Native cardiac environment and its impact on engineering cardiac tissue

Versatile human cardiac tissues engineered with perfusable heart extracellular microenvironment for biomedical applications

Engineered human cardiac tissues have been utilized for various biomedical applications, including drug testing, disease modeling, and regenerative medicine. However, the applications of cardiac tissues derived from human pluripotent stem cells are often limited due to their immaturity and lack of functionality. Therefore, in this study, we establish a perfusable culture system based on in vivo-like heart microenvironments to improve human cardiac tissue fabrication. The integrated culture platform of a microfluidic chip and a three-dimensional heart extracellular matrix enhances human cardiac tissue development and their structural and functional maturation. These tissues are comprised of cardiovascular lineage cells, including cardiomyocytes and cardiac fibroblasts derived from human induced pluripotent stem cells, as well as vascular endothelial cells. The resultant macroscale human cardiac tissues exhibit improved efficacy in drug testing (small molecules with various levels of arrhythmia risk), disease modeling (Long QT Syndrome and cardiac fibrosis), and regenerative therapy (myocardial infarction treatment). Therefore, our culture system can serve as a highly effective tissue-engineering platform to provide human cardiac tissues for versatile biomedical applications.

Recent advances in soluble decellularized extracellular matrix for heart tissue engineering and organ modeling

Despite the advent of tissue engineering (TE) for the remodeling, restoring, and replacing damaged cardiovascular tissues, the progress is hindered by the optimal mechanical and chemical properties required to induce cardiac tissue-specific cellular behaviors including migration, adhesion, proliferation, and differentiation. Cardiac extracellular matrix (ECM) consists of numerous structural and functional molecules and tissue-specific cells, therefore it plays an important role in stimulating cell proliferation and differentiation, guiding cell migration, and activating regulatory signaling pathways. With the improvement and modification of cell removal methods, decellularized ECM (dECM) preserves biochemical complexity, and bio-inductive properties of the native matrix and improves the process of generating functional tissue. In this review, we first provide an overview of the latest advancements in the utilization of dECM in in vitro model systems for disease and tissue modeling, as well as drug screening. Then, we explore the role of dECM-based biomaterials in cardiovascular regenerative medicine (RM), including both invasive and non-invasive methods. In the next step, we elucidate the engineering and material considerations in the preparation of dECM-based biomaterials, namely various decellularization techniques, dECM sources, modulation, characterizations, and fabrication approaches. Finally, we discuss the limitations and future directions in fabrication of dECM-based biomaterials for cardiovascular modeling, RM, and clinical translation.

Cardiac organoid: multiple construction approaches and potential applications

The human cardiac organoid (hCO) is three-dimensional tissue model that is similar to an in vivo organ and has great potential on heart development biology, disease modeling, drug screening and regenerative medicine. However, the construction of hCO presents a unique challenge compared with other organoids such as the lung, small intestine, pancreas, liver. Since heart disease is the dominant cause of death and the treatment of such disease is one of the most unmet medical needs worldwide, developing technologies for the construction and application of hCO is a critical task for the scientific community. In this review, we discuss the current classification and construction methods of hCO. In addition, we describe its applications in drug screening, disease modeling, and regenerative medicine. Finally, we propose the limitations of the cardiac organoid and future research directions. A detailed understanding of hCO will provide ways to improve its construction and expand its applications.

Bioprinting of Cardiac Tissue in Space: Where Are We?

Bioprinting in space is the next frontier in tissue engineering. In the absence of gravity, novel opportunities arise, as well as new challenges. The cardiovascular system needs particular attention in tissue engineering, not only to develop safe countermeasures for astronauts in future deep and long-term space missions, but also to bring solutions to organ transplantation shortage. In this perspective, the challenges encountered when using bioprinting techniques in space and current gaps that need to be overcome are discussed. The recent developments that have been made in the bioprinting of heart tissues in space and an outlook on potential future bioprinting opportunities in space are described.

Heart-derived collagen promotes maturation of engineered heart tissue

Although the extracellular matrix (ECM) plays essential roles in heart tissue engineering, the optimal ECM components for heart tissue organization have not previously been elucidated. Here, we focused on the main ECM component, fibrillar collagen, and analyzed the effects of collagens on heart tissue engineering, by comparing the use of porcine heart-derived collagen and other organ-derived collagens in generating engineered heart tissue (EHT). We demonstrate that heart-derived collagen induces better contraction and relaxation of human induced pluripotent stem cell-derived EHT (hiPSC-EHT) and that hiPSC-EHT with heart-derived collagen exhibit more mature profiles than those with collagens from other organs. Further, we found that collagen fibril formation and gel stiffness influence the contraction, relaxation, and maturation of hiPSC-EHT, suggesting the importance of collagen types III and type V, which are relatively abundant in the heart. Thus, we demonstrate the effectiveness of organ-specific collagens in tissue engineering and drug discovery.

