Mechanisms of Post-Infarct Left Ventricular Remodeling

Hypertension, microvascular obstruction and infarct size in patients with STEMI undergoing PCI: Pooled analysis from 7 cardiac magnetic resonance imaging studies

BACKGROUND

Mortality after ST-segment elevation myocardial infarction (STEMI) is increased in patients with hypertension. The mechanisms underlying this association are uncertain. We sought to investigate whether patients with STEMI and prior hypertension have greater microvascular obstruction (MVO) and infarct size (IS) compared with those without hypertension.

METHODS

We pooled individual patient data from 7 randomized trials of patients with STEMI undergoing primary percutaneous coronary intervention (PCI) in whom cardiac magnetic resonance imaging was performed within 1 month after reperfusion. The associations between hypertension and MVO, IS, and mortality were assessed in multivariable adjusted models.

RESULTS

Among 2174 patients (61.3 ± 12.6 years, 76% male), 1196 (55.0%) had hypertension. Patients with hypertension were older, more frequently diabetic and had more extensive coronary artery disease than those without hypertension. MVO and IS measured as percent LV mass were not significantly different in patients with and without hypertension (adjusted differences 0.1, 95% CI -0.3 to 0.6, P = .61 and -0.2, 95% CI -1.5 to 1.2, P = .80, respectively). Hypertension was associated with a higher unadjusted risk of 1-year death (hazard ratio [HR] 2.28, 95% CI 1.44-3.60, P < .001), but was not independently associated with higher mortality after multivariable adjustment (adjusted HR 1.04, 95% CI 0.60-1.79, P = .90).

CONCLUSION

In this large-scale individual patient data pooled analysis, hypertension was not associated with larger IS or MVO after primary PCI for STEMI.

Ribonucleicacid interference or small molecule inhibition of Runx1 in the border zone prevents cardiac contractile dysfunction following myocardial infarction

AIMS

Myocardial infarction (MI) is a major cause of death worldwide. Effective treatments are required to improve recovery of cardiac function following MI, with the aim of improving patient outcomes and preventing progression to heart failure. The perfused but hypocontractile region bordering an infarct is functionally distinct from the remote surviving myocardium and is a determinant of adverse remodelling and cardiac contractility. Expression of the transcription factor RUNX1 is increased in the border zone 1-day after MI, suggesting potential for targeted therapeutic intervention.

OBJECTIVE

This study sought to investigate whether an increase in RUNX1 in the border zone can be therapeutically targeted to preserve contractility following MI.

METHODS AND RESULTS

In this work we demonstrate that Runx1 drives reductions in cardiomyocyte contractility, calcium handling, mitochondrial density, and expression of genes important for oxidative phosphorylation. Both tamoxifen-inducible Runx1-deficient and essential co-factor common β subunit (Cbfβ)-deficient cardiomyocyte-specific mouse models demonstrated that antagonizing RUNX1 function preserves the expression of genes important for oxidative phosphorylation following MI. Antagonizing RUNX1 expression via short-hairpin RNA interference preserved contractile function following MI. Equivalent effects were obtained with a small molecule inhibitor (Ro5-3335) that reduces RUNX1 function by blocking its interaction with CBFβ.

CONCLUSIONS

Our results confirm the translational potential of RUNX1 as a novel therapeutic target in MI, with wider opportunities for use across a range of cardiac diseases where RUNX1 drives adverse cardiac remodelling.

Post-infarct evolution of ventricular and myocardial function

Adverse ventricular remodeling following acute myocardial infarction (MI) may induce ventricular dilation, fibrosis, and loss of global contractile function, possibly resulting in heart failure (HF). Understanding the relation between the time-dependent changes in material properties of the myocardium and the contractile function of the heart may further our understanding of the development of HF post-MI and guide the development of novel therapies. A finite element model of cardiac mechanics was used to model MI in a thick-walled truncated ellipsoidal geometry. Infarct core and border zone comprised 9.6 and 8.1% of the LV wall volume, respectively. Acute MI was modeled by inhibiting active stress generation. Chronic MI was modeled by the additional effect of infarct material stiffening, wall thinning and fiber reorientation. In acute MI, stroke work decreased by 25%. In the infarct core, fiber stress was reduced but fiber strain was increased, depending on the degree of infarct stiffening. Fiber work density was equal to zero. Healthy tissue adjacent to the infarct showed decreased work density depending on the degree of infarct stiffness and the orientation of the myofibers with respect to the infarct region. Thinning of the wall partially restored this loss in work density while the effects of fiber reorientation were minimal. We found that the relative loss in pump function in the infarcted heart exceeds the relative loss in healthy myocardial tissue due to impaired mechanical function in healthy tissue adjacent to the infarct. Infarct stiffening, wall thinning and fiber reorientation did not affect pump function but did affect the distribution of work density in tissue adjacent to the infarct.

Keeping the Heart Healthy: The Role of Exercise in Cardiac Repair and Regeneration

Significance: Heart failure is often accompanied by a decrease in the number of cardiomyocytes. Although the adult mammalian hearts have limited regenerative capacity, the rate of regeneration is extremely low and decreases with age. Exercise is an effective means to improve cardiovascular function and prevent cardiovascular diseases. However, the molecular mechanisms of how exercise acts on cardiomyocytes are still not fully elucidated. Therefore, it is important to explore the role of exercise in cardiomyocytes and cardiac regeneration. Recent Advances: Recent advances have shown that the effects of exercise on cardiomyocytes are critical for cardiac repair and regeneration. Exercise can induce cardiomyocyte growth by increasing the size and number. It can induce physiological cardiomyocyte hypertrophy, inhibit cardiomyocyte apoptosis, and promote cardiomyocyte proliferation. In this review, we have discussed the molecular mechanisms and recent studies of exercise-induced cardiac regeneration, with a focus on its effects on cardiomyocytes. Critical Issues: There is no effective way to promote cardiac regeneration. Moderate exercise can keep the heart healthy by encouraging adult cardiomyocytes to survive and regenerate. Therefore, exercise could be a promising tool for stimulating the regenerative capability of the heart and keeping the heart healthy. Future Directions: Although exercise is an important measure to promote cardiomyocyte growth and subsequent cardiac regeneration, more studies are needed on how to do beneficial exercise and what factors are involved in cardiac repair and regeneration. Thus, it is important to clarify the mechanisms, pathways, and other critical factors involved in the exercise-mediated cardiac repair and regeneration. Antioxid. Redox Signal. 39, 1088-1107.

Enzyme-Responsive Nanoparticles for the Targeted Delivery of an MMP Inhibitor to Acute Myocardial Infarction

Herein, we have developed a drug-loaded matrix metalloproteinase (MMP)-responsive micellar nanoparticle (NP) intended for minimally invasive intravenous injection during the acute phase of myocardial infarction (MI) and prolonged retention in the heart for small-molecule drug delivery. Peptide-polymer amphiphiles (PPAs) bearing a small-molecule MMP inhibitor (MMPi), PD166793, were synthesized via ring-opening metathesis polymerization (ROMP) and formulated into spherical micelles by transitioning to aqueous solution. The resulting micellar NPs underwent MMP-induced aggregation, demonstrating enzyme responsiveness. Using a rat MI model, we observed that these NPs were capable of successfully extravasating into the infarcted region of the heart where they were retained due to the active, enzyme-mediated targeting, remaining detectable after 1 week post administration without increasing macrophage recruitment. Furthermore, in vitro studies show that these NPs demonstrated successful drug release following MMP treatment and maintained drug bioactivity as evidenced by comparable MMP inhibition to free MMPi. This work establishes a targeted NP platform for delivering small-molecule therapeutics to the heart after MI, opening possibilities for myocardial infarction treatment.

Mesenchymal Stem Cell-Derived Exosomes and Their MicroRNAs in Heart Repair and Regeneration

Mesenchymal stem cells (MSCs) can be differentiated into cardiac, endothelial, and smooth muscle cells. Therefore, MSC-based therapeutic approaches have the potential to deal with the aftermaths of cardiac diseases. However, transplanted stem cells rarely survive in damaged myocardium, proposing that paracrine factors other than trans-differentiation may involve in heart regeneration. Apart from cytokines/growth factors, MSCs secret small, single-membrane organelles named exosomes. The MSC-secreted exosomes are enriched in lipids, proteins, nucleic acids, and microRNA (miRNA). There has been an increasing amount of data that confirmed that MSC-derived exosomes and their active molecule microRNA (miRNAs) regulate signaling pathways involved in heart repair/regeneration. In this review, we systematically present an overview of MSCs, their cardiac differentiation, and the role of MSC-derived exosomes and exosomal miRNAs in heart regeneration. In addition, biological functions regulated by MSC-derived exosomes and exosomal-derived miRNAs in the process of heart regeneration are reviewed.

Collagen matricryptin promotes cardiac function by mediating scar formation

AIMS

A peptide mimetic of a collagen-derived matricryptin (p1159) was shown to reduce left ventricular (LV) dilation and fibrosis after 7 days delivery in a mouse model of myocardial infarction (MI). This suggested p1159 long-term treatment post-MI could have beneficial effects and reduce/prevent adverse LV remodeling. This study aimed to test the potential of p1159 to reduce adverse cardiac remodeling in a chronic MI model and to elucidate p1159 mode-of-action.

