Myocardial Infarction Model Research Articles

MiR-let-7a inhibits sympathetic nerve remodeling after myocardial infarction by downregulating the expression of nerve growth factor.

Sympathetic hyperinnervation following myocardial infarction (MI) is one of the primary causes of ventricular arrhythmias (VAs) after MI. Nerve growth factor (NGF) is a key molecule that induces sympathetic nerve remodeling. Previous studies have confirmed that microRNA (miR)-let-7a interacts with NGF. However, whether miR-let-7a is involved in sympathetic remodeling after MI remains unknown. We aimed to investigate whether miR-let-7a was associated with the occurrence of VA after MI. A rat model of myocardial infarction was established using left coronary artery ligation. miR-let-7a expression levels were analyzed by reverse transcription-quantitative PCR. Western blotting was also used to examine NGF expression levels in vivo and in M1 macrophages in vitro. The relationship between miR-let-7a and NGF levels was investigated using a luciferase reporter assay. The results revealed that the expression of miR-let-7a decreased significantly after MI, while NGF expression was significantly upregulated. In addition, overexpression of miR-let-7a effectively inhibited NGF expression in rats, which was also verified in M1 macrophages. Tyrosine hydroxylase and growth-associated protein 43 immunofluorescence results revealed that the administration of a miR-let-7a overexpression lentivirus to rats inhibited sympathetic remodeling after MI. Programmed electrical stimulation, renal sympathetic nerve activity recording, and heart rate variability measurements showed that miR-let-7a overexpression decreased sympathetic activity. These findings provide novel insights into the molecular mechanisms by which miR-let-7a and NGF contribute to the progression of sympathetic nerve remodeling after MI. Therefore, miR-let-7a may be a promising therapeutic target to reduce the incidence of arrhythmia following MI.

Metabolite profiling of liquiritin in acute myocardial infarction model rat after intragastric administration using an information-dependent acquisition-mediated ultra-high-performance liquid chromatography-tandem mass spectrometry method.

Liquiritin (LQ), a kind of flavonoid isolated from licorice, was proven to have great potential in treating heart failure. Pharmacokinetic evaluation is important for demonstrating clinical efficacy and mechanisms, and the prototype drug and its metabolite profiling are important for drug discovery and development. However, the metabolism of LQ in acute myocardial infarction (AMI) model rats still needs to be studied in depth. An information-dependent acquisition (IDA)-ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was applied to profile LQ metabolites in AMI model rat plasma. Protein precipitation and extraction were used for sample preparation. Chromatographic separation was achieved using an XSelect BEH C18 column (2.1 × 150 mm, 2.5μm) using gradient elution method combining 0.1% formic acid and acetonitrile with a flow rate of 0.3mL/min. Twelve metabolites were identified in IDA mode, sulfation, glucuronidation, methylation, methyl esterification, glutamine conjugation, and valine conjugation, and their composite reactions were presumed as the primary pathways of LQ metabolism. The variation in the peak areas showed that the time to reach the peak drug concentration of LQ and 12 metabolites was within 5h. In summary, IDA-bridged UHPLC-MS/MS from characteristic fragment ions toward confidence-enhanced identification could effectively screen and profile metabolites.

MODEL FORMULATION AND COMPUTATION FOR FACTORS INFLUENCING MYOCARDIAL INFARCTION IN HUMANS

Myocardial infarction commonly known as heart attack, is a medical emergency caused by other diseases in humans. In this paper, a mathematical model based on the factors influencing myocardial infarction is generated. The solution of the model is obtained with the help of the Homotopy Perturbation Method. The analytical results are verified with the exact solution by using MATLAB. The behavior of each parameter is discussed. The main aim of this paper is to develop a model for myocardial infarction and discuss the parameters that help in reducing the rate of myocardial infarction.

Inhibition of Extracellular Signal-Regulated Kinase Activity Improves Cognitive Function in Mice Subjected to Myocardial Infarction.

