Animal Models Of Myocardial Infarction Research Articles

Cardiac function in a large animal model of myocardial infarction at 7 T: deep learning based automatic segmentation increases reproducibility

Cardiac magnetic resonance (CMR) imaging allows precise non-invasive quantification of cardiac function. It requires reliable image segmentation for myocardial tissue. Clinically used software usually offers automatic approaches for this step. These are, however, designed for segmentation of human images obtained at clinical field strengths. They reach their limits when applied to preclinical data and ultrahigh field strength (such as CMR of pigs at 7 T). In our study, eleven animals (seven with myocardial infarction) underwent four CMR scans each. Short-axis cine stacks were acquired and used for functional cardiac analysis. End-systolic and end-diastolic images were labelled manually by two observers and inter- and intra-observer variability were assessed. Aiming to make the functional analysis faster and more reproducible, an established deep learning (DL) model for myocardial segmentation in humans was re-trained using our preclinical 7 T data (n = 772 images and labels). We then tested the model on n = 288 images. Excellent agreement in parameters of cardiac function was found between manual and DL segmentation: For ejection fraction (EF) we achieved a Pearson’s r of 0.95, an Intraclass correlation coefficient (ICC) of 0.97, and a Coefficient of variability (CoV) of 6.6%. Dice scores were 0.88 for the left ventricle and 0.84 for the myocardium.

Transcriptome analysis revealed the new mechanism of the intra-myocardial injectable alginate-hydrogel in the treatment of ventricular function degradation.

Myocardial infarction (MI) is one of the most lethal cardiovascular diseases. The loss of cardiomyocytes and the degradation of the extracellular matrix leads to high ventricular wall stress, which further drives the pathological thinning of the ventricular wall during MI. Injecting biomaterials to thicken the infarct ventricular wall provides mechanical support, thereby inhibiting the continued expansion of the heart. As an injectable biomaterial, alginate hydrogel has achieved exciting results in clinical trials, but further research needs to be conducted to determine whether it can improve cardiac function in addition to providing mechanical support. This study sought to explore these mechanisms in an animal model of MI. A MI model was established in male C57BL/6J mice by ligation of the proximal left anterior descending (LAD) coronary artery. Intramyocardial injections (hydrogel or saline group) were performed in the proximal wall regions bordering the infarct area (with one 20-µL injection). Four weeks after MI, RNA sequencing revealed that 342 messenger RNAs (mRNAs) from the infarcted hearts were differentially expressed between the saline group and hydrogel group. We subsequently conducted a Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis to analyze the RNA sequencing data. In addition, we employed both western blotting and quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) techniques to verify a number of genes that were differentially expressed and could potentially affect cardiac function after MI. Subsequently, we confirmed these findings through in vitro experiments. We found that compared with hydrogel treatment group, 250 mRNAs were upregulated and 92 mRNAs were downregulated in saline group (P<0.05). And by exploring the GO and KEGG signaling pathways as well as the protein-protein interaction (PPI) network, we found that administration of alginate hydrogel modulated cardiomyocyte inflammation-associated proteins as well as chemokine-related proteins during the inflammatory response phase after MI. In addition, our analysis at both the protein and RNA level revealed that B2M was effective in improving cardiac function after MI in the hydrogel treatment group, which was consistent in the myocardium oxygen and glucose deprivation (OGD) injury model. We explored the transcriptome changes of infarcted hearts after alginate-hydrogel injection during the inflammatory response period. Our findings suggest that the injectable hydrogel directly alters the inflammatory response and the chemokine-mediated signaling pathway of cardiomyocytes, ultimately improving cardiac function.

To Repair a Broken Heart: Stem Cells in Ischemic Heart Disease.

Despite improvements in contemporary medical and surgical therapies, cardiovascular disease (CVD) remains a significant cause of worldwide morbidity and mortality; more specifically, ischemic heart disease (IHD) may affect individuals as young as 20 years old. Typically managed with guideline-directed medical therapy, interventional or surgical methods, the incurred cardiomyocyte loss is not always completely reversible; however, recent research into various stem cell (SC) populations has highlighted their potential for the treatment and perhaps regeneration of injured cardiac tissue, either directly through cellular replacement or indirectly through local paracrine effects. Different stem cell (SC) types have been employed in studies of infarcted myocardium, both in animal models of myocardial infarction (MI) as well as in clinical studies of MI patients, including embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), Muse cells, multipotent stem cells such as bone marrow-derived cells, mesenchymal stem cells (MSCs) and cardiac stem and progenitor cells (CSC/CPCs). These have been delivered as is, in the form of cell therapies, or have been used to generate tissue-engineered (TE) constructs with variable results. In this text, we sought to perform a narrative review of experimental and clinical studies employing various stem cells (SC) for the treatment of infarcted myocardium within the last two decades, with an emphasis on therapies administered through thoracic incision or through percutaneous coronary interventions (PCI), to elucidate possible mechanisms of action and therapeutic effects of such cell therapies when employed in a surgical or interventional manner.

