Cardiomyocyte Remodeling Research Articles

Adipocyte-Mediated Electrophysiological Remodeling of PKP-2 Mutant Human Pluripotent Stem Cell-Derived Cardiomyocytes.

Arrhythmogenic cardiomyopathy (ACM) is a genetic disorder responsible for nearly a quarter of sports-related sudden cardiac deaths. ACM cases caused by mutations in desmosome proteins lead to right ventricular enlargement, the loss of cardiomyocytes, and fibrofatty tissue replacement, disrupting electrical and mechanical stability. It is currently unknown how paracrine factors secreted by infiltrating fatty tissues affect ACM cardiomyocyte electrophysiology. A normal and a PKP2 mutant (c.971_972InsT) ACM hiPSC line were cultivated and differentiated into cardiomyocytes (CMs). Adipocytes were differentiated from human adipose stem cells, and adipocyte conditioned medium (AdCM) was collected. Optical mapping and phenotypic analyses were conducted on human iPSC-cardiomyocytes (hiPSC-CMs) cultured in cardiac maintenance medium (CMM) and either with AdCM or specific cytokines. Significant differences were observed in voltage parameters such as the action potential duration (APD80, APD30), conduction velocity (CV), and CV heterogeneity. When cultured in AdCM relative to CMM, the APD80 increased and the CV decreased significantly in both groups; however, the magnitudes of changes often differed significantly between 1 and 7 days of cultivation. Cytokine exposure (IL-6, IL-8, MCP-1, CFD) affected the APD and CV in both the normal and PKP2 mutant hiPSC-CMs, with opposite effects. NF-kB signaling was also found to differ between the normal and PKP2 mutant hiPSC-CMs in response to AdCM and IL-6. Our study shows that hiPSC-CMs from normal and mPKP2 ACM lines exhibit distinct molecular and functional responses to paracrine factors, with differences in RNA expression and electrophysiology. These different responses to paracrine factors may contribute to arrhythmogenic propensity.

Abstract 4139187: Electrophysiological and Mechanical Characterization of Human Ventricular Myocardium from Patients with Primary or Secondary Cardiac Hypertrophy

Left-ventricular hypertrophy (LVH) is an adaptive condition to hemodynamic stress often involving the left ventricle (LV). This pathological condition is associated with clinical complications such as ventricular arrhythmias and diastolic dysfunction, the molecular and cellular mechanisms of which have been poorly investigated in the human heart. We collected myocardial samples from the upper interventricular septum of 132 patients with hypertrophic cardiomyopathy (HCM), 42 patients with aortic stenosis and severe LVH (AoS-LVH) and 12 non-failing non-hypertrophic patients with valve disease (NF-NH), who underwent myectomy operations at our cardiac surgery center. Samples were used to isolate single viable cardiomyocytes from the left ventricle to perform patch-clamp electrophysiological studies and intracellular calcium measurements with fluorescent dyes. Intact trabeculae were also dissected to perform isometric force measurements of electrically-stimulated twitches. Single-cell patch-clamp studies revealed a marked prolongation of action potential duration (APD) in HCM (N=82, mean APD at 90% repolarization=763±252ms at 0.5Hz) and AoS-LVH (N=22, APD90%=579±147ms) samples with respect to NF-NH (N=12, APD90%=447±88ms). In both HCM and AoS-LVH cardiomyocytes, APD prolongation was associated with increased late-Na + current with respect to NF-NH, while L-type Ca 2+ current was enlarged only in HCM samples. Ca 2+ -fluorescence studies revealed markedly slower Ca-transient (CaT) kinetics in myocardial samples from HCM (N=38, mean CaT 50% decay time at 0.5 Hz = 658±179ms) and AoS-LVH patients (N=9, CaT50%= 568±187ms), when compared with NF-NH samples (N=8, CaT50%=283±59ms), paralleled by elevated diastolic [Ca 2+ ]. Twitch force measurements in intact trabeculae revealed prolonged isometric contractions in HCM (N=78, overall twitch duration at 0.5Hz= 730±147ms) and in AoS-LVH patient-samples (N=24, TwD=669±116ms), as compared with NF-NH (N=7, TwD=511±73ms). Force-frequency relationship was flat in pathological samples, while NF-NH trabeculae showed a clear increase in twitch amplitude while increasing pacing rate to 2Hz. Our results suggest that the main features of functional cardiomyocyte remodeling (that is, changes in the expression and/or function of ion-channel and EC-coupling proteins) are qualitatively similar in primary vs. secondary LVH, albeit abnormalities are quantitatively more extensive in HCM samples.

