Basement membrane in middle ear cholesteatoma. Immunohistochemical and ultrastructural observations

Pathogenesis and Bone Resorption in Acquired Cholesteatoma: Current Knowledge and Future Prospectives

Cholesteatoma is a cystic non tumorous lesion of the temporal bone that has the ability to destroy nearby structures by its power to cause bone resorption and as a result, fatal complications prevail. We aimed to conduct a comprehensive review for pathogenesis of acquired cholesteatoma, bone resorption mechanisms, and offer a future vision of this serious disease. We have reviewed different theories for pathogenesis of acquired cholesteatoma including the most relevant and updated ones with special emphasis on the mechanisms of bone resorption through Medline/PubMed research using the keywords 'aetiopathogenesis, bone resorption, acquired cholesteatoma, temporal bone, and cytokines.' In order to strengthen our study, we searched the reference lists of identified reviews. Cholesteatoma is a subject of debate among otolaryngologists since it was prescribed firstly. Over many decades, several theories were postulated for aetiopathogenesis of cholesteatoma with a tendency to follow more than one theory to explain the proper nature of that disease. Until now, the mechanism of bone resorption has yet to be more clarified. In the last century, a leap has occurred in the field of biomolecular cholesteatoma research which improved our knowledge about its pathophysiology and bone destructive mechanism. However, surgery is still the only available treatment. We conclude that discovery of new therapeutic choices for cholesteatoma other than surgery by the use of anti-growth, anti-proliferative, apoptotic agents as well as medications that antagonize osteoclastogenesis should be the main concern in the future clinical and experimental research work. Also, searching for predictors of the aggressiveness of cholesteatoma can affect the timing of intervention and prevent occurrence of complications.

A new theory on the pathogenesis of acquired cholesteatoma: Mucosal traction

OBJECTIVES/HYPOTHESIS

Although the migration of its squamous outer surface of the tympanic membrane has been well characterized, there is a paucity of data available concerning the migratory behavior of its medial mucosal surface. Existing theories of primary acquired cholesteatoma pathogenesis do not adequately explain the observed characteristics of the disease. We propose a new hypothesis, based upon a conjecture that mucosal membrane interactions are the driving force in cholesteatoma.

STUDY DESIGN

A retrospective chart review and a prospective observational cohort study in rats.

METHODS

After developing the new theory, it was tested through both clinical and experimental observations. To evaluate whether impairment of middle ear mucociliary migration would influence cholesteatoma formation, a retrospective chart review evaluating cholesteatoma occurrence in a sizable population of patients with either primary ciliary dyskinesia (PCD) or cystic fibrosis (CF) was performed. To study mucosal migration on the medial aspect of the tympanic membrane, ink tattoos were monitored over time in a rat model.

RESULTS

No cholesteatomas were identified in either PCD patients (470) or in CF patients (1,910). In the rat model, mucosa of the posterior pars tensa migrated toward the posterior superior quadrant, whereas the mucosa of the anterior pars tensa migrated radially toward the annulus.

CONCLUSION

Mucosal coupling with traction generated by interaction of migrating opposing surfaces provides the first comprehensive theory that explains the observed characteristics of primary acquired cholesteatoma. The somewhat counterintuitive hypothesis that cholesteatoma is fundamentally a mucosal disease has numerous therapeutic implications.

Large-scale proteomics differentiates cholesteatoma from surrounding tissues and identifies novel proteins related to the pathogenesis

