Effects of inflammatory mediators on middle ear pathology and on inner ear function

Treatment of Acute Otitis Media with Inner Ear Involvement in Adults

Inner ear involvement (IED) is a rare local complication of the very common acute otitis media (AOM). The most beneficial treatment for IED remains a matter of debate. The aim of this study is to analyze different treatment modalities based on hearing outcomes to contribute to the discussion of therapy for IED in AOM. This retrospective study includes 112 adult patients diagnosed with AOM with IED between 2000 and 2020. Patients either received conservative (systemic antibiotic and systemic steroid therapy), interventional (conservative plus myringotomy and tympanic tube) or operative (interventional plus antrotomy) treatment. Pre- and post-treatment pure tone audiometry was performed. The hearing outcome was compared, and hearing recovery was analyzed based on modified Siegel's criteria. The pre-treatment pure tone average (PTA) was significantly (p < 0.05) higher in the operative group than in the other groups. All treatment modalities led to a significant hearing improvement (p < 0.001). The pre- and post-treatment hearing loss was predominantly observed in high frequencies 2-4 kHz. The operative group showed the highest rate of complete hearing recovery. While all treatment modalities led to a significant improvement in hearing, the operative group showed the most beneficial hearing results in patients with high pre-treatment hearing loss. It remains to be shown if the findings in patients with high pre-treatment hearing loss can be generalized to patients with mild or moderate pre-treatment hearing loss.

Evaluation of the Presence of Sensorineural Hearing Loss and the Relationship With Intraoperative Findings in Cholesteatoma

We investigated whether cholesteatoma is associated with sensorineural hearing loss (SNHL) and the effects of a lateral semicircular canal (LSCC) fistula, destruction of stapes, localization of cholesteatoma, and air-bone gap (ABG) size on SNHL. The charts of 159 patients who had received surgery for unilateral cholesteatoma were examined retrospectively. In all patients, air conduction and bone conduction (BC) thresholds in both ears were measured at 500, 1000, 2000, and 4000 Hz. Differences in BC thresholds between ears with cholesteatoma and contralateral ears were calculated. Demographics, localization of cholesteatoma, presence of LSCC fistula, condition of stapes, and ABG size on the affected ear were evaluated. There were significantly greater BC thresholds in ears with cholesteatoma than in normal ears for each frequency. Comparing the average BC differences at the different cholesteatoma locations, there were significant differences between the tympanic cavity + all mastoid cell group and attic, attic + antrum, and tympanic cavity + antrum groups. The BC differences at 4000 Hz were significantly high in patients with LSCC fistula. There were no significant relationships between the condition of the stapes and BC differences at any frequencies. There were significant correlations between average ABG and BC threshold differences at all frequencies. A significant relationship was found between cholesteatoma and SNHL. Patients with advanced cholesteatoma had significantly higher levels of SNHL. The BC threshold differences increased with increases in the ABG.

An Integrative Model Accounting for the Symptom Cluster Triggered After an Acoustic Shock

Acoustic shocks and traumas sometimes result in a cluster of debilitating symptoms, including tinnitus, hyperacusis, ear fullness and tension, dizziness, and pain in and outside the ear. The mechanisms underlying this large variety of symptoms remain elusive. In this article, we elaborate on the hypothesis that the tensor tympani muscle (TTM), the trigeminal nerve (TGN), and the trigeminal cervical complex (TCC) play a central role in generating these symptoms. We argue that TTM overuse (due to the acoustic shock), TTM overload (due to muscle tension), and ultimately, TTM injury (due to hypoxia and "energy crisis") lead to inflammation, thereby activating the TGN, TCC, and cortex. The TCC is a crossroad structure integrating sensory inputs coming from the head-neck complex (including the middle ear) and projecting back to it. The multimodal integration of the TCC may then account for referred pain outside the ear when the middle ear is inflamed and activates the TGN. We believe that our model proposes a synthetic and explanatory framework to explain the phenomena occurring postacoustic shock and potentially also after other nonauditory causes. Indeed, due to the bidirectional properties of the TCC, musculoskeletal disorders in the region of the head-neck complex, including neck injury due to whiplash or temporomandibular disorders, may impact the middle ear, thereby leading to otic symptoms. This previously unavailable model type is experimentally testable and must be taken as a starting point for identifying the mechanisms responsible for this particular subtype of tinnitus and its associated symptoms.

Safety of transtympanic application of probiotics in a chinchilla animal model

Background

Chronic suppurative otitis media can be recalcitrant and difficult to treat, particularly with the increasing occurrence of antibiotic resistance. Lactobacillus plantarum is a probiotic that has been shown to decrease S. aureus and P. aeruginosa growth in wounds, making it a good candidate for the treatment of chronic suppurative otitis media. However, before it can be applied in the ear, its ototoxicity potential must be evaluated.