Convergence of melt electrowriting and extrusion-based bioprinting for vascular patterning of a myocardial construct

To progress cardiac tissue engineering strategies closer to the clinic, thicker constructs are required to meet the functional need following a cardiac event. Consequently, pre-vascularization of these constructs needs to be investigated to ensure survival and optimal performance of implantable engineered heart tissue. The aim of this research is to investigate the potential of combining extrusion-based bioprinting (EBB) and melt electrowriting for the fabrication of a myocardial construct with a precisely patterned pre-vascular pathway. Gelatin methacryloyl (GelMA) was investigated as a base hydrogel for the respective myocardial and vascular bioinks with collagen, Matrigel and fibrinogen as interpenetrating polymers to support myocardial functionality. Subsequently, extrusion-based printability and viability were investigated to determine the optimal processing parameters for printing into melt electrowritten meshes. Finally, an anatomically inspired vascular pathway was implemented in a dual EBB set-up into melt electrowritten meshes, creating a patterned pre-vascularized myocardial construct. It was determined that a blend of 5% GelMA and 0.8 mg·ml-1collagen with a low crosslinked density was optimal for myocardial cellular arrangement and alignment within the constructs. For the vascular fraction, the optimized formulation consisted of 5% GelMA, 0.8 mg·ml-1collagen and 1 mg·ml-1fibrinogen with a higher crosslinked density, which led to enhanced vascular cell connectivity. Printability assessment confirmed that the optimized bioinks could effectively fill the microfiber mesh while supporting cell viability (∼70%). Finally, the two bioinks were applied using a dual EBB system for the fabrication of a pre-vascular pathway with the shape of a left anterior descending artery within a myocardial construct, whereby the distinct cell populations could be visualized in their respective patterns up to D14. This research investigated the first step towards developing a thick engineered cardiac tissue construct in which a pre-vascularization pathway is fabricated within a myocardial construct.

Additive Manufacturing and Physicomechanical Characteristics of PEGDA Hydrogels: Recent Advances and Perspective for Tissue Engineering

In this brief review, we discuss the recent advancements in using poly(ethylene glycol) diacrylate (PEGDA) hydrogels for tissue engineering applications. PEGDA hydrogels are highly attractive in biomedical and biotechnology fields due to their soft and hydrated properties that can replicate living tissues. These hydrogels can be manipulated using light, heat, and cross-linkers to achieve desirable functionalities. Unlike previous reviews that focused solely on material design and fabrication of bioactive hydrogels and their cell viability and interactions with the extracellular matrix (ECM), we compare the traditional bulk photo-crosslinking method with the latest three-dimensional (3D) printing of PEGDA hydrogels. We present detailed evidence combining the physical, chemical, bulk, and localized mechanical characteristics, including their composition, fabrication methods, experimental conditions, and reported mechanical properties of bulk and 3D printed PEGDA hydrogels. Furthermore, we highlight the current state of biomedical applications of 3D PEGDA hydrogels in tissue engineering and organ-on-chip devices over the last 20 years. Finally, we delve into the current obstacles and future possibilities in the field of engineering 3D layer-by-layer (LbL) PEGDA hydrogels for tissue engineering and organ-on-chip devices.

Dynamic mechanobiology of cardiac cells and tissues: Current status and future perspective

Mechanical forces impact cardiac cells and tissues over their entire lifespan, from development to growth and eventually to pathophysiology. However, the mechanobiological pathways that drive cell and tissue responses to mechanical forces are only now beginning to be understood, due in part to the challenges in replicating the evolving dynamic microenvironments of cardiac cells and tissues in a laboratory setting. Although many in vitro cardiac models have been established to provide specific stiffness, topography, or viscoelasticity to cardiac cells and tissues via biomaterial scaffolds or external stimuli, technologies for presenting time-evolving mechanical microenvironments have only recently been developed. In this review, we summarize the range of in vitro platforms that have been used for cardiac mechanobiological studies. We provide a comprehensive review on phenotypic and molecular changes of cardiomyocytes in response to these environments, with a focus on how dynamic mechanical cues are transduced and deciphered. We conclude with our vision of how these findings will help to define the baseline of heart pathology and of how these in vitro systems will potentially serve to improve the development of therapies for heart diseases.

Nanoindentation Response of 3D Printed PEGDA Hydrogels in a Hydrated Environment

Hydrogels are commonly used materials in tissue engineering and organ-on-chip devices. This study investigated the nanomechanical properties of monolithic and multilayered poly(ethylene glycol) diacrylate (PEGDA) hydrogels manufactured using bulk polymerization and layer-by-layer projection lithography processes, respectively. An increase in the number of layers (or reduction in layer thickness) from 1 to 8 and further to 60 results in a reduction in the elastic modulus from 5.53 to 1.69 and further to 0.67 MPa, respectively. It was found that a decrease in the number of layers induces a lower creep index (CIT) in three-dimensional (3D) printed PEGDA hydrogels. This reduction is attributed to mesoscale imperfections that appear as pockets of voids at the interfaces of the multilayered hydrogels attributed to localized regions of unreacted prepolymers, resulting in variations in defect density in the samples examined. An increase in the degree of cross-linking introduced by a higher dosage of ultraviolet (UV) exposure leads to a higher elastic modulus. This implies that the elastic modulus and creep behavior of hydrogels are governed and influenced by the degree of cross-linking and defect density of the layers and interfaces. These findings can guide an optimal manufacturing pathway to obtain the desirable nanomechanical properties in 3D printed PEGDA hydrogels, critical for the performance of living cells and tissues, which can be engineered through control of the fabrication parameters.

