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Yolk sac macrophages are the first to seed the developing heart, however we have no understanding of their roles in human heart development and function due to a lack of accessible tissue. Here, we bridge this gap by differentiating human embryonic stem cells (hESCs) into primitive LYVE1+ macrophages (hESC-macrophages) that stably engraft within contractile cardiac microtissues composed of hESC-cardiomyocytes and fibroblasts. Engraftment induces a human fetal cardiac macrophage gene program enriched in efferocytic pathways. Functionally, hESC-macrophages trigger cardiomyocyte sarcomeric protein maturation, enhance contractile force and improve relaxation kinetics. Mechanistically, hESC-macrophages engage in phosphatidylserine dependent ingestion of apoptotic cardiomyocyte cargo, which reduces microtissue stress, leading hESC-cardiomyocytes to more closely resemble early human fetal ventricular cardiomyocytes, both transcriptionally and metabolically. Inhibiting hESC-macrophage efferocytosis impairs sarcomeric protein maturation and reduces cardiac microtissue function. Taken together, macrophage-engineered human cardiac microtissues represent a considerably improved model for human heart development, and reveal a major beneficial role for human primitive macrophages in enhancing early cardiac tissue function.
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Diabetes mellitus (DM) confers an increased risk of sudden cardiac death (SCD) independent of its associated cardiovascular comorbidities. DM induces adverse structural, electrophysiologic, and autonomic cardiac remodeling that can increase one's risk of ventricular arrhythmias and SCD. Although glycemic control and prevention of microvascular and macrovascular complications are cornerstones in the management of DM, they are not adequate for the prevention of SCD. In this narrative review, we describe the contribution of DM to the pathophysiologic mechanism of SCD beyond its role in atherosclerotic cardiovascular disease and heart failure. On the basis of this pathophysiologic framework, we outline potential preventive and therapeutic strategies to mitigate the risk of SCD in this population of high-risk patients.
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BACKGROUND: We recently demonstrated that acute administration of ibrutinib, a Bruton's tyrosine kinase inhibitor used in chemotherapy for blood malignancies, increases ventricular arrhythmia (VA) vulnerability. A pathway of ibrutinib-induced vulnerability to VA that can be modulated for cardioprotection remains unclear. METHODS AND RESULTS: The effects of ibrutinib on cardiac electrical activity and Ca2+ dynamics were investigated in Langendorff-perfused hearts using optical mapping. We also conducted Western blotting analysis to evaluate the impact of ibrutinib on various regulatory and Ca2+-handling proteins in rat cardiac tissues. Treatment with ibrutinib (10 mg/kg per day) for 4 weeks was associated with an increased VA inducibility (72.2%±6.3% versus 38.9±7.0% in controls, P<0.002) and shorter action potential durations during pacing at various frequencies (P<0.05). Ibrutinib also decreased heart rate thresholds for beat-to-beat duration alternans of the cardiac action potential (P<0.05). Significant changes in myocardial Ca2+ transients included lower amplitude alternans ratios (P<0.05), longer times-to-peak (P<0.05), and greater spontaneous intracellular Ca2+ elevations (P<0.01). We also found lower abundance and phosphorylation of myocardial AMPK (5'-adenosine monophosphate-activated protein kinase), indicating reduced AMPK activity in hearts after ibrutinib treatment. An acute treatment with the AMPK activator 5-aminoimidazole-4-carboxamide-1-ß-D-ribofuranoside ameliorated abnormalities in action potential and Ca2+ dynamics, and significantly reduced VA inducibility (37.1%±13.4% versus 72.2%±6.3% in the absence of 5-aminoimidazole-4-carboxamide-1-ß-D-ribofuranoside, P<0.05) in hearts from ibrutinib-treated rats. CONCLUSIONS: VA vulnerability inflicted by ibrutinib may be mediated in part by an impairment of myocardial AMPK activity. Pharmacological activation of AMPK may be a protective strategy against ibrutinib-induced cardiotoxicity.