Injectable hydrogel-based combination therapy for myocardial infarction: a systematic review and Meta-analysis of preclinical trials

IntroductionThis study evaluates the effectiveness of a combined regimen involving injectable hydrogels for the treatment of experimental myocardial infarction.Patient concernsMyocardial infarction is an acute illness that negatively affects quality of life and increases mortality rates. Experimental models of myocardial infarction can aid in disease research by allowing for the development of therapies that effectively manage disease progression and promote tissue repair.DiagnosisExperimental animal models of myocardial infarction were established using the ligation method on the anterior descending branch of the left coronary artery (LAD).InterventionsThe efficacy of intracardiac injection of hydrogels, combined with cells, drugs, cytokines, extracellular vesicles, or nucleic acid therapies, was evaluated to assess the functional and morphological improvements in the post-infarction heart achieved through the combined hydrogel regimen.OutcomesA literature review was conducted using PubMed, Web of Science, Scopus, and Cochrane databases. A total of 83 papers, including studies on 1332 experimental animals (rats, mice, rabbits, sheep, and pigs), were included in the meta-analysis based on the inclusion and exclusion criteria.The overall effect size observed in the group receiving combined hydrogel therapy, compared to the group receiving hydrogel treatment alone, resulted in an ejection fraction (EF) improvement of 8.87% [95% confidence interval (CI): 7.53, 10.21] and a fractional shortening (FS) improvement of 6.31% [95% CI: 5.94, 6.67] in rat models, while in mice models, the improvements were 16.45% [95% CI: 11.29, 21.61] for EF and 5.68% [95% CI: 5.15, 6.22] for FS.The most significant improvements in EF (rats: MD = 9.63% [95% CI: 4.02, 15.23]; mice: MD = 23.93% [95% CI: 17.52, 30.84]) and FS (rats: MD = 8.55% [95% CI: 2.54, 14.56]; mice: MD = 5.68% [95% CI: 5.15, 6.22]) were observed when extracellular vesicle therapy was used. Although there have been significant results in large animal experiments, the number of studies conducted in this area is limited.ConclusionThe present study demonstrates that combining hydrogel with other therapies effectively improves heart function and morphology. Further preclinical research using large animal models is necessary for additional study and validation.Graphical abstract

Evaluation of Tyrosine Kinase Inhibitors Loaded Injectable Hydrogels for Improving Connexin43 Gap Junction Intercellular Communication.

Myocardial infarction (MI) is one of the leading causes of death in the developed world, and the loss of cardiomyocytes plays a critical role in the pathogenesis of heart failure. Implicated in this process is a decrease in gap junction intercellular communication due to remodeling of Connexin43 (Cx43). We previously identified that intraperitoneal injection of the Pyk2 inhibitor PF4618433 reduced infarct size, maintained Cx43 at the intercalated disc in left ventricle hypertrophic myocytes, and improved cardiac function in an MI animal model of heart failure. With the emergence of injectable hydrogels as a therapeutic toward the regeneration of cardiac tissue after MI, here, we provide proof of concept that the release of tyrosine kinase inhibitors from hydrogels could have beneficial effects on cardiomyocytes. We developed an injectable hydrogel consisting of thiolated hyaluronic acid and P123-maleimide micelles that can incorporate PF4618433 as well as the Src inhibitor Saracatinib and achieved sustained release (of note, Src activates Pyk2). Using neonatal rat ventricular myocytes in the presence of a phorbol ester, endothelin-1, or phenylephrine to stimulate cardiac hypertrophy, the release of PF4618433 from the hydrogel had the same ability to decrease Cx43 tyrosine phosphorylation and maintain Cx43 localization at the plasma membrane as when directly added to the growth media. Additional beneficial effects included decreases in apoptosis, the hypertrophic marker atrial natriuretic peptide (ANP), and serine kinases upregulated in hypertrophy. Finally, the presence of both PF4618433 and Saracatinib further decreased the level of ANP and apoptosis than each inhibitor alone, suggesting that a combinatorial approach may be most beneficial. These findings provide the groundwork to test if tyrosine kinase inhibitor release from hydrogels will have a beneficial effect in an animal model of MI-induced heart failure.

