Immunohistochemical study on proliferative activity of experimental cholesteatoma

The Role of Rho/Rho-Kinase Pathway in the Pathogenesis of Cholesteatoma

OBJECTIVE

To assess the role of Rho/Rho-kinase pathway in the pathogenesis of cholesteatoma.

MATERIALS AND METHODS

Thirty-eight patients with cholesteatoma, who had gone mastoidectomies were enrolled in this prospective study. Cholesteatomas matrix (CM) and a piece of the external ear canal skin (EECS as control) were taken and transferred to the liquid nitrogen and kept at -86 °C for Rho A and Rho-kinase (ROCK) analysis with Western blotting and commercial ELISA kits (Cell Biolabs Inc., San Diego, CA). The tissues were homogenized by an appropriate ice-cold lysis buffer. Following centrifugation, the supernatant was taken and total protein amount was detected by the Bradford method. Thereafter, tissue homogenates were subjected to sodium dodecyl sulphate (SDS)-polyacrylamide gel electrophoresis electrophoresis then transferred to nitrocellulose membrane where it was treated with specific monoclonal primary antibody against to ROCK-2 and HRP-conjugated seconder antibody, respectively. The protein blots were visualized with commercial x-ray film and dansitometrically analyzed by the Scion Image Program (Cell Biolabs Inc., San Diego, CA). In another series of experiments, Rho-kinase activities were assessed by ROCK-2 ELISA kits.

RESULTS

There were no statistical differences in Rho A translocation between CM and EECS. However, ROCK activity was found to be lower in CM than EECS as detected by ELISA kits. Furthermore, ROCK protein expression was also significantly lower in CM than EECS as demonstrated by Western blotting.

CONCLUSION

Given Rho-kinase could take essential roles in cell differentiation, the results of this study implicate that down-regulated Rho-kinase could be responsible for the keratinocyte undifferentiation seen in cholesteatoma pathogenesis.

Comparative analysis of the expression of involucrin, filaggrin and cytokeratin 4, 10, 16 in cholesteatoma

Background and Objectives

The aim of this study is to determine whether the hyperproliferative and hyperkeratotic characters of cholesteatoma are associated with differentiation of keratinocytes in cholesteatoma by examining the localization of marker proteins, such as involucrin, filaggrin, and cytokeratins.

Materials and Methods

Immunohistochemical study was carried out in 30 cholesteatoma tissues and 10 retroauricular skins to examine the expression of involucrin, filaggrin, cytokeratin 4, 10 and 16. The staining results were graded as negative, weakly positive (<10%), moderately positive (10-70%), and strongly positive (>70%).

Results

Involucrin was strongly expressed in upper spinous, granular, and corneal layer of cholesteatoma. Filaggrin was strongly expressed in granular and corneal layer of cholesteatoma. Cytokeratin 4 was expressed in basal layer of retroauricular skin, but occasionally expressed in suprabasal layer of cholesteatoma. Cytokeratin 10 was homogenously expressed in all suprabasal layer of retroauricular skin, whereas pattern of shift to surface layer was showed in cholesteatoma. Cytokeratin 16 was moderately expressed at suprabasal layer in cholesteatoma.

Conclusions

It can be suggested that early differentiation of suprabasal layer may lead to hyperdifferentiation and hyperkeratosis. Different expression of cytokeratins possibly indicates the altered differentiation of cholesteatoma.

EGFR expression in acquired middle ear cholesteatoma in children and adults

Middle ear cholesteatomas are characterized by the presence of keratinized stratified squamous epithelium inside this cavity. It is considered to be more aggressive in childhood. In normal skin, the epidermal growth factor receptor (EGFR) is expressed in the cytoplasmic membrane of epithelial cells of the basal layer. In contrast, its expression in middle ear cholesteatoma extends to suprabasal layers. The objective of this study is to detect the presence of EGFR in cases of acquired cholesteatoma of the middle ear and correlate the expression of this receptor with patients' ages. In this cross-sectional study, cholesteatoma samples were collected from 50 patients (35 adults and 15 children) who underwent otological surgery, throughout 1 year of study. These samples were subjected to histological and immunohistochemical assays. Results were submitted to statistical analyses and main findings were: EGFR was present in the parabasal layers in 27 cases and EGFR expression was extended to all layers of the matrix in 17 cases. There were no statistically significant differences in what concerns age-related variances in EGFR expression. The intensity and location of EGFR expression in acquired cholesteatoma of the middle ear confirm the hyperproliferative capacity of keratinocytes.

