Abstract 404: Endothelial Cell MicroRNA Expression in Response to Laminar Shear Stress
In this study, we sought to determine the effect of laminar shear stress on expression of microRNAs in human endothelial cells. Mechanical forces created by the cardiac cycle and blood flow are important modulators of cellular function in the cardiovascular system. One of these forces is laminar shear stress (LSS), and endothelial cells respond to LSS by modulating expression of genes involved in cell migration, remodeling, proliferation, and apoptosis. MicroRNAs (miRNAs) are a class of highly conserved, small, noncoding RNAs that regulate gene expression by binding to the 3′ untranslated region (3′UTR) of target mRNAs and either blocking their translation or enhancing their degradation. Recent work indicates that miRNAs may act as key regulators of processes as diverse as cell differentiation, growth, proliferation, and apoptosis. We used TaqMan Low Density Array (TLDA) cards ( n = 3) to assess the expression of 380 miRNAs in human umbilical vein endothelial cells exposed to LSS (15 dynes/cm2) for 6 hours. LSS led to the upregulation of fourteen miRNAs ( p < 0.05), and, among these miRNAs, three were upregulated greater than 2 fold. These included let-7c (2.5 fold, p < 0.002), miR-21 (2.5 fold, p < 0.04), and miR-27b (2.2 fold, p < 0.03). None of the miRNAs on the TLDA cards were significantly downregulated in response to LSS. Upregulation of let-7c, and miR-21 was validated by separate analysis (n = 3). A separate microarray analysis (Affymetrix) of all human genes (n = 2) in endothelial cells, identified multiple potential molecular targets for let-7c and miR-21 that are significantly downregulated by LSS. These targets were predicted by bioinformatics programs, and, for miR-21, include PTEN, FBXO11, PDLIM5, NF1, UBE2D3, ARHGAP, genes that have been implicated in cell growth, proliferation, migration, and apoptosis. In conclusion, our data indicate that mechanical forces can selectively upregulate endothelial cell expression of microRNAs; this information provides insight into how LSS modulates diverse cellular functions.