Modeling Heart Diseases on a Chip: Advantages and Future Opportunities

Towards advanced regenerative therapeutics to tackle cardio-cerebrovascular diseases

The development of vascularized organoids as novel modelling tools of the human cardio-cerebrovascular system for preclinical research has become an essential platform for studying human vascularized tissues/organs for development of personalized therapeutics during recent decades. Organ-on-chip technology is promising for investigating physiological in vitro responses in drug screening development and advanced disease models. Vascularized tissue/organ-on-a-chip benefits every step of drug discovery pipeline as a screening tool with close human genome relevance to investigate human systems biology. Simultaneously, cardio-cerebrovascular-on-chip-integrated microfluidic system serves as an alternative to preclinical animal research for studying (patho-)physiological processes of human blood vessels during embryonic development and cardio-cerebrovascular disease. Integrated with next-generation techniques, such as three-dimensional bioprinting of both cells and matrix, may enable vascularized organoid-on-chip-based novel drug development as personalized therapeutics.

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.

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.

Cardiac-Focused Multi-Organ Chips: Advanced Disease Modeling, Drug Testing, and Inter-Organ Communication

Heart disease remains a leading cause of mortality worldwide, posing a significant challenge to global healthcare systems. Traditional animal models and cell culture techniques are instrumental in advancing the understanding of cardiac pathophysiology. However, these methods are limited in their ability to fully replicate the heart's intricate functions. This underscores the need for a deeper investigation into the fundamental mechanisms of heart disease. Notably, cardiac pathology is often influenced by systemic factors, with conditions in other organs contributing to disease onset and progression. Cardiac-focused multi-organ chip technology has emerged to better elucidate these complex inter-organ communications and address the limitations of current in vitro models. This technology offers a novel approach by recreating the cardiac microenvironment and integrating it with other organ systems, thereby enabling more precise disease modeling and drug toxicity assessment. This review provides a comprehensive overview of the heart's structure and function, explores the advancements in cardiac organ chip development, and highlights the applications of cardiac-focused multi-organ chips in medical research. Finally, the future potential of this technology in enhancing disease modeling and therapeutic evaluation is discussed.

Microfluidic organoid-slice-on-a-chip system for studying anti-cholangiocarcinoma drug efficacy and hepatorenal toxicity

Organ-chip technology, in contrast to cell culture and animal models, offers a promising platform for accelerating drug development. However, current chip designs simulate human organ functions and there is a lack of multi-organ chip designs that can simultaneously study drug efficacy and hepatorenal toxicity. Here, we developed a novel microfluidic multi-organ chip that integrated cholangiocarcinoma organoids (CCOs) with recellularized liver slices (RLS) and recellularized kidney slices (RKS), to simultaneously assess anti-cholangiocarcinoma drug efficacy and hepatorenal toxicity. Co-culture of patient-derived CCOs with RLS and RKS was successfully achieved for 7 days under flow conditions with enhanced liver and renal cell functions. Furthermore, an in vitro biomimetic model showed IC50 values of trastuzumab emtansine (T-DM1) of around 6.42 ± 7.34 μg mL-1 in four clinical cases, with one outlier of 77.77 μg mL-1 due to patient variability. Post-treatment, RLS and RKS cell viability remained high at 75.67% and 81.03%, respectively, suggesting low hepatorenal toxicity of T-DM1 for treating cholangiocarcinoma. Our study demonstrates the use of an organoid-slice-on-a-chip (OSOC) platform for personalized drug efficacy and toxicity assessment, particularly aiming at leveraging anticancer drugs for off-label use to save patient lives.

Bioengineering Approaches to In Vitro Modeling of Genetic and Acquired Cardiac Diseases

PURPOSE OF REVIEW

This review aims to explore recent advancements in bioengineering approaches used in developing and testing in vitro cardiac disease models. It seeks to find out how these tools can address the limitations of traditional in vitro models and be applied to improve our understanding of cardiac disease mechanisms, facilitate preclinical drug screening, and equip the development of personalized therapeutics.

