Immunohistochemical analysis of proliferating cells in a sterile labyrinthitis animal model

Developmental expression of high-mobility group box 1 (HMGB1) in the mouse cochlea

The expression changes of high-mobility group box 1 (HMGB1) in the mouse cochlea have recently been implicated in noise-induced hearing loss, suggesting that HMGB1 participates in regulating cochlear function. However, the precise role of HMGB1 in the auditory system remains largely unclear. This study aimed to investigate its function in the developing mouse cochlea by examining the expression pattern of HMGB1 in the mouse cochlea from embryonic day (E) 18.5 to postnatal day (P) 28 using double immunofluorescence on frozen sections. Our findings revealed that HMGB1 was extensively expressed in the cell nucleus across various regions of the mouse cochlea, including the organ of Corti. Furthermore, its expression underwent developmental regulation during mouse cochlear development. Specifically, HMGB1 was found to be localized in the tympanic border cells at each developmental stage, coinciding with the gradual anatomical in this region during development. In addition, HMGB1 was expressed in the greater epithelial ridge (GER) and supporting cells of the organ of Corti, as validated by the supporting cell marker Sox2 at P1 and P8. However, at P14, the expression of HMGB1 disappeared from the GER, coinciding with the degeneration of the GER into the inner sulcus cells. Moreover, we observed that HMGB1 co-localized with Ki-67-positive proliferating cells in several cochlear regions during late embryonic and early postnatal stages, including the GER, the tympanic border cells, cochlear lateral wall, and cochlear nerves. Furthermore, by dual-staining Ki-67 with neuronal marker TUJ1 and glial marker Sox10, we determined the expression of Ki-67 in the neonatal glial cells. Our spatial-temporal analysis demonstrated that HMGB1 exhibited distinct expression patterns during mouse cochlear development. The co-localization of HMGB1 with Ki-67-positive proliferating cells suggested that HMGB1 may play a role in cochlear development.

Cochlear Impairment and Autoimmune Ear Disorder in a Patient with Breast Cancer

The purpose of this study was to consider the possible role of autoimmune diseases and paraneoplastic syndrome in the genesis of tinnitus. The incidence of autoimmune inner ear disease (AIED) is rare, accounting for <1% of all cases of hearing impairment and dizziness. In presence of auditory and vestibular deficit in oncological patients, a paraneoplastic syndrome with cochleovestibulopathy should be considered. We described a 50-year-old Caucasian woman came to our attention with complaints of severe disabling bilateral tinnitus (Tinnitus Handicap Inventory, THI: 96), ear fullness and headache. The onset of tinnitus was associated to the last breast implant and prolonged antibiotic therapy. Serological autoimmunity tests were positive and a diagnosis of mixed connective tissue disease with notes of fibromyalgia was made. Pure tone audiometry testing revealed bilateral fluctuating mild hearing loss on high frequencies. The tinnitus was successfully treated with bilateral wideband sound generators (listening 8-9 h for day) regulated at the mixing point. At 12 months follow up THI has shrunk considerably (THI: 4) and the patient has continued treatment only with the sound pillow.

In conclusion significant progress is needed to better understand the role of autoantibodies in the pathogenesis and diagnosis of paraneoplastic cochleovestibulopathy. To our knowledge, our study is the first in which hearing loss and tinnitus is considered as a manifestation of a paraneoplastic syndrome.

AAO: Autoimmune and Autoinflammatory (Disease) in Otology: What is New in Immune-Mediated Hearing Loss

OBJECTIVES

Autoinflammatory diseases are a family of immune-mediated, rare diseases, some of which, exhibit sensorineural hearing loss (SNHL), suggesting potentially similar mechanisms of molecular pathogenesis between autoinflammatory-mediated hearing loss and autoimmune inner ear disease (AIED) may exist. The purpose of this review is to compare the clinical features of autoimmune and autoinflammatory diseases that affect hearing, discuss the limitations of our knowledge, and highlight potential new disease mechanisms and therapeutics.

DATA SOURCES

Pubmed Literature Review; Google Scholar Literature review.

REVIEW METHODS

A focused comparison of AIED with a number of autoinflammatory diseases that manifest with sensorineural hearing loss was performed. The pathogenesis of these diseases is reviewed in the context of the innate and adaptive immune system, cytokine expression and genetic polymorphisms.

RESULTS

AIED, since first described by Cogan and Lehnhardt and first clinically characterized by McCabe, has remained an enigmatic disease, with limited advances in both new diagnostics and new therapeutics. Since the discovery of autoinflammatory diseases, a number of systemic autoimmune diseases have either been re-classed as autoinflammatory diseases or identified to have features of autoinflammatory disease.

