Nonischemic Myocardium Research Articles

P4436Impaired myocardial healing in patients with diabetes after ST-Elevation Myocardial Infarction

Abstract Background Diabetes mellitus (DM) significantly increases mortality following myocardial infarction (MI). The underlying mechanism explaining this adverse prognosis is not completely understood. Purpose This study sought to investigate the characteristics of myocardial healing after MI in DM patients. Methods 62 recruited ST-elevation myocardial infarction (STEMI) patients (21 with DM and 41 controls) underwent acute (1–3 days post-STEMI) and 6 months (6M) follow-up cardiac magnetic resonance scans (CMR). Control cases were matched for the peak troponin levels and area at risk on the acute CMR scans. Blood samples were obtained 6, 24, 48 hours and 6 months after STEMI. Results Despite similar severity of the initial ischaemic injury, DM patients had lower myocardial salvage index (MSI) and as a result larger final infarct size at 6 months. Further segment-based analysis of the acute CMR scans showed significantly prolonged T1-mapping values in all segments including non-ischaemic myocardium in DM patients and poorer recovery of the late gadolinium enhancement (LGE) of the infarcted segments in that group. Additionally, DM patients had higher monocyte counts 24 hours post-MI (1.2±0.4x109/μl DM vs 0.88±0.3 x109/μl control, p=0.001). We found that HbA1C correlated with monocyte count measured 24 hours after STEMI (r=0.577, p=0.006, n=21). HbA1C also predicted myocardial salvage index (MSI) at 6M post STEMI in the DM patients (r=0.891, p=0.017, n=13). Conclusions DM patients presenting with STEMI have increased peripheral blood monocytosis and larger final infarct size compared with STEMI patients without DM. Poorly controlled DM predisposes to adverse cardiac remodelling after STEMI. Acknowledgement/Funding OHSRC Research Grant, National Institute for Health Research (NIHR), British Heart Foundation Centre of Excellence Oxford

Extracellular Vesicles Promote Arteriogenesis in Chronically Ischemic Myocardium in the Setting of Metabolic Syndrome.

BackgroundIschemic heart disease continues to be a leading cause of mortality in patients. Extracellular vesicles (EVs) provide a potential for treatment that may induce collateral vessel growth to increase myocardial perfusion.Methods and ResultsNineteen male Yorkshire pigs were given a high‐fat diet for 4 weeks, then underwent placement of an ameroid constrictor on the left circumflex artery to induce chronic myocardial ischemia. Two weeks later, the pigs received either intramyocardial vehicle (n=6), EVs (high‐fat diet with myocardial EV injection [HVM]; n=8), or HVM and calpain inhibition (n=5). Five weeks later, myocardial function, perfusion, coronary vascular density, and cell signaling were examined. Perfusion in the collateral‐dependent myocardium was increased during rapid ventricular pacing in the HVM group in both nonischemic (P=0.04) and ischemic areas of the ventricle (P=0.05). Cardiac output and stroke volume were significantly improved in the HVM group compared with the control group during ventricular pacing (P=0.006). Increased arteriolar density was seen in the HVM group in both nonischemic and ischemic myocardium (P=0.003 for both). However, no significant changes in the capillary density were observed between the control, HVM, and HVM and calpain inhibition groups (P=0.07). The group that received EVs with oral calpain inhibition had neither increased vessel density (P>0.99) nor improvement in blood flow or cardiac function (P=0.48) when compared with the control group.ConclusionsThese findings suggest that EVs promote angiogenesis in areas of chronic myocardial ischemia and improve cardiac function under conditions of diet‐induced metabolic syndrome.

High serum CRP influences myocardial miRNA profiles in ischemia-reperfusion injury of rat heart.