RECENT FINDINGS

Human induced pluripotent stem cells have enabled the generation of diverse cardiac cell types and patient-specific models. Techniques like 3D tissue engineering, heart-on-a-chip platforms, biomechanical conditioning, and CRISPR-based gene editing have enabled faithful recreation of complex cardiac microenvironments and disease conditions. These models have advanced the study of both genetic and acquired cardiac disorders. Bioengineered in vitro models are transforming the basic science and clinical research in cardiovascular disease by improving the biomimicry and complexity of tissue analogues, increasing throughput and reproducibility of screening platforms, as well as offering patient and disease specificity. Despite challenges in scalability and functional maturity, integrating multiple bioengineering techniques with advanced analytical tools in in vitro modeling platforms holds promise for future precision and personalized medicine and therapeutic innovations.

Modeling Heart Failure With Preserved Ejection Fraction Using Human Induced Pluripotent Stem Cell-Derived Cardiac Organoids

BACKGROUND

The therapeutic armamentarium for heart failure with preserved ejection fraction (HFpEF) remains notably constrained. A factor contributing to this problem could be the scarcity of in vitro models for HFpEF, which hinders progress in developing new therapeutic strategies. Here, we aimed at developing a novel, comorbidity-inspired, human, in vitro model for HFpEF.

METHODS

Human induced pluripotent stem cells-derived cardiomyocytes were used to produce cardiac organoids. The generated organoids were then subjected to HFpEF-associated, comorbidity-inspired conditions, such as hypertension, diabetes, and obesity-related inflammation. To assess the development of HFpEF pathophysiological features, organoids were thoroughly evaluated for their structural, functional, electrophysiological, and metabolic properties.

RESULTS

Exposure to the combination of all comorbidity-mimicking conditions resulted in the largest cellular volume of 1692±52 versus 1346±84 µm3 in RPMI (Roswell Park Memorial Institute medium) control group (P=0.003), while lower in obesity, hypertension, and diabetes groups: 1059±40 µm3 (P=0.014), 1276±35 µm3 (P=0.940), and 1575±70 µm3 (P=0.146), respectively. Similarly, ultrastructural fibrosis was most significantly observed after exposure to the combination of all HFpEF-inducing conditions 14.6±1.2% compared with single condition exposure 5.2±1.3% (obesity), 6.7±3.5% (hypertension), and 9.0±1.1% (diabetes; P<0.001). Moreover, HFpEF-related conditions led to an increase in passive force compared with control (7.52±1.08 versus 2.33±0.46 mN/mm, P<0.001), whereas no significant alterations were noted in active contractile forces. Relaxation constant τ was significantly prolonged after exposure to HFpEF conditions showing a prolongation of 95.9 ms (36.4-106.4; P=0.028) compared with a shortening of 35.6 ms (43.3-67.3; P=0.80) in the control. Finally, organoid exposure to HFpEF conditions led to a significant increase in oxidative stress levels and a significant decline in oxygen consumption rate.

CONCLUSIONS

We established a novel, human, in vitro model for HFpEF, based on comorbidity-inspired conditions. The model faithfully recapitulated the structural, functional, and mechanistic features of HFpEF. This model holds the potential to provide mechanistic insights and facilitate the identification of novel therapeutic targets.

Organ-on-a-Chip Applications in Microfluidic Platforms

Microfluidic technology plays a crucial role in organ-on-a-chip (OoC) systems by replicating human physiological processes and disease states, significantly advancing biomedical research and drug discovery. This article reviews the design and fabrication processes of microfluidic devices. It also explores how these technologies are integrated into OoC platforms to simulate human physiological environments, highlighting key principles, technological advances, and diverse applications. Through case studies involving the simulation of multiple organs such as the heart, liver, and lungs, the article evaluates the impact of OoC systems' integrated microfluidic technology on drug screening, toxicity assessment, and personalized medicine. In addition, this article considers technical challenges, ethical issues, and future directions, and looks ahead to further optimizing the functionality and biomimetic precision of OoCs through innovation, emphasizing its critical role in promoting personalized medicine and precision treatment strategies.

