Advanced maturation of human cardiac tissue grown from pluripotent stem cells

Development of an electroconductive Heart-on-a-chip model to investigate cellular and molecular response of human cardiac tissue to gold nanomaterials

To date, various strategies have been developed to construct biomimetic and functional in vitro cardiac tissue models utilizing human induced pluripotent stem cells (hiPSCs). Among these approaches, microfluidic-based Heart-on-a-chip (HOC) models are promising, as they enable the engineering of miniaturized, physiologically relevant in vitro cardiac tissues with precise control over cellular constituents and tissue architecture. Despite significant advancements, previously reported HOC models often lack the electroconductivity features of the native human myocardium. In this study, we developed a 3D electroconductive HOC (referred to as eHOC) model through the co-culture of isogenic hiPSC-derived cardiomyocytes (hiCMs) and cardiac fibroblasts (hiCFs), embedded within an electroconductive hydrogel scaffold in a microfluidic-based chip system. Functional and gene expression analyses demonstrated that, compared to non-conductive HOC, the eHOC model exhibited enhanced contractile functionality, improved calcium transients, and increased expression of structural and calcium handling genes. The eHOC model was further leveraged to investigate the underlying electroconduction-induced pathway(s) associated with cardiac tissue development through single-cell RNA sequencing (scRNA-seq). Notably, scRNA-seq analyses revealed a significant downregulation of a set of cardiac genes, associated with the fetal stage of heart development, as well as upregulation of sarcomere- and conduction-related genes within the eHOC model. Additionally, upregulation of the cardiac muscle contraction and motor protein pathways were observed in the eHOC model, consistent with enhanced contractile functionality of the engineered cardiac tissues. Comparison of scRNA-seq data from the 3D eHOC model with published datasets of adult human hearts demonstrated a similar expression pattern of fetal- and adult-like cardiac genes. Overall, this study provides a unique eHOC model with improved biomimcry and organotypic features, which could be potentially used for drug testing and discovery, as well as disease modeling applications.

Construction of engineered cardiac tissue on a heart-on-a-chip device enables modeling of arrhythmogenic right ventricular cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a progressive cardiac disorder characterized by the replacement of the right ventricular myocardium with fibrofatty tissue, with an incidence rate of approximately 1 in 5000. To advance our understanding of its pathology and facilitate drug screening, there is an urgent need for myocardial models that closely replicate human physiological conditions. In this study, we developed an engineered cardiac tissue (ECT) model on a chip using cardiomyocytes differentiated from induced pluripotent stem cells (iPSCs) derived from ARVC patients. The disease ECT model successfully recapitulated key phenotypic features of ARVC, including reduced contractility, arrhythmic events, and abnormal calcium transients. We further assessed the drug responses of the model to isoproterenol and amiodarone, confirming increased sensitivity to isoproterenol in the ARVC model, while amiodarone effectively alleviated the arrhythmic events. In conclusion, our ECT model successfully reproduced ARVC phenotypes, providing a novel platform for drug screening and pathological studies.

Multiphysics Simulations of a Bioprinted Pulsatile Fontan Conduit

For single ventricle congenital heart patients, Fontan surgery is the final stage in a series of palliative procedures, bypassing the heart to enable passive flow of de-oxygenated blood from the inferior vena cava (IVC) to the pulmonary arteries. This circulation leads to severely elevated central venous pressure, diminished cardiac output, and thus numerous sequelae and premature mortality. To address these issues, we propose a bioprinted pulsatile conduit to provide a secondary power source for the Fontan circulation. A multiphysics computational framework was developed to predict conduit performance and to guide design prior to printing. Physics components included electrophysiology, cardiomyocyte contractility, and fluid-structure interaction coupled to a closed-loop lumped parameter network representing Fontan physiology. A range of myocardial contractility was considered and simulated. The initial conduit design with adult ventricular cardiomyocyte contractility values coupled to a Purkinje network demonstrated potential to reduce liver (IVC) pressure from 16.4 to 9.3 mmHg and increase cardiac output by 29%. After systematically assessing the impacts of contraction duration, fiber direction, and valve placement on conduit performance, we identified a favorable design that successfully reduces liver pressure to 7.3 mmHg and increases cardiac output by 38%, almost normalizing adverse hemodynamics in the lower venous circulation. Valves at the input and output of the conduit are essential to achieve these satisfactory results; without valves, performance is compromised. However, a potential drawback of the design is the elevation of superior vena cava (SVC) pressure, which varies linearly with liver pressure reduction.

Advances in human induced pluripotent stem cell (hiPSC)-based disease modelling in cardiogenetics

Human induced pluripotent stem cell (hiPSC)-based disease modelling has significantly advanced the field of cardiogenetics, providing a precise, patient-specific platform for studying genetic causes of heart diseases. Coupled with genome editing technologies such as CRISPR/Cas, hiPSC-based models not only allow the creation of isogenic lines to study mutation-specific cardiac phenotypes, but also enable the targeted modulation of gene expression to explore the effects of genetic and epigenetic deficits at the cellular and molecular level. hiPSC-based models of heart disease range from two-dimensional cultures of hiPSC-derived cardiovascular cell types, such as various cardiomyocyte subtypes, endothelial cells, pericytes, vascular smooth muscle cells, cardiac fibroblasts, immune cells, etc., to cardiac tissue cultures including organoids, microtissues, engineered heart tissues, and microphysiological systems. These models are further enhanced by multi-omics approaches, integrating genomic, transcriptomic, epigenomic, proteomic, and metabolomic data to provide a comprehensive view of disease mechanisms. In particular, advances in cardiovascular tissue engineering enable the development of more physiologically relevant systems that recapitulate native heart architecture and function, allowing for more accurate modelling of cardiac disease, drug screening, and toxicity testing, with the overall goal of personalised medical approaches, where therapies can be tailored to individual genetic profiles. Despite significant progress, challenges remain in the maturation of hiPSC-derived cardiomyocytes and the complexity of reproducing adult heart conditions. Here, we provide a concise update on the most advanced methods of hiPSC-based disease modelling in cardiogenetics, with a focus on genome editing and cardiac tissue engineering.

Establishing a context of use for three-dimensional cardiac tissue derived from human-induced pluripotent stem cell-derived cardiomyocytes using inotropes

Safety attrition due to drug-induced inotropic changes remains a significant risk factor for drug development. Mitigating these events during early screening remains challenging. Several in vitro predictive models have been developed to address these issues, with varying success in detecting drug-induced inotropic changes. In this study, we compared traditional two-dimensional human-induced pluripotent stem cell-derived cardiomyocytes (2D hiPSC-CMs) with three-dimensional engineered cardiac tissues (3D ECTs) to assess their ability to detect drug-induced inotropic changes in 17 drugs with known mechanisms of action. The models were exposed to various test compounds, and their responses were evaluated by measuring either the active force or maximum contraction speed. The 3D ECTs successfully detected all the tested positive inotropes, whereas the 2D hiPSC-CMs failed to detect the 2 compounds. Both models demonstrated high predictability for negative inotropy and showed similar results for detecting non-active compounds, except for higher concentrations of phentolamine, zimelidine, and tamsulosin. Irregular beating was less likely to occur in the 3D ECTs, suggesting that 3D ECTs provided superior detection of contractility compared to 2D hiPSC-CMs. Genetic analysis revealed a more mature phenotype for the 3D ECTs compared to the 2D hiPSC-CMs, and the compound-related target expression was comparable to that in the adult human heart tissues. The 3D ECTs captured inotropic changes more accurately and thus represented a more translatable model than the 2D hiPSC-CMs. Overall, contractility assessment using the 3D ECTs could be advantageous for profiling candidate compounds and mechanistic investigations of hemodynamic changes during in vivo or clinical studies.

