Generation of human induced pluripotent stem cell-derived cardiomyocytes in 2D monolayer and scalable 3D suspension bioreactor cultures with reduced batch-to-batch variations

Hypothermic and cryogenic preservation of cardiac tissue-engineered constructs

Cardiac tissue engineering (cTE) has already advanced towards the first clinical trials, investigating safety and feasibility of cTE construct transplantation in failing hearts. However, the lack of well-established preservation methods poses a hindrance to further scalability, commercialization, and transportation, thereby reducing their clinical implementation. In this study, hypothermic preservation (4 °C) and two methods for cryopreservation (i.e., a slow and fast cooling approach to -196 °C and -150 °C, respectively) were investigated as potential solutions to extend the cTE construct implantation window. The cTE model used consisted of human induced pluripotent stem cell-derived cardiomyocytes and human cardiac fibroblasts embedded in a natural-derived hydrogel and supported by a polymeric melt electrowritten hexagonal scaffold. Constructs, composed of cardiomyocytes of different maturity, were preserved for three days, using several commercially available preservation protocols and solutions. Cardiomyocyte viability, function (beat rate and calcium handling), and metabolic activity were investigated after rewarming. Our observations show that cardiomyocytes' age did not influence post-rewarming viability, however, it influenced construct function. Hypothermic preservation with HypoThermosol® ensured cardiomyocyte viability and function. Furthermore, fast freezing outperformed slow freezing, but both viability and function were severely reduced after rewarming. In conclusion, whereas long-term preservation remains a challenge, hypothermic preservation with HypoThermosol® represents a promising solution for cTE construct short-term preservation and potential transportation, aiding in off-the-shelf availability, ultimately increasing their clinical applicability.

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.

Efficient and reproducible generation of human iPSC-derived cardiomyocytes and cardiac organoids in stirred suspension systems

Human iPSC-derived cardiomyocytes (hiPSC-CMs) have proven invaluable for cardiac disease modeling and regeneration. Challenges with quality, inter-batch consistency, cryopreservation and scale remain, reducing experimental reproducibility and clinical translation. Here, we report a robust stirred suspension cardiac differentiation protocol, and we perform extensive morphological and functional characterization of the resulting bioreactor-differentiated iPSC-CMs (bCMs). Across multiple different iPSC lines, the protocol produces 1.2E6/mL bCMs with ~94% purity. bCMs have high viability after cryo-recovery (>90%) and predominantly ventricular identity. Compared to standard monolayer-differentiated CMs, bCMs are more reproducible across batches and have more mature functional properties. The protocol also works with magnetically stirred spinner flasks, which are more economical and scalable than bioreactors. Minor protocol modifications generate cardiac organoids fully in suspension culture. These reproducible, scalable, and resource-efficient approaches to generate iPSC-CMs and organoids will expand their applications, and our benchmark data will enable comparison to cells produced by other cardiac differentiation protocols.

Standardized production of hPSC-derived cardiomyocyte aggregates in stirred spinner flasks

A promising cell-therapy approach for heart failure aims at differentiating human pluripotent stem cells (hPSCs) into functional cardiomyocytes (CMs) in vitro to replace the disease-induced loss of patients' heart muscle cells in vivo. But many challenges remain for the routine clinical application of hPSC-derived CMs (hPSC-CMs), including good manufacturing practice (GMP)-compliant production strategies. This protocol describes the efficient generation of hPSC-CM aggregates in suspension culture, emphasizing process simplicity, robustness and GMP compliance. The strategy promotes clinical translation and other applications that require large numbers of CMs. Using a simple spinner-flask platform, this protocol is applicable to a broad range of users with general experience in handling hPSCs without extensive know-how in biotechnology. hPSCs are expanded in monolayer to generate the required cell numbers for process inoculation in suspension culture, followed by stirring-controlled formation of cell-only aggregates at a 300-ml scale. After 48 h at checkpoint (CP) 0, chemically defined cardiac differentiation is induced by WNT-pathway modulation through use of the glycogen-synthase kinase-3 inhibitor CHIR99021 (WNT agonist), which is replaced 24 h later by the chemical WNT-pathway inhibitor IWP-2. The exact application of the described process parameters is important to ensure process efficiency and robustness. After 10 d of differentiation (CP I), the production of ≥100 × 106 CMs is expected. Moreover, to 'uncouple' cell production from downstream applications, continuous maintenance of CM aggregates for up to 35 d in culture (CP II) is demonstrated without a reduction in CM content, supporting downstream logistics while potentially overcoming the requirement for cryopreservation.

Functional dissection of human cardiac enhancers and noncoding de novo variants in congenital heart disease

Rare coding mutations cause ∼45% of congenital heart disease (CHD). Noncoding mutations that perturb cis-regulatory elements (CREs) likely contribute to the remaining cases, but their identification has been problematic. Using a lentiviral massively parallel reporter assay (lentiMPRA) in human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs), we functionally evaluated 6,590 noncoding de novo variants (ncDNVs) prioritized from the whole-genome sequencing of 750 CHD trios. A total of 403 ncDNVs substantially affected cardiac CRE activity. A majority increased enhancer activity, often at regions with undetectable reference sequence activity. Of ten DNVs tested by introduction into their native genomic context, four altered the expression of neighboring genes and iPSC-CM transcriptional state. To prioritize future DNVs for functional testing, we used the MPRA data to develop a regression model, EpiCard. Analysis of an independent CHD cohort by EpiCard found enrichment of DNVs. Together, we developed a scalable system to measure the effect of ncDNVs on CRE activity and deployed it to systematically assess the contribution of ncDNVs to CHD.

Efficient and reproducible generation of human iPSC-derived cardiomyocytes using a stirred bioreactor

In the last decade human iPSC-derived cardiomyocytes (hiPSC-CMs) proved to be valuable for cardiac disease modeling and cardiac regeneration, yet challenges with scale, quality, inter-batch consistency, and cryopreservation remain, reducing experimental reproducibility and limiting clinical translation. Here, we report a robust cardiac differentiation protocol that uses Wnt modulation and a stirred suspension bioreactor to produce on average 124 million hiPSC-CMs with >90% purity using a variety of hiPSC lines (19 differentiations; 10 iPSC lines). After controlled freeze and thaw, bioreactor-derived CMs (bCMs) showed high viability (>90%), interbatch reproducibility in cellular morphology, function, drug response and ventricular identity, which was further supported by single cell transcriptomes. bCMs on microcontact printed substrates revealed a higher degree of sarcomere maturation and viability during long-term culture compared to monolayer-derived CMs (mCMs). Moreover, functional investigation of bCMs in 3D engineered heart tissues showed earlier and stronger force production during long-term culture, and robust pacing capture up to 4 Hz when compared to mCMs. bCMs derived from this differentiation protocol will expand the applications of hiPSC-CMs by providing a reproducible, scalable, and resource efficient method to generate cardiac cells with well-characterized structural and functional properties superior to standard mCMs.

Large-scale cultivation of human iPS cells in bioreactor with reciprocal mixing

A substantial number of human iPS cells (hiPSCs) is needed for cell therapy to be successful against various diseases. We previously reported on a bioreactor with reciprocal mixing that produces specific physical properties that differ from those of conventional bioreactors with rotary paddle stirring. Moreover, such reactors not only provide a homogeneous environment but also allow the control of spheroid size by changing the mixing speed. In this study, we applied this bioreactor to the large-scale cultivation of hiPSCs. Approximately 10 billion hiPSCs were obtained from 2.0 L of culture, and the high expression of pluripotency markers was maintained. Our findings indicate that a bioreactor with reciprocal mixing can be used for large-scale hiPSC cultivation.

