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Histological analysis with 2,3,5-triphenyltetrazolium chloride (TTC) staining is the most frequently used tool to detect myocardial ischemia/reperfusion injury. However, its practicality is often challenged by poor image quality in gross histology, leading to an equivocal infarct-boundary delineation and potentially compromised measurement accuracy. Here, we introduce several crucial refinements in staining protocol and sample processing, which enable TTC images to be analyzed with light microscopy. The refined protocol involves a two-step TTC staining process (perfusion and immersion) and subsequent Zamboni fixation to differentiate myocardial viability and necrosis, and use of Coomassie brilliant blue to label area-at-risk. After the duo-staining steps were completed, the heart sample was embedded and sliced transversally by a cryostat into a series of thin sections (50 µm) for microscopic analysis. The refined TTC (redTTC) assay yielded remarkably high-quality images with striking color intensity and sharply defined boundaries, permitting unambiguous and reliable delineation of the infarct and area-at-risk. In the same animals, the redTTC assay showed good agreement with the in-vivo gold standard measurements (LGE and MEMRI). Meanwhile, redTTC imaging allows tracking of viable cardiomyocytes at cellular resolution, and with this enhanced capability, we convincingly demonstrated the pro-survival action of stem cells based-therapy. Therefore, the redTTC assay represents a significant technical advance that permits precise detection of the true extent of cardiac injury and cardiomyocyte viability. This approach is cost-effective and may be adapted for use in diverse applications, making it highly appealing to many laboratories performing ischemia/reperfusion injury experiments., (© 2024. The Author(s).)

Recanalization therapy can significantly improve the prognosis of patients with acute myocardial infarction (AMI). However, infarction or reperfusion-induced cardiomyocyte death, immune cell infiltration, fibroblast proliferation, and scarring formation lead to cardiac remodeling and gradually progress to heart failure or arrhythmia, resulting in a high mortality rate. Due to the inability of cardiomyocytes to regenerate, the healing of infarcted myocardium mainly relies on the formation of scars. Cardiac fibroblasts, as the main effector cells involved in repair and scar formation, play a crucial role in maintaining the structural integrity of the heart after MI. Recent studies have revealed that exosome-mediated intercellular communication plays a huge role in myocardial repair and signaling transduction after myocardial infarction (MI). Exosomes can regulate the biological behavior of fibroblasts by activating or inhibiting the intracellular signaling pathways through their contents, which are derived from cardiomyocytes, immune cells, endothelial cells, mesenchymal cells, and others. Understanding the interactions between fibroblasts and other cell types during cardiac remodeling will be the key to breakthrough therapies. This review examines the role of exosomes from different sources in the repair process after MI injury, especially the impacts on fibroblasts during myocardial remodeling, and explores the use of exosomes in the treatment of myocardial remodeling after MI., Competing Interests: The authors report no conflicts of interest in this work., (© 2024 Feng et al.)

Acute myocardial infarction (AMI) and related cardiovascular disease complications are the leading causes of mortality worldwide. Brown adipose tissue (BAT) is thermogenic and characterized by the uncoupling protein expression. Recent studies have found that in cardiovascular diseases, activated BAT can effectively improve the prognosis of AMI and concurrent heart failure through intercellular communication. However, a clear and systematic understanding of the myocardial protective mechanism of BAT after AMI is lacking, especially in the endocrine function of BAT. This review describes the effects of BAT on various cells in the heart after AMI. BAT plays a protective role on cardiac cells and fibroblasts during ischemia/reperfusion (I/R), myocardial remodeling, and myocardial fibrosis. This review also discusses the changes caused by BAT activation in different stages of heart failure. Finally, this review summarizes the treatment methods that target BAT to improve AMI. Further in-depth researches are still needed to clarify the underlying mechanism of the connection between BAT and different cells in cardiac tissue in order to identify potential therapeutic targets., (© 2024. The Author(s).)

Migratory cells exist in the heart, such as immune cells, fibroblasts, endothelial cells, etc. During myocardium injury, such as ischemia-reperfusion (MIRI), cells migrate to the site of injury to perform repair functions. However, excessive aggregation of these cells may exacerbate damage to the structure and function of the heart, such as acute myocarditis and myocardial fibrosis. Myocardial injury releases exosomes, which are a type of vesicle with signal transduction function and the miRNA carried by exosomes can control cell migration function. Therefore, regulating this migratory cell population through cardiac-derived exosomal miRNA is crucial for protecting and maintaining cardiac function. Through whole transcriptome RNA sequencing, exosomal miRNA sequencing and single-cell dataset analysis, we (1) determined the potential molecular regulatory role of the lncRNA‒miRNA‒mRNA axis in MIRI, (2) screened four important exosomal miRNAs that could be released by cardiac tissue, and (3) screened seven genes related to cell locomotion that are regulated by four miRNAs, among which Tradd and Ephb6 may be specific for promoting migration of different cells of myocardial tissue in myocardial infarct. We generated a core miRNA‒mRNA network based on the functions of the target genes, which may be not only a target for cardiac repair but also a potential diagnostic marker for interactions between the heart and other tissues or organs. In conclusion, we elucidated the potential mechanism of MIRI in cardiac remodeling from the perspective of cell migration, and inhibition of cellular overmigration based on this network may provide new therapeutic targets for MIRI and to prevent MIRI from developing into other diseases., (© 2024. The Author(s).)

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.

Aims: The histone deacetylase 6 (HDAC6) inhibitor, tubastatin A (TubA), reduces myocardial ischaemia/reperfusion injury (MIRI) in type 1 diabetic rats. It remains unclear whether HDAC6 regulates MIRI in type 2 diabetic animals. Diabetes augments the activity of HDAC6 and the generation of tumour necrosis factor alpha (TNF-α) and impairs mitochondrial complex I (mCI). Here, we examined how HDAC6 regulates TNF-α production, mCI activity, mitochondria, and cardiac function in type 1 and type 2 diabetic mice undergoing MIRI., Methods and Results: HDAC6 knockout, streptozotocin-induced type 1 diabetic, and obese type 2 diabetic db/db mice underwent MIRI in vivo or ex vivo in a Langendorff-perfused system. We found that MIRI and diabetes additively augmented myocardial HDAC6 activity and generation of TNF-α, along with cardiac mitochondrial fission, low bioactivity of mCI, and low production of adenosine triphosphate. Importantly, genetic disruption of HDAC6 or TubA decreased TNF-α levels, mitochondrial fission, and myocardial mitochondrial nicotinamide adenine dinucleotide levels in ischaemic/reperfused diabetic mice, concomitant with augmented mCI activity, decreased infarct size, and improved cardiac function. Moreover, HDAC6 knockout or TubA treatment decreased left ventricular dilation and improved cardiac systolic function 28 days after MIRI. H9c2 cardiomyocytes with and without HDAC6 knockdown were subjected to hypoxia/reoxygenation injury in the presence of high glucose. Hypoxia/reoxygenation augmented HDAC6 activity and TNF-α levels and decreased mCI activity. These negative effects were blocked by HDAC6 knockdown., Conclusion: HDAC6 is an essential negative regulator of MIRI in diabetes. Genetic deletion or pharmacologic inhibition of HDAC6 protects the heart from MIRI by limiting TNF-α-induced mitochondrial injury in experimental diabetes., Competing Interests: Conflict of interest: none declared., (© The Author(s) 2024. Published by Oxford University Press on behalf of the European Society of Cardiology. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Background: Myocardial infarction (MI) remains a significant global health concern, characterized by cardiomyocyte apoptosis and adverse ventricular remodeling. Nevertheless, the interplay between exosomal miR-21-5p and Yes-associated protein 1 (YAP1) in the context of MI remains unexplored., Methods: Rat mesenchymal stem cells (MSCs) and H9c2 cardiomyocytes were cultured, characterized, and instrumental in our experiments. Exosomes were meticulously isolated, and their identity confirmed. The internalization of these exosomes by H9c2 cells was assessed, while RNA and protein expression were quantified using Quantitative Real-Time PCR and Western blot, respectively. MTT assay was implemented for cell viability, and apoptosis was evaluated via flow cytometric analysis. To elucidate gene interactions, we conducted microarray profiling of miRNA expression, dual luciferase reporter assays, and RNA Immunoprecipitation., Results: MSC-derived exosomes exhibited a remarkable capacity to attenuate hypoxia-induced inflammation and apoptosis in H9c2 cells. Notably, these exosomes significantly upregulated miR-21-5p levels within H9c2 cells, and the abrogation of miR-21-5p function abated their protective effects. Through computational analysis, we unveiled a miR-21-5p binding site in the 3'UTR of YAP1, which directly inhibited YAP1 expression. Importantly, the inhibition of YAP1 effectively reinstated the protective effects of exosomes in cells with impaired exosomal miR-21-5p., Conclusion: This study underscores the pivotal role played by MSC-derived exosomes in safeguarding against MI, primarily by mediating the transfer of miR-21-5p, which targets YAP1 signaling pathways., Clinical Trial Number: N/A., (© 2024. The Author(s).)

Cyclin-dependent kinase 1 ( Cdk1 ) is a master regulator of the G2-M transition between DNA replication and cell division. This study investigates the regulation of cardiomyocyte (CM) proliferation during the early neonatal period and following ischemic injury in adult mice. We analyzed cell cycle dynamics with the assessment of DNA synthesis, and cytokinesis in murine hearts during the first 15 days after birth. A distinct proliferative block was observed at 1 day, followed by a second wave of DNA synthesis at 4 days, leading to CM binucleation (CMBN) by day 5. Genome-wide mRNA profiling revealed the differential expression of cell cycle regulatory genes during this period, with a downregulation of factors involved in cell division and mitosis. The loss of Cdk1 impaired CMBN but extended the neonatal CM proliferation window until day 10 post-birth. In adult hearts, the cardiac-specific ablation of Cdk1 triggered CM proliferation post-myocardial-infarction (MI) in specific zones, driven by the activation of EGFR1 signaling and suppression of the anti-proliferative p38 and p53 signaling. This was accompanied by restoration of fractional shortening, mitochondrial function, and decreased reactive oxygen species. Additionally, cardiac hypertrophy was mitigated, and survival rates post-MI were increased in Cdk1 -knockout mice. These findings reveal a novel role of Cdk1 in regulating cell cycle exit and re-entry in differentiated CMs and offer insights into potential strategies for cardiac repair.

