Comprehensive in vitro cardiac safety assessment using human stem cell technology: Overview of CSAHi HEART initiative

Multiscale mapping of transcriptomic signatures for cardiotoxic drugs

Drug-induced gene expression profiles can identify potential mechanisms of toxicity. We focus on obtaining signatures for cardiotoxicity of FDA-approved tyrosine kinase inhibitors (TKIs) in human induced-pluripotent-stem-cell-derived cardiomyocytes, using bulk transcriptomic profiles. We use singular value decomposition to identify drug-selective patterns across cell lines obtained from multiple healthy human subjects. Cellular pathways affected by cardiotoxic TKIs include energy metabolism, contractile, and extracellular matrix dynamics. Projecting these pathways to published single cell expression profiles indicates that TKI responses can be evoked in both cardiomyocytes and fibroblasts. Integration of transcriptomic outlier analysis with whole genomic sequencing of our six cell lines enables us to correctly reidentify a genomic variant causally linked to anthracycline-induced cardiotoxicity and predict genomic variants potentially associated with TKI-induced cardiotoxicity. We conclude that mRNA expression profiles when integrated with publicly available genomic, pathway, and single cell transcriptomic datasets, provide multiscale signatures for cardiotoxicity that could be used for drug development and patient stratification.

Bayesian approach enabled objective comparison of multiple human iPSC-derived Cardiomyocytes' Proarrhythmia sensitivities

The one-size-fits-all approach has been the mainstream in medicine, and the well-defined standards support the development of safe and effective therapies for many years. Advancing technologies, however, enabled precision medicine to treat a targeted patient population (e.g., HER2+ cancer). In safety pharmacology, computational population modeling has been successfully applied in virtual clinical trials to predict drug-induced proarrhythmia risks against a wide range of pseudo cohorts. In the meantime, population modeling in safety pharmacology experiments has been challenging. Here, we used five commercially available human iPSC-derived cardiomyocytes growing in 384-well plates and analyzed the effects of ten potential proarrhythmic compounds with four concentrations on their calcium transients (CaTs). All the cell lines exhibited an expected elongation or shortening of calcium transient duration with various degrees. Depending on compounds inhibiting several ion channels, such as hERG, peak and late sodium and L-type calcium or IKs channels, some of the cell lines exhibited irregular, discontinuous beating that was not predicted by computational simulations. To analyze the shapes of CaTs and irregularities of beat patterns comprehensively, we defined six parameters to characterize compound-induced CaT waveform changes, successfully visualizing the similarities and differences in compound-induced proarrhythmic sensitivities of different cell lines. We applied Bayesian statistics to predict sample populations based on experimental data to overcome the limited number of experimental replicates in high-throughput assays. This process facilitated the principal component analysis to classify compound-induced sensitivities of cell lines objectively. Finally, the association of sensitivities in compound-induced changes between phenotypic parameters and ion channel inhibitions measured using patch clamp recording was analyzed. Successful ranking of compound-induced sensitivity of cell lines was in lined with visual inspection of raw data.

Perfluorooctanoic acid induces cardiac dysfunction in human induced pluripotent stem cell-derived cardiomyocytes

Perfluorooctanoic acid (PFOA), commonly found in drinking water, leads to widespread exposure through skin contact, inhalation, and ingestion, resulting in detectable levels of PFOA in the bloodstream. In this study, we found that exposure to PFOA disrupts cardiac function in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). We observed reductions in field and action potentials in hiPSC-CMs exposed to PFOA. Furthermore, PFOA demonstrated a dose-dependent inhibitory effect on various ion channels, including the calcium, sodium, and potassium channels. Additionally, we noted dose-dependent inhibition of the expression of these ion channels in hiPSC-CMs following exposure to PFOA. These findings suggest that PFOA exposure can impair cardiac ion channel function and decrease the transcription of genes associated with these channels, potentially contributing to cardiac dysfunction such as arrhythmias. Our study sheds light on the electrophysiological and epigenetic consequences of PFOA-induced cardiac dysfunction, underscoring the importance of further research on the cardiovascular effects of perfluorinated compounds (PFCs).