Single cell multi-omics analysis unveils a distinct mechanism of exercise-mediated cardioprotection in ischemic cardiomyopathy

Abstract Background Exercise is pivotal in heart disease prevention, with proven cardioprotective effects in clinical trials. However, its precise molecular mechanisms remain elusive. Recent advancements in single-cell omics have revealed cellular heterogeneity within heart tissues, offering a deeper understanding of the pathophysiology of cardiac diseases. Purpose To investigate the exercise-induced physiological changes in heart tissue at the single-cell level and elucidate the molecular mechanisms underlying its cardioprotective effect on ischemic cardiomyopathy. Methods Murine myocardial infarction (MI) model was established by ligating the left ascending coronary artery, and a six-week voluntary wheel running exercise regimen was implemented to investigate the effect of aerobic exercise on ischemic cardiomyopathy. Integrated multi-omics analyses of single-cell DNA methylation profiling, single-nucleus assay for transposase-accessible chromatin sequencing (snATAC-seq) and single-nucleus RNA sequencing (snRNA-seq) were conducted to clarify the molecular mechanism of exercise-mediated cardioprotection at single-cell resolution. Overexpression and short hairpin RNA-mediated knockdown of gene X were conducted for murine MI model using cardiomyocyte-specific Myo-AAV2a vector. snRNA-seq of heart tissues from heart failure patients was performed to validate the clinical significance of the expression of gene X in cardiomyocytes. Results Exercise attenuates pathological cardiac remodeling, inducing physiological hypertrophy in non-infarcted areas while suppressing pathological remodeling of cardiomyocytes in infarct border zones. Single-cell epigenetic analysis unveiled intricate molecular mechanisms underlying exercise-induced transcriptome changes, providing insights into the gene regulatory networks modulated by exercise in the heart. In addition, integrated with snRNA-seq, we identified exercise-specific cardiomyocyte clusters, highlighting the substantial role of gene X in the molecular mechanism of exercise. Functional studies confirmed the essential role of gene X in exercise-induced cardioprotection, as its overexpression suppressed the adverse remodeling after MI and knockdown abolished the beneficial effects of exercise. Furthermore, snRNA-seq of heart failure patients revealed that higher expression of gene X was associated with ventricular reverse remodeling and favorable clinical outcomes, underscoring its significance in the pathophysiology of patients with heart failure. Conclusion Our study elucidates exercise-specific gene expression regulation networks in ischemic cardiomyopathy by unraveling the cellular heterogeneity and molecular changes associated with exercise. We identified gene X as a central player in exercise-mediated cardioprotection and further confirmed its significance in clinical settings, providing a potential therapeutic target for heart failure.

Cardiomyocyte Reduction of Hybrid/Complex N-Glycosylation in the Adult Causes Heart Failure With Reduced Ejection Fraction in the Absence of Cellular Remodeling.

Heart failure (HF) presents a massive burden to health care with a complex pathophysiology that results in HF with reduced left ventricle ejection fraction (EF) or HF with preserved EF. It has been shown that relatively modest changes in protein glycosylation, an essential posttranslational modification, are associated with clinical presentations of HF. We and others previously showed that such aberrant protein glycosylation in animal models can lead to HF. We develop and characterize a novel, tamoxifen-inducible, cardiomyocyte Mgat1 knockout mouse strain, achieved through deletion of Mgat1, alpha-1,3-mannosyl-glycoproten 2-beta-N-acetlyglucosaminyltransferase, which encodes N-acetylglucosaminyltransferase I. We investigate the role of hybrid/complex N-glycosylation in adult HFrEF pathogenesis at the ion channel, cardiomyocyte, tissue, and gross cardiac level. The data demonstrate successful reduction of N-acetylglucosaminyltransferase I activity and confirm that hybrid/complex N-glycans modulate gating of cardiomyocyte voltage-gated calcium channels. A longitudinal study shows that the tamoxifen-inducible, cardiomyocyte Mgat1 knockout mice present with significantly reduced systolic function by 28 days post induction that progresses into HFrEF by 8 weeks post induction, without significant ventricular dilation or hypertrophy. Further, there was minimal, if any, physiologic or pathophysiologic cardiomyocyte electromechanical remodeling or fibrosis observed before (10-21 days post induction) or after (90-130 days post induction) HFrEF development. The tamoxifen-inducible, cardiomyocyte Mgat1 knockout mouse strain created and characterized here provides a model to describe novel mechanisms and causes responsible for HFrEF onset in the adult, likely occurring primarily through tissue-level reductions in electromechanical activity in the absence of (or at least before) cardiomyocyte remodeling and fibrosis.

