Biochemical and immunochemical characteristics of middle ear effusions in relation to bacteriological findings

Ectodysplasin signalling deficiency in mouse models of hypohidrotic ectodermal dysplasia leads to middle ear and nasal pathology

Hypohidrotic ectodermal dysplasia (HED) results from mutation of the EDA, EDAR or EDARADD genes and is characterized by reduced or absent eccrine sweat glands, hair follicles and teeth, and defective formation of salivary, mammary and craniofacial glands. Mouse models with HED also carry Eda, Edar or Edaradd mutations and have defects that map to the same structures. Patients with HED have ear, nose and throat disease, but this has not been investigated in mice bearing comparable genetic mutations. We report that otitis media, rhinitis and nasopharyngitis occur at high frequency in Eda and Edar mutant mice and explore the pathogenic mechanisms related to glandular function, microbial and immune parameters in these lines. Nasopharynx auditory tube glands fail to develop in HED mutant mice and the functional implications include loss of lysozyme secretion, reduced mucociliary clearance and overgrowth of nasal commensal bacteria accompanied by neutrophil exudation. Heavy nasopharynx foreign body load and loss of gland protection alters the auditory tube gating function and the auditory tubes can become pathologically dilated. Accumulation of large foreign body particles in the bulla stimulates granuloma formation. Analysis of immune cell populations and myeloid cell function shows no evidence of overt immune deficiency in HED mutant mice. Our findings using HED mutant mice as a model for the human condition support the idea that ear and nose pathology in HED patients arises as a result of nasal and nasopharyngeal gland deficits, reduced mucociliary clearance and impaired auditory tube gating function underlies the pathological sequelae in the bulla.

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

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

Hualuronic acid in secretory otitis media

Middle-ear effusions of the mucoid type were collected from 14 children with secretory otitis media and analysed by a sensitive assay for hyaluronic acid. The concentration of the polysaccharide varied between three and 42 μg/g. in different patients but was in the same range in effusion material taken from the two ears of the same patient. As the hyaluronic acid concentrations were high compared to the serum levels, the results indicate that the effusion material contains a component derived from connective tissue.

Tumor necrosis factor-alpha and interleukin-1beta levels in recurrent and persistent otitis media with effusion

OBJECTIVE

Based on interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha levels in effusions, our goals were to specify either recurrent or persistent otitis media with effusion (OME) is a mid stage in the development of chronic disease and to identify the factors that have an influence on cytokine levels.

STUDY DESIGN

Samples from groups with recurrent (n = 15) and persistent (n = 39) OME were assayed for IL-1beta and TNF-alpha. Children were also grouped with respect to age, sex, quality of effusion, and the presence of pharyngeal adenoid tissue.

SETTING

Tertiary referral center.

RESULTS

In recurrent and persistent OME groups, IL-1beta was higher than TNF-alpha (P < 0.01). IL-beta was higher in recurrent OME than in persistent OME (P < 0.05).

CONCLUSION

Recurrent OME seems to be closer to the chronic stage of the disease relative to persistent OME in terms of higher IL-1beta levels. Each exacerbation of acute disease in recurrent otitis media is likely to be mediated by IL-1beta.

SIGNIFICANCE

We were able to clarify that recurrent OME is a stage that occurs before chronic OME. Therefore, the prevention of acute attacks in recurrent disease would also impede long-term damage to the middle ear.

A quantitative study of the ciliary area of experimental otitis media with effusion in cats

A quantitative electron microscopic study was performed to determine the extent of the ciliary surface area of the middle ear epithelium in cats. In normal cats, 97.8% of the middle ear mucosa in the hypotympanum and 45.9% in the upper part of the bulla were covered by cilia. Eustachian tube obstruction (ETO) significantly reduced the ciliary area to 73.1% in the hypotympanum and to 16.2% in the upper part of bulla at 1 week after ETO. Instillation of Escherichia coli lipopolysaccharide (LPS) or cat polymorphonuclear leukocyte (PMN) lysate into the middle ear cavity followed by ETO did not reduce the ciliary area, compared with ETO induced alone. Our results indicate that ETO reduces the ciliary area of the middle ear mucosa and that LPS or neutrophils do not enhance reduction of the ciliary area compared to ETO induced alone in this experimental condition.

Morphologic and biochemical study of vascular permeability of the middle ear mucosa in experimental otitis media

The vascular permeability of the middle ear mucosa of chinchillas was examined by light and electron microscopy using horseradish peroxidase (HRP). Two kinds of experimental otitis media were used: serous otitis media (SOM) produced by eustachian tube obstruction and purulent otitis media (POM) produced by inoculation with Streptococcus pneumoniae type 7F. Normal mucosa showed no leakage of HRP. In SOM, vessels were dilated and tortuous, but they did not show HRP leakage. In POM, vessel leakage of HRP was extensive. Biochemically, we measured the middle ear effusion-to-serum ratio of both albumin and alpha 2-macroglobulin by an immunodiffusion method. The ratios of the two marker proteins for vascular permeability were significantly higher in POM than in SOM. This suggests that POM increases vascular permeability to a higher degree than SOM, and morphologic findings in the middle ear mucosa correlate with the biochemical composition of the middle ear effusion.

