Expression of mucins in mucoid otitis media

Middle Ear microRNAs Drive Mucin Gene Response

OBJECTIVE(S)

To investigate the role of microRNA-378 (miR-378) in the regulation of mucin gene expression and inflammatory response in human middle ear epithelial cells (HMEEC) during bacterial infection by non-typeable Haemophilus influenzae (NTHi).

METHODS

Human middle ear epithelial cells (HMEEC) were cultured and transfected with miR-378 or control miRNA. Post-transfection, cells were exposed to NTHi lysates. mRNA levels of MUC5B, MUC5AC, and IL-8 were quantified using RT-qPCR, and promoter activity was measured via luciferase assays. The effects of miR-378 on mucin and cytokine gene expression were analyzed.

RESULTS

Transfection with miR-378 significantly increased the expression of MUC5B (3.6 fold, p < 0.01), MUC5AC (19.1 fold, p < 0.01), and IL-8 (2.01 fold, p < 0.05) in HMEEC. NTHi exposure reduced MUC5B (1.385 fold, p < 0.05) and MUC5AC (1.61 fold, p < 0.05) gene expression in miR-378 transfected cells but significantly increased IL-8 levels (1.32 fold, p < 0.05). Luciferase assays showed that miR-378 upregulated the promoter activity of MUC5B (1.4 fold, p < 0.01) and MUC5AC (1.6 fold, p < 0.01) genes, indicating its role in transcriptional regulation.

CONCLUSION

miR-378 plays a crucial role in promoting mucin overproduction and an inflammatory response in the middle ear epithelium during OM. Targeting miR-378 could offer a novel therapeutic strategy for preventing the progression from AOM to COM.

LEVEL OF EVIDENCE

NA Laryngoscope, 135:1815-1820, 2025.

Mucin-induced surface dispersal of Staphylococcus aureus and Staphylococcus epidermidis via quorum-sensing dependent and independent mechanisms

Nasopharyngeal carriage of staphylococci spreads potentially pathogenic strains into (peri)oral regions and increases the chance of cross-infections. Some laboratory strains can also move rapidly on hydrated agar surfaces, but the biological relevance of these observations is not clear. Using soft-agar [0.3% (wt/vol)] plate assays, we demonstrate the rapid surface dispersal of (peri)oral isolates of Staphylococcus aureus and Staphylococcus epidermidis and closely related laboratory strains in the presence of mucin glycoproteins. Mucin-induced dispersal was a stepwise process initiated by the passive spreading of the growing colonies followed by their rapid branching (dendrites) from the colony edge. Although most spreading strains used mucin as a growth substrate, dispersal was primarily dependent on the lubricating and hydrating properties of the mucins. Using S. aureus JE2 as a genetically tractable representative, we demonstrate that mucin-induced dendritic dispersal, but not colony spreading, is facilitated by the secretion of surfactant-active phenol-soluble modulins (PSMs) in a process regulated by the agr quorum-sensing system. Furthermore, the dendritic dispersal of S. aureus JE2 colonies was further stimulated in the presence of surfactant-active supernatants recovered from the most robust (peri)oral spreaders of S. aureus and S. epidermidis. These findings suggest complementary roles for lubricating mucins and staphylococcal PSMs in the active dispersal of potentially pathogenic strains from perioral to respiratory mucosae, where gel-forming, hydrating mucins abound. They also highlight the impact that interspecies interactions have on the co-dispersal of S. aureus with other perioral bacteria, heightening the risk of polymicrobial infections and the severity of the clinical outcomes.

IMPORTANCE

Despite lacking classical motility machinery, nasopharyngeal staphylococci spread rapidly in (peri)oral and respiratory mucosa and cause cross-infections. We describe laboratory conditions for the reproducible study of staphylococcal dispersal on mucosa-like surfaces and the identification of two dispersal stages (colony spreading and dendritic expansion) stimulated by mucin glycoproteins. The mucin type mattered as dispersal required the surfactant activity and hydration provided by some mucin glycoproteins. While colony spreading was a passive mode of dispersal lubricated by the mucins, the more rapid and invasive form of dendritic expansion of Staphylococcus aureus and Staphylococcus epidermidis required additional lubrication by surfactant-active peptides (phenol-soluble modulins) secreted at high cell densities through quorum sensing. These results highlight a hitherto unknown role for gel-forming mucins in the dispersal of staphylococcal strains associated with cross-infections and point at perioral regions as overlooked sources of carriage and infection by staphylococci.

17β-estradiol Attenuates the Middle Ear Inflammatory Response to Nontypeable Haemophilus influenzae

OBJECTIVES

17β-estradiol (E2) is a steroidal hormone with immunomodulatory functions that play a role in infectious and inflammatory diseases. E2 was recently identified as the leading upstream regulator of differentially expressed genes in a comparative RNA sequencing study of pediatric patients with otitis media (OM) versus OM-free counterparts and may therefore play a role in the inflammatory response to bacterial otopathogens during pediatric OM. This study examined the effect of E2 on bacterial-induced inflammatory cytokine expression in an in vitro pediatric OM model.

METHODS

An immortalized middle ear (ME) epithelial cell line, ROM-SV40, was developed from a pediatric recurrent OM patient. The culture was exposed to E2 at physiological levels for 1-48 h prior to 6 h-stimulation with nontypeable Haemophilus influenzae (NTHi) whole cell lysate. TNFA, IL1B, IL6, and IL8 were assayed by qPCR and ELISA.

RESULTS

E2 pretreatment (24 h) abrogated NTHi induction of IL6; a longer pretreatment (1-10 nM, 48 h) abrogated IL1B induction (p < 0.05). E2 pretreatment (5 nM, 48 h) abrogated NTHi-induced IL8 secretion (p = 0.017).

CONCLUSION

E2 pretreatment partially rescued NTHi-induced cytokine production by ME epithelia. These data support a role for E2 in moderating the excessive inflammatory response to middle ear infection that contributes to OM pathophysiology.

LEVELS OF EVIDENCE

NA Laryngoscope, 134:3815-3819, 2024.

Predictors of effusion viscosity in otitis media with effusion: neutrophil lymphocyte ratio versus mean platelet volume

OBJETIVOS

comparar entre el índice de neutrófilos linfocitos (NLR) y el volumen plaquetario medio (VPM) en la predicción de la viscosidad del derrame en la otitis media con derrame. MATERIALES Y MéTODOS: Se incluyeron en el estudio 248 niños con derrame en el oído medio. Se evaluaron los hemogramas completos (CBC) preoperatorios. Se registraron los valores de NLR y MPV. La viscosidad del derrame se evaluó durante la cirugía mientras se aspiraba el derrame después de la miringotomía. Se clasificaron 2 tipos de derrames; tipos serosos y mucoides.

RESULTADOS

se reportaron diferencias estadísticamente significativas en NLR y MPV entre los derrames serosos y mucoides. Los valores de corte de NLR y MPV para diferenciar entre derrames serosos y mucoides fueron 1,21 y 7,95 respectivamente. Cuando se compararon NLR y MPV, NLR pareció tener mayor sensibilidad, especificidad y precisión diagnóstica que MPV. CONCLUSIóN: NLR es superior a MPV como predictor de la viscosidad del derrame en otitis media con derrame. Ambos marcadores se consideran rentables y fiables para la evaluación de la viscosidad del derrame.

