Infarction Registry Research Articles

99mTc]-PentixaTec SPECT/CT for Imaging of Chemokine Receptor 4 Expression After Myocardial Infarction.

Accumulation of CXCR4 (C-X-C motif chemokine receptor 4)-positive immune cells after acute myocardial infarction (AMI) can be visualized by positron emission tomography. For a broader clinical application, there is a need for CXCR4-directed radiotracers labeled with isotopes that can be used with single-photon emission computed tomography (SPECT). We report on the detection of CXCR4 expression after AMI in humans using the novel tracer [99mTc]-PentixaTec. In this retrospective analysis, 9 patients with AMI after mechanical revascularization underwent myocardial inflammation imaging with [99mTc]-PentixaTec SPECT/computed tomography and rest perfusion SPECT imaging. Tracer uptake in the infarcted area, spleen, bone marrow, and blood pool were used for semiquantitative analysis and calculation of signal-to-background ratios. The extent and intensity of SPECT-derived inflammatory changes were compared with serological markers and perfusion defects. CXCR4-directed SPECT was positive in all patients. Increased CXCR4 expression was only detected in areas with diminished perfusion corresponding to the affected vessel in coronary angiography, with a signal-to-background ratio (infarcted area-to-blood pool) of 2.36±0.74. Uptake in bone marrow and spleen showed a significant correlation with CXCR4 expression in the infarcted areas (r=0.73 and P=0.03 for spleen and r=0.81 and P=0.008 for bone marrow, respectively). The extent and intensity of SPECT-derived inflammatory changes showed no significant association with serum troponin, CK (creatine kinase), leukocyte, or CRP (C-reactive protein) levels. This is the first report of in vivo CXCR4 imaging after AMI using a 99mTc-labeled tracer. Increased CXCR4 expression was observed locally in the infarcted region and was related to a systemic inflammatory response in the reticuloendothelial system. This proof-of-concept investigation demonstrates the general feasibility of evaluating the inflammation-related CXCR4 expression in the myocardium after AMI using conventional scintigraphy or SPECT and might, thus, broaden its worldwide application in clinical practice.

Abstract 4136234: Increased Reactive Oxygen Species using [18F]ROStrace PET and Dihydroethidium Staining in Myocardial Infarction Reperfusion injury

Introduction: Patients with reperfusion injury following myocardial infarction (MI) are at a higher risk of heart failure. Reactive oxygen species (ROS) activity can further damage cardiomyocytes and compromise heart function. Imaging methods are needed to assess ROS in vivo to investigate targeted adjunctive therapies. Our group developed a novel ROS-activated PET radiotracer [18F]ROStrace to fill this gap. In this study, we measured [18F]ROStrace fractional uptake rate (FUR) and for the first time compared it with histologic assessment of infarct and myocardium specimens. We hypothesized that [18F]ROStrace FUR was increased in the infarct and that [18F]ROStrace FUR was supported by [18F]ROStrace analogue dihydroethidium (DHE) staining. Methods: MI was induced in five swine, followed by reperfusion after 90 minutes. In vivo LGE CMR imaging and [18F]ROStrace and [82]Rb PET were performed at ~3-4 days after infarction. A terminal procedure was then performed. DHE and 4′,6-diamidino-2-phenylindole (DAPI) staining was done. Two swine received injections of DHE in the right and left coronary arteries to assess ROS. ROS activity was determined from [18F]ROStrace by computing the [82]Rb myocardial blood flow (MBF) corrected FUR. The linear relationship between infarct and MVO size, and MBF-corrected [18F]ROStrace FUR were calculated using the Pearson’s r. Results: There was a strong and positive correlation between infarct and MVO size (r=0.9, p=0.04). The MBF-corrected ROStrace FUR at baseline was 0.07±0.06 ml/g, infarct was 0.15 ± 0.05 ml/g, and remote was 0.09 ± 0.05 ml/g. We observed a significant difference between ROS in the infarct and remote region (p=0.01), which is also seen in the increased DHE staining in the infarct. We also observed increased DAPI staining in the infarct region compared to free wall due to the presence of inflammatory cells, thus increasing the number of nuclei. Conclusion: [18F]ROStrace is increased in the infarct during the subacute period post-MI compared to healthy and remote myocardium and supported by histological assessment. This work may lead to the use of in vivo [18F]ROStrace PET to support development of therapeutic strategies targeting ROS to reduce MI.

