Porcine Model Of Myocardial Infarction Research Articles

Infliximab Limits Injury in Myocardial Infarction.

The purpose of this study was to investigate a therapeutic approach targeting the inflammatory response and consequent remodeling from ischemic myocardial injury. Coronary thrombus aspirates were collected from patients at the time of ST-segment-elevation myocardial infarction and subjected to array-based proteome analysis. Clinically indistinguishable at myocardial infarction (MI), patients were stratified into vulnerable and resilient on the basis of 1-year left ventricular ejection fraction and death. Network analysis from coronary aspirates revealed prioritization of tumor necrosis factor-α signaling in patients with worse clinical outcomes. Infliximab, a tumor necrosis factor-α inhibitor, was infused intravenously at reperfusion in a porcine MI model to assess whether infliximab-mediated immune modulation impacts post-MI injury. At 3 days after MI (n=7), infliximab infusion increased proregenerative M2 macrophages in the myocardial border zone as quantified by immunofluorescence (24.1%±23.3% in infliximab versus 9.29%±8.7% in sham; P<0.01). Concomitantly, immunoassays of coronary sinus samples quantified lower troponin I levels (41.72±7.34 pg/mL versus 58.11±10.75 pg/mL; P<0.05) and secreted protein analysis revealed upregulation of injury-modifying interleukin-2, -4, -10, -12, and -18 cytokines in the infliximab-treated cohort. At 4 weeks (n=12), infliximab treatment resulted in significant protective influence, improving left ventricular ejection fraction (53.9%±5.4% versus 36.2%±5.3%; P<0.001) and reducing scar size (8.31%±10.9% versus 17.41%±12.5%; P<0.05). Profiling of coronary thrombus aspirates in patients with ST-segment-elevation MI revealed highest association for tumor necrosis factor-α in injury risk. Infliximab-mediated immune modulation offers an actionable pathway to alter MI-induced inflammatory response, preserving contractility and limiting adverse structural remodeling.

Pre-clinical evaluation of the efficacy and safety of human induced pluripotent stem cell-derived cardiomyocyte patch

BackgroundCell- or tissue-based regenerative therapy is an attractive approach to treat heart failure. A tissue patch that can safely and effectively repair damaged heart muscle would greatly improve outcomes for patients with heart failure. In this study, we conducted a preclinical proof-of-concept analysis of the efficacy and safety of clinical-grade human induced pluripotent stem cell-derived cardiomyocyte (hiPSC-CM) patches.MethodsA clinical-grade hiPSC line was established using peripheral blood mononuclear cells from a healthy volunteer that was homozygous for human leukocyte antigens. The hiPSCs were differentiated into cardiomyocytes. The obtained hiPSC-CMs were cultured on temperature-responsive culture dishes for patch fabrication. The cellular characteristics, safety, and efficacy of hiPSCs, hiPSC-CMs, and hiPSC-CM patches were analyzed.ResultsThe hiPSC-CMs expressed cardiomyocyte-specific genes and proteins, and electrophysiological analyses revealed that hiPSC-CMs exhibit similar properties to human primary myocardial cells. In vitro and in vivo safety studies indicated that tumorigenic cells were absent. Moreover, whole-genome and exome sequencing revealed no genomic mutations. General toxicity tests also showed no adverse events posttransplantation. A porcine model of myocardial infarction demonstrated significantly improved cardiac function and angiogenesis in response to cytokine secretion from hiPSC-CM patches. No lethal arrhythmias were observed.ConclusionshiPSC-CM patches are promising for future translational research and may have clinical application potential for the treatment of heart failure.

A novel intracoronary hypothermia device reduces myocardial reperfusion injury in pigs.