Fusogenic Coiled-Coil Peptides Enhance Lipid Nanoparticle-Mediated mRNA Delivery upon Intramyocardial Administration

Heart failure is a serious condition that results from the extensive loss of specialized cardiac muscle cells called cardiomyocytes (CMs), typically caused by myocardial infarction (MI). Messenger RNA (mRNA) therapeutics are emerging as a very promising gene medicine for regenerative cardiac therapy. To date, lipid nanoparticles (LNPs) represent the most clinically advanced mRNA delivery platform. Yet, their delivery efficiency has been limited by their endosomal entrapment after endocytosis. Previously, we demonstrated that a pair of complementary coiled-coil peptides (CPE4/CPK4) triggered efficient fusion between liposomes and cells, bypassing endosomal entrapment and resulting in efficient drug delivery. Here, we modified mRNA-LNPs with the fusogenic coiled-coil peptides and demonstrated efficient mRNA delivery to difficult-to-transfect induced pluripotent stem-cell-derived cardiomyocytes (iPSC-CMs). As proof of in vivo applicability of these fusogenic LNPs, local administration via intramyocardial injection led to significantly enhanced mRNA delivery and concomitant protein expression. This represents the successful application of the fusogenic coiled-coil peptides to improve mRNA-LNPs transfection in the heart and provides the potential for the advanced development of effective regenerative therapies for heart failure.

Optical Mapping of Cardiomyocytes in Monolayer Derived from Induced Pluripotent Stem Cells

Optical mapping is a powerful imaging technique widely adopted to measure membrane potential changes and intracellular Ca2+ variations in excitable tissues using voltage-sensitive dyes and Ca2+ indicators, respectively. This powerful tool has rapidly become indispensable in the field of cardiac electrophysiology for studying depolarization wave propagation, estimating the conduction velocity of electrical impulses, and measuring Ca2+ dynamics in cardiac cells and tissues. In addition, mapping these electrophysiological parameters is important for understanding cardiac arrhythmia mechanisms. In this review, we delve into the fundamentals of cardiac optical mapping technology and its applications when applied to hiPSC-derived cardiomyocytes and discuss related advantages and challenges. We also provide a detailed description of the processing and analysis of optical mapping data, which is a crucial step in the study of cardiac diseases and arrhythmia mechanisms for extracting and comparing relevant electrophysiological parameters.

In vitro effect of hydroxychloroquine on pluripotent stem cells and their cardiomyocytes derivatives

Introduction: Hydroxychloroquine (HDQ) is an antimalarial drug that has also shown its effectiveness in autoimmune diseases. Despite having side effects such as retinopathy, neuromyopathy and controversial cardiac toxicity, HDQ has been presented and now intensively studied for the treatment and prevention of coronavirus disease 2019 (COVID-19). Recent works revealed both beneficial and toxic effects during HDQ treatment. The cardiotoxic profile of HDQ remains unclear and identifying risk factors is challenging. Methods: Here, we used well-established cell-cultured to study the cytotoxic effect of HDQ, mouse induced pluripotent stem cells (miPSC) and their cardiomyocytes (CMs) derivatives were exposed to different concentrations of HDQ. Cell colony morphology was assessed by microscopy whereas cell viability was measured by flow cytometry and impedance-based methods. The effect of HDQ on beating activity of mouse and human induced pluripotent stem cell-derived CMs (miPSC-CMs and hiPSC-CMs, respectively) and mouse embryonic stem cell-derived CMs (mESC-CMs) were captured by the xCELLigence RTCA and microelectrode array (MEA) systems. Results and discussion: Our results revealed that 20 µM of HDQ promotes proliferation of stem cells used suggesting that if appropriately monitored, HDQ may have a cardioprotective effect and may also represent a possible candidate for tissue repair. In addition, the field potential signals revealed that higher doses of this medication caused bradycardia that could be reversed with a higher concentration of ß-adrenergic agonist, Isoproterenol (Iso). On the contrary, HDQ caused an increase in the beating rate of hiPSC-CMs, which was further helped upon application of Isoproterenol (Iso) suggesting that HDQ and Iso may also work synergistically. These results indicate that HDQ is potentially toxic at high concentrations and can modulate the beating activity of cardiomyocytes. Moreover, HDQ could have a synergistic inotropic effect with isoproterenol on cardiac cells.

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

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

Suspension culture on microcarriers and as aggregates enables expansion and differentiation of pluripotent stem cells (PSCs)

BACKGROUND AIMS

Human pluripotent stem cells (PSCs) hold a great promise for promoting regenerative medical therapies due to their ability to generate multiple mature cell types and for their high expansion potential. However, cell therapies require large numbers of cells to achieve desired therapeutic effects, and traditional two-dimensional static culture methods cannot meet the required production demand for cellular therapies. One solution to this problem is scaling up expansion of PSCs in bioreactors using culture strategies such as growing cells on microcarriers or as aggregates in suspension culture.

METHODS

In this study, we directly compared PSC expansion and quality parameters in microcarrier- and aggregate-cultures grown in single-use vertical-wheel bioreactors.

RESULTS

We showed comparable expansion of cells on microcarriers and as aggregates by day 6 with a cell density reaching 2.2 × 10⁶ cells/mL and 1.8 × 10⁶ cells/mL and a fold-expansion of 22- and 18-fold, respectively. PSCs cultured on microcarriers and as aggregates were comparable with parallel two-dimensional cultures and with each other in terms of pluripotency marker expression and retention of other pluripotency characteristics as well as differentiation potential into three germ layers, neural precursor cells and cardiomyocytes.

CONCLUSIONS

Our study did not demonstrate a clear advantage between the two three-dimensional methods for the quality parameters assessed. This analysis adds support to the use of bioreactor systems for large scale expansion of PSCs, demonstrating that the cells retain key characteristics of PSCs and differentiation potential in suspension culture.

The Exciting Realities and Possibilities of iPS-Derived Cardiomyocytes

Induced pluripotent stem cells (iPSCs) have become a prevalent topic after their discovery, advertised as an ethical alternative to embryonic stem cells (ESCs). Due to their ability to differentiate into several kinds of cells, including cardiomyocytes, researchers quickly realized the potential for differentiated cardiomyocytes to be used in the treatment of heart failure, a research area with few alternatives. This paper discusses the differentiation process for human iPSC-derived cardiomyocytes and the possible applications of said cells while answering some questions regarding ethical issues.

Recent advances in biological pumps as a building block for bioartificial hearts

The field of biological pumps is a subset of cardiac tissue engineering and focused on the development of tubular grafts that are designed generate intraluminal pressure. In the simplest embodiment, biological pumps are tubular grafts with contractile cardiomyocytes on the external surface. The rationale for biological pumps is a transition from planar 3D cardiac patches to functional biological pumps, on the way to complete bioartificial hearts. Biological pumps also have applications as a standalone device, for example, to support the Fontan circulation in pediatric patients. In recent years, there has been a lot of progress in the field of biological pumps, with innovative fabrication technologies. Examples include the use of cell sheet engineering, self-organized heart muscle, bioprinting and in vivo bio chambers for vascularization. Several materials have been tested for biological pumps and included resected aortic segments from rodents, type I collagen, and fibrin hydrogel, to name a few. Multiple bioreactors have been tested to condition biological pumps and replicate the complex in vivo environment during controlled in vitro culture. The purpose of this article is to provide an overview of the field of the biological pumps, outlining progress in the field over the past several years. In particular, different fabrication methods, biomaterial platforms for tubular grafts and examples of bioreactors will be presented. In addition, we present an overview of some of the challenges that need to be overcome for the field of biological pumps to move forward.