ObjectivePrognosis of myocardial infarction tends to be worse when serum C-reactive protein (CRP) level is high. miRNAs are also known to be involved in different pathogeneses of heart diseases such as myocardial infarction. However, how CRP is involved in myocardial infarction has not been fully elucidated. We hypothesized that serum CRP changes the miRNA profile during ischemia-reperfusion injury (IRI) of the myocardium. To confirm this hypothesis, we performed global miRNA expression profiling of myocardium using IRI and CRP infusion rat model.MethodsAfter ligation of the coronary artery of rat hearts, human serum CRP was intravenously injected, and reperfusion was performed (I/R+CRP group, n = 6). Control group consisted of the sham group (n = 3), IV CRP infusion group (CRP only, n = 3), and the I/R-only group (I/R only, n = 5). We evaluated 423 miRNA expression in non-ischemic areas and areas at risk (AAR) of each group using NanoString nCounter miRNA expression assay.ResultsMiR-124 was downregulated in non-ischemic myocardium in CRP-only group. In AAR, 7 miRNAs were commonly upregulated in both I/R-only and I/R+CRP groups. And additional 6 miRNAs were upregulated in the I/R+CRP group (miR-33, miR-409-3p, miR-384-3p, miR-3562, miR-101a, and miR-340-5p). Similarly, in the non-ischemic areas, 6 miRNAs were commonly upregulated in both I/R-only and I/R+CRP groups, and additional 5 miRNAs changed in the I/R+CRP group (upregulation of miR-3559-5p, miR-499, and miR-21 and downregulation of miR-500 and miR-532-3p).ConclusionWe showed that when serum CRP level is high, IRI results in multiple miRNA profile changes not only in ischemic areas but also in non-ischemic myocardium. Our results may provide a strong basis for studying the role of CRP and miRNAs in ischemic heart disease.

Characterization of dynamic gene networks in response to thoracotomy, ischemia-reperfusion in mouse heart

Myocardial infarction is an irreversible death of cardiac cells in response to prolonged ischemia and ischemia-reperfusion injury. Experimental designs and analytical pipelines used in time-series ischemia-reperfusion (IR) transcriptomic studies represent major challenges in the understanding of progression of such multifactorial diseases. In this study, we aim to provide a pipeline for the analysis of kinetical transcriptomics, characterize the change in gene expression profiles in response to surgical preparations prior IR and measure the dynamic gene regulation during IR in the left ventricle of mouse heart. Eight to twelve- weeks old C57BL/6 mice were anesthetized, undergone surgical preparations with and without IR and sacrificed at different time points (8 animals per time point) of the IR sequence. RNA-seq data from sham myocardium, ischemic and non-ischemic myocardium of IR mice are analyzed, clustered and functionally characterized. Gene expression analysis by DESeq2 yielded a total of 1006, 446 and 3878 differentially expressed genes in response to surgical interventions, remote and ischemia-reperfusion effect. Temporal clustering by weighted gene co-expression network analysis (WGCNA) and gene ontology analysis have shown that surgical preparations prior IR initiates inflammatory response mediated mainly by the phenotypic shift between the different macrophages’ subtypes and the infiltration of neutrophils to the heart few hours post-surgery. This study not only provides a comprehensive framework for kinetical transcriptomic studies, but also sheds light on the importance of considering the change of gene expression profiles driven by the thoracotomy effect.

Characterization of dynamic gene networks of control ischemic reperfused mouse heart

Myocardial infarction (MI) is a leading cause of death worldwide. Although some targets associated with MI are extensively studied, their dynamic characteristics of gene expressions during the disease progression haven’t been fully elucidated yet. In this study, we aim to measure the dynamic regulation of gene expression during ischemia-reperfusion (IR) in mouse heart, infer gene regulatory networks and decipher the main hubs linking cellular processes. 8–12 weeks old C57BL/6 mice are anesthetized, undergone IR and sacrificed at different times (8 animals per time point) of the IR sequence. RNA-seq data from controls, ischemic and non-ischemic myocardium are analyzed, clustered and functionally characterized. RNA-seq data normalized as fragments per kilobase per million analyzed by PCA implemented in R software, are not clustered based on their temporal profiles. We hypothesized that analyzing the data directly by PCA disqualified it as a method for temporal analysis of gene expression. We thus shifted to analyzing raw counts data by DESeq2. 975 , 446 and 3878 genes are significantly induced by thoracotomy, anesthesia, remote and IR specific effect respectively. These genes are further analyzed by WGCNA analysis splitting them into modules. These modules are then studied separately by gene ontology (GO) so that molecular functions, biological processes and cellular components involved in MI progression are clarified. This kinetical study not only provides comprehensive framework and transcriptional resource in the myocardium during MI, but also sheds new light on the importance of taking thoracotomy effect and the different analytical methods into account.

