Approaches to Improving Cardiac Structure and Function During and After an Acute Myocardial Infarction: Acute and Chronic Phases

Hypoxia-induced circRNAs encoded by PPARA are highly expressed in human cardiomyocytes and are potential clinical biomarkers of acute myocardial infarction

BACKGROUND

Acute myocardial infarction (AMI) is a serious cardiovascular disease that adversely affects human health. Circular RNAs (circRNAs) are involved in the pathological and physiological processes of AMI, but the biological mechanism of their involvement and their clinical significance remain unknown. We aimed to identify circRNAs that are significantly associated with morbidity in the peripheral blood of patients with AMI and evaluate their diagnostic utility.

METHODS

High-throughput sequencing was used to screen for differentially expressed circRNAs in peripheral blood samples obtained from five patients with AMI and five sex- and age-matched healthy controls. A series of bioinformatics tools and databases were used to determine the biological functional classification and pathway enrichment of the circRNAs based on data obtained from sequencing. A hypoxia model was established and used to evaluate the effect of hypoxia on circRNA expression in human cardiomyocytes. A cytoplasmic separation assay and enzyme resistance assay were employed to identify the biological characteristics of circRNA. Polymerase chain reaction validity testing and receiver operating characteristic (ROC) curve analysis were used to evaluate the utility of circRNA assessments in the diagnosis of AMI.

RESULTS

A large number of circRNAs were found to be differentially expressed in the peripheral blood of patients with AMI, and significantly more of these circRNAs were highly expressed than lowly expressed. The genes encoding these circRNAs have a wide range of effects on various functions in the body. A hypoxic environment promoted the upregulation of circRNA expression in human cardiomyocytes, and hsa_circ_0116795 encoded by PPARA was highly expressed in the peripheral blood of the patients with AMI. In terms of biological characteristics, under physiological conditions, hsa_circ_0116795 (circ_PPARA) was mainly located in the cytoplasm of cardiomyocytes and found to be resistant to exonuclease. The ROC curve analysis showed that the expression levels of circ_PPARA in the peripheral blood of patients with AMI were significantly different from those in the peripheral blood of healthy controls.

CONCLUSION

A large number of abnormally expressed circRNAs are detectable in the peripheral blood of patients with AMI. In particular, circ_PPARA is highly expressed in human myocardial cells under hypoxic conditions, and its biological characteristics indicate that it could be employed as a biomarker for the early diagnosis of AMI.

Death-Associated Protein Kinase 1 (DAPK1) Protects against Myocardial Injury Induced by Myocardial Infarction in Rats via Inhibition of Inflammation and Oxidative Stress

Objective

Heart failure and ventricular remodeling after acute myocardial infarction (AMI) are important factors affecting the prognosis of patients. Therefore, we expected to explore the therapeutic target of AMI by studying the effect of death-associated protein kinase 1 (DAPK1) on AMI rat model.

Materials and Methods

We used male Sprague-Dawley rats to make AMI model, and after 1, 3, 7, and 14 d, we detect the success rate of modeling and the expression change of DAPK1 through 2, 3, 5-triphenyl tetrazolium chloride staining, myocardial injury markers detection, echocardiographic detection, and histological experiment. In addition, we determined the effect of DAPK1 on AMI by subcutaneous injection of the DAPK1 inhibitor (TC-DAPK 6). The effect of DAPK1 on cardiomyocytes has also been verified in cell experiments on H9c2 cells.

Results

The expression of DAPK1 in AMI rats was significantly higher than that in sham group, and it increased with time. The expression of inflammatory factors (interleukin- (IL-) 1β, IL-6, and tumor necrosis factor-α) in AMI rats treated by TC-DAPK 6 was reduced. In addition, TC-DAPK 6 also reduced the activity of malonaldehyde and increased the activities of superoxide dismutase, glutathione, and catalase. The expression of antioxidant molecules such as peroxiredoxin1/4 and glutathione peroxidase1/3 was also promoted by TC-DAPK 6. In H9c2 cells, TC-DAPK 6 also reduced its oxidative stress level.