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Proteínas Quinases Ativadas por AMP , Potenciais de Ação , Adenina , Arritmias Cardíacas , Piperidinas , Pirazóis , Pirimidinas , Animais , Adenina/análogos & derivados , Adenina/farmacologia , Piperidinas/farmacologia , Potenciais de Ação/efeitos dos fármacos , Pirimidinas/farmacologia , Proteínas Quinases Ativadas por AMP/metabolismo , Pirazóis/farmacologia , Masculino , Arritmias Cardíacas/induzido quimicamente , Arritmias Cardíacas/metabolismo , Arritmias Cardíacas/fisiopatologia , Arritmias Cardíacas/prevenção & controle , Inibidores de Proteínas Quinases/farmacologia , Frequência Cardíaca/efeitos dos fármacos , Preparação de Coração Isolado , Cálcio/metabolismo , Ratos , Modelos Animais de Doenças , Ratos Sprague-Dawley , Miócitos Cardíacos/efeitos dos fármacos , Miócitos Cardíacos/metabolismo , Miócitos Cardíacos/enzimologia , Miócitos Cardíacos/patologia , Sinalização do Cálcio/efeitos dos fármacos , Fatores de TempoRESUMO
Cardiac arrhythmias remain a significant concern with Ibrutinib (IBR), a first-generation Bruton's tyrosine kinase inhibitor (BTKi). Acalabrutinib (ABR), a next-generation BTKi, is associated with reduced atrial arrhythmia events. However, the role of ABR in ventricular arrhythmia (VA) has not been adequately evaluated. Our study aimed to investigate VA vulnerability and ventricular electrophysiology following chronic ABR therapy in male Sprague-Dawley rats utilizing epicardial optical mapping for ventricular voltage and Ca2+ dynamics and VA induction by electrical stimulation in ex-vivo perfused hearts. Ventricular tissues were snap-frozen for protein analysis for sarcoplasmic Ca2+ and metabolic regulatory proteins. The results show that both ABR and IBR treatments increased VA vulnerability, with ABR showing higher VA regularity index (RI). IBR, but not ABR, is associated with the abbreviation of action potential duration (APD) and APD alternans. Both IBR and ABR increased diastolic Ca2+ leak and Ca2+ alternans, reduced conduction velocity (CV), and increased CV dispersion. Decreased SERCA2a expression and AMPK phosphorylation were observed with both treatments. Our results suggest that ABR treatment also increases the risk of VA by inducing proarrhythmic changes in Ca2+ signaling and membrane electrophysiology, as seen with IBR. However, the different impacts of these two BTKi on ventricular electrophysiology may contribute to differences in VA vulnerability and distinct VA characteristics.
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Tirosina Quinase da Agamaglobulinemia , Arritmias Cardíacas , Benzamidas , Piperidinas , Ratos Sprague-Dawley , Animais , Benzamidas/farmacologia , Benzamidas/uso terapêutico , Masculino , Ratos , Tirosina Quinase da Agamaglobulinemia/metabolismo , Tirosina Quinase da Agamaglobulinemia/antagonistas & inibidores , Arritmias Cardíacas/metabolismo , Arritmias Cardíacas/induzido quimicamente , Piperidinas/farmacologia , Piperidinas/uso terapêutico , Potenciais de Ação/efeitos dos fármacos , Remodelação Ventricular/efeitos dos fármacos , Inibidores de Proteínas Quinases/farmacologia , Pirazinas/farmacologia , Cálcio/metabolismo , Adenina/análogos & derivados , Adenina/farmacologia , Adenina/efeitos adversos , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/metabolismo , Ventrículos do Coração/efeitos dos fármacos , Ventrículos do Coração/metabolismo , Ventrículos do Coração/fisiopatologia , Pirimidinas/farmacologia , Sinalização do Cálcio/efeitos dos fármacos , Pirazóis/farmacologiaRESUMO
The current antiarrhythmic paradigm is mainly centered around modulating membrane voltage. However, abnormal cytosolic calcium (Ca2+) signaling, which plays an important role in driving membrane voltage, has not been targeted for therapeutic purposes in arrhythmogenesis. There is clear evidence for bidirectional coupling between membrane voltage and intracellular Ca2+. Cytosolic Ca2+ regulates membrane voltage through Ca2+-sensitive membrane currents. As a component of Ca2+-sensitive currents, Ca2+-activated nonspecific cationic current through the TRPM4 (transient receptor potential melastatin 4) channel plays a significant role in Ca2+-driven changes in membrane electrophysiology. In myopathic and ischemic ventricles, upregulation and/or enhanced activity of this current is associated with the generation of afterdepolarization (both early and delayed), reduction of repolarization reserve, and increased propensity to ventricular arrhythmias. In this review, we describe a novel concept for the management of ventricular arrhythmias in the remodeled ventricle based on mechanistic concepts from experimental studies, by uncoupling the Ca2+-induced changes in membrane voltage by inhibition of this TRPM4-mediated current.
