Tissue engineering of vascularized cardiac muscle from human embryonic stem cells

A versatile high-throughput assay based on 3D ring-shaped cardiac tissues generated from human induced pluripotent stem cell-derived cardiomyocytes

We developed a 96-well plate assay which allows fast, reproducible, and high-throughput generation of 3D cardiac rings around a deformable optically transparent hydrogel (polyethylene glycol [PEG]) pillar of known stiffness. Human induced pluripotent stem cell-derived cardiomyocytes, mixed with normal human adult dermal fibroblasts in an optimized 3:1 ratio, self-organized to form ring-shaped cardiac constructs. Immunostaining showed that the fibroblasts form a basal layer in contact with the glass, stabilizing the muscular fiber above. Tissues started contracting around the pillar at D1 and their fractional shortening increased until D7, reaching a plateau at 25±1%, that was maintained up to 14 days. The average stress, calculated from the compaction of the central pillar during contractions, was 1.4±0.4 mN/mm2. The cardiac constructs recapitulated expected inotropic responses to calcium and various drugs (isoproterenol, verapamil) as well as the arrhythmogenic effects of dofetilide. This versatile high-throughput assay allows multiple in situ mechanical and structural readouts.

Vascularization of PEGylated fibrin hydrogels increases the proliferation of human iPSC-cardiomyocytes

Studies have long sought to develop engineered heart tissue for the surgical correction of structural heart defects, as well as other applications and vascularization of this tissue has presented a challenge. Recent studies suggest that vascular cells and a vascular network may have regenerative effects on implanted cardiomyocytes (CM) and nearby heart tissue separate from perfusion of oxygen and nutrients. The goal of this study was to test whether vascular cells or a formed vascular network in a fibrin-based hydrogel would alter the proliferation of human iPSC-derived CM. First, vascular network formation in a slowly degrading PEGylated fibrin hydrogel was optimized by altering the cell ratio of human umbilical vein endothelial cells to human dermal fibroblasts, the inclusion of growth factors, and the total cell concentration. An endothelial to fibroblast ratio of 5:1 and a total cell concentration of 1.1 × 106 cells/mL without additional growth factors generated robust vascular networks while minimizing the number of cells required. Using this optimized system, human iPSC-derived CM were cultured on hydrogels without vascular cells, hydrogels with unorganized encapsulated vascular cells, or hydrogels with encapsulated vascular cells organized into networks for 7 days. CM proliferation and gene expression were assayed following 7 days of culture on the hydrogels. The presence of vascular cells in the hydrogel, whether unorganized or in vascular networks, significantly increased CM proliferation compared to an acellular hydrogel. Hydrogels with unorganized vascular cells resulted in lower CM maturity evidenced by decreased expression of cardiac troponin t (TNNT2), myosin light chain 7, and phospholamban compared to hydrogels without vascular cells and hydrogels with vascular networks. Altogether, this study details a robust method of forming rudimentary vascular networks in a fibrin-based hydrogel and shows that a hydrogel containing endothelial cells and fibroblasts can induce proliferation in adjacent CM, and these cells do not hinder CM gene expression when organized into a vascular network.

Advances in cardiac tissue engineering and heart-on-a-chip

Recent advances in both cardiac tissue engineering and hearts-on-a-chip are grounded in new biomaterial development as well as the employment of innovative fabrication techniques that enable precise control of the mechanical, electrical, and structural properties of the cardiac tissues being modelled. The elongated structure of cardiomyocytes requires tuning of substrate properties and application of biophysical stimuli to drive its mature phenotype. Landmark advances have already been achieved with induced pluripotent stem cell-derived cardiac patches that advanced to human testing. Heart-on-a-chip platforms are now commonly used by a number of pharmaceutical and biotechnology companies. Here, we provide an overview of cardiac physiology in order to better define the requirements for functional tissue recapitulation. We then discuss the biomaterials most commonly used in both cardiac tissue engineering and heart-on-a-chip, followed by the discussion of recent representative studies in both fields. We outline significant challenges common to both fields, specifically: scalable tissue fabrication and platform standardization, improving cellular fidelity through effective tissue vascularization, achieving adult tissue maturation, and ultimately developing cryopreservation protocols so that the tissues are available off the shelf.

Improved Neural Inductivity of Size-Controlled 3D Human Embryonic Stem Cells Using Magnetic Nanoparticles

Background: To improve the efficiency of neural development from human embryonic stem cells, human embryoid body (hEB) generation is vital through 3-dimensional formation. However, conventional approaches still have limitations: long-term cultivation and laborious steps for lineage determination. Methods: In this study, we controlled the size of hEBs for ectodermal lineage specification using cell-penetrating magnetic nanoparticles (MNPs), which resulted in reduced time required for initial neural induction. The magnetized cells were applied to concentrated magnetic force for magnet-derived multicellular organization. The uniformly sized hEBs were differentiated in neural induction medium (NIM) and suspended condition. This neurally induced MNP-hEBs were compared with other groups. Results: As a result, the uniformly sized MNP-hEBs in NIM showed significantly improved neural inductivity through morphological analysis and expression of neural markers. Signaling pathways of the accelerated neural induction were detected via expression of representative proteins; Wnt signaling, dopaminergic neuronal pathway, intercellular communications, and mechanotransduction. Consequently, we could shorten the time necessary for early neurogenesis, thereby enhancing the neural induction efficiency. Conclusion: Overall, this study suggests not only the importance of size regulation of hEBs at initial differentiation stage but also the efficacy of MNP-based neural induction method and stimulations for enhanced neural tissue regeneration.

Micro-Engineered Heart Tissues On-Chip with Heterotypic Cell Composition Display Self-Organization and Improved Cardiac Function

Advanced in vitro models that recapitulate the structural organization and function of the human heart are highly needed for accurate disease modeling, more predictable drug screening, and safety pharmacology. Conventional 3D Engineered Heart Tissues (EHTs) lack heterotypic cell complexity and culture under flow, whereas microfluidic Heart-on-Chip (HoC) models in general lack the 3D configuration and accurate contractile readouts. In this study, an innovative and user-friendly HoC model is developed to overcome these limitations, by culturing human pluripotent stem cell (hPSC)-derived cardiomyocytes (CMs), endothelial (ECs)- and smooth muscle cells (SMCs), together with human cardiac fibroblasts (FBs), underflow, leading to self-organized miniaturized micro-EHTs (µEHTs) with a CM-EC interface reminiscent of the physiological capillary lining. µEHTs cultured under flow display enhanced contractile performance and conduction velocity. In addition, the presence of the EC layer altered drug responses in µEHT contraction. This observation suggests a potential barrier-like function of ECs, which may affect the availability of drugs to the CMs. These cardiac models with increased physiological complexity, will pave the way to screen for therapeutic targets and predict drug efficacy.

