequencies over 3 kHz than less-exposed ones. Their individual susceptibility factors were low. Music deteriorates hearing, but by less than what ISO 1999-1990 predicted. The low number of individual susceptibility factors explained the difference, but only reduced hearing loss and not the prevalence of tinnitus.

Nuclear entry of hyperbranched polylysine nanoparticles into cochlear cells

Background:

Gene therapy is a potentially effective therapeutic modality for treating sensorineural hearing loss. Nonviral gene delivery vectors are expected to become extremely safe and convenient, and nanoparticles are the most promising types of vectors. However, infrequent nuclear localization in the cochlear cells limits their application for gene therapy. This study aimed to investigate the potential nuclear entry of hyperbranched polylysine nanoparticles (HPNPs) for gene delivery to cochlear targets.

Methods:

Rat primary cochlear cells and cochlear explants generated from newborn rats were treated with different concentrations of HPNPs. For the in vivo study, HPNPs were administered to the rats’ round window membranes. Subcellular distribution of HPNPs in different cell populations was observed with confocal microscope 24 hours after administration.

Results:

Nuclear entry was observed in various cochlear cell types in vitro and in vivo. In the primary cochlear cell culture, concentration-dependent internalization was observed. In the cochlear organotypic culture, abundant HPNPs were found in the modiolus, including the spiral ganglion, organ of Corti, and lateral wall tissues. In the in vivo study, a gradient distribution of HPNPs through different layers of the round window membrane was observed. HPNPs were also distributed in the cells of the middle ear tissue. Additionally, efficient internalization of HPNPs was observed in the organ of Corti and spiral ganglion cells. In primary cochlear cells, HPNPs induced higher transfection efficiency than did Lipofectamine^™.

Conclusion:

These results suggest that HPNPs are potentially an ideal carrier for gene delivery into the cochlea.

Balloon dilation of the cartilaginous eustachian tube

OBJECTIVES

(1) To translate techniques developed in a previous cadaver study of balloon dilation of the cartilaginous eustachian tube (ET) into clinical treatment for refractory dilatory dysfunction and (2) to study the safety/efficacy of the technique in a pilot clinical trial.

STUDY DESIGN

Prospective with subjects as their own historical controls since June 2009.

SETTING

Regional academic center.

SUBJECTS AND METHODS

Eleven consecutive adult patients with longstanding otitis media with effusion (OME) who were unable to autoinsufflate their ET by Valsalva, swallow, or yawn and who had previous tympanostomies (average, 4.7). At the time of intervention, 5 of 11 had a tube; 2 of 11 had a tympanic membrane (TM) perforation. Four of 11 had intact TMs, 2 with OME and tympanogram type B and 2 with TM retraction and tympanogram types B and C. Balloon dilation of the cartilaginous ET was performed with sinus dilation instruments via transnasal endoscopic approach under general anesthesia in a day surgery setting. Inflation was to a maximum of 12 atm for 1 minute.

OUTCOME MEASURES

ability to Valsalva, rating of ET mucosal inflammation, tympanogram, and otomicroscopy findings.

RESULTS

All cases successfully dilated. Eleven of 11 could self-insufflate by Valsalva (P < .001); tympanograms were A (4/11), C (1/11), or open (6/11). All atelectases resolved. Procedures were well tolerated, without pain or complications related to dilation.

CONCLUSION

Dilation of the cartilaginous ET appeared to be beneficial and without significant adverse effects in the treatment of ET dilatory dysfunction. Larger controlled trials with long-term results are now justified and needed.

Manufacturing and in vivo inner ear visualization of MRI traceable liposome nanoparticles encapsulating gadolinium

BACKGROUND

Treatment of inner ear diseases remains a problem because of limited passage through the blood-inner ear barriers and lack of control with the delivery of treatment agents by intravenous or oral administration. As a minimally-invasive approach, intratympanic delivery of multifunctional nanoparticles (MFNPs) carrying genes or drugs to the inner ear is a future therapy for treating inner ear diseases, including sensorineural hearing loss (SNHL) and Meniere's disease. In an attempt to track the dynamics and distribution of nanoparticles in vivo, here we describe manufacturing MRI traceable liposome nanoparticles by encapsulating gadolinium-tetra-azacyclo-dodecane-tetra-acetic acid (Gd-DOTA) (abbreviated as LPS+Gd-DOTA) and their distribution in the inner ear after either intratympanic or intracochlear administration.

RESULTS

Measurements of relaxivities (r1 and r2) showed that LPS+Gd-DOTA had efficient visible signal characteristics for MRI. In vivo studies demonstrated that LPS+Gd-DOTA with 130 nm size were efficiently taken up by the inner ear at 3 h after transtympanic injection and disappeared after 24 h. With intracochlear injection, LPS+Gd-DOTA were visualized to distribute throughout the inner ear, including the cochlea and vestibule with fast dynamics depending on the status of the perilymph circulation.