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Myocardial calcium (Ca2+) signaling plays a crucial role in contractile function and membrane electrophysiology. An abnormal myocardial Ca2+ transient is linked to heart failure and ventricular arrhythmias. At the subcellular level, the synchronous release of Ca2+ sparks from sarcoplasmic Ca2+ release units determines the configuration and amplitude of the global Ca2+ transient. This narrative review evaluates the role of aberrant Ca2+ release synchrony in the pathophysiology of cardiomyopathies and ventricular arrhythmias. The potential therapeutic benefits of restoration of Ca2+ release synchrony in heart failure and ventricular arrhythmias are also discussed.
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Cálcio , Insuficiência Cardíaca , Humanos , Cálcio/metabolismo , Miócitos Cardíacos/metabolismo , Arritmias Cardíacas , Miocárdio/metabolismo , Sinalização do Cálcio/fisiologia , Retículo Sarcoplasmático/metabolismo , Canal de Liberação de Cálcio do Receptor de Rianodina/metabolismoRESUMO
BACKGROUND: Atrial myopathy may underlie the progression of atrial fibrillation (AF) from a treatable disease to an irreversible condition with poor ablation outcomes. Electrophysiological methods to unmask areas prone to re-entry initiation could be key to defining latent atrial myopathy. METHODS: Consecutive patients referred for AF ablation were prospectively included at four institutions. Decrement evoked potential mapping (DEEP) was performed in eight left atrial sites and five right atrial sites, from two different pacing locations (endocardially from the left atrial appendage, epicardially from the proximal coronary sinus). The electrograms (EGMs) during S1 600 ms drive and after an extra stimulus (S2 at +30 ms above atrial refractoriness) were studied at each location and assessed for decremental properties. Follow-up was 12 months. RESULTS: Seventy-four patients were included and 85% had persistent AF. A total of 17,614 EGMs were individually analysed and measured. Nine percent of the EGMs showed DEEP properties (local delay of >10 ms after S2) with a mean decrement of 33±26 ms. DEEPs were more frequent in the left atrium than the right atrium (9.4% vs 8.0%; p<0.001) and more prevalent in persistent AF patients than paroxysmal AF patients (9.8% vs 4.6% p=0.001). Atrial DEEPs were more frequently unmasked in normal bipolar voltage areas and by epicardial pacing than endocardial pacing (9.6% vs 8.4%, respectively; p=0.004). Within the left atrium, the roof had the highest prevalence of DEEP EGMs. CONCLUSIONS: DEEP mapping of both atria is useful for highlighting areas with a tendency for unidirectional block and re-entry initiation. Those areas are more easily unmasked by epicardial pacing from the coronary sinus and more prevalent in persistent AF patients than in paroxysmal AF patients.