Matured hiPSC-derived cardiomyocytes possess dematuration plasticity

Human induced Pluripotent Stem Cell-derived cardiomyocytes (hiPSC-CMs) are increasingly used to identify potential factors capable of inducing endogenous cardiomyocyte proliferation to regenerate the injured heart. L-type calcium channel blockers have previously been identified as a class of factors capable of inducing matured hiPSC-CMs to proliferate. However, the mechanism by which L-type calcium channel blockers promote hiPSC-CM proliferation remains unclear. Here we provide evidence that matured hiPSC-CMs possess plasticity to undergo dematuration in response to certain pharmacological compounds. Consistent with primary cardiomyocyte maturation during perinatal development, we found that centrosome disassembly occurs in hiPSC-CMs during plate-based, temporal, maturation. A small molecule screen identified nitrendipine, an L-type calcium channel blocker, and 1-NA-PP1, a Src kinase inhibitor, as factors capable of inducing centrosome reassembly in a subpopulation of hiPSC-CMs. Furthermore, centrosome-positive hiPSC-CMs were more likely to exhibit cell cycle activity than centrosome-negative hiPSC-CMs. In contrast, neither nitrendipine or 1-NA-PP1 induced centrosome reassembly, or cell cycle activity, in neonatal rat ventricular myocytes (NRVMs). Differential bulk transcriptome analysis indicated that matured hiPSC-CMs, but not NRVMs, treated with nitrendipine or 1-NA-PP1 undergo dematuration. ScRNA transcriptome analysis supported that matured hiPSC-CMs treated with either nitrendipine or 1-NA-PP1 undergo dematuration. Collectively, our results indicate that matured hiPSC-CMs, but not primary NRVMs, possess plasticity to undergo dematuration in response to certain pharmacological compounds such as L-type calcium channel blockers and Src-kinase inhibitors. This study shows that once mature, hiPSC-CMs may not maintain their maturity under experimental conditions which may have implications for experimental systems where the state of hiPSC-CM maturation is relevant.

A Human Engineered Heart Tissue-Derived Lipotoxic Diabetic Cardiomyopathy Model Revealed Early Benefits of Empagliflozin

Diabetic cardiomyopathy (DbCM) is increasingly prevalent, but intervention targets remain unclear due to the lack of appropriate models and the complexity of risk factors. Here, this work establishes an in vitro assessment system for DbCM function using cardiomyocytes derived from human pluripotent stem cells and engineered heart tissue. This work finds high-fat status in complex diabetes risk factors majorly contributes most to cardiomyocyte death and contractile dysfunction. Notably, PA induced early electrophysiological abnormalities, and lately is associated with cardiac fibrosis, mitochondrial fission, and systolic and diastolic dysfunction at tissue level. Using this in vitro assessment system, this work finds that empagliflozin (EMPA), a first-line glucose-lowering drug, effectively alleviated early PA-induced cardiomyocyte injury. Treatment with EMPA enhanced abnormal diastolic and electrophysiological functions in the PA-hEHT model and significantly reduced endoplasmic reticulum stress, and apoptosis. Furthermore, these promising results are confirmed in a type 2 diabetes mellitus mouse model, reinforcing the potential of EMPA as a therapeutic option to alleviate cardiomyocyte injury under diabetic conditions. These findings suggest that this work has developed an engineered model of diabetic cardiomyopathy that mimics the various stages of lipotoxic myocardial injury and support the use of EMPA as a potential therapeutic option for diabetic or lipotoxic cardiomyopathy.

In Vitro Modeling of Interorgan Crosstalk: Multi-Organ-on-a-Chip for Studying Cardiovascular-Kidney-Metabolic Syndrome

Cardiovascular-kidney-metabolic syndrome is a progressive disorder driven by perturbed interorgan crosstalk among adipose, liver, kidney, and heart, leading to multiorgan dysfunction. Capturing the complexity of human cardiovascular-kidney-metabolic syndrome pathophysiology using conventional models has been challenging. Multi-organ-on-a-chip platforms offer a versatile means to study underlying interorgan signaling at different stages of cardiovascular-kidney-metabolic syndrome and bolster clinical translation.

Au@Pt Nanoparticles Enhance Maturation and Contraction of Mouse Embryonic Stem Cells-Derived and Neonatal Mouse Cardiomyocytes

BACKGROUND

Cardiomyocytes derived from pluripotent stem cells (PSCs) hold great promise in heart damage repair in vivo and drug screening in vitro. However, PSC-derived cardiomyocytes exhibit immature structural and functional properties, which hinder their widespread application. To address this challenge, we designed bimetallic gold-platinum nanoparticles (Au@Pt NPs) endowed with intrinsic oxidase-like, peroxidase-like, and catalase-like activities and high electrical conductivity for promoting cardiomyocyte maturation.

METHODS

Mouse embryonic stem cell (ESC)-derived and neonatal mouse cardiomyocytes were used to evaluate the effects of Au@Pt NPs on cardiomyocyte maturation. The expression and alignment of cardiomyocyte myofibril proteins were analyzed by qRT-PCR, western blot, and immunofluorescence staining. Cellular functionality was analyzed by the multi-electrode array.

RESULTS

By adding Au@Pt NPs at different stages of cardiac differentiation of mouse ESCs, we found that treatment with Au@Pt NPs at the late stage could promote the maturation of differentiated cardiomyocytes, evidenced by increased expression of mature myofibril protein isoforms, more aligned myofibrils, and enhanced sarcomere length. Additionally, Au@Pt NPs can enhance the expression of mature sarcomere components, increase sarcomere length, and significantly boost beating amplitude and conduction velocity in neonatal mouse cardiomyocytes. Furthermore, Au@Pt NPs promoted cell cycle arrest, increased intracellular reactive oxygen species levels, and promoted contractility by inducing the ERK1/2 signaling pathway.

CONCLUSION

Our results indicate that the bimetallic Au@Pt NPs with intrinsic oxidase-like, peroxidase-like, and catalase-like activities and high electrical conductivity could promote the maturation of ESCs-derived and neonatal mouse cardiomyocytes, providing a promising approach for cardiomyocyte maturation and cell therapy for cardiovascular disease.

Musculoskeletal organoids: An emerging toolkit for establishing personalized models of musculoskeletal disorders and developing regenerative therapies

Musculoskeletal (MSK) conditions are the primary cause of physical disability globally. These disorders are physically and mentally debilitating and severely impact the patients' quality of life. As the median age of the world's population increases, there has been an intensifying urgency of developing efficacious therapies for various orthopaedic conditions. Furthermore, the highly heterogeneous nature of MSK conditions calls for a personalized approach to studying disease mechanisms and developing regenerative treatments. Organoids have emerged as an advanced approach to generating functional tissue/organ mimics in vitro, which hold promise in MSK regeneration, disease modeling, and therapeutic development. Herein, we review the preparation, characterization, and application of various MSK organoids. We highlight the potential of patient-specific organoids in the development of personalized medicine and discuss the challenges and opportunities in the future development of MSK organoids. STATEMENT OF SIGNIFICANCE: Despite decades of research, translation of MSK research into clinical applications remains limited, partially attributed to our inadequate understanding of disease mechanisms. To advance therapeutic development, there are critical needs for MSK disease models with higher clinical relevance and predictive power. Additionally, engineered constructs that closely mimic the structural and functional features of native MSK tissues are highly desirable. MSK organoids have emerged as a promising approach to meet the above requirements. To unleash the full potential of MSK organoids necessitates a comprehensive understanding of their categories, construction, development, functions, applications, and challenges. This review aims to fulfill this crucial need, aiming to accelerate the clinical translation of MSK organoid platforms to benefit millions of patients afflicted with MSK conditions.

Bioelectric and physicochemical foundations of bioelectronics in tissue regeneration

Understanding and exploiting bioelectric signaling pathways and physicochemical properties of materials that interface with living tissues is central to advancing tissue regeneration. In particular, the emerging field of bioelectronics leverages these principles to develop personalized, minimally invasive therapeutic strategies tailored to the dynamic demands of individual patients. By integrating sensing and actuation modules into flexible, biocompatible devices, clinicians can continuously monitor and modulate local electrical microenvironments, thereby guiding regenerative processes without extensive surgical interventions. This review provides a critical examination of how fundamental bioelectric cues and physicochemical considerations drive the design and engineering of next-generation bioelectronic platforms. These platforms not only promote the formation and maturation of new tissues across neural, cardiac, musculoskeletal, skin, and gastrointestinal systems but also precisely align therapies with the unique structural, functional, and electrophysiological characteristics of each tissue type. Collectively, these insights and innovations represent a convergence of biology, electronics, and materials science that holds tremendous promise for enhancing the efficacy, specificity, and long-term stability of regenerative treatments, ushering in a new era of advanced tissue engineering and patient-centered regenerative medicine.