Background: Histone deacetylase 4 (HDAC4) and histone deacetylase 5 (HDAC5) are two isoforms of class IIa HDACs, and LMK235 is an HDAC inhibitor with higher selectivity for HDAC4/5. This study aimed to explore the expression and subcellular localization of HDAC4/5 and determine the mechanisms underlying the impact of LMK235 on ventricular remodelling post-MI., Methods: The MI model was established by left anterior descending branch (LAD) ligation, and LMK235 or vehicle was intraperitoneally injected daily for 21 days. Cardiac function was determined by echocardiography. Inflammation was evaluated by HE staining and measuring inflammatory cytokine expression, and fibrosis was evaluated by Masson staining and measuring fibrotic biomarker expression., Results: We found that LMK235 ameliorated cardiac dysfunction post-MI by suppressing inflammation and fibrosis, and LMK235 inhibited upregulation of lysine-specific demethylase 1 (LSD1) expression post-MI. In macrophages, LMK235 attenuated lipopolysaccharide (LPS) - induced inflammatory cytokine expression and inhibited LSD1 expression, while overexpression of LSD1 abrogated the anti-inflammatory effect of LMK235. In cardiac fibroblasts, LMK235 attenuated transforming growth factor-β1 (TGF-β1) - induced fibrotic biomarker expression and inhibited LSD1 expression, while overexpression of LSD1 abrogated the antifibrotic effect of LMK235., Conclusion: LMK235 attenuates chronic inflammation and fibrosis post-MI, leading to improved cardiac function. The anti-inflammatory effect of LMK235 may result from inhibition of the LSD1-NF-κB pathway in macrophages. The antifibrotic effect of LMK235 may result from inhibition of the LSD1-Smad2/3 pathway in cardiac fibroblasts., (© 2024. The Author(s).)

Background: Myocardial infarction (MI) induces complex transcriptional changes across diverse cardiac cell types. Single-cell RNA sequencing (scRNA-seq) provides an unparalleled ability to discern cellular diversity during infarction, yet the veracity of these discoveries necessitates confirmation. This investigation sought to elucidate MI mechanisms by integrating scRNA-seq and bulk RNA-seq data., Methods: Publicly available scRNA-seq (GSE136088) and bulk RNA-seq (GSE153485) data from mice MI models were analyzed. Cell types were annotated, and differential expression analysis conducted. Bulk RNA-seq underwent quality control, principal component analysis, and differential expression analysis., Results: In scRNA-seq data, the comparison between MI and sham groups unveiled a reduction in endothelial cell populations, but macrophages and monocytes increased. Within fibroblast subgroups, three distinct categories were discerned, with two exhibiting upregulation in MI. Notably, endothelial cells exhibited an elevated expression of genes associated with apoptosis and ferroptosis. In bulk RNA-seq analysis, distinct patterns emerged when comparing MI and sham groups. Specifically, six genes linked to endothelial ferroptosis exhibited heightened expression in MI group, thereby corroborating the scRNA-seq findings. Moreover, the examination of isolated cardiac macrophages from mice MI model revealed increased expression of Spp1, Col1a2, Col3a1, Ctsd, and Lgals3 compared to sham group, thus substantiating the dysregulation of macrophage apoptosis-related proteins following MI., Conclusion: MI altered the transcriptomic landscapes of cardiac cells with increased expression of apoptotic genes. Moreover, the upregulation of macrophage apoptosis marker was confirmed within MI models. The presence of endothelial cell depletion and ferroptosis in MI has been demonstrated., (© 2024. The Author(s).)

Background: After myocardial infarction (MI), adverse left ventricular (LV) remodeling may occur. This is followed by LV hypertrophy and eventually heart failure. The remodeling process is complex and goes through multiple phases. The aim of this study was to investigate the expression of HMGB1 , TGF-β1 , BIRC3 , ADAM17 , CDKN1A , and FTO , each involved in a specific step of LV remodeling, in association with the change in the echocardiographic parameters of LV structure and function used to assess the LV remodeling process in the peripheral blood mononuclear cells (PBMCs) of patients six months after the first MI. The expression of selected genes was also determined in PBMCs of controls. Methods: The study group consisted of 99 MI patients, who were prospectively followed-up for 6 months, and 25 controls. Cardiac parameters, measured via conventional 2D echocardiography, were evaluated at two time points: 3-5 days and 6 months after MI. The mRNA expression six-months-post-MI was detected using TaqMan ® technology (Applied Biosystems, Thermo Fisher Scientific, Waltham, MA, USA). Results: HMGB1 mRNA was significantly higher in patients with adverse LV remodeling six-months-post-MI than in patients without adverse LV remodeling ( p = 0.04). HMGB1 mRNA was significantly upregulated in patients with dilated LV end-diastolic diameter (LVEDD) ( p = 0.03); dilated LV end-diastolic volume index (LVEDVi) ( p = 0.03); severely dilated LV end-systolic volume index (LVESVi) ( p = 0.006); impaired LV ejection fraction (LVEF) ( p = 0.01); and LV enlargement ( p = 0.03). It was also significantly upregulated in PBMCs from patients compared to controls ( p = 0.005). TGF-β1 and BIRC3 mRNA were significantly lower in patients compared to controls ( p = 0.02 and p = 0.05, respectively). Conclusions: Our results suggest that HMGB1 is involved in adverse LV remodeling six-months-post-MI, even on the mRNA level. Further research and validation are needed.

Background: Myocardial ischemia/reperfusion (I/R) injury stands as a primary contributor to ischemic heart disease. Sevoflurane (SEVO), a commonly used inhalation anesthetic, has been shown to exert a direct protective effect on ischemic heart injury. However, the specific mechanism by which it exerts the protective effect remains unclear. This study was designed to investigate the role of SEVO in myocardial I/R injury and its potential molecular mechanisms., Methods: Blood samples were collected from patients with acute myocardial infarction (AMI) (n = 20) and healthy volunteers (n = 20). The human cardiomyocytes AC16 models of I/R injury were induced by hypoxia/reoxygenation. The mRNA expression levels of growth differentiation factor 11 ( GDF11 ) in the cells and blood were determined by reverse transcription quantitative real-time PCR (RT-qPCR). The cell proliferation was detected by Cell Counting Kit-8 (CCK-8). Enzyme-Linked Immunosorbent Assay (ELISA) was utilized to detect the levels of inflammatory factors interleukin (IL)-8, IL-1β and IL-6 in the cells. And biochemical assay kits were applied for the measurement of the activity of lactate dehydrogenase (LDH) and superoxide dismutase (SOD) as well as the malondialdehyde (MDA) level in the cells. Moreover, western blot was employed to evaluate the levels of the p-serine-threonine protein kinase (AKT), AKT, and phosphatidylinositol 3-kinase (PI3K), protein expression in the cells., Results: The GDF11 expression was decreased in the blood of AMI patients and cardiomyocytes induced by I/R ( p < 0.01). Besides, 1% SEVO was presented to promote cardiomyocyte proliferation, inhibit apoptosis, oxidative stress and inflammation, and activate the PI3K/AKT signaling pathway through up-regulation of GDF11 expression ( p < 0.01)., Conclusion: SEVO promotes proliferation and inhibits inflammatory response, apoptosis, and oxidative stress of I/R-treated cardiomyocytes by elevating GDF11 expression, thereby reducing myocardial I/R injury. Notably, the mechanism underlying the alleviation of the I/R injury may involve the activation of PI3K/AKT signaling pathway.

Cold-inducible RNA-binding protein (CIRP) is a stress-response protein that has been shown to protect cardiomyocytes under a variety of stress conditions from apoptosis. Our recent study showed that the expression of CIRP protein in the heart was downregulated in patients with heart failure and an animal model of ischaemia heart failure, but its role in heart failure is still unknown. The present study aimed at evaluating the potential role of CIRP on the heart in an animal model of myocardial infarction (MI). MI model of rats was induced by the ligation of the left coronary artery. CIRP overexpression was mediated by direct intracardiac injection of adeno-associated virus serotype 9 (AAV9) vectors carrying a CIRP coding sequence with a cardiac-specific promoter before the induction of the MI model. The effects of CIRP elevation on MI-induced heart were analysed through echocardiographic, pathological and molecular analysis. Our results showed that the intracardiac injection of AAV9 successfully mediated CIRP upregulation in cardiomyocytes. Upregulation of cardiac CIRP prevented MI-induced cardiac dysfunction and adverse remodelling, coupled with the reduced inflammatory response in the heart. Collectively, these results demonstrated the beneficial role of intracellular CIRP on the heart and suggest that CIRP may be a therapeutic target in ischaemic heart disease., (© 2024 The Author(s). Journal of Cellular and Molecular Medicine published by Foundation for Cellular and Molecular Medicine and John Wiley & Sons Ltd.)