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Apêndice Atrial , Fibrilação Atrial , Ablação por Cateter , Doenças Musculares , Humanos , Átrios do Coração , Apêndice Atrial/cirurgia , Doenças Musculares/cirurgia , Potenciais EvocadosRESUMO
Chronic stress among young patients (≤ 45 years old) could result in autonomic dysfunction. Autonomic dysfunction could be exhibited via sympathetic hyperactivity, sympathetic nerve sprouting, and diffuse adrenergic stimulation in the atria. Adrenergic spatial densities could alter atrial electrophysiology and increase arrhythmic susceptibility. Therefore, we examined the role of adrenergic spatial densities in creating arrhythmogenic substrates in silico. We simulated three 25 cm2 atrial sheets with varying adrenergic spatial densities (ASD), activation rates, and external transmembrane currents. We measured their effects on spatial and temporal heterogeneity of action potential durations (APD) at 50% and 20%. Increasing ASD shortens overall APD, and maximum spatial heterogeneity (31%) is achieved at 15% ASD. The addition of a few (5% to 10%) adrenergic elements decreases the excitation threshold, below 18 µA/cm2, while ASDs greater than 10% increase their excitation threshold up to 22 µA/cm2. Increase in ASD during rapid activation increases APD50 and APD20 by 21% and 41%, respectively. Activation times of captured beats during rapid activation could change by as much as 120 ms from the baseline cycle length. Rapidly activated atrial sheets with high ASDs significantly increase temporal heterogeneity of APD50 and APD20. Rapidly activated atrial sheets with 10% ASD have a high likelihood (0.7 ± 0.06) of fragmenting otherwise uniform wavefronts due to the transient inexcitability of adrenergically stimulated elements, producing an effective functional block. The likelihood of wave fragmentation due to ASD highly correlates with the spatial variations of APD20 (ρ = 0.90, p = 0.04). Our simulations provide a novel insight into the contributions of ASD to spatial and temporal heterogeneities of APDs, changes in excitation thresholds, and a potential explanation for wave fragmentation in the human atria due to sympathetic hyperactivity. Our work may aid in elucidating an electrophysiological link to arrhythmia initiation due to chronic stress among young patients.
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Fibrilação Atrial , Transtorno do Espectro Autista , Comunicação Interatrial , Disautonomias Primárias , Humanos , Pessoa de Meia-Idade , Adrenérgicos , Potenciais de AçãoRESUMO
To better understand sodium channel (SCN5A)-related cardiomyopathies, we generated ventricular cardiomyocytes from induced pluripotent stem cells obtained from a dilated cardiomyopathy patient harbouring the R222Q mutation, which is only expressed in adult SCN5A isoforms. Because the adult SCN5A isoform was poorly expressed, without functional differences between R222Q and control in both embryoid bodies and cell sheet preparations (cultured for 29-35 days), we created heart-on-a-chip biowires which promote myocardial maturation. Indeed, biowires expressed primarily adult SCN5A with R222Q preparations displaying (arrhythmogenic) short action potentials, altered Na+ channel biophysical properties and lower contractility compared to corrected controls. Comprehensive RNA sequencing revealed differential gene regulation between R222Q and control biowires in cellular pathways related to sarcoplasmic reticulum and dystroglycan complex as well as biological processes related to calcium ion regulation and action potential. Additionally, R222Q biowires had marked reductions in actin expression accompanied by profound sarcoplasmic disarray, without differences in cell composition (fibroblast, endothelial cells, and cardiomyocytes) compared to corrected biowires. In conclusion, we demonstrate that in addition to altering cardiac electrophysiology and Na+ current, the R222Q mutation also causes profound sarcomere disruptions and mechanical destabilization. Possible mechanisms for these observations are discussed.