Methods

A prospective controlled trial was conducted in a chinchilla animal model at the Animal care research facilities of the Montreal Children’s Hospital Research Institute to determine whether Lactobacillus plantarum is ototoxic when applied transtympanically. Ten chinchillas each had one ear randomly assigned to receive 10⁹ CFU/mL of Lactobacillus plantarum solution, while the contralateral ear received saline. Auditory brainstem responses were measured bilaterally at 8, 20, 25 kHz before, at 7–10 days after application, and at 28 days after application of probiotic or saline. Facial nerve and vestibular function were assessed clinically.

Results

There were no statistically significant differences in hearing thresholds between control and experimental ears at 28 days after application. A difference of 11 dB was noted in the 25 kHz range at day 7–10, but resolved by day 28. No animals receiving probiotics developed vestibular nerve dysfunction. There was no histologic evidence of auditory hair cell damaged evidenced by scanning electron microscopy.

Conclusion

Our study suggests that a single application of Lactobacillus plantarum at 10⁹ CFU/mL does not cause ototoxicity in a chinchilla animal model. These preliminary safety evaluations and the pathogen inhibitory effects of L. plantarum demonstrated by previous studies present this probiotic as a candidate of interest for further investigation.

Electronic supplementary material

The online version of this article (10.1186/s40463-017-0242-y) contains supplementary material, which is available to authorized users.

The Severity of Infection Determines the Localization of Damage and Extent of Sensorineural Hearing Loss in Experimental Pneumococcal Meningitis

Hearing loss is an important sequela of pneumococcal meningitis (PM), occurring in up to 30% of survivors. The role of the severity of infection on hearing function and pathomorphological consequences in the cochlea secondary to PM have not been investigated to date. Using a well-established model of PM, we systematically investigated the functional hearing outcome and the long-term fate of neurosensory cells in the cochlea, i.e., hair cells and spiral ganglion neurons (SGNs), with a focus on their tonotopic distribution. Intracisternal infection of infant rats with increasing inocula of Streptococcus pneumoniae resulted in a dose-dependent increase in CSF levels of interleukin-1β, interleukin-6, tumor necrosis factor α, interleukin-10, and interferon-γ in acute disease. The severity of long-term hearing loss at 3 weeks after infection, measured by auditory brainstem response recordings, correlated to the initial inoculum dose and to the levels of proinflammatory cytokines determined in the acute phase of PM. Quantitative cochlear histomorphology revealed a significant loss of SGNs and outer hair cells that strongly correlated to the level of infection, with the most severe damage occurring in the basal part of the cochlea. Inner hair cells (IHCs) were not significantly affected throughout the entire cochlea. However, surviving IHCs lost synaptic connectivity to remaining SGNs in all cochlear regions. These findings provide evidence that the inoculum concentration, i.e., severity of infection, is the major determinant of long-term morphological cell pathologies in the cochlea and functional hearing loss.

SIGNIFICANCE STATEMENT

Hearing loss is a neurofunctional deficit occurring in up to 30% of patients surviving pneumococcal meningitis (PM). Here, we analyze the correlation between the severity of infection and the inflammatory response in the CSF, the tonotopic distribution of neurosensory pathologies in the cochlea, and the long-term hearing function in a rat model of pneumococcal meningitis. Our study identifies the severity of infection as the key determinant of long-term hearing loss, underlining the importance of the prompt institution of antibiotic therapy in patients suffering from PM. Furthermore, our findings reveal in detail the spatial loss of cochlear neurosensory cells, providing new insights into the pathogenesis of meningitis-associated hearing loss that reveal new starting points for the development of otoprotective therapies.

Pathologic Changes of the Peripheral Vestibular System Secondary to Chronic Otitis Media

OBJECTIVE

To evaluate the histopathologic changes of dark, transitional, and hair cells of the vestibular system in human temporal bones from patients with chronic otitis media.

STUDY DESIGN

Comparative human temporal bone study.

SETTING

Otopathology laboratory.

SUBJECTS AND METHODS

To compare the density of vestibular dark, transitional, and hair cells in temporal bones with and without chronic otitis media, we used differential interference contrast microscopy.

RESULTS

In the chronic otitis media group (as compared with the age-matched control group), the density of type I and type II hair cells was significantly decreased in the lateral semicircular canal, saccule, and utricle (P < .05). The density of type I cells was also significantly decreased in the chronic otitis media group in the posterior semicircular canal (P = .005), but that of type II cells was not (P = .168). The mean number of dark cells was significantly decreased in the chronic otitis media group in the lateral semicircular canal (P = .014) and in the posterior semicircular canal (P = .002). We observed no statistically significant difference in the density of transitional cells between the 2 groups (P > .1).

CONCLUSION

The findings of our study suggest that the decrease in the number of vestibular sensory cells and dark cells could be the cause of the clinical symptoms of imbalance of some patients with chronic otitis media.

