A Universal and Robust Integrated Platform for the Scalable Production of Human Cardiomyocytes From Pluripotent Stem Cells

Hydrogel microsphere stem cell encapsulation enhances cardiomyocyte differentiation and functionality in scalable suspension system

A reliable suspension-based platform for scaling engineered cardiac tissue (ECT) production from human induced pluripotent stem cells (hiPSCs) is crucial for regenerative therapies. Here, we compared the production and functionality of ECTs formed using our scaffold-based, engineered tissue microsphere differentiation approach with those formed using the prevalent scaffold-free aggregate platform. We utilized a microfluidic system for the rapid (1 million cells/min), high density (30, 40, 60 million cells/ml) encapsulation of hiPSCs within PEG-fibrinogen hydrogel microspheres. HiPSC-laden microspheres and aggregates underwent suspension-based cardiac differentiation in chemically defined media. In comparison to aggregates, microspheres maintained consistent size and shape initially, over time, and within and between batches. Initial size and shape coefficients of variation for microspheres were eight and three times lower, respectively, compared to aggregates. On day 10, microsphere cardiomyocyte (CM) content was 27 % higher and the number of CMs per initial hiPSC was 250 % higher than in aggregates. Contraction and relaxation velocities of microspheres were four and nine times higher than those of aggregates, respectively. Microsphere contractile functionality also improved with culture time, whereas aggregate functionality remained unchanged. Additionally, microspheres displayed improved β-adrenergic signaling responsiveness and uniform calcium transient propagation. Transcriptomic analysis revealed that while both microspheres and aggregates demonstrated similar gene regulation patterns associated with cardiomyocyte differentiation, heart development, cardiac muscle contraction, and sarcomere organization, the microspheres exhibited more pronounced transcriptional changes over time. Taken together, these results highlight the capability of the microsphere platform for scaling up biomanufacturing of ECTs in a suspension-based culture platform.

Functional and Structural Improvement of Engineered Cardiac Microtissue Using Aligned Microfilaments Scaffold

To enhance therapeutic strategies for cardiovascular diseases, the development of more reliable in vitro preclinical systems is imperative. These models, crucial for disease modeling and drug testing, must accurately replicate the 3D architecture of native heart tissue. In this study, we engineered a scaffold with aligned poly(lactic-co-glycolic acid) (PLGA) microfilaments to induce cellular alignment in the engineered cardiac microtissue (ECMT). Consequently, the coculture of three cell types, including cardiac progenitor cells (CPC), human umbilical cord endothelial cells (HUVEC), and human foreskin fibroblasts (HFF), within this 3D scaffold significantly improved cellular alignment compared to the control. Additionally, cells in the ECMT exhibited a more uniaxial anisotropic and oriented cytoskeleton, characterized by immunostaining of F-actin. This approach not only enhanced cell structure and microtissue architecture but also improved functionality, evident in synchronized electrophysiological signals. Therefore, our engineered cardiac microtissue using this aligned microfilament scaffold (AMFS) holds great potential for pharmaceutical research and other biomedical applications.

The molecular mechanisms of cardiac development and related diseases

Cardiac development is a complex and intricate process involving numerous molecular signals and pathways. Researchers have explored cardiac development through a long journey, starting with early studies observing morphological changes and progressing to the exploration of molecular mechanisms using various molecular biology methods. Currently, advancements in stem cell technology and sequencing technology, such as the generation of human pluripotent stem cells and cardiac organoids, multi-omics sequencing, and artificial intelligence (AI) technology, have enabled researchers to understand the molecular mechanisms of cardiac development better. Many molecular signals regulate cardiac development, including various growth and transcription factors and signaling pathways, such as WNT signaling, retinoic acid signaling, and Notch signaling pathways. In addition, cilia, the extracellular matrix, epigenetic modifications, and hypoxia conditions also play important roles in cardiac development. These factors play crucial roles at one or even multiple stages of cardiac development. Recent studies have also identified roles for autophagy, metabolic transition, and macrophages in cardiac development. Deficiencies or abnormal expression of these factors can lead to various types of cardiac development abnormalities. Nowadays, congenital heart disease (CHD) management requires lifelong care, primarily involving surgical and pharmacological treatments. Advances in surgical techniques and the development of clinical genetic testing have enabled earlier diagnosis and treatment of CHD. However, these technologies still have significant limitations. The development of new technologies, such as sequencing and AI technologies, will help us better understand the molecular mechanisms of cardiac development and promote earlier prevention and treatment of CHD in the future.

Chemically defined production of engineered cardiac tissue microspheres from hydrogel-encapsulated pluripotent stem cells

Chemically defined, suspension culture conditions are a key requirement in realizing clinical translation of engineered cardiac tissues (ECTs). Building on our previous work producing functional ECT microspheres through differentiation of biomaterial encapsulated human induced pluripotent stem cells (hiPSCs), here we establish the ability to use chemically defined culture conditions, including stem cell media (E8) and cardiac differentiation media (chemically defined differentiation media with three components, CDM3). A custom microfluidic cell encapsulation system was used to encapsulate hiPSCs at a range of initial cell concentrations and diameters in the hybrid biomaterial, poly(ethylene glycol)-fibrinogen (PF), for the formation of highly spherical and uniform ECT microspheres for subsequent cardiac differentiation. Initial microsphere diameter could be tightly controlled, and microspheres could be produced with an initial diameter between 400 and 800 µm. Three days after encapsulation, cardiac differentiation was initiated through small molecule modulation of Wnt signaling in CDM3. Cardiac differentiation occurred resulting in in situ ECT formation; results showed that this differentiation protocol could be used to achieve cardiomyocyte (CM) contents greater than 90%, although there was relatively high variability in CM content and yield between differentiation batches. Spontaneous contraction of ECT microspheres initiated between Days 7 and 10 of differentiation and ECT microspheres responded to electrical pacing up to 1.5 Hz. Resulting CMs had well-defined sarcomeres and the gap junction protein, connexin 43, and had appropriate temporal changes in gene expression. In summary, this study demonstrated the proof-of-concept to produce functional ECT microspheres with chemically defined media in suspension culture in combination with biomaterial support of microsphere encapsulated hiPSCs.

Expandable hESC-derived cardiovascular progenitor cells generate functional cardiac lineage cells for microtissue construction

BACKGROUND

Cardiovascular progenitor cells (CPCs) derived from human embryonic stem cells (hESCs) are considered valuable cell sources for investigating cardiovascular physiology in vitro. Meeting the diverse needs of this application requires the large-scale production of CPCs in an in vitro environment. This study aimed to use an effective culture system utilizing signaling factors for the large-scale expansion of hESC-derived CPCs with the potential to differentiate into functional cardiac lineage cells.

METHODS AND RESULTS

Initially, CPCs were generated from hESCs using a 4-day differentiation protocol with a combination of four small molecules (CHIR99021, IWP2, SB-431542, and purmorphamine). These CPCs were then expanded and maintained in a medium containing three factors (bFGF, CHIR, and A83-01), resulting in a > 6,000-fold increase after 8 passages. These CPCs were successfully cryopreserved for an extended period in late passages. The expanded CPCs maintained their gene and protein expression signatures as well as their differentiation capacity through eight passages. Additionally, these CPCs could differentiate into four types of cardiac lineage cells: cardiomyocytes, endothelial cells, smooth muscle cells, and fibroblasts, demonstrating appropriate functionality. Furthermore, the coculture of these CPC-derived cardiovascular lineage cells in rat tail collagen resulted in cardiac microtissue formation, highlighting the potential of this 3D platform for studying cardiovascular physiology in vitro.

CONCLUSION

In conclusion, expandable hESC-derived CPCs demonstrated the ability to self-renewal and differentiation into functional cardiovascular lineage cells consistently across passages, which may apply as potential cell sources for in vitro cardiovascular studies.

The Kids Heart BioBank: supporting 20 years of patient care and research into CHD

INTRODUCTION

The cause of most CHD is unknown and considered complex, implicating genetic and environmental factors in disease causation. The Kids Heart BioBank was established in 2003 to accelerate genetic investigations into CHD.

METHODS

Recruitment includes patients undergoing interventions for CHD at The Children's Hospital at Westmead. Informed consent is obtained from parents/guardians, and blood is collected at the time of cardiac intervention from which DNA is extracted and stored. Associated detailed clinical information and a family history are stored in the purpose-designed database.

RESULTS

To date, the Kids Heart BioBank contains biospecimens and associated clinical information from over 4,900 patients with CHD and their families. Two-thirds (64.1%) of probands have been included in research studies with 28.9% of participants who underwent genomic sequencing receiving a molecular diagnosis with direct clinical utility. The value of this resource to patients and families is highlighted by the high consent rate (94.6%) and the low withdrawal of consent rate (0.4%). The Kids Heart BioBank has supported many large national and international collaborations and contributed significantly to CHD research.