Minimally invasive trans-tympanic eustachian tube occlusion animal model

OBJECTIVE

Eustachian tube dysfunction is believed to be involved in the pathogenesis of many middle ear diseases including chronic suppurative otitis media. We aimed to describe a simple and reliable animal model of Eustachian Tube obstruction to further research into middle ear disorders.

STUDY DESIGN

Prospective cohort study in animals.

SETTING

University laboratory.

SUBJECTS AND METHODS

30 mice C57Bl/6J (n = 15) and CBA/CaJ (n = 15) aged 6-8 weeks received transtympanic Eustachian tube occlusion on left ear trough an acute tympanic membrane perforation using thermoplastic latex used in dental procedures (gutta percha). Control mice (n = 6) received tympanic membrane perforation only. At two and four weeks, the mice were observed for signs of Eustachian tube dysfunction and compared to control ears. ET dysfunction was defined as presence of effusion in the middle ear.

RESULTS

100% (n = 30) of the treated ears had otoscopic signs of Eustachian tube dysfunction at two weeks and the endpoint time of four weeks, compared to 0% in control mice (0/6). Temporary head tilt lasting up to 2 days were observed in 3 mice (10%). No other potential adverse events were recorded. No bacterial growth was determined in the middle ear fluid.

CONCLUSION

We describe a technically easy and reliable method for Eustachian tube occlusion in mice with an excellent success rate and minimal morbidity.

DNA Methylation Patterns of Chronic Explosive Breaching in U.S. Military Warfighters

Background: Injuries from exposure to explosions rose dramatically during the Iraq and Afghanistan wars, which motivated investigation of blast-related neurotrauma. We have undertaken human studies involving military "breachers" -exposed to controlled, low-level blast during a 3-days explosive breaching course. Methods: We screened epigenetic profiles in peripheral blood samples from 59 subjects (in two separate U.S. Military training sessions) using Infinium MethylationEPIC BeadChips. Participants had varying numbers of exposures to blast over their military careers (empirically defined as high ≥ 40, and conversely, low < 39 breaching exposures). Daily self-reported physiological symptoms were recorded. Tinnitus, memory problems, headaches, and sleep disturbances are most frequently reported. Results: We identified 14 significantly differentially methylated regions (DMRs) within genes associated with cumulative blast exposure in participants with high relative to low cumulative blast exposure. Notably, NTSR1 and SPON1 were significantly differentially methylated in high relative to low blast exposed groups, suggesting that sleep dysregulation may be altered in response to chronic cumulative blast exposure. In comparing lifetime blast exposure at baseline (prior to exposure in current training), and top associated symptoms, we identified significant DMRs associated with tinnitus, sleep difficulties, and headache. Notably, we identified KCNN3, SOD3, MUC4, GALR1, and WDR45B, which are implicated in auditory function, as differentially methylated associated with self-reported tinnitus. These findings suggest neurobiological mechanisms behind auditory injuries in our military warfighters and are particularly relevant given tinnitus is not only a primary disability among veterans, but has also been demonstrated in active duty medical records for populations exposed to blast in training. Additionally, we found that differentially methylated regions associated with the genes CCDC68 and COMT track with sleep difficulties, and those within FMOD and TNXB track with pain and headache. Conclusion: Sleep disturbances, as well as tinnitus and chronic pain, are widely reported in U.S. military service members and veterans. As we have previously demonstrated, DNA methylation encapsulates lifetime exposure to blast. The current data support previous findings and recapitulate transcriptional regulatory alterations in genes involved in sleep, auditory function, and pain. These data uncovered novel epigenetic and transcriptional regulatory mechanism underlying the etiological basis of these symptoms.

MUC5B induces in vitro neutrophil extracellular trap formation: Implication in otitis media

BACKGROUND

Chronic otitis media (COM) is characterized by middle ear fluid predominantly containing cytokines, Nontypeable haemophilus influenzae (NTHi), the mucin MUC5B, and neutrophil extracellular traps (NETs). NETs consist of extracellular DNA coated with antibacterial proteins such as myeloperoxidase (MPO) and citrullinated histone 3 (CitH3). NETs can damage tissues and sustain inflammation. Our study aimed to develop an in vitro model of NETosis, testing COM inductors.

METHODS

NETosis was evaluated in fresh blood human neutrophils attached to collagen-coated plates and in suspension exposed to phorbol myristate acetate (PMA) as a control, and COM relevant mediators. Confocal microscopy, DNA fluorescence assay and flow cytometry were used to quantify NETosis.

RESULTS

PMA exposure induced DNA, MPO, and CitH3 by immunofluorescence (IF) most significantly at 3 hours (3.8-fold for DAPI, 7.6-fold for MPO, and 6.9-fold for CitH3, all P < .05). IL-8 and TNF-α cytokines showed milder increases of DAPI, MPO, and CitH3 positive cells. NTHi had no effect on these NETs markers. Purified salivary MUC5B (10 to 40 μg/mL) produced potent increases, comparable to PMA. A composite NET score summing the fold-increases for DAPI, MPO, and CitH3 demonstrated PMA at 13.6 to 19 relative to control set at 1; and MUC5B at 8.6 to 16.3 (all P < .05). IL-8 and TNF-α showed scores of 5.4 and 3, respectively, but these were not statistically significant.

CONCLUSION

We developed a reliable in vitro assay for NETosis which demonstrated that salivary MUC5B is a potent inductor of NETs whereas IL-8, TNF-α, live and lyzed NTHi demonstrated minimal to no NETosis.

LEVEL OF EVIDENCE

NA.

Analysis of Inflammatory Signaling in Human Middle Ear Cell Culture Models of Pediatric Otitis Media

OBJECTIVES/HYPOTHESIS

Cell culture models are valuable tools for investigation of the molecular pathogenesis of diseases including otitis media (OM). Previous study indicates that age-, sex-, and race-associated differences in molecular signaling may impact disease pathophysiology. Currently, a singular immortalized middle ear epithelial (MEE) cell line exists, HMEEC-1, derived from an adult without known middle ear disease. In this study, HMEEC-1 and primary MEE cultures from pediatric patients with and without OM were stimulated with inflammatory cytokines or OM-pathogenic bacterial lysates to examine differences in the response of molecules associated with OM pathogenesis.

STUDY DESIGN

Case-control series.

METHODS

MEE cultures were established from patients aged <6 years: two with recurrent OM (ROM), two with OM with effusion (OME), and one patient without OM who was undergoing cochlear implant surgery control undergoing cochlear implantation (Peds CI). Primary MEE cultures and HMEEC-1 cells were stimulated with tumor necrosis factor-α, interleukin (IL)-1β, or nontypeable Haemophilus influenzae lysate. TNFA, IL1B, IL6, IL8, IL10, and MUC5B were assayed via quantitative polymerase chain reaction. IL-8 was assayed by enzyme-linked immunosorbent assay.

