Circular RNA circ_0021001 regulates miR-148b-3p/GREM1 axis to modulate proliferation and apoptosis of vascular smooth muscle cells.

Intracranial aneurysm (IA) is an abnormal expression in the intracranial arteries, which is related to the growth and apoptosis of vascular smooth muscle cells (VSMCs). Circular RNA (circRNA) circ_0021001 (also named circARFIP2) has been identified to mediate the regulation of VSMCs proliferation. However, the molecular mechanism of circ_0021001 involved in VSMC dysfunction in IA is poorly defined. The expression levels of circ_0021001, microRNA-148b-3p (miR-148b-3p), and Gremlin 1 (GREM1) were detected by real-time quantitative polymerase chain reaction (RT-qPCR). Cell viability, proliferation, cell cycle progression, and apoptosis were detected by Cell Counting Kit-8 (CCK-8), 5-ethynyl-2'-deoxyuridine (EdU), and flow cytometry assays. Protein levels of proliferating cell nuclear antigen (PCNA), p21, B-cell lymphoma-2 (Bcl-2), Bcl-2 related X protein (Bax), and GREM1 were examined by western blot assay. The binding relationship between miR-148b-3p and circ_0021001 or GREM1 was predicted by StarBase and then verified using a dual-luciferase reporter assay. The expression levels of circ_0021001 and GREM1 were increased, and that of miR-148b-3p was decreased in IA tissues and HUASMCs. Moreover, the downregulation of circ_0021001 could repress proliferation ability and induce apoptosis of HUASMCs. The mechanical analysis uncovered that circ_0021001 served as a sponge of miR-148b-3p to regulate GREM1 expression. Circ_0021001 silencing could suppress cell growth and induce apoptosis of HUASMCs partially through modulating the miR-148b-3p/GREM1, presented circ_0021001 as a promising therapeutic target for IA.