CONCLUSIONS

The Kids Heart BioBank is an invaluable resource and, together with other similar resources, the resulting research has paved the way for clinical genetic testing options for CHD patients, previously not possible. With research in the field moving away from diagnosing monogenic disease, the Kids Heart BioBank is ideally placed to support the next chapter of research efforts into complex disease mechanisms, requiring large patient cohorts with detailed phenotypic information.

Protein-free media for cardiac differentiation of hPSCs in 2000 mL suspension culture

BACKGROUND

Commonly used media for the differentiation of human pluripotent stem cells into cardiomyocytes (hPSC-CMs) contain high concentrations of proteins, in particular albumin, which is prone to quality variations and presents a substantial cost factor, hampering the clinical translation of in vitro-generated cardiomyocytes for heart repair. To overcome these limitations, we have developed chemically defined, entirely protein-free media based on RPMI, supplemented with L-ascorbic acid 2-phosphate (AA-2P) and either the non-ionic surfactant Pluronic F-68 or a specific polyvinyl alcohol (PVA).

METHODS AND RESULTS

Both media compositions enable the efficient, directed differentiation of embryonic and induced hPSCs, matching the cell yields and cardiomyocyte purity ranging from 85 to 99% achieved with the widely used protein-based CDM3 medium. The protein-free differentiation approach was readily up-scaled to a 2000 mL process scale in a fully controlled stirred tank bioreactor in suspension culture, producing > 1.3 × 109 cardiomyocytes in a single process run. Transcriptome analysis, flow cytometry, electrophysiology, and contractile force measurements revealed that the mass-produced cardiomyocytes differentiated in protein-free medium exhibit the expected ventricular-like properties equivalent to the well-established characteristics of CDM3-control cells.

CONCLUSIONS

This study promotes the robustness and upscaling of the cardiomyogenic differentiation process, substantially reduces media costs, and provides an important step toward the clinical translation of hPSC-CMs for heart regeneration.

Promotion of cardiac microtissue assembly within G-CSF-enriched collagen I-cardiogel hybrid hydrogel

Tissue engineering as an interdisciplinary field of biomedical sciences has raised many hopes in the treatment of cardiovascular diseases as well as development of in vitro three-dimensional (3D) cardiac models. This study aimed to engineer a cardiac microtissue using a natural hybrid hydrogel enriched by granulocyte colony-stimulating factor (G-CSF), a bone marrow-derived growth factor. Cardiac ECM hydrogel (Cardiogel: CG) was mixed with collagen type I (ColI) to form the hybrid hydrogel, which was tested for mechanical and biological properties. Three cell types (cardiac progenitor cells, endothelial cells and cardiac fibroblasts) were co-cultured in the G-CSF-enriched hybrid hydrogel to form a 3D microtissue. ColI markedly improved the mechanical properties of CG in the hybrid form with a ratio of 1:1. The hybrid hydrogel demonstrated acceptable biocompatibility and improved retention of encapsulated human foreskin fibroblasts. Co-culture of three cell types in G-CSF enriched hybrid hydrogel, resulted in a faster 3D structure shaping and a well-cellularized microtissue with higher angiogenesis compared to growth factor-free hybrid hydrogel (control). Immunostaining confirmed the presence of CD31+ tube-like structures as well as vimentin+ cardiac fibroblasts and cTNT+ human pluripotent stem cells-derived cardiomyocytes. Bioinformatics analysis of signaling pathways related to the G-CSF receptor in cardiovascular lineage cells, identified target molecules. The in silico-identified STAT3, as one of the major molecules involved in G-CSF signaling of cardiac tissue, was upregulated in G-CSF compared to control. The G-CSF-enriched hybrid hydrogel could be a promising candidate for cardiac tissue engineering, as it facilitates tissue formation and angiogenesis.

Efficient and cost-effective differentiation of induced neural crest cells from induced pluripotent stem cells using laminin 211

Introduction

Neural crest cells (NCCs) are cell populations that originate during the formation of neural crest in developmental stages. They are characterized by their multipotency, self-renewal and migration potential. Given their ability to differentiate into various types of cells such as neurons and Schwann cells, NCCs hold promise for cell therapy applications. The conventional method for obtaining NCCs involves inducing them from stem cells like induced pluripotent stem cells (iPSCs), followed by a long-term passage or purification using fluorescence-activated cell sorting (FACS). Although FACS allows high purity induced neural crest cells (iNCCs) to be obtained quickly, it is complex and costly. Therefore, there is a need for a simpler, cost-effective and less time-consuming method for cell therapy application.

Methods

To select differentiated iNCCs from heterogeneous cell populations quickly without using FACS, we adopted the use of scaffold material full-length laminin 211 (LN211), a recombinant, xeno-free protein suitable for cell therapy. After fist passage on LN211, iNCCs characterization was performed using polymerase chain reaction and flow cytometry. Additionally, proliferation and multipotency to various cells were evaluated.

Result

The iNCCs obtained using our new method expressed cranial NCC- related genes and exhibited stable proliferation ability for at least 57 days, while maintaining high expression level of the NCCs marker CD271. They demonstrated differentiation ability into several cell types: neurons, astrocytes, melanocytes, smooth muscle cells, osteoblasts, adipocytes and chondrocytes. Furthermore, they could be induced to differentiate into induced mesenchymal stem cells (iMSCs) which retain the essential functions of somatic MSCs.

Conclusion

In this study, we have developed novel method for obtaining high purity iNCCs differentiated from iPSCs in a short time using LN211 under xeno-free condition. Compared with traditional methods, like FACS or long-term passage, this approach enables the acquisition of a large amount of cells at a lower cost and labor, and it is expected to contribute to stable supply of large scale iNCCs for future cell therapy applications.

A Non-Apoptotic Pattern of Caspase-9/Caspase-3 Activation During Differentiation of Human Embryonic Stem Cells into Cardiomyocytes

In vitro studies have demonstrated that the differentiation of embryonic stem cells (ESCs) into cardiomyocytes requires activation of caspases through the mitochondrial pathway. These studies have relied on synthetic substrates for activity measurements, which can be misleading due to potential none-specific hydrolysis of these substrates by proteases other than caspases. Hence, caspase-9 and caspase-3 activation are investigated during the differentiation of human ESCs (hESCs) by directly assessing caspase-9 and -3 cleavage. Western blot reveals the presence of the cleaved caspase-9 prior to and during the differentiation of human ESCs (hESCs) into cardiomyocytes at early stages, which diminishes as the differentiation progresses, without cleavage and activation of endogenous procaspase-3. Activation of exogenous procaspase-3 by endogenous caspase-9 and subsequent cleavage of chromogenic caspase-3 substrate i.e. DEVD-pNA during the course of differentiation confirmes that endogenous caspase-9 has the potency to recognize and activate procaspase-3, but for reasons that are unknown to us fails to do so. These observations suggest the existence of distinct mechanisms of caspase regulation in differentiation as compared to apoptosis. Bioinformatics analysis suggests the presence of caspase-9 regulators, which may influence proteolytic function under specific conditions.

Contractile and Genetic Characterization of Cardiac Constructs Engineered from Human Induced Pluripotent Stem Cells: Modeling of Tuberous Sclerosis Complex and the Effects of Rapamycin

The implementation of three-dimensional tissue engineering concurrently with stem cell technology holds great promise for in vitro research in pharmacology and toxicology and modeling cardiac diseases, particularly for rare genetic and pediatric diseases for which animal models, immortal cell lines, and biopsy samples are unavailable. It also allows for a rapid assessment of phenotype-genotype relationships and tissue response to pharmacological manipulation. Mutations in the TSC1 and TSC2 genes lead to dysfunctional mTOR signaling and cause tuberous sclerosis complex (TSC), a genetic disorder that affects multiple organ systems, principally the brain, heart, skin, and kidneys. Here we differentiated healthy (CC3) and tuberous sclerosis (TSP8-15) human induced pluripotent stem cells (hiPSCs) into cardiomyocytes to create engineered cardiac tissue constructs (ECTCs). We investigated and compared their mechano-elastic properties and gene expression and assessed the effects of rapamycin, a potent inhibitor of the mechanistic target of rapamycin (mTOR). The TSP8-15 ECTCs had increased chronotropy compared to healthy ECTCs. Rapamycin induced positive inotropic and chronotropic effects (i.e., increased contractility and beating frequency, respectively) in the CC3 ECTCs but did not cause significant changes in the TSP8-15 ECTCs. A differential gene expression analysis revealed 926 up- and 439 down-regulated genes in the TSP8-15 ECTCs compared to their healthy counterparts. The application of rapamycin initiated the differential expression of 101 and 31 genes in the CC3 and TSP8-15 ECTCs, respectively. A gene ontology analysis showed that in the CC3 ECTCs, the positive inotropic and chronotropic effects of rapamycin correlated with positively regulated biological processes, which were primarily related to the metabolism of lipids and fatty and amino acids, and with negatively regulated processes, which were predominantly associated with cell proliferation and muscle and tissue development. In conclusion, this study describes for the first time an in vitro TSC cardiac tissue model, illustrates the response of normal and TSC ECTCs to rapamycin, and provides new insights into the mechanisms of TSC.

