The Use of iPSC-Derived Cardiomyocytes and Optical Mapping for Erythromycin Arrhythmogenicity Testing

Advanced Cardiovascular Toxicity Screening: Integrating Human iPSC-Derived Cardiomyocytes with 2D In Silico Models

The pharmaceutical industry is evolving with the use of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) for in vitro cardiac safety screening. Traditional reliance on QT-interval prolongation as a main arrhythmogenicity marker is being challenged. In addition, the Comprehensive In Vitro Proarrhythmia Assay (CiPA) initiative recommends using computer modeling and in silico platforms as a more comprehensive approach for arrhythmogenicity testing in conjunction with hiPSC-CM in vitro screening. Our study presents an innovative platform that integrates in vitro hiPSC-CM propagation test with in silico models to assess the potential arrhythmogenic effect of drug-induced impact on ionic currents and electrophysiological intercellular coupling. Utilizing the electrophysiological and morphological characteristics of hiPSC-CM, we offer a thorough evaluation of potential drug-induced cardiac risks by computer modeling. We show, using the examples of lidocaine (100-300 μM) and Cyclophosphamide (639, 852 μM), that with the use of an integrative experimental and computer platform, it is possible to correctly display the clinical manifestations of side effects in advance.

Arrhythmogenic Potential of Myocardial Edema: The Interstitial Osmolality Induces Spiral Waves and Multiple Excitation Wavelets

Myocardial edema is a common symptom of pathological processes in the heart, causing aggravation of cardiovascular diseases and leading to irreversible myocardial remodeling. Patient-based studies show that myocardial edema is associated with arrhythmias. Currently, there are no studies that have examined how edema may influence changes in calcium dynamics in the functional syncytium. We performed optical mapping of calcium dynamics on a monolayer of neonatal rat cardiomyocytes with Fluo-4. The osmolality of the solutions was adjusted using the NaCl content. The initial Tyrode solution contained 140 mM NaCl (1T) and the hypoosmotic solutions contained 105 (0.75T) and 70 mM NaCl (0.5T). This study demonstrated a sharp decrease in the calcium wave propagation speed with a decrease in the solution osmolality. The successive decrease in osmolality also showed a transition from a normal wavefront to spiral wave and multiple wavelets of excitation with wave break. Our study demonstrated that, in a cellular model, hypoosmolality and, as a consequence, myocardial edema, could potentially lead to fatal ventricular arrhythmias, which to our knowledge has not been studied before. At 0.75T spiral waves appeared, whereas multiple wavelets of excitation occurred in 0.5T, which had not been recorded previously in a two-dimensional monolayer under conditions of cell edema without changes in the pacing protocol.

Human sodium current voltage-dependence at physiological temperature measured by coupling a patch-clamp experiment to a mathematical model

Voltage-gated Na+ channels are crucial to action potential propagation in excitable tissues. Because of the high amplitude and rapid activation of the Na+ current, voltage-clamp measurements are very challenging and are usually performed at room temperature. In this study, we measured Na+ current voltage-dependence in stem cell-derived cardiomyocytes at physiological temperature. While the apparent activation and inactivation curves, measured as the dependence of current amplitude on voltage, fall within the range reported in previous studies, we identified a systematic error in our measurements. This error is caused by the deviation of the membrane potential from the command potential of the amplifier. We demonstrate that it is possible to account for this artifact using computer simulation of the patch-clamp experiment. We obtained surprising results through patch-clamp model optimization: a half-activation of -11.5 mV and a half-inactivation of -87 mV. Although the half-activation deviates from previous research, we demonstrate that this estimate reproduces the conduction velocity dependence on extracellular potassium concentration. KEY POINTS: Voltage-gated Na+ currents play a crucial role in excitable tissues including neurons, cardiac and skeletal muscle. Measurement of Na+ current is challenging because of its high amplitude and rapid kinetics, especially at physiological temperature. We have used the patch-clamp technique to measure human Na+ current voltage-dependence in human induced pluripotent stem cell-derived cardiomyocytes. The patch-clamp data were processed by optimization of the model accounting for voltage-clamp experiment artifacts, revealing a large difference between apparent parameters of Na+ current and the results of the optimization. We conclude that actual Na+ current activation is extremely depolarized in comparison to previous studies. The new Na+ current model provides a better understanding of action potential propagation; we demonstrate that it explains propagation in hyperkalaemic conditions.