Cardiac ultrastructure inspired matrix induces advanced metabolic and functional maturation of differentiated human cardiomyocytes

The vast potential of human induced pluripotent stem-cell-derived cardiomyocytes (hiPSC-CMs) in preclinical models of cardiac pathologies, precision medicine, and drug screening remains to be fully realized because hiPSC-CMs are immature without adult-like characteristics. Here, we present a method to accelerate hiPSC-CM maturation on a substrate, cardiac mimetic matrix (CMM), mimicking adult human heart matrix ligand chemistry, rigidity, and submicron ultrastructure, which synergistically mature hiPSC-CMs rapidly within 30 days. hiPSC-CMs matured on CMM exhibit systemic transcriptomic maturation toward an adult heart state, are aligned with high strain energy, metabolically rely on oxidative phosphorylation and fatty acid oxidation, and display enhanced redox handling capability, efficient calcium handling, and electrophysiological features of ventricular myocytes. Endothelin-1-induced pathological hypertrophy is mitigated on CMM, highlighting the role of a native cardiac microenvironment in withstanding hypertrophy progression. CMM is a convenient model for accelerated development of ventricular myocytes manifesting highly specialized cardiac-specific functions.

Accelerating Cardiovascular Research: Recent Advances in Translational 2D and 3D Heart Models

In vitro modelling the complex (patho-) physiological conditions of the heart is a major challenge in cardiovascular research. In recent years, methods based on three-dimensional (3D) cultivation approaches have steadily evolved to overcome the major limitations of conventional adherent monolayer cultivation (2D). These 3D approaches aim to study, reproduce or modify fundamental native features of the heart such as tissue organization and cardiovascular microenvironment. Therefore, these systems have great potential for (patient-specific) disease research, for the development of new drug screening platforms, and for the use in regenerative and replacement therapy applications. Consequently, continuous improvement and adaptation is required with respect to fundamental limitations such as cardiomyocyte maturation, scalability, heterogeneity, vascularization, and reproduction of native properties. In this review, 2D monolayer culturing and the 3D in vitro systems of cardiac spheroids, organoids, engineered cardiac microtissue and bioprinting as well as the ex vivo technique of myocardial slicing are introduced with their basic concepts, advantages, and limitations. Furthermore, recent advances of various new approaches aiming to extend as well as to optimize these in vitro and ex vivo systems are presented. This article is protected by copyright. All rights reserved.

Bioelectricity-coupling patches for repairing impaired myocardium

Cardiac abnormalities, which account for extensive burdens on public health and economy, drive necessary attempts to revolutionize the traditional therapeutic system. Advances in cardiac tissue engineering have expanded a highly efficacious platform to address cardiovascular events, especially cardiac infarction. Current efforts to overcome biocompatible limitations highlight the constructs of a conductive cardiac patch to accelerate the industrial and clinical landscape that is amenable for patient-accurate therapy, regenerative medicine, disease modeling, and drug delivery. With the notion that cardiac tissue synchronically contracts triggered by electrical pulses, the cardiac patches based on conductive materials are developed and treated on the dysfunctional heart. In this review, we systematically summarize distinct conductive materials serving as the most promising alternatives (conductive nanomaterials, conductive polymers, piezoelectric polymers, and ionic electrolytes) to achieve electric signal transmission and engineered cardiac tissues. Existing applications are discussed considering how these patches containing conductive candidates are fabricated into diverse forms with major strategies. Ultimately, we try to define a new concept as a bioelectricity-coupling patch that provides a favorable cardiac micro-environment for cardiac functional activities. Underlying challenges and prospects are presented regarding industrial processing and cardiovascular treatment of conductive patch progress. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Cardiovascular Disease.

Electrospun piezoelectric scaffolds for cardiac tissue engineering

The use of smart materials in tissue engineering is becoming increasingly appealing to provide additional functionalities and control over cell fate. The stages of tissue development and regeneration often require various electrical and electromechanical cues supported by the extracellular matrix, which is often neglected in most tissue engineering approaches. Particularly, in cardiac cells, electrical signals modulate cell activity and are responsible for the maintenance of the excitation-contraction coupling. Addition of electroconductive and topographical cues improves the biomimicry of cardiac tissues and plays an important role in driving cells towards the desired phenotype. Current platforms used to apply electrical stimulation to cells in vitro often require large external equipment and wires and electrodes immersed in the culture media, limiting the scalability and applicability of this process. Piezoelectric materials represent a shift in paradigm in materials and methods aimed at providing electrical stimulation to cardiac cells since they can produce and deliver electrical signals to cells and tissues by mechanoelectrical transduction. Despite the ability of piezoelectric materials to mimic the mechanoelectrical transduction of the heart, the use of these materials is limited in cardiac tissue engineering and methods to characterise piezoelectricity are often built in-house, which poses an additional difficulty when comparing results from the literature. In this work, we aim at providing an overview of the main challenges in cardiac tissue engineering and how piezoelectric materials could offer a solution to them. A revision on the existing literature in electrospun piezoelectric materials applied to cardiac tissue engineering is performed for the first time, as electrospinning plays an important role in the manufacturing of scaffolds with enhanced piezoelectricity and extracellular matrix native-like morphology. Finally, an overview of the current techniques used to evaluate piezoelectricity and their limitations is provided.