Repeat administration of human umbilical cord mesenchymal stem cells improves left ventricular diastolic function in mice with heart failure with preserved ejection fraction

Currently, no therapy is proven to effectively improve heart failure with preserved ejection fraction (HFpEF). Although stem cell therapy has demonstrated promising results in treating ischemic heart disease, the effectiveness of treating HFpEF with human umbilical cord mesenchymal stem cells (hucMSCs) remains unclear. To answer this question, we administered hucMSCs intravenously (i.v.), either once or repetitively, in a mouse model of HFpEF induced by a high-fat diet and NG-nitroarginine methyl ester hydrochloride. hucMSC treatment improved left ventricular diastolic dysfunction, reduced heart weight and pulmonary edema, and attenuated cardiac modeling (inflammation, interstitial fibrosis, and hypertrophy) in HFpEF mice. Repeat hucMSC administration had better outcomes than a single injection. In vitro, hucMSC culture supernatants reduced maladaptive remodeling in neonatal-rat cardiomyocytes. Ribonucleic acid sequencing and protein level analysis of left ventricle (LV) tissues suggested that hucMSCs activated the protein kinase B (Akt)/forkhead box protein O1 (FoxO1) signaling pathway to treat HFpEF. Inhibition of this pathway reversed the efficacy of hucMSC treatment. In conclusion, these findings indicated that hucMSCs could be a viable therapeutic option for HFpEF.

PFOS impairs cardiac function and energy metabolism under high-fat diet: Insights into role of circulating macrophage emphasized by exposure distribution

Per- and polyfluoroalkyl substances (PFAS), widely utilized in consumer products, have been linked to an increased risk of cardiovascular disease (CVD). With the increasing prevalence of high-fat diet, a common risk factor for CVD, the PFAS exposed populations who consume a high-fat diet will inevitably grow and may have a higher CVD risk. However, the potential toxic effect and mode of action remain elusive. We constructed a mouse model orally exposed to perfluorooctane sulfonate (PFOS), a prototypical PFAS, and fed a high-fat diet. PFOS exposure induced cardiomyopathy and structural abnormalities in the mice heart. Moreover, a characteristic of energy metabolism remodeling from aerobic to anaerobic process was observed. Interestingly, PFOS was rarely detected in heart but showed high level in serum, suggesting an indirect route of action for PFOS-caused cardiac toxicity. We further demonstrated that PFOS-caused circulating inflammation promoted metabolic remodeling and contractile dysfunction in cardiomyocytes. Wherein, PFOS stimulated the release of IL-1β from circulating proinflammatory macrophages mediated by NF-κB and caspase-1. This study provides valuable data on PFAS-induced cardiac risks associated with exposed populations with increasing high-fat diet consumption, highlighting the significance of indirect pathways in PFOS's impact on the heart, based on the distribution of internal exposure.

Expression of Osteopontin and Gremlin 1 Proteins in Cardiomyocytes in Ischemic Heart Failure.

A relevant role of osteopontin (OPN) and gremlin 1 (Grem1) in regulating cardiac tissue remodeling and formation of heart failure (HF) are documented, with the changes of OPN and Grem1 levels in blood plasma due to acute ischemia, ischemic heart disease-induced advanced HF or dilatative cardiomyopathy being the primary focus in most of these studies. However, knowledge on the early OPN and Grem1 proteins expression changes within cardiomyocytes during remodeling due to chronic ischemia remains insufficient. The aim of this study was to determine the OPN and Grem1 proteins expression changes in human cardiomyocytes at different stages of ischemic HF. A semi-quantitative immunohistochemical analysis was performed in 105 myocardial tissue samples obtained from the left cardiac ventricles. Increased OPN immunostaining intensity was already detected in the stage A HF group, compared to the control group (p < 0.001), and continued to increase in the stage B HF (p < 0.001), achieving the peak of immunostaining in the stages C/D HF group (p < 0.001). Similar data of Grem1 immunostaining intensity changes in cardiomyocytes were documented. Significantly positive correlations were detected between OPN, Grem1 expression in cardiomyocytes and their diameter as well as the length, in addition to positive correlation between OPN and Grem1 expression changes within cardiomyocytes. These novel findings suggest that OPN and Grem1 contribute significantly to reorganization of cellular geometry from the earliest stage of cardiomyocyte remodeling, providing new insights into the ischemic HF pathogenesis.