Risk factors for sensorineural hearing loss in pediatric chronic otitis media

OBJECTIVES

To assess the clinical significance of sensorineural hearing loss (SNHL) in a group of pediatric patients suffering from unilateral chronic otitis media (COM) with or without cholesteatoma, using the contralateral healthy ear as a control, and to define risk factors for the development of SNHL in such patients.

METHODS

The subjects of this retrospective study were 124 pediatric patients with unilateral COM admitted for surgery. Mean age at surgery was 13.3±3.2 years (range, 7-18) and mean duration of the disease was 88.4±45.0 months (range, 6-192 months). The preoperative pure-tone average value (PTA) for bone conduction (BC) was calculated in each ear (BC-PTA) as the average of BC thresholds at 500, 1000, 2000, and 4000Hz. Potential risk factors for SNHL that we evaluated were demographics, duration of disease, presence of cholesteatoma, and previous otologic history.

RESULTS

Mean BC-PTA values in the diseased ears prior to surgery differed significantly from those in the healthy ears (12.74±8.75dB and 9.36±6.33dB, respectively; P<0.01). The degree of SNHL in the diseased ear at 2000Hz was found to be significantly correlated with the presence of cholesteatoma and with age above 10 years.

CONCLUSIONS

One of the complications of COM, with or without cholesteatoma, in addition to the conductive hearing loss, is the development of clinically significant SNHL. It is therefore imperative to actively treat pediatric patients diagnosed with COM, with the aim of preventing the possible development of SNHL.

ALH-L1005 attenuates endotoxin induced inner ear damage

OBJECTIVE

To assess whether this compound (ALH-L1005) is conceivably an effective agent in protecting against cochlear damage induced by LPS.

MATERIALS AND METHODS

Tube formation using human umbilical vein endothelial cell (HUVEC) and matrix metalloproteinase (MMP)-9 inhibition assay was performed. 24 guinea pigs were randomly divided into three groups. Intratympanic instillation of LPS (n=8) as negative control, instillation of oxytetracycline 1h after LPS as positive control (n=8), and intratympanic instillation of ALH-L1005 (n=8) 1h after LPS were considered experimental group. Evaluation by auditory brainstem response (ABR) measurement, cochlear blood flow, and blood-labyrinth barrier (BLB) permeability were performed. Cochlear hair cells were observed by field emission-scanning electron microscopy (FE-SEM). MMP-9 activation was measured by gelatin zymography.

RESULTS

For HUVEC, the tube formation was suppressed in a dose dependant manner. ALH-L1005 inhibited the MMP-9 activity prominently. It also attenuated the elevation of LPS-induced hearing threshold shift and recovery of CBF. By FE-SEM, cochlear hair cells could be preserved in experimental group. ALH-L1005 significantly reduced the BLB opening compared to LPS group. Active MMP-9 expression could be detected in the LPS group. In contrast to ALH-L1005 group, active MMP-9 expression was not detected.

CONCLUSION

Our results conclude that ALH-L1005 showed a protective effect in the cochlear lateral wall damage induced by LPS.

Relationship between CT findings and sensorineural hearing loss in chronic otitis media

OBJECTIVE

To investigate the relationships between the temporal bone CT findings and sensorineural hearing loss in ears with non-cholesteatomatous chronic otitis media (COM).

METHODS

Preoperative bone conduction (BC) hearing thresholds of 266 patients (304 ears) with COM were compared with those of 342 normal individuals (440 ears) by audiometry. The incidence of abnormal BC threshold at lower frequencies (250-1000 Hz) and at higher frequencies (2000-4000 Hz) were examined and the differences between control and COM groups were compared by using χ2 test. In the COM group, the cross-sectional area of the mastoid air cells based on the axial CT image (n=255) were correlated with the results of BC threshold.

RESULTS

The percentage in the COM group exceeds 15% in their 50s at lower frequencies while in their 40s at higher frequencies. The BC thresholds were significantly better in the group with normal mastoid area than in those with smaller mastoid area at each decadal age group. The BC impairment from COM becomes worse as the course of the disease progresses and deteriorated from 40s rapidly, especially at higher frequencies and in the group with smaller mastoid area.

CONCLUSION

These results recommend that early treatment, including surgery, should be considered as early as possible before BC impairment occurs, especially for COM cases with smaller mastoid area, which may indicate the existence of more severe otitis media since earlier childhood.

Otitis media impacts hundreds of mouse middle and inner ear genes

Objective

Otitis media is known to alter expression of cytokine and other genes in the mouse middle ear and inner ear. However, whole mouse genome studies of gene expression in otitis media have not previously been undertaken. Ninety-nine percent of mouse genes are shared in the human, so these studies are relevant to the human condition.

Methods

To assess inflammation-driven processes in the mouse ear, gene chip analyses were conducted on mice treated with trans-tympanic heat-killed Hemophilus influenza using untreated mice as controls. Middle and inner ear tissues were separately harvested at 6 hours, RNA extracted, and samples for each treatment processed on the Affymetrix 430 2.0 Gene Chip for expression of its 34,000 genes.