Conclusions

The increase of DAPK1 may be related to the pathogenesis of AMI. DAPK1 inhibitors protect cardiomyocytes from AMI-induced myocardial injury by reducing levels of inflammation and oxidative stress in myocardial tissue and cells.

Study on the interaction mechanism between C-reactive protein and platelets in the development of acute myocardial infarction

Background

Myocardial infarction (MI) is the single most critical event in coronary disease. Platelets are involved in the processes of acute MI (AMI). They lack nuclear DNA but retain megakaryocyte mRNAs, hence, their transcriptome could provide information preceding coronary events. However, their mechanisms are not clear. In this study, we obtained a gene expression atlas of platelets from patients after their very first AMI, and our purpose was to clarify the mechanisms of platelet involvement in the occurrence of AMI through bioinformatics analyses and animal models of AMI in vivo.

Methods

We obtained a gene expression atlas of platelets from patients after their very first AMI from the Gene Expression Omnibus (GEO). Differentially expressed genes (DEGs) were retrieved using R language. Weighted gene co-expression network analysis (WGCNA) was implemented in order to construct a gene co-expression correlation network among DEGs. Animal models of AMI in vivo were constructed to confirm the results of the bioinformatics analysis.

Results

Gene integration analysis yielded 2,852 DEGs (P<0.05, |log2FC| >1). Bioinformatics analysis demonstrated a significant association between C-reactive protein (CRP) and Staphylococcus aureus infection (SAI) (P=0.015). Data from in vivo experiments showed that CRP increased significantly in AMI rats (P<0.001), and the expression of FCGR2B mRNA and HLA-DRB4 mRNA was elevated in response to the increase of CRP (P<0.001).

Conclusions

From the results of this study, we speculate that in the development of AMI, the increase in CRP activates platelets and induces platelets to play an anti-inflammatory role.

SCD leads to the development and progression of acute myocardial infarction through the AMPK signaling pathway

Background

Acute myocardial infarction (AMI) is myocardial necrosis caused by acute coronary ischemia and hypoxia. It can be complicated by arrhythmia, shock, heart failure and other symptoms that can be life-threatening. A multi-regulator driven dysfunction module for AMI was constructed. It is intended to explore the pathogenesis and functional pathways regulation of acute myocardial infarction.

Methods

Combining differential expression analysis, co-expression analysis, and the functional enrichment analysis, a set of expression disorder modules related to AMI was obtained. Hypergeometric test was performed to calculate the potential regulatory effects of multiple factors on the module, identifying a range of non-coding RNA and transcription factors.

Results

A total of 4551 differentially expressed genes for AMI and seven co-expression modules were obtained. These modules are primarily involved in the metabolic processes of prostaglandin transport processes, regulating DNA recombination and AMPK signal transduction. Based on this set of functional modules, 3 of 24 transcription factors (TFs) including NFKB1, MECP2 and SIRT1, and 3 of 782 non-coding RNA including miR-519D-3P, TUG1 and miR-93-5p were obtained. These core regulators are thought to be involved in the progression of AMI disease. Through the AMPK signal transduction, the critical gene stearoyl-CoA desaturase (SCD) can lead to the occurrence and development of AMI.

Conclusions

In this study, a dysfunction module was used to explore the pathogenesis of multifactorial mediated AMI and provided new methods and ideas for subsequent research. It helps researchers to have a deeper understanding of its potential pathogenesis. The conclusion provides a theoretical basis for biologists to design further experiments related to AMI.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-021-02011-8.

Bone marrow mesenchymal stem cells transfer in patients with ST-segment elevation myocardial infarction: single-blind, multicenter, randomized controlled trial

OBJECTIVE

Our aim was to evaluate the efficacy and safety of intracoronary autologous bone marrow mesenchymal stem cell (BM-MSC) transplantation in patients with ST-segment elevation myocardial infarction (STEMI).

