Mouse microRNA expression study identifying the nature of age-related hearing loss

MicroRNAs （miRNAs）大约是22个核苷酸，双链，非编码rna。它们被证明调节目标rna的稳定性和翻译，并与许多疾病和衰老有关。本研究旨在探讨老年性听力损失小鼠耳蜗中miRNA表达的时间变化，阐明老年性听力损失的本质。采用C57BL/6小鼠作为老年性听力损失小鼠模型。采用听觉脑干反应（ABRs）和畸变产物耳声发射（dpoae）来评价听觉功能。8、16和32 kHz的ABR阈值在10月龄时迅速增加，到16月龄时达到无法检测的水平。DPOAE水平在12月龄时逐渐降至噪声水平。使用18只1月龄小鼠的36只耳朵、18只10月龄小鼠的36只耳朵和15只16月龄小鼠的30只耳朵进行mirna表达分析。在RNAlater溶液中从耳膜囊中剥离膜迷路。每个年龄组分别纯化总rna（包括小rna）。使用2100型安捷伦生物分析仪测定每种RNA制剂的质量和数量。miRCURY LNA microRNA Array （Exiqon）用于miRNA表达谱。miRNA表达的非分层聚类分析检测到42种可能与年龄相关性听力损失相关的miRNA。

MicroRNAs (miRNAs) are approximately 22 nucleotide, double-stranded, non-coding RNAs. They are shown to regulate the stability and translation of the target RNAs, and are associated with many disorders and aging. The aims of the present study are to investigate the time-course changes in miRNA expressions in the cochlea of age-related hearing loss mouse and to clarify the nature of age-related hearing loss.C57BL/6 mouse was used as a mouse model of age-related hearing loss.Auditory brainstem responses (ABRs) and distortion-product otoacoustic emissions (DPOAEs) were carried out to evaluate the auditory functions. ABR thresholds for tone-burst stimuli at 8, 16, and 32 kHz rapidly increased at 10 months of age, and reached undetectable levels by 16 months of age. DPOAE levels gradually decreased to the noise levels by 12 months of age. Thirty-six ears from 18 mice at the age of 1 month, 36 ears from 18 mice at the age of 10 months, and 30 ears from 15 mice at the age of 16 months were used for miRNAexpression analyses. Membranous labyrinths were dissected from otic capsules in RNAlater solution. Total RNAs including small RNAs were purified by each age group. The quality and quantity of each RNA preparation were determined using a Model 2100 Agilent BioAnalyser. miRCURY LNA microRNA Array (Exiqon) was used for miRNA expression profiles. Non-hierarchical cluster analysis of miRNA expressions detected 42 miRNAs that could be associated with age-related hearing loss.