Search

Hybrid or electro-acoustic stimulation (EAS) cochlear implants (CIs) are designed to provide high-frequency electric hearing together with residual low-frequency acoustic hearing. However, 30-50% of EAS CI recipients lose residual hearing after implantation. The objective of this study was to determine the mechanisms of EAS-induced hearing loss in an animal model with high-frequency hearing loss. Guinea pigs were exposed to 24 h of noise (12-24 kHz at 116 dB) to induce a high-frequency hearing loss. After recovery, two groups of animals were implanted (n = 6 per group), with one group receiving chronic acoustic and electric stimulation for 10 weeks, and the other group receiving no stimulation during this time frame. A third group (n = 6) was not implanted, but received chronic acoustic stimulation. Auditory brainstem responses were recorded biweekly to monitor changes in hearing. The organ of Corti was immunolabeled with phalloidin, anti-CtBP2, and anti-GluR2 to quantify hair cells, ribbons and post-synaptic receptors. The lateral wall was immunolabeled with phalloidin and lectin to quantify stria vascularis capillary diameters. Bimodal or trimodal diameter distributions were observed; the number and location of peaks were objectively determined using the Aikake Information Criterion and Expectation Maximization algorithm. Noise exposure led to immediate hearing loss at 16-32 kHz for all groups. Cochlear implantation led to additional hearing loss at 4-8 kHz; this hearing loss was negatively and positively correlated with minimum and maximum peaks of the bimodal or trimodal distributions of stria vascularis capillary diameters, respectively. After chronic stimulation, no significant group changes in thresholds were seen; however, elevated thresholds at 1 kHz in implanted, stimulated animals were significantly correlated with decreased presynaptic ribbon and postsynaptic receptor counts. Inner and outer hair cell counts did not differ between groups and were not correlated with threshold shifts at any frequency. As in the previous study in a normal-hearing model, stria vascularis capillary changes were associated with immediate hearing loss after implantation, while little to no hair cell loss was observed even in cochlear regions with threshold shifts as large as 40-50 dB. These findings again support a role of lateral wall blood flow changes, rather than hair cell loss, in hearing loss after surgical trauma, and implicate the endocochlear potential as a factor in implantation-induced hearing loss. Further, the analysis of the hair cell ribbons and post-synaptic receptors suggest that delayed hearing loss may be linked to synapse or peripheral nerve loss due to stimulation excitotoxicity or inflammation. Further research is needed to separate these potential mechanisms of delayed hearing loss., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Hearing loss may be genetic, associated with aging or exposure to noise or ototoxic substances. Its aetiology can be attributed to vascular injury, trauma, tumours, infections or autoimmune response. All these factors could be related to alterations in cochlear microcirculation resulting in hypoxia, which in turn may damage cochlear hair cells and neurons, leading to deafness. Hypoxia could underlie the aetiology of deafness, but very few data about it are presently available. The aim of this work is to develop animal models of hypoxia and ischemia suitable for study of cochlear vascular damage, characterizing them by electrophysiology and gene/protein expression analyses. The effects of hypoxia in infarction were mimicked in rat by partial permanent occlusion of the left coronary artery, and those of ischemia in thrombosis by complete temporary carotid occlusion. In our models both hypoxia and ischemia caused a small but significant hearing loss, localized at the cochlear apex. A slight induction of the coagulation cascade and of oxidative stress pathways was detected as cell survival mechanism, and cell damages were found on the cuticular plate of outer hair cells only after carotid ischemia. Based on these data, the two developed models appear suitable for in vivo studies of cochlear vascular damage., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Tight control over cochlear blood flow (CoBF) and the blood-labyrinth barrier (BLB) in the striavascularis is critical for maintaining the ionic, fluid and energy balance necessary for hearing function. Inefficient CoBF and disruption of BLB integrity have long been considered major etiologic factors in a variety of hearing disorders. In this study, we investigate structural changes in the BLB of the striavascularis in age-graded C57BL/6 mice (1 to 21 months) with a focus on changes in two blood barrier accessory cells, namely pericytes (PCs) and perivascular-resident macrophage-like melanocytes (PVM/Ms). Decreased capillary density was detectable at 6 months, with significant capillary degeneration seen in 9- to 21-month-old mice. Reduced capillary density was highly correlated with lower numbers of PCs and PVM/Ms. "Drop-out" of PCs and "activation" of PVM/Ms were seen at 6 months, with drastic changes being observed by 21 months. With newly established in vitro three-dimensional cell-based co-culture models, we demonstrate that PCs and PVM/Ms are essential for maintaining cochlear vascular architecture and stability.

Objective: Betahistine augments cochlear blood flow and is currently used as an efficient therapeutic agent. Amikacin is used in a wide range of areas, but its ototoxic effect continues to be problematic. This study investigates the effect of betahistine on amikacin-induced ototoxicity., Methods: Thirty-two healthy rats were randomized to 4 groups of 8 rats in each group (amikacin, amikacin+betahistine, betahistine, and no treatment). Amikacin was administered intramuscularly to groups 1 and 2 for 14 days. Betahistine was delivered by oral gavage to groups 2 and 3 for 21 days. Distortion-product otoacoustic emissions (DPOAE) and auditory brainstem response (ABR) tests were conducted on all rats., Results: There were significant decreases in the DPOAE levels and significant increases in the ABR thresholds of the amikacin and amikacin+betahistine groups on the 7th, 14th, and 21st days, as compared to their basal values. The DPOAE levels of the amikacin+betahistine group significantly decreased on days 7, 14, and 21, and the ABR thresholds significantly increased on the same days, as compared to the amikacin group., Conclusion: Our study implies that amikacin's ototoxic effects are augmented by the concurrent use of betahistine. Experimental and clinical research, supported by histopathological studies, is needed to affirm our findings., (© The Author(s) 2014.)

The oto-renal axis describes the relationship between hearing loss and chronic nephropathy. Several clinical studies have investigated the incidence of hypoacusia in patients affected by chronic renal failure, but the etiopathogenic mechanism is not fully understood. In this context, there is a general agreement that hypoacusia is usually neurosensorial and the cochlea is the main site of lesion. Inner ear and kidney present an interesting similarity in terms of structure and function. In particular, the presence of pericytes and podocytes in inner ear and in glomeruli, respectively, evidence common characteristics of microcirculation. Defects in microcirculation in the inner ear mainly cause an electrolytic imbalance with the consequent impairment of endocochlear potential and sensorial transduction. In kidney, microvessels and podocytes contribute to glomerular stability and function. Microcirculation dysfunction often occurs during the inflammatory status, frequently reported both in chronic nephropathy and in cardiovascular disease. Clinical studies aimed to describe the hypoacusia in nephropathy patients are summarized. Then, in order to speculate the etiopathogenic mechanism of hearing loss in chronic nephropathy, we report the similarities between pericytes and podocytes in inner ear and glomeruli microcirculation in terms of structure and function. Finally, we propose a model in which inflammation plays an important role in oto-renal dysfunction. Our model proposes the inflammation, as an etiopathogenic mechanism of hypoacusia in chronic nephropathy and the defective cross-talk between pericytes/podocytes and vascular endothelium, as the initial event of the degenerative process., (© 2014 The Authors. Therapeutic Apheresis and Dialysis © 2014 International Society for Apheresis.)

Impairment of cochlear blood flow has been discussed as factor in the pathophysiology of various inner ear disorders. However, the microscopic study of cochlear microcirculation is limited due to small scale and anatomical constraints. Here, two-photon fluorescence microscopy is applied to visualize cochlear microvessels. Guinea pigs were injected with Fluorescein isothiocyanate- or Texas red-dextrane as plasma marker. Intravital microscopy was performed in four animals and explanted cochleae from four animals were studied. The vascular architecture of the cochlea was visualized up to a depth of 90.0±22.7 μm. Imaging yielded a mean contrast-to-noise ratio (CNR) of 3.3±1.7. Mean diameter in vivo was 16.5±6.0 μm for arterioles and 8.0±2.4 μm for capillaries. In explanted cochleae, the diameter of radiating arterioles and capillaries was measured with 12.2±1.6 μm and 6.6±1.0 μm, respectively. The difference between capillaries and arterioles was statistically significant in both experimental setups (P<0.001 and P=0.022, two-way ANOVA). Measured vessel diameters in vivo and ex vivo were in agreement with published data. We conclude that two-photon fluorescence microscopy allows the investigation of cochlear microvessels and is potentially a valuable tool for inner ear research.