METHODS

In this randomized, single-blind, controlled trial, patients with STEMI (aged 39-76 years) were enrolled at 6 centers in Beijing (The People's Liberation Army Navy General Hospital, Beijing Armed Police General Hospital, Chinese People's Liberation Army General Hospital, Beijing Huaxin Hospital, Beijing Tongren Hospital, Beijing Chaoyang Hospital West Hospital). All patients underwent optimum medical treatment and percutaneous coronary intervention and were randomly assigned in a 1:1 ratio to BM-MSC group or control group. The primary endpoint was the change of myocardial viability at the 6th month's follow-up and left ventricular (LV) function at the 12th month's follow-up. The secondary endpoints were the incidence of cardiovascular event, total mortality, and adverse event during the 12 months' follow-up. The myocardial viability assessed by single-photon emission computed tomography (SPECT). The left ventricular ejection fraction (LVEF) was used to assess LV function. All patients underwent dynamic ECG and laboratory evaluations. This trial is registered with ClinicalTrails.gov, number NCT04421274.

RESULTS

Between March 2008 and July 2010, 43 patients who had underwent optimum medical treatment and successful percutaneous coronary intervention were randomly assigned to BM-MSC group (n = 21) or control group (n = 22) and followed-up for 12 months. At the 6th month's follow-up, there was no significant improvement in myocardial activity in the BM-MSC group before and after transplantation. Meanwhile, there was no statistically significant difference between the two groups in the change of myocardial perfusion defect index (p = 0.37) and myocardial metabolic defect index (p = 0.90). The LVEF increased from baseline to 12 months in the BM-MSC group and control group (mean baseline-adjusted BM-MSC treatment differences in LVEF 4.8% (SD 9.0) and mean baseline-adjusted control group treatment differences in LVEF 5.8% (SD 6.04)). However, there was no statistically significant difference between the two groups in the change of the LVEF (p = 0.23). We noticed that during the 12 months' follow-up, except for one death and one coronary microvascular embolism in the BM-MSC group, no other events occurred and alanine transaminase (ALT) and C-reactive protein (CRP) in BM-MSC group were significantly lower than that in the control group.

CONCLUSIONS

The present study may have many methodological limitations, and within those limitations, we did not identify that intracoronary transfer of autologous BM-MSCs could largely promote the recovery of LV function and myocardial viability after acute myocardial infarction.

Copper promotion of myocardial regeneration

IMPACT STATEMENT

Copper promotes angiogenesis, but the mechanistic insights have not been fully elucidated until recently. In addition, the significance of copper promotion of angiogenesis in myocardial regeneration was increasingly revealed. Copper critically participates in the regulation of hypoxia-inducible factor 1 (HIF-1) of angiogenic gene expression. Interestingly, myocardial ischemia causes copper efflux from the heart, leading to suppression of angiogenesis, although HIF-1α, the critical subunit of HIF-1, remains accumulated in the ischemic myocardium. Strategies targeting copper specific delivery to the ischemic myocardium lead to selective activation of HIF-1-regulated angiogenic gene expression. Vascularization of the ischemic myocardium re-establishes the tissue injury microenvironment, and rebuilds the conduit for communication between the tissue injury signals and the remote regenerative responses including stem cells. This process promotes myocardial regeneration. Thus, a simple and effective copper supplementation to the ischemic myocardium would become a novel therapeutic approach to the treatment of patients with ischemic heart diseases.

Iodide Improves Outcome After Acute Myocardial Infarction in Rats and Pigs

OBJECTIVES

In this study, we tested whether iodide would reduce heart damage in rat and pig models of acute myocardial infarction as a risk analysis for a human trial.

DESIGN

Prospective blinded and randomized laboratory animal investigation.

SETTING

Animal research laboratories.

SUBJECTS

Sexually mature rats and pigs.

INTERVENTIONS

Acute myocardial infarction was induced by temporary ligation of the coronary artery followed by reperfusion. Iodide was administered orally in rats or IV in rats and pigs just prior to reperfusion.

MEASUREMENTS AND MAIN RESULTS

Damage was assessed by blood cardiac troponin and infarct size; heart function was determined by echocardiography. Blood peroxide scavenging activity was measured enzymatically, and blood thyroid hormone was determined using radioimmune assay. Iodide administration preserved heart function and reduced blood cardiac troponin and infarct size by approximately 45% in pigs and approximately 60% in rats. Iodide administration also increased blood peroxide scavenging activity and maintained thyroid hormone levels.

CONCLUSIONS

Iodide administration improved the structure and function of the heart after acute myocardial infarction in rats and pigs.