Neutrophils are critical mediators of both the initiation and resolution of inflammation after myocardial infarction (MI). Overexuberant neutrophil signaling after MI exacerbates cardiomyocyte apoptosis and cardiac remodeling while neutrophil apoptosis at the injury site promotes macrophage polarization toward a pro-resolving phenotype. Here, we describe a nanoparticle that provides spatiotemporal control over neutrophil fate to both stymie MI pathogenesis and promote healing. Intravenous injection of roscovitine/catalase-loaded poly(lactic-co-glycolic acid) nanoparticles after MI leads to nanoparticle uptake by circulating neutrophils migrating to the infarcted heart. Activated neutrophils at the infarcted heart generate reactive oxygen species, triggering intracellular release of roscovitine, a cyclin-dependent kinase inhibitor, from the nanoparticles, thereby inducing neutrophil apoptosis. Timely apoptosis of activated neutrophils at the infarcted heart limits neutrophil-driven inflammation, promotes macrophage polarization toward a pro-resolving phenotype, and preserves heart function. Modulating neutrophil fate to tune both inflammatory and reparatory processes may be an effective strategy to treat MI., (© 2024. The Author(s).)

Background: Myocardial ischemia-reperfusion injury (MI/RI) is an unavoidable risk event for acute myocardial infarction, with ferroptosis showing close involvement. We investigated the mechanism of MI/RI inducing myocardial injury by inhibiting the ferroptosis-related SLC7A11/glutathione (GSH)/glutathione peroxidase 4 (GPX4) pathway and activating mitophagy., Methods: A rat MI/RI model was established, with myocardial infarction area and injury assessed by TTC and H&E staining. Rat cardiomyocytes H9C2 were cultured in vitro, followed by hypoxia/reoxygenation (H/R) modeling and the ferroptosis inhibitor lipoxstatin-1 (Lip-1) treatment, or 3-Methyladenine or rapamycin treatment and overexpression plasmid (oe-SLC7A11) transfection during modeling. Cell viability and death were evaluated by CCK-8 and LDH assays. Mitochondrial morphology was observed by transmission electron microscopy. Mitochondrial membrane potential was detected by fluorescence dye JC-1. Levels of inflammatory factors, reactive oxygen species (ROS), Fe 2+ , malondialdehyde, lipid peroxidation, GPX4 enzyme activity, glutathione reductase, GSH and glutathione disulfide, and SLC7A11, GPX4, LC3II/I and p62 proteins were determined by ELISA kit, related indicator detection kits and Western blot., Results: The ferroptosis-related SLC7A11/GSH/GPX4 pathway was repressed in MI/RI rat myocardial tissues, inducing myocardial injury. H/R affected GSH synthesis and inhibited GPX4 enzyme activity by down-regulating SLC7A11, thus promoting ferroptosis in cardiomyocytes, which was averted by Lip-1. SLC7A11 overexpression improved H/R-induced cardiomyocyte ferroptosis via the GSH/GPX4 pathway. H/R activated mitophagy in cardiomyocytes. Mitophagy inhibition reversed H/R-induced cellular ferroptosis. Mitophagy activation partially averted SLC7A11 overexpression-improved H/R-induced cardiomyocyte ferroptosis. H/R suppressed the ferroptosis-related SLC7A11/GSH/GPX4 pathway by inducing mitophagy, leading to cardiomyocyte injury., Conclusions: Increased ROS under H/R conditions triggered cardiomyocyte injury by inducing mitophagy to suppress the ferroptosis-related SLC7A11/GSH/GPX4 signaling pathway activation., (© 2024. The Author(s).)

Heart failure (HF) represents the terminal stage of cardiovascular diseases, with limited therapeutic options currently available. Calotropin (CAL), a cardenolide isolated from Calotropis gigantea, exhibits a similar chemical structure and inhibitory effect on Na+/K+-ATPase to digoxin, a positive inotropic drugs used in heart failure treatment. However, the specific effect of calotropin in ischemic HF (IHF) remains unknown. The objective of this study is to assess the anti-HF effect and clarify its underlying mechanisms. The left anterior descending (LAD) artery ligation on Male Sprague-Dawley (SD) rats was used to construct ischemic HF model. Daily administration of CAL at 0.05 mg/kg significantly enhanced ejection fraction (EF) and fractional shortening (FS), while inhibiting cardiac fibrosis in IHF rats. CAL reduced the OGD/R-induced H9c2 cell injury. Furthermore, CAL upregulated the expression of SERCA2a and SIRT1. The cardioprotective effect of CAL against IHF was abrogated in the presence of the SIRT1 inhibitor EX527. Notably, we identified FOXD3 as a pivotal transcription factor mediating CAL-induced SERCA2a regulation. CAL promoted the deacetylation and nuclear translocation of FOXD3 in a SIRT1-dependent manner. In conclusion, our study explores a novel mechanism of calotropin for improving cardiac dysfunction in ischemic heart failure by regulating SIRT1/FOXD3/SERCA2a pathway., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Masson SAS.. All rights reserved.)

Background: Coronary atherosclerotic burden and adverse coronary heart disease events are related phenotypes with likely shared genetic cause., Methods: We analyzed 6021 patients with available coronary angiography, genotyping, and exome sequencing data. We tested for associations of polygenic risk scores for coronary heart disease (PRS CHD ) with multiple measures of coronary artery disease (CAD) severity. We assessed the joint associations of PRS CHD and pathogenic/likely pathogenic variants in 3 familial hypercholesterolemia genes, with CAD severity. We performed mediation analyses to explore whether CAD severity mediated the association of PRS CHD with prevalent coronary heart disease and incident myocardial infarction., Results: A 1-SD increase in PRS CHD was associated with multiple measures of CAD severity, including the log Gensini score (β, 0.31 [95% CI, 0.28-0.33]). Carrying a pathogenic/likely pathogenic familial hypercholesterolemia variant was associated with a higher log Gensini score after adjustment for PRS CHD (β, 0.21 [95% CI, 0.03-0.38]). A 1-SD increase in PRS CHD was associated with incident myocardial infarction over a mean follow-up of 9.2 years (hazard ratio, 1.20 [95% CI, 1.13-1.27]; P =5×10 - 10 ), and the Gensini score mediated 90% of this association., Conclusions: PRS CHD was associated with multiple measures of CAD severity. The association of PRS CHD with incident myocardial infarction was almost fully mediated by CAD severity, indicating a considerable genetic overlap between the 2 phenotypes., Competing Interests: None.

Background: Activation of the immune system contributes to cardiovascular diseases. The role of human-specific long noncoding RNAs in cardioimmunology is poorly understood., Methods: Single-cell sequencing in peripheral blood mononuclear cells revealed a novel human-specific long noncoding RNA called HEAT4 (heart failure-associated transcript 4). HEAT4 expression was assessed in several in vitro and ex vivo models of immune cell activation, as well as in the blood of patients with heart failure (HF), acute myocardial infarction, or cardiogenic shock. The transcriptional regulation of HEAT4 was verified through cytokine treatment and single-cell sequencing. Loss-of-function and gain-of-function studies and multiple RNA-protein interaction assays uncovered a mechanistic role of HEAT4 in the monocyte anti-inflammatory gene program. HEAT4 expression and function was characterized in a vascular injury model in NOD.CB17-Prkdc scid/Rj mice., Results: HEAT4 expression was increased in the blood of patients with HF, acute myocardial infarction, or cardiogenic shock. HEAT4 levels distinguished patients with HF from people without HF and predicted all-cause mortality in a cohort of patients with HF over 7 years of follow-up. Monocytes, particularly anti-inflammatory CD16 + monocytes, which are increased in patients with HF, are the primary source of HEAT4 expression in the blood. HEAT4 is transcriptionally activated by treatment with anti-inflammatory interleukin-10. HEAT4 activates anti-inflammatory and inhibits proinflammatory gene expression. Increased HEAT4 levels result in a shift toward more CD16 + monocytes. HEAT4 binds to S100A9, causing a monocyte subtype switch, thereby reducing inflammation. As a result, HEAT4 improves endothelial barrier integrity during inflammation and promotes vascular healing after injury in mice., Conclusions: These results characterize a novel endogenous anti-inflammatory pathway that involves the conversion of monocyte subtypes into anti-inflammatory CD16 + monocytes. The data identify a novel function for the class of long noncoding RNAs by preventing protein secretion and suggest long noncoding RNAs as potential targets for interventions in the field of cardioimmunology., Competing Interests: None.

Placental growth factor (PlGF)-2 induces angio- and arteriogenesis in rodents but its therapeutic potential in a clinically representative post-infarction left ventricular (LV) dysfunction model remains unclear. We, therefore, investigated the safety and efficacy of recombinant human (rh)PlGF-2 in the infarcted porcine heart in a randomized, placebo-controlled blinded study. We induced myocardial infarction (MI) in pigs using 75 min mid-LAD balloon occlusion followed by reperfusion. After 4 w, we randomized pigs with marked LV dysfunction (LVEF < 40%) to receive continuous intravenous infusion of 5, 15, 45 µg/kg/day rhPlGF-2 or PBS (CON) for 2 w using osmotic pumps. We evaluated the treatment effect at 8 w using comprehensive MRI and immunohistochemistry and measured myocardial PlGF-2 receptor transcript levels. At 4 w after MI, infarct size was 16-18 ± 4% of LV mass, resulting in significantly impaired systolic function (LVEF 34 ± 4%). In the pilot study (3 pigs/dose), PIGF administration showed sustained dose-dependent increases in plasma concentrations for 14 days without systemic toxicity and was associated with favorable post-infarct remodeling. In the second phase (n = 42), we detected no significant differences at 8 w between CON and PlGF-treated pigs in infarct size, capillary or arteriolar density, global LV function and regional myocardial blood flow at rest or during stress. Molecular analysis showed significant downregulation of the main PlGF-2 receptor, pVEGFR-1, in dysfunctional myocardium. Chronic rhPIGF-2 infusion was safe but failed to induce therapeutic neovascularization and improve global cardiac function after myocardial infarction in pigs. Our data emphasize the critical need for properly designed trials in representative large animal models before translating presumed promising therapies to patients., (© 2024. Springer-Verlag GmbH Germany, part of Springer Nature.)

