Improving cardiac regeneration after injury: Are we a step closer?

During regeneration, lost functional tissue can, in general, be replaced by different mechanisms, including proliferation of terminally differentiated cells or through differentiation of resident stem cells. It is a well-accepted dogma that the mammalian heart cannot efficiently regenerate upon injury as a consequence of insufficient oxygen supply. This is in sharp contrast to the hearts of adult zebrafish or newts that are able to replace lost ventricular tissue. Novel data indicate that the young murine heart also has the ability to regenerate within the first week after birth using mechanisms apparently quite similar to those observed in fish. This now provides us with a good starting point to identify the molecular mechanisms that led to the loss of the regenerative capacity of the adult mammalian heart. These future studies will also indicate whether it will be possible to reawaken the regenerative capability of cardiomyocytes in the human heart by treatment with selected pharmaceuticals.     

MRI and PET in Mouse Models of Myocardial Infarction

Myocardial infarction is one of the leading causes of death in the Western world. The similarity of the mouse heart to the human heart has made it an ideal model for testing novel therapeutic strategies.In vivo magnetic resonance imaging (MRI) gives excellent views of the heart noninvasively with clear anatomical detail, which can be used for accurate functional assessment. Contrast agents can provide basic measures of tissue viability but these are nonspecific. Positron emission tomography (PET) is a complementary technique that is highly specific for molecular imaging, but lacks the anatomical detail of MRI. Used together, these techniques offer a sensitive, specific and quantitative tool for the assessment of the heart in disease and recovery following treatment.In this paper we explain how these methods are carried out in mouse models of acute myocardial infarction. The procedures described here were designed for the assessment of putative protective drug treatments. We used MRI to measure systolic function and infarct size with late gadolinium enhancement, and PET with fluorodeoxyglucose (FDG) to assess metabolic function in the infarcted region. The paper focuses on practical aspects such as slice planning, accurate gating, drug delivery, segmentation of images, and multimodal coregistration. The methods presented here achieve good repeatability and accuracy maintaining a high throughput.     

血清同型半胱氨酸水平对急性ST段抬高型心肌梗死PCI术后患者左心室重构、心肌灌注和预后的影响

摘要 目的：探讨血清同型半胱氨酸（Hcy）水平与急性ST段抬高型心肌梗死（STEMI）患者经皮冠状动脉介入（PCI）术后左心室重构、心肌灌注以及预后的关系。方法：选择2018年2月至2020年1月我院收治的70例STEMI患者,根据入院时血清Hcy水平分为高水平Hcy组（Hcy＞30 μmol/L,41例）和低水平Hcy组（15≤Hcy≤30 μmol/L,29例）。PCI术后1个月、6个月、12个月检测左室重量指数(LVMI)和左心室射血分数(LVEF),复查冠脉造影,评价TIMI心肌灌注分级（TMPG）。Pearson相关或Spearman秩相关性分析Hcy水平与LVMI、LVEF、TMPG分级相关性。所有患者PCI术后随访12个月,记录患者随访期间全因死亡和主要不良心脏事件（MACE）发生情况。Cox风险比例回归分析PCI术后STEMI患者预后的影响因素。结果：高水平Hcy组PCI术后6、12个月 LVEF低于低水平Hcy组（P＜0.05）,LVMI高于低水平Hcy组（P＜0.05）,高水平Hcy组PCI术后心肌灌注不良发生率高于低水平Hcy组（P＜0.05）。Hcy水平与PCI术后6、12个月 LVEF呈负相关（P＜0.05）,与LVMI呈正相关（P＜0.05）,与PCI术后TMPG分级呈负相关（P＜0.05）。高水平Hcy组随访期间全因死亡和MACE发生率均高于低水平Hcy组（P＜0.05）。Cox风险比例回归分析结果显示Hcy、术前Gensini评分是STEMI患者PCI术后预后不良的影响因素（P＜0.05）。结论：高水平Hcy与STEMI患者PCI术后左心室重构、心肌灌注有关,且Hcy是STEMI患者PCI术后发生全因死亡和MACE的影响因素。     

Inhibition of adenosine kinase attenuates myocardial ischaemia/reperfusion injury