Sotagliflozin attenuates cardiac dysfunction and remodeling in myocardial infarction rats

ObjectiveSotagliflozin is a dual sodium-glucose co-transporter-1 and 2 (SGLT1/2) inhibitor with selectivity towards SGLT2. Previous studies showed that SGLT2 inhibitors can improve cardiac function and reduce myocardial infarction size in animal models of myocardial infarction (MI). However, it remains unknown whether the dual inhibition of SGLT1/2 by sotagliflozin has beneficial effects in this context. In this study, we investigated the potential cardioprotective effects of sotagliflozin in an animal model of MI. MethodsSprague Dawley (SD) rats underwent left anterior descending coronary artery ligation or sham ligation then were randomly assigned to receive either sotagliflozin (10 mg/kg) or vehicle via intraperitoneal injection. Fourteen days post-MI, we assessed cardiac function using echocardiography and evaluated histological and molecular markers of cardiac remodeling and inflammation in the left ventricle. ResultsOur findings indicate that sotagliflozin treatment resulted in improved cardiac function and reduced infarct size compared with the vehicle-treated group. Additionally, sotagliflozin improved cardiac remodeling as shown by the decreased cardiac hypertrophy and cardiac apoptosis in the post-MI heart. Mechanistically, an apparent reduction in the cardiac inflammatory response in sotagliflozin-treated hearts was observed in the post-MI rats. ConclusionOverall, our results suggest that sotagliflozin may have cardioprotective effects against myocardial infarction.

Preliminary Evaluation of 18F-Labeled Benzylguanidine Analogs as NET Tracers for Myocardial Infarction Diagnosis.

Heart failure (HF) remains a major cause of late morbidity and mortality after myocardial infarction (MI). To date, no clinically established 18F-labeled sympathetic nerve PET tracers for monitoring myocardial infarction are available. Therefore, in this study, we synthesized a series of 18F-labeled benzyl guanidine analogs and evaluated their efficacy as cardiac neuronal norepinephrine transporter (NET) tracers for myocardial imaging. We also investigated the preliminary diagnostic capabilities of these tracers in myocardial infarction animal models, as well as the structure-activity relationship of these tracers. Three benzyl guanidine-NET tracers, including [18F]1, [18F]2, and [18F]3, were synthesized and evaluated in vivo as PET tracers in a myocardial infarction mouse model. [18F]LMI1195 was used as a positive control for the tracers. H&E staining of the isolated myocardial infarction heart tissue sections was performed to verify the efficacy of the selected PET tracer. Our data show that [18F]3 had a moderate decay corrected labeling yield (~10%) and high radiochemical purity (>95%) compared to other tracers. The uptake of [18F]3 in normal mouse hearts was 1.7±0.1%ID/cc at 1 h post-injection (p. i.), while it was 2.4±0.1, 2.6±0.9, and 2.1±0.4%ID/cc in the MI mouse hearts at 1, 2, and 3 days after surgery, respectively. Compared with [18F]LMI1195, [18F]3 had a better myocardial imaging effect in terms of the contrast between normal and MI hearts. The area of myocardial infarction shown by PET imaging corresponded well with the infarcted tissue demonstrated by H&E staining. With an obvious cardiac uptake contrast between normal mice and the myocardial infarction mouse model, [18F]3 appears to be a potential tool in the diagnosis of myocardial infarction. Therefore, it is necessary to conduct further structural modification studies on the chemical structure of [18F]3 to improve its in vivo stability and diagnostic detection ability to achieve reliable and practical imaging effects.

Abstract P3184: Catalase Knockdown Reverses The Activation Of Akt And The Increase In Mitochondrial Complex I Induced By MnSOD Overexpression In Mouse Heart Endothelial Cells

Introduction: We have recently showed that endothelial cell (EC)-specific overexpression of mitochondrial antioxidant MnSOD (MnSOD-OE) induced Akt and ERK activation, mitochondrial complex I (C-I) biogenesis, supercomplex assembly, and a shift from glycolysis to mitochondrial respiration in mouse heart ECs (MHEC). In vivo, MnSOD-OE induced coronary angiogenesis and improved cardiac function in a transgenic animal model of myocardial infarction. Hypothesis: We hypothesize that antioxidant catalase mediated neutralization of MnSOD-induced conversion of superoxide to H 2 O 2 within mitochondria (mito) is crucial for C-I biogenesis, ATP synthesis, and Akt and ERK activation in MnSOD-OE MHEC. Methods: We used an EC-specific, tetracycline (Tet)-controlled, transgenic MnSOD-OE model. Isolated MHECs (Tet-ON=Control, Tet-OFF=MnSOD-OE) were reverse transfected with either negative control (NC)- or catalase-siRNA (Tet-ON NC or CAT siRNA, Tet-OFF NC or CAT siRNA) and evaluated by western blot and ATP luminescence. Data were analyzed by Two-Way ANOVA and Tukey’s post-hoc. A p -value ≤0.05 was considered statistically significant. Results: Catalase-siRNA resulted in 54% decrease in catalase expression (2.01±0.05 in Tet-OFF NC vs. 0.93±0.05 in Tet-OFF CAT siRNA) in MHEC, resulting in 69% increase in mito-ROS (17.33±1.71 in Tet-OFF NC vs. 29.33±2.42 in Tet-OFF CAT siRNA). Catalase knockdown and increased mito-ROS resulted in 30% decrease in p-44/42 ERK (1.92±0.08 in Tet-OFF NC vs 1.35±0.17 in Tet-OFF CAT siRNA) and 17% decrease in p-Akt ser473 /t-Akt ratio in MnSOD-OE MHECs (1.57±0.07 in Tet-OFF NC vs 1.30±0.08 in Tet-OFF CAT siRNA). MnSOD-OE MHECs also showed decreased expression of mitochondrial C-l (by 31%; 1.43±0.06 in Tet-OFF NC vs 0.99±0.03 in Tet-OFF CAT siRNA) and C-III (by 29%; 0.90±0.06 in Tet-OFF NC vs 0.64±0.03 in Tet-OFF CAT siRNA), and decreased ATP luminescence when compared with the control group (by 27%; 12836±568.6 in Tet-ON CAT siRNA vs 9319±650.8 in Tet-OFF CAT siRNA). Conclusions: Catalase appears to play crucial role in reducing mito-ROS and inducing C-I biogenesis, ATP synthesis, and activation of Akt and ERK in MnSOD-OE MHECs.