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.

Heart-on-a-chip: a revolutionary organ-on-chip platform for cardiovascular disease modeling

Heart-on-a-chip (HoC) devices have emerged as a powerful tool for studying the human heart's intricate functions and dysfunctions in vitro. Traditional preclinical models, such as 2D cell cultures model and animal model, have limitations in accurately predicting human response to cardiovascular diseases and treatments. The HoC approach addresses these shortcomings by recapitulating the microscale anatomy, physiology, and biomechanics of the heart, thereby providing a more clinically relevant platform for drug testing, disease modeling, and personalized therapy. Recent years have seen significant strides in HoC technology, driven by advancements in biomaterials, bioelectronics, and tissue engineering. Here, we first review the construction and on-chip detection in HoC. Then we introduce the current proceedings of in vitro models for studying cardiovascular diseases (CVD) based on the HoC platform, including ischemia and myocardial infarction, cardiac fibrosis, cardiac scar, myocardial hypertrophy and other CVD models. Finally, we discuss the future directions of HoC and related emerging technologies.

Advances in cardiac organoid research: implications for cardiovascular disease treatment

Globally, cardiovascular diseases remain among the leading causes of mortality, highlighting the urgent need for innovative research models. Consequently, the development of accurate models that simulate cardiac function holds significant scientific and clinical value for both disease research and therapeutic interventions. Cardiac organoids, which are three-dimensional structures derived from the induced differentiation of stem cells, are particularly promising. These organoids not only replicate the autonomous beating and essential electrophysiological properties of the heart but are also widely employed in studies related to cardiac diseases, drug efficacy testing, and regenerative medicine. This review comprehensively surveys the various fabrication techniques used to create cardiac organoids and their diverse applications in modeling a range of cardiac diseases. We emphasize the role of advanced technologies in enhancing the maturation and functionality of cardiac cells, ensuring that these models closely resemble native cardiac tissue. Furthermore, we discuss monitoring techniques and evaluation parameters critical for assessing the performance of cardiac organoids, considering the complex interactions within multi-organ systems. This approach is vital for enhancing precision and efficiency in drug development, allowing for more effective therapeutic strategies. Ultimately, this review aims to provide a thorough and innovative perspective on both fundamental research and clinical treatment of cardiovascular diseases, offering insights that could pave the way for future advancements in understanding and addressing these prevalent health challenges.

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.

Advancing 3D Engineered In Vitro Models for Heart Failure Research: Key Features and Considerations

Heart failure is characterized by intricate myocardial remodeling that impairs the heart's pumping and/or relaxation capacity, ultimately reducing cardiac output. It represents a major public health burden, given its high prevalence and associated morbidity and mortality rates, which continue to challenge healthcare systems worldwide. Despite advancements in medical science, there are no treatments that address the disease at its core. The development of three-dimensional engineered in vitro models that closely mimic the (patho)physiology and drug responses of the myocardium has the potential to revolutionize our insights and uncover new therapeutic avenues. Key aspects of these models include the precise replication of the extracellular matrix structure, cell composition, micro-architecture, mechanical and electrical properties, and relevant physiological and pathological stimuli, such as fluid flow, mechanical load, electrical signal propagation, and biochemical cues. Additionally, to fully capture heart failure and its diversity in vivo, it is crucial to consider factors such as age, gender, interactions with other organ systems and external influences-thereby recapitulating unique patient and disease phenotypes. This review details these model features and their significance in heart failure research, with the aim of enhancing future platforms that will deepen our understanding of the disease and facilitate the development of novel, effective therapies.

Clinical trials in-a-dish for cardiovascular medicine

Cardiovascular diseases persist as a global health challenge that requires methodological innovation for effective drug development. Conventional pipelines relying on animal models suffer from high failure rates due to significant interspecies variation between humans and animal models. In response, the recently enacted Food and Drug Administration Modernization Act 2.0 encourages alternative approaches including induced pluripotent stem cells (iPSCs). Human iPSCs provide a patient-specific, precise, and screenable platform for drug testing, paving the way for cardiovascular precision medicine. This review discusses milestones in iPSC differentiation and their applications from disease modelling to drug discovery in cardiovascular medicine. It then explores challenges and emerging opportunities for the implementation of 'clinical trials in-a-dish'. Concluding, this review proposes a framework for future clinical trial design with strategic incorporations of iPSC technology, microphysiological systems, clinical pan-omics, and artificial intelligence to improve success rates and advance cardiovascular healthcare.

