Controlling expansion and cardiomyogenic differentiation of human pluripotent stem cells in scalable suspension culture

Progress in preclinical research on induced pluripotent stem cell therapy for acute myocardial infarction

Induced pluripotent stem cells (iPSCs) are obtained by introducing exogenous genes or adding chemicals to the culture medium to induce somatic cell differentiation. Similarly to embryonic stem cells, iPSCs have the ability to differentiate into all three embryonic cell lines. iPSCs can differentiate into cardiac muscle cells through two-dimensional differentiation methods such as monolayer cell culture and co-culture, or through embryoid body and scaffold-based three-dimensional differentiation methods. In addition, the process of iPSCs differentiation into cardiac muscle cells also requires activation or inhibition of specific signaling pathways,such as Wnt, BMP, Notch signaling pathways to mimic the development of the heart in vivo. In recent years, suspension culturing in bioreactors has been shown to produce large number of iPSCs derived cardiac muscle cells (iPSC-CMs). Before transplantation, it is necessary to purify iPSC-CMs through metabolic regulation or cell sorting to eliminate undifferentiated iPSCs, which may lead to teratoma formation. The transplantation methods for iPSC-CMs are mainly injection of cell suspension and transplantation of cell patches into the infarcted myocardium. Animal studies have shown that transplantation of iPSC-CMs into the infarcted myocardium can improve cardiac function. This article reviews the progress in preclinical studies on iPSC-CMs therapy for acute myocardial infarction and discusses the limitations and challenges of its clinical application to provide references for further clinical research and application.

Assessment of the feasibility of human amniotic membrane stem cell-derived cardiomyocytes in vitro

Myocardial infarction (MI) is a leading cause of death worldwide, resulting in extensive loss of cardiomyocytes and subsequent heart failure. Inducing cardiac differentiation of stem cells is a potential approach for myocardial regeneration therapy to improve post-MI prognosis. Mesenchymal stem cells (MSCs) have several advantages, including immune privilege and multipotent differentiation potential. This study aimed to explore the feasibility of chemically inducing human amniotic membrane MSCs (hAMSCs) to differentiate into cardiomyocytes in vitro. Human amniotic membrane (AM) samples were obtained from routine cesarean sections at Far Eastern Memorial Hospital. The isolated cells exhibited spindle-shaped morphology and expressed surface antigens CD73, CD90, CD105, and CD44, while lacking expression of CD19, CD11b, CD19, CD45, and HLA-DR. The SSEA-1, SSEA-3, and SSEA-4 markers were also positive, and the cells displayed the ability for tri-lineage differentiation into adipocytes, chondrocytes, and osteoblasts. The expression levels of MLC2v, Nkx2.5, and MyoD were analyzed using qPCR after applying various protocols for chemical induction, including BMP4, ActivinA, 5-azacytidine, CHIR99021, and IWP2 on hAMSCs. The group treated with 5 ng/ml BMP4, 10 ng/ml Activin A, 10 μM 5-azacytidine, 7.5 μM CHIR99021, and 5 μM IWP 2 expressed the highest levels of these genes. Furthermore, immunofluorescence staining demonstrated the expression of α-actinin and Troponin T in this group. In conclusion, this study demonstrated that hAMSCs can be chemically induced to differentiate into cardiomyocyte-like cells in vitro. However, to improve the functionality of the differentiated cells, further investigation of inductive protocols and regimens is needed.

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.

Analysis of the effects of bench-scale cell culture platforms and inoculum cell concentrations on PSC aggregate formation and culture

Introduction: Human pluripotent stem cells (hPSCs) provide many opportunities for application in regenerative medicine due to their ability to differentiate into cells from all three germ layers, proliferate indefinitely, and replace damaged or dysfunctional cells. However, such cell replacement therapies require the economical generation of clinically relevant cell numbers. Whereas culturing hPSCs as a two-dimensional monolayer is widely used and relatively simple to perform, their culture as suspended three-dimensional aggregates may enable more economical production in large-scale stirred tank bioreactors. To be more relevant to this biomanufacturing, bench-scale differentiation studies should be initiated from aggregated hPSC cultures. Methods: We compared five available bench-scale platforms for generating undifferentiated cell aggregates of human embryonic stem cells (hESCs) using AggreWell™ plates, low attachment plates on an orbital shaker, roller bottles, spinner flasks, and vertical-wheel bioreactors (PBS-Minis). Thereafter, we demonstrated the incorporation of an hPSC aggregation step prior to directed differentiation to pancreatic progenitors and endocrine cells. Results and discussion: The AggreWell™ system had the highest aggregation yield. The initial cell concentrations had an impact on the size of aggregates generated when using AggreWell™ plates as well as in roller bottles. However, aggregates made with low attachment plates, spinner flasks and PBS-Minis were similar regardless of the initial cell number. Aggregate morphology was compact and relatively homogenously distributed in all platforms except for the roller bottles. The size of aggregates formed in PBS-Minis was modulated by the agitation rate during the aggregation. In all cell culture platforms, the net growth rate of cells in 3D aggregates was lower (range: -0.01-0.022 h-1) than cells growing as a monolayer (range: 0.039-0.045 h-1). Overall, this study describes operating ranges that yield high-quality undifferentiated hESC aggregates using several of the most commonly used bench-scale cell culture platforms. In all of these systems, methods were identified to obtain PSC aggregates with greater than 70% viability, and mean diameters between 60 and 260 mm. Finally, we showed the capacity of hPSC aggregates formed with PBS-Minis to differentiate into viable pancreatic progenitors and endocrine cell types.