An Experimental Model of Myocardial Infarction for Studying Cardiac Repair and Remodeling in Knockout Mice.

Cardiovascular disease is the most prevalent cause of death in Western countries, with acute myocardial infarction (MI) being the most prevalent form. This paper describes a protocol for studying the role of galectin 3 (Gal-3) in the temporal evolution of cardiac healing and remodeling in an experimental animal model of MI. The procedures described include an experimental model of MI with a permanent coronary ligature in male C57BL/6J (control) and Gal-3 knockout (KO) mice, an echocardiography procedure to study cardiac remodeling and systolic function in vivo, a histological evaluation of interstitial myocardial fibrosis with picrosirius red-stained and rhodamine-conjugated lectin-stained sections for studying myocyte hypertrophy by the cross-sectional area (MCSA), and the quantification of infarct size and cardiac remodeling (scar thinning, septum thickness, and expansion index) by planimetry in slices stained with Masson's trichrome and triphenyl tetrazolium chloride. Gal-3 KO mice with MI showed disrupted cardiac remodeling and an increase in the scar thinning ratio and the expansion index. At the onset of MI, myocardial function and cardiac remodeling were also severely affected. At 4 weeks post MI, the natural evolution of fibrosis in infarcted Gal-3 KO mice was also affected. In summary, the experimental model of MI is a suitable model for studying the temporal evolution of cardiac repair and remodeling in mice with the genetic deletion of Gal-3 and other animal models. The lack of Gal-3 affects the dynamics of cardiac repair and disrupts the evolution of cardiac remodeling and function after MI.

Gentianella acuta-derived Gen-miR-1 suppresses myocardial fibrosis by targeting HAX1/HMG20A/Smads axis to attenuate inflammation in cardiac fibroblasts

BackgroundContinuous activation and inflammation of cardiac fibroblasts (CFs) are essential for myocardial fibrosis. Gentianella acuta (Michx.) Hiitonen (G. acuta), that contains xanthones with cardioprotective properties, a typical healthful herb extensively used to treat cardiovascular diseases in Inner Mongolia region of China. However, it remains unknown whether or not G. acuta-derived miRNAs can shield CFs from activation by inflammatory stimulation. Therefore, we tend to investigated the role and core mechanism of G. acuta-derived Gen-miR-1 in regulating fibrosis and inflammation induced by TGF-β1. MethodsAn animal model for myocardial infarction was built by subcutaneous injections of ISO and treated with Gen-miR-1 using intragastric administration. The protective effect of Gen-miR-1 on the heart was assessed by pathomorphological analysis of myocardial fibrosis. Using loss- and gain-of-function approaches, Gen-miR-1 regulation of HAX1/HMG20A/Smads axis was investigated by utilizing luciferase assay, Western blot, co-immunoprecipitation, etc. ResultsScreened and identified Gen-miR-1 from G. acuta. Gen-miR-1 can enter the mouse body, and markedly inhibit myocardial infarction induced by ISO in mice, as well as suppresses fibrosis in CFs and attenuates the inflammatory response elicited by TGF-β1 in vitro. Gen-miR-1 downregulates HCLS1-related Protein X-1 (HAX1) expression through direct binding to the 3′ UTR of HAX1, which in turn relieves HAX1 from promoting the expression of high-mobility group protein 20A (HMG20A), whereas HMG20A downregulation restrains the activation of TGF-β1/Smads signaling pathways, subsequently resulting in a decrease of fibrosis and in facilitating CFs anti-inflammatory effects induced by Gen-miR-1 in the context of CFs activation induced by TGF-β1. ConclusionsOur results first uncovered unique bioactive components in G. acuta and elucidated the molecular mechanism by which G. acuta-derived Gen-miR-1 suppress inflammation and myocardial fibrosis. These findings expand our understanding of G. acuta's therapeutic properties and bioactive constituents. Gen-miR-1-regulated HAX1/HMG20A/Smads axis will be one potential therapeutic target for cardiac remodeling.