MATERIALS AND METHODS

Using a permanent occlusion MI rodent model, animals received p1159 or vehicle solution up to 28 days. We assessed peptide treatment effects on scar composition and structure and on systolic function. To assess peptide effects on scar vascularization, a cohort of mice were injected with Griffonia simplicifolia isolectin-B4. To investigate p1159 mode-of-action, LV fibroblasts from naïve animals were treated with increasing doses of p1159.

KEY FINDINGS

Matricryptin p1159 significantly improved systolic function post-MI (2-fold greater EF compared to controls) by reducing left ventricular dilation and inducing the formation of a compliant and organized infarct scar, which promoted LV contractility and preserved the structural integrity of the heart. Specifically, infarcted scars from p1159-treated animals displayed collagen fibers aligned parallel to the epicardium, to resist circumferential stretching, with reduced levels of cross-linking, and improved tissue perfusion. In addition, we found that p1159 increases cardiac fibroblast migration by activating RhoA pathways via the membrane receptor integrin α4.

SIGNIFICANCE

Our data indicate p1159 treatment reduced adverse LV remodeling post-MI by modulating the deposition, arrangement, and perfusion of the fibrotic scar.

Prognostic significance of non-infarcted myocardium correlated with microvascular impairment evaluated dynamically by native T1 mapping

OBJECTIVES

This study aimed to investigate the influence of microvascular impairment on myocardial characteristic alterations in remote myocardium at multiple time points, and its prognostic significance after acute ST-segment elevation myocardial infarction (STEMI).

METHODS

Patients were enrolled prospectively and performed CMR at baseline, 30 days, and 6 months. The primary endpoint was major adverse cardiac events (MACE): death, myocardial reinfarction, malignant arrhythmia, and hospitalization for heart failure. Cox proportional hazards regression modeling was analyzed to estimate the correlation between T1 mapping of remote myocardium and MACE in patients with and without microvascular obstruction (MVO).

RESULTS

A total of 135 patients (mean age 60.72 years; 12.70% female, median follow-up 510 days) were included, of whom 86 (63.70%) had MVO and 26 (19.26%) with MACE occurred in patients. Native T1 values of remote myocardium changed dynamically. At 1 week and 30 days, T1 values of remote myocardium in the group with MVO were higher than those without MVO (p = 0.030 and p = 0.001, respectively). In multivariable cox regression analysis of 135 patients, native_1w T1 (HR 1.03, 95%CI 1.01-1.04, p = 0.002), native_30D T1 (HR 1.05, 95%CI 1.03-1.07, p < 0.001) and LGE (HR 1.10, 95%CI 1.05-1.15, p < 0.001) were joint independent predictors of MACE. In multivariable cox regression analysis of 86 patients with MVO, native_30D T1 (HR 1.05, 95%CI 1.04-1.07, p < 0.001) and LGE (HR 1.10, 95%CI 1.05-1.15, p < 0.001) were joint independent predictors of MACE.

CONCLUSIONS

The evolution of native T1 in remote myocardium was associated with the extent of microvascular impairment after reperfusion injury. In patients with MVO, native_30D T1 and LGE were joint independent predictors of MACE.

The impact of angiotensin-converting-enzyme inhibitors versus angiotensin receptor blockers on 3-year clinical outcomes in elderly (≥ 65) patients with acute myocardial infarction without hypertension

OBJECTIVE

This study aimed to investigate the impact of angiotensin-converting-enzyme inhibitors (ACEI) and angiotensin II type 1 receptor blockers (ARB) on 3-year clinical outcomes in elderly (≥ 65) acute myocardial infarction (AMI) patients without a history of hypertension who underwent successful percutaneous coronary intervention (PCI) with drug-eluting stents (DES).

METHODS

A total of 13,104 AMI patients who were registered in the Korea AMI registry (KAMIR)-National Institutes of Health (NIH) were included in the study. The primary endpoint was 3-year major adverse cardiac events (MACE), which was defined as the composite of all-cause death, recurrent myocardial infarction (MI), and any repeat revascularization. To adjust baseline potential confounders, an inverse probability weighting (IPTW) analysis was performed.

RESULTS

The patients were divided into two groups: the ACEI group, n = 872 patients and the ARB group, n = 508 patients. After IPTW matching, baseline characteristics were balanced. During the 3-year clinical follow-up, the incidence of MACE was not different between the two groups. However, incidence of stroke (hazard ratio [HR], 0.375; 95% confidence interval [CI], 0.166-0.846; p = 0.018) and re-hospitalization due to heart failure (HF) (HR, 0.528; 95% CI, 0.289-0.965; p = 0.038) in the ACEI group were significantly lower than in the ARB group.

CONCLUSION

In elderly AMI patients who underwent PCI with DES without a history of hypertension, the use of ACEI was significantly associated with reduced incidences of stroke, and re-hospitalization due to HF than those with the use of ARB.

Unfavorable left ventricular remodeling due to experience of chronic sleep restriction after myocardial infarction: The role of matrix metalloproteinases & oxidative stress

Disturbed sleep or sleep loss due to vocational or lifestyle changes following MI is a common problem that may affect many physiological processes involved in left ventricle (LV) remodeling. Herein, we proposed that experience of sleep disruption and/or restriction after myocardial infarction (MI) may aggravate cardiac extracellular matrix remodeling and induce apoptosis in the cardiomyocytes. MI was induced in adult male rats by permanent ligation of the left anterior descending coronary artery. Twenty-four hours after surgery, some animals experienced chronic sleep restriction (CSR) for 6 days. Serum levels of CK-MB, PAB, and TNF-α were evaluated at days 1, 8, and 21 postsurgery. Twenty-one days after surgery, hemodynamic parameters and expression of MMP-2, MMP-9, TIMP-1, and TNF-α, as well as myocardial fibrosis and apoptosis in the noninfarcted area of the LV were assessed. Our results showed a clear decrease in serum concentrations of CK-MB, PAB and TNF-α at day 21 postsurgery in the MI group as compared to MI+SR animals in which these markers remained at high levels. CSR following MI deteriorated LV hemodynamic indexes and also impaired the balance between MMPs and TIMP-1. Further, it yielded an increase in oxidant and inflammatory state which caused deleterious fibrotic and apoptotic effects on cardiomycytes. Our data suggest post-MI sleep loss may cause adverse LV remodeling due to increased inflammatory reactions as well as oxidative burden and/or anti-oxidative insufficiency that in turn impede the balance between MMPs and their inhibitors.

Temporal Changes in Extracellular Vesicle Hemostatic Protein Composition Predict Favourable Left Ventricular Remodeling after Acute Myocardial Infarction

The subset of plasma extracellular vesicles (EVs) that coprecipitate with low-density lipoprotein (LDL-EVs) carry coagulation and fibrinolysis pathway proteins as cargo. We investigated the association between LDL-EV hemostatic/fibrinolysis protein ratios and post-acute myocardial infarction (post-AMI) left ventricular (LV) remodeling which precedes heart failure. Protein concentrations of von Willebrand factor (VWF), SerpinC1 and plasminogen were determined in LDL-EVs extracted from plasma samples obtained at baseline (within 72 h post-AMI), 1 month and 6 months post-AMI from 198 patients. Patients were categorized as exhibiting adverse (n = 98) or reverse (n = 100) LV remodeling based on changes in LV end-systolic volume (increased or decreased ≥15) over a 6-month period. Multiple level longitudinal data analysis with structural equation (ML-SEM) model was used to assess predictive value for LV remodeling independent of baseline differences. At baseline, protein levels of VWF, SerpinC1 and plasminogen in LDL-EVs did not differ between patients with adverse versus reverse LV remodeling. At 1 month post-AMI, protein levels of VWF and SerpinC1 decreased whilst plasminogen increased in patients with adverse LV remodeling. In contrast, VWF and plasminogen decreased whilst SerpinC1 remained unchanged in patients with reverse LV remodeling. Overall, compared with patients with adverse LV remodeling, higher levels of SerpinC1 and VWF but lower levels of plasminogen resulted in higher ratios of VWF:Plasminogen and SerpinC1:Plasminogen at both 1 month and 6 months post-AMI in patients with reverse LV remodeling. More importantly, ratios VWF:Plasminogen (AUC = 0.674) and SerpinC1:Plasminogen (AUC = 0.712) displayed markedly better prognostic power than NT-proBNP (AUC = 0.384), troponin-I (AUC = 0.467) or troponin-T (AUC = 0.389) (p < 0.001) to predict reverse LV remodeling post-AMI. Temporal changes in the ratios of coagulation to fibrinolysis pathway proteins in LDL-EVs outperform current standard plasma biomarkers in predicting post-AMI reverse LV remodeling. Our findings may provide clinical cues to uncover the cellular mechanisms underpinning post-AMI reverse LV remodeling.

Association of left ventricular flow energetics with remodeling after myocardial infarction: New hemodynamic insights for left ventricular remodeling

BACKGROUND

Myocardial infarction leads to complex changes in left ventricular (LV) hemodynamics. It remains unknown how four-dimensional acute changes in LV-cavity blood flow kinetic energy affects LV-remodeling.

