Comparison of changes in mitochondrial bioenergetics between keratinocytes in human external auditory canal skin and cholesteatomas from normoxia to hypoxia

Cheng-Ping Shih,Yu-Ting Chen,Yi-Chun Lin,Hsin-Chien Chen,Hang-Kang Chen,Jen-Tin Lee,Chih-Hung Wang,Chao-Yin Kuo,Yuan-Yung Lin

doi:10.1038/s41598-017-18536-y

Cheng-Ping Shih, Yu-Ting Chen + Show 7 more

Open Access

https://doi.org/10.1038/s41598-017-18536-y

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Journal: Scientific Reports	Publication Date: Jan 9, 2018
Citations: 7	License type: open-access

Affiliation: National Defense Medical Center

Abstract

Cholesteatoma has attracted many studies seeking to uncover its nature and the pathogenesis of related diseases. However, no researchers have explored the mitochondrial bioenergetics of cholesteatoma. The aim of this study was to investigate the energy demand and differential mitochondrial respiration profiles between keratinocytes in external auditory canal (EAC) skin and cholesteatoma samples cultured in normoxic (20% O2) and hypoxic (5% O2) conditions. Enhanced cellular proliferation of both types of keratinocytes was found in hypoxia compared to normoxia. In 20% O2 conditions, cholesteatoma keratinocytes exhibited less mitochondrial mass, lower ATP levels, and significantly lower basal oxygen consumption rate (OCR) and reserve capacity compared to normal skin keratinocytes. In contrast, in hypoxic conditions, cholesteatoma keratinocytes showed markedly higher levels in maximal OCR and reserve capacity, as well as lower proton leak OCRs, compared to normal skin keratinocytes. Hypoxia induced the reverse mitochondrial bioenergy profile from that in normoxia between these two types of keratinocytes, implying that an adaptive change of mitochondrial respiration to oxygen fluctuations may develop in cases of cholesteatoma. Such adaptation in response to hypoxic conditions may play a role in explaining the pathogenesis of acquired cholesteatoma.

Highlights

Cholesteatoma derives from an abnormal growth of the keratinizing squamous epithelium, which consists of a thin layer of stratified squamous epithelium and an adjacent subepithelial connective tissue layer[1]
In testing whether cells retained a stable mitochondrial membrane potential under hypoxic conditions, the values were relatively low compared to normoxia, the results demonstrated that there was no significant loss of mitochondrial membrane potential in either the cholesteatoma keratinocytes (CKs) or EAC keratinocytes (EACKs) after 24 h of hypoxia (Fig. 1D)
To further explore why the mitochondrial mass of EACK was dramatically decreased after 24 h of hypoxic culture, we evaluated the role of autophagy in both types of keratinocytes, especially in response to differential oxygen tension

Summary

Introduction

Cholesteatoma derives from an abnormal growth of the keratinizing squamous epithelium, which consists of a thin layer of stratified squamous epithelium (matrix) and an adjacent subepithelial connective tissue layer (perimatrix)[1]. Recent bioinformatics analysis of proteomic data even indicated that a lower grade of differentiation and cancer-like alterations may be involved in the cholesteatoma epithelium[22]. All these published reports strongly suggest that cholesteatoma keratinocytes are distinct from normal skin keratinocytes in many respects. Hypoxia has long been recognized as one of the main promoters in cholesteatoma initiation and progression[25,26], as hypoxic conditions in the tympanic cavity can result in eardrum retraction pockets developing in the middle ear, followed by cholesteatoma onset and formation. The cholesteatoma has been identified as a hypoxic tissue, suggesting that hypoxia may be one of the main promoters in cholesteatoma initiation and progression[25,26,27,28,29]

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