Human heart explant-derived cell extracellular vesicles inhibit NLRP3 inflammasome activation in macrophages

Background: Abnormal activation of NLRP3 (NOD-, LRR- and pyrin domain-containing protein 3) inflammasome plays a crucial role in promoting myocardial inflammation and adverse remodeling. Extracellular vesicles (EVs) secreted by heart explant-derived cells (HDCs) have been shown to reduce inflammation and confer cardioprotection in animal models of myocardial infarction. These salutary effects are suggested to be mediated by antiinflammatory microRNA (miRNA) cargo found within the EVs. However, whether HDC EVs can modulate NLRP3 inflammasome activation is not known. Hypothesis &amp; Study Objective: Given their antiinflammatory effects and abundantly enriched miRNA transcripts, we hypothesized that HDC EVs attenuate NLRP3 inflammasome activation. Therefore, the objective of this study was to assess the inhibitory effect of HDC EVs on NLRP3 inflammasome activation in macrophages-a major proinflammatory cell type recruited to myocardium after an ischemic insult. Methods: Human HDCs were cultured from cardiac biopsies in a clinical grade cell manufacturing facility. EVs were isolated from conditioned media (ultracentrifugation) and characterized for their identity (Nanosight &amp; antibody array). Monocytes (THP-1) were differentiated into macrophages with phorbol-myristate acetate (PMA; 3 days) and treated with EVs (4E+10 EVs/mL; 20 hours) before priming (lipopolysaccharide; 4 hours) and activating (nigericin; 1 hour) NLRP3 inflammasome. Caspase-1 activity, IL-1β and IL-18 levels in the culture supernatants were measured using a Caspase-Glo® 1 assay and ELISA respectively. EV miRNA cargo was profiled using nCounter ® human miRNA expression assay. Functional enrichment analysis and miRNA target prediction were performed using bioinformatic tools (Tam 2.0 &amp; miRWalk v3). Results: EV size (160±2 nm) and markers (ICAM, ALIX, CD81, CD63, EPCAM, ANXAS, TSG101, FLOT-1) confirmed EV identity. EV treatment significantly inhibited NLRP3 inflammasome induced caspase-1 activity (67% lower vs. no EV treated, n=4-6, p&lt;0.0001). Further, EV treated macrophages showed a significant reduction in IL-18 (623±8 vs.1462±43 pg/mL, n=3, p=0.0025) and a trend towards reduction in IL-1β levels (1292±115 vs. 2535±115 pg/mL, n=3, p=0.08). MicroRNA set analysis revealed that EVs are enriched with 22 anti-inflammatory miRNAs and importantly 3 of the top 10 significantly enriched functional terms (overrepresentation, p&lt;0.05) are found to be related to immunity and inflammation. Interestingly, EVs are enriched with 4 miRNAs (miR-100, miR-181a, miR-21, miR-22) predicted to inhibit NLRP3 inflammasome. Conclusion: Our findings show that human heart explant-derived cell EVs inhibit activation of NLRP3 inflammasome in macrophages and this effect in part is possibly mediated via transfer of their anti-inflammatory miRNA cargo. These preliminary findings encourage a preclinical investigation to assess EV modulatory effect on NLRP3 inflammasome in models of ischemic heart disease. Canadian Institutes of Health Research Project Grant 410103 (DRD) and University of Ottawa Heart Institute Strategic Research Endowed Fellowship (RV) This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Idebenone attenuates ferroptosis by inhibiting excessive autophagy via the ROS-AMPK-mTOR pathway to preserve cardiac function after myocardial infarction

Cardiovascular diseases (CVDs) are the leading causes of mortality worldwide. As a type of CVDs, myocardial infarction (MI) induces ischemia hypoxia, which leads to excessive reactive oxygen species (ROS), resulting in multiple cell deaths and contributing to the subsequent development of heart failure or premature death. Recent evidence indicates that ROS-induced lipid peroxidation promotes autophagy and ferroptosis, leading to the loss of healthy myocardium and resulting in the dysfunction of cardiac tissue. Theoretically, cardiac function would be preserved after MI by inhibiting autophagy and ferroptosis. As an analog of coenzyme Q10 (CoQ10) and a clinically approved drug, idebenone would be used to inhibit ferroptosis and preserve cardiac function due to its capacity to improve mitochondrial physiology with antioxidant and anti-inflammatory properties. Here, we confirmed that the addition of idebenone inhibited H2O2-induced and RSL3-induced ferroptosis. Furthermore, the ROS-AMPK-mTOR pathway axis was identified as the signaling pathway that idebenone stimulated to prevent excessive autophagy and consequent ferroptosis. In the MI animal model, idebenone demonstrated a cardioprotective role by regulating ROS-dependent autophagy and inhibiting ferroptosis, which paves the way for the future clinical translation of idebenone in MI management.