Early Differentiation Signatures in Human Induced Pluripotent Stem Cells Determined by Non-Targeted Metabolomics Analysis

Human induced pluripotent stem cells (hiPSCs) possess immense potential as a valuable source for the generation of a wide variety of human cells, yet monitoring the early cell differentiation towards a specific lineage remains challenging. In this study, we employed a non-targeted metabolomic analysis technique to analyze the extracellular metabolites present in samples as small as one microliter. The hiPSCs were subjected to differentiation by initiating culture under the basal medium E6 in combination with chemical inhibitors that have been previously reported to direct differentiation towards the ectodermal lineage such as Wnt/β-catenin and TGF-β kinase/activin receptor, alone or in combination with bFGF, and the inhibition of glycogen kinase 3 (GSK-3), which is commonly used for the diversion of hiPSCs towards mesodermal lineage. At 0 h and 48 h, 117 metabolites were identified, including biologically relevant metabolites such as lactic acid, pyruvic acid, and amino acids. By determining the expression of the pluripotency marker OCT3/4, we were able to correlate the differentiation status of cells with the shifted metabolites. The group of cells undergoing ectodermal differentiation showed a greater reduction in OCT3/4 expression. Moreover, metabolites such as pyruvic acid and kynurenine showed dramatic change under ectodermal differentiation conditions where pyruvic acid consumption increased 1-2-fold, while kynurenine secretion decreased 2-fold. Further metabolite analysis uncovered a group of metabolites specifically associated with ectodermal lineage, highlighting the potential of our findings to determine the characteristics of hiPSCs during cell differentiation, particularly under ectodermal lineage conditions.

Primary Ciliary Dyskinesia Patient-Specific hiPSC-Derived Airway Epithelium in Air-Liquid Interface Culture Recapitulates Disease Specific Phenotypes In Vitro

Primary ciliary dyskinesia (PCD) is a rare heterogenic genetic disorder associated with perturbed biogenesis or function of motile cilia. Motile cilia dysfunction results in diminished mucociliary clearance (MCC) of pathogens in the respiratory tract and chronic airway inflammation and infections successively causing progressive lung damage. Current approaches to treat PCD are symptomatic, only, indicating an urgent need for curative therapeutic options. Here, we developed an in vitro model for PCD based on human induced pluripotent stem cell (hiPSC)-derived airway epithelium in Air-Liquid-Interface cultures. Applying transmission electron microscopy, immunofluorescence staining, ciliary beat frequency, and mucociliary transport measurements, we could demonstrate that ciliated respiratory epithelia cells derived from two PCD patient-specific hiPSC lines carrying mutations in DNAH5 and NME5, respectively, recapitulate the respective diseased phenotype on a molecular, structural and functional level.

Heart in a dish - choosing the right in vitro model

The heart is the first functional organ established during embryogenesis. Investigating heart development and disease is a fascinating and crucial field of research because cardiovascular diseases remain the leading cause of morbidity and mortality worldwide. Therefore, there is great interest in establishing in vitro models for recapitulating both physiological and pathological aspects of human heart development, tissue function and malfunction. Derived from pluripotent stem cells, a large variety of three-dimensional cardiac in vitro models have been introduced in recent years. In this At a Glance article, we discuss the available methods to generate such models, grouped according to the following classification: cardiac organoids, cardiac microtissues and engineered cardiac tissues. For these models, we provide a systematic overview of their applications for disease modeling and therapeutic development, as well as their advantages and limitations to assist scientists in choosing the most suitable model for their research purpose.

Cost-Effective Mechanical Aggregation of Cardiac Progenitors and Encapsulation in Matrigel Support Self-Organization in a Dynamic Culture Environment

Human iPSC-derived self-organized cardiac tissues can be valuable for the development of platforms for disease modeling and drug screening, enhancing test accuracy and reducing pharmaceutical industry financial burden. However, current differentiation systems still rely on static culture conditions and specialized commercial microwells for aggregation, which hinders the full potential of hiPSC-derived cardiac tissues. Herein, we integrate cost-effective and reproducible manual aggregation of hiPSC-derived cardiac progenitors with Matrigel encapsulation and a dynamic culture to support hiPSC cardiac differentiation and self-organization. Manual aggregation at day 7 of cardiac differentiation resulted in 97% of beating aggregates with 78% of cTnT-positive cells. Matrigel encapsulation conjugated with a dynamic culture promoted cell migration and the creation of organized structures, with observed cell polarization and the creation of lumens. In addition, encapsulation increased buoyancy and decreased coalescence of the hiPSC-derived cardiac aggregates. Moreover, VEGF supplementation increased over two-fold the percentage of CD31-positive cells resulting in the emergence of microvessel-like structures. Thus, this study shows that the explored culture parameters support the self-organization of hiPSC-derived cardiac microtissues containing multiple cardiac cell types. Additional stimuli (e.g., BMP) in long-term scalable and fully automatized cultures can further potentiate highly structured and mature hiPSC-derived cardiac models, contributing to the development of reliable platforms for high-throughput drug screening and disease modeling.

Computational profiling of hiPSC-derived heart organoids reveals chamber defects associated with NKX2-5 deficiency

Heart organoids have the potential to generate primary heart-like anatomical structures and hold great promise as in vitro models for cardiac disease. However, their properties have not yet been fully studied, which hinders their wide spread application. Here we report the development of differentiation systems for ventricular and atrial heart organoids, enabling the study of heart diseases with chamber defects. We show that our systems generate chamber-specific organoids comprising of the major cardiac cell types, and we use single cell RNA sequencing together with sample multiplexing to characterize the cells we generate. To that end, we developed a machine learning label transfer approach leveraging cell type, chamber, and laterality annotations available for primary human fetal heart cells. We then used this model to analyze organoid cells from an isogeneic line carrying an Ebstein’s anomaly associated genetic variant in NKX2-5, and we successfully recapitulated the disease’s atrialized ventricular defects. In summary, we have established a workflow integrating heart organoids and computational analysis to model heart development in normal and disease states.