CONCLUSION

Novel LPS+Gd-DOTA were visible by MRI in the inner ear in vivo demonstrating transport from the middle ear to the inner ear and with dynamics that correlated to the status of the perilymph circulation.

Magnetic resonance imaging of the inner ear in Meniere's disease

Recent magnetic resonance imaging (MRI) techniques have made it possible to examine the compartments of the cochlea using gadolidium-chelate (GdC) as a contrast agent. As GdC loads into the perilymph space without entering the endolymph in healthy inner ears, the technique provides possibilities to visualize the different cochlear compartments and evaluate the integrity of the inner ear barriers. This critical review presents the recent advancements in the inner ear MRI technology, contrast agent application and the correlated ototoxicity study, and the uptake dynamics of GdC in the inner ear. GdC causes inflammation of the mucosa of the middle ear, but there are no reports or evidence of toxicity-related changes in vivo either in animals or in humans. Intravenously administered GdC reached the guinea pig cochlea about 10 minutes after administration and loaded the scala tympani and scala vestibuli with the peak at 60 minutes. However, the perilymphatic loading peak was 80 to 100 minutes in mice after intravenous administration of GdC. In healthy animals the scala media did not load GdC. In mice in which GdC was administered topically onto the round window, loading of the cochlea peaked at 4 hours, at which time it reached the apex. The initial portions of the organ to be filled were the basal turn of the cochlea and vestibule. In animal models with endolymphatic hydrops (EH), bulging of the Reissner's membrane was observed as deficit of GdC in the scala vestibuli. Histologically the degree of bulging correlated with the MR images. In animals with immune reaction-induced EH, MRI showed that EH could be limited to restricted regions of the inner ear, and in the same inner ear both EH and leakage of GdC into the scala media were visualized. More than 100 inner ear MRI scans have been performed to date in humans. Loading of GdC followed the pattern seen in animals, but the time frame was different. In intravenous delivery of double-dose GdC, the inner ear compartments were visualized after 4 hours. The uptake pattern of GdC in the perilymph of humans between 2 hours and 7 hours after local delivery needs to be clarified. In almost all patients with probable or suspected Ménière's disease, EH was verified. Specific algorithms with a 12-pole coil using fluid attenuation inversion recovery sequences are recommended for initial imaging in humans.

MRI manifestation of novel superparamagnetic iron oxide nanoparticles in the rat inner ear

AIM

Superparamagnetic iron oxide nanoparticles hierarchically coated with oleic acid and Pluronic F127 copolymers (POA@SPION) have shown exceptional T2 contrast enhancement. The aim of the present work was to investigate the MRI manifestation of POA@SPION in the inner ear.

MATERIALS & METHODS

A total of 26 male Wister rats were selected for testing POA@SPION administered through intracochlear, intratympanic and intravenous routes. MRI was performed with a 4.7 T MR scanner.

RESULTS & CONCLUSION

POA@SPION can be introduced into the perilymph space, after which it becomes widely distributed and can demonstrate the integrity of the perilymph-endolymph barrier. Positive highlighting of the endolymph compartment against the darkened perilymph was visualized for the first time. POA@SPION passed through the middle-inner ear barriers in only small amounts, but stayed in the perilymph for 3 days. They did not traverse the blood-perilymph barrier or blood-endolymph barrier. The inner ear distribution of POA@SPION was confirmed by histology. POA@SPION is a promising T2 negative contrast agent.

Use of ICF in assessing the effects of Meniere's disorder on life

OBJECTIVES

We sought to determine the value of the World Health Organization's International Classification of Functioning, Disability and Health (ICF) in subjects with Meniere's disorder in relation to their quality of life.

METHODS

We asked 228 members of the Finnish Meniere Federation to report the effects that Meniere's disorder had on their lives. The replies were classified on the basis of the ICF classification and related to the EuroQol 5D score and disease-specific impact. Logistic regression and decision tree analyses were used to determine the relationships.

RESULTS

Seventy percent of the patients listed impairments, 39% activity limitations, 47% participation restrictions, 16% effects on environmental contextual factors, and 28% effects on personal contextual factors. The EuroQol 5D score was explained by reported vertigo, anxiety, fatigue, restriction of life, and communication problems. The disease-specific impact was explained by episodes of vertigo, fatigue, communication problems, inability to work, restriction of life, and uncertainty of life. Both analysis models provided the same outcome variables, although the decision tree separated the results better (80%) into correct classes than did logistic regression analysis (60%).

