Abstract 19038: KLF2-regulated microRNAs in the Interplay Between Endothelial and Smooth Muscle Cells
Introduction: Recently, the shear-responsive transcription factor Krüppel-like factor 2 (KLF2) has emerged as the central mediator of flow-induced atheroprotection and its overexpression in HUVECs establishes functional quiescent differentiation of the endothelium. Since microRNAs, small non-coding RNAs that exhibit diverse spatial expression patterns and regulate gene expression, were shown to play key roles in many pathogenic and physiological processes, we investigated the regulation of microRNAs by KLF2 and prolonged shear stress in endothelial cells.
Results: KLF2 regulates the expression of several microRNAs, as assessed by real-time PCR after lentiviral overexpression of KLF2 in HUVECs. The most down-regulated microRNA, miR-146a (16-fold down, p<0.05), is known to be inflammation associated and is a transcriptional target of NFκB, which is in accordance with the known inhibitory effect of KLF2 on NFκB function. Amongst the most up-regulated microRNAs was the miR−143/−145 cluster (10-fold up, p<0.01) which plays a critical role in modulating vascular smooth muscle cell (SMC) phenotype by promoting differentiation and repressing proliferation of SMCs. This microRNA cluster was also found to be significantly upregulated in HUVECs by statins (2-fold up, p<0.05), which are known pharmacological inducers of KLF2, as well as by prolonged shear stress (143: 5.5-fold up, p<0.01, 145: 7.1-fold up, p<0.01) in a KLF2-dependent manner. Bioinformatics revealed a conserved binding site for KLF2 upstream of the miR−143/−145 cluster, which we confirmed to be occupied by KLF2 using ChIP-PCR. Since miR−143/−145 play an important role in SMCs, we investigated the possibility of transport of these miRNAs between endothelial cells and SMCs. Intriguingly, we found that microvesicles secreted by KLF2-transduced HUVECs were highly enriched in miR−143/−145 and that miRNAs are transported to SMCs, as determined by co-culture experiments.
Conclusions: KLF2 overexpression and prolonged shear stress exposure in HUVECs regulate a distinct set of microRNAs that are partly secreted in microvesicles enabling cell to cell trafficking of microRNAs between endothelial cells and SMCs, providing a mechanism for the known effects of endothelial KLF2 on SMC function.
- © 2010 by American Heart Association, Inc.