Abstract 4138272: CMR Quantification of Myocardial Oxygenation Extraction Fraction Maps Using a Model-based Self-supervised Learning Network: Initial Experience in Patients with Cardiomyopathies

Background: Measurements of myocardial oxygenation extraction fraction (mOEF) maps with cardiovascular magnetic resonance (CMR) has been recently developed to assess myocardial oxygen metabolism in healthy. Recent studies focus on developing supervised machine learning methods to improve the quantification of mOEF. However, these supervised learning methods may be limited by the lack of ground-truth mOEF maps because MRI cannot directly measure mOEF with the same precision as PET. Hypothesis: Model-based self-supervised learning neural networks maybe feasible to generate mOEF maps accurately. Aims: To develop a physical model-based self-supervised learning neural network to accurately estimate mOEF for the patients with a variety of cardiomyopathies. Methods: An ECG triggered, two-dimensional asymmetric spin-echo (ASE) prepared sequence was employed to scan 71 patients with dilated, hypertrophic, or ischemic cardiomyopathies. At least 3 slices were scanned for each patient and each ASE scan was performed free-breathing with a spatial resolution of 1.7 × 1.7 × 8 mm 3 and scan time of 18 RR-interval. Acquisition of late gadolinium enhancement (LGE) was performed in each patient after the administration of 0.15 mmol/kg gadolinium agent for the visualization of myocardial infarction regions. A fully convolutional neural network with U-Net architecture was optimized with a physical model-based signal loss function (see Figure 1) on the ASE training dataset from 67 patients to generate mOEF maps. To evaluate if the method can accurately quantify abnormal mOEF, four patients with myocardial infarction were selected as the test set. Results: A previous publication reported normal mOEF levels at approximately 0.6-0.7 in healthy subjects. Figure 2 shows our proposed method generated mOEF maps from two representative patients and their LGE images for comparisons. In comparison with the remote region (mOEF = 0.70±0.10), the mOEF of myocardial regions with infarction was significantly lower (mOEF = 0.36±0.12, p < 0.001). The infarction areas predicted by the network overlapped well with the LGE. Conclusion: Quantification of mOEF using the proposed model-based self-supervised U-Net is feasible to detect abnormalities in regional myocardial oxygenation. Current study is ongoing to evaluate the proposed technique in a large cardiac patient dataset.

Hypoxia-inducible factor-2α enhances neutrophil survival to promote cardiac injury following myocardial infarction.

Heart failure is a major cause of mortality following myocardial infarction. Neutrophils are among the first immune cells to accumulate in the infarcted region. Although beneficial functions of neutrophils in heart injury are now appreciated, neutrophils are also well known for their ability to exacerbate inflammation and promote tissue damage. Myocardial infarction induces hypoxia, where hypoxia-inducible factors (HIFs) are activated and play critical roles in cellular functions. In this context, the role of Hif2α in neutrophils during myocardial infarction is unknown. Here, we demonstrate that neutrophil Hif2α deletion markedly attenuates myocardial infarct size, improves cardiac function, reduces neutrophil survival and tissue accumulation, and correlates with increased macrophage engulfment rates. Mechanistic studies revealed that Hif2α promotes neutrophil survival through binding to hypoxia response element (HRE) in the promoter region of Birc2 to regulate expression of the prosurvival factor, cellular inhibitor of apoptosis protein-1 (cIAP1). Inhibition of cIAP1 in neutrophils using the pharmacological agent, Birinapant resulted in increased cell death, establishing a critical role of cIAP1 downstream of Hif2α in neutrophil survival. Taken together, our data demonstrate a protective effect of Hif2α deletion in neutrophils on cardiac injury outcomes through modulation of neutrophil cell survival.NEW & NOTEWORTHY Hif2α in neutrophils increases infarct size, cardiac dysfunction, and ventricular scar after myocardial infarction. Hif2α in neutrophils supports neutrophil survival via cIAP-1 signaling and delays macrophage engulfment.

TLR7 deficiency alleviated myocardial ischemia reperfusion injury via regulating macrophage-neutrophil interaction