Evaluation of epithelial proliferation in paediatric and adult cholesteatomas using the Ki-67 proliferation marker

INTRODUCTION

The aggressiveness of cholesteatoma in children compared with adults is well known. However, the factors influencing the poorer prognosis of paediatric cholesteatoma are not well understood. This study compared the proliferative potential of paediatric cholesteatoma with that of adult cholesteatoma, using Ki-67 as a proliferation marker.

METHODS

A prospective study of 67 patients with aural cholesteatoma was performed. Thirty-eight adult and 29 paediatric cases were evaluated using clinical parameters including bone erosion, complications and extent of disease. A surgical specimen underwent histological evaluation and measurement of the proliferation index using Ki-67 labelling. Normal epithelium from a control group was also examined.

RESULTS

Cholesteatoma epithelium has a greater rate of proliferation than normal skin. There were however no statistical differences between the paediatric and adult cholesteatoma groups in terms of clinical behaviour or proliferation potential. Paediatric cholesteatoma was similar to adult cholesteatoma in terms of complications, bone erosion and disease spread.

CONCLUSION

Cholesteatoma is a disorder of epithelial proliferation. Although postulated to be more aggressive in children than adults, this study found no clinicopathological differences between paediatric and adult cases.

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

CONCLUSION

The results of this study showed upregulated expression and a change in localization of both connexin 43 (Cx43) and Cx26 in human middle ear cholesteatoma compared to those in normal retroauricular skins (RASs) and ear canal skins (ECSs). This suggests that perturbations of intercellular communication through gap junctions may be associated with the pathology of human cholesteatomas.

OBJECTIVE

Cholesteatomas in the middle ear require intercellular signal exchange through gap junctions as well as intracellular signal pathways for the hyperproliferation and differentiation of epithelial cells. Cx is a gap junction protein involved in intercellular communication. The objective of this study was to analyze the expression and possible roles of Cx43 and Cx26 in human cholesteatoma compared to normal epithelium.

MATERIAL AND METHODS

Ten RASs, 10 ECSs and 10 cholesteatomas were obtained during middle ear operations. Immunohistochemical staining, Western blotting and reverse transcriptase polymerase chain reaction (RT-PCR) were used to detect Cx43 and Cx26. The expression patterns of Cx43 and Cx26 were also compared with that of the proliferation marker Ki67.

RESULTS

In human cholesteatomas, Cx43 was expressed in whole suprabasal layers, except in the basal layer, and Cx26 was usually expressed in the suprabasal and basal layers. However, normal RASs showed weak expression of Cx43 in the upper spinosal and granular layers (with no expression in the basal layers) and restricted localization of Cx26 in the basal layer. The expression of Cx43 and Cx26 in ECSs was weak but showed similar patterns to that of cholesteatoma. RT-PCR and Western blotting showed that the expression of Cx43 and Cx26 was higher in cholesteatoma than in RASs. Epithelial cells expressing Cx43 and Cx26 in cholesteatoma were not exactly identical to Ki67-expressing cells on immunohistochemical staining.

Nucleoplasm staining patterns and cell cycle-associated expression of Ki-67 in middle ear cholesteatoma

OBJECTIVES

To compare Ki-67 expression patterns in middle ear cholesteatoma with the corresponding retroauricular and external auditory canal skins, and to determine the cell cycle-dependent localization of Ki-67.