A Biomimetic Optical Cardiac Fibrosis-on-a-Chip for High-Throughput Anti-Fibrotic Drug Screening

Cardiac fibrosis has emerged as the primary cause of morbidity, disability, and even mortality in numerous nations. In light of the advancements in precision medicine strategies, substantial attention has been directed toward the development of a practical and precise drug screening platform customized for individual patients. In this study, we introduce a biomimetic cardiac fibrosis-on-a-chip incorporating structural color hydrogels (SCHs) to enable optical high-throughput drug screening. By cocultivating a substantial proportion of cardiac fibroblasts (CFBs) with cardiomyocytes on the SCH, this biomimetic fibrotic microtissue successfully replicates the structural components and biomechanical properties associated with cardiac fibrosis. More importantly, the structural color shift observed in the SCH can be indicative of cardiac contraction and relaxation, making it a valuable tool for evaluating fibrosis progression. By incorporating such fibrotic microtissue into a microfluidic gradient chip, we develop a biomimetic optical cardiac fibrosis-on-a-chip platform that accurately and efficiently screens potential anti-fibrotic drugs. These characteristics suggest that this microphysiological platform possesses the capability to establish a preclinical framework for screening cardiac drugs, and may even contribute to the advancement of precision medicine.

Intercellular pathways of cancer treatment-related cardiotoxicity and their therapeutic implications: the paradigm of radiotherapy

Advances in cancer therapeutics have improved patient survival rates. However, cancer survivors may suffer from adverse events either at the time of therapy or later in life. Cardiovascular diseases (CVD) represent a clinically important, but mechanistically understudied complication, which interfere with the continuation of best-possible care, induce life-threatening risks, and/or lead to long-term morbidity. These concerns are exacerbated by the fact that targeted therapies and immunotherapies are frequently combined with radiotherapy, which induces durable inflammatory and immunogenic responses, thereby providing a fertile ground for the development of CVDs. Stressed and dying irradiated cells produce 'danger' signals including, but not limited to, major histocompatibility complexes, cell-adhesion molecules, proinflammatory cytokines, and damage-associated molecular patterns. These factors activate intercellular signaling pathways which have potentially detrimental effects on the heart tissue homeostasis. Herein, we present the clinical crosstalk between cancer and heart diseases, describe how it is potentiated by cancer therapies, and highlight the multifactorial nature of the underlying mechanisms. We particularly focus on radiotherapy, as a case known to often induce cardiovascular complications even decades after treatment. We provide evidence that the secretome of irradiated tumors entails factors that exert systemic, remote effects on the cardiac tissue, potentially predisposing it to CVDs. We suggest how diverse disciplines can utilize pertinent state-of-the-art methods in feasible experimental workflows, to shed light on the molecular mechanisms of radiotherapy-related cardiotoxicity at the organismal level and untangle the desirable immunogenic properties of cancer therapies from their detrimental effects on heart tissue. Results of such highly collaborative efforts hold promise to be translated to next-generation regimens that maximize tumor control, minimize cardiovascular complications, and support quality of life in cancer survivors.

Fibrosis-on-Chip: A Guide to Recapitulate the Essential Features of Fibrotic Disease

Fibrosis, which is primarily marked by excessive extracellular matrix (ECM) deposition, is a pathophysiological process associated with many disorders, which ultimately leads to organ dysfunction and poor patient outcomes. Despite the high prevalence of fibrosis, currently there exist few therapeutic options, and importantly, there is a paucity of in vitro models to accurately study fibrosis. This review discusses the multifaceted nature of fibrosis from the viewpoint of developing organ-on-chip (OoC) disease models, focusing on five key features: the ECM component, inflammation, mechanical cues, hypoxia, and vascularization. The potential of OoC technology is explored for better modeling these features in the context of studying fibrotic diseases and the interplay between various key features is emphasized. This paper reviews how organ-specific fibrotic diseases are modeled in OoC platforms, which elements are included in these existing models, and the avenues for novel research directions are highlighted. Finally, this review concludes with a perspective on how to address the current gap with respect to the inclusion of multiple features to yield more sophisticated and relevant models of fibrotic diseases in an OoC format.