Cognitive impairment is a commonly observed complication following myocardial infarction; however, the underlying mechanisms are still not well understood. The most recent research suggests that extracellular signal-regulated kinase (ERK) plays a critical role in the development and occurrence of cognitive dysfunction-related diseases. This study aims to explore whether the ERK inhibitor U0126 targets the ERK/Signal Transducer and Activator of Transcription 1 (STAT1) pathway to ameliorate cognitive impairment after myocardial infarction. To establish a mouse model of myocardial infarction, we utilized various techniques including Echocardiography, Hematoxylin-eosin (HE) staining, Elisa, Open field test, Elevated plus maze test, and Western blot analysis to assess mouse cardiac function, cognitive function, and signal transduction pathways. For further investigation into the mechanisms of cognitive function and signal transduction, we administered the ERK inhibitor U0126 via intraperitoneal injection. Reduced total distance and activity range were observed in mice subjected to myocardial infarction during the open field test, along with decreased exploration of the open arms in the elevated plus maze test. However, U0126 treatment exhibited a significant improvement in cognitive decline, indicating a protective effect through the inhibition of the ERK/STAT1 signaling pathway. Hence, this study highlights the involvement of the ERK/STAT1 pathway in regulating cognitive dysfunction following myocardial infarction and establishes U0126 as a promising therapeutic target.

Optimizing cell therapy by sorting cells with high extracellular vesicle secretion

Critical challenges remain in clinical translation of extracellular vesicle (EV)-based therapeutics due to the absence of methods to enrich cells with high EV secretion. Current cell sorting methods are limited to surface markers that are uncorrelated to EV secretion or therapeutic potential. Here, we utilize a nanovial technology for enrichment of millions of single cells based on EV secretion. This approach is applied to select mesenchymal stem cells (MSCs) with high EV secretion as therapeutic cells for improving treatment. The selected MSCs exhibit distinct transcriptional profiles associated with EV biogenesis and vascular regeneration and maintain high levels of EV secretion after sorting and regrowth. In a mouse model of myocardial infarction, treatment with high-secreting MSCs improves heart functions compared to treatment with low-secreting MSCs. These findings highlight the therapeutic importance of EV secretion in regenerative cell therapies and suggest that selecting cells based on EV secretion could enhance therapeutic efficacy.

Modified mRNA-Mediated CCN5 Gene Transfer Ameliorates Cardiac Dysfunction and Fibrosis without Adverse Structural Remodeling.

Modified mRNAs (modRNAs) are an emerging delivery method for gene therapy. The success of modRNA-based COVID-19 vaccines has demonstrated that modRNA is a safe and effective therapeutic tool. Moreover, modRNA has the potential to treat various human diseases, including cardiac dysfunction. Acute myocardial infarction (MI) is a major cardiac disorder that currently lacks curative treatment options, and MI is commonly accompanied by fibrosis and impaired cardiac function. Our group previously demonstrated that the matricellular protein CCN5 inhibits cardiac fibrosis (CF) and mitigates cardiac dysfunction. However, it remains unclear whether early intervention of CF under stress conditions is beneficial or more detrimental due to potential adverse effects such as left ventricular (LV) rupture. We hypothesized that CCN5 would alleviate the adverse effects of myocardial infarction (MI) through its anti-fibrotic properties under stress conditions. To induce the rapid expression of CCN5, ModRNA-CCN5 was synthesized and administrated directly into the myocardium in a mouse MI model. To evaluate CCN5 activity, we established two independent experimental schemes: (1) preventive intervention and (2) therapeutic intervention. Functional analyses, including echocardiography and magnetic resonance imaging (MRI), along with molecular assays, demonstrated that modRNA-mediated CCN5 gene transfer significantly attenuated cardiac fibrosis and improved cardiac function in both preventive and therapeutic models, without causing left ventricular rupture or any adverse cardiac remodeling. In conclusion, early intervention in CF by ModRNA-CCN5 gene transfer is an efficient and safe therapeutic modality for treating MI-induced heart failure.

How preclinical models help to improve outcome in cardiogenic shock.

Preclinical experimentation of cardiogenic shock resuscitation on large animal models represents a powerful tool to decipher its complexity and improve its poor outcome, when small animal models are lacking external validation, and clinical investigation are limited due to technical and ethical constraints. This review illustrates the currently available preclinical models addressing reliably the physiopathology and hemodynamic phenotype of cardiogenic shock, highlighting on the opposite questionable translation based on low severity acute myocardial infarction (AMI) models. Three types of preclinical models replicate reliably AMI-related cardiogenic shock, either with coronary microembolization, coronary deoxygenated blood perfusion or double critical coronary sub-occlusion. These models overcame the pitfall of frequent periprocedural cardiac arrest and offer, to different extents, robust opportunities to investigate pharmacological and/or mechanical circulatory support therapeutic strategies, cardioprotective approaches improving heart recovery and mitigation of the systemic inflammatory reaction. They all came with their respective strengths and weaknesses, allowing the researcher to select the right preclinical model for the right clinical question. AMI-related cardiogenic shock preclinical models are now well established and should replace low severity AMI models. Technical and ethical constraints are not trivial, but this translational research is a key asset to build up meaningful future clinical investigations.