A human cardiac organoid system, coupled with single cell RNA sequencing and machine learning for transcriptional phenotyping, was developed. This allowed investigation of a genetic variant associated with Ebstein’s Anomaly, a congenital heart disease with chamber defects.

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.

From Spheroids to Organoids: The Next Generation of Model Systems of Human Cardiac Regeneration in a Dish

Organoids are tiny, self-organized, three-dimensional tissue cultures that are derived from the differentiation of stem cells. The growing interest in the use of organoids arises from their ability to mimic the biology and physiology of specific tissue structures in vitro. Organoids indeed represent promising systems for the in vitro modeling of tissue morphogenesis and organogenesis, regenerative medicine and tissue engineering, drug therapy testing, toxicology screening, and disease modeling. Although 2D cell cultures have been used for more than 50 years, even for their simplicity and low-cost maintenance, recent years have witnessed a steep rise in the availability of organoid model systems. Exploiting the ability of cells to re-aggregate and reconstruct the original architecture of an organ makes it possible to overcome many limitations of 2D cell culture systems. In vitro replication of the cellular micro-environment of a specific tissue leads to reproducing the molecular, biochemical, and biomechanical mechanisms that directly influence cell behavior and fate within that specific tissue. Lineage-specific self-organizing organoids have now been generated for many organs. Currently, growing cardiac organoid (cardioids) from pluripotent stem cells and cardiac stem/progenitor cells remains an open challenge due to the complexity of the spreading, differentiation, and migration of cardiac muscle and vascular layers. Here, we summarize the evolution of biological model systems from the generation of 2D spheroids to 3D organoids by focusing on the generation of cardioids based on the currently available laboratory technologies and outline their high potential for cardiovascular research.

Generation of heart-forming organoids from human pluripotent stem cells

Heart-forming organoids (HFOs) derived from human pluripotent stem cells (hPSCs) are a complex, highly structured in vitro model of early heart, foregut and vasculature development. The model represents a potent tool for various applications, including teratogenicity studies, gene function analysis and drug discovery. Here, we provide a detailed protocol describing how to form HFOs within 14 d. In an initial 4 d preculture period, hPSC aggregates are individually formed in a 96-well format and then Matrigel-embedded. Subsequently, the chemical WNT pathway modulators CHIR99021 and IWP2 are applied, inducing directed differentiation. This highly robust protocol can be used on many different hPSC lines and be combined with manipulation technologies such as gene targeting and drug testing. HFO formation can be assessed by numerous complementary methods, ranging from various imaging approaches to gene expression studies. Here, we highlight the flow cytometry-based analysis of individual HFOs, enabling the quantitative monitoring of lineage formation.

High-throughput 3D Spheroid Formation and Effective Cardiomyocyte Differentiation from Human iPS Cells Using the Microfabric Vessels EZSPHERETM

High-throughput 3D spheroid formation from human induced pluripotent stem cells (hiPSCs) can be easily performed using the unique microfabric vessels EZSPHERE, resulting in effective and large scale generation of differentiated cells such as cardiomyocytes or neurons. Such hiPSC-derived cardiomyocytes (hiPSC-CMs) or neurons are very useful in the fields of regenerative medicine or cell-based drug safety tests. Previous studies indicated that 3D spheroids arising from hiPSCs are effectively differentiated into high quality hiPSC-CMs by controlling Wnt signals through utilization of the microfabric vessels EZSPHERE. Here, we describe a simple and highly efficient protocol for generating a large number of uniformly sized hiPSC spheroids and inducing them for cardiac differentiation using the EZSPHERE. This method comprises the collection and dissociation of the spheroids from cardiac differentiation medium, in the middle stage of the whole cardiac differentiation process, and re-seeding the obtained single cells into the EZSPHERE to re-aggregate them into uniform hiPSC-CM spheroids with controlled size. This re-aggregation process promotes non-canonical Wnt signal-related cardiac development and improves the purity and maturity of the hiPSC-CMs generated. Graphic abstract: Overview of cardiac differentiation from iPSCs by spheroid formation and reaggregation using EZSPHERE.

Critical Analysis of cGMP Large-Scale Expansion Process in Bioreactors of Human Induced Pluripotent Stem Cells in the Framework of Quality by Design

Human induced pluripotent stem cells (hiPSCs) are manufactured as advanced therapy medicinal products for tissue replacement applications. With this aim, the feasibility of hiPSC large-scale expansion in existing bioreactor systems under current good manufacturing practices (cGMP) has been tested. Yet, these attempts have lacked a paradigm shift in culture settings and technologies tailored to hiPSCs, which jeopardizes their clinical translation. The best approach for industrial scale-up of high-quality hiPSCs is to design their manufacturing process by following quality-by-design (QbD) principles: a scientific, risk-based framework for process design based on relating product and process attributes to product quality. In this review, we analyzed the hiPSC expansion manufacturing process implementing the QbD approach in the use of bioreactors, stressing the decisive role played by the cell quantity, quality and costs, drawing key QbD concepts directly from the guidelines of the International Council for Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use.

Proteomic Analysis of Exosomes during Cardiogenic Differentiation of Human Pluripotent Stem Cells

Efforts to direct the specification of human pluripotent stem cells (hPSCs) to therapeutically important somatic cell types have focused on identifying proper combinations of soluble cues. Yet, whether exosomes, which mediate intercellular communication, play a role in the differentiation remains unexplored. We took a first step toward addressing this question by subjecting hPSCs to stage-wise specification toward cardiomyocytes (CMs) in scalable stirred-suspension cultures and collecting exosomes. Samples underwent liquid chromatography (LC)/mass spectrometry (MS) and subsequent proteomic analysis revealed over 300 unique proteins from four differentiation stages including proteins such as PPP2CA, AFM, MYH9, MYH10, TRA2B, CTNNA1, EHD1, ACTC1, LDHB, and GPC4, which are linked to cardiogenic commitment. There was a significant correlation of the protein composition of exosomes with the hPSC line and stage of commitment. Differentiating hPSCs treated with exosomes from hPSC-derived CMs displayed improved efficiency of CM formation compared to cells without exogenously added vesicles. Collectively, these results demonstrate that exosomes from hPSCs induced along the CM lineage contain proteins linked to the specification process with modulating effects and open avenues for enhancing the biomanufacturing of stem cell products for cardiac diseases.