CONCLUSION

AIED has clinical features of both autoimmune and autoinflammatory disease. It is critical that autoinflammatory diseases be correctly identified, as failure to do so may result in systemic amyloidosis and kidney damage.

Controversies and Criticisms on Designs for Experimental Autoimmune Labyrinthitis

Although immune-mediated inner ear disease was reported around 25 years ago, numerous attempts to identify the inner ear antigens have been performed. Experimental animal models have been used to study the immune mechanisms involved in hearing loss and to develop new therapies. Because animal models of autoimmune labyrinthitis have been developed by means of different antigens, we cannot yet show a valid immunopathologic explanation. A critical analysis of the more relevant experimental models employed has been performed in order to validate the methodology. Comparison between these models and animals with spontaneous systemic autoimmune disease has raised more questions concerning the pathophysiology of autoimmune hearing loss. A new pathogenetic theory is suggested, involving the supporting cells of the organ of Corti.

Prevention of trauma-induced cochlear fibrosis using intracochlear application of anti-inflammatory and antiproliferative drugs

Cochlear fibrosis is a common finding following cochlear implantation. Evidence suggests that cochlear fibrosis could be triggered by inflammation and epithelial-to-mesenchymal cell transition (EMT). In this study, we investigate the mechanisms of cochlear fibrosis and the risk/benefit ratio of local administration of the anti-inflammatory drug dexamethasone (DEX) and antimitotic drug aracytine (Ara-C). Cochlear fibrosis was evaluated in cochlear fibrosis models of rat cochlear slices in vitro and in KLH-induced immune labyrinthitis and platinum wire cochlear implantation-induced fibrosis in vivo. Cochleae were invaded with tissue containing fibroblastic cells expressing α-SMA (alpha smooth muscle actin), which along with collagen I, fibronectin, and laminin in the extracellular matrix, suggests the involvement of a fibrotic process triggered by EMT in vitro and in vivo. After perilymphatic injection of an adenoviral vector expressing GFP in vivo, we demonstrated that the fibroblastic cells derived from the mesothelial cells of the scalae tympani and vestibuli. Activation of inflammatory and EMT pathways was further assessed by ELISA analysis of the expression of IL-1β and TGF-β1. Both markers were elevated in vitro and in vivo, and DEX and Ara-C were able to reduce IL-1β and TGF-β1 production. After 5days of culture in vitro, quantification of calcein-positive cells revealed that Ara-C was 30-fold more efficient in preventing fibrosis, and provoked less sensory hair cell loss, than DEX. In KLH-induced immune labyrinthitis and platinum wire-implanted models, Ara-C was more efficient in preventing proliferation of fibrosis with less side effects on hair cells and neurons than DEX. In conclusion, DEX and Ara-C both prevent fibrosis in the cochlea. Analysis of the risk/benefit ratio favors the use of Ara-C for preventing cochlear fibrosis.

An open label study to evaluate the safety and efficacy of intratympanic golimumab therapy in patients with autoimmune inner ear disease

OBJECTIVE

To evaluate the safety and efficacy of intratympanically injected golimumab (GLM), a TNF-α inhibitor, as a steroid-sparing agent for patients with steroid-dependent autoimmune inner ear disease (AIED).

STUDY DESIGN

Open label.

SETTING

Tertiary referral center.

PATIENTS

Ten patients with steroid-dependent AIED were enrolled in Stage 2. The average patient age at enrollment was 59, with an average of 12.5 years from the start of bilateral hearing loss symptoms. The average dose of daily prednisone at the start of injections was 18 mg.

INTERVENTION

Intratympanic injection of GLM.

MAIN OUTCOME MEASURE

Hearing loss progression (treatment failure) was defined as either an increase in pure-tone thresholds by frequency or a decrease in word recognition score.

RESULTS

There were no serious adverse events. Five of seven per-protocol subjects experienced stable pure-tone thresholds in the injected ear, whereas 4 had stable word recognition scores. Two subjects experienced an improvement in word recognition scores. The results support the hypothesis that GLM may be a promising treatment.

CONCLUSIONS

The TNF-α inhibitor GLM stabilized hearing in 3 of 7 per-protocol subjects with AIED and allowed a complete tapering off of prednisone in those 7 subjects. Studies with larger samples sizes are warranted.

Systemic immunity influences hearing preservation in cochlear implantation

HYPOTHESIS

To determine whether a systemic immune response influences hearing thresholds and tissue response after cochlear implantation of hearing guinea pigs.