METHODS AND RESULTS

In total, 69 revascularised ST-segment elevation myocardial infarction (STEMI) patients were enrolled. All patients underwent cardiovascular magnetic resonance (CMR) examination within 2 days of the index event and at 3-month. CMR examination included cine, late gadolinium enhancement, and whole-heart four-dimensional flow acquisitions. LV volume-function, infarct size (indexed to body surface area), microvascular obstruction, mitral inflow, and blood flow KEi (kinetic energy indexed to end-diastolic volume) characteristics were obtained. Adverse LV-remodeling was defined and categorized according to increase in LV end-diastolic volume of at least 10%, 15%, and 20%. Twenty-four patients (35%) developed at least 10%, 17 patients (25%) at least 15%, 11 patients (16%) at least 20% LV-remodeling. Demographics and clinical history were comparable between patients with/without LV-remodeling. In univariable regression-analysis, A-wave KEi was associated with at least 10%, 15%, and 20% LV-remodeling (p = 0.03, p = 0.02, p = 0.02, respectively), whereas infarct size only with at least 10% LV-remodeling (p = 0.02). In multivariable regression-analysis, A-wave KEi was identified as an independent marker for at least 10%, 15%, and 20% LV-remodeling (p = 0.09, p < 0.01, p < 0.01, respectively), yet infarct size only for at least 10% LV-remodeling (p = 0.03).

CONCLUSION

In patients with STEMI, LV hemodynamic assessment by LV blood flow kinetic energetics demonstrates a significant inverse association with adverse LV-remodeling. Late-diastolic LV blood flow kinetic energetics early after acute MI was independently associated with adverse LV-remodeling.

Trajectories of Cardiac Function Following Treatment With an Impella Device in Patients With Acute Anterior ST-Elevation Myocardial Infarction

Background

Left ventricular (LV) unloading via the percutaneous micro-axial Impella pump is increasingly used in patients with anterior ST-segment elevation myocardial infarction (STEMI) and overt cardiogenic shock. In this context, the evolution of cardiac function and dimensions beyond hospital discharge remains uncertain. We aimed to characterize echocardiographic changes over time in patients with acute anterior STEMI treated with an Impella device.

Methods

From an ongoing prospective registry, consecutive patients with acute anterior STEMI managed with an Impella device were extracted. Transthoracic echocardiography was performed at index hospitalization and at first outpatient follow-up. Predictors of response, defined as a ≥ 10% absolute increase in left ventricular ejection fraction (LVEF) at follow-up, were sought.

Results

A total of 66 patients (89.4% male, aged 64.3 ± 11.6 years) with anterior STEMI were treated with an Impella device in the first 24 hours of hospitalization, from 2014 to 2022. In-hospital mortality was 24%. Major bleeding and vascular complications requiring surgery occurred in 24% and 11% of patients, respectively. At baseline, mean LVEF was 34% ±12%. At follow-up, survivors showed a significant increase in LVEF (P < 0.0001), whereas LV dimensions, diastolic parameters, and measures of right ventricular dimension and function remained stable. Overall, 28 patients had a ≥ 10% absolute increase in LVEF at follow-up. Baseline creatinine was the only significant predictor of response at univariate analysis.

Conclusions

Among patients with anterior STEMI requiring mechanical hemodynamic support with an Impella device, the majority of survivors showed a sustained increase in LV function, without evidence of adverse remodelling. This signal warrants further investigation in dedicated trials.

Effect of changes in perfusion defect size during serial stress myocardial perfusion imaging on cardiovascular outcomes in patients treated with primary percutaneous coronary intervention after myocardial infarction

BACKGROUND

We evaluated the prognostic value of changes in perfusion defect size (PDS) on serial MPS in patients treated with primary percutaneous coronary intervention (PCI) after acute myocardial infarction (AMI).

METHODS

We enrolled 112 patients treated with primary PCI after AMI who underwent two stress MPS within 1 month and after 6 months. Improvement in PDS was defined as a reduction ≥5%. Remodeling was defined as an increase in left ventricular (LV) end-diastolic volume index ≥20%. Cardiac events included cardiac death, nonfatal MI, unstable angina, repeated revascularization, and heart failure.

RESULTS

During a median follow-up of 86 months, 22 events occurred. Event rate was higher (P < .01) in patients with worsening of PDS compared to those with unchanged or improved PDS. Moreover, patients with remodeling had a higher (P < .001) event rate compared to those without. At Cox analysis, worsening of PDS and remodeling resulted independent predictors of events (both P < .01). Patients with both worsening of PDS and remodeling had the worst event-free survival (P <.001).

CONCLUSION

In patients treated with primary PCI after AMI, worsening of PDS and remodeling are associated to higher risk of events at long-term follow-up. Gated stress MPS improves risk stratification in these patients.

Midterm Outcome of Hybrid Transcatheter and Minimally Invasive Left Ventricular Reconstruction for the Treatment of Ischemic Heart Failure

Background

Left ventricular (LV) remodeling after anterior myocardial infarction (AMI) can cause a pathological increase in LV volume, reduction in LV ejection fraction (EF), and symptomatic heart failure (HF). This study evaluates the midterm results of a hybrid transcatheter and minimally invasive surgical technique to reconstruct the negatively remodeled LV by myocardial scar plication and exclusion with microanchoring technology.

Methods

Retrospective single-center analysis of patients who underwent hybrid LV reconstruction (LVR) with the Revivent TransCatheter System. Patients were accepted for the procedure when they presented with symptomatic HF (New York Heart Association class ≥ II, EF < 40%) after AMI, in the presence of a dilated LV with either akinetic or dyskinetic scar in the anteroseptal wall and/or apex of ≥50% transmurality.

Results

Between October 2016 and November 2021, 30 consecutive patients were operated. Procedural success was 100%. Comparing echocardiographic data preoperatively and directly postoperatively, LVEF increased from 33 ± 8% to 44 ± 10% (p < 0.0001). LV end-systolic volume index decreased from 58 ± 24 mL/m2 to 34 ± 19 mL/m2 (p < 0.0001) and LV end-diastolic volume index decreased from 84 ± 32 mL/m2 to 58 ± 25 mL/m2 (p < 0.0001). Hospital mortality was 0%. After a mean follow-up of 3.4 ± 1.3 years, there was a significant improvement of New York Heart Association class (p = 0.001) with 76% of surviving patients in class I-II.

Conclusions

Hybrid LVR for symptomatic HF after AMI is safe and results in significant improvement in EF, reduction in LV volumes, and sustained improvement in symptoms.

Interaction of ARRDC4 With GLUT1 Mediates Metabolic Stress in the Ischemic Heart

BACKGROUND

An ancient family of arrestin-fold proteins, termed alpha-arrestins, may have conserved roles in regulating nutrient transporter trafficking and cellular metabolism as adaptor proteins. One alpha-arrestin, TXNIP (thioredoxin-interacting protein), is known to regulate myocardial glucose uptake. However, the in vivo role of the related alpha-arrestin, ARRDC4 (arrestin domain-containing protein 4), is unknown.

METHODS

We first tested whether interaction with GLUTs (glucose transporters) is a conserved function of the mammalian alpha-arrestins. To define the in vivo function of ARRDC4, we generated and characterized a novel Arrdc4 knockout (KO) mouse model. We then analyzed the molecular interaction between arrestin domains and the basal GLUT1.

RESULTS

ARRDC4 binds to GLUT1, induces its endocytosis, and blocks cellular glucose uptake in cardiomyocytes. Despite the closely shared protein structure, ARRDC4 and its homologue TXNIP operate by distinct molecular pathways. Unlike TXNIP, ARRDC4 does not increase oxidative stress. Instead, ARRDC4 uniquely mediates cardiomyocyte death through its effects on glucose deprivation and endoplasmic reticulum stress. At baseline, Arrdc4-KO mice have mild fasting hypoglycemia. Arrdc4-KO hearts exhibit a robust increase in myocardial glucose uptake and glycogen storage. Accordingly, deletion of Arrdc4 improves energy homeostasis during ischemia and protects cardiomyocytes against myocardial infarction. Furthermore, structure-function analyses of the interaction of ARRDC4 with GLUT1 using both scanning mutagenesis and deep-learning Artificial Intelligence identify specific residues in the C-terminal arrestin-fold domain as the interaction interface that regulates GLUT1 function, revealing a new molecular target for potential therapeutic intervention against myocardial ischemia.

CONCLUSIONS

These results uncover a new mechanism of ischemic injury in which ARRDC4 drives glucose deprivation-induced endoplasmic reticulum stress leading to cardiomyocyte death. Our findings establish ARRDC4 as a new scaffold protein for GLUT1 that regulates cardiac metabolism in response to ischemia and provide insight into the therapeutic strategy for ischemic heart disease.