Cholesteatoma is the growth of keratinizing squamous epithelium in the middle ear. It is associated with severe complications and has a poorly understood etiopathogenesis. Here, we present the results from extensive bioinformatics analyses of the first large-scale proteomic investigation of cholesteatoma. The purpose of this study was to take an unbiased approach to identifying alterations in protein expression and in biological processes, in order to explain the characteristic phenotype of this skin-derived tumor. Five different human tissue types (cholesteatoma, neck of cholesteatoma, tympanic membrane, external auditory canal skin, and middle ear mucosa) were analyzed. More than 2,400 unique proteins were identified using nanoLC-MS/MS based proteomics (data deposited to the ProteomeXchange), and 295 proteins were found to be differentially regulated in cholesteatoma. Validation analyses were performed by SRM mass spectrometry. Proteins found to be up- or down-regulated in cholesteatoma were analyzed using Ingenuity Pathway Analysis and clustered into functional groups, for which activation state and associations to disease processes were predicted. Cholesteatoma contained high levels of pro-inflammatory S100 proteins, such as S100A7A and S100A7. Several proteases, such as ELANE, were up-regulated, whereas extracellular matrix proteins, such as COL18A1 and NID2, were under-represented. This may lead to alterations in integrity and differentiation of the tissue (as suggested by the up-regulation of KRT4 in the cholesteatoma). The presented data on the differential protein composition in cholesteatoma corroborate previous studies, highlight novel protein functionalities involved in the pathogenesis, and identify new areas for targeted research that hold therapeutic potential for the disease.

Expression of disintegrin and metalloproteinase family proteins 10, 12 and 17 in cholesteatoma

Objective:

Proteases of the disintegrin and metalloproteinase family (also known as ADAM proteins) are involved in various physiological and pathological processes. This study assessed the expression of disintegrin and metalloproteinase family proteins 10, 12 and 17 in cholesteatoma.

Materials and methods:

The study evaluated cholesteatoma specimens from 19 patients, and external ear canal skin samples from 7 of the same patients (as controls), for the expression of disintegrin and metalloproteinase family proteins 10, 12 and 17, using immunohistochemical methods.

Results and analysis:

The study observed over-expression of proteins 10 and 17 in blood vessels, and over-expression of proteins 12 and 17 in cholesteatoma stroma. Immunostaining scores for proteins 10, 12 and 17 in epithelial and inflammatory cells from cholesteatoma specimens versus control specimens showed no statistically significant differences.

Conclusion:

Over-expression of disintegrin and metalloproteinase family proteins 10, 12 and 17 in cholesteatoma may be related to cholesteatoma pathogenesis. These proteins deserve further study as they may represent potential targets for cholesteatoma treatment.

Neuroradiology of cholesteatomas

The relevant aspects of cholesteatomas are reviewed with the emphasis on their diagnosis by using cross-sectional imaging. The indications and limitations of CT and MR imaging and the use of novel MR imaging techniques in the diagnosis of cholesteatomas are described. HRCT of the temporal bone has an excellent spatial resolution, thus even small soft-tissue lesions can be accurately delineated (high sensitivity). However, CT has poor specificity (ie, soft-tissue structures cannot be differentiated). MR imaging with the conventional sequences (T1WI, T2WI, postcontrast T1WI) provides additional information for distinguishing different pathologic entities and for accurately diagnosing primary (nonsurgical) and residual/recurrent (surgical) cholesteatomas. Higher diagnostic specificity is achieved by introducing DW-EPI, delayed postcontrast imaging, DW-non-EPI, and DWI-PROPELLER techniques. Studies using DW-non-EPI and DWI-PROPELLER sequences show promising results related to improved diagnostic sensitivity and specificity for even small (<5 mm) cholesteatomas, thus allowing avoidance of second-look surgery in the future.

Elevated level of tenascin and matrix metalloproteinase 9 correlates with the bone destruction capacity of cholesteatomas

OBJECTIVES

Bone destruction is a key step in the progression of cholesteatomas. Some of the lesions can grow without affecting the surrounding anatomic structures, whereas others can cause severe bone destruction despite their limited size. This study aims to identify factors that could play important role during the invasion of the disease.

METHODS

Cholesteatoma tissue samples were examined immunohistochemically. Tissue samples were arranged on the basis of bone destruction (destructive cholesteatomas [DC] and nondestructive cholesteatomas [NDC]). Double-immunofluorescent labeling was performed to detect simultaneously 1) tenascin (TN) and cytokeratin; 2) matrix metalloproteinase 9 (MMP-9) and TN; 3) TN and Ki-67. An in situ apoptosis detection kit was used to detect apoptotic cells. External auditory canal skin samples were used as control.

