Learning Objectives: Cholesteatomas is characterized by a more rapid growth and extensive bone destruction in the middle ear and mastoid cavities. MicroRNAs (miRNAs) are posttranscriptional regulators of gene expression. The goal of this study was to investigate the posttranscriptional regulatory effects controlling proliferation, apoptosis and invasion in cholesteatoma keratinocytes. Specifically, the potential role of microRNA-21(miR-21) was focused on in this study.

Methods: Cholesteatoma tissues, taking from the patients at the time of surgery, were processed for RNA and cell culture. The cholesteatoma keratinocytes were transfected with miR-21 mimics, miR-21 inhibitor or negative control miRNA, and then growth curves were drawn. Real-time reverse-transcription polymerase chain reaction was used to assess the expression levels of miR-21. EdU incorporation assay and TUNEL staining were used to assess the proliferation and apoptosis of cholesteatoma keratinocytes, respectively. The invasive abilities of cholesteatoma keratinocytes were examined using 6-well Transwell plates.

Results: MicroRNA-21 showed an up-regulation respectively cholesteatoma keratinocytes transfected miR-21 mimics as compared with cells transfected miR-21 inhibitor or control miRNA. The number of proliferative EdU-positive(EdU+) cells increased in cholesteatoma keratinocytes transfected miR-21 mimics, as compared with cells transfected miR-21 inhibitor or control miRNA. The number of TUNEL-positive cells was increased in cholesteatoma keratinocytes transfected miR-21 mimics, as compared with cells transfected miR-21 inhibitor or control miRNA. The migrated cholesteatoma keratinocytes transfected miR-21 mimics was higher, as compared with the migrated cells transfected miR-21 inhibitor or control miRNA.

Conclusions: The present study showed that miR-21 promotes proliferation and invision of cholesteatoma keratinocytes. The results give a partial explanation for the more aggressive clinical behavior abserved in choleateatoma.