The nature of the epithelium in acquired cholesteatoma

Expression and Regulatory Mechanisms of MicroRNA in Cholesteatoma: A Systematic Review

Cholesteatoma is a temporal bone disease characterized by dysfunctions of keratinocytes. MicroRNAs (miRNAs) are evolutionary conserved noncoding RNAs that regulate mRNA expression. They can be packaged into exosomes and transported to target cells that can be used in the future therapy of cholesteatoma. This study aimed to collect knowledge on the role of miRNAs and exosomal miRNAs in cholesteatoma and was conducted according to the PRISMA guidelines for systematic reviews. Four databases were screened: Pubmed/MEDLINE, Web of Science, Scopus, and the Cochrane Library. The last search was run on the 6th of June 2023. We included full-text original studies written in English, which examined miRNAs in cholesteatoma. The risk of bias was assessed using the Office of Health Assessment and Translation (OHAT) Risk of Bias Rating Tool, modified for the needs of this review. We identified 118 records and included 18 articles. Analyses revealed the downregulation of exosomal miR-17 as well as miR-10a-5p, miR-125b, miR-142-5p, miR34a, miR-203a, and miR-152-5p and the overexpression of exosomal miR-106b-5p as well as miR-1297, miR-26a-5p, miR-199a, miR-508-3p, miR-21-3p, miR-584-5p, and miR-16-1-3p in cholesteatoma. The role of differentially expressed miRNAs in cholesteatoma, including cell proliferation, apoptosis, the cell cycle, differentiation, bone resorption, and the remodeling process, was confirmed, making them a potential therapeutic target in this disease.

Transcription and microRNA Profiling of Cultured Human Tympanic Membrane Epidermal Keratinocytes

The human tympanic membrane (TM) has a thin outer epidermal layer which plays an important role in TM homeostasis and ear health. The specialised cells of the TM epidermis have a different physiology compared to normal skin epidermal keratinocytes, displaying a dynamic and constitutive migration that maintains a clear TM surface and assists in regeneration. Here, we characterise and compare molecular phenotypes in keratinocyte cultures from TM and normal skin. TM keratinocytes were isolated by enzymatic digestion and cultured in vitro. We compared global mRNA and microRNA expression of the cultured cells with that of human epidermal keratinocyte cultures. Genes with either relatively higher or lower expression were analysed further using the biostatistical tools g:Profiler and Ingenuity Pathway Analysis. Approximately 500 genes were found differentially expressed. Gene ontology enrichment and Ingenuity analyses identified cellular migration and closely related biological processes to be the most significant functions of the genes highly expressed in the TM keratinocytes. The genes of low expression showed a marked difference in homeobox (HOX) genes of clusters A and C, giving the TM keratinocytes a strikingly low HOX gene expression profile. An in vitro scratch wound assay showed a more individualised cell movement in cells from the tympanic membrane than normal epidermal keratinocytes. We identified 10 microRNAs with differential expression, several of which can also be linked to regulation of cell migration and expression of HOX genes. Our data provides clues to understanding the specific physiological properties of TM keratinocytes, including candidate genes for constitutive migration, and may thus help focus further research.

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.

Cholesteatoma growth and proliferation: posttranscriptional regulation by microRNA-21

OBJECTIVES

The goal of this study was to identify novel regulatory mechanisms controlling the growth and proliferation of cholesteatoma. Specifically, the potential role of microRNAs, regulators of protein translation, was studied in cholesteatoma.

STUDY DESIGN

This study represents a molecular biologic investigation characterizing and comparing microRNA and protein expression in cholesteatoma and normal postauricular skin.

METHODS

Cholesteatoma and normal skin were taken from patients at the time of surgery. Tissue was processed for RNA and protein extraction. Real-time reverse-transcriptase-polymerase chain reaction was used to assess levels of human microRNAs, reverse-transcriptase-polymerase chain reaction was used to confirm the presence of upstream regulators, and Western blot analyses were used to assess levels of downstream target proteins.

RESULTS

Among the microRNAs investigated, human microRNA-21 (hsa-miR-21) showed a 4.4-fold higher expression in cholesteatoma as compared with normal skin (p = 0.0011). The downstream targets of hsa-miR-21, PTEN and programmed cell death 4, were found to be greatly reduced in 3 of 4 cholesteatoma samples. Proposed upstream regulators of hsa-miR-21 expression (CD14, interleukin 6R, gp130, and signal transducer and activator of transcription 3) were present in all cholesteatoma tissues.

CONCLUSION

MicroRNAs represent powerful regulators of protein translation, and their dysregulation has been implicated in many neoplastic diseases. This study specifically identified up-regulation of hsa-miR-21 concurrent with down-regulation of potent tumor suppressor proteins PTEN and programmed cell death 4. These proteins control aspects of apoptosis, proliferation, invasion, and migration. The results of this study were used to develop a model for cholesteatoma proliferation through microRNA dysregulation. This model can serve as a template for further study into potential RNA-based therapies for the treatment of cholesteatoma.

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.

