Genome-wide analysis of mechanosensitive genes using in vivo model of mouse carotid artery endothelium exposed to disturbed flow
ABSTRACT: Recently, we have shown that disturbed flow caused by partial ligation of mouse carotid artery rapidly induces endothelial dysfunction and atherosclerosis within two weeks. To understand the molecular mechanisms by which disturbed flow induces atherosclerosis, we carried out genome-wide microarray study using endothelial RNAs isolated from the flow-disturbed left and the contralateral right common carotid artery (LCA and RCA) in C57BL/6 mice. Overall design: Total intimal RNAs were obtained from LCA and RCA at 12hr and at 48hr post-ligation. Intimal RNAs from three LCAs or RCAs were pooled to obtain ~30ng total RNA.
Project description:Recently, we have shown that disturbed flow caused by partial ligation of mouse carotid artery rapidly induces endothelial dysfunction and atherosclerosis within two weeks. To understand the molecular mechanisms by which disturbed flow induces atherosclerosis, we carried out genome-wide microarray study using endothelial RNAs isolated from the flow-disturbed left and the contralateral right common carotid artery (LCA and RCA) in C57BL/6 mice. Total intimal RNAs were obtained from LCA and RCA at 12hr and at 48hr post-ligation. Intimal RNAs from three LCAs or RCAs were pooled to obtain ~30ng total RNA.
Project description:Recently, we showed that disturbed ﬂow caused by a partial ligation ofmouse carotid artery rapidly induces atherosclerosis. Analysis of mechanosenstive microRNA in the mouse carotid endothelium. In this study, we examined the microRNAs that respond differentially to blood flow pattern in the mouse carotid endothelium. We surgically induced disturbed blood flow in the left common carotid cartery (LCA) using partial carotid ligation surgery while the right carotid artery was left undisturbed. The hypothesis tested here is that turbulent or disturbed blood flow across the left carotid artery endothelium will affect endothelial genes and microRNAS. Identifying flow-sensitive microRNAs will provide important information about how endothelium responds to d-flow and regulates endothelial function and progression of atherosclerosis. Deter- mining the functional importance of these novel mechanosensitive microRNAS may provide important insights into understanding vascular biology and 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.
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.
Project description: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. Overall design: Endothelial-enriched RNA was isolated from WT carotids exposed to stable flow or disturbed flow. Three replicates each.
Project description:Atherosclerosis is causally related to disturbed flow through low and oscillatory shear stress. In order to study the miR expression profile in atherosclerotic plaques induced by disturbed flow, partial ligation of the carotid artery was performed. This procedure results acutely in severly reduced blood flow and in stenotic lesion formation within 6 weeks in apoe-/- mice on a high fat diet. We compared the miR expression profile in partially ligated left carotid arteries with the untreated right carotid artery to identify miRs which are involved in plaque formation through flow disturbances. The left carotid arteries of 6 female apoe-/- mice (6-8 weeks) were partially ligated (i.e. the external and internal carotid artery as well as the occipital artery were occluded; blood flow out of the common carotid artery occurs mainly through the superior thyroid artery). Following partial ligation the animals were fed a high fat diet for 6 weeks. Total RNA was isolated from partially ligated left carotid arteries and untreated right carotid arteries (control). MiRs expression profile of the partially ligated carotid arteries were compared with the control group. Biological replicates: 6 per group. One replicate per array.