Increased adenosine helps limit infarct size in ischaemia/reperfusion-injured hearts. In cardiomyocytes, 90% of adenosine is catalysed by adenosine kinase (ADK) and ADK inhibition leads to higher concentrations of both intracellular adenosine and extracellular adenosine. However, the role of ADK inhibition in myocardial ischaemia/reperfusion (I/R) injury remains less obvious. We explored the role of ADK inhibition in myocardial I/R injury using mouse left anterior ligation model. To inhibit ADK, the inhibitor ABT-702 was intraperitoneally injected or AAV9 (adeno-associated virus)—ADK—shRNA was introduced via tail vein injection. H9c2 cells were exposed to hypoxia/reoxygenation (H/R) to elucidate the underlying mechanisms. ADK was transiently increased after myocardial I/R injury. Pharmacological or genetic ADK inhibition reduced infarct size, improved cardiac function and prevented cell apoptosis and necroptosis in I/R-injured mouse hearts. In vitro, ADK inhibition also prevented cell apoptosis and cell necroptosis in H/R-treated H9c2 cells. Cleaved caspase-9, cleaved caspase-8, cleaved caspase-3, MLKL and the phosphorylation of MLKL and CaMKII were decreased by ADK inhibition in reperfusion-injured cardiomyocytes. X-linked inhibitor of apoptosis protein (XIAP), which is phosphorylated and stabilized via the adenosine receptors A2B and A1/Akt pathways, should play a central role in the effects of ADK inhibition on cell apoptosis and necroptosis. These data suggest that ADK plays an important role in myocardial I/R injury by regulating cell apoptosis and necroptosis.     

Exosomes derived from MSC pre-treated with oridonin alleviates myocardial IR injury by suppressing apoptosis via regulating autophagy activation

This study aimed to investigate the molecular mechanisms underlying the role of bone marrow mesenchymal stem cells (BMMSCs)-derived exosomes in ischaemia/reperfusion (IR)-induced damage, and the role of oridonin in the treatment of IR. Exosomes were isolated from BMMSCs. Western blot analysis was done to examine the expression of proteins including CD63, CD8, apoptotic-linked gene product 2 interacting protein X (AliX), Beclin-1, ATG13, B-cell lymphoma-2 (Bcl-2), apoptotic peptidase activating factor 1 (Apaf1) and Bcl2-associated X (Bax) in different treatment groups. Accordingly, the expression of CD63, CD81 and AliX was higher in BMMSCs-EXOs and IR + BMMSCs-EXOs + ORI groups compared with that in the BMMSCs group. And BMMSCs-derived exosomes inhibited the progression of IR-induced myocardial damage, while this protective effect was boosted by the pre-treatment with oridonin. Moreover, Beclin-1, ATG13 and Bcl-2 were significantly down-regulated while Apaf1 and Bax were significantly up-regulated in IR rats. And the presence of BMMSCs-derived exosomes partly alleviated IR-induced dysregulation of these proteins, while the oridonin pre-treatment boosted the effect of these BMMSCs-derived exosomes. The inhibited proliferation and promoted apoptosis of H9c2 cells induced by hypoxia/reperfusion (HR) were mitigated by the administration of BMMSCs-derived exosomes. Meanwhile, HR also induced down-regulation of Beclin-1, ATG13 and Bcl-2 expression and up-regulation of Apaf1 and Bax, which were mitigated by the administration of BMMSCs-derived exosomes. And oridonin pre-treatment boosted the effect of BMMSCs-derived exosomes. In conclusion, our results validated that BMMSCs-derived exosomes suppressed the IR-induced damages by participating in the autophagy process, while the pre-treatment with oridonin could boost the protective effect of BMMSCs-derived exosomes.     

Potential Myocardial Protection of 3,4-seco-Lupane Triterpenoids from Acanthopanax sessiliflorus Leaves

A rich of 3,4-seco-lupane triterpenoids including chiisanoside (CSS), divaroside (DVS), sessiloside-A1 (SSA) and chiisanogenin (CSG) were isolated from the ethanol extract of the leaves of Acanthopanax sessiliflorus. On the basis of previous studies, this article focused on four important components of 3,4-seco-lupane triterpenoids in Acanthopanax sessiliflorus leaves and explored their protective effects against aconitine-induced cardiomyocyte injury and their molecular mechanisms. The results showed that pretreatment with 3,4-seco-lupane triterpenoids could effectively increase cell viability, reduce CK-MB and LDH activities, reduce ROS production, maintain calcium concentration balance, and inhibit apoptosis, with divaroside having the best effect. In addition, Western blot results showed that divaroside down-regulated Cleaved caspase-3 and Bax and up-regulated Bcl-2 expression through activating the PI3 K/AKT pathway. However, the LY294002 inhibitor reversed this situation. This suggests that 3,4-seco-lupane triterpenoids may be a new hotspot for potential myocardial protective drugs research.     

