F015 Role des fibroblastes cardiaques dans la tolérance des cardiomyocytes à l’ischémie reperfusion

ObjectifLes fibroblastes cardiaques sont la population cellulaire majoritaire du tissu cardiaque. Leurs possibles implications au cours de la séquence ischémie-reperfusion n’a jamais été étudiée. Le présent travail a donc pour but de déterminer si les fibroblastes sont impliqués dans une modulation de la cardioprotection.Matériel et MéthodesNous avons utilisé dans cette étude un modèle de cardiomyocytes de rats nouveau-nés soumis à une séquence d’ischémie-reperfusion simulées. Les cellules ont été isolées à partir de ventricules de rats nouveau nés. Les myocytes cardiaques ont été purifiés par attachements différentiels puis cultivés en présence d’un milieu de culture supplémenté en cytosine arabinoside (Ara C, 10μm). Les cardiomyocytes et les fibroblastes ont été cultivés séparément puis placés en contact direct (cultures mixtes) ou indirect (insert). Ces co-cultures ont subi une ischémie de 3H en absence de nutriments et d’O2 suivie d’une reperfusion de 20H en présence de nutriments et d’O2. Des tests de viabilité (test MTT) et de mortalité cellulaire (dosage de l’activité LDH et Troponine I) ont été effectués à la fin de la reperfusion.RésultatsNous avons montré qu’il était possible de simuler des séquences d’ischémie reperfusion et d’induire une souffrance cellulaire détectable pour une durée d’ischémie de 3H et de reperfusion de 20H. Dans les cultures mixtes (cardiomyocytes + fibroblastes), les tests MTT et LDH ont montré une amélioration de la viabilité cellulaire globale en comparaison avec la viabilité spécifique de chaque type cellulaire seul. Pour les cultures placées en insert, les tests MTT et Troponine I ont montré une amélioration de la viabilité des cardiomyocytes en présence des fibroblastes (p<0.001).ConclusionsNos résultats indiquent que les fibroblastes cardiaques semblent être impliqués dans une modulation de la cardioprotection lors de l’ischémie reperfusion. Cette modulation passe au moins en partie par des mécanismes de type paracrine et elle est dépendante de la quantité de fibroblastes en co-culture avec les cardiomyocytes

D010 Mesenchymal stem cells protect cardiomyocytes from reperfusion injury through a paracrine activation of the PI3 kinase pathway

ObjectivesPrevious data suggest that implantation of mesenchymal stem cells (MSCs) improves heart function after myocardial infarction. We investigated whether protection afforded by MSCs might involve a paracrine activation of the PI3 kinase pathway in reperfused cardiomyocytes.MethodMSCs and neonatal rat cardiomyocytes (NRCs) were isolated and cultured separately. NRCs (2.106) were subjected to 5 hours of ischemia followed by 16 hours of reperfusion. At the time of reperfusion, NRCs (n=8-14/group) received either fresh medium (control group), or the following treatments: MSCs (2.105 MSCs in fresh medium), conditioned SN (MSCs supernatant alone (i.e. without MSCs) obtained after 8 hours of serum deprived culture), [conditioned SN + LY294002] (15 microM of LY294002 a specifi c inhibitor of PI3K), [conditioned SN + Wortmannin] (100 nM of wortmannin, a non specifi c inhibitor of PI3K), or CsA (200 nM in fresh medium) a potent inhibitor of the mitochondrial permeability transition pore. Cell death was assessed by LDH release in NRCs supernatant at the end of reperfusion.ResultsAs expected, LDH activity was dramatically reduced by CsA, averaging 4 % of control values. LDH activity was signifi cantly reduced by MSCs alone and by conditioned SN, averaging 29 % and 12 % of control value, respectively. Both LY294002 and wortmannin signifi cantly attenuated conditioned SN induced protection.Conclusionour data suggest that MSCs can protect NRCs from reperfusion injury through a paracrine activation of the PI3K pathway

Targeting reperfusion injury in patients with ST-segment elevation myocardial infarction : trials and tribulations

Altres ajuts: D.J.H. and D.M.Y. are funded by the British Heart Foundation and the Rosetrees Trust, and are supported by the National Institute for Health Research University College London Hospitals Biomedical Research Centre of which D.M.Y. is a senior investigator. G.H. is supported by the German Research Foundation (He 1320/18-3; SFB 1116 B8)