Enhancing the functional maturity of hiPSC-derived cardiomyocytes to assess inotropic compounds

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) present an attractive in vitro platform to model safety and toxicity assessments-notably screening pro-arrhythmic compounds. The utility of the platform is stymied by a hiPSC-CM contractile apparatus and calcium handling mechanism akin to fetal phenotypes, evidenced by a negative force-frequency relationship. As such, hiPSC-CMs are limited in their ability to assess compounds that modulate contraction mediated by ionotropic compounds (Robertson, Tran, & George, 2013). To address this limitation, we utilize Agilent's xCELLigence Real-Time Cell Analyzer ePacer (RTCA ePacer) to enhance hiPSC-CM functional maturity. A continuous, progressive increase of electrical pacing is applied to hiPSC-CMs for up to 15 days. Contraction and viability are recorded by measurement of impedance using the RTCA ePacer. Our data confirms hiPSC-CMs inherently demonstrate a negative impedance amplitude frequency that is reversed after long-term electrical pacing. The data also indicate positive inotropic compounds increase the contractility of paced cardiomyocytes and calcium handling machinery is improved. Increased expression of genes critical to cardiomyocyte maturation further underscores the maturity of paced cells. In summary, our data suggest the application of continuous electrical pacing can functionally mature hiPSC-CMs, enhancing cellular response to positive inotropic compounds and improving calcium handling. SUMMARY: Long-term electrical stimulation of hiPSC-CM leads to functional maturation enabling predictive assessment of inotropic compounds.

CardioMotion: identification of functional and structural cardiotoxic liabilities in small molecules through brightfield kinetic imaging

Cardiovascular toxicity is an important cause of drug failures in the later stages of drug development, early clinical safety assessment, and even postmarket withdrawals. Early-stage in vitro assessment of potential cardiovascular liabilities in the pharmaceutical industry involves assessment of interactions with cardiac ion channels, as well as induced pluripotent stem cell-derived cardiomyocyte-based functional assays, such as calcium flux and multielectrode-array assays. These methods are appropriate for the identification of acute functional cardiotoxicity but structural cardiotoxicity, which manifests effects after chronic exposure, is often only captured in vivo. CardioMotion is a novel, label-free, high throughput, in vitro assay and analysis pipeline which records and assesses the spontaneous beating of cardiomyocytes and identifies compounds which impact beating. This is achieved through the acquisition of brightfield images at a high framerate, combined with an optical flow-based python analysis pipeline which transforms the images into waveform data which are then parameterized. Validation of this assay with a large dataset showed that cardioactive compounds with diverse known direct functional and structural mechanisms-of-action on cardiomyocytes are identified (sensitivity = 72.9%), importantly, known structural cardiotoxins also disrupt cardiomyocyte beating (sensitivity = 86%) in this method. Furthermore, the CardioMotion method presents a high specificity of 82.5%.

Generation of left ventricle-like cardiomyocytes with improved structural, functional, and metabolic maturity from human pluripotent stem cells

Decreased left ventricle (LV) function caused by genetic mutations or injury often leads to debilitating and fatal cardiovascular disease. LV cardiomyocytes are, therefore, a potentially valuable therapeutical target. Human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) are neither homogeneous nor functionally mature, which reduces their utility. Here, we exploit cardiac development knowledge to instruct differentiation of hPSCs specifically toward LV cardiomyocytes. Correct mesoderm patterning and retinoic acid pathway blocking are essential to generate near-homogenous LV-specific hPSC-CMs (hPSC-LV-CMs). These cells transit via first heart field progenitors and display typical ventricular action potentials. Importantly, hPSC-LV-CMs exhibit increased metabolism, reduced proliferation, and improved cytoarchitecture and functional maturity compared with age-matched cardiomyocytes generated using the standard WNT-ON/WNT-OFF protocol. Similarly, engineered heart tissues made from hPSC-LV-CMs are better organized, produce higher force, and beat more slowly but can be paced to physiological levels. Together, we show that functionally matured hPSC-LV-CMs can be obtained rapidly without exposure to current maturation regimes.

Long-term in vitro recording of cardiac action potentials on microelectrode arrays for chronic cardiotoxicity assessment

The reliable identification of chronic cardiotoxic effects in in vitro screenings is fundamental for filtering out toxic molecular entities before in vivo animal experimentation and clinical trials. Present techniques such as patch-clamp, voltage indicators, and standard microelectrode arrays do not offer at the same time high sensitivity for measuring transmembrane ion currents and low-invasiveness for monitoring cells over long time. Here, we show that optoporation applied to microelectrode arrays enables measuring action potentials from human-derived cardiac syncytia for more than 1 continuous month and provides reliable data on chronic cardiotoxic effects caused by known compounds such as pentamidine. The technique has high potential for detecting chronic cardiotoxicity in the early phases of drug development.