The harder the climb the better the view: The impact of substrate stiffness on cardiomyocyte fate

The quest for novel methods to mature human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) for cardiac regeneration, modelling and drug testing has emphasized a need to create microenvironments with physiological features. Many studies have reported on how cardiomyocytes sense substrate stiffness and adapt their morphological and functional properties. However, these observations have raised new biological questions and a shared vision to translate it into a tissue or organ context is still elusive. In this review, we will focus on the relevance of substrates mimicking cardiac extracellular matrix (cECM) rigidity for the understanding of the biomechanical crosstalk between the extracellular and intracellular environment. The ability to opportunely modulate these pathways could be a key to regulate in vitro hiPSC-CM maturation. Therefore, both hiPSC-CM models and substrate stiffness appear as intriguing tools for the investigation of cECM-cell interactions. More understanding of these mechanisms may provide novel insights on how cECM affects cardiac cell function in the context of genetic cardiomyopathies.

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.

A porcine cholecystic extracellular matrix conductive scaffold for cardiac tissue repair

Cardiac tissue engineering using cells, scaffolds or signaling molecules is a promising approach for replacement or repair of damaged myocardium. This study addressed the contemporary need for a conductive biomimetic nanocomposite scaffold for cardiac tissue engineering by examining the use of a gold nanoparticle-incorporated porcine cholecystic extracellular matrix for the same. The scaffold had an electrical conductivity (0.74 ± 0.03 S/m) within the range of native myocardium. It was a suitable substrate for the growth and differentiation of cardiomyoblast (H9c2) as well as rat mesenchymal stem cells to cardiomyocyte-like cells. Moreover, as an epicardial patch, the scaffold promoted neovascularisation and cell proliferation in infarcted myocardium of rats. It was concluded that the gold nanoparticle coated cholecystic extracellular matrix is a prospective biomaterial for cardiac tissue engineering.

Human-induced pluripotent stem cells in cardiovascular research: current approaches in cardiac differentiation, maturation strategies, and scalable production

Manifestations of cardiovascular diseases (CVDs) in a patient or a population differ based on inherent biological makeup, lifestyle, and exposure to environmental risk factors. These variables mean that therapeutic interventions may not provide the same benefit to every patient. In the context of CVDs, human-induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) offer an opportunity to model CVDs in a patient-specific manner. From a pharmacological perspective, iPSC-CM models can serve as go/no-go tests to evaluate drug safety. To develop personalized therapies for early diagnosis and treatment, human-relevant disease models are essential. Hence, to implement and leverage the utility of iPSC-CMs for large-scale treatment or drug discovery, it is critical to (i) carefully evaluate the relevant limitations of iPSC-CM differentiations, (ii) establish quality standards for defining the state of cell maturity, and (iii) employ techniques that allow scalability and throughput with minimal batch-to-batch variability. In this review, we briefly describe progress made with iPSC-CMs in disease modelling and pharmacological testing, as well as current iPSC-CM maturation techniques. Finally, we discuss current platforms for large-scale manufacturing of iPSC-CMs that will enable high-throughput drug screening applications.

Recent advances on bioengineering approaches for fabrication of functional engineered cardiac pumps: A review

The field of cardiac tissue engineering has advanced over the past decades; however, most research progress has been limited to engineered cardiac tissues (ECTs) at the microscale with minimal geometrical complexities such as 3D strips and patches. Although microscale ECTs are advantageous for drug screening applications because of their high-throughput and standardization characteristics, they have limited translational applications in heart repair and the in vitro modeling of cardiac function and diseases. Recently, researchers have made various attempts to construct engineered cardiac pumps (ECPs) such as chambered ventricles, recapitulating the geometrical complexity of the native heart. The transition from microscale ECTs to ECPs at a translatable scale would greatly accelerate their translational applications; however, researchers are confronted with several major hurdles, including geometrical reconstruction, vascularization, and functional maturation. Therefore, the objective of this paper is to review the recent advances on bioengineering approaches for fabrication of functional engineered cardiac pumps. We first review the bioengineering approaches to fabricate ECPs, and then emphasize the unmatched potential of 3D bioprinting techniques. We highlight key advances in bioprinting strategies with high cell density as researchers have begun to realize the critical role that the cell density of non-proliferative cardiomyocytes plays in the cell-cell interaction and functional contracting performance. We summarize the current approaches to engineering vasculatures both at micro- and meso-scales, crucial for the survival of thick cardiac tissues and ECPs. We showcase a variety of strategies developed to enable the functional maturation of cardiac tissues, mimicking the in vivo environment during cardiac development. By highlighting state-of-the-art research, this review offers personal perspectives on future opportunities and trends that may bring us closer to the promise of functional ECPs.