Pluripotent stem cell-based cardiac regenerative therapy for heart failure

Cardiac regenerative therapy using human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) is expected to become an alternative to heart transplantation for severe heart failure. It is now possible to produce large numbers of human pluripotent stem cells (hPSCs) and eliminate non-cardiomyocytes, including residual undifferentiated hPSCs, which can cause teratoma formation after transplantation. There are two main strategies for transplanting hPSC-CMs: injection of hPSC-CMs into the myocardium from the epicardial side, and implantation of hPSC-CM patches or engineered heart tissues onto the epicardium. Transplantation of hPSC-CMs into the myocardium of large animals in a myocardial infarction model improved cardiac function. The engrafted hPSC-CMs matured, and microvessels derived from the host entered the graft abundantly. Furthermore, as less invasive methods using catheters, injection into the coronary artery and injection into the myocardium from the endocardium side have recently been investigated. Since transplantation of hPSC-CMs alone has a low engraftment rate, various methods such as transplantation with the extracellular matrix or non-cardiomyocytes and aggregation of hPSC-CMs have been developed. Post-transplant arrhythmias, imaging of engrafted hPSC-CMs, and immune rejection are the remaining major issues, and research is being conducted to address them. The clinical application of cardiac regenerative therapy using hPSC-CMs has just begun and is expected to spread widely if its safety and efficacy are proven in the near future.

Advances in the design, generation, and application of tissue-engineered myocardial equivalents

Due to the limited regenerative ability of cardiomyocytes, the disabling irreversible condition of myocardial failure can only be treated with conservative and temporary therapeutic approaches, not able to repair the damage directly, or with organ transplantation. Among the regenerative strategies, intramyocardial cell injection or intravascular cell infusion should attenuate damage to the myocardium and reduce the risk of heart failure. However, these cell delivery-based therapies suffer from significant drawbacks and have a low success rate. Indeed, cardiac tissue engineering efforts are directed to repair, replace, and regenerate native myocardial tissue function. In a regenerative strategy, biomaterials and biomimetic stimuli play a key role in promoting cell adhesion, proliferation, differentiation, and neo-tissue formation. Thus, appropriate biochemical and biophysical cues should be combined with scaffolds emulating extracellular matrix in order to support cell growth and prompt favorable cardiac microenvironment and tissue regeneration. In this review, we provide an overview of recent developments that occurred in the biomimetic design and fabrication of cardiac scaffolds and patches. Furthermore, we sift in vitro and in situ strategies in several preclinical and clinical applications. Finally, we evaluate the possible use of bioengineered cardiac tissue equivalents as in vitro models for disease studies and drug tests.

Activation of AMPK promotes cardiac differentiation by stimulating the autophagy pathway

Autophagy, a critical catabolic process for cell survival against different types of stress, has a role in the differentiation of various cells, such as cardiomyocytes. Adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) is an energy-sensing protein kinase involved in the regulation of autophagy. In addition to its direct role in regulating autophagy, AMPK can also influence other cellular processes by regulating mitochondrial function, posttranslational acetylation, cardiomyocyte metabolism, mitochondrial autophagy, endoplasmic reticulum stress, and apoptosis. As AMPK is involved in the control of various cellular processes, it can influence the health and survival of cardiomyocytes. This study investigated the effects of an AMPK inducer (Metformin) and an autophagy inhibitor (Hydroxychloroquine) on the differentiation of human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs). The results showed that autophagy was upregulated during cardiac differentiation. Furthermore, AMPK activation increased the expression of CM-specific markers in hPSC-CMs. Additionally, autophagy inhibition impaired cardiomyocyte differentiation by targeting autophagosome-lysosome fusion. These results indicate the significance of autophagy in cardiomyocyte differentiation. In conclusion, AMPK might be a promising target for the regulation of cardiomyocyte generation by in vitro differentiation of pluripotent stem cells.

Systematic discovery of transcription factors that improve hPSC-derived cardiomyocyte maturation via temporal analysis of bioengineered cardiac tissues

Human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) have the potential to become powerful tools for disease modeling, drug testing, and transplantation; however, their immaturity limits their applications. Transcription factor (TF) overexpression can improve hPSC-CM maturity, but identifying these TFs has been elusive. Toward this, we establish here an experimental framework for systematic identification of maturation enhancing factors. Specifically, we performed temporal transcriptome RNAseq analyses of progressively matured hPSC-derived cardiomyocytes across 2D and 3D differentiation systems and further compared these bioengineered tissues to native fetal and adult-derived tissues. These analyses revealed 22 TFs whose expression did not increase in 2D differentiation systems but progressively increased in 3D culture systems and adult mature cell types. Individually overexpressing each of these TFs in immature hPSC-CMs identified five TFs (KLF15, ZBTB20, ESRRA, HOPX, and CAMTA2) as regulators of calcium handling, metabolic function, and hypertrophy. Notably, the combinatorial overexpression of KLF15, ESRRA, and HOPX improved all three maturation parameters simultaneously. Taken together, we introduce a new TF cocktail that can be used in solo or in conjunction with other strategies to improve hPSC-CM maturation and anticipate that our generalizable methodology can also be implemented to identify maturation-associated TFs for other stem cell progenies.

Progress and promise of cell sheet assisted cardiac tissue engineering in regenerative medicine

Cardiovascular diseases (CVDs) are the most common leading causes of premature deaths in all countries. To control the harmful side effects of CVDs on public health, it is necessary to understand the current and prospective strategies in prevention, management, and monitoring CVDs.In vitro,recapitulating of cardiac complex structure with its various cell types is a challenging topic in tissue engineering. Cardiac tissue engineering (CTE) is a multi-disciplinary strategy that has been considered as a novel alternative approach for cardiac regenerative medicine and replacement therapies. In this review, we overview various cell types and approaches in cardiac regenerative medicine. Then, the applications of cell-sheet-assisted CTE in cardiac diseases were discussed. Finally, we described how this technology can improve cardiac regeneration and function in preclinical and clinical models.

Conditioned media from human pluripotent stem cell-derived cardiomyocytes inhibit the growth and migration of lung cancer cells

Conditioned media (CM) from various cell types contain significant levels of paracrine factors. Recently, therapeutic properties of CM derived from stem cells have been revealed. Based on the fact that heart cancer is extremely rarely, we hypothesized that the CM obtained from human pluripotent stem cell-derived cardiomyocytes might inhibit cancer cell growth and survival. To this end, lung cancer cell line A549 along with human foreskin fibroblasts (HFF) were treated with serial concentrations of cardiomyocyte CM (CCM) or fibroblast CM (FCM). We found that CCM markedly reduced the viability of lung cancer cells, while FCM did not compromise the viability of neither cancer cells nor HFF cells. Furthermore, we determined an optimized CCM concentration, 30 mg/mL, at which the growth, clonogenicity, and migration of A549 and Calu6 lung cancer cell lines were substantially impaired, whereas FCM did not influence these properties. Moreover, lung cancer cells exhibited cell cycle regulation upon treatment with CCM and the rate of apoptosis was markedly increased by cardiomyocyte CM in both lung cancer cell lines tested. Finally, in response to CCM treatment, A549 and Calu6 cells expressed lower levels of antiapoptotic and stemness genes, but higher levels of proapoptotic genes. In conclusion, this study provides cellular and molecular evidence for the antitumor ability of secretome obtained from stem cell-derived cardiomyocytes.

Effective derivation of ventricular cardiomyocytes from hPSCs using ascorbic acid-containing maturation medium

Cardiomyocytes derived from human pluripotent stem cells (hPSCs) can be used in various applications including disease modeling, drug safety screening, and novel cell-based cardiac therapies. Here, we report an optimized selection and maturation method to induce maturation of cardiomyocytes into a specific subtype after differentiation driven by the regulation of Wnt signaling. The medium used to optimize selection and maturation was in a glucose starvation conditions, supplemented with either a nutrition complex or ascorbic acid. Following optimized selection and maturation, more cardiac Troponin T (cTnT)-positive cardiomyocytes were detected using albumin and ascorbic acid than B27. In addition, ascorbic acid enriched maturation of ventricular cardiomyocytes. We compared cardiomyocyte-specific gene expression patterns under different selection and maturation conditions by next-generation sequencing (NGS) analysis. Our optimized conditions will enable simple and efficient maturation and specification of the desired cardiomyocyte subtype, facilitating both biomedical research and clinical applications.