RESULTS

Gene/protein target expressions were frequently higher in pediatric OM lines than in HMEEC-1 and Peds CI. HMEEC-1 cells were frequently less responsive to stimuli than all pediatric lines. OME lines were often more responsive than ROM lines.

CONCLUSIONS

OM may be associated with specific molecular phenotypes that are retained in primary cell culture. Adult-derived HMEEC-1 cells differ significantly in baseline expression and response of OM-associated molecules relative to pediatric MEE cells. Work is underway to immortalize pediatric OM MEE cultures as improved tools for the OM research community.

LEVEL OF EVIDENCE

4 Laryngoscope, 131:410-416, 2021.

Unsolved problems and new medical approaches to otitis media

INTRODUCTION

Otitis media (OM) is a spectrum of infectious and inflammatory diseases that involve the middle ear. It includes acute otitis media (AOM), otitis media with effusion (OME) and chronic suppurative otitis media (CSOM).

AREAS COVERED

This manuscript discusses some of the emerging and unsolved problems regarding OM, and some of the newly developed prophylactic and therapeutic medical measures.

EXPERT OPINION

In recent years, considerable progress in the knowledge of OM physiopathology has been made. However, although extremely common, diseases included under OM have not been adequately studied, and many areas of development, evolution and possible treatments of these pathologies are not defined. It is necessary that these deficiencies be quickly overcome if we want to reduce the total burden of a group of diseases that still have extremely high medical, social and economic relevance.

Antibiotic modulation of mucins in otitis media; should this change our approach to watchful waiting?

BACKGROUND

Gel-forming mucins (GFMs) play important roles in otitis media (OM) pathogenesis. Increased mucin expression is activated by pathogens and proinflammatory cytokines. Bacterial biofilms influence inflammation and resolution of OM and may contribute to prolonged mucin production. The influence of specific pathogens on mucin expression and development of chronic OM with effusion (OME) remains an area of significant knowledge deficit.

OBJECTIVES

To assess the relationship between GFM expression, specific pathogens, middle ear mucosal (MEM) changes, biofilm formation, and antibiotic utilization.

METHODS

Mixed gender chinchillas were inoculated with nontypeable Haemophilus influenzae (NTHi) strain 86028NP or Streptococcus pneumoniae (SP) strain TIGR4 via transbulla injection. Antibiotic was administered on day 3-5 post inoculation. GFM expression was measured by quantitative PCR. Biofilm formation was identified and middle ear histologic changes were measured.

RESULTS

SP infection resulted in higher incidence of biofilm and ME effusion compared with NTHi infection. However, NTHi persisted in the ME longer than SP with no substantive bacterial clearance detected on day 10 compared with complete bacterial clearance on day 10 for 50-60% of the SP-infected chinchillas. Both infections increased MEM inflammatory cell infiltration and thickening. NTHi upregulated the Muc5AC, Muc5B and Muc19 expression on day 10 (p = 0.0004, 0.003, and 0.002 respectively). SP-induced GFM upregulations were trended toward significant. In both NTHi and SP infections, the degree of GFM upregulation had a direct relationship to increased MEM hypertrophy, inflammatory cell infiltration and biofilm formation. Antibiotic treatment reduced the incidence of ME effusion and biofilm, limited the MEM changes and reversed the GFM upregulation. In NTHi infection, the rate of returning to baseline level of GFMs in treated chinchillas was quicker than those without treatment.

CONCLUSIONS

In an animal model of OM, GFM genes are upregulated in conjunction with MEM hypertrophy and biofilm formation. This upregulation is less robust and more quickly ameliorated to a significant degree in the NTHi infection with appropriate antibiotic therapy. These findings contribute to the understanding of pathogen specific influences on mucin expression during OM pathogenesis and provide new data which may have implications in clinical approach for OM treatment.

Cellular content plays a crucial role in Non-typeable Haemophilus influenzae infection of preinflamed Junbo mouse middle ear

Non-typeable Haemophilus influenzae (NTHi) is a major pathogen causing acute otitis media (AOM). The relationship between the cellular content of the middle ear fluid (MEF) during AOM and infection of NTHi is poorly understood. Using the Junbo mouse, a characterised NTHi infection model, we analysed the cellular content of MEF and correlated the data with NTHi titres. The MEF of the Junbo mouse was heterogeneous between ears and was graded from 1 to 5; 1 being highly serous/clear and 5 being heavily viscous/opaque. At seven-day post-intranasal inoculation, NTHi was not found in grade-1 or 2 fluids, and the proportion of MEF that supported NTHi increased with the grade. Analyses by flow cytometry indicated that the cellular content was highest in grade-4 and 5 fluids, with a greater proportion of necrotic cells and a low-live cell count. NTHi infection of the middle ear increased the cell count and led to infiltration of immune cells and changes in the cytokine and chemokine levels. Following NTHi inoculation, high-grade infected MEFs had greater neutrophil infiltration whereas monocyte infiltration was significantly higher in serous noninfected low-grade fluids. These data underline a role for immune cells, specifically monocytes and neutrophils, and cell necrosis in NTHi infection of the Junbo mouse middle ear.

Characterization of mucoid and serous middle ear effusions from patients with chronic otitis media: implication of different biological mechanisms?

BACKGROUND

Chronic otitis media with effusion (COME) is characterized by persistent middle ear effusions that are in most cases highly viscous, but some patients present with serous fluid. This study aimed at comprehensively characterizing the macromolecular composition of mucoid vs. serous middle ear effusions (MEEs).

METHODS

MEEs from patients with COME were analyzed for proteins by mass spectrometry (MS) and western blot techniques, total DNA quantity, bacterial DNA (16S sequencing), and cytokine content. Proteomics datasets were studied in Ingenuity Pathway Analysis (IPA).

RESULTS

Mucoid samples showed a global tendency of increased pro-inflammatory mediators. Interleukin-1β (IL-1β) and IL-10 were significantly more abundant in serous samples (p < 0.01). Mucoid samples had higher DNA quantity (p = 0.04), more likely to be positive in MUC5B protein (p = 0.008) and higher peptide counts (12,786 vs. 2225), as well as an overall larger number of identified proteins (331 vs. 177), compared to serous. IPA found the mucoid sample dataset to be related to immune cell function and epithelial remodeling, whereas the serous sample dataset showed acute responses and blood-related proteins. Interestingly, serous samples showed more bacterial DNA than mucoid ones, with less bacterial genera variability.

CONCLUSION

This study demonstrates divergent immune responses in children with COME by effusion quality.