Macrophage-based therapeutic approaches for cardiovascular diseases

Despite the advances in treatment options, cardiovascular disease (CVDs) remains the leading cause of death over the world. Chronic inflammatory response and irreversible fibrosis are the main underlying pathophysiological causes of progression of CVDs. In recent decades, cardiac macrophages have been recognized as main regulatory players in the development of these complex pathophysiological conditions. Numerous approaches aimed at macrophages have been devised, leading to novel prospects for therapeutic interventions. Our review covers the advancements in macrophage-centric treatment plans for various pathologic conditions and examines the potential consequences and obstacles of employing macrophage-targeted techniques in cardiac diseases.

Endothelial dysfunction and cardiovascular diseases: The role of human induced pluripotent stem cells and tissue engineering

Cardiovascular disease (CVD) remains to be the leading cause of death globally today and therefore the need for the development of novel therapies has become increasingly important in the cardiovascular field. The mechanism(s) behind the pathophysiology of CVD have been laboriously investigated in both stem cell and bioengineering laboratories. Scientific breakthroughs have paved the way to better mimic cell types of interest in recent years, with the ability to generate any cell type from reprogrammed human pluripotent stem cells. Mimicking the native extracellular matrix using both organic and inorganic biomaterials has allowed full organs to be recapitulated in vitro. In this paper, we will review techniques from both stem cell biology and bioengineering which have been fruitfully combined and have fueled advances in the cardiovascular disease field. We will provide a brief introduction to CVD, reviewing some of the recent studies as related to the role of endothelial cells and endothelial cell dysfunction. Recent advances and the techniques widely used in both bioengineering and stem cell biology will be discussed, providing a broad overview of the collaboration between these two fields and their overall impact on tissue engineering in the cardiovascular devices and implications for treatment of cardiovascular disease.

Construction of millimeter-scale vascularized engineered myocardial tissue using a mixed gel

Engineering myocardium has shown great clinal potential for repairing permanent myocardial injury. However, the lack of perfusing blood vessels and difficulties in preparing a thick-engineered myocardium result in its limited clinical use. We prepared a mixed gel containing fibrin (5 mg/ml) and collagen I (0.2 mg/ml) and verified that human umbilical vein endothelial cells (HUVECs) and human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) could form microvascular lumens and myocardial cell clusters by harnessing the low-hardness and hyperelastic characteristics of fibrin. hiPSC-CMs and HUVECs in the mixed gel formed self-organized cell clusters, which were then cultured in different media using a three-phase approach. The successfully constructed vascularized engineered myocardial tissue had a spherical structure and final diameter of 1-2 mm. The tissue exhibited autonomous beats that occurred at a frequency similar to a normal human heart rate. The internal microvascular lumen could be maintained for 6 weeks and showed good results during preliminary surface re-vascularization in vitro and vascular remodeling in vivo. In summary, we propose a simple method for constructing vascularized engineered myocardial tissue, through phased cultivation that does not rely on high-end manufacturing equipment and cutting-edge preparation techniques. The constructed tissue has potential value for clinical use after preliminary evaluation.

Building blocks of microphysiological system to model physiology and pathophysiology of human heart

Microphysiological systems (MPS) are drawing increasing interest from academia and from biomedical industry due to their improved capability to capture human physiology. MPS offer an advanced in vitro platform that can be used to study human organ and tissue level functions in health and in diseased states more accurately than traditional single cell cultures or even animal models. Key features in MPS include microenvironmental control and monitoring as well as high biological complexity of the target tissue. To reach these qualities, cross-disciplinary collaboration from multiple fields of science is required to build MPS. Here, we review different areas of expertise and describe essential building blocks of heart MPS including relevant cardiac cell types, supporting matrix, mechanical stimulation, functional measurements, and computational modelling. The review presents current methods in cardiac MPS and provides insights for future MPS development with improved recapitulation of human physiology.

Human Stem Cells for Cardiac Disease Modeling and Preclinical and Clinical Applications-Are We on the Road to Success?

Cardiovascular diseases (CVDs) are pointed out by the World Health Organization (WHO) as the leading cause of death, contributing to a significant and growing global health and economic burden. Despite advancements in clinical approaches, there is a critical need for innovative cardiovascular treatments to improve patient outcomes. Therapies based on adult stem cells (ASCs) and embryonic stem cells (ESCs) have emerged as promising strategies to regenerate damaged cardiac tissue and restore cardiac function. Moreover, the generation of human induced pluripotent stem cells (iPSCs) from somatic cells has opened new avenues for disease modeling, drug discovery, and regenerative medicine applications, with fewer ethical concerns than those associated with ESCs. Herein, we provide a state-of-the-art review on the application of human pluripotent stem cells in CVD research and clinics. We describe the types and sources of stem cells that have been tested in preclinical and clinical trials for the treatment of CVDs as well as the applications of pluripotent stem-cell-derived in vitro systems to mimic disease phenotypes. How human stem-cell-based in vitro systems can overcome the limitations of current toxicological studies is also discussed. Finally, the current state of clinical trials involving stem-cell-based approaches to treat CVDs are presented, and the strengths and weaknesses are critically discussed to assess whether researchers and clinicians are getting closer to success.

Human Stem Cells for Cardiac Disease Modeling and Preclinical and Clinical Applications—Are We on the Road to Success?