β-Adrenergic Receptor Stimulation Maintains NCX-CaMKII Axis and Prevents Overactivation of IL6R-Signaling in Cardiomyocytes upon Increased Workload

Excessive β-adrenergic stimulation and tachycardia are potent triggers of cardiac remodeling; however, their exact cellular effects remain elusive. Here, we sought to determine the potency of β-adrenergic stimulation and tachycardia to modulate gene expression profiles of cardiomyocytes. Using neonatal rat ventricular cardiomyocytes, we showed that tachycardia caused a significant upregulation of sodium–calcium exchanger (NCX) and the activation of calcium/calmodulin-dependent kinase II (CaMKII) in the nuclear region. Acute isoprenaline treatment ameliorated NCX-upregulation and potentiated CaMKII activity, specifically on the sarcoplasmic reticulum and the nuclear envelope, while preincubation with the β-blocker propranolol abolished both isoprenaline-mediated effects. On a transcriptional level, screening for hypertrophy-related genes revealed tachycardia-induced upregulation of interleukin-6 receptor (IL6R). While isoprenaline prevented this effect, pharmacological intervention with propranolol or NCX inhibitor ORM-10962 demonstrated that simultaneous CaMKII activation on the subcellular Ca²⁺ stores and prevention of NCX upregulation are needed for keeping IL6R activation low. Finally, using hypertensive Dahl salt-sensitive rats, we showed that blunted β-adrenergic signaling is associated with NCX upregulation and enhanced IL6R signaling. We therefore propose a previously unrecognized protective role of β-adrenergic signaling, which is compromised in cardiac pathologies, in preventing IL6R overactivation under increased workload. A better understanding of these processes may contribute to refinement of therapeutic options for patients receiving β-blockers.

Predictors and prognostic impact of left ventricular ejection fraction trajectories in patients with ST-segment elevation myocardial infarction

Background

There is little evidence on left ventricular ejection fraction (LVEF) trajectories after ST-segment elevation myocardial infarction (STEMI).

Aim

We aim to identify the LVEF trajectories after STEMI and explore their predictors and association with prognosis.

Methods

This is a retrospective, observational study of STEMI patients. The LVEF trajectories were identified by the latent class trajectory model in patients with baseline LVEF < 50%. We used logistic regression analysis to investigate the predictors for LVEF trajectories. The Cox proportional hazard model was used to assess the impact of LVEF trajectories on prognosis. The primary outcomes were cardiovascular mortality and heart failure (HF) rehospitalization.

Results

572 of 1179 patients presented with baseline normal LVEF (≥ 50%) and 607 with baseline reduced LVEF (< 50%). Two distinct LVEF trajectories were identified in patients with baseline reduced LVEF: recovered LVEF group and persistently reduced LVEF group. Higher baseline LVEF, lower peak troponin T, non-anterior MI, and lower heart rates were all found to be independently associated with LVEF recovery. After multivariate adjustments, patients with persistently reduced LVEF experienced an increased risk of cardiovascular mortality (HR 7.49, 95% CI 1.94–28.87, P = 0.003) and HF rehospitalization (HR 3.54, 95% CI 1.56–8.06 P = 0.003) compared to patients with baseline normal LVEF. Patients with recovered LVEF, on the other hand, showed no significant risk of cardiovascular mortality and HF rehospitalization.

Conclusion

Our study indicated two distinct LVEF trajectories after STEMI and that the persistently reduced LVEF trajectory was related to poor prognosis. In addition, several baseline characteristics can predict LVEF recovery.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40520-022-02087-y.

Therapeutic hypothermia for acute myocardial infarction: a narrative review of evidence from animal and clinical studies

Myocardial infarction (MI) is the leading cause of death from coronary heart disease and requires immediate reperfusion therapy with thrombolysis, primary percutaneous coronary intervention, or coronary artery bypass grafting. However, myocardial reperfusion therapy is often accompanied by cardiac ischemia/reperfusion (I/R) injury, which leads to myocardial injury with detrimental consequences. The causes of I/R injury are unclear, but are multifactorial, including free radicals, reactive oxygen species, calcium overload, mitochondria dysfunction, inflammation, and neutrophil-mediated vascular injury. Mild hypothermia has been introduced as one of the potential inhibitors of myocardial I/R injury. Although animal studies have demonstrated that mild hypothermia significantly reduces or delays I/R myocardium damage, human trials have not shown clinical benefits in acute MI (AMI). In addition, the practice of hypothermia treatment is increasing in various fields such as surgical anesthesia and intensive care units. Adequate sedation for anesthetic procedures and protection from body shivering has become essential during therapeutic hypothermia. Therefore, anesthesiologists should be aware of the effects of therapeutic hypothermia on the metabolism of anesthetic drugs. In this paper, we review the existing data on the use of therapeutic hypothermia for AMI in animal models and human clinical trials to better understand the discrepancy between perceived benefits in preclinical animal models and the absence thereof in clinical trials thus far.

Seamens' Sign: a novel electrocardiogram prediction tool for left ventricular hypertrophy

Introduction

Patients with left ventricular hypertrophy (LVH) diagnosed by electrocardiogram (ECG) have increased mortality and higher risk for life-threatening cardiovascular disease. ECGs offer an opportunity to identify patients with increased risk for potential risk-modifying therapy. We developed a novel, quick, easy to use ECG screening criterion (Seamens' Sign) for LVH. This new criterion was defined as the presence of QRS complexes touching or overlapping in two contiguous precordial leads.

Methods

This study was a retrospective chart review of 2,184 patient records of patients who had an ECG performed in the emergency department and a transthoracic echocardiogram performed within 90 days. The primary outcome was whether Seamens' Sign was noninferior in confirming LVH compared to other common diagnostic criteria. Test characteristics were calculated for each of the LVH criteria. Inter-rater agreement was assessed on a random sample using Cohen's Kappa.

Results

Median age was 63, 52% of patients were male and there was a 35% prevalence of LVH by transthoracic echocardiogram (TTE). Nine percent were positive for LVH on ECG based on Seamens' Sign. Seamens' Sign had a specificity of 0.92. Tests assessing noninferiority indicated Seamens' Sign was non-inferior to all criteria (p < 0.001) except for Cornell criterion for women (p = 0.98). Seamens' Sign had 90% (0.81-1.00) inter-rater agreement, the highest of all criteria in this study.

Conclusion

When compared to both the Sokolow-Lyon criteria and the Cornell criterion for men, Seamens' Sign is noninferior in ruling in LVH on ECG. Additionally, Seamens' Sign has higher inter-rater agreement compared to both Sokolow-Lyon criteria as well as the Cornell criteria for men and women, perhaps related to its ease of use.

PM2.5 Exposure Lowers Mitochondrial Endurance During Cardiac Recovery in a Rat Model of Myocardial Infarction

Many studies have reported the negative effect of PM_2.5 exposure on heart function which is likely to impair postcardiac surgery rehabilitation that is involved in recovery and wound healing, yet the direct effects of PM_2.5 from diesel exhaust (DPM) on cardiac recovery is unknown. To study the impact of DPM on cardiac recovery and repair, we utilized isoproterenol induced myocardial infarction (MI) model where female rats were exposed to DPM prior and after MI induction. The experimental groups comprise of normal, ISO control, DPM control (42 days of exposure), DPM exposed prior (21 days) and after (21 days) MI induction (D + I + D) and DPM exposed (21 days) after MI (I + D). Post-MI rat hearts from D + I + D group exhibited higher fibrosis, elevated cardiac injury and altered electrophysiology, where this pathology was also observed in I + D group animals which was mild. Loss of mitochondrial quality was evident in DPM exposed animals with and without MI, where severe mitochondrial damage persisted in D + I + D group. In addition, these animals showed striking decline in ETC enzyme activity, ATP levels, mitochondrial copy number and down regulation of PGC1-α, TFAM and POLG along with the genes involved in mitophagy and mitofusion. Besides, the MI associated inactivation of cardio protective signalling pathways like PI3K and Akt were persistent in D + I + D group. In fact, I + D group animals also showed a similar pattern of change, but in a mild form. Taken together, exposure to PM_2.5 increases the risk, frequency or progression of MI by impairing the recovery potential of the myocardium.

Calpains as Potential Therapeutic Targets for Myocardial Hypertrophy

Despite advances in its treatment, heart failure remains a major cause of morbidity and mortality, evidencing an urgent need for novel mechanism-based targets and strategies. Myocardial hypertrophy, caused by a wide variety of chronic stress stimuli, represents an independent risk factor for the development of heart failure, and its prevention constitutes a clinical objective. Recent studies performed in preclinical animal models support the contribution of the Ca²⁺-dependent cysteine proteases calpains in regulating the hypertrophic process and highlight the feasibility of their long-term inhibition as a pharmacological strategy. In this review, we discuss the existing evidence implicating calpains in the development of cardiac hypertrophy, as well as the latest advances in unraveling the underlying mechanisms. Finally, we provide an updated overview of calpain inhibitors that have been explored in preclinical models of cardiac hypertrophy and the progress made in developing new compounds that may serve for testing the efficacy of calpain inhibition in the treatment of pathological cardiac hypertrophy.

IL-6, IL-1β and MDA correlate with Thrombolysis in Myocardial Infarction (TIMI) risk score in patients with Acute Coronary Syndrome

BACKGROUND

Inflammation plays a significant role in the pathophysiology of Acute Coronary Syndrome (ACS) but is not included in current risk stratification.

OBJECTIVE

To determine the association between Thrombolysis in Myocardial Infarction (TIMI) risk score and inflammatory biomarkers in the ACS, including unstable angina (UA), non-ST segment elevation myocardial infarction (NSTEMI), and ST-segment elevation myocardial infarction (STEMI). We hypothesized that including inflammatory biomarkers could add prognostic value to the TIMI risk score.