Objective: Betahistine is a histamine-like drug that is considered beneficial in Ménière's disease by increasing cochlear blood flow. Acting as an agonist at the histamine H1-receptor and as an inverse agonist at the H3-receptor, these receptors as well as the adrenergic α2-receptor were investigated for betahistine effects on cochlear blood flow., Materials and Methods: A total of 54 Dunkin-Hartley guinea pigs were randomly assigned to one of nine groups treated with a selection of H1-, H3- or α2-selective agonists and antagonists together with betahistine. Cochlear blood flow and mean arterial pressure were recorded for 3 min before and 15 min after infusion., Results: Blockage of the H3- or α2-receptors caused a suppression of betahistine-mediated typical changes in cochlear blood flow or blood pressure. Activation of H3-receptors caused a drop in cochlear blood flow and blood pressure. H1-receptors showed no involvement in betahistine-mediated changes of cochlear blood flow., Conclusion: Betahistine most likely affects cochlear blood flow through histaminergic H3-heteroreceptors., (© 2015 S. Karger AG, Basel.)

In cerebellopontine angle (CPA) surgery, postoperative deafness can be due to alteration of cochlear blood flow that is supplied by the labyrinthine artery (LA). In particular, vasospasm is likely to occur and, if so, can be reversed. This work attempted to track down vascular events occurring during CPA surgery. Twenty consecutive patients with vestibular schwannoma were tested with useful preoperative hearing and presence of otoacoustic emissions (OAEs). Distortion-product otoacoustic emissions (DPOAEs), well-known to react within seconds to cochlear ischemia, were used intraoperatively to indirectly monitor cochlear blood flow. Continuous intraoperative monitoring of DPOAEs revealed three different time patterns associated with distinct auditory outcomes. Pattern P1-acute (n = 4) happened when the LA was severed: DPOAEs immediately and irreversibly foundered and led to postoperative deafness. Pattern P2-protracted (n = 7) revealed a progressive deterioration of DPOAEs from the beginning of tumor debulking, likely due to a steady decrease of cochlear blood flow, with postoperative deafness. Pattern P3-unstable (n = 5) corresponded to large DPOAE oscillations between their normal level and noise floor. It was due to acute LA vasospasm that could be reversed in three cases by topical nimodipin. Last, four patients had uneventful cochlear monitoring. In conclusion, cochlear ischemia can occur in vestibular schwannoma surgery, giving three different patterns among which vasospasm can be reversed if detected early.

Objective: Betahistine is a histamine-like drug that is used in the treatment of Ménière's disease. It is commonly believed that betahistine increases cochlear blood flow and thus decreases the endolymphatic hydrops that is the cause of Ménière's. Despite common clinical use, there is little understanding of the kinetics or effects of its metabolites. This study investigated the effect of the betahistine metabolites aminoethylpyridine, hydroxyethylpyridine, and pyridylacetic acid on cochlear microcirculation., Design: Guinea pigs were randomly assigned to one of the groups: placebo, betahistine, or equimolar amounts of aminoethylpyridine, hydroxyethylpyridine, or pyridylacetic acid. Cochlear blood flow and mean arterial pressure were recorded for three minutes before and 15 minutes after treatment., Study Sample: Thirty Dunkin-Hartley guinea pigs assigned to one of five groups with six guinea pigs per group., Results: Betahistine, aminoethylpyridine, and hydroxyethylpyridine caused a significant increase in cochlear blood flow in comparison to placebo. The effect seen under aminoethylpyridin was greatest. The group treated with pyridylacetic acid showed no significant effect on cochlear blood flow., Conclusion: Aminoethylpyridine and hydroxyethylpyridine are, like betahistine, able to increase cochlear blood flow significantly. The effect of aminoethylpyridine was greatest. Pyridylacetic acid had no effect on cochlear microcirculation.

Normal microvessel structure and function in the cochlea is essential for maintaining the ionic and metabolic homeostasis required for hearing function. Abnormal cochlear microcirculation has long been considered an etiologic factor in hearing disorders. A better understanding of cochlear blood flow (CoBF) will enable more effective amelioration of hearing disorders that result from aberrant blood flow. However, establishing the direct relationship between CoBF and other cellular events in the lateral wall and response to physio-pathological stress remains a challenge due to the lack of feasible interrogation methods and difficulty in accessing the inner ear. Here we report on new methods for studying the CoBF in a mouse model using a thin or open vessel-window in combination with fluorescence intra-vital microscopy (IVM). An open vessel-window enables investigation of vascular cell biology and blood flow permeability, including pericyte (PC) contractility, bone marrow cell migration, and endothelial barrier leakage, in wild type and fluorescent protein-labeled transgenic mouse models with high spatial and temporal resolution. Alternatively, the thin vessel-window method minimizes disruption of the homeostatic balance in the lateral wall and enables study CoBF under relatively intact physiological conditions. A thin vessel-window method can also be used for time-based studies of physiological and pathological processes. Although the small size of the mouse cochlea makes surgery difficult, the methods are sufficiently developed for studying the structural and functional changes in CoBF under normal and pathological conditions., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Objective: To describe an endoscopic perspective of the surgical anatomy of the trigeminal nerve., Methods: Nine adult cadaveric heads were dissected endoscopically., Results: Opening the pterygopalatine fossa is important because many key anatomical structures (V2, pterygopalatine ganglion, vidian nerve) can be identified and traced to other areas of the trigeminal nerve. From the pterygopalatine ganglion, the maxillary nerve and vidian nerve can be identified, and they can be traced to the gasserian ganglion and internal carotid artery. An anteromedial maxillectomy increases the angle of approach from the contralateral nares due to an increase in diameter of the piriform aperture, and provides excellent access to the mandibular nerve, the petrous carotid, and the cochlea., Conclusions: Identification of key anatomical structures in the pterygopalatine fossa can be used to identify other areas of the trigeminal nerve, and an anteromedial maxillectomy is necessary to expose the ipsilateral mandibular nerve and contralateral cranial level of the trigeminal nerve., (Copyright © 2013 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.)

Aim: The aim of this supplement registry was to evaluate the efficacy of the Pycnogenol® in improving cochlear flow and symptoms in a 6-month follow-up for patients with Meniere's disease (MD), tinnitus and cochlear hypoperfusion., Methods: Main signs/symptoms were considered: Spontaneous vertigo, positional vertigo, hearing loss, tinnitus, pressure in the ear, unsteady gait, associated clinical problems, alterations in daily life. All subjects were managed with the best available management (BM); one group used the supplement Pycnogenol (150 mg/day). Cochlear flow and tinnitus were also evaluated. Out of 120 patients incuded in the registry, 55 used Pycnogenol and 52 (controls) were managed only with BM., Results: There was a more significant improvement in all registry items at 3 and 6 months in the Pycnogenol group (P<0.05). The number of lost working days was lower in the Pycnogenol group. At 3 months, 45.4% of subjects using Pycnogenol were completely asymptomatic in comparison with 23.07% of controls. At 6 months 87.3% of the Pycnogenol subjects were asymptomatic compared with 34.6% of controls. Cochlear flow velocity was significantly better (higher flow, higher diastolic component) in the Pycnogenol group (P<0.05). The subjective tinnitus scale decreased in both groups (P<0.05); the decrease was more significant in Pycnogenol subjects (P<0.05) at 3 and 6 months., Conclusion: Symptoms of Meniere's disease, flow at cochlear level and tinnitus improved in Pycnogenol subjects in comparison with best management.