Cardiovascular diseases (CVDs) are pointed out by the World Health Organization (WHO) as the leading cause of death, contributing to a significant and growing global health and economic burden. Despite advancements in clinical approaches, there is a critical need for innovative cardiovascular treatments to improve patient outcomes. Therapies based on adult stem cells (ASCs) and embryonic stem cells (ESCs) have emerged as promising strategies to regenerate damaged cardiac tissue and restore cardiac function. Moreover, the generation of human induced pluripotent stem cells (iPSCs) from somatic cells has opened new avenues for disease modeling, drug discovery, and regenerative medicine applications, with fewer ethical concerns than those associated with ESCs. Herein, we provide a state-of-the-art review on the application of human pluripotent stem cells in CVD research and clinics. We describe the types and sources of stem cells that have been tested in preclinical and clinical trials for the treatment of CVDs as well as the applications of pluripotent stem-cell-derived in vitro systems to mimic disease phenotypes. How human stem-cell-based in vitro systems can overcome the limitations of current toxicological studies is also discussed. Finally, the current state of clinical trials involving stem-cell-based approaches to treat CVDs are presented, and the strengths and weaknesses are critically discussed to assess whether researchers and clinicians are getting closer to success.

Vascular cells improve functionality of human cardiac organoids

Crosstalk between cardiac cells is critical for heart performance. Here we show that vascular cells within human cardiac organoids (hCOs) enhance their maturation, force of contraction, and utility in disease modeling. Herein we optimize our protocol to generate vascular populations in addition to epicardial, fibroblast, and cardiomyocyte cells that self-organize into in-vivo-like structures in hCOs. We identify mechanisms of communication between endothelial cells, pericytes, fibroblasts, and cardiomyocytes that ultimately contribute to cardiac organoid maturation. In particular, (1) endothelial-derived LAMA5 regulates expression of mature sarcomeric proteins and contractility, and (2) paracrine platelet-derived growth factor receptor β (PDGFRβ) signaling from vascular cells upregulates matrix deposition to augment hCO contractile force. Finally, we demonstrate that vascular cells determine the magnitude of diastolic dysfunction caused by inflammatory factors and identify a paracrine role of endothelin driving dysfunction. Together this study highlights the importance and role of vascular cells in organoid models.

Modeling the human heart ex vivo-current possibilities and strive for future applications

The high organ specification of the human heart is inversely proportional to its functional recovery after damage. The discovery of induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) has accelerated research in human heart regeneration and physiology. Nevertheless, due to the immaturity of iPSC-CMs, they are far from being an representative model of the adult heart physiology. Therefore, number of laboratories strive to obtain a heart tissues by engineering methods by structuring iPSC-CMs into complex and advanced platforms. By using the iPSC-CMs and arranging them in 3D cultures it is possible to obtain a human heart muscle with physiological capabilities potentially similar to the adult heart, while remaining in vitro. Here, we attempt to describe existing examples of heart muscle either in vitro or ex vivo models and discuss potential options for the further development of such structures. This will be a crucial step for ultimate derivation of complete heart tissue-mimicking organs and their future use in drug development, therapeutic approaches testing, pre-clinical studies, and clinical applications. This review particularly aims to compile available models of advanced human heart tissue for scientists considering which model would best fit their research needs.

Advancing Engineered Heart Muscle Tissue Complexity with Hydrogel Composites

A heart attack results in the permanent loss of heart muscle and can lead to heart disease, which kills more than 7 million people worldwide each year. To date, outside of heart transplantation, current clinical treatments cannot regenerate lost heart muscle or restore full function to the damaged heart. There is a critical need to create engineered heart tissues with structural complexity and functional capacity needed to replace damaged heart muscle. The inextricable link between structure and function suggests that hydrogel composites hold tremendous promise as a biomaterial-guided strategy to advance heart muscle tissue engineering. Such composites provide biophysical cues and functionality as a provisional extracellular matrix that hydrogels cannot on their own. This review describes the latest advances in the characterization of these biomaterial systems and using them for heart muscle tissue engineering. The review integrates results across the field to provide new insights on critical features within hydrogel composites and perspectives on the next steps to harnessing these promising biomaterials to faithfully reproduce the complex structure and function of native heart muscle.

Strategies to improve the therapeutic effect of pluripotent stem cell-derived cardiomyocytes on myocardial infarction

Myocardial infarction (MI) is a common cardiovascular disease caused by permanent loss of cardiomyocytes and the formation of scar tissue due to myocardial ischemia. Mammalian cardiomyocytes lose their ability to proliferate almost completely in adulthood and are unable to repair the damage caused by MI. Therefore, transplantation of exogenous cells into the injured area for treatment becomes a promising strategy. Pluripotent stem cells (PSCs) have the ability to proliferate and differentiate into various cellular populations indefinitely, and pluripotent stem cell-derived cardiomyocytes (PSC-CMs) transplanted into areas of injury can compensate for part of the injuries and are considered to be one of the most promising sources for cell replacement therapy. However, the low transplantation rate and survival rate of currently transplanted PSC-CMs limit their ability to treat MI. This article focuses on the strategies of current research for improving the therapeutic efficacy of PSC-CMs, aiming to provide some inspiration and ideas for subsequent researchers to further enhance the transplantation rate and survival rate of PSC-CMs and ultimately improve cardiac function.

Tissue-engineered heart chambers as a platform technology for drug discovery and disease modeling

Current drug screening approaches are incapable of fully detecting and characterizing drug effectiveness and toxicity of human cardiomyocytes. The pharmaceutical industry uses mathematical models, cell lines, and in vivo models. Many promising drugs are abandoned early in development, and some cardiotoxic drugs reach humans leading to drug recalls. Therefore, there is an unmet need to have more reliable and predictive tools for drug discovery and screening applications. Biofabrication of functional cardiac tissues holds great promise for developing a faithful 3D in vitro disease model, optimizing drug screening efficiencies enabling precision medicine. Different fabrication techniques including molding, pull spinning and 3D bioprinting were used to develop tissue-engineered heart chambers. The big challenge is to effectively organize cells into tissue with structural and physiological features resembling native tissues. Some advancements have been made in engineering miniaturized heart chambers that resemble a living pump for drug screening and disease modeling applications. Here, we review the currently developed tissue-engineered heart chambers and discuss challenges and prospects.

