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Title: Low shear stress promotes atherosclerosis through activation of EndMT
Author: Mahmoud, Marwa
ISNI:       0000 0004 5370 049X
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2015
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Introduction: Atherosclerosis is influenced by local blood flow patterns that exert wall shear stress (WSS) on endothelial cells (EC). Low, oscillatory WSS promotes atherosclerosis by influencing EC dysfunction (inflammation, permeability and proliferation), while high WSS is athero-protective. A recent microarray study by our laboratory of EC at athero-prone or athero-protective WSS regions of the porcine aorta revealed differential expression of GATA4 and TWIST1. These transcriptional activators can promote endothelial-mesenchymal transition (EndMT). We hypothesised that GATA4 and TWIST1 may control EC dysfunction and atherogenesis at sites of low WSS by inducing EndMT. Methods & Results: Quantitative RT-PCR and en face staining confirmed enhanced GATA4, Twist1 and EndMT marker gene (Snail, Slug and N cadherin) expression at the inner curvature (lower-WSS) compared to the outer curvature (higher-WSS) of porcine and murine aortae. To establish a causal link, WSS was modified in murine carotid arteries using a constrictive cuff, this elevated TWIST1, GATA4 and SNAIL expression at the low WSS site. EC-specific deletion of Twist1 reduced SNAIL and Ncadherin expression and proliferation at the inner curvature of the murine aorta. Consistent with this, TWIST1 expression and EC proliferation at the inner curvature of the murine aorta was reduced by EC deletion of GATA4. Similarly, Gata4, Twist1 and EndMT effector genes were induced in PAEC or HUVEC exposed to low, oscillatory WSS using in vitro flow systems. Gene silencing demonstrated that GATA4 and TWIST1 are required for SNAIL induction in EC exposed to low, oscillatory WSS, and chromatin immunoprecipitation revealed GATA4 interaction with Twist1 and Snail. Low, oscillatory WSS promoted EndMT-characteristic changes including Ncadherin induction, VE-cadherin disorganization and enhanced proliferation and migration. Silencing of GATA4, Twist1 and Snail significantly reduced these processes alongside EC permeability. These results reveal that low WSS changes EC function via GATA4-TWIST1 activation. Conclusion: Low WSS induces EndMT and subsequent EC proliferation and permeability through GATA4 and TWIST1. Our observations illuminate for the first time, the role of EndMT in arterial biomechanics and dysfunction. Future studies should define the role of EndMT in focal atherosclerosis.
Supervisor: Evans, Paul C. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available