Results

Statistical analysis of gene expression compared to control mice showed significant alteration of gene expression in 2,355 genes, 11% of the genes tested and 8% of the mouse genome. Significant middle and inner ear upregulation (fold change >1.5, p<0.05) was seen in 1,081 and 599 genes respectively. Significant middle and inner ear downregulation (fold change <0.67, p<0.05) was seen in 978 and 287 genes respectively. While otitis media is widely believed to be an exclusively middle ear process with little impact on the inner ear, the inner ear changes noted in this study were numerous and discrete from the middle ear responses. This suggests that the inner ear does indeed respond to otitis media and that its response is a distinctive process. Numerous new genes, previously not studied, are found to be affected by inflammation in the ear.

Conclusion

Whole genome analysis via gene chip allows simultaneous examination of expression of hundreds of gene families influenced by inflammation in the middle ear. Discovery of new gene families affected by inflammation may lead to new approaches to the study and treatment of otitis media.

Mcph1-deficient mice reveal a role for MCPH1 in otitis media

Otitis media is a common reason for hearing loss, especially in children. Otitis media is a multifactorial disease and environmental factors, anatomic dysmorphology and genetic predisposition can all contribute to its pathogenesis. However, the reasons for the variable susceptibility to otitis media are elusive. MCPH1 mutations cause primary microcephaly in humans. So far, no hearing impairment has been reported either in the MCPH1 patients or mouse models with Mcph1 deficiency. In this study, Mcph1-deficient (Mcph1^tm1a/tm1a) mice were produced using embryonic stem cells with a targeted mutation by the Sanger Institute's Mouse Genetics Project. Auditory brainstem response measurements revealed that Mcph1^tm1a/tm1a mice had mild to moderate hearing impairment with around 70% penetrance. We found otitis media with effusion in the hearing-impaired Mcph1^tm1a/tm1a mice by anatomic and histological examinations. Expression of Mcph1 in the epithelial cells of middle ear cavities supported its involvement in the development of otitis media. Other defects of Mcph1^tm1a/tm1a mice included small skull sizes, increased micronuclei in red blood cells, increased B cells and ocular abnormalities. These findings not only recapitulated the defects found in other Mcph1-deficient mice or MCPH1 patients, but also revealed an unexpected phenotype, otitis media with hearing impairment, which suggests Mcph1 is a new gene underlying genetic predisposition to otitis media.

Otitis Interna Induced by Cryptococcus neoformans var. grubii in a Cat

Cryptococcus neoformans var. grubii was identified at necropsy in a case of bilateral otitis interna in a 7-year-old, female, domestic shorthair cat with a 9-day history of acute onset of vestibular disease. Gross examination, including that of the middle and inner ears, was unremarkable. Histologically, the auricular vestibuli, cochleae, and semicircular canals were bilaterally affected by granulomatous inflammation with extracellular and intrahistiocytic yeasts. The yeasts and associated inflammation obstructed and disrupted perilymphatic and endolymphatic spaces of the inner ears. Disruption of the saccular and utricular maculae, cristae ampularis, and organ of Corti, as well as changes in the endolymphatic and perilymphatic fluids, probably impaired the vestibular and auditory functions of this cat. The route of infection was most likely hematogenous.

Matrix metalloproteinase inhibitor attenuates cochlear lateral wall damage induced by intratympanic instillation of endotoxin

OBJECTIVE

Oxytetracycline and ilomastat are inhibitors of matrix metalloproteinases (MMPs). Their efficacy in protecting against cochlear damage induced by the intratympanic instillation of lipopolysaccharide (LPS), as a means of inducing labyrinthitis, was investigated.

MATERIALS AND METHODS

Experiments were performed in 21 young male guinea pigs. Intratympanic instillation of LPS was done in the control group (n=7). Intratympanic instillation of oxytetracycline or ilomastat was done after LPS instillation in the experimental group. Measurements of auditory brainstem response (ABR) and cochlear blood flow (CBF) were performed. The organ of Corti was evaluated by field emission scanning electron microscopy (FE-SEM). The blood-labyrinth barrier (BLB) integrity was evaluated with Evans blue uptake. Gelatin zymography was used to assess the expression of active MMP-2 and MMP-9.

RESULTS

Ears treated with MMP inhibitors were significantly protected from hearing loss compared to the LPS group. In LPS group, there was a significant decrease of CBF. However, experimental group displayed a statistically significant recovery of CBF. FE-SEM revealed hair cell damage in the LPS-treated group, but hair cells presented a normal appearance in MMP inhibitors. The LPS group showed a marked increase of Evans blue extravasation in the cochlea. However, MMP inhibitors significantly reduced the BLB opening. Active MMP-9 was expressed in the LPS group. Treatment with MMP inhibitors attenuated active MMP-9 expression.

CONCLUSION

The MMP inhibitors oxytetracycline and ilomastat protect from cochlear lateral wall damage caused by LPS-induced labyrinthitis.

