Middle Ear Response of Muc5ac and Muc5b Mucins to Nontypeable Haemophilus influenzae

PANEL 3: Otitis media animal models, cell culture, tissue regeneration & pathophysiology

OBJECTIVE

To review and summarize recently published key articles on the topics of animal models, cell culture studies, tissue biomedical engineering and regeneration, and new models in relation to otitis media (OM).

DATA SOURCE

Electronic databases: PubMed, National Library of Medicine, Ovid Medline.

REVIEW METHODS

Key topics were assigned to the panel participants for identification and detailed evaluation. The PubMed reviews were focused on the period from June 2019 to June 2023, in any of the objective subject(s) or keywords listed above, noting the relevant references relating to these advances with a global overview and noting areas of recommendation(s). The final manuscript was prepared with input from all panel members.

CONCLUSIONS

In conclusion, ex vivo and in vivo OM research models have seen great advancements in the past 4 years. From the usage of novel genetic and molecular tools to the refinement of in vivo inducible and spontaneous mouse models, to the introduction of a wide array of reliable middle ear epithelium (MEE) cell culture systems, the next five years are likely to experience exponential growth in OM pathophysiology discoveries. Moreover, advances in these systems will predictably facilitate rapid means for novel molecular therapeutic studies.

Establishment of novel immortalized middle ear cell lines as models for otitis media

Objective

Otitis media (OM) is among the most frequently diagnosed pediatric diseases in the US. Despite the significant public health burden of OM and the contribution research in culture models has made to understanding its pathobiology, a singular immortalized human middle ear epithelial (MEE) cell line exists (HMEEC-1, adult-derived). We previously developed MEE cultures from pediatric patients with non-inflamed MEE (PCI), recurrent OM (ROM), or OM with effusion (OME) and demonstrated differences in their baseline inflammatory cytokine expression and response to stimulation with an OM-relevant pathogen lysate and cytokines. Herein, we sought to immortalize these cultures and assess retention of their phenotypes.

Methods

MEE cultures were immortalized via lentivirus encoding temperature-sensitive SV40 T antigen. Immortalized MEE lines and HMEEC-1 grown in monolayer were stimulated with non-typeable Haemophilus influenzae (NTHi) lysate. Gene expression (TNFA, IL1B, IL6, IL8, MUC5AC, and MUC5B) was assessed by qPCR.

Results

Similar to parental cultures, baseline cytokine expressions were higher in pediatric OM lines than in HMEEC-1 and PCI, and HMEEC-1 cells were less responsive to stimulation than pediatric lines.

Conclusion

Immortalized MEE lines retained the inflammatory expression and responsiveness of their tissues of origin and differences between non-OM versus OM and pediatric versus adult cultures, supporting their value as novel in vitro culture models for OM.

Transgenic Mouse Reporter to Study Muc5b In Vivo

Dysregulation of gel-forming mucins is associated with many airway diseases. Better knowledge of the pathophysiological mechanisms linking mucins and respiratory diseases will advance the understanding of their pathogenesis and should provide opportunities to develop new therapeutic compounds for treatment. MUC5B and MUC5AC are the two main gel-forming mucins in the respiratory tract. The organization in domains and the expression profile of mouse Muc5b are very similar to those in humans, which makes the mouse a relevant model for studies of the translational activities of human mucins. To assess the in vivo biological functions of Muc5b, a mouse reporter tagged in frame with the green fluorescent protein marker has been engineered by homologous recombination. The proof of concept that this reporter model may be informative for translational studies was confirmed by the finding that interleukin-13 administration in living mice upregulated Muc5b production.

