Shear stress induces endothelial-to-mesenchumal transition via the transcription factor Snail

Blood flow influences atherosclerosis by generating wall shear stress, which alters endothelial cell (EC) physiology. Low shear stress induces dedifferentiation of EC through a process termed endothelial-to-mesenchymal transition (EndoMT). The mechanism underlying shear stress-regulation of EndoMT is uncertain. Here we investigated the role of the transcription factor Snail in low shear stress-induced EndoMT. Studies of cultured EC exposed to flow revealed that low shear stress induced Snail expression. Using gene silencing it was demonstrated that Snail positively regulated the expression of EndoMT markers (Slug, N-cadherin, aSMA) in EC exposed to low shear stress. Gene silencing also revealed that Snail enhanced the permeability of endothelial monolayers to macromolecules by promoting EC proliferation and migration. En face staining of the murine aorta or carotid arteries modified with flow-altering cuffs demonstrated that Snail was expressed preferentially at low shear stress sites that are predisposed to atherosclerosis. Snail was also expressed in EC overlying atherosclerotic plaques in coronary arteries from patients with ischemic heart disease implying a role in human arterial disease. We conclude that Snail is an essential driver of EndoMT under low shear stress conditions and may promote early atherogenesis by enhancing vascular permeability.