Replacement in angiogenesis research: Studying mechanisms of blood vessel development by animal-free in vitro, in vivo and in silico approaches

Angiogenesis, the development of new blood vessels from pre-existing ones, is an essential process determining numerous physiological and pathological conditions. Accordingly, there is a high demand for research approaches allowing the investigation of angiogenic mechanisms and the assessment of pro- and anti-angiogenic therapeutics. The present review provides a selective overview and critical discussion of such approaches, which, in line with the 3R principle, all share the common feature that they are not based on animal experiments. They include in vitro assays to study the viability, proliferation, migration, tube formation and sprouting activity of endothelial cells in two- and three-dimensional environments, the degradation of extracellular matrix compounds as well as the impact of hemodynamic forces on blood vessel formation. These assays can be complemented by in vivo analyses of microvascular network formation in the chorioallantoic membrane assay and early stages of zebrafish larvae. In addition, the combination of experimental data and physical laws enables the mathematical modeling of tissue-specific vascularization, blood flow patterns, interstitial fluid flow as well as oxygen, nutrient and drug distribution. All these animal-free approaches markedly contribute to an improved understanding of fundamental biological mechanisms underlying angiogenesis. Hence, they do not only represent essential tools in basic science but also in early stages of drug development. Moreover, their advancement bears the great potential to analyze angiogenesis in all its complexity and, thus, to make animal experiments superfluous in the future.

Cardiac Cell Therapy with Pluripotent Stem Cell-Derived Cardiomyocytes: What Has Been Done and What Remains to Do?

PURPOSE OF REVIEW

Exciting pre-clinical data presents pluripotent stem cell-derived cardiomyocytes (PSC-CM) as a novel therapeutic prospect following myocardial infarction, and worldwide clinical trials are imminent. However, despite notable advances, several challenges remain. Here, we review PSC-CM pre-clinical studies, identifying key translational hurdles. We further discuss cell production and characterization strategies, identifying markers that may help generate cells which overcome these barriers.

RECENT FINDINGS

PSC-CMs can robustly repopulate infarcted myocardium with functional, force generating cardiomyocytes. However, current differentiation protocols produce immature and heterogenous cardiomyocytes, creating related issues such as arrhythmogenicity, immunogenicity and poor engraftment. Recent efforts have enhanced our understanding of cardiovascular developmental biology. This knowledge may help implement novel differentiation or gene editing strategies that could overcome these limitations. PSC-CMs are an exciting therapeutic prospect. Despite substantial recent advances, limitations of the technology remain. However, with our continued and increasing biological understanding, these issues are addressable, with several worldwide clinical trials anticipated in the coming years.

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.

Cardiovascular Regeneration via Stem Cells and Direct Reprogramming: A Review

Despite recent advancements in treatment strategies, cardiovascular disease such as heart failure remains a significant source of global mortality. Stem cell technology and cellular reprogramming are rapidly growing fields that will continue to prove useful in cardiac regenerative therapeutics. This review provides information on the role of human pluripotent stem cells (hPSCs) in cardiac regeneration and discusses the practical applications of hPSC-derived cardiomyocytes (CMCs). Moreover, we discuss the practical applications of hPSC-derived CMCs while outlining the relevance of directly-reprogrammed CMCs in regenerative medicine. This review critically summarizes the most recent advances in the field will help to guide future research in this developing area.

Cardiovascular disease (CVD) is the leading causes of morbidity and death globally. In particular, a heart failure remains a major problem that contributes to global mortality. Considerable advancements have been made in conventional pharmacological therapies and coronary intervention surgery for cardiac disorder treatment. However, more than 15% of patients continuously progress to end-stage heart failure and eventually require heart transplantation. Over the past year, numerous numbers of protocols to generate cardiomyocytes (CMCs) from human pluripotent stem cells (hPSCs) have been developed and applied in clinical settings. Number of studies have described the therapeutic effects of hPSCs in animal models and revealed the underlying repair mechanisms of cardiac regeneration. In addition, biomedical engineering technologies have improved the therapeutic potential of hPSC-derived CMCs in vivo. Recently substantial progress has been made in driving the direct differentiation of somatic cells into mature CMCs, wherein an intermediate cellular reprogramming stage can be bypassed. This review provides information on the role of hPSCs in cardiac regeneration and discusses the practical applications of hPSC-derived CMCs; furthermore, it outlines the relevance of directly reprogrammed CMCs in regenerative medicine.

The Present State and Future Perspectives of Cardiac Regenerative Therapy Using Human Pluripotent Stem Cells

The number of patients with heart failure (HF) is increasing with aging in our society worldwide. Patients with HF who are resistant to medication and device therapy are candidates for heart transplantation (HT). However, the shortage of donor hearts is a serious issue. As an alternative to HT, cardiac regenerative therapy using human pluripotent stem cells (hPSCs), such as human embryonic stem cells and induced pluripotent stem cells, is expected to be realized. Differentiation of hPSCs into cardiomyocytes (CMs) is facilitated by mimicking normal heart development. To prevent tumorigenesis after transplantation, it is important to eliminate non-CMs, including residual hPSCs, and select only CMs. Among many CM selection systems, metabolic selection based on the differences in metabolism between CMs and non-CMs is favorable in terms of cost and efficacy. Large-scale culture systems have been developed because a large number of hPSC-derived CMs (hPSC-CMs) are required for transplantation in clinical settings. In large animal models, hPSC-CMs transplanted into the myocardium improved cardiac function in a myocardial infarction model. Although post-transplantation arrhythmia and immune rejection remain problems, their mechanisms and solutions are under investigation. In this manner, the problems of cardiac regenerative therapy are being solved individually. Thus, cardiac regenerative therapy with hPSC-CMs is expected to become a safe and effective treatment for HF in the near future. In this review, we describe previous studies related to hPSC-CMs and discuss the future perspectives of cardiac regenerative therapy using hPSC-CMs.

Human Induced Pluripotent Stem Cell as a Disease Modeling and Drug Development Platform-A Cardiac Perspective

A comprehensive understanding of the pathophysiology and cellular responses to drugs in human heart disease is limited by species differences between humans and experimental animals. In addition, isolation of human cardiomyocytes (CMs) is complicated because cells obtained by biopsy do not proliferate to provide sufficient numbers of cells for preclinical studies in vitro. Interestingly, the discovery of human-induced pluripotent stem cell (hiPSC) has opened up the possibility of generating and studying heart disease in a culture dish. The combination of reprogramming and genome editing technologies to generate a broad spectrum of human heart diseases in vitro offers a great opportunity to elucidate gene function and mechanisms. However, to exploit the potential applications of hiPSC-derived-CMs for drug testing and studying adult-onset cardiac disease, a full functional characterization of maturation and metabolic traits is required. In this review, we focus on methods to reprogram somatic cells into hiPSC and the solutions for overcome immaturity of the hiPSC-derived-CMs to mimic the structure and physiological properties of the adult human CMs to accurately model disease and test drug safety. Finally, we discuss how to improve the culture, differentiation, and purification of CMs to obtain sufficient numbers of desired types of hiPSC-derived-CMs for disease modeling and drug development platform.

Disease Modeling of Mitochondrial Cardiomyopathy Using Patient-Specific Induced Pluripotent Stem Cells

Mitochondrial cardiomyopathy (MCM) is characterized as an oxidative phosphorylation disorder of the heart. More than 100 genetic variants in nuclear or mitochondrial DNA have been associated with MCM. However, the underlying molecular mechanisms linking genetic variants to MCM are not fully understood due to the lack of appropriate cellular and animal models. Patient-specific induced pluripotent stem cell (iPSC)-derived cardiomyocytes (iPSC-CMs) provide an attractive experimental platform for modeling cardiovascular diseases and predicting drug efficacy to such diseases. Here we introduce the pathological and therapeutic studies of MCM using iPSC-CMs and discuss the questions and latest strategies for research using iPSC-CMs.

The conserved long noncoding RNA CARMA regulates cardiomyocyte differentiation

AIMS

Production of functional cardiomyocytes from pluripotent stem cells requires tight control of the differentiation process. Long noncoding RNAs (lncRNAs) exert critical regulatory function in cell specification during development. In this study, we designed an integrated approach to identify lncRNAs implicated in cardiogenesis in differentiating human embryonic stem cells (ESCs).