Effect of Platelet GPIIb/IIIa Receptor Blockade With MK383 on Infarct Size and Myocardial Blood Flow in a Canine Reocclusion Model.

Platelet activation and aggregation during ischemia influence reperfusion-related myocyte necrosis, myocardial perfusion at the microvascular level, and thereby eventual recovery of cardiac performance. Inhibition of platelet activity therefore represents a worthwhile target to reduce cellular injury. The current study examined the effects of MK383 (tirofiban), a potent inhibitor of platelet aggregation, on infarct size and myocardial perfusion in canine subjects to either reocclusion (ie, 120-minute + 60-minute ischemia with intervening reperfusion) or prolonged occlusion (ie, 3 hours) followed by reperfusion (180 minutes). Platelet aggregation, infarct size (tetrazolium staining), coronary blood flow (flow probe), coronary vascular reserve, and myocardial perfusion (microspheres) were evaluated. MK383, administered at the time of reperfusion, produced a modest reduction of tissue necrosis (compared to saline-treated controls) in the reocclusion and prolonged occlusion studies. Blood flow in the infarct-related artery after coronary occlusion was comparable between treatment groups, as was myocardial perfusion in the deeper layers of the ischemic region; coronary vascular reserve decreased progressively during reperfusion. Of note, compensatory changes in blood flow within the adjacent nonischemic myocardium were not observed. In conclusion, we report that that limiting platelet aggregation during reperfusion impacted infarct development. Continued investigation into the mechanisms by which inhibition of platelet activity protects myocardium against ischemia-reperfusion injury and improves clinical outcomes is necessary.

Etiology-dependent impairment of relaxation kinetics in right ventricular end-stage failing human myocardium

BackgroundIn patients with end-stage heart failure, the primary etiology often originates in the left ventricle, and eventually the contractile function of the right ventricle (RV) also becomes compromised. RV tissue-level deficits in contractile force and/or kinetics need quantification to understand involvement in ischemic and non-ischemic failing human myocardium. Methods and resultsThe human population suffering from heart failure is diverse, requiring many subjects to be studied in order to perform an adequately powered statistical analysis. From 2009-present we assessed live tissue-level contractile force and kinetics in isolated myocardial RV trabeculae from 44 non-failing and 41 failing human hearts. At 1 Hz stimulation rate (in vivo resting state) the developed active force was not different in non-failing compared to failing ischemic nor non-ischemic failing trabeculae. In sharp contrast, the kinetics of relaxation were significantly impacted by disease, with 50% relaxation time being significantly shorter in non-failing vs. non-ischemic failing, while the latter was still significantly shorter than ischemic failing. Gender did not significantly impact kinetics. Length-dependent activation was not impacted. Although baseline force was not impacted, contractile reserve was critically blunted. The force-frequency relation was positive in non-failing myocardium, but negative in both ischemic and non-ischemic myocardium, while the β-adrenergic response to isoproterenol was depressed in both pathologies. ConclusionsForce development at resting heart rate is not impacted by cardiac pathology, but kinetics are impaired and the magnitude of the impairment depends on the underlying etiology. Focusing on restoration of myocardial kinetics will likely have greater therapeutic potential than targeting force of contraction.