Objectives: To investigate the effects of isoflurane and propofol on mean arterial pressure (MAP), cochlear blood flow (CoBF), distortion-product otoacoustic emission (DPOAE), and the ultrastructure of outer hair cells (OHCs) in guinea pig cochleae., Methods: Forty-eight male guinea pigs were randomly assigned to one of six treatment groups. Groups 1 to 3 were infused (i.v.) with a loading dose of propofol (5 mg/kg) for 5 min and three maintenance doses (10, 20, or 40 mg kg-1·h-1, respectively) for 115 min. Groups 4 to 6 were inhaled with isoflurane at concentrations of 1.15 vol%, 2.30 vol% or 3.45 vol% respectively for 120 min. CoBF and MAP were recorded prior to and at 5 min intervals during drug administration. DPOAE was measured before, immediately after, and 1 h after administration. Following the final DPOAE test, cochleae were examined using scanning electron microscopy., Results: Propofol treatment reduced MAP in a dose-dependent manner. CoBF and DPOAE showed increases at propofol maintenance doses of 10 and 20 mg kg-1·h-1. Inhalation of isoflurane at concentrations of 2.30 vol% and 3.45 vol% reduced MAP and CoBF. DPOAE amplitude increased following inhalation of 1.15 vol% isoflurane, but decreased following inhalations of 2.30 vol% and 3.45 vol%. Cochlear structure was changed following inhalation of either 2.30 vol% or 3.45 vol% isoflurane., Conclusions: Propofol could decrease MAP and increase both CoBF and DPOAE without affecting OHC structure. Inhalation of isoflurane at concentrations >2.30 vol% decreased CoBF and DPOAE, and produced injury to OHCs.

Objective: For diagnostic purposes and a better understanding of the pathophysiology of inner ear hearing disorders it would be of great interest to have parameters available that indicate inner ear hypoxia. In animal studies typical hypoxia-related alterations of the 2f1-f2 distortion product otoacoustic emissions (DPOAE) such as a reversible level decrease and destabilization could be demonstrated. The goal of this study was to investigate whether these hypoxia-associated alterations can also be observed in humans because this might help develop a new diagnostic tool for patients with inner ear disorders., Methods: In 16 volunteers DPOAE levels were continuously measured at first under normal room air conditions, during and after 8.5h of oxygen deprivation (13% O2) and during re-oxygenation. Saturation of oxygen of arterial blood (SaO2) was monitored., Results: The mean SaO2 during the hypoxic interval was 78%. A significant decrease in DPOAE level under hypoxia occurred in five different test persons at one or more frequencies (f2=1, 1.5, 2, 3, and 4kHz). A destabilization of the DPOAE level with considerable fluctuations during hypoxia was observed in nine subjects at one or more frequencies. Furthermore, the so called 'post hypoxia effect' could be observed in five participants., Conclusion: The observations made here have been described similarly in animal studies and seem to be characteristic of metabolic disorders of the cochlea caused by hypoxia. To our knowledge, this is the first study to examine DPOAE level alterations over time in humans under conditions of normobaric hypoxia. If DPOAE destabilization is observed in a clinical setting in patients with certain inner ear hearing disorders hypoxia can be suspected as one underlying pathophysiological cause which might influence treatment decisions., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)

This study was designed to investigate the impact of lead (Pb(2+)) on the auditory system and its molecular mechanisms. Pb(AC)2 was administrated to male SD rats aged 21-22 d for 8 weeks at a dose of 300ppm. Male guinea pigs were also administrated with 50mg/kg Pb(AC)2 two times a week for 8 weeks. The auditory nerve-brainstem evoked responses (ABR) was recorded and the morphological changes of the outer hair cells (OHCs) were observed with Phallodin-FITC staining. In addition, the integrity of the blood-labyrinth barrier was observed by TEM and the expression of tight junction proteins (TJPs) in the cochlear stria vascularis was determined by immunofluorescence. Our results showed that Pb(2+) exposure resulted in increased ABR threshold in both rats and guinea pigs. Abnormal shapes and loss of OHCs were found in the cochlear basilar membrane following the Pb(2+) exposure. TEM study showed that the tight junctions between the endothelial cells and the border cells were lost and disrupted. Down-regulation of the occludin, ZO-1 and claudin-5 in the stria vascularis suggested that the increased permeability of the blood-labyrinth barrier may attribute to the Pb(2+)-induced decrease of TJPs' expression. Additionally, Fe(2+) supplement partly reversed the Pb(2+)-induced hearing loss and down-regulation of TJPs. Taken together, these data indicate that the disruption of blood-labyrinth barrier by down-regulating the expression of TJPs plays a role in the Pb(2+)-induced hearing loss, and Fe(2+) supplement protects the auditory system against Pb(2+)-induced toxicity and may have significant clinical implications., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Objective: To investigate the relationship between IL-1β and TNF-α mRNA and Fas protein expressions and cochlear ischemia reperfusion injury and investigate the protective mechanism of PPTA against cochlear reperfusion injury., Methods: Sixty-four guinea pigs were randomly divided into normal control group, blank control group, ischemia/reperfusion (by clamping the bilateral vertebral artery and right common carotid artery for 1 h) control group, and ischemia/reperfusion with PPTA treatment group. In PPTA group, PPTA was injected via the femoral vein immediately after reperfusion, and ischemia/reperfusion control group received saline injection. In 6 guinea pigs from each group, the cochlear tissues were removed after 24 h of reperfusion for examination of expressions of IL-1β and TNF-α mRNA by real-time PCR, and the rest animals were used for immunohistochemical detection of Fas protein., Results: Compared with those of normal group and blank control group, the expressions of IL-1β and TNF-β mRNA increased significantly after cochlear ischemia/reperfusion (P<0.001), but were lowered significantly by PPTA (P<0.001). Positive expression of Fas protein expression was detected in the Corti organ, spiral ganglion and stria vascularis in ischemia/reperfusion control group with significantly higher IOD values than those of the other 3 groups (P<0.05). The IOD value showed no significant difference between PPTA-treated group, normal control group, and blank control group (P>0.05)., Conclusions: PPTA can suppress the expression of Fas protein and IL-1β and TNF-β mRNAs in the cochlea of guinea pigs with cochlear ischemia/reperfusion. The protective effect of PPTA against cochlear ischemia/reperfusion is mediated probably by inhibition of inflammatory responses and cell apoptosis.

The effects of liposome-encapsulated hemoglobin (LEH), an artificial oxygen carrier, were experimentally investigated in gerbils in the context of alleviation of hearing loss after transient cochlear ischemia. Animals were randomly assigned to receive 2 mL/kg of either LEH (P₅₀O₂=15 mmHg) or saline 1h after the experimental induction of 15 min of ischemia. Sequential recordings of auditory brainstem response (ABR) showed that administration of LEH prevented hearing loss due to cochlear ischemia. The mean ABR threshold at 32 kHz on day 1 was 21 ± 7 dB in the LEH group (n=6) and 45 ± 6 dB in the saline group (n=6). Thereafter, hearing impairment gradually improved up to day 7 in both groups. The animals were then subjected to histological study, which revealed that there was more substantial loss of the inner hair cells, but not the outer hair cells, in the saline group as compared to the LEH group. These results suggest that LEH is an efficient agent with regard to protection against hearing loss and underlying hair cell damager due to ischemic insult., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)

Objective: Exposure to loud noise can impair cochlear microcirculation and cause noise-induced hearing loss (NIHL). TNF-α signaling has been shown to be activated in NIHL and to control spiral modiolar artery vasoconstriction that regulates cochlear microcirculation. It was the aim of this experimental study to analyse the effects of the TNF-α inhibitor etanercept on cochlear microcirculation and hearing threshold shift in NIHL in vivo., Design: After assessment of normacusis using ABR, loud noise (106 dB SPL, 30 minutes) was applied on both ears in guinea pigs. Etanercept was administered systemically after loud noise exposure while control animals received a saline solution. In vivo fluorescence microscopy of strial capillaries was performed after surgical exposure of the cochlea for microcirculatory analysis. ABR measurements were derived from the contralateral ear., Study Sample: Guinea pigs (n = 6, per group)., Results: Compared to controls, cochlear blood flow in strial capillary segments was significantly increased in etanercept-treated animals. Additionally, hearing threshold was preserved in animals receiving the TNF-α inhibitor in contrast to a significant threshold raising in controls., Conclusions: TNF-α inhibition using etanercept improves cochlear microcirculation and protects hearing levels after loud noise exposure and appears as a promising treatment strategy for human NIHL.

