• 3D models
• biomimetic scaffolds
• cardiac fibrosis
• cardiac tissue engineering
• cell maturation
• extracellular matrix
• heart failure
• in vitro modeling
• myocardial remodeling
• translational research

• Animals
• Humans
• Open Reading Frames/genetics
• Protein Biosynthesis/genetics
• Evolution, Molecular
• Myocytes, Cardiac/metabolism
• Species Specificity
• Transcriptome
• Gene Expression Profiling/methods
• Induced Pluripotent Stem Cells/metabolism
• Ribosomes/metabolism
• Ribosomes/genetics
• Primates/genetics
• Cells, Cultured

• CIPA
• electrophysiology
• experimental reproducibility
• hiPSC-CMs
• microelectrode array

• Myocytes, Cardiac/drug effects
• Myocytes, Cardiac/physiology
• Humans
• Induced Pluripotent Stem Cells/drug effects
• Reproducibility of Results
• Time Factors
• Action Potentials/drug effects
• Cells, Cultured
• Isoproterenol/pharmacology
• Heart Rate/drug effects
• Microelectrodes
• Cell Line
• Cardiotoxicity

• 23PRE1021149 American Heart Association (AHA)
• R01 HD108839 NICHD NIH HHS
• F31HL165818 HHS | National Institutes of Health (NIH)
• R01HD108839 HHS | National Institutes of Health (NIH)
• F31 HL165818 NHLBI NIH HHS
• Children’s National Heart Institute
• Children’s Research Institute

• Arrythmia
• cardiomyocytes
• disease modeling
• drug development
• human induced pluripotent stem cells

• Humans
• Induced Pluripotent Stem Cells
• Arrhythmias, Cardiac/drug therapy
• Arrhythmias, Cardiac/physiopathology
• Drug Discovery/methods
• Myocytes, Cardiac/drug effects
• Animals
• Cell Differentiation
• Drug Development/methods
• Machine Learning
• Gene Editing/methods
• Models, Biological
• Anti-Arrhythmia Agents/pharmacology

• P41 EB027062 NIBIB NIH HHS
• R01 HL166387 NHLBI NIH HHS

• cardiac regeneration
• induced pluripotent stem cells
• mesenchymal stem cells
• myocardial ischemia

• Humans
• Heart
• Heart Diseases/therapy
• Heart Diseases/metabolism
• Stem Cell Transplantation
• Regeneration
• Embryonic Stem Cells

• cardiomyocyte proliferation
• heart regeneration
• immune system
• stem cells

• Animals
• Adult
• Humans
• Myocytes, Cardiac/physiology
• Zebrafish/physiology
• Cell Proliferation
• Myocardium
• Research
• Mammals

• R01 HL160819 NHLBI NIH HHS
• R16GM14664 NIH HHS
• R16 GM146643 NIGMS NIH HHS
• R01HL157280 NIH HHS
• R01 HL138456 NHLBI NIH HHS
• R01HL138456 NIH HHS

• cardiomyocytes
• endothelial cells
• endothelial dysfunction
• heart disease
• paracrine signaling

• R01 HL161090 NHLBI NIH HHS
• R21 HL152367 NHLBI NIH HHS
• T32 GM144273 NIGMS NIH HHS

• F31 HL165818 NHLBI NIH HHS

• Cardiac function
• Cell therapy
• Conduction
• Corticosteroids
• Endocrine system
• Hormone-based therapy
• IGF1
• Metabolic switch
• Sarcomere maturation
• Thyroid hormone

• Humans
• Myocytes, Cardiac
• Heart
• Cell Differentiation
• Hormones/pharmacology

• Forschungsinstitut für Nutztierbiologie (FBN) (2113)

• R01 HL159094 NHLBI NIH HHS

• Lmnb2
• cardiomyocyte maturation
• human fetal heart
• human iPSCs
• lamin B2
• proliferation
• single-cell RNA-seq