Resident Macrophages and Their Potential in Cardiac Tissue Engineering

Many facets of tissue engineered models aim at understanding cellular mechanisms to recapitulate in vivo behavior, to study and mimic diseases for drug interventions, and to provide a better understanding toward improving regenerative medicine. Recent and rapid advances in stem cell biology, material science and engineering, have made the generation of complex engineered tissues much more attainable. One such tissue, human myocardium, is extremely intricate, with a number of different cell types. Recent studies have unraveled cardiac resident macrophages as a critical mediator for normal cardiac function. Macrophages within the heart exert phagocytosis and efferocytosis, facilitate electrical conduction, promote regeneration, and remove cardiac exophers to maintain homeostasis. These findings underpin the rationale of introducing macrophages to engineered heart tissue (EHT), to more aptly capitulate in vivo physiology. Despite the lack of studies using cardiac macrophages in vitro, there is enough evidence to accept that they will be key to making EHTs more physiologically relevant. In this review, we explore the rationale and feasibility of using macrophages as an additional cell source in engineered cardiac tissues. Impact statement Macrophages play a critical role in cardiac homeostasis and in disease. Over the past decade, we have come to understand the many vital roles played by cardiac resident macrophages in the heart, including immunosurveillance, regeneration, electrical conduction, and elimination of exophers. There is a need to improve our understanding of the resident macrophage population in the heart in vitro, to better recapitulate the myocardium through tissue engineered models. However, obtaining them in vitro remains a challenge. Here, we discuss the importance of cardiac resident macrophages and potential ways to obtain cardiac resident macrophages in vitro. Finally, we critically discuss their potential in realizing impactful in vitro models of cardiac tissue and their impact in the field.

Characteristics of Marine Biomaterials and Their Applications in Biomedicine

Oceans have vast potential to develop high-value bioactive substances and biomaterials. In the past decades, many biomaterials have come from marine organisms, but due to the wide variety of organisms living in the oceans, the great diversity of marine-derived materials remains explored. The marine biomaterials that have been found and studied have excellent biological activity, unique chemical structure, good biocompatibility, low toxicity, and suitable degradation, and can be used as attractive tissue material engineering and regenerative medicine applications. In this review, we give an overview of the extraction and processing methods and chemical and biological characteristics of common marine polysaccharides and proteins. This review also briefly explains their important applications in anticancer, antiviral, drug delivery, tissue engineering, and other fields.

Cardiac Organoids: A 3D Technology for Modeling Heart Development and Disease

Cardiac organoids (COs) are miniaturized and simplified organ structures that can be used in heart development biology, drug screening, disease modeling, and regenerative medicine. This cardiac organoid (CO) model is revolutionizing our perspective on answering major cardiac physiology and pathology issues. Recently, many research groups have reported various methods for modeling the heart in vitro. However, there are differences in methodologies and concepts. In this review, we discuss the recent advances in cardiac organoid technologies derived from human embryonic stem cells (hESCs) and human-induced pluripotent stem cells (hiPSCs), with a focus on the summary of methods for organoid generation. In addition, we introduce CO applications in modeling heart development and cardiovascular diseases and discuss the prospects for and common challenges of CO that still need to be addressed. A detailed understanding of the development of CO will help us design better methods, explore and expand its application in the cardiovascular field.

Opportunities and challenges in cardiac tissue engineering from an analysis of two decades of advances

Engineered human cardiac tissues facilitate progress in regenerative medicine, disease modelling and drug development. In this Perspective, we reflect on the most notable advances in cardiac tissue engineering from the past two decades by analysing pivotal studies and critically examining the most consequential developments. This retrospective analysis led us to identify key milestones and to outline a set of opportunities, along with their associated challenges, for the further advancement of engineered human cardiac tissues.

Bioengineering Strategies to Create 3D Cardiac Constructs from Human Induced Pluripotent Stem Cells

Human induced pluripotent stem cells (hiPSCs) can be used to generate various cell types in the human body. Hence, hiPSC-derived cardiomyocytes (hiPSC-CMs) represent a significant cell source for disease modeling, drug testing, and regenerative medicine. The immaturity of hiPSC-CMs in two-dimensional (2D) culture limit their applications. Cardiac tissue engineering provides a new promise for both basic and clinical research. Advanced bioengineered cardiac in vitro models can create contractile structures that serve as exquisite in vitro heart microtissues for drug testing and disease modeling, thereby promoting the identification of better treatments for cardiovascular disorders. In this review, we will introduce recent advances of bioengineering technologies to produce in vitro cardiac tissues derived from hiPSCs.

Restoring Ravaged Heart: Molecular Mechanisms and Clinical Application of miRNA in Heart Regeneration

Human heart development is a complex and tightly regulated process, conserving proliferation, and multipotency of embryonic cardiovascular progenitors. At terminal stage, progenitor cell type gets suppressed for terminal differentiation and maturation. In the human heart, most cardiomyocytes are terminally differentiated and so have limited proliferation capacity. MicroRNAs (miRNAs) are non-coding single-stranded RNA that regulate gene expression and mRNA silencing at the post-transcriptional level. These miRNAs play a crucial role in numerous biological events, including cardiac development, and cardiomyocyte proliferation. Several cardiac cells specific miRNAs have been discovered. Inhibition or overexpression of these miRNAs could induce cardiac regeneration, cardiac stem cell proliferation and cardiomyocyte proliferation. Clinical application of miRNAs extends to heart failure, wherein the cell cycle arrest of terminally differentiated cardiac cells inhibits the heart regeneration. The regenerative capacity of the myocardium can be enhanced by cardiomyocyte specific miRNAs controlling the cell cycle. In this review, we focus on cardiac-specific miRNAs involved in cardiac regeneration and cardiomyocyte proliferation, and their potential as a new clinical therapy for heart regeneration.

Bioengineering approaches to treat the failing heart: from cell biology to 3D printing

Successfully engineering a functional, human, myocardial pump would represent a therapeutic alternative for the millions of patients with end-stage heart disease and provide an alternative to animal-based preclinical models. Although the field of cardiac tissue engineering has made tremendous advances, major challenges remain, which, if properly resolved, might allow the clinical implementation of engineered, functional, complex 3D structures in the future. In this Review, we provide an overview of state-of-the-art studies, challenges that have not yet been overcome and perspectives on cardiac tissue engineering. We begin with the most clinically relevant cell sources used in this field and discuss the use of topological, biophysical and metabolic stimuli to obtain mature phenotypes of cardiomyocytes, particularly in relation to organized cytoskeletal and contractile intracellular structures. We then move from the cellular level to engineering planar cardiac patches and discuss the need for proper vascularization and the main strategies for obtaining it. Finally, we provide an overview of several different approaches for the engineering of volumetric organs and organ parts - from whole-heart decellularization and recellularization to advanced 3D printing technologies.