Modeling the human heart ex vivo-current possibilities and strive for future applications

The high organ specification of the human heart is inversely proportional to its functional recovery after damage. The discovery of induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) has accelerated research in human heart regeneration and physiology. Nevertheless, due to the immaturity of iPSC-CMs, they are far from being an representative model of the adult heart physiology. Therefore, number of laboratories strive to obtain a heart tissues by engineering methods by structuring iPSC-CMs into complex and advanced platforms. By using the iPSC-CMs and arranging them in 3D cultures it is possible to obtain a human heart muscle with physiological capabilities potentially similar to the adult heart, while remaining in vitro. Here, we attempt to describe existing examples of heart muscle either in vitro or ex vivo models and discuss potential options for the further development of such structures. This will be a crucial step for ultimate derivation of complete heart tissue-mimicking organs and their future use in drug development, therapeutic approaches testing, pre-clinical studies, and clinical applications. This review particularly aims to compile available models of advanced human heart tissue for scientists considering which model would best fit their research needs.

Identifying Acute Cardiac Hazard in Early Drug Discovery Using a Calcium Transient High-Throughput Assay in Human-Induced Pluripotent Stem Cell-Derived Cardiomyocytes

Introduction: Early identification of cardiac risk is essential for reducing late-stage attrition in drug development. We adapted the previously published cardiac hazard risk-scoring system using a calcium transient assay in human stem cell-derived CMs for the identification of cardiac risks recorded from the new hiPSC-CM line and investigated its predictivity and translational value based on the screening of a large number of reference and proprietary compounds. Methods: Evaluation of 55 reference drugs provided the translation of various pharmacological effects into a single hazard label (no, low, high, or very high hazard) using a Ca²⁺-sensitive fluorescent dye assay recorded by -by FDSS/µCell Functional Drug Screening System (Hamamatsu on hiPSC-CM line (FCDI iCell Cardiomyocytes²). Results: Application of the adapted hazard scoring system in the Ca²⁺ transient assay, using a second hiPS-CM line, provided comparable scoring results and predictivity of hazard, to the previously published scoring approach, with different pharmacological drug classes, as well as screening new chemical entities (NCE's) using a single hazard label from four different scoring levels (no, low, high, or very high hazard). The scoring system results also showed minimal variability across three different lots of hiPSC-CMs, indicating good reproducibility of the cell line. The predictivity values (sensitivity and specificity) for drug-induced acute cardiac risk for QT-interval prolongation and Torsade de pointes (TdPs) were >95% and statistical modeling confirmed the prediction of proarrhythmic risk. The outcomes of the NCEs also showed consistency with findings in other well-established in vitro and in vivo cardiac risk assays. Conclusion: Evaluation of a large list of reference compounds and internal NCEs has confirmed the applicability of the adaptations made to the previously published novel scoring system for the hiPSC-CMs. The validation also established the predictivity for drug-induced cardiac risks with good translation to other established preclinical in vitro and in vivo assays, confirming the application of this novel scoring system in different stem cell-CM lines for early cardiac hazard identification.

Assessment of endocrine disruptive properties of PFOS: EFSA/ECHA guidance case study utilising AOP networks and alternative methods

Endocrine disruptors (EDs) are chemical substances that interfere with the endocrine system, adversely affecting human health and environment. Legislation with aim to eliminate and ban EDs have been introduced in EU, but the identification of EDs remains challenging and crucial step towards regulation and risk management. A guidance for ED assessment has been recently established for pesticides and biocides in the EU, which heavily relies on traditional toxicological testing in vivo. Most notably lacking mechanistic methods for some ED modalities and not covering many other modalities that might be affected by EDs. In this project, we focus on the ED assessment according to the valid legislation and explore the possibility to employ alternative methods to bolster the mechanistic understanding of the ED effects and eventually decrease the need for in vivo testing. We selected a well‐studied industrial chemical perfluorooctanesulfonic acid (PFOS) to be a model compound in a case study for ED assessment where the EU criteria were applied in the frame of human health risk assessment with focus on thyroid disruption and developmental neurotoxicity. A systematic literature review has been conducted for these effects (Scopus, Pubmed, Embase), and relevant studies were selected by title/abstract screening (RAYYAN) and full‐text examination. Selected studies were assessed for reliability (SciRAP), and all relevant data were extracted into a database and assessed by Weight of Evidence (WoE) approach. The initial analysis showed potential endocrine adverse effects and endocrine activity, meeting the ED criteria. The use of mechanistic and alternative methods enhanced the outcomes of WoE assessment. Also, the study provides a great hands‐on experience with the most up‐to‐date development in the area of risk assessment and EDs.

