Circular RNAs (circRNAs) are endogenous RNA formed by the back splicing
process. They are ubiquitous, stable, evolutionally conserved, and are
tissue-specific. CircRNAs have numerous latent modes of action, from
acting as sponges for microRNAs and RNA binding proteins to serving as
transcriptional regulators, epigenetic alterations, etc. Dysregulated
functioning of several circular RNAs leads to the progression of a
plethora of diseases. CircRNAs have paved the way for advanced clinical
studies as a novel method of disease diagnosis. This review
systematically summarized and evaluated the role of differentially
expressed circRNAs in four human diseases, including neurodegenerative
diseases, diabetes, osteoarthritis, and cardiovascular diseases.