Abstract Background Toll-like receptor 7 (TLR7) is an intracellular innate immune receptor activated by single-stranded RNA. We previously reported that TLR7 could recognize RNA from dying cardiac cells and thereby deteriorating post myocardial infarction left ventricular remodeling. However, its effect on myocardial ischemia reperfusion (IR) injury is still unknown. Purpose In this study, we aimed to investigate the role of TLR7 in myocardial IR injury and the underlying mechanisms. Methods C57BL/6J wild type (WT) and TLR7 deficient (TLR7-/-) mice underwent left anterior descending artery occlusion for 30min followed by reperfusion. Myocardial infarct size was measured by Evan’s blue and TTC staining. mRNA expression levels of cytokines and phagocytosis-related receptors were detected by qPCR. TUNEL assay was conducted to determine apoptosis in the heart. Influx of neutrophils and macrophages in ischemic myocardium was analyzed by flow cytometry and Histone Cit3 was imaged to examine formation of neutrophils extracellular traps (NETs), cardiac function was evaluated by echocardiography during post-IR injury follow-up. Results TLR7 expression was up-regulated after IR injury in ischemic myocardium of WT mice. Compared to WT mice, fewer apoptotic cells and smaller infarct size (34±2% vs. 23±3% of area at risk, p<0.01) were observed in TLR7-/- mice at 24 hours post-IR, which was accompanied by reduced inflammatory cytokines (IL-1β: 110.5±14.1 vs. 54.8±13.7, p<0.05; TNF-α: 4.6±1.0 vs. 2.0±0.4, p<0.05) and increased anti-inflammatory factors (TNF-β: 2.9±0.3 vs. 8.6±2.6, p<0.05; IL-10: 14.2±2.1 vs. 32.3±8.8, p<0.05). Surprisingly, although the influx of neutrophils and macrophages increased to a similar extent in WT and TLR7-/- mice, the latter exhibited remarkably less NETs formation and enhanced macrophage phagocytosis in the infarct region. Moreover, TLR7 deficiency improved cardiac function, as indicated by increased left ventricular ejection fraction (LVEF) and fraction shortening (FS) at 56d post-IR. Conclusions TLR7 deficiency alleviates myocardial IR injury and improves cardiac function probably via enhancing macrophage clearance of NETs in the injured myocardium.TLR7 deficiency in cardiac functionTLR7 deficiency decreased NETs formation

Bnip3 promotes the release of mitochondria-derived extracellular vesicles in cardiac fibroblasts to exacerbate inflammation response after myocardial infarction

Abstract Background Cardiac fibroblasts (CFs) play a crucial role in tissue repair and remodeling following myocardial infarction (MI). Furthermore, CFs possess the ability to sense signals of myocardial injury and secrete cytokines, thereby eliciting a pro-inflammatory response during the early post-MI phase. Our previous studies have demonstrated that CFs located in the infarcted region release small extracellular vesicles (sEVs) abundant in damaged mitochondria, termed "mt-sEVs". These mt-sEVs are internalized by macrophages, prompting the secretion of IL-6 and IL-1β via NLRP3/Caspase-1 pathway. Nonetheless, the precise mechanisms underlying the promotion of mt-sEVs release remain elusive. Objective This study aimed to investigate the pivotal genes involved in mediating the release of CFs-derived mt-sEVs, with potential implications for post-MI therapeutic strategies. Methods Primary CFs were cultured for 24 hours in sugar-free medium with 1% oxygen (OGD) in vitro. Conditioned medium was subjected to ultracentrifugation to isolate sEVs. The presence of damaged mitochondrial components within the sEVs was confirmed using Mito-tracker and nanoflowmetry. Subcellular structures were visualized via transmission electron microscopy (TEM). Protein interactions were validated through co-immunoprecipitation (co-IP) assays. CF-specific gene knockout mice were generated and subjected to MI surgery. The proportion of F4/80+/CD86+ cells was quantified using flow cytometry. Cardiac function was evaluated using echocardiography, and the extent of cardiac fibrosis was assessed via Masson staining. Results Re-analysis of single-cell RNA sequencing data (GSE153480) unveiled a significant upregulation of the mitophagy receptor Bnip3 in CF sub-populations following MI, and the up-regulated trend was also observed in OGD-CFs. Deletion of Bnip3 hindered the expression of LC3 and its co-localization with mitochondria. TEM observed extensive fusion of mitophagosomes with multivesicular bodies in OGD-CFs. Fluorescence signal detected by nano flowmetry significantly decreased in Bnip3 knockdown sEVs incubated with Mito-tracker. Bnip3 deletion in CFs resulted in a significant downregulation of the sEVs release key factor Rab27a, concomitant with a striking increase in Rab27a ubiquitination. Predicted binding sites of both Bnip3 and Rab27a with the deubiquitinase Usp7 were validated through co-IP assays. Immunofluorescence staining demonstrated the co-localization of Usp7 with Bnip3 in OGD-CFs. CF-specific deletion of Bnip3 reduced the proportion of M1 macrophages, reversed left ventricular dysfunction, and mitigated myocardial fibrosis in post-MI hearts. Conclusion Collectively, our study reveals that Bnip3-mediated mitochondrial secretory autophagy in CFs was significantly activated to drive the release of mt-sEVs. Additionally, Bnip3 interacts with Usp7 to deubiquitinate Rab27a, promoting the release of mt-sEVs in CFs, exacerbating the inflammatory response after MI.Graphical abstract

Detection, Isolation and Quantification of Myocardial Infarct with Four Different Histological Staining Techniques.