Designing multicellular cardiac tissue engineering technologies for clinical translation

Cardiovascular diseases remain the leading cause of death worldwide-claiming one-third of all deaths every year. Current two-dimensional in vitro cell culture systems and animal models cannot completely recapitulate the clinical complexity of these diseases in humans. Therefore, there is a dire need for higher fidelity biological systems capable of replicating these phenotypes to inform clinical outcomes and therapeutic development. Cardiac tissue engineering (CTE) strategies have emerged to fulfill this need by the design of in vitro three-dimensional myocardial tissue systems from human pluripotent stem cells. In this way, CTE systems serve as highly controllable human models for a variety of applications-including for physiological and pathological modeling, drug discovery and preclinical testing platforms, and even direct therapeutic interventions in the clinic. Although significant progress has been made in the development of these CTE technologies, critical challenges remain and necessary refinements are required to derive more advanced human heart tissue technologies. In this review, we distill three focus areas for the field to address: I) Generating cardiac muscle cell types and scalable manufacturing methods, II) Engineering tissue structure, function, and analyses, and III) Curating system design for specific application. In each of our focus areas, we emphasize the importance of designing CTE systems capable of mimicking the intricate intercellular connectivity of the human heart and discuss fundamental design considerations that subsequently arise. We conclude by highlighting cutting-edge applications that use CTE technologies for clinical modeling and the direct repair of damaged and diseased hearts.

From function to structure: how myofibrillogenesis influences the transverse-axial tubular system development and its peculiarities

The transverse-axial tubular system (TATS) is the extension of sarcolemma growing to the cell interior, providing sufficient calcium signaling to induce calcium release from sarcoplasmic reticulum cisternae and stimulate the contraction of neighboring myofibrils. Interestingly, the development of TATS is delayed and matures during the post-partum period. It starts with small invaginations near the sarcolemma, proceeding to grow an irregular network that is later assembled into the notably transversally oriented tubular network. Accumulating evidence supports the idea that the development of TATS is linked to cell dimensions, calcium signaling, and increasing myofibrillar content orchestrated by electromechanical stimulation. However, the overall mechanism has not yet been described. The topic of this review is the development of TATS with an emphasis on the irregular phase of tubule growth. The traditional models of BIN1-related tubulation are also discussed. We summarized the recently described protein interactions during TATS development, mainly mediated by costameric and sarcomeric proteins, supporting the idea of the coupling sites between TATS and the myofibrils. We hypothesize that the formation and final organization of the tubular system is driven by the simultaneous development of the contractile apparatus under cycling electromechanical stimulus.

Maturation of human induced pluripotent stem cell-derived cardiomyocytes promoted by Brachyury priming

Cardiac differentiation of human induced pluripotent stem cells is readily achievable, yet derivation of mature cardiomyocytes has been a recognized limitation. Here, a mesoderm priming approach was engineered to boost the maturation of cardiomyocyte progeny derived from pluripotent stem cells under standard cardiac differentiation conditions. Functional and structural hallmarks of maturity were assessed through multiparametric evaluation of cardiomyocytes derived from induced pluripotent stem cells following transfection of the mesoderm transcription factor Brachyury prior to initiation of lineage differentiation. Transfection with Brachyury resulted in earlier induction of a cardiopoietic state as hallmarked by early upregulation of the cardiac-specific transcription factors NKX2.5, GATA4, TBX20. Enhanced sarcomere maturity following Brachyury conditioning was documented by an increase in the proportion of cells expressing the ventricular isoform of myosin light chain and an increase in sarcomere length. Mesoderm primed cells displayed increased reliance on mitochondrial respiration as determined by increased mitochondrial size and a greater basal oxygen consumption rate. Further, Brachyury priming drove maturation of calcium handling enabling transfected cells to maintain calcium transient morphology at higher external field stimulation rates and augmented both calcium release and sequestration kinetics. In addition, transfected cells displayed a more mature action potential morphology with increased depolarization and repolarization kinetics. Derived cells transfected with Brachyury demonstrated increased toxicity response to doxorubicin as determined by a compromise in calcium transient morphology. Thus, Brachyury pre-treatment here achieved a streamlined strategy to promote maturity of human pluripotent stem cell-derived cardiomyocytes establishing a generalizable platform ready for deployment.

Cardiomyocyte sheet stacking using fibrin enables high-speed construction of three-dimensional myocardial tissue and high transplantation efficiency

Despite the development of three-dimensional (3D) tissues that promises remarkable advances in myocardial therapies and pharmaceutical research, vascularization is required for the repair of damaged hearts using cardiac tissue engineering. In this study, we developed a method for rapid generation of a 3D cardiac tissue, with extremely high engraftment efficiency, by stacking cardiomyocyte sheets using fibrin as an adhesive. Cell sheets were created by peeling off confluent cultured cells from a culture dish grafted with a polymer that induced surface hydrophilicity in response to low temperatures. The high engraftment rate was attributed to the retention of the adhesive protein. The multistacked vascularized cell sheets prepared using fibrin, when transplanted into the subcutaneous tissue and at myocardial infarction site in rats, yielded a transplanted 3D myocardial tissue. Furthermore, multilayered cardiomyocyte sheets were transplanted twice at 1 week intervals to create a 3D myocardial tissue. Our data suggest that fibrin-based rapidly layered cell sheets can advance tissue-engineered transplantation therapy and should aid the development of next-generation tissue-engineered products in the fields of regenerative medicine and drug screening.

Characteristics and pharmacological responsiveness in hiPSC models of inherited cardiomyopathy

Inherited cardiomyopathies are a major cause of heart failure in all age groups, often with an onset in adolescence or early adult life. More than a thousand variants in approximately one hundred genes are associated with cardiomyopathies. Interestingly, many genetic cardiomyopathies display overlapping phenotypical defects in patients, despite the diversity of the initial pathogenic variants. Understanding how the underlying pathophysiology of genetic cardiomyopathies leads to these phenotypes will improve insights into a patient's disease course, and creates the opportunity for conceiving treatment strategies. Moreover, therapeutic strategies can be used to treat multiple cardiomyopathies based on shared phenotypes. Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) offer reliable, high-throughput models for studying molecular and cellular characteristics of hereditary cardiomyopathies. hiPSC-CMs are produced relatively easily, either by directly originating them from patients, or by introducing patient-specific genetic variants in healthy lines. This review evaluates 90 studies on 24 cardiomyopathy-associated genes and systematically summarises the morphological and functional phenotypes observed in hiPSC-CMs. Additionally, treatment strategies applied in cardiomyopathic hiPSC-CMs are compiled and scored for effectiveness. Multiple overlapping phenotypic defects were identified in cardiomyocytes with different variants, whereas certain characteristics were only associated with specific genetic variants. Based on these findings, common mechanisms, therapeutic prospects, and considerations for future research are discussed with the aim to improve clinical translation from hiPSC-CMs to patients.

Human induced pluripotent stem cell-derived cardiomyocytes and their use in a cardiac organ-on-a-chip to assay electrophysiology, calcium and contractility

Cardiac organs-on-a-chip (OoCs) or microphysiological systems have the potential to predict cardiac effects of new drug candidates, including unanticipated cardiac outcomes, which are among the main causes for drug attrition. This protocol describes how to prepare and use a cardiac OoC containing cardiomyocytes differentiated from human induced pluripotent stem cells (hiPS cells). The use of cells derived from hiPS cells as reliable sources of human cells from diverse genetic backgrounds also holds great potential, especially when cultured in OoCs that are physiologically relevant culture platforms. To promote the broad adoption of hiPS cell-derived cardiac OoCs in the drug development field, there is a need to first ensure reproducibility in their preparation and use. This protocol aims to provide key information on how to reduce sources of variability during hiPS cell maintenance, differentiation, loading and maturation in OoCs. Variability in these procedures can lead to inconsistent purity after differentiation and variable function between batches of microtissues formed in OoCs. This protocol also focuses on describing the handling and functional assessment of cardiac microtissues using live-cell microscopy approaches to quantify parameters of cellular electrophysiology, calcium transients and contractility. The protocol consists of five stages: (1) thaw and maintain hiPS cells, (2) differentiate hiPS cell cardiomyocytes, (3) load differentiated cells into OoCs, (4) maintain and characterize loaded cells, and (5) evaluate and utilize cardiac OoCs. Execution of the entire protocol takes ~40 days. The required skills to carry out the protocol are experience with sterile techniques, mammalian cell culture and maintaining hiPS cells in a pluripotent state.