Biomimetic Cardiac Tissue Models for In Vitro Arrhythmia Studies

Cardiac arrhythmias are a major cause of cardiovascular mortality worldwide. Many arrhythmias are caused by reentry, a phenomenon where excitation waves circulate in the heart. Optical mapping techniques have revealed the role of reentry in arrhythmia initiation and fibrillation transition, but the underlying biophysical mechanisms are still difficult to investigate in intact hearts. Tissue engineering models of cardiac tissue can mimic the structure and function of native cardiac tissue and enable interactive observation of reentry formation and wave propagation. This review will present various approaches to constructing cardiac tissue models for reentry studies, using the authors' work as examples. The review will highlight the evolution of tissue engineering designs based on different substrates, cell types, and structural parameters. A new approach using polymer materials and cellular reprogramming to create biomimetic cardiac tissues will be introduced. The review will also show how computational modeling of cardiac tissue can complement experimental data and how such models can be applied in the biomimetics of cardiac tissue.

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.

Regeneration of T cells from human-induced pluripotent stem cells for CAR-T cell medicated immunotherapy

Background: Chimeric antigen receptor (CAR) T cell treatment involves in vitro production of T cells from patient blood with synthetic receptors specific to a cancer antigen. They circumvent the major histocompatibility complex to recognize the tumor antigen, reducing hematologic malignancy remission rates by 80%. Considering the efficacy of CAR-T treatment, the present work aimed at generating functional clusters of differentiation (CD)8 + T cells from human induced pluripotent stem cells (hiPSC) and to generate hiPS-CAR-T cells with high antigen-specific cytotoxicity. Methods: The Alkaline phosphatase assay and MycoEasy rapid mycoplasma detection kit was implemented for detection of hiPSCs and mycoplasma, respectively. The CD34⁺ HSPCs were harvested in AggreWellTM 400 using a 37-micron reversible strainer. Likewise, the lymphoid progenitor and CD4⁺CD8⁺ DP T cells were also harvested. The Cell Counting Kit-8 (CCK-8) assay was used to mark cytotoxicity and ELISA was used to detect IFN-γ secretion. Further, flow cytometry and transwell chambers were used to assess cell cycle, and migration and invasion. Finally, the in vivo antitumor effects of the CAR-T cells were evaluated using experimental animals (mice). Results: Results revealed that a serum-free, feeder layer-free differentiation system significantly yielded hiPSC-based T cell immunotherapy with interleukin-2, interleukin-15, and activators at the differentiation stage to promote the maturation of these cells into human induced pluripotent stem (hiPS)-T cells. The infection of hiPSCs with the CD19 CAR lentivirus resulted in the production of the hiPSC-CAR-T cells. We validated the function of hiPS-CAR-T cells in vivo and in vitro experimentation which revealed no significant differences in cell morphology and function between hiPSC-derived hiPS-CAR-T cells and peripheral blood-derived CAR-T cells. Conclusion: This study developed a culture method that is efficient and clinically useful to make functional CD8⁺ T cells from hiPSC and to get hiPS-CAR-T cells with high antigen-specific cytotoxicity that are not very different from CAR T cells found in peripheral blood. As a result, our findings may open the way for the clinical use of hiPSC to create functional CD8⁺ T and hiPS-CAR-T cells cells for use in cell-based cancer therapy.

Cellular electrophysiological effects of botulinum toxin A on neonatal rat cardiomyocytes and on cardiomyocytes derived from human-induced pluripotent stem cells

Botulinum toxin A is a well-known neurotransmitter inhibitor with a wide range of applications in modern medicine. Recently, botulinum toxin A preparations have been used in clinical trials to suppress cardiac arrhythmias, especially in the postoperative period. Its antiarrhythmic action is associated with inhibition of the nervous system of the heart, but its direct effect on heart tissue remains unclear. Accordingly, we investigate the effect of botulinum toxin A on isolated cardiac cells and on layers of cardiac cells capable of conducting excitation. Cardiomyocytes of neonatal rat pups and human cardiomyocytes obtained through cell reprogramming were used. A patch-clamp study showed that botulinum toxin A inhibited fast sodium currents and L-type calcium currents in a dose-dependent manner, with no apparent effect on potassium currents. Optical mapping showed that in the presence of botulinum toxin A, the propagation of the excitation wave in the layer of cardiac cells slows down sharply, conduction at high concentrations becomes chaotic, but reentry waves do not form. The combination of botulinum toxin A with a preparation of chitosan showed a stronger inhibitory effect by an order of magnitude. Further, the inhibitory effect of botulinum toxin A is not permanent and disappears after 12 days of cell culture in a botulinum toxin A-free medium. The main conclusion of the work is that the antiarrhythmic effect of botulinum toxin A found in clinical studies is associated not only with depression of the nervous system but also with a direct effect on heart tissue. Moreover, the combination of botulinum toxin A and chitosan reduces the effective dose of botulinum toxin A.