Macrophages in cardiovascular diseases: molecular mechanisms and therapeutic targets

The immune response holds a pivotal role in cardiovascular disease development. As multifunctional cells of the innate immune system, macrophages play an essential role in initial inflammatory response that occurs following cardiovascular injury, thereby inducing subsequent damage while also facilitating recovery. Meanwhile, the diverse phenotypes and phenotypic alterations of macrophages strongly associate with distinct types and severity of cardiovascular diseases, including coronary heart disease, valvular disease, myocarditis, cardiomyopathy, heart failure, atherosclerosis and aneurysm, which underscores the importance of investigating macrophage regulatory mechanisms within the context of specific diseases. Besides, recent strides in single-cell sequencing technologies have revealed macrophage heterogeneity, cell-cell interactions, and downstream mechanisms of therapeutic targets at a higher resolution, which brings new perspectives into macrophage-mediated mechanisms and potential therapeutic targets in cardiovascular diseases. Remarkably, myocardial fibrosis, a prevalent characteristic in most cardiac diseases, remains a formidable clinical challenge, necessitating a profound investigation into the impact of macrophages on myocardial fibrosis within the context of cardiac diseases. In this review, we systematically summarize the diverse phenotypic and functional plasticity of macrophages in regulatory mechanisms of cardiovascular diseases and unprecedented insights introduced by single-cell sequencing technologies, with a focus on different causes and characteristics of diseases, especially the relationship between inflammation and fibrosis in cardiac diseases (myocardial infarction, pressure overload, myocarditis, dilated cardiomyopathy, diabetic cardiomyopathy and cardiac aging) and the relationship between inflammation and vascular injury in vascular diseases (atherosclerosis and aneurysm). Finally, we also highlight the preclinical/clinical macrophage targeting strategies and translational implications.

Heart-on-a-chip systems with tissue-specific functionalities for physiological, pathological, and pharmacological studies

Recent advances in heart-on-a-chip systems hold great promise to facilitate cardiac physiological, pathological, and pharmacological studies. This review focuses on the development of heart-on-a-chip systems with tissue-specific functionalities. For one thing, the strategies for developing cardiac microtissues on heart-on-a-chip systems that closely mimic the structures and behaviors of the native heart are analyzed, including the imitation of cardiac structural and functional characteristics. For another, the development of techniques for real-time monitoring of biophysical and biochemical signals from cardiac microtissues on heart-on-a-chip systems is introduced, incorporating cardiac electrophysiological signals, contractile activity, and biomarkers. Furthermore, the applications of heart-on-a-chip systems in intelligent cardiac studies are discussed regarding physiological/pathological research and pharmacological assessment. Finally, the future development of heart-on-a-chip toward a higher level of systematization, integration, and maturation is proposed.

Advances in the Generation of Constructed Cardiac Tissue Derived from Induced Pluripotent Stem Cells for Disease Modeling and Therapeutic Discovery

The human heart lacks significant regenerative capacity; thus, the solution to heart failure (HF) remains organ donation, requiring surgery and immunosuppression. The demand for constructed cardiac tissues (CCTs) to model and treat disease continues to grow. Recent advances in induced pluripotent stem cell (iPSC) manipulation, CRISPR gene editing, and 3D tissue culture have enabled a boom in iPSC-derived CCTs (iPSC-CCTs) with diverse cell types and architecture. Compared with 2D-cultured cells, iPSC-CCTs better recapitulate heart biology, demonstrating the potential to advance organ modeling, drug discovery, and regenerative medicine, though iPSC-CCTs could benefit from better methods to faithfully mimic heart physiology and electrophysiology. Here, we summarize advances in iPSC-CCTs and future developments in the vascularization, immunization, and maturation of iPSC-CCTs for study and therapy.

