Discovery of mechanosensitive microrna and messenger RNA in mouse arterial endothelium and in cultured endothelial cells
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Atherosclerosis is a major contributor to cardiovascular disease and accounts for an estimated one third of deaths overall. In order to address the hemodynamic components of disease pathogenesis, researchers have focused on mechanotransduction of flow-dependent shear stress in the vascular endothelium as a source of novel pathological mechanisms. Understanding how unidirectional, laminar blood flow protects vessels from atherogenesis, while disturbed, oscillatory blood flow promotes it, stands to provide enormous insight into disease pathogenesis and may provide powerful, specific new therapies for cardiovascular disease intervention. The overall objective of this dissertation was to determine which microRNAs (miRNAs) and mRNAs are regulated by different flow conditions in vascular endothelial cells in vitro and in mouse carotid artery endothelium in vivo, and to identify which miRNAs mediate flow-dependent vascular inflammation. The overall hypothesis of this project was that oscillatory shear (OS) and laminar shear (LS) stress differentially alter the expression of mechanosensitive miRNAs each capable of regulating complex networks of gene expression, which in turn leads to inflammation in endothelial cells. This hypothesis was tested using both in vitro and in vivo approaches, high throughput microarray analyses, and functional validation of specific targets by PCR. The findings from the partial carotid ligation model show that acute exposure to disturbed flow results in accelerated endothelial dysfunction and atherosclerosis in vivo. High-throughput microarrays reveal distinct expression profiles of both miRNAs and mRNAs in mouse endothelium exposed to disturbed flow suggesting the regulatory mechanisms by which miRNAs regulate mRNAs resulting in EC inflammation, the earliest stage of atherosclerosis. This in vivo study provides new insight into the mechanisms of flow induced atherosclerosis. In particular, the upregulation of miR-663 due to OS in HUVEC causes monocyte adhesion, but not endothelial apoptosis, in an ICAM-1 dependent manner. miR-663 regulates a group of genes including transcriptional factors and inflammatory genes which may also mediate OS-induced EC inflammation. Collectively, revealing the profiles of miRNAs and mRNAs regulated by hemodynamic flow provides a better understanding in vascular diseases and provide potential target for developing effective preventative therapeutic approaches in cardiovascular diseases.