Myocardial tissue salvage is correlated with ischemic border region temperature at reperfusion

OBJECTIVES

Our pilot study investigated the association between region-specific myocardial tissue temperature and tissue salvage using a novel tri-lumen cooling catheter to provide rapid localized cooling directly to the heart in an open-chest porcine model of ischemia-reperfusion.

BACKGROUND

Therapeutic hypothermia remains a promising strategy to limit reperfusion injury following myocardial ischemia.

METHODS

Large swine underwent 60 min of coronary occlusion followed by 3 hr of reperfusion. Prior to inducing ischemia, six temperature probes were placed directly on the heart, monitoring myocardial temperatures in different locations. Hemodynamic parameters and core temperature were also collected. Approximately 15 min prior to reperfusion, the cooling catheter was inserted via femoral artery and the distal tip advanced proximal to the occluded coronary vessel under fluoroscopic guidance. Autologous blood was pulled from the animal via femoral sheath and delivered through the central lumen of the cooling catheter, delivering at 50 ml/min, 27°C at the distal tip. Cooling was continued for an additional 25 min after reperfusion followed by a 5-min controlled rewarming. Hearts were excised and assessed for infarct size per area at risk.

RESULTS

Although cooling catheter performance was consistent throughout the study (38 W), the resulting tissue cooling was not. Our results show a correlation between myocardial tissue salvage and ischemic border region (IBR) temperature at the time of reperfusion (R² = 0.59, p = 0.027). IBR tissue is the tissue located at the boundary between healthy and ischemic tissues.

CONCLUSIONS

Our findings suggest that localized, rapid, short-term myocardial tissue cooling has the potential to limit reperfusion injury in humans.

Aspirin in combination with clopidogrel in the treatment of acute myocardial infarction patients undergoing percutaneous coronary intervention

Objective:

To investigate the clinical effect of aspirin combined with clopidogrel on acute myocardial infarction after percutaneous coronary intervention (PCI).

Methods:

One hundred thirty two patients with acute myocardial infarction who were admitted to the hospital between December 2016 and December 2017 were divided into a control group and an observation group according to random number table, 66 each group. Both groups were given emergency PCI and symptomatic treatment. The control group was given aspirin on the basis of conventional treatment before and after operation, while the observation group was given clopidogrel treatment on the basis of the treatment the same as the control group. The treatment lasted for 4 months. The clinical efficacy of the two groups was analyzed, and the cardiac function indicator, coagulation indicator and occurrence of adverse reactions were compared before and after treatment.

Results:

There was no thrombosis at the infarct site in coronary angiography after treatment in both groups. The efficacy in the observation group and control group were 89.4% and 81.8%, respectively; there was no significant difference between the two groups. The incidence of re-thrombosis in the two groups was 1.5% and 12.1% respectively, which was significantly lower in the observation group than in the control group (P<0.05). The cardiac function indicator of both groups improved after treatment, especially the observation group (P<0.05). There was no significant difference in prothrombin time (PT), activated partial thromboplastin time (APTT), prothrombin activity (PA) and platelet aggregation rate (PAR) in the two groups before treatment (P>0.05). There was also no significant difference in PT and PA before and after treatment (P>0.05). The APTT and PAR were significantly different after treatment (P<0.05), and the PAR of the observation group was significantly higher than that of the control group (P<0.05). The incidence of adverse reactions in the observation group was 7.58%, which was not significantly different with that of the control group (12.12%) (P<0.05).

Conclusion:

Aspirin combined with clopidogrel can effectively reduce the occurrence of re-thrombosis after PCI and improve the recovery of cardiac function after acute operation, moreover the safety is high. It has important clinical application values.

