Circular RNAs: regulators of vascular smooth muscle cells in cardiovascular diseases.

The aberrant expansion and dysfunction of vascular smooth muscle cells (VSMCs) contribute to the occurrence and development of many cardiovascular diseases. Circular RNAs, a new class of non-coding RNAs with the 3' and 5' ends covalently linked together due to back-splicing, have recently been revealed to function as new regulators of VSMCs. These circular RNAs mainly act as RNA sponge to downregulate other regulatory non-coding RNAs such as microRNAs, influencing the overgrowth and transformation of VSMCs under pathogenic conditions. The purpose of this review is to summarize how circular RNAs fluctuate their own expression in response to multiple stimuli in vitro and in vivo and how they modulate the phenotypic adaptation, proliferation, migration, apoptosis, and senescence of VSMCs, which in turn affects the progression of cardiovascular diseases. Finally, we highlight the potential of circular RNAs as the biomarkers and therapeutic targets for abnormal VSMCs and cardiovascular diseases.