The combination of dextran sulphate and polyvinyl alcohol prevents excess aggregation and promotes proliferation of pluripotent stem cells in suspension culture

OBJECTIVES

For clinical applications of cell-based therapies, a large quantity of human pluripotent stem cells (hPSCs) produced in standardized and scalable culture processes is required. Currently, microcarrier-free suspension culture shows potential for large-scale expansion of hPSCs; however, hPSCs tend to aggregate during culturing leading to a negative effect on cell yield. To overcome this problem, we developed a novel protocol to effectively control the sizes of cell aggregates and enhance the cell proliferation during the expansion of hPSCs in suspension.

MATERIALS AND METHODS

hPSCs were expanded in suspension culture supplemented with polyvinyl alcohol (PVA) and dextran sulphate (DS), and 3D suspension culture of hPSCs formed cell aggregates under static or dynamic conditions. The sizes of cell aggregates and the cell proliferation as well as the pluripotency of hPSCs after expansion were assessed using cell counting, size analysis, real-time quantitative polymerase chain reaction, flow cytometry analysis, immunofluorescence staining, embryoid body formation, teratoma formation and transcriptome sequencing.

RESULTS

Our results demonstrated that the addition of DS alone effectively prevented hPSC aggregation, while the addition of PVA significantly enhanced hPSC proliferation. The combination of PVA and DS not only promoted cell proliferation of hPSCs but also produced uniform and size-controlled cell aggregates. Moreover, hPSCs treated with PVA, or DS or a combination, maintained the pluripotency and were capable of differentiating into all three germ layers. mRNA-seq analysis demonstrated that the combination of PVA and DS significantly promoted hPSC proliferation and prevented cell aggregation through improving energy metabolism-related processes, regulating cell growth, cell proliferation and cell division, as well as reducing the adhesion among hPSC aggregates by affecting expression of genes related to cell adhesion.

CONCLUSIONS

Our results represent a significant step towards developing a simple and robust approach for the expansion of hPSCs in large scale.

Efficient Method to Dissociate Induced Pluripotent Stem Cell-Derived Cardiomyocyte Aggregates into Single Cells

The human adult heart consists of approximately four billion cardiomyocytes, which do not possess self-renewal abilities. Severe myocardial infarction and dilated cardiomyopathy result in the loss of more than a billion cardiomyocytes. Induced pluripotent stem cells (iPSCs) can differentiate into various types of cells. Due to this ability, these cells could potentially serve as a new resource for cell therapy. Many studies have utilized cardiomyocytes derived from iPSCs for myocardial regeneration therapy. To obtain large number of cardiomyocytes for transplantation, we need to develop effective methods that would allow us to dissociate multiple cardiomyocyte aggregates simultaneously. Here, we describe a method to efficiently dissociate large number of iPSC-derived cardiomyocyte aggregates.

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.

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.

Application of hiPSCs in tooth regeneration via cellular modulation

BACKGROUND

Induced pluripotent stem cell (iPSC)-based technology provides limitless resources for customized development of organs without any ethical concerns. In theory, iPSCs generated from terminally differentiated cells can be induced to further differentiate into all types of organs that are derived from the embryonic germ layers. Since iPSC reprogramming technology is relatively new, extensive efforts by the researchers have been put together to optimize the protocols to establish in vitro differentiation of human iPSCs (hiPSCs) into various desirable cell types/organs.

HIGHLIGHTS

In the present study, we review the potential application of iPSCs as an efficient alternative to primary cells for modulating signal molecules. Furthermore, an efficient culture system that promotes the differentiation of cell lineages and tissue formation has been reviewed. We also summarize the recent studies wherein tissue engineering of the three germ layers has been explored. Particularly, we focus on the current research strategies for iPSC-based tooth regeneration via molecular modulation.

CONCLUSION

In recent decades, robust knowledge regarding the hiPSC-based regenerative therapy has been accumulated, especially focusing on cellular modulation. This review provides the optimization of the procedures designed to regenerate specific organs.

A Comparative Assessment of Marker Expression Between Cardiomyocyte Differentiation of Human Induced Pluripotent Stem Cells and the Developing Pig Heart

The course of differentiation of pluripotent stem cells into cardiomyocytes and the intermediate cell types are characterized using molecular markers for different stages of development. These markers have been selected primarily from studies in the mouse and from a limited number of human studies. However, it is not clear how well mouse cardiogenesis compares with human cardiogenesis at the molecular level. We tackle this issue by analyzing and comparing the expression of common cardiomyogenesis markers [platelet-derived growth factor receptor, alpha polypeptide (PDGFR-α), fetal liver kinase 1 (FLK1), ISL1, NK2 homeobox 5 (NKX2.5), cardiac troponin T (CTNT), connexin43 (CX43), and myosin heavy chain 7 (MYHC-B)] in the developing pig heart at embryonic day (E)15, E16, E18, E20, E22, and E24 and in differentiating cardiomyocytes from human induced pluripotent stem cells (hiPSCs). We found that porcine expression of the mesoderm marker FLK1 and the cardiac progenitor marker ISL1 was in line with our differentiating hiPSC and reported murine expression. The cardiac lineage marker NKX2.5 was expressed at almost all stages in the pig and hiPSC, with an earlier onset in the hiPSC compared with reported murine expression. Markers of immature cardiomyocytes, CTNT, and MYHC-B were consistently expressed throughout E16-E70 in the pig, which is comparable with mouse development, whereas the markers increased over time in the hiPSC. However, the commonly used mature cardiomyocyte marker, CX43, should be used with caution, as it was also expressed in the pig mesoderm, as well as hiPSC immature cardiomyocytes, while this has not been reported in mice. Based on our observations in the various species, we suggest to use FLK1/PDGFR-α for identifying cardiac mesoderm and ISL1/NKX2.5 for cardiac progenitors. Furthermore, a combination of two or more of the following, CTNT⁺/MYHC-B⁺/ISL1⁺ could mark immature cardiomyocytes and CTNT⁺/ISL1^- mature cardiomyocytes. CX43 should be used together with sarcomeric proteins. This knowledge may help improving differentiation of hiPSC into more in vivo-like cardiac tissue in the future.