Insights to Heart Development and Cardiac Disease Models Using Pluripotent Stem Cell Derived 3D Organoids

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

A Prevascularized Polyurethane-Reinforced Fibrin Patch Improves Regenerative Remodeling in a Rat Right Ventricle Replacement Model

Congenital heart defects (CHDs) affect 1 in 120 newborns in the United States. Surgical repair of structural heart defects often leads to arrhythmia and increased risk of heart failure. The laboratory has previously developed an acellular fibrin patch reinforced with a biodegradable poly(ether ester urethane) urea mesh that result in improved heart function when tested in a rat right ventricle wall replacement model compared to fixed pericardium. However, this patch does not drive significant neotissue formation. The patch materials are modified here and this patch is prevascularized with human umbilical vein endothelial cells and c-Kit⁺ human amniotic fluid stem cells. Rudimentary capillary-like networks form in the fibrin after culture of cell-encapsulated patches for 3 d in vitro. Prevascularized patches and noncell loaded patch controls are implanted onto full-thickness heart wall defects created in the right ventricle of athymic nude rats. Two months after surgery, defect repair with prevascularized patches results in improved heart function and the patched heart area exhibited greater vascularization and muscularization, less fibrosis, and increased M2 macrophage infiltration compared to acellular patches.

Mechanism-Based Cardiac Regeneration Strategies in Mammals

Heart failure in adults is a leading cause of morbidity and mortality worldwide. It can arise from a variety of diseases, with most resulting in a loss of cardiomyocytes that cannot be replaced due to their inability to replicate, as well as to a lack of resident cardiomyocyte progenitor cells in the adult heart. Identifying and exploiting mechanisms underlying loss of developmental cardiomyocyte replicative capacity has proved to be useful in developing therapeutics to effect adult cardiac regeneration. Of course, effective regeneration of myocardium after injury requires not just expansion of cardiomyocytes, but also neovascularization to allow appropriate perfusion and resolution of injury-induced inflammation and interstitial fibrosis, but also reversal of adverse left ventricular remodeling. In addition to overcoming these challenges, a regenerative therapy needs to be safe and easily translatable. Failure to address these critical issues will delay the translation of regenerative approaches. This review critically analyzes current regenerative approaches while also providing a framework for future experimental studies aimed at enhancing success in regenerating the injured heart.

A framework for developing sex-specific engineered heart models

The convergence of tissue engineering and patient-specific stem cell biology has enabled the engineering of in vitro tissue models that allow the study of patient-tailored treatment modalities. However, sex-related disparities in health and disease, from systemic hormonal influences to cellular-level differences, are often overlooked in stem cell biology, tissue engineering and preclinical screening. The cardiovascular system, in particular, shows considerable sex-related differences, which need to be considered in cardiac tissue engineering. In this Review, we analyse sex-related properties of the heart muscle in the context of health and disease, and discuss a framework for including sex-based differences in human cardiac tissue engineering. We highlight how sex-based features can be implemented at the cellular and tissue levels, and how sex-specific cardiac models could advance the study of cardiovascular diseases. Finally, we define design criteria for sex-specific cardiac tissue engineering and provide an outlook to future research possibilities beyond the cardiovascular system.

Improvement of Heart Function After Transplantation of Encapsulated Stem Cells Induced with miR-1/Myocd in Myocardial Infarction Model of Rat

Cardiovascular disease is one of the most common causes of death worldwide. Mesenchymal stem cells (MSCs) are one of the most common sources in cell-based therapies in heart regeneration. There are several methods to differentiate MSCs into cardiac-like cells, such as gene induction. Moreover, using a three-dimensional (3D) culture, such as hydrogels increases efficiency of differentiation. In the current study, mouse adipose-derived MSCs were co-transduced with lentiviruses containing microRNA-1 (miR-1) and Myocardin (Myocd). Then, expression of cardiac markers, such as NK2 homeobox 5(Nkx2-5), GATA binding protein 4 (Gata4), and troponin T type 2 (Tnnt2) was investigated, at both gene and protein levels in two-dimensional (2D) culture and chitosan/collagen hydrogel (CS/CO) as a 3D culture. Additionally, after induction of myocardial infarction (MI) in rats, a patch containing the encapsulated induced cardiomyocytes (iCM/P) was implanted to MI zone. Subsequently, 30 days after MI induction, echocardiography, immunohistochemistry staining, and histological examination were performed to evaluate cardiac function. The results of quantitative real -time polymerase chain reaction (qRT-PCR) and immunocytochemistry showed that co-induction of miR-1 and Myocd in MSCs followed by 3D culture of transduced cells increased expression of cardiac markers. Besides, results of in vivo study implicated that heart function was improved in MI model of rats in iCM/P-treated group. The results suggested that miR-1/Myocd induction combined with encapsulation of transduced cells in CS/CO hydrogel increased efficiency of MSCs differentiation into iCMs and could improve heart function in MI model of rats after implantation.

3D Bioprinting of Engineered Tissue Flaps with Hierarchical Vessel Networks (VesselNet) for Direct Host-To-Implant Perfusion

Engineering hierarchical vasculatures is critical for creating implantable functional thick tissues. Current approaches focus on fabricating mesoscale vessels for implantation or hierarchical microvascular in vitro models, but a combined approach is yet to be achieved to create engineered tissue flaps. Here, millimetric vessel-like scaffolds and 3D bioprinted vascularized tissues interconnect, creating fully engineered hierarchical vascular constructs for implantation. Endothelial and support cells spontaneously form microvascular networks in bioprinted tissues using a human collagen bioink. Sacrificial molds are used to create polymeric vessel-like scaffolds and endothelial cells seeded in their lumen form native-like endothelia. Assembling endothelialized scaffolds within vascularizing hydrogels incites the bioprinted vasculature and endothelium to cooperatively create vessels, enabling tissue perfusion through the scaffold lumen. Using a cuffing microsurgery approach, the engineered tissue is directly anastomosed with a rat femoral artery, promoting a rich host vasculature within the implanted tissue. After two weeks in vivo, contrast microcomputer tomography imaging and lectin perfusion of explanted engineered tissues verify the host ingrowth vasculature's functionality. Furthermore, the hierarchical vessel network (VesselNet) supports in vitro functionality of cardiomyocytes. Finally, the proposed approach is expanded to mimic complex structures with native-like millimetric vessels. This work presents a novel strategy aiming to create fully-engineered patient-specific thick tissue flaps.

