Dataset Information

Biomechanical Regulation of Endothelium-dependent Events Critical for Adaptive Remodeling.

ABSTRACT: Alterations in hemodynamic shear stress acting on the vascular endothelium are critical for adaptive arterial remodeling. The molecular mechanisms regulating this process, however, remain largely uncharacterized. Here, we sought to define the responses evoked in endothelial cells exposed to shear stress waveforms characteristic of coronary collateral vessels and the subsequent paracrine effects on smooth muscle cells. A lumped parameter model of the human coronary collateral circulation was used to simulate normal and adaptive remodeling coronary collateral shear stress waveforms. These waveforms were then applied to cultured human endothelial cells (EC), and the resulting differences in EC gene expression were assessed by genome-wide transcriptional profiling to identify genes distinctly regulated by collateral flow. Analysis of these transcriptional programs identified several genes to be differentially regulated by collateral flow, including genes important for endothelium-smooth muscle interactions. In particular, the transcription factor KLF2 was up-regulated by the adaptive remodeling coronary collateral waveform, and several of its downstream targets displayed the expected modulation, including the down-regulation of connective tissue growth factor. To assess the effect of endothelial KLF2 expression on smooth muscle cell migration, a three-dimensional microfluidic assay was developed. Using this three-dimensional system, we showed that KLF2-expressing EC co-cultured with SMC significantly reduce SMC migration compared with control EC and that this reduction can be rescued by the addition of exogenous connective tissue growth factor. Collectively, these results demonstrate that collateral flow evokes distinct EC gene expression profiles and functional phenotypes that subsequently influence vascular events important for adaptive remodeling.

SUBMITTER: Mack PJ

PROVIDER: S-EPMC2659199 | biostudies-literature | 2009 Mar

REPOSITORIES: biostudies-literature

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Biomechanical Regulation of Endothelium-dependent Events Critical for Adaptive Remodeling.

Mack Peter J PJ Zhang Yuzhi Y Chung Seok S Vickerman Vernella V Kamm Roger D RD García-Cardeña Guillermo G

The Journal of biological chemistry 20081201 13

Alterations in hemodynamic shear stress acting on the vascular endothelium are critical for adaptive arterial remodeling. The molecular mechanisms regulating this process, however, remain largely uncharacterized. Here, we sought to define the responses evoked in endothelial cells exposed to shear stress waveforms characteristic of coronary collateral vessels and the subsequent paracrine effects on smooth muscle cells. A lumped parameter model of the human coronary collateral circulation was used ...[more]

PMID: 19047056

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Project description:Key pointsIncreased pressure suppresses endothelial control of vascular tone but it remains uncertain (1) how pressure is sensed by the endothelium and (2) how the vascular response is inhibited. This study used a novel imaging method to study large numbers of endothelial cells in arteries that were in a physiological configuration and held at normal blood pressures. Increased pressure suppressed endothelial IP3 -mediated Ca(2+) signals. Pressure modulated endothelial cell shape. The changes in cell shape may alter endothelial Ca(2+) signals by modulating the diffusive environment for Ca(2+) near IP3 receptors. Endothelial pressure-dependent mechanosensing may occur without a requirement for a conventional molecular mechanoreceptor.AbstractThe endothelium is an interconnected network upon which haemodynamic mechanical forces act to control vascular tone and remodelling in disease. Ca(2+) signalling is central to the endothelium's mechanotransduction and networked activity. However, challenges in imaging Ca(2+) in large numbers of endothelial cells under conditions that preserve the intact physical configuration of pressurized arteries have limited progress in understanding how pressure-dependent mechanical forces alter networked Ca(2+) signalling. We developed a miniature wide-field, gradient-index (GRIN) optical probe designed to fit inside an intact pressurized artery that permitted Ca(2+) signals to be imaged with subcellular resolution in a large number (∼200) of naturally connected endothelial cells at various pressures. Chemical (acetylcholine) activation triggered spatiotemporally complex, propagating inositol trisphosphate (IP3 )-mediated Ca(2+) waves that originated in clusters of cells and progressed from there across the endothelium. Mechanical stimulation of the artery, by increased intraluminal pressure, flattened the endothelial cells and suppressed IP3 -mediated Ca(2+) signals in all activated cells. By computationally modelling Ca(2+) release, endothelial shape changes were shown to alter the geometry of the Ca(2+) diffusive environment near IP3 receptor microdomains to limit IP3 -mediated Ca(2+) signals as pressure increased. Changes in cell shape produce a geometric microdomain regulation of IP3 -mediated Ca(2+) signalling to explain macroscopic pressure-dependent, endothelial mechanosensing without the need for a conventional mechanoreceptor. The suppression of IP3 -mediated Ca(2+) signalling may explain the decrease in endothelial activity as pressure increases. GRIN imaging provides a convenient method that gives access to hundreds of endothelial cells in intact arteries in physiological configuration.

Project description:The temporal nature of chromatin structural changes underpinning pathologic transcription are poorly understood. We measured chromatin accessibility and DNA methylation to study the contribution of chromatin remodeling at different stages of cardiac hypertrophy and failure. ATAC-seq and reduced representation bisulfite sequencing were performed in cardiac myocytes after transverse aortic constriction (TAC) or depletion of the chromatin structural protein CTCF. Early compensation to pressure overload showed changes in chromatin accessibility and DNA methylation preferentially localized to intergenic and intronic regions. Most methylation and accessibility changes observed in enhancers and promoters at the late phase (3 weeks after TAC) were established at an earlier time point (3 days after TAC), before heart failure manifests. Enhancers were paired with genes based on chromatin conformation capture data: while enhancer accessibility generally correlated with changes in gene expression, this feature, nor DNA methylation, was alone sufficient to predict transcription of all enhancer interacting genes. Enrichment of transcription factors and active histone marks at these regions suggests that enhancer activity coordinates with other epigenetic factors to determine gene transcription. In support of this hypothesis, ChIP-qPCR demonstrated increased enhancer and promoter occupancy of GATA4 and NKX2.5 at Itga9 and Nppa, respectively, concomitant with increased transcription of these genes in the diseased heart. Lastly, we demonstrate that accessibility and DNA methylation are imperfect predictors of chromatin structure at the scale of A/B compartmentalization-rather, accessibility, DNA methylation, transcription factors and other histone marks work within these domains to determine gene expression. These studies establish that chromatin reorganization during early compensation after pathologic stimuli is maintained into the later decompensatory phases of heart failure. The findings reveal the rules for how local chromatin features govern gene expression in the context of global genomic structure and identify chromatin remodeling events for therapeutic targeting in disease.

Dataset Information

Biomechanical Regulation of Endothelium-dependent Events Critical for Adaptive Remodeling.

Publications

Biomechanical Regulation of Endothelium-dependent Events Critical for Adaptive Remodeling.

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