Chronic ventricular sympathectomy elicits changes in the coronary circulation, myocardial oxygen consumption and size of infarction resulting fromcoronary occlusion. These changes indicate a change occurring in the basic metabolism of the heart in response to the removal of its sympathetic nervous input. This hypothesis was tested using two groups of dogs, a shamoperated control and a ventricular sympathectomized group. The sympathectomy procedure was an intrapericardial surgical technique which selectively removes ventricular sympathetic input. Four weeks after surgery, left ventricular tissue samples were obtained and rapidly frozen to -80°C. Selected metabolic variables were then compared between the two groups.

The epicardium is a single layer of epithelial (mesothelial) cells that covers the entire heart surface, but whose function in adult mammals is poorly understood. Defining the role of epicardial cells during homeostasis, growth and injury has potential to provide new treatment strategies for human diseases that result in heart failure, due to extensive loss of viable cardiac tissue. We hypothesized that epicardial cells contribute to repair as transplantable progenitor cells for cellular regeneration and as a source of secreted growth factors for cell protection after myocardial infarction. Adult epicardial cells were prospectively isolated as uncommitted epithelial cells using epithelial-specific beta-4 integrin (CD104). These cells underwent epithelial to mesenchymal transformation in culture to generate epicardial cell derivatives (EPDCs). We demonstrate that the C-terminal peptide from Connective Tissue Growth Factor (CTGF-D4), when combined with insulin, effectively primes EPDCs for robust cardiac engraftment in rats and contributes to improvement in cardiac function at one month after MI. Furthermore, we define a signaling axis comprised of CTGF-D4, low density lipoprotein receptor-related protein 6 (LRP6), sex determining region Y-box 9 (Sox9) and Endothelin Receptor B (ETBR) that controls several key processes that impact EPDC graft success: cell survival, proliferation and migration. Interestingly, conditional deletion of ETBR using epicardial-specific transgenic mice prevented epicardial cell proliferation and migration into myocardium after MI. We therefore observed a congruence in the signals and signaling pathways that control the proliferation and migration of endogenous EPDCs after MI and EPDCs that can be generated in cell culture and grafted back to the heart. To gain additional insight into the cellular contribution of the epicardium, we utilized a non-injurious running exercise model to evaluate epicardial activity as a consequence of cardiac hypertrophy (i.e. myocardial growth model). We employed an inducible lineage-tracing system to specifically label and track epicardial cells by GFP expression. Prolonged exercise resulted in a significant number of GFP-positive proliferating epicardial cells and epicardial-derived GFP-positive endothelial cells and few GFP-positive smooth muscle cells in the heart. These observations highlight the cellular plasticity of the adult epicardium and its function as a cardiac progenitor cell niche, maintaining a source of replacement cells. To investigate the paracrine properties of adult epicardial cells for their role in cell protection after MI and reperfusion, human epicardial cells were isolated from donor atrial tissue explants. We predicted that medium conditioned by cultured epicardial cells (EPI CdM) contained secreted reparative factors that would promote endothelial cell survival. Administration of EPI CdM promoted endothelial cell survival in culture and in vivo, 24 hours after ischemia-reperfusion injury. By screening EPI CdM, we detected protein complexes containing hepatocyte growth factor (HGF) with polyclonal IgG that imparted vascular protection in vivo in a manner similar to EPI CdM. Overall, the studies presented here illustrate the unique biology of epicardial cells, their signaling networks, and their contribution to cardiac cell protection and regeneration. Importantly, these properties have the potential to be exploited in translational applications for cardiac repair.

