Dicer Is Down-regulated and Correlated with Drosha in Idiopathic Sudden Sensorineural Hearing Loss

Previously, we reported the expression levels of specific microRNA machinery components, DGCR8 and AGO2, and their clinical association in patients with idiopathic sudden hearing loss (SSNHL). In the present study, we investigated the other important components of microRNA machinery and their association with clinical parameters in SSNHL patients. Fifty-seven patients diagnosed with SSNHL and fifty healthy volunteers were included in this study. We evaluated mRNA expression levels of Dicer and Drosha in whole blood of patients with SSNHL and the control group, using RT & real-time PCR analysis. The Dicer mRNA expression level was down-regulated in patients with SSNHL. However, the Drosha mRNA expression level was not significantly altered in patients with SSNHL. Neither the Dicer nor Drosha mRNA expression level was not associated with any clinical parameters, including age, sex, duration of initial treatment from onset (days), initial Pure tone average, Siegel's criteria, WBC, and Erythrocyte sedimentation rate. However, mRNA expression levels of Dicer and Drosha were positively correlated to each other in patients with SSNHL. In this study, we demonstrated for the first time that the Dicer mRNA expression level was down-regulated in patients with SSNHL, suggesting its important role in pathobiology of SSNHL development.