METHODS AND RESULTS

We identified CARMA (CARdiomyocyte Maturation-Associated lncRNA), a conserved lncRNA controlling cardiomyocyte differentiation and maturation in human ESCs. CARMA is located adjacent to MIR-1-1HG, the host gene for two cardiogenic miRNAs: MIR1-1 and MIR-133a2, and transcribed in an antisense orientation. The expression of CARMA and the miRNAs is negatively correlated, and CARMA knockdown increases MIR1-1 and MIR-133a2 expression. In addition, CARMA possesses MIR-133a2 binding sites, suggesting the lncRNA could be also a target of miRNA action. Upon CARMA downregulation, MIR-133a2 target protein-coding genes are coordinately downregulated. Among those, we found RBPJ, the gene encoding the effector of the NOTCH pathway. NOTCH has been shown to control a binary cell fate decision between the mesoderm and the neuroectoderm lineages, and NOTCH inhibition leads to enhanced cardiomyocyte differentiation at the expense of neuroectodermal derivatives. Interestingly, two lncRNAs, linc1230 and linc1335, which are known repressors of neuroectodermal specification, were found upregulated upon Notch1 silencing in ESCs. Forced expression of either linc1230 or linc1335 improved ESC-derived cardiomyocyte production. These two lncRNAs were also found upregulated following CARMA knockdown in ESCs.

CONCLUSIONS

Altogether, these data suggest the existence of a network, implicating three newly identified lncRNAs, the two myomirs MIR1-1 and MIR-133a2 and the NOTCH signaling pathway, for the coordinated regulation of cardiogenic differentiation in ESCs.

TRANSLATIONAL PERSPECTIVE

Cardiac dysfunction and heart failure develop secondary to a massive loss of cardiomyocytes in the damaged myocardium. Several avenues have been evaluated to promote regeneration following injury. Cell therapy for heart disease envisages the production of functional cardiomyocytes from differentiating pluripotent stem cells prior transfer into the injured heart muscle. Here, we report the functional characterization of CARMA, a lncRNA implicated in cardiogenesis. CARMA knockdown in differentiating human embryonic stem cells (ESCs) promotes cardiogenic commitment and cardiomyocyte differentiation. CARMA represents therefore a novel target for improving human ESC-derived cardiomyocyte production, and cell-based regenerative strategies for heart disease.

A Novel Insight into Endothelial and Cardiac Cells Phenotype in Systemic Sclerosis Using Patient-Derived Induced Pluripotent Stem Cell

Objective

Systemic sclerosis (SSc) is a connective tissue disease associated with vascular damage and multi organ fibrotic changes with unknown pathogenesis. Most SSc patients suffer from defective angiogenesis/vasculogenesis and cardiac conditions leading to high mortality rates. We aimed to investigate the cardiovascular phenotype of SSc by cardiogenic differentiation of SSc induced pluripotent stem cells (iPSC).

Materials and Methods

In this experimental study, we generated iPSC from two diffuse SSc patients, followed by successful differentiation into endothelial cells (ECs) and cardiomyocytes (CMs).

Results

SSc-derived EC (SSc-EC) expressed KDR, a nearly EC marker, similar to healthy control-EC (C1-EC). After sorting and culturing KDR+ cells, the resulting EC expressed CD31, a late endothelial marker, but vascular endothelial (VE)-cadherin expression markedly dropped resulting in a functional defect as reflected in tube formation failure of SSc-EC. Interestingly, upregulation of SNAI1 (snail family transcriptional repressor 1) was observed in SSc-EC which might underlie VE-cadherin downregulation. Furthermore, SSc-derived CM (SSc-CM) successfully expressed cardiac- specific markers including ion channels, resulting in normal physiological behavior and responsiveness to cardioactive drugs.

Conclusion

This study provides an insight into impaired angiogenesis observed in SSc patients by evaluating in vitro cardiovascular differentiation of SSc iPSC.

Engineered cardiac tissue microsphere production through direct differentiation of hydrogel-encapsulated human pluripotent stem cells

Engineered cardiac tissues that can be directly produced from human induced pluripotent stem cells (hiPSCs) in scalable, suspension culture systems are needed to meet the demands of cardiac regenerative medicine. Here, we demonstrate successful production of functional cardiac tissue microspheres through direct differentiation of hydrogel encapsulated hiPSCs. To form the microspheres, hiPSCs were suspended within the photocrosslinkable biomaterial, PEG-fibrinogen (25 million cells/mL), and encapsulated at a rate of 420,000 cells/minute using a custom microfluidic system. Even at this high cell density and rapid production rate, high intra-batch and batch-to-batch reproducibility was achieved. Following microsphere formation, hiPSCs maintained high cell viability and continued to grow within and beyond the original PEG-fibrinogen matrix. These initially soft microspheres (<250 Pa) supported efficient cardiac differentiation; spontaneous contractions initiated by differentiation day 8, and the microspheres contained >75% cardiomyocytes (CMs). CMs responded appropriately to pharmacological stimuli and exhibited 1:1 capture up to 6.0 Hz when electrically paced. Over time, cells formed cell-cell junctions and aligned myofibril fibers; engineered cardiac microspheres were maintained in culture over 3 years. The capability to rapidly generate uniform cardiac microsphere tissues is critical for advancing downstream applications including biomanufacturing, multi-well plate drug screening, and injection-based regenerative therapies.

Heart Repair Induced by Cardiac Progenitor Cell Delivery within Polypyrrole-Loaded Cardiogel Post-ischemia

Myocardial infarction (MI) irreversibly injures the heart tissue. Cardiovascular tissue engineering has been developed as a promising therapeutic approach for post-MI repair. Previously, we discovered the ability of a polypyrrole (PPy)-incorporated cardiogel (CG) for improvement of maturity and functional synchrony of rat neonatal cardiomyocytes. Here, we used the cross-linked form of PPy-incorporated CG (CG-PPy), in order to improve electromechanical properties of scaffold, for application in cardiac progenitor cell (CPC) transplantation on post-MI rat hearts. Improved mechanical property and electrical conductivity (sixfold) were evident in the cross-linked CG-PPy (P1) compared to cross-linked CG (C1) scaffolds. Transplantation of CPC-loaded P1 (P1-CPC) resulted in substantial improvement of cardiac functional properties. Furthermore, lower fibrotic tissue and higher CPC retention were observed. The grafted cells showed cardiomyocyte characteristics when stained with human cardiac troponin T and connexin43 antibodies, while neovessel formation was similarly prominent. These findings highlight the therapeutic promise of the P1 scaffold as a CPC carrier for functional restoration of the heart post-MI.

Bioreactor Suspension Culture: Differentiation and Production of Cardiomyocyte Spheroids From Human Induced Pluripotent Stem Cells

Human induced-pluripotent stem cells (hiPSCs) can be efficiently differentiated into cardiomyocytes (hiPSC-CMs) via the GiWi method, which uses small-molecule inhibitors of glycogen synthase kinase (GSK) and tankyrase to first activate and then suppress Wnt signaling. However, this method is typically conducted in 6-well culture plates with two-dimensional (2D) cell sheets, and consequently, cannot be easily scaled to produce the large numbers of hiPSC-CMs needed for clinical applications. Cell suspensions are more suitable than 2D systems for commercial biomanufacturing, and suspended hiPSCs form free-floating aggregates (i.e., spheroids) that can also be differentiated into hiPSC-CMs. Here, we introduce a protocol for differentiating suspensions of hiPSC spheroids into cardiomyocytes that is based on the GiWi method. After optimization based on cardiac troponin T staining, the purity of hiPSC-CMs differentiated via our novel protocol exceeded 98% with yields of about 1.5 million hiPSC-CMs/mL and less between-batch purity variability than hiPSC-CMs produced in 2D cultures; furthermore, the culture volume could be increased ∼10-fold to 30 mL with no need for re-optimization, which suggests that this method can serve as a framework for large-scale hiPSC-CM production.

Role of induced pluripotent stem cells in diagnostic cardiology

Ethical concerns about stem cell-based research have delayed important advances in many areas of medicine, including cardiology. The introduction of induced pluripotent stem cells (iPSCs) has supplanted the need to use human stem cells for most purposes, thus eliminating all ethical controversies. Since then, many new avenues have been opened in cardiology research, not only in approaches to tissue replacement but also in the design and testing of antiarrhythmic drugs. This methodology has advanced to the point where induced human cardiomyocyte cell lines can now also be obtained from commercial sources or tissue banks. Initial studies with readily available iPSCs have generally confirmed that their behavioral characteristics accurately predict the behavior of beating cardiomyocytes in vivo. As a result, iPSCs can provide new ways to study arrhythmias and heart disease in general, accelerating the development of new, more effective antiarrhythmic drugs, clinical diagnoses, and personalized medical care. The focus on producing cardiomyocytes that can be used to replace damaged heart tissue has somewhat diverted interest in a host of other applications. This manuscript is intended to provide non-specialists with a brief introduction and overview of the research carried out in the field of heart rhythm disorders.