Effect of Ginkgo biloba extract on endotoxin-induced labyrinthitis

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.

Altered expression of middle and inner ear cytokines in mouse otitis media

OBJECTIVES/HYPOTHESIS

The inner ear is at risk for sensorineural hearing loss in both acute and chronic otitis media (OM), but the mechanisms underlying sensorineural hearing loss are unknown. Previous gene expression array studies have shown that cytokine genes might be upregulated in the cochleas of mice with acute and chronic OM. This finding implies that the inner ear could manifest a direct inflammatory response to OM that may cause sensorineural damage. Therefore, to better understand inner ear cytokine gene expression during OM, quantitative real-time polymerase chain reaction and immunohistochemistry were used in mouse models to evaluate middle and inner ear inflammatory and remodeling cytokines.

STUDY DESIGN

Basic science experiment.

METHODS

An acute OM model was created in Balb/c mice by a transtympanic injection of Streptococcus pneumoniae in one ear; the other ear was used as a control. C3H/HeJ mice were screened for unilateral chronic OM, with the noninfected ear serving as a control.

RESULTS

Both acute and chronic OM caused both the middle ear and inner tissues in these two mouse models to overexpress numerous cytokine genes related to tissue remodeling (tumor necrosis factor-α, bone morphogenetic proteins, fibroblast growth factors) and angiogenesis (vascular endothelial growth factor), as well as inflammatory cell proliferation (interleukin [IL]-1α,β, IL-2, IL-6). Immunohistochemistry confirmed that both the middle ear and inner ear tissues expressed these cytokines.

CONCLUSIONS

Cochlear tissues are capable of expressing cytokine mRNA that contributes to the inflammation and remodeling that occur in association with middle ear disease. This provides a potential molecular basis for the transient and permanent sensorineural hearing loss often reported with acute and chronic OM.

Murine malaria is associated with significant hearing impairment

BACKGROUND

Plasmodium falciparum malaria has been suspected to cause hearing loss. Developmental, cognitive and language disorders have been observed in children, surviving cerebral malaria. This prospective study aims to evaluate whether malaria influences hearing in mice.

METHODS

Twenty mice were included in a standardized murine cerebral malaria model. Auditory evoked brainstem responses were assessed before infection and at the peak of the illness.

RESULTS

A significant hearing impairment could be demonstrated in mice with malaria, especially the cerebral form. The control group did not show any alterations. No therapy was used.

CONCLUSION

This suggests that malaria itself leads to a hearing impairment in mice.

Cochlear pathology in human temporal bones with otitis media

CONCLUSION

Middle and inner ear interactions in otitis media can lead to cochlear pathology. More severe pathological changes observed in the basal turn of the cochlea are consistent with prevalence of sensorineural hearing loss at higher frequencies in patients with otitis media.

METHODS

Of 614 temporal bones with otitis media, 47 with chronic and 35 with purulent otitis media were selected following strict exclusion of subjects with a history of acoustic trauma, head trauma, ototoxic drugs, and other diseases affecting the cochlear labyrinth. Temporal bones with labyrinthine inflammatory changes were further evaluated for loss of hair cells and other histopathologic changes compared to age-matched controls.

RESULTS

In all, 19% of temporal bones with chronic and 9% with purulent otitis media showed labyrinthine inflammatory changes. In chronic otitis media, inflammatory changes were: 56% localized purulent, 22% localized serous, 11% generalized seropurulent, and 11% generalized serous. Inflammatory changes in temporal bones with purulent otitis media included 67% localized purulent and 33% were generalized seropurulent. Pathological findings included: serofibrinous precipitates and inflammatory cells in scala tympani of basal turn and cochlear aqueduct, significant loss of outer and inner hair cells, and significant decrease in area of stria vascularis in the basal turn of the cochlea, as compared to controls.

Effect of lipooligosaccharide mutations of Haemophilus influenzae on the middle and inner ears

OBJECTIVE

The purpose of this study was to determine the virulence of nontypeable Haemophilus influenzae 2019 (NTHi 2019) and its two lipooligosaccharide (LOS) mutant strains, B29 (gene htrB) and DK1 (gene rfaD), and compare their effect on the middle ear, round window membrane, and inner ear.

RESULTS

Fifteen chinchillas were divided into three equal groups and their bullas inoculated bilaterally with 0.5 ml of 10(2)CFU/ml of parent NTHi 2019, B29 or DK1 mutant strains. Two days after inoculation all animals had otitis media and inflamed middle ear mucosa. There was a trend of greater thickness and infiltration of the round window membrane in animals inoculated with the wild-type NTHi strain compared to the mutant strains and a significant increase in both inflammatory cell infiltration and bacteria presence in the scala tympani area of the inner ear. Strial edema was only observed in the wild-type-inoculated group.

CONCLUSIONS

LOS mutants of NTHi appear to have a reduced ability to pass through the round window membrane resulting in less inner ear inflammation and pathological changes.