METHODS

Guinea pigs were inoculated with sterile antigen (Keyhole limpet hemocyanin) 3 weeks before cochlear implantation. Pure-tone auditory brainstem response thresholds were performed before implantation and 1 and 4 weeks later. Dexamethasone phosphate 20% was adsorbed onto a hyaluronic acid carboxymethylcellulose sponge and was applied to the round window for 30 minutes before electrode insertion. Normal saline was used for controls. Cochlear histology was performed at 4 weeks after implantation to assess the tissue response to implantation. To control for the effect of keyhole limpet hemocyanin priming, a group of unprimed animals underwent cochlear implantation with a saline-soaked pledget applied to the round window.

RESULTS

Keyhole limpet hemocyanin priming had no significant detrimental effect on thresholds without implantation. Thresholds were elevated after implantation across all frequencies tested (2-32 kHz) in primed animals but only at higher frequencies (4-32 kHz) in unprimed controls. In primed animals, dexamethasone treatment significantly reduced threshold shifts at 2 and 8 kHz. Keyhole limpet hemocyanin led to the more frequent observation of lymphocytes in the tissue response to the implant.

CONCLUSION

Systemic immune activation at the time of cochlear implantation broadened the range of frequencies experiencing elevated thresholds after implantation. Local dexamethasone provides partial protection against this hearing loss, but the degree and extent of protection are less compared to previous studies with unprimed animals.

The perceived angle of the round window affects electrode insertion trauma in round window insertion - an anatomical study

CONCLUSION

In this study round window (RW) insertion of cochlear implant was performed with a lower degree of trauma in 86.6% of cases. Therefore RW insertion is a valid option to be considered in selected cochlear implant patients, especially when hearing preservation is a goal. In most cases drilling of the overhangs is required.

OBJECTIVES

To systematically examine the potential for minimizing electrode insertion trauma with RW insertion.

METHODS

Fifteen temporal bones were inserted with a 0.5 mm electrode analog in an anterior or antero-inferior vector from a reference point along the facial recess. Surface preparation of the inferior segment of the basal turn was performed and the point of first contact was analyzed using computerized morphometric software. The same software was used to measure the RW dimensions before and after drill down of the bony overhangs. An insertion was considered 'traumatic' if the point of first contact was the medial wall of the scala, whereas 'less traumatic' was an insertion in which the point of first contact was the inferior or posterior wall of the scala.

RESULTS

Less traumatic insertion was achieved in 13 of the 15 bones, and in these the mean RW angle, as observed from a surgical point of view, was 137°. The mean RW angle in the traumatic insertion group was 147°. The difference was statistically significant.

Cochlear microperfusion: experimental evaluation of a potential new therapy for severe hearing loss caused by inflammation

HYPOTHESIS

Cochlear microperfusion will be a useful treatment of severe sensorineural hearing loss caused by inflammation.

BACKGROUND

Viruses, bacteria, and autoimmunity can initiate inflammation in the inner ear. The acute phase is associated with elevations in cytokines, nitrous oxide, and cellular infiltrates and the breakdown of the blood-labyrinthine barrier. The chronic phase leads to irreversible ossification of the labyrinth.

METHODS

The authors developed cochlear microperfusion to facilitate removal of inflammatory cells and their byproducts during the acute phase of inflammation. Using a ventral approach to the guinea pig cochlea, the authors displaced resident perilymph by delivering perfusate into the scala vestibuli and collecting the effluent from the scala tympani. The authors evaluated the benefit of the procedure in an animal model of severe hearing loss caused by inflammation.

RESULTS

Healthy controls undergoing cochlear microperfusion with phosphate-buffered saline incurred a mean hearing loss of 16 dB (n=4). This hearing loss was associated with the creation of two cochleostomies and not the perfusion itself. Sterile labyrinthitis (n=5) generated by perfusion of the cochlea with antigen consistently produced severe hearing loss over the initial 48 hours, and this hearing loss persisted for the subsequent 7 days. Therapeutic cochlear microperfusion, performed within the first 24 hours of developing severe hearing loss (n=9), immediately restored on average 24 dB (p <0.007) of hearing.

CONCLUSION

Cochlear microperfusion is a promising new technique for treating severe deafness caused by inflammation. The benefit may be sustained when combined with local delivery of immunosuppressive agents to the inner ear.