CONCLUSIONS

Self-reported participation restriction, activity limitation, and personal contextual factors describe the limitations of general life in subjects with Meniere's disorder. The use of the ICF classification provides an instrument that can be used in enablement of subjects with Meniere's disorder.

Inner ear biocompatibility of lipid nanocapsules after round window membrane application

Nanoparticle-mediated drug delivery represents the future in terms of treating inner ear diseases. Lipid core nanocapsules (LNCs), 50 nm in size, were shown to pass though the round window membrane (RWM) and reached the spiral ganglion cells and nerve fibers, among other cell types in the inner ear. The present study aimed to evaluate the toxicity of the LNCs in vitro and in vivo, utilizing intact round window membrane delivery in rats. The primary cochlear cells and mouse fibroblast cells treated with LNCs displayed dosage dependant toxicity. In vivo study showed that administration of LNCs did not cause hearing loss, nanoparticle application-related cell death, or morphological changes in the inner ear, at up to 28 days of observation. The cochlear neural elements, such as synaptophysin, ribbon synapses, and S-100, were not affected by the administration of LNCs. However, expression of neurofilament-200 decreased in SGCs and in cochlear nerve in osseous spiral lamina canal after LNC delivery, a phenomenon that requires further investigation. LNCs are potential vectors for the delivery of drugs to the inner ear.

Gadolinium uptake in the rat inner ear perilymph evaluated with 4.7 T MRI: a comparison between transtympanic injection and gelatin sponge-based diffusion through the round window membrane

OBJECTIVE

To investigate the inner ear uptake of the contrast agent gadolinium administered intratympanically through transtympanic injection or using a gelatin sponge placed on the round window.

MATERIALS AND METHODS

The T1 contrast agent Gadolinium-tetra-azacyclo-dodecane-tetra-acetic acid (Gd-DOTA) was administrated to the middle ear cavities of 12 male Wistar rats by a transtympanic injection technique (TTI group; 40 microl), gelatin sponge diffusion (GelD40 group; 40 microl), or gelatin sponge diffusion (GelD8 group; 8 microl). Magnetic resonance imaging was performed with a 4.7-T scanner using a T1-weighted 2-dimensional rapid acquisition with relaxation enhancement sequence and a high-resolution T1-weighted 3-dimensional rapid acquisition with relaxation enhancement sequence.

RESULTS

The uptake of Gd-DOTA into the perilymph was more pronounced at 3 than at 1 hour after intratympanic administration for all methods studied. Transtympanic injection and GelD40 induced similar uptake of Gd-DOTA in the lower turns of the rat cochlea. Transtympanic injection induced less efficient Gd-DOTA uptake in the apex than GelD40. GelD8 was less efficient at Gd-DOTA uptake than either TTI or GelD40.

CONCLUSION

Both TTI and GelD40 are able to efficiently deliver substances to inner ear destinations. Considering its simplicity, TTI is more practical for use in the clinic for the administration of substances to the inner ear, although it provided less efficient uptake in the apex than GelD40.

Improving the visualization of fluorescently tagged nanoparticles and fluorophore-labeled molecular probes by treatment with CuSO(4) to quench autofluorescence in the rat inner ear

Fluorescent tags and fluorophore-conjugated molecular probes have been extensively employed in histological studies to demonstrate nanoparticle distribution in inner ear cell populations. However, autofluorescence that exists in the rodent cochleae disturbs visualization of the fluorescent tags and fluorophore labeling. In the present work, we aimed to improve the visualization of fluorescently tagged nanoparticles and fluorophore-labeled molecular probes by treatment with CuSO(4) to quench autofluorescence in the rat inner ear. The in vivo study was performed on eight- to nine-month-old rats using confocal laser scanning microscopy, and the in vitro study was carried out with DiI-tagged poly(ethylene glycol) and poly(capro-lactone) polymersomes and different fluorescent-labeling agents using a spectrofluorometer. The nanoparticles were intratympanically administered using either an osmotic pump or transtympanic injection. Abundant autofluorescence was detected in spiral ganglion cells (SGCs), stria marginal cells, spiral ligament fibrocytes (SL) and the subcuticular cytoplasm of inner hair cells (IHCs). Sparsely distributed faint autofluorescence was also visualized in outer hair cells (OHCs). The autofluorescence was eliminated by treatment with 1 mM CuSO(4) (in 0.01 M ammonium acetate buffer) for 70-90 min, while the fluorescent tag in the nanoparticle was absolutely preserved and the labeling fluorescence signals of the molecular probes were mostly retained.

