The knockout of miR-143 and -145 alters smooth muscle cell maintenance and vascular homeostasis in mice: correlates with human disease

Mechanisms controlling vascular smooth muscle cell (VSMC) plasticity and renewal still remain to be completely elucidated. A class of small RNAs called microRNAs (miRs) regulate gene expression at the post-transcriptional level. Here we demonstrate a critical role of the miR-143/145 cluster in SMC differentiation and vascular pathogenesis, also through the generation of a mouse model of miR-143 and -145 knockout. We determined that the expression of miR-143 and -145 is decreased in acute and chronic vascular stress (transverse aortic constriction and in aortas of the ApoE knockout mouse). In human aortic aneurysms, the expression of miR-143 and -145 was significantly decreased compared to control aortas. In addition, overexpression of miR-143 and -145 decreased neointimal formation in a rat model of acute vascular injury. An in-depth analysis of the miR-143/145 knockout mouse model demonstrated that this miR cluster is expressed mostly in the SMC compartment, both during development and post-natally, in vessels and SMC-containing organs. Loss of miR-143 and miR-145 expression induces structural modifications of the aorta, due to an incomplete differentiation of VSMCs. In conclusion, our results demonstrate that the miR-143/145 gene cluster plays a critical role during SMC differentiation and strongly suggest its involvement in the reversion of the VSMC differentiation phenotype that occurs during vascular disease.