The localization of matrix metalloproteinases-8 and -13 in cholesteatoma, deep-meatal and post-auricular skin: a comparative analysis

CONCLUSION

The presence of matrix metalloproteinase (MMP)-8 and MMP-13 was found to be significantly higher in cholesteatoma compared with post-auricular skin. The results show that the control group used has implications for further studies.

OBJECTIVES

To compare the presence of MMP-8 and MMP-13 in cholesteatoma, deep meatal and post-auricular skin. Our null hypothesis was that there was no difference in expressions of MMP-8 and MMP-13 in the three groups.

MATERIALS AND METHODS

The study was carried out in a secondary care specialist centre and used prospective retrieval of specimens for immunohistological localization of MMP-8 and MMP-13. Eleven patients undergoing cholesteatoma surgery were recruited for the study. Eleven cholesteatoma specimens, 10 deep meatal skin specimens and 10 post-auricular skin specimens were analysed. Specimens were analysed by immunohistochemistry using monoclonal antibodies to MMP-8 and MMP-13. Two observers scored the slides independently in a blind fashion.

RESULTS

The presence of MMP-8 and MMP-13 was found to be significantly higher in cholesteatoma compared to post-auricular skin (p=0.02, p=0.03, respectively). There were no significant differences in expression of MMP-8 and MMP-13 between cholesteatoma and deep meatal skin (p=0.08, p=0.09, respectively). There were no significant differences in the control groups.

Photodynamic effect of argon and diode laser on cholesteatoma cell cultures after intravital staining with absorption enhancers

Chronic epitympanic otitis media, or chronic suppurative osteitis, is a destructive form of chronic middle-ear inflammation. The therapy of choice is complete surgical removal of the squamous epithelium from the middle ear. It is often impossible to inspect all areas of the middle ear with the posterior canal wall intact. Not all recesses can be reliably monitored with the microscope, particularly in the area of the antrum and hypotympanum. Residual squamous epithelium here causes frequent recurrences following cholesteatoma surgery. This study examines the effect of argon and diode lasers on cholesteatoma tissue. The aim is to develop a laser treatment selectively directed against cholesteatoma cells that can be performed after cholesteatoma surgery to eliminate any residual squamous epithelium. Intraoperatively harvested monolayer-cultured cholesteatoma cells stained in vivo with various absorption enhancers served as the in vitro examination model. Argon (499 nm) and diode lasers (810 nm) were applied since their irradiation has an appropriate tissue penetration depth and is absorbed by various chromophores such as neutral red (475-500 nm), fluorescein (488 nm), and indocyanine green (790-810). Intracellular staining of cultured cells increased the optical density at the wavelength corresponding to the dye. Neutral red damaged 50-60% of cultured cells merely by intracellular accumulation at high concentrations. An additive cell destruction of about 30% was achieved by also applying argon laser irradiation. Fluorescein diacetate caused no appreciable stain-induced damage to cultured cholesteatoma cells. Argon laser irradiation destroyed up to 60% of the cultures. Indocyanine green resulted in only minor damage to cultured cells. The diode laser destroyed up to 60% of the irradiated cells. Selective staining of cholesteatoma cells was not achieved with any of the dyes examined. Thus, other stained tissue could be damaged. Staining and subsequent laser irradiation destroys up to 60% of cultured cholesteatoma cells. Unstained irradiated cells are not affected. Indocyanine green and fluorescein are nontoxic and may thus be used as absorption enhancers. The diode and argon lasers appear to be basically suitable. Cell staining is not selective, i.e., other tissues would also be stained and damaged. To avoid such unwanted damage, it would be desirable to couple the chromophore to a specific antibody that binds only to cholesteatoma cells.

Localization of matrix metalloproteinase 1 in cholesteatoma and deep meatal skin

HYPOTHESIS

Matrix metalloproteinase 1 (MMP-1) is overexpressed in cholesteatoma.

BACKGROUND

Cholesteatoma destroys bone, whereas deep meatal skin does not. MMP-1 is a type I collagenase that may be responsible for this destruction. This prospective study was designed to identify overexpression of MMP-1 by cholesteatoma in comparison with deep meatal skin.

METHODS

Ten cholesteatoma specimens and nine deep meatal skin specimens were removed during otologic surgery and then fixed in formalin and embedded in paraffin. Immunocytochemistry studies were performed using a monoclonal antibody to MMP-1. A pathologist assessed the slides in a blinded fashion. Expression of MMP-1 protein in epidermis and in stroma was scored from 0 to 10. Five further cholesteatoma specimens and three deep meatal skin specimens underwent reverse transcriptase polymerase chain reactions to assess messenger ribonucleic acid production. Paired and unpaired Student's t tests were used to assess the difference in expression levels.

RESULTS

Cholesteatoma stroma expressed significantly more MMP-1 protein than did deep meatal skin stroma (p = 0.04). MMP-1 was localized to stromal fibroblasts. There was no difference in the epidermal expression levels of the two tissue types (p = 0.42). The reverse transcriptase polymerase chain reaction showed expression at the messenger ribonucleic acid size of MMP-1 (262 base pair) in all cholesteatoma specimens examined. One deep meatal skin specimen showed a weak signal; no signal was seen in the other specimens.