The precise quantification of myocardial infarction is crucial for evaluating therapeutic strategies. We developed a robust, color-based semi-automatic algorithm capable of infarct region detection, isolation and quantification with four different histological staining techniques, and of the isolation and quantification of diffuse fibrosis in the heart. Our method is developed based on the color difference in the infarct and non-infarct regions after histological staining. Mouse cardiac tissues stained with Masson's trichrome (MTS), hematoxylin and eosin (H&E), 2,3,5-Triphenyltetrazolium chloride and picrosirius red were included to demonstrate the performance of our method. We demonstrate that our algorithm can effectively identify and produce a clear visualization of infarct tissue in the four staining techniques. Notably, the infarct region on an H&E-stained tissue section can be clearly visualized after processing. The MATLAB-based program we developed holds promise for infarct quantification. Additionally, our program can isolate and quantify diffuse fibrotic elements from an MTS-stained cardiac section, which suggests the algorithm's potential for evaluating pathological cardiac fibrosis in diseased cardiac tissues. We demonstrate that this color-based algorithm is capable of accurately identifying, isolating and quantifying cardiac infarct regions with different staining techniques, as well as diffuse and patchy fibrosis in MTS-stained cardiac tissues.

Yap Is a Nutrient Sensor Sensitive to the Amino Acid L-Isoleucine and Regulates the Expression of Ctgf in Cardiomyocytes.

Myocardial infarction and reperfusion constitute a complex injury consisting of many distinct molecular stress patterns that influence cardiomyocyte survival and adaptation. Cell signalling, which is essential to cardiac development, also presents potential disease-modifying opportunities to recover and limit myocardial injury or maladaptive remodelling. Here, we hypothesized that Yap signalling could be sensitive to one or more molecular stress patterns associated with early acute ischemia. We found that Yap, and not Taz, expression patterns differed in a post-myocardial infarct compared to a peri-infarct region of rat hearts post-myocardial infarction, suggesting cell specificity that would be challenging to resolve for causation in vivo. Using H9c2 ventricular myotubes in vitro as a model, Yap levels were determined to be more sensitive to nutrient deprivation than other stress patterns typified by ischemia within the first hour of stress. Moreover, this is mediated by amino acid availability, predominantly L-isoleucine, and influences the expression of connective tissue growth factor (Ctgf)-a major determinant of myocardial adaptation after injury. These findings present novel opportunities for future therapeutic development and risk assessment for myocardial injury and adaptation.

Multiscale Fiber Remodeling in the Infarcted Left Ventricle using a Stress-Based Reorientation Law

The organization of myofibers and extra cellular matrix within the myocardium plays a significant role in defining cardiac function. When pathological events occur, such as myocardial infarction (MI), this organization can become disrupted, leading to degraded pumping performance. The current study proposes a multiscale finite element (FE) framework to determine realistic fiber distributions in the left ventricle (LV). This is achieved by implementing a stress-based fiber reorientation law, which seeks to align the fibers with local traction vectors, such that contractile force and load bearing capabilities are maximized. By utilizing the total stress (passive and active), both myofibers and collagen fibers are reoriented. Simulations are conducted to predict the baseline fiber configuration in a normal LV as well as the adverse fiber reorientation that occurs due to different size MIs. The baseline model successfully captures the transmural variation of helical fiber angles within the LV wall, as well as the transverse fiber angle variation from base to apex. In the models of MI, the patterns of fiber reorientation in the infarct, border zone, and remote regions closely align with previous experimental findings, with a significant increase in fibers oriented in a left-handed helical configuration and increased dispersion in the infarct region. Furthermore, the severity of fiber reorientation and impairment of pumping performance both showed a correlation with the size of the infarct. The proposed multiscale modeling framework allows for the effective prediction of adverse remodeling and offers the potential for assessing the effectiveness of therapeutic interventions in the future. Statement of SignificanceThe organization of muscle and collagen fibers within the heart plays a significant role in defining cardiac function. This organization can become disrupted after a heart attack, leading to degraded pumping performance. In the current study, we implemented a stress-based fiber reorientation law into a computer model of the heart, which seeks to realign the fibers such that contractile force and load bearing capabilities are maximized. The primary goal was to evaluate the effects of different sized heart attacks. We observed substantial fiber remodeling in the heart, which matched experimental observations. The proposed computational framework allows for the effective prediction of adverse remodeling and offers the potential for assessing the effectiveness of therapeutic interventions in the future.

Association between ASPECTS region of infarction and clinical outcome in non-acute large vessel occlusion ischaemic stroke after endovascular recanalisation

PurposeThis study retrospectively investigated whether infarction in specific Alberta Stroke Program Early CT Score (ASPECTS) regions is associated with clinical outcome in patients with symptomatic non-acute internal carotid or middle...