Mouse models for human otitis media

Otitis media (OM) remains the most common childhood disease and its annual costs exceed $5 billion. Its potential for permanent hearing impairment also emphasizes the need to better understand and manage this disease. The pathogenesis of OM is multifactorial and includes infectious pathogens, anatomy, immunologic status, genetic predisposition, and environment. Recent progress in mouse model development is helping to elucidate the respective roles of these factors and to significantly contribute toward efforts of OM prevention and control. Genetic predisposition is recognized as an important factor in OM and increasing numbers of mouse models are helping to uncover the potential genetic bases for human OM. Furthermore, the completion of the mouse genome sequence has offered a powerful set of tools for investigating gene function and is generating a rich resource of mouse mutants for studying the genetic factors underlying OM.

Role of pneumococcal proteins in sensorineural hearing loss due to otitis media

HYPOTHESIS

Two Streptococcus pneumoniae proteins, pneumococcal surface protein A (PspA) and pneumolysin (Ply), have functional and histopathologic effects on the inner ear.

BACKGROUND

Temporary or permanent sensorineural hearing loss is known to be a sequela of pneumococcal otitis media. Several pneumococcal proteins such as PspA and Ply have been shown to contribute to the pathogenesis of the middle ear; however, effects of these proteins on the inner ear and hearing loss are unknown.

METHODS

Middle ears of chinchillas were inoculated with either wild-type S. pneumoniae or its mutants, deficient in PspA or Ply proteins. After 28 days, auditory brainstem response of animals was tested, and their bullae were processed for histopathologic analysis by light microscopy.

RESULTS

Twenty-eight days after instillation of 20 colony-forming units of wild-type pneumococci, auditory brainstem response test showed threshold changes of 10 to 15 dB for 4 to 32 kHz and more than 20 dB for 1 to 2 kHz. No significant hearing loss was observed after instillation of the same or even higher doses of isogenic S. pneumoniae mutants of PspA or Ply proteins, or saline injection, after the same period. Histologic analysis showed no fluid, inflammatory cells, or bacteria in the middle ear, indicating that hearing loss was sensorineural. Inner ear morphology showed pathologic changes in the stria vascularis, suggesting it as the target of otitis media-induced damage, which may lead to sensorineural hearing loss.

CONCLUSION

The virulence PspA and Ply proteins of S. pneumoniae affect the inner ear and auditory function.

The role of inflammatory mediators in the pathogenesis of otitis media and sequelae

This review deals with the characteristics of various inflammatory mediators identified in the middle ear during otitis media and in cholesteatoma. The role of each inflammatory mediator in the pathogenesis of otitis media and cholesteatoma has been discussed. Further, the relation of each inflammatory mediator to the pathophysiology of the middle and inner ear along with its mechanisms of pathological change has been described. The mechanisms of hearing loss including sensorineural hearing loss (SNHL) as a sequela of otitis media are also discussed. The passage of inflammatory mediators through the round window membrane into the scala tympani is indicated. In an experimental animal model, an application of cytokines and lipopolysaccharide (LPS), a bacterial toxin, on the round window membrane induced sensorineural hearing loss as identified through auditory brainstem response threshold shifts. An increase in permeability of the blood-labyrinth barrier (BLB) was observed following application of these inflammatory mediators and LPS. The leakage of the blood components into the lateral wall of the cochlea through an increase in BLB permeability appears to be related to the sensorineural hearing loss by hindering K⁺ recycling through the lateral wall disrupting the ion homeostasis of the endolymph. Further studies on the roles of various inflammatory mediators and bacterial toxins in inducing the sensorineumral hearing loss in otitis media should be pursued.

Toll-like receptor 2-dependent NF-kappaB activation is involved in nontypeable Haemophilus influenzae-induced monocyte chemotactic protein 1 up-regulation in the spiral ligament fibrocytes of the inner ear

Inner ear dysfunction secondary to chronic otitis media (OM), including high-frequency sensorineural hearing loss or vertigo, is not uncommon. Although chronic middle ear inflammation is believed to cause inner ear dysfunction by entry of OM pathogen components or cytokines from the middle ear into the inner ear, the underlying mechanisms are not well understood. Previously, we demonstrated that the spiral ligament fibrocyte (SLF) cell line up-regulates monocyte chemotactic protein 1 (MCP-1) expression after treatment with nontypeable Haemophilus influenzae (NTHI), one of the most common OM pathogens. We hypothesized that the SLF-derived MCP-1 plays a role in inner ear inflammation secondary to OM that is responsible for hearing loss and dizziness. The purpose of this study was to investigate the signaling pathway involved in NTHI-induced MCP-1 up-regulation in SLFs. Here we show for the first time that NTHI induces MCP-1 up-regulation in the SLFs via Toll-like receptor 2 (TLR2)-dependent activation of NF-kappaB. TLR2(-/-)- and MyD88(-/-)-derived SLFs revealed involvement of TLR2 and MyD88 in NTHI-induced MCP-1 up-regulation. Studies using chemical inhibitors and dominant-negative constructs demonstrated that it is mediated by the IkappaKbeta-dependent IkappaBalpha phosphorylation and NTHI-induced NF-kappaB nuclear translocation. Furthermore, we demonstrated that the binding of NF-kappaB to the enhancer region of MCP-1 is involved in this up-regulation. In addition, we have identified a potential NF-kappaB motif that is responsive and specific to certain NTHI molecules or ligands. Further studies are necessary to reveal specific ligands of NTHI that activate host receptors. These results may provide us with new therapeutic strategies for prevention of inner ear dysfunction secondary to chronic middle ear inflammation.