Differential diagnosis of otitis media with effusion using label-free Raman spectroscopy: A pilot study

Otitis media with effusion (OME) is an important and common condition affecting hearing in pediatric patients characterized by the presence of fluid in the middle ear space. The fluid is normally described as serous or mucoid based on differences in the fluid viscosity. The differential diagnosis of two OMEs, namely serous and mucoid is of significant clinical value because while the former is self-limiting, surgical procedure is commonly required for the latter. However, accurate identification of fluid types remains a challenging target unattainable with current clinical modalities due to unavailability of nonperturbative molecular tools. Here, we report an emerging spectroscopy approach featuring Raman scattering and multivariate analysis of spectral patterns to discern serous and mucoid fluids, obtained from pediatric patients undergoing myringotomy and tube placement, by providing information of differentially expressed molecules with high specificity. We demonstrate the feasibility of Raman spectroscopy-based approach to categorize middle ear effusion based on the characteristic spectral markers, notably of mucin, with classification accuracy of 91% and 93% for serous and mucoid, respectively. Our findings pave the way for further development of such a tool for fully noninvasive application that will lead to objective and accurate diagnosis thereby reducing unnecessary visits and surgical procedures.

Nontypeable Haemophilus influenzae lysates increase heterogeneous nuclear ribonucleoprotein secretion and exosome release in human middle-ear epithelial cells

Nontypeable Haemophilus influenzae (NTHi), one of the most common acute otitis media (OM) pathogens, is postulated to promote middle-ear epithelial remodeling in the progression of OM from acute to chronic. The goal of this study was to examine early quantitative proteomic secretome effects of NTHi lysate exposure in a human middle-ear epithelial cell (HMEEC) line. NTHi lysates were used to stimulate HMEEC, and conditional quantitative stable isotope labeling with amino acids in cell culture of cell secretions was performed. Mass spectrometry analysis identified 766 proteins across samples. Of interest, several heterogeneous nuclear ribonucleoproteins (hnRNPs) were regulated by NTHi lysate treatment, especially hnRNP A2B1 and hnRNP Q, known to be implicated in microRNA (miRNA) packaging in exosomes. After purification, the presence of exosomes in HMEEC secretions was characterized by dynamic light scattering (<100 nm), transmission electron microscopy, and CD63/heat shock protein 70 positivity. hnRNP A2B1 and hnRNP Q were confirmed to be found in exosomes by Western blot and proteomic analysis. Finally, exosomal miRNA content comprised 110 unique miRNAs, with 5 found to be statistically induced by NTHi lysate (miR-378a-3p + miR-378i, miR-200a-3p, miR-378g, miR30d-5p, and miR-222-3p), all known to target innate immunity genes. This study demonstrates that NTHi lysates promote release of miRNA-laden exosomes from middle-ear epithelium in vitro. -Val, S., Krueger, A., Poley, M., Cohen, A., Brown, K., Panigrahi, A., Preciado, D. Nontypeable Haemophilus influenzae lysates increase heterogeneous nuclear ribonucleoprotein secretion and exosome release in human middle-ear epithelial cells.

Association of Gel-Forming Mucins and Aquaporin Gene Expression With Hearing Loss, Effusion Viscosity, and Inflammation in Otitis Media With Effusion

Importance

Persistent, viscous middle ear effusion in pediatric otitis media (OM) contributes to increased likelihood of anesthesia and surgery, conductive hearing loss, and subsequent developmental delays. Biomarkers of effusion viscosity and hearing loss have not yet been identified despite the potential that such markers hold for targeted therapy and screening.

Objective

To investigate the association of gel-forming mucins and aquaporin 5 (AQP5) gene expression with inflammation, effusion viscosity, and hearing loss in pediatric OM with effusion (OME).

Design, Setting, and Participants

Case-control study of 31 pediatric patients (aged 6 months to 12 years) with OME undergoing tympanostomy tube placement and control individuals (aged 1 to 10 years) undergoing surgery for cochlear implantation from February 1, 2013, through November 30, 2014. Those with 1 or more episodes of OM in the previous 12 months, immunologic abnormality, anatomical or physiologic ear defect, OM-associated syndrome (ie, Down syndrome, cleft palate), chronic mastoiditis, or history of cholesteatoma were excluded from the study. All patients with OME and 1 control were recruited from Children's Hospital of Wisconsin, Milwaukee. The remainder of the controls were recruited from Sick Kids Hospital in Toronto, Ontario, Canada.

Main Outcomes and Measures

Two to 3 middle ear biopsy specimens, effusions, and preoperative audiometric data (obtained <3 weeks before surgery) were collected from patients; only biopsy specimens were collected from controls. Expression of the mucin 2 (MUC2), mucin 5AC (MUC5AC), mucin 5B (MUC5B), and AQP5 genes were assayed in middle ear biopsy specimens by quantitative polymerase chain reaction. One middle ear biopsy specimen was sectioned for histopathologic analysis. Reduced specific viscosity of effusions was assayed using rheometry.

Results

Of the 31 study participants, 24 patients had OME (mean [SD] age, 50.4 [31.9] months; 15 [62.5%] male; 16 [66.7%] white) and 7 acted as controls (mean [SD] age, 32.6 [24.4] months; 2 [26.6%] male; 6 [85.7%] white). Mucins and AQP5 gene expression were significantly higher in patients with OME relative to controls (MUC2: ratio, 127.6 [95% CI, 33.7-482.7]; MUC5AC: ratio, 3748.8 [95% CI, 558.1-25 178.4]; MUC5B: ratio, 471.1 [95% CI, 130.7-1697.4]; AQP5: ratio, 2.4 [95% CI, 1.1-5.6]). A 2-fold increase in MUC5B correlated with increased hearing loss (air-bone gap: 7.45 dB [95% CI, 2.65-12.24 dB]; sound field: 6.66 dB [95% CI, 6.63-6.69 dB]), effusion viscosity (2.75 mL/mg; 95% CI, 0.89-4.62 mL/mg), middle ear epithelial thickness (3.5 μm; 95% CI, 1.96-5.13 μm), and neutrophil infiltration (odds ratio, 1.7; 95% CI, 1.07-2.72). A 2-fold increase in AQP5 correlated with increased effusion viscosity (1.94 mL/mg; 95% CI, 0.08-3.80 mL/mg).

Conclusions and Relevance

Further exploration of the role of MUC5B in the pathophysiology of OME holds promise for development of novel, targeted therapies to reduce effusion viscosity, facilitation of effusion clearance, and prevention of disease chronicity and hearing loss in patients with OME.

The Role of the Notch Signal Pathway in Mucosal Cell Metaplasia in Mouse Acute Otitis Media

Otitis media (OM) is a major cause of morbidity in pediatric and adult patients. This inflammatory condition is characterized by mucous cell hyperplasia that is thought to produce mucins from the middle ear mucosa. We are interested in the role of Notch signalling pathway in this inflammatory process. Using an acute otitis media (AOM) mouse model through injection of Streptococcus Pneumoniae into the middle ear, histopathologic examination and quantitative RT-PCR, acute inflammation with the thickness of mucosa, Goblet cell hyperplasia, and cilia loss were determined and gene expression related to the Notch signaling pathway were evaluated. Upregulation of the mucous cell markers, Argr2 and Muc5AC, and downregulation of the cilia cell marker, Foxj1 and Dnai2, were observed in AOM. In addition, genes encoding Notch receptors and ligands (Notch1, Notch2, Notch3, Notch4 and Dll1) and the Notch target genes (Hes1, Hes5, Hey1, NRARP) in AOM decreased significantly. The expression of the Notch1 and Jagged1 also showed down-regulation throughout the mouse middle ear epithelium. Taken together, this study suggests that downregulation of the Notch signaling pathway is involved in the mucosa hyperplasia during AOM.