Gender-specific characteristics of hypertrophic response in cardiomyocytes derived from human embryonic stem cells

Introduction: Gender-specific phenotypes of the heart were reported with respect to both physiology and pathology. While most differences were associated with the sex hormones, differential expression of genes received special attention, particularly X-Y chromosomes’ genes.

Methods: Here, we compared cardiogenesis by gene expression analysis of lineage specific markers and X-Y chromosomes’ genes, during in vitro differentiation of XY and XX human embryonic stem cells (hESC), in a hormone-free setup.

Results: Downregulation of pluripotency marker (NANOG) and upregulation of cardiac mesoderm and progenitor markers (GATA4, TBX5, NKX2.5, ISL1) was remained temporally similar in differentiating XY and XX hESCs. Isoproterenol treatment of XY and XX hESC-derived cardiomyocytes (hESCCM) induced hypertrophy in a sex-specific manner, with female cardiomyocytes showing response at higher isoproterenol concentration and a later time point of differentiation. Interestingly, KDM5C as an X-linked gene, was markedly upregulated in both hypertrophied male and female cardiomyocytes.

Conclusion: Collectively, our results indicated a temporally identical cardiogenesis, but more susceptibility of XY hESC-CM to hypertrophic stimulus in a hormone-free condition.

Differentiation and Application of Human Pluripotent Stem Cells Derived Cardiovascular Cells for Treatment of Heart Diseases: Promises and Challenges

Human pluripotent stem cells (hPSCs) are derived from human embryos (human embryonic stem cells) or reprogrammed from human somatic cells (human induced pluripotent stem cells). They can differentiate into cardiovascular cells, which have great potential as exogenous cell resources for restoring cardiac structure and function in patients with heart disease or heart failure. A variety of protocols have been developed to generate and expand cardiovascular cells derived from hPSCs in vitro. Precisely and spatiotemporally activating or inhibiting various pathways in hPSCs is required to obtain cardiovascular lineages with high differentiation efficiency. In this concise review, we summarize the protocols of differentiating hPSCs into cardiovascular cells, highlight their therapeutic application for treatment of cardiac diseases in large animal models, and discuss the challenges and limitations in the use of cardiac cells generated from hPSCs for a better clinical application of hPSC-based cardiac cell therapy.

Oxygen-rich Environment Ameliorates Cell Therapy Outcomes of Cardiac Progenitor Cells for Myocardial Infarction

To some extent, cell therapy for myocardial infarction (MI) has supported the idea of cardiac repair; however, further optimizations are inevitable. Combined approaches that comprise suitable cell sources and supporting molecules considerably improved its effect. Here, we devised a strategy of simultaneous transplantation of human cardiac progenitor cells (CPCs) and an optimized oxygen generating microparticles (MPs) embedded in fibrin hydrogel, which was injected into a left anterior descending artery (LAD) ligating-based rat model of acute myocardial infarction (AMI). Functional parameters of the heart, particularly left ventricular systolic function, markedly improved and reached pre-AMI levels. This functional restoration was well correlated with substantially lower fibrotic tissue formation and greater vascular density in the infarct area. Our novel approach promoted CPCs retention and differentiation into cardiovascular lineages. We propose this novel co-transplantation strategy for more efficient cell therapy of AMI which may function by providing an oxygen-rich microenvironment, and thus regulate cell survival and differentiation.

The quest of cell surface markers for stem cell therapy

Stem cells and their derivatives are novel pharmaceutics that have the potential for use as tissue replacement therapies. However, the heterogeneous characteristics of stem cell cultures have hindered their biomedical applications. In theory and practice, when cell type-specific or stage-specific cell surface proteins are targeted by unique antibodies, they become highly efficient in detecting and isolating specific cell populations. There is a growing demand to identify reliable and actionable cell surface markers that facilitate purification of particular cell types at specific developmental stages for use in research and clinical applications. The identification of these markers as very important members of plasma membrane proteins, ion channels, transporters, and signaling molecules has directly benefited from proteomics and tools for proteomics-derived data analyses. Here, we review the methodologies that have played a role in the discovery of cell surface markers and introduce cutting edge single cell proteomics as an advanced tool. We also discuss currently available specific cell surface markers for stem cells and their lineages, with emphasis on the nervous system, heart, pancreas, and liver. The remaining gaps that pertain to the discovery of these markers and how single cell proteomics and identification of surface markers associated with the progenitor stages of certain terminally differentiated cells may pave the way for their use in regenerative medicine are also discussed.

Cell-Based Therapy Manufacturing in Stirred Suspension Bioreactor: Thoughts for cGMP Compliance

Cell-based therapy (CBT) is attracting much attention to treat incurable diseases. In recent years, several clinical trials have been conducted using human pluripotent stem cells (hPSCs), and other potential therapeutic cells. Various private- and government-funded organizations are investing in finding permanent cures for diseases that are difficult or expensive to treat over a lifespan, such as age-related macular degeneration, Parkinson’s disease, or diabetes, etc. Clinical-grade cell manufacturing requiring current good manufacturing practices (cGMP) has therefore become an important issue to make safe and effective CBT products. Current cell production practices are adopted from conventional antibody or protein production in the pharmaceutical industry, wherein cells are used as a vector to produce the desired products. With CBT, however, the “cells are the final products” and sensitive to physico- chemical parameters and storage conditions anywhere between isolation and patient administration. In addition, the manufacturing of cellular products involves multi-stage processing, including cell isolation, genetic modification, PSC derivation, expansion, differentiation, purification, characterization, cryopreservation, etc. Posing a high risk of product contamination, these can be time- and cost- prohibitive due to maintenance of cGMP. The growing demand of CBT needs integrated manufacturing systems that can provide a more simple and cost-effective platform. Here, we discuss the current methods and limitations of CBT, based upon experience with biologics production. We review current cell manufacturing integration, automation and provide an overview of some important considerations and best cGMP practices. Finally, we propose how multi-stage cell processing can be integrated into a single bioreactor, in order to develop streamlined cGMP-compliant cell processing systems.

A Concise Review on Induced Pluripotent Stem Cell-Derived Cardiomyocytes for Personalized Regenerative Medicine

The induced pluripotent stem cells (iPSCs) are derived from somatic cells by using reprogramming factors such as Oct4, Sox2, Klf4, and c-Myc (OSKM) or Oct4, Sox2, Nanog and Lin28 (OSNL). They resemble embryonic stem cells (ESCs) and have the ability to differentiate into cell lineage of all three germ-layer, including cardiomyocytes (CMs). The CMs can be generated from iPSCs by inducing embryoid bodies (EBs) formation and treatment with activin A, bone morphogenic protein 4 (BMP4), and inhibitors of Wnt signaling. However, these iPSC-derived CMs are a heterogeneous population of cells and require purification and maturation to mimic the in vivo CMs. The matured CMs can be used for various therapeutic purposes in regenerative medicine by cardiomyoplasty or through the development of tissue-engineered cardiac patches. In recent years, significant advancements have been made in the isolation of iPSC and their differentiation, purification, and maturation into clinically usable CMs. Newer small molecules have also been identified to substitute the reprogramming factors for iPSC generation as well as for direct differentiation of somatic cells into CMs without an intermediary pluripotent state. This review provides a concise update on the generation of iPSC-derived CMs and their application in personalized cardiac regenerative medicine. It also discusses the current limitations and challenges in the application of iPSC-derived CMs. Graphical abstract.

Cellular model systems to study cardiovascular injury from chemotherapy

In spite of all the efforts for generating efficient pharmacological treatment options for cancer patients, the unwanted side effect of these substances on the cardiovascular system is becoming a major issue for cancer survivors. The fast pacing oncology field necessitate the quest for more accurate and reliable preclinical screenings. hiPSCs derived cardiomyocytes, endothelial and vascular smooth muscle cells provide unlimited source of physiologically relevant cells that could be used in the screening platforms. Cells derived from hiPSCs can measure drug induced alterations to different aspect of the heart including electrophysiology, contractility and structure. In this review, we will give an overview of the different in vivo and in vitro preclinical drug safety screenings. In following sections, we will focus on hiPSCs derived cardiomyocytes, endothelial and vascular smooth muscle cells and present the current knowledge of the application of these cells in unicellular cardiotoxicity assays. In the final part, we will focus on cardiac organoids as multi cell type platform and their role in cardiotoxicity screening of the chemotherapeutic drugs.