Hydrogel sensing platforms for monitoring contractility in in vitro cardiac models

Heart failure (HF) affects over 64 million people globally, marked by high incidence and mortality rates. Accurate measurements of myocardial contractility are crucial for evaluating cardiac pathomechanisms and monitoring disease progression. Hydrogel sensing devices, known for their flexibility, programmable structures, biocompatibility, and cell adhesion, are ideal for studying cardiac function, minimizing disruption to cardiomyocytes, and supporting long-term culture and monitoring. These platforms, while employing diverse detection principles to accurately measure cell contractility, still face challenges in achieving long-term stability and durability. This review summarizes current methods for monitoring cardiomyocyte contractility, emphasizes the significant impact of substrate mechanical properties on cellular function, and explores recent advances in hydrogel-based platforms for monitoring cell contraction forces. It also discusses the technical challenges and future prospects for measuring cardiac systolic function with these devices.

Engineering cardiology with miniature hearts

Cardiac organoids offer sophisticated 3D structures that emulate key aspects of human heart development and function. This review traces the evolution of cardiac organoid technology, from early stem cell differentiation protocols to advanced bioengineering approaches. We discuss the methodologies for creating cardiac organoids, including self-organization techniques, biomaterial-based scaffolds, 3D bioprinting, and organ-on-chip platforms, which have significantly enhanced the structural complexity and physiological relevance of in vitro cardiac models. We examine their applications in fundamental research and medical innovations, highlighting their potential to transform our understanding of cardiac biology and pathology. The integration of multiple cell types, vascularization strategies, and maturation protocols has led to more faithful representations of the adult human heart. However, challenges remain in achieving full functional maturity and scalability. We critically assess the current limitations and outline future directions for advancing cardiac organoid technology. By providing a comprehensive analysis of the field, this review aims to catalyze further innovation in cardiac tissue engineering and facilitate its translation to clinical applications.

Transient chemical-mediated epigenetic modulation confers unrestricted lineage potential on human primed pluripotent stem cells

Human primed pluripotent stem cells are capable of generating all the embryonic lineages. However, their extraembryonic trophectoderm potentials are limited. It remains unclear how to expand their developmental potential to trophectoderm lineages. Here we show that transient treatment with a cocktail of small molecule epigenetic modulators imparts trophectoderm lineage potentials to human primed pluripotent stem cells while preserving their embryonic potential. These chemically treated cells can generate trophectoderm-like cells and downstream trophoblast stem cells, diverging into syncytiotrophoblast and extravillous trophoblast lineages. Transcriptomic and CUT&Tag analyses reveal that these induced cells share transcriptional profiles with in vivo trophectoderm and cytotrophoblast, and exhibit reduced H3K27me3 modification at gene loci specific to trophoblast lineages compared with primed pluripotent cells. Mechanistic exploration highlighted the critical roles of epigenetic modulators HDAC2, EZH1/2, and KDM5s in the activation of trophoblast lineage potential. Our findings demonstrate that transient epigenetic resetting activates unrestricted lineage potential in human primed pluripotent stem cells, and offer new mechanistic insights into human trophoblast lineage specification and in vitro models for studying placental development and related disorders.

Application of human cardiac organoids in cardiovascular disease research

With the progression of cardiovascular disease (CVD) treatment technologies, conventional animal models face limitations in clinical translation due to interspecies variations. Recently, human cardiac organoids (hCOs) have emerged as an innovative platform for CVD research. This review provides a comprehensive overview of the definition, characteristics, classifications, application and development of hCOs. Furthermore, this review examines the application of hCOs in models of myocardial infarction, heart failure, arrhythmias, and congenital heart diseases, highlighting their significance in replicating disease mechanisms and pathophysiological processes. It also explores their potential utility in drug screening and the development of therapeutic strategies. Although challenges persist regarding technical complexity and the standardization of models, the integration of multi-omics and artificial intelligence (AI) technologies offers a promising avenue for the clinical translation of hCOs.

Advances in humanoid organoid-based research on inter-organ communications during cardiac organogenesis and cardiovascular diseases

The intimate correlation between cardiovascular diseases and other organ pathologies, such as metabolic and kidney diseases, underscores the intricate interactions among these organs. Understanding inter-organ communications is crucial for developing more precise drugs and effective treatments for systemic diseases. While animal models have traditionally been pivotal in studying these interactions, human-induced pluripotent stem cells (hiPSCs) offer distinct advantages when constructing in vitro models. Beyond the conventional two-dimensional co-culture model, hiPSC-derived humanoid organoids have emerged as a substantial advancement, capable of replicating essential structural and functional attributes of internal organs in vitro. This breakthrough has spurred the development of multilineage organoids, assembloids, and organoids-on-a-chip technologies, which allow for enhanced physiological relevance. These technologies have shown great potential for mimicking coordinated organogenesis, exploring disease pathogenesis, and facilitating drug discovery. As the central organ of the cardiovascular system, the heart serves as the focal point of an extensively studied network of interactions. This review focuses on the advancements and challenges of hiPSC-derived humanoid organoids in studying interactions between the heart and other organs, presenting a comprehensive exploration of this cutting-edge approach in systemic disease research.

Comprehensive promotion of iPSC-CM maturation by integrating metabolic medium with nanopatterning and electrostimulation

The immaturity of human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) is a major limitation for their use in drug screening to identify pro-arrhythmogenic or cardiotoxic molecules. Here, we demonstrate an approach that combines lipid-enriched maturation medium with a high concentration of calcium, nanopatterning of culture surfaces and electrostimulation to generate iPSC-CMs with advanced electrophysiological, structural and metabolic phenotypes. Systematic testing reveals that electrostimulation is the key driver of enhanced mitochondrial development and metabolic maturation and improved electrophysiological properties of iPSC-CMs. Increased calcium concentration strongly promotes electrophysiological maturation, while nanopatterning primarily facilitates sarcomere organisation with minor effect on electrophysiological properties. Transcriptome analysis reveals that activation of HMCES and TFAM targets contributes to mitochondrial development, whereas downregulation of MAPK/PI3K and SRF targets is associated with iPSC-CM polyploidy. These findings provide mechanistic insights into iPSC-CM maturation, paving the way for pharmacological responses that more closely resemble those of adult CMs.

Human iPSC-Derived Motor Neuron Innervation Enhances the Differentiation of Muscle Bundles Engineered with Benchtop Fabrication Techniques

Engineered skeletal muscle tissues are critical tools for disease modeling, drug screening, and regenerative medicine, but are limited by insufficient maturation. Because innervation is a critical regulator of skeletal muscle development and regeneration in vivo, motor neurons are hypothesized to improve the maturity of engineered skeletal muscle tissues. However, the impact of motor neurons on muscle phenotype when added prior to the onset of muscle differentiation is not clearly established. In this study, benchtop fabrication equipment was used to facilely fabricate chambers for engineering three-dimensional (3D) skeletal muscles bundles and measuring their contractile performance. Primary chick myoblasts were embedded in an extracellular matrix hydrogel solution and differentiated into engineered muscle bundles, with or without the addition of human induced pluripotent stem cell (hiPSC)-derived motor neurons. Muscle bundles differentiated with motor neurons had neurites distributed throughout their volume and a higher myogenic index compared to muscle bundles without motor neurons. Innervated muscle bundles also generated significantly higher twitch and tetanus forces in response to electrical field stimulation after 1 and 2 weeks of differentiation compared to noninnervated muscle bundles cultured with or without neurotrophic factors. Noninnervated muscle bundles also experienced a decline in rise and fall times as the culture progressed, whereas innervated muscle bundles and noninnervated muscle bundles with neurotrophic factors maintained more consistent rise and fall times. Innervated muscle bundles also expressed the highest levels of the genes for slow myosin light chain 3 (MYL3) and myoglobin (MB), which are associated with slow twitch fibers. These data suggest that motor neuron innervation enhances the structural and functional development of engineered skeletal muscle constructs and maintains them in a more oxidative phenotype.