Glycan characteristics of human heart constituent cells maintaining organ function: relatively stable glycan profiles in cellular senescence

Cell surface glycoproteins, which are good indicators of cellular types and biological function; are suited for cell evaluation. Tissue remodeling using various cells is a key feature of regenerative therapy. For artificial heart remodeling, a mixture of heart constituent cells has been investigated for organ assembly, however, the cellular characteristics remain unclear. In this study, the glycan profiles of human cardiomyocytes (HCMs), human cardiac fibroblasts (HCFs), and human vascular endothelial cells (ECs) were analyzed using evanescent-field lectin microarray analysis, a tool of glycan profiling, to clarify the required cellular characteristics. We found that ECs had more “α1-2fucose” and “core α1-6fucose” residues than other cells, and that “α2-6sialic acid” residue was more abundant in ECs and HCMs than in HCFs. HCFs showed higher abundance of “β-galactose” and “β-N-acetylgalactosamine” residues on N-glycan and O-glycan, respectively, compared to other cells. Interestingly, cardiac glycan profiles were insignificantly changed with cellular senescence. The residues identified in this study may participate in organ maintenance by contributing to the preservation of glycan components. Therefore, future studies should investigate the roles of glycans in optimal tissue remodeling since identifying cellular characteristics is important for the development of regenerative therapies.

Exposure to nanoplastics impairs collective contractility of neonatal cardiomyocytes under electrical synchronization

Nanoplastics are global pollutants that have been increasingly released into the environment following the degradation process of industrial and consumer products. These tiny particles have been reported to adversely affect various organs in the body, including the heart. Since it is probable that the less-developed hearts of newborn offspring are more vulnerable to nanoplastic insult during the infant feeding compared with mature hearts of adults, the acute effects of nanoplastics on the collective contractility of neonatal cardiomyocytes are to be elucidated. Here, we traced the aggregation of nanoplastics on the cell membrane and their internalization into the cytosol of neonatal rat ventricular myocytes (NRVMs) for 60 min in the presence of electrical pulses to synchronize the cardiac contraction in vitro. The time-coursed linkage of collective contraction forces, intracellular Ca²⁺ concentrations, mitochondrial membrane potentials, extracellular field potentials, and reactive oxygen species levels enabled us to build up the sequence of the cellular events associated with the detrimental effects of nanoplastics with positive surface charges on the immature cardiomyocytes. A significant decrease in intracellular Ca²⁺ levels and electrophysiological activities of NRVMs resulted in the reduction of contraction forces in the early phase (0-15 min). The further reduction of contraction force in the late phase (30-60 min) was attributed to remarkable decreases in mitochondrial membrane potentials and cellular metabolism. Our multifaceted assessments on the effect of positively surface charged nanoplastics on NRVM may offer better understanding of substantial risks of ever-increasing nanoplastic pollution in the hearts of human infants or adults.

The role of bFGF in preventing the shrinkage of cardiac progenitor cell-engineered conduction tissue by downregulating α-SMA expression

AIMS

Engineered conduction tissues (ECTs) fabricated from cardiac progenitor cells (CPCs) and collagen sponges were precisely targeted for the treatment of atrioventricular conduction block in our previous studies. However, obvious shrinkage and deformation of ECTs was observed during in vitro culture. According to the literature, it can be speculated that basic fibroblast growth factor (bFGF) may downregulate alpha-smooth muscle actin (α-SMA) produced by CPCs to prevent the shrinkage of CPC-engineered conduction tissues.

MAIN METHODS

In this study, culture media with or without bFGF were used for both cell culture and 3D tissue construction. The expression of α-SMA and the size change of engineered tissue were analyzed to evaluate the feasibility of adding bFGF to regulate α-SMA expression and shrinkage of constructs. In addition, cardiac-specific examinations were performed to evaluate the effect of bFGF on cardiac tissue formation.

KEY FINDINGS

Supplementation with bFGF efficiently relieved shrinkage of engineered tissue by downregulating the expression of α-SMA at both the cellular and 3D tissue levels. Moreover, bFGF had a positive influence on cardiac tissue formation in terms of cell viability, tissue organization and electrical conduction velocity.

SIGNIFICANCE

This study provides a guide for both shape control and quality improvement of CPC-engineered cardiac tissues.

Developmental lineage of human pluripotent stem cell-derived cardiac fibroblasts affects their functional phenotype

Cardiac fibroblasts (CFBs) support heart function by secreting extracellular matrix (ECM) and paracrine factors, respond to stress associated with injury and disease, and therefore are an increasingly important therapeutic target. We describe how developmental lineage of human pluripotent stem cell-derived CFBs, epicardial (EpiC-FB), and second heart field (SHF-FB) impacts transcriptional and functional properties. Both EpiC-FBs and SHF-FBs exhibited CFB transcriptional programs and improved calcium handling in human pluripotent stem cell-derived cardiac tissues. We identified differences including in composition of ECM synthesized, secretion of growth and differentiation factors, and myofibroblast activation potential, with EpiC-FBs exhibiting higher stress-induced activation potential akin to myofibroblasts and SHF-FBs demonstrating higher calcification and mineralization potential. These phenotypic differences suggest that EpiC-FBs have utility in modeling fibrotic diseases while SHF-FBs are a promising source of cells for regenerative therapies. This work directly contrasts regional and developmental specificity of CFBs and informs CFB in vitro model selection.