Several studies have shown cellular replacement therapy as a treatment strategy of myocardial infarction but results have been limited. Therefore, enhancing the therapeutic potential of stem cells injected into ischemic microenvironments by novel preconditioning (PC) techniques is critical for improving cellular therapy. Recent studies have shown that inhibition of phosphodiesterase-5 (PDE-5) is a powerful strategy to precondition the heart and cardiomyocytes against ischemia/reperfusion injury. We therefore tested the hypothesis that inhibition of PDE-5 with sildenafil (Viagra®) or selective knockdown with a silencing vector in adipose derived stem cells (ASCs) would improve their survival after ischemia/reoxygenation in vitro and enhance cardiac function following myocardial implantation in vivo. ASCs were treated with sildenafil or infected with PDE-5 silencing vector shRNA (shRNAPDE-5). The cells were subjected to simulated ischemia (SI) and reoxygenation (RO). Both sildenafil and shRNAPDE-5 significantly reduced cell injury, as shown by improved viability, decreased lactate dehydrogenase, and apoptosis. The preconditioned ASCs also demonstrated an increase in the release of growth factors including VEGF, b-FGF, and IGF. The protective effect against SI/RO injury was abolished by inhibition of protein kinase G (PKG) using both a pharmacological inhibitor and selective knockdown with shRNAPKG1α suggesting a PKG-mediated mechanism. To show the effect of preconditioned ASCs in vivo, adult male CD-1 mice underwent myocardial infarction (MI) by occlusion of the left descending coronary artery, followed by direct injection of PBS (control), non-preconditioned ASCs, or preconditioned ASCs (4x105) ASCs into the left ventricle (LV). Preconditioned ASC-treated hearts showed consistently superior cardiac function by all measures as compared with PBS and non-preconditioned ASCs after 4 weeks of treatment. Post-mortem histological analysis demonstrated that preconditioned ASC-treated mice had significantly reduced fibrosis, increased vascular density and reduced resident myocyte apoptosis as compared to mice receiving non-preconditioned ASCs or PBS. VEGF, b-FGF, and Ang-1 were also significantly elevated 4 weeks after cell therapy with preconditioned ASCs. Our data suggests that genetic or pharmacological inhibition of PDE-5 is a powerful new approach to improve stem cell therapy following myocardial infarction.

Administration of small interfering RNA (siRNA) specific for prolyl-4 hydroxylase-2 (PHD2) results in PHD2 inhibition, Hypoxia Inducible Factor-I (HIF-1) activation, and cardioprotection versus Ischemia Reperfusion (IR). This study observes the effects of siRNA-mediated PHD2 inhibition on the distribution of cardioprotective proteins by immunofluorescence and basic histology. Fifteen mice were divided into 5 groups: PHD2 Control, Non-Targeting scramble (NTS) Control, IR Control, PHD2 IR, and NTS IR. Histologically, tissue damage was reduced dramatically in the PHD2 IR group compared to the NTS IR and IR control groups. From confocal images, total fluorescent pixels and intensities were quantified. The PHD2 IR group yielded the highest pixel quantity and intensity for HIF-1 and possessed increased pixels and intensity for Inducible Nitric Oxide Synthase, another cardioprotective protein. These results further demonstrate the cardioprotection and HIF-1 activation conferred by PHD2 siRNA administration and supports its role as a potential therapy to alleviate cardiac IR injury.

Heart disease is a major cause of morbidity and mortality in the United States with coronary artery disease (CAD) representing more than half of all cardiovascular events. Stable patients presenting with symptoms suggestive of CAD are likely to undergo either an exercise ECG and/or imaging study as a first line diagnostic assessment. A cardiopulmonary exercise test (CPX) is an ECG stress test plus ventilatory gas analysis. Recently CPX has been used to detect exercise-induced myocardial ischemia suggestive of underlying CAD. Currently there are a number of diagnostic tests available for the identification of CAD with the most widely used being exercise ECG, myocardial perfusion imaging (MPI) and cardiac catheterization. Exercise ECG, although inexpensive, has a number of well-recognized limitations, including low sensitivity resulting in false positive results. MPI and catheterization are more accurate but also more invasive and expensive. It appears that CPX may improve the diagnostic accuracy of exercise ECG in a cost effective manner.