Hypothermia therapy has been suggested to attenuate myocardial necrosis; however, the clinical implementation as a valid therapeutic strategy has failed, and new approaches are needed to translate into clinical applications. This study aimed to assess the feasibility, safety, and efficacy of a novel selective intracoronary hypothermia (SICH) device in mitigating myocardial reperfusion injury. This study comprised two phases. The first phase of the SICH was performed in a normal porcine model for 30 minutes ( n = 5) to evaluate its feasibility. The second phase was conducted in a porcine myocardial infarction (MI) model of myocardial ischemia/reperfusion was performed by balloon occlusion of the left anterior descending coronary artery for 60 minutes and maintained for 42 days. Pigs in the hypothermia group ( n = 8) received hypothermia intervention onset reperfusion for 30 minutes and controls ( n = 8) received no intervention. All animals were followed for 42 days. Cardiac magnetic resonance analysis (5 and 42 days post-MI) and a series of biomarkers/histological studies were performed. The average time to lower temperatures to a steady state was 4.8±0.8 s. SICH had no impact on blood pressure or heart rate and was safely performed without complications by using a 3.9 F catheter. Interleukin-6 (IL-6), tumor necrosis factor-α, C-reactive protein (CRP), and brain natriuretic peptide (BNP) were lower at 60 min post perfusion in pigs that underwent SICH as compared with the control group. On day 5 post MI/R, edema, intramyocardial hemorrhage, and microvascular obstruction were reduced in the hypothermia group. On day 42 post MI/R, the infarct size, IL-6, CRP, BNP, and matrix metalloproteinase-9 were reduced, and the ejection fraction was improved in pigs that underwent SICH. The SICH device safely and effectively reduced the infarct size and improved heart function in a pig model of MI/R. These beneficial effects indicate the clinical potential of SICH for treatment of myocardial reperfusion injury.

Cellular heterogeneity of pluripotent stem cell-derived cardiomyocyte grafts is mechanistically linked to treatable arrhythmias

Preclinical data have confirmed that human pluripotent stem cell-derived cardiomyocytes (PSC-CMs) can remuscularize the injured or diseased heart, with several clinical trials now in planning or recruitment stages. However, because ventricular arrhythmias represent a complication following engraftment of intramyocardially injected PSC-CMs, it is necessary to provide treatment strategies to control or prevent engraftment arrhythmias (EAs). Here, we show in a porcine model of myocardial infarction and PSC-CM transplantation that EAs are mechanistically linked to cellular heterogeneity in the input PSC-CM and resultant graft. Specifically, we identify atrial and pacemaker-like cardiomyocytes as culprit arrhythmogenic subpopulations. Two unique surface marker signatures, signal regulatory protein α (SIRPA)+CD90−CD200+ and SIRPA+CD90−CD200−, identify arrhythmogenic and non-arrhythmogenic cardiomyocytes, respectively. Our data suggest that modifications to current PSC-CM-production and/or PSC-CM-selection protocols could potentially prevent EAs. We further show that pharmacologic and interventional anti-arrhythmic strategies can control and potentially abolish these arrhythmias.

Automatic measurement of short-term variability of repolarization to indicate ventricular arrhythmias in a porcine model of cardiac ischaemia.

An automated method for determination of short-term variability (STV) of repolarization on intracardiac electrograms (STV-ARIauto) has previously been developed for arrhythmic risk monitoring by cardiac implantable devices, and has proved effective in predicting ventricular arrhythmias (VA) and guiding preventive high-rate pacing (HRP) in a canine model. Current study aimed to assess (i) STV-ARIauto in relation to VA occurrence and secondarily (ii-a) to confirm the predictive capacity of STV from the QT interval and (ii-b) explore the effect of HRP on arrhythmic outcomes in a porcine model of acute myocardial infarction (MI). Myocardial infarction was induced in 15 pigs. In 7/15 pigs, STV-QT was assessed at baseline, occlusion, 1 min before VA, and just before VA. Eight of the 15 pigs were additionally monitored with an electrogram catheter in the right ventricle, underwent echocardiography at baseline and reperfusion, and were randomized to paced or control group. Paced group received atrial pacing at 20 beats per min faster than sinus rhythm 1 min after occlusion. Short-term variability increased prior to VA in both STV modalities. The percentage change in STV from baseline to successive timepoints correlated well between STV-QT and STV-ARIauto. High-rate pacing did not improve arrhythmic outcomes and was accompanied by a stronger decrease in ejection fraction. STV-ARIauto values increase before VA onset, alike STV-QT in a porcine model of MI, indicating imminent arrhythmias. This highlights the potential of automatic monitoring of arrhythmic risk by cardiac devices through STV-ARIauto and subsequently initiates preventive strategies. Continuous HRP during onset of acute MI did not improve arrhythmic outcomes.

Myocardial oxidative stress is increased in early reperfusion, but systemic antioxidative therapy does not prevent ischemia-reperfusion arrhythmias in pigs.

