An immunocytochemical study of cytokeratin expression in human middle ear cholesteatoma

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.

Cytokeratin expression pattern in congenital and acquired pediatric cholesteatoma

Pediatric cholesteatoma can be classified as congenital or acquired based on clinical criteria. We studied the expression patterns of five distinctive cytokeratins in both types of cholesteatoma in order to improve understanding of their pathogenesis and origin. A comparable expression pattern for CK10, CK14, CK18, CK19 and 34betaE12 antigens was found in the matrix of congenital and acquired pediatric cholesteatoma. Our results demonstrate that congenital and acquired pediatric cholesteatoma exhibit an identical cytokeratin distribution pattern, suggesting that they share a common origin. Therefore, it seems possible that a portion of the so-called "acquired" cholesteatoma may actually originate from advanced congenital cholesteatoma with secondary destruction of the tympanic membrane in the pediatric patient population.

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.

A study on epidermal proliferation ability in cholesteatoma

With the objective of estimating proliferation ability of epidermis of middle ear cholesteatoma, the difference in proliferating cell nuclear antigen (PCNA) staining between the skin of the bone region of the external ear canal (control skin) and cholesteatoma epidermis and the effects on PCNA staining of subepidermal inflammatory cell infiltration of cholesteatoma were immunohistochemically studied using an antibody against PCNA. Transforming growth factor-alpha (TGF-alpha) is known to promote epidermal proliferation based on autocrine mechanism. But it is not clear that cholesteatoma epidermis is actually in the state of hyperproliferation under the effect of this growth factor. To estimate the effect of TGF-alpha on epidermal proliferation ability, the authors compared the location of PCNA and TGF-alpha in the same specimen. Unlike the control skin, not only epidermal basal cell layer and suprabasal cell layer, but also more superior layers were found to have high levels of PCNA staining in the epidermis of cholesteatoma. However, in the same cholesteatoma epidermal tissue, the PCNA staining was varied and the difference was ascribable to subepidermal cell inflammation. It appeared that the proliferation ability was high in regions where subepidermal inflammatory cell infiltration was severe. These differences in microenvironment are inferred to greatly affect proliferation ability of cholesteatoma epidermis.

Human-papillomavirus DNA in cholesteatomas

Cholesteatoma of the middle ear is a relatively common disorder, often with severe consequences. Histologically, the aggressively growing, bone-destructing form shows papillary growth and koilocytosis, which are characteristic of papillomavirus-induced lesions. A PCR (polymerase chain reaction) method using degenerate primers for the detection of any known or as yet unknown HPV (human papillomavirus) type was applied in screening 51 biopsies from 42 patients. A resulting 36% (16/45) of the cholesteatomas were found to contain papillomavirus DNA, which hybridized under stringent conditions with an HPV-II DNA probe. In 3 cases the presence of HPV-II DNA could be confirmed by sequencing the PCR products. The mere presence of this HPV DNA does not prove an etiological role of this group of viruses in the induction of cholesteatomas. It does, however, identify another group of human proliferative lesions putatively linked to papillomavirus infections.

Expression of cytokeratins 13 and 16 in middle ear cholesteatoma

The accumulation of keratinizing epithelium in the middle ear cavity is a crucial factor in the pathogenesis of cholesteatoma. We hypothesize that keratinocytes from the skin of the ear canal migrate and hyperproliferate in response to inflammation in the middle ear cavity to cause accumulation of keratin debris. In the present study, we investigated the expression of specific cytokeratins (CKs) in the cholesteatoma matrix to determine whether cholesteatoma is a hyperproliferative disease. Cytokeratin expression was examined in cholesteatoma, meatal skin, and tympanic membrane with two monoclonal antibodies, one for both cytokeratins 13 and 16 (antibody K8.12), and another for cytokeratin 13 only (antibody KS-1A3). CK 13 (MW 51 KD) is a marker of differentiation and CK 16 (MW 48 KD) is a marker of hyperproliferation of keratinocytes. The use of immunoblot probes showed that CKs 13 and 16 were present in cholesteatoma. Immunofluorescent staining showed the presence of CK 16 in the suprabasal layer of cholesteatoma, which was located near the external ear canal. CK 13 was localized in the suprabasal layer of meatal skin and tympanic membrane. CK 13 was localized in the basal layer of the cholesteatoma, distal to the external ear canal, but not in the meatal skin and tympanic membrane. Taken together, the present data suggest that cholesteatoma is a hyperproliferative disease and that cholesteatoma expresses CK 16 near the external ear canal and transforms to express CK 13 during growth distally.

A review of the definition, terminology and pathology of aural cholesteatoma

Despite a considerable amount of discussion and research in the course of many years, aural cholesteatoma has remained a matter of controversy. This review concerns only the definition, terminology and pathology of this common and severe disease.

Hyperproliferation-associated keratin expression in human middle ear cholesteatoma

Cholesteatoma is characterized by the presence of a squamous epithelium invading the middle ear altering its growth properties. This epithelium is believed to have hyperproliferative properties. Keratin 16 is accepted as a molecular marker for hyperproliferative epithelia. Two monoclonal antibodies K8.12 (directed against keratin 13) and KS.1A3 (directed against keratin 13 and 16) were used in an alkaline phosphatase anti-alkaline-phosphatase (APAAP)-technique to compare the expression of both keratin 13 and keratin 16 in normal human skin and aural cholesteatoma. Furthermore, the cytokeratin expression was compared to that of normal skin and palatine tonsil using one-dimensional gel electrophoresis. For both monoclonal antibodies, normal ear skin was stained only in the basal layer. In contrast, in the cholesteatoma samples the immunostaining of the antibody KS-1A3 was done not only in the basal cell layer but also in the suprabasal cells of the stratum spinosum and stratum granulosum. Using gel-electrophoresis, the presence of cytokeratin 16 was demonstrated in the cholesteatoma samples only. These results support the hyperproliferative character of cholesteatoma epithelium.