Ilex pubescens inhibits pyroptosis post-myocardial infarction through suppression of the ROS/NLRP3 pathway

IntroductionIlex pubescens (IPES), a traditional Chinese herb widely used in cardiovascular diseases, has shown potential anti-inflammatory capabilities in myocardial infarction. Reactive Oxygen Species (ROS) and the NOD-like Receptor Protein 3 (NLRP3) pathway are significant contributors to aseptic inflammation in heart diseases. This study aims to elucidate the primary mechanism by which IPES inhibits pyroptosis post-myocardial infarction. MethodsBy ligating the left coronary artery in C57BL/6 mice, a myocardial infarction model was established to be conducted in vivo. To establish pyroptosis in vitro, primary neonatal cardiomyocytes, extracted from the hearts of Sprague-Dawley rats, were treated in an oxygen-glucose deprivation way. ROS scavenger, NLRP3 inhibitor, and NLRP3 was overexpressed by adenovirus to confirm IPES inhibiting myocardial pyroptosis through the ROS/NLRP3 pathway. ResultsIn vivo, IPES exerted significant cardioprotective effects, as evidenced by reducing heart injury, improving cardiac function, and decreasing serum markers of cardiac damage. Furthermore, IPES treatment significantly inhibits ROS generation and reduces the expression levels of NLRP3 and its downstream pyroptosis-related proteins. In vitro, IPES therapy significantly decreased cell damage and pyroptosis in a concentration-dependent manner in an oxygen-glucose deprivation/re-oxygenation (OGD/R) cell model. Additionally, IPES demonstrates synergistic cardiomyocyte protection with the ROS scavenger NAC, whereas its inhibition of pyroptosis is not significantly different from that of the NLRP3 inhibitor. More importantly, the inhibitory impacts of IPES on pyroptosis were partially reversed by NLRP3 overexpression. The active components of IPES exhibit the ability to stably and efficiently bind with NLRP3. DiscussionThese results demonstrate that IPES inhibit pyroptosis post-MI by suppressing the ROS/NLRP3 pathway, providing a new insight into its potential application in treating MI.

Pharmacological inhibition of RUNX1 reduces infarct size after acute myocardial infarction in rats and underlying mechanism revealed by proteomics implicates repressed cathepsin levels

Myocardial infarction (MI) results in prolonged ischemia and the subsequent cell death leads to heart failure which is linked to increased deaths or hospitalizations. New therapeutic targets are urgently needed to prevent cell death and reduce infarct size among patients with MI. Runt-related transcription factor-1 (RUNX1) is a master-regulator transcription factor intensively studied in the hematopoietic field. Recent evidence showed that RUNX1 has a critical role in cardiomyocytes post-MI. The increased RUNX1 expression in the border zone of the infarct heart contributes to decreased cardiac contractile function and can be therapeutically targeted to protect against adverse cardiac remodelling. This study sought to investigate whether pharmacological inhibition of RUNX1 function has an impact on infarct size following MI. In this work we demonstrate that inhibiting RUNX1 with a small molecule inhibitor (Ro5-3335) reduces infarct size in an in vivo rat model of acute MI. Proteomics study using data-independent acquisition method identified increased cathepsin levels in the border zone myocardium following MI, whereas heart samples treated by RUNX1 inhibitor present decreased cathepsin levels. Cathepsins are lysosomal proteases which have been shown to orchestrate multiple cell death pathways. Our data illustrate that inhibition of RUNX1 leads to reduced infarct size which is associated with the suppression of cathepsin expression. This study demonstrates that pharmacologically antagonizing RUNX1 reduces infarct size in a rat model of acute MI and unveils a link between RUNX1 and cathepsin-mediated cell death, suggesting that RUNX1 is a novel therapeutic target that could be exploited clinically to limit infarct size after an acute MI.

Periostin regulates lysyl oxidase through ERK1/2 MAPK-dependent serum response factor in activated cardiac fibroblasts.