Targeting reperfusion injury in patients with ST-segment elevation myocardial infarction: trials and tribulations

D.J.H. and D.M.Y. are funded by the British Heart Foundation and the Rosetrees Trust, and are supported by the National Institute for Health Research University College London Hospitals Biomedical Research Centre of which D.M.Y. is a senior investigator. D.G.-D. is funded by the Cardiovascular Research Network of the Spanish Institute of Health Instituto de Salud Carlos III (ISCiii RETICS-RIC, RD12/0042/0021). G.H. is supported by the German Research Foundation (He 1320/18-3; SFB 1116 B8). B.I. is funded by the Carlos III Institute of Health and European Regional Development Fund (ERDF/FEDER) (PI13/01979), and the ISCiii Cardiovascular Research Network (RD12/0042/0054). Funding to pay the Open Access publication charges for this article was provided by Red de Investigacion Cardiovascular del Instituto de Salud Carlos III, grupo Hospital Universitari Vall d'Hebron (RETICS 2012 RD12/0042/0021).S

Translating novel strategies for cardioprotection: the Hatter Workshop Recommendations

Ischemic heart disease (IHD) is the leading cause of death worldwide. Novel cardioprotective strategies are therefore required to improve clinical outcomes in patients with IHD. Although a large number of novel cardioprotective strategies have been discovered in the research laboratory, their translation to the clinical setting has been largely disappointing. The reason for this failure can be attributed to a number of factors including the inadequacy of the animal ischemia–reperfusion injury models used in the preclinical cardioprotection studies and the inappropriate design and execution of the clinical cardioprotection studies. This important issue was the main topic of discussion of the UCL-Hatter Cardiovascular Institute 6th International Cardioprotection Workshop, the outcome of which has been published in this article as the “Hatter Workshop Recommendations”. These have been proposed to provide guidance on the design and execution of both preclinical and clinical cardioprotection studies in order to facilitate the translation of future novel cardioprotective strategies for patient benefit

The 10th Biennial Hatter Cardiovascular Institute workshop: cellular protection—evaluating new directions in the setting of myocardial infarction, ischaemic stroke, and cardio-oncology

Due to its poor capacity for regeneration, the heart is particularly sensitive to the loss of contractile cardiomyocytes. The onslaught of damage caused by ischaemia and reperfusion, occurring during an acute myocardial infarction and the subsequent reperfusion therapy, can wipe out upwards of a billion cardiomyocytes. A similar program of cell death can cause the irreversible loss of neurons in ischaemic stroke. Similar pathways of lethal cell injury can contribute to other pathologies such as left ventricular dysfunction and heart failure caused by cancer therapy. Consequently, strategies designed to protect the heart from lethal cell injury have the potential to be applicable across all three pathologies. The investigators meeting at the 10th Hatter Cardiovascular Institute workshop examined the parallels between ST-segment elevation myocardial infarction (STEMI), ischaemic stroke, and other pathologies that cause the loss of cardiomyocytes including cancer therapeutic cardiotoxicity. They examined the prospects for protection by remote ischaemic conditioning (RIC) in each scenario, and evaluated impasses and novel opportunities for cellular protection, with the future landscape for RIC in the clinical setting to be determined by the outcome of the large ERIC-PPCI/CONDI2 study. It was agreed that the way forward must include measures to improve experimental methodologies, such that they better reflect the clinical scenario and to judiciously select combinations of therapies targeting specific pathways of cellular death and injury

Multitarget Strategies to Reduce Myocardial Ischemia/Reperfusion Injury

Many treatments have been identified that confer robust cardioprotection in experimental animal models of acute ischemia and reperfusion injury. However, translation of these cardioprotective therapies into the clinical setting of acute myocardial infarction (AMI) for patient benefit has been disappointing. One important reason might be that AMI is multifactorial, causing cardiomyocyte death via multiple mechanisms, as well as affecting other cell types, including platelets, fibroblasts, endothelial and smooth muscle cells, and immune cells. Many cardioprotective strategies act through common end-effectors and may be suboptimal in patients with comorbidities. In this regard, emerging data suggest that optimal cardioprotection may require the combination of additive or synergistic multitarget therapies. This review will present an overview of the state of cardioprotection today and provide a roadmap for how we might progress towards successful clinical use of cardioprotective therapies following AMI, focusing on the rational combination of judiciously selected, multitarget therapies. This paper emerged as part of the discussions of the European Union (EU)-CARDIOPROTECTION Cooperation in Science and Technology (COST) Action, CA16225