Arrhythmias in the early phase of reperfusion after myocardial infarction (MI) are common, and can lead to hemodynamic instability or even cardiac arrest. Reactive oxygen species (ROS) are thought to play a key role in the underlying mechanisms, but evidence from large animal models is scarce, and effects of systemic antioxidative treatment remain contentious. MI was induced in 7 male and 7 female pigs (Norwegian landrace, 35-40 kg) by clamping of the left anterior descending artery (LAD) during open thorax surgery. Ischemia was maintained for 90 min, before observation for 1 h after reperfusion. Pigs were randomized 1:1 in an operator-blinded fashion to receive either i.v. N-acetylcysteine (NAC) from 70 min of ischemia and onwards, or 0.9% NaCl as a control. Blood samples and tissue biopsies were collected at baseline, 60 min of ischemia, and 5 and 60 min of reperfusion. ECG and invasive blood pressure were monitored throughout. The protocol was completed in 11 pigs. Oxidative stress, as indicated by immunoblotting for Malondialdehyde in myocardial biopsies, was increased at 5 min of reperfusion compared to baseline, but not at 60 min of reperfusion, and not reduced with NAC. We found no significant differences in circulating biomarkers of myocardial necrosis, nor in the incidence of idioventricular rhythm (IVR), non-sustained ventricular tachycardia (NSVT), ventricular tachycardia (VT) or ventricular fibrillation (VF) between NAC-treated and control pigs during reperfusion. Myocardial oxidation was increased early after reperfusion in a porcine model of MI, but systemic antioxidative treatment did not protect against reperfusion arrhythmias.

Abstract P1072: Microneedle Patch Loaded With Il-4 Macroparticles Facilitates Heart Repair Through Macrophages Mediated Cardiomyocyte Phenotype Transition

Ischemic heart disease remains the leading cause of mortality worldwide, but significant progress has been made in optimizing the treatment of acute myocardial infarction (MI) with percutaneous coronary intervention techniques. However, the increased pool of post-MI survivors has led to a higher prevalence of heart failure (HF) secondary to coronary artery disease, making it a major public health issue. Monocytes recruited from circulation differentiate into pro-inflammatory macrophages (M1-like) responsible for post-MI inflammation and cellular debris removal. As a unique Th2 cell cytokine, Interleukin 4 (IL-4) has been widely established as a powerful agent for the polarization of anti-inflammatory macrophages that promote tissue repair. However, there are limitations such as local and targeted delivery have hampered the successful translation of IL-4 therapy. In this study, we created an IL-4 microparticle-loaded microneedle patch (IL-4 MP-MN) for localized delivery of IL-4 to the MI region and tested the therapeutic effects in a rat model of MI. Our preliminary data suggested that IL-4 MP-MN treatment promoted cardiomyocyte proliferation and induced an anti-inflammatory microenvironment, which further led to a cardiomyocyte phenotype shift from "self-rescue" to "assisted-rescue" mode. Additionally, we successfully translated the therapeutic effects of IL-4 MP-MN in a porcine model of MI for testing therapeutic feasibility, safety, and efficacy.

Abstract P1114: Preclinical Large Animal Assessment Of Safety And Engraftment Of Hicms Nanofiber Cardiac Patch Transplantation For Cardiac Repair

Background: Myocardial infarction (MI) is a leading cause of death in the United States. However, none of the therapies can regenerate the damaged heart muscle. Objective: The objective of this study was to assess the safety and engraftment of a nanofiber cardiac patch laden with human iPSC-derived cardiomyocytes (hiCMs) and transplanted in a preclinical porcine MI model. Methodology: MI was induced in pigs via advancing a balloon catheter from the femoral artery into the left anterior descending coronary artery (LAD) below the first diagonal branch (D1) and the balloon was inflated for 90-min to induce myocardial ischemia. Immunosuppressant drug Tacrolimus was given orally one-week before the cardiac patch transplantation and continued for up to 4-weeks post-cardiac patch transplantation. Epicardial transplantation of aligned nanofiber cardiac patch (2 layers) loaded with hiCMs was performed at one-week post MI. Magnetic resonance Imaging (MRI) was performed prior to the MI induction (Baseline), 1-week post-MI and at 4-weeks post cardiac patch transplantation to assess severity of MI and cardiac function. At 4-weeks post-MI, pigs were euthanized, and the heart tissues were processed for immunostaining to confirm the retention and engraftment (Human Nuclear Antibody staining) of the implanted cells in the host myocardium. Results: (a) A significant increase in ST-elevation following 90-min of MI, (b) Incidence of cardiac arrhythmias were not observed post cardiac patch transplantation, confirming the safety of cardiac patch, (c) No teratomas were observed at the transplanted site, indicating safety of terminally differentiated hiCMs and (d) Immunofluorescence staining of cardiac sections in the transplanted cardiac patch area confirmed engraftment of transplanted cells via anti-human nuclear antibody, which demonstrates the survival and engraftment of implanted cells. Conclusions: In summary, we have demonstrated for the first time that aligned nanofiber cardiac patch loaded with hiCMs is safe and can enhance retention of transplanted cells. Further studies are warranted to assess the long-term efficacy of cardiac patch transplantation in improving the cardiac function and to perform first-in-human clinical trials in the near future.