RESULTS

1) In DCs, more widespread stromal TN labeling was seen compared with NDCs or external auditory canal skin samples. 2) More enhanced MMP-9 staining was detected in DCs compared with NDCs. 3) The proportion of Ki-67-positive cells in DC samples was significantly higher than in NDCs. 4) The percentage of apoptotic cells was higher in NDC than in DC samples.

CONCLUSION

Our present study demonstrates that levels of TN, MMP-9, and proliferative activity are increased in cholesteatomas. It has also been shown that increased levels of TN, MMP-9-positive cells, and proliferative activity of the lesions, as well as decreased levels of apoptosis, can be linked to more aggressive clinical behavior of cholesteatomas. Our findings also indicate that TN and MMP-9 can be key molecules of bone destruction during cholesteatoma progression.

Evidence-based review of aetiopathogenic theories of congenital and acquired cholesteatoma

Cholesteatoma is a non-neoplastic, keratinising lesion which has two forms: congenital and acquired. Congenital cholesteatoma develops behind a normal, intact tympanic membrane, whilst acquired cholesteatoma is associated with a defect in the tympanic membrane. The pathological substrate of cholesteatoma is keratinising stratified squamous epithelium, but the origin of this epidermal tissue in the middle ear is controversial. Here, we review the most relevant and recent evidence for the principal aetiopathogenic theories of both forms of cholesteatoma, in the light of recent otopathological findings. Congenital cholesteatoma is most plausibly explained by the persistence of fetal epidermoid formation. Conclusive 'proof' awaits the unambiguous demonstration of the metamorphosis of an epidermoid nidus into a lesion in vivo. Acquired cholesteatoma may develop by various mechanisms: immigration, basal hyperplasia, retraction pocket and/or trauma (iatrogenic or non-iatrogenic). However, squamous metaplasia of the normal cuboidal epithelium of the middle ear is a highly unlikely explanation. Chronic inflammation seems to play a fundamental role in multiple aetiopathogenic mechanisms of acquired cholesteatoma. Therefore early treatment of inflammatory conditions might reduce their sequelae, perhaps by preventing the development of hyperplastic papillary protrusions. Continued otopathological, cellular and molecular research would enhance our limited understanding of cholesteatoma and may lead to new therapeutic strategies for this erosive disease, which often defies surgical treatment.

Comparative analysis of the epithelium stroma interaction of acquired middle ear cholesteatoma in children and adults

In the clinical setting, pediatric cholesteatomas frequently behave more aggressively than similar lesions in adults. The reason for the difference in behavior is still unclear. The purpose of the present study was to investigate the cell to cell and epithelial-stroma interaction of acquired cholesteatoma in adults and children and search for differences on the cellular level, which might explain the different behavior of these lesions. Operative specimens of 54 patients [40 adults (average age of 39.7 years), 14 children (average age of 8.3 years)] who underwent primary surgery for an acquired cholesteatoma of the middle ear were examined by histopathology and DNA-image cytometry (DNA-ICM). Immunohistochemical investigations included expression of proliferation markers (proliferation cell nuclear antigen and MIB-1) along with cell surface markers reflecting the cell-to-cell interaction (i.e. alpha1beta6-integrin, E-cadherin, I-CAM = CD54), and the epithelial to stroma interaction (i.e. alphav and beta3 intergin chains, V-CAM = CD106, CD44v6 and fibronectin). Pediatric cholesteatomas demonstrated higher incidence of acute inflammation and more extensive disease relative to those from the adults. Indices of DNA-ICM, however, revealed normal diploid DNA content in both groups. Higher proliferation scores occurred in the pediatric group compared to adult cholesteatoma. Cell surface markers and cell adhesion molecules were equally expressed in both groups except alpha1beta6-integrin and fibronectin, which were over expressed in pediatric cholesteatomas. Statistically, however, these differences showed only a trend towards significance. According to the results of the present study, pediatric and adult cholesteatomas do not show any marked differences on the cellular level. Thus the observed clinical more aggressive behavior of pediatric cholesteatoma is likely due to other secondary factors such as more intense inflammation, disturbed middle ear ventilation or the diminished calcium salt content of pediatric bone.