Integrated Strategies for Targeting Arteriogenesis and Angiogenesis After Stroke.

The interdependence between arteriogenesis and angiogenesis is crucial for enhancing perfusion by synchronously improving leptomeningeal collaterals (LMCs) and microvascular networks after stroke. However, current approaches often focus on promoting arteriogenesis and angiogenesis separately, neglecting the potential synergistic benefits of targeting both processes simultaneously. Therefore, it is imperative to consider both arteriogenesis and angiogenesis as integral and complementary strategies for post-stroke revascularization. To gain a deeper understanding of their relationships after stroke and to facilitate the development of targeted revascularization strategies, we compared them based on their timescale, space, and pathophysiology. The temporal differences in the occurrence of arteriogenesis and angiogenesis allow them to restore blood flow at different stages after stroke. The spatial differences in the effects of arteriogenesis and angiogenesis enable them to specifically target the ischemic penumbra and core infarct region. Additionally, the endothelial cell, as the primary effector cell in their pathophysiological processes, is promising target for enhancing both. Therefore, we provide an overview of key signals that regulate endothelium-mediated arteriogenesis and angiogenesis. Finally, we summarize current therapeutic strategies that involve these signals to promote both processes after stroke, with the aim of inspiring future therapeutic advances in revascularization.

Sympathetic structural and electrophysiological remodeling in a rabbit model of reperfused myocardial infarction.

Chondroitin sulfate proteoglycans (CSPGs) inhibit sympathetic reinnervation in rodent hearts post-myocardial infarction (MI), causing regional hypoinnervation that is associated with supersensitivity of β-adrenergic receptors and increased arrhythmia susceptibility. To investigate the role of CSPGs and hypoinnervation in the heart of larger mammals, we used a rabbit model of reperfused MI and tested electrophysiological responses to sympathetic nerve stimulation (SNS). Innervated hearts from MI and sham rabbits were optically mapped using voltage and Ca2+-sensitive dyes. SNS was performed with electrical stimulation of the spinal cord, and β-adrenergic responsiveness was tested using isoproterenol. Sympathetic nerve density and CSPG expression were evaluated using immunohistochemistry. CSPGs were robustly expressed in the infarct region of all MI hearts, and the presence of CSPGs was associated with reduced sympathetic nerve density in the infarct versus remote region. Action potential duration (APD) dispersion and tendency for induction of ventricular tachycardia/fibrillation (VT/VF) were increased with SNS in MI but not sham hearts. SNS decreased APD at 80% repolarization (APD80) in MI but not sham hearts, whereas isoproterenol decreased APD80 in both groups. Isoproterenol also shortened Ca2+ transient duration at 80% repolarization in both groups but to a greater extent in MI hearts. Our data suggest that sympathetic remodeling post-MI is similar between rodents and rabbits, with CSPGs associated with sympathetic hypoinnervation. Despite a reduction in sympathetic nerve density, the infarct region of MI hearts remained responsive to both physiological SNS and isoproterenol, potentially through preserved or elevated β-adrenergic responsiveness, which may underlie increased APD dispersion and tendency for VT/VF.NEW & NOTEWORTHY Here, we show that CSPGs are present in the infarcts of rabbit hearts with reperfused MI, where they are associated with reduced sympathetic nerve density. Despite hypoinnervation, sympathetic responsiveness is maintained or enhanced in MI rabbit hearts, which also demonstrate increased APD dispersion and tendency for arrhythmias following sympathetic modulation. Together, this study indicates that the mechanisms of sympathetic remodeling post-MI are similar between rodents and rabbits, with hypoinnervation likely associated with enhanced β-adrenergic sensitivity.

Stereotactically intracerebral transplantation of neural stem cells for ischemic stroke attenuated inflammatory responses and promoted neurogenesis: an experimental study with monkeys.

Ischemic stroke is a common neurovascular disorder with high morbidity and mortality. However, the underlying mechanism of stereotactically intracerebral transplantation of human neural stem cells (hNSCs) is not well elucidated. Four days after ischemic stroke induced by Rose Bengal photothrombosis, seven cynomolgus monkeys were transplanted with hNSCs or vehicles stereotactically and followed up for 84 days. Behavioral assessments, magnetic resonance imaging, blood tests, and pathological analysis were performed before and after treatment. The proteome profiles of the left and right precentral gyrus and hippocampus were evaluated. Extracellular vesicle micro-RNA (miRNA) from the peripheral blood was extracted and analyzed. hNSC transplantation reduced the remaining infarcted lesion volume of cynomolgus monkeys with ischemic stroke without remarkable side effects. Proteomic analyses indicated that hNSC transplantation promoted GABAergic and glutamatergic neurogenesis and restored the mitochondrial electron transport chain function in the ischemic infarcted left precentral gyrus or hippocampus. Immunohistochemical staining and quantitative real-time reverse transcription PCR confirmed the promoting effects on neurogenesis and revealed that hNSCs attenuated post-infarct inflammatory responses by suppressing resident glia activation and mediating peripheral immune cell infiltration. Consistently, miRNA-sequencing revealed the miRNAs that were related to these pathways were downregulated after hNSC transplantation. This study indicates that hNSCs can be effectively and safely used to treat ischemic stroke by promoting neurogenesis, regulating post-infarct inflammatory responses, and restoring mitochondrial function in both the infarct region and hippocampus.