Tetramethylpyrazine and Astragaloside IV Synergistically Ameliorate Left Ventricular Remodeling and Preserve Cardiac Function in a Rat Myocardial Infarction Model

Tetramethylpyrazine (TMP) and astragaloside IV (AGS-IV) are herbal ingredients that have been demonstrated in animal models to limit infarct size and protect cardiomyocytes in the acute phase of myocardial infarction (MI), yet their long-term cardioprotective effects have not been evaluated. In this study, TMP and/or AGS-IV were administrated to rats for 14 days after MI. Echocardiography revealed that the left ventricular (LV) dimensions and cardiac function were preserved in the MI rats with TMP and AGS-IV treatment, compared with untreated MI rats. Moreover, the LV dimensions and cardiac function in the MI rats with TMP and AGS-IV cotreatment were comparable with the sham-operated rats. In addition, TMP and AGS-IV synergistically inhibited LV fibrosis by attenuating MI-induced collagen deposition and elevation of transforming growth factor β1. TMP and AGS-IV, alone or in synergy, enhanced angiogenesis in the infarcted myocardium and reduced cardiac hypertrophy of the remote myocardium after MI. Furthermore, TMP and AGS-IV mutually upregulated the expression of Sonic hedgehog (Shh), Smoothened, and Glioblastoma-2, the receptor and signal transducer of Shh signaling pathway, in the infarcted myocardium. In summary, in the circumstance of the irreversible ischemic injury, the antifibrotic, and pro-angiogenic properties of TMP and AGS-IV on the nonaffected tissues contribute to the cardioprotection in the healing phase post MI, and the cardioprotective effects are likely to be mediated through the Shh pathway.

New and revisited approaches to preserving the reperfused myocardium

Early coronary artery reperfusion improves outcomes for patients with ST-segment elevation myocardial infarction (STEMI), but morbidity and mortality after STEMI remain unacceptably high. The primary deficits seen in these patients include inadequate pump function, owing to rapid infarction of muscle in the first few hours of treatment, and adverse remodelling of the heart in the months that follow. Given that attempts to further reduce myocardial infarct size beyond early reperfusion in clinical trials have so far been disappointing, effective therapies are still needed to protect the reperfused myocardium. In this Review, we discuss several approaches to preserving the reperfused heart, such as therapies that target the mechanisms involved in mitochondrial bioenergetics, pyroptosis, and autophagy, as well as treatments that harness the cardioprotective properties of inhaled anaesthetic agents. We also discuss potential therapies focused on correcting the no-reflow phenomenon and its effect on healing and adverse left ventricular remodelling.

Delayed therapeutic hypothermia protects against the myocardial no-reflow phenomenon independently of myocardial infarct size in a rat ischemia/reperfusion model

BACKGROUND

Adjunctive therapies, given in addition to reperfusion to reduce myocardial infarct size, have been disappointing based on clinical trials. New therapeutic targets independent of infarct size modification are needed. The no-reflow phenomenon occurs commonly after the infarct-related coronary artery is opened and predicts poor clinical outcome. We investigated the effects of a single application of delayed (post-reperfusion) therapeutic hypothermia (TH) in a rat model of coronary artery occlusion/reperfusion.

METHODS

Rats were subjected to 60min of coronary artery occlusion followed by 3h of reperfusion. Rats were divided into normothermic (n=5) and TH (n=5) groups. In the TH, hypothermia was initiated at 1min after coronary artery reperfusion by pumping room-temperature (22°C) saline into and out of the thoracic cavity for 1h. This decreased intrathoracic temperature to around 26°C within 12min. At 3h after reperfusion, hearts were excised for infarct size and no-reflow zone measurement.

RESULTS

Ischemic risk area and infarct size were similar between the 2 groups. No-reflow area (expressed as % of risk area) was significantly reduced in TH group (18.0±4.4%) compared with normothermic group (39.5±2.9%,P=0.005). When expressed as % of necrotic area, no-reflow area was reduced by more than half in TH group (25.5±6.4%) versus innormothermic group (54.4±5.3%,P=0.01).

CONCLUSIONS

In this preliminary study, hypothermia initiated after reperfusion following 60min of coronary artery occlusion had no effect on infarct size yet substantially reduced the extent of no-reflow.

Cardioprotective Effects of Mitochondria-Targeted Peptide SBT-20 in two Different Models of Rat Ischemia/Reperfusion

PURPOSE

Dysfunctional mitochondria are considered to be the major source of intracellular reactive oxygen species and play a central role in the pathophysiology of myocardial ischemia/reperfusion. This study sought to determine effects of mitochondria-targeted cytoprotective peptide SBT-20 on myocardial infarct size in two different models of ischemia/reperfusion.

