The expression level of each microRNA in ONIHL group was individually normalized to control.
To identify the differentially expressed microRNAs in the blood serum between controls and ONIHL subjects, microarray analysis was utilized.
MicroRNA microarray assay showed that among 2549 tested microRNAs, 2362 (92.7%) were not expressed in either groups, while 34 (1.3%) and 6 (0.2%) microRNAs were found to be exclusively expressed in controls and ONIHL subjects, respectively (Figure 1A).
There were seven differentially expressed microRNAs between control and ONIHL subjects, with a fold change >1.5 and P<0.05.
As fold changes of upregulated microRNAs were greatly higher than that of the downregulated ones, the levels of the differentially expressed miR-3162-5p, miR4484, and miR-1229-5p in the blood serum of ONIHL subjects and controls were verified using real time qPCR.
In this study, 10 controls and 10 ONIHL subjects were enrolled.
ONIHL is due to destruction of cochlear hair cells or damage to their mechano-sensory hair bundles caused by continuous noise exposure of >85dB(A) for 8 hours at the work place.
(2) Even though ONIHL is preventable, there is no evidence that this is realized in practice.
As ONIHL progresses, individuals may have difficulty understanding high-pitched voices (e.g., women's, children's) even in quiet conversational situations.
The presence of 4000Hz notch is a classical sign of ONIHL. The presence of 4000Hz notch may be attributed to many factors, the human hearing is more sensitive at 100-500 Hz due to the fact that the tympanic reflex attenuates loud noise below 2000Hz and also due to the resonance characteristics of the external ear to loud sound.
They are responsible for transducing higher frequencies and this accounts for the high frequency hearing loss found in ONIHL. (25, 26, 27)
(28) Various studies have shown that ONIHL affected higher frequencies and mainly concentrated at 4000Hz or 6000Hz.