Extracellular Matrix Protein Ratios in the Human Heart and Vessels: How to Distinguish Pathological From Physiological Changes?

Cardiovascular pathology is often accompanied by changes in relative content and/or ratios of structural extracellular matrix (ECM) proteins within the heart and elastic vessels. Three of these proteins, collagen-I, collagen-III, and elastin, make up the bulk of the ECM proteins in these tissues, forming a microenvironment that strongly dictates the tissue biomechanical properties and effectiveness of cardiac and vascular function. In this review, we aim to elucidate how the ratios of collagen-I to collagen-III and elastin to collagen are altered in cardiovascular diseases and the aged individuum. We elaborate on these major cardiovascular ECM proteins in terms of structure, tissue localization, turnover, and physiological function and address how their ratios change in aging, dilated cardiomyopathy, coronary artery disease with myocardial infarction, atrial fibrillation, aortic aneurysms, atherosclerosis, and hypertension. To the end of guiding in vitro modeling approaches, we focus our review on the human heart and aorta, discuss limitations in ECM protein quantification methodology, examine comparability between studies, and highlight potential in vitro applications. In summary, we found collagen-I relative concentration to increase or stay the same in cardiovascular disease, resulting in a tendency for increased collagen-I/collagen-III and decreased elastin/collagen ratios. These ratios were found to fall on a continuous scale with ranges defining distinct pathological states as well as a significant difference between the human heart and aortic ECM protein ratios.

Patient-Specific 3D Bioprinted Models of Developing Human Heart

The heart is the first organ to develop in the human embryo through a series of complex chronological processes, many of which critically rely on the interplay between cells and the dynamic microenvironment. Tight spatiotemporal regulation of these interactions is key in heart development and diseases. Due to suboptimal experimental models, however, little is known about the role of microenvironmental cues in the heart development. This study investigates the use of 3D bioprinting and perfusion bioreactor technologies to create bioartificial constructs that can serve as high-fidelity models of the developing human heart. Bioprinted hydrogel-based, anatomically accurate models of the human embryonic heart tube (e-HT, day 22) and fetal left ventricle (f-LV, week 33) are perfused and analyzed both computationally and experimentally using ultrasound and magnetic resonance imaging. Results demonstrate comparable flow hemodynamic patterns within the 3D space. We demonstrate endothelial cell growth and function within the bioprinted e-HT and f-LV constructs, which varied significantly in varying cardiac geometries and flow. This study introduces the first generation of anatomically accurate, 3D functional models of developing human heart. This platform enables precise tuning of microenvironmental factors, such as flow and geometry, thus allowing the study of normal developmental processes and underlying diseases.

Polymeric Biomaterials for the Treatment of Cardiac Post-Infarction Injuries

Cardiac regeneration aims to reconstruct the heart contractile mass, preventing the organ from a progressive functional deterioration, by delivering pro-regenerative cells, drugs, or growth factors to the site of injury. In recent years, scientific research focused the attention on tissue engineering for the regeneration of cardiac infarct tissue, and biomaterials able to anatomically and physiologically adapt to the heart muscle have been proposed as valuable tools for this purpose, providing the cells with the stimuli necessary to initiate a complete regenerative process. An ideal biomaterial for cardiac tissue regeneration should have a positive influence on the biomechanical, biochemical, and biological properties of tissues and cells; perfectly reflect the morphology and functionality of the native myocardium; and be mechanically stable, with a suitable thickness. Among others, engineered hydrogels, three-dimensional polymeric systems made from synthetic and natural biomaterials, have attracted much interest for cardiac post-infarction therapy. In addition, biocompatible nanosystems, and polymeric nanoparticles in particular, have been explored in preclinical studies as drug delivery and tissue engineering platforms for the treatment of cardiovascular diseases. This review focused on the most employed natural and synthetic biomaterials in cardiac regeneration, paying particular attention to the contribution of Italian research groups in this field, the fabrication techniques, and the current status of the clinical trials.

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.

3D bioprinting of cardiac tissue: current challenges and perspectives

Demand for donor hearts has increased globally due to cardiovascular diseases. Recently, three-dimensional (3D) bioprinting technology has been aimed at creating clinically viable cardiac constructs for the management of myocardial infarction (MI) and associated complications. Advances in 3D bioprinting show promise in aiding cardiac tissue repair following injury/infarction and offer an alternative to organ transplantation. This article summarizes the basic principles of 3D bioprinting and recent attempts at reconstructing functional adult native cardiac tissue with a focus on current challenges and prospective strategies.