Detection of silent myocardial ischemia in asymptomatic patients with diabetes: results of a randomized trial and meta-analysis assessing the effectiveness of systematic screening

<p>Abstract</p> <p>Background</p> <p>Most guidelines recommend a systematic screening of asymptomatic high risk patients with diabetes for silent ischemia, but the clinical benefit of this strategy has not been demonstrated compared with the simple control of cardiovascular risk factors. We sought to determine whether referring asymptomatic diabetic patients for screening of silent ischemia decreases the risk of cardiovascular events compared with usual care.</p> <p>Methods</p> <p>DYNAMIT was a prospective, randomized, open, blinded end-point multicenter trial run between 2000 and 2005, with a 3.5 year mean follow-up in ambulatory care in 45 French hospitals. The study included 631 male and female with diabetes aged 63.9 ± 5.1 years, with no evidence of coronary artery disease and at least 2 additional cardiovascular risk factors, receiving appropriate medical treatment. The patients were randomized centrally to either screening for silent ischemia using a bicycle exercise test or Dipyridamole Single Photon Emission Computed Tomography (N = 316), or follow-up without screening (N = 315). The main study end point was time to death from all causes, non-fatal myocardial infarction, non-fatal stroke, or heart failure requiring hospitalization or emergency service intervention. The results of a meta-analysis of DYNAMIT and DIAD, a similar study, are also presented.</p> <p>Results</p> <p>The study was discontinued prematurely because of difficulties in recruitment and a lower-than expected event rate. Follow-up was complete for 98.9% patients regarding mortality and for 97.5% regarding the main study end point. Silent ischemia detection procedure was positive or uncertain in 68 (21.5%) patients of the screening group. There was no significant difference between the screening and the usual care group for the main outcome (hazard ratio = 1.00 95%CI 0.59 to 1.71). The meta-analysis of these and DIAD results gave similar results, with narrower confidence intervals for each endpoint.</p> <p>Conclusions</p> <p>These results suggest that the systematic detection of silent ischemia in high-risk asymptomatic patients with diabetes is unlikely to provide any major benefit on hard outcomes in patients whose cardiovascular risk is controlled by an optimal medical treatment.</p> <p>Trial registration</p> <p>ClinicalTrials.gov: <a href="http://www.clinicaltrials.gov/ct2/show/NCT00627783">NCT00627783</a></p

Phosphomimetic Modulation of eNOS Improves Myocardial Reperfusion and Mimics Cardiac Postconditioning in Mice

Objective: Myocardial infarction resulting from ischemia-reperfusion injury can be reduced by cardiac postconditioning, in which blood flow is restored intermittently prior to full reperfusion. Although key molecular mechanisms and prosurvival pathways involved in postconditioning have been identified, a direct role for eNOS-derived NO in improving regional myocardial perfusion has not been shown. The objective of this study is to measure, with high temporal and spatial resolution, regional myocardial perfusion during ischemia-reperfusion and postconditioning, in order to determine the contribution of regional blood flow effects of NO to infarct size and protection. Methods and Results: We used myocardial contrast echocardiography to measure regional myocardial blood flow in mice over time. Reperfusion after myocardial ischemia-reperfusion injury is improved by postconditioning, as well as by phosphomimetic eNOS modulation. Knock-in mice expressing a phosphomimetic S1176D form of eNOS showed improved myocardial reperfusion and significantly reduced infarct size. eNOS knock-out mice failed to show cardioprotection from postconditioning. The size of the no-reflow zone following ischemia-reperfusion is substantially reduced by postconditioning and by the phosphomimetic eNOS mutation. Conclusions and Significance: Using myocardial contrast echocardiography, we show that temporal dynamics of regional myocardial perfusion restoration contribute to reduced infarct size after postconditioning. eNOS has direct effects on myocardial blood flow following ischemia-reperfusion, with reduction in the size of the no-reflow zone. These results have important implications for ongoing clinical trials on cardioprotection, because the degree of protective benefit may be significantly influenced by the regional hemodynamic effects of eNOS-derived NO.American Heart Association (Predoctoral Fellowship)National Institutes of Health (U.S.) (R01 NS33335)National Institutes of Health (U.S.) (R01 HL57818