Detection, Isolation and Quantification of Myocardial Infarct with Four Different Histological Staining Techniques.

Precise quantification of myocardial infarction is crucial for evaluating the therapeutic strategies. We developed a robust, color-based semi-automatic algorithm capable of infarct region detection, isolation and quantification with four different histological staining techniques, and the isolation and quantification of diffuse fibrosis in the heart. Our method is developed based on the color difference in the infarct and non-infarct regions after histological staining. Mouse cardiac tissues stained with Masson's trichrome (MTS), hematoxylin and eosin (H&E), 2,3,5-Triphenyltetrazolium chloride and picrosirius red were included to demonstrate the performance of our method. We demonstrate that our algorithm can effectively identify and produce a clear visualization of infarct tissue for the four staining techniques. Notably, the infarct region on a H&E-stained tissue section can be clearly visualized after processing. The MATLAB-based program we developed holds promise in the infarct quantification. Additionally, our program can isolate and quantify the diffuse fibrotic elements from an MTS-stained cardiac section, which suggested the algorithm's potential for evaluating pathological cardiac fibrosis in diseased cardiac tissues. In conclusion, we demonstrate that this color-based algorithm is capable of accurately identifying, isolating and quantifying cardiac infarct regions with different staining techniques, as well as the diffuse and patchy fibrosis in MTS-stained cardiac tissues.

Pericardial Delivery of Sodium Alginate-Infusible Extracellular Matrix Composite Hydrogel Promotes Angiogenesis and Intercellular Electrical Conduction after Myocardial Infarction.

Injectable extracellular matrix (iECM) is a versatile biological material with beneficial properties such as good degradability, promotion of cell survival, immunomodulation, and facilitation of vascular formation. However, intravenous injection of iECM faces challenges like a short retention time in vivo and low concentration at the lesion site. To address these issues, we prepared a composite hydrogel composed of sodium alginate and iECM and administered it via intrapericardial injection, forming a structure akin to cardiac patches within the pericardium. Compared with intramyocardial injection, intrapericardial injection avoids direct myocardial injury and ectopic tumor formation, offering less invasiveness and better biocompatibility. This study demonstrates that the sodium alginate/infusible extracellular matrix (SA/iECM) composite hydrogel can effectively prolong the local retention time of iECM in the heart, enhance electrical conduction between cardiomyocytes, promote angiogenesis at ischemic myocardial sites, inhibit apoptosis in the infarcted region, mitigate left ventricular remodeling postmyocardial infarction (MI), and improve cardiac function after infarction. Precise coordination of cardiomyocyte contraction and relaxation depends on the rhythmic occurrence of calcium-dependent action potentials. Cardiac dysfunction is partially attributed to the disruption of the excitation-contraction coupling (ECC) mechanism, which is associated with prolonged intracellular Ca2+ transients and alterations in contraction and relaxation Ca2+ levels. Our results show that the SA/iECM composite hydrogel improves electrical conduction, as evidenced by increased Cx43 expression and enhanced intercellular electrical connectivity. This research establishes that intrapericardial injection of a SA/iECM composite hydrogel is a safe and effective treatment modality, providing a theoretical basis for the use of biomaterials in MI therapy.

Abstract We060: Hypoxia Inducible Factor-2α Enhances Neutrophil Survival and Promotes Cardiac Injury Following Myocardial Infarction via cIAP-1 Signaling

