Project description:Objectives: To test whether (1) electromechanical dyssynchrony induces region-specific alterations in the myocardial transcriptome and (2) dyssynchrony-induced gene expression changes can be corrected by cardiac resynchronization (CRT). Background: To date, CRT is the only heart failure treatment that can both acutely and chronically increase systolic function and prolong survival, something not yet achieved by a drug therapy. However, the mechanisms underlying the benefits of CRT remain elusive. Methods: Adult dogs underwent left bundle branch ablation (LBBB) and right atrial pacing at 200 bpm for either 6 weeks (dyssynchronous heart failure, DHF, n=12) or 3 weeks followed by 3 weeks of resynchronization by bi-ventricular pacing at the same pacing rate (CRT, n=10). Control animals without LBBB were not paced (NF, n=14). Echocardiography and invasive hemodynamic measurements were performed at 3 and 6 weeks. At 6 weeks, RNA was isolated from the anterior and lateral LV walls and hybridized onto canine-specific 44K microarrays. Results: In DHF, transcriptional changes consistent with re-expression of a fetal gene program were primarily observed in the anterior LV, resulting in increased regional heterogeneity of gene expression within the left ventricle. Dyssynchrony-induced region-specific expression changes in 1050 transcripts were reversed by CRT to levels of NF hearts (false discovery rate <5%). CRT remodeled transcripts with metabolic and cell signaling function and greatly reduced regional heterogeneity of gene expression compared with DHF. Conclusions: 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 by reversing the fetal gene expression pattern, supporting a global effect of biventricular pacing on the ventricular transcriptome that extends beyond the pacing site in the lateral wall. Designed as a 1-color experiments, samples from anterior and lateral left ventricular myocardium from non-failing, DHF and CRT animals were labeled with Cy3 and hybridized onto Agilent 44K long oligonucleotide arrays.

Project description:Objectives: To test whether (1) electromechanical dyssynchrony induces region-specific alterations in the myocardial transcriptome and (2) dyssynchrony-induced gene expression changes can be corrected by cardiac resynchronization (CRT). Background: To date, CRT is the only heart failure treatment that can both acutely and chronically increase systolic function and prolong survival, something not yet achieved by a drug therapy. However, the mechanisms underlying the benefits of CRT remain elusive. Methods: Adult dogs underwent left bundle branch ablation (LBBB) and right atrial pacing at 200 bpm for either 6 weeks (dyssynchronous heart failure, DHF, n=12) or 3 weeks followed by 3 weeks of resynchronization by bi-ventricular pacing at the same pacing rate (CRT, n=10). Control animals without LBBB were not paced (NF, n=14). Echocardiography and invasive hemodynamic measurements were performed at 3 and 6 weeks. At 6 weeks, RNA was isolated from the anterior and lateral LV walls and hybridized onto canine-specific 44K microarrays. Results: In DHF, transcriptional changes consistent with re-expression of a fetal gene program were primarily observed in the anterior LV, resulting in increased regional heterogeneity of gene expression within the left ventricle. Dyssynchrony-induced region-specific expression changes in 1050 transcripts were reversed by CRT to levels of NF hearts (false discovery rate <5%). CRT remodeled transcripts with metabolic and cell signaling function and greatly reduced regional heterogeneity of gene expression compared with DHF. Conclusions: 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 by reversing the fetal gene expression pattern, supporting a global effect of biventricular pacing on the ventricular transcriptome that extends beyond the pacing site in the lateral wall. Complementary study to GSE14327. While GSE14327 was designed as a 1-color microarray experiment, this series was carried out following a 2-color design (anterior and lateral LV wall labeled with Cy3 and Cy5, respectively, including dye swaps).