Bactericidal activity of middle ear effusion on a single isolate of non-typable Haemophilus influenzae

Bactericidal activity of middle ear effusion (MEE) from children with otitis media with effusion (OME) on one strain of non-typable Haemophilus influenzae was measured and was compared with that of normal human serum. H. influenzae culture negative MEEs had a bactericidal activity on one strain of non-typable H. influenzae (P less than 0.01), and the activity of serous effusions was significantly stronger than that of mucoid ones (P less than 0.01). The bactericidal activity of 20% pooled MEE was almost equal to that of 4% normal human serum. Heat treatment (56 degrees C, 30 min) abolished this activity of both pooled MEE and normal human serum. Addition of fresh guinea pig serum (GPS) as a complement source to the heat-treated pooled MEE restored this activity, while its addition to the heat-treated normal human serum failed to do so. These results suggest that complement factor is important in the bactericidal activity of MEE.

Secondary immune response in the middle ear: immunological, morphological, and physiological observations

A model of secondary immune response in the middle ear (ME) was developed in the guinea pig. Animals were immunized intradermally with keyhole limpet hemocyanin (KLH) and challenged with KLH in the ME 8 weeks later. The ME displayed effusion, mucosal hyperplasia, mucosal edema, and leukocytic infiltration. These responses were maximal at 3 days postchallenge, and persisted for 2 to 3 weeks. High levels of antibody were observed in the ME effusions, and serum titers increased significantly. Immunohistochemical localization of antibody indicated that substantial free IgG was present in the submucosa, with much less in the mucosal epithelium. IgA plasma cells were observed in the submucosa at 1 week postchallenge, but no IgM was detected. In contrast to the response observed in sensitized animals, antigen presented to the ME of unimmunized control animals resulted in no effusion, minimal mucosal inflammation, and little or no antibody in either the ME or serum. However, substantial neutrophilic infiltration of the ME cavity was observed. The effusion and inflammation produced by secondary ME immune responses were not affected by tympanostomy tubes. Eustachian tube function as measured by a forced response test was not affected by ME immune response. This suggests that the immunologically induced effusion was not the result of eustachian tube obstruction. We postulate that increased vascular permeability in the ME mucosa, induced by chemical mediators, resulted in the transudation of serum.

Bacterial and Polymorphonuclear Leukocyte Contribution to Middle Ear Inflammation in Chronic Otitis Media with Effusion

Bacteria can be cultured from approximately one third of chronic middle ear effusions, yet the contribution of these bacteria to the pathogenesis of chronic otitis media with effusion (OME) is not clear due to the absence of signs and symptoms of acute infection in most children with this disease. To explore the role of bacteria in chronic OME, lysozyme, lactoferrin, serum complement factors C3 and C5a, and polymorphonuclear leukocyte (PMNL) chemotaxin content was measured in 21 chronic middle ear effusion samples. Concentrations of lysozyme, lactoferrin, and chemotaxin were significantly higher in culture-positive than in sterile effusions. Lysozyme appeared to be contributed by both PMNL and non-PMNL sources in the middle ear space. These non-PMNL sources, presumably middle ear epithelial cells, accounted for 50% to 80% of the lysozyme variation in middle ear effusion. Although C3 and C5a were present in effusion, chemotaxin content correlated poorly with the C3 and C5a content, suggesting that chemotaxins were derived from bacterial peptides rather than from complement activation products. These results suggest that bacteria contribute to chronic middle ear inflammation with effusion. The eradication of bacteria from chronic middle ear effusion might disrupt the host responses which maintain chronic OME.

Passive transfer of immune-mediated middle ear inflammation and effusion

Antigenic challenge in the middle ear of animals previously sensitized intradermally results in an immunologically mediated inflammatory response, including the generation of serous effusion in the middle ear cavity. The mechanisms which contribute to this immune-mediated otitis media with effusion (OME) were investigated by passive transfer with either purified IgG or with sensitized lymphocytes. A peritoneal exudate was raised in strain 13 guinea pigs by repeated injection of keyhole limpet hemocyanin (KLH) with complete Freund's adjuvant. IgG and lymphocytes were isolated from exudates and used for passive sensitization. Middle ear challenge following passive transfer of IgG specific to KLH produced effusion and inflammation which was equivalent to that observed in actively immunized animals, but resulted in significantly greater numbers of leukocytes infiltrating the middle ear. Unlike in the active response, few of the cells infiltrating the middle ear mucosa and middle ear cavity were eosinophils. Middle ear challenge with KLH following passive transfer with sensitized lymphocytes produced no middle ear effusion, relatively little mucosal inflammation, and sharply reduced exocytosis of leukocytes into the middle ear when compared with the active immune response or even with unimmunized controls. It is concluded that middle ear effusion, inflammation, and leukocytic exocytosis are mediated primarily by the IgG fraction of humoral immunity in our model of immune OME.