Vascularisation of pluripotent stem cell-derived myocardium: biomechanical insights for physiological relevance in cardiac tissue engineering

The myocardium is a diverse environment, requiring coordination between a variety of specialised cell types. Biochemical crosstalk between cardiomyocytes (CM) and microvascular endothelial cells (MVEC) is essential to maintain contractility and healthy tissue homeostasis. Yet, as myocytes beat, heterocellular communication occurs also through constantly fluctuating biomechanical stimuli, namely (1) compressive and tensile forces generated directly by the beating myocardium, and (2) pulsatile shear stress caused by intra-microvascular flow. Despite endothelial cells (EC) being highly mechanosensitive, the role of biomechanical stimuli from beating CM as a regulatory mode of myocardial-microvascular crosstalk is relatively unexplored. Given that cardiac biomechanics are dramatically altered during disease, and disruption of myocardial-microvascular communication is a known driver of pathological remodelling, understanding the biomechanical context necessary for healthy myocardial-microvascular interaction is of high importance. The current gap in understanding can largely be attributed to technical limitations associated with reproducing dynamic physiological biomechanics in multicellular in vitro platforms, coupled with limited in vitro viability of primary cardiac tissue. However, differentiation of CM from human pluripotent stem cells (hPSC) has provided an unlimited source of human myocytes suitable for designing in vitro models. This technology is now converging with the diverse field of tissue engineering, which utilises in vitro techniques designed to enhance physiological relevance, such as biomimetic extracellular matrix (ECM) as 3D scaffolds, microfluidic perfusion of vascularised networks, and complex multicellular architectures generated via 3D bioprinting. These strategies are now allowing researchers to design in vitro platforms which emulate the cell composition, architectures, and biomechanics specific to the myocardial-microvascular microenvironment. Inclusion of physiological multicellularity and biomechanics may also induce a more mature phenotype in stem cell-derived CM, further enhancing their value. This review aims to highlight the importance of biomechanical stimuli as determinants of CM-EC crosstalk in cardiac health and disease, and to explore emerging tissue engineering and hPSC technologies which can recapitulate physiological dynamics to enhance the value of in vitro cardiac experimentation.

Harnessing organs-on-a-chip to model tissue regeneration

Tissue engineering has markedly matured since its early beginnings in the 1980s. In addition to the original goal to regenerate damaged organs, the field has started to explore modeling of human physiology "in a dish." Induced pluripotent stem cell (iPSC) technologies now enable studies of organ regeneration and disease modeling in a patient-specific context. We discuss the potential of "organ-on-a-chip" systems to study regenerative therapies with focus on three distinct organ systems: cardiac, respiratory, and hematopoietic. We propose that the combinatorial studies of human tissues at these two scales would help realize the translational potential of tissue engineering.

The next generation of endothelial differentiation: Tissue-specific ECs

Endothelial cells (ECs) sense and respond to fluid flow and regulate immune cell trafficking in all organs. Despite sharing the same mesodermal origin, ECs exhibit heterogeneous tissue-specific characteristics. Human pluripotent stem cells (hPSCs) can potentially be harnessed to capture this heterogeneity and further elucidate endothelium behavior to satisfy the need for increased accuracy and breadth of disease models and therapeutics. Here, we review current strategies for hPSC differentiation to blood vascular ECs and their maturation into continuous, fenestrated, and sinusoidal tissues. We then discuss the contribution of hPSC-derived ECs to recent advances in organoid development and organ-on-chip approaches.

Maturation of human pluripotent stem cell derived cardiomyocytes in vitro and in vivo

Human pluripotent stem cell derived cardiomyocytes (hPSC-CMs) represent an inexhaustible cell source for in vitro disease modeling, drug discovery and toxicity screening, and potential therapeutic applications. However, currently available differentiation protocols yield populations of hPSC-CMs with an immature phenotype similar to cardiomyocytes in the early fetal heart. In this review, we consider the developmental processes and signaling cues involved in normal human cardiac maturation, as well as how these insights might be applied to the specific maturation of hPSC-CMs. We summarize the state-of-the-art and relative merits of reported hPSC-CM maturation strategies including prolonged duration in culture, metabolic manipulation, treatment with soluble or substrate-based cues, and tissue engineering approaches. Finally, we review the evidence that hPSC-CMs mature after implantation in injured hearts as such in vivo remodeling will likely affect the safety and efficacy of a potential hPSC-based cardiac therapy.

Cardiac Tissue Engineering: Inclusion of Non-cardiomyocytes for Enhanced Features

Engineered cardiac tissues (ECTs) are 3D physiological models of the heart that are created and studied for their potential role in developing therapies of cardiovascular diseases and testing cardio toxicity of drugs. Recreating the microenvironment of the native myocardium in vitro mainly involves the use of cardiomyocytes. However, ECTs with only cardiomyocytes (CM-only) often perform poorly and are less similar to the native myocardium compared to ECTs constructed from co-culture of cardiomyocytes and nonmyocytes. One important goal of co-culture tissues is to mimic the native heart’s cellular composition, which can result in better tissue function and maturity. In this review, we investigate the role of nonmyocytes in ECTs and discuss the mechanisms behind the contributions of nonmyocytes in enhancement of ECT features.

Drawing Inspiration from Developmental Biology for Cardiac Tissue Engineers

A sound understanding of developmental biology is part of the foundation of effective stem cell-derived tissue engineering. Here, the key concepts of cardiac development that are successfully applied in a bioinspired approach to growing engineered cardiac tissues, are reviewed. The native cardiac milieu is studied extensively from embryonic to adult phenotypes, as it provides a resource of factors, mechanisms, and protocols to consider when working toward establishing living tissues in vitro. It begins with the various cell types that constitute the cardiac tissue. It is discussed how myocytes interact with other cell types and their microenvironment and how they change over time from the embryonic to the adult states, with a view on how such changes affect the tissue function and may be used in engineered tissue models. Key embryonic signaling pathways that have been leveraged in the design of culture media and differentiation protocols are presented. The cellular microenvironment, from extracellular matrix chemical and physical properties, to the dynamic mechanical and electrical forces that are exerted on tissues is explored. It is shown that how such microenvironmental factors can inform the design of biomaterials, scaffolds, stimulation bioreactors, and maturation readouts, and suggest considerations for ongoing biomimetic advancement of engineered cardiac tissues and regeneration strategies for the future.

