Murine Model Of Acute Myocardial Infarction Research Articles

Hydrocortisone cardioprotection in ischaemia/reperfusion injury involves antioxidant mechanisms.

Glucocorticoid (GR) and mineralocorticoid (MR) receptors are highly expressed in cardiac tissue, and both can be activated by corticosteroids. MR activation, in acute myocardial infarction (AMI), worsens cardiac function, and increase NHE activity contributing to the deleterious process. In contrast, effects of GR activation are not fully understood, probably because of the controversial scenario generated by using different doses or potencies of corticosteroids. We tested the hypothesis that an acute dose of hydrocortisone (HC), a low-potency glucocorticoid, in a murine model of AMI could be cardioprotective by regulating NHE1 activity, leading to a decrease in oxidative stress. Isolated hearts from Wistar rats were subjected to regional ischemic protocol. HC (10 nmol/L) was added to the perfusate during early reperfusion. Infarct size and oxidative stress were determined. Isolated papillary muscles from non-infarcted hearts were used to evaluate HC effect on sodium-proton exchanger 1 (NHE1) by analysing intracellular pH recovery from acute transient acidosis. HC treatment decreased infarct size, improved cardiac mechanics, reduced oxidative stress after AMI, while restoring the decreased level of the pro-fusion mitochondrial protein MFN-2. Co-treatment with the GR-blocker Mifepristone avoided these effects. HC reduced NHE1 activity by increasing the NHE1 pro-inhibiting Ser648 phosphorylation site and its upstream kinase AKT. HC restored the decreased AKT phosphorylation and anti-apoptotic BCL-2 protein expression detected after AMI. Our results provide the first evidence that acute HC treatment during early reperfusion induces cardioprotection against AMI, associated with a non-genomic HC-triggered NHE1 inhibition by AKT and antioxidant action that might involves mitochondrial dynamics improvement.

Rapid custom prototyping of soft poroelastic biosensor for simultaneous epicardial recording and imaging

The growing need for the implementation of stretchable biosensors in the body has driven rapid prototyping schemes through the direct ink writing of multidimensional functional architectures. Recent approaches employ biocompatible inks that are dispensable through an automated nozzle injection system. However, their application in medical practices remains challenged in reliable recording due to their viscoelastic nature that yields mechanical and electrical hysteresis under periodic large strains. Herein, we report sponge-like poroelastic silicone composites adaptable for high-precision direct writing of custom-designed stretchable biosensors, which are soft and insensitive to strains. Their unique structural properties yield a robust coupling to living tissues, enabling high-fidelity recording of spatiotemporal electrophysiological activity and real-time ultrasound imaging for visual feedback. In vivo evaluations of custom-fit biosensors in a murine acute myocardial infarction model demonstrate a potential clinical utility in the simultaneous intraoperative recording and imaging on the epicardium, which may guide definitive surgical treatments.

Abstract 17388: Loss of Bone Morphogenetic Protein 9 (BMP9) Limits Survival and Paradoxically Increases Collagen Abundance, but Limits Collagen Cross-Linking in a Murine Model of Acute Myocardial Infarction