Polymer Kernels as Compact Carriers for Suspended Cardiomyocytes

Induced pluripotent stem cells (iPSCs) constitute a potential source of patient-specific human cardiomyocytes for a cardiac cell replacement therapy via intramyocardial injections, providing a major benefit over other cell sources in terms of immune rejection. However, intramyocardial injection of the cardiomyocytes has substantial challenges related to cell survival and electrophysiological coupling with recipient tissue. Current methods of manipulating cell suspensions do not allow one to control the processes of adhesion of injected cells to the tissue and electrophysiological coupling with surrounding cells. In this article, we documented the possibility of influencing these processes using polymer kernels: biocompatible fiber fragments of subcellular size that can be adsorbed to a cell, thereby creating the minimum necessary adhesion foci to shape the cell and provide support for the organization of the cytoskeleton and the contractile apparatus prior to adhesion to the recipient tissue. Using optical excitation markers, the restoration of the excitability of cardiomyocytes in suspension upon adsorption of polymer kernels was shown. It increased the likelihood of the formation of a stable electrophysiological coupling in vitro. The obtained results may be considered as a proof of concept that the stochastic engraftment process of injected suspension cells can be controlled by smart biomaterials.

NSC Physiological Features in Spinal Muscular Atrophy: SMN Deficiency Effects on Neurogenesis

While the U.S. Food and Drug Administration and the European Medicines Evaluation Agency have recently approved new drugs to treat spinal muscular atrophy 1 (SMA1) in young patients, they are mostly ineffective in older patients since many motor neurons have already been lost. Therefore, understanding nervous system (NS) physiology in SMA patients is essential. Consequently, studying neural stem cells (NSCs) from SMA patients is of significant interest in searching for new treatment targets that will enable researchers to identify new pharmacological approaches. However, studying NSCs in these patients is challenging since their isolation damages the NS, making it impossible with living patients. Nevertheless, it is possible to study NSCs from animal models or create them by differentiating induced pluripotent stem cells obtained from SMA patient peripheral tissues. On the other hand, therapeutic interventions such as NSCs transplantation could ameliorate SMA condition. This review summarizes current knowledge on the physiological properties of NSCs from animals and human cellular models with an SMA background converging on the molecular and neuronal circuit formation alterations of SMA fetuses and is not focused on the treatment of SMA. By understanding how SMA alters NSC physiology, we can identify new and promising interventions that could help support affected patients.

Identification of specific gene methylation patterns during motor neuron differentiation from spinal muscular atrophy patient-derived iPSC

Spinal muscular atrophy is a progressive motor neuron disorder caused by deletions or point mutations in the SMN1 gene. It is not known why motor neurons are particularly sensitive to a decrease in SMN protein levels and what factors besides SMN2 underlie the high clinical heterogeneity of the disease. Here we studied the methylation patterns of genes on sequential stages of motor neuron differentiation from induced pluripotent stem cells derived from the patients with SMA type I and II. The genes involved in the regulation of pluripotency, neural differentiation as well as those associated with spinal muscular atrophy development were included. The results show that the PAX6, HB9, CHAT, ARHGAP22, and SMN2 genes are differently methylated in cells derived from SMA patients compared to the cells of healthy individuals. This study clarifies the specificities of the disease pathogenesis and extends the knowledge of pathways involved in the SMA progression.

Cyclophosphamide arrhythmogenicitytesting using human-induced pluripotent stem cell-derived cardiomyocytes

Cyclophosphamide (CP) is an anticancer drug, an alkylating agent. Cardiotoxicity of CP is associated with one of its metabolites, acrolein, and clinical cardiotoxicity manifestations are described for cases of taking CP in high doses. Nevertheless, modern arrhythmogenicity prediction assays in vitro include evaluation of beat rhythm and rate as well as suppression of cardiac late markers after acute exposure to CP, but not its metabolites. The mechanism of CP side effects when taken at low doses (i.e., < 100 mg/kg), especially at the cellular level, remains unclear. In this study conduction properties and cytoskeleton structure of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) obtained from a healthy donor under CP were evaluated. Arrhythmogenicity testing including characterization of 3 values: conduction velocity, maximum capture rate (MCR) measurements and number of occasions of re-entry on a standard linear obstacle was conducted and revealed MCR decrease of 25% ± 7% under CP. Also, conductivity area reduced by 34 ± 15%. No effect of CP on voltage-gated ion channels was found. Conduction changes (MCR and conductivity area decrease) are caused by exposure time-dependent alpha-actinin disruption detected both in hiPSC-CMs and neonatal ventricular cardiomyocytes in vitro. Deviation from the external stimulus frequency and appearance of non-conductive areas in cardiac tissue under CP is potentially arrhythmogenic and could develop arrhythmic effects in vivo.