The role of major immune cells in myocardial infarction.

Myocardial infarction (MI) is a cardiovascular disease (CVD) with high morbidity and mortality worldwide, often leading to adverse cardiac remodeling and heart failure, which is a serious threat to human life and health. The immune system makes an important contribution to the maintenance of normal cardiac function. In the disease process of MI, necrotic cardiomyocytes release signals that activate nonspecific immunity and trigger the action of specific immunity. Complex immune cells play an important role in all stages of MI progression by removing necrotic cardiomyocytes and tissue and promoting the healing of damaged tissue cells. With the development of biomaterials, cardiac patches have become an emerging method of repairing MI, and the development of engineered cardiac patches through the construction of multiple animal models of MI can help treat MI. This review introduces immune cells involved in the development of MI, summarizes the commonly used animal models of MI and the newly developed cardiac patch, so as to provide scientific reference for the accurate diagnosis and effective treatment of MI.

Fibrin-Enriched Cardiac Extracellular Matrix Hydrogel Promotes In Vitro Angiogenesis.

Angiogenesis is essential for cardiac repair after myocardial infarction. Promoting angiogenesis has been demonstrated as an effective approach for myocardial infarction treatment. Several different strategies for inducing myocardial angiogenesis have been explored, including exogenous delivery of angiogenic genes, proteins, microRNAs, cells, and extracellular vesicles. Various types of injectable hydrogels have been investigated for cardiac tissue repair. One of the most promising injectable hydrogels in cardiac regeneration is a cardiac extracellular matrix hydrogel that is derived from decellularized porcine myocardium. It can be delivered minimally invasively via transendocardial delivery. The safety and efficacy of cardiac extracellular matrix hydrogels have been shown in small and large animal myocardial infarction models as well as clinical trials. The main mechanisms underlying the therapeutic benefits of cardiac extracellular matrix hydrogels have been elucidated and involved in the modulation of the immune response, downregulation of pathways related to heart failure progression and fibrosis, upregulation of genes important for cardiac muscle contraction, and enhancing cardiomyocyte differentiation and maturation from stem cells. However, no potent capillary network formation induced by cardiac extracellular matrix hydrogels has been reported. In this study, we tested the feasibility of incorporating a fibrin matrix into cardiac extracellular matrix hydrogels to improve the angiogenic properties of the hydrogel. Our in vitro results demonstrate that fibrin-enriched cardiac extracellular matrix hydrogels can induce robust endothelial cell tube formation from human umbilical vein endothelial cells and promote the sprouting of human mesenchymal stem cell spheroids. The obtained information from this study is very critical toward the future in vivo evaluation of fibrin-enriched cardiac extracellular matrix hydrogels in promoting myocardial angiogenesis.

Uric acid promotes myocardial infarction injury via activating pyrin domain-containing 3 inflammasome and reactive oxygen species/transient receptor potential melastatin 2/Ca2+pathway

Cardiomyocytes injury has been considered as a key contributor for myocardial infarction (MI). Uric acid (UA) can induce cardiomyocytes injury, which is closely related to NLRP3 activation and inflammatory factor generation. However, the mechanism how UA modulates cardiomyocytes remains elusive. Western blotting and qRT-PCR were applied for measuring protein and mRNA expression, respectively. ROS production and Ca2+ influx were measured by flow cytometry. Patch clamp technique was used for measuring transient receptor potential melastatin 2 (TRPM2) channel. Ligation of left anterior descending for 2 h was performed to induce MI animal model. The rats were treated by different concentration of uric acid. The artery tissues were stained by HE and collected for measurement of NLRP3 and inflammatory factors. Supplementation of UA significantly promoted apoptosis, and augmented the expression of intercellular adhesion molecule-1, chemoattractant protein-1, vascular cell adhesion molecule-1, and NLRP3 inflammasome. Knockdown of NLRP3 reversed the influence of UA on MI by decreasing collagen deposition, fibrotic area, apoptosis. The expression of NLRP3 inflammasome increased markedly after treatment of UA. UA activated ROS/TRPM2/Ca2+ pathway through targeting NLRP3. UA activated NLRP3 inflammasome and augments inflammatory factor production, which in turn exacerbates cardiomyocytes injury. Knockdown of NLRP3 reversed the influence of UA on apoptosis and cell cycle. UA may promote cardiomyocytes injury through activating NLRP3 inflammasome and ROS/TRPM2 channel/Ca2+ pathway.