Self-Adhesion Conductive Sub-micron Fiber Cardiac Patch from Shape Memory Polymers to Promote Electrical Signal Transduction Function

Myocardial infarction (MI) constitutes the first cause of morbidity and mortality in our life, so using highly conductive and elastic materials to produce an engineered cardiac patch is an effective way to improve the myocardium infarction area function. Here, shape memory polymers of the polyurethane/polyaniline/silicon oxide (PU/PANI/SiO₂) electrospinning sub-micron fiber patch were precisely produced in the case of the hydrogen bonding effect and interaction between the carboxyl groups to provide compatibility, phase mixing/miscibility, and stability. The sub-micron fiber patch prepared by our group has some remarkable characteristics, such as sub-micron fibers, 3D porous structure, special thickness to simulate the extracellular matrix (ECM), elastic deformation, good properties in conducting weak electrical signals, stability to maintain the whole structure, and self-adhesion. This sub-micron fiber material has been proven to be effective, easy, and reliable. Through precise design of the material system, structure regulation, and performance optimization, the aim is to produce a sub-micron fiber cardiac patch to simulate the myocardium ECM and improve conductive signal transduction for potential MI therapy.

Recapitulating Cardiac Structure and Function In Vitro from Simple to Complex Engineering

Cardiac tissue engineering aims to generate in vivo-like functional tissue for the study of cardiac development, homeostasis, and regeneration. Since the heart is composed of various types of cells and extracellular matrix with a specific microenvironment, the fabrication of cardiac tissue in vitro requires integrating technologies of cardiac cells, biomaterials, fabrication, and computational modeling to model the complexity of heart tissue. Here, we review the recent progress of engineering techniques from simple to complex for fabricating matured cardiac tissue in vitro. Advancements in cardiomyocytes, extracellular matrix, geometry, and computational modeling will be discussed based on a technology perspective and their use for preparation of functional cardiac tissue. Since the heart is a very complex system at multiscale levels, an understanding of each technique and their interactions would be highly beneficial to the development of a fully functional heart in cardiac tissue engineering.

Recent advances in bioprinting technologies for engineering cardiac tissue

Annually increasing incidence of cardiac-related disorders and cardiac tissue's minimal regenerative capacity have motivated the researchers to explore effective therapeutic strategies. In the recent years, bioprinting technologies have witnessed a great wave of enthusiasm and have undergone steady advancements over a short period, opening the possibilities for recreating engineered functional cardiac tissue models for regenerative and diagnostic applications. With this perspective, the current review delineates recent developments in the sphere of engineered cardiac tissue fabrication, using traditional and advanced bioprinting strategies. The review also highlights different printing ink formulations, available cellular opportunities, and aspects of personalized medicines in the context of cardiac tissue engineering and bioprinting. On a concluding note, current challenges and prospects for further advancements are also discussed.

Preparation and characterization of gelatin-polysaccharide composite hydrogels for tissue engineering

Background

Tissue engineering, which involves the selection of scaffold materials, presents a new therapeutic strategy for damaged tissues or organs. Scaffold design based on blends of proteins and polysaccharides, as mimicry of the native extracellular matrix, has recently become a valuable strategy for tissue engineering.

Objective

This study aimed to construct composite hydrogels based on natural polymers for tissue engineering.

Methods

Composite hydrogels based on blends of gelatin with a polysaccharide component (chitosan or alginate) were produced and subsequently enzyme crosslinked. The other three hydrogels, chitosan hydrogel, sodium alginate hydrogel, and microbial transglutaminase-crosslinked gelatin (mTG/GA) hydrogel were also prepared. All hydrogels were evaluated for in vitro degradation property, swelling capacity, and mechanical property. Rat adipose-derived stromal stem cells (ADSCs) were isolated and seeded on (or embedded into) the above-mentioned hydrogels. The morphological features of ADSCs were observed and recorded. The effects of the hydrogels on ADSC survival and adhesion were investigated by immunofluorescence staining. Cell proliferation was tested by thiazolyl blue tetrazolium bromide (MTT) assay.

Results

Cell viability assay results showed that the five hydrogels are not cytotoxic. The mTG/GA and its composite hydrogels showed higher compressive moduli than the single-component chitosan and alginate hydrogels. MTT assay results showed that ADSCs proliferated better on the composite hydrogels than on the chitosan and alginate hydrogels. Light microscope observation and cell cytoskeleton staining showed that hydrogel strength had obvious effects on cell growth and adhesion. The ADSCs seeded on chitosan and alginate hydrogels plunged into the hydrogels and could not stretch out due to the low strength of the hydrogel, whereas cells seeded on composite hydrogels with higher elastic modulus, could spread out, and grew in size.

Conclusion

The gelatin-polysaccharide composite hydrogels could serve as attractive biomaterials for tissue engineering due to their easy preparation and favorable biophysical properties.