Ramifications of secreted mucin MUC5AC in malignant journey: a holistic view

Heavily glycosylated secreted mucin MUC5AC, by the virtue of its cysteine-rich repeats, can form inter- and intramolecular disulfide linkages resulting in complex polymers, which in turn craft the framework of the polymeric mucus gel on epithelial cell surfaces. MUC5AC is a molecule with versatile functional implications including barrier functions to epithelial cells, host-pathogen interaction, immune cell attraction to sites of premalignant or malignant lesions and tumor progression in a context-dependent manner. Differential expression, glycosylation and localization of MUC5AC have been associated with a plethora of benign and malignant pathologies. In this era of robust technologies, overexpression strategies and genetically engineered mouse models, MUC5AC is emerging as a potential diagnostic, prognostic and therapeutic target for various malignancies. Considering the clinical relevance of MUC5AC, this review holistically encompasses its genomic organization, domain structure, glycosylation patterns, regulation, functional and molecular connotation from benign to malignant pathologies. Furthermore, we have here explored the incipient and significant experimental tools that are being developed to study this structurally complex and evolutionary conserved gel-forming mucin.

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.

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.

Relationship of the Middle Ear Effusion Microbiome to Secretory Mucin Production in Pediatric Patients With Chronic Otitis Media

BACKGROUND

Acute otitis media, an infection of the middle ear, can become chronic after multiple episodes. Microbial influence on chronic otitis media remains unclear. It has been reported that mucin glycoproteins are required for middle ear immune defense against pathogens. We aim to characterize the middle ear effusion (MEE) microbiome using high-throughput sequencing and assess potential associations in microbiome diversity with the presence of the secretory mucins MUC5B and MUC5AC. We hypothesize that MEEs containing MUC5B will exhibit a microbiome largely devoid of typical acute otitis media bacteria.

METHODS

Fifty-five MEEs from children undergoing myringotomy at Children's National Health System were recovered. Mucin was semiquantitatively determined through Western blot analysis. DNA was subjected to 16S rRNA amplicon sequencing using the Illumina MiSeq platform. Raw data were processed in mothur (SILVA reference database). Alpha- and beta-diversity metrics were determined. Abundance differences between sample groups were estimated.

RESULTS

MUC5B was present in 94.5% and MUC5AC in 65.5% of MEEs. Sequencing revealed 39 genera with a relative abundance ≥0.1%. Haemophilus (22.54%), Moraxella (11.11%) and Turicella (7.84%) were the most abundant. Turicella and Pseudomonas proportions were greater in patients older than 24 months of age. In patients with hearing loss, Haemophilus was more abundant, while Turicella and Actinobacteria were less abundant. Haemophilus was also more abundant in samples containing both secretory mucins.

CONCLUSIONS

The microbiome of MEEs from children with chronic otitis media differs according to specific clinical features, such as mucin content, age and presence of hearing loss. These associations provide novel pathophysiologic insights across the spectrum of otitis media progression.

Younger patients with COME are more likely to have mucoid middle ear fluid containing mucin MUC5B

BACKGROUND

Chronic otitis media (COM) is one of the most common childhood diseases. Its pathophysiology is complex and multifactorial. The role of specific mucin glycoprotein subtypes in OM is only recently being elucidated.

OBJECTIVE

To determine the relationship between middle ear fluid mucins and clinical variables of patients needing tympanostomy tubes (TT).

METHODS

Middle ear effusions (MEE) from children receiving TT were collected over a 2-year period. Western blot characterization of mucins MUC5B and MUC5AC along with chart review of age, gender, effusion viscosity, hearing loss >30 dB, history of allergies, and/or respiratory disease were performed.

RESULTS

MEE samples from 58 patients were available for analysis. Overall, MUC5B was significantly more often detected in middle ear fluid relative to MUC5AC (90% vs. 51%, p = 0.005). MUC5B presence was statistically associated with mucoid effusions relative to serous effusions (100% vs. 57%, p = 0.0064), MUC5AC presence was not significantly different in mucoid and serous fluid (55.1% vs. 37.5%, p = 0.447). Patients younger than 48 months were more likely to present with mucoid effusion, compared to those older than 48 months of age (p = 0.038). Finally, patients with effusions positive for MUC5B were younger than those with effusions negative for MUC5B (35.1 vs. 76 months, p = 0.045). No other variables correlated to either effusion viscosity or specific mucin content.

CONCLUSION

Patients younger in age needing TT placement are more likely to present with mucoid effusions, predominantly containing MUC5B mucin. As such, we postulate a distinct pathophysiology for mucoid and serous effusions across ages in children with COM.