Pathogenesis of sinus cholesteatoma

The aim of the present study was to provide evidence for the establishment of sinus cholesteatoma, defined as postero-superior pars tensa retraction extending into the posterior tympanum and tympanic sinuses.

BACKGROUND

There is clinical evidence for formation of a retraction, but there is a lack of explanation for the transition from a retraction pocket to an active and expanding sinus cholesteatoma. Epidemiological studies on incidence of postero-superior retractions of pars tensa and follow-up studies on patients with similar pars tensa retractions were performed. Additionally, expression of proliferation marker and analysis of basement membrane were studied in samples of sinus cholesteatoma. The prevalence of pars tensa pathology was between 9.2 and 24% of investigated ears. In children with manifest secretory otitis there were some sinus cholesteatomas and 5-6% severe retractions, some of those became pre-cholesteatomas, requiring treatment and controls. Immunohistochemistry of sinus cholesteatomas showed that proliferating keratinocytes were very often found within epithelial cones growing towards the underlying stroma. These growth cones exhibit focal discontinuities of the basement membrane especially in areas of intense subepithelial inflammation. As a possible explanation based on clinical and immunohistochemical findings, we propose a four-step concept for pathogenesis of sinus cholesteatoma combining the retraction and proliferation theory: (1) The retraction pocket stage. (2) The proliferation stage of the retraction pocket, subdivided in (a) Cone formation, (b) Cone fusion. (3) Expansion stage of attic cholesteatoma. (4) Bone resorption.

Prevalence of human papillomavirus DNA in cholesteatomas

Cholesteatomas show histomorphological features like papillary growth and koilocytosis, which are characteristic of lesions induced by human papillomaviruses (HPV). Two previous studies investigating the possible role of HPV in the development of cholesteatoma had detected HPV-6 and HPV-11 DNA with a prevalence differing from 3 to 36%. The aim of the presented study was to evaluate the prevalence of different HPV types in cholesteatomas using a sensitive detection system for HPV DNA. Twenty-nine biopsies from cholesteatomas were screened for HPV DNA with a 2-step broad-spectrum PCR (PCR and nested PCR). HPV-positive products were directly sequenced by means of a cycle sequencing approach. Sensitivity of the applied broad-spectrum PCR was 0.1 copy/genome. One out of 29 biopsies showed a positive signal on the nested PCR level. Considering the low prevalence (1/29 biopsies) of detected HPV DNA in cholesteatomas, infections with common HPV types are unlikely to be a causative factor.

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.

Increased proliferation and migration of epithelium in advancing experimental cholesteatomas

HYPOTHESIS

Hyperproliferative and migratory process of keratinocytes are part of the pathogenesis of cholesteatoma.

BACKGROUND

Cytokeratin (CK) changes were prominent in the most rapidly expanding regions of cholesteatoma formation.

METHODS

The three types of animal model-canal ligation (CL), retraction pocket (RP), and propylene glycol (PG)-were induced in Mongolian gerbils. The monoclonal antibodies to CK1/10, CK5/6, and CK13/16 were used for immunohistochemistry. The intensity of immunostaining in the pars tensa of the tympanic membrane was measured using the densitometry and compared with respect to the stage of cholesteatoma and the type of animal model.

RESULTS

With cholesteatoma formation, CK expressions were significantly increased at the peripheral part of the pars tensa, the expanding part of cholesteatoma. Among the CKs tested, the prominent changes were observed in expression of CK13/16, a marker for hyperproliferation. Among the animal models, CK changes of CK5/6 and CK1/10 were most prominent in the CL type, whereas those of CK13/16 were more persistent in the RP type.

