Porcine Acute Myocardial Infarction Research Articles

The effect of distal coronary embolization on infarct size in a porcine acute myocardial infarction model

Background Reperfusion no-reflow (R-NR), characterized by TIMI 0/1 flow grade, is a phenomenon that occurs in up to 20% of percutaneous coronary intervention cases for acute myocardial infarction (AMI). R-NR involves reduced myocardial tissue perfusion in the presence of a reperfused and patent epicardial coronary artery. This phenomenon is associated with worse patient outcome and increased mortality. Potential contributing factors of R-NR include the initial ischemic insult, injury as a result of reperfusion, and possibly distal coronary embolization (DCE) of thrombotic material. The objective of this study was to develop a novel large animal model to investigate the effects of DCE in the setting of ischemia-reperfusion using microthrombi derived from autologous porcine blood. Methods 3.0 T CMR was performed on 25-30kg female Yorkshire pigs to determine baseline values of cardiac function, as well as the myocardial perfusion territory at risk using direct intracoronary injection of dilute GadoliniumDTPA. Pigs were then subjected to balloon occlusion mediated myocardial ischemia distal to the second diagonal branch of the left anterior descending coronary artery (LAD) for 60 minutes. Following reperfusion, intracoronary injection of sterile saline (n=4) or microthrombi particles to simulate DCE (n=7) was performed. Epicardial coronary blood flow was assessed at each stage using x-ray angiography. At 72 hours following ischemia-reperfusion, CMR was used to assess changes in cardiac function, extent of edema/hemorrhage using T2/T2* relaxation times, evaluate infarct size, and to determine the presence/absence of microvascular obstruction (MVO). Myocardial tissue samples were subsequently collected for biochemical and histological analysis.

INTRAMYOCARDIAL INJECTION OF INDUCED PLURIPOTENT STEM CELLS IMPROVES LEFT VENTRICULAR FUNCTION AND PERFUSION: A PRECLINICAL STUDY IN A PORCINE MODEL OF ACUTE MYOCARDIAL INFARCTION

ObjectivesInduced pluripotent stem (iPS) cells, a novel embryonic stem cell-like pluripotent stem cell, have potential to differentiate into different cardiovascular cells and repair the injured heart. The potential therapeutic benefits...

Secretome of apoptotic peripheral blood cells (APOSEC) attenuates microvascular obstruction in a porcine closed chest reperfused acute myocardial infarction model: role of platelet aggregation and vasodilation

Although epicardial blood flow can be restored by an early intervention in most cases, a lack of adequate reperfusion at the microvascular level is often a limiting prognostic factor of acute myocardial infarction (AMI). Our group has recently found that paracrine factors secreted from apoptotic peripheral blood mononuclear cells (APOSEC) attenuate the extent of myocardial injury. The aim of this study was to determine the influence of APOSEC on microvascular obstruction (MVO) in a porcine AMI model. A single dose of APOSEC was intravenously injected in a closed chest reperfused infarction model. MVO was determined by magnetic resonance imaging and cardiac catheterization. Role of platelet function and vasodilation were monitored by means of ELISA, flow cytometry, aggregometry, western blot and myographic experiments in vitro and in vivo. Treatment of AMI with APOSEC resulted in a significant reduction of MVO. Platelet activation markers were reduced in plasma samples obtained during AMI, suggesting an anti-aggregatory capacity of APOSEC. This finding was confirmed by in vitro tests showing that activation and aggregation of both porcine and human platelets were significantly impaired by co-incubation with APOSEC, paralleled by vasodilator-stimulated phosphoprotein (VASP)-mediated inhibition of platelets. In addition, APOSEC evidenced a significant vasodilatory capacity on coronary arteries via p-eNOS and iNOS activation. Our data give first evidence that APOSEC reduces the extent of MVO during AMI, and suggest that modulation of platelet activation and vasodilation in the initial phase after myocardial infarction contributes to the improved long-term outcome in APOSEC treated animals.Electronic supplementary materialThe online version of this article (doi:10.1007/s00395-012-0292-2) contains supplementary material, which is available to authorized users.

A novel methodology of balloon plus micro-embolis on porcine acute myocardial infarction model

ObjectiveTo develop and establish an alternative acute myocardial infarction porcine model which is much safer, faster and more convenient than routine methods. Compare performance between two modified methods for establishing...