METHODS

In this cross-sectional study, serum levels of interleukins (IL)-6 and IL-1β and MDA (malondialdehyde) were quantified by ELISA and colorimetry, respectively , patients with ACS (n = 48; 31.3% with UA, 33.3% with NSTEMI, and 35.4% with STEMI) and healthy controls (n = 43). We assessed the TIMI scores in the first 24 h after symptom onset.

RESULTS

The results showed that patients with ACS had significantly higher levels (p<0.05) of the inflammatory biomarkers IL-6, IL-1β, and MDA compared to the control group. However, we found no significant differences in IL-6, IL-1β, and MDA levels among the patients with ACS according to their classification as UA, NSTEMI, and STEMI. Positive correlations were observed between TIMI and IL-6 (r=0.68), IL-1β (r= 0.53), and MDA (r=0.58) in patients with UA and between TIMI and IL-1β (r= 0.62) in STEMI patients.

CONCLUSION

These data suggest the presence of a pro-inflammatory profile in patients with ACS as well as positive correlations between TIMI scores and the inflammatory biomarkers IL-6, IL-1β, and MDA in patients with UA and between TIMI scores and IL-1β in patients with STEMI. Combining inflammatory biomarkers with the TIMI risk score could provide better insight into the processes involved in ACS.

Deep Learning Analyses to Delineate the Molecular Remodeling Process after Myocardial Infarction

Specific proteins and processes have been identified in post-myocardial infarction (MI) pathological remodeling, but a comprehensive understanding of the complete molecular evolution is lacking. We generated microarray data from swine heart biopsies at baseline and 6, 30, and 45 days after infarction to feed machine-learning algorithms. We cross-validated the results using available clinical and experimental information. MI progression was accompanied by the regulation of adipogenesis, fatty acid metabolism, and epithelial-mesenchymal transition. The infarct core region was enriched in processes related to muscle contraction and membrane depolarization. Angiogenesis was among the first morphogenic responses detected as being sustained over time, but other processes suggesting post-ischemic recapitulation of embryogenic processes were also observed. Finally, protein-triggering analysis established the key genes mediating each process at each time point, as well as the complete adverse remodeling response. We modeled the behaviors of these genes, generating a description of the integrative mechanism of action for MI progression. This mechanistic analysis overlapped at different time points; the common pathways between the source proteins and cardiac remodeling involved IGF1R, RAF1, KPCA, JUN, and PTN11 as modulators. Thus, our data delineate a structured and comprehensive picture of the molecular remodeling process, identify new potential biomarkers or therapeutic targets, and establish therapeutic windows during disease progression.

Timing of Nonculprit Percutaneous Coronary Intervention after ST-Elevation Myocardial Infarction

INTRODUCTION

Complete revascularization of ST-elevation myocardial infarction (STEMI) patients with multivessel disease (MVD) has recently shown to reduce risk of adverse cardiovascular events, including cardiovascular death. Optimal timing of revascularization of nonculprit lesions remains controversial. We aimed to measure cardiac outcomes related to duration between primary percutaneous coronary intervention (pPCI) of the culprit lesion and staged PCI (sPCI) of nonculprit lesions.

METHODS

From a prospectively collected consecutive registry of 3,002 patients treated for STEMI by pPCI, 1,555 patients with MVD requiring sPCI were identified. Patients were placed into quartiles of duration to sPCI: 0-7 days (Q1), 7-22 days (Q2), 22-42 days (Q3), >42 days (Q4), excluding those who had complete revascularization at the index event. Major adverse cardiac events (MACEs) included all-cause mortality, myocardial infarction, target vessel revascularization, and coronary artery bypass surgery. Cox regression and propensity score matching were performed correcting for confounding factors.

RESULTS

The average age at presentation was 65.7 ± 11.5 years. 333 were female (21.4%). Mean time between pPCI and sPCI was 28.3 days (±24.8). Rates of MACE were Q1 - 16.5%, Q2 - 21.2%, Q3 - 25.8%, and Q4 - 30.1% (log-rank <0.001). Following regression analysis, sPCI remained an independent risk factor for MACE (hazard ratio [HR] = 1.226 [95% confidence interval {CI}: 1.129-1.331, p < 0.001]). There was no association between the time interval up to sPCI with all-cause death (HR = 1.022 [95% CI: 0.925-1.129, p = 0.671]).

CONCLUSIONS

Patients with MVD are at increased risk of experiencing MACE after revascularization of nonculprit vessels with increasing time delay between pPCI and sPCI.

Preclinical models of myocardial infarction: from mechanism to translation

Approximately 7 million people are affected by acute myocardial infarction (MI) each year, and despite significant therapeutic and diagnostic advancements, MI remains a leading cause of mortality worldwide. Preclinical animal models have significantly advanced our understanding of MI and have enabled the development of therapeutic strategies to combat this debilitating disease. Notably, some drugs currently used to treat MI and heart failure (HF) in patients had initially been studied in preclinical animal models. Despite this, preclinical models are limited in their ability to fully reproduce the complexity of MI in humans. The preclinical model must be carefully selected to maximise the translational potential of experimental findings. This review describes current experimental models of MI and considers how they have been used to understand drug mechanisms of action and support translational medicine development.

Resveratrol improves cardiac function and left ventricular fibrosis after myocardial infarction in rats by inhibiting NLRP3 inflammasome activity and the TGF-β1/SMAD2 signaling pathway

Background

Several studies have shown that resveratrol (RES), a naturally occurring polyphenol found in many plants, is beneficial for preventing cardiovascular diseases. However, the mechanism underlying the RES-mediated protection against myocardial infarction has not yet been revealed entirely. In this study, we investigated the protective effects of RES on cardiac function in a rat model of acute myocardial infarction (AMI) and the related underlying mechanisms.

Methods

Male Sprague-Dawley rats were randomly divided into four groups: Sham (sham operation), Sham-RES, AMI (AMI induction), and AMI-RES. The rat AMI model was established by the permanent ligation of left anterior descending coronary artery method. The rats in the RES-treated groups were gavaged with RES (50 mg/kg/day) daily for 45 days after the Sham operation or AMI induction; rats in the Sham and AMI groups were gavaged with deionized water. Cardiac function was evaluated by echocardiography. Atrial interstitial fibrosis was assessed by hematoxylin-eosin or Masson’s trichrome staining. Real-time PCR and western blotting analyses were performed to examine the levels of signaling pathway components.

Results

RES supplementation decreased the inflammatory cytokine levels, improved the cardiac function, and ameliorated atrial interstitial fibrosis in the rats with AMI. Furthermore, RES supplementation inhibited NLRP3 inflammasome activity, decreased the TGF-β1 production, and downregulated the p-SMAD2/SMAD2 expression in the heart.

Conclusion

RES shows notable cardioprotective effects in a rat model of AMI; the possible mechanisms underlying these effects may involve the improvement of cardiac function and atrial interstitial fibrosis via the RES-mediated suppression of NLRP3 inflammasome activity and inhibition of the TGF-β1/SMAD2 signaling pathway in the heart.

Impact of renin angiotensin system inhibitor on 3-year clinical outcomes in acute myocardial infarction patients with preserved left ventricular systolic function: a prospective cohort study from Korea Acute Myocardial Infarction Registry (KAMIR)

BACKGROUND

Patients with acute myocardial infarction (AMI) are usually treated with angiotensin-converting enzyme inhibitors (ACEIs), or angiotensin receptor blockers (ARBs) if ACEIs are not tolerated. However, there is no data regarding the impact of switching from ACEIs to ARBs on long-term clinical outcomes in AMI patients with preserved left ventricular (LV) systolic function especially beyond 1 year. To investigate the effectiveness of treatment with ACEIs or ARBs on clinical outcomes over 3 years in AMI patients with preserved LV systolic function following percutaneous coronary intervention.

METHOD

It is a prospective cohort study using data from a nationwide large scale registry with 53 hospitals involved in treatment of acute myocardial infarction (AMI) in Korea. Between March 2011 and September 2015, we enrolled 6236 patients with AMI who underwent primary percutaneous coronary intervention and had a left ventricular ejection fraction ≥ 50%. Main outcome measures composite of total death or recurrent AMI over 3 years after AMI. Patients were divided into an ACEI group (n = 2945), ARB group (n = 2197), or no renin-angiotensin system inhibitor (RASI) treatment (n = 1094). We analyzed patients who changed treatment. Inverse probability of treatment weighting (IPTW) analysis was also performed.

RESULTS

After the adjustment with inverse probability weighting, the primary endpoints at 1 year, AMI patients receiving ACEIs showed overall better outcomes than ARBs [ARBs hazard ratio (HR) compared with ACEIs 1.384, 95% confidence interval (CI) 1.15-1.71; P = 0.003]. However, 33% of patients receiving ACEIs switched to ARBs during the first year, while only about 1.5% switched from ARBs to ACEIs. When landmark analysis was performed from 1 year to the end of the study, RASI group showed a 31% adjusted reduction in primary endpoint compared to patients with no RASI group (HR, 0.74; 95% CI 0.56-0.97; P = 0.012).

CONCLUSIONS

This result suggests that certain patients got benefit from treatment with ACEIs in the first year if tolerated, but switching to ARBs beyond the first year produced similar outcomes. RASI beyond the first year reduced death or recurrent AMI in AMI patients with preserved LV systolic function. CRIS Registration number: KCT0004990.