Purification and characterization of microRNAs within middle ear fluid exosomes: implication in otitis media pathophysiology

BACKGROUND

Otitis media (OM) is characterized by acute infection progressing to chronic middle ear effusion (MEE). Extracellular secretion of microRNAs (miRNAs) in exosomes is a newly discovered mechanism for cells exerting distant cell genetic regulation. Whether MEE contains exosomes with specific miRNAs is unknown. This study aimed to purify and characterize the exosomal and miRNA content of MEE.

METHOD

MEEs were subjected to Exoquick exosomal purification and EXOCET exosomal quantification. Extracted vesicles were analyzed by dynamic light scattering (DLS), transmission electron microscopy (TEM), and immunoblotting of HSP-70. NanoString hybridization was performed to profile miRNAs. Exosomal protein content was profiled by Liquid chromatography tandem mass spectrometry (LC-MS/MS).

RESULTS

EXOCET assays showed presence of exosomes (0-0.5 × 10⁷/ml) in MEEs. DLS confirmed exosomal size between 10 and 200 nm. Western blot analysis showed presence of HSP-70. Twenty-nine miRNAs were found to be unique to MEEs. The most abundant miRNA was miR-223, a miRNA typically secreted by neutrophils. Proteomics demonstrated typical neutrophil markers as well as common innate immune molecules.

CONCLUSION

To our knowledge, this the first report demonstrating the presence of exosomes transporting miRNAs in MEEs. These findings open a broad and novel area of research in OM pathophysiology as driven by miRNA cell communication.

In vivo imaging of the Muc5b gel-forming mucin

Gel-forming mucins are macromolecules produced by goblet cells and responsible for the mucus gel formation. Changes in goblet cell density and in gel-forming mucin production have emerged as sensitive indicators for mucosal diseases. A Muc5b-GFP tagged reporter mouse was used to assess Muc5b production in mouse tissues by immunofluorescence microscopy and fluorescent activity using stereromicroscopy and probe-based confocal laser endomicroscopy. Muc5b production was followed longitudinally by recording the fluorescent activity in vagina and in embryonic lung explants under stimulation by interleukin 13. We show that the GFP is easily visualized in the mouse adult ear, nose, trachea, gallbladder, and cervix. Live Muc5b is also easily monitored in the nasal cavity, trachea and vagina where its production varies during the estrus cycle with a peak at the proestrus phase and in pregnant mice. Explant culture of reporter mouse embryonic whole lung shows that interleukin 13 stimulates Muc5b production. The transgenic Muc5b-GFP mouse is unique and suitable to study the mechanisms that regulate Muc5b production/secretion and mucous cell differentiation by live imaging and can be applied to test drug efficacy in mucosal disease models.

Proteomic Characterization of Middle Ear Fluid Confirms Neutrophil Extracellular Traps as a Predominant Innate Immune Response in Chronic Otitis Media

BACKGROUND

Chronic Otitis Media (COM) is characterized by middle ear effusion (MEE) and conductive hearing loss. MEE reflect mucus hypersecretion, but global proteomic profiling of the mucosal components are limited.

OBJECTIVE

This study aimed at characterizing the proteome of MEEs from children with COM with the goal of elucidating important innate immune responses.

METHOD

MEEs were collected from children (n = 49) with COM undergoing myringotomy. Mass spectrometry was employed for proteomic profiling in nine samples. Independent samples were further analyzed by cytokine multiplex assay, immunoblotting, neutrophil elastase activity, next generation DNA sequencing, and/or immunofluorescence analysis.

RESULTS

109 unique and common proteins were identified by MS. A majority were innate immune molecules, along with typically intracellular proteins such as histones and actin. 19.5% percent of all mapped peptide counts were from proteins known to be released by neutrophils. Immunofluorescence and immunoblotting demonstrated the presence of neutrophil extracellular traps (NETs) in every MEE, along with MUC5B colocalization. DNA found in effusions revealed unfragmented DNA of human origin.

CONCLUSION

Proteomic analysis of MEEs revealed a predominantly neutrophilic innate mucosal response in which MUC5B is associated with NET DNA. NETs are a primary macromolecular constituent of human COM middle ear effusions.

A novel predictive marker for the viscosity of otitis media with effusion

OBJECTIVES

To evaluate the significance of neutrophil-to-lymphocyte ratio and platelet-to-lymphocyte ratio for the prediction of the viscosity of otitis media with effusion.

METHODS

This retrospective study was performed on 81 patients who were admitted to the otolaryngology clinic.The patients were divided into two groups according to their effusion type, as serous or mucoid, which was defined intraoperatively after myringotomy. The NLR and PLR were calculated as a simple ratio between the absolute neutrophil/platelet and absolute lymphocyte counts.Tympanostomy tube insertion was performed for all cases.Under direct visualization, the effusion was aspirated and classified as serous or mucous.

RESULTS

We postulated that an NLR value of less than 1.38 may show mucoid effusion and if the PLR value is less than 97.96, the effusion is mucoid.

CONCLUSIONS

We speculate that a useful predictor of viscosity for a middle ear effusion could prevent unnecessary surgeries and additional costs in the treatment of EMO. Additional studies are needed to confirm our results.

Impact of Staphylococcus epidermidis lysates on middle ear epithelial proinflammatory and mucogenic response

BACKGROUND

Chronic otitis media with effusion (COME) develops after sustained inflammation and is characterized by secretory middle ear epithelial metaplasia and effusion, most frequently mucoid. Staphylococcus epidermidis, typically considered a commensal organism, is very frequently recovered in chronic middle ear fluid and in middle ear biofilms. Although it has been shown to drive inflammation in sinonasal epithelium, the impact of S. epidermidis on COME is markedly understudied. The goal of this study was to examine the in vitro effects of S. epidermidis lysates on murine and human middle ear epithelial cells.

METHODS

Staphylococcus epidermidis lysates were generated and used to stimulate submerged and differentiated human and murine epithelial cells (MEECs) for 24 to 48 hours. Quantitative real time-polymerase chain reaction, Western blot, enzyme-linked immunosorbent assay, and immunocytochemistry techniques were performed to interrogate the mucin gene MUC5AC and MUC5B expression and protein production, chemokine response, as well as NF-κB activation. Luciferase reporter assays were performed to further evaluate nuclear factor κB (NF-κB) activation and query specific promoter responses after S. epidermidis exposure.

RESULTS

Staphylococcus epidermidis induced a time- and dose-dependent MUC5AC and MUC5B overexpression along with a parallel overexpression of Cxcl2 in mouse MEEC and IL-8 in human MEEC. Further investigations in mMEEC showed a 1.3 to 1.5 induction of the MUC5AC and MUC5B promoters. As potential mechanisms for these responses, induction of an oxidative stress marker, along with early nuclear translocation and activation of NF-κB, was found. Finally, chronic exposure induced marked epithelial thickening of cells differentiated at the air liquid interface.

