Abstract 162: MicroRNAs Mediate the Hemodynamic Regulation of Endothelium-to-Smooth Muscle Signaling

Abstract

Vascular endothelial cells (ECs) at arterial branches and curvatures experience disturbed blood flow and induce a quiescent-to-activated phenotypic transition of the adjacent smooth muscle cells (SMCs) and a subsequent smooth muscle hyperplasia. However, the mechanism underlying the flow pattern-specific initiation of EC-to-SMC signaling remains elusive. Our previous study has demonstrated that endothelial microRNA-126-3p (miR-126-3p) acts as a key intercellular molecule to increase turnover of the recipient SMCs, and that its release is reduced by atheroprotective laminar shear (LS) to ECs. In the current study we found that atherogenic oscillatory shear (OS), but not atheroprotective pulsatile shear (PS), promotes the regulated exocytosis, particularly the secretion of non-membrane-bound miR-126-3p and other microRNAs (miRNAs) via the activation of soluble N-ethyl-maleimide-sensitive fusion protein attachment protein receptors (SNAREs), VAMP3 and SNAP23. Quantitative PCR arrays identify 15 EC-secreted miRNAs whose levels in the vesicle-poor supernatant of flow perfusate are differentially regulated (P<0.05) by OS versus PS. The fold changes of 11 miRNAs are either greater than 2.0 or less than 0.5. Knockdown of VAMP3 and SNAP23 reduces the secretion of miR-126-3p and miR-200a-3p, as well as the proliferation, migration, and suppression of contractile markers in SMCs caused by EC-coculture. Pharmacological intervention of mTORC1 in ECs blocks endothelial secretion and EC-to-SMC transfer of miR-126-3p through transcriptional inhibition of VAMP3 and SNAP23. Systemic inhibition of VAMP3 and SNAP23 by rapamycin or periadventitial application of the endocytosis inhibitor dynasore ameliorates the disturbed flow-induced neointimal formation, whereas intraluminal overexpression of SNAP23 aggravates it. Our findings demonstrate the flow-pattern-specificity of SNAREs activation and its contribution to the miRNA-mediated EC-SMC communication, uncovering potential targets for future diagnosis and therapeutic interventions for proliferative vascular diseases.