Purpose: Myocardial infarction (MI) with subsequent inflammation is one of the most common heart conditions leading to progressive tissue damage. A reliable imaging marker to assess tissue viability after MI would help determine the risks and benefits of any intervention. In this study, we investigate whether a new mitochondria-targeted imaging agent, 18 F-labeled 2'-deoxy-2'- 18 F-fluoro-9-β-d-arabinofuranosylguanine ([ 18 F]F-AraG), a positron emission tomography (PET) agent developed for imaging activated T cells, is suitable for cardiac imaging and to test the myocardial viability after MI., Procedure: To test whether the myocardial [ 18 F]-F-AraG signal is coming from cardiomyocytes or immune infiltrates, we compared cardiac signal in wild-type (WT) mice with that of T cell deficient Rag1 knockout (Rag1 KO) mice. We assessed the effect of dietary nucleotides on myocardial [ 18 F]F-AraG uptake in normal heart by comparing [ 18 F]F-AraG signals between mice fed with purified diet and those fed with purified diet supplemented with nucleotides. The myocardial viability was investigated in rodent model by imaging rat with [ 18 F]F-AraG and 2-deoxy-2[ 18 F]fluoro-D-glucose ([ 18 F]FDG) before and after MI. All PET signals were quantified in terms of the percent injected dose per cc (%ID/cc). We also explored [ 18 F]FDG signal variability and potential T cell infiltration into fibrotic area in the affected myocardium with H&E analysis., Results: The difference in %ID/cc for Rag1 KO and WT mice was not significant (p = ns) indicating that the [ 18 F]F-AraG signal in the myocardium was primarily coming from cardiomyocytes. No difference in myocardial uptake was observed between [ 18 F]F-AraG signals in mice fed with purified diet and with purified diet supplemented with nucleotides (p = ns). The [ 18 F]FDG signals showed wider variability at different time points. Noticeable [ 18 F]F-AraG signals were observed in the affected MI regions. There were T cells in the fibrotic area in the H&E analysis, but they did not constitute the predominant infiltrates., Conclusions: Our preliminary preclinical data show that [ 18 F]F-AraG accumulates in cardiomyocytes indicating that it may be suitable for cardiac imaging and to evaluate the myocardial viability after MI., (© 2024. The Author(s), under exclusive licence to World Molecular Imaging Society.)

Heart failure and myocardial infarction, global health concerns, stem from limited cardiac regeneration post-injury. Myocardial infarction, typically caused by coronary artery blockage, leads to cardiac muscle cell damage, progressing to heart failure. Addressing the adult heart's minimal self-repair capability is crucial, highlighting cardiac regeneration research's importance. Studies reveal a metabolic shift from anaerobic glycolysis to oxidative phosphorylation in neonates as a key factor in impaired cardiac regeneration, with mitochondria being central. The heart's high energy demands rely on a robust mitochondrial network, essential for cellular energy, cardiac health, and regenerative capacity. Mitochondria's influence extends to redox balance regulation, signaling molecule interactions, and apoptosis. Changes in mitochondrial morphology and quantity also impact cardiac cell regeneration. This article reviews mitochondria's multifaceted role in cardiac regeneration, particularly in myocardial infarction and heart failure models. Understanding mitochondrial function in cardiac regeneration aims to enhance myocardial infarction and heart failure treatment methods and insights., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Splenic leukocytes, particularly macrophage-expressed lipoxygenases, facilitate the biosynthesis of resolution mediators essential for cardiac repair. Next, we asked whether deletion of 12/15 lipoxygenase (12/15LOX) in macrophages impedes the resolution of inflammation following myocardial infarction (MI). Using 12/15flox/flox and LysMcre scheme, we generated macrophage-specific 12/15LOX (Mɸ-12/15LOX-/-) mice. Young C57BL/6J wild-type and Mɸ-12/15LOX-/- male mice were subjected to permanent coronary ligation microsurgery. Mice were monitored at day 1 (d1) to d5 (as acute heart failure [AHF]) and to d56 (chronic HF) post-MI, maintaining no MI as d0 naïve control animals. Post ligation, Mɸ-12/15LOX-/- mice showed increased survival (88% vs 56%) and limited heart dysfunction compared with wild-type. In AHF, Mɸ-12/15LOX-/- mice have increased biosynthesis of epoxyeicosatrienoic acid by 30%, with the decrease in D-series resolvins, protectin, and maresin by 70% in the infarcted heart. Overall, myeloid cell profiling from the heart and spleen indicated that Mɸ-12/15LOX-/- mice showed higher immune cells with reparative Ly6Clow macrophages during AHF. In addition, the detailed immune profiling revealed reparative macrophage phenotype (Ly6Clow) in Mɸ-12/15LOX-/- mice in a splenocardiac manner post-MI. Mɸ-12/15LOX-/- mice showed an increase in myeloid population that coordinated increase of T regulatory cells (CD4+/Foxp3+) in the spleen and injured heart at chronic HF compared with wild-type. Thus, macrophage-specific deletion of 12/15LOX directs reparative macrophage phenotype to facilitate cardiac repair. The presented study outlines the complex role of 12/15LOX in macrophage plasticity and T regulatory cell signaling that indicates that resolution mediators are viable targets to facilitate cardiac repair in HF post-MI., Competing Interests: Conflict of interest statement. None declared., (© The Author(s) 2024. Published by Oxford University Press on behalf of Society for Leukocyte Biology. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Recreating the natural heart's mechanical and electrical environment is crucial for engineering functional cardiac tissue and repairing infarcted myocardium in vivo. In this study, multimaterial-printed serpentine microarchitectures are presented with synergistic mechanical/piezoelectric stimulation, incorporating polycaprolactone (PCL) microfibers for mechanical support, polyvinylidene fluoride (PVDF) microfibers for piezoelectric stimulation, and magnetic PCL/Fe 3 O 4 for controlled deformation via an external magnet. Rat cardiomyocytes in piezoelectric constructs, subjected to dynamic mechanical stimulation, exhibit advanced maturation, featuring superior sarcomeric structures, improved calcium transients, and upregulated maturation genes compared to non-piezoelectric constructs. Furthermore, these engineered piezoelectric cardiac constructs demonstrate significant structural and functional repair of infarcted myocardium, as evidenced by enhanced ejection and shortening fraction, reduced fibrosis and inflammation, and increased angiogenesis. The findings underscore the therapeutic potential of piezoelectric cardiac constructs for myocardial infarction therapy., (© 2024 Wiley‐VCH GmbH.)

Combined [ 18 F]FDG PET-cardiac MRI imaging (PET/CMR) is a useful tool to assess myocardial viability and cardiac function in patients with acute myocardial infarction (AMI). Here, we evaluated the prognostic value of PET/CMR in a porcine closed-chest reperfused AMI (rAMI) model. Late gadolinium enhancement by PET/CMR imaging displayed tracer uptake defect at the infarction site by 3 days after the rAMI in the majority of the animals (group Match, n = 28). Increased [ 18 F]FDG uptake at the infarcted area (metabolism/contractility mismatch) with reduced tracer uptake in the remote viable myocardium (group Mismatch, n = 12) 3 days after rAMI was observed in the animals with larger infarct size and worse left ventricular ejection fraction (LVEF) (34 ± 8.7 vs 42.0 ± 5.2%), with lower LVEF also at the 1-month follow-up (35.8 ± 9.5 vs 43.0 ± 6.3%). Transcriptome analyses by bulk and single-nuclei RNA sequencing of the infarcted myocardium and border zones (n = 3 of each group, and 3 sham-operated controls) revealed a strong inflammatory response with infiltration of monocytes and macrophages in the infarcted and border areas in Mismatch animals. Our data indicate a high prognostic relevance of combined PET/MRI in the subacute phase of rAMI for subsequent impairment of heart function and underline the adverse effects of an excessive activation of the innate immune system in the initial phase after rAMI., (© 2024. The Author(s).)

Myocardial infarction (MI) is a leading cause of morbidity and mortality worldwide, and endoplasmic reticulum stress (ERS) and mitochondrial Ca 2+ overload have been involved in apoptotic cardiomyocyte death during MI. 13-Methylpalmatine (13-Me-PLT) is a natural isoquinoline alkaloid isolated from Coptis chinensis and has not been systematically studied for their potential pharmacological effects in cardiovascular diseases. We conducted the present study to elucidate whether 13-Me-PLT modulates MI pathology in animal MI and cellular hypoxic models, employing state-of-the-art molecular techniques. The results demonstrated that 13-Me-PLT preserved post-ischemic cardiac function and alleviated cardiomyocyte apoptosis. 13-Me-PLT decreased ERS and the communication between ER and mitochondria, which serves as a protective mechanism against mitochondrial Ca 2+ overload and structural and functional injuries to mitochondria. Our data revealed mitigating mitochondrial Ca 2+ overload and apoptosis by inhibiting CHOP-mediated Ca 2+ transfer between inositol 1,4,5-trisphosphate receptor (IP 3 R) in ER and VDAC1 in mitochondria as an underlying mechanism for 13-Me-PLT action. Furthermore, 13-Me-PLT produced superior effects in alleviating cardiac dysfunction and apoptosis post-MI to diltiazem and palmatine. Collectively, our research suggests that the CHOP/IP 3 R/VDAC1 signaling pathway mediates ER-mitochondrial Ca 2+ transfer and 13-Me-PLT activates this axis to maintain cellular and organellar Ca 2+ homeostasis, protecting against ischemic myocardial injury. These findings may offer an opportunity to develop new agents for the therapy of ischemic heart disease., Competing Interests: Declaration of Competing Interest All the authors declare no competing financial interest., (Copyright © 2024 The Authors. Published by Elsevier Masson SAS.. All rights reserved.)