Dietary Branched Chain Amino Acids Modify Post-Infarct Cardiac Remodeling and Function in the Murine Heart.

Branch-chain amino acids (BCAA) are markedly elevated in the heart following myocardial infarction (MI) in both humans and animal models. Nevertheless, it remains unclear whether dietary BCAA levels influence post-MI remodeling. We hypothesize that lowering dietary BCAA levels prevents adverse cardiac remodeling after MI. To assess whether altering dietary BCAA levels would impact circulating BCAA concentrations, mice were fed a low (1/3×), normal (1×), or high (2×) BCAA diet over a 7-day period. We found that mice fed the low BCAA diet had >2-fold lower circulating BCAA concentrations when compared with normal and high BCAA diet feeding strategies; notably, the high BCAA diet did not further increase BCAA levels over the normal chow diet. To investigate the impact of dietary BCAAs on cardiac remodeling and function after MI, male and female mice were fed either the low or high BCAA diet for 2 wk prior to MI and for 4 wk after MI. Although body weights or heart masses were not different in female mice fed the custom diets, male mice fed the high BCAA diet had significantly higher body and heart masses than those on the low BCAA diet. Echocardiographic assessments revealed that the low BCAA diet preserved stroke volume and cardiac output for the duration of the study, while the high BCAA diet led to progressive decreases in cardiac function. Although no discernible differences in cardiac fibrosis, scar collagen topography, or cardiomyocyte cross-sectional area were found between the dietary groups, male mice fed the high BCAA diet showed longer cardiomyocytes and higher capillary density compared with the low BCAA group. Provision of a diet low in BCAAs to mice mitigates eccentric cardiomyocyte remodeling and loss of cardiac function after MI, with dietary effects more prominent in males.

Global ischemia induces stemness and dedifferentiation in human adult cardiomyocytes after cardiac arrest

Global ischemia has been shown to induce cardiac regenerative response in animal models. One of the suggested mechanisms behind cardiac regeneration is dedifferentiation of cardiomyocytes. How human adult cardiomyocytes respond to global ischemia is not fully known. In this study, biopsies from the left ventricle (LV) and the atrioventricular junction (AVj), a potential stem cell niche, were collected from multi-organ donors with cardiac arrest (N = 15) or without cardiac arrest (N = 6). Using immunohistochemistry, we investigated the expression of biomarkers associated with stem cells during cardiomyogenesis; MDR1, SSEA4, NKX2.5, and WT1, proliferation markers PCNA and Ki67, and hypoxia responsive factor HIF1α. The myocyte nuclei marker PCM1 and cardiac Troponin T were also included. We found expression of cardiac stem cell markers in a subpopulation of LV cardiomyocytes in the cardiac arrest group. The same cells showed a low expression of Troponin T indicating remodeling of cardiomyocytes. No such expression was found in cardiomyocytes from the control group. Stem cell biomarker expression in AVj was more pronounced in the cardiac arrest group. Furthermore, co-expression of PCNA and Ki67 with PCM1 was only found in the cardiac arrest group in the AVj. Our results indicate that a subpopulation of human cardiomyocytes in the LV undergo partial dedifferentiation upon global ischemia and may be involved in the cardiac regenerative response together with immature cardiomyocytes in the AVj.

Activation of Exchange Proteins directly Activated by cAMP (EPAC) promotes electrophysiological remodeling and arrhythmogenic activity in human atrial cardiomyocytes

Activation of Exchange Proteins directly Activated by cAMP (EPAC) promotes electrophysiological remodeling and arrhythmogenic activity in human atrial cardiomyocytes

Spatial relationship between left peri-atrial fat with underlying arrhythmogenic substrate in patients with atrial fibrillation - innocent bystander or culprit?