Human iPSCs 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.

Human heart-forming organoids recapitulate early heart and foregut development

Organoid models of early tissue development have been produced for the intestine, brain, kidney and other organs, but similar approaches for the heart have been lacking. Here we generate complex, highly structured, three-dimensional heart-forming organoids (HFOs) by embedding human pluripotent stem cell aggregates in Matrigel followed by directed cardiac differentiation via biphasic WNT pathway modulation with small molecules. HFOs are composed of a myocardial layer lined by endocardial-like cells and surrounded by septum-transversum-like anlagen; they further contain spatially and molecularly distinct anterior versus posterior foregut endoderm tissues and a vascular network. The architecture of HFOs closely resembles aspects of early native heart anlagen before heart tube formation, which is known to require an interplay with foregut endoderm development. We apply HFOs to study genetic defects in vitro by demonstrating that NKX2.5-knockout HFOs show a phenotype reminiscent of cardiac malformations previously observed in transgenic mice.

Heart-forming organoids model early cardiac development.

Dual Function of iPSC-Derived Pericyte-Like Cells in Vascularization and Fibrosis-Related Cardiac Tissue Remodeling In Vitro

Myocardial interstitial fibrosis (MIF) is characterized by excessive extracellular matrix (ECM) deposition, increased myocardial stiffness, functional weakening, and compensatory cardiomyocyte (CM) hypertrophy. Fibroblasts (Fbs) are considered the principal source of ECM, but the contribution of perivascular cells, including pericytes (PCs), has gained attention, since MIF develops primarily around small vessels. The pathogenesis of MIF is difficult to study in humans because of the pleiotropy of mutually influencing pathomechanisms, unpredictable side effects, and the lack of available patient samples. Human pluripotent stem cells (hPSCs) offer the unique opportunity for the de novo formation of bioartificial cardiac tissue (BCT) using a variety of different cardiovascular cell types to model aspects of MIF pathogenesis in vitro. Here, we have optimized a protocol for the derivation of hPSC-derived PC-like cells (iPSC-PCs) and present a BCT in vitro model of MIF that shows their central influence on interstitial collagen deposition and myocardial tissue stiffening. This model was used to study the interplay of different cell types—i.e., hPSC-derived CMs, endothelial cells (ECs), and iPSC-PCs or primary Fbs, respectively. While iPSC-PCs improved the sarcomere structure and supported vascularization in a PC-like fashion, the functional and histological parameters of BCTs revealed EC- and PC-mediated effects on fibrosis-related cardiac tissue remodeling.

Exosomes Enhance Adhesion and Osteogenic Differentiation of Initial Bone Marrow Stem Cells on Titanium Surfaces

Successful osseointegration involves the biological behavior of bone marrow stem cells (BMSCs) on an implant surface; however, the role of BMSC-derived extracellular vesicles (EVs)/exosomes in osseointegration is little known. This study aimed to: (i) explore the interaction force between exosomes (Exo) and cells on a titanium surface; (ii) discuss whether the morphology and biological behavior of BMSCs are affected by exosomes; and (iii) preliminarily investigate the mechanism by which exosomes regulate cells on Ti surface. Exosomes secreted by rat BMSCs were collected by ultracentrifugation and analyzed using transmission electron microscopy and nanoparticle tracking analysis. Confocal fluorescence microscopy, scanning electron microscopy, Cell Counting Kit-8 (CCK-8), quantitative real-time polymerase chain reaction techniques, and alkaline phosphatase bioactivity, Alizarin Red staining, and quantification were used to investigate the exosomes that adhere to the Ti plates under different treatments as well as the morphological change, adhesion, spread, and differentiation of BMSCs. We found that exosomes were efficiently internalized and could regulate cell morphology and promoted the adhesion, spreading, and osteogenic differentiation of BMSCs. These were achieved partly by activating the RhoA/ROCK signaling pathway. Our discovery presents a new insight into the positive regulatory effect of exosomes on the biological behaviors of BMSCs on Ti surface and provides a novel route to modify the surface of a Ti implant.

The Dynamic Proteome of Oligodendrocyte Lineage Differentiation Features Planar Cell Polarity and Macroautophagy Pathways

Background

Generation of oligodendrocytes is a sophisticated multistep process, the mechanistic underpinnings of which are not fully understood and demand further investigation. To systematically profile proteome dynamics during human embryonic stem cell differentiation into oligodendrocytes, we applied in-depth quantitative proteomics at different developmental stages and monitored changes in protein abundance using a multiplexed tandem mass tag-based proteomics approach.

Findings

Our proteome data provided a comprehensive protein expression profile that highlighted specific expression clusters based on the protein abundances over the course of human oligodendrocyte lineage differentiation. We identified the eminence of the planar cell polarity signalling and autophagy (particularly macroautophagy) in the progression of oligodendrocyte lineage differentiation—the cooperation of which is assisted by 106 and 77 proteins, respectively, that showed significant expression changes in this differentiation process. Furthermore, differentially expressed protein analysis of the proteome profile of oligodendrocyte lineage cells revealed 378 proteins that were specifically upregulated only in 1 differentiation stage. In addition, comparative pairwise analysis of differentiation stages demonstrated that abundances of 352 proteins differentially changed between consecutive differentiation time points.