Cardiac fibrosis is a detrimental pathological process, which constitutes the key factor for adverse cardiac structural remodeling leading to heart failure and other critical conditions. Circular RNAs (circRNAs) have emerged as important regulators of various cardiovascular diseases. It is known that several circRNAs regulate gene expression and pathological processes by binding miRNAs. In this study we investigated whether a novel circRNA, named circNSD1, and miR-429-3p formed an axis that controls cardiac fibrosis. We established a mouse model of myocardial infarction (MI) for in vivo studies and a cellular model of cardiac fibrogenesis in primary cultured mouse cardiac fibroblasts treated with TGF-β1. We showed that miR-429-3p was markedly downregulated in the cardiac fibrosis models. Through gain- and loss-of-function studies we confirmed miR-429-3p as a negative regulator of cardiac fibrosis. In searching for the upstream regulator of miR-429-3p, we identified circNSD1 that we subsequently demonstrated as an endogenous sponge of miR-429-3p. In MI mice, knockdown of circNSD1 alleviated cardiac fibrosis. Moreover, silence of human circNSD1 suppressed the proliferation and collagen production in human cardiac fibroblasts in vitro. We revealed that circNSD1 directly bound miR-429-3p, thereby upregulating SULF1 expression and activating the Wnt/β-catenin pathway. Collectively, circNSD1 may be a novel target for the treatment of cardiac fibrosis and associated cardiac disease., (© 2024. The Author(s), under exclusive licence to Shanghai Institute of Materia Medica, Chinese Academy of Sciences and Chinese Pharmacological Society.)

Intravenous infusion has been used as the method of cell delivery in many preclinical studies as well as in some early clinical trials. Among its advantages are broad distribution, ability to handle a large-volume infusion, and ease of access. Progenitor cells used in cell-based therapy act through their secretomes, rather than their ability to differentiate into lineage-specific cell type. Since not all progenitor cells have similar secretome potency, the innate abilities of the secretome of cells used in clinical trials will obviously dictate their effectiveness. We previously found that cardiac neonatal mesenchymal stromal cells (nMSCs) are more effective in repairing the infarcted myocardium compared to adult mesenchymal stromal cells (aMSCs) due to their robust secretome (Sharma et al Circulation Research 120:816-834, 2017). In this study, we explored the efficacy of intravenous (IV) delivery of nMSCs for myocardial recovery. Six-week-old male Brown Norway rats underwent acute MI by ligation of the left anterior descending artery, followed by IV infusion of cell dose 5 × 10 6 nMSCs/rat body weight (kg) or saline on days 0 and 5. We found that cardiac parameters in the rodent ischemia model improved 1 month after nMSCs infusion, and the result is comparable with the intramyocardial injection of nMSCs. Tracking the infused cells in target organ revealed that their movement after IV delivery was mediated by the cell surface receptor CD44. Systemic injection of nMSCs stimulated immunomodulatory responses specifically by increasing FoxP3 + T-regulatory cell influenced anti-inflammatory macrophages (M2) in heart. These data demonstrate that nMSCs promote immunogenic tolerance via CD44-driven T-reg/M2 stimulation that helps nMSCs for longer viability in the injured myocardium for better functional recovery. Our data also demonstrate a rationale for a clinical trial of IV infusion of nMSCs to promote cardiac function improvement in the ischemic patients., (© 2024. The Author(s).)

Hyperglycaemia is common during acute coronary syndromes (ACS) irrespective of diabetic status and portends excess infarct size and mortality, but the mechanisms underlying this effect are poorly understood. We hypothesized that sodium/glucose linked transporter-1 (SGLT1) might contribute to the effect of high-glucose during ACS and examined this using an ex-vivo rodent heart model of ischaemia-reperfusion injury. Langendorff-perfused rat hearts were subjected to 35 min ischemia and 2 h reperfusion, with variable glucose and reciprocal mannitol given during reperfusion in the presence of pharmacological inhibitors of SGLT1. Myocardial SGLT1 expression was determined in rat by rtPCR, RNAscope and immunohistochemistry, as well as in human by single-cell transcriptomic analysis. High glucose in non-diabetic rat heart exacerbated reperfusion injury, significantly increasing infarct size from 45 ± 3 to 65 ± 4% at 11-22 mmol/L glucose, respectively (p < 0.01), an association absent in diabetic heart (32 ± 1-37 ± 5%, p = NS). Rat heart expressed SGLT1 RNA and protein in vascular endothelium and cardiomyocytes, with similar expression found in human myocardium by single-nucleus RNA-sequencing. Rat SGLT1 expression was significantly reduced in diabetic versus non-diabetic heart (0.608 ± 0.08 compared with 1.116 ± 0.13 probe/nuclei, p < 0.01). Pharmacological inhibitors phlorizin, canagliflozin or mizagliflozoin in non-diabetic heart revealed that blockade of SGLT1 but not SGLT2, abrogated glucose-mediated excess reperfusion injury. Elevated glucose is injurious to the rat heart during reperfusion, exacerbating myocardial infarction in non-diabetic heart, whereas the diabetic heart is resistant to raised glucose, a finding which may be explained by lower myocardial SGLT1 expression. SGLT1 is expressed in vascular endothelium and cardiomyocytes and inhibiting SGLT1 abrogates excess glucose-mediated infarction. These data highlight SGLT1 as a potential clinical translational target to improve morbidity/mortality outcomes in hyperglycemic ACS patients., (© 2024. The Author(s).)

Revascularization of ischemic myocardium following cardiac damage is an important step in cardiac regeneration. However, the mechanism of arteriogenesis has not been well described during cardiac regeneration. Here we investigated coronary artery remodeling and collateral growth during cardiac regeneration. Neonatal MI was induced by ligature of the left descending artery (LAD) in postnatal day (P) 1 or P7 pups from the Cx40-GFP mouse line and the arterial tree was reconstructed in 3D from images of cleared hearts collected at 1, 2, 4, 7 and 14 days after infarction. We show a rapid remodeling of the left coronary arterial tree induced by neonatal MI and the formation of numerous collateral arteries, which are transient in regenerating hearts after MI at P1 and persistent in non-regenerating hearts after MI at P7. This difference is accompanied by restoration of a perfused or a non-perfused LAD following MI at P1 or P7 respectively. Interestingly, collaterals ameliorate cardiac perfusion and drive LAD repair, and lineage tracing analysis demonstrates that the restoration of the LAD occurs by remodeling of pre-existing arterial cells independently of whether they originate in large arteries or arterioles. These results demonstrate that the restoration of the LAD artery during cardiac regeneration occurs by pruning as the rapidly forming collaterals that support perfusion of the disconnected lower LAD subsequently disappear on restoration of a unique LAD. These results highlight a rapid phase of arterial remodeling that plays an important role in vascular repair during cardiac regeneration., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Cardiogenic shock (CS) is characterized by impaired cardiac function, very high mortality, and limited treatment options. The proinflammatory signaling during different phases of CS is incompletely understood. We collected serum and plasma ( n = 44) as well as freshly isolated peripheral blood mononuclear cells (PBMCs, n = 7) of patients with CS complicating acute myocardial infarction on admission and after revascularization (24, 48, and 72 h) and of healthy controls (serum and plasma, n = 75; PBMCs, n = 12). PBMCs of patients with CS had increased gene expression of NLRP3 , CASP1 , PYCARD , IL1B , and IL18 and showed increased rates of pyroptosis (control, 4.7 ± 0.3 vs. 9.9 ± 1.7% in patients with CS, P = 0.02). Serum interleukin (IL)-1β levels were increased after revascularization. IL-18 and IL-6 were higher in patients with CS than in healthy controls but comparable before and after revascularization. Proinflammatory apoptosis-associated speck-like proteins containing CARD (ASC) specks were elevated in the serum of patients with CS on admission and increased after revascularization (admission, 11.1 ± 4.4 specks/µL; after 24 h, 19.0 ± 3.9, P = 0.02). ASC specks showed a significant association with 30-day mortality in patients with CS ( P < 0.05). The estimated regression coefficients and odds ratios indicated a positive relationship between ASC specks and mortality (odds ratio: 1.029, 95% confidence interval, 1.000 to 1.072; P = 0.02). Pyroptosis and circulating ASC specks are increased in patients with CS and are particularly induced after reperfusion. This underscores their potential role as a biomarker for poor outcomes in patients with CS. ASC specks represent promising new therapeutic targets for patients with CS with high inflammatory burden. NEW & NOTEWORTHY The expression of NLR family pyrin domain containing-3 (NLRP3) inflammasome-related genes and the rate of pyroptosis are increased in PBMCs from patients with CS. Furthermore, patients with CS are characterized by higher serum concentrations of ASC specks and IL-1β, IL-6, and IL-18. This current study adds circulating ASC specks to the portfolio of biomarkers for the identification of patients with a high inflammatory burden paving the way for precision medicine approaches to improve clinical outcomes.