A Biomimetic Cardiac Fibrosis-on-a-Chip as a Visible Disease Model for Evaluating Mesenchymal Stem Cell-Derived Exosome Therapy

Cardiac fibrosis acts as a serious worldwide health issue due to its prevalence in numerous forms of cardiac disease and its essential link to cardiac failure. Considering the efficiency of stem cell therapy for cardiac fibrosis, great efforts have been dedicated to developing accurate models for investigating their underlying therapeutic mechanisms. Herein we present an elaborate biomimetic cardiac fibrosis-on-a-chip based on Janus structural color film (SCF) to provide microphysiological visuals for stem cell therapeutic studies. By coculturing cardiomyocytes (CMs) and cardiac fibroblasts (FBs) on Janus SCF with fibrosis induction, the chip can recreate physiological intercellular crosstalk within the fibrotic microenvironment, elucidating the physiological alterations of fibrotic hearts. In particular, the Janus structural color film possesses superior perceptual capabilities for capturing and responding to a weak cardiac force, demonstrating synchronized structural color shifts. Based on these features, we have not only explored the dynamic relationship between color mapping and the evaluated disease phenotype but also demonstrated the self-reporting capacity of the cardiac fibrosis-on-a-chip for the assessment of mesenchymal stem cell-derived exosome therapy. These features suggest that such a chip can potentially facilitate the evolution of precision medicine strategies and create a protocol for preclinical cardiac drug screening.

Extracellular vesicles from differentiated stem cells contain novel proangiogenic miRNAs and induce angiogenic responses at low doses

Extracellular vesicles (EVs) released from healthy endothelial cells (ECs) have shown potential for promoting angiogenesis, but their therapeutic efficacy remains poorly understood. We have previously shown that transplantation of a human embryonic stem cell-derived endothelial cell product (hESC-ECP), promotes new vessel formation in acute ischemic disease in mice, likely via paracrine mechanism(s). Here, we demonstrated that EVs from hESC-ECPs (hESC-eEVs) significantly increased EC tube formation and wound closure in vitro at ultralow doses, whereas higher doses were ineffective. More important, EVs isolated from the mesodermal stage of the differentiation (hESC-mEVs) had no effect. Small RNA sequencing revealed that hESC-eEVs have a unique transcriptomic profile and are enriched in known proangiogenic microRNAs (miRNAs, miRs). Moreover, an in silico analysis identified three novel hESC-eEV-miRNAs with potential proangiogenic function. Differential expression analysis suggested that two of those, miR-4496 and miR-4691-5p, are highly enriched in hESC-eEVs. Overexpression of miR-4496 or miR-4691-5p resulted in increased EC tube formation and wound closure in vitro, validating the novel proangiogenic function of these miRNAs. In summary, we demonstrated that hESC-eEVs are potent inducers of EC angiogenic response at ultralow doses and contain a unique EV-associated miRNA repertoire, including miR-4496 and miR-4691-5p, with novel proangiogenic function.

Bioethical implications of organ-on-a-chip on modernizing drug development

Organ-on-chips are three-dimensional microdevices that emulate the structure, functionality, and behavior of specific tissues or organs using human cells. Combining organoids with microfabricated fluidic channels and microelectronics, these systems offer a promising platform for studying disease mechanisms, drug responses, and tissue performance. By replicating the in vivo microenvironment, these devices can recreate complex cell interactions in controlled conditions and facilitate research in various fields, including drug toxicity and efficacy studies, biochemical analysis, and disease pathogenesis. Integrating human induced pluripotent stem cells further enhances their applicability, thereby enabling patient-specific disease modeling for precision medicine. Although challenges like economy-of-scale, multichip integration, and regulatory compliance exist, advances in this modular technology show promise for lowering drug development costs, improving reproducibility, and reducing the reliance on animal testing. The ethical landscape surrounding organ-on-chip usage presents both benefits and concerns. While these chips offer an alternative to animal testing and potential cost savings, they raise ethical considerations related to community engagement, informed consent, and the need for standardized guidelines. Ensuring public acceptance and involvement in decision-making is vital to address misinformation and mistrust. Furthermore, personalized medicine models using patient-derived cells demand careful consideration of potential ethical dilemmas, such as modeling physiological functions of fetuses or brains and determining the extent of protection for these models. To achieve the full potential of organ-on-a-chip models, collaboration between scientists, ethicists, and regulators is essential to fulfil the promise of transforming drug development, advancing personalized medicine, and contributing to a more ethical and efficient biomedical research landscape.