Impaired Ca2+ cycling of nonischemic myocytes contributes to sarcomere dysfunction early after myocardial infarction

Changes in the nonischemic remote myocardium of the heart contribute to left ventricular dysfunction after ischemia and reperfusion (I/R). Understanding the underlying mechanisms early after I/R is crucial to improve the adaptation of the viable myocardium to increased mechanical demands. Here, we investigated the role of myocyte Ca2+ handling in the remote myocardium 24 h after 60 min LAD occlusion. Cardiomyocytes isolated from the basal noninfarct-related parts of wild type mouse hearts demonstrated depressed beat-to-beat Ca2+ handling. The amplitude of the Ca2+ transients as well as the kinetics of Ca2+ transport were reduced by up to 25%. These changes were associated with impaired sarcomere contraction. While expression levels of Ca2+ regulatory proteins were unchanged in remote myocardium compared to the corresponding regions of sham-operated hearts, mobility shift analyses of phosphorylated protein showed 2.9 ± 0.4-fold more unphosphorylated phospholamban (PLN) monomers, the PLN species that inhibits the Ca2+ ATPase SERCA2a (P ≤ 0.001). Phospho-specific antibodies revealed normal phosphorylation of PLN at T17 in remote myocardium, but markedly reduced phosphorylation at its PKA-dependent phosphorylation site, S16 (P ≤ 0.01). The underlying cause involved enhanced activity of protein phosphatases, particularly PP2A (P ≤ 0.01). In contrast, overall PKA activity was normal. The PLN interactome, as determined by co-immunoprecipitation and mass spectrometry, and the phosphorylation state of PKA targets other than PLN were also unchanged. Isoproterenol enhanced cellular Ca2+ cycling much stronger in remote myocytes than in healthy controls and improved sarcomere function. We conclude that the reduced phosphorylation state of PLN at S16 impairs myocyte Ca2+ cycling in the remote myocardium 24 h after I/R and contributes to contractile dysfunction.

Matrix Metalloproteinase-2 Impairs Homing of Intracoronary Delivered Mesenchymal Stem Cells in a Porcine Reperfused Myocardial Infarction: Comparison With Intramyocardial Cell Delivery.

Intracoronary (IC) injection of mesenchymal stem cells (MSCs) results in a prompt decrease of absolute myocardial blood flow (AMF) with late and incomplete recovery of myocardial tissue perfusion. Here, we investigated the effect of decreased AMF on oxidative stress marker matrix metalloproteinase-2 (MMP-2) and its influence on the fate and homing and paracrine character of MSCs after IC or intramyocardial cell delivery in a closed-chest reperfused myocardial infarction (MI) model in pigs. Porcine MSCs were transiently transfected with Ad-Luc and Ad-green fluorescent protein (GFP). One week after MI, the GFP-Luc-MSCs were injected either IC (group IC, 11.00 ± 1.07 × 106) or intramyocardially (group IM, 9.88 ± 1.44 × 106). AMF was measured before, immediately after, and 24 h post GFP-Luc-MSC delivery. In vitro bioluminescence signal was used to identify tissue samples containing GFP-Luc-MSCs. Myocardial tissue MMP-2 and CXCR4 receptor expression (index of homing signal) were measured in bioluminescence positive and negative infarcted and border, and non-ischemic myocardial areas 1-day post cell transfer. At 7-day follow-up, myocardial homing (cadherin, CXCR4, and stromal derived factor-1alpha) and angiogenic [fibroblast growth factor 2 (FGF2) and VEGF] were quantified by ELISA of homogenized myocardial tissues from the bioluminescence positive and negative infarcted and border, and non-ischemic myocardium. Biodistribution of the implanted cells was quantified by using Luciferase assay and confirmed by fluorescence immunochemistry. Global left ventricular ejection fraction (LVEF) was measured at baseline and 1-month post cell therapy using magnet resonance image. AMF decreased immediately after IC cell delivery, while no change in tissue perfusion was found in the IM group (42.6 ± 11.7 vs. 56.9 ± 16.7 ml/min, p = 0.018). IC delivery led to a significant increase in myocardial MMP-2 64 kD expression (448 ± 88 vs. 315 ± 54 intensity × mm2, p = 0.021), and decreased expression of CXCR4 (592 ± 50 vs. 714 ± 54 pg/tissue/ml, p = 0.006), with significant exponential decay between MMP-2 and CXCR4 (r = 0.679, p < 0.001). FGF2 and VEGF of the bioluminescence infarcted and border zone of homogenized tissues were significantly elevated in the IM goups as compared to IC group. LVEF increase was significantly higher in IM group (0.8 ± 8.4 vs 5.3 ± 5.2%, p = 0.046) at the 1-month follow up. Intracoronary stem cell delivery decreased AMF, with consequent increase in myocardial expression of MMP-2 and reduced CXCR4 expression with lower level of myocardial homing and angiogenic factor release as compared to IM cell delivery.