Collagen crosslinking, mediated by lysyl oxidase, is an adaptive mechanism of the cardiac repair process initiated by cardiac fibroblasts postmyocardial injury. However, excessive crosslinking leads to cardiac wall stiffening, which impairs the contractile properties of the left ventricle and leads to heart failure. In this study, we investigated the role of periostin, a matricellular protein, in the regulation of lysyl oxidase in cardiac fibroblasts in response to angiotensin II and TGFβ1. Our results indicated that periostin silencing abolished the angiotensin II and TGFβ1-mediated upregulation of lysyl oxidase. Furthermore, the attenuation of periostin expression resulted in a notable reduction in the activity of lysyl oxidase. Downstream of periostin, ERK1/2 MAPK signaling was found to be activated, which in turn transcriptionally upregulates the serum response factor to facilitate the enhanced expression of lysyl oxidase. The periostin-lysyl oxidase association was also positively correlated in an in vivo rat model of myocardial infarction. The expression of periostin and lysyl oxidase was upregulated in the collagen-rich fibrotic scar tissue of the left ventricle. Remarkably, echocardiography data showed a reduction in the left ventricular wall movement, ejection fraction, and fractional shortening, indicative of enhanced stiffening of the cardiac wall. These findings shed light on the mechanistic role of periostin in the collagen crosslinking initiated by activated cardiac fibroblasts. Our findings signify periostin as a possible therapeutic target to reduce excessive collagen crosslinking that contributes to the structural remodeling associated with heart failure.

Identification of New, Translatable ProtectomiRs against Myocardial Ischemia/Reperfusion Injury and Oxidative Stress: The Role of MMP/Biglycan Signaling Pathways.

Ischemic conditionings (ICon) were intensively investigated and several protective signaling pathways were identified. Previously, we have shown the role of matrix metalloproteinases (MMP) in myocardial ischemia/reperfusion injury (MIRI) and the cardioprotective role of biglycan (BGN), a small leucine-rich proteoglycan in vitro. Here, we hypothesized that cardiac MMP and BGN signaling are involved in the protective effects of ICon. A reverse target-microRNA prediction was performed by using the miRNAtarget™ 2.0 software to identify human microRNAs with a possible regulatory effect on MMP and BGN, such as on related genes. To validate the identified 1289 miRNAs in the predicted network, we compared them to two cardioprotective miRNA omics datasets derived from pig and rat models of MIRI in the presence of ICons. Among the experimentally measured miRNAs, we found 100% sequence identity to human predicted regulatory miRNAs in the case of 37 porcine and 24 rat miRNAs. Upon further analysis, 42 miRNAs were identified as MIRI-associated miRNAs, from which 24 miRNAs were counter-regulated due to ICons. Our findings highlight 24 miRNAs that potentially regulate cardioprotective therapeutic targets associated with MMPs and BGN in a highly translatable porcine model of acute myocardial infarction.

Targeting serotonin receptor 7 to improve survival after myocardial infarction

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Deutsche Forschungsgemeinschaft (DFG) Background Myocardial infarction (MI) is among the leading causes of death worldwide. Survival and long-term recovery are highly dependent on regeneration of the cardiac tissue, mediated by precisely regulated inflammatory processes and invading immune cells. The serotonergic system is known to regulate the functions of various cells of the immune system, and is also affected in several cardiovascular diseases. Purpose We investigated the role of the serotonin receptor 7 (5-HT7R) in regulation of the inflammatory response after MI and its contribution to cardiac outcome. Methods Permanent left ascending coronary artery ligation (LAD) in mice was used as a model for MI. We compared the impact of MI on heart function and tissue integrity in WT and 5-HT7R-KO mice. In addition, we performed a systemic treatment with the selective 5-HT7R agonist LP-211. Results Murine C57BL/6N hearts reveal an upregulation of 5-HT7R mRNA expression in the infarct region compared to remote myocardium and sham operated mice at 3, 7 and 14 days after MI. Immunohistochemistry demonstrates 5-HT7R expression mainly on CD68+, CD206+ and CD80+ macrophages but not on cardiomyocytes and fibroblasts. Systemic 5-HT7R-KO mice display normal cardiac function and dimensions at 3-4 months of age comparable to their wildtype (WT) littermates. In response to MI, 5-HT7R-KO mice show a higher decrease in left ventricular (LV) function (assessed by transthoracic echocardiography as fractional area change, FAC%) and increased signs of tissue inflammation 14 days post-MI, while the infarct size remains unchanged. Interestingly, systemic treatment with the selective 5-HT7R agonist LP-211 enhances survival rates 14d post MI, without improving cardiac functional output. Conclusion 5-HT7R expression is upregulated post-MI in heart-invading inflammatory cells, such as macrophages. Loss of systemic 5-HT7R may contribute to pronounced functional cardiac impairment 14 days after MI, while systemic activation of 5-HT7R shows positive effects on survival, possibly through mediated inflammatory signalling of immune cells. Therefore, 5-HT7R activity could represent a novel therapeutic target to dampen inflammation and improve cardiac repair.