• cardiomyocyte
• iPSC-CMs
• micropatterned iPSC-CMs
• micropatterning

• Adult
• Animals
• Humans
• Induced Pluripotent Stem Cells
• Myocytes, Cardiac
• Laminin/pharmacology
• Silicones/metabolism

• R00 HL133482 NHLBI NIH HHS

Cardiac pathological hypertrophy is the major risk factor that usually progresses to heart failure. We hypothesized that extracellular vesicles (EVs), known to act as important mediators in regulating physiological and pathological functions, could have the potential to reduce the cardiac hypertrophy and the ensuing cardiovascular diseases. Herein, the effects of mesenchymal stem cell-derived extracellular vesicles (EV-MSCs) on cardiac hypertrophy were investigated. EVs were isolated from the secretome of human adipose tissue-derived stem cells (EV-ADSCs) or bone marrow-derived stem cells (EV-BMMSCs). Human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) were stimulated with AngII and TGF-β1, in absence or presence of EVs. The results showed that exposure of hiPSC-CMs to AngII and TGF-β1 generated in vitro model of hypertrophic cardiomyocytes characterized by increases in surface area, reactive oxygen species production, protein expression of cardiac-specific biomarkers atrial natriuretic factor, migration inhibitory factor, cTnI, COL1A1, Cx43, α-SMA and signalling molecules SMAD2 and NF-kBp50. The presence of EV-ADSCs or EV-BMMSCs in the hiPSC-CM culture along with hypertrophic stimuli reduced the protein expressions of hypertrophic specific markers (ANF, MIF, cTnI, COL1A1) and the gene expressions of IL-6 molecule involved in inflammatory process associated with cardiac hypertrophy and transcription factors SMAD2, SMAD3, cJUN, cFOS with role in cardiomyocyte hypertrophic response induced by AngII and TGF-β1. The EV-ADSCs were more effective in reducing the protein expressions of hypertrophic and inflammatory markers, while EV-BMMSCs in reducing the gene expressions of transcription factors. Notably, neither EV-ADSCs nor EV-BMMSCs induced significant changes in cardiac biomarkers Cx43, α-SMA and fibronectin. These different effects of stem cell-derived EVs could be attributed to their miRNA content: some miRNAs (miR-126-3p, miR-222-3p, miR-30e-5p, miR-181b-5p, miR-124-3p, miR-155-5p, miR-210-3p hsa-miR-221-3p) were expressed in both types of EVs and others only in EV-ADSCs (miR-181a-5p, miR-185-5p, miR-21-5p) or in EV-BMMSCs (miR-143-3p, miR-146a-5p, miR-93-5p), some of these attenuating the cardiac hypertrophy while others enhance it. In conclusion, in hiPSC-CMs the stem cell-derived EVs through their cargo reduced the expression of hypertrophic specific markers and molecules involved in inflammatory process associated with cardiac hypertrophy. The data suggest the EV potential to act as therapeutic mediators to reduce cardiac hypertrophy and possibly the subsequent cardiovascular events.

• Unitatea Executiva pentru Finantarea Invatamantului Superior, a Cercetarii, Dezvoltarii si Inovarii

Diabetes is a global epidemic, with cardiovascular disease being the leading cause of death in diabetic patients. There is a pressing need for an in vitro model to aid understanding of the mechanisms driving diabetic heart disease, and to provide an accurate, reliable tool for drug testing. Human induced-pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have potential as a disease modelling tool. There are several factors that drive molecular changes inside cardiomyocytes contributing to diabetic cardiomyopathy, including hyperglycaemia, lipotoxicity and hyperinsulinemia. Here we discuss these factors and how they can be seen in animal models and utilised in cell culture to mimic the diabetic heart. The use of human iPSC-CMs will allow for a greater understanding of disease pathogenesis and open up new avenues for drug testing.