Myocardial infarction (MI) triggers a complex inflammatory response that is essential for cardiac repair but can also lead to adverse outcomes if left uncontrolled. Recent studies have highlighted the importance of epigenetic modifications in regulating post-MI inflammation. This study investigated the role of the autotaxin (ATX)/lysophosphatidic acid (LPA) signaling axis in modulating myocardial inflammation through epigenetic pathways in a mouse model of MI. C57BL/6 J mice underwent left anterior descending coronary artery ligation to induce MI and were treated with the ATX inhibitor, PF-8380, or vehicle. Cardiac tissue from the border zone was collected at 6 h, 1, 3, and 7 days post-MI for epigenetic gene profiling using RT 2 Profiler PCR Arrays. The results revealed distinct gene expression patterns across sham, MI + Vehicle, and MI + PF-8380 groups. PF-8380 treatment significantly altered the expression of genes involved in inflammation, stress response, and epigenetic regulation compared to the vehicle group. Notably, PF-8380 downregulated Hdac5, Prmt5, and Prmt6, which are linked to exacerbated inflammatory responses, as early as 6 h post-MI. Furthermore, PF-8380 attenuated the reduction of Smyd1, a gene important in myogenic differentiation, at 7 days post-MI. This study demonstrates that the ATX/LPA signaling axis plays a pivotal role in modulating post-MI inflammation via epigenetic pathways. Targeting ATX/LPA signaling may represent a novel therapeutic strategy to control inflammation and improve outcomes after MI. Further research is needed to validate these findings in preclinical and clinical settings and to elucidate the complex interplay between epigenetic mechanisms and ATX/LPA signaling in the context of MI., (© 2024. This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply.)

Cardiovascular diseases, including myocardial infarction (MI), constitute the leading cause of morbidity and mortality worldwide. Protein-aggregate deposition is a hallmark of aging and neurodegeneration. Our previous study reported that aggregation is strikingly elevated in hearts of hypertensive and aged mice; however, no prior study has addressed MI effects on aggregation in heart or brain. Here, we present novel data on heart and brain aggregation in mice following experimental MI, induced by left coronary artery (LCA) ligation. Infarcted and peri-infarcted heart tissue, and whole cerebra, were isolated from mice at sacrifice, 7 days following LCA ligation. Sham-MI mice (identical surgery without ligation) served as controls. We purified detergent-insoluble aggregates from these tissues, and quantified key protein constituents by high-resolution mass spectrometry (LC-MS/MS). Infarct heart tissue had 2.5- to 10-fold more aggregates than non-infarct or sham-MI heart tissue (each P = 0.001). Protein constituents from MI cerebral aggregates overlapped substantially with those from human Alzheimer's disease brain. Prior injection of mice with mesenchymal stem cell (MSC) exosomes, shown to limit infarct size after LCA ligation, reduced cardiac aggregation ~ 60%, and attenuated markers of endoplasmic reticulum (ER) stress in heart and brain (GRP78, ATF6, P-PERK) by 50-75%. MI also elevated aggregate constituents enriched in Alzheimer's disease (AD) aggregates, such as proteasomal subunits, heat-shock proteins, complement C3, clusterin/ApoJ, and other apolipoproteins. These data provide novel evidence that aggregation is elevated in mouse hearts and brains after myocardial ischemia, leading to cognitive impairment resembling AD, but can be attenuated by exosomes or drug (CDN1163) interventions that oppose ER stress., (© 2023. This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply.)

Ischemic heart failure rates rise despite decreased acute myocardial infarction (MI) mortality. Excessive myofibroblast activation post-MI leads to adverse remodeling. LIM kinases (LIMK1 and LIMK2) regulate cytoskeleton homeostasis and are pro-fibrotic markers in atrial fibrillation. However, their roles and mechanisms in postinfarction fibrosis and ventricular remodeling remain unclear. This study found that the expression of LIMKs elevated in the border zone (BZ) in mice MI models. LIMK1/2 double knockout (DKO) restrained pathological remodeling and reduced mortality by suppressing myofibroblast activation. By using adeno-associated virus (AAV) with a periostin promoter to overexpress LIMK1 or LIMK2, this study found that myofibroblast-specific LIMK2 overexpression diminished these effects in DKO mice, while LIMK1 did not. LIMK2 kinase activity was critical for myofibroblast proliferation by using AAV overexpressing mutant LIMK2 lack of kinase activity. According to phosphoproteome analysis, functional rescue experiments, co-immunoprecipitation, and protein-protein docking, LIMK2 led to the phosphorylation of β-catenin at Ser 552. LIMK2 nuclear translocation also played a role in myofibroblast proliferation after MI with the help of AAV overexpressing mutant LIMK2 without nuclear location signal. Chromatin immunoprecipitation sequencing identified that LIMK2 bound to Lrp6 promoter region in TGF-β treated cardiac fibroblasts, positively regulating Wnt signaling via Wnt receptor internalization. This study demonstrated that LIMK2 promoted myofibroblast proliferation and adverse cardiac remodeling after MI, by enhancing phospho-β-catenin (Ser552) and Lrp6 signaling. This suggested that LIMK2 could be a target for the treatment of postinfarction injury., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Aerobic exercise (AE) has attracted considerable research attention as a non-invasive therapeutic tool in recent years. Accumulating evidence has revealed its protective role against a wide range of diseases. In this study, we aimed to establish whether AE could inhibit apoptosis in infarcted cardiomyocytes and protect the heart. AE in post-myocardial infarction (post-MI) mice improved their cardiac and physical functions. Transmission electron microscopy of myocardial tissue and adenosine 5'-triphosphate (ATP) assay findings revealed an increased mitochondrial number but decreased ATP content in the post-MI mice. Notably, this change was significantly reversed by AE. Immunofluorescence/ TUNEL staining assay results showed that AE inhibited cardiomyocyte apoptosis. Using immunoblotting of myocardial tissues, we found that AE increased the level of the anti-apoptotic protein Bcl-2/Bax, significantly decreased the expression of the pro-apoptotic protein caspase-3, and activated the AMPK/PGC-1α signaling pathway. Our findings provide evidence that AE activates the AMPK/PGC-1α signaling pathway, improves mitochondrial energy supply capacity, and effectively inhibits apoptosis in cardiomyocytes. Therefore, AE can be considered a promising post-infarction therapeutic intervention., (© 2024. Pleiades Publishing, Ltd.)

Determination of infarct and scar size following myocardial infarction (MI) is commonly used to evaluate the efficacy of potential cardioprotective treatments in animal models. However, histological methods to determine morphological features in the infarcted heart have barely improved since implementation while still consuming large parts of the tissue and offering little options for parallel analyses. We aim to develop a new fluorescence technology for determining infarct area and area at risk that is comparable to 2,3,5-triphenyltetrazolium chloride (TTC) staining but allows for multiple analyses on the same heart tissue. For early and late time points following MI, we compared classical histochemical approaches with fluorescence staining methods. Reperfused MI was induced in male mice, the hearts were extracted 24 h, 7-, 21-, or 28-days later and fluorescently stained by combining Hoechst and phalloidin. This approach allowed for clear visualization of the infarct area, the area at ischemic risk and the remote area not affected by MI. The combined fluorescence staining correlated with the classic TTC/Evans Blue staining 24 h after MI (r = 0.8334). In later phases (>7 d) post-MI, wheat germ agglutinin (WGA) is equally accurate as classical Sirius Red (r = 0.9752), Masson's (r = 0.9920) and Gomori's Trichrome (r = 0.8082) staining for determination of scar size. Additionally, feasibility to co-localize fluorescence-stained immune cells in specific regions of the infarcted myocardium was demonstrated with this protocol. In conclusion, this new procedure for determination of post-MI infarct size is not inferior to classical TTC staining, yet provides substantial benefits, including the option for unbiased software-assisted analysis while sparing ample residual tissue for additional analyses. Overall, this enhances the data quality and reduces the required animal numbers consistent with the 3R concept of animal experimentation.

Unlike adult mammals, the hearts of neonatal mice possess the ability to completely regenerate from myocardial infarction (MI). This observation has sparked vast interest in deciphering the potentially lifesaving and morbidity-reducing mechanisms involved in neonatal cardiac regeneration. In mice, the regenerative potential is lost within the first week of life and coincides with a reduction of Insulin-like growth factor 1 receptor (Igf1r) expression in the heart. Igf1r is a well-known regulator of cardiomyocyte maturation and proliferation in neonatal mice. To test the role of Igf1r as a pivotal factor in cardiac regeneration, we knocked down (KD) Igf1r specifically in cardiomyocytes using recombinant adeno-associated virus (rAAV) delivery and troponin T promotor driven shRNAmirs. Cardiomyocyte specific Igf1r KD versus control mice were subjected to experimental MI by permanent ligation of the left anterior descending artery (LAD). Cardiac functional and morphological data were analyzed over a 21-day period. Neonatal Igf1r KD mice showed reduced systolic cardiac function and increased fibrotic cardiac remodeling 21 days post injury. This cardiac phenotype was associated with reduced cardiomyocyte nuclei mitosis and decreased AKT and ERK phosphorylation in Igf1r KD, compared to control neonatal mouse hearts. Our in vivo murine data show that Igf1r KD shifts neonatal cardiac regeneration to a more adult-like scarring phenotype, identifying cardiomyocyte-specific Igf1r signaling as a crucial component of neonatal cardiac regeneration., (© 2024. The Author(s).)

In the healing process of myocardial infarction, cardiac fibroblasts are activated to produce collagen, leading to adverse remodeling and heart failure. Our previous study showed that ASPP1 promotes cardiomyocyte apoptosis by enhancing the nuclear trafficking of p53. We thus explored the influence of ASPP1 on myocardial fibrosis and the underlying mechanisms. Here, we observed that ASPP1 was increased after 4 weeks of MI. Both global and myofibroblast knockout of ASPP1 in mice mitigated cardiac dysfunction and fibrosis after MI. Strikingly, ASPP1 produced the opposite influence on p53 level and cell fate in cardiac fibroblasts and cardiomyocytes. Knockdown of ASPP1 increased p53 levels and inhibited the activity of cardiac fibroblasts. ASPP1 accumulated in the cytoplasm of fibroblasts while the level of p53 was reduced following TGF-β1 stimulation; however, inhibition of ASPP1 increased the p53 level and promoted p53 nuclear translocation. Mechanistically, ASPP1 is directly bound to deubiquitinase OTUB1, thereby promoting the ubiquitination and degradation of p53, attenuating myofibroblast activity and cardiac fibrosis, and improving heart function after MI., (© 2024. The Author(s).)