Cardiac Organoids to Model and Heal Heart Failure and Cardiomyopathies

Cardiac tissue engineering aims at creating contractile structures that can optimally reproduce the features of human cardiac tissue. These constructs are becoming valuable tools to model some of the cardiac functions, to set preclinical platforms for drug testing, or to alternatively be used as therapies for cardiac repair approaches. Most of the recent developments in cardiac tissue engineering have been made possible by important advances regarding the efficient generation of cardiac cells from pluripotent stem cells and the use of novel biomaterials and microfabrication methods. Different combinations of cells, biomaterials, scaffolds, and geometries are however possible, which results in different types of structures with gradual complexities and abilities to mimic the native cardiac tissue. Here, we intend to cover key aspects of tissue engineering applied to cardiology and the consequent development of cardiac organoids. This review presents various facets of the construction of human cardiac 3D constructs, from the choice of the components to their patterning, the final geometry of generated tissues, and the subsequent readouts and applications to model and treat cardiac diseases.

A Simple Method for Generating, Clearing, and Imaging Pre-vascularized 3D Adipospheres Derived from Human iPS Cells

Beige/brite/brown-like adipocytes (BAs), dispersed in white adipose tissue, represent promising cell targets to counteract obesity and associated diseases. However, there are major limitations for a BA-based treatment of obesity, among which the main ones are the rareness of BAs in adult humans and the lack of a relevant cell culture condition for modeling the development of BAs. We describe in this chapter the capacity of human induced pluripotent stem cells-derived BA progenitors (hiPSC-BAPs) to self-organize in spheroids and a method for their differentiation at a high efficiency in hiPSC-derived 3D adipospheres containing UCP1-expressing cells. Enrichment of adipospheres with human dermal microvascular endothelial cells (HDMECs) allows to better mimic native adipose tissue. To observe the accumulation of lipid droplets, organization of the extracellular matrix and expression of adipogenic markers on the surface of hiPSC-adipospheres, we detail how to combine Oil Red O staining with immunostaining both imaged by fluorescence microscopy. Furthermore, to have a global view of pre-vascularized network formed by HDMECs inside of hiPSC-adipospheres, we describe a method which consists of the whole adipospheres fixation, multicolor immunostaining, clearing, and imaging.

Considerations for the Bioengineering of Advanced Cardiac In Vitro Models of Myocardial Infarction

Despite the latest advances in cardiovascular biology and medicine, myocardial infarction (MI) remains one of the major causes of deaths worldwide. While reperfusion of the myocardium is critical to limit the ischemic damage typical of a MI event, it causes detrimental morphological and functional changes known as "reperfusion injury." This complex scenario is poorly represented in currently available models of ischemia/reperfusion injury, leading to a poor translation of findings from the bench to the bedside. However, more recent bioengineered in vitro models of the human heart represent more clinically relevant tools to prevent and treat MI in patients. These include 3D cultures of cardiac cells, the use of patient-derived stem cells, and 3D bioprinting technology. This review aims at highlighting the major features typical of a heart attack while comparing current in vitro, ex vivo, and in vivo models. This information has the potential to further guide in developing novel advanced in vitro cardiac models of ischemia/reperfusion injury. It may pave the way for the generation of advanced pathophysiological cardiac models with the potential to develop personalized therapies.

Engineering Vascularized Organoid-on-a-Chip Models

Recreating human organ-level function in vitro is a rapidly evolving field that integrates tissue engineering, stem cell biology, and microfluidic technology to produce 3D organoids. A critical component of all organs is the vasculature. Herein, we discuss general strategies to create vascularized organoids, including common source materials, and survey previous work using vascularized organoids to recreate specific organ functions and simulate tumor progression. Vascularization is not only an essential component of individual organ function but also responsible for coupling the fate of all organs and their functions. While some success in coupling two or more organs together on a single platform has been demonstrated, we argue that the future of vascularized organoid technology lies in creating organoid systems complete with tissue-specific microvasculature and in coupling multiple organs through a dynamic vascular network to create systems that can respond to changing physiological conditions.

Evolution of organoid technology: Lessons learnt in Co-Culture systems from developmental biology

In recent years, the development of 3D organoids has opened new avenues of investigation into development, physiology, and regenerative medicine. Organoid formation and the process of organogenesis share common developmental pathways; thus, our knowledge of developmental biology can help model the complexity of different organs to refine organoids into a more sophisticated platform. The developmental process is strongly dependent on complex networks and communication of cell-cell and cell-matrix interactions among different cell populations and their microenvironment, during embryogenesis. These interactions affect cell behaviors such as proliferation, survival, migration, and differentiation. Co-culture systems within the organoid technology were recently developed and provided the highly physiologically relevant systems. Supportive cells including various types of endothelial and stromal cells provide the proper microenvironment, facilitate organoid assembly, and improve vascularization and maturation of organoids. This review discusses the role of the co-culture systems in organoid generation, with a focus on how knowledge of developmental biology has directed and continues to shape the development of more evolved 3D co-culture system-derived organoids.

Engineering Human Cardiac Muscle Patch Constructs for Prevention of Post-infarction LV Remodeling

Tissue engineering combines principles of engineering and biology to generate living tissue equivalents for drug testing, disease modeling, and regenerative medicine. As techniques for reprogramming human somatic cells into induced pluripotent stem cells (iPSCs) and subsequently differentiating them into cardiomyocytes and other cardiac cells have become increasingly efficient, progress toward the development of engineered human cardiac muscle patch (hCMP) and heart tissue analogs has accelerated. A few pilot clinical studies in patients with post-infarction LV remodeling have been already approved. Conventional methods for hCMP fabrication include suspending cells within scaffolds, consisting of biocompatible materials, or growing two-dimensional sheets that can be stacked to form multilayered constructs. More recently, advanced technologies, such as micropatterning and three-dimensional bioprinting, have enabled fabrication of hCMP architectures at unprecedented spatiotemporal resolution. However, the studies working on various hCMP-based strategies for in vivo tissue repair face several major obstacles, including the inadequate scalability for clinical applications, poor integration and engraftment rate, and the lack of functional vasculature. Here, we review many of the recent advancements and key concerns in cardiac tissue engineering, focusing primarily on the production of hCMPs at clinical/industrial scales that are suitable for administration to patients with myocardial disease. The wide variety of cardiac cell types and sources that are applicable to hCMP biomanufacturing are elaborated. Finally, some of the key challenges remaining in the field and potential future directions to address these obstacles are discussed.