CONCLUSIONS

Staphylococcus epidermidis lysates activate a proinflammatory response in MEEC, including mucin gene expression and protein production. Although typically considered a nonpathogenic commensal organism in the ear, these results suggest that they may play a role in the perpetuation of an inflammatory and mucogenic response in COME.

Noninvasive depth-resolved optical measurements of the tympanic membrane and middle ear for differentiating otitis media

OBJECTIVE/HYPOTHESIS

In this study, optical coherence tomography (OCT) is used to noninvasively and quantitatively determine tympanic membrane (TM) thickness and the presence and thickness of any middle-ear biofilm located behind the TM. These new metrics offer the potential to differentiate normal, acute, and chronic otitis media (OM) infections in pediatric subjects.

STUDY DESIGN

Case series with comparison group.

METHODS

The TM thickness of 34 pediatric subjects was acquired using a custom-built, handheld OCT system following a traditional otoscopic ear exam.

RESULTS

Overall thickness (TM and any associated biofilm) was shown to be statistically different for normal, acute, and chronic infection groups (normal-acute and normal-chronic: P value < 0.001; acute-chronic: P value = 0.0016). Almost all observed scans from the chronic group had an accompanying biofilm structure. When the thickness of the TM and biofilm were considered separately in chronic OM, the chronic TM thickness correlated with the normal group (P value = 0.68) yet was still distinct from the acute OM group (P value < 0.001), indicating that the TM in chronic OM returns to relatively normal thickness levels.

CONCLUSION

Identifying these physical changes in vivo provides new metrics for noninvasively and quantitatively differentiating normal, acute, and chronic OM. This new diagnostic information has the potential to assist physicians to more effectively and efficiently screen, manage, and refer patients based on quantitative data.

LEVEL OF EVIDENCE

4.

Otitis media in sperm-associated antigen 6 (Spag6)-deficient mice

Mammalian SPAG6 protein is localized to the axoneme central apparatus, and it is required for normal flagella and cilia motility. Recent studies demonstrated that the protein also regulates ciliogenesis and cilia polarity in the epithelial cells of brain ventricles and trachea. Motile cilia are also present in the epithelial cells of the middle ear and Eustachian tubes, where the ciliary system participates in the movement of serous fluid and mucus in the middle ear. Cilia defects are associated with otitis media (OM), presumably due to an inability to efficiently transport fluid, mucus and particles including microorganisms. We investigated the potential role of SPAG6 in the middle ear and Eustachian tubes by studying mice with a targeted mutation in the Spag6 gene. SPAG6 is expressed in the ciliated cells of middle ear epithelial cells. The orientation of the ciliary basal feet was random in the middle ear epithelial cells of Spag6-deficient mice, and there was an associated disrupted localization of the planar cell polarity (PCP) protein, FZD6. These features are associated with disordered cilia orientation, confirmed by scanning electron microscopy, which leads to uncoordinated cilia beating. The Spag6 mutant mice were also prone to develop OM. However, there were no significant differences in bacterial populations, epithelial goblet cell density, mucin expression and Eustachian tube angle between the mutant and wild-type mice, suggesting that OM was due to accumulation of fluid and mucus secondary to the ciliary dysfunction. Our studies demonstrate a role for Spag6 in the pathogenesis of OM in mice, possibly through its role in the regulation of cilia/basal body polarity through the PCP-dependent mechanisms in the middle ear and Eustachian tubes.

The adenocarcinoma cell surface mucin receptor for alpha-fetoprotein: is the same receptor present on circulating monocytes and macrophages? A commentary

The mucin family of proteins is largely expressed on sedentary epithelial cells lining the gastrointestinal, pulmonary, and reproductive tracts and their associated organs and malignant tumors. It is less well-known that mucins are also expressed on circulatory cells of the immune and inflammatory systems, such as monocytes, macrophages, leukemic, and lymphoma cells. The epithelial mucins function in (a) protection and lubrication of mucosal linings, (b) cell adhesion and cell-to-cell contact, (c) cell migration and metastasis, and (d) signal transduction. It would be logical to presume that mucins expressed on circulating mononuclear cells could perform similar functions. Recently, it was proposed that the alpha-fetoprotein (AFP) receptor, known to be present on solid epithelial-derived malignant tumor cells, can be identified as a mucin glycoprotein. Interestingly, it was also reported that AFP binds to a receptor on circulating cells and sedentary tumor cells of lymphoreticular origin, especially monocytes associated with lymphomas and leukemias. The primary objective of the present commentary is to present literature-based evidence that some of the cell surface mucins on sedentary epithelial tumor cells and certain mucins expressed on circulating monocytes/macrophages are identical to the AFP receptor. The secondary objective is to discuss the role of AFP and its derived peptides in the growth suppression of adenocarcinomas and lymphomas using the AFP-mucin receptor concept as a key to the mechanism of tumor growth inhibition.

Math1, retinoic acid, and TNF-α synergistically promote the differentiation of mucous cells in mouse middle ear epithelial cells in vitro

BACKGROUND

A key issue in otitis media (OM) is mucous cell metaplasia in the middle ear mucosa, a condition for hyperproduction of mucus in the middle ear mucosa and development of chronic OM. However, little is known about the driving force for the differentiation of mucous cells in OM.

METHODS

Mouse middle ear epithelial cells (mMEECs) were used in this study to test whether Math1, a critical transcription factor for the development of mucous cells in the intestine, synergizes with inflammatory cytokines (tumor necrosis factor-α (TNF-α)) and other epithelial differentiation factors (retinoid acid (RA)) to induce the differentiation of mMEECs into mucus-like cells in vitro. Simultaneously, Math1 was transduced into the middle ear mucosa in order to observe whether it induces mucous cell hyperplasia in vivo.

RESULTS

Math1 significantly increased the mucus cell numbers in the middle ear mucosa of mice. Math1, in the presence of TNF-α and epithelial differentiation factor RA, synergistically promoted the differentiation of mMEECs into mucus-like cells through upregulation of mucins and their chaperones: trefoil factors in vitro. RA treatment for 12 h activated Math1, although RA alone had very limited effects on mucus-like cell differentiation.

CONCLUSION

Math1 plays a critical role in the pathogenesis of OM by induction of mucous cell differentiation in the presence of TNF-α and RA.

Middle ear fluid characteristics in pediatric otitis media with effusion

OBJECTIVE

Persistent otitis media with effusion is caused by poor clearance of middle ear fluid usually following an episode of acute otitis media. This fluid is thought to be viscous and poorly transportable by cilia. Because a subset of children require multiple myringotomy and tube placements for recurrent disease, we hypothesized that children requiring repeated procedures would have effusion fluid that was more viscous and less transportable than those having their first procedure.

DESIGN

Prospective clinical study.

SETTING

Tertiary care center.

PATIENTS AND INTERVENTIONS

Middle ear secretions were collected at the time of myringotomy and tube insertion in 36 children accrued sequentially. Twenty-six of these children were having their first procedure and 10 had previously undergone myringotomy and tube placement.