Contraction and Relaxation Coupling Unaffected by Disease in Canine and Human Myocardium

In healthy rodent isolated ventricular myocardium, a strong positive correlation (R2&gt;0.95) has been observed between the rate of contraction versus rate of relaxation. Additionally, this correlation remains when muscles are stimulated to contract at different length, different frequency and various levels of beta‐adrenergic stimulation. However, there are drastic differences in EC coupling in small rodents versus larger mammals, including humans. Human and other large mammals, such as dogs, have a much wider range (~10 fold) of modulation of cardiac force and kinetics, thus it is unclear if a contraction‐relaxation coupling exists in larger mammals. In addition, it is unknown if such a relationship would be effected by disease. In this study, we investigated whether there is a correlation between maximal speed of contraction (dF/dt) and relaxation (‐dF/dt) in normal and exercise trained canines, with or without a myocardial infarction, as well as in normal human non‐failing, failing ischemic and failing non‐ischemic myocardium. Preliminary analysis on n=42 canines and N=54 humans suggests that there is a tight coupling between the maximal speed of contraction and relaxation in normal canine (R2=0.99) and non‐failing human myocardium (R2=0.99), with nearly identical slopes of this correlation. Additionally, within exercise or diseased hearts, there is no significant change with this correlation or slope of contraction‐relaxation coupling. We conclude that contraction‐relaxation coupling is a fundamental property that is unaffected by physiological contractile regulatory mechanisms.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Characterization of dynamic gene networks of control ischemic reperfused mouse heart

Myocardial infarction (MI) is a leading cause of death worldwide. Although some targets associated with MI have been extensively studied, their dynamic characteristics in gene expressions during the disease progression haven’t been fully elucidated to date. In this study, we aim to measure the dynamic regulation of gene expression during ischemia-reperfusion (IR) in the left ventricle of mouse heart, infer gene regulatory networks and decipher the main hubs linking cellular processes. 8–12 weeks old C57BL/6 mice are anesthetized, undergone IR and sacrificed at different time points (8 animals per time point) of the IR sequence. RNA-seq data from controls, ischemic and non-ischemic myocardium are analyzed, clustered and functionally characterized. RNA-seq data normalized as fragments per kilobase per million analyzed by principal component analysis (PCA) implemented in R software, are not clustered based on their time profiles. We hypothesize that analyzing the data directly by PCA disqualified it as a method for temporal analysis of gene expression. We thus shifted to analyzing raw counts data by DESeq2. 975 , 446 and 3878 genes are significantly induced by thoracotomy, anesthesia, remote and IR specific effect respectively. These genes are further analyzed by weighted gene co-expression network analysis (WGCNA) splitting them into modules based on their temporal behavior. These modules are then functionally characterized separately by gene ontology (GO) so that molecular functions, biological processes and cellular components involved in MI progression are clarified. This kinetical study not only provides a comprehensive framework and transcriptional resource in the myocardium during MI, but also sheds new light on the importance of taking thoracotomy effect and the different analytical methods into account.

Inducible NO Synthase mRNA Expression and Infiltration of Rats Myocardium with Inflammatory Cells in 2-4 Hours after Modeled Permanent Ischemia or Ischemia/Reperfusion.