Myocardial infarction (MI) is a major cause of heart failure (HF). HF is associated with adverse cardiac remodeling that is primarily driven by Transforming growth factor beta (TGFb1) mediated fibrosis and myocyte hypertrophy. We previously reported that loss of bone morphogenetic protein 9 (BMP9) promotes cardiac fibrosis in pressure-overload induced HF. No studies have explored a role for BMP9 in post MI cardiac remodeling. We hypothesize that loss of BMP9 may promote cardiac healing by stabilizing LV scar formation. To test this hypothesis, we subjected whole body BMP9 knockout (-/-) mice to left coronary artery ligation for two weeks followed by PV loop analysis and studied indices of cardiac remodeling. Compared to wild type (WT) controls BMP9-/- mice had significantly lower survival (83% vs 61%, p<0.001, respectively) with a higher rate of cardiac rupture(15% vs 90%). Compared to WT controls, surviving BMP9-/- mice had higher LVEDP, reduced LV dP/dt, and higher lung weight. Compared to WT mice, BMP9-/- mice had significantly higher levels of Type I collagen (2 fold p<0.05). Compared to WT mice, BMP9-/- mice had increased matrix metalloproteinases (MMP)-2 and MMP-9 (2.5 fold p<0.05) activity levels in the LV. Treatment of cultured primary human cardiac fibroblasts with recombinant BMP9 attenuated TGFb1-mediated Type I collagen and MMP-9 protein expression. To assess collagen content and cross-linking, two-photon excitation fluorescence imaging was performed and identified an increase in collagen abundance, but a trend towards lower collagen cross-linking in the LV of BMP9-/- mice compared to WT mice 2 weeks after MI. Our central finding is that loss of BMP9 is associated with reduced survival, increased propensity towards cardiac rupture, and increased LV collagen abundance, but reduced collagen integrity in a murine model of acute MI. These identify a potentially important functional role for BMP9 in post-infarct cardiac remodeling.

Transplantation of telomerase/myocardin-co-expressing mesenchymal cells in the mouse promotes myocardial revascularization and tissue repair

Cell therapies are hampered by poor survival and growth of grafts. We tested whether forced co-expression of telomerase reverse transcriptase (TERT) and myocardin (MYOCD) improves post-infarct revascularization and tissue repair by adipose tissue-derived mesenchymal stromal cells (AT-MSCs). We transplanted AT-MSCs overexpressing MYOCD and TERT in a murine model of acute myocardial infarction (AMI). We characterized paracrine effects of AT-MSCs. When transplanted into infarcted hearts of C57BL/6 mice, AT-MSCs overexpressing TERT and MYOCD decreased scar tissue and the intra-scar CD3 and B220 lymphocyte infiltration; and increased arteriolar density as well as ejection fraction compared with saline or mock-transduced AT-MSCs. These effects were accompanied by higher persistence of the injected cells in the heart, increased numbers of Ki-67+ and CD117+ cells, and the expression of cardiac actin and β-myosin heavy chain. Intramyocardial delivery of the secretome and its extracellular vesicle (EV)-enriched fraction also decreased scar tissue formation and increased arteriolar density in the murine AMI model. Proteomic analysis of AT-MSCs-EV-enriched fraction predicted the activation of vascular development and the inhibition of immune cell trafficking. Elevated concentrations of miR-320a, miR-150-5p and miR-126-3p associated with regulation of apoptosis and vasculogenesis were confirmed in the AT-MSCs-EV-enriched fraction. AT-MSCs overexpressing TERT and MYOCD promote persistence of transplanted aged AT-MSCs and enhance arteriolar density in a murine model of AMI. EV-enriched fraction is the component of the paracrine secretion by AT-MSCs with pro-angiogenic and anti-fibrotic activities.

MiR-134-5p inhibition reduces infarct-induced cardiomyocyte apoptosis via Creb1 upregulation

Following the recent discovery that microRNA-134-5p (miR-134-5p) is elevated in the early stages of acute myocardial infarction (AMI), we examined the specific role of miR-134-5p in cardiomyocytes during AMI. To study miR-134-5p's role in the context of AMI, we used a combination of in vitro experiments in H2O2-treated or hypoxic cardiomyocyte cell cultures as well as in vivo experiments in a murine model of AMI. H2O2- and hypoxia-induced cardiomyocyte injury upregulated miR-134-5p expression. miR-134-5p overexpression increased cardiomyocyte apoptosis, whereas miR-134-5p inhibition reduced cardiomyocyte apoptosis. We discovered that the transcription factor cAMP-responsive element binding protein 1 (Creb1) is a functional target of miR-134-5p responsible for regulating cardiomyocyte apoptosis. In vivo AMI resulted in the upregulation and downregulation of miR-134-5p and Creb1 in the infarct area, respectively. Circulating miR-134-5p levels were also increased at days 1 and 2 post-AMI. Modulation of myocardial miR-124-5p expression by intramyocardial injection of antagomiR-134-5p or agomiR-134-5p significantly affected cardiomyocyte apoptosis, infarct size, and cardiac function in vivo. miR-134-5p/Creb1 axis dysregulation plays a role in hypoxia- or oxidative stress-induced cardiomyocyte apoptosis as well as AMI. Circulating miR-134-5p may show promise as a biomarker for AMI or post-AMI cardiac dysfunction. Manipulating the miR-134-5p/Creb1 axis through either inhibition of miR-134-5p or overexpression of Creb1 may show promise as a novel therapeutic strategy to attenuate cardiac dysfunction following AMI.