Rationale: Heart failure is a major cause of mortality following myocardial infarction (MI). Neutrophils (PMNs) are among the first immune cells to accumulate in the infarcted region. While some long-term beneficial functions of PMN in heart injury are now appreciated, en mase PMN accumulation in injured hearts is still associated with worsened resolution of inflammation and disease outcomes. MI causes extensive hypoxic injury to heart tissue, where hypoxia-inducible factors (HIFs) play critical roles in cellular functions. While HIF1α regulation of cell survival, migration and metabolism have been well-studied, the role of HIF-2α in these processes is not well-understood. Even less is known of HIF-2α contributions to PMN effector functions, especially in the context of MI. Objectives: The current study aimed to 1. Mechanistically explore how HIF-2α regulates survival of tissue infiltrating PMNs post-MI and 2. Determine how HIF-2α activity in PMNs impacts heart injury resolution post-MI, and whether specific HIF-2α deletion in PMNs can alleviate MI-induced tissue injury. Methods & Results: Infarct size, cardiac functions monitored by echocardiography, and scar tissue formation after left anterior descending coronary ligation injury model were compared between littermate control and specific PMN HIF-2α depletion (Ly6G-cre +/- HIF-2α fl/fl ) mice. Myocardial infarction size, cardiac dysfunction, scare tissue deposit and survival of tissue infiltrating PMNs post-MI were substantially attenuated in mice with PMN HIF-2α deletion. A significantly reduced lifespan of HIF-2α knockout PMNs was further confirmed by fate-mapping EdU pulse chase experiments. Mechanistically, molecular studies revealed that HIF-2α transcriptionally regulates expression of the pro-survival factor cIAP1 in PMNs binding to an HRE located in the promoter region of BIRC2 , in a hypoxia-inducible manner. Ex-vivo pharmacological inhibition of cIAP1 expression in PMNs using Birinapant resulted in dramatic cell death, establishing the critical role of cIAP1 in PMN survival. Finally, our data demonstrate that the protective effect of HIF-2α deletion in PMNs on MI outcomes was due to elevated recruitment of reparative macrophages into infarcted hearts. Conclusion: HIF-2α, through cIAP1 regulation, promotes PMN survival and tissue retention post-MI, leading to worsen cardiac functions and scar formation.

Abstract We008: Hallmark Maturation of the Human Pluripotent Stem Cells-derived Cardiovascular Progenitors in Myocardial Infarcted Large Animal Model

For the goal of regenerative cardiology, cellular therapy may be used to restore injured heart muscle. The molecular mechanisms behind the engraftment and maturation of these transplanted cells, however, remain poorly understood. Thus, to obtain a comprehensive understanding of the complex transcriptional landscapes within their transplanted spatial context, we utilized spatial transcriptomics in this study. We have previously demonstrated the safety and effectiveness of transplanting our cardiovascular progenitors (CVPs) produced from laminin-221 into pig hearts that had suffered myocardial infarction (MI). Here, we undertake 10x spatial transcriptomics in chronic MI pig models at 1-, 4-, and 12 weeks post-transplantation to further our understanding of these cells in vivo. With confidence, we can distinguish between the transcripts from the pigs and the humans in the infarcted region. By using human-specific anti-Ku80 antibodies for immunohistochemical labeling of the pig tissue samples, this in silico prediction was verified. The CVPs' engraftment and longevity in the infracted region were shown by the long-term identification and staining of human cells at various time points. It is interesting to note that after 12 weeks, ribosomal and mitochondrial activity were higher than at 1 and 2 weeks. These results are consistent with the hallmarks of cardiac maturation, in which cells transit from immature fetal-like cells to mature cardiomyocytes (CMs) by switching their metabolic energy source from glucose to fatty acids. Also, by comparing the heart-specific genes, including MYH6 and MYH7, we were able to quantify the myosin isoform switches in the xenograft over time. Furthermore, to delineate the fate of the transplanted cells, we performed a ligand-receptor interaction analysis. Intriguing, we identified the midkine protein as a possible secreted human paracrine factor that enhances angiogenesis in the graft. In conclusion, we have shown the successful engraftment and maturation of human CVPs toward CMs using spatial transcriptomic technology. These data will be used to understand other aspects of regenerative cardiology such as the mechanism of VTs and in vivo cellular repair mechanisms. A shiny app atlas has been generated to share our transcriptomics data for all to explore gene expression of human transplanted cells in myocardial infarcted pig hearts.

Abstract Tu102: The Role of the β IV -spectrin/STAT3 Complex in Regulating Ischemic Cardiac Remodeling

