MicroRNA expression in the aging mouse thymus

MicroRNAs (miRNAs) have been implicated in the process of aging in many model organisms, such as Caenorhabditis elegans, and in many organs, such as the mouse lung and human epididymis. However, the role of miRNAs in the thymus tissues of the aging mouse remains unclear. To address this question, we investigated the miRNA expression profiles in the thymuses of 1-, 10- and 19-month-old mice using miRNA array and qRT-PCR assays. A total of 223 mouse miRNAs were screened, and the expression levels of those miRNAs exhibited gradual increases and decreases over the course of thymus aging. Fifty miRNAs in the 10-month-old thymus and 81 miRNAs in the 19-month-old thymus were defined as differentially expressed miRNAs (p < 0.05) in comparison with their levels in the 1-month-old mouse, and approximately one-third of these miRNAs were grouped within 11 miRNA clusters. Each miRNA cluster contained 2 to 5 miRNA genes, and most of the cluster members displayed similar expression patterns, being either increased or decreased. In addition, Ingenuity Pathway Analysis (IPA) software and the IPA database were used to analyze the 12 miRNAs that exhibited significant expression changes, revealing that as many as 15 pathways may be involved. Thus, our current study determined the expression profiles of miRNAs in the mouse thymus during the process of aging. The results suggested that these miRNAs could become meaningful biomarkers for studying thymus aging and that the aging-related alternations in miRNA expression may be involved in the regulation of cell proliferation, apoptosis, development and carcinogenesis/tumorigenesis.