Small molecule-mediated rapid maturation of human induced pluripotent stem cell-derived cardiomyocytes

BACKGROUND

Human induced pluripotent stem cell (iPSC)-derived cardiomyocytes (iPSC-CMs) do not display all hallmarks of mature primary cardiomyocytes, especially the ability to use fatty acids (FA) as an energy source, containing high mitochondrial mass, presenting binucleation and increased DNA content per nuclei (polyploidism), and synchronized electrical conduction. This immaturity represents a bottleneck to their application in (1) disease modelling-as most cardiac (genetic) diseases have a middle-age onset-and (2) clinically relevant models, where integration and functional coupling are key. So far, several methods have been reported to enhance iPSC-CM maturation; however, these protocols are laborious, costly, and not easily scalable. Therefore, we developed a simple, low-cost, and rapid protocol to promote cardiomyocyte maturation using two small molecule activators of the peroxisome proliferator-activated receptor β/δ and gamma coactivator 1-alpha (PPAR/PGC-1α) pathway: asiatic acid (AA) and GW501516 (GW). METHODS AND RESULTS: Monolayers of iPSC-CMs were incubated with AA or GW every other day for ten days resulting in increased expression of FA metabolism-related genes and markers for mitochondrial activity. AA-treated iPSC-CMs responsiveness to the mitochondrial respiratory chain inhibitors increased and exhibited higher flexibility in substrate utilization. Additionally, structural maturity improved after treatment as demonstrated by an increase in mRNA expression of sarcomeric-related genes and higher nuclear polyploidy in AA-treated samples. Furthermore, treatment led to increased ion channel gene expression and protein levels.

CONCLUSIONS

Collectively, we developed a fast, easy, and economical method to induce iPSC-CMs maturation via PPAR/PGC-1α activation. Treatment with AA or GW led to increased metabolic, structural, functional, and electrophysiological maturation, evaluated using a multiparametric quality assessment.

Metabolic Maturation Increases Susceptibility to Hypoxia-induced Damage in Human iPSC-derived Cardiomyocytes

The development of new cardioprotective approaches using in vivo models of ischemic heart disease remains challenging as differences in cardiac physiology, phenotype, and disease progression between humans and animals influence model validity and prognostic value. Furthermore, economical and ethical considerations have to be taken into account, especially when using large animal models with relevance for conducting preclinical studies. The development of human-induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) has opened new opportunities for in vitro studies on cardioprotective compounds. However, the immature cellular phenotype of iPSC-CMs remains a roadblock for disease modeling. Here, we show that metabolic maturation renders the susceptibility of iPSC-CMs to hypoxia further toward a clinically representative phenotype. iPSC-CMs cultured in a conventional medium did not show significant cell death after exposure to hypoxia. In contrast, metabolically matured (MM) iPSC-CMs showed inhibited mitochondrial respiration after exposure to hypoxia and increased cell death upon increased durations of hypoxia. Furthermore, we confirmed the applicability of MM iPSC-CMs for in vitro studies of hypoxic damage by validating the known cardioprotective effect of necroptosis inhibitor necrostatin-1. Our results provide important steps to improving and developing valid and predictive human in vitro models of ischemic heart disease.

High-efficient serum-free differentiation of endothelial cells from human iPS cells

Introduction

Endothelial cells (ECs) form the inner lining of all blood vessels of the body play important roles in vascular tone regulation, hormone secretion, anticoagulation, regulation of blood cell adhesion and immune cell extravasation. Limitless ECs sources are required to further in vitro investigations of ECs’ physiology and pathophysiology as well as for tissue engineering approaches. Ideally, the differentiation protocol avoids animal-derived components such as fetal serum and yields ECs at efficiencies that make further sorting obsolete for most applications.

Method

Human induced pluripotent stem cells (hiPSCs) are cultured under serum-free conditions and induced into mesodermal progenitor cells via stimulation of Wnt signaling for 24 h. Mesodermal progenitor cells are further differentiated into ECs by utilizing a combination of human vascular endothelial growth factor A165 (VEGF), basic fibroblast growth factor (bFGF), 8-Bromoadenosine 3′,5′-cyclic monophosphate sodium salt monohydrate (8Bro) and melatonin (Mel) for 48 h.

Result

This combination generates hiPSC derived ECs (hiPSC-ECs) at a fraction of 90.9 ± 1.5% and is easily transferable from the two-dimensional (2D) monolayer into three-dimensional (3D) scalable bioreactor suspension cultures. hiPSC-ECs are positive for CD31, VE-Cadherin, von Willebrand factor and CD34. Furthermore, the majority of hiPSC-ECs express the vascular endothelial marker CD184 (CXCR4).

Conclusion

The differentiation method presented here generates hiPSC-ECs in only 6 days, without addition of animal sera and at high efficiency, hence providing a scalable source of hiPSC-ECs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02924-x.

Follistatin-like 1 promotes proliferation of matured human hypoxic iPSC-cardiomyocytes and is secreted by cardiac fibroblasts

The human heart has limited regenerative capacity. Therefore, patients often progress to heart failure after ischemic injury, despite advances in reperfusion therapies generally decreasing mortality. Depending on its glycosylation state, Follistatin-like 1 (FSTL1) has been shown to increase cardiomyocyte (CM) proliferation, decrease CM apoptosis, and prevent cardiac rupture in animal models of ischemic heart disease. To explore its therapeutic potential, we used a human in vitro model of cardiac ischemic injury with human induced pluripotent stem cell-derived CMs (iPSC-CMs) and assessed regenerative effects of two differently glycosylated variants of human FSTL1. Furthermore, we investigated the FSTL1-mediated interplay between human cardiac fibroblasts (cFBs) and iPSC-CMs in hypoxia. Both FSTL1 variants increased viability, while only hypo-glycosylated FSTL1 increased CM proliferation post-hypoxia. Human fetal cardiac fibroblasts (fcFBs) expressed and secreted FSTL1 under normoxic conditions, while FSTL1 secretion increased by iPSC-cFBs upon hypoxia but decreased in iPSC-CMs. Co-culture of iPSC-CMs and cFBs increased FSTL1 secretion compared with cFB mono-culture. Taken together, we confirm that FSTL1 induces iPSC-CM proliferation in a human cardiac in vitro hypoxia damage model. Furthermore, we show hypoxia-related FSTL1 secretion by human cFBs and indications for FSTL1-mediated intercellular communication between cardiac cell types in response to hypoxic conditions.

Modeling hypertrophic cardiomyopathy with human cardiomyocytes derived from induced pluripotent stem cells

One of the obstacles in studying the pathogenesis of hypertrophic cardiomyopathy (HCM) is the poor availability of myocardial tissue samples at the early stages of disease development. This has been addressed by the advent of induced pluripotent stem cells (iPSCs), which allow us to differentiate patient-derived iPSCs into cardiomyocytes (iPSC-CMs) in vitro. In this review, we summarize different approaches to establishing iPSC models and the application of genome editing techniques in iPSC. Because iPSC-CMs cultured at the present stage are immature in structure and function, researchers have attempted several methods to mature iPSC-CMs, such as prolonged culture duration, and mechanical and electrical stimulation. Currently, many researchers have established iPSC-CM models of HCM and employed diverse methods for performing measurements of cellular morphology, contractility, electrophysiological property, calcium handling, mitochondrial function, and metabolism. Here, we review published results in humans to date within the growing field of iPSC-CM models of HCM. Although there is no unified consensus, preliminary results suggest that this approach to modeling disease would provide important insights into our understanding of HCM pathogenesis and facilitate drug development and safety testing.