Objectives: Tumor necrosis factor alpha (TNF-alpha) is a mediator of inflammation and microcirculation in the cochlea. This study aimed to quantify the effect of a local increase of TNF-alpha and study the effect of its interaction with etanercept on cochlear microcirculation., Methods: Cochlear lateral wall vessels were exposed surgically and assessed by intravital microscopy in guinea pigs in vivo. First, 24 animals were randomly distributed into 4 groups of 6 each. Exposed vessels were superfused repeatedly either with 1 of 3 different concentrations of TNF-alpha (5.0, 0.5, and 0.05 ng/mL) or with placebo (0.9% saline solution). Second, 12 animals were randomly distributed into 2 groups of 6 each. Vessels were pretreated with etanercept (1.0 microg/ mL) or placebo (0.9% saline solution), and then treated by repeated superfusion with TNF-alpha (5.0 ng/mL)., Results: TNF-alpha was shown to be effective in decreasing cochlear blood flow at a dose of 5.0 ng/mL (p < 0.01, analysis of variance on ranks). Lower concentrations or placebo treatment did not lead to significant changes. After pretreatment with etanercept, TNF-alpha at a dose of 5.0 ng/mL no longer led to a change in cochlear blood flow., Conclusions: The decreasing effect that TNF-alpha has on cochlear blood flow is dose-dependent. Etanercept abrogates this effect.

Objective: The application of intratympanic latanoprost (PGF2α analog) has been recently used to alleviate vertigo, disequilibrium and to improve hearing in Meniere's disease patients. However, there is no known report on the effect of topically applied latanoprost on hearing and cochlear hemodynamic parameters including cochlear blood flow (CBF) and vascular conductance. Our goal was to assess the influence of topically applied latanoprost on cochlear blood flow (CBF) and hearing., Materials and Methods: Twenty male Sprague-Dawley rats were randomly divided into the group A, 50 μl of latanoprost (1 ml containing 50 μg, n=10) and group B, 100 μl (1 ml containing 50 μg, n=10). Topical application of latanoprost was performed at the right side, and the left side was applied with phosphate buffered saline (PBS) as a negative control. Five rats at each group were used to measure cochlear blood flow (CBF). And the others at each group were used for hearing test by auditory brainstem response (ABR). After physiological examination, bullas were extracted. The changes of cochlear hair cells were observed by performing the field emission-scanning electron microscopy (FE-SEM)., Results: The CBF of both groups was found to be decreased compared to the PBS applied left side. Significant decrement of CBF was observed in group B compared to the group A. Significant elevation of hearing threshold at high frequencies was observed in both groups compared to the PBS applied group. However, inner and outer hair cells were intact., Conclusion: Topically administered latanoprost decreased the CBF and impaired hearing. Based on our findings, additional studies are required to evaluate the side effects of intratympanic latanoprost before its use in clinical practice., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)

Conclusion: An 18-mer peptide derived from the neurotrophic region of prosaposin (PS-pep) prevents hearing loss and cochlear damage due to transient cochlear ischaemia by activating an anti-apoptotic pathway. PS-pep is a potent candidate molecule for alleviating ischaemia-induced hearing loss., Objective: PS-pep was investigated for its protective effects against ischaemia-induced hearing loss and cochlear damage., Methods: Ischaemia was induced in both cochleae in Mongolian gerbils by pulling the ligatures around both vertebral arteries in an anterior direction using 5 g weights for 15 min. PS-pep was synthesized artificially and administered subcutaneously four times after the induction of transient cochlear ischaemia., Results: An increase in the auditory brainstem response threshold was alleviated in animals treated with 2.0 mg/kg PS-pep. Histological examinations conducted on day 7 showed that the loss of inner hair cells (IHCs) was more prominent than that of outer hair cells. Higher doses of PS-pep significantly alleviated IHC loss. An increase in the anti-apoptotic factor bcl-2 was also noted in the IHCs treated with PS-pep.

Objective: This study was performed to investigate the vascular structures of the cochlea that are potentially vulnerable to mechanical trauma during cochlear implant surgery., Background: Despite improvements in surgical technique and electrode design, residual hearing is lost in a significant percentage of cochlear implant patients. Although a variety of factors may contribute, it is widely believed that mechanical trauma plays an important role. This study focused on the vasculature of scala tympani and its potential susceptibility to injury during implant surgery., Methods: Anatomic study of normal human temporal bones prepared by either conventional cross sectioning or by microdissection for examination by light or scanning electron microscopy., Results: Blood vessels located at or near the perilymphatic surface of scala tympani are predominately of the venous type, and they are situated so as to be at risk for trauma during implantation. Those vessels include veins on the lateral wall and floor of scala tympani, the modiolar wall and the undersurface of the osseous lamina and basilar membrane., Conclusion: Injury or occlusion of blood vessels associated with scala tympani may adversely affect inner ear function, potentially contributing to hearing loss following cochlear implantation.

The integrity of the fluid-blood barrier in the stria vascularis is critical for maintaining inner ear homeostasis, especially for sustaining the endocochlear potential, an essential driving force for hearing function. However, the mechanisms that control intrastrial fluid-blood barrier permeability remain largely unknown. At the cellular level, the intrastrial fluid-blood barrier comprises cochlear microvascular endothelial cells connected to each other by tight junctions (TJs), an underlying basement membrane, and a second line of support consisting of cochlear pericytes and perivascular resident macrophage-type melanocytes. In this study, we use a newly established primary cell culture-based in vitro model to show that endothelial cells, pericytes, and perivascular resident macrophage-type melanocytes interact to control intrastrial fluid-blood barrier permeability. When the endothelial cell monolayer was treated with pericyte--or perivascular resident macrophage-type melanocyte--conditioned media, the permeability of the endothelial cell monolayer was significantly reduced relative to an untreated endothelial cell monolayer. Further study has shown the pericytes and perivascular resident macrophage-type melanocytes to regulate TJ expression in the endothelial cell monolayer. The new cell culture-based in vitro model offers a unique opportunity to obtain information on the organ-specific characteristics of the cochlear blood/tissue barrier. Our finding demonstrates the importance of signaling among pericytes, endothelial cells, and perivascular resident macrophage-type melanocytes to the integrity of the intrastrial fluid-blood barrier.

The auditory system is the most susceptible to damages from blast waves. Blast injuries always lead to varying degrees of hearing impairment. Although a disorder of the cochlear blood flow (CoBF) has been considered to be related to many pathological processes of the auditory system and to contribute to various types of hearing loss, changes in the CoBF induced by blast waves and the relationship between such changes and hearing impairment are undefined. To observe the changes in the cochlear microcirculation after exposure to an explosion blast, investigate the relationship between changes in the CoBF and hearing impairment and subsequently explore the mechanism responsible for the changes in the CoBF, we detected the perfusion of the cochlear microcirculation and hearing threshold shift after exposure to an explosion blast. Then, an N-nitro-L-arginine-methyl ester (L-NAME, NO synthase inhibitor) solution and artificial perilymph were applied to the round window (RW) of the cochlea before the blast exposure, followed by an evaluation of the CoBF and hearing function. The results indicated that the changes in the CoBF were correlated to the strength of the blast wave. The cochlear blood flow significantly increased when the peak value of the blast overpressure was greater than approximately 45 kPa, and there was no significant change in the cochlear blood flow when the peak value of the blast overpressure was less than approximately 35 kPa. Following local administration of the NO synthase inhibitor L-NAME, the increase in the CoBF induced by the blast was inhibited, and this reduction was significantly associated with the hearing threshold.