Arrhythmia Mechanisms in Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes

ABSTRACT

Despite major efforts by clinicians and researchers, cardiac arrhythmia remains a leading cause of morbidity and mortality in the world. Experimental work has relied on combining high-throughput strategies with standard molecular and electrophysiological studies, which are, to a great extent, based on the use of animal models. Because this poses major challenges for translation, the progress in the development of novel antiarrhythmic agents and clinical care has been mostly disappointing. Recently, the advent of human induced pluripotent stem cell-derived cardiomyocytes has opened new avenues for both basic cardiac research and drug discovery; now, there is an unlimited source of cardiomyocytes of human origin, both from healthy individuals and patients with cardiac diseases. Understanding arrhythmic mechanisms is one of the main use cases of human induced pluripotent stem cell-derived cardiomyocytes, in addition to pharmacological cardiotoxicity and efficacy testing, in vitro disease modeling, developing patient-specific models and personalized drugs, and regenerative medicine. Here, we review the advances that the human induced pluripotent stem cell-derived-based modeling systems have brought so far regarding the understanding of both arrhythmogenic triggers and substrates, while also briefly speculating about the possibilities in the future.

Rheumatoid Arthritis: Applicability of Ready-to-Use Human Cartilaginous Cells for Screening of Compounds with TNF-Alpha Inhibitory Activity

In the context of modern drug discovery, there is an obvious advantage to designing phenotypic bioassays based on human disease-relevant cells that express disease-relevant markers. The specific aim of the study was to develop a convenient and reliable method for screening compounds with Tumor Necrosis Factor-alpha (TNF-α) inhibitory activity. This assay was developed using cryopreserved ready-to-use cartilage-derived cells isolated from juvenile donors diagnosed with polydactyly. It has been demonstrated that all donor (10 donors) cells were able to respond to TNF-α treatment by increased secretion of pro-inflammatory cytokine IL-6 into subcultural medium. Inhibition of TNF-α using commercially available TNF-α inhibitor etanercept resulted in a dose-dependent decrease in IL-6 production which was measured by Enzyme-Linked Immunosorbent Assay (ELISA). TNF-α dependent IL-6 production was detected in the cells after both their prolonged cultivation in vitro (≥20 passages) and cryopreservation. This phenotypic bioassay based on ready-to-use primary human cells was developed for detection of novel TNF-α inhibitory compounds and profiling of biosimilar drugs.

Muscular Thin Films for Label-Free Mapping of Excitation Propagation in Cardiac Tissue

Muscular thin films (MTFs), have already found a variety of applications in cardiac tissue engineering and in building of lab-on-a-chip systems. Here we present a novel approach to label-free mapping of excitation waves in the cardiomyocyte cell cultures with the use of MTFs. Neonatal rat ventricular cardiomyocytes were cultured on polydimethylsiloxane (PDMS) thin films and observed by means of off-axis illumination. Inflexions of the membrane created by the contraction of cardiomyocytes led to formation of patterns of bright and dark areas on the surface of the membrane. These patterns were recorded and analyzed for the monitoring of the contraction propagation. The method was compared with a standard optical mapping technique based on the use of a Ca²⁺-sensitive fluorescent dye. A good consistency of the results obtained by these two methods was demonstrated. The proposed method is non-toxic and might be of particular interest for the purpose of continuous monitoring in test systems based on human induced pluripotent stem cells.

Multicellular In vitro Models of Cardiac Arrhythmias: Focus on Atrial Fibrillation

Atrial fibrillation (AF) is the most common cardiac arrhythmia in clinical practice with a large socioeconomic impact due to its associated morbidity, mortality, reduction in quality of life and health care costs. Currently, antiarrhythmic drug therapy is the first line of treatment for most symptomatic AF patients, despite its limited efficacy, the risk of inducing potentially life-threating ventricular tachyarrhythmias as well as other side effects. Alternative, in-hospital treatment modalities consisting of electrical cardioversion and invasive catheter ablation improve patients' symptoms, but often have to be repeated and are still associated with serious complications and only suitable for specific subgroups of AF patients. The development and progression of AF generally results from the interplay of multiple disease pathways and is accompanied by structural and functional (e.g., electrical) tissue remodeling. Rational development of novel treatment modalities for AF, with its many different etiologies, requires a comprehensive insight into the complex pathophysiological mechanisms. Monolayers of atrial cells represent a simplified surrogate of atrial tissue well-suited to investigate atrial arrhythmia mechanisms, since they can easily be used in a standardized, systematic and controllable manner to study the role of specific pathways and processes in the genesis, perpetuation and termination of atrial arrhythmias. In this review, we provide an overview of the currently available two- and three-dimensional multicellular in vitro systems for investigating the initiation, maintenance and termination of atrial arrhythmias and AF. This encompasses cultures of primary (animal-derived) atrial cardiomyocytes (CMs), pluripotent stem cell-derived atrial-like CMs and (conditionally) immortalized atrial CMs. The strengths and weaknesses of each of these model systems for studying atrial arrhythmias will be discussed as well as their implications for future studies.