Temporal activation of LRH-1 and RAR-γ in human pluripotent stem cells induces a functional naïve-like state

Naïve pluripotency can be established in human pluripotent stem cells (hPSCs) by manipulation of transcription factors, signaling pathways, or a combination thereof. However, differences exist in the molecular and functional properties of naïve hPSCs generated by different protocols, which include varying similarities with pre-implantation human embryos, differentiation potential, and maintenance of genomic integrity. We show here that short treatment with two chemical agonists (2a) of nuclear receptors, liver receptor homologue-1 (LRH-1) and retinoic acid receptor gamma (RAR-γ), along with 2i/LIF (2a2iL) induces naïve-like pluripotency in human cells during reprogramming of fibroblasts, conversion of pre-established hPSCs, and generation of new cell lines from blastocysts. 2a2iL-hPSCs match several defined criteria of naïve-like pluripotency and contribute to human-mouse interspecies chimeras. Activation of TGF-β signaling is instrumental for acquisition of naïve-like pluripotency by the 2a2iL induction procedure, and transient activation of TGF-β signaling substitutes for 2a to generate naïve-like hPSCs. We reason that 2a2iL-hPSCs are an easily attainable system to evaluate properties of naïve-like hPSCs and for various applications.

Vascular endothelial growth factor sustained delivery augmented cell therapy outcomes of cardiac progenitor cells for myocardial infarction

Cell therapy has become a novel promising approach for improvement of cardiac functional capacity in the instances of ventricular remodeling and fibrosis caused by episodes of coronary artery occlusion and hypoxia. The challenge toward enhancing cell engraftment as well as formation of functional tissue, however, necessitated combinatorial approaches. Here, we complemented human embryonic stem cell-derived cardiac progenitor cell (hESC-CPC) therapy by heparin-conjugated, vascular endothelial growth factor (VEGF)-loaded fibrin hydrogel as VEGF delivery system. Transplantation of these cardiac committed cells along with sustained VEGF release could surpass the cardiac repair effects of each constituent alone in a rat model of acute myocardial infarction. The histological sections of rat hearts revealed improved vascularization as well as inclusion of hESC-CPC-derived cardiomyocytes, endothelial, and smooth muscle cells in host myocardium. Thus, co-transplantation of hESC-CPC and proangiogenic factor by a suitable delivery rate may resolve the shortcomings of conventional cell therapy.

Dissolved oxygen concentration regulates human hepatic organoid formation from pluripotent stem cells in a fully controlled bioreactor

Developing technologies for scalable production of human organoids has gained increased attention for "organoid medicine" and drug discovery. We developed a scalable and integrated differentiation process for generation of hepatic organoid from human pluripotent stem cells (hPSCs) in a fully controlled stirred tank bioreactor with 150 ml working volume by application of physiological oxygen concentrations in different liver tissue zones. We found that the 20-40% dissolved oxygen concentration [DO] (corresponded to 30-60 mmHg pO₂ within the liver tissue) significantly influences the process outcome via regulating the differentiation fate of hPSC aggregates by enhancing mesoderm induction. Regulation of the [DO] at 30% DO resulted in efficient generation of human fetal-like hepatic organoids that had a uniform size distribution and were comprised of red blood cells and functional hepatocytes, which exhibited improved liver-specific marker gene expressions, key liver metabolic functions, and, more important, higher inducible cytochrome P450 activity compared to the other trials. These hepatic organoids were successfully engrafted in an acute liver injury mouse model and produced albumin after implantation. These results demonstrated the significant impact of the dissolved oxygen concentration on hPSC hepatic differentiation fate and differentiation efficacy that should be considered ascritical translational aspect of established scalable liver organoid generation protocols for potential clinical and drug discovery applications.

From Human Pluripotent Stem Cells to 3D Cardiac Microtissues: Progress, Applications and Challenges

The knowledge acquired throughout the years concerning the in vivo regulation of cardiac development has promoted the establishment of directed differentiation protocols to obtain cardiomyocytes (CMs) and other cardiac cells from human pluripotent stem cells (hPSCs), which play a crucial role in the function and homeostasis of the heart. Among other developments in the field, the transition from homogeneous cultures of CMs to more complex multicellular cardiac microtissues (MTs) has increased the potential of these models for studying cardiac disorders in vitro and for clinically relevant applications such as drug screening and cardiotoxicity tests. This review addresses the state of the art of the generation of different cardiac cells from hPSCs and the impact of transitioning CM differentiation from 2D culture to a 3D environment. Additionally, current methods that may be employed to generate 3D cardiac MTs are reviewed and, finally, the adoption of these models for in vitro applications and their adaptation to medium- to high-throughput screening settings are also highlighted.

Prediction of Human Induced Pluripotent Stem Cell Cardiac Differentiation Outcome by Multifactorial Process Modeling

Human cardiomyocytes (CMs) have potential for use in therapeutic cell therapy and high-throughput drug screening. Because of the inability to expand adult CMs, their large-scale production from human pluripotent stem cells (hPSC) has been suggested. Significant improvements have been made in understanding directed differentiation processes of CMs from hPSCs and their suspension culture-based production at chemically defined conditions. However, optimization experiments are costly, time-consuming, and highly variable, leading to challenges in developing reliable and consistent protocols for the generation of large CM numbers at high purity. This study examined the ability of data-driven modeling with machine learning for identifying key experimental conditions and predicting final CM content using data collected during hPSC-cardiac differentiation in advanced stirred tank bioreactors (STBRs). Through feature selection, we identified process conditions, features, and patterns that are the most influential on and predictive of the CM content at the process endpoint, on differentiation day 10 (dd10). Process-related features were extracted from experimental data collected from 58 differentiation experiments by feature engineering. These features included data continuously collected online by the bioreactor system, such as dissolved oxygen concentration and pH patterns, as well as offline determined data, including the cell density, cell aggregate size, and nutrient concentrations. The selected features were used as inputs to construct models to classify the resulting CM content as being "sufficient" or "insufficient" regarding pre-defined thresholds. The models built using random forests and Gaussian process modeling predicted insufficient CM content for a differentiation process with 90% accuracy and precision on dd7 of the protocol and with 85% accuracy and 82% precision at a substantially earlier stage: dd5. These models provide insight into potential key factors affecting hPSC cardiac differentiation to aid in selecting future experimental conditions and can predict the final CM content at earlier process timepoints, providing cost and time savings. This study suggests that data-driven models and machine learning techniques can be employed using existing data for understanding and improving production of a specific cell type, which is potentially applicable to other lineages and critical for realization of their therapeutic applications.

Selection of human induced pluripotent stem cells lines optimization of cardiomyocytes differentiation in an integrated suspension microcarrier bioreactor

Background

The production of large quantities of cardiomyocyte is essential for the needs of cellular therapies. This study describes the selection of a human-induced pluripotent cell (hiPSC) line suitable for production of cardiomyocytes in a fully integrated bioprocess of stem cell expansion and differentiation in microcarrier stirred tank reactor.

Methods

Five hiPSC lines were evaluated first for their cardiac differentiation efficiency in monolayer cultures followed by their expansion and differentiation compatibility in microcarrier (MC) cultures under continuous stirring conditions.

Results

Three cell lines were highly cardiogenic but only one (FR202) of them was successfully expanded on continuous stirring MC cultures. FR202 was thus selected for cardiac differentiation in a 22-day integrated bioprocess under continuous stirring in a stirred tank bioreactor. In summary, we integrated a MC-based hiPSC expansion (phase 1), CHIR99021-induced cardiomyocyte differentiation step (phase 2), purification using the lactate-based treatment (phase 3) and cell recovery step (phase 4) into one process in one bioreactor, under restricted oxygen control (< 30% DO) and continuous stirring with periodic batch-type media exchanges. High density of undifferentiated hiPSC (2 ± 0.4 × 10⁶ cells/mL) was achieved in the expansion phase. By controlling the stirring speed and DO levels in the bioreactor cultures, 7.36 ± 1.2 × 10⁶ cells/mL cardiomyocytes with > 80% Troponin T were generated in the CHIR99021-induced differentiation phase. By adding lactate in glucose-free purification media, the purity of cardiomyocytes was enhanced (> 90% Troponin T), with minor cell loss as indicated by the increase in sub-G1 phase and the decrease of aggregate sizes. Lastly, we found that the recovery period is important for generating purer and functional cardiomyocytes (> 96% Troponin T). Three independent runs in a 300-ml working volume confirmed the robustness of this process.