Determination of the myocardial area at risk with pre- versus post-reperfusion imaging techniques in the pig model

The purpose of this study was to compare the accuracy of post-reperfusion cardiac magnetic resonance (CMR) and pre-reperfusion multidetector computed tomography (MDCT) imaging to measure the size of the area at risk (AAR), using pathology as a reference technique in a porcine acute myocardial infarction model. Fifteen pigs underwent balloon-induced coronary artery occlusion for 40 min followed by reperfusion. The AAR was assessed with arterial enhanced MDCT performed during occlusion, while two different T2 weighted (T2W) CMR imaging sequences and the contrast-enhanced (ce-) CMR endocardial surface length (ESL) were performed after 90 min of reperfusion. Animals were euthanized and the AAR was assessed by pathology. Additional measurements of the myocardial water content in the AAR, remote and the AAR border zones were performed. AAR by pathology best correlated with measurements made by MDCT (R(2) = 0.88; p < 0.001) with little bias on Bland-Altman plots (bias 2.5%, SD 6.1% LV area). AAR measurements obtained by T2W STIR, T2W ACUTE sequences or the ESL on ce-CMR showed a fair correlation with pathology (R(2) = 0.72, R(2) = 0.65 and R(2) = 0.69, respectively; all p ≤ 0.001), but significantly overestimated the size of the AAR with important bias (17.4 ± 10.8% LV area; 11.7 ± 11.0% LV area; 13.0 ± 10.3% LV area, respectively). The myocardial water content in the AAR border zones was significantly higher than the remote (82.8 vs. 78.8%; p < 0.001). Our data suggest that post-reperfusion imaging methods overestimated the AAR likely due to the presence of edema outside of the boundaries of the AAR. Pre-reperfusion arterial enhanced MDCT showed the greatest accuracy for the assessment of the AAR.

Early Erythropoietin Therapy Attenuates Remodeling and Preserves Function of Left Ventricle in Porcine Myocardial Infarction

Erythropoietin (EPO) has been shown to have anti-inflammatory, antiapoptotic, and proangiogenic effects. This study investigated whether early EPO treatment effectively preserves left ventricular (LV) function in porcine acute myocardial infarction...

Cell distribution after intracoronary bone marrow stem cell delivery in damaged and undamaged myocardium: implications for clinical trials

IntroductionEarly randomized clinical trials of autologous bone marrow cardiac stem cell therapy have reported contradictory results highlighting the need for a better evaluation of protocol designs. This study was designed to quantify and compare whole body and heart cell distribution after intracoronary or peripheral intravenous injection of autologous bone marrow mononuclear cells in a porcine acute myocardial infarction model with late reperfusion.MethodsMyocardial infarction was induced using balloon inflation in the left coronary artery in domestic pigs. At seven days post-myocardial infarction, 1 × 10(8) autologous bone marrow mononuclear cells were labeled with fluorescent marker and/or 99mTc radiotracer, and delivered using intracoronary or peripheral intravenous injection (leg vein).ResultsScintigraphic analyses and Υ-emission radioactivity counting of harvested organs showed a significant cell fraction retained within the heart after intracoronary injection (6 ± 1.7% of injected radioactivity at 24 hours), whereas following peripheral intravenous cell injection, no cardiac homing was observed at 24 hours and cells were mainly detected within the lungs. Importantly, no difference was observed in the percentage of retained cells within the myocardium in the presence or absence of myocardial infarction. Histological evaluation did not show arterial occlusion in both animal groups and confirmed the presence of bone marrow mononuclear cells within the injected myocardium area.ConclusionsIntravenous bone marrow mononuclear cell injection was ineffective to target myocardium. Myocardial cell distribution following intracoronary injection did not depend on myocardial infarction presence, a factor that could be useful for cardiac cell therapy in patients with chronic heart failure of non-ischemic origin or with ischemic myocardium without myocardial infarction.

Progenitor Cell Therapy in a Porcine Acute Myocardial Infarction Model Induces Cardiac Hypertrophy, Mediated by Paracrine Secretion of Cardiotrophic Factors Including TGFβ1