Principal component analysis detects sleepiness-related changes in balance control

Computerized posturography exploits balance scores that quantify the size, dynamics, or structure of the recorded sway. Since people employ different balance strategies, one single balance score will not detect balance changes in all subjects. Principal component analysis (PCA) can combine balance scores that quantify different features into one new balance score. We tested the score with 20 subjects by measuring their balance every 2 h during 28 h of sustained waking. The new balance score was more sensitive than its components (p<0.001 vs. p≥0.051) to the small sleepiness-related balance decrements that occurred during the short 28-h period. PCA provided a more sensitive balance score that applied to all of the subjects.

Quantitative test for sensory hand symptoms based on mechanoreceptor-specific vibrotactile thresholds

A vibrotactile test for assessing the presence or absence of sensory symptoms in the hand has been developed from thresholds believed mediated by Merkel disks and Meissner corpuscles at the fingertips. It is constructed from the summed differences between the thresholds recorded at the fingertip of an individual and the mean values of the threshold for healthy persons at the same stimulation frequencies. The summed normalized threshold shift, TS(Sum(SD)), is shown to be related to reports by subjects of numbness and pain using three statistical tests for evaluating the significance of associations in 2x2 contingency tables. The small number of subjects (15) restricts direct calculation of a fence value for TS(Sum(SD)), t, between the presence and absence of symptoms: accordingly, interpolation between calculated t values has been performed graphically. A common range of t values can be identified that is judged significantly by each statistical test (3.3<or=t<3.9 for numbness; 3.6<or=t<4.1 for pain). The range encompasses the boundary previously identified between "normal" and "abnormal" vibrotactile thresholds, that is, thresholds for which the (two-sided) probability of occurrence in the hands of healthy persons is p approximately 0.05.

Hearing acuity as a predictor of walking difficulties in older women

OBJECTIVES

To examine whether hearing acuity correlates with walking ability and whether impaired hearing at baseline predicts new self-reported walking difficulties after 3 years.

DESIGN

Prospective follow-up.

SETTING

Research laboratory and community.

PARTICIPANTS

Four hundred thirty-four women aged 63 to 76.

MEASUREMENTS

Hearing was measured using clinical audiometry. A person was defined as having a hearing impairment if a pure-tone average of thresholds at 0.5 to 4 kHz in the better ear was 21 dB or greater. Maximal walking speed was measured over 10 m (m/s), walking endurance as the distance (m), covered in 6 minutes and difficulties in walking 2 km according to self-report.

RESULTS

At baseline, women with hearing impairment (n=179) had slower maximal walking speed (1.7 +/- 0.3 m/s vs 1.8 +/- 0.3 m/s, P=.007), lower walking endurance (520 +/- 75 m vs 536 +/- 75 m, P=.08), and more selfreported major difficulties in walking 2 km (12.8% vs 5.5%, P=.02) than those without hearing impairment. During follow-up, major walking difficulties developed for 33 participants. Women with hearing impairment at baseline had a twice the age-adjusted risk for new walking difficulties as those without hearing impairment (odds ratio=2.04, 95% confidence interval=0.96-4.33).

CONCLUSION

Hearing acuity correlated with mobility, which may be explained by the association between impaired hearing and poor balance and greater risk for falls, both of which underlie decline in mobility. Prevention of hearing loss is not only important for the ability to communicate, but may also have more wide-ranging influences on functional ability.

Differential passage of gadolinium through the mouse inner ear barriers evaluated with 4.7T MRI

Magnetic resonance imaging (MRI), supplemented by contrast agents, is a powerful tool that can be used to visualise the structures of the inner ear in vivo and assess some aspects of physiology, such as the permeability of agents through membranes. The mouse is an excellent animal species for investigating human diseases, including hearing loss but detailed MRI studies with contrast have not been reported. In this work, we aimed to demonstrate the limits of MR imaging resolution of the fine inner ear structures in the mouse and to explore the permeability of the intracochlear barriers to gadolinium-tetra-azacyclo-dodecane-tetra-acetic acid (Gd-DOTA) administered by intravenous injection (IV) or intratympanic (IT) routes. Twenty-three female FVB mice were imaged with a 4.7-T MR scanner using both 2D and high resolution 3D sequences. Inner ear region of interest (ROI) signal intensities and perilymph volumes were evaluated. Finer structures were studied using 3D acquisition and reconstruction techniques and comparisons were made to similarly oriented histological sections that were examined by light microscopy. Gd-DOTA enhancement occurred in the perilymphatic compartment and highlighted the contiguous inner ear structures, but enhancement did not appear within the endolymph. The dynamic uptake of Gd-DOTA in the perilymphatic compartments reached an initial plateau 80min after IV administration and continued to slightly increase to a maximum level by 100min. The perilymph volume demonstrated by Gd-DOTA uptake was statistically significantly larger in the IV group (1.72mm(3)) than in the IT group (1.28mm(3)) (p<0.05).