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Cardiomiopatia Dilatada , Células-Tronco Pluripotentes Induzidas , Adulto , Humanos , Miócitos Cardíacos , Cardiomiopatia Dilatada/genética , Células Endoteliais , Dispositivos Lab-On-A-ChipRESUMO
AIMS: Electroanatomical maps using automated conduction velocity (CV) algorithms are now being calculated using two-dimensional (2D) mapping tools. We studied the accuracy of mapping surface 2D CV, compared to the three-dimensional (3D) vectors, and the influence of mapping resolution in non-scarred animal and human heart models. METHODS AND RESULTS: Two models were used: a healthy porcine Langendorff model with transmural needle electrodes and a computer stimulation model of the ventricles built from an MRI-segmented, excised human heart. Local activation times (LATs) within the 3D volume of the mesh were used to calculate true 3D CVs (direction and velocity) for different pixel resolutions ranging between 500 µm and 4 mm (3D CVs). CV was also calculated for endocardial surface-only LATs (2D CV). In the experimental model, surface (2D) CV was faster on the epicardium (0.509 m/s) compared to the endocardium (0.262 m/s). In stimulation models, 2D CV significantly exceeded 3D CVs across all mapping resolutions and increased as resolution decreased. Three-dimensional and 2D left ventricle CV at 500 µm resolution increased from 429.2 ± 189.3 to 527.7 ± 253.8 mm/s (P < 0.01), respectively, with modest correlation (R = 0.64). Decreasing the resolution to 4 mm significantly increased 2D CV and weakened the correlation (R = 0.46). The majority of CV vectors were not parallel (<30°) to the mapping surface providing a potential mechanistic explanation for erroneous LAT-based CV over-estimation. CONCLUSION: Ventricular CV is overestimated when using 2D LAT-based CV calculation of the mapping surface and significantly compounded by mapping resolution. Three-dimensional electric field-based approaches are needed in mapping true CV on mapping surfaces.
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Sistema de Condução Cardíaco , Ventrículos do Coração , Humanos , Animais , Suínos , Endocárdio , Pericárdio , Imageamento por Ressonância MagnéticaRESUMO
Background: Doxorubicin-induced cardiomyopathy (DICM) is one of the complications that can limit treatment for a significant number of cancer patients. In animal models, the administration of statins can prevent the development of DICM. Therefore, the use of statins with anthracyclines potentially could enable cancer patients to complete their chemotherapy without added cardiotoxicity. The precise mechanism mediating the cardioprotection is not well understood. The purpose of this study is to determine the molecular mechanism by which rosuvastatin confers cardioprotection in a mouse model of DICM. Methods: Rosuvastatin was intraperitoneally administered into adult male mice at 100 µg/kg daily for 7 days, followed by a single intraperitoneal doxorubicin injection at 10 mg/kg. Animals continued to receive rosuvastatin daily for an additional 14 days. Cardiac function was assessed by echocardiography. Optical calcium mapping was performed on retrograde Langendorff perfused isolated hearts. Ventricular tissue samples were analyzed by immunofluorescence microscopy, Western blotting, and quantitative polymerase chain reaction. Results: Exposure to doxorubicin resulted in significantly reduced fractional shortening (27.4% ± 1.11% vs 40% ± 5.8% in controls; P < 0.001) and re-expression of the fetal gene program. However, we found no evidence of maladaptive cardiac hypertrophy or adverse ventricular remodeling in mice exposed to this dose of doxorubicin. In contrast, rosuvastatin-doxorubicin-treated mice maintained their cardiac function (39% ± 1.26%; P < 0.001). Mechanistically, the effect of rosuvastatin was associated with activation of Akt and phosphorylation of phospholamban with preserved sarcoplasmic/endoplasmic reticulum Ca2+ transporting 2 (SERCA2)-mediated Ca2+ reuptake. These effects occurred independently of perturbations in ryanodine receptor 2 function. Conclusions: Rosuvastatin counteracts the cardiotoxic effects of doxorubicin by directly targeting sarcoplasmic calcium cycling.