Administration of endothelial progenitor cells (EPC) is a promising therapy for post-infarction cardiac repair. However, the mechanisms that underlie apparent beneficial effects on myocardial remodeling are unclear. In a porcine model of acute myocardial infarction, we investigated the therapeutic effects of a mixed population of culture modified peripheral blood mononuclear cells (termed hereafter porcine EPC). Porcine EPC were isolated using methods identical to those previously adopted for harvest of EPC in human cell therapy studies. In addition the therapeutic effects of paracrine factors secreted by these cells was evaluated in vitro and in vivo. Intracoronary injection of autologous porcine EPC was associated with increased infarct territory mass and improved regional ventricular systolic function at 2 months compared to control. Treatment with conditioned media derived from autologous EPC was associated with similar improved effects on infarct territory mass and function. Histologic analysis of the infarct territory revealed significantly increased cardiomyocyte size in EPC and conditioned media treated groups, when compared to controls. A paracrine EPC effect was also verified in a pure myocardial preparation in which cardiomyocytes devoid of fibroblast, neuronal and vascular elements directly responded by increasing cell mass when exposed to the same conditioned media. Analysis of conditioned media revealed elevated levels of TGFbeta1 (human 267.3+/-11.8 pg/ml, porcine 57.1+/-6.1 pg/ml), a recognized mediator of hypertrophic signaling in the heart. Neutralizing antibodies to TGFbeta1 attenuated the pro-hypertrophic effect of conditioned media, and use of recombinant TGFbeta1 added to fresh media replicated the pro-hypertrophic effects of conditioned media in vitro. These data demonstrate the potential of paracrine factors secreted from endothelial progenitor cells to induce cardiomyocyte hypertrophy contributing to increased infarct territory LV mass, with favorable medium term effects on regional function following myocardial infarction.

Preserved coronary endothelial function by inhibition of δ protein kinase C in a porcine acute myocardial infarction model

Background Previous studies demonstrate impairment of endothelial-dependent vasodilation after ischemia/reperfusion (I/R). Though we have demonstrated that inhibition of δ protein kinase C (δPKC) at reperfusion reduces myocyte damage and improves cardiac function in a porcine acute myocardial infarction (AMI) model, impact of the selective δPKC inhibitor on epicardial coronary endothelial function remains unknown. Methods Either δPKC inhibitor (δV1-1, n = 5) or saline ( n = 5) was infused into the left anterior descending artery at the last 1 min of the 30-min ischemia by balloon occlusion. In vivo responses to bradykinin (endothelium-dependent vasodilator) or nitroglycerin (endothelium-independent vasodilator) were analyzed at 24 h after I/R using intravascular ultrasound. Vascular responses were calculated as the ratio of vessel area at each time point (30, 60, 90 and 120 s after the infusion), divided by values at baseline (before the infusion). Results In control pigs, endothelial-dependent vasodilation following bradykinin infusion in infarct-related epicardial coronary artery was impaired, whereas in δPKC inhibitor-treated pigs the endothelial-dependent vasodilation was preserved. Nitroglycerin infusion caused similar vasodilatory responses in the both groups. Conclusions This is the first demonstration that a δPKC inhibitor preserves vasodilator capacity in epicardial coronary arteries in an in vivo porcine AMI model. Because endothelial dysfunction correlates with worse outcome in patients with AMI, this preserved endothelial function in epicardial coronary arteries might result in a better clinical outcome.

Highly proliferative endothelial colony forming cells isolated from pigs with acute myocardial infarction showing high affinity on bare metal stent

Background: Coronary stent implantation can cause significant injury of vessel endothelium with an inflammatory reaction which contributes to neointimal proliferation and thrombosis resulting in-stent restenosis. Endothelial progenitor cells (EPCs) can be differentiated into endothelial cells that protect the vascular wall from damage. Acute myocardial infarction (AMI) induced in a porcine model leads to an increase in circulating high proliferative potential-endothelial colony forming cells (HPP-ECFC). This study was designed to test whether isolated porcine HPP-ECFC could be grown on bare metal coronary stent. Methods and Results: AMI was created by a PTCA balloon catheter with the proximal left anterior descending (LAD) artery being occluded just distal to the first septal perforator for 45min. Peripheral blood samples were drawn at baseline and immediately post deflation of the balloon. Circulating mononuclear cells (MNC) were isolated and cultured. Colonies of HPP-ECFC (>2000 cells/colony) were identified by a single cell assay and sorted by flow cytometry. After labeling with PKH26, the HPP-ECFC were seeded into culture slides at a density of 5 x 104 cells/cm2 with bare coronary stents (AVE, NIR, and ACS; 3 stents/each group). At day 5, the cells seeded on the stents were labeled with a nuclear DAPI stain. HPP-ECFC can only be detected in the post-MI samples and were increased 15-fold. In co-culture, HPP-ECFC coverage on the stent surface began on day 3 and complete coverage of stents occurred after day 5. The cells displayed a similar growth pattern in all of the stents and cell quantification is ongoing. Conclusion: This preliminary data demonstrates that the number of circulating HPP-ECFC significantly increases in the acute stress situation in a porcine AMI model. These cells had a high affinity to adhere to bare metal stent surfaces. HPP-ECFC coated stents may accelerate reendothelization after interventional procedures. Dongni Fong, Lan Huang, Mervin C. Yoder, Keith L. March, Dongming Hou www.iupui.edu/~icvbm Figure 1A & B. ‘Cobblestone’ morphology and Cytometry shows expression of CD31 and rare CD45. Conclusions Our findings demonstrate that peripheral blood HPP-ECFCs were increased in number following the myocardial ischemia insult in our porcine model. These cells showed a great affinity to adhere to the BMS surface. We postulate that HPP-ECFC coated stents may accelerate the re-endothelization process, prevent neointimal proliferation, and stent thrombosis. • The HPP-ECFCs were labeled by PKH26 (Sigma-Aldrich) according to the manufacturer’s instructions. • The expanded and sterilized AVE, ACS and NIR stents (n = 3/each) were separately placed into each well of 24-well plate after rinsing with culture medium.