P2572Human iPSC-derived cardiomyocytes preserve murine heart function after myocardial infarction unlike adipose tissue-derived stromal cells

Abstract Introduction Despite progress in pharmacological treatment of myocardial infarction (MI), there is still an immense need for novel therapies for this life-threatening condition. Accordingly, cell-based therapies have been extensively investigated with most studies focusing on mesenchymal stromal cells. However due to their inability to differentiate into cardiomyocytes as well as limited survival upon in vivo administration, no effective treatment of MI has been developed. In contrast, application of hiPSC-derived cardiomyocytes (hiPSC-CM) represent biologically rational approach with pre-clinical studies confirming their therapeutic potential in various models of MI. However further optimization is required due to limited survival of hiPSC-CM upon in vivo administration. Therefore, we evaluated the therapeutic potential of genetically modified hiPSC-CM in murine model of acute MI and compared it to the effect of adipose tissue-derived stromal cells (ADSC). Methods In the first step hiPSC overexpressing GFP, luciferase (Luc) and pro-angiogenic and cardioprotective factors: heme oxygenase-1 (HO-1, heme degrading enzyme) or stromal cell-derived factor-1 (SDF-1, pro-angiogenic chemokine) were subjected to cardiac differentiation which yielded in each group 70–90% cardiac troponin T-positive contracting cells. hiPSC-CM (5x105 in 10 μl) were administered into NOD-SCID mice which underwent permanent ligation of left anterior descending (LAD) coronary artery. The cells were injected into the peri-infarct zone. Mice subjected to sham operation as well as injected with saline after MI were used as controls. The ultrasonography of hearts was performed on day 7, 14, 28 and 42 whereas the presence of hiPSC-CM was monitored using IVIS Spectrum system upon administration of luciferin and analysed in sections of collected hearts. The same experimental scheme was used to assess therapeutic potential of ADSC (CD105+CD73+CD90+CD44+CD146-CD34-) overexpressing luciferase and GFP. Results Ultrasonography demonstrated that upon delivery of hiPSC-CM the left ventricle ejection fraction (LVEF) was very significantly higher in comparison to control group injected with saline after induction of MI. In contrast, no improvement of LVEF was observed after administration of ADSC. Interestingly, measurements of luciferase activity revealed the strongest bioluminescent signal in the hearts of mice transplanted with iPSC-CM-HO1 42 days after MI. Importantly, the survival of hiPSC-CM in murine myocardium six weeks upon administration was further confirmed with immunofluorescent analysis of heart sections using human specific anti-Ku80 antibody. Again, luciferase activity was not observed upon delivery of ADSC. Conclusion These results strongly indicate that administration of hiPSC-CM, unlike ADSC, preserve murine heart function in acute MI model. Additionally, overexpression of HO-1 may positively influence their survival upon in vivo delivery into infarcted tissue. Acknowledgement/Funding The National Centre for Research and Development (STRATEGMED 2/269415/11/NCBR/2015), National Science Centre of Poland (HARMONIA 2014/14/M/NZ1/00010)

Abstract 792: Core Cell Survival Requirements of Hypoxia Inducible Factors in Macrophages Dominate Isoform-Specific Function during Cardiac Repair