• 3D cardiac organoids
• animal models
• cardiomyocytes
• diabetes
• diabetic cardiomyopathy
• engineered heart tissue
• environmental factors
• heart disease
• hiPSCs
• in vitro disease modelling
• maturation
• metabolism

• cell signaling
• hiPSC-derived cardiomyocyte
• mTOR pathway
• preterm heart
• transcriptional regulation

• Canadian Institutes of Health Research
• Stem Cell Network

One of the obstacles in studying the pathogenesis of hypertrophic cardiomyopathy (HCM) is the poor availability of myocardial tissue samples at the early stages of disease development. This has been addressed by the advent of induced pluripotent stem cells (iPSCs), which allow us to differentiate patient-derived iPSCs into cardiomyocytes (iPSC-CMs) in vitro. In this review, we summarize different approaches to establishing iPSC models and the application of genome editing techniques in iPSC. Because iPSC-CMs cultured at the present stage are immature in structure and function, researchers have attempted several methods to mature iPSC-CMs, such as prolonged culture duration, and mechanical and electrical stimulation. Currently, many researchers have established iPSC-CM models of HCM and employed diverse methods for performing measurements of cellular morphology, contractility, electrophysiological property, calcium handling, mitochondrial function, and metabolism. Here, we review published results in humans to date within the growing field of iPSC-CM models of HCM. Although there is no unified consensus, preliminary results suggest that this approach to modeling disease would provide important insights into our understanding of HCM pathogenesis and facilitate drug development and safety testing.

• Disease modeling
• Hypertrophic cardiomyopathy
• Induced pluripotent stem cells
• iPSC-derived cardiomyocytes

• actin
• chromatin
• desmin
• phenotype
• sarcomere

• Cardiac tissue engineering
• Cardiotoxicity
• Drug screening
• Pluripotent stem cells

• Arrhythmias, Cardiac/chemically induced
• Cell Differentiation
• Drug Development
• Humans
• Induced Pluripotent Stem Cells
• Myocytes, Cardiac/physiology
• Pluripotent Stem Cells
• Tissue Engineering

• P50 AR065139 NIAMS NIH HHS
• R01 AR076978 NIAMS NIH HHS
• R01 HL149734 NHLBI NIH HHS
• R03 DE029827 NIDCR NIH HHS
• National Science Foundation
• National Institutes of Health
• Institute for Stem Cell and Regenerative Medicine, University of Washington (US)
• Senator Paul D Wellstone Muscular Dystrophy Cooperative Research Center
• Jesse's Journey Foundation (US)

One of the major goals in cardiac regeneration research is to replace lost ventricular tissue with new cardiomyocytes. However, cardiomyocyte proliferation drops to low levels in neonatal hearts and is no longer efficient in compensating for the loss of functional myocardium in heart disease. We generated a human induced pluripotent stem cell (iPSC)-derived cardiomyocyte-specific cell cycle indicator system (TNNT2-FUCCI) to characterize regular and aberrant cardiomyocyte cycle dynamics. We visualized cell cycle progression in TNNT2-FUCCI and found G2 cycle arrest in endoreplicating cardiomyocytes. Moreover, we devised a live-cell compound screening platform to identify pro-proliferative drug candidates. We found that the alpha-adrenergic receptor agonist clonidine induced cardiomyocyte proliferation in vitro and increased cardiomyocyte cell cycle entry in neonatal mice. In conclusion, the TNNT2-FUCCI system is a versatile tool to characterize cardiomyocyte cell cycle dynamics and identify pro-proliferative candidates with regenerative potential in the mammalian heart.