Extracellular Matrix/Glycopeptide Hybrid Hydrogel as an Immunomodulatory Niche for Endogenous Cardiac Repair after Myocardial Infarction.

The treatment of myocardial infarction (MI) remains a substantial challenge due to excessive inflammation, massive cell death, and restricted regenerative potential, leading to maladaptive healing process and eventually heart failure. Current strategies of regulating inflammation or improving cardiac tissue regeneration have limited success. Herein, a hybrid hydrogel coassembled by acellular cardiac extracellular matrix (ECM) and immunomodulatory glycopeptide is developed for endogenous tissue regeneration after MI. The hydrogel constructs a niche recapitulating the architecture of native ECM for attracting host cell homing, controlling macrophage differentiation via glycopeptide unit, and promoting endotheliocyte proliferation by enhancing the macrophage-endotheliocyte crosstalk, which coordinate the innate healing mechanism for cardiac tissue regeneration. In a rodent MI model, the hybrid hydrogel successfully orchestrates a proreparative response indicated by enhanced M2 macrophage polarization, increased angiogenesis, and improved cardiomyocyte survival, which alleviates infarct size, improves wall thicknesses, and enhances cardiac contractility. Furthermore, the safety and effectiveness of the hydrogel are demonstrated in a porcine MI model, wherein proteomics verifies the regulation of immune response, proangiogenesis, and accelerated healing process. Collectively, the injectable composite hydrogel serving as an immunomodulatory niche for promoting cell homing and proliferation, inflammation modulation, tissue remodeling, and function restoration provides an effective strategy for endogenous cardiac repair.

Preclinical Large Animal Porcine Models for Cardiac Regeneration and Its Clinical Translation: Role of hiPSC-Derived Cardiomyocytes.

Myocardial Infarction (MI) occurs due to a blockage in the coronary artery resulting in ischemia and necrosis of cardiomyocytes in the left ventricular heart muscle. The dying cardiac tissue is replaced with fibrous scar tissue, causing a decrease in myocardial contractility and thus affecting the functional capacity of the myocardium. Treatments, such as stent placements, cardiac bypasses, or transplants are beneficial but with many limitations, and may decrease the overall life expectancy due to related complications. In recent years, with the advent of human induced pluripotent stem cells (hiPSCs), newer avenues using cell-based approaches for the treatment of MI have emerged as a potential for cardiac regeneration. While hiPSCs and their derived differentiated cells are promising candidates, their translatability for clinical applications has been hindered due to poor preclinical reproducibility. Various preclinical animal models for MI, ranging from mice to non-human primates, have been adopted in cardiovascular research to mimic MI in humans. Therefore, a comprehensive literature review was essential to elucidate the factors affecting the reproducibility and translatability of large animal models. In this review article, we have discussed different animal models available for studying stem-cell transplantation in cardiovascular applications, mainly focusing on the highly translatable porcine MI model.

Adenoviral VEGF-DΔN ΔC gene therapy for myocardial ischemia.

Background: Cardiovascular diseases are the leading cause of death globally. In spite of the availability of improved treatments, there is still a large group of chronic ischemia patients who suffer from significant symptoms and disability. Thus, there is a clear need to develop new treatment strategies for these patients. Therapeutic angiogenesis is a novel therapy method which has shown promising results in preclinical studies. In this study, we evaluated safety and efficacy of adenoviral (Ad) VEGF-DΔNΔC gene transfer for the treatment of myocardial ischemia in a pig model. Methods: Adenoviral VEGF-DΔNΔC gene transfer was given to pigs (n = 26) via intramyocardial injections using an electromechanical injection catheter. Angiogenic effects were evaluated in an acute myocardial infarction model (n = 18) and functionality of the lymphatic vessels were tested in healthy porcine myocardium (n = 8). AdLacZ was used as a control. Results: AdVEGF-DΔNΔC induced safe and effective myocardial angiogenesis by inducing a four-fold increase in mean capillary area at the edge of the myocardial infarct six days after the gene transfer relative to the control AdLacZ group. The effect was sustained over 21 days after the gene transfer, and there were no signs of vessels regression. AdVEGF-DΔNΔC also increased perfusion 3.4-fold near the infarct border zone relative to the control as measured by fluorescent microspheres. Ejection fraction was 8.7% higher in the AdVEGF-DΔNΔC treated group 21days after the gene transfer relative to the AdLacZ control group. Modified Miles assay detected a transient increase in plasma protein extravasation after the AdVEGF-DΔNΔC treatment and a mild accumulation of pericardial effusate was observed at d6. However, AdVEGF-DΔNΔC also induced the growth of functional lymphatic vasculature, and the amount of pericardial fluid and level of vascular permeability had returned to normal by d21. Conclusion: Endovascular intramyocardial AdVEGF-DΔNΔC gene therapy proved to be safe and effective in the acute porcine myocardial infarction model and provides a new potential treatment option for patients with severe coronary heart disease.