Human Extracellular-Matrix Functionalization of 3D hiPSC-Based Cardiac Tissues Improves Cardiomyocyte Maturation

Human induced pluripotent stem cells (hiPSC) possess significant therapeutic potential due to their high self-renewal capability and potential to differentiate into specialized cells such as cardiomyocytes. However, generated hiPSC-derived cardiomyocytes (hiPSC-CM) are still immature, with phenotypic and functional features resembling the fetal rather than their adult counterparts, which limits their application in cell-based therapies, in vitro cardiac disease modeling, and drug cardiotoxicity screening. Recent discoveries have demonstrated the potential of the extracellular matrix (ECM) as a critical regulator in development, homeostasis, and injury of the cardiac microenvironment. Within this context, this work aimed to assess the impact of human cardiac ECM in the phenotype and maturation features of hiPSC-CM. Human ECM was isolated from myocardium tissue through a physical decellularization approach. The cardiac tissue decellularization process reduced DNA content significantly while maintaining ECM composition in terms of sulfated glycosaminoglycans (s-GAG) and collagen content. These ECM particles were successfully incorporated in three-dimensional (3D) hiPSC-CM aggregates (CM+ECM) with no impact on viability and metabolic activity throughout 20 days in 3D culture conditions. Also, CM+ECM aggregates displayed organized and longer sarcomeres, with improved calcium handling when compared to hiPSC-CM aggregates. This study shows that human cardiac ECM functionalization of hiPSC-based cardiac tissues improves cardiomyocyte maturation. The knowledge generated herein provides essential insights to streamline the application of ECM in the development of hiPSC-based therapies targeting cardiac diseases.

Micromechanobiology: Focusing on the Cardiac Cell-Substrate Interface

Engineered, in vitro cardiac cell and tissue systems provide test beds for the study of cardiac development, cellular disease processes, and drug responses in a dish. Much effort has focused on improving the structure and function of engineered cardiomyocytes and heart tissues. However, these parameters depend critically on signaling through the cellular microenvironment in terms of ligand composition, matrix stiffness, and substrate mechanical properties-that is, matrix micromechanobiology. To facilitate improvements to in vitro microenvironment design, we review how cardiomyocytes and their microenvironment change during development and disease in terms of integrin expression and extracellular matrix (ECM) composition. We also discuss strategies used to bind proteins to common mechanobiology platforms and describe important differences in binding strength to the substrate. Finally, we review example biomaterial approaches designed to support and probe cell-ECM interactions of cardiomyocytes in vitro, as well as open questions and challenges.

Human Pluripotent Stem Cell-Derived Cardiomyocytes for Assessment of Anticancer Drug-Induced Cardiotoxicity

Cardiotoxicity is a major cause of high attrition rates among newly developed drugs. Moreover, anti-cancer treatment-induced cardiotoxicity is one of the leading reasons of mortality in cancer survivors. Cardiotoxicity screening in vitro may improve predictivity of cardiotoxicity by novel drugs, using human pluripotent stem cell (hPSC)-derived-cardiomyocytes. Anthracyclines, including Doxorubicin, are widely used and highly effective chemotherapeutic agents for the treatment of different forms of malignancies. Unfortunately, anthracyclines cause many cardiac complications early or late after therapy. Anthracyclines exhibit their potent anti-cancer effect primarily via induction of DNA damage during the DNA replication phase in proliferative cells. In contrast, studies in animals and hPSC-cardiomyocytes have revealed that cardiotoxic effects particularly arise from (1) the generation of oxidative stress inducing mitochondrial dysfunction, (2) disruption of calcium homeostasis, and (3) changes in transcriptome and proteome, triggering apoptotic cell death. To increase the therapeutic index of chemotherapeutic Doxorubicin therapy several protective strategies have been developed or are under development, such as (1) reducing toxicity through modification of Doxorubicin (analogs), (2) targeted delivery of anthracyclines specifically to the tumor tissue or (3) cardioprotective agents that can be used in combination with Doxorubicin. Despite continuous progress in the field of cardio-oncology, cardiotoxicity is still one of the major complications of anti-cancer therapy. In this review, we focus on current hPSC-cardiomyocyte models for assessing anthracycline-induced cardiotoxicity and strategies for cardioprotection. In addition, we discuss latest developments toward personalized advanced pre-clinical models that are more closely recapitulating the human heart, which are necessary to support in vitro screening platforms with higher predictivity. These advanced models have the potential to reduce the time from bench-to-bedside of novel antineoplastic drugs with reduced cardiotoxicity.

Cardiac tissue engineering therapeutic products to enhance myocardial contractility

Researchers continue to develop therapeutic products for the repair and replacement of myocardial tissue that demonstrates contractility equivalent to normal physiologic states. As clinical trials focused on pure adult stem cell populations undergo meta-analysis for preclinical through clinical design, the field of tissue engineering is emerging as a new clinical frontier to repair the myocardium and improve cardiac output. This review will first discuss the three primary tissue engineering product themes that are advancing in preclinical to clinical models: (1) cell-free scaffolds, (2) scaffold-free cellular, and (3) hybrid cell and scaffold products. The review will then focus on the products that have advanced from preclinical models to clinical trials. In advancing the cardiac regenerative medicine field, long-term gains towards discovering an optimal product to generate functional myocardial tissue and eliminate heart failure may be achieved.