• Vetenskapsr#x000E5;det
• Fondation Leducq
• Ragnar Söderbergs stiftelse

The left atrial appendage (LAA) of the adult heart has been shown to contain cardiac and myeloid progenitor cells. The resident myeloid progenitor population expresses an array of pro-regenerative paracrine factors. Cardiac constructs have been shown to inhibit deleterious remodeling of the heart using physical support. Due to these aspects, LAA holds promise as a regenerative transplant. LAAs from adult mT/mG mice were transplanted to the recipient 129X1-SvJ mice simultaneously as myocardial infarction (MI) was performed. A decellularized LAA patch was implanted in the control group. Two weeks after MI, the LAA patch had integrated to the ventricular wall, and migrated cells were seen in the MI area. The cells had two main phenotypes: small F4/80+ cells and large troponin C+ cells. After follow-up at 8 weeks, the LAA patch remained viable, and the functional status of the heart improved. Cardiac echo demonstrated that, after 6 weeks, the mice in the LAA-patch-treated group showed an increasing and statistically significant improvement in cardiac performance when compared to the MI and MI + decellularized patch controls. Physical patch-support (LAA and decellularized LAA patch) had an equal effect on the inhibition of deleterious remodeling, but only the LAA patch inhibited the hypertrophic response. Our study demonstrates that the LAA transplantation has the potential for use as a treatment for myocardial infarction. This method can putatively combine cell therapy (regenerative effect) and physical support (inhibition of deleterious remodeling).

• adult stem cells
• atrial appendage
• heart failure
• macrophages
• tissue transplant

Medical research in the recent years has achieved significant progress due to the increasing prominence of organoid technology. Various developed tissue organoids bridge the limitations of conventional 2D cell culture and animal models by recapitulating in vivo cellular complexity. Current 3D cardiac organoid cultures have shown their utility in modelling key developmental hallmarks of heart organogenesis, but the complexity of the organ demands a more versatile model that can investigate more fundamental parameters, such as structure, organization and compartmentalization of a functioning heart. This review will cover the prominence of cardiac organoids in recent research, unpack current in vitro 3D models of the developing heart and look into the prospect of developing physiologically appropriate cardiac organoids with translational applicability. In addition, we discuss some of the limitations of existing cardiac organoid models in modelling embryonic development of the heart and manifestation of cardiac diseases.

• biomaterials
• cardiovascular disease modelling
• drug screening
• embryonic development
• organoid systems
• stem cell

• cardiac disease modeling
• functional proteomics
• hypertrophic cardiomyopathy
• mass spectrometry

• Animals
• Cardiomyopathy, Hypertrophic/metabolism
• Disease Models, Animal
• Disease Progression
• Humans
• In Vitro Techniques
• Mass Spectrometry
• Phosphoproteins/analysis
• Phosphorylation
• Proteomics/methods
• Systems Biology

• Mass Spectrometry-Based Identification of Paracrine Signals Driving Fibrosis in a New Model of Hypertrophic Cardiomyopathy BioDesign Center
• Mass Spectrometry-Based Identification of Paracrine Signals Driving Fibrosis in a New Model of Hypertrophic Cardiomyopathy Boston University

• engineered heart tissue
• induced pluripotent stem cells
• pulmonary arterial hypertension
• right heart dysfunction

• Adult
• Case-Control Studies
• Cell Differentiation
• Female
• Gene Expression Regulation
• Heart/physiopathology
• Humans
• Imaging, Three-Dimensional
• Induced Pluripotent Stem Cells/metabolism
• Models, Cardiovascular
• Myocytes, Cardiac/pathology
• Pulmonary Arterial Hypertension/diagnostic imaging
• Pulmonary Arterial Hypertension/genetics
• Pulmonary Arterial Hypertension/physiopathology
• Tissue Engineering

• NWO-VICI 918.16.610 Netherlands Organization for Scientific Research
• NWO-VIDI 917.18.338 Netherlands Organization for Scientific Research
• 2018T059 Dutch Heart Foundation Dekker senior post-doc grant
• CVON-2017-10 DOLPHIN-GENESIS Netherlands CardioVascular Research Initiative
• CVON-2018-29 PHAEDRA-IMPACT Netherlands CardioVascular Research Initiative

With the in-depth study of heart development, many human cardiomyocytes (CMs) have been generated in a laboratory environment. CMs derived from pluripotent stem cells (PSCs) have been widely used for a series of applications such as laboratory studies, drug toxicology screening, cardiac disease models, and as an unlimited resource for cell-based cardiac regeneration therapy. However, the low maturity of the induced CMs significantly impedes their applicability. Scientists have been committed to improving the maturation of CMs to achieve the purpose of heart regeneration in the past decades. In this review, we take CMs maturation as the main object of discussion, describe the characteristics of CMs maturation, summarize the key regulatory mechanism of regulating maturation and address the approaches to promote CMs maturation. The maturation of CM is gradually improving due to the incorporation of advanced technologies and is expected to continue.