ECG Markers of Acute Melatonin Treatment in a Porcine Model of Acute Myocardial Ischemia.

In myocardial ischemia, melatonin confers antiarrhythmic action, but its electrocardiographic expression is unclear. We aimed to evaluate the effects of melatonin treatment on electrocardiogram (ECG) parameters reflecting major arrhythmogenic factors and to test the association of these parameters with ventricular fibrillation (VF) incidence. Myocardial ischemia was induced by 40 min coronary artery occlusion in 25 anesthetized pigs. After induction of ischemia, 12 and 13 animals were given melatonin or placebo, respectively. Twelve-lead ECGs were recorded and durations of QRS, QT, Tpeak-Tend intervals and extrasystolic burden were measured at baseline and during occlusion. During ischemia, VF episodes clustered into early and delayed phases (<10 and >20 min, respectively), and QRS duration was associated with VF incidence. QT interval and extrasystolic burden did not differ between the groups. The Tpeak-Tend interval was progressively prolonged, and the prolongation was less pronounced in the treated animals. QRS duration increased, demonstrating two maxima (5–10 and 25 min, respectively). In the melatonin group, the earlier maximum was blunted, and VF development in this period was prevented. Thus, acute melatonin treatment prevented excessive prolongation of the QRS and Tpeak-Tend intervals in the porcine myocardial infarction model, and QRS duration can be used for the assessment of antiarrhythmic action of melatonin.

Protective Effect of CXCR4 Antagonist DBPR807 against Ischemia-Reperfusion Injury in a Rat and Porcine Model of Myocardial Infarction: Potential Adjunctive Therapy for Percutaneous Coronary Intervention.

CXCR4 antagonists have been claimed to reduce mortality after myocardial infarction in myocardial infarction (MI) animals, presumably due to suppressing inflammatory responses caused by myocardial ischemia-reperfusion injury, thus, subsequently facilitating tissue repair and cardiac function recovery. This study aims to determine whether a newly designed CXCR4 antagonist DBPR807 could exert better vascular-protective effects than other clinical counterparts (e.g., AMD3100) to alleviate cardiac damage further exacerbated by reperfusion. Consequently, we find that instead of traditional continuous treatment or multiple-dose treatment at different intervals of time, a single-dose treatment of DBPR807 before reperfusion in MI animals could attenuate inflammation via protecting oxidative stress damage and preserve vascular/capillary density and integrity via mobilizing endothelial progenitor cells, leading to a desirable fibrosis reduction and recovery of cardiac function, as evaluated with the LVEF (left ventricular ejection fraction) in infarcted hearts in rats and mini-pigs, respectively. Thus, it is highly suggested that CXCR4 antagonists should be given at a single high dose prior to reperfusion to provide the maximal cardiac functional improvement. Based on its favorable efficacy and safety profiles indicated in tested animals, DBPR807 has a great potential to serve as an adjunctive medicine for percutaneous coronary intervention (PCI) therapies in acute MI patients.

Artificial Intelligence for Contrast-Free MRI: Scar Assessment in Myocardial Infarction Using Deep Learning-Based Virtual Native Enhancement.

