Background/Objective Vascular smooth muscle cell (VSMC) proliferation and migration play a pronounced role in the pathophysiology of atherosclerosis and neointima formation. microRNAs are short, single stranded, non-coding 22 nucleotide RNAs involved in post transcriptional gene silencing. Increasing evidence has suggested an important role of miRNAs in regulating VSMC functions. However, little is known about the functional involvements of miR-214 in VSMC proliferation/migration and vessel injury-induced neointima formation. In the current study, we aimed to study the functional importance of miR-214 and its target genes in VSMC proliferation, migration and neointima SMC hyperplasia.

Methods and Results miR-214 expression was closely associated with VSMC phenotypic modulation in response to different pathological stimuli. miR-214 over-expression in serum-starved VSMCs significantly decreased VSMC proliferation and migration, while knockdown of miR-214 dramatically increased VSMC proliferation and migration, respectively. Proteomic analyses pinpointed that NCK-associated protein 1 (NCKAP1), a major component of the WAVE complex that regulates lamellipodia formation and cell motility, was negatively regulated by miR-214 in VSMCs. NCKAP1 has also been predicted as one of the top targets of miR-214 by using several computational miRNA target prediction tools, and was indeed negatively regulated by miR-214 in VSMCs. Luciferase assay showed miR-214 substantially repressed wild type, but not the miR-214 binding site mutated version of NCKAP1–3’-UTR-luciferase activity in VSMCs, confirming the NCKAP1 is the functional target of miR-214 in VSMCs. Data from co-transfection experiments also revealed that inhibition of NCKAP1 is required for miR-214-mediated lamellipodia formation and cell motility. Importantly, locally enforced expression of miR-214 in the injured vessels significantly reduced NCKAP1 expression levels, inhibited VSMC proliferation, and prevented neointima SMC hyperplasia after injury.

Conclusions/implications We have uncovered an important role of miR-214 in modulating VSMC functions and neointima  hyperplasia. Our findings have suggested that miR-214 represents a potential therapeutic target for vascular diseases.