Objective: Hypoxia inducible factors (HIF) regulate the adaptive response to ischemic injury and enhancement of HIF levels has been proposed as a therapeutic target to improve tissue repair after acute myocardial infarction (MI). HIFs also regulate the inflammatory function of macrophages, the main protagonists of tissue repair after MI, but it is unknown whether changes in macrophage HIF levels will affect outcomes after MI. Using a murine model of acute MI and conditional knockouts, we investigated a role for macrophage HIFs in tissue repair after MI. Methods and Results: In mice subjected to permanent occlusion MI, we observed an accumulation of hypoxic cardiac macrophages and sequential stabilization of HIF-2α followed by HIF-1α, which persisted into the development of heart failure. In patients with ischemic cardiomyopathy, flow cytometry and single-cell transcriptomics revealed a parallel stabilization of HIFs and hypoxia signaling in cardiac macrophages. Since HIFs were stabilized early after MI in cardiac macrophages, we selectively targeted macrophage HIFs using conditional knockouts. Selective deletion of macrophage HIF-2α promoted cardiac macrophage production of IL-10, activating fibroblasts and stimulating collagen deposition, culminating in improved ventricular remodeling and preservation of systolic function. Similarly, selective deletion of macrophage HIF-1α improved cardiac repair; however, this was mechanistically distinct from HIF-2α, inhibiting HIF-1α-dependent proteolytic destruction of MerTK and leading to improved efferocytosis by cardiac macrophages. Contrary to our expectations, loss of both HIF-1α and HIF-2α in hypoxic macrophages enhanced mitochondrial reactive oxygen species and activated necroptosis, leading to increased cell death and cardiac rupture after acute MI. Inhibition of necroptosis with necrostatin-1 attenuated hypoxic macrophage cell death and significantly improved survival after acute MI. Conclusions: These data imply strategies that broadly enhance or inhibit HIFs will lead to catastrophic outcomes after MI, while selective inhibition of macrophage HIF-1α or HIF-2α may enhance tissue repair, preserve systolic function, and limit progression to heart failure.

Regenerative Cardiovascular Therapies: Stem Cells and Beyond.

Although reperfusion therapy has improved outcomes, acute myocardial infarction (AMI) is still associated with both significant mortality and morbidity. Once irreversible myocardial cell death due to ischemia and reperfusion sets in, scarring leads to reduction in left ventricular function and subsequent heart failure. Regenerative cardiovascular medicine experienced a boost in the early 2000s when regenerative effects of bone marrow stem cells in a murine model of AMI were described. Translation from an animal model to stem cell application in a clinical setting was rapid and the first large trials in humans suffering from AMI were conducted. However, high initial hopes were early shattered by inconsistent results of randomized clinical trials in patients suffering from AMI treated with stem cells. Hence, we provide an overview of both basic science and clinical trials carried out in regenerative cardiovascular therapies. Possible pitfalls in specific cell processing techniques and trial design are discussed as these factors influence both basic science and clinical outcomes. We address possible solutions. Alternative mechanisms and explanations for effects seen in both basic science and some clinical trials are discussed here, with special emphasis on paracrine mechanisms via growth factors, exosomes, and microRNAs. Based on these findings, we propose an outlook in which stem cell therapy, or therapeutic effects associated with stem cell therapy, such as paracrine mechanisms, might play an important role in the future. Optimizing stem cell processing and a better understanding of paracrine signaling as well as its effect on cardioprotection and remodeling after AMI might improve not only AMI research, but also our patients’ outcomes.

Cyclic helix B peptide ameliorates acute myocardial infarction in mice by inhibiting apoptosis and inflammatory responses

Cyclic helix B peptide (CHBP) is a peptide derivant of erythropoietin with powerful tissue-protective efficacies in a variety of organ injuries, but without erythropoietic effect. However, the role of CHBP in acute myocardial infarction (AMI) and related mechanisms are not studied yet. In this study, we found in a murine AMI model that the administration of CHBP could ameliorate cardiac injury, increase the survival rate, inhibit cardiomyocyte apoptosis, improve cardiac function and remodeling, and reduce the expression of inflammatory cytokines in the serum and kidney tissue both at 24 h and 8 weeks following AMI. This study suggests that CHBP has the potential to be used as an effective drug in the treatment of AMI.

Inhibition of MicroRNA-9-5p Protects Against Cardiac Remodeling Following Myocardial Infarction in Mice.