MAIN OUTCOME MEASURES

The secretions were evaluated for in vitro mucociliary transportability, and dynamic rheology in a magnetic microrheometer.

RESULTS

Children with the need for repeated procedures had effusions with lower mucociliary transportability, and overall higher mean measures of surface mechanical impedance/frictional adhesion, but these did not reach statistical significance. Mucopurulent effusions had significantly greater transportability than both the mucoid and serous effusions in both groups.

CONCLUSIONS

Persistent or recurrent otitis media with effusion is associated with poorly transportable middle ear fluid, which may have higher frictional adhesion. The best mucociliary transportability was measured in mucopurulent effusions.

Mucin production and mucous cell metaplasia in otitis media

Otitis media (OM) with mucoid effusion, characterized by mucous cell metaplasia/hyperplasia in the middle ear cleft and thick fluid accumulation in the middle ear cavity, is a subtype of OM which frequently leads to chronic OM in young children. Multiple factors are involved in the developmental process of OM with mucoid effusion, especially disorders of mucin production resulting from middle ear bacterial infection and Eustachian tube dysfunction. In this review, we will focus on several aspects of this disorder by analyzing the cellular and molecular events such as mucin production and mucous cell differentiation in the middle ear mucosa with OM. In addition, infectious agents, mucin production triggers, and relevant signaling pathways will be discussed.

Sh3pxd2b mice are a model for craniofacial dysmorphology and otitis media

Craniofacial defects that occur through gene mutation during development increase vulnerability to eustachian tube dysfunction. These defects can lead to an increased incidence of otitis media. We examined the effects of a mutation in the Sh3pxd2b gene (Sh3pxd2b^nee) on the progression of otitis media and hearing impairment at various developmental stages. We found that all mice that had the Sh3pxd2b^nee mutation went on to develop craniofacial dysmorphologies and subsequently otitis media, by as early as 11 days of age. We found noteworthy changes in cilia and goblet cells of the middle ear mucosa in Sh3pxd2b^nee mutant mice using scanning electronic microscopy. By measuring craniofacial dimensions, we determined for the first time in an animal model that this mouse has altered eustachian tube morphology consistent with a more horizontal position of the eustachian tube. All mutants were found to have hearing impairment. Expression of TNF-α and TLR2, which correlates with inflammation in otitis media, was up-regulated in the ears of mutant mice when examined by immunohistochemistry and semi-quantitative RT-PCR. The mouse model with a mutation in the Sh3pxd2b gene (Sh3pxd2b^nee) mirrors craniofacial dysmorphology and otitis media in humans.

MUC5AC expression in human middle ear epithelium of patients with otitis media

OBJECTIVE

To compare levels of middle ear (ME) MUC5AC expression in patients with otitis media (OM) with patients without OM. Mucin gene 5AC has been identified as a major secretory mucin in the ME and is fundamentally important in the development of ME mucoid effusions, hearing loss and also provides ME mucosal protection and bacterial clearance.

DESIGN

Case control.

SETTING

Tertiary, academic, pediatric otolaryngology practice.

PATIENTS

Patients 9 months to 7 years old undergoing routine tympanostomy tube (TT) insertion for recurrent otitis media (RecOM) or chronic otitis media with effusion (COME) were compared with control patients without a history of OM undergoing cochlear implantation.

METHODS

During routine TT placement or cochlear implantation, a 1-mm biopsy sample of the ME epithelium was obtained. RNA was extracted, and real-time reverse transcriptase-polymerase chain reaction was used to quantify levels of MUC5AC expression.

RESULTS

Twenty-three patients with OM (12 with RecOM and with 11 COME) were evaluated using 5 controls. Mean age was not different between groups. In the RecOM group, mean expression of MUC5AC was 25.92 times greater than in controls. In the COME group, the mean expression was 155.40 times greater than in controls.

CONCLUSIONS

Levels of MUC5AC expression in the human ME are significantly increased in patients with RecOM and COME compared with controls. This study demonstrates MUC5AC gene changes in patients with OM and highlights the need for greater understanding of the molecular responses in OM; particularly that of mucin. A thorough exploration of these factors will provide opportunities to develop novel interventions for the extremely common problem of OM.

MUC5B Is the predominant mucin glycoprotein in chronic otitis media fluid

Chronic otitis media (COM), e.g. "glue" ear is characterized by middle ear effusion and conductive hearing loss. Although mucous glycoproteins (mucins), which contribute to increased effusion viscosity, have been analyzed in ear tissue specimens, no studies have been reported that characterize the molecular identity of secreted mucin proteins present in actual middle ear fluid. For this study, effusions from children with COM undergoing myringotomy at Children's National Medical Center, Washington, DC were collected. These were solubilized and gel fractionated, and the protein content was identified using a liquid chromatography tandem mass spectrometry (LC-MS/MS) proteomics approach. Western blot analyses with mucin specific antibodies and densitometry were performed to validate the mass spectrometry findings. LC-MS/MS results identified mucin MUC5B by >26 unique peptides in six of six middle ear effusion samples, whereas mucin MUC5AC was only identified in one of six middle ear effusions. These findings were validated by Western blot performed on the same six and on an additional 11 separate samples where densitometry revealed on average a 6.4-fold increased signal in MUC5B when compared with MUC5AC (p = 0.0009). In summary, although both MUC5AC and MUC5B mucins are detected in middle ear effusions, MUC5B seems to be predominant mucin present in COM secretions.

Mucin gene expression and mouse middle ear epithelium

OBJECTIVES

To investigate the expression of recently identified human mucin genes in an in vitro model of cultured mouse middle ear epithelial cells (MMEEC).

METHODS

MMEEC were established, RNA was extracted and primers were designed for RT-PCR to assess for expression of mucin genes Muc1, Muc2, Muc3, Muc4, Muc5AC, Muc5B, Muc6, Muc7, Muc8, Muc9, Muc10, Muc11/12, Muc13, Muc15, Muc16, Muc17, Muc18, Muc19 and Muc20 expression.

RESULTS

Mucin genes Muc1, Muc2, Muc3, Muc4, Muc5AC, Muc5B, Muc9, Muc10, Muc13, Muc15, Muc16, Muc18, Muc19 and Muc20 were identified and expressed in MMEEC. The genes Muc6, Muc7, Muc8, Muc11/12 and Muc17 were not identified.

CONCLUSION

Many of the mucin genes that have been recently identified in human MEE and chinchilla MEE are also expressed in MMEEC. There are differences in expression, however, which may have implications in utilizing various animal models for study of middle ear physiology and pathogenesis; specifically as it relates to mucin gene expression.

Expression of fibroblast growth factor binding protein in head and neck cancer

OBJECTIVES

To characterize the expression of fibroblast growth factor binding protein (FGF-BP) messenger RNA (mRNA) in head and neck squamous cell carcinoma (HNSCC) and to study the association of FGF-BP with vascularity.

DESIGN

The expression of FGF-BP mRNA in HNSCC was studied in 35 primary and 8 metastatic HNSCC specimens and 7 control tissues using in situ hybridization and reverse transcriptase-polymerase chain reaction (RT-PCR). Microvessels in tumor specimens were identified with endothelial cell markers (von Willebrand factor [vWF] and CD34-specific antibodies). Correlates between FGF-BP and microvessel counts were evaluated statistically.