Conclusions

Our study provides a comprehensive systematic proteomics profile of oligodendrocyte lineage cells that can serve as a resource for identifying novel biomarkers from these cells and for indicating numerous proteins that may contribute to regulating the development of myelinating oligodendrocytes and other cells of oligodendrocyte lineage. We showed the importance of planar cell polarity signalling in oligodendrocyte lineage differentiation and revealed the autophagy-related proteins that participate in oligodendrocyte lineage differentiation.

Xenogeneic-Free System for Biomanufacturing of Cardiomyocyte Progeny From Human Pluripotent Stem Cells

Functional heart cells and tissues sourced from human pluripotent stem cells (hPSCs) have great potential for substantially advancing treatments of cardiovascular maladies. Realization of this potential will require the development of cost-effective and tunable bioprocesses for manufacturing hPSC-based cell therapeutics. Here, we report the development of a xeno-free platform for guiding the cardiogenic commitment of hPSCs. The system is based on a fully defined, open-source formulation without complex supplements, which have varied and often undetermined effects on stem cell physiology. The formulation was used to systematically investigate factors inducing the efficient commitment to cardiac mesoderm of three hPSC lines. Contractile clusters of cells appeared within a week of differentiation in planar cultures and by day 13 over 80% of the cells expressed cardiac progeny markers such as TNNT2. In conjunction with expansion, this differentiation strategy was employed in stirred-suspension cultures of hPSCs. Scalable differentiation resulted in 0.4-2 million CMs/ml or ∼5-20 TNNT2-positive cells per seeded hPSC without further enrichment. Our findings will contribute to the engineering of bioprocesses advancing the manufacturing of stem cell-based therapeutics for heart diseases.

Emerging routes to the generation of functional β-cells for diabetes mellitus cell therapy

Diabetes mellitus, which affects more than 463 million people globally, is caused by the autoimmune ablation or functional loss of insulin-producing β-cells, and prevalence is projected to continue rising over the next decades. Generating β-cells to mitigate the aberrant glucose homeostasis manifested in the disease has remained elusive. Substantial advances have been made in producing mature β-cells from human pluripotent stem cells that respond appropriately to dynamic changes in glucose concentrations in vitro and rapidly function in vivo following transplantation in mice. Other potential avenues to produce functional β-cells include: transdifferentiation of closely related cell types (for example, other pancreatic islet cells such as α-cells, or other cells derived from endoderm); the engineering of non-β-cells that are capable of modulating blood sugar; and the construction of synthetic 'cells' or particles mimicking functional aspects of β-cells. This Review focuses on the current status of generating β-cells via these diverse routes, highlighting the unique advantages and challenges of each approach. Given the remarkable progress in this field, scalable bioengineering processes are also discussed for the realization of the therapeutic potential of derived β-cells.

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.

A novel cardiac differentiation method of a large number and uniformly-sized spheroids using microfabricated culture vessels

Cardiomyocytes differentiated from human induced pluripotent stem cells (hiPSCs) have great potential for regenerative medicine and drug discovery. In this study, we developed a novel protocol to more reproducibly and efficiently induce cardiomyocytes. A large quantity of uniformly sized spheroids were generated from hiPSCs using microfabricated vessels and induced into cardiac differentiation. In the middle of the cardiac differentiation process, spheroids were then dissociated into single cells and reaggregated into smaller spheroids using the microfabricated vessels. This reaggregation process raised WNT5A and WNT11 expression levels and improved the quality of cardiomyocyte population compared to that in a control group in which dissociation and reaggregation were not performed.

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Microfabricated culture vessels were used to form large number of hiPSC spheroids.

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High purity cardiomyocytes were obtained by reaggregation of hiPSC-derived spheroids.

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Maturation of cardiomyocyte was promoted by the reaggregation process.

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WNTs were also increased the reaggregation process during cardiac differentiation.

Clinical-based Cell Therapies for Heart Disease-Current and Future State

Patients have an ongoing unmet need for effective therapies that reverse the cellular and functional damage associated with heart damage and disease. The discovery that ~1%-2% of adult cardiomyocytes turn over per year provided the impetus for treatments that stimulate endogenous repair mechanisms that augment this rate. Preclinical and clinical studies provide evidence that cell-based therapy meets these therapeutic criteria. Recent and ongoing studies are focused on determining which cell type(s) works best for specific patient population(s) and the mechanism(s) by which these cells promote repair. Here we review clinical and preclinical stem cell studies and anticipate future directions of regenerative medicine for heart disease.

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.

Preclinical development of a miR-132 inhibitor for heart failure treatment

Despite proven efficacy of pharmacotherapies targeting primarily global neurohormonal dysregulation, heart failure (HF) is a growing pandemic with increasing burden. Treatments mechanistically focusing at the cardiomyocyte level are lacking. MicroRNAs (miRNA) are transcriptional regulators and essential drivers of disease progression. We previously demonstrated that miR-132 is both necessary and sufficient to drive the pathological cardiomyocytes growth, a hallmark of adverse cardiac remodelling. Therefore, miR-132 may serve as a target for HF therapy. Here we report further mechanistic insight of the mode of action and translational evidence for an optimized, synthetic locked nucleic acid antisense oligonucleotide inhibitor (antimiR-132). We reveal the compound’s therapeutic efficacy in various models, including a clinically highly relevant pig model of HF. We demonstrate favourable pharmacokinetics, safety, tolerability, dose-dependent PK/PD relationships and high clinical potential for the antimiR-132 treatment scheme.

miR-132 was shown to drive pathological cardiac remodeling, a hallmark of heart failure. Here, the authors show that an antisense inhibitor of miR-132 has favourable pharmacokinetics, safety-tolerability and preclinical efficacy in mouse and porcine models of heart failure.