Abstract Introduction Peri-atrial fat may have pro-inflammatory and pro-fibrotic effects on atrial myocardium and increase the risk of developing atrial fibrillation. Consistent with prior evidence, we have previously shown that peri-atrial fat volume, but not fat attenuation (an imaging biomarker of inflammation), was associated with prevalent atrial fibrillation. Whether this association is secondary to "outside-to-inside" tissue cross talk with local adverse electrical remodelling of adjacent atrial cardiomyocytes is not known. Purpose In this novel proof of concept study, we aimed to identify a spatial relationship between left peri-atrial fat and potentially arrhythmogenic substrate (low voltage areas and slow conduction pathways) in the left atrial myocardium. Methods Contrast-enhanced cardiac computed tomography (CT) imaging and electroanatomic mapping, during coronary sinus pacing, were performed pre-ablation in atrial fibrillation patients (n=27). The left atrium and surrounding peri-atrial fat were segmented and quantified using seg3D2 and CEMRGapp. We performed registration of the electroanatomic map onto the CT-derived left atrial mesh using OpenEP and EP Workbench. Mean fat volume and attenuation around each electroanatomic point (within a 3mm radial region of interest) were correlated with local voltage and conduction velocity. Results A total of 24,839 electroanatomic points were registered onto the 3D CT-derived left atrial mesh, with a median of 935 points (range 673 to 1150) per patient. The average bipolar voltage and conduction velocity in the left atrium was 1.92±1.91 mV and 0.66±0.47 ms-1 respectively. In comparison to areas with little/no surrounding periatrial fat (Quartile 1, ≤0.93 mm3 fat per electroanatomic point), areas with the highest burden of fat (Quartile 4, ≥17.6 mm3) had significantly lower bipolar voltage (1.69±1.7 vs 2.09±2.0 mV, p&amp;lt;0.001) and conduction velocity (0.627±0.43 vs 0.700±0.47 ms-1, p&amp;lt;0.001). However, the overall correlation between periatrial fat volume with bipolar voltage (r=-0.06, p&amp;lt;0.001) and conduction velocity (r=-0.07, p&amp;lt;0.001) was weak. High, not low, fat attenuation (Quartile 4; &amp;gt;-46.5HU vs Quartile 1; ≤-75.5HU) was associated with increased bipolar voltage (2.23±2.1 vs 1.63±1.6 mV) and conduction velocity (0.703±0.42 vs 0.623±0.39 ms-1 respectively). Conclusion There is a weak correlation between periatrial fat and localized adverse electrical remodelling. The relationship between fat attenuation and electrophysiological properties was inverted. These findings confirm an association between peri-atrial fat burden but call question as to whether peri-atrial fat inflammation is implicated in atrial fibrillation pathogenesis.

Supersulfide catabolism participates in maladaptive remodeling of cardiac cells

The atrophic myocardium resulting from mechanical unloading and nutritional deprivation is considered crucial as maladaptive remodeling directly associated with heart failure, as well as interstitial fibrosis. Conversely, myocardial hypertrophy resulting from hemodynamic loading is perceived as compensatory stress adaptation. We previously reported the abundant presence of highly redox-active polysulfide molecules, termed supersulfide, with two or more sulfur atoms catenated in normal hearts, and the supersulfide catabolism in pathologic hearts after myocardial infarction correlated with worsened prognosis of heart failure. However, the impact of supersulfide on myocardial remodeling remains unclear. Here, we investigated the involvement of supersulfide metabolism in cardiomyocyte remodeling, using a model of adenosine 5′-triphosphate (ATP) receptor-stimulated atrophy and endothelin-1 receptor-stimulated hypertrophy in neonatal rat cardiomyocytes. Results revealed contrasting changes in intracellular supersulfide and its catabolite, hydrogen sulfide (H2S), between cardiomyocyte atrophy and hypertrophy. Stimulation of cardiomyocytes with ATP decreased supersulfide activity, while H2S accumulation itself did not affect cardiomyocyte atrophy. This supersulfide catabolism was also involved in myofibroblast formation of neonatal rat cardiac fibroblasts. Thus, unraveling supersulfide metabolism during myocardial remodeling may lead to the development of novel therapeutic strategies to improve heart failure.

Modeling cardiomyocyte signaling and metabolism predicts genotype-to-phenotype mechanisms in hypertrophic cardiomyopathy