Engineering of cardiac microtissues by microfluidic cell encapsulation in thermoshrinking non-crosslinked PNIPAAm gels

Multicellular agglomerates in form of irregularly shaped or spherical clusters can recapitulate cell-cell interactions and are referred to as microtissues. Microtissues gain increasing attention in several fields including cardiovascular research. Cardiac microtissues are evolving as excellent model systems for drug testing in vitro (organ-on-a-chip), are used as tissue bricks in 3D printing processes and pave the way for improved cell replacement therapies in vivo. Microtissues are formed for example in hanging drop culture or specialized microwell plates; truly scalable methods are not yet available. In this study, a novel method of encapsulation of cells in Poly-N-isopropylacrylamid (PNIPAAm) spheres is introduced. Murine induced pluripotent stem cell-derived cardiomyocytes (CMs) and bone marrow-derived mesenchymal stem cells (MSCs) were encapsulated in PNIPAAm by raising the temperature of droplets formed in a microfluidics setup above the lower critical solute temperature (LCST) of 32°C. PNIPAAM precipitates to a water-insoluble physically linked gel above the LCST and shrinks by the expulsion of water, thereby trapping the cells in a collapsing polymer network and increasing the cell density by one order of magnitude. Within 24 hours, stable cardiac microtissues were first formed and later released from their polymer shell by washout of PNIPAAm at temperatures below the LCST. Rhythmically contracting microtissues showed homogenous cell distribution, age-dependent sarcomere organizations and action potential generation. The novel approach is applicable for microtissue formation from various cell types and can be implemented into scalable workflows.

Scalable manufacturing of clinical-grade differentiated cardiomyocytes derived from human-induced pluripotent stem cells for regenerative therapy

Basic research on human pluripotent stem cell (hPSC)‐derived cardiomyocytes (CMs) for cardiac regenerative therapy is one of the most active and complex fields to achieve this alternative to heart transplantation and requires the integration of medicine, science, and engineering. Mortality in patients with heart failure remains high worldwide. Although heart transplantation is the sole strategy for treating severe heart failure, the number of donors is limited. Therefore, hPSC‐derived CM (hPSC‐CM) transplantation is expected to replace heart transplantation. To achieve this goal, for basic research, various issues should be considered, including how to induce hPSC proliferation efficiently for cardiac differentiation, induce hPSC‐CMs, eliminate residual undifferentiated hPSCs and non‐CMs, and assess for the presence of residual undifferentiated hPSCs in vitro and in vivo. In this review, we discuss the current stage of resolving these issues and future directions for realizing hPSC‐based cardiac regenerative therapy.

Stem Cell Differentiation into Cardiomyocytes: Current Methods and Emerging Approaches

Cardiovascular diseases (CVDs) are globally known to be important causes of mortality and disabilities. Common treatment strategies for CVDs, such as pharmacological therapeutics impose serious challenges due to the failure of treatments for myocardial necrosis. By contrast, stem cells (SCs) based therapies are seen to be promising approaches to CVDs treatment. In such approaches, cardiomyocytes are differentiated from SCs. To fulfill SCs complete potential, the method should be appointed to generate cardiomyocytes with more mature structure and well-functioning operations. For heart repairing applications, a greatly scalable and medical-grade cardiomyocyte generation must be used. Nonetheless, there are some challenges such as immune rejection, arrhythmogenesis, tumorigenesis, and graft cell death potential. Herein, we discuss the types of potential SCs, and commonly used methods including embryoid bodies related techniques, co-culture, mechanical stimulation, and electrical stimulation and their applications, advantages and limitations in this field. An estimated 17.9 million people died from CVDs in 2019, representing 32 % of all global deaths. Of these deaths, 85 % were due to heart attack and stroke.

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

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

The porcupine inhibitor WNT974 provokes ectodermal lineage differentiation of human embryonic stem cells

Porcupine (Porcn) enzyme plays an essential role in Wnt signaling activation. Stearoyl-CoA desaturase-1 (SCD1) is required to provide Porcn substrates. The aim of this study was to determine the effect of a novel Porcn inhibitor on the fate of human embryonic stem cells (hESCs) and the reliance of Porcn on SCD1 activity. hESCs were cultured on a feeder layer or Matrigel-coated plates. Small molecules WNT974 (LGK-974) and CAY10566 were used to inhibit Porcn and SCD1 activity, respectively. We assessed the effect of Porcn inhibition on viability, expression of Wnt signaling targets, pluripotency markers, proliferation, differentiation, and protein fatty acylation. hESCs' conditioned medium (CM) containing secreted Wnt proteins were applied in rescue experiments. To examine the catalytic dependency of Porcn on SCD1, the results of combined inhibitor treatment were compared with the SCD1 inhibitor alone. LGK-974 at the selected concentrations showed mild effects on hESCs viability, but significantly reduced messenger RNA and protein expression of Wnt signaling targets (Axin-2 and c-Myc) and pluripotency markers (OCT-4 and SOX-2) (p < .05). Adding 1 μM of Porcn inhibitor reduced proliferation (p = .03) and enhanced differentiation capacity into ectodermal progenitors (p = .02), which were reverted by CM. Click chemistry reaction did not show significant alteration in protein fatty acylation upon LGK-974 treatment. Moreover, combined inhibitor treatment caused no further substantial reduction in Wnt signaling targets, pluripotency markers, and protein fatty acylation relative to CAY10566-treated cultures. The substrate availability for Porcn activity is regulated by SCD1 and targeting Porcn by LGK-974 prompts the transition of hESCs from self-renewal state to ectodermal lineage.

Temporal Control of the WNT Signaling Pathway During Cardiac Differentiation Impacts Upon the Maturation State of Human Pluripotent Stem Cell Derived Cardiomyocytes

Inefficient differentiation and insufficient maturation are barriers to the application of human pluripotent stem cell (hPSC)-derived cardiomyocytes (CMs) for research and therapy. Great strides have been made to the former, and multiple groups have reported cardiac differentiation protocol that can generate hPSC-CMs at high efficiency. Although many such protocols are based on the modulation of the WNT signaling pathway, they differ in their timing and in the WNT inhibitors used. Little is currently known about whether and how conditions of differentiation affect cardiac maturation. Here we adapted multiple cardiac differentiation protocols to improve cost-effectiveness and consistency, and compared the properties of the hPSC-CMs generated. Our results showed that the schedule of differentiation, but not the choice of WNT inhibitors, was a critical determinant not only of differentiation efficiency, which was expected, but also CM maturation. Among cultures with comparable purity, hPSC-CMs generated with different differentiation schedules vary in the expression of genes which are important for developmental maturation, and in their structural, metabolic, calcium transient and proliferative properties. In summary, we demonstrated that simple changes in the schedule of cardiac differentiation could promote maturation. To this end, we have optimized a cardiac differentiation protocol that can simultaneously achieve high differentiation efficiency and enhanced developmental maturation. Our findings would advance the production of hPSC-CMs for research and therapy.

Advances in Manufacturing Cardiomyocytes from Human Pluripotent Stem Cells

The emergence of human pluripotent stem cell (hPSC) technology over the past two decades has provided a source of normal and diseased human cells for a wide variety of in vitro and in vivo applications. Notably, hPSC-derived cardiomyocytes (hPSC-CMs) are widely used to model human heart development and disease and are in clinical trials for treating heart disease. The success of hPSC-CMs in these applications requires robust, scalable approaches to manufacture large numbers of safe and potent cells. Although significant advances have been made over the past decade in improving the purity and yield of hPSC-CMs and scaling the differentiation process from 2D to 3D, efforts to induce maturation phenotypes during manufacturing have been slow. Process monitoring and closed-loop manufacturing strategies are just being developed. We discuss recent advances in hPSC-CM manufacturing, including differentiation process development and scaling and downstream processes as well as separation and stabilization. Expected final online publication date for the Annual Review of Chemical and Biomolecular Engineering, Volume 13 is October 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Regenerative Neurology and Regenerative Cardiology: Shared Hurdles and Achievements

From the first success in cultivation of cells in vitro, it became clear that developing cell and/or tissue specific cultures would open a myriad of new opportunities for medical research. Expertise in various in vitro models has been developing over decades, so nowadays we benefit from highly specific in vitro systems imitating every organ of the human body. Moreover, obtaining sufficient number of standardized cells allows for cell transplantation approach with the goal of improving the regeneration of injured/disease affected tissue. However, different cell types bring different needs and place various types of hurdles on the path of regenerative neurology and regenerative cardiology. In this review, written by European experts gathered in Cost European action dedicated to neurology and cardiology-Bioneca, we present the experience acquired by working on two rather different organs: the brain and the heart. When taken into account that diseases of these two organs, mostly ischemic in their nature (stroke and heart infarction), bring by far the largest burden of the medical systems around Europe, it is not surprising that in vitro models of nervous and heart muscle tissue were in the focus of biomedical research in the last decades. In this review we describe and discuss hurdles which still impair further progress of regenerative neurology and cardiology and we detect those ones which are common to both fields and some, which are field-specific. With the goal to elucidate strategies which might be shared between regenerative neurology and cardiology we discuss methodological solutions which can help each of the fields to accelerate their development.