MATERIAL AND METHODS

MIB-1 monoclonal antibody was used for comparative assessment of proliferative activity of middle ear cholesteatoma, external auditory canal skin, and retroauricular skin samples on formalin-fixed paraffin-embedded tissue sections. Primary keratinocytes from cholesteatoma tissue were isolated and subjected to kinetic analysis of the cell cycle.

RESULTS

Higher proliferative activity was established in cholesteatoma in comparison with retroauricular and external auditory canal skins. Three different staining patterns have been described. Kinetic analysis revealed continuous expression of Ki-67 during all active phases of the cell cycle and remained "silent" in resting cells.

CONCLUSION

The established correlation between the staining patterns and cell cycle-associated expression of Ki-67 specifies Ki-67 as a reliable and stable marker of proliferation for middle ear cholesteatoma.

Reversibility of experimental cholesteatoma epithelium using Mongolian gerbils

CONCLUSION

The results of this study encourage our belief that some cholesteatomas can be managed using only conservative treatments.

OBJECTIVE

We hypothesized that once cholesteatoma is in a normal environment, its cellular or molecular pathology can revert to those characteristic of normal epidermis. The aim of this study was to determine whether or not common molecular characteristics of cholesteatoma were reversible after removal of inductive factors in experimental cholesteatoma induced in gerbils.

MATERIAL AND METHODS

We induced cholesteatoma using ear canal ligation in Mongolian gerbils. After ligation, the animals in the treated group were managed for 2 weeks. We examined differences between treated and untreated cholesteatomas using terminal deoxynucleotide transferase-mediated dUTP nick-end labeling (TUNEL) staining and an immunohistochemical technique using the proliferation markers proliferating cell nuclear antigen (PCNA) and cytokeratin (CK).

RESULTS

With PCNA and CK 13/16, the untreated group showed positive staining in the suprabasal and basal cells, but the treated group showed weakly positive staining only in the basal cell layer. With TUNEL staining, there were more positive cells in the untreated than the treated group.

Proteomic analysis of cholesteatoma

OBJECTIVE

Proteomic analysis with 2D electrophoresis and matrix-assisted laser desorption and ionization time-of-flight mass spectrometry (MALDI-TOF MS) may be a powerful tool for identifying and characterizing the specific proteins relating to the pathogenesis of some diseases, including cholesteatoma. The purpose of this study was to identify upregulated proteins in human cholesteatoma in comparison with canal skin using proteomic analysis.

MATERIAL AND METHODS

Three cholesteatoma matrices and three samples of normal retroauricular skin were obtained intraoperatively from cholesteatoma patients. We performed 2D electrophoresis in order to separate the proteins by molecular weight and approximately detected 600 protein spots. We then analyzed the 17 upregulated spots from the cholesteatoma matrices using MALDI-TOF MS. Upregulation of proliferating cell nuclear antigen (PCNA) and osteoclast stimulating factor-1 (OSF-1), two candidate proteins in the pathogenesis of cholesteatoma, was confirmed by means of immunohistochemistry and reverse transcriptase polymerase chain reaction.

RESULTS

Interestingly, two candidate proteins, PCNA and OSF-1, relating to cellular proliferation and bone destruction were identified in the cholesteatoma matrices and we also detected nine proteins relating to the mechanism of signal transduction in the pathogenesis of cholesteatoma, including P-13-kinase P55 gamma subunit, RET proto-oncogene tyrosine kinase receptor and adenosine kinase.

CONCLUSION

Proteomic analysis may be a powerful tool for the identification and characterization of many promising candidate proteins relating to cholesteatoma.