Project description:Objectives: To test whether (1) electromechanical dyssynchrony induces region-specific alterations in the myocardial transcriptome and (2) dyssynchrony-induced gene expression changes can be corrected by cardiac resynchronization (CRT). Background: To date, CRT is the only heart failure treatment that can both acutely and chronically increase systolic function and prolong survival, something not yet achieved by a drug therapy. However, the mechanisms underlying the benefits of CRT remain elusive. Methods: Adult dogs underwent left bundle branch ablation (LBBB) and right atrial pacing at 200 bpm for either 6 weeks (dyssynchronous heart failure, DHF, n=12) or 3 weeks followed by 3 weeks of resynchronization by bi-ventricular pacing at the same pacing rate (CRT, n=10). Control animals without LBBB were not paced (NF, n=14). Echocardiography and invasive hemodynamic measurements were performed at 3 and 6 weeks. At 6 weeks, RNA was isolated from the anterior and lateral LV walls and hybridized onto canine-specific 44K microarrays. Results: In DHF, transcriptional changes consistent with re-expression of a fetal gene program were primarily observed in the anterior LV, resulting in increased regional heterogeneity of gene expression within the left ventricle. Dyssynchrony-induced region-specific expression changes in 1050 transcripts were reversed by CRT to levels of NF hearts (false discovery rate <5%). CRT remodeled transcripts with metabolic and cell signaling function and greatly reduced regional heterogeneity of gene expression compared with DHF. Conclusions: 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 by reversing the fetal gene expression pattern, supporting a global effect of biventricular pacing on the ventricular transcriptome that extends beyond the pacing site in the lateral wall.

Project description:Right ventricular free wall (RVFW) pacing results in left ventricular dyssynchrony with early septal shortening followed by late lateral contraction that reciprocally stretches the septum. Dyssynchrony is disadvantageous to cardiac mechano-energetics, yet little is known about its molecular consequences. We tested the hypothesis that dyssynchrony selectively alters regional gene expression in mice, employing a novel miniature implantable cardiac pacemaker. Mice were subjected to 1-week overdrive RVFW pacing (720 min-1, baseline HR 520-620 min-1) to induce dyssynchrony (pacemaker: 3V lithium battery, rate programmable, 0.8 grams, bipolar lead). Electrical capture was confirmed by pulsed-wave Doppler at implantation and terminal study, and dyssynchrony by echocardiography. Gene expression from left ventricular septal and lateral-wall myocardium were assessed by microarray (dual-dye method, Agilent) using oligonucleotide probes and dye swap. Identical analysis was applied to 4 synchronously contracting controls. Of 22,000 genes surveyed, only 18 genes displayed significant (p<0.01) differential expression between septal/lateral walls exceeding 1.5-fold relative to any disparities in synchronous controls. These changes were confirmed by qPCR with excellent correlations. Most (16) of the genes showed greater septal expression. Of particular interest were 7 genes coding proteins involved with stretch responses, matrix remodeling, stem cell differentiation to myocyte lineage, and Purkinje fiber differentiation. One-week cardiac dyssynchrony triggers regional differential expression differences in relatively few select genes. Such analysis using a murine implantable pacemaker should facilitate molecular studies of cardiac dyssynchrony and help elucidate novel mechanisms by which stress/stretch stimuli due to dyssynchrony impact the normal and failing heart. Keywords: Murine cardiac dyssynchrony and differential gene expression, Agilent, microarray, pacing