Assessment of the Hematopoietic Differentiation Potential of Human Pluripotent Stem Cells in 2D and 3D Culture Systems

BACKGROUND

In vitro methods for hematopoietic differentiation of human pluripotent stem cells (hPSC) are a matter of priority for the in-depth research into the mechanisms of early embryogenesis. So-far, published results regarding the generation of hematopoietic cells come from studies using either 2D or 3D culture formats, hence, it is difficult to discern their particular contribution to the development of the concept of a unique in vitro model in close resemblance to in vivo hematopoiesis.

AIM OF THE STUDY

To assess using the same culture conditions and the same time course, the potential of each of these two formats to support differentiation of human pluripotent stem cells to primitive hematopoiesis without exogenous activation of Wnt signaling.

METHODS

We used in parallel 2D and 3D formats, the same culture environment and assay methods (flow cytometry, IF, qPCR) to investigate stages of commitment and specification of mesodermal, and hemogenic endothelial cells to CD34 hematopoietic cells and evaluated their clonogenic capacity in a CFU system.

RESULTS

We show an adequate formation of mesoderm, an efficient commitment to hemogenic endothelium, a higher number of CD34 hematopoietic cells, and colony-forming capacity potential only in the 3D format-supported differentiation.

CONCLUSIONS

This study shows that the 3D but not the 2D format ensures the induction and realization by endogenous mechanisms of human pluripotent stem cells' intrinsic differentiation program to primitive hematopoietic cells. We propose that the 3D format provides an adequate level of upregulation of the endogenous Wnt/β-catenin signaling.

Scalable Generation of Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes

Human induced pluripotent stem cells (hiPSCs) can be expanded at limitless scale in vitro and give rise to various organotypic cells, cardiomyocytes (CMs) among them. Advanced protocols shape the differentiation process of pluripotent stem cells by controlled growth factor application. Modulating the Wnt signaling pathway is effective to direct hiPSCs to CMs (hiPSC-CMs) and native growth factors were replaced by small chemical compounds. Here, we describe a refined protocol for scalable generation of hiPSC-CMs that manipulates porcupine and tankyrase sub-pathways of Wnt signaling for tight inhibition of non-canonical Wnt signaling. The approach results in a differentiation efficiency toward hiPSC-CMs of 87 ± 0.9% in stirred bioreactor cultures and yields about 70 million hiPSC-CMs per 100 mL serum free cardiac differentiation medium. The differentiation protocol is easily adapted from 3D to 2D culture and vice versa and has been demonstrated to work with different hiPSC lines.

Environmental Alterations during Embryonic Development: Studying the Impact of Stressors on Pluripotent Stem Cell-Derived Cardiomyocytes

Non-communicable diseases (NCDs) sauch as diabetes, obesity and cardiovascular diseases are rising rapidly in all countries world-wide. Environmental maternal factors (e.g., diet, oxidative stress, drugs and many others), maternal illnesses and other stressors can predispose the newborn to develop diseases during different stages of life. The connection between environmental factors and NCDs was formulated by David Barker and colleagues as the Developmental Origins of Health and Disease (DOHaD) hypothesis. In this review, we describe the DOHaD concept and the effects of several environmental stressors on the health of the progeny, providing both animal and human evidence. We focus on cardiovascular diseases which represent the leading cause of death worldwide. The purpose of this review is to discuss how in vitro studies with pluripotent stem cells (PSCs), such as embryonic and induced pluripotent stem cells (ESC, iPSC), can underpin the research on non-genetic heart conditions. The PSCs could provide a tool to recapitulate aspects of embryonic development “in a dish”, studying the effects of environmental exposure during cardiomyocyte (CM) differentiation and maturation, establishing a link to molecular mechanism and epigenetics.

Modeling genetic cardiac channelopathies using induced pluripotent stem cells - Status quo from an electrophysiological perspective

Long QT syndrome (LQTS), Brugada syndrome (BrS), and catecholaminergic polymorphic ventricular tachycardia (CPVT) are genetic diseases of the heart caused by mutations in specific cardiac ion channels and are characterized by paroxysmal arrhythmias, which can deteriorate into ventricular fibrillation. In LQTS3 and BrS different mutations in the SCN5A gene lead to a gain-or a loss-of-function of the voltage-gated sodium channel Nav1.5, respectively. Although sharing the same gene mutation, these syndromes are characterized by different clinical manifestations and functional perturbations and in some cases even present an overlapping clinical phenotype. Several studies have shown that Na⁺ current abnormalities in LQTS3 and BrS can also cause Ca²⁺-signaling aberrancies in cardiomyocytes (CMs). Abnormal Ca²⁺ homeostasis is also the main feature of CPVT which is mostly caused by heterozygous mutations in the RyR2 gene. Large numbers of disease-causing mutations were identified in RyR2 and SCN5A but it is not clear how different variants in the SCN5A gene produce different clinical syndromes and if in CPVT Ca²⁺ abnormalities and drug sensitivities vary depending on the mutation site in the RyR2. These questions can now be addressed by using patient-specific in vitro models of these diseases based on induced pluripotent stem cells (iPSCs). In this review, we summarize different insights gained from these models with a focus on electrophysiological perturbations caused by different ion channel mutations and discuss how will this knowledge help develop better stratification and more efficient personalized therapies for these patients.

QuinoMit Q10-Fluid attenuates hydrogen peroxide-induced irregular beating in mouse pluripotent stem cell-derived cardiomyocytes

BACKGROUND

Coenzyme Q10 (CoQ10) is a crucial component of the mitochondrial structure which is involved in producing more than 90% of cellular ATP. This study aimed to investigate the protective effects and underlying mechanisms of QuinoMit Q10-Fluid against hydrogen peroxide (H₂O₂)-induced arrhythmias on cardiomyocytes (CMs).

METHODS

Undifferentiated stem cell-derived CMs were cultured in the presence of different concentrations of QuinoMit Q10-Fluid. To investigate if CoQ10 has anti-apoptotic activity, CMs were exposed to H₂O₂ for up to 100 h with or without CoQ10. The expression levels of cardiac reference genes were determined by RT-PCR. The structural and functional properties of CMs were examined by immunofluorescence and the xCELLigence system. Caspase 3/7 assay was also performed for cell apoptosis study.

RESULTS

The study showed that QuinoMit Q10-Fluid inhibits the proliferation of pluripotent stem cells at high concentrations and had less effect on cardiomyogenesis. However, the beating rate of clusters containing CMs generated under QuinoMit Q10-Fluid (1:100) was significantly increased. This increase was accompanied by the up-regulated expression level of some important cardiac markers during differentiation. Treatment of CMs with H₂O₂ notably induced irregular beating and decreased the amplitude of the beating signal of CMs, concomitantly with increased caspase-3/7 activity. However, CMs pretreated with QuinoMit exhibited a protective effect against H₂O₂-induced arrhythmia.

CONCLUSION

Our results reveal that QuinoMit Q10-Fluid attenuates H₂O₂-induced irregular beating in mouse pluripotent stem cell-derived CMs, at least partly by reducing the generation of ROS, suggesting a protective effect against CM dysfunctions.