Inducing human induced pluripotent stem cell differentiation through embryoid bodies: A practical and stable approach

Human induced pluripotent stem cells (hiPSCs) are invaluable resources for producing high-quality differentiated cells in unlimited quantities for both basic research and clinical use. They are particularly useful for studying human disease mechanisms in vitro by making it possible to circumvent the ethical issues of human embryonic stem cell research. However, significant limitations exist when using conventional flat culturing methods especially concerning cell expansion, differentiation efficiency, stability maintenance and multicellular 3D structure establishment, differentiation prediction. Embryoid bodies (EBs), the multicellular aggregates spontaneously generated from iPSCs in the suspension system, might help to address these issues. Due to the unique microenvironment and cell communication in EB structure that a 2D culture system cannot achieve, EBs have been widely applied in hiPSC-derived differentiation and show significant advantages especially in scaling up culturing, differentiation efficiency enhancement, ex vivo simulation, and organoid establishment. EBs can potentially also be used in early prediction of iPSC differentiation capability. To improve the stability and feasibility of EB-mediated differentiation and generate high quality EBs, critical factors including iPSC pluripotency maintenance, generation of uniform morphology using micro-pattern 3D culture systems, proper cellular density inoculation, and EB size control are discussed on the basis of both published data and our own laboratory experiences. Collectively, the production of a large quantity of homogeneous EBs with high quality is important for the stability and feasibility of many PSCs related studies.

Stem cell-derived cell sheet transplantation for heart tissue repair in myocardial infarction

Stem cell-derived sheet engineering has been developed as the next-generation treatment for myocardial infarction (MI) and offers attractive advantages in comparison with direct stem cell transplantation and scaffold tissue engineering. Furthermore, induced pluripotent stem cell-derived cell sheets have been indicated to possess higher potential for MI therapy than other stem cell-derived sheets because of their capacity to form vascularized networks for fabricating thickened human cardiac tissue and their long-term therapeutic effects after transplantation in MI. To date, stem cell sheet transplantation has exhibited a dramatic role in attenuating cardiac dysfunction and improving clinical manifestations of heart failure in MI. In this review, we retrospectively summarized the current applications and strategy of stem cell-derived cell sheet technology for heart tissue repair in MI.

Cryopreservation of human pluripotent stem cell-derived cardiomyocytes is not detrimental to their molecular and functional properties

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have emerged as a powerful platform for in vitro modelling of cardiac diseases, safety pharmacology and drug screening. All these applications require large quantities of well-characterised and standardised batches of hiPSC-CMs. Cryopreservation of hiPSC-CMs without affecting their biochemical or biophysical phenotype is essential for facilitating this, but ideally requires the cells being unchanged by the freeze-thaw procedure. We therefore compared the in vitro functional and molecular characteristics of fresh and cryopreserved hiPSC-CMs generated from multiple independent hiPSC lines. While the frozen hiPSC-CMs exhibited poorer replating than their freshly-derived counterparts, there was no difference in the proportion of cardiomyocytes retrieved from the mixed population when this was factored in, although for several lines a higher percentage of ventricular-like hiPSC-CMs were recovered following cryopreservation. Furthermore, cryopreserved hiPSC-CMs from one line exhibited longer action potential durations. These results provide evidence that cryopreservation does not compromise the in vitro molecular, physiological and mechanical properties of hiPSC-CMs, though can lead to an enrichment in ventricular myocytes. It also validates this procedure for storing hiPSC-CMs, thereby allowing the same batch of hiPSC-CMs to be used for multiple applications and evaluations.

Computational fluid dynamics modeling, a novel, and effective approach for developing scalable cell therapy manufacturing processes

Induced pluripotent stem cells (iPSCs) hold great potential to generate novel, curative cell therapy products. However, current methods to generate these novel therapies lack scalability, are labor-intensive, require a large footprint, and are not suited to meet clinical and commercial demands. Therefore, it is necessary to develop scalable manufacturing processes to accommodate the generation of high-quality iPSC derivatives under controlled conditions. The current scale-up methods used in cell therapy processes are based on empirical, geometry-dependent methods that do not accurately represent the hydrodynamics of 3D bioreactors. These methods require multiple iterations of scale-up studies, resulting in increased development cost and time. Here we show a novel approach using computational fluid dynamics modeling to effectively scale-up cell therapy manufacturing processes in 3D bioreactors. Using a GMP-compatible iPSC line, we translated and scaled-up a small-scale cardiomyocyte differentiation process to a 3-L computer-controlled bioreactor in an efficient manner, showing comparability in both systems.

Cardiac Progenitor Cells from Stem Cells: Learning from Genetics and Biomaterials

Cardiac Progenitor Cells (CPCs) show great potential as a cell resource for restoring cardiac function in patients affected by heart disease or heart failure. CPCs are proliferative and committed to cardiac fate, capable of generating cells of all the cardiac lineages. These cells offer a significant shift in paradigm over the use of human induced pluripotent stem cell (iPSC)-derived cardiomyocytes owing to the latter’s inability to recapitulate mature features of a native myocardium, limiting their translational applications. The iPSCs and direct reprogramming of somatic cells have been attempted to produce CPCs and, in this process, a variety of chemical and/or genetic factors have been evaluated for their ability to generate, expand, and maintain CPCs in vitro. However, the precise stoichiometry and spatiotemporal activity of these factors and the genetic interplay during embryonic CPC development remain challenging to reproduce in culture, in terms of efficiency, numbers, and translational potential. Recent advances in biomaterials to mimic the native cardiac microenvironment have shown promise to influence CPC regenerative functions, while being capable of integrating with host tissue. This review highlights recent developments and limitations in the generation and use of CPCs from stem cells, and the trends that influence the direction of research to promote better application of CPCs.