We aimed to investigate the pathophysiology of diabetes-associated hearing impairment in type 1 diabetes using mice with streptozotocin-induced diabetes (C57BL/6J; male). Hearing function was evaluated 1, 3, and 5 months after induction of diabetes (five diabetic and five control animals per time point) using auditory-evoked brain stem responses (ABRs). Mice (four diabetic and four control) were exposed to loud noise (105 dB) 5 months after induction of diabetes. ABRs were measured before and after noise exposure. Cochlear blood flows were measured by laser-Doppler flowmeter. Spiral ganglion cells (SGCs) were counted. Vessel endothelial cells were observed by CD31 immunostaining. Chronologic changes in the ABR threshold shift were not significantly different between the diabetic and control groups. However, vessel walls in the modiolus of the cochleae were significantly thicker in the diabetic group than the control group. Additionally, recovery from noise-induced injury was significantly impaired in diabetic mice. Reduced cochlea blood flows and SGC loss were observed in diabetic mice cochleae after noise exposure. Our data suggest that diabetic cochleae are more susceptible than controls to loud noise exposure, and decreased cochlear blood flow due to sclerosis of the vessels and consequent loss of SGCs are possible mechanisms of hearing impairment in diabetic patients.

Reduced cochlear blood flow (CoBF) is a main contributor to hearing loss. Studying CoBF has remained a challenge due to the lack of available tools. Doppler optical microangiography (DOMAG), a method to quantify single-vessel absolute blood flow, and laser Doppler flowmetry (LDF), a method for measuring the relative blood flow within a large volume of tissue, were used for determining the changes in CoBF due to systemic hypoxia in mice. DOMAG determined the change in blood flow in the apical turn (AT) with single-vessel resolution, while LDF averaged the change in the blood flow within a large volume of the cochlea (hemisphere with ∼1 to 1.5 mm radius). Hypoxia was induced by decreasing the concentration of oxygen-inspired gas, so that the oxygen saturation was reduced from >95% to ∼80%. DOMAG determined that during hypoxia the blood flow in two areas of the AT near and far from the helicotrema were increased and decreased, respectively. The LDF detected a decrease in blood flow within a larger volume of the cochlea (several turns averaged together). Therefore, the use of DOMAG as a tool for studying cochlear blood flow due to its ability to determine absolute flow values with single-vessel resolution was proposed.

Background and Aims: Disturbances of microcirculation and hemorheological changes in the inner ear are the results of noise-induced hearing loss (NIHL). Both the disturbances of microcirculation and hemorheological changes are the etiologies of NIHL development, but they are also the results. Although previous reports that inhalation of high concentration of CO(2) may increase cochlear blood flow (CoBF), the effects of carbogen on the cochlear microcirculation and NIHL remain unclear., Methods: Changes induced by noise, carbogen and pure oxygen within the cochlear lateral wall microvasculature and in hearing thresholds were observed in guinea pigs using intravital microscopy and the auditory brainstem response. At the same time, arterial oxygen saturation and morphologic changes of cochlear hair cells were observed., Results: Carbogen inhalation increased vessel diameters and blood flow velocities. Hearing thresholds elevation in the carbogen group was smaller than those in the control and oxygen group (p <0.05). Carbogen inhalation produced a trend toward less threshold shift after noise exposure, which reached statistical significance after day 3 (p <0.01). Respiratory acidosis was not found in our study. The segmented basal membranes of Corti in three groups indicated that no losses or discorders of hair cells were found., Conclusions: Carbogen inhalation can preserve hearing in animal models after acute acoustic trauma., (Copyright © 2012 IMSS. All rights reserved.)

Objective: This article is reporting a method for establishment primary cultures of vascular smooth muscle cells (VSMCs) from the spiral modiolar artery (SMA)., Methods: VSMCs were isolated from guinea pig SMAs. Arterial tissues were cut and enzymatically digested at 37 °C for 20 min using a 0.1% trypsin solution. After digestion, tissue fragments were explanted in a 35-mm culture dish. Contaminated fibroblasts were separated from VSMCs because of their different adhesion abilities. The cells migrated from the explants within 7-10 days and grew to confluence in approximately 4 weeks., Results: We obtained pure and viable VSMCs from the confluent third passage. The morphological and immunofluorescence analyses demonstrated a "hill-and-valley" growth pattern that is characteristics of VSMCs, and the expression of cell type-specific markers (α-smooth muscle actin and myosin), respectively. The change of intracellular calcium concentration induced by angiotensin II and CaCl(2) showed that the VSMCs had good cell viability., Conclusion: We obtained purified VSMCs using this method. All cell cultures expressed smooth muscle markers (α-SM actin, and myosin) and were negative for vWF. This article provides a simple method to obtain VSMCs for in vitro studies of physiology and pathophysiology in the circulation disturbances of the inner ear. In addition, VSMCs are regarded to be an excellent model to evaluate drugs in vitro., (Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.)

Background: Presbycusis is the most common degenerative otologic condition. New research is pointing toward vascular changes within the cochlea with age. Vascular endothelial growth factor (VEGF) and its receptors, Flt-1 and Flk-1, are important regulators of angiogenesis., Objective: The aim of this study was to characterize the hearing, VEGF expression, and vasculature of young and old Swiss Webster (SW) mice., Methods: Young (4 weeks, n = 14) and aged (32-36 weeks; n = 14) SW mice were used. Hearing was evaluated using the auditory brainstem response. Changes in VEGF, Flt-1, and Flk-1 expression and histology were evaluated by immunohistochemistry and real-time polymerase chain reaction (quantitative PCR)., Results: Aged SW mice demonstrated clinically stable hearing with age with mean hearing thresholds dropping 5.7, 4.2, 6.5, and 10.9 dB peSPL with age at 4, 8, 16, and 32 kHz pure-tone stimuli, respectively. Immunohistochemistry showed the presence of VEGF, Flt-1, and Flk-1 in the stria vascularis, spiral ganglion, and organ of Corti. Strong expression was found within the hair cells and the stria vascularis. Immunohistochemistry and qPCR demonstrated no difference in expression levels between age groups or between apical and basal turns of the cochlea. Microscopy demonstrated no difference in the number or density of stria vascularis vessels between age groups., Conclusions: We describe a mouse model of stable hearing with aging. Stria vascularis vasculature and expression of VEGF, Flt-1, and Flk-1 do not change with age, and there appears to be no apical to basal differential expression. These results provide valuable normalized data to compare VEGF expression and vasculature patterns to other mouse strains.

Objective: Impairment of microcirculation is a possible cause of sudden sensorineural hearing loss (SSNHL). Fibrinogen is known as a risk factor for both microvascular dysfunction and SSNHL. Therefore, the aim of this study was to investigate the effect of elevated serum levels of fibrinogen on cochlear blood flow and hearing function in vivo., Design: One group of guinea pigs received two consecutive injections of 100 mg fibrinogen while a control group received equimolar doses of albumin. Measurements of cochlear microcirculation by intravital microscopy and of hearing thresholds by auditory brainstem response (ABR) recordings were carried out before, after first and after second injection., Study Sample: Ten healthy guinea pigs were randomly assigned to a treatment group or a control group of five animals each., Results: Serum fibrinogen levels were elevated after the first and second injections of fibrinogen compared to basal values and control group respectively. Increasing levels of fibrinogen were paralleled by decreasing cochlear blood flow as well as increasing hearing thresholds. Hearing threshold correlated negatively with cochlear blood flow., Conclusions: The effect of microcirculatory impairment on hearing function could be explained by a malfunction of the cochlear amplifier. Further investigation is needed to quantify cochlear potentials under elevated serum fibrinogen levels.

Objective: A variety of inner ear disease is related to microcirculation disturbance of inner ear, but smooth muscle cells (SMC) and endothelial cells (EC) of the spiral modiolar artery (SMA), which is the main blood supply to the inner ear, physiological feature is not very clear., Methods: In this study, two-intracellular microelectrode recording technique and cell staining techniques to study the SMC and EC resting membrane potential characteristics and communication links between cells of SMA., Results: Study found that SMC and EC have high and low resting membrane potential state, two state of the resting membrane potential of cells to ACh and high K+ response is completely different. The different types of cells, EC-EC, SMC-SMC and SMC-EC, can simultaneously record by two-microelectrode, two cell resting membrane potential can also be a double-high RP, double-low RP and one high- and one low- RP. Experiment recorded in one high- and one low- RP are the SMC-EC types, and ECs initial membrane potential are high potential, SMCs membrane potential are low initial potential. The double-high and double-low RP can be SMC-SMC or EC-EC or SMC-EC types., Conclusion: The results show that SMC and EC in the 0.3 - 0.5 mm range, similar type of cells have very good communication, can function together to maintain good and consistent, heterogeneous cell performance is more different.