Myocardial scars are assessed noninvasively using cardiovascular magnetic resonance late gadolinium enhancement (LGE) as an imaging gold standard. A contrast-free approach would provide many advantages, including a faster and cheaper scan without contrast-associated problems. Virtual native enhancement (VNE) is a novel technology that can produce virtual LGE-like images without the need for contrast. VNE combines cine imaging and native T1 maps to produce LGE-like images using artificial intelligence. VNE was developed for patients with previous myocardial infarction from 4271 data sets (912 patients); each data set comprises slice position-matched cine, T1 maps, and LGE images. After quality control, 3002 data sets (775 patients) were used for development and 291 data sets (68 patients) for testing. The VNE generator was trained using generative adversarial networks, using 2 adversarial discriminators to improve the image quality. The left ventricle was contoured semiautomatically. Myocardial scar volume was quantified using the full width at half maximum method. Scar transmurality was measured using the centerline chord method and visualized on bull's-eye plots. Lesion quantification by VNE and LGE was compared using linear regression, Pearson correlation (R), and intraclass correlation coefficients. Proof-of-principle histopathologic comparison of VNE in a porcine model of myocardial infarction also was performed. VNE provided significantly better image quality than LGE on blinded analysis by 5 independent operators on 291 data sets (all P<0.001). VNE correlated strongly with LGE in quantifying scar size (R, 0.89; intraclass correlation coefficient, 0.94) and transmurality (R, 0.84; intraclass correlation coefficient, 0.90) in 66 patients (277 test data sets). Two cardiovascular magnetic resonance experts reviewed all test image slices and reported an overall accuracy of 84% for VNE in detecting scars when compared with LGE, with specificity of 100% and sensitivity of 77%. VNE also showed excellent visuospatial agreement with histopathology in 2 cases of a porcine model of myocardial infarction. VNE demonstrated high agreement with LGE cardiovascular magnetic resonance for myocardial scar assessment in patients with previous myocardial infarction in visuospatial distribution and lesion quantification with superior image quality. VNE is a potentially transformative artificial intelligence-based technology with promise in reducing scan times and costs, increasing clinical throughput, and improving the accessibility of cardiovascular magnetic resonance in the near future.

Epicardial transplantation of autologous atrial appendage micrografts: evaluation of safety and feasibility in pigs after coronary artery occlusion

Objectives. Several approaches devised for clinical utilization of cell-based therapies for heart failure often suffer from complex and lengthy preparation stages. Epicardial delivery of autologous atrial appendage micrografts (AAMs) with a clinically used extracellular matrix (ECM) patch provides a straightforward therapy alternative. We evaluated the operative feasibility and the effect of micrografts on the patch-induced epicardial foreign body inflammatory response in a porcine model of myocardial infarction. Design. Right atrial appendages were harvested and mechanically processed into AAMs. The left anterior descending coronary artery was ligated to generate acute infarction. Patches of ECM matrix with or without AAMs were transplanted epicardially onto the infarcted area. Four pigs received the ECM and four received the AAMs patch. Cardiac function was studied by echocardiography both preoperatively and at 3-week follow-up. The primary outcome measures were safety and feasibility of the therapy administration, and the secondary outcome was the inflammatory response to ECM. Results. Neither AAMs nor ECM patch-related complications were detected during the follow-up time. AAMs patch preparation was feasible according to time and safety. Inflammation was greatly reduced in AAMs when compared with ECM patches as measured by the amount of infiltrated inflammatory cells and area of inflammation. Immunohistochemistry demonstrated an increased CD3+ cell density in the AAMs patch infiltrate. Conclusions. Epicardial AAMs transplantation demonstrated safety and clinical feasibility. The use of micrografts significantly inhibited ECM-induced foreign body inflammatory reactivity. Transplantation of AAMs shows good clinical applicability as adjuvant therapy to cardiac surgery and can suppress acute inflammatory reactivity.

Preclinical study of human umbilical cord mesenchymal stem cell sheets for the recovery of ischemic heart tissue