Expression of epidermal growth factor receptor in human middle ear cholesteatoma

Middle ear cholesteatoma is destructive to auditory ossicles and temporal bone, and treatment usually includes surgical removal of all epithelial content in the tympanomastoid cavity. Epidermal growth factor receptor (EGFR) is a 170 kd to 180 kd transmembrane glycoprotein and its distribution density is related to the ability of the keratinocytes to differentiate and their state of differentiation. We used the avidin-biotin complex technique and EGFR monoclonal antibody to evaluate the expression of EGFR in 29 cases of cholesteatoma and 34 samples of normal postauricular skin. Of patients with cholesteatoma, 79% (23 cases) had EGFR-positive cells in the basal layer, 66% (19 cases) in the parabasal layer, and 62% (18 cases) in the upper layer of the epithelial tissue. Among patients with normal postauricular skin, 85% (29 cases) had EGFR-positive cells in the basal layer, 79% (27 cases) in the parabasal layer, and 79% (27 cases) in the upper layer of the epithelial tissue. No statistical difference in EGFR expression between each layer of cholesteatoma and postauricular skin was noted. However, there was an intensity gradient of positive EGFR immunoreactivity from the basal to the higher layers in cholesteatoma. Our results showed that the distribution of EGFR in middle ear cholesteatoma is not deranged, but is similar to that in normal skin tissue.

Epidermal Growth Factor Expression in Middle Ear Cholesteatoma

Middle ear cholesteatoma is destructive to auditory ossicles and temporal bone, and treatment usually requires surgical removal of all epithelial content. Epidermal growth factor (EGF) can stimulate the growth and differentiation of a variety of mammalian cells, including epithelial cells. Our study used the avidin-biotin complex technique to evaluate the expression of EGF in 40 cases of middle ear cholesteatoma (active cholesteatoma, 31 cases; inactive cholesteatoma, 9 cases) and 34 normal postauricular skin samples. In middle ear cholesteatoma, EGF was expressed in squamous epithelium in 21 cases (53%), fibroblasts in two cases (5%), and cholesteatoma endothelium in two cases (5%). In normal postauricular skin, EGF was expressed in squamous epithelium in 14 samples (41%), fibroblasts in one sample (3%), and endothelium in none. No statistical difference in EGF expression was found between cholesteatoma and normal postauricular skin samples. These results show that the distribution of EGF in middle ear cholesteatoma is not deranged and that the progression of cholesteatoma might be induced by the release of factors from the cholesteatoma matrix via autocrine stimulation, or by inflammatory cells of the subepithelial tissue through paracrine stimulation, or in both of these ways.

Etiopathogenesis of cholesteatoma

Cholesteatoma is a destructive lesion of the temporal bone that gradually expands and causes complications by erosion of the adjacent bony structures. Bone resorption can result in destruction of the ossicular chain and otic capsule with consecutive hearing loss, vestibular dysfunction, facial paralysis and intracranial complications. Surgery is the only treatment of choice. The etiopathogenesis of cholesteatoma, however, is still controversial. This review was designed to understand the reasons for these disparities and to reduce or eliminate them. Future studies focused on developmental, epidemiological, hormonal and genetic factors as well as on treatment are likely to contribute to further understanding of cholesteatoma pathogenesis.

Expression of hypoxia inducible factor 1 alpha and Von Hippel Lindau protein in human middle ear cholesteatoma

OBJECTIVE

To evaluate the role of hypoxia in cholesteatoma progression.

STUDY DESIGN

Immunohistochemical analysis of paraffin-embedded human specimens.

METHODS

Thirteen middle ear cholesteatomas and 10 samples of normal human external ear canal skin were stained immunohistochemically for the presence of hypoxia inducible factor 1 alpha (HIF 1 alpha) and Von Hippel Lindau protein. Specimens were then analyzed semiquantitatively.

RESULTS

Staining for both antibodies could be detected in all cholesteatomas (perimatrix and matrix), as well as in the samples of normal human ear canal skin. Cholesteatoma specimens showed statistically significant increased staining when compared with normal human skin and mucosa. The age of patients and relapse surgery affected immunohistochemical staining of HIF 1 alpha and Von Hippel Lindau protein.

CONCLUSIONS

Elevated staining intensities for HIF 1 alpha and Von Hippel Lindau protein in cholesteatoma tissue indicated that cholesteatoma may be hypoxic. In addition, our data indicated that relapse cholesteatomas yield a higher degree of hypoxia than ears without surgery.