• Cardiac maturation
• Maturation regulation
• Pluripotent stem cell
• Regenerative medicine

• Cardiomyocyte maturation
• Heart development
• Maturation metrics
• Pluripotent stem cells
• Single-cell transcriptomics
• Tissue engineering

• Cell Differentiation
• Humans
• Myocytes, Cardiac/physiology
• Tissue Engineering/methods
• Transcriptome/physiology

• R01 HL152249 NHLBI NIH HHS
• R01 HL156947 NHLBI NIH HHS
• T32 GM007057 NIGMS NIH HHS
• T32 HL007227 NHLBI NIH HHS

• iPSC-derived cardiomyocyte
• induced pluripotent stem cells (iPSC)
• mitochondrial cardiomyopathy
• mitochondrial disease

Although it is widely accepted that human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) are readily available, robustly reproducible, and physiologically appropriate human cells for clinical applications and research in the cardiovascular field, hiPSC-CMs cultured in vitro retain an immature metabolic phenotype that limits their application, and little is known about the underlying molecular mechanism controlling mitochondrial metabolic maturation during human induced pluripotent stem cells (hiPSCs ) differentiation into cardiomyocytes. In this study, we found that peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) played an important role in inducing mitochondrial biogenesis and establishing oxidative phosphorylation (OXPHOS) during the cardiac differentiation of hiPSCs. Knocking down PGC-1α by siRNA impaired mitochondrial respiration, while upregulating PGC-1α by ZLN005 promoted mitochondrial biosynthesis and function by regulating the expression of downstream genes involved in mitochondrial dynamics and oxidative metabolism in hiPSC-CMs. Furthermore, we found that estrogen-related receptor α (ERRα) was required for the induction of PGC-1α stimulatory effects in hiPSC-CMs. These findings provide key insights into the molecular control of mitochondrial metabolism during cardiac differentiation and may be used to generate more metabolically mature cardiomyocytes for application.

• Cardiac differentiation
• Maturation
• Mitochondrial metabolism
• PGC-1α
• hiPSCs

• Benchmarking
• Gene Expression
• Hepatocytes/cytology
• Humans
• Insulin-Secreting Cells/cytology
• Myocytes, Cardiac/cytology
• Pluripotent Stem Cells/cytology
• Sequence Analysis, RNA/methods
• Single-Cell Analysis/methods
• Tissue Engineering
• Transcriptome

• R01 HL152249 NHLBI NIH HHS
• R01 HL156947 NHLBI NIH HHS
• T32 GM136577 NIGMS NIH HHS
• American Heart Association
• TEDCO/Maryland stem cell research fund
• National Institutes of Health/NHLBI

• CRISPR/Cas9
• engineered heart tissue
• genome editing
• hypertrophic cardiomyopathy
• induced pluripotent stem cells

We performed a comprehensive analysis of the transcriptional changes occurring during human induced pluripotent stem cell (hiPSC) differentiation to cardiomyocytes. Using single cell RNA-seq, we sequenced > 20,000 single cells from 55 independent samples representing two differentiation protocols and multiple hiPSC lines. Samples included experimental replicates ranging from undifferentiated hiPSCs to mixed populations of cells at D90 post-differentiation. Differentiated cell populations clustered by time point, with differential expression analysis revealing markers of cardiomyocyte differentiation and maturation changing from D12 to D90. We next performed a complementary cluster-independent sparse regression analysis to identify and rank genes that best assigned cells to differentiation time points. The two highest ranked genes between D12 and D24 (MYH7 and MYH6) resulted in an accuracy of 0.84, and the three highest ranked genes between D24 and D90 (A2M, H19, IGF2) resulted in an accuracy of 0.94, revealing that low dimensional gene features can identify differentiation or maturation stages in differentiating cardiomyocytes. Expression levels of select genes were validated using RNA FISH. Finally, we interrogated differences in cardiac gene expression resulting from two differentiation protocols, experimental replicates, and three hiPSC lines in the WTC-11 background to identify sources of variation across these experimental variables.