82Rb-PET is feasible in rodent AMI model after positron range correction

Abstract Funding Acknowledgements Type of funding sources: Other. Main funding source(s): Prof. Andreas Kjær Department of Clinical Physiology, Nuclear Medicine & PET and Cluster for Molecular Imaging, Department of Biomedical Sciences, Rigshospitalet and University of Copenhagen, Copenhagen, Denmark Background Myocardial infarction (MI) remains a leading cause of morbidity and mortality worldwide, necessitating innovative approaches for accurate diagnosis and treatment. Positron emission tomography (PET) using 82-Rubidium (82Rb) is well-established as non-invasive myocardial perfusion imaging (MPI). However, the long position range of 82Rb disables MPI and analysis of MI through 82Rb-scans in rats. Exact assessment of myocardial infarction (MI) in small animal models is important for translational research. Purpose To investigates if positron range correction (PRC) of 82Rb PET can improve the quantification of infarct size in a rat model of MI. Method 10 Sprague-Dawley rats were included. 8 rats with MI established through coronary artery ligation and 2 rats with sham operations, where the rats underwent the same open chest procedure as the MI-rats except for the ligation of the coronary artery. Rats were PET scanned with ~ 60 MBq 82Rb PET one week after MI induction/sham operation (acute scan) in a preclinical PET/CT scanner. At 30-days following MI induction/sham operation the rats were re-scanned with 82Rb PET and 18 flu-deoxy-glucose (18F-FDG) to assess final infarct size. 82Rb PET data were reconstructed both with and without positron range correction. All acquisitions were gated by pulse and respiratory frequency. The image analysis of the static reconstructions was conducted using Corridor4DM version 2023. Infarct size was quantified by summed rest score (SRS). Due to n=10 Spearman’s rank correlation was used. Results Acute 82Rb SRS without PRC showed no correlation to the SRS of 18F-FDG follow-up PET (r=0,015 and p=0,67). Nor was there a correlation between the acute 82Rb with PRC and 18F-FDG-scans (r=0,067, p= 0,85). (Figure1) However, the follow up scan at 30 days post MI induction showed a significant correlation between infarct size of 82Rb with PRC and infarct size of the 18F-FDG scans (r=0,71 and p=0,02). No such correlation was found 82Rb results without PRC and the 18F-FDG results (r=0,51 and p=0,13) (Figure2). The 82Rb PRC scans revealed a significant correlation with 18F-FDG scans, indicating improved alignment between the two in assessing infarct size. This contrasted with the original 82Rb-images. Conclusion In this study we show the possibility of utilizing 82Rb-PET as a cardiac perfusion radioisotope in small animal research by applying positron range correction. 82Rb-PET with positron range correction provides a useful tool to delineate perfusion defects more accurately in a rodent MI-model and shows significant correlation to 18F-FDG results. Further research is warranted to validate the translational potential of these findings.Figure 1Figure 2

Novel method for induction of myocardial infarction in rats by ultrasound guided electrocoagulation of the left anterior descending artery

Abstract Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): Minerva Imaging Background Murine models of acute myocardial infarction (MI) are commonly established through ligation of the left anterior descending artery (LAD). Despite inherent procedural challenges, including high mortality rates, limited improvements of the induction procedure have been made. Ultrasound-guided electrocoagulation of the LAD could be advantageous by improving animal welfare and decreasing procedural mortality. Purpose To investigate the feasibility of MI induction by ultrasound guided electrocoagulation in rats in comparison to traditional LAD ligation. Methods Thirty-eight female Sprague Dawley rats were randomized to MI by either of the two induction methods leading to 19 rats in each group. Infarct size and left ventricular ejection fraction (LVEF) were evaluated using positron emission tomography (PET) with [18F]fluorodeoxyglucose ([18F]FDG) 9 days post-MI. Myocardial infarct size was categorized as non-infarcted, mild, moderate, or severe based on [18F]FDG uptake. Animal welfare was assessed twice daily for the initial 48h post-surgery using a behavioural scoring system. Results There was no significant difference in the mortality rate of rats with MI induced by electrocoagulation compared to LAD ligation (16% vs 37%, P=0.27). Among the surviving animals both methods produced an equal number of myocardial infarcts (n=5). Electrocoagulation resulted in 1 mild, 2 moderate, and 2 severe MIs, while LAD ligation produced 1 mild, 0 moderate, and 4 severe MIs. Infarct size was similar in the electrocoagulation group compared to the LAD ligation group (mean±SD electrocoagulation: 15±5% vs ligation: 28±13%, P=0.13). The number of non-infarcted surviving rats in the electrocoagulation group was 11 compared to 7 in the LAD ligation group (P=0.33). The LVEF of infarcted rats showed no significant difference between groups (electrocoagulation: 47±8% vs ligation: 38±10%, P=0.14). The LVEF for non-infarcted rats was 53±5%. Post-surgical animal welfare appeared to be improved in the electrocoagulation group, however, the accumulated behavioural score did not reveal a significant difference (median [interquartile range] electrocoagulation: 0 [0-1] vs ligation 2 [0-2], P=0.19). Conclusion Induction of myocardial infarction by ultrasound-guided electrocoagulation is feasible in rats and should be considered as an alternative to LAD ligation. Further development is needed to improve the rate of success and consistency in infarct size.