A total closed chest swine model of acute myocardial infarction-related cardiogenic shock: A critical double coronary sub-occlusion approach

The management of acute myocardial infarction-related cardiogenic shock (AMICS) represents a significant challenge, with mortality rates remaining high (40–60%), despite recent advances. Current animal models of myocardial infarction are either associated with a very high rate of per-procedure malignant arrhythmia, or with very low impairment of hemodynamic parameters, or with the inability to have complete coronary reperfusion. We sought to develop a closed chest and clinically relevant large animal model of severe AMICS, with high survival rate. Adult pigs were anaesthetized and mechanically ventilated. Percutaneous cardiac catheterization was performed under fluoroscopy. Advanced left ventricular dysfunction was induced by 120 minutes of critical sub-occlusion of the proximal left anterior descending coronary artery and the mid circumflex artery. A thorough hemodynamic assessment was obtained by invasive and non-invasive monitoring devices. Repeated blood samples were obtained to determine blood gas parameters, lactate, and haemoglobin concentration. After death, the heart was retrieved for further histological analyses. All animals (n = 12) developed significant circulatory failure associated with AMICS upon reperfusion and beyond. No animal died during the ischemia process. However, all animals that did not benefited from vasopressor support (“sham” group, n = 4) spontaneously died within 30 minutes of reperfusion, confirming the severity of the model. Cardiogenic shock was characterized by a drop in mean arterial pressure below 60 mmHg (58 ± 5 mmHg at 120 min of ischemia), a significant decrease in mean cardiac output (−44% from 5.7 ± 0.4 at baseline to 3.2 ± 0.4 at 120 minutes of ischemia) and SvO2 (−32% from 57 ± 8 at baseline to 39 ± 6 at 120 minutes of ischemia) and a significant increase in left ventricle end-diastolic pressure (LVEDP) (+110% from 10 ± 3 at baseline to 21 ± 3 at 120 minutes of ischemia). CO2 gap and coronary sinus venous oxygen saturation increased significantly upon ischemia and reperfusion and remained elevated throughout (P ≤ 0.001 for all comparisons). Myocardial samples corroborated extensive cellular necrosis and inflammatory infiltrates. We present, for the first time, a stable and clinically relevant model of severe AMICS obtained by critical double coronary sub-occlusion. The greater severity of the model did not lead to an increase in the frequency of malignant arrythmias and per-procedure mortality.

A novel phosphocholine-mimetic inhibits a pro-inflammatory conformational change in C-reactive protein.

C-reactive protein (CRP) is an early-stage acute phase protein and highly upregulated in response to inflammatory reactions. We recently identified a novel mechanism that leads to a conformational change from the native, functionally relatively inert, pentameric CRP (pCRP) structure to a pentameric CRP intermediate (pCRP*) and ultimately to the monomeric CRP (mCRP) form, both exhibiting highly pro-inflammatory effects. This transition in the inflammatory profile of CRP is mediated by binding of pCRP to activated/damaged cell membranes via exposed phosphocholine lipid head groups. We designed a tool compound as a low molecular weight CRP inhibitor using the structure of phosphocholine as a template. X-ray crystallography revealed specific binding to the phosphocholine binding pockets of pCRP. We provide invitro and invivo proof-of-concept data demonstrating that the low molecular weight tool compound inhibits CRP-driven exacerbation of local inflammatory responses, while potentially preserving pathogen-defense functions of CRP. The inhibition of the conformational change generating pro-inflammatory CRP isoforms via phosphocholine-mimicking compounds represents a promising, potentially broadly applicable anti-inflammatory therapy.

Abstract 9808: Deletion of Arrdc4 Enhances Myocardial Glucose Transport and Ameliorates Ischemic Injury

Cardiomyocytes depend on glycolysis instead of oxidative phosphorylation during hypoxia and utilize glucose as a primary anaerobic energy source. Cardiac glucose transport is facilitated by the expression of glucose transporters (GLUT1 and GLUT4) on the cell surface. The arrestins are a family of proteins that regulate the signaling and trafficking of different receptors and transporters on the plasma membrane. As a scaffold protein, beta-arrestins mediate endocytosis and signal termination of beta-adrenergic receptors in cardiomyocytes. However, unlike the well-characterized beta-arrestins, the physiological roles of the related proteins termed alpha-arrestins remain largely unknown in the heart. In this study, we discovered for the first time that a member of alpha-arrestins, Arrestin Domain-Containing Protein 4 (Arrdc4), functions as a regulatory scaffold protein of GLUT1 and controls cardiac glucose metabolism. We found that Arrdc4 interacts with GLUT1 and promotes its endocytosis in cardiomyocytes. Interestingly, the cardiac expression of Arrdc4 is significantly upregulated by myocardial ischemia. Arrdc4 decreases cell surface expression of GLUT1 and suppresses glucose transport in the wild-type (WT) mouse heart. Then, we generated a novel Arrdc4 knockout (KO) mouse using CRISPR/Cas9 genome editing and characterized the effects of Arrdc4 in an animal model of myocardial infarction (MI) by coronary artery ligation in vivo. Surprisingly, Arrdc4-KO mice exhibit smaller infarct size, fewer apoptotic cells, and higher left ventricular (LV) fractional shortening, resulting in better post-MI survival than WT mice. Furthermore, using the Langendorff perfusion system, we found that Arrdc4-KO hearts augment cardiac glucose transport and preserve better LV mechanical function during anaerobic perfusion than WT hearts ex vivo. These results demonstrate that Arrdc4-KO cardiomyocytes coordinately maintain the optimal expression of GLUT1 on the cell surface, which leads to a metabolic rearrangement to secure energy homeostasis under oxygen- and nutrient-limited environments. In conclusion, we identified Arrdc4 as a new adaptor protein for GLUT1 in cardiomyocytes and a key player in cardiac metabolism in the ischemic heart.