Location and Timing of Initial Osteoid Deposition in Postmeningitic Labyrinthitis Ossificans Determined by Multiple Fluorescent Labels

OBJECTIVES/HYPOTHESIS

Variable amounts of fibrosis and neo-ossification fill the cochlea following bacterial meningitis. The purpose of the study was to delineate the timing and location of initial ossification following pneumococcal meningitis, as well as subsequent remodeling and resorption, over the 3-month period after infection.

STUDY DESIGN

Randomized, double-blind study.

METHODS

Fluorochromes are compounds that specifically incorporate into ossifying bone. Sequential addition of different colored fluorochromes during osteoneogenesis define the timing and location of osteoid deposition and mineralization. Mongolian gerbils were infected by intrathecal injection of Streptococcus pneumoniae type 3, and control gerbils received saline. Both groups were injected with calcein on postoperative day 3, followed by xylenol orange, oxytetracycline, and alizarin red on days 7, 14, and 28 respectively. Ten experimental gerbils were killed 24 hours after each label, and an additional group at 84 days after infection. Two groups of 10 control gerbils were killed at 29 and 84 days after treatment. The temporal bones and tibias were harvested, embedded in plastic, and sliced with a diamond saw. Wafers at a thickness of 200 microm were mounted in sequence and examined.

RESULTS

Sixteen of 49 experimental animals (33%) were positive for at least one of the fluorescent labels. Fluorescent labeled osteoid was present at all sampling times. Label extended from the endosteal wall into the lumen of the scala tympani between the vestibule and the round window membrane. Discrete sites of fluorescence varied among specimens and were associated with the opening of the cochlear aqueduct, the scala tympani, organ of Corti, and the stria vascularis and spiral ligament in all turns from base to apex.

CONCLUSION

The results indicate that osteoid is deposited and begins mineralization by day 3 after infection, at least, and continues, at least, through the first 28 days after infection. There was no apparent resorption of new bone and remodeling by 84 days after infection.

Cell proliferation in the endolymphatic sac in situ after the rat Waldeyer ring equivalent immunostimulation

OBJECTIVES/HYPOTHESIS

It has been recognized that immunological mechanisms could be involved in the pathogenesis of different inner ear disorders, such as progressive sensorineural hearing loss, Meniere's disease, and even sudden deafness. The endolymphatic sac acts as an immune control organ for the inner ear and has been considered as an effector site of the mucosa-associated lymphoid tissue. The purpose of the study was to determine the potentially immunological relationship between endolymphatic sac and Waldeyer ring equivalent, one of the most important affector organs in mucosa-associated lymphoid tissue.

STUDY DESIGN

Animal model.

METHODS

Thirty-six rats were employed. Two animals were killed for histological observation of Waldeyer ring equivalent, and another 34 animals were randomly divided into experimental and control groups and received bilateral intranasal immunizations with keyhole limpet hemocyanin or Freund adjuvant, respectively. The ears of immunized animals and control animals were examined for keyhole limpet hemocyanin-positive memory cells and immunoglobulin G-positive plasma cells with the technique of immunohistochemical analysis. The histopathological changes and cell proliferation in those ears were also assessed.

RESULTS

There were paired and organized lymphoid tissues in the lateral wall of the first choana in the rat. Keyhole limpet hemocyanin-positive lymphocytes appeared within the endolymphatic sac at 3 days after the first anti-genetic stimulus of the Waldeyer ring equivalent. Endolymphatic hydrops in the cochlea, elevated amounts of immunocompetent cells, and increased activity of cell proliferation within the endolymphatic sac were also considered after four intranasal injections of keyhole limpet hemocyanin.

CONCLUSION

Presumably, endolymphatic sac is supplied with immunocompetent cells from Waldeyer ring equivalent and has an ability of co-reaction with Waldeyer ring equivalent.

Proinflammatory cytokine expression in the endolymphatic sac during inner ear inflammation

The inner ear is capable of rapidly mounting an immune response that can ultimately lead to cochlear degeneration and permanent hearing loss. The role of the endolymphatic sac in this immune process is not clear. In order to investigate the cytokine expression of cells within the endolymphatic sac, a secondary inner ear immune response to keyhole limpet hemocyanin (KLH) was created in mice. The animals were sacrificed 3-48 h and 7 days following initiation of the immune response. The cochleas and endolymphatic sacs were assayed by immunocytochemistry for IL-1beta, TNFalpha, and IL-6. Three hours after KLH challenge of the scala tympani, the perisaccular tissue of the endolymphatic sac contained more inflammatory cells than the scala tympani or endolymphatic sac lumen. Only a few of these cells, however, expressed the proinflammatory cytokines IL-1beta and TNFalpha between 3 and 12 h after KLH injection. On the other hand, TNFalpha, which plays an important role in the cochlear secondary immune response, was expressed in cells in the endolymphatic sac lumen. The maximum percentage of cells expressing TNFalpha was seen later than in the scala tympani. Animals treated with systemic injection of the TNF blocker, etanercept, showed a reduction in the number of cells in the endolymphatic sac lumen. It is concluded that the cells in the endolymphatic sac lumen contribute to the amplification of the adaptive immune response by expressing TNFalpha, while the infiltration of cells into the perisaccular connective tissue is part of the nonspecific, innate, cochlear immune response.