Project description:Right ventricular free wall (RVFW) pacing results in left ventricular dyssynchrony with early septal shortening followed by late lateral contraction that reciprocally stretches the septum. Dyssynchrony is disadvantageous to cardiac mechano-energetics, yet little is known about its molecular consequences. We tested the hypothesis that dyssynchrony selectively alters regional gene expression in mice, employing a novel miniature implantable cardiac pacemaker. Mice were subjected to 1-week overdrive RVFW pacing (720 min-1, baseline HR 520-620 min-1) to induce dyssynchrony (pacemaker: 3V lithium battery, rate programmable, 0.8 grams, bipolar lead). Electrical capture was confirmed by pulsed-wave Doppler at implantation and terminal study, and dyssynchrony by echocardiography. Gene expression from left ventricular septal and lateral-wall myocardium were assessed by microarray (dual-dye method, Agilent) using oligonucleotide probes and dye swap. Identical analysis was applied to 4 synchronously contracting controls. Of 22,000 genes surveyed, only 18 genes displayed significant (p<0.01) differential expression between septal/lateral walls exceeding 1.5-fold relative to any disparities in synchronous controls. These changes were confirmed by qPCR with excellent correlations. Most (16) of the genes showed greater septal expression. Of particular interest were 7 genes coding proteins involved with stretch responses, matrix remodeling, stem cell differentiation to myocyte lineage, and Purkinje fiber differentiation. One-week cardiac dyssynchrony triggers regional differential expression differences in relatively few select genes. Such analysis using a murine implantable pacemaker should facilitate molecular studies of cardiac dyssynchrony and help elucidate novel mechanisms by which stress/stretch stimuli due to dyssynchrony impact the normal and failing heart. Experiment Overall Design: Left ventricle segments from the mouse heart - septal and lateral, were isolated from 4 dyssynchronous mice that were kept separate. RNA from the synchronous mice were pooled into a control septal and lateral sample. Functional genomic analysis was conducted on these 10 RNA samples with fluorophore reversal, such that each sample was assayed on two different microarrays. Corresponding septal and lateral samples from the same heart were paired on the same microarray to measure the relative differences in gene expression between the different regions of the heart then differences were compared across multiple mice to find overlapping genes that were affected by the pacememaker implantation.

Project description:OBJECTIVE: To study the genetic regulatory mechanisms in the remote zone of left ventricular (LV) free wall in order to partly explain the more frequent progression to heart failure after acute myocardial infarction (AMI) in diabetic rats. METHODS: 10 weeks after diabetes mellitus (DM) induction with Streptozotocin (STZ), the left anterior descending coronary arteries of uncontrolled diabetic Sprague-Dawley (SD) rats and non-diabetic ones were ligated without reperfusion. Then, the remote zone tissues of LV free wall were taken as samples at day 1, 7, 14, 28, and 56 post AMI. Significant different expression genes were filterd from Affymetrix Genechip U230 2.0 array by GCOS software. Genetic changes post myocardial infarction were classified by hierarchical clustering of 10 gene chips. And then, the differential expressions of 10 selected transcripts identified by the microarray were examined in greater detail by Real Time-PCR. RESULTS: According to hierarchical clustering, we find that the molecular regulatory expression related to cardiac remodeling in the remote zone to myocardial infarction is quite different as time elapses in both diabetic and non-diabetic rats. The gene expression at day 1 and 7 post AMI in both groups is similar, while the genetic changes at day 14 post AMI in diabetic rats and the ones at day 14 and 28 in non-diabetic rats are classified into the same cluster. And then the genetic changes at day 28 and 56 post AMI in diabetic rats and the ones at day 56 in non-diabetic rats are classified into the same cluster. (Figure.1) The patterns of numerous products of genes expression were used in the cluster, including 118 genes, such as leucine-rich PPR-motif containing (IL-6 signaling pathway), procollagen type I, VI, VIII, and XV, fibronectin1, RT1, and TIMP-1, etc. CONCLUSION: The genetic findings in this study might be the possible mechanism that diabetes mellitus can accerate the progression of post-infarction genetic regulatory expression. Experiment Overall Design: All studies were performed with male SD rats (200-220g), aged 8 weeks, which were obtained from laboratorial animal center of Chinese University of Agriculture. DM was induced with a singleintraperitoneal injection of STZ (65 mg/kg in 0.1mmol/L, pH 4.5 sodium citrate buffer) . Age and body weight matched rats that used as non-diabetic controls were injected with the same dose of sodium citrate buffer (0.1mmol/L, pH 4.5). Ultrastructure changes of myocardium were observed 10 weeks after DM induction by TEM. 10 weeks after DM induction,both diabetic and non-diabetic rats were subjected to left anterior descending coronary artery (LADCA) ischemia for 1-56 days without reperfusion. Two-dimensional echocardiography was utilized to obtain LV dimensions and LV percent fractional shortening at baseline, DM 10weeks, and at 1d, 7d, 14d, 28d, 56d after AMI; the remote zone tissues of LV free wall were taken as samples at day 1, 7, 14, 28, and 56 post AMI for gene chip microarray analysis (10 samples from 30 rats); in addition, heart-to-body weight and heart to tibial length ratios and masson's trichrome staining was measured as an index of cardiac hypertrophy and fibrosis at baseline, DM 10weeks, and at 1d, 7d, 14d, 28d, 56d after AMI.