Multi-layered electrode constructs for neural tissue engineering

Although neural tissue engineering holds great therapeutic potential for multiple clinical applications, one important challenge is the development of scaffolds that provide cues required for neural tissue development. To achieve this, biomaterial systems can be leveraged to present appropriate biological, mechanical, topographical and electrical cues that could direct cell fate. In this study, a multi-layered electrode construct was engineered to be used as a platform for 3D cell encapsulation for in vitro applications. The first layer is a conductive hydrogel coating, that improves electrical conductivity from the underlying platinum electrode. The second layer is a biosynthetic hydrogel, specifically tailored to support neural development. This layered electrode construct was electrochemically characterised, and a numerical model was applied to study electrical stimuli reaching the biosynthetic hydrogel layer. The construct was shown to effectively support the growth and proliferation of encapsulated astrocytes within the biosynthetic layer, while the numerical model will enable computational experimentation for benchmarking and study validation. This highly versatile system represents a robust tool to study the influence of electrical stimuli on neural fate, as well as investigating the development of biohybrid interfaces in vitro.

Engineering Highly Aligned and Densely Populated Cardiac Muscle Bundles via Fibrin Remodeling in 3D-Printed Anisotropic Microfibrous Lattices

Replicating the structural and functional features of native myocardium, particularly its high-density cellular alignment and efficient electrical connectivity, is essential for engineering functional cardiac tissues. Here, novel electrohydrodynamically printed InterPore microfibrous lattices with anisotropic architectures are introduced to promote high-density cellular alignment and enhanced tissue interconnectivity. The interconnected pores in the microfibrous lattice enable dynamic, cell-mediated remodeling of fibrous hydrogels, resulting in continuous, mechanically stable tissue bundles. Compared to lattices with isolated pores, the engineered aligned cardiac tissues from neonatal rat cardiomyocytes exhibit improved electrophysiological properties and synchronous contractions. Using a multiseeding strategy, an equivalent cell seeding density of 8 × 107 cells mL-1, facilitating the formation of multicellular, vascularized cardiac structures with maintained tissue viability and integrity, is achieved. As a demonstration, human-induced pluripotent stem cell-derived cardiac tissues are engineered with progressive maturation and functional integration over time. These findings underscore the potential of InterPore microfibrous lattices for applications in cardiac tissue engineering, drug discovery, and therapeutic development.

A novel perspective on the regulation of cardiac cell beating: cardiac cell under mechanical stimulation acts as "cell activation button" to activate adjacent cardiac cell

The regulation of cardiac cell beating is of great significance for understanding cardiac coordination mechanisms and the treatment of cardiovascular diseases. Inspired by this natural "cell regulates cell" mode in which sinoatrial node cells regulate atrial myocytes, this study presented a novel method to replicate this behavior in vitro through mechanical stimulation. Primary cardiac cells from Sprague-Dawley rats were isolated, cultured in 2D substrates, and applied to precise mechanical stimulation by developing a micro-manipulation platform. We demonstrated that a mechanical probe can act as an external activation device for quiescent cardiac cells, transforming them into "activation cells" capable of activating adjacent "target cells" through bioelectrical coupling. Calcium imaging with Fluo-4 probes revealed that this "cell activates cell" mechanism relies on mechano-electric feedback and calcium-mediated signal propagation via cell junctions. Our findings provide a non-destructive strategy to regulate target cardiac cell, deepen insights into the mechanical modulation of intercellular communication, and offer a framework for studying arrhythmias linked to abnormal cell-cell communication. This work combined mechanical intervention with biological signaling, advancing potential applications in cardiovascular therapeutics.

FORCETRACKER: A versatile tool for standardized assessment of tissue contractile properties in 3D Heart-on-Chip platforms

Engineered heart tissues (EHTs) have shown great potential in recapitulating tissue organization, functions, and cell-cell interactions of the human heart in vitro. Currently, multiple EHT platforms are used by both industry and academia for different applications, such as drug discovery, disease modelling, and fundamental research. The tissues' contractile force, one of the main hallmarks of tissue function and maturation level of cardiomyocytes, can be read out from EHT platforms by optically tracking the movement of elastic pillars induced by the contractile tissues. However, existing optical tracking algorithms which focus on calculating the contractile force are customized and platform-specific, often not available to the broad research community, and thus hamper head-to-head comparison of the model output. Therefore, there is the need for robust, standardized and platform-independent software for tissues' force assessment. To meet this need, we developed ForceTracker: a standalone and computationally efficient software for analyzing contractile properties of tissues in different EHT platforms. The software uses a shape-detection algorithm to single out and track the movement of pillars' tips for the most common shapes of EHT platforms. In this way, we can obtain information about tissues' contractile performance. ForceTracker is coded in Python and uses a multi-threading approach for time-efficient analysis of large data sets in multiple formats. The software efficiency to analyze circular and rectangular pillar shapes is successfully tested by analyzing different format videos from two EHT platforms, developed by different research groups. We demonstrate robust and reproducible performance of the software in the analysis of tissues over time and in various conditions. ForceTracker's detection and tracking shows low sensitivity to common incidental defects, such as alteration of tissue shape or air bubbles. Detection accuracy is determined via comparison with manual measurements using the software ImageJ. We developed ForceTracker as a tool for standardized analysis of contractile performance in EHT platforms to facilitate research on disease modeling and drug discovery in academia and industry.

A Platform Integrating Biophysical and Biochemical Stimuli to Enhance Differentiation and Maturation of Cardiomyocyte Subtypes Derived from Human Induced Pluripotent Stem Cells

To enhance the differentiation and maturation of cardiomyocytes derived from human induced pluripotent stem cells, we developed a bioreactor system that simultaneously imposes biophysical and biochemical stimuli on these committed cardiomyocytes. The cells were cultured within biohydrogels composed of the extracellular matrix extracted from goat ventricles and purchased rat-origin collagen, which were housed in the elastic PDMS culture chambers of the bioreactor. Elastic and flexible electrodes composed of PEDOT/PSS, latex, and graphene flakes were embedded in the hydrogels and chamber walls, allowing cyclic stretch and electrical pulses to be simultaneously and coordinately applied to the cultured cells. Furthermore, a dynamic analysis method employing the transverse forced oscillation theory of a cantilever was used to analyze and discriminate the subtype-specific beating behavior of the cardiomyocytes. It was found that myosin light chain 2v (MLC2v), a ventricular cell marker, was primarily upregulated in cells aggregated on the (+) electrode side, while cardiomyocytes with faint MLC2v but strong cardiac troponin T (cTNT) expression aggregated at the ground electrode (GND) side. mRNA analysis using rtPCR and the gel beating dynamics further suggested a subtype deviation on the different electrode sides. This study demonstrated the potential of our bioreactor system in enhancing cardiac differentiation and maturation, and it showed an intriguing phenomenon of cardiomyocyte subtype aggregation on different electrodes, which may be developed into a new method to enhance the maturation and separation of cardiomyocyte subtypes.

Novel, low-cost bioreactor for in vitro electrical stimulation of cardiac cells

Introduction

The successful implantation of laboratory-grown cardiac tissue requires phenotypically mature cardiomyocytes capable of electrophysiological integration with native heart tissue. Pulsed electrical stimulation (ES) has been identified as a promising strategy for enhancing cardiomyocyte maturation. However, there are discrepancies in the literature as to best practices for promoting cardiac differentiation using ES.

Methods

This study presents a novel, 3D printed bioreactor that delivers in vitro ES to human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs), promoting cell maturity and functional readiness for implantation. Finite element analysis and mathematical modeling were used to model the fluid dynamics and to characterize in detail the delivery of pulsatile electrical signals, providing precise control over stimulation parameters such as voltage, current, and charge.

Results

The bioreactor developed here provides an easy-to-use, inexpensive platform for culturing hiPSC-CMs under the influence of ES and low-shear fluid flow for enhanced nutrient availability, while its "drop-in" design facilitates real-time observation of cultured cells. The electrical stimulation provided is controlled, modeled, and predictable, enabling reproducible experimental conditions and promoting comparability across future studies. Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) grown in the bioreactor with ES showed improved differentiation and an enhanced ability to respond to external electrical pacing signals.

Discussion

By offering a standardized platform for ES-based cardiomyocyte maturation, this bioreactor aims to accelerate advancements in cardiac tissue engineering. Future research will explore how variations in ES parameters influence cardiomyocyte phenotype and maturation, contributing to a deeper understanding of cardiac cell development and optimization for therapeutic applications.