Role of inflammatory populations and their intermediates in post-ischemic adverse remodeling in rat model of myocardial infarction

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Junta de Andalucía- Fondos FEDER Background Compelling evidence demonstrated the critical role of inflammation in ventricular adverse remodeling after acute myocardial infarction. However, it remains unclear how inflammatory cell population and their intermediates participate in the progress of the disease. Purpose This study aims to elucidate the role of inflammatory population in cardiac remodeling after myocardial infarction in a rat model, focusing on their role in fibrosis. Methods We used a surgical procedure by transient ligation of the left descendant coronary artery, to evoke ischemia-reperfusion (I/R) in rats. We performed FACS analysis to evaluate counts of neutrophils and two monocytes’ subsets: CD43lowHis48high (classical monocytes), and CD43highHis48low (non-classical monocytes), which are the most pro-inflammatory subset in peripheral blood. Subsequently, we performed immunofluorescence to detect pro-inflammatory M1 and M2 macrophages (CD68+ and CD163+) in the rat infarcted myocardium. Moreover, we sorted the two monocyte subsets and performed genes and microRNAs Array. Results FACS analysis of neutrophils and monocytes subsets showed an increased level of these cells in the rat model of myocardial infarction, one week after the post-ischemic event. In parallel, the infiltration of M1 macrophages was increased in the myocardium until 1 week after surgery, indicating a long extravasation of inflammatory cells after the ischemic event. Moreover, co-culture of fibroblasts and cardiomyocytes with intermediates released by inflammatory cells subjected to I/R increased the expression of fibrotic and apoptotic genes. In addition, the analysis of genes’ Array by GSEA indicated that CD43highHis48low monocytes had an enrichment score in pathways associated with angiogenesis, fibrosis and inflammation, while CD43lowHis48high population exhibited an enrichment in cytokines and inflammation, apoptosis and fibrosis. Finally, we found significant overexpression of microRNAs, for instance, miR-27a-3p, miR-29b-3p, miR-30e-5p and miR-194-5p in CD43highHis48low 24h after the I/R procedure. Those miRNAs are predicted to modulate pro-fibrotic genes. Conclusions The level of inflammatory cell populations is increased in I/R rat model. Moreover, these cells infiltrate in the myocardium likely to change the transcriptome of resident cells towards a pro-apoptotic and pro-fibrotic phenotype.

The effect of ageing in an experimental model of myocardial infarction in senescent mice