Familial hypertrophic cardiomyopathy (HCM) is a significant precursor of heart failure and sudden cardiac death, primarily caused by mutations in sarcomeric and structural proteins. Despite the extensive research on the HCM genotype, the complex and context-specific nature of many signaling and metabolic pathways linking the HCM genotype to phenotype has hindered therapeutic advancements for patients. Here, we have developed a computational model of HCM encompassing cardiomyocyte signaling and metabolic networks and their associated interactions. Utilizing a stochastic logic-based ODE approach, we linked cardiomyocyte signaling to the metabolic network through a gene regulatory network and post-translational modifications. We validated the model against published data on activities of signaling species in the HCM context and transcriptomes of two HCM mouse models (i.e., R403Q-αMyHC and R92W-TnT). Our model predicts that HCM mutation induces changes in metabolic functions such as ATP synthase deficiency and a transition from fatty acids to carbohydrate metabolism. The model indicated major shifts in glutamine-related metabolism and increased apoptosis after HCM-induced ATP synthase deficiency. We predicted that the transcription factors STAT, SRF, GATA4, TP53, and FoxO are the key regulators of cardiomyocyte hypertrophy and apoptosis in HCM in alignment with experiments. Moreover, we identified shared (e.g., activation of PGC1α by AMPK, and FHL1 by titin) and context-specific mechanisms (e.g., regulation of Ca2+ sensitivity by titin in HCM patients) that may control genotype-to-phenotype transition in HCM across different species or mutations. We also predicted potential combination drug targets for HCM (e.g., mavacamten plus ROS inhibitors) preventing or reversing HCM phenotype (i.e., hypertrophic growth, apoptosis, and metabolic remodeling) in cardiomyocytes. This study provides new insights into mechanisms linking genotype to phenotype in familial hypertrophic cardiomyopathy and offers a framework for assessing new treatments and exploring variations in HCM experimental models.

Subcutaneous BNP Injections in Rabbits: A Novel Approach to Mitigate Myocardial Remodeling in Atrial Fibrillation.

Atrial fibrillation (AF) is a prevalent cardiac arrhythmia associated with increased morbidity and mortality, highlighting the need for novel therapeutic strategies. This study aimed to evaluate the effects of B-type natriuretic peptide (BNP) on cardiac structural remodeling in a rabbit model of AF. Rabbits were subjected to rapid pacing to induce an AF model, and BNP was delivered subcutaneously at a dose of 20 μg/kg/d twice per day for three weeks. Electrophysiological measurements were taken to assess the AF induction rate and atrial effective refractory period (AERP), while echocardiographic measurements evaluated left atrial size and function. Histological examinations included hematoxylin and eosin (H&E) staining and Masson's trichrome staining to observe myocardial tissue structure and fibrosis. The ultrastructure of myocardial tissue was observed using a transmission electron microscope. The study found that BNP treatment significantly reduced the AF induction rate (p < 0.001), improved AERP (p < 0.001), and ameliorated structural and functional changes in the left atrial (p < 0.05). Histological analysis demonstrated decreased myocardial fibrosis post-BNP treatment (p < 0.05). Results also showed that BNP attenuated the cardiomyocyte remodeling caused by AF, as evidenced by significant effects on the expression levels of transforming growth factor-β 1 (TGF-β1), tissue inhibitors of matrix metalloproteinases 1 (TIMP1), matrix metalloproteinase 9 (MMP9), and Collagen I/III (p < 0.05). These findings suggest that subcutaneous injections of BNP may serve as an effective therapeutic agent in mitigating cardiac structural remodeling in AF, offering significant clinical implications for treating this condition.

COX6A2 deficiency leads to cardiac remodeling in human pluripotent stem cell-derived cardiomyocytes

BackgroundCardiac remodeling is the initiating factor for the development of heart failure, which can result from various cardiomyopathies. Cytochrome c oxidase subunit 6A2 (COX6A2) is one of the components of cytochrome c oxidase that drives oxidative phosphorylation. The pathogenesis of myocardial remodeling caused by COX6A2 deficiency in humans remains unclear because there are no suitable research models. In this study, we established a COX6A2-deficient human cardiac myocyte (CM) model that mimics the human COX6A2 homozygous mutation and determined the effects of COX6A2 dysfunction and its underlying mechanism.MethodsA human COX6A2 homozygous knockout cardiomyocyte model was established by combining CRISPR/Cas9 gene editing technology and hiPSC-directed differentiation technology. Cell model phenotypic assays were done to characterize the pathological features of the resulting COX6A2-deficient cardiomyocytes.ResultsCOX6A2 gene knockout did not affect the pluripotency and differentiation efficiency of hiPSCs. Myocardial cells with a COX6A2 gene knockout showed abnormal energy metabolism, increased oxidative stress levels, abnormal calcium transport activity, and decreased contractility. In addition, L-carnitine and trimetazidine significantly improved energy metabolism in the COX6A2-deficient human myocardial model.ConclusionsWe have established a COX6A2-deficient human cardiomyocyte model that exhibits abnormal energy metabolism, elevated oxidative stress levels, abnormal calcium transport, and reduced contractility. This model represents an important tool to gain insight into the mechanism of action of energy metabolism disorders resulting in myocardial remodeling, elucidate the gene-phenotype relationship of COX6A2 deficiency, and facilitate drug screening.