Expression of inducible NO-synthase mRNA and myocardial infiltration with neutrophils were studied in rats with modeled permanent ischemia and ischemia/reperfusion models. Expression of inducible NO synthase mRNA in the ischemic region increased significantly in 3, 3.5, and 4 h in modeled ischemia/reperfusion and in 3.5 and 4 h in permanent ischemia. Myocardial infiltration with neutrophils was significantly higher than in intact controls throughout the experiment without significant intergroup differences. In non-ischemic myocardium, enhanced expression of inducible NO synthase mRNA and moderate neutrophilic-lymphocytic myocardial infiltration were also observed in 3.5, and 4 h after ischemia.

Imaging of \u03b1v\u03b23 integrin expression in experimental myocardial ischemia with [68Ga]NODAGA-RGD positron emission tomography

BackgroundRadiolabeled RGD peptides detect αvβ3 integrin expression associated with angiogenesis and extracellular matrix remodeling after myocardial infarction. We studied whether cardiac positron emission tomography (PET) with [68Ga]NODAGA-RGD detects increased αvβ3 integrin expression after induction of flow-limiting coronary stenosis in pigs, and whether αvβ3 integrin is expressed in viable ischemic or injured myocardium.MethodsWe studied 8 Finnish landrace pigs 13 ± 4 days after percutaneous implantation of a bottleneck stent in the proximal left anterior descending coronary artery. Antithrombotic therapy was used to prevent stent occlusion. Myocardial uptake of [68Ga]NODAGA-RGD (290 ± 31 MBq) was evaluated by a 62 min dynamic PET scan. The ischemic area was defined as the regional perfusion abnormality during adenosine-induced stress by [15O]water PET. Guided by triphenyltetrazolium chloride staining, tissue samples from viable and injured myocardial areas were obtained for autoradiography and histology.ResultsStent implantation resulted in a partly reversible myocardial perfusion abnormality. Compared with remote myocardium, [68Ga]NODAGA-RGD PET showed increased tracer uptake in the ischemic area (ischemic-to-remote ratio 1.3 ± 0.20, p = 0.0034). Tissue samples from the injured areas, but not from the viable ischemic areas, showed higher [68Ga]NODAGA-RGD uptake than the remote non-ischemic myocardium. Uptake of [68Ga]NODAGA-RGD correlated with immunohistochemical detection of αvβ3 integrin that was expressed in the injured myocardial areas.ConclusionsCardiac [68Ga]NODAGA-RGD PET demonstrates increased myocardial αvβ3 integrin expression after induction of flow-limiting coronary stenosis in pigs. Localization of [68Ga]NODAGA-RGD uptake indicates that it reflects αvβ3 integrin expression associated with repair of recent myocardial injury.

Spinal cord stimulation reduces ventricular arrhythmias during acute ischemia by attenuation of regional myocardial excitability.

Myocardial ischemia creates autonomic nervous system imbalance and can trigger cardiac arrhythmias. We hypothesized that neuromodulation by spinal cord stimulation (SCS) will attenuate local cardiac sympathoexcitation from ischemia-induced increases in afferent signaling, reduce ventricular arrhythmias, and improve myocardial function during acute ischemia. Yorkshire pigs (n = 20) were randomized to SCS (50 Hz at 200-μs duration, current 90% motor threshold) or sham operation (sham) for 30 min before ischemia. A four-pole SCS lead was placed percutaneously in the epidural space (T1-T4), and a 56-electrode mesh was placed over the heart for high-resolution electrophysiological recordings, including activation recovery intervals (ARIs), activation time, repolarization time, and dispersion of repolarization. Electrophysiological and hemodynamic measures were recorded at baseline, after SCS/sham, during acute ischemia (300-s coronary artery ligation), and throughout reperfusion. SCS 1) reduced sympathoexcitation-induced ARI and repolarization time shortening in the ischemic myocardium; 2) attenuated increases in the dispersion of repolarization; 3) reduced ventricular tachyarrythmias [nonsustained ventricular tachycardias: 24 events (3 sham animals) vs. 1 event (1 SCS animal), P < 0.001]; and 4) improved myocardial function (dP/dt from baseline to ischemia: 1,814 ± 213 to 1,596 ± 282 mmHg/s in sham vs. 1,422 ± 299 to 1,380 ± 299 mmHg/s in SCS, P < 0.01). There was no change in ventricular electrophysiology during baseline conditions without myocardial stress or in the nonischemic myocardium. In conclusion, in a porcine model of acute ventricular ischemia, SCS reduced regional myocardial sympathoexcitation, decreased ventricular arrhythmias, and improved myocardial function. SCS decreased sympathetic nerve activation locally in the ischemic myocardium with no effect observed in the normal myocardium, thus providing mechanistic insights into the antiarrhythmic and myocardial protective effects of SCS.NEW & NOTEWORTHY In a porcine model of ventricular ischemia, spinal cord stimulation decreased sympathetic nerve activation regionally in ischemic myocardium with no effect on normal myocardium, demonstrating that the antiarrhythmic effects of spinal cord stimulation are likely due to attenuation of local sympathoexcitation in the ischemic myocardium and not changes in global myocardial electrophysiology.