One of the earliest maturation steps in cardiomyocytes (CMs) is the sarcomere protein isoform switch between TNNI1 and TNNI3 (fetal and neonatal/adult troponin I). Here, we generate human induced pluripotent stem cells (hiPSCs) carrying a TNNI1^EmGFP and TNNI3^mCherry double reporter to monitor and isolate mature sub-populations during cardiac differentiation. Extensive drug screening identifies two compounds, an estrogen-related receptor gamma (ERRγ) agonist and an S-phase kinase-associated protein 2 inhibitor, that enhances cardiac maturation and a significant change to TNNI3 expression. Expression, morphological, functional, and molecular analyses indicate that hiPSC-CMs treated with the ERRγ agonist show a larger cell size, longer sarcomere length, the presence of transverse tubules, and enhanced metabolic function and contractile and electrical properties. Here, we show that ERRγ-treated hiPSC-CMs have a mature cellular property consistent with neonatal CMs and are useful for disease modeling and regenerative medicine.

Cardiomyocytes (CMs) derived from human induced pluripotent stem cells (hiPSCs) suffer from limited maturation. Here the authors identify ERRγ agonist as a factor that enhances cardiac morphological, metabolic, contractile and electrical maturation of hiPSC-derived CMs with T-tubule formation.

• cardiomyocyte
• maturation
• pluripotent stem cell
• robust scale-up
• suspension culture

• T32 EB023872 NIBIB NIH HHS
• U01 HL134764 NHLBI NIH HHS
• P30 DK079626 NIDDK NIH HHS
• R01 HL114120 NHLBI NIH HHS
• R01 HL131017 NHLBI NIH HHS
• R01 HL149137 NHLBI NIH HHS
• T32 GM008361 NIGMS NIH HHS

Precision Medicine (PM) is an innovative approach that, by relying on large populations’ datasets, patients’ genetics and characteristics, and advanced technologies, aims at improving risk stratification and at identifying patient-specific management through targeted diagnostic and therapeutic strategies. Cardiac channelopathies are being progressively involved in the evolution brought by PM and some of them are benefiting from these novel approaches, especially the long QT syndrome. Here, we have explored the main layers that should be considered when developing a PM approach for cardiac channelopathies, with a focus on modern in vitro strategies based on patient-specific human-induced pluripotent stem cells and on in silico models. PM is where scientists and clinicians must meet and integrate their expertise to improve medical care in an innovative way but without losing common sense. We have indeed tried to provide the cardiologist’s point of view by comparing state-of-the-art techniques and approaches, including revolutionary discoveries, to current practice. This point matters because the new approaches may, or may not, exceed the efficacy and safety of established therapies. Thus, our own eagerness to implement the most recent translational strategies for cardiac channelopathies must be tempered by an objective assessment to verify whether the PM approaches are indeed making a difference for the patients. We believe that PM may shape the diagnosis and treatment of cardiac channelopathies for years to come. Nonetheless, its potential superiority over standard therapies should be constantly monitored and assessed before translating intellectually rewarding new discoveries into clinical practice.