Background: Combined valvular and coronary artery bypass grafting (CAB G) surgery requires a long period of cardioplegic arrest (CA) that predisposes the heart to ischaemiareperfusion injury, low cardiac output syndrome, reperfusion dysrhythmias, inhospital mortality and increased costs. Procedures that can reduce the duration of CA would be expected to reduce intraoperative and postoperative complications. Mehods: Adults undergoing combined valvular and CABG surgery were randomized to either coronary surgery performed on the beating heart with cardiopulmonary bypass (CPB) support followed by CA for the valvular procedure (hybrid group) or surgery with both procedures carried out under CA (conventional group). The primary outcome was a composite of in-hospital death, postoperative myocardial infarction, cardiac dysrhythmias, requirements for cardiac pacing for more than 12 hours and/or inotropic support for more than 12 hours postoperativeiy. Results: One hundred and sixty patients (80 hybrid, 80 conventional) were randomized between March 2008 and July 2012. Mean age was 66.5 years and 74% were male. Valvular procedures included aortic (61.8%) and mitral (33.1%) alone or in combination (5.l %). The primary outcome occurred in 64/80 of the conventional group patients and 67/80 of the hybrid group patients (odds ratio 1.24, 95% Cl 0.54 to 2.86, p=0.61). The CA time was, on average, 16% shorter in the hybrid group (median 98 minutes vs. 89 minutes, geometric mean ration (GMR) 0.84, 95% Cl 0.77 to 0.93 , p=0.0004), but the overall duration of CPB was on average 7% longer in the hybrid group (GMR 1.07, 95% Cl 0.98 to 1.16, p=0.12). Cardiac troponin T plasma concentrations and levels of metabolites measured in heart biopsies were similar between the two treatment groups. Conclusion: The hybrid technique reduced the CA time, but this did not result in a significant reduction in the frequency of the primary outcome. In this trial the clinical outcomes and the extent of the myocardial injury were similar between the two surgical methods.

L'infarctus du myocarde (IDM) est l'une des principales causes de morbi-mortalité dans le monde et ce malgré une revascularisation rapide de l’artère coronaire occlue. L'obésité est un facteur de risque majeur pour l’IDM, et concerne 15 % de la population française (enquête ObEpi-Roche/INSERM, 2012). L'objectif de notre étude a été d'étudier l'efficacité de stratégies cardioprotectrices comme l’exercice physique chronique ou l’administration d’un donneur de CO (CORM-3) dans un contexte d’obésité. Un effet cardioprotecteur de l'exercice physique chronique a été démontré sur un modèle d’ischémie-reperfusion chez la souris ob/ob (génétiquement dépourvu en leptine). Cet effet implique l’activation de la voie de signalisation cardioprotectrice RISK associée à une diminution des taux cytosoliques des protéines phosphatases inhibitrices correspondantes PTEN et MK3P ce qui aboutit à une amélioration des fonctions mitochondriales. Ce travail montre la capacité différentielle de stratégies à réduire la taille de l’infarctus en cas d’obésité. Par ailleurs, il souligne l’importance du rôle des mécanismes HCO3- dépendants dans le contrôle du pH intracellulaire à la reperfusion. Ils pourraient représenter une étape clef dans la cardioprotection. / Myocardial infarction (MI) remains the leading cause of morbidity and mortality in the developing countries despite significant therapeutic advances over the last years. Obesity is a major risk factor for coronary heart disease and concern 15% of the French population (ObEpi-Roche/INSERM survey, 2012). The aim of our studie was to investigate the efficacy of cardioprotective strategies such as regular treadmill exercice or CO donor administration (CORM-3) against MI during obesity. In ob/ob mice, regular exercise induces a robust cardioprotection by increasing kinase phosphorylation of RISK pathway, decreasing levels of corresponding phosphatases and improving the resistance of mitochondrial permeability transition pore opening. The present study shows differential capabilities of cardioprotective strategies at reducing myocardial infarct size with obesity. In addition, it underlines the role of HCO3- dependent mechanisms in the control of intracellular pH at reperfusion. They could represent a key step for mediating cardioprotection.