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Funded by the Spanish Ministry of Science and Innovation (ISCIII) PI19/01714 and PI22/1083 co-financed by the European Regional Development Fund (ERDF), and by the Generalitat Valenciana. Introduction The murine experimental model of myocardial infarction allows the study of underlying molecular and cellular mechanisms in cardiac function. Specifically, intercellular communication mediated by small non-coding RNAs, microRNAs (miRNAs) which can modulate gene expression post-transcriptionally, is one of the fundamental processes in the investigation of this pathology that needs to be explored in animal models. The Senescence-Accelerated Mouse Prone (SAMP8) and its control strain SAM Resistant (SAMR1) have been established as an experimental model to study ageing-associated vascular dysfunction but scarcely used in epigenetic studies. Purpose To assess the suitability of the SAMR1/SAMP8 ageing model for the study of miRNAs expression following an acute myocardial infarction (AMI), and to determine the optimal time after AMI to measure circulating miRNA levels. Methods Six-month old male and female SAMR1 and SAMP8 (n = 6 per group) underwent AMI by ligation of the left anterior descending coronary artery and sham surgery. All interventions were performed under full anesthesia and analgesia. Animals were euthanized at different times (1h, 4h and 24h) and blood were collected. AMI was confirmed by immediate discoloration of the left ventricle, by ST segment elevation in the electrocardiogram, and by triphenyltetrazolium chloride staining of the non-ischemic areas of heart sections. RNA was obtained from non-hemolyzed serum. Circulating miRNA previously considered as possible AMI biomarkers, miR-1-3p, miR-133-3p, miR-208-3p and miR-499-5p, were measured by qRT-PCR. Results are shown as mean ± SEM of the relative expression (2-ΔΔCt), using U6 snRNA as endogenous control. p-values were calculated using ANOVA and statistical significance was considered when p<0.05. The investigation complies with ethical standards and was approved by the Ethics Committee for Animal Welfare of University of Valencia (2020/VSC/PEA/0128). Results miR-1-3p, miR-133-3p, miR-208-3p and miR-499-5p were significantly increased 4 hours after AMI when compared with sham group in both SAMR1 and SAMP8. It was noteworthy that only with the sham surgery all biomarkers exhibited a time-dependent decrease (p < 0.05). While miR-1-3p rose at 4 hours after AMI (6.46 ± 1.32, p<0.001), miR-133-3p, miR-208-3p and miR-499-5p showed a time-dependent upregulation, being maximal at 24 hours after AMI (p < 0.001 vs. sham group). When comparing samples from SAMR1 and SAMP8, the expression of the analyzed miRNAs was higher in SAMP8 4 hours after AMI (p < 0.05), to a greater extent than in SAMR1. Conclusion Through the use of the SAMR1/SAMP8 mice model, the impact of ageing on miRNA expression following an AMI was notably confirmed, particularly at 4 hours after AMI. Consequently, this study proposes the SAMR1/SAMP8 mouse model as suitable for studying the effects of both AMI and ageing on circulating miRNA expression.

MiR-106a targets ATG7 to inhibit autophagy and angiogenesis after myocardial infarction.

Myocardial infarction (MI) is an acute condition in which the heart muscle dies due to the lack of blood supply. Previous research has suggested that autophagy and angiogenesis play vital roles in the prevention of heart failure after MI, and miR-106a is considered to be an important regulatory factor in MI. But the specific mechanism remains unknown. In this study, using cultured venous endothelial cells and a rat model of MI, we aimed to identify the potential target genes of miR-106a and discover the mechanisms of inhibiting autophagy and angiogenesis. We first explored the biological functions of miR-106a on autophagy and angiogenesis on endothelial cells. Then we identified ATG7, which was the downstream target gene of miR-106a. The expression of miR-106a and ATG7 was investigated in the rat model of MI. We found that miR-106a inhibits the proliferation, cell cycle, autophagy and angiogenesis, but promoted the apoptosis of vein endothelial cells. Moreover, ATG7 was identified as the target of miR-106a, and ATG7 rescued the inhibition of autophagy and angiogenesis by miR-106a. The expression of miR-106a in the rat model of MI was decreased but the expression of ATG7 was increased in the infarction areas. Our results indicate that miR-106a may inhibit autophagy and angiogenesis by targeting ATG7. This mechanism may be a potential therapeutic treatment for MI.

Extracellular vesicles from dental pulp mesenchymal stem cells modulate macrophage phenotype during acute and chronic cardiac inflammation in athymic nude rats with myocardial infarction

Background/aimsExtracellular vesicles (EVs) derived from dental pulp mesenchymal stem cells (DP-MSCs) are a promising therapeutic option for the treatment of myocardial ischemia. The aim of this study is to determine whether MSC-EVs could promote a pro-resolving environment in the heart by modulating macrophage populations.MethodsEVs derived from three independent biopsies of DP-MSCs (MSC-EVs) were isolated by tangential flow-filtration and size exclusion chromatography and were characterized by omics analyses. Biological processes associated with these molecules were analyzed using String and GeneCodis platforms. The immunomodulatory capacity of MSC-EVs to polarize macrophages towards a pro-resolving or M2-like phenotype was assessed by evaluating surface markers, cytokine production, and efferocytosis. The therapeutic potential of MSC-EVs was evaluated in an acute myocardial infarction (AMI) model in nude rats. Infarct size and the distribution of macrophage populations in the infarct area were evaluated 7 and 21 days after intramyocardial injection of MSC-EVs.ResultsLipidomic, proteomic, and miRNA-seq analysis of MSC-EVs revealed their association with biological processes involved in tissue regeneration and regulation of the immune system, among others. MSC-EVs promoted the differentiation of pro-inflammatory macrophages towards a pro-resolving phenotype, as evidenced by increased expression of M2 markers and decreased secretion of pro-inflammatory cytokines. Administration of MSC-EVs in rats with AMI limited the extent of the infarcted area at 7 and 21 days post-infarction. MSC-EV treatment also reduced the number of pro-inflammatory macrophages within the infarct area, promoting the resolution of inflammation.ConclusionEVs derived from DP-MSCs exhibited similar characteristics at the omics level irrespective of the biopsy from which they were derived. All MSC-EVs exerted effective pro-resolving responses in a rat model of AMI, indicating their potential as therapeutic agents for the treatment of inflammation associated with AMI.