Myocardial Infarction Induces Cardiac Fibroblast Transformation within Injured and Noninjured Regions of the Mouse Heart

Heart failure (HF) is associated with pathological remodeling of the myocardium, including the initiation of fibrosis and scar formation by activated cardiac fibroblasts (CFs). Although early CF-dependent scar formation helps prevent cardiac rupture by maintaining the heart's structural integrity, ongoing deposition of the extracellular matrix in the remote and infarct regions can reduce tissue compliance, impair cardiac function, and accelerate progression to HF. In our study, we conducted mass spectrometry (MS) analysis to identify differentially altered proteins and signaling pathways between CFs isolated from 7 day sham and infarcted murine hearts. Surprisingly, CFs from both the remote and infarct regions of injured hearts had a wide number of similarly altered proteins and signaling pathways that were consistent with fibrosis and activation into pathological myofibroblasts. Specifically, proteins enriched in CFs isolated from MI hearts were involved in pathways pertaining to cell-cell and cell-matrix adhesion, chaperone-mediated protein folding, and collagen fibril organization. These results, together with principal component analyses, provided evidence of global CF activation postinjury. Interestingly, however, direct comparisons between CFs from the remote and infarct regions of injured hearts identified 15 differentially expressed proteins between MI remote and MI infarct CFs. Eleven of these proteins (Gpc1, Cthrc1, Vmac, Nexn, Znf185, Sprr1a, Specc1, Emb, Limd2, Pawr, and Mcam) were higher in MI infarct CFs, whereas four proteins (Gstt1, Gstm1, Tceal3, and Inmt) were higher in MI remote CFs. Collectively, our study shows that MI injury induced global changes to the CF proteome, with the magnitude of change reflecting their relative proximity to the site of injury.

In Vitro Methods to Model Cardiac Mechanobiology in Health and Disease

In vitro cardiac modeling has taken great strides in the past decade. While most cell and engineered tissue models have focused on cell and tissue contractile function as readouts, mechanobiological cues from the cell environment that affect this function, such as matrix stiffness or organization, are less well explored. In this study, we review two-dimensional (2D) and three-dimensional (3D) models of cardiac function that allow for systematic manipulation or precise control of mechanobiological cues under simulated (patho)physiological conditions while acquiring multiple readouts of cell and tissue function. We summarize the cell types used in these models and highlight the importance of linking 2D and 3D models to address the multiscale organization and mechanical behavior. Finally, we provide directions on how to advance in vitro modeling for cardiac mechanobiology using next generation hydrogels that mimic mechanical and structural environmental features at different length scales and diseased cell types, along with the development of new tissue fabrication and readout techniques. Impact statement Understanding the impact of mechanobiology in cardiac (patho)physiology is essential for developing effective tissue regeneration and drug discovery strategies and requires detailed cause-effect studies. The development of three-dimensional in vitro models allows for such studies with high experimental control, while integrating knowledge from complementary cell culture models and in vivo studies for this purpose. Complemented by the use of human-induced pluripotent stem cells, with or without predisposed genetic diseases, these in vitro models will offer promising outlooks to delineate the impact of mechanobiological cues on human cardiac (patho)physiology in a dish.

Surgery for heart failure: Treatment options and implications

Heart failure is considered one of the leading causes of death worldwide. Over the years, etiological risk factors, diagnostic criteria, and classifications have been revised to create guide management needed to alleviate the global health burden caused by heart failure. Pharmacological treatments have progressed over time but are insufficient in reducing mortality. This leads to many patients developing advanced heart failure who will require surgical intervention often in the form of the gold standard, a heart transplant. However, the number of patients requiring a transplant far exceeds the number of donors. Other surgical inventions have been utilized, yet the rate of patients being diagnosed with heart failure is still increasing. Future developments in the surgical field of heart failure include the 77SyncCardia and atrial shunting but long-term clinical trials involving larger cohorts of patients have not yet taken place to view how effective these approaches can be.

Apparent growth tensor of left ventricular post myocardial infarction - In human first natural history study

An outstanding challenge in modelling biomechanics after myocardial infarction (MI) is to estimate the so-called growth tensor. Since it is impossible to track pure growth induced geometry change from in vivo magnetic resonance images alone, in this work, we propose a way of estimating a surrogate or apparent growth tensor of the human left ventricle using cine magnetic resonance (CMR) and late gadolinium enhanced (LGE) images of 16 patients following acute MI. The apparent growth tensor is evaluated at four time-points following myocardial reperfusion: 4-12 h (baseline), 3 days, 10 days and 7 months. We have identified three different growth patterns classified as the Dilation, No-Change and Shrinkage groups defined by the left ventricle end-diastole cavity volume change from baseline. We study the- trends in both the infarct and remote regions. Importantly, although the No-Change group has little change in the ventricular cavity volume, significant remodelling changes are seen within the myocardial wall, both in the infarct and remote regions. Through statistical analysis, we show that the growth tensor invariants can be used as effective biomarkers for adverse and favourable remodelling of the heart from 10 days onwards post-MI with statistically significant changes over time, in contrast to most of the routine clinical indices. We believe this is the first time that the apparent growth tensor has been estimated from in vivo CMR images post-MI. Our study not only provides much-needed information for understanding growth and remodelling in the human heart following acute MI, but also identifies novel biomarker for assessing heart disease progression.

MTX Treatment Does Not Improve Outcome in Mice with AMI

BACKGROUND

Targeting inflammation in patients with coronary artery disease and/or acute myocardial infarction (AMI) is a matter of debate. Methotrexate (MTX) is one of the most widely used immunosuppressants. Cardiovascular Inflammation Reduction Trial (CIRT) recently failed to demonstrate reduced cardiovascular events in MTX-treated patients. However, it is not known if long-term MTX treatment improves cardiac outcome in AMI. Therefore, in this study, we investigated the postischemic phase in MTX-treated mice undergoing AMI.

METHODS

Wild-type mice received MTX medication intraperitoneally for 2 weeks. Afterward, AMI was induced by transient left anterior ascending artery ligation. Postischemic cardiac damage after 24 h was assessed.

RESULTS

MTX treatment did not affect infarct size as compared to control (IS/AAR: Con 76.20% ± 12.37%/AAR vs. MTX 73.51 ± 11.72%/AAR, p = 0.64). Moreover, systolic function and structural parameters did not differ between groups (24hejection fraction: Con 36.49 ± 3.23% vs. MTX 32.77 ± 2.29%, p = 0.41; 24hLVID; d: Con 3.57 ± 0.17 mm vs. MTX 3.19 ± 0.13 mm, p = 0.14). Platelets were increased by MTX (Con 1,442 ± 69.20 × 103/mm3 vs. MTX 1,920 ± 68.68 × 103/mm3, p < 0.0001). White blood cell and RBC as well as rate of monocytes, granulocytes, lymphocytes, and serum amyloid P levels were equal.

CONCLUSION

MTX medication did not improve postischemic cardiac damage in a murine model of AMI. Future trials are needed to identify and investigate other anti-inflammatory targets to improve cardiovascular outcome.

Atglistatin Pretreatment Preserves Remote Myocardium Function Following Myocardial Infarction

The pathological role of adipose derived fatty acids following myocardial infarction has long been hypothesized. However, most methods for reducing adipocyte lipolysis have significant non-adipose effects. Atglistatin, a direct inhibitor of the initial lipase in the lipolysis cascade, has been recently shown to inhibit adipose tissue lipolysis after oral administration. To explore the ability of Atglistatin to impact the pathophysiology of cardiac ischemia we performed prophylactic treatment of mice with Atglistatin for 2 days before 1-hour cardiac ischemia. After 7 days of reperfusion, hearts of Atglistatin treated mice showed significantly improved systolic pump function while infarct and scar size were unaffected. Strain analysis of echocardiographic data revealed an enhanced performance of the remote myocardium as cause for overall improved systolic function. The present study provides evidence that inhibition of adipocyte adipose triglyceride lipase (ATGL) using Atglistatin is able to improve cardiac function after MI by targeting the remote myocardium.

The Role of Natural Killer (NK) Cells in Acute Coronary Syndrome: A Comprehensive Review

With poor outcomes and an immense financial burden, acute coronary syndrome (ACS) and its ischemic repercussions still present a major global health problem. Unfavorable outcomes seem to be mainly due to adverse cardiac remodeling. Since the inflammatory response takes an important role in remodeling secondary to myocardial infarction (MI), and as inflammation in this manner has not been completely elucidated, we attempted to give rise to a further understanding of ACS pathophysiology. Hence, in this review, we integrated current knowledge of complex communication networks between natural killer (NK) cells and immune and resident heart cells in the context of ACS. Based on available data, the role of NK cells seems to be important in the infarcted myocardium, where it affects heart remodeling. On the other hand, in atherosclerotic plaque, NK cells seem to be mere passers-by, except in the case of chronic infections by atherogenic pathogens. In that case, NK cells seem to support proinflammatory milieu. NK cell research is challenging due to ethical reasons, convergent evolution, and phenotypic diversity among individuals. Therefore, we argue that further research of NK cells in ACS is valuable, given their therapeutic potential in improving postischemic heart remodeling.

