Expression of the gap junction proteins connexin 26 and connexin 43 in human middle ear cholesteatoma

The Interplay of Cx26, Cx32, Cx37, Cx40, Cx43, Cx45, and Panx1 in Inner-Ear Development of Yotari (dab1−/−) Mice and Humans

We investigated DAB1-protein deficiency in the inner-ear development of yotari in comparison to humans and wild-type (wt) mice by immunofluorescence for the expression of connexins (Cxs) and the pannexin Panx1. The spatial and temporal dynamics of Cx26, Cx32, Cx37, Cx40, Cx43, Cx45, and Panx1 were determined in the sixth and eighth weeks of human development and at the corresponding mouse embryonic E13.5 and E15.5, in order to examine gap junction intercellular communication (GJIC) and hemichannel formation. The quantification of the area percentage covered by positive signal was performed for the epithelium and mesenchyme of the cochlear and semicircular ducts and is expressed as the mean ± SD. The data were analysed by one-way ANOVA. Almost all of the examined Cxs were significantly decreased in the cochlear and semicircular ducts of yotari compared to wt and humans, except for Cx32, which was significantly higher in yotari. Cx40 dominated in human inner-ear development, while yotari and wt had decreased expression. The Panx1 expression in yotari was significantly lower than that in the wt and human inner ear, except at E13.5 in the mesenchyme of the wt and epithelium and mesenchyme of humans. Our results emphasize the relevance of GJIC during the development of vestibular and cochlear functions, where they can serve as potential therapeutic targets in inner-ear impairments.

Updates and knowledge gaps in cholesteatoma research

The existence of acquired cholesteatoma has been recognized for more than three centuries; however, the nature of the disorder has yet to be determined. Without timely detection and intervention, cholesteatomas can become dangerously large and invade intratemporal structures, resulting in numerous intra- and extracranial complications. Due to its aggressive growth, invasive nature, and the potentially fatal consequences of intracranial complications, acquired cholesteatoma remains a cause of morbidity and death for those who lack access to advanced medical care. Currently, no viable nonsurgical therapies are available. Developing an effective management strategy for this disorder will require a comprehensive understanding of past progress and recent advances. This paper presents a brief review of background issues related to acquired middle ear cholesteatoma and deals with practical considerations regarding the history and etymology of the disorder. We also consider issues related to the classification, epidemiology, histopathology, clinical presentation, and complications of acquired cholesteatoma and examine current diagnosis and management strategies in detail.

Etiopathogenesis of acquired cholesteatoma: prominent theories and recent advances in biomolecular research

OBJECTIVE

To review recent biomolecular advances in etiopathogenesis of acquired cholesteatoma.

DATA SOURCES

MEDLINE via OVID (to March 2014) and PubMed (to March 2014).

REVIEW METHODS

All articles referring to etiopathogenesis of acquired cholesteatoma were identified in the above databases, from which 89 articles were included in this review.

RESULTS

The mechanisms underlying the etiopathogenesis of acquired cholesteatoma remain a subject of competing hypotheses. Four theories dominate the debate, including theories of invagination, immigration, squamous metaplasia, and basal cell hyperplasia. However, no single theory has been able to explain the clinical characteristics of all cholesteatoma types: uncoordinated hyperproliferation, invasion, migration, altered differentiation, aggressiveness, and recidivism. Modern technologies have prompted a number of researchers to seek explanations at the molecular level. First, cholesteatomas could be considered an example of uncontrolled cell growth, capable of altering the balance toward cellular hyperproliferation and enhancing the capacity for invasion and osteolysis. Second, the dysregulation of cell growth control involves internal genomic or epigenetic alterations and external stimuli, which induce excessive host immune response to inflammatory and infectious processes. This comprises several complex and dynamic pathophysiologic changes that involve extracellular and intracellular signal transduction cascades.

CONCLUSIONS

This article summarizes the existing theories and provides conceptual insights into the etiopathogenesis of acquired cholesteatoma, with the aim of stimulating continued efforts to develop a nonsurgical means of treating the disorder.

The oncoprotein, gankyrin, is up-regulated in middle ear cholesteatoma

CONCLUSION

Gankyrin seems to be a better biomarker for cholesteatoma compared with Ki-67.

OBJECTIVE

Gankyrin is an oncoprotein, and occurs in cancers but not in benign diseases. The goal of this study was to compare expression of gankyrin, p53, and a proliferation marker (Ki-67) in cholesteatoma and retroauricular skin (RAS), and to evaluate their significance as clinical parameters.

METHODS

The levels of expression of gankyrin, Ki-67, and p53 in 10 cholesteatoma and 10 paired samples of normal RAS were evaluated by immunohistochemical staining and Western blot. The results were compared with clinical profiles to investigate a correlation.

RESULTS

The expression of gankyrin, Ki-67, and p53 proteins was observed in both basal and suprabasal layers of cholesteatoma. The intensity of gankyrin expression was 'positive' in two cases (20%) and 'strongly positive' in eight cases (80%); p53 expression in the suprabasal layer was 'positive' in 70% of cases; and the Ki-67 staining was 'focal' in 80% of cases. In RAS, these proteins were expressed dominantly in the basal layer. Western blot analysis showed that the gankyrin band was more intense in cholesteatoma than in RAS for three of four cases (p < 0.05). However, there was no significant difference in the expression of gankyrin, Ki-67, and p53 according to clinical variables.

Pediatric cholesteatoma and variants in the gene encoding connexin 26

OBJECTIVES/HYPOTHESIS

Connexin 26 is a gap junction protein encoded by the GJB2 gene. It is expressed in cholesteatoma, and mutations cause proliferative skin disorders and sensorineural hearing loss (SNHL). Deletions of GJB6, which encodes connexin 30, cause SNHL in a digenic manner with a heterozygous GJB2 mutation. We hypothesize that GJB2 and GJB6 mutations might influence the development of cholesteatoma.

STUDY DESIGN

Prospective observational study to identify GJB mutations in pediatric cholesteatoma.

METHODS

Peripheral blood samples from 98 children with cholesteatoma were screened for mutations in the GJB2 gene by direct sequencing of the coding region (exon 2 and the intron/exon boundary). Deletions of the GJB6 gene were tested using multiple ligation probe amplification methods. GJB status was compared with other populations and patient age and extent of cholesteatoma at presentation.

RESULTS

Fourteen children had at least one GJB2 variant (14%). Of these, three had two variants. Two of the variants were neutral polymorphisms. One child with the GJB2 genotype 35delG/35delG also had SNHL. No correlation was found between GJB2 status and patient age or cholesteatoma severity at presentation. No GJB6 deletions were found.

CONCLUSIONS

GJB2 gene variants are present in a minority of children with cholesteatoma, but may be more common than in normal populations. It is conceivable that alterations of connexin 26 expression could contribute to the multifactorial disease process in cholesteatoma by modifying the cell-to-cell communication that is important in proliferation and migration of keratinocytes.

Cochlear implantation and connexin expression in the child with keratitis-ichthyosis-deafness syndrome

We report one child with keratitis-ichthyosis-deafness (KID) syndrome. The child showed sparse, short scalp and body hairs, ichthyotic skin, bilateral sensorineural hearing loss, and visual loss. These are associated with a nucleotide substitution, 148G>A, which results in amino acid change in codon 50 of gap junctional protein connexin (Cx) 26. Immunohistochemistry of skins showed up-regulation of Cx26 and down-regulation of Cx43. He has benefited from cochlear implantation for hearing even though low visual function and skin problems with high risk of infections. This is the very rare report about Cx expression in skins and cochlear implantation in KID syndrome.