Beyond Glycemic Control: Mechanistic Insights Into SGLT-2 Inhibitors in Heart Failure Management.

Heart failure is a common and clinically significant cardiac condition that causes significant morbidity and mortality in the United States. Diabetes and hypertension are 2 of the most common comorbidities associated with heart failure. Other risk factors for heart failure include smoking, obesity, and intrinsic cardiac diseases such as myocardial infarction and valvular pathologies. All of these conditions, to some extent, cause remodeling within the cardiomyocyte, which eventually leads to the development of congestive heart failure. Over the years, using diuretics and medications that inhibit the Renin-Angiotensin-Aldosterone System has been the traditional treatment for congestive heart failure. But in recent years studies in the diabetic population revealed that sodium-glucose cotransporter-2 inhibitors had a negative impact on the remodeling of cardiomyocytes. In this review, we discuss the numerous molecular mechanisms by which these recently developed medicines inhibit remodeling in cardiomyocytes, independent of their intended effect of decreasing blood glucose levels. Furthermore, it emphasizes the use of these drugs in diabetic as well as non-diabetic patients as a promising adjunct to ongoing heart failure treatment.

HIPSC model reveals M1 macrophages cause atrial arrhythmia correlated to electrophysiological remodelling of atrial cardiomyocytes in 2D and 3D engineered heart tissue

Abstract Atrial fibrillation (AF) is the most common sustained arrhythmia with an estimated prevalence of 1.5–2%. Current treatments lack effectiveness and do not prevent recurrence. Inflammation is reported in AF patients, however, a causal connection remains elusive. In this study, we investigated the arrhythmic effects of pro-inflammatory macrophages (M1) on human induced pluripotent stem cell (hiPSC)-derived atrial cardiomyocytes (aCM), to better understand their role in AF. Macrophages are known to play a role in cardiac electrophysiology, but their role in arrhythmia is unclear. Three healthy hiPSC lines were differentiated to aCM and M1. Multi-electrode array recordings of isogenic, 2D cocultures of M1 and aCM showed a significant increase in beat rate irregularity compared to control conditions (P&amp;lt;0.001). Furthermore, spike amplitude of aCM and M1 cocultures was significantly decreased (P&amp;lt;0.001). Arrhythmias occurred only after activation of macrophages in the coculture. Addition of anti-inflammatory glucocorticoids significantly reduced beat irregularity in aCM and M1 cocultures compared to vehicle (1.9-fold decrease for Hydrocortisone, P&amp;lt;0.005) further supporting macrophage mediated inflammation to be the cause of the arrhythmia. RNA sequencing of aCM and M1 cocultures revealed aberrant expression of arrhythmia associated cardiac sodium and atrial potassium ion channels (SCN5A, KCNA5). Normal expression was restored through hydrocortisone addition. In addition, inflammation-induced arrhythmia was observed in 3D engineered heart tissues containing hiPSC derived aCM, M1 and cardiac fibroblasts. Tissues showed a significant increase in beating irregularity (P&amp;lt;0.005) compared to controls and had a significant, median reduction (&amp;gt;30%) of contraction amplitude (P&amp;lt;0.05). Our findings suggest a causal relationship between M1 and the occurrence of atrial arrhythmia. The reduction of arrhythmia using glucocorticoids correlates to clinical observations, that show their use being linked to reduced post operative AF burden. These results strongly support the relevance of the proposed hiPSC coculture model and elucidate a new potential AF mechanism.

Characterization of atrial cardiomyopathy subtypes - A cellular electrophysiological comparison and evaluation of appropriate treatment options