Conclusion

A streamlined and controllable platform for large quantity manufacturing of pure functional atrial, ventricular and nodal cardiomyocytes on MCs in conventional-type stirred tank bioreactors was established, which can be further scaled up and translated to a good manufacturing practice-compliant production process, to fulfill the quantity requirements of the cellular therapeutic industry.

Supplementary information

The online version of this article (10.1186/s13287-020-01618-6) contains supplementary material, which is available to authorized users.

Stem cell therapy of myocardial infarction: a promising opportunity in bioengineering

Myocardial infarction (MI) is a life-threatening disease resulting from irreversible death of cardiomyocytes (CMs) and weakening of the heart blood-pumping function. Stem cell-based therapies have been studied for MI treatment over the last two decades with promising outcome. In this review, we critically summarize the past work in this field to elucidate the advantages and disadvantages of treating MI using pluripotent stem cells (PSCs) including both embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), adult stem cells, and cardiac progenitor cells. The main advantage of the latter is their cytokine production capability to modulate immune responses and control the progression of healing. However, human adult stem cells have very limited (if not 'no') capacity to differentiate into functional CMs in vitro or in vivo. In contrast, PSCs can be differentiated into functional CMs although the protocols for the cardiac differentiation of PSCs are mainly for adherent cells under 2D culture. Derivation of PSC-CMs in 3D, allowing for large-scale production of CMs via modulation of the Wnt/β-catenin signal pathway with defined chemicals and medium, may be desired for clinical translation. Furthermore, the technology of purification and maturation of the PSC-CMs may need further improvements to eliminate teratoma formation after in vivo implantation of the PSC-CMs for treating MI. In addition, in vitro derived PSC-CMs may have mechanical and electrical mismatch with the patient's cardiac tissue, which causes arrhythmia. This supports the use of PSC-derived cells committed to cardiac lineage without beating for implantation to treat MI. In this case, the PSC derived cells may utilize the mechanical, electrical, and chemical cues in the heart to further differentiate into mature/functional CMs in situ. Another major challenge facing stem cell therapy of MI is the low retention/survival of stem cells or their derivatives (e.g., PSC-CMs) in the heart for MI treatment after injection in vivo. This may be resolved by using biomaterials to engineer stem cells for reduced immunogenicity, immobilization of the cells in the heart, and increased integration with the host cardiac tissue. Biomaterials have also been applied in the derivation of CMs in vitro to increase the efficiency and maturation of differentiation. Collectively, a lot has been learned from the past failure of simply injecting intact stem cells or their derivatives in vivo for treating MI, and bioengineering stem cells with biomaterials is expected to be a valuable strategy for advancing stem cell therapy towards its widespread application for treating MI in the clinic.

A novel miRNA located in the GATA4 gene regulates the expression of IGF-1R and AKT1/2 genes and controls cell proliferation

GATA4 gene is a zinc-finger transcription factor known to be involved in cardiogenesis and the progression of different cancer types. Its diverse functions might be attributed to noncoding RNAs that could be embedded within its sequence. Here, we predicted a stable RNA stem-loop structure that is located in the second intron of the GATA4 gene. Available microRNA (miRNA) sequencing data and molecular genetics tools confirmed the identity of a mature miRNA (named GATA4-miR1) originating from the predicted stem-loop. In silico analysis predicted IGF-1R and AKT1/2 genes as potential targets for GATA4-miR1. Indeed, direct interactions between GATA4-miR1 and 3' untranslated regions sequences of IGF-1R and AKT1/2 genes were documented by dual luciferase assay. In addition, overexpression of GATA4-miR1 in SW480 cells resulted in the reduction of IGF-1R and AKT1/2 genes' expression, detected by reverse transcription quantitative (RT-q) polymerase chain reaction and Western blot analysis. This observation was consistent with a deduced negative correlation between the expression patterns of GATA4-miR1 and IGF-1R genes during cardiomyocyte differentiation. Moreover, overexpressing GATA4-miR1 in SW480 and PC3 cells resulted in a significant increase of the sub-G1 population in both cell lines, as detected by propidium iodide flow cytometry. Further analysis by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay indicated a reduction in the survival and proliferation rates of SW480 cells overexpressing GATA4-miR1, but no impact was observed on apoptosis progression, as indicated by Annexin-V flow cytometry. Overall, GATA4-miR1 represents a promising candidate for further research in the fields of cancer and cardiovascular therapeutics.

Developmentally Engineered Callus Organoid Bioassemblies Exhibit Predictive In Vivo Long Bone Healing

Clinical translation of cell-based products is hampered by their limited predictive in vivo performance. To overcome this hurdle, engineering strategies advocate to fabricate tissue products through processes that mimic development and regeneration, a strategy applicable for the healing of large bone defects, an unmet medical need. Natural fracture healing occurs through the formation of a cartilage intermediate, termed "soft callus," which is transformed into bone following a process that recapitulates developmental events. The main contributors to the soft callus are cells derived from the periosteum, containing potent skeletal stem cells. Herein, cells derived from human periosteum are used for the scalable production of microspheroids that are differentiated into callus organoids. The organoids attain autonomy and exhibit the capacity to form ectopic bone microorgans in vivo. This potency is linked to specific gene signatures mimicking those found in developing and healing long bones. Furthermore, callus organoids spontaneously bioassemble in vitro into large engineered tissues able to heal murine critical-sized long bone defects. The regenerated bone exhibits similar morphological properties to those of native tibia. These callus organoids can be viewed as a living "bio-ink" allowing bottom-up manufacturing of multimodular tissues with complex geometric features and inbuilt quality attributes.

Expansion of Human Pluripotent Stem Cell-derived Early Cardiovascular Progenitor Cells by a Cocktail of Signaling Factors

Cardiovascular progenitor cells (CPCs) derived from human pluripotent stem cells (hPSCs) are proposed to be invaluable cell sources for experimental and clinical studies. This wide range of applications necessitates large-scale production of CPCs in an in vitro culture system, which enables both expansion and maintenance of these cells. In this study, we aimed to develop a defined and efficient culture medium that uses signaling factors for large-scale expansion of early CPCs, called cardiogenic mesodermal cells (CMCs), which were derived from hPSCs. Chemical screening resulted in a medium that contained a reproducible combination of three factors (A83-01, bFGF, and CHIR99021) that generated 1014 CMCs after 10 passages without the propensity for tumorigenicity. Expanded CMCs retained their gene expression pattern, chromosomal stability, and differentiation tendency through several passages and showed both the safety and possible cardio-protective potentials when transplanted into the infarcted rat myocardium. These CMCs were efficiently cryopreserved for an extended period of time. This culture medium could be used for both adherent and suspension culture conditions, for which the latter is required for large-scale CMC production. Taken together, hPSC-derived CMCs exhibited self-renewal capacity in our simple, reproducible, and defined medium. These cells might ultimately be potential, promising cell sources for cardiovascular studies.

Optimized conditions for the supplementation of human-induced pluripotent stem cell cultures with a GSK-3 inhibitor during embryoid body formation with the aim of inducing differentiation into mesodermal and cardiac lineage

We optimized the conditions for the differentiation of human induced pluripotent stem cells (hiPSCs) into mesoderm lineage-committed cells by supplementing the cultures with CHIR, a selective GSK-3 inhibitor, during embryoid body (EB) formation. In vitro treatment with 4 μM CHIR during the late 2 days of a 4-day suspension culture period was most effective at promoting mesodermal differentiation. The resulting EBs showed a significant increase in the expression levels of mesoderm-associated genes (WNT3A, T, DKK1, GATA4, FOXC1, and MESP1) and a maintenance of OCT3/4 and NANOG expressions. Upon subsequent differentiation into a cardiac cell lineage, these EBs were shown to generate contractile cardiomyocytes. When shortening the CHIR treatment period to 1 day, the resulting EBs showed reduced expression of mesoderm-associated genes in comparison to the 2-day CHIR treatment. In particular, the expression level of FOXC1 in the 1-day CHIR-treated EBs was much lower than that of the 2-day CHIR-treated EBs. When the treatment period with CHIR was extended to 4 days, the resulting EBs presented significantly reduced expression of WNT3A, OCT3/4, and NANOG upon CHIR concentrations above 4 μM. Similarly, when CHIR treatment was conducted after the formation of EBs, the effectiveness of the GSK-3 inhibitor was reduced compared to a treatment performed during EB formation. Our results indicate that spatiotemporal constraints associated with EB formation, i.e., three-dimensional structuration and cell development in EBs, should be taken into account when designing EB formation-based differentiation protocol involving CHIR treatment.