The emerging roles of exosomal circRNAs in diseases

Exosomes, the nanoscale phospholipid bilayer vesicles, enriched in selected proteins, nucleic acids and lipids, which they participated in a variety of biological processes in the body, including physiology and pathology. CircRNAs (circular RNAs) are a class of single-stranded closed molecules with tissue development specific expression patterns that have crucial regulatory functions in various diseases. Non-coding RNAs (such as microRNAs and long non-coding RNAs) in exosomes have also been shown to play an important regulatory role in humans. However, little research has focused on exosomal circRNAs. Recently, CircRNAs have been identified to be enriched and stably expressed in exosomes. In this review, we summarize the biogenesis and biological functions of exosomes and circRNA, and further revealed the potential role of exosome-derived circRNA in different diseases. Besides, we propose its use as a diagnostic marker and therapeutic punctuation for diseases, especially in cancer.