Sixty-four-MSCT in the characterization of porcine acute and subacute myocardial infarction: Determination of transmurality in comparison to magnetic resonance imaging and histopathology

Objective The aim of this study was to assess the accuracy of MSCT in characterizing myocardial infarction (MI) and, thereby, determine the extent of early perfusion defect (ED), microvascular obstruction (MO) and transmural depth of late enhancement (LE) in comparison to MRI and histology. Materials and methods Seven pigs were studied with MSCT (Somatom Sensation 64) and MRI (Magnetom Sonata) a median 1 and 21 days following temporary occlusion of a diagonal branch and creation of small reperfused infarction. For depiction of ED, CT images were acquired in the early arterial phase and following 35 s; LE and MO were evaluated on images obtained at 3, 5, 10 and 15 min. Thereby, a bolus/low-flow contrast injection protocol was used. Triphenyltetrazolium-chloride (TTC) stain and histology were obtained. Volumes of enhancement patterns were assessed as percentage of the ventricle and compared by Bland–Altman analysis. Segmental co-localization and graded transmurality was evaluated with weighted-kappa-test. Results Close spatial agreement was observed for MRI–MO and MSCT–MO (bias = 0.55; CI = −1.49 to 2.60 at 5 min MSCT), TTC and MSCT–LE (bias = −1.28; CI = −3.76 to 1.19) or MRI–LE and MSCT–LE (bias = −0.79; CI = −4.19 to 2.60). There was good segmental co-localization for MO (weighted kappa = 0.93) and high agreement for transmural extent of TTC, MRI–LE and MSCT–LE (weighted kappa = 0.84 TTC versus MSCT; 0.86 MRI versus MSCT). Arterial and 35 s ED significantly underestimated infarct size and showed poor segmental or transmural agreement (weighted kappa = 0.33; 0.44). Conclusions MSCT late-scans not only reliably depict size of MO and LE in acute or subacute infarct phases but, moreover, allow for accurate determination of LE transmurality.

Yin and Yang of Myocardial Transforming Growth Factor-β 1

Ischemic heart disease is a leading cause of chronic myocardial failure and mortality in the United States.1 After myocardial infarction (MI), the heart undergoes a well-characterized process of deleterious structural and molecular remodeling, marked by ventricular dilation, infarct wall thinning, and replacement fibrosis, with a corresponding progressive impairment of contractile function.2 Recent work has suggested that supplementation of myocardial cells with exogenous bone marrow–derived stem cell populations may have the potential to regenerate lost cardiomyocytes and slow, or even reverse, the remodeling process.3 Although the importance of both postinjury myocardial remodeling and regeneration are well accepted, the critical mechanisms that underlie these processes remain unclear. As insight into the biology of myocardial injury and dysfunction increases, the role of stress-activated cytokines has achieved particular prominence.4 Two articles in this issue of Circulation highlight the importance of the stress-activated cytokine, transforming growth factor (TGF)-β1, in mediating the complex processes of cardiac remodeling and regeneration. See pp 2430 and 2438 First isolated >20 years ago, TGF-β was identified from sarcoma cells based on its ability to potentiate the transforming and proliferative actions of epidermal growth factor on non-neoplastic fibroblasts.5,6 Since then, the TGF-β family has grown rapidly and at present consists of >30 structurally related members, including TGF-β1. This diverse cytokine superfamily has been subgrouped according to sequence similarity and specific downstream signaling pathways into the TGF-β/activin/nodal family and the bone morphogenic protein/growth and differentiation factor/Muellerian inhibiting …