Cardioprotective Role of Scopoletin on Isoproterenol-Induced Myocardial Infarction in Rats.

Scopoletin is a phenolic coumarin isolated from a variety of plants and was originally used to treat various diseases including arthritis as well as bone-related diseases. The goal of this study was to determine scopoletin's therapeutic potential in an animal model of myocardial infarction induced with ISO. There were five groups of albino male rats. Group I (control) animals were orally treated with olive oil. Group II (scopoletin) animals were pre-treated orally with a 50-mg dosage of scopoletin for 28 days. Group III (ISO-treated) animals were treated with 85mg/kg of ISO subcutaneously for 2 consecutive days (29th and 30th day). Group IV (scopoletin and ISO) animals were pre-treated orally with 25mg of scopoletin for 28 days before exposure to ISO. Group V (scopoletin and ISO) animals were pre-treated with 50mg of scopoletin for 28 days before exposure to ISO. In the ISO-administered animals, a wider heart-to-body weight ratio, a higher heart weight, higher cardiac diagnostic markers, higher MDA levels and related antioxidant levels, inflammatory, and apoptotic markers were observed. Scopoletin pre-treatment with ISO (25 and 50mg/kg b.wt) significantly reduced heart-to-body weight ratio, cardiac diagnostic markers, MDA, inflammatory markers, and apoptotic markers. Meantime, a pre-treatment with scopoletin increased the levels of antioxidant enzymes. Inflammation and necrosis were observed in the histopathology of heart tissue of ISO-treated animals and these histopathological conditions were reversed by scopoletin pretreatment. The antioxidant and anti-inflammatory properties of ISO-treated rats were shown to be increased by scopoletin, showing its therapeutic potential against cardiovascular diseases. Through the use of its antioxidant and anti-inflammatory properties, scopoletin exhibited anti-myocardial infarction properties. However, further preclinical studies will be required to demonstrate the mechanism of action of scopoletin involved in anti-myocardial infarction.

Thin-cap fibroatheroma and increased coronary intima-media thickness are associated with an altered balance of arginine metabolites.

Arginase inhibition increases plasma citrulline and citrulline / ornithine (C/O) ratio, and reduces plasma ornithine and ornithine / arginine (O/A) ratio in an animal model of myocardial infarction (MI). We hypothesized that the presence of thin‑cap fibroatheroma (TCFA) in the culprit lesion and increased non‑culprit intima‑media thickness of an infarct‑related artery (IRA) are associated with an altered balance of arginine metabolites. Arginine and its metabolites were measured using liquid chromatography and tandem mass spectrometry in 100 consecutive MI patients upon admission and at 6‑month follow‑up. TCFA and adjacent to culprit lesion proximal and distal 10‑mm segments were assessed with optical coherence tomography in the acute phase. Twenty five patients without coronary lesions on angiography served as controls. The C/O ratio increased 5.33 times (P <0.001), while the O/A ratio decreased 2.53 times (P <0.001) at the 6‑month follow‑up, as compared with the acute phase of MI. The patients with (n = 75) vs without (n = 25) TCFA had lower C/O ratio by 29% (P = 0.003), while the mean intima‑media diameter of adjacent non‑culprit region correlated with the follow‑up O/A ratio (R = 0.337; P = 0.003). In a multivariable analysis, a higher acute phase C/O ratio was associated with a lower risk of TCFA presence (odds ratio, 0.978; 95% CI, 0.962-0.994; P = 0.006), whereas a higher follow‑up O/A ratio correlated with larger intima‑media diameter of the adjacent segments (β coefficient, 0.227; 95% CI for β coefficient, 0.045-0.409; P = 0.018). Enhanced arginase activity over nitric oxide synthase following ischemia was associated with the presence of TCFA in the culprit lesion, while a similar metabolic shift in the chronic phase correlated with a greater thickness of the intima‑media in the adjacent non‑culprit IRA segments.