Project description:Surgical interventions on blood vessels bear a risk for intimal hyperplasia and atherosclerosis as a consequence of injury. A specific feature of intimal hyperplasia is the loss of vascular smooth muscle cell (VSMC) differentiation gene expression. We hypothesized that immediate responses following injury induce vascular remodeling. To differentiate injury due to trauma, reperfusion and pressure changes we analyzed vascular responses to carotid artery bypass grafting in mice compared to transient ligation. As a control, the carotid artery was surgically laid open only. In both, bypass or ligation models, the inflammatory responses were transient, peaking after 6h, whereas the loss of VSMC differentiation gene expression persisted. Extended time kinetics showed that transient carotid artery ligation was sufficient to induce a persistent VSMC phenotype change throughout 28 days. Transient arterial ligation in ApoE knockout mice resulted in atherosclerosis in the transiently ligated vascular segment but not on the not-ligated contralateral side. The VSMC phenotype change could not be prevented by anti-TNF antibodies, Sorafenib, Cytosporone B or N-acetylcysteine treatment. Surgical interventions involving hypoxia/reperfusion are sufficient to induce VSMC phenotype changes and vascular remodeling. In situations of a perturbed lipid metabolism this bears the risk to precipitate atherosclerosis. Overall design: Comparison of mRNA changes between control tissue and bypass grafts perfused for 1, 6 and 24h. Number of replicated per group =4-5
Project description:Low and disturbed blood flow drives the progression of arterial diseases including atherosclerosis and aneurysms. The endothelial response to flow and its interactions with recruited platelets and leukocytes determine disease progression. Here, we report widespread changes in alternative splicing of pre-mRNA in the flow-activated murine arterial endothelium in vivo. Alternative splicing was suppressed by depletion of platelets and macrophages recruited to the arterial endothelium under low and disturbed flow. Binding motifs for the Rbfox-family are enriched adjacent to many of the regulated exons. Endothelial deletion of Rbfox2, the only family member expressed in arterial endothelium, suppresses a subset of the changes in transcription and RNA splicing induced by low flow. Our data reveal an alternative splicing program activated by Rbfox2 in the endothelium on recruitment of platelets and macrophages and demonstrate its relevance in transcriptional responses during flow-driven vascular inflammation. Overall design: Samples include arterial intima from carotid artery in vivo, and isolated aortic endothelial cells under various flow conditions, and with or without depletion of specific splice factors or recruited innate immune cells.
Project description:Affymetrix Mouse Gene 2.0 ST Gene Expression Microarrays were used to analyze differentially expressed genes after carotid artery ligation. The aim of this experiment was to detect genes regulated in Has3 deficient as compared to wildtype controls that might be involved in neointimal hyperplasia. Neointimal hyperplasia was induced in female Has3 deficient mice and wildtype controls by ligation of the left common carotid artery. Carotid transcriptome was analyzed 5 days after surgery in ligated and non-ligated carotid arteries.
Project description:High-flow causes the remodeling of arteries, in which smooth muscle cells play an important role. To know the profile of smooth muscle gene expression under high-flow conditions in vivo, flow of rabbit basilar artery was increased by ligation of both common carotid arteries. Microarrays were performed to profile the gene expression of smooth muscle cells isolated from rabbit basilar artery. Expression profiles indicate 43603 differentially expressed genes in smooth muscle cells exposed to high-flow insult compared with the sham control, of which 1470 genes were upregulated and 780 genes downregulated using 2 fold-changes and P<0.05 as a cut-off. Bilateral common carotid arteries of female New Zealand White rabbits were ligated to increase vascular flow.The control group was performed the same procedure to expose the CCAs without ligation. Rabbits were euthanized at day 5 after ligation or exposure of bilateral CCAs in both groups (n=3 for each group). The rabbits used and all procedures in this study were approved by the local Institutional Animal Care and Use Committee. Smooth muscle cells were isolated. After euthanization of rabbits, the whole basilar arteries were removed. The arteries were cleaned in PBS buffer,cannulated and perfused at a constant flow with a cocktail which contains PBS and 0.4 mg/ml elastase (Sigma) and 1 mg/ml collagenase (type 1A, Sigma). After an incubation time of 45 min, the tissue left was removed and stored in PBS. SMCs were released from the artery by trituration. Then Total RNA was extracted and gene chip tests were performed.
Project description:We used microarrays to profile monocytes to identify gene expression differences correlating with disease status in carotid artery atherosclerosis. We identified 1302 genes differentially expressed between control and affected subjects after correcting for clinical covariates. Differential expression was likely caused by unidentified risk factors or systematic manifestations of atherosclerosis itself. Overall design: Monocytes were extracted from subjects with and without carotid atherosclerosis. Microarray hybridization was used to determine if expression patterns distinguish the subjects.