CONCLUSION

These results suggested that complex alterations of epidermal keratinocytes occur during cholesteatoma formation and that hyperproliferative and migratory processes play important roles in the pathogenesis of cholesteatoma.

Cholesteatoma behind an intact tympanic membrane: histopathologic evidence for a tympanic membrane origin

BACKGROUND

Several theories have been proposed with respect to the origin and pathogenesis of cholesteatoma behind an intact tympanic membrane.

CASE REPORT

The authors describe a case of cholesteatoma behind an intact tympanic membrane in a 71-year-old man with a history of tympanic membrane retraction fixed to the incus without evidence of a perforation. The membrane eventually became detached, and remnants of keratinizing squamous epithelium were found on the incus.

DISCUSSION

Mechanisms such as metaplasia, ectopic epidermis rests, or ingrowth of meatal epidermis have been proposed to explain the pathogenesis of cholesteatoma behind an intact tympanic membrane. These findings, based on temporal bone histopathology, support the role of an acquired epidermal rest.

CONCLUSIONS

This case report provides evidence that cholesteatoma behind an intact tympanic membrane can be established from a resolved retraction of the pars tensa of the tympanic membrane.

[Alterations of the basal membrane in middle ear cholesteatoma]

Cholesteatoma epithelium is characterized by a keratinocyte disregulation accompanied by destruction of the ossicles and other bony parts of the temporal bone. Immunohistochemical methods using antibodies to fibronectin, tenascin and metalloproteinases were used to assess the alterations of the instrinsic and extrinsic components of the basement membrane. Spatial orientation of the basement membrane was preserved in histological sections. Collagen type IV, tenascin, fibronectin, basic fibroblastic growth factor (bFGF), and matrix metalloproteinases (MMPs) are related to the matrix, perimatrix of normal or pathological tissues. They were studied immunohistologically in twenty cholesteatomas, eight samples of normal auditory canal skin, and six specimens of normal middle ear mucosa. Cholesteatomas displayed alterations of the basal membrane, with presence of MMPs and a linear immunoreactivity for collagen type IV and laminin, disrupted in areas with intense inflammation. The electronic microscope revealed protrusions, duplications, thickening and disruptions of the lamina densa of the basement membrane. Thus, we conclude, that MMPs and bFGF could play an important role maintaining the proliferative activity and the aggressive behaviour of cholesteatoma in the middle ear.

Expression pattern of the plasminogen activator-plasmin system in human cholesteatoma

The plasminogen activator-plasmin system plays a pivotal role in the delicately regulated process of extracellular matrix remodeling. Recent studies have shown that an imbalance of proteolytic enzymes over specific inhibitors in this system may lead to an aggressive, expanding, and infiltrating cellular phenotype. As cholesteatoma resembles a tumor in many ways, we investigated the pattern of expression for members of the plasminogen activator-plasmin system in 12 human cholesteatomas, using immunohistochemistry. As controls, 3 tympanic membranes and 4 ear canal skin specimens were used. In contrast to the tympanic membranes, all cholesteatoma specimens showed a strong expression of plasminogen at the basal epithelial cell layers. In ear canal skin, only the basal surface of the most basal epithelia stained discretely positive. The urokinase-type plasminogen activator (uPA) could be detected in the basal stratum of the cholesteatoma matrix and in the surrounding granulation tissue, while tissue-type plasminogen activator (tPA) was not detectable at all. Plasminogen activator inhibitor-1 (PAI-1) was expressed in both the granulation tissue and the granular cell layer of the matrix, but not in the basal epithelial cells; PAI-2 showed a pericellular expression pattern in the subbasal and granular cell layers. Neither uPA, tPA, nor the PAIs could be detected in tympanic membrane controls; ear canal skin showed the same staining pattern as cholesteatoma only for PAI-2. Our data demonstrate that there is a clear imbalance in favor of proteolytic activity in the basal epithelial layers of the cholesteatoma matrix, which might at least partly account for the aggressive behavior of this tumorlike lesion. Further, the pattern of expression resembles the pattern described for several epithelial malignancies.