BackgroundHuman umbilical cord mesenchymal stem cells (hUC-MSCs) have been widely used due to their multipotency, a broad range of sources, painless collection, and compliance with standard amplification. Cell sheet technology is a tissue engineering methodology requiring scaffolds free, and it provides an effective method for cell transplantation. To improve the therapeutic efficacy, we combined hUC-MSCs with cell sheet technology to evaluate the safety and efficacy of hUC-MSC sheets in preclinical studies using appropriate animal models.MethodshUC-MSC sheets were fabricated by hUC-MSCs from a cell bank established by a standard operation process and quality control. Cytokine secretion, immunoregulation, and angiopoiesis were evaluated in vitro. Oncogenicity and cell diffusion assays of hUC-MSC sheets were conducted to verify the safety of hUC-MSCs sheet transplantation in mice. To provide more meaningful animal experimental data for clinical trials, porcine myocardial infarction (MI) models were established by constriction of the left circumflex, and hUC-MSC sheets were transplanted onto the ischemic area of the heart tissue. Cardiac function was evaluated and compared between the experimental and MI groups.ResultsThe in vitro results showed that hUC-MSC sheets could secrete multiple cellular factors, including VEGF, HGF, IL-6, and IL-8. Peripheral blood mononuclear cells had a lower proliferation rate and lower TNF-α secretion when co-cultured with hUC-MSC sheets. TH1 cells had a smaller proportion after activation. In vivo safety results showed that the hUC-MSCs sheet had no oncogenicity and was mainly distributed on the surface of the ischemic myocardial tissue. Echocardiography showed that hUC-MSC sheets effectively improved the left ventricular ejection fraction (LVEF), and the LVEF significantly changed (42.25 ± 1.23% vs. 66.9 ± 1.10%) in the hUC-MSC transplantation group compared with the MI group (42.52 ± 0.65% vs. 39.55 ± 1.97%) at 9 weeks. The infarct ratio of the hUC-MSCs sheet transplantation groups was also significantly reduced (14.2 ± 4.53% vs. 4.00 ± 2.00%) compared with that of the MI group.ConclusionAllogeneic source and cell bank established by the standard operation process and quality control make hUC-MSCs sheet possible to treat MI by off-the-shelf drug with universal quality instead of individualized medical technology.

Intrapericardial Administration of Secretomes from Menstrual Blood-Derived Mesenchymal Stromal Cells: Effects on Immune-Related Genes in a Porcine Model of Myocardial Infarction

Acute myocardial infarction (AMI) is a manifestation of ischemic heart disease where the immune system plays an important role in the re-establishment of homeostasis. We hypothesize that the anti-inflammatory activity of secretomes from menstrual blood-derived mesenchymal stromal cells (S-MenSCs) and IFNγ/TNFα-primed MenSCs (S-MenSCs*) may be considered a therapeutic option for the treatment of AMI. To assess this hypothesis, we have evaluated the effect of S-MenSCs and S-MenSCs* on cardiac function parameters and the involvement of immune-related genes using a porcine model of AMI. Twelve pigs were randomly divided into three biogroups: AMI/Placebo, AMI/S-MenSCs, and AMI/S-MenSCs*. AMI models were generated using a closed chest coronary occlusion-reperfusion procedure and, after 72 h, the different treatments were intrapericardially administered. Cardiac function parameters were monitored by magnetic resonance imaging before and 7 days post-therapy. Transcriptomic analyses in the infarcted tissue identified 571 transcripts associated with the Gene Ontology term Immune response, of which 57 were differentially expressed when different biogroups were compared. Moreover, a prediction of the interactions between differentially expressed genes (DEGs) and miRNAs from secretomes revealed that some DEGs in the infarction area, such as STAT3, IGFR1, or BCL6 could be targeted by previously identified miRNAs in secretomes from MenSCs. In conclusion, the intrapericardial administration of secretome early after infarction has a significant impact on the expression of immune-related genes in the infarcted myocardium. This confirms the immunomodulatory potential of intrapericardially delivered secretomes and opens new therapeutic perspectives in myocardial infarction treatment.

Border zone repolarization duration as a predictor of early ischemic ventricular fibrillation

Ventricular fibrillation (VF) is a dangerous complication of acute myocardial infarction. Within an episode of acute ischemia, VFs are clustered into early (1A) and delayed (1B) phases based on different mechanisms. Our previous work demonstrated that prolonged repolarization duration in the border zone predisposed to VF development. A prolongation of action potential duration in the affected area is a frequent though not inevitable change at the very beginning of ischemia. However, the role of this phenomenon in arrhythmogenesis is unclear. The objective of the present study was to evaluate an association between early (1A phase) VF with repolarization duration in the border zone in an experimental porcine myocardial infarction model.Myocardial ischemia was induced in 19 anesthetized domestic pigs by ligation of the left anterior descending (n=9) or left circumflex (n=10) coronary arteries. Epicardial mapping was done with a 64‐lead epicardial array placed on the affected area with adjacent regions. Recordings were done in the baseline state and during ischemia with a custom‐designed system (16 bits; bandwidth 0.05 to 1000 Hz; sampling rate 4000 Hz). Local activation time (AT) and end of repolarization time (RT) were measured in each epicardial lead as the instants of a dV/dt minimum during QRS‑complex and dV/dt maximum during T‑wave, respectively. Activation‐repolarization interval (ARI, a surrogate for action potential duration) was taken as a rate‐corrected difference between RT and AT. Dispersion of repolarization (DOR) was calculated as a difference between the latest and earliest RTs throughout all recorded epicardial leads.Ten early VF episodes developed during first minutes of ischemia (1‐8 min). In logistic regression analysis, VF incidence was associated with ARI duration in the border zone (regression coefficient 1.02, 95% CI 1.003‐1.037, p=0.023), but not DOR (regression coefficient 1.005, 95%CI 0.990‐1.021, p=0.508) during first ten minutes of ischemia. In multivariate logistic regression analysis (baseline ARI duration vs the fact of ARI prolongation), VF incidence was associated only with the baseline ARI duration (regression coefficient 1.025, 95%CI 1.007‐1.044, p=0.005).Our data demonstrated the role of the prolonged repolarization duration in the development of 1A phase VF, which was independent of DOR and related to its baseline duration. Since the border zone is by definition at least partly accessible for blood flow, it may present a target for VF prevention therapy in a setting of acute myocardial ischemia.

