Abstract 19616: Down-Regulation of miR-23/27/24 Clusters by TGF-β1 Signalling Induces Phenotypic Switching of Vascular Smooth Muscle Cells in vitro and in Response to Vascular Injury in vivo
Background: The differentiated state of SMCs plays a key role in the pathogenesis of several major human diseases, including atherosclerosis and restenosis after vascular injury. Several miRNAs have recently been implicated in vascular smooth muscle cells differentiation and/or phenotypic switching. Members of the miR-23/27/24 clusters are highly expressed in smooth muscle cells and are involved in cell cycle control, proliferation and differentiation of various cell types. However, the role of miR-23/27/24 clusters in vascular disease is currently unknown. Thus, the aim of the present study was to evaluate the role of miR-23/27/24 cluster on SMC differentiation and proliferation in vitro and after vascular injury in vivo.
Methods and Results: To determine the expression changes of miRNAs in vascular wall with neointimal formation in vivo, we used the standard rat carotid artery balloon injury model. Using real-time PCR, we demonstrated for the first time that expression of miR-24 and miRNAs that are clustered with it (members of the miR-23 and miR-27 families) are consistently downregulated 3 and 7 days after vascular injury. Furthermore, in vitro studies showed that TGF-β1 down-regulated miR-23/27/24 clusters expression in a dose- and time-dependent manner. By using both gain-of-function and loss-of-function approaches, we found that members of the miR-23/27/24 clusters promote multiple aspects of vascular smooth muscle cell contractile phenotype and alter TGF-β1 pathway signalling. Inhibition of miR-23a/b increased gene expression of SMAD-2 and SMAD-3, while ectopic expression of miR-24 reduces the mRNA and protein levels of different genes that regulate cell-cycle progression. Also, using BrdU incorporation and cell migration assay, we demonstrate that miR-24 inhibits vascular smooth muscle cell proliferation and migration. Furthermore, systemic delivery of miR-24 mimics markedly decreased neointimal hyperplasia after balloon injury.
Conclusions: We demonstrated that miR-23/27/24 clusters control TGF-β1 pathway signalling in vascular smooth muscle cell in vitro and in vivo. These findings suggest that members of the miR-23/27/24 clusters may have the potential to suppress neointimal hyperplasia after arterial injury.
- © 2012 by American Heart Association, Inc.