Characterization of rat spiral ligament cell line immortalized by adenovirus 12-simian virus 40 hybrid virus

OBJECTIVES

Spiral ligament fibrocytes play an important role in inner ear ion homeostasis and are classified into several subtypes according to expression of specific enzymes such as Na+, K+ -ATPase, Ca++ -ATPase, and carbonic anhydrase. Although our understanding of the cell and molecular biology of spiral ligament fibrocytes has increased over time, access to these cells still remains a significant hurdle hindering future studies. In this study, we aimed to establish a rat spiral ligament cell line with minimal disruption of the original characteristics.

METHODS

The primary spiral ligament fibrocytes were exposed to adenovirus 12-simian virus 40 hybrid virus for immortalization. Karyotypic analysis was performed after stabilization of the infected cells, and the population doubling time was compared to that of the primary cell. The cell line was characterized by immunolabeling and electron microscopy.

RESULTS

We describe the establishment and characterization of a line of type I spiral ligament fibrocytes immortalized with an adenovirus 12-simian virus 40 hybrid virus.

CONCLUSIONS

This cell line can be a useful research tool for investigating the role of spiral ligament fibrocytes in homeostasis and inflammation of the inner ear.

Cochlear Cytokine Gene Expression in Murine Acute Otitis Media

OBJECTIVE

Recurrent acute otitis media (AOM) causes sensorineural hearing loss by unknown mechanisms. It is widely accepted that inflammatory cytokines diffuse across the round window membrane to exert cytotoxic effects. This study addresses whether inner ear cells are capable of expressing genes for inflammatory cytokines.

STUDY DESIGN

The authors conducted a prospective animal study.

METHODS

BALB/C mice underwent transtympanic injection of heat-killed Haemophilus influenzae to create an acute inflammatory response. These mice were compared with a control group in addition to a group of uninjected mice found to have otomicroscopic changes consistent with persistent or chronic otitis media. The cochleas of these mice were obtained, their RNA harvested, and cytokine gene expression analyzed using prefabricated cDNA arrays.

RESULTS

Four groups of mice (control, 3-day postinjection, 7-day postinjection, and mice with chronic otitis media) with five mice in each group were analyzed. Numerous classes of genes were found to be upregulated or downregulated by more than twofold. Some genes differed from control mice by more than 10-fold. These genes included numerous fibroblast growth factors, interleukins, tumor necrosis factors, and colony-stimulating factors.

CONCLUSION

The genes of numerous inflammatory cytokines are either up- or downregulated by murine inner ear cells in response to either acute or chronic inflammation of the middle ear. This study provides a novel site of production of cytokines that may be responsible for the damage seen in sensorineural hearing loss.

Effect of inhibitors of leukotriene and/or platelet activating factor on killed H. influenzae induced experimental otitis media with effusion

Our previous studies have shown that leukotriene (LT) and platelet activating factor (PAF) are important inflammatory mediators (IMs) in the pathogenesis of otitis media with effusion (OME). The purpose of this study was to determine the effect of a LT-inhibitor and/or PAF-antagonist on experimentally induced OME by killed H. influenzae in chinchillas. LT-inhibitor SCH-37224 and/or PAF-antagonist WEB-2170 were systematically administered, each separately or in combination, 2h prior and then at regular intervals after the injection of killed H. influenzae into the superior bullae. After 48h, OME was completely prevented in the combination group while it was only partially prevented in the other two separately treated groups. Animals in the control group all developed OME. Findings of this study suggest the importance of LT and PAF in the pathogenesis of OME and the usefulness of their blockers in the prevention of OME suggesting possible future therapeutic implication.

Candidate???s Thesis: Platelet-Activating Factor???Induced Hearing Loss: Mediated by Nitric Oxide?

OBJECTIVES/HYPOTHESIS

Platelet-activating factor (PAF)in middle ear effusion is thought to induce hearing loss. The purpose of this study is to investigate the role of nitric oxide (NO) in the mechanism of PAF-induced hearing loss by studying the effects of PAF application on the round window membrane (RWM) with and without PAF-antagonist NO-blocker.