Comparative assessment of motion averaged free-breathing or breath-held cardiac magnetic resonance imaging protocols in a porcine myocardial infarction model

Breath-held (BH) cardiac magnetic resonance imaging (CMR) is the gold standard for volumetric quantification. However, large animals for pre-clinical research are unable to voluntarily breath-hold, necessitating general anaesthesia and mechanical ventilation, increasing research costs and affecting cardiovascular physiology. Conducting CMR in lightly sedated, free-breathing (FB) animal subjects is an alternative strategy which can overcome these constraints, however, may result in poorer image quality due to breathing motion artefact. We sought to assess the reproducibility of CMR metrics between FB and BH CMR in a porcine model of ischaemic cardiomyopathy. FB or BH CMR was performed in 38 porcine subjects following percutaneous induction of myocardial infarction. Analysis was performed by two independent, blinded observers according to standard reporting guidelines. Subjective and objective image quality was significantly improved in the BH cohort (image quality score: 3.9/5 vs. 2.4/5; p < 0.0001 and myocardium:blood pool intensity ratio: 2.6–3.3 vs. 1.9–2.3; p < 0.001), along with scan acquisition time (4 min 06 s ± 1 min 55 s vs. 8 min 53 s ± 2 min 39 s; p < 0.000). Intra- and inter-observer reproducibility of volumetric analysis was substantially improved in BH scans (correlation coefficients: 0.94–0.99 vs. 0.76–0.91; coefficients of variation: < 5% in BH and > 5% in FB; Bland–Altman limits of agreement: < 10 in BH and > 10 in FB). Interstudy variation between approaches was used to calculate sample sizes, with BH CMR resulting in greater than 85% reduction in animal numbers required to show clinically significant treatment effects. In summary, BH porcine CMR produces superior image quality, shorter scan acquisition, greater reproducibility, and requires smaller sample sizes for pre-clinical trials as compared to FB acquisition.

Effect of scar and pacing location on repolarization in a porcine myocardial infarction model.

BackgroundThe effect of chronic ischemic scar on repolarization is unclear, with conflicting results from human and animal studies. An improved understanding of electrical remodeling within scar and border zone tissue may enhance substrate-guided ablation techniques for treatment of ventricular tachycardia. Computational modeling studies have suggested increased dispersion of repolarization during epicardial, but not endocardial, left ventricular pacing, in close proximity to scar. However, the effect of endocardial pacing near scar in vivo is unknown.ObjectiveThe purpose of this study was to investigate the effect of scar and pacing location on local repolarization in a porcine myocardial infarction model.MethodsSix model pigs underwent late gadolinium enhancement cardiac magnetic resonance (LGE-CMR) imaging followed by electroanatomic mapping of the left ventricular endocardium. LGE-CMR images were registered to the anatomic shell and scar defined by LGE. Activation recovery intervals (ARIs), a surrogate for action potential duration, and local ARI gradients were calculated from unipolar electrograms within areas of late gadolinium enhancement (aLGE) and healthy myocardium.ResultsThere was no significant difference between aLGE and healthy myocardium in mean ARI (304.20 ± 19.44 ms vs 300.59 ± 19.22 ms; P = .43), ARI heterogeneity (23.32 ± 11.43 ms vs 24.85 ± 12.99 ms; P = .54), or ARI gradients (6.18 ± 2.09 vs 5.66 ± 2.32 ms/mm; P = .39). Endocardial pacing distance from scar did not affect ARI gradients.ConclusionOur findings suggest that changes in ARI are not an intrinsic property of surviving myocytes within scar, and endocardial pacing close to scar does not affect local repolarization.