Project description:We report a genome-wide survey of early responses of the mouse heart transcriptome to acute myocardial infarction (AMI). For three regions of the left ventricle (LV), namely ischemic/infarcted tissue (IF), the surviving LV free wall (FW) and the interventricular septum (IVS), 36,899 transcripts were assayed at six time points from 15 min to 48 h post-AMI in both AMI and sham surgery mice. For each transcript, temporal expression patterns were systematically compared between AMI and sham groups, which identified 515 AMI-responsive genes in IF tissue, 35 in the FW, 7 in the IVS, with three genes induced in all three regions. Using the literature, we assigned functional annotations to all 519 nonredundant AMI-induced genes and present two testable models for central signaling pathways induced early post-AMI. First, the early induction of 15 genes involved in assembly and activation of the activator protein-1 (AP-1) family of transcription factors implicates AP-1 as a dominant regulator of earliest post-ischemic molecular events. Second, dramatic increases in transcripts for arginase 1 (ARG1), the enzymes of polyamine biosynthesis and protein inhibitor of nitric oxide synthase (NOS) activity indicates that NO production may be regulated, in part, by inhibition of NOS and coordinate depletion of the NOS substrate, L-arginine. ARG1 was the single most highly induced transcript in the database (121-fold in IF region) and its induction in heart has not been previously reported. Keywords: heart attack, mouse, time course, regional responses We report temporal and regional changes in steady state mRNA levels in the mouse LV following a surgically-induced AMI. Three regions of the infarcted LV were surveyed: IF, FW and IVS. For each region, mRNA levels were assayed at t=0 and six time points after occlusion of the left anterior descending coronary artery (t = 15 min, 1 h, 4 h, 12 h, 24 h, 48 h). As control, an identical time course was carried out in the mouse LV after sham surgery in which the suture was passed under the artery, but not ligated. For sham surgical mice and naïve mice (t=0), the IVS and the LV free wall were harvested and assayed. The AMI and sham time courses were repeated for a total of two independent repetitions of the experiment. For each repetition, 96 GeneChips were hybridized. Thus, for two repetitions, 192 GeneChips (2 x 96) were hybridized. In addition, the naïve time point was assayed a second time during Repetition 1 for six additional GeneChips (two tissues x three chips). The overall total number of samples is 198 GeneChips (192 + 6). Total RNA was isolated from each individual tissue sample. Equal weights of total RNA from 4-10 mice were combined for each LV region, time point and treatment. Copy RNA mixtures were synthesized from each total RNA pool and hybridized to the Affymetrix GeneChip set MG U74 v2 (A, B, and C) that carries 36,899 probe sets. The global normalization of fluorescence emissions for the 198 GeneChips used in this study and their conversion to relative transcript concentrations measured in relative fluorescence units (RFU) was conducted using Robust Multi-array Averaging (RMA; www.bioconductor.org). Each of the 198 Accessions is titled as follows: time point / treatment / tissue, repetition, GeneChip. The additional assays of naïve mice in Repetition 1 are labeled “Naive2”.

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Cardiac Resynchronization Therapy (2-color design)

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