Follistatin-like 1 (Fstl1) protects cardiomyocytes from a broad spectrum of pathologic injuries including myocardial infarction (MI). It is worthy of note that although cardiac Fstl1 is elevated in post-MI microenvironment, its cardioprotective role is still restricted to a limited extent considering the frequency and severity of adverse cardiac remodeling following MI. We therefore propose that intrinsic Fstl1-suppressing microRNA (miRNA) may exist in the heart and its neutralization may further facilitate post-MI recovery. Here, miR-9-5p is predicted as one of the potential Fstl1-targeting miRNAs whose expression is decreased in ischemic myocardium and reversely correlated with Fstl1. Luciferase activity assay further validated Fstl1 as a direct target of miR-9-5p. In addition, forced expression of miR-9-5p in H9c2 cells is concurrent with diminished expression of Fstl1 and vice versa. Importantly, transfection of miR-9-5p mimics in hypoxic H9c2 cells exacerbates cardiac cell death, lactate dehydrogenase release, reactive oxygen species accumulation, and malonyldialdehyde concentration. More importantly, in vivo silencing of miR-9-5p by a specific antagomir in a murine acute MI model effectively preserves post-MI heart function with attenuated fibrosis and inflammatory response. Further studies demonstrated that antagomir treatment stabilizes Fstl1 expression as well as blocks cardiac cell death and reactive oxygen species generation in both ischemia-challenged hearts and hypoxia-treated cardiomyoblasts. Finally, cytoprotection against hypoxic challenge by miR-9-5p inhibitor is partially reversed by knockdown of Fstl1, indicating a novel role of miR-9-5p/Fstl1 axis in survival defense against hypoxic challenge. In summary, these findings identified miR-9-5p as a mediator of hypoxic injury in cardiomyoblasts and miR-9-5p suppression prevents cardiac remodeling after acute MI, providing a potential strategy for early treatment against MI.

Formyl Peptide Receptor 2 Is Involved in Cardiac Repair After Myocardial Infarction Through Mobilization of Circulating Angiogenic Cells.

Increasing evidence suggests that circulating angiogenic cells (CACs) promote repair of ischemic tissues. Activation of formyl peptide receptor 2 (Fpr2) has been reported to stimulate repair of ischemic heart. This study was conducted to investigate the role of Fpr2 on CAC mobilization and cardiac protection in myocardial infarction (MI). WKYMVm, a strong agonist for Fpr2, was administered in a murine model of acute MI, and mobilization of CACs including endothelial progenitor cells (CD34+ Flk1+ or Sca1+ Flk1+ cells) in peripheral blood was monitored. CAC mobilization by daily injection of WKYMVm for the first 4 days after MI was as efficient as granulocyte colony-stimulating factor and provided myocardial protection from apoptosis with increased vascular density and preservation of cardiac function. Transplantation of bone marrow (BM) from green fluorescent protein mice showed that BM-derived cells homed to ischemic heart after WKYMVm treatment and contributed to tissue protection. Transplantation of BM from Fpr2 knockout mice showed that Fpr2 in BM cells is critical in mediation of WKYMVm-stimulated myocardial protection and neovascularization after MI. These results suggest that activation of Fpr2 in BM after WKYMVm treatment provides cardiac protection through mobilization of CACs after MI, which may lead to the development of a new clinical protocol for treating patients with ischemic heart conditions. Stem Cells 2017;35:654-665.

HMGB1 Inhibits Apoptosis Following MI and Induces Autophagy via mTORC1 Inhibition.