An effective detachment system for human induced pluripotent stem cells cultured on multilayered cultivation substrates using resonance vibrations

Clinical application of human induced pluripotent stem cells (hiPSCs) has been hampered by the lack of a practical, scalable culture system. Stacked culture plates (SCPs) have recently attracted attention. However, final cell yields depend on the efficiency of cell detachment, and inefficient cell recovery from SCPs presents a major challenge to their use. We have developed an effective detachment method using resonance vibrations (RVs) of substrates with sweeping driving frequency. By exciting RVs that have 1–3 antinodes with ultra-low-density enzyme spread on each substrate of SCPs, 87.8% of hiPSCs were successfully detached from a 5-layer SCP compared to 30.8% detached by the conventional enzymatic method. hiPSC viability was similar after either method. Moreover, hiPSCs detached by the RV method maintained their undifferentiated state. Additionally, hiPSCs after long-term culture (10 passages) kept excellent detachment efficiency, had the normal karyotypes, and maintained the undifferentiated state and pluripotency. These results indicated that the RV method has definite advantages over the conventional enzymatic method in the scalable culture of hiPSCs using SCPs.

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.

Modeling methodology for defining a priori the hydrodynamics of a dynamic suspension bioreactor. Application to human induced pluripotent stem cell culture

Three-dimensional dynamic suspension is becoming an effective cell culture method for a wide range of bioprocesses, with an increasing number of bioreactors proposed for this purpose. The complex hydrodynamics establishing within these devices affects bioprocess outcomes and efficiency, and usually expensive in vitro trial-and-error experiments are needed to properly set the working parameters. Here we propose a methodology to define a priori the hydrodynamic working parameters of a dynamic suspension bioreactor, selected as a test case because of the complex hydrodynamics characterizing its operating condition. A combination of computational and analytical approaches was applied to generate operational guideline graphs for defining a priori specific working parameters. In detail, 43 simulations were performed under pulsed flow regime to characterize advective transport within the device depending on different operative conditions, i.e., culture medium flow rate and its duty cycle, cultured particle diameter, and initial particle suspension volume. The operational guideline graphs were then used to set specific hydrodynamic working parameters for an in vitro proof-of-principle test, where human induced pluripotent stem cell (hiPSC) aggregates were cultured for 24 h within the bioreactor. The in vitro findings showed that, under the selected pulsed flow regime, sedimentation was avoided, hiPSC aggregate circularity and viability were preserved, and culture heterogeneity was reduced, thus confirming the appropriateness of the a priori method. This methodology has the potential to be adaptable to other dynamic suspension devices to support experimental studies by providing in silico-based a priori knowledge, useful to limit costs and to optimize culture bioprocesses.

Comparing human iPSC-cardiomyocytes versus HEK293T cells unveils disease-causing effects of Brugada mutation A735V of NaV1.5 sodium channels

Loss-of-function mutations of the SCN5A gene encoding for the sodium channel α-subunit Na_V1.5 result in the autosomal dominant hereditary disease Brugada Syndrome (BrS) with a high risk of sudden cardiac death in the adult. We here engineered human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) carrying the CRISPR/Cas9 introduced BrS-mutation p.A735V-Na_V1.5 (g.2204C > T in exon 14 of SCN5A) as a novel model independent of patient´s genetic background. Recent studies raised concern regarding the use of hiPSC-CMs for studying adult-onset hereditary diseases due to cells’ immature phenotype. To tackle this concern, long-term cultivation of hiPSC-CMs on a stiff matrix (27–42 days) was applied to promote maturation. Patch clamp recordings of A735V mutated hiPSC-CMs revealed a substantially reduced upstroke velocity and sodium current density, a prominent rightward shift of the steady state activation curve and decelerated recovery from inactivation as compared to isogenic hiPSC-CMs controls. These observations were substantiated by a comparative study on mutant A735V-Na_V1.5 channels heterologously expressed in HEK293T cells. In contrast to mutated hiPSC-CMs, a leftward shift of sodium channel inactivation was not observed in HEK293T, emphasizing the importance of investigating mechanisms of BrS in independent systems. Overall, our approach supports hiPSC-CMs’ relevance for investigating channelopathies in a dish.

Continuous WNT Control Enables Advanced hPSC Cardiac Processing and Prognostic Surface Marker Identification in Chemically Defined Suspension Culture

Aiming at clinical translation, robust directed differentiation of human pluripotent stem cells (hPSCs), preferentially in chemically defined conditions, is a key requirement. Here, feasibility of suspension culture based hPSC-cardiomyocyte (hPSC-CM) production in low-cost, xeno-free media compatible with good manufacturing practice standards is shown. Applying stirred tank bioreactor systems at increasing dimensions, our advanced protocol enables routine production of about 1 million hPSC-CMs/mL, yielding ∼1.3 × 10⁸ CM in 150 mL and ∼4.0 × 10⁸ CMs in 350–500 mL process scale at >90% lineage purity. Process robustness and efficiency is ensured by uninterrupted chemical WNT pathway control at early stages of differentiation and results in the formation of almost exclusively ventricular-like CMs. Modulated WNT pathway regulation also revealed the previously unappreciated role of ROR1/CD13 as superior surrogate markers for predicting cardiac differentiation efficiency as soon as 72 h of differentiation. This monitoring strategy facilitates process upscaling and controlled mass production of hPSC derivatives.

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Chemically defined hPSC cardiac differentiation applicable to stirred tank reactors

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Protocol generates >90% purity of ventricular-like cardiomyocytes

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Uninterrupted WNT pathway control enables superior cardiac mesoderm formation

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Novel ROR1/CD13 combination as superior, predictive marker of cardiomyogenesis