SETTING

University of Minnesota Hospitals and Clinics.

PATIENTS

Forty-two surgically treated patients with HNSCC.

INTERVENTIONS

The patients were routinely treated in the study hospitals and clinics.

MAIN OUTCOME MEASURES

The expression of FGF-BP and angiogenesis in tumors were evaluated.

RESULTS

In situ hybridization and RT-PCR demonstrated that FGF-BP mRNA transcripts were expressed in 34 of 35 primary HNSCC specimens and 5 of 8 metastatic tumor specimens but not in adjacent control tissues. The microvessel counts in HNSCC specimens were closely related to the expression level of FGF-BP (P < .001).

CONCLUSION

The expression of FGF-BP is statistically linked to the angiogenesis of HNSCC, suggesting that FGF-BP participates in the angiogenesis of HNSCC.

Interleukin-10 is an essential modulator of mucoid metaplasia in a mouse otitis media model

OBJECTIVES

Inflammatory cytokines are involved in the development of mucous cell metaplasia and hyperplasia (MCM) in otitis media (OM). However, which cytokines play an essential role in the MCM of OM is not clear at the moment.

METHODS

In this study, we hypothesized that interleukin-10 (IL-10) played an indispensable role in the MCM of bacterial OM, and we used IL-10 knockout mice to test this hypothesis.

RESULTS

In wild-type mice, both Streptococcus pneumoniae and Haemophilus influenzae triggered the development of MCM in the middle ear mucosa. In IL-10 knockout mice, the number of goblet cells and mucin-producing cells in the middle ear was significantly reduced after bacterial middle ear infection compared with that in wild-type mice.

CONCLUSIONS

We conclude that IL-10 plays an essential role in the MCM of bacterial OM. Interleukin-10 is a potential target for the treatment of MCM in OM.

Cigarette smoke activates NF kappa B and induces Muc5b expression in mouse middle ear cells

OBJECTIVES

Cigarette smoke exposure is a significant risk factor in the development of otitis media (OM). Nuclear factor kappa B (NF-kappa B) is a ubiquitous transcription factor known to mediate cigarette smoke effects on gene regulation in multiple cell types. The MUC5B mucin gene contains several putative NF-kappa B sites in its promoter and is the predominant mucin expressed in human OM. We hypothesized that in vitro stimulation of a recently developed model system, murine middle ear epithelial cells (MEEC), with cigarette smoke condensate (CSC) activates NF-kappa B and subsequently induces Muc5b gene expression.

METHODS

Luciferase reporter assays, electromobility shift assays (EMSA), and quantitative microplate transcription factor assays (TFA) were performed to evaluate NF-kappaB activation with CSC in immortalized murine MEEC (mMEEC). Reverse transcriptase polymerase chain reaction (RT-PCR) assays and quantitative real time RT-PCR were performed to determine whether time course CSC stimulation upregulates Muc5b mRNA levels in differentiated mMEEC. Luciferase reporter assays were performed to determine whether CSC activates the Muc5b promoter.

RESULTS

Reporter assays, EMSA, and TFA demonstrated three- to five-fold dose-dependent activation of NF-kappa B with CSC in mMEEC. CSC stimulation likewise increased Muc5b mRNA abundance and induced reporter activity 1.8- to 4.8-fold in plasmids containing -556 and -255 base pairs upstream of the Muc5b transcriptional start site in mMEEC.

CONCLUSIONS

CSC activates NF-kappaB in immortalized MEEC. Furthermore, this activation correlates with CSC-induced Muc5b promoter activation and gene expression. Taken together, these results hint that much as in lung cells, the activation of mucins by cigarette smoke is mediated in part by NF-kappa B.

Respiratory tract mucin genes and mucin glycoproteins in health and disease

This review focuses on the role and regulation of mucin glycoproteins (mucins) in airway health and disease. Mucins are highly glycosylated macromolecules (> or =50% carbohydrate, wt/wt). MUC protein backbones are characterized by numerous tandem repeats that contain proline and are high in serine and/or threonine residues, the sites of O-glycosylation. Secretory and membrane-tethered mucins contribute to mucociliary defense, an innate immune defense system that protects the airways against pathogens and environmental toxins. Inflammatory/immune response mediators and the overproduction of mucus characterize chronic airway diseases: asthma, chronic obstructive pulmonary diseases (COPD), or cystic fibrosis (CF). Specific inflammatory/immune response mediators can activate mucin gene regulation and airway remodeling, including goblet cell hyperplasia (GCH). These processes sustain airway mucin overproduction and contribute to airway obstruction by mucus and therefore to the high morbidity and mortality associated with these diseases. Importantly, mucin overproduction and GCH, although linked, are not synonymous and may follow from different signaling and gene regulatory pathways. In section i, structure, expression, and localization of the 18 human MUC genes and MUC gene products having tandem repeat domains and the specificity and application of MUC-specific antibodies that identify mucin gene products in airway tissues, cells, and secretions are overviewed. Mucin overproduction in chronic airway diseases and secretory cell metaplasia in animal model systems are reviewed in section ii and addressed in disease-specific subsections on asthma, COPD, and CF. Information on regulation of mucin genes by inflammatory/immune response mediators is summarized in section iii. In section iv, deficiencies in understanding the functional roles of mucins at the molecular level are identified as areas for further investigations that will impact on airway health and disease. The underlying premise is that understanding the pathways and processes that lead to mucus overproduction in specific airway diseases will allow circumvention or amelioration of these processes.

Characterization of a temperature-sensitive mouse middle ear epithelial cell line

CONCLUSION

Temperature-sensitive mouse middle ear epithelial cells have been successfully established and characterized.

OBJECTIVE

Temperature-sensitive middle ear epithelial cell lines are essential for pathophysiologic studies of otitis media. They are useful for studying the pathogen-host interaction, receptor identification, signal transduction, cytokine/mucin production and cellular responses, especially for cell proliferation and differentiation. The purpose of this study was to establish a large T-antigen [simian virus 40 A-gene (SV40)] mutant-immortalized mouse middle ear epithelial cell line for otitis media studies.

MATERIAL AND METHODS

Primary culture of middle ear epithelial cells was established from the middle ear mucosa of an Immortomouse. The cells were transduced by a temperature-sensitive large T-antigen mutant and cultured for >50 passages. The expression of mRNA transcripts and proteins for epithelial cells was characterized by reverse transcriptase polymerase chain reaction (RT-PCR) and immunohistochemistry. The temperature-sensitive properties of cells cultured at 33 degree C and 39 degree C were evaluated using 3H-thymidine incorporation, Trypan blue exclusion and peroxisome proliferator-activated receptor-gamma activity.

RESULTS

Immortalized middle ear epithelial cells demonstrated a cobblestone-like monolayer culture. The cells expressed mucosal cell markers such as mucins, keratins and collagens. They proliferated at 33 degree C when the SV40 antigen was active and differentiated at 39 degree C when the SV40 antigen was inactive.