Sudden sensorineural hearing loss: supporting the immunologic theory

Sudden deafness constitutes a diagnostic challenge. Classically, 2 causes, viral and vascular, are considered in the origin of idiopathic sudden hearing loss. More recently added to the list of possibilities are rupture of the membranous labyrinth and immune-mediated sensorineural hearing loss. The latter can be either primary and localized to the inner ear or, in perhaps fewer than one third of cases, secondary to generalized systemic autoimmune disease. The purpose of the present review is to define immune-mediated sudden sensorineural hearing loss as a distinctive entity, on the basis of clinical, immunologic, and pathological findings, and suggest a profile of the typical patient.

Tumor necrosis factor-alpha, an initiator, and etanercept, an inhibitor of cochlear inflammation

OBJECTIVES/HYPOTHESIS

The inner ear rapidly mounts an immune response that can lead to cochlear degeneration and permanent hearing loss. Identification of proinflammatory cytokine expression during the initiation of the response should lead to rational therapeutic strategies that block the response, reducing damaging sequelae.

STUDY DESIGN

A cochlear immune response to keyhole limpet hemocyanin (KLH) injected into the inner ear or subarachnoid space of sensitized animals was created. Etanercept was administered to a group of animals to blunt the immune response.

METHODS

Cochleae were immunoassayed for expression of interleukin-1beta, tumor necrosis factor-alpha, and interleukin-6 and evaluated for the amount of cochlear-infiltrated cells.

RESULTS

Tumor necrosis factor-alpha and interleukin-1beta were expressed by infiltrated cells shortly after KLH injection. Tumor necrosis factor-alpha was expressed whether the antigen was introduced with or without surgical trauma. Interleukin-1beta was also expressed by the cochlear fibrocytes during the immune response and in surgical control animals, but not after intrathecal injection of antigen. Interleukin-6 expression was minimal during the response. Based on this observation, animals were treated with systemic injection of Etanercept, which reduced cochlear infiltrating cell number and cochlear fibrosis.

CONCLUSION

Interleukin-1beta expression is a general cochlear response to trauma, whereas tumor necrosis factor-alpha expression in the infiltrated immunocompetent cells is the cytokine that induces amplification of the response that leads to cochlear disease.

Chronology of labyrinthitis ossificans induced by Streptococcus pneumoniae meningitis

OBJECTIVE

Labyrinthitis ossificans consists of novel osteogenesis that fills the normally patent cochlear and vestibular lumen as an end-stage sequelae to various pathologies. This study was designed to establish the sequence of events and chronology of the osteoneogenesis and calcification.

STUDY DESIGN

A prospective randomized double-blind study.

METHODS

By using serial application of different colored fluorochromes, which deposit in newly forming bone, the timing of bone deposition and bone remodeling can be established. Labyrinthitis ossificans was induced in six groups (n = 5) of gerbils by an intrathecal injection of live Streptococcus pneumoniae. Group 1 received no fluorochrome labels, group 2 received one label, group 3 received three labels, and groups 4, 5, and 6 received four labels. The temporal bones were harvested after 2 weeks (group 1), 1 month (group 2), 3 months (group 3), 4 months (group 4), 6 months (group 5), and 12 months (group 6).

RESULTS

Sixteen of the 25 animals that received labels developed ossification, demonstrated with fluorescent microscopy. In the animals that developed labyrinthitis ossificans, newly formed disorganized bone began calcifying as early as 3 weeks (label 1) after S. pneumoniae injection. Osteoneogenesis continued as evidenced by the presence of the other labels when first applied at 6 weeks (label 2), and 10 weeks (label 3). Ossification, calcification, and remodeling proceeded through a 12-month course, wherein a reduction of labels was present at 6 months and total disappearance by 12 months.

CONCLUSIONS

The use of fluorescent stains in this animal model provides a means to establish a timeline of the ossification seen in labyrinthitis ossificans.