The 10 Most Read Articles Published in Circulation Research in 2016.

The 10 Most Read Articles Published in Circulation Research in 2016.

The Role of Inflammation in Cardiovascular Outcome

The aim of this review is to update the pathophysiological role of innate immune response in the cardiovascular (CV) disease outcomes, particularly focusing on coronary atherosclerosis and heart failure. Inflammatory processes comprised with the innate immunity reaction are believed to actively trigger CV disease development and final clinical events. For instance, by releasing proteases and neutrophil extracellular traps, neutrophil recruitment and activation might strongly influence atherosclerotic plaque stability. Similarly, neutrophils drive the early inflammatory response following a myocardial infarction. However, these cells contribute themselves to infarct healing by orchestrating monocyte/macrophage recruitment and polarization within the ischemic myocardium. Given their heterogeneity and plasticity, the balance between recruitment, proliferation, and polarization of monocyte/macrophage is a further leading determinant of advanced plaque maturation. Moreover, timely shift from a pro-inflammatory to a resolving macrophage phenotype may influence cardiac remodeling as well as development of heart failure (HF). Alongside macrophage recruitment and activation into the remote, non-ischemic myocardium also contributes to cardiac remodeling and HF development. Innate immune response is a tightly regulated process where a timely modulation of the balance between damaging and resolving properties critically impacts on CV outcome. Further progress may improve the determination of the prognostic relevance of inflammatory biomarkers on clinical CV outcome.

Calpain inhibition modulates glycogen synthase kinase 3β pathways in ischemic myocardium: A proteomic and mechanistic analysis

BackgroundCalpain inhibition has an enhancing effect on myocardial perfusion and improves myocardial density by inhibiting glycogen synthase kinase 3β (GSK-3β) and up-regulating downstream signaling pathways, including the insulin/PI3K and WNT/β-catenin pathways, in a pig model of chronic myocardial ischemia in the setting of metabolic syndrome. MethodsPigs were fed a high-fat diet for 4 weeks, then underwent placement of an ameroid constrictor to the left circumflex artery. Three weeks later, the animals received no drug (high-cholesterol controls [HCC]), a high-dose calpain inhibitor (HCI), a low-dose calpain inhibitor (LCI), or a GSK-3β inhibitor (GSK-3βI). The diets and drug regimens were continued for 5 weeks and the myocardial tissue was harvested. ResultsCalpain and GSK-3β inhibition caused an increase in myocardial perfusion ratios at rest and during pacing compared with controls. Pigs in the LCI and HCI groups had increased vessel density in the ischemic myocardium, and pigs in the GSK-3βI group had increased vessel density in the ischemic and nonischemic myocardium compared with the HCC group. Calpain inhibition modulates proteins involved in the insulin/PI3K and WNT/β-catenin pathways. Quantitative proteomics revealed that calpain and GSK-3β inhibition significantly modulated the expression of proteins enriched in cytoskeletal regulation, metabolism, respiration, and calcium-binding pathways. ConclusionsIn the setting of metabolic syndrome, calpain or GSK-3β inhibition increases vessel density in both ischemic and nonischemic myocardial tissue. Calpain inhibition may exert these effects through the inhibition of GSK-3β and up-regulation of downstream signaling pathways, including the insulin/PI3K and WNT/β-catenin pathways.