Association between Circular RNA CDR1as and Post-Infarction Cardiac Function in Pig Ischemic Heart Failure: Influence of the Anti-Fibrotic Natural Compounds Bufalin and Lycorine

Anti-fibrotic therapies are of increasing interest to combat cardiac remodeling and heart failure progression. Recently, anti-fibrotic circular RNAs (circRNAs) have been identified in human and rodent cardiac tissue. In vivo (rodent) experiments proved cardiac anti-fibrotic effects of the natural compounds bufalin and lycorine by downregulating miRNA-671-5p, associated with a theoretic increase in the tissue level of circRNA CDR1as. Accordingly, we hypothesized that both anti-fibrotic drugs may inhibit focal myocardial fibrosis of the remodeled left ventricle (LV) also in a translational large animal model of heart failure (HF). Domestic pigs were repeatedly treated with subcutaneous injections of either bufalin, lycorine, or saline, (n = 5/group) between days 7-21 post acute myocardial infarction (AMI). At the 2-month follow-up, both bufalin and lycorine led to significantly reduced cardiac fibrosis. Bufalin treatment additionally led to smaller end-diastolic volumes, higher LV ejection fraction (EF), and increased expression of CDR1as of the AMI region. Elevated tissue levels of the circRNA CDR1as in the AMI region of the pig heart correlated significantly with LV and right ventricular EF, LV stroke volume, and negatively with infarct size. In conclusion, we successfully identified the circRNA CDR1as in pig hearts and show a significant association with improved LV and RV function by anti-fibrotic therapies in a translational animal model of HF.

Toll-like receptor 7 deficiency promotes survival and reduces adverse left ventricular remodelling after myocardial infarction

AIMS

The Toll-like receptor 7 (TLR7) is an intracellular innate immune receptor activated by nucleic acids shed from dying cells leading to activation of the innate immune system. Since innate immune system activation is involved in the response to myocardial infarction (MI), this study aims to identify if TLR7 is involved in post-MI ischaemic injury and adverse remodelling after MI.

METHODS AND RESULTS

TLR7 involvement in MI was investigated in human tissue from patients with ischaemic heart failure, as well as in a mouse model of permanent left anterior descending artery occlusion in C57BL/6J wild type and TLR7 deficient (TLR7-/-) mice. TLR7 expression was up-regulated in human and mouse ischaemic myocardium after MI. Compared to wild type mice, TLR7-/- mice had less acute cardiac rupture associated with blunted activation of matrix metalloproteinase 2, increased expression of tissue inhibitor of metalloproteinase 1, recruitment of more myofibroblasts, and the formation of a myocardial scar with higher collagen fibre density. Furthermore, inflammatory cell influx and inflammatory cytokine expression post-MI were reduced in the TLR7-/- heart. During a 28-day follow-up after MI, TLR7 deficiency resulted in less chronic adverse left ventricular remodelling and better cardiac function. Bone marrow (BM) transplantation experiments showed that TLR7 deficiency in BM-derived cells preserved cardiac function after MI.

CONCLUSIONS

In acute MI, TLR7 mediates the response to acute cardiac injury and chronic remodelling probably via modulation of post-MI scar formation and BM-derived inflammatory infiltration of the myocardium.

The role of stretch, tachycardia and sodium-calcium exchanger in induction of early cardiac remodelling

Stretch and tachycardia are common triggers for cardiac remodelling in various conditions, but a comparative characterization of their role in the excitation‐transcription coupling (ETC) and early regulation of gene expression and structural changes is lacking. Here, we show that stretch and tachycardia directly induced hypertrophy of neonatal rat cardiac myocytes and also of non‐myocytes. Both triggers induced similar patterns of hypertrophy but had largely distinct gene expression profiles. ACTA1 served as good hypertrophy marker upon stretch, while RCAN1 was found increased in response to tachycardia in a rate‐dependent fashion. Mechanistically, several calcium‐handling proteins, including the sodium‐calcium exchanger (NCX), contributed to ETC. Phosphorylation of the calcium/calmodulin‐dependent protein kinase II (CaMKII) was elevated and occurred downstream of NCX activation upon tachycardia, but not stretch. Microarray profiling revealed that stretch and tachycardia regulated around 33% and 20% genes in a NCX‐dependent manner, respectively. In conclusion, our data show that hypertrophy induction by stretch and tachycardia is associated with different gene expression profiles with a significant contribution of the NCX.

Therapeutic Efficacy of Alpha-Lipoic Acid against Acute Myocardial Infarction and Chronic Left Ventricular Remodeling in Mice

Background

We hypothesized that daily administration of a potent antioxidant (α-lipoic acid: ALA) would protect the heart against both acute myocardial infarction (AMI) and left ventricular remodeling (LVR) post-AMI.

Methods and Results

Two separate studies were conducted. In the AMI study, C57Bl/6 mice were fed ALA daily for 7 d prior to a 45-minute occlusion of the left coronary artery (LCA). Mean infarct size in control mice (fed water) was 60 ± 2%. Mean infarct size in ALA-treated mice was 42 ± 3% in the 15 mg/kg·d group and 39 ± 3% in the 75 mg/kg·d group (both P < 0.05 vs. control). In the LVR study, AMI increased LV end-systolic volume (LVESV) and reduced LV ejection fraction (LVEF) to a similar extent in both groups when assessed by cardiac MRI 1 day after a 2-hour LCA occlusion. Treatment with ALA (75 mg/kg·d) or H₂O was initiated 1 day post-AMI and continued until study's end. Both LVESV and LVEF in ALA-treated mice were significantly improved over control when assessed 28 or 56 days post-AMI. Furthermore, the survival rate in ALA-treated mice was 63% better than in control mice by 56 days post-AMI.

Conclusions

Daily oral ingestion of ALA not only protects mice against AMI but also attenuates LVR and preserves contractile function in the months that follow.

Alginate Formulations: Current Developments in the Race for Hydrogel-Based Cardiac Regeneration

Cardiovascular diseases, including myocardial infarction (MI), represent the main worldwide cause of mortality and morbidity. In this scenario, to contrast the irreversible damages following MI, cardiac regeneration has emerged as a novel and promising solution for in situ cellular regeneration, preserving cell behavior and tissue cytoarchitecture. Among the huge variety of natural, synthetic, and hybrid compounds used for tissue regeneration, alginate emerged as a good candidate for cellular preservation and delivery, becoming one of the first biomaterial tested in pre-clinical research and clinical trials concerning cardiovascular diseases. Although promising results have been obtained, recellularization and revascularization of the infarcted area present still major limitations. Therefore, the demand is rising for alginate functionalization and its combination with molecules, factors, and drugs capable to boost the regenerative potential of the cardiac tissue. The focus of this review is to elucidate the promising properties of alginate and to highlight its benefits in clinical trials in relation to cardiac regeneration. The definition of hydrogels, the alginate characteristics, and recent biomedical applications are herewith described. Afterward, the review examines in depth the ongoing developments to refine the material relevance in cardiac recovery and regeneration after MI and presents current clinical trials based on alginate.

Novel Applications of Mesenchymal Stem Cell-derived Exosomes for Myocardial Infarction Therapeutics

Cardiovascular diseases (CVDs) are the leading cause of mortality and morbidity globally, representing approximately a third of all deaths every year. The greater part of these cases is represented by myocardial infarction (MI), or heart attack as it is better known, which occurs when declining blood flow to the heart causes injury to cardiac tissue. Mesenchymal stem cells (MSCs) are multipotent stem cells that represent a promising vector for cell therapies that aim to treat MI due to their potent regenerative effects. However, it remains unclear the extent to which MSC-based therapies are able to induce regeneration in the heart and even less clear the degree to which clinical outcomes could be improved. Exosomes, which are small extracellular vesicles (EVs) known to have implications in intracellular communication, derived from MSCs (MSC-Exos), have recently emerged as a novel cell-free vector that is capable of conferring cardio-protection and regeneration in target cardiac cells. In this review, we assess the current state of research of MSC-Exos in the context of MI. In particular, we place emphasis on the mechanisms of action by which MSC-Exos accomplish their therapeutic effects, along with commentary on the current difficulties faced with exosome research and the ongoing clinical applications of stem-cell derived exosomes in different medical contexts.

Biomechanics of infarcted left Ventricle-A review of experiments

Myocardial infarction (MI) is one of leading diseases to contribute to annual death rate of 5% in the world. In the past decades, significant work has been devoted to this subject. Biomechanics of infarcted left ventricle (LV) is associated with MI diagnosis, understanding of remodelling, MI micro-structure and biomechanical property characterizations as well as MI therapy design and optimization, but the subject has not been reviewed presently. In the article, biomechanics of infarcted LV was reviewed in terms of experiments achieved in the subject so far. The concerned content includes experimental remodelling, kinematics and kinetics of infarcted LVs. A few important issues were discussed and several essential topics that need to be investigated further were summarized. Microstructure of MI tissue should be observed even carefully and compared between different methods for producing MI scar in the same animal model, and eventually correlated to passive biomechanical property by establishing innovative constitutive laws. More uniaxial or biaxial tensile tests are desirable on MI, border and remote tissues, and viscoelastic property identification should be performed in various time scales. Active contraction experiments on LV wall with MI should be conducted to clarify impaired LV pumping function and supply necessary data to the function modelling. Pressure-volume curves of LV with MI during diastole and systole for the human are also desirable to propose and validate constitutive laws for LV walls with MI.

