Discrepant expression of microRNAs in transparent and cataractous human lenses

Age-related cataracts are considered to be a pathological condition that arise as senescence progresses. However, little is known about the function of microRNAs (miRNAs) in the formation of age-related cataracts. The purpose of this study was to identify possible differences in miRNA expression in the central epithelium of transparent and age-related cataractous human lenses. Microarrays were used to determine the miRNA expression profiles of both transparent and cataractous lenses. The results were analyzed by significance analyses performed by the microarray software, and the results were confirmed by stem-loop RT-PCR. Algorithms were used to predict the target genes of the differentially expressed miRNAs. Two hundred and six miRNAs were identified in all human lenses. The top eight miRNAs according to expression levels were miR-184, let-7b, miR-923, miR-1826, miR-125b, miR-1308, miR-26a, and miR-638 in transparent lenses. In contrast, the top eight miRNAs in cataractous lenses were miR-184, miR-1826, let-7b/c, miR-24, miR-23b, miR-923, and miR-23a. The expression levels of 20 miRNAs were increased and the levels of 12 miRNAs were decreased by more than 2-fold in transparent lenses relative to the levels in cataractous lenses. These findings were confirmed by stem-loop RT-PCR. In addition, several genes that were predicted to be targets of the identified miRNAs have been reported to be involved in lens development or cataract formation. The authors report, for the first time, the distinct expression profiles of miRNAs in the central epithelium of transparent and age-related cataractous human lenses. Significant differences in miRNA expression were identified, and the genes targeted by the relevant miRNAs were predicted. The differential expression of miRNAs suggests that these miRNAs have potential roles in lens development and/or cataract formation.