Abstract Background Atrial fibrillation occurs in the context of atrial remodeling processes which are the result of an underlying atrial cardiomyopathy (AC). Insufficient understanding of the pathophysiological mechanisms behind AC contributes significantly to the fact that current clinical strategies for the treatment of atrial fibrillation are often ineffective. A systematic investigation of these cellular remodeling processes in the context of the various cardiac diseases underlying AC is still missing. Purpose The aim of this study was to characterize different subtypes of AC associated with common cardiac disease entities by systematic cellular electrophysiological characterization of the atria in combination with molecular and structural investigations. Methods For a comprehensive analysis of the molecular changes associated with AC, we characterized several mouse models of common heart diseases, including models for dilated cardiomyopathy (DCM), HFpEF, mitral regurgitation and immune checkpoint inhibitor (ICI-)mediated myocarditis. Patch clamp experiments were performed on isolated atrial cardiomyocytes to study atrial action potentials (aAP) and different ion currents contributing to the aAP. The cellular electrophysiological parameters of the different models were correlated to clinical parameters (ecg, echocardiography of the atria) of the mouse models and with data from RNA sequencing of the mice’ atria. Results Patch clamp measurements performed on isolated left and right atrial cardiomyocytes revealed distinct differences among the examined models. In all pathophysiological models, the aAP was significantly shorter than in the corresponding wild type mice. The different ion current components we measured various changes in potassium, sodium and calcium currents. The repolarizing TASK-1 potassium current was significantly increased in all models. The DCM model caused by an R636Q mutation in the RBM20 gene showed the most severe changes in cellular electrophysiology. Considering the detected atrial changes, we investigated the effects of SGLTi on atrial cardiomyocytes of the different models. When elevated concentrations of dapa-, empa- and sotagliflozin were administrated on atrial cardiomyocytes, a class-I-antiarrhythmic effect with reduced aAP inducibility and changes in the aAP duration could be observed. Conclusion Characterization of murine models of cardiac disease with respect to classification of AC subtypes revealed various electrical remodeling processes at the level of ion currents involved in aAP formation. A potent inductor of atrial proarrhythmogenity in the AC subtypes was an aAP shortening caused by an increase in repolarizing potassium currents, mediated especially by TASK-1. The most severe electrical remodeling in atria cardiomyocytes was observed in the RBM20-mutant model (DCM). SGLTi exhibit anti-arrhythmic effects in different murine disease models and may provide future treatment options for patients with AC.

Remodeling of Cardiomyocytes: Study of Morphological Cellular Changes Preceding Symptomatic Ischemic Heart Failure.

Although major pathogenesis mechanisms of heart failure (HF) are well established, the significance of early (mal)adaptive structural changes of cardiomyocytes preceding symptomatic ischemic HF remains ambiguous. The aim of this study is to present the morphological characterization of changes in cardiomyocytes and their reorganization of intermediate filaments during remodeling preceding symptomatic ischemic HF in an adult human heart. A total of 84 myocardial tissue samples from middle-left heart ventricular segments were analyzed histomorphometrically and immunohistochemically, observing the cardiomyocyte's size, shape, and desmin expression changes in the remodeling process: Stage A of HF, Stage B of HF, and Stages C/D of HF groups (ACC/AHA classification). Values p < 0.05 were considered significant. The cellular length, diameter, and volume of Stage A of HF increased predominantly by the diameter vs. the control group (p < 0.001) and continued to increase in Stage B of HF in a similar pattern (p < 0.001), increasing even more in the C/D Stages of HF predominantly by length (p < 0.001). Desmin expression was increased in Stage A of HF vs. the control group (p < 0.001), whereas it was similar in Stages A and B of HF (p > 0.05), and most intense in Stages C/D of HF (p < 0.001). Significant morphological changes of cardiomyocytes and their cytoskeletal reorganization were observed during the earliest remodeling events preceding symptomatic ischemic HF.

Prematurity and Low Birth Weight and Their Impact on Childhood Growth Patterns and the Risk of Long-Term Cardiovascular Sequelae.

Preterm birth (before 37 completed weeks of gestation) is a global health problem, remaining the main reason for neonatal mortality and morbidity. Improvements in perinatal and neonatal care in recent decades have been associated with a higher survival rate of extremely preterm infants, leading to a higher risk of long-term sequelae in this population throughout life. Numerous surveillance programs for formerly premature infants continue to focus on neurodevelopmental disorders, while long-term assessment of the impact of preterm birth and low birth weight on child growth and the associated risk of cardiovascular disease in young adults is equally necessary. This review will discuss the influence of prematurity and low birth weight on childhood growth and cardiovascular risk in children, adolescents and young adults. The risk of cardiovascular and metabolic disorders is increased in adult preterm survivors. In early childhood, preterm infants may show elevated blood pressure, weakened vascular growth, augmented peripheral vascular resistance and cardiomyocyte remodeling. Increased weight gain during the early postnatal period may influence later body composition, promote obesity and impair cardiovascular results. These adverse metabolic alterations contribute to an increased risk of cardiovascular incidents, adult hypertension and diabetes. Preterm-born children and those with fetal growth restriction (FGR) who demonstrate rapid changes in their weight percentile should remain under surveillance with blood pressure monitoring. A better understanding of lifelong health outcomes of preterm-born individuals is crucial for developing strategies to prevent cardiovascular sequelae and may be the basis for future research to provide effective interventions.