Cardiac Fibrosis in heart failure: Focus on non-invasive diagnosis and emerging therapeutic strategies

Heart failure is a leading cause of mortality and hospitalization worldwide. Cardiac fibrosis, resulting from the excessive deposition of collagen fibers, is a common feature across the spectrum of conditions converging in heart failure. Eventually, either reparative or reactive in nature, in the long-term cardiac fibrosis contributes to heart failure development and progression and is associated with poor clinical outcomes. Despite this, specific cardiac antifibrotic therapies are lacking, making cardiac fibrosis an urgent unmet medical need. In this context, a better patient phenotyping is needed to characterize the heterogenous features of cardiac fibrosis to advance toward its personalized management. In this review, we will describe the different phenotypes associated with cardiac fibrosis in heart failure and we will focus on the potential usefulness of imaging techniques and circulating biomarkers for the non-invasive characterization and phenotyping of this condition and for tracking its clinical impact. We will also recapitulate the cardiac antifibrotic effects of existing heart failure and non-heart failure drugs and we will discuss potential strategies under preclinical development targeting the activation of cardiac fibroblasts at different levels, as well as targeting additional extracardiac processes.

Modelling the pathology and treatment of cardiac fibrosis in vascularised atrial and ventricular cardiac microtissues

Introduction

Recent advances in human cardiac 3D approaches have yielded progressively more complex and physiologically relevant culture systems. However, their application in the study of complex pathological processes, such as inflammation and fibrosis, and their utility as models for drug development have been thus far limited.

Methods

In this work, we report the development of chamber-specific, vascularised human induced pluripotent stem cell-derived cardiac microtissues, which allow for the multi-parametric assessment of cardiac fibrosis.

Results

We demonstrate the generation of a robust vascular system in the microtissues composed of endothelial cells, fibroblasts and atrial or ventricular cardiomyocytes that exhibit gene expression signatures, architectural, and electrophysiological resemblance to in vivo-derived anatomical cardiac tissues. Following pro-fibrotic stimulation using TGFβ, cardiac microtissues recapitulated hallmarks of cardiac fibrosis, including myofibroblast activation and collagen deposition. A study of Ca2+ dynamics in fibrotic microtissues using optical mapping revealed prolonged Ca2+ decay, reflecting cardiomyocyte dysfunction, which is linked to the severity of fibrosis. This phenotype could be reversed by TGFβ receptor inhibition or by using the BET bromodomain inhibitor, JQ1.

Discussion

In conclusion, we present a novel methodology for the generation of chamber-specific cardiac microtissues that is highly scalable and allows for the multi-parametric assessment of cardiac remodelling and pharmacological screening.

The heterocellular heart: identities, interactions, and implications for cardiology

The heterocellular nature of the heart has been receiving increasing attention in recent years. In addition to cardiomyocytes as the prototypical cell type of the heart, non-myocytes such as endothelial cells, fibroblasts, or immune cells are coming more into focus. The rise of single-cell sequencing technologies enables  identification of ever more subtle differences and has reignited the question of what defines a cell's identity. Here we provide an overview of the major cardiac cell types, describe their roles in homeostasis, and outline recent findings on non-canonical functions that may be of relevance for cardiology. We highlight modes of biochemical and biophysical interactions between different cardiac cell types and discuss the potential implications of the heterocellular nature of the heart for basic research and therapeutic interventions.