Dose‐dependent actions of curcumin in experimentally induced myocardial necrosis: a biochemical,histopathological, and electron microscopic evidence

Curcumin, an active component of turmeric, is a well‐known antioxidant due to its reactive oxygen species (ROS) scavenging property. However, some in vitro studies have suggested that curcumin induces generation of ROS at higher doses and thus exerts pro‐oxidant effect. We demonstrate, for the first time, the dose‐dependent effects of curcumin in isoprenaline‐induced model of myocardial necrosis in rats. The animals were assigned to control, isoprenaline and three curcumin treatment groups. Curcumin (100, 200, and 400 mg/kg) and vehicle (dimethyl sulfoxide) were administrated orally for 15 days and isoprenaline (85 mg/kg, s.c.) was given to curcumin treated and isoprenaline group on 13th and 14th day, respectively. Thereafter, on 15th day, the animals were sacrificed for biochemical analysis along with histopathological and ultrastructural examination. There was an increase in glutathione, superoxide dismutase (SOD), creatine kinase‐MB (CK‐MB) and lactate dehydrogenase (LDH) levels, decrease in thiobarbituric acid reactive substances (TBARS), and preservation of myocardial architecture in the curcumin (100 and 200 mg/kg) treated groups. However, at 400 mg/kg dose there was ineffectual protection against isoprenaline‐induced myocardial damage. Instead, there was significant lipid peroxidation as evident by increased levels of TBARS (93.87 ± 9.93, p < 0.0001) and decrease in CK‐MB (206.32 ± 13.54, p < 0.0001) and LDH (134.26 ± 9.13, p < 0.01) as compared to the two lower doses. Hence, it can be concluded that curcumin augments endogenous antioxidant system at lower doses but mediates ROS induction at higher concentration leading to myocardial damage. Copyright © 2009 John Wiley & Sons, Ltd.     

External triggers of onset of myocardial infarction-an update

Coronary heart disease is one of the leading causes of death in both industrialised and developing countries. About two thirds of all coronary deaths occur outside the hospital and before any medical care can be reached. Therefore, the prevention of coronary events appears to be of utmost importance. Rupture of an atherosclerotic plaque and subsequent coronary thrombosis is the most common underlying pathophysiological mechanism of coronary events. External stresses or 'triggers' imposing on coronary plaques may precipitate plaque rupture. External triggers include physical activity, various emotional stresses, eating, environmental factors, and sexual activity. The increased relative risk of myocardial infarction may be induced by external triggers via the activation of internal triggering mechanisms such as biomechanical and hemodynamic stresses and changes in platelet aggregability and blood viscosity. Recent prospective studies have confirmed the results of earlier retrospective studies and have, similarly, shown the importance of external triggers in increasing the risk of myocardial infarction and other coronary events. Particularly, sedentary individuals with underlying coronary heart disease appear to be at risk when exposed to external triggers. Regular physical activity, on the other hand, is a protective factor against the increased risk associated with external triggers. However, health education needs to be provided about the risks associated with strenuous exercise in untrained individuals. Apart from lifestyle factors, pharmacological protection of the population at risk during vulnerable periods plays an important role as well. Medication such as beta-blockers and aspirin may lower the increased risk of coronary events during exposure to external triggers. Also, further research is needed with regard to psychosocial stressors and their potential role as external triggers of myocardial infarction and other coronary events.     

Myocardial Infarction and Functional Outcome Assessment in Pigs

Introduction of newly discovered cardiovascular therapeutics into first-in-man trials depends on a strictly regulated ethical and legal roadmap. One important prerequisite is a good understanding of all safety and efficacy aspects obtained in a large animal model that validly reflect the human scenario of myocardial infarction (MI). Pigs are widely used in this regard since their cardiac size, hemodynamics, and coronary anatomy are close to that of humans. Here, we present an effective protocol for using the porcine MI model using a closed-chest coronary balloon occlusion of the left anterior descending artery (LAD), followed by reperfusion. This approach is based on 90 min of myocardial ischemia, inducing large left ventricle infarction of the anterior, septal and inferoseptal walls. Furthermore, we present protocols for various measures of outcome that provide a wide range of information on the heart, such as cardiac systolic and diastolic function, hemodynamics, coronary flow velocity, microvascular resistance, and infarct size. This protocol can be easily tailored to meet study specific requirements for the validation of novel cardioregenerative biologics at different stages (i.e. directly after the acute ischemic insult, in the subacute setting or even in the chronic MI once scar formation has been completed). This model therefore provides a useful translational tool to study MI, subsequent adverse remodeling, and the potential of novel cardioregenerative agents.