Development and application of 3D cardiac tissues derived from human pluripotent stem cells

Recently human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) have become an attractive platform to evaluate drug responses for cardiotoxicity testing and disease modeling. Moreover, three-dimensional (3D) cardiac models, such as engineered heart tissues (EHTs) developed by bioengineering approaches, and cardiac spheroids (CSs) formed by spherical aggregation of hPSC-CMs, have been established as useful tools for drug discovery and transplantation. These 3D models overcome many of the shortcomings of conventional 2D hPSC-CMs, such as immaturity of the cells. Cardiac organoids (COs), like other organs, have also been studied to reproduce structures that resemble a heart in vivo more closely and optimize various culture conditions. Heart-on-a-chip (HoC) developed by a microfluidic chip-based technology that enables real-time monitoring of contraction and electrical activity, provides multifaceted information that is essential for capturing natural tissue development in vivo. Recently, 3D experimental systems have been developed to study organ interactions in vitro. This review aims to discuss the developments and advancements of hPSC-CMs and 3D cardiac tissues.

Utilizing Tissues Self-Assembled in Fiber Optic-Based "Chinese Guzheng Strings" for Contractility Sensing and Drug Efficacy Evaluation: A Practical Approach

Recent advances in drug design and compound synthesis have highlighted the increasing need for effective methods of toxicity evaluation. A specialized force sensor, known as the light wavelength-encoded "Chinese guzheng" is developed. This innovative sensor is equipped with optical fiber strings and utilizes a wavelength-encoded fiber Bragg grating (FBG) that is chemically etched to reduce its diameter. This design allows the sensor to detect minimal forces as low as l µN. This sensor is successfully applied to monitor human-induced pluripotent stem cell-derived human-engineered heart tissue (hEHT) models that can self-assemble and contact optical fiber-based strings. The sensor detects micro newton contraction forces in real-time by measuring the wavelength drift resulting from hEHT contractions. In addition, the sensor is precise and durable, exhibiting a fatigue resistance of up to 800 000 cycles, making it suitable for long-term monitoring. The device effectively measured the contractile force of the hEHTs under various physiological conditions, including natural contraction, electrical stimulation, and stretching. Moreover, multichannel detection enables the study and demonstration of short- and long-term effectiveness of multiple drugs. This breakthrough sensor addresses the critical need for high-precision real-time monitoring in drug evaluation and provides a solid foundation for screening drugs to treat cardiomyopathy.

Heart-on-a-Miniscope: A Miniaturized Solution for Electrophysiological Drug Screening in Cardiac Organoids

Cardiovascular toxicity remains a primary concern in drug development, accounting for a significant portion of post-market drug withdrawals due to adverse reactions such as arrhythmias. Traditional preclinical models, predominantly based on animal cells, often fail to replicate human cardiac physiology accurately, complicating the prediction of drug-induced effects. Although human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) provide a more genetically relevant system, their use in 2D, static cultures does not sufficiently mimic the dynamic, 3D environment of the human heart. 3D cardiac organoids made from human iPSC-CMs can potentially bridge this gap. However, most traditional electrophysiology assays, developed for single cells or 2D monolayers, are not readily adaptable to 3D organoids. This study uses optical calcium analysis of human organoids combined with miniaturized fluorescence microscopy (miniscope) and heart-on-a-chip technology. This simple, inexpensive, and efficient platform provides robust on-chip calcium imaging of human cardiac organoids. The versatility of the system is demonstrated through cardiotoxicity assay of drugs known to impact cardiac electrophysiology, including dofetilide, quinidine, and thapsigargin. The platform promises to advance drug testing by providing a more reliable and physiologically relevant assessment of cardiovascular toxicity, potentially reducing drug-related adverse effects in clinical settings.

Revolutionizing cardiovascular research: Human organoids as a Beacon of hope for understanding and treating cardiovascular diseases

Organoids, exhibiting the capability to undergo differentiation in specific in vitro growth environments, have garnered significant attention in recent years due to their capacity to recapitulate human organs with resemblant in vivo structures and physiological functions. This groundbreaking technology offers a unique opportunity to study human diseases and address the limitations of traditional animal models. Cardiovascular diseases (CVDs), a leading cause of mortality worldwide, have spurred an increasing number of researchers to explore the great potential of human cardiovascular organoids for cardiovascular research. This review initiates by elaborating on the development and manufacture of human cardiovascular organoids, including cardiac organoids and blood vessel organoids. Next, we provide a comprehensive overview of their applications in modeling various cardiovascular disorders. Furthermore, we shed light on the prospects of cardiovascular organoids in CVDs therapy, and unfold an in-depth discussion of the current challenges of human cardiovascular organoids in the development and application for understanding and treating CVDs.

Applications of carbon dot-mediated cardiomyocyte maturation in regenerative medicine: a review

The maturation of cardiomyocytes (CMs) plays key roles in regenerative medicine and the treatment of cardiovascular diseases via stem cell-derived CMs. Carbon dots (CDs) have good biocompatibility, optical properties, and electrophysical properties and have been widely applied in bioimaging, biosensors, and biotherapy. In this review, we comprehensively summarize recent advances in promoting the maturation of CMs, mainly human pluripotent stem cell-derived CMs, and related regenerative medicine. Moreover, we explore the innovative application of CDs to enhance the maturation of these CMs. Finally, we look forward to the future design and application of CDs in the maturation of CMs in terms of cell therapies.

Stretchable impedance electrode array with high durability for monitoring of cells under mechanical and chemical stimulations

Electrochemical impedance spectroscopy (EIS) serves as a non-invasive technique for assessing cell status, while mechanical stretching plays a pivotal role in stimulating cells to emulate their natural environment. Integrating these two domains enables the concurrent application of mechanical stimulation and EIS in a stretchable cell culture system. However, challenges arise from the difficulty in creating a durable and stable stretchable impedance electrode array. To overcome this limitation, we have developed a cell culture system integrated with a stretchable impedance electrode array (SIEA). This design enabled impedance monitoring during cell proliferation under mechanical stimulation over a long period of time due to the high mechanical durability and electrochemical stability of the SIEA. Our evaluation also involved testing the cytotoxicity of doxorubicin on H9C2 cells directly on the SIEA. The results underscore the significant potential of our SIEA device as an effective tool for monitoring cells subjected to mechanical stimulation and as a platform for drug toxicity testing.

LMNA-related cardiomyopathy: From molecular pathology to cardiac gene therapy

BACKGROUND

The genetic variants of LMNA cause an array of diseases that often affect the heart. LMNA-related cardiomyopathy exhibits high-penetrance and early-onset phenotypes that lead to late-stage heart failure or lethal arrhythmia. As a subtype of dilated cardiomyopathy and arrhythmogenic cardiomyopathy, LMNA-related cardiac dysfunction is resistant to existing cardiac therapeutic strategies, leaving a major unmet clinical need in cardiomyopathy management.

AIM OF REVIEW

Here we comprehensively summarize current knowledge about the genetic basis, disease models and pathological mechanisms of LMNA-related cardiomyopathy. Recent translational studies were highlighted to indicate new therapeutic modalities such as gene supplementation, gene silencing and genome editing therapy, which offer potential opportunities to overcome the difficulties in the development of specific drugs for this disease.

KEY SCIENTIFIC CONCEPTS OF REVIEW

LMNA-related cardiomyopathy involves many diverse disease mechanisms that preclude small-molecule drugs that target only a small fraction of the mechanisms. Agreeing to this notion, the first-in-human clinical trial for this disease recently reported futility. By contrast, gene therapy offers the new hope to directly intervene LMNA variants and demonstrates a tremendous potential for breakthrough therapy for this disease. Concepts in this review are also applicable to studies of other genetic diseases that lack effective therapeutics.

Bioprinting approaches in cardiac tissue engineering to reproduce blood-pumping heart function

The heart, with its complex structural and functional characteristics, plays a critical role in sustaining life by pumping blood throughout the entire body to supply nutrients and oxygen. Engineered heart tissues have been introduced to reproduce heart functions to understand the pathophysiological properties of the heart and to test and develop potential therapeutics. Although numerous studies have been conducted in various fields to increase the functionality of heart tissue to be similar to reality, there are still many difficulties in reproducing the blood-pumping function of the heart. In this review, we discuss advancements in cells, biomaterials, and biofabrication in cardiac tissue engineering to achieve cardiac models that closely mimic the pumping function. Moreover, we provide insight into future directions by proposing future perspectives to overcome remaining challenges, such as scaling up and biomimetic patterning of blood vessels and nerves through bioprinting.