• Cardiac arrhythmias
• Cardiac channelopathies
• Genetics
• Long QT syndrome
• Pluripotent stem cells
• Precision Medicine

• development
• gene expression
• human evolution
• stem cells
• tissue models

• cell biology
• stem cells

• cardiac tissue
• drug discovery
• heart failure
• humans
• stem cells

• Animals
• Cellular Reprogramming Techniques/methods
• Heart/physiology
• Humans
• Myocytes, Cardiac/cytology
• Myocytes, Cardiac/metabolism
• Pluripotent Stem Cells/cytology
• Pluripotent Stem Cells/metabolism
• Regeneration
• Tissue Engineering/methods

The regenerative capacity of cardiomyocytes is insufficient to functionally recover damaged tissue, and as such, ischaemic heart disease forms the largest proportion of cardiovascular associated deaths. Human-induced pluripotent stem cells (hiPSCs) have enormous potential for developing patient specific cardiomyocytes for modelling heart disease, patient-based cardiac toxicity testing and potentially replacement therapy. However, traditional protocols for hiPSC-derived cardiomyocytes yield mixed populations of atrial, ventricular and nodal-like cells with immature cardiac properties. New insights gleaned from embryonic heart development have progressed the precise production of subtype-specific hiPSC-derived cardiomyocytes; however, their physiological immaturity severely limits their utility as model systems and their use for drug screening and cell therapy. The long-entrenched challenges in this field are being addressed by innovative bioengingeering technologies that incorporate biophysical, biochemical and more recently biomimetic electrical cues, with the latter having the potential to be used to both direct hiPSC differentiation and augment maturation and the function of derived cardiomyocytes and cardiac tissues by mimicking endogenous electric fields.

• bioengineering
• cardiac tissue
• cardiomyocyte
• electrical stimulation
• human pluripotent stem cells
• regenerative therapy
• tissue modelling

• Animals
• Bioengineering
• Cell Differentiation
• Electric Stimulation
• Heart/physiology
• Humans
• Myocytes, Cardiac/cytology
• Pluripotent Stem Cells/cytology

Brugada syndrome (BrS) is an inherited cardiac arrhythmia that predisposes to ventricular fibrillation and sudden cardiac death. It originates from oligogenic alterations that affect cardiac ion channels or their accessory proteins. The main hurdle for the study of the functional effects of those variants is the need for a specific model that mimics the complex environment of human cardiomyocytes. Traditionally, animal models or transient heterologous expression systems are applied for electrophysiological investigations, each of these models having their limitations. The ability to create induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs), providing a source of human patient-specific cells, offers new opportunities in the field of cardiac disease modelling. Contemporary iPSC-CMs constitute the best possible in vitro model to study complex cardiac arrhythmia syndromes such as BrS. To date, thirteen reports on iPSC-CM models for BrS have been published and with this review we provide an overview of the current findings, with a focus on the electrophysiological parameters. We also discuss the methods that are used for cell derivation and data acquisition. In the end, we critically evaluate the knowledge gained by the use of these iPSC-CM models and discuss challenges and future perspectives for iPSC-CMs in the study of BrS and other arrhythmias.

• brugada syndrome
• electrophysiology
• iPSC-cardiomyocytes
• induced pluripotent stem cells
• inherited cardiac arrhythmia

Heme oxygenase-1 (HO-1, encoded by HMOX1) is a cytoprotective enzyme degrading heme into CO, Fe²⁺, and biliverdin. HO-1 was demonstrated to affect cardiac differentiation of murine pluripotent stem cells (PSCs), regulate the metabolism of murine adult cardiomyocytes, and influence regeneration of infarcted myocardium in mice. However, the enzyme’s effect on human cardiogenesis and human cardiomyocytes’ electromechanical properties has not been described so far. Thus, this study aimed to investigate the role of HO-1 in the differentiation of human induced pluripotent stem cells (hiPSCs) into hiPSC-derived cardiomyocytes (hiPSC-CMs). hiPSCs were generated from human fibroblasts and peripheral blood mononuclear cells using Sendai vectors and subjected to CRISPR/Cas9-mediated HMOX1 knock-out. After confirming lack of HO-1 expression on the protein level, isogenic control and HO-1-deficient hiPSCs were differentiated into hiPSC-CMs. No differences in differentiation efficiency and hiPSC-CMs metabolism were observed in both cell types. The global transcriptomic analysis revealed, on the other hand, alterations in electrophysiological pathways in hiPSC-CMs devoid of HO-1, which also demonstrated increased size. Functional consequences in changes in expression of ion channels genes were then confirmed by patch-clamp analysis. To the best of our knowledge, this is the first report demonstrating the link between HO-1 and electrophysiology in human cardiomyocytes.

