Evaluation of the polymorphism in the Toll-like receptor 4 (TLR4) genes of tympanosclerosis patients

Polymorphisms in Toll-like receptors 2 and 4 genes and their expression in chronic suppurative otitis media

OBJECTIVE

Toll-like receptors (TLRs) have a prominent role in inducing innate immune response. It has been suggested that regulation of TLRs is involved in the pathogenesis of chronic otitis media. TLR 2 and TLR 4 polymorphisms were connected with susceptibility to acute otitis and chronic otitis with effusion. The objective of this study was to establish expression of TLR 2 and 4 on middle ear mucosa in different types of chronic suppurative otitis media (CSOM), and the influence of gene polymorphisms TLR 2 Arg753Gln and TLR 4 Thr399Ile and Asp299Gly to susceptibility to CSOM.

MATERIAL AND METHODS

Middle ear mucosa and full blood samples were obtained from 85 patients with chronic suppurative otitis media with and without cholesteatoma. Control group for mucosal TLR expression consisted of 71 samples of middle ear mucosa taken from patients with otosclerosis, and control group for DNA polymorphism consisted of 100 full blood samples in healthy subjects. DNA polymorphism detection was done with restriction fragment length polymorphism in RT PCR. Expression of TLR 2 and 4 was determined with immunohistochemical staining.

RESULTS

TLR 2 and TLR 4 expression on the middle ear mucosa was not influenced by age of the patients with chronic otitis media. Incidence of TLR 2 Arg753Gln polymorphism was significantly higher in patients with chronic otitis media, compared to control group. Significant association between TLR 2 Arg753Gln polymorphism and different types of mucosal changes in patients with chronic otitis media was established. TLR 2 and 4 expression on experimental group mucosa was significantly different compared to control group, where there was no expression (p=0.000). Strong dependence of TLR 2 and TLR 4 expression on middle ear mucosa with different mucosal changes and immunohistochemical activity after staining was detected.

CONCLUSION

Certain polymorphisms in TLR genes could be indicative for susceptibility to chronic otitis media. Expression of TLR 2 and 4 on middle ear mucosa was more dependable on different types of mucosal changes and type of CSOM than on bacteria found in the specimens. This can indicate that the type of mucosal changes are closely correlated with TLRs activity in middle ear.

[Assessment of Tumor Necrosis Factor alpha gene expression profile in selected structures of middle ear in patients with tympanosclerosis]

AIM OF THE STUDY

Tympanosclerosis is a middle ear disease located in submucous membrane. It leads to the tympanic membrane and ear ossicles fixation which results in severe conductive hearing impairment. The etiology of tympanosclerosis remains unclear. Cytokines play very important role in development of tympanosclerosis. The research aimed to assess gene expression level of pro inflammatory cytokine TNF-α in selected structures of middle ear in patients with chronic otitis media with tympanosclerosis.

METHODOLOGY

The research was performed on middle ear tissues with tympanosclerosis achieved from 30 patients operated on in the Otolaryngology Department of the Medical University of Gdańsk. The control group was formed by tympanic membranes sampled from 17 corpses of patients who died suddenly. Advancement of tympanosclerotic changes were grouped based on Tos classification. The TNF-α gene expression level was measured by real time PCR with specific hydrolysed probes (TaqMan). The gene expression level for TNF-α was correlated with clinical classification of tympanosclerosis.

RESULTS

The level of gene profile expression for TNF-α in selected structures of the middle ear with tympanosclerosis was statistically significant, higher in comparison with the control group. The highest level of expression was observed in group two which is relevant to more advanced tympanosclerosis.

CONCLUSION

Tympanosclerosis is a result of constant inflammatory process and it is modulated by cytokines including TNF-α. The positive correlation between gene expression level of TNF-α and tympanosclerosis could in the future contribute to antiinflammatory, medical treatment of tympanosclerosis.

Exome sequencing identifies a missense mutation in Isl1 associated with low penetrance otitis media in dearisch mice

Background

Inflammation of the middle ear (otitis media) is very common and can lead to serious complications if not resolved. Genetic studies suggest an inherited component, but few of the genes that contribute to this condition are known. Mouse mutants have contributed significantly to the identification of genes predisposing to otitis media

Results

The dearisch mouse mutant is an ENU-induced mutant detected by its impaired Preyer reflex (ear flick in response to sound). Auditory brainstem responses revealed raised thresholds from as early as three weeks old. Pedigree analysis suggested a dominant but partially penetrant mode of inheritance. The middle ear of dearisch mutants shows a thickened mucosa and cellular effusion suggesting chronic otitis media with effusion with superimposed acute infection. The inner ear, including the sensory hair cells, appears normal. Due to the low penetrance of the phenotype, normal backcross mapping of the mutation was not possible. Exome sequencing was therefore employed to identify a non-conservative tyrosine to cysteine (Y71C) missense mutation in the Islet1 gene, Isl1^Drsh. Isl1 is expressed in the normal middle ear mucosa. The findings suggest the Isl1^Drshmutation is likely to predispose carriers to otitis media.

Conclusions

Dearisch, Isl1^Drsh, represents the first point mutation in the mouse Isl1 gene and suggests a previously unrecognized role for this gene. It is also the first recorded exome sequencing of the C3HeB/FeJ background relevant to many ENU-induced mutants. Most importantly, the power of exome resequencing to identify ENU-induced mutations without a mapped gene locus is illustrated.

Unraveling the genetics of otitis media: from mouse to human and back again

Otitis media (OM) is among the most common illnesses of early childhood, characterised by the presence of inflammation in the middle ear cavity. Acute OM and chronic OM with effusion (COME) affect the majority of children by school age and have heritability estimates of 40-70%. However, the majority of genes underlying this susceptibility are, as yet, unidentified. One method of identifying genes and pathways that may contribute to OM susceptibility is to look at mouse mutants displaying a comparable phenotype. Single-gene mouse mutants with OM have identified a number of genes, namely, Eya4, Tlr4, p73, MyD88, Fas, E2f4, Plg, Fbxo11, and Evi1, as potential and biologically relevant candidates for human disease. Recent studies suggest that this "mouse-to-human" approach is likely to yield relevant data, with significant associations reported between polymorphisms at the FBXO11, TLR4, and PAI1 genes and disease in humans. An association between TP73 and chronic rhinosinusitis has also been reported. In addition, the biobanks of available mouse mutants provide a powerful resource for functional studies of loci identified by future genome-wide association studies of OM in humans. Mouse models of OM therefore are an important component of current approaches attempting to understand the complex genetic susceptibility to OM in humans, and which aim to facilitate the development of preventative and therapeutic interventions for this important and common disease.