Induced pluripotent stem cell-derived cardiomyocyte in vitro models: benchmarking progress and ongoing challenges

Recent innovations in differentiating cardiomyocytes from human induced pluripotent stem cells (hiPSCs) have unlocked a viable path to creating in vitro cardiac models. Currently, hiPSC-derived cardiomyocytes (hiPSC-CMs) remain immature, leading many in the field to explore approaches to enhance cell and tissue maturation. Here, we systematically analyzed 300 studies using hiPSC-CM models to determine common fabrication, maturation and assessment techniques used to evaluate cardiomyocyte functionality and maturity and compiled the data into an open-access database. Based on this analysis, we present the diversity of, and current trends in, in vitro models and highlight the most common and promising practices for functional assessments. We further analyzed outputs spanning structural maturity, contractile function, electrophysiology and gene expression and note field-wide improvements over time. Finally, we discuss opportunities to collectively pursue the shared goal of hiPSC-CM model development, maturation and assessment that we believe are critical for engineering mature cardiac tissue.

Conductive Microfibers Improve Stem Cell-Derived Cardiac Spheroid Maturation

Conventional two-dimensional (2D) cardiomyocyte differentiation protocols create cells with limited maturity, which impairs their predictive capacity and has driven interest in three-dimensional (3D) engineered cardiac tissue models of varying maturity and scalability. Cardiac spheroids are attractive high-throughput models that have demonstrated improved functional and transcriptional maturity over conventional 2D differentiations. However, these 3D models still tend to have limited contractile and electrical maturity compared to highly engineered cardiac tissues; hence, we incorporated a library of conductive polymer microfibers in cardiac spheroids to determine if fiber properties could accelerate maturation. Conductive microfibers improved contractility parameters of cardiac spheroids over time versus nonconductive fibers, specifically, when they were short, for example, 5 μm, and when there was moderate fiber mass per spheroid, for example, 20 μg. Spheroids with optimal conductive microfiber length and concentration developed a thicker ring-like perimeter and a less compacted cavity, improving their contractile work compared to control cardiac spheroids. Functional improvements correlated with increased expression of contractility and calcium handling-related cardiac proteins, as well as improved calcium handling abilities and drug response. Taken together, these data suggest that conductive microfibers can improve cardiac spheroid performance to improve cardiac disease modeling.

[Safety and efficacy assessments using human iPS cell-derived cardiomyocytes]

The delay and loss of drugs are serious problems in Japan. To overcome this issue, it is important to strengthen drug development capabilities. For drug development, the establishment and advancement of non-clinical testing methods are necessary for safe and effective clinical trials. Recently, the movement toward alternatives to animal testing has accelerated internationally. New Approach Methodologies (NAMs), such as human inducible pluripotent stem cell (hiPSC) technology and in silico modeling & simulation, are considered valuable for drug development. It has been demonstrated that hiPSC-derived cardiomyocytes (hiPSC-CMs) are useful tools to assess drug-induced cardiotoxicity, including arrhythmia and cardiac contractile dysfunction, leading to the use of hiPSC-CMs in the drug review process. Advancing hiPSC technologies have enabled the generation of mature hiPSC-CMs and engineered heart tissues, which are expected to provide novel information in drug safety and efficacy evaluation. Furthermore, it would be possible to establish the non-clinical evaluation that takes into account individual differences by developing hiPSCs bearing characteristics specific to certain populations, such as pediatrics or rare disease patients. Here, we present the recent findings and future perspectives on non-clinical evaluation using hiPSC technology.

Promising tools for future drug discovery and development in antiarrhythmic therapy

Arrhythmia refers to irregularities in the rate and rhythm of the heart, with symptoms spanning from mild palpitations to life-threatening arrhythmias and sudden cardiac death. The complex molecular nature of arrhythmias complicates the selection of appropriate treatment. Current therapies involve the use of antiarrhythmic drugs (class I-IV) with limited efficacy and dangerous side effects and implantable pacemakers and cardioverter-defibrillators with hardware-related complications and inappropriate shocks. The number of novel antiarrhythmic drugs in the development pipeline has decreased substantially during the last decade and underscores uncertainties regarding future developments in this field. Consequently, arrhythmia treatment poses significant challenges, prompting the need for alternative approaches. Remarkably, innovative drug discovery and development technologies show promise in helping advance antiarrhythmic therapies. In this article, we review unique characteristics and the transformative potential of emerging technologies that offer unprecedented opportunities for transitioning from traditional antiarrhythmics to next-generation therapies. We assess stem cell technology, emphasizing the utility of innovative cell profiling using multiomics, high-throughput screening, and advanced computational modeling in developing treatments tailored precisely to individual genetic and physiological profiles. We offer insights into gene therapy, peptide, and peptibody approaches for drug delivery. We finally discuss potential strengths and weaknesses of such techniques in reducing adverse effects and enhancing overall treatment outcomes, leading to more effective, specific, and safer therapies. Altogether, this comprehensive overview introduces innovative avenues for personalized rhythm therapy, with particular emphasis on drug discovery, aiming to advance the arrhythmia treatment landscape and the prevention of sudden cardiac death. SIGNIFICANCE STATEMENT: Arrhythmias and sudden cardiac death account for 15%-20% of deaths worldwide. However, current antiarrhythmic therapies are ineffective and have dangerous side effects. Here, we review the field of arrhythmia treatment underscoring the slow progress in advancing the cardiac rhythm therapy pipeline and the uncertainties regarding evolution of this field. We provide information on how emerging technological and experimental tools can help accelerate progress and address the limitations of antiarrhythmic drug discovery.

The Low Tumorigenic Risk and Subtypes of Cardiomyocytes Derived from Human-induced Pluripotent Stem Cells

BACKGROUND

Clinical application of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) is a promising approach for the treatment of heart diseases. However, the tumorigenicity of hiPSC-CMs remains a concern for their clinical applications and the composition of the hiPSC-CM subtypes need to be clearly identified.

METHODS

In the present study, hiPSC-CMs were induced from hiPSCs via modulation of Wnt signaling followed by glucose deprivation purification. The structure, function, subpopulation composition, and tumorigenic risk of hiPSC-CMs were evaluated by single-cell RNA sequencing (scRNAseq), whole exome sequencing (WES), and integrated molecular biology, cell biology, electrophysiology, and/or animal experiments.

RESULTS

The high purity of hiPSC-CMs, determined by flow cytometry analysis, was generated. ScRNAseq analysis of differentiation day (D) 25 hiPSC-CMs did not identify the transcripts representative of undifferentiated hiPSCs. WES analysis showed a few newly acquired confidently identified mutations and no mutations in tumor susceptibility genes. Further, no tumor formation was observed after transplanting hiPSC-CMs into NOD-SCID mice for 3 months. Moreover, D25 hiPSC-CMs were composed of subtypes of ventricular-like cells (23.19%) and atrial-like cells (66.45%) in different cell cycle stages or mature levels, based on the scRNAseq analysis. Furthermore, a subpopulation of more mature ventricular cells (3.21%) was identified, which displayed significantly up-regulated signaling pathways related to myocardial contraction and action potentials. Additionally, a subpopulation of cardiomyocytes in an early differentiation stage (3.44%) experiencing nutrient stress-induced injury and heading toward apoptosis was observed.

CONCLUSIONS

This study confirmed the biological safety of hiPSC-CMs and described the composition and expression profile of cardiac subtypes in hiPSC-CMs which provide standards for quality control and theoretical supports for the translational applications of hiPSC-CMs.

Current Advances and Future Directions of Pluripotent Stem Cells-Derived Engineered Heart Tissue for Treatment of Cardiovascular Diseases

Cardiovascular diseases resulting from myocardial infarction (MI) remain a leading cause of death worldwide, imposing a substantial burden on global health systems. Current MI treatments, primarily pharmacological and surgical, do not regenerate lost myocardium, leaving patients at high risk for heart failure. Engineered heart tissue (EHT) offers a promising solution for MI and related cardiac conditions by replenishing myocardial loss. However, challenges like immune rejection, inadequate vascularization, limited mechanical strength, and incomplete tissue maturation hinder clinical application. The discovery of human-induced pluripotent stem cells (hiPSCs) has transformed the EHT field, enabling new bioengineering innovations. This review explores recent advancements and future directions in hiPSC-derived EHTs, focusing on innovative materials and fabrication methods like bioprinting and decellularization, and assessing their therapeutic potential through preclinical and clinical studies. Achieving functional integration of EHTs in the heart remains challenging due to the need for synchronized contraction, sufficient vascularization, and mechanical compatibility. Solutions such as genome editing, personalized medicine, and AI technologies offer promising strategies to address these translational barriers. Beyond MI, EHTs also show potential in treating ischemic cardiomyopathy, heart valve engineering, and drug screening, underscoring their promise in cardiovascular regenerative medicine.