Adverse fibrotic remodeling contributes to high morbidity and mortality in patients following myocardial infarction (MI). The healing process after MI requires necrotic tissue to be cleared and replaced with fibrosis, which is driven by the coordinated effort of several distinct cardiac cell populations, including macrophages and cardiac fibroblasts (CFs). While previous studies have focused on identifying the stimuli that drives fibrotic remodeling in the infarcted myocardium, the contribution of specific cell populations to the signaling cascade and the manner of how these communication networks are tuned in response to chronic stress remains unclear. Prior work has identified a role for the cytoskeletal protein, β IV -spectrin, in coordinating the activity of the transcription factor, STAT3, with implications for CF activation and profibrotic signaling. Specifically, it was found that mice expressing truncated β IV -spectrin ( qv 3J ) are resistant to cardiac fibrosis in the setting of chronic pressure overload, with maintained β IV -spectrin expression and STAT3 localization/activity in CFs. Further, β IV -spectrin deficiency causes increased secretion of profibrotic and proinflammatory factors, including matrix metallopeptidases (MMPs). Therefore, we hypothesized that stress-induced loss of β IV -spectrin and subsequent dysregulation of STAT3 signaling in CFs proximal to the infarct promotes fibroblast activation, an important first step in repairing the infarct region. In this study, we subjected WT and qv 3J mice to permanent ligation of the left anterior descending artery and assessed cardiac function and survival through 28 days. A subset of mice were sacrificed at 7 days for histology, qPCR, and flow cytometry. Compared to WT, qv 3J mice showed a significant decrease in 28-day survival with increased mortality in the first week post-MI. Autopsy identified increased incidence of cardiac rupture in qv 3J animals. Immunohistochemistry revealed impaired scar formation at 7 days post-MI in qv 3J compared to WT. Quantitative PCR showed altered expression of matrix metallopeptidases (MMPs 3, 8, 9, and 14) in the qv 3J hearts at day 7. MMP activity was assessed in whole heart lysates using gelatin-zymography. Collagen uptake was assessed in CFs and bone marrow-derived macrophages isolated from WT and qv 3J mice. Our work identifies a novel role of the spectrin-based pathway in facilitating fibrotic remodeling in response to ischemic stress.

Panax notoginseng saponins promotes angiogenesis after cerebral ischemia-reperfusion injury

BackgroundIschemic stroke is a devastating disease that can result in permanent disability and death, and angiogenesis plays a critical role in the recovery and survival of patients and animal models of ischemic stroke. Panax notoginseng has been used as a key herb in the treatment of stroke diseases due to its effect in promoting blood circulation and removing blood stasis. However, the role of Panax notoginseng saponins, in promoting angiogenesis is unclear. PurposeThis study is aimed to investigate the effect of Xueshuantong (XST) injection, composed of Panax notoginseng saponins in post-stroke revascularization. MethodIn the present study, a middle cerebral artery occlusion/reperfusion model was established in Sprague-Dawley rats, with XST and the positive drug Dl-3-n-butylphthalide (NBP) administered via intraperitoneal injection to observe vascular changes after stroke. The protective and pro-angiogenic effects of XST after stroke were demonstrated by Triphenyltetrazolium chloride staining and optical coherence tomography angiography. Subsequently, network pharmacology and molecular docking techniques, as well as in vitro experimental validation, were used to further analyze the potential mechanism by which XST promotes angiogenesis. ResultsThe results showed that XST could reduce the cerebral infarction region in rats. And the neovascularization in the ischemic area of the rat brain significantly increased after 7 or 14 days of XST administration. Furthermore, XST could activate the vascular endothelial growth factor A (VEGFA)/vascular endothelial growth factor receptor 2 (VEGFR2), and hypoxia-inducible factor 1 (HIF-1) signaling pathways. ConclusionXST may promote post-stroke angiogenesis by affecting the HIF1-α/VEGFA/VEGFR2 signaling pathways.

Ischemic perfusion radiomics: assessing neurological impairment in acute ischemic stroke.

Accurate neurological impairment assessment is crucial for the clinical treatment and prognosis of patients with acute ischemic stroke (AIS). However, the original perfusion parameters lack the deep information for characterizing neurological impairment, leading to difficulty in accurate assessment. Given the advantages of radiomics technology in feature representation, this technology should provide more information for characterizing neurological impairment. Therefore, with its rigorous methodology, this study offers practical implications for clinical diagnosis by exploring the role of ischemic perfusion radiomics features in assessing the degree of neurological impairment. This study employs a meticulous methodology, starting with generating perfusion parameter maps through Dynamic Susceptibility Contrast-Perfusion Weighted Imaging (DSC-PWI) and determining ischemic regions based on these maps and a set threshold. Radiomics features are then extracted from the ischemic regions, and the t-test and least absolute shrinkage and selection operator (Lasso) algorithms are used to select the relevant features. Finally, the selected radiomics features and machine learning techniques are used to assess the degree of neurological impairment in AIS patients. The results show that the proposed method outperforms the original perfusion parameters, radiomics features of the infarct and hypoxic regions, and their combinations, achieving an accuracy of 0.926, sensitivity of 0.923, specificity of 0.929, PPV of 0.923, NPV of 0.929, and AUC of 0.923, respectively. The proposed method effectively assesses the degree of neurological impairment in AIS patients, providing an objective auxiliary assessment tool for clinical diagnosis.