Circular RNAs: Promising Molecular Biomarkers of Human Aging-Related Diseases via Functioning as an miRNA Sponge

ABSTRACT Circular RNAs (circRNAs) are a new class of non-coding single-stranded RNAs which differ from linear microRNAs (miRNAs), since they form covalently closed loop structures without free 3’ poly A tails or 5’ caps. CircRNAs are the competitive endogenous RNAs (ceRNAs) by binding to miRNA through miRNA response elements (MREs) (i.e “miRNA sponge”), thereby reducing the quantity of miRNA available to target mRNA, subsequently promoting mRNA stability or protein expression which involves in the initiation and progress of human diseases. Owing to these features of abundance, stability, conservative property, tissue- and stage-specificity, widely distributing in the extracellular space and in various bodily fluids, circNRAs can be considered as potential biomarkers for various diseases. Here, we reviewed the promising circRNAs being as disease biomarkers, focused on their regulatory function by acting as miRNAs sponges, and described their roles in cancer, cardiovascular or neurodegenerative diseases, osteoarthritis, rheumatoid arthritis, diabetes and other human ageing-related diseases, which provide a new direction for pathogenesis, diagnosis and treatment of human ageing-related diseases.