Recent Advances in Scaffolding from Natural-Based Polymers for Volumetric Muscle Injury

Volumetric Muscle Loss (VML) is associated with muscle loss function and often untreated and considered part of the natural sequelae of trauma. Various types of biomaterials with different physical and properties have been developed to treat VML. However, much work remains yet to be done before the scaffolds can pass from the bench to the bedside. The present review aims to provide a comprehensive summary of the latest developments in the construction and application of natural polymers-based tissue scaffolding for volumetric muscle injury. Here, the tissue engineering approaches for treating volumetric muscle loss injury are highlighted and recent advances in cell-based therapies using various sources of stem cells are elaborated in detail. An overview of different strategies of tissue scaffolding and their efficacy on skeletal muscle cells regeneration and migration are presented. Furthermore, the present paper discusses a wide range of natural polymers with a special focus on proteins and polysaccharides that are major components of the extracellular matrices. The natural polymers are biologically active and excellently promote cell adhesion and growth. These bio-characteristics justify natural polymers as one of the most attractive options for developing scaffolds for muscle cell regeneration.

Human endothelial colony-forming cells provide trophic support for pluripotent stem cell-derived cardiomyocytes via distinctively high expression of neuregulin-1

The search for a source of endothelial cells (ECs) with translational therapeutic potential remains crucial in regenerative medicine. Human blood-derived endothelial colony-forming cells (ECFCs) represent a promising source of autologous ECs due to their robust capacity to form vascular networks in vivo and their easy accessibility from peripheral blood. However, whether ECFCs have distinct characteristics with translational value compared to other ECs remains unclear. Here, we show that vascular networks generated with human ECFCs exhibited robust paracrine support for human pluripotent stem cell-derived cardiomyocytes (iCMs), significantly improving protection against drug-induced cardiac injury and enhancing engraftment at ectopic (subcutaneous) and orthotopic (cardiac) sites. In contrast, iCM support was notably absent in grafts with vessels lined by mature-ECs. This differential trophic ability was due to a unique high constitutive expression of the cardioprotective growth factor neuregulin-1 (NRG1). ECFCs, but not mature-ECs, were capable of actively releasing NRG1, which, in turn, reduced apoptosis and increased the proliferation of iCMs via the PI3K/Akt signaling pathway. Transcriptional silencing of NRG1 abrogated these cardioprotective effects. Our study suggests that ECFCs are uniquely suited to support human iCMs, making these progenitor cells ideal for cardiovascular regenerative medicine.

Bioprinting of Complex Vascularized Tissues

Functional vasculature is crucial for the maintenance of living tissues via the transport of oxygen, nutrients, and metabolic waste products. As a result, insufficient vascularization in thick engineered tissues will lead to cell death and necrosis due to mass transport and diffusional constraints. To circumvent these limitations, we describe the development of a microscale continuous optical bioprinting (μCOB) platform for 3D printing complex vascularized tissues with superior resolution and speed. By using the μCOB system, endothelial cells and other supportive cells can be printed directly into hydrogels with precisely controlled distribution and subsequent formation of lumen-like structures in vitro.

Engineering Myocardium for Heart Regeneration-Advancements, Considerations, and Future Directions

Heart disease is the leading cause of death in the United States among both adults and infants. In adults, 5-year survival after a heart attack is <60%, and congenital heart defects are the top killer of liveborn infants. Problematically, the regenerative capacity of the heart is extremely limited, even in newborns. Furthermore, suitable donor hearts for transplant cannot meet the demand and require recipients to use immunosuppressants for life. Tissue engineered myocardium has the potential to replace dead or fibrotic heart tissue in adults and could also be used to permanently repair congenital heart defects in infants. In addition, engineering functional myocardium could facilitate the development of a whole bioartificial heart. Here, we review and compare in vitro and in situ myocardial tissue engineering strategies. In the context of this comparison, we consider three challenges that must be addressed in the engineering of myocardial tissue: recapitulation of myocardial architecture, vascularization of the tissue, and modulation of the immune system. In addition to reviewing and analyzing current progress, we recommend specific strategies for the generation of tissue engineered myocardial patches for heart regeneration and repair.

Human Pluripotent Stem Cell-Derived Cardiovascular Cells: From Developmental Biology to Therapeutic Applications

Advances in our understanding of cardiovascular development have provided a roadmap for the directed differentiation of human pluripotent stem cells (hPSCs) to the major cell types found in the heart. In this Perspective, we review the state of the field in generating and maturing cardiovascular cells from hPSCs based on our fundamental understanding of heart development. We then highlight their applications for studying human heart development, modeling disease-performing drug screening, and cell replacement therapy. With the advancements highlighted here, the promise that hPSCs will deliver new treatments for degenerative and debilitating diseases may soon be fulfilled.

Human Cell Modeling for Cardiovascular Diseases

The availability of appropriate and reliable in vitro cell models recapitulating human cardiovascular diseases has been the aim of numerous researchers, in order to retrace pathologic phenotypes, elucidate molecular mechanisms, and discover therapies using simple and reproducible techniques. In the past years, several human cell types have been utilized for these goals, including heterologous systems, cardiovascular and non-cardiovascular primary cells, and embryonic stem cells. The introduction of induced pluripotent stem cells and their differentiation potential brought new prospects for large-scale cardiovascular experiments, bypassing ethical concerns of embryonic stem cells and providing an advanced tool for disease modeling, diagnosis, and therapy. Each model has its advantages and disadvantages in terms of accessibility, maintenance, throughput, physiological relevance, recapitulation of the disease. A higher level of complexity in diseases modeling has been achieved with multicellular co-cultures. Furthermore, the important progresses reached by bioengineering during the last years, together with the opportunities given by pluripotent stem cells, have allowed the generation of increasingly advanced in vitro three-dimensional tissue-like constructs mimicking in vivo physiology. This review provides an overview of the main cell models used in cardiovascular research, highlighting the pros and cons of each, and describing examples of practical applications in disease modeling.