METHODS

For in vivo studies, anesthetized Sprague Dawley rats were subjected to 30 min of coronary artery occlusion followed by 3 h of reperfusion. Rats received saline (control), low dose SBT-20 (0.3 mg/kg/h) or high dose SBT-20 (3 mg/kg/h) treatment (n = 15 rats in each group). Saline or SBT-20 were delivered into the jugular vein starting 5 min after coronary artery occlusion and were continued for one hour post coronary artery reperfusion. Body temperature, heart rate and blood pressure were monitored during the procedure. At the end of 3 h reperfusion, the ischemic risk area, no-reflow area, and infarct size were measured. In separate in vitro studies, isolated rat hearts were exposed to 20 min global ischemia, followed by SBT-20 administration (1 μM) or no SBT-20 (control) throughout the 2 h reperfusion. In vitro studies were conducted in cells and heart mitochondria to ascertain the mitochondrial effects of SBT-20 on mitochondrial respiration and reactive oxygen species production.

RESULTS

In the in vivo study, the ischemic risk areas (as a percentage of the left ventricle) were similar among the saline (49.5 ± 2.3 %), low dose SBT-20 (48.6 ± 2.1 %), and high dose SBT-20 groups (48.7 ± 3.0 %). Treatment with SBT-20 significantly reduced infarct size ( as a percentage of risk area) in low dose (62.1 ± 4.4 %) and high dose (64.0 ± 4.9 %) compared with saline treatment (77.6 ± 2.6 %, p = 0.001 for both doses). There was no difference in infarct size between low and high dose SBT-20 treatment. The no-reflow areas (as a percentage of the risk area) were comparable among the saline (23.9 ± 1.7 %), low dose SBT-20 (23.7 ± 2.8 %), and high dose groups (25.0 ± 2.1 %). Body temperature, heart rate and blood pressure were comparable among the 3 groups at baseline, during ischemia, and at the end of 3 h of reperfusion. In the in vitro study, infarct size was reduced from 43.3 ± 2.6 % in control group (n = 11) to 17.2 ± 2.8 % in the SBT-20 treatment group (n = 5, p < 0.05). There were no benefits of SBT-20 on recovery of left ventricular developed pressure, coronary flow, or maximal rates of contraction/relaxation. In cell studies, treatment with SBT-20 significantly improved maximal mitochondrial respiration in response to an H2O2 challenge. In isolated mitochondria, reactive oxygen species production was significantly blunted following treatment with SBT-20.

CONCLUSIONS

In summary, SBT-20 significantly reduced infarct size in two different models of myocardial injury, but did not affect hemodynamics or no-reflow area in rat heart. The reduction in injury is postulated to involve stabilization of mitochondrial function and reduced mitochondrial production of ROS.

Effective Factors in Door-to-Needle Time for Streptokinase Administration in Patients With Acute Myocardial Infarction Admitted to the Emergency Department

Background:

Cardiovascular incidents are a common cause of death around the world. Acute myocardial infarction (AMI) poses high risks for the patient due to plaque rupture or erosion along with a superimposed non-occlusive thrombus; therefore, timely treatment with antithrombotic agents plays a key role in reducing an AMI mortality rate.

Objectives:

The present study aimed to assess the time interval between the admission of AMI-suspected patients and treatment initiation.

Patients and Methods:

This cross-sectional study was conducted on 110 patients admitted to the emergency department of Imam Hussein hospital in Tehran, Iran. Data were collected using checklists, completed by the patients’ next of kin or the emergency staff. To analyze the data, student t- test and analysis of variance were used.

Results:

In this study, 31 female and 79 male subjects were included, respectively. The mean time to receive the first dose of streptokinase was 66.39 minutes (73.74 minutes for females and 63.5 minutes for male patients), varying from 49.92 minutes in the morning to 69.78 minutes in the afternoon and 72.68 minutes during night shifts.

Conclusions:

The door-to-needle (DTN) time, in a standard setting, is recommended to be less than 30 minutes. According to the results of this study, the DTN time is comparatively two times longer in females and afternoon and night shifts. Different variables including emergency staff, physicians, patients’ characteristics, and environmental/physical factors induced this difference.