Pharmacological Manipulation of Wnt/β-Catenin Signaling Pathway in Human Neural Precursor Cells Alters Their Differentiation Potential and Neuronal Yield

The canonical Wnt/β-catenin pathway is a master-regulator of cell fate during embryonic and adult neurogenesis and is therefore a major pharmacological target in basic and clinical research. Chemical manipulation of Wnt signaling during in vitro neuronal differentiation of stem cells can alter both the quantity and the quality of the derived neurons. Accordingly, the use of Wnt activators and blockers has become an integral part of differentiation protocols applied to stem cells in recent years. Here, we investigated the effects of the glycogen synthase kinase-3β inhibitor CHIR99021, which upregulates β-catenin agonizing Wnt; and the tankyrase-1/2 inhibitor XAV939, which downregulates β-catenin antagonizing Wnt. Both drugs and their potential neurogenic and anti-neurogenic effects were studied using stable lines human neural precursor cells (hNPCs), derived from embryonic stem cells, which can be induced to generate mature neurons by chemically-defined conditions. We found that Wnt-agonism by CHIR99021 promotes induction of neural differentiation, while also reducing cell proliferation and survival. This effect was not synergistic with those of pro-neural growth factors during long-term neuronal differentiation. Conversely, antagonism of Wnt by XAV939 consistently prevented neuronal progression of hNPCs. We show here how these two drugs can be used to manipulate cell fate and how self-renewing hNPCs can be used as reliable human in vitro drug-screening platforms.

Application of Patient-Specific iPSCs for Modelling and Treatment of X-Linked Cardiomyopathies

Inherited cardiomyopathies are among the major causes of heart failure and associated with significant mortality and morbidity. Currently, over 70 genes have been linked to the etiology of various forms of cardiomyopathy, some of which are X-linked. Due to the lack of appropriate cell and animal models, it has been difficult to model these X-linked cardiomyopathies. With the advancement of induced pluripotent stem cell (iPSC) technology, the ability to generate iPSC lines from patients with X-linked cardiomyopathy has facilitated in vitro modelling and drug testing for the condition. Nonetheless, due to the mosaicism of the X-chromosome inactivation, disease phenotypes of X-linked cardiomyopathy in heterozygous females are also usually more heterogeneous, with a broad spectrum of presentation. Recent advancements in iPSC procedures have enabled the isolation of cells with different lyonisation to generate isogenic disease and control cell lines. In this review, we will summarise the current strategies and examples of using an iPSC-based model to study different types of X-linked cardiomyopathy. The potential application of isogenic iPSC lines derived from a female patient with heterozygous Danon disease and drug screening will be demonstrated by our preliminary data. The limitations of an iPSC-derived cardiomyocyte-based platform will also be addressed.

Transcryptomic Analysis of Human Brain -Microvascular Endothelial Cell Driven Changes in -Vascular Pericytes

Many pathological conditions of the brain are associated with structural abnormalities within the neurovascular system and linked to pericyte (PC) loss and/or dysfunction. Since crosstalk between endothelial cells (ECs) and PCs greatly impacts the function of the blood–brain barrier (BBB), effects of PCs on endothelial integrity and function have been investigated extensively. However, the impact of ECs on the function and activity of PCs remains largely unknown. Hence, using co-cultures of human brain vascular PCs with human cerebral microvascular ECs on opposite sides of porous Transwell inserts which facilitates direct EC–PC contact and improves EC barrier function, we analyzed EC-driven transcriptomic changes in PCs using microarrays and changes in cytokines/chemokines using proteome arrays. Gene expression analysis (GEA) in PCs co-cultured with ECs versus PCs cultured alone showed significant upregulation of 1′334 genes and downregulation of 964 genes. GEA in co-cultured PCs revealed increased expression of five prominent PC markers as well as soluble factors, such as transforming growth factor beta, fibroblast growth factor, angiopoietin 1, brain-derived neurotrophic factor, all of which are involved in EC–PC crosstalk and BBB induction. Pathway enrichment analysis of modulated genes showed a strong impact on many inflammatory and extracellular matrix (ECM) pathways including interferon and interleukin signaling, TGF-β and interleukin-1 regulation of ECM, as well as on the mRNA processing pathway. Interestingly, while co-culture induced the mRNA expression of many chemokines and cytokines, including several CCL- and CXC-motif ligands and interleukins, we observed a decreased expression of the same inflammatory mediators on the protein level. Importantly, in PCs, ECs significantly induced interferon associated proteins (IFIT1, IFI44L, IF127, IFIT3, IFI6, IFI44) with anti-viral actions; downregulated prostaglandin E receptor 2 (prevent COX-2 mediated BBB damage); upregulated fibulin-3 and connective tissue growth factor essential for BBB integrity; and multiple ECMs (collagens and integrins) that inhibit cell migration. Our findings suggest that via direct contact, ECs prime PCs to induce molecules to promote BBB integrity and cell survival during infection and inflammatory insult. Taken together, we provide first evidence that interaction with ECs though porous membranes induces major changes in the transcriptomic and proteomic profile of PCs. ECs influence genes involved in diverse aspects of PC function including PC maturation, cell survival, anti-viral defense, blood flow regulation, immuno-modulation and ECM deposition.

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.

Cell surface markers for immunophenotyping human pluripotent stem cell-derived cardiomyocytes

Human pluripotent stem cells (hPSC) self-renew and represent a potentially unlimited source for the production of cardiomyocytes (CMs) suitable for studies of human cardiac development, drug discovery, cardiotoxicity testing, and disease modelling and for cell-based therapies. However, most cardiac differentiation protocols yield mixed cultures of atrial-, ventricular-, and pacemaker-like cells at various stages of development, as well as non-CMs. The proportions and maturation states of these cell types result from disparities among differentiation protocols and time of cultivation, as well as hPSC reprogramming inconsistencies and genetic background variations. The reproducible use of hPSC-CMs for research and therapy is therefore limited by issues of cell population heterogeneity and functional states of maturation. A validated method that overcomes issues of cell heterogeneity is immunophenotyping coupled with live cell sorting, an approach that relies on accessible surface markers restricted to the desired cell type(s). Here we review current progress in unravelling heterogeneity in hPSC-cardiac cultures and in the identification of surface markers suitable for defining cardiac identity, subtype specificity, and maturation states.

Transcryptomic Analysis of Human Brain-Microvascular Endothelial Response to -Pericytes: Cell Orientation Defines Barrier Function

Pericytes facilitate blood-brain barrier (BBB) integrity; however, the mechanisms involved remain unclear. Hence, using co-cultures of human cerebral microvascular endothelial cells (ECs) and vascular pericytes (PCs) in different spatial arrangements, as well as PC conditioned media, we investigated the impact of PC-EC orientation and PC-derived soluble factors on EC barrier function. We provide the first evidence that barrier-inducing properties of PCs require basolateral contact with ECs. Gene expression analysis (GEA) in ECs co-cultured with PCs versus ECs alone showed significant upregulation of 38 genes and downregulation of 122 genes. Pathway enrichment analysis of modulated genes showed significant regulation of several pathways, including transforming growth factor-β and interleukin-1 regulated extracellular matrix, interferon and interleukin signaling, immune system signaling, receptor of advanced glycation end products (RAGE), and cytokine-cytokine receptor interaction. Transcriptomic analysis showed a reduction in molecules such as pro-inflammatory cytokines and chemokines, which are known to be induced during BBB disruption. Moreover, cytokine proteome array confirmed the downregulation of key pro-inflammatory cytokines and chemokines on the protein level. Other molecules which influence BBB and were favorably modulated upon EC-PC co-culture include IL-18 binding protein, kallikrein-3, CSF2 CSF3, CXCL10, CXCL11 (downregulated) and IL-1-R4; HGF, PDGF-AB/BB, PECAM, SERPIN E1 (upregulated). In conclusion, we provide the first evidence that (1) basolateral contact between ECs and PCs is essential for EC barrier function and integrity; (2) in ECs co-cultured with PCs, the profile of BBB disrupting pro-inflammatory molecules and cytokines/chemokines is downregulated; (3) PCs significantly modulate EC mechanisms known to improve barrier function, including TGF-β regulated ECM pathway, anti-inflammatory cytokines, growth factors and matrix proteins. This human PC-EC co-culture may serve as a viable in vitro model for investigating BBB function and drug transport.