Objective: The effect of cochlear blood flow (CBF) on speech perception ability in cochlear implant (CI) users has not been reported. We investigated various factors influencing speech perception including CBF in CI users., Patients: Eighty-two patients who received CI surgery at an academic hospital., Methods: CBF was measured during CI surgery using laser Doppler flowmetry. The speech perception level was measured after a sufficient interval after CI surgery. Multivariate analysis was used to evaluate the influences of age, duration of deafness, sex, cause of deafness, and CBF on the speech perception level., Results: CBF decreased significantly with age but was not related to the speech perception level. In patients with congenital hearing loss, the speech perception level was significantly worse in children who received a CI at 3 years of age than in those who received a CI at 2 years of age or younger. Duration of deafness before CI surgery had deteriorative effects on the speech perception level., Conclusion: CBF may be associated with progression of hearing loss. However, measuring CBF during CI surgery is not useful for predicting postoperative speech perception.

Background: Hearing loss in Paget's disease of bone (PDB) is typically mixed and bilateral. Although different mechanisms have been proposed, the pathophysiology of hearing impairment remains unclear., Objective: The purpose of this study is to describe the histopathologic findings of temporal bones in patients with PDB and elucidate possible pathologic mechanisms related to hearing impairment., Methods: This is an archival human temporal bone study of 8 subjects diagnosed with Paget's disease from the temporal bone collection of the UCL Ear Institute., Results: A fractured stapes footplate was observed in 1 temporal bone and stapes footplate fixation in 2 other specimens. Obliteration of Cotugno's canal by extensive bone remodeling was observed in 78% of temporal bones. An intracochlear vestibular schwannoma was observed in 1 specimen (previously reported in the literature). Other findings include microfissures and microfractures of the otic capsule, bleeding in the scalae, strial atrophy, and cystic lesions in the spiral ligament., Conclusion: This study is the first to report a fractured stapes footplate, as a causative lesion of conductive hearing loss in PDB. Extensive bone remodeling around Cotugno canal also was a frequent finding, not reported before in the literature. We hypothesize that sensorineural hearing loss in patients with PDB of the temporal bone may, in some cases, be attributed to obliteration of Cotugno's canal by remodeling pagetoid bone, thus obstructing the venous drainage of the cochlea, with a subsequent effect on the function of stria vascularis and spiral ligament. This seems to be consistent with experimental studies in animals.

An impaired cochlear perfusion seems to be an important etiopathogenetic event in idiopathic sudden sensorineural hearing loss (ISSNHL). Recently, oxidative stress has been proposed as risk factors of microvascular damage. This observational study aimed to evaluate the possible role of oxidative stress in ISSNHL. In thirty-nine ISSNHL patients and seventy healthy subjects serum reactive oxygen species concentrations (ROS) and total antioxidant capacity (TAC) were measured by spectrophotometric methods on F.R.E.E. analyzer (Diacron International, Italy). Moreover, a global oxidative stress index (Oxidative-INDEX), reflecting both oxidative and antioxidant counterparts, was also calculated. 25/39 patients showed oxidative stress due to ROS levels significantly higher than controls (348.2 ± 84.8 vs. 306.75 ± 46.7 UCarr; p = 0.001). The Oxidative-INDEX was significantly higher in patients than in controls (0.75 ± 2.4 vs. -0.0007 ± 1.28 AU, p = 0.03). As oxidative stress is a key determinant in endothelial dysfunction, our findings could suggest vascular impairment involvement in ISSNHL etiopathogenesis.

More than 29 million adults in the United States have been diagnosed with hearing loss. Interestingly, elevated homocysteine (Hcy) levels, known as hyperhomocysteinemia (HHcy), are also associated with impaired hearing. However, the associated mechanism remains obscure. The collagen receptor such as discoidin domain receptor 1 and matrix metalloproteinase (MMP) play a significant role in inner ear structure and function. We hypothesize that HHcy increases hearing thresholds by compromise in inner ear vasculature resulted from impaired Hcy metabolism, increased oxidative stress, collagen IVa and collagen Ia turnover. The treatment with folic acid (FA) protects elevated hearing thresholds and prevents reduction in vessel density by lowering abundant collagen deposition and oxidative stress in inner ear. To test this hypothesis we employed 8 weeks old male wild type (WT), cystathionine-beta-synthase heterozygote knockout (CBS+/-) mice, WT + FA (0.0057 μg/g/day, equivalent to a 400 μg/70 kg/day human dose in drinking water); and CBS(+/-) +FA. The mice were treated for four weeks. The hearing thresholds were determined by recording the auditory brainstem responses. Integrity of vessels was analyzed by perfusion of horseradish peroxidase (HRP) tracer. Endothelial permeability was assessed, which indicated restoration of HRP leakage by FA treatment. A total Hcy level was increased in stria vascularis (SV) and spiral ligament (SL) of CBS+/- mice which was lowered by FA. Interestingly, FA treatment lowered Col IVa Immunostaining by affecting its turnover. The levels of MMP-2, -9, methylenetetrahydrofolate reductase (MTHFR) and cystathione gamma lyase (CSE) were measured by Western blot analysis. The oxidative stress was high in SV and SL of CBS+/- compared to WT however the treatment with FA lowered oxidative stress in CBS+/- mice. These data suggested that hearing loss in CBS+/- mice was primarily due to leakage in inner ear circulation, also partly by induced collagen imbalance, increase in Hcy and oxidative stress in inner ear., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Measuring the abundance of many proteins over a broad dynamic range requires accurate quantitation. We show empirically that, in MS experiments, relative quantitation using summed dissociation-product ion-current intensities is accurate, albeit variable from protein to protein, and outperforms spectral counting. By applying intensities to quantify proteins in two complex but related tissues, chick auditory and vestibular sensory epithelia, we find that glycolytic enzymes are enriched threefold in auditory epithelia, whereas enzymes responsible for oxidative phosphorylation are increased at least fourfold in vestibular epithelia. This striking difference in relative use of the two ATP-production pathways likely reflects the isolation of the auditory epithelium from its blood supply, necessary to prevent heartbeat-induced mechanical disruptions. The global view of protein expression afforded by label-free quantitation with a wide dynamic range reveals molecular specialization at a tissue or cellular level.

A synchronized dual-wavelength laser speckle contrast imaging (DWLSCI) system and a Doppler optical microangiography (DOMAG) system was developed to determine several ischemic parameters in the cochlea due to a systemic hypoxic challenge. DWLSCI can obtain two-dimensional data, and was used to determine the relative changes in cochlear blood flow, and change in the concentrations of oxyhemoglobin (HbO), deoxyhemoglobin (Hb) and total hemoglobin (HbT) in mice. DOMAG can obtain three-dimensional data, and was used to determine the changes in cochlear blood flow with single vessel resolution. It was demonstrated that during a hypoxic challenge there was an increase in the concentrations of Hb, a decrease in the concentrations of HbO and cochlear blood flow, and a slight decrease in the concentration of HbT. Also, the rate of change in the concentrations of Hb and HbO was quantified during and after the hypoxic challenge. The ability to simultaneously measure these ischemic parameters with high spatio-temporal resolution will allow the detailed quantitative analysis of several hearing disorders, and will be useful for diagnosing and developing treatments.