Exogenous High Mobility Group Box-1 protein (HMGB1) has been reported to protect the infarcted heart but the underlying mechanism is quite complex. In particular, its effect on ischemic cardiomyocytes has been poorly investigated. Aim of the present study was to verify whether and how autophagy and apoptosis were involved in HMGB1-induced heart repair following myocardial infarction (MI). HMGB1 (200 ng) or denatured HMGB1 were injected in the peri-infarcted region of mouse hearts following acute MI. Three days after treatment, an upregulation of autophagy was detected in infarcted HMGB1 treated hearts compared to controls. Specifically, HMGB1 induced autophagy by significantly upregulating the protein expression of LC3, Beclin-1, and Atg7 in the border zone. To gain further insights into the molecular mechanism of HMGB1-mediated autophagy, WB analysis were performed in cardiomyocytes isolated from 3 days infarcted hearts in the presence and in the absence of HMGB1 treatment. Results showed that upregulation of autophagy by HMGB1 treatment was potentially related to activation of AMP-activated protein kinase (AMPK) and inhibition of the mammalian target of rapamycin complex 1 (mTORC1). Accordingly, in these hearts, phospho-Akt signaling pathway was inhibited. The induction of autophagy was accompanied by reduced cardiomyocyte apoptotic rate and decreased expression levels of Bax/Bcl-2 and active caspase-3 in the border zone of 3 days infarcted mice following HMGB1 treatment. We report the first in vivo evidence that HMGB1 treatment in a murine model of acute MI might induce cardiomyocyte survival through attenuation of apoptosis and AMP-activated protein kinase-dependent autophagy. J. Cell. Physiol. 232: 1135-1143, 2017. © 2016 Wiley Periodicals, Inc.

Tissue Engineering and Repair of the Damaged Heart490Transplantation of adipose mesenchymal cells overexpressing telomerase and myocardin preserved cardiac function and promoted tissue repair in murine myocardial infarction491Targeting the hippo signalling pathway to enhance the therapeutic potential of iPS-derived cardiomyocytes492Porous silicon nanoneedles for localised in situ gene transfer for cardiac therapy

Tissue Engineering and Repair of the Damaged Heart490Transplantation of adipose mesenchymal cells overexpressing telomerase and myocardin preserved cardiac function and promoted tissue repair in murine myocardial infarction491Targeting the hippo signalling pathway to enhance the therapeutic potential of iPS-derived cardiomyocytes492Porous silicon nanoneedles for localised in situ gene transfer for cardiac therapy

Thymosin-β4 prevents cardiac rupture and improves cardiac function in mice with myocardial infarction.

Thymosin-β4 (Tβ4) promotes cell survival, angiogenesis, and tissue regeneration and reduces inflammation. Cardiac rupture after myocardial infarction (MI) is mainly the consequence of excessive regional inflammation, whereas cardiac dysfunction after MI results from a massive cardiomyocyte loss and cardiac fibrosis. It is possible that Tβ4 reduces the incidence of cardiac rupture post-MI via anti-inflammatory actions and that it decreases adverse cardiac remodeling and improves cardiac function by promoting cardiac cell survival and cardiac repair. C57BL/6 mice were subjected to MI and treated with either vehicle or Tβ4 (1.6 mg·kg(-1)·day(-1) ip via osmotic minipump) for 7 days or 5 wk. Mice were assessed for 1) cardiac remodeling and function by echocardiography; 2) inflammatory cell infiltration, capillary density, myocyte apoptosis, and interstitial collagen fraction histopathologically; 3) gelatinolytic activity by in situ zymography; and 4) expression of ICAM-1 and p53 by immunoblot analysis. Tβ4 reduced cardiac rupture that was associated with a decrease in the numbers of infiltrating inflammatory cells and apoptotic myocytes, a decrease in gelatinolytic activity and ICAM-1 and p53 expression, and an increase in the numbers of CD31-positive cells. Five-week treatment with Tβ4 ameliorated left ventricular dilation, improved cardiac function, markedly reduced interstitial collagen fraction, and increased capillary density. In a murine model of acute MI, Tβ4 not only decreased mortality rate as a result of cardiac rupture but also significantly improved cardiac function after MI. Thus, the use of Tβ4 could be explored as an alternative therapy in preventing cardiac rupture and restoring cardiac function in patients with MI.