Objective: This study aims to systematically analyze the potential active components of Eucommiae cortex in the treatment of post- myocardial infarction heart failure through network analysis and molecular docking methods. In vitro experiments were conducted to verify that medioresinol, a component of Eucommiae cortex, improves oxygen-glucose deprivation-induced cell failure through its anti-inflammatory and antioxidant capacities., Methods: Potential active components of Eucommiae cortex were screened using specific data. The targets of these components were predicted using Swiss Institute of Bioinformatics database and TargetNet, and key targets were identified by intersecting with the disease targets of myocardial infarction and heart failure. Protein-Protein Interaction analysis was performed on the key targets to screen for core targets. Genomics Institute of the Novartis Research Foundation and Human Protein Atlas were used to identify myocardial highly expressed targets. Kyoto Encyclopedia of Genes and Genomes and Gene Ontology enrichment analyses were conducted using the Database for Annotation, Visualization, and Integrated Discovery. Molecular docking was performed for the final components and target proteins. In vitro experiments were carried out using H9c2 cells subjected to oxygen and glucose deprivation conditions to validate the effects of the screened potential active components., Results: Network analysis revealed that Eucommiae cortex might exert its effects through the phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/AKT/mTOR), hypoxia-inducible factor 1, and Janus kinase/signal transducer and activator of transcription pathways, which are crucial for myocardial contraction, vascular tone regulation, inflammatory response, and oxidative stress. Molecular docking indicated stable binding of the selected compounds to PI3K, AKT, and mTOR. Medioresinol was selected for further study and shown to significantly improve oxidative stress and inflammatory response in myocardial ischemia-hypoxia model cells by activating the PI3K/AKT/mTOR pathway., Conclusion: This study confirms the role of the PI3K/AKT/mTOR pathway in the cardiovascular protective effects of Eucommiae cortex and provides evidence at the cellular level. Medioresinol demonstrated potential therapeutic effects on myocardial infarction induced heart failure by reducing oxidative stress and inflammatory responses. These findings offer a theoretical basis for the application of Eucommiae cortex in the treatment of heart failure and support the development of new therapeutic drugs for cardiovascular diseases. Future research should further validate these effects in animal models and explore the overall efficacy of Eucommiae cortex., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Qin et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Myocardial fibrosis (MF) is a major cause of morbidity and mortality worldwide. Qili Qiangxin capsule (QLQX) is a traditional Chinese medicine (TCM) formula used for treating MF, QLQX can affect ventricular remodeling by regulating collagen deposition; however, the specific mechanism by which QLQX modulates collagen homeostasis remains unclear. Thus, this study aimed to explore the effect of QLQX on collagen fibers and its mechanism of action in rats after myocardial infarction (MI). Rats were subjected to left anterior descending artery ligation and then were divided equally into five groups: sham, model, low-dose QLQX, high-dose QLQX and empagliflozin groups. QLQX treatment for 28 days significantly improved cardiac function, as evidenced by decreases in heart mass index, cardiac volume, left ventricular end-diastolic diameter, left ventricular end-systolic diameter, N-terminal B-type natriuretic peptide levels, and high-sensitivity cardiac troponin I levels and increases in left ventricular ejection fraction and left ventricular fraction shortening. Hematoxylin and eosin, Masson, and Picrosirius red staining under a light microscope indicated that QLQX treatment suppressed fibrosis and promoted angiogenesis by decreasing the protein expression levels of proteins related to cardiac remodeling including transforming growth factor-β1, metalloproteinase-9 and α-smooth muscle actin and increasing the expression of tissue inhibitor of matrix metalloproteinase-1 concentration. Picrosirius red staining under the polarized light microscope and western blotting showed that MI increased the contents of collagen I and III, and reduced the contents of collagen II and IV. QLQX treatment improved cardiac function and attenuated MF by modulating collagen homeostasis and promoting angiogenesis. This study provides novel insights into the mechanism of action of QLQX in preventing MF after MI., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Sun et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Background: Excess fibrotic remodeling causes cardiac dysfunction in ischemic heart disease, driven by MAP (mitogen-activated protein) kinase-dependent TGF-ß1 (transforming growth factor-ß1) activation by coagulation signaling of myeloid cells. How coagulation-inflammatory circuits can be specifically targeted to achieve beneficial macrophage reprogramming after myocardial infarction (MI) is not completely understood., Methods: Mice with permanent ligation of the left anterior descending artery were used to model nonreperfused MI and analyzed by single-cell RNA sequencing, protein expression changes, confocal microscopy, and longitudinal monitoring of recovery. We probed the role of the tissue factor (TF)-FVIIa (activated factor VII)-integrin ß1-PAR2 (protease-activated receptor 2) signaling complex by utilizing genetic mouse models and pharmacological intervention., Results: Cleavage-insensitive PAR2 R38E and myeloid cell integrin ß1-deficient mice had improved cardiac function after MI compared with controls. Proximity ligation assays of monocytic cells demonstrated that colocalization of FVIIa with integrin ß1 was diminished in monocyte/macrophage FVII-deficient mice after MI. Compared with controls, F7 fl/fl CX3CR1 (CX3C motif chemokine receptor 1) Cre mice showed reduced TGF-ß1 and MAP kinase activation, as well as cardiac dysfunction after MI, despite unaltered overall recruitment of myeloid cells. Single-cell mRNA sequencing of CD45 (cluster of differentiation 45) + cells 3 and 7 days after MI uncovered a trajectory from recruited monocytes to inflammatory TF + /TREM (triggered receptor expressed on myeloid cells) 1 + macrophages requiring F7. As early as 7 days after MI, macrophage F7 deletion led to an expansion of reparative Olfml 3 (olfactomedin-like protein 3) + macrophages and, conversely, to a reduction of TF + /TREM1 + macrophages, which were also reduced in PAR2 R38E mice. Short-term treatment from days 1 to 5 after nonreperfused MI with a monoclonal antibody inhibiting the macrophage TF-FVIIa-PAR2 signaling complex without anticoagulant activity improved cardiac dysfunction, decreased excess fibrosis, attenuated vascular endothelial dysfunction, and increased survival 28 days after MI., Conclusions: Extravascular TF-FVIIa-PAR2 complex signaling drives inflammatory macrophage polarization in ischemic heart disease. Targeting this signaling complex for specific therapeutic macrophage reprogramming following MI attenuates cardiac fibrosis and improves cardiovascular function., Competing Interests: W. Ruf is a consultant and received research support from Endpoint Health. W. Ruf and P. Wenzel have filed a patent application on the use of inhibitors of the tissue factor (TF)-PAR2 (protease activated receptor 2) signaling for the treatment or prevention of heart failure (PCT/EP2021/082355). The other authors report no conflicts.

MAPKK4 has been implicated in the pathological mechanisms underlying myocardial and vascular injury, specifically influencing endothelial cell damage and programmed cell death via subcellular pathways. Nevertheless, the regulatory role of MAPKK4 in coronary microvascular injury following myocardial infarction remains unconfirmed, and the exploration of targeted mitochondrial protective therapeutic agents remains unaddressed. In light of this gap, we established a MAPKK4 gene-modified mouse model of ischemia-reperfusion injury and employed Buyang Huanwu decoction (BYHW), a traditional cardiovascular therapeutic formula, to assess its efficacy in treating coronary microvascular injury post-ischemia-reperfusion. The study aimed to elucidate the mechanism by which BYHW mitigates coronary microvascular injury induced by ischemia-reperfusion through the attenuation of endothelial cell apoptosis. Experimental outcomes revealed that high-dose BYHW significantly ameliorated coronary microvascular injury post-ischemia-reperfusion, restoring the structural integrity of the coronary microvasculature and reducing inflammation and oxidative stress. Contrarily, in transgenic mice overexpressing MAPKK4, BYHW intervention failed to attenuate microvascular inflammation and oxidative stress. To further investigate, we simulated hypoxia/reoxygenation injury in vascular endothelial cells using a MAPKK4-related cellular gene modification model. The results indicated that BYHW attenuates inflammatory damage and enhances the viability of vascular endothelial cells following hypoxic stress, inhibiting apoptosis via the mitochondrial pathway. However, overexpression of MAPKK4/p38 negated the therapeutic effects of BYHW, showing no impact on endothelial cell apoptosis and oxidative stress under hypoxic conditions. Molecular interaction studies confirmed that the active components of BYHW, Astragaloside IV and Ligustrazine, interact with the MAPKK4/P38 axis. In vitro experiments further suggested that the interaction between MAPKK4 and P38 play a crucial role in the ability of BYHW to inhibit apoptosis in coronary microvascular endothelial cells. Therapeutically, MAPKK4 may potentiate the apoptotic pathway in microvascular endothelial cells by modulating downstream P38 expression and phosphorylation, thereby exacerbating ischemia-reperfusion-induced coronary microvascular endothelial injury. From an in vivo perspective, the transgenic overexpression of MAPKK4 and P38 inhibited the microvascular protective effects of BYHW. These findings collectively underscore the significance of the MAPKK4-P38 axis in the protection of coronary microvascular endothelial cells., Competing Interests: Competing Interests: The authors have declared that no competing interest exists., (© The author(s).)