Ce travail de thèse avait pour objectif d'évaluer l'intérêt des peptides collagéniques sanguins dans différentes populations à haut risque de développer une insuffisance cardiaque (patients présentant une obésité abdominale ou en post-infarctus du myocarde) ou déjà symptomatiques (post-infarctus du myocarde). En effet la fibrose myocardique est un élément essentiel de l'évolution péjorative de l'insuffisance cardiaque.Ces travaux ont permis de montrer la pertinence clinique des dosages sanguins des peptides collagéniques tout au long du processus de l'insuffisance cardiaque : du stade asymptomatique aux stades symptomatiques. Nous avons mis en évidence, à travers l'expression des peptides collagéniques que : 1/ des patients asymptomatiques ayant une obésité abdominale présentent un remodelage cardiaque précoce tant structurel que fonctionnel (augmentation de la masse ventriculaire gauche, dysfonction diastolique associée au PIIINP) : R2C2 Study. 2/ le ratio PIIINP/ICTP ≤ 1, mesuré 1 mois après un infarctus, est indépendamment associé à la survenue d'un remodelage ventriculaire gauche à un an et améliore la prédiction de survenue d'évènements cardiovasculaires (décès cardiovasculaires et hospitalisation pour décompensation cardiaque) à 3 ans : REVE-2 study. 3/ les antagonistes des récepteurs aux minéralocorticoïdes (éplérénone), traitement anti-fibrotique par excellence, sont efficaces et sûrs (hyperkaliémie et insuffisance rénale) chez des patients à haut risque de remodelage et de complications: EMPHASIS-HF study. Ce travail doit conduire à la validation dans d'autres populations du rôle prépondérant de la fibrose mais surtout au bénéfice thérapeutique des classes anti-fibrotiques dans l'insuffisance cardiaque. / No abstract available

Master of Science / Department of Kinesiology / Timothy I. Musch / Both cardiac and peripheral vasculature dysfunction likely contribute, in part, to elevations in TNF-[alpha] and exercise intolerance in chronic heart failure (CHF). The pharmaceutical TNF-[alpha] synthesis suppressor pentoxifylline (PTX) reduces plasma [TNF-[alpha]] and improves left ventricular (LV) function in CHF rats, but the effects of PTX on skeletal muscle blood flow (BF) and vascular conductance (VC) during exercise are unknown. We tested the hypothesis that PTX would elevate skeletal muscle BF and VC at rest and during submaximal treadmill exercise in CHF rats (coronary artery ligation). CHF rats received i.p. injections of 30 mg·kg[superscript]-[superscript]1·day[superscript]-[superscript]1 of PTX (CHF+PTX, n=13) or saline (CHF, n=8) for 21 days. Mean arterial pressure (MAP) and BF (radiolabeled microsphere infusions) were measured at rest and during treadmill exercise (20 m/min, 5% grade). Myocardial infarct (MI) size was not different between groups (CHF: 37±4, CHF+PTX: 37±3% of LV wall; p>0.05). Resting and exercising MAP was greater in CHF+PTX compared to CHF (p<0.05 for both). At rest, total hindlimb skeletal muscle BF and VC were not different between groups (p>0.05). However, during exercise PTX increased total hindlimb BF (CHF: 83±9, CHF+PTX: 114±8 ml·min[superscript]-[superscript]1·100g[superscript]-[superscript]1, p<0.05) and VC (CHF: 0.75±0.08, CHF+PTX: 0.88±0.06 ml·min[superscript]-[superscript]1·100g[superscript]-[superscript]1·mmHg[superscript]-[superscript]1, p<0.05). Furthermore, exercising BF was increased in 21, and VC in 11, of the 28 individual hindlimb muscles or muscle parts with no apparent fiber-type specificity. Thus, PTX administration augments skeletal muscle BF and VC during locomotory exercise in CHF rats, which carries important therapeutic implications for CHF patients.

No description available.