Introduction: Inner ear decompression sickness (IEDCS) has become more frequently reported in recreational diving., Methods: We examined 34 divers after IEDCS and analyzed their dive profiles, pattern of symptoms, time of symptom onset and the association with a right-to left shunt (r/l shunt)., Results: Four divers used mixed gas and were excluded from the analysis. Of the remaining 30 divers, 25 presented with isolated IEDCS alone, while five divers had additional skin and neurological symptoms. All divers presented with vertigo (100%), and 12 divers reported additional hearing loss (40%). All symptoms occurred within 120 minutes (median 30 minutes) of ascent. Twenty-two of 30 divers (73.3%) showed a r/l shunt., Conclusion: A possible explanation for the frequent association of a r/l shunt and the dominance of vestibular rather than cochlear symptoms could be attributed to the different blood supply of the inner ear structures and the different size of the labyrinthine compartments. The cochlea has a blood supply up to four times higher than the vestibular part of the inner ear, whereas the vestibular fluid space is 30% larger. The higher prevalence of symptoms referrable to the less well-perfused vestibular organ provides further evidence that persistent local inert gas supersaturation may cause growth of incoming arterial bubbles and may therefore be an important pathophysiological factor in IEDCS.

Hearing impairment, although uncommon, may occur in patients with a vertebrobasilar artery occlusion disease. The pathogenesis may be an ischemic lesion involving the auditory pathways in the pons and midbrain, the cochlear nucleus, cochlear nerve or the cochlea. The AICA and IAA are the main arteries that supply the peripheral audiovestibular structures of the inner ear and central audiovestibular pathways of the middle cerebellar peduncle and lateral pons., (Copyright © 2012 S. Karger AG, Basel.)

The spiral modiolar artery supplies blood and essential nutrients to the cochlea. Our previous functional study indicates the α(1A)-adrenergic receptor subtype mediates vasoconstriction of the gerbil spiral modiolar artery. Although the gerbil cochlea is often used as a model in hearing research, the molecular and pharmacological characteristics of the cloned gerbil α(1a)-adrenergic receptor have not been determined. Thus we cloned, expressed and characterized the gerbil α(1a)-adrenergic receptor and then compared its molecular and pharmacological properties to those of other mammalian α(1a)-adrenergic receptors. The cDNA clone contained 1404 nucleotides, which encoded a 467 amino acid peptide with a deduced sequence having 96.8, 96.4 and 91.6% identity to rat, mouse and human α(1a)-receptors, respectively. We transiently transfected the α(1a)-adrenergic receptor into COS-1 cells and determined its pharmacological characteristics by [(3)H]prazosin binding. Unlabeled prazosin had a K(i) of 0.89±0.1nM. The α(1A)-adrenergic receptor-selective antagonists, 5-methylurapidil and WB-4101, bound with high affinity and had K(i) values of 4.9±1 and 1.0±0.1nM, respectively. BMY-7378, an α(1D)-adrenergic receptor-selective antagonist, bound with low affinity (260±60nM). The 91.6% amino acid sequence identity and K(i)s of the cloned gerbil α(1a)-adrenergic receptor are similar to those of the human α(1a)-adrenergic receptor clone. These results show that the gerbil α(1a)-adrenergic receptor is representative of the human α(1a)-adrenergic receptor, lending validity to the use of the gerbil spiral modiolar artery as a model in studies of vascular disorders of the cochlea., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Objective: AM-111, a cell-permeable peptide inhibitor of c-Jun N-terminal kinase, was investigated for its protective effects against ischemic damage of the cochlea in gerbils., Methods: Transient cochlear ischemia was introduced in animals by occluding the bilateral vertebral arteries for l5 minutes. Then, 10 μl of AM-111 at a concentration of l, 10, or 100 μM in hyaluronic acid gel formulation was applied onto the round window 30 minutes after the insult. Gel without active substance was used in a control group. Treatment effects were evaluated by auditory brainstem response (ABR) and histology of the inner ear., Results: In controls, transient cochlear ischemia caused a 25.0 ± 5.0 dB increase in the ABR threshold at 8 kHz and a decrease of 13.3 ± 2.3% in inner hair cells at the basal turn on Day 7. Ischemic damage was mild at 2 and 4 kHz. When the animals were treated with AM-111 at 100 μM, cochlear damage was significantly reduced: the increase in ABR threshold was 3.3 ± 2.4 dB at 8 kHz, and the inner hair cell loss was 3.1 ± 0.6% at the basal turn on Day 7. The effects of AM-111 were concentration dependent: 100 μM was more effective than 1 or 10 μM., Conclusion: Direct application of AM-111 in gel formulation on the round window was effective in preventing acute hearing loss because of transient cochlear ischemia.

Normal blood supply to the cochlea is critically important for establishing the endocochlear potential and sustaining production of endolymph. Abnormal cochlear microcirculation has long been considered an etiologic factor in noise-induced hearing loss, age-related hearing loss (presbycusis), sudden hearing loss or vestibular function, and Meniere's disease. Knowledge of the mechanisms underlying the pathophysiology of cochlear microcirculation is of fundamental clinical importance. A better understanding of cochlear blood flow (CoBF) will enable more effective management of hearing disorders resulting from aberrant blood flow. This review focuses on recent discoveries and findings related to the physiopathology of the cochlear microvasculature., (Published by Elsevier B.V.)

Transduction of sound in the inner ear demands tight control over delivery of oxygen and glucose. However, the mechanisms underlying the control of regional blood flow are not yet fully understood. In this study, we report a novel local control mechanism that regulates cochlear blood flow to the stria vascularis, a high energy-consuming region of the inner ear. We found that extracellular lactate had a vasodilatory effect on the capillaries of the spiral ligament under both in vitro and in vivo conditions. The lactate, acting through monocarboxylate transporter 1 (MCT1), initiated neuronal nitric oxide (NO) synthase (nNOS) and catalyzed production of NO for the vasodilation. Blocking MCT1 with the MCT blocker, α-cyano-4-hydroxycinnamate (CHC), or a suppressing NO production with either the nonspecific inhibitor of NO synthase, N(G)-nitro-L-arginine methyl ester (L-NAME), or either of two selective nNOS inhibitors, 3-bromo-7-nitroindazole or (4S)-N-(4-amino-5[aminoethyl]aminopentyl)-N'-nitroguanidine (TFA), totally abolished the lactate-induced vasodilation. Pretreatment with the selective endothelial NO synthase inhibitor, L-N(5)-(1-iminoethyl)ornithine (L-NIO), eliminated the inhibition of lactate-induced vessel dilation. With immunohistochemical labeling, we found the expression of MCT1 and nNOS in capillary-coupled type V fibrocytes. The data suggest that type V fibrocytes are the source of the lactate-induced NO. Cochlear microvessel tone, regulated by lactate, is mediated by an NO-signaled coupling of fibrocytes and capillaries.

Aim: Patients with tinnitus constitute a very large group without a real, specific therapeutic solution. With noninvasive, color duplex it is possible to measure flow in the cochlear artery and to follow duplex flow changes due to treatments in most patients. The aim of this preliminary evaluation was to study flow variations in patients with "mild-to-moderate" tinnitus, possibly associated to cochlear hypo-perfusion, after administration of Acustop (used as a food supplement). The aim was to improve cochlear flow decreasing the level of tinnitus., Methods: Patients with "mild-to-moderate", "idiopathic", monolateral tinnitus, present for at least 4 weeks were included; no vertigo or important hearing loss had been observed. The origin of tinnitus had been sudden (hours or days). The tinnitus was associated to a decrease in cochlear flow measured by color Duplex at the affected ear. A group of 42 patients was evaluated; 25 used Acustop; there were 17 controls (follow-up only). Groups were comparable for their clinical problem and other details. The average duration of treatment was 4 weeks., Results: No side effects were observed and no drop-outs were recorded. Flow velocity at the level of the affected inner ear was significantly lower (both the diastolic and systolic components; P<0.05) in comparison with the other ear. This was considered an indication of the vascular origin of the tinnitus. With Acustop treatment there was a significant improvement in systolic (P<0.05) and diastolic flow velocity (P<0.05). The increase in flow velocity was not significant in controls. An analogue scale line was used to measure symptoms in the Acustop group: it was 8.2;2 at inclusion; it decreased to 3.1;1.5 at 4 weeks (P<0.05). The score was 8.4;2 in controls at inclusion; at 4 weeks the score was 7.1;2.2 (not significant). Tinnitus scale: the value at inclusion of the tinnitus scale in the Acustop group a was 8.5;1.1 versus 8.3;1.2 in controls. After 4 weeks the score was 3.1;1.1 (P<0.05) in the Acustop group vs 7.2 in controls; the difference between the two groups was significant; P<0.025)., Conclusion: In conclusion, these results suggest that in selected patients with tinnitus and altered inner ear perfusion Acustop appears to be effective in relieving tinnitus possibly by improving cochlear flow. More studies should be planned to evaluate better the potential applications of Acustop in this very interesting field. This clinical problem affects a large number of patients, without a real therapeutic solution at the moment, decreasing their quality of life and their performing abilities.