After myocardial infarction (MI), patients with type 2 diabetes have an increased rate of adverse outcomes, compared to patients without. Diabetes confers a 1.5-2-fold increase in early mortality and, importantly, this discrepancy has been consistent over recent decades, despite advances in treatment and overall survival. Certain assumptions have emerged to explain this increased risk, such as differences in infarct size or coronary artery disease severity. Here, we re-evaluate that evidence and show how contemporary analyses using state-of-the-art characterization tools suggest that the received wisdom tells an incomplete story. Simultaneously, epidemiological and mechanistic biological data suggest additional factors relating to processes of diabetes-related inflammation might play a prominent role. Inflammatory processes after MI mediate injury and repair and are thus a potential therapeutic target. Recent studies have shown how diabetes affects immune cell numbers and drives changes in the bone marrow, leading to pro-inflammatory gene expression and functional suppression of healing and repair. Here, we review and re-evaluate the evidence around adverse prognosis in patients with diabetes after MI, with emphasis on how targeting processes of inflammation presents unexplored, yet valuable opportunities to improve cardiovascular outcomes in this vulnerable patient group., Competing Interests: Conflict of interest: RPC has received payment for consultancy from NovoNordisk, Nodthera, and Velakor., (© The Author(s) 2024. Published by Oxford University Press on behalf of the European Society of Cardiology.)

Aims: βII spectrin is a cytoskeletal protein known to be tightly linked to heart development and cardiovascular electrophysiology. However, the roles of βII spectrin in cardiac contractile function and pathological post-myocardial infarction remodelling remain unclear. Here, we investigated whether and how βII spectrin, the most common isoform of non-erythrocytic spectrin in cardiomyocytes, is involved in cardiac contractile function and ischaemia/reperfusion (I/R) injury., Methods and Results: We observed that the levels of serum βII spectrin breakdown products (βII SBDPs) were significantly increased in patients with acute myocardial infarction (AMI). Concordantly, βII spectrin was degraded into βII SBDPs by calpain in mouse hearts after I/R injury. Using tamoxifen-inducible cardiac-specific βII spectrin knockout mice, we found that deletion of βII spectrin in the adult heart resulted in spontaneous development of cardiac contractile dysfunction, cardiac hypertrophy, and fibrosis at 5 weeks after tamoxifen treatment. Moreover, at 1 week after tamoxifen treatment, although spontaneous cardiac dysfunction in cardiac-specific βII spectrin knockout mice had not developed, deletion of βII spectrin in the heart exacerbated I/R-induced cardiomyocyte death and heart failure. Furthermore, restoration of βII spectrin expression via adenoviral small activating RNA (saRNA) delivery into the heart reduced I/R injury. Immunoprecipitation coupled with mass spectrometry (IP-LC-MS/MS) analyses and functional studies revealed that βII spectrin is indispensable for mitochondrial complex I activity and respiratory function. Mechanistically, βII spectrin promotes translocation of NADH:ubiquinone oxidoreductase 75-kDa Fe-S protein 1 (NDUFS1) from the cytosol to mitochondria by crosslinking with actin filaments (F-actin) to maintain F-actin stability., Conclusion: βII spectrin is an essential cytoskeletal element for preserving mitochondrial homeostasis and cardiac function. Defects in βII spectrin exacerbate cardiac I/R injury., Competing Interests: Conflict of interest: The authors declare no competing interests., (© The Author(s) 2024. Published by Oxford University Press on behalf of the European Society of Cardiology. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

This article focuses on screening the major secreted proteins by the ischemia-challenged cardiac stromal fibroblasts (CF), the assessment of their expression status and functional role in the post-ischemic left ventricle (LV) and in the ischemia-challenged CF culture and to phenotype CF at single cell resolution based on the positivity of the identified mediators. The expression level of CRSP2, HSP27, IL-8, Cofilin-1, and HSP90 in the LV tissues following coronary artery bypass graft (CABG) and myocardial infarction (MI) and CF cells followed the screening profile derived from the MS/MS findings. The histology data unveiled ECM disorganization, inflammation and fibrosis reflecting the ischemic pathology. CRSP2, HSP27, and HSP90 were significantly upregulated in the LV-CABG tissues with a concomitant reduction ion LV-MI whereas Cofilin-1, IL8, Nrf2, and Troponin I were downregulated in LV-CABG and increased in LV-MI. Similar trends were exhibited by ischemic CF. Single cell transcriptomics revealed multiple sub-phenotypes of CF based on their respective upregulation of CRSP2, HSP27, IL-8, Cofilin-1, HSP90, Troponin I and Nrf2 unveiling pathological and pro-healing phenotypes. Further investigations regarding the underlying signaling mechanisms and validation of sub-populations would offer novel translational avenues for the management of cardiac diseases., (© 2024. The Author(s).)

Background: Myocardial infarction (MI) significantly contributes to the global mortality rate, often leading to heart failure (HF) due to left ventricular remodeling. Key factors in the pathomechanism of HF include nitrosative/oxidative stress, inflammation, and endoplasmic reticulum (ER) stress. Furthermore, while a high-fat diet (HFD) is known to exacerbate post-MI cardiac remodeling, its impact on these critical factors in the context of HF is not as well understood., Aims: This study aimed to assess the impact of post-MI HF and HFD on inflammation, nitro-oxidative stress, ER stress, and unfolded protein response (UPR)., Methods: The study was performed on fragments of the left ventricle harvested from 30 male adult Sprague Dawley rats, which were divided into four groups based on diet (normal-fat vs. high-fat) and surgical procedure (sham operation vs. coronary artery ligation to induce MI). We assessed body weight, NT-proBNP levels, protein levels related to nitrosative/oxidative stress, ER stress, UPR, apoptosis, and nitric oxide synthases, through Western Blot and ELISA., Results: HFD and MI significantly influenced body weight and NT-proBNP concentrations. HFD elevated 3-nitrotyrosine and myeloperoxidase levels and altered nitric oxide synthase levels. HFD and MI significantly affected ER stress markers and activated or inhibited UPR pathways., Conclusions: The study demonstrates significant impacts of post-MI HF and dietary fat content on cardiac function and stress markers in a rat model. The interaction between HFD and MI on UPR activation suggests the importance of dietary management in post-MI recovery and HF prevention., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Momot et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Background: Mineralocorticoid receptor (MR) induces cardiac inflammation cooperatively with nuclear factor-κB and signal transducer and activator of transcription 3 (STAT3); MR blockers exert anti-inflammatory effects. However, the underlying mechanism remains unclear. We investigated the anti-inflammatory effect of esaxerenone, a novel MR blocker, in experimental myocardial infarction (MI) and its underlying mechanisms., Methods and Results: Male C57BL/6J mice subjected to ligation of the left anterior descending artery were randomly assigned to either the vehicle or esaxerenone group. Esaxerenone was provided with a regular chow diet. The mice were euthanized at either 4 or 15 days after MI. Cardiac function, fibrosis, and inflammation were evaluated. Esaxerenone significantly improved cardiac function and attenuated cardiac fibrosis at 15 days after MI independently of its antihypertensive effect. Inflammatory cell infiltration, inflammatory-related gene expression, and elevated serum interleukin-6 levels at 4 days after MI were significantly attenuated by esaxerenone. In vitro experiments using mouse macrophage-like cell line RAW264.7 cells demonstrated that esaxerenone- and spironolactone-attenuated lipopolysaccharide-induced interleukin-6 expression without altering the posttranslational modification and nuclear translocation of p65 and STAT3. Immunoprecipitation assays revealed that MR interacted with both p65 and STAT3 and enhanced the p65-STAT3 interaction, leading to a subsequent increase in interleukin-6 promoter activity, which was reversed by esaxerenone., Conclusions: Esaxerenone ameliorated postinfarct remodeling in experimental MI through its anti-inflammatory properties exerted by modulating the transcriptional activity of the MR-p65-STAT3 complex. These results suggest that the MR-p65-STAT3 complex can be a novel therapeutic target for treating MI.

Human-based modelling and simulation offer an ideal testbed for novel medical therapies to guide experimental and clinical studies. Myocardial infarction (MI) is a common cause of heart failure and mortality, for which novel therapies are urgently needed. Although cell therapy offers promise, electrophysiological heterogeneity raises pro-arrhythmic safety concerns, where underlying complex spatio-temporal dynamics cannot be investigated experimentally. Here, after demonstrating credibility of the modelling and simulation framework, we investigate cell therapy in acute versus chronic MI and the role of cell heterogeneity, scar size and the Purkinje system. Simulations agreed with experimental and clinical recordings from ionic to ECG dynamics in acute and chronic infarction. Following cell delivery, spontaneous beats were facilitated by heterogeneity in cell populations, chronic MI due to tissue depolarisation and slow sinus rhythm. Subsequent re-entrant arrhythmias occurred, in some instances with Purkinje involvement and their susceptibility was enhanced by impaired Purkinje-myocardium coupling, large scars and acute infarction. We conclude that homogeneity in injected ventricular-like cell populations minimises their spontaneous beating, which is enhanced by chronic MI, whereas a healthy Purkinje-myocardium coupling is key to prevent subsequent re-entrant arrhythmias, particularly for large scars., (© 2024. The Author(s).)

Cardiomyocyte proliferation is a challenging metric to assess. Current methodologies have limitations in detecting the generation of new cardiomyocytes and technical challenges that reduce widespread applicability. Here, we describe an improved cell suspension and imaging-based methodology that can be broadly employed to assess cardiomyocyte cell division in standard laboratories across a multitude of model organisms and experimental conditions. We highlight additional metrics that can be gathered from the same cell preparations to enable additional relevant analyses to be performed. We incorporate additional antibody stains to address potential technical concerns of miscounting. Finally, we employ this methodology with a dual-thymidine analog-labeling approach to a post-infarction murine model, which allowed us to robustly identify unique cycling events, such as cardiomyocytes undergoing multiple rounds of cell division., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)