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.

Current Challenges and Solutions to Tissue Engineering of Large-scale Cardiac Constructs

PURPOSE OF REVIEW

Large-scale tissue engineering of cardiac constructs is a rapidly advancing field; however, there are several barriers still associated with the creation and clinical application of large-scale engineered cardiac tissues. We provide an overview of the current challenges and recently (within the last 5 years) described promising solutions to overcoming said challenges.

RECENT FINDINGS

The five major criteria yet to be met for clinical application of engineered cardiac tissues are successful electrochemical/mechanical cell coupling, efficient maturation of cardiomyocytes, functional vascularization of large tissues, balancing appropriate immune response, and large-scale generation of constructs. Promising solutions include the use of carbon/graphene in conjunction with existing scaffold designs, utilization of biological hormones, 3D bioprinting, and gene editing. While some of the described barriers to generation of large-scale cardiac tissue have seen encouraging advancements, there is no solution that yet achieves all 5 described criteria. It is vital then to consider a combination of techniques to achieve the optimal construct. Critically, following the demonstration of a viable construct, there remain important considerations to address associated with good manufacturing practices and establishing a standard for clinical trials.

Recent advances in organoid development and applications in disease modeling

An improved understanding of stem cell niches, organogenesis, and disease models has paved the way for developing a three-dimensional (3D) organoid culture system. Organoid cultures can be derived from primary tissues (single cells or tissue subunits), adult stem cells (ASCs), induced pluripotent stem cells (iPSCs), or embryonic stem cells (ESCs). As a significant technological breakthrough, 3D organoid models offer a promising approach for understanding the complexities of human diseases ranging from the mechanistic investigation of disease pathogenesis to therapy. Here, we discuss the recent applications, advantages, and limitations of organoids as in vitro models for studying metabolomics, drug development, infectious diseases, and the gut microbiome. We further discuss the use of organoids in cancer modeling using high throughput sequencing approaches.

Human Induced Pluripotent Stem Cells as a Disease Model System for Heart Failure

PURPOSE OF REVIEW

Heart failure is among the most prevalent disease complexes overall and is associated with high morbidity and mortality. The underlying aetiology is manifold including coronary artery disease, genetic alterations and mutations, viral infections, adverse immune responses, and cardiac toxicity. To date, no specific therapies have been developed despite notable efforts. This can especially be attributed to hurdles in translational research, mainly due to the lack of proficient models of heart failure limited translation of therapeutic approaches from bench to bedside.

RECENT FINDINGS

Human induced pluripotent stem cells (hiPSCs) are rising in popularity, granting the ability to divide infinitely, to hold human, patient-specific genome, and to differentiate into any human cell, including cardiomyocytes (hiPSC-CMs). This brings magnificent promise to cardiological research, providing the possibility to recapitulate cardiac diseases in a dish. Advances in yield, maturity, and in vivo resemblance due to straightforward, low-cost protocols, high-throughput approaches, and complex 3D cultures have made this tool widely applicable. In recent years, hiPSC-CMs have been used to model a wide variety of cardiac diseases, bringing along the possibility to not only elucidate molecular mechanisms but also to test novel therapeutic approaches in the dish. Within the last decade, hiPSC-CMs have been exponentially employed to model heart failure. Constant advancements are aiming at improvements of differentiation protocols, hiPSC-CM maturity, and assays to elucidate molecular mechanisms and cellular functions. However, hiPSC-CMs are remaining relatively immature, and in vitro models can only partially recapitulate the complex interactions in vivo. Nevertheless, hiPSC-CMs have evolved as an essential model system in cardiovascular research.

Immunomodulation by systemic administration of human-induced pluripotent stem cell-derived mesenchymal stromal cells to enhance the therapeutic efficacy of cell-based therapy for treatment of myocardial infarction

Rationale: Poor survival and engraftment are major hurdles of stem cell therapy in the treatment of myocardial infarction (MI). We sought to determine whether pre-transplantation systemic intravenous administration of human induced pluripotent stem cell (hiPSC)-derived mesenchymal stromal cells (hiPSC-MSCs) could improve the survival of hiPSC-MSCs or hiPSC-derived cardiomyocytes (hiPSC-CMs) following direct intramyocardial transplantation in a mouse model of MI.

Methods: Mice were randomized to undergo intravenous administration of saline or 5×10⁵ hiPSC-MSCs one week prior to MI, induced by ligation of the left anterior descending coronary artery. Mice were further assigned to undergo direct intramyocardial transplantation of hiPSC-MSCs (1×10⁶) or hiPSC-CMs (1×10⁶) 10 minutes following MI. Echocardiographic and invasive hemodynamic assessment were performed to determine cardiac function. In-vivo fluorescent imaging analysis, immunofluorescence staining and polymerase chain reaction were performed to detect cell engraftment. Flow cytometry of splenic regulatory T cells (Tregs) and natural killer (NK) cells was performed to assess the immunomodulatory effects.

Results: Pre-transplantation systemic administration of hiPSC-MSCs increased systemic Tregs activation, decreased the number of splenic NK cells and inflammation, and enhanced survival of transplanted hiPSC-MSCs and hiPSC-CMs. These improvements were associated with increased neovascularization and decreased myocardial inflammation and apoptosis at the peri-infract zone with consequent improved left ventricular function four weeks later. Co-culture of splenic CD4 cells with hiPSC-MSCs also modulated their cytokine expression profile with a decreased level of interferon-γ, tumor necrosis factor-α, and interleukin (IL)-17A, but not IL-2, IL-6 and IL-10.

Conclusion: Pre-transplantation systemic intravenous administration of hiPSC-MSCs induced immunomodulation and facilitated the survival of intramyocardially transplanted cells to improve cardiac function in MI.

Enhancing Matured Stem-Cardiac Cell Generation and Transplantation: A Novel Strategy for Heart Failure Therapy

Heart failure (HF) remains one of the major causes of morbidity and mortality worldwide. Recent studies have shown that stem cells (SCs) including bone marrow mesenchymal stem (BMSC), embryonic bodies (EB), embryonic stem (ESC), human induced pluripotent stem (hiPSC)-derived cardiac cells generation, and transplantation treated myocardial infarction (MI) in vivo and in human. However, the immature phenotypes compromise their clinical application requiring immediate intervention to improve stem-derived cardiac cell (S-CCs) maturation. Recently, an unbiased multi-omic analysis involving genomics, transcriptomics, epigenomics, proteomics, and metabolomics identified specific strategies for the generation of matured S-CCs that may enhance patients' recovery processes upon transplantation. However, these strategies still remain undisclosed. Here, we summarize the recently discovered strategies for the matured S-CC generation. In addition, cardiac patch formation and transplantation that accelerated HF recuperation in clinical trials are discussed. A better understanding of this work may lead to efficient generation of matured S-CCs for regenerative medicine. Graphical abstract.