STUDY DESIGN

Longitudinal study on randomized guinea pigs using PAF to induce hearing loss. METHODS Guinea pigs were divided into four groups: PBS, PAF, PAF-antagonist, and L-NAME. The PBS group received phosphate buffered saline (PBS) and the PAF groups received 10, 20, and 40 microg of PAF soaked into gelfoam and placed on the RWM. PAF-antagonist (WEB 2170) and NOS inhibitor NG-nitro-l-arginine-methylester (L-NAME) were injected intraperitoneally prior to PAF 20 microg application on the RWM. The following three tests were performed on each animal group: Hearing was tested with an auditory brainstem response (ABR) test over 24 hours. At the end of 24 hours, cochlear hair cells were examined by scanning electron microscopy (SEM) and immunohistochemistry was carried out on the cochlea to test the expression of inducible nitric oxide synthase (iNOS).

RESULTS

The PAF group developed significant elevation of ABR threshold and cochlear hair cell damage in the SEM group as compared with the PBS control group. The PAF-antagonist (WEB 2170) and the L-NAME groups did not show significant elevation of ABR threshold and cochlear hair cell damage compared with the group administered PAF 20 microg, but in the PAF-antagonist group, the elevation of ABR threshold was significant compared with that of the PBS control group, whereas it was not significant compared with the PBS group in the L-NAME group. Strong expression of iNOS on cochlea was observed in the PAF group and lighter expression was seen in PBS, WEB 2170, and L-NAME groups.

CONCLUSIONS

This study demonstrated that PAF placed on the RWM induced hearing loss and cochlear hair cell damage. The PAF-antagonists and L-NAME prevented the PAF-induced hearing loss and inhibited iNOS expression in the cochlea. These findings suggest that the PAF-induced hearing loss caused by cochlear hair cell damage may have been mediated by NO. PAF-antagonists and L-NAME may have future therapeutic implications in preventing sensorineural hearing loss associated with chronic otitis media. The results of this study have significant potential clinical application.

A randomized, placebo-controlled trial of the effect of antihistamine or corticosteroid treatment in acute otitis media

OBJECTIVES

To determine whether the adjunctive drugs antihistamine and corticosteroid improve immediate and long-term outcomes of acute otitis media (AOM).

STUDY DESIGN

Children with AOM (3 mos-6 y) were enrolled in a randomized, double-blind, placebo-controlled trial. All 179 children received one dose of intramuscular ceftriaxone and were assigned to receive either chlorpheniramine maleate (0.35 mg/kg/d) and/or prednisolone (2 mg/kg/day) or placebo for 5 days. Main outcome measures were rate of treatment failure during the first 2 weeks, duration of middle ear effusion, and rate of recurrences of AOM to 6 months.

RESULTS

Clinical outcomes and recurrence rates did not differ significantly with treatment. Children who received antihistamine alone had significantly longer duration of middle ear effusion (median, 73 days) than subjects in other treatment groups (median, 23 to 36 days, P=.04). Temporary normalization of tympanometric findings on day 5 occurred more frequently in the corticosteroid-treated group (P=.04).

CONCLUSIONS

Five-day treatment with antihistamine or corticosteroid, in addition to antibiotic, did not improve AOM outcomes. Antihistamine use during an acute episode of OM should be avoided, since the drug may prolong the duration of middle ear effusion. The efficacy of 7- to 10-day treatment of AOM with corticosteroid, in addition to antibiotic, deserves further investigation.

Effect of 10 pharmacologic probes on mRNA levels of inducible nitric oxide synthetase and selected inflammatory cytokines in a rat model of acute otitis media

Ten drugs were screened for their ability to decrease inflammatory mediator (IL-6, inducible nitric oxide synthetase [iNOS], IL-1beta and monocyte chemotactic protein [MCP-1]) expression in a rat model of acute otitis media caused by Streptococcus pneumoniae. Six adult rats were randomly assigned to each of 12 groups corresponding to uninfected controls and treatments with saline, aminoguanidine, anisomycin, dexamethasone, ketorolac, L-N(G)-nitroarginine methylester, methylprednisolone, mycophenolic acid, pentoxiphylline, tacrolimus or WEB2086. Forty-eight h after the start of treatment, the ears of the animals in the 11 treatment groups were challenged with S. pneumoniae. Forty-eight h later, all animals were killed and middle ear mucosa was harvested and assayed for RNA message. Messages for IL-6, iNOS and MCP-1 were significantly increased as a result of infection. Most treatments decreased MCP-1 and four decreased IL-6 and iNOS. Tacrolimus and dexamethasone decreased IL-6, iNOS and MCP-1. These results show that pharmacological agents can modify the expression of inflammatory mediators in this model and may have clinically relevant effects.

Classification of otitis media and surgical principles

Otitis media is an important disease of children and adults and is caused by multiple interrelated factors, including infection, eustachian tube dysfunction, allergy, and barotrauma. This article includes a pertinent review of the literature regarding otitis media. The pathogenesis, classification, and treatment of otitis media in children and adults are also reviewed in this article. Additionally, therapy is discussed with emphasis on the surgical options appropriate at each stage.