An AI-Cyborg System for Adaptive Intelligent Modulation of Organoid Maturation

Recent advancements in flexible bioelectronics have enabled continuous, long-term stable interrogation and intervention of biological systems. However, effectively utilizing the interrogated data to modulate biological systems to achieve specific biomedical and biological goals remains a challenge. In this study, we introduce an AI-driven bioelectronics system that integrates tissue-like, flexible bioelectronics with cyber learning algorithms to create a long-term, real-time bidirectional b ioelectronic interface with o ptimized a daptive intelligent m odulation (BIO-AIM). When integrated with biological systems as an AI-cyborg system, BIO-AIM continuously adapts and optimizes stimulation parameters based on stable cell state mapping, allowing for real-time, closed-loop feedback through tissue-embedded flexible electrode arrays. Applied to human pluripotent stem cell-derived cardiac organoids, BIO-AIM identifies optimized stimulation conditions that accelerate functional maturation. The effectiveness of this approach is validated through enhanced extracellular spike waveforms, increased conduction velocity, and improved sarcomere organization, outperforming both fixed and no stimulation conditions.

Enhancing the Maturation of Human Pluripotent Stem Cell-Derived Cardiomyocytes with an n-Type Organic Semiconductor Coating

Human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) are a promising cell source for cardiac regenerative medicine and in vitro modeling. However, hPSC-CMs exhibit immature structural and functional properties compared with adult cardiomyocytes. Various electrical, mechanical, and biochemical cues have been applied to enhance hPSC-CM maturation but with limited success. In this work, we investigated the potential application of the semiconducting polymer poly{[N,N'-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)} (P(NDI2OD-T2)) as a light-sensitive material to stimulate hPSC-CMs optically. Our results indicated that P(NDI2OD-T2)-mediated photostimulation caused cell damage at irradiances applied long-term above 36 μW/mm2 and did not regulate cardiac monolayer beating (after maturation) at higher intensities applied in a transient fashion. However, we discovered that the cells grown on P(NDI2OD-T2)-coated substrates showed significantly enhanced expression of cardiomyocyte maturation markers in the absence of a light exposure stimulus. A combination of techniques, such as atomic force microscopy, scanning electron microscopy, and quartz crystal microbalance with dissipation monitoring, which we applied to investigate the interface of the cell with the n-type coating, revealed that P(NDI2OD-T2) impacted the nanostructure, adsorption, and viscoelasticity of the Matrigel coating used as a cell adhesion promoter matrix. This modified cellular microenvironment promoted the expression of cardiomyocyte maturation markers related to contraction, calcium handling, metabolism, and conduction. Overall, our findings demonstrate that conjugated polymers such as P(NDI2OD-T2) can be used as passive coatings to direct stem cell fate through interfacial engineering of cell growth substrates.

Advancing Cardiac Organoid Engineering Through Application of Biophysical Forces

Cardiac organoids represent an important bioengineering opportunity in the development of models to study human heart pathophysiology. By incorporating multiple cardiac cell types in three-dimensional culture and developmentally-guided biochemical signaling, cardiac organoids recapitulate numerous features of heart tissue. However, cardiac tissue also experiences a variety of mechanical forces as the heart develops and over the course of each contraction cycle. It is now clear that these forces impact cellular specification, phenotype, and function, and should be incorporated into the engineering of cardiac organoids in order to generate better models. In this review, we discuss strategies for engineering cardiac organoids and report the effects of organoid design on the function of cardiac cells. We then discuss the mechanical environment of the heart, including forces arising from tissue elasticity, contraction, blood flow, and stretch, and report on efforts to mimic these biophysical cues in cardiac organoids. Finally, we review emerging areas of cardiac organoid research, for the study of cardiac development, the formation of multi-organ models, and the simulation of the effects of spaceflight on cardiac tissue and consider how these investigations might benefit from the inclusion of mechanical cues.

Human iPSC-derived motor neuron innervation enhances the differentiation of muscle bundles engineered with benchtop fabrication techniques

Engineered skeletal muscle tissues are critical tools for disease modeling, drug screening, and regenerative medicine, but are limited by insufficient maturation. Because innervation is a critical regulator of skeletal muscle development and regeneration in vivo, motor neurons are hypothesized to improve the maturity of engineered skeletal muscle tissues. Although motor neurons have been added to pre-engineered muscle constructs, the impact of motor neurons added prior to the onset of muscle differentiation has not been evaluated. In this study, benchtop fabrication equipment was used to facilely fabricate chambers for engineering 3-dimensional (3-D) skeletal muscles bundles and measuring their contractile performance. Primary chick myoblasts were embedded in an extracellular matrix hydrogel solution and differentiated into engineered muscle bundles, with or without the addition of human induced pluripotent stem cell (hiPSC)-derived motor neurons. Muscle bundles differentiated with motor neurons had neurites distributed throughout their volume and a higher myogenic index compared to muscle bundles without motor neurons. Innervated muscle bundles also generated significantly higher twitch and tetanus forces in response to electrical field stimulation after one and two weeks of differentiation compared to non-innervated muscle bundles cultured with or without neurotrophic factors. Non-innervated muscle bundles also experienced a decline in rise and fall times as the culture progressed, whereas innervated muscle bundles and non-innervated muscle bundles with neurotrophic factors maintained more consistent rise and fall times. Innervated muscle bundles also expressed the highest levels of the genes for slow myosin light chain 3 (MYL3) and myoglobin (MB), which are associated with slow twitch fibers. These data suggest that motor neuron innervation enhances the structural and functional development of engineered skeletal muscle constructs and maintains them in a more oxidative phenotype.

Matrix Architecture and Mechanics Regulate Myofibril Organization, Costamere Assembly, and Contractility in Engineered Myocardial Microtissues

The mechanical function of the myocardium is defined by cardiomyocyte contractility and the biomechanics of the extracellular matrix (ECM). Understanding this relationship remains an important unmet challenge due to limitations in existing approaches for engineering myocardial tissue. Here, they established arrays of cardiac microtissues with tunable mechanics and architecture by integrating ECM-mimetic synthetic, fiber matrices, and induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs), enabling real-time contractility readouts, in-depth structural assessment, and tissue-specific computational modeling. They found that the stiffness and alignment of matrix fibers distinctly affect the structural development and contractile function of pure iPSC-CM tissues. Further examination into the impact of fibrous matrix stiffness enabled by computational models and quantitative immunofluorescence implicates cell-ECM interactions in myofibril assembly, myofibril maturation, and notably costamere assembly, which correlates with improved contractile function of tissues. These results highlight how iPSC-CM tissue models with controllable architecture and mechanics can elucidate mechanisms of tissue maturation and disease.

Contractile responses of engineered human μmyometrium to prostaglandins and inflammatory cytokines

Preterm labor is a prevalent public health problem and occurs when the myometrium, the smooth muscle layer of the uterus, begins contracting before the fetus reaches full term. Abnormal contractions of the myometrium also underlie painful menstrual cramps, known as dysmenorrhea. Both disorders have been associated with increased production of prostaglandins and cytokines, yet the functional impacts of inflammatory mediators on the contractility of human myometrium have not been fully established, in part due to a lack of effective model systems. To address this, we engineered human myometrial microtissues (μmyometrium) on compliant hydrogels designed for traction force microscopy. We then measured μmyometrium contractility in response to a panel of compounds with known contractile effects and inflammatory mediators. We observed that prostaglandin F2α, interleukin 6, and interleukin 8 induced contraction, while prostaglandin E1 and prostaglandin E2 induced relaxation. Our data suggest that inflammation may be a key factor modulating uterine contractility in conditions including, but not limited to, preterm labor or dysmenorrhea. More broadly, our μmyometrium model can be used to systematically identify the functional impact of many small molecules on human myometrium.