• CRISPR/Cas9
• HO-1
• IGF2
• electrophysiology
• hiPSC-CMs
• hypertrophy

Cardiovascular disease (CVD) complications have contributed significantly toward poor survival of cancer patients worldwide. These complications that result in myocardial and vascular damage lead to long-term multisystemic disorders. In some patient cohorts, the progression from acute to symptomatic CVD state may be accelerated due to exacerbation of underlying comorbidities such as obesity, diabetes and hypertension. In such situations, cardio-oncologists are often left with a clinical predicament in finding the optimal therapeutic balance to minimize cardiovascular risks and maximize the benefits in treating cancer. Hence, prognostically there is an urgent need for cost-effective, rapid, sensitive and patient-specific screening platform to allow risk-adapted decision making to prevent cancer therapy related cardiotoxicity. In recent years, momentous progress has been made toward the successful derivation of human cardiovascular cells from induced pluripotent stem cells (iPSCs). This technology has not only provided deeper mechanistic insights into basic cardiovascular biology but has also seamlessly integrated within the drug screening and discovery programs for early efficacy and safety evaluation. In this review, we discuss how iPSC-derived cardiovascular cells have been utilized for testing oncotherapeutics to pre-determine patient predisposition to cardiovascular toxicity. Lastly, we highlight the convergence of tissue engineering technologies and precision medicine that can enable patient-specific cardiotoxicity prognosis and treatment on a multi-organ level.

• 3D platforms
• cancer drugs
• cardio-oncology
• cardiomyocytes
• drug testing
• induced pluripotent stem cells
• multicellular crosstalk

• foetal gene programme
• heart failure

To understand the intrinsic cardiac developmental and functional abnormalities in pulmonary atresia with intact ventricular septum (PAIVS) free from effects secondary to anatomic defects, we performed and compared single‐cell transcriptomic and phenotypic analyses of patient‐ and healthy subject–derived human‐induced pluripotent stem cell–derived cardiomyocytes (hiPSC‐CMs) and engineered tissue models.

We derived hiPSC lines from 3 patients with PAIVS and 3 healthy subjects and differentiated them into hiPSC‐CMs, which were then bioengineered into the human cardiac anisotropic sheet and human cardiac tissue strip custom‐designed for electrophysiological and contractile assessments, respectively. Single‐cell RNA sequencing (scRNA‐seq) of hiPSC‐CMs, human cardiac anisotropic sheet, and human cardiac tissue strip was performed to examine the transcriptomic basis for any phenotypic abnormalities using pseudotime and differential expression analyses. Through pseudotime analysis, we demonstrated that bioengineered tissue constructs provide pro‐maturational cues to hiPSC‐CMs, although the maturation and development were attenuated in PAIVS hiPSC‐CMs. Furthermore, reduced contractility and prolonged contractile kinetics were observed with PAIVS human cardiac tissue strips. Consistently, single‐cell RNA sequencing of PAIVS human cardiac tissue strips and hiPSC‐CMs exhibited diminished expression of cardiac contractile apparatus genes. By contrast, electrophysiological aberrancies were absent in PAIVS human cardiac anisotropic sheets.

Our findings were the first to reveal intrinsic abnormalities of cardiomyocyte development and function in PAIVS free from secondary effects. We conclude that hiPSC‐derived engineered tissues offer a unique method for studying primary cardiac abnormalities and uncovering pathogenic mechanisms that underlie sporadic congenital heart diseases.

• hypoplastic right heart syndrome
• induced pluripotent stem cells
• pulmonary atresia with intact ventricular septum
• single cell transcriptomics

• carnegie stage
• heart development
• human embryonic heart
• transcriptome

• Cardiomyocyte
• Cardiomyocyte differentiation
• Single-cell Western
• Single-cell protein expression
• hiPSC
• hiPSC-CM