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Disturbed flow promotes arterial stiffening through thrombospondin-1 (TSP-1) signaling pathways

ABSTRACT: Arterial stiffness is a prevalent, independent cardiovascular risk factor, but the underlying mechanisms are not well understood. Wall shear stress and shear-sensitive genes may promote arterial stiffening through clinically important signaling pathways. Our goal was to identify how disturbed blood flow leads to arterial stiffness using the mouse partial carotid ligation model. Here we used our in vivo partial carotid ligation model to induce d-flow in the LCA while the contralateral RCA continues to experience stable laminar flow using the C57BL/6x129SvEv mice, TSP-1 knockout (KO), and C57Bl/6J mice. We compared these to aged (80 week) mice which had increased arterial stiffness due to aging. Changes in gene expression were identified using microarrays that were performed on the endothelial-enriched RNA isolated from the carotids exposed to stable flow (RCA) and compared to disturbed flow (LCA). Arterial stiffness was determined ex vivo by biaxial mechanical testing and in vivo by ultrasound techniques. Myointimal hyperplasia and immunohistochemistry were performed in sectioned carotid arteries. In vitro testing of signaling pathways utilized oscillatory and laminar wall shear stress. Human arteries were tested ex vivo to validate critical results found in the animal model.

ORGANISM(S): Mus musculus

PROVIDER: GSE87199 | GEO | 2017/09/01

SECONDARY ACCESSION(S): PRJNA343845

REPOSITORIES: GEO

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Project description:Atherosclerosis preferentially occurs in arterial regions of disturbed blood flow (d-flow), which alters gene expression, endothelial function, and atherosclerosis. Here, we show that d-flow regulates genome-wide DNA methylation patterns in a DNA methyltransferase (DNMT)-dependent manner. D-flow induced expression of DNMT1 in mouse arterial endothelium in vivo and in cultured endothelial cells by oscillatory shear (OS) in vitro. The DNMT inhibitor 5-Aza-2’deoxycytidine (5Aza) or DNMT1 siRNA significantly reduced OS-induced endothelial inflammation. Moreover, 5Aza reduced lesion formation in two ApoE-/- mouse atherosclerosis models. To identify the 5Aza mechanisms, we conducted two genome-wide studies: reduced representation bisulfite sequencing (RRBS) and microarray using endothelial-enriched gDNA and RNA, respectively, from the partially-ligated left carotid artery (LCA exposed to d-flow) and the right contralateral control (RCA) of mice treated with 5Aza or vehicle. Systems biological analyses using RRBS and transcriptome data revealed 11 mechanosensitive genes whose promoters were hypermethylated under d-flow conditions, but rescued by 5Aza treatment. Of those, the two transcription factors HoxA5 and Klf3 contain cAMP- response-elements, and their methylation status could serve as a mechanosensitive master switch in gene expression. Our results demonstrate that d-flow controls epigenomic DNA methylation patterns in a DNMT-dependent manner, which in turn alters endothelial gene expression and induces atherosclerosis. We used 6- to 8-week-old male C57Bl/6 mice (The Jackson Laboratory) according to the approved Institutional Animal Care and Use Committee protocol by Emory University. Mice were subjected to partial carotid ligation surgery under anesthesia. Brieﬂy, 3 of 4 caudal branches of LCA (left external carotid, internal carotid, and occipital artery) were ligated with 6-0 silk suture, although the superior thyroid artery was left intact. Development of low and oscillatory blood flow in the Left Carotid Artery of each mouse was determined by ultrasound measurements. Each sample contained total RNA from 3 pooled RCAs or LCAs. We ran 3 samples of LCA, RCA, AzaLCA, and AzaRCA on 2 microarrays.

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Disturbed flow promotes arterial stiffening through thrombospondin-1 (TSP-1) signaling pathways

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