CPP-conjugated Anti-apoptotic Peptides as Therapeutic Tools of Ischemiareperfusion Injuries

Acute myocardial infarction (AMI) is a frequent and disabling disease, which is the first cause of cardiovascular mortality worldwide. Infarct size is a major determinant of myocardial functional recovery and mortality after AMI. Limitation of infarct size thus appears as an appropriate strategy to prevent post-ischemic heart failure and improve survival. Reperfusion is the only treatment recommended to reduce infarct size but despite obvious benefits, it may also have deleterious effects called ischemia-reperfusion (IR) injury including myocyte cell death. Proteins involved in the apoptosis cascade generally interact over large surfaces lacking well-defined pockets. Therefore, inhibitory peptides are optimal biomolecules to target these large protein surfaces, they are often more selective to their target than conventional small organic molecules, and they can be tailored for optimal affinity or desired metabolic property. Since peptides do not cross freely biological membranes, they are generally administered in association with cell penetrating peptides (CPPs) and with homing peptides (HPs) for selective organs or tissues targeting. As a first approach in vivo, we made use of the already known BH4 peptidic inhibitor of the mitochondrial apoptotic pathway, which showed cardioprotective properties in a murine model of AMI after a single bolus of intravenous administration. More importantly, similar peptidic strategies and tools are likely to be adaptable to many other situations in which cells have to be protected from apoptosis such as stroke or organ transplantation.

Wnt signalling: a mediator of the heart-bone marrow axis after myocardial injury?

Wnt signalling: a mediator of the heart-bone marrow axis after myocardial injury?

Emodin-mediated protection from acute myocardial infarction via inhibition of inflammation and apoptosis in local ischemic myocardium

Acute myocardial infarction (AMI) is associated with inflammation and apoptosis. Emodin plays an anti-inflammatory role in several inflammatory diseases. Recent studies have demonstrated that emodin protects against myocardial ischemia/reperfusion injury. However, its mechanism underlying its effects remains unknown. In a murine model of AMI, based on ligation of the left coronary artery, administration of emodin reduced myocardial infarct size (MIS) in a dose-dependent manner. Emodin significantly suppressed TNF-alpha expression and NF-kappaB activation in the local myocardial infarction area. Treatment with emodin inhibited myocardial cell apoptosis by inhibiting caspase-3 activation. Therefore, these studies demonstrate that emodin protects against myocardial cell injury via suppression of local inflammation and apoptosis.

Quantitative assessment of infarct size in vivo by myocardial contrast echocardiography in a murine acute myocardial infarction model

In vivo measurement of the infarct size in a small animal model is still challenging. The purpose of this study was to evaluate the feasibility of quantitative assessment of infarct size by myocardial contrast echocardiography (MCE) in the acute myocardial infarction (AMI) model of the rat. In 32 Sprague-Dawley rats with AMI, we measured total myocardial area (TMA) and infarct area (IA) of the rats by MCE study (MCE method). They were compared with those of postmortem heart measured by planimetry after histochemical staining with triphenyl tetrazolium chloride solution (TTC method). Simple TTC staining was done in 13 rats (Group 1). To reduce the postmortem change, continuous aortic and left ventricular (LV) pressure was loaded during TTC staining in 19 rats (Group 2). The TMA, IA, and IA/TMA ratio measured by the MCE method were 38.4+/-3.4 mm2, 18.3+/-0.8 mm2, and 0.37+/-0.02 in Group 1, and 43.7+/-1.8 mm2, 15.8+/-1.1 mm2, and 0.37+/-0.02 Group 2, respectively. Those measured by the TTC method were 66.1+/-2.2 mm2, 29.3+/-1.1 mm2, and 0.44+/-0.01 in Group 1, and 65.9+/-2.5 mm2, 26.5+/-1.7 mm2, and 0.40+/-0.02 in Group 2, and 65.9+/-2.5 mm2, 26.5+/-1.7 mm2, and 0.44+/-0.02 in Group 2, respectively. Compared with the TTC method, the MCE method underestimated the TMA and IA in both groups (p<0.001). There was no difference in TMA and IA between the two groups in both methods. IA/TMA ratio showed significant correlation between the two methods in both groups (r=0.85, p<0.001). The IA/TMA ratio measured by the MCE method may be useful for in vivo estimation of the myocardial infarct size in the AMI model of the rat.