Mechanosensitive Smad5 Enhances MiR‐487a Processing to Regulate Vascular Endothelial Cell Proliferation in Response to Disturbed Flow

Abstract

MicroRNAs (miRs) and bone morphogenetic protein receptor‐specific Smads are mechano‐responsive molecules that play vital roles in modulating endothelial cell (EC) functions in the face of blood flow. However, the roles of interplay between these molecules in modulating EC functions under different flows remain unclear. We elucidated the roles of interplay between miRs and Smad5 in modulating EC proliferation in response to different flows. Microarray and quantitative RT‐PCR showed that disturbed flow with oscillatory shear stress (OS, 0.5±4 dynes/cm2) up‐regulates EC miR‐487a in comparison to static controls and pulsatile shear stress (12±4 dynes/cm2). MiR‐487a was up‐regulated in ECs in the inner curvature (OS region) of rat aortic arch and diseased human coronary arteries. MiR‐487a expression was promoted by nuclear phospho‐Smad5, which bound to primary‐miR‐487a to facilitate miR‐487a processing. Algorithm prediction, luciferase reporter, and argonaute 2‐immunoprecipitation assays showed that miR‐487a binds to 3’UTR of CREB binding protein (CBP) and p53. Knockdown or overexpression of miR‐487a decreased and increased, respectively, phospho‐Rb and cyclin A expressions through CBP and p53. BrdU incorporation assay showed that miR‐487a enhances EC proliferation under OSS in vitro and in disturbed flow regions of experimentally‐stenosed rat abdominal aorta in vivo. In summary, disturbed flow with OSS induces EC expression of miR‐487a through its enhanced processing by activated‐Smad5. MiR‐487 inhibits its direct targets CBP and p53 to induce EC cycle progression and proliferation. Our findings suggest that EC miR‐487 is an important molecular target for intervention against disturbed flow‐associated vascular diseases resulting from atherosclerosis.