Intracellular calcium current disorder and disease phenotype in OBSCN mutant iPSC-based cardiomyocytes in arrhythmogenic right ventricular cardiomyopathy

Obscurin participates in the development of striated muscles and maintenance of the functional sarcoplasmic reticulum. However, the role of obscurin in arrhythmogenic right ventricular cardiomyopathy (ARVC) is not well understood. We aimed to study the novel obscurin mutations in the pathogenesis of ARVC and the underlying mechanisms. Methods: We generated induced pluripotent stem cells (iPSC) through retroviral reprogramming of peripheral blood mononuclear cells isolated from a 46-year-old female diagnosed with ARVC, carrying a mutation in OBSCN. The cells differentiated into functional iPSC-based cardiomyocytes (iPSC-CMs), whose phenotype was determined by transmission electron microscopy, electrophysiological description, immunofluorescence staining, and Oil Red O staining. Molecular characterization was performed by bioinformatic analyses, and identification by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting. Results: ARVC-iPSC-CMs mutation in OBSCN showed significant accumulation of lipids, increased pleomorphism, irregular Z-bands, and increased L type calcium currents. Functional enrichment analysis identified pathways involved in focal adhesion and structure formation; the adipocytokines and PPAR signaling pathways were also activated in the ARVC group. Moreover, our results from ultra-high-resolution microscopy, qRT-PCR and Western blotting confirmed that the mutant OBSCN protein and its anchor protein, Ank1.5, showed structural disorder and decreased expression, but there was increased expression of junctional protein N-Cadherin. Further analysis revealed the gene expression of other desmosomal proteins in ARVC-iPSC-CMs was also decreased but some adipogenesis pathway-related proteins (PPARγ, C/EBPα, and FABP4) were increased. Conclusion: A novel frameshift mutation in OBSCN caused phenotypic alteration accompanied by disrupted localization and decreased expression of its anchoring protein Ank1.5. Furthermore, there was an accumulation of lipids with an increase in fatty fibrosis area and myocardial structural disorder, possibly leading to dysrhythmia in calcium channel-related myocardial contraction. These observations suggested the possibility of attenuating ARVC progression by therapeutic modulation of OBSCN expression.

Practical choice for robust and efficient differentiation of human pluripotent stem cells

Human pluripotent stem cells (hPSCs) have the distinct advantage of being able to differentiate into cells of all three germ layers. Target cells or tissues derived from hPSCs have many uses such as drug screening, disease modeling, and transplantation therapy. There are currently a wide variety of differentiation methods available. However, most of the existing differentiation methods are unreliable, with uneven differentiation efficiency and poor reproducibility. At the same time, it is difficult to choose the optimal method when faced with so many differentiation schemes, and it is time-consuming and costly to explore a new differentiation approach. Thus, it is critical to design a robust and efficient method of differentiation. In this review article, we summarize a comprehensive approach in which hPSCs are differentiated into target cells or organoids including brain, liver, blood, melanocytes, and mesenchymal cells. This was accomplished by employing an embryoid body-based three-dimensional (3D) suspension culture system with multiple cells co-cultured. The method has high stable differentiation efficiency compared to the conventional 2D culture and can meet the requirements of clinical application. Additionally, ex vivo co-culture models might be able to constitute organoids that are highly similar or mimic human organs for potential organ transplantation in the future.

Retinoic acid promotes metabolic maturation of human Embryonic Stem Cell-derived Cardiomyocytes

Cardiomyocytes differentiated from human embryonic stem cells (hESCs) represent a promising cell source for heart repair, disease modeling and drug testing. However, improving the differentiation efficiency and maturation of hESC-derived cardiomyocytes (hESC-CMs) is still a major concern. Retinoic acid (RA) signaling plays multiple roles in heart development. However, the effects of RA on cardiomyocyte differentiation efficiency and maturation are still unknown.

Methods: RA was added at different time intervals to identify the best treatment windows for cardiomyocyte differentiation and maturation. The efficiency of cardiomyocyte differentiation was detected by quantitative real-time PCR and flow cytometry. Cardiomyocytes maturation was detected by immunofluorescence staining, metabolic assays and patch clamp to verify structural, metabolic and electrophysiological maturation, respectively. RNA sequencing was used for splicing analysis.

Results: We found that RA treatment at the lateral mesoderm stage (days 2-4) significantly improved cardiomyocyte differentiation, as evidenced by the upregulation of TNNT2, NKX2.5 and MYH6 on day 10 of differentiation. In addition, flow cytometry showed that the proportion of differentiated cardiomyocytes in the RA-treated group was significantly higher than that in control group. RA treatment on days 15-20 increased cardiomyocyte area, sarcomere length, multinucleation and mitochondrial copy number. RNA sequencing revealed RA promoted RNA isoform switch to the maturation-related form. Meanwhile, RA promoted electrophysiological maturation and calcium handling of hESC-CMs. Importantly, RA-treated cardiomyocytes showed decreased glycolysis and enhanced mitochondrial oxidative phosphorylation, with the increased utilization of fatty acid and exogenous pyruvate but not glutamine.

Conclusion: Our data indicated that RA treatment at an early time window (days 2-4) promotes the efficiency of cardiomyocyte differentiation and that RA treatment post beating (days 15-20) promotes cardiomyocyte maturation. The biphasic effects of RA provide new insights for improving cardiomyocyte differentiation and quality.

Automation, Monitoring, and Standardization of Cell Product Manufacturing

Although regenerative medicine products are at the forefront of scientific research, technological innovation, and clinical translation, their reproducibility and large-scale production are compromised by automation, monitoring, and standardization issues. To overcome these limitations, new technologies at software (e.g., algorithms and artificial intelligence models, combined with imaging software and machine learning techniques) and hardware (e.g., automated liquid handling, automated cell expansion bioreactor systems, automated colony-forming unit counting and characterization units, and scalable cell culture plates) level are under intense investigation. Automation, monitoring and standardization should be considered at the early stages of the developmental cycle of cell products to deliver more robust and effective therapies and treatment plans to the bedside, reducing healthcare expenditure and improving services and patient care.

Fgfr3 mutation disrupts chondrogenesis and bone ossification in zebrafish model mimicking CATSHL syndrome partially via enhanced Wnt/β-catenin signaling

CATSHL syndrome, characterized by camptodactyly, tall stature and hearing loss, is caused by loss-of-function mutations of fibroblast growth factor receptors 3 (FGFR3) gene. Most manifestations of patients with CATSHL syndrome start to develop in the embryonic stage, such as skeletal overgrowth, craniofacial abnormalities, however, the pathogenesis of these phenotypes especially the early maldevelopment remains incompletely understood. Furthermore, there are no effective therapeutic targets for this skeleton dysplasia. Methods: We generated fgfr3 knockout zebrafish by CRISPR/Cas9 technology to study the developmental mechanisms and therapeutic targets of CATSHL syndrome. Several zebrafish transgenic lines labeling osteoblasts and chondrocytes, and live Alizarin red staining were used to analyze the dynamical skeleton development in fgfr3 mutants. Western blotting, whole mount in situ hybridization, Edu labeling based cell proliferation assay and Wnt/β-catenin signaling antagonist were used to explore the potential mechanisms and therapeutic targets. Results: We found that fgfr3 mutant zebrafish, staring from early development stage, showed craniofacial bone malformation with microcephaly and delayed closure of cranial sutures, chondroma-like lesion and abnormal development of auditory sensory organs, partially resembling the clinical manifestations of patients with CATSHL syndrome. Further studies showed that fgfr3 regulates the patterning and shaping of pharyngeal arches and the timely ossification of craniofacial skeleton. The abnormal development of pharyngeal arch cartilage is related to the augmented hypertrophy and disordered arrangement of chondrocytes, while decreased proliferation, differentiation and mineralization of osteoblasts may be involved in the delayed maturation of skull bones. Furthermore, we revealed that deficiency of fgfr3 leads to enhanced IHH signaling and up-regulated canonical Wnt/β-catenin signaling, and pharmacological inhibition of Wnt/β-catenin could partially alleviate the phenotypes of fgfr3 mutants. Conclusions: Our study further reveals some novel phenotypes and underlying developmental mechanism of CATSHL syndrome, which deepens our understanding of the pathogenesis of CATSHL and the role of fgfr3 in skeleton development. Our findings provide evidence that modulation of Wnt/β-catenin activity could be a potential therapy for CATSHL syndrome and related skeleton diseases.