Cardiac resynchronization therapy corrects dyssynchrony-induced regional gene expression changes on a genomic level.
ABSTRACT Cardiac electromechanical dyssynchrony causes regional disparities in workload, oxygen consumption, and myocardial perfusion within the left ventricle. We hypothesized that such dyssynchrony also induces region-specific alterations in the myocardial transcriptome that are corrected by cardiac resynchronization therapy (CRT).
Adult dogs underwent left bundle branch ablation and right atrial pacing at 200 bpm for either 6 weeks (dyssynchronous heart failure, n=12) or 3 weeks, followed by 3 weeks of resynchronization by biventricular pacing at the same pacing rate (CRT, n=10). Control animals without left bundle branch block were not paced (n=13). At 6 weeks, RNA was isolated from the anterior and lateral left ventricular (LV) walls and hybridized onto canine-specific 44K microarrays. Echocardiographically, CRT led to a significant decrease in the dyssynchrony index, while dyssynchronous heart failure and CRT animals had a comparable degree of LV dysfunction. In dyssynchronous heart failure, changes in gene expression were primarily observed in the anterior LV, resulting in increased regional heterogeneity of gene expression within the LV. Dyssynchrony-induced expression changes in 1050 transcripts were reversed by CRT to levels of nonpaced hearts (false discovery rate <5%). CRT remodeled transcripts with metabolic and cell signaling function and greatly reduced regional heterogeneity of gene expression as compared with dyssynchronous heart failure.
Our results demonstrate a profound effect of electromechanical dyssynchrony on the regional cardiac transcriptome, causing gene expression changes primarily in the anterior LV wall. CRT corrected the alterations in gene expression in the anterior wall, supporting a global effect of biventricular pacing on the ventricular transcriptome that extends beyond the pacing site in the lateral wall.
Article: Selection of reference genes in different myocardial regions of an in vivo ischemia/reperfusion rat model for normalization of antioxidant gene expression.[show abstract] [hide abstract]
ABSTRACT: Changes in cardiac gene expression due to myocardial injury are usually assessed in whole heart tissue. However, as the heart is a heterogeneous system, spatial and temporal heterogeneity is expected in gene expression. In an ischemia/reperfusion (I/R) rat model we evaluated gene expression of mitochondrial and cytoplasmatic superoxide dismutase (MnSod, Cu-ZnSod) and thioredoxin reductase (trxr1) upon short (4 h) and long (72 h) reperfusion times in the right ventricle (RV), and in the ischemic/reperfused (IRR) and the remote region (RR) of the left ventricle. Gene expression was assessed by Real-time reverse-transcription quantitative PCR (RT-qPCR). In order to select most stable reference genes suitable for normalization purposes, in each myocardial region we tested nine putative reference genes by geNorm analysis. The genes investigated were: Actin beta (actb), Glyceraldehyde-3-P-dehydrogenase (gapdh), Ribosomal protein L13A (rpl13a), Tyrosine 3-monooxygenase (ywhaz), Beta-glucuronidase (gusb), Hypoxanthine guanine Phosphoribosyltransferase 1 (hprt), TATA binding box protein (tbp), Hydroxymethylbilane synthase (hmbs), Polyadenylate-binding protein 1 (papbn1). According to our findings, most stable reference genes in the RV and RR were hmbs/hprt and hmbs/tbp/hprt respectively. In the IRR, six reference genes were recommended for normalization purposes; however, in view of experimental feasibility limitations, target gene expression could be normalized against the three most stable reference genes (ywhaz/pabp/hmbs) without loss of sensitivity. In all cases MnSod and Cu-ZnSod expression decreased upon long reperfusion, the former in all myocardial regions and the latter in IRR alone. trxr1 expression did not vary. This study provides a validation of reference genes in the RV and in the anterior and posterior wall of the LV of cardiac ischemia/reperfusion model and shows that gene expression should be assessed separately in each region.BMC Research Notes 02/2012; 5:124.
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ABSTRACT: By studying genome-wide expression patterns in healthy and diseased tissues across a wide range of pathophysiological conditions, DNA microarrays have revealed unique insights into complex diseases. However, the high-dimensionality of microarray data makes interpretation of heterogeneous gene expression studies inherently difficult. Using a large-scale analysis of more than 40 microarray studies encompassing ~2400 mammalian tissue samples, we identified a common theme across heterogeneous microarray studies evident by a robust genome-wide inverse regulation of metabolic and cell signaling pathways: We found that upregulation of cell signaling pathways was invariably accompanied by downregulation of cell metabolic transcriptional activity (and vice versa). Several findings suggest that this characteristic gene expression pattern represents a new principle of mammalian transcriptional regulation. First, this coordinated transcriptional pattern occurred in a wide variety of physiological and pathophysiological conditions and was identified across all 20 human and animal tissue types examined. Second, the differences in metabolic gene expression predicted the magnitude of differences for signaling and all other pathways, i.e. tissue samples with similar expression levels of metabolic transcripts did not show any differences in gene expression for all other pathways. Third, this transcriptional pattern predicted a profound effect on the proteome, evident by differences in structure, stability and post-translational modifications of proteins belonging to signaling and metabolic pathways, respectively. Our data suggest that in a wide range of physiological and pathophysiological conditions, gene expression changes exhibit a recurring pattern along a transcriptional axis, characterized by an inverse regulation of major metabolic and cell signaling pathways. Given its widespread occurrence and its predicted effects on protein structure, protein stability and post-translational modifications, we propose a new principle for transcriptional regulation in mammalian biology.BMC Genomics 03/2010; 11:197. · 4.07 Impact Factor
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ABSTRACT: The hemodynamic, mechanical and electrical effects of cardiac resynchronization therapy (CRT) occur immediate and are lasting as long as CRT is delivered. Therefore, it is reasonable to assume that acute hemodynamic effects should predict long-term outcome. However, in the literature there is more evidence against than in favour of this idea. This raises the question of what factor(s) do relate to the benefit of CRT. There is increasing evidence that dyssynchrony, presumably through the resultant abnormal local mechanical behaviour, induces extensive remodelling, comprising structure, as well as electrophysiological and contractile processes. Resynchronization has been shown to reverse these processes, even in cases of limited hemodynamic improvement. These data may indicate the need for a paradigm shift in order to achieve maximal long-term CRT response.Journal of Cardiovascular Translational Research 11/2011; 5(2):188-95. · 2.61 Impact Factor