Substance P Administered after Myocardial Infarction Upregulates Microphthalmia-Associated Transcription Factor, GATA4, and the Expansion of c-Kit+ Cells

Microphthalmia-associated transcription factor (MITF), a basic helix-loop-helix leucine zipper transcription factor, can govern gene expression by binding to E box elements in the promoter region of its target gene. Although high levels of MITF have been observed in cardiomyocytes and the heart, the role of MITF after myocardial infarction (MI) remains unclear. We investigated the association between substance P (SP)/neurokinin-1 receptor (NK₁R) signaling and MITF expression after MI. Male Sprague-Dawley rats (8 weeks) were randomly divided in two groups: ischemia/reperfusion injury (I/R) and SP injection (5 nmol/kg, SP+I/R). At the end of 7 days, the left ventricle (LV; LV^7daysI/R, LV^7daysSP+I/R) and infarct-related areas (IA; IA^7daysI/R, IA^7daysSP+I/R) from the hearts were collected. Immunofluorescence staining demonstrated that the LV^7daysSP+I/R had a larger population of c-Kit⁺ GATA4^high cells, which markedly upregulated MITF, c-Kit, and GATA4. c-Kit⁺ cells in the explant-derived cells (EDCs) derived from IA^7daysSP+I/R migrated more widely than EDCs IA^7daysI/R. Immunofluorescence staining, western blot analysis, and qRT-PCR assay showed that SP-treated c-Kit⁺ cells exhibited a high expression of c-Kit, GATA4, and MITF. FTY720 (a MITF inhibitor), RP67580 (NK₁R inhibitor), or both inhibited the migration and proliferation of c-Kit⁺ cells increased by SP and blocked the upregulation of c-Kit, GATA4, and MITF. Overall, we suggest that MITF might be a potential regulator in SP-mediated c-Kit⁺ cell expansion post-MI via c-Kit and GATA4.

The role of end-diastolic myocardial fibre stretch on infarct extension

Myocardial infarct extension, a process involving the enlargement of infarct and border zone, leads to progressive degeneration of left ventricular (LV) function and eventually gives rise to heart failure. Despite carrying a high risk, the causation of infarct extension is still a subject of much speculation. In this study, patient-specific LV models were developed to investigate the correlation between infarct extension and impaired regional mechanics. Subsequently, sensitivity analysis was performed to examine the causal factors responsible for the impaired regional mechanics observed in regions surrounding the infarct and border zone. From our simulations, fibre strain, fibre stress and fibre stress-strain loop (FSSL) were the key biomechanical variables affected in these regions. Among these variables, only FSSL was correlated with infarct extension, as reflected in its work density dissipation (WDD) index value, with high WDD indices recorded at regions with infarct extension. Impaired FSSL is caused by inadequate contraction force generation during the isovolumic contraction and ejection phases. Our further analysis revealed that the inadequacy in contraction force generation is not necessarily due to impaired myocardial intrinsic contractility, but at least in part, due to inadequate muscle fibre stretch at end-diastole, which depresses the ability of myocardium to generate adequate contraction force in the subsequent systole (according to the Frank-Starling law). Moreover, an excessively stiff infarct may cause its neighbouring myocardium to be understretched at end-diastole, subsequently depressing the systolic contractile force of the neighbouring myocardium, which was found to be correlated with infarct extension.

Effects of exercise training and stem cell therapy on the left ventricle of infarcted rats

INTRODUCTION AND OBJECTIVES

Stem cell therapy and aerobic exercise are non-pharmacological therapies following myocardial infarction. The aim of this study was to test whether aerobic exercise training enhances the benefits of mesenchymal stem cell (MSC) therapy on remodeling of the extracellular matrix and fetal gene expression in the left ventricle of infarcted rats.

METHODS

Myocardial infarction was surgically induced in six-week old male Wistar rats. Animals were divided into four groups: sedentary control (SC) and sedentary and stem cell treated (SCMSC); exercised (EX) and exercised and stem cell treated (EXMSC). Bone marrow-derived MSCs were immediately transplanted via the tail vein (concentration: 1×10⁶ cells). Exercise training (five days/week, 60 min/day; 60% of maximal running speed) started 24 hours after myocardial infarction and lasted for 12 weeks.

RESULTS

Exercise capacity was higher in exercised than in sedentary groups. Animals in the SCMSC, EX and EXMSC groups exhibited better cardiac function than those in SC. Collagen content was lower in the SCMSC, EX and EXMSC groups than in SC and skeletal α-actin expression was lower in EX and EXMSC than in SC. The α/β-MHC ratio was higher in EX and EXMSC than in SC. The combination of therapies further reduced collagen content in the remote region of the infarct (∼24%) and skeletal α-actin expression (∼30%).

CONCLUSION

Aerobic exercise training appears to enhance the beneficial effects of stem cell therapy on remodeling of the extracellular matrix and fetal gene expression in the left ventricle of rats with moderate infarction.

A novel small molecule compound VCP979 improves ventricular remodeling in murine models of myocardial ischemia/reperfusion injury

Persistent ventricular remodeling following myocardial ischemia/reperfusion (MI/R) injury results in functional decompensation and eventual progression to heart failure. VCP979, a novel small‑molecule compound developed in‑house, possesses anti‑inflammatory and anti‑fibrotic activities. In the present study, no significant pathological effect was observed following the administration of VCP979 on multiple organs in mice and no difference of aspartate transaminase/alanine aminotransferase/lactate dehydrogenase levels was found in murine serum. Treatment with VCP979 ameliorated cardiac dysfunction, pathological myocardial fibrosis and hypertrophy in murine MI/R injury models. The administration of VCP979 also inhibited the infiltration of inflammatory cells and the pro‑inflammatory cytokine expression in hearts post MI/R injury. Further results revealed that the addition of VCP979 prevented the primary neonatal cardiac fibroblasts (NCFs) from Angiotensin II (Ang II)‑induced collagen synthesis and neonatal cardiac myocytes (NCMs) hypertrophy. In addition, VCP979 attenuated the activation of p38‑mitogen‑activated protein kinase in both Ang II‑induced NCFs and hearts subjected to MI/R injury. These findings indicated that the novel small‑molecule compound VCP979 can improve ventricular remodeling in murine hearts against MI/R injury, suggesting its potential therapeutic function in patients subjected to MI/R injury.

Emerging roles of GSK-3α in pathophysiology: Emphasis on cardio-metabolic disorders

Glycogen synthase kinase-3 (GSK-3) is a widely expressed serine/threonine kinase regulates a variety of cellular processes including proliferation, differentiation and death. Mammals harbor two structurally similar isoforms GSK-3α and β that have overlapping as well as unique functions. Of the two, GSK-3β has been studied (and reviewed) in far greater detail with analysis of GSK-3α often as an afterthought. It is now evident that systemic, chronic inhibition of either GSK-3β or both GSK-3α/β is not clinically feasible and if achieved would likely lead to adverse clinical conditions. Emerging evidence suggests important and specific roles for GSK-3α in fatty acid accumulation, insulin resistance, amyloid-β-protein precursor metabolism, atherosclerosis, cardiomyopathy, fibrosis, aging, fertility, and in a variety of cancers. Selective targeting of GSK-3α may present a novel therapeutic opportunity to alleviate a number of pathological conditions. In this review, we assess the evidence for roles of GSK-3α in a variety of pathophysiological settings.

Nicotinamide riboside kinase-2 alleviates ischemia-induced heart failure through P38 signaling

Nicotinamide riboside kinase-2 (NRK-2), a muscle-specific β1 integrin binding protein, predominantly expresses in skeletal muscle with a trace amount expressed in healthy cardiac tissue. NRK-2 expression dramatically increases in mouse and human ischemic heart however, the specific role of NRK-2 in the pathophysiology of ischemic cardiac diseases is unknown. We employed NRK2 knockout (KO) mice to identify the role of NRK-2 in ischemia-induced cardiac remodeling and dysfunction. Following myocardial infarction (MI), or sham surgeries, serial echocardiography was performed in the KO and littermate control mice. Cardiac contractile function rapidly declined and left ventricular interior dimension (LVID) was significantly increased in the ischemic KO vs. control mice at 2 weeks post-MI. An increase in mortality was observed in the KO vs. control group. The KO hearts displayed increased cardiac hypertrophy and heart failure reflected by morphometric analysis. Consistently, histological assessment revealed an extensive and thin scar and dilated LV chamber accompanied with elevated fibrosis in the KOs post-MI. Mechanistically, we observed that loss of NRK-2 enhanced p38α activation following ischemic injury. Consistently, ex vivo studies demonstrated that the gain of NRK-2 function suppresses the p38α as well as fibroblast activation (α-SMA expression) upon TGF-β stimulation, and limits cardiomyocytes death upon hypoxia/re‑oxygenation. Collectively our findings show, for the first time, that NRK-2 plays a critical role in heart failure progression following ischemic injury. NRK-2 deficiency promotes post-MI scar expansion, rapid LV chamber dilatation, cardiac dysfunction and fibrosis possibly due to increased p38α activation.