Meteorin‑like/meteorin‑β protects against cardiac dysfunction after myocardial infarction in mice by inhibiting autophagy.

Meteorin-β (Metrnβ) is a protein that is secreted by skeletal muscle and adipose tissue, and participates in cardiovascular diseases. However, its role in myocardial infarction (MI) has not been fully elucidated to date. The aim of the present study was to investigate the role and underlying mechanism of Metrnβ in MI. In the present study, mice were subjected to left coronary ligation to induce a MI model before being injected with adeno-associated virus 9 (AAV9)-Metrnβ to overexpress Metrnβ. Mice were subjected to echocardiography and pressure-volume measurements 2 weeks after ligation. Cardiac injury was measured from the levels of cardiac troponin T and pro-inflammatory factors, which were detected using ELISA kits. Cardiac remodelling was determined from the cross-sectional areas detected using H&E and wheat germ agglutinin staining as well as from the transcriptional levels of hypertrophic and fibrosis markers detected using reverse transcription-quantitative PCR. Cardiac function was detected using echocardiography and pressure-volume measurements. In addition, H9c2 cardiomyocytes were transfected with Ad-Metrnβ to overexpress Metrnβ, before being exposed to hypoxia to induce ischaemic injury. Apoptosis was determined using TUNEL staining and caspase 3 activity. Cell inflammation was detected using ELISA assays for pro-inflammatory factors. Autophagy was detected using LC3 staining and assessing the protein level of LC3II using western blotting. H9c2 cells were also treated with rapamycin to induce autophagy. It was revealed that Metrnβ expression was reduced in both mouse serum and heart tissue 2 weeks post-MI. Metrnβ overexpression using AAV9-Metrnβ delivery reduced the mortality rate, decreased the infarction size and reduced the extent of myocardial injury 2 weeks post-MI. Furthermore, Metrnβ overexpression inhibited cardiac hypertrophy, fibrosis and inflammation post-MI. In ischaemic H9c2 cells, Metrnβ overexpression using adenovirus also reduced cell injury, cell death and inflammatory response. Metrnβ overexpression suppressed MI-induced autophagy in vitro. Following autophagy activation using rapamycin in vitro, the protective effects induced by Metrnβ were reversed. Taken together, these results indicated that Metrnβ could protect against cardiac dysfunction post-MI in mice by inhibiting autophagy.

Shexiang Baoxin Pill enriches Lactobacillus to regulate purine metabolism in patients with stable coronary artery disease

BackgroundIt has been clinically confirmed that the Shexiang Baoxin Pill (SBP) dramatically reduces the frequency of angina in patients with stable coronary artery disease (SCAD). However, potential therapeutic mechanism of SBP has not been fully explored. PurposeThe study explored the therapeutic mechanism of SBP in the treatment of SCAD patients. MethodsWe examined the serum metabolic profiles of patients with SCAD following SBP treatment. A rat model of acute myocardial infarction (AMI) was established, and the potential therapeutic mechanism of SBP was explored using metabolomics, transcriptomics, and 16S rRNA sequencing. ResultsSBP decreased inosine production and improved purine metabolic disorders in patients with SCAD and in animal models of AMI. Inosine was implicated as a potential biomarker for SBP efficacy. Furthermore, SBP inhibited the expression of genes involved in purine metabolism, which are closely associated with thrombosis, inflammation, and platelet function. The regulation of purine metabolism by SBP was associated with the enrichment of Lactobacillus. Finally, the effects of SBP on inosine production and vascular function could be transmitted through the transplantation of fecal microbiota. ConclusionOur study reveals a novel mechanism by which SBP regulates purine metabolism by enriching Lactobacillus to exert cardioprotective effects in patients with SCAD. The data also provide previously undocumented evidence indicating that inosine is a potential biomarker for evaluating the efficacy of SBP in the treatment of SCAD.