Reduced mitochondrial respiration in the ischemic as well as in the remote nonischemic region in postmyocardial infarction remodeling.

Scarring and remodeling of the left ventricle (LV) after myocardial infarction (MI) results in ischemic cardiomyopathy with reduced contractile function. Regional differences related to persisting ischemia may exist. We investigated the hypothesis that mitochondrial function and structure is altered in the myocardium adjacent to MI with reduced perfusion (MIadjacent) and less so in the remote, nonischemic myocardium (MIremote). We used a pig model of chronic coronary stenosis and MI (n = 13). Functional and perfusion MR imaging 6 wk after intervention showed reduced ejection fraction and increased global wall stress compared with sham-operated animals (Sham; n = 14). Regional strain in MIadjacent was reduced with reduced contractile reserve; in MIremote strain was also reduced but responsive to dobutamine and perfusion was normal compared with Sham. Capillary density was unchanged. Cardiac myocytes isolated from both regions had reduced basal and maximal oxygen consumption rate, as well as through complex I and II, but complex IV activity was unchanged. Reduced respiration was not associated with detectable reduction of mitochondrial density. There was no significant change in AMPK or glucose transporter expression levels, but glycogen content was significantly increased in both MIadjacent and MIremote Glycogen accumulation was predominantly perinuclear; mitochondria in this area were smaller but only in MIadjacent where also subsarcolemmal mitochondria were smaller. In conclusion, after MI reduction of mitochondrial respiration and glycogen accumulation occur in all LV regions suggesting that reduced perfusion does not lead to additional specific changes and that increased hemodynamic load is the major driver for changes in mitochondrial function.

Proliferation and Recruitment Contribute to Myocardial Macrophage Expansion in Chronic Heart Failure.

Macrophages reside in the healthy myocardium, participate in ischemic heart disease, and modulate myocardial infarction (MI) healing. Their origin and roles in post-MI remodeling of nonischemic remote myocardium, however, remain unclear. This study investigated the number, origin, phenotype, and function of remote cardiac macrophages residing in the nonischemic myocardium in mice with chronic heart failure after coronary ligation. Eight weeks post MI, fate mapping and flow cytometry revealed that a 2.9-fold increase in remote macrophages results from both increased local macrophage proliferation and monocyte recruitment. Heart failure produced by extensive MI, through activation of the sympathetic nervous system, expanded medullary and extramedullary hematopoiesis. Circulating Ly6C(high) monocytes rose from 64±5 to 108±9 per microliter of blood (P<0.05). Cardiac monocyte recruitment declined in Ccr2(-/-) mice, reducing macrophage numbers in the failing myocardium. Mechanical strain of primary murine and human macrophage cultures promoted cell cycle entry, suggesting that the increased wall tension in post-MI heart failure stimulates local macrophage proliferation. Strained cells activated the mitogen-activated protein kinase pathway, whereas specific inhibitors of this pathway reduced macrophage proliferation in strained cell cultures and in the failing myocardium (P<0.05). Steady-state cardiac macrophages, monocyte-derived macrophages, and locally sourced macrophages isolated from failing myocardium expressed different genes in a pattern distinct from the M1/M2 macrophage polarization paradigm. In vivo silencing of endothelial cell adhesion molecules curbed post-MI monocyte recruitment to the remote myocardium and preserved ejection fraction (27.4±2.4 versus 19.1±2%; P<0.05). Myocardial failure is influenced by an altered myeloid cell repertoire.

Differentiation of infarcted, ischemic, and non-ischemic LV myocardium using post-systolic strain index assessed by resting two-dimensional speckle tracking transthoracic echocardiography

Differentiation of infarcted, ischemic, and non-ischemic LV myocardium using post-systolic strain index assessed by resting two-dimensional speckle tracking transthoracic echocardiography