Contexte: La cardiomyopathie induite par la doxorubicine (CMID) est l'une des complications pouvant limiter le traitement d'un nombre considérable de patients atteints de cancer. Dans des modèles animaux, l'administration de statines peut prévenir l'apparition d'une CMID. Ainsi, l'utilisation de statines avec les anthracyclines pourrait vraisemblablement permettre aux patients de compléter leur chimiothérapie en évitant une cardiotoxicité supplémentaire. Le mécanisme précis qui sous-tend cet effet cardioprotecteur n'est pas entièrement élucidé. Cette étude a pour objectif de déterminer dans un modèle murin de CMID le mécanisme moléculaire par lequel la rosuvastatine confère une cardioprotection. Méthodologie: La rosuvastatine a été administrée par voie intrapéritonéale à des souris adultes mâles à une dose de 100 µg/kg par jour pendant sept jours, suivie d'une dose unique de doxorubicine de 10 mg/kg administrée par injection intrapéritonéale. Les animaux poursuivaient ensuite le traitement par la rosuvastatine une fois par jour pendant 14 jours supplémentaires. La fonction cardiaque a été mesurée par échocardiographie. Une cartographie optique du calcium a été réalisée sur des cÅurs isolés soumis à une perfusion rétrograde selon la méthode de Langendorff. Des échantillons de tissu ventriculaire ont été analysés par microscopie en immunofluorescence, par buvardage de western et par mesure quantitative de l'amplification en chaîne par polymérase. Résultats: L'exposition à la doxorubicine a entraîné une diminution significative de la fraction de raccourcissement (27,4 % ± 1,11 % vs 40 % ± 5,8 % dans le groupe témoin; p < 0,001) et la réexpression du programme génique fÅtal. Toutefois, aucune hypertrophie cardiaque inadaptée ni aucun remodelage ventriculaire indésirable n'ont été observés chez les souris ayant été exposées à la dose de doxorubicine étudiée. En revanche, la fonction cardiaque a été préservée chez les souris traitées par l'association rosuvastatine-doxorubicine (39 % ± 1,26 %; p < 0,001). Sur le plan du mode d'action, l'effet de la rosuvastatine a été associé à une activation de l'Akt et à une phosphorylation du phospholambane, avec préservation du recaptage de Ca2+ médié par la pompe SERCA2 (sarcoplasmic/endoplasmic reticulum Ca 2+ transporting 2). Ces effets sont survenus indépendamment des perturbations de la fonction du récepteur RyR2 (ryanodine receptor 2). Conclusions: La rosuvastatine neutralise les effets cardiotoxiques de la doxorubicine en ciblant directement la circulation sarcoplasmique du calcium.
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Background: Post-defibrillation myocardial contractile dysfunction adversely affects the survival of patients after cardiac arrest. Attenuation of diastolic calcium (Ca2+) overload by stabilization of the cardiac ryanodine receptor (RyR2) is found to reduce refibrillation after long-duration ventricular fibrillation (LDVF). Objective: In the present study, we explored the effects of RyR2 stabilization by azumolene on systolic Ca2+ release synchrony and myocardial contractility. Methods: After completion of baseline optical mapping, Langendorff-perfused rabbit hearts were subjected to global ischemia followed by reperfusion with azumolene or deionized distilled water (vehicle). Following reperfusion, LDVF was induced with burst pacing. In the first series of experiments (n = 16), epicardial Ca2+ transient was analyzed for Ca2+ transient amplitude alternans and dispersion of Ca2+ transient amplitude alternans index (CAAI). In the second series of experiments following the same protocol (n = 12), ventricular contractility was assessed by measuring the left ventricular pressure. Results: Ischemic LDVF led to greater CAAI (0.06 ± 0.02 at baseline vs 0.12 ± 0.02 post-LDVF, P < .01) and magnitude of dispersion of CAAI (0.04 ± 0.01 vs 0.09 ± 0.01, P < .01) in control hearts. In azumolene-treated hearts, no significant changes in CAAI (0.05 ± 0.01 vs 0.05 ± 0.01, P = .84) and dispersion of CAAI (0.04 ± 0.01 vs 0.04 ± 0.01, P = .99) were noted following ischemic LDVF. Ischemic LDVF was associated with reduction in left ventricular developed pressure (100% vs 36.8% ± 6.1%, P = .002) and dP/dtmax (100% vs 45.3% ± 6.5%, P = .003) in control hearts, but these reductions were mitigated (left ventricular developed pressure: 100% vs 74.0% ± 8.1%, P = .052, dP/dtmax: 100% vs 80.8% ± 7.9%, P = .09) in azumolene-treated hearts. Conclusion: Treatment with azumolene is associated with improvement of systolic Ca2+ release synchrony and myocardial contractility following ischemic LDVF.