CONCLUSIONS

MMP-1 is overexpressed by the stromal fibroblasts present in cholesteatoma as compared with deep meatal skin. It is possible that these cells rather than the keratinocytes are responsible for bone destruction in this disease.

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.

Matrix metalloproteinase-1 in cholesteatoma, middle ear granulations and deep meatal skin: a comparative analysis

Nine cholesteatomas, seven middle ear granulations and five deep meatal skin specimens were analysed for gelatinase activity at molecular weights corresponding to those of matrix metalloproteinase-1 (MMP-1) using SDS PAGE zymography. Gelatinase activity at 41-43 kDa and 45-47 kDa was investigated. Western blotting was employed using a primary monoclonal antibody to MMP-1 to provide a qualitative assessment of MMP-1. Western blotting was also used with a monoclonal antibody to MMP-3 to discover if MMP-3 gelatinase activity occurring around the molecular weight of MMP-1 may have contributed to the results. A significantly higher expression of activity was recorded in cholesteatoma and middle ear granulations at 45-47 kDa in comparison with deep meatal skin. Western blotting indices were to be present in all of the cholesteatoma specimens tested. Only one of the specimens (cholesteatoma) tested showed any MMP-3 presence.

Matrix metalloproteinase-2 and matrix metalloproteinase-9 in cholesteatoma and deep meatal skin

A qualitative and quantitative study of the presence of Matrix metalloproteinase-2 (MMP-2) and Matrix metalloproteinase-9 (MMP-9) in cholesteatoma was performed. Ten cholesteatoma and four deep meatal skin specimens were analysed for gelatinase activity at molecular weights corresponding to MMP-2 and MMP-9 using Sodium Dodecyl Sulphate Polyacrylamide Gel Electrophoresis (SDS PAGE) Zymography. Gelatinase activity at 72 kDa and 92 kDa was investigated. Western blotting was employed using primary monoclonal antibodies to provide a qualitative assessment of MMP-2 and MMP-9. Non-parametric data analysis using the Mann-Whitney U test did not show a significant difference in expression of MMP-2 (P = 0.51) or MMP-9 (P = 0.14) between the two tissue types. Western blotting showed the presence of both MMP-2 and MMP-9 in the majority of specimens, both cholesteatoma and deep meatal skin.

Clinicopathological consultation. Ear cholesteatoma versus cholesterol granuloma

Cholesteatoma and cholesterol granuloma of the ear are two different pathologic conditions that have often been confused in the past, and even in the present, in the literature. The features differentiating the two lesions are presented.

The nature of the epithelium in acquired cholesteatoma: Part 3--Cytokeratin patterns in aural epithelial and cholesteatoma cells grown in cell culture

The nature and origin of the epithelial layers in acquired cholesteatoma is still unclear. Although previous morphological studies comparing external meatal and cholesteatoma epithelium have shown no significant difference, bone resorption is generally much more severe with cholesteatoma than with chronic otitis media without cholesteatoma. It is possible that cholesteatoma epithelium has undergone transformation leading to its enhanced bone destroying role. In this study the cytokeratin patterns of aural and cholesteatoma epithelia grown in cell culture were compared using monoclonal antibodies. No significant difference in staining patterns were found suggesting that there has been no change in cell phenotype which maintains that of external auditory meatus epithelium. This study therefore supports the immigration theory of cholesteatoma genesis.

Antigen expression of epithelial markers, collagen IV and Ki67 in middle ear cholesteatoma. An immunohistochemical Study

The expression of epithelial markers (cytokeratins, Filaggrin, BerEp4 and EMA), collagen IV and Ki67 was studied immunohistochemically in cholesteatoma and compared with that in epidermis of meatal skin, squamous epithelium of eardrum and simple epithelium of middle ear mucosa. MNF116 (cytokeratin 10, 17, 18) stained the full layer of normal epithelium and all cholesteatoma specimens. CK10 and Filaggrin were expressed in the upper layer of epidermis but more diffusely in cholesteatoma. BerEp4 was found in the basal layer of normal epithelium but was detected in most epithelial cells in cholesteatoma matrix. Variability was observed in EMA and CK14 immunostaining. Collagen IV was localized in the basement membrane of normal epithelium with a continuously staining pattern, an observation also made in the cholesteatomas studied. However, in one of these small areas the basement membrane was not stained with collagen IV. Ki67 was expressed in nuclei of the cells in the basal layer of normal epithelium but extended to epithelial cells in the upper layers of cholesteatoma matrix. The results of the present study indicate that the expression pattern of epithelial markers in cholesteatoma corresponds to that in normal epidermis. The increasing expression of BerEp4 and Ki67 confirms the hyperproliferative nature of cholesteatoma. Whether or not the lack of expression of collagen IV in one of the cholesteatomas reflects a true degradation of the basement membrane needs further investigation in extended materials.

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.