Objective: Recent findings support the crucial role of microcirculatory disturbance and ischemia for hearing impairment especially after noise-induced hearing loss (NIHL). The aim of this study was to establish an animal model for in vivo analysis of cochlear microcirculation and hearing function after a loud noise to allow precise measurements of both parameters in vivo., Study Design: Randomized controlled trial. Setting. Animal study. Subjects and Methods. After assessment of normacusis (0 minutes) using evoked auditory brainstem responses (ABRs), noise (106-dB sound pressure level [SPL]) was applied to both ears in 6 guinea pigs for 30 minutes while unexposed animals served as controls. In vivo fluorescence microscopy of the stria vascularis capillaries was performed after surgical exposure of 1 cochlea. ABR measurements were derived from the contralateral ear., Results: After noise exposure, red blood cell velocity was reduced significantly by 24.3% (120 minutes) and further decreased to 44.5% at the end of the observation (210 minutes) in contrast to stable control measurements. Vessel diameters were not affected in both groups. A gradual decrease of segmental blood flow became significant (38.1%) after 150 minutes compared with controls. Hearing thresholds shifted significantly from 20.0 ± 5.5 dB SPL (0 minutes) to 32.5 ± 4.2 dB SPL (60 minutes) only in animals exposed to loud noise., Conclusion: With regard to novel treatments targeting the stria vascularis in NIHL, this standardized model allows us to analyze in detail cochlear microcirculation and hearing function in vivo.

Background: Calcium sparks are ryanodine receptor mediated transient calcium signals that have been shown to hyperpolarize the membrane potential by activating large conductance calcium activated potassium (BK) channels in vascular smooth muscle cells. Along with voltage-dependent calcium channels, they form a signaling unit that has a vasodilatory influence on vascular diameter and regulation of myogenic tone. The existence and role of calcium sparks has hitherto been unexplored in the spiral modiolar artery, the end artery that controls blood flow to the cochlea. The goal of the present study was to determine the presence and properties of calcium sparks in the intact gerbil spiral modiolar artery., Results: Calcium sparks were recorded from smooth muscle cells of intact arteries loaded with fluo-4 AM. Calcium sparks occurred with a frequency of 2.6 Hz, a rise time of 17 ms and a time to half-decay of 20 ms. Ryanodine reduced spark frequency within 3 min from 2.6 to 0.6 Hz. Caffeine (1 mM) increased spark frequency from 2.3 to 3.3 Hz and prolonged rise and half-decay times from 17 to 19 ms and from 20 to 23 ms, respectively. Elevation of potassium (3.6 to 37.5 mM), presumably via depolarization, increased spark frequency from 2.4 to 3.2 Hz. Neither ryanodine nor depolarization changed rise or decay times., Conclusions: This is the first characterization of calcium sparks in smooth muscle cells of the spiral modiolar artery. The results suggest that calcium sparks may regulate the diameter of the spiral modiolar artery and cochlear blood flow.

Novel thiazolidinedione analogues as 15-hydroxyprostaglandin dehydrogenase (15-PGDH) inhibitors were synthesized. Compounds 2, 3, and 4 exhibited IC(50) of 25, 8, and 19 nM, respectively. They also significantly increased levels of PGE(2) in A549 cells. To assess the influence of 15-PGDH inhibitor on cochlear blood flow (CBF), 2 was applied intravenously to guinea pigs. It increased their CBFs. Scratch wounds were also analyzed in confluent monolayers of HaCaT cells. Cells exposed to 4 showed significantly improved wound healing with respect to a control.

Objective: There are no reports on the therapeutic effect of Ginkgo biloba extract (GBE) on otitis media-induced labyrinthitis. The present study examined whether GBE can protect against cochlear damage induced by intratympanic instillation of lipopolysaccharide (LPS)-induced labyrinthitis., Materials and Methods: Experiments were performed in 20 healthy young male guinea pigs. The control group (n=10) received an intratympanic instillation of LPS (20 μl, 3mg/ml). The experimental group (n=10) received intratympanic instillation of LPS immediately after instillation of GBE (10mg/kg) and then experimental groups received GBE (100mg/kg) by intraperitoneal injection every day for 3 days. Instillation of LPS or LPS immediately after GBE was done in the right ear; the untreated left ear was considered normal. Physiological and morphological changes were evaluated., Results: Statistical analysis of treatment of GBE revealed significantly less hearing loss than LPS group (p<0.05). The ratio of the value of cochlear blood flow (CBF) compared to untreated left side was significantly higher in the GBE treated group than in the LPS-treated group (p<0.05). This result indicated the recovery of CBF in GBE treated group compared to LPS treated group. In the LPS group, scanning electron microscopy revealed hair cell damage with edema. Missing stereocilia in the third layer of the outer hair cell was revealed. However, both the inner hair cells and the outer hair cells had normal appearance in the GBE group. LPS group showed that cochlear Evans blue extravasation was increased strongly in the stria vascularis, spiral limbus, and in the spiral ligament compared with the GBE treated group., Conclusion: GBE significantly minimizes cochlear damage against LPS-induced otitis media with labyrinthitis in a guinea pig model. GBE has potential as an adjunctive therapy to antibiotics in the treatment of acute otitis media with complicated labyrinthitis., (Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.)

Aminoglycoside ototoxicity is a common cause of drug-induced hearing loss. Toxicity is dose related, but some patients may still develop hearing loss even under safe dosage. Apart for genetic idiosyncrasy, indirect evidences imply that ischemia may increase the aminoglycoside ototoxic sensitivity because common clinical situations associated with cochlear ischemia such as noise, sepsis, and shock are known to augment the development of aminoglycoside ototoxicity. At present, a direct interaction of cochlear ischemia and aminoglycoside ototoxicity is still lacking. This study demonstrated a direct evidence of increased gentamicin (GM) ototoxic sensitivity in chronic guinea pig models of transient cochlear ischemia. No permanent auditory changes were observed after a single dose of GM (125 mg/kg) or after transient cochlear ischemia for 30 min. Persistent and significant auditory threshold shift was detected when GM was given after transient cochlear ischemia. Cochlear hair cells and spiral ganglion neurons are the major regions affected. Apoptosis contributes to hair cell death during acute interaction of ischemia and GM ototoxicity. Increased apoptotic cell death was also depicted when GM crossreacted with hypoxia in vitro, using cochlear cell lines. Generation of reactive oxygen species, loss of mitochondrial membrane potential, calcium release, and caspase-dependent apoptotic cell death were shown during the interaction of hypoxia and GM ototoxicity in vitro. This synergistic ototoxicity may be critical to aminoglycoside-induced hearing loss in clinical scenarios. The results should improve our understanding of the interacting mechanism and potential preventive strategy to aminoglycoside ototoxicity.

Presbycusis is the most common cause of hearing loss in aged subjects, reducing individual's communicative skills. Age related hearing loss can be defined as a progressive, bilateral, symmetrical hearing loss due to age related degeneration and it can be considered a multifactorial complex disorder, with both environmental and genetic factors contributing to the aetiology of the disease. The decline in hearing sensitivity caused by ageing is related to the damage at different levels of the auditory system (central and peripheral). Histologically, the aged cochlea shows degeneration of the stria vascularis, the sensorineural epithelium, and neurons of the central auditory pathways. The mechanisms responsible for age-associated hearing loss are still incompletely characterized. This work aims to give a broad overview of the scientific findings related to presbycusis, focusing mainly on experimental studies in animal models., (Copyright © 2011 Elsevier Inc. All rights reserved.)