High-Throughput Analysis of Drug Safety Responses in Induced Pluripotent Stem Cell-Derived Cardiomyocytes Using Multielectrode Array

Microelectrode array (MEA) is an electrophysiological instrument used to track activities of ion channels in excitable cells. Neurons and cardiomyocytes are seeded to form a cell monolayer on a field of sensors able to detect electrical signals, called extracellular field potentials (EFPs). This noninvasive tool allows researchers to investigate key parameters such as EFP amplitude, duration, and arrhythmias. MEA is progressively considered the gold standard for high-throughput in vitro electrophysiological evaluation, particularly for cardiac disease modeling and cardiac toxicity assessment.

Ventricular voltage-gated ion channels: Detection, characteristics, mechanisms, and drug safety evaluation

Cardiac voltage-gated ion channels (VGICs) play critical roles in mediating cardiac electrophysiological signals, such as action potentials, to maintain normal heart excitability and contraction. Inherited or acquired alterations in the structure, expression, or function of VGICs, as well as VGIC-related side effects of pharmaceutical drug delivery can result in abnormal cellular electrophysiological processes that induce life-threatening cardiac arrhythmias or even sudden cardiac death. Hence, to reduce possible heart-related risks, VGICs must be acknowledged as important targets in drug discovery and safety studies related to cardiac disease. In this review, we first summarize the development and application of electrophysiological techniques that are employed in cardiac VGIC studies alone or in combination with other techniques such as cryoelectron microscopy, optical imaging and optogenetics. Subsequently, we describe the characteristics, structure, mechanisms, and functions of various well-studied VGICs in ventricular myocytes and analyze their roles in and contributions to both physiological cardiac excitability and inherited cardiac diseases. Finally, we address the implications of the structure and function of ventricular VGICs for drug safety evaluation. In summary, multidisciplinary studies on VGICs help researchers discover potential targets of VGICs and novel VGICs in heart, enrich their knowledge of the properties and functions, determine the operation mechanisms of pathological VGICs, and introduce groundbreaking trends in drug therapy strategies, and drug safety evaluation.

Cardiotoxicity assessment using 3D vascularized cardiac tissue consisting of human iPSC-derived cardiomyocytes and fibroblasts

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) are used for cardiac safety assessment but have limitations for the evaluation of drug-induced contractility. Three-dimensional (3D) cardiac tissues are similar to native tissue and valuable for the assessment of contractility. However, a longer time and specialized equipment are required to generate 3D tissues. We previously developed a simple method to generate 3D tissue in a short period by coating the cell surfaces with extracellular matrix proteins. We hypothesized that this 3D cardiac tissue could be used for simultaneous evaluation of drug-induced repolarization and contractility. In the present work, we examined the effects of several compounds with different mechanisms of action by cell motion imaging. Consequently, human ether-a-go-go-related gene (HERG) channel blockers with high arrhythmogenic risk caused prolongation of contraction-relaxation duration and arrhythmia-like waveforms. Positive inotropic drugs, which increase intracellular Ca²⁺ levels or myocardial Ca²⁺ sensitivity, caused an increase in maximum contraction speed (MCS) or average deformation distance (ADD) (ouabain, 138% for MCS at 300 nM; pimobendane, 132% for ADD at 3 μM). For negative inotropic drugs, verapamil reduced both MCS and ADD (61% at 100 nM). Thus, this 3D cardiac tissue detected the expected effects of various cardiovascular drugs, suggesting its usefulness for cardiotoxicity evaluation.

Investigation of cardiac glycosides from oleander in a human induced pluripotent stem cells derived cardiomyocyte model

The ingestion of Nerium oleander and Thevetia peruviana are common causes for poisoning in Southeast Asia. All parts of the oleander shrub contain cardiac glycosides of the cardenolide type. These glycosides act via inhibition of a Na⁺/K⁺-ATPase which might cause severe arrhythmia and subsequent death in oleander-poisoned patients. The current study uses human induced pluripotent stem cells derived cardiomyocytes (hiPSC-CM) in a microelectrode array (MEA) system to assess the cardiac effects of neriifolin, oleandrin, digitoxigenin, peruvoside and thevetin A from the oleander plant. Digoxin was used as established reference compound. All tested compounds showed a corrected field potential duration (FPDc) shortening and was the lowest for 600 nM digitoxigenin with -36.9 ± 1.2 %. Next to the dose-dependent pro-arrhythmic potential, a complete beat arrest of the spontaneously beating hiPSC-CM was observed at a concentration of 300 nM for neriifolin, 600 nM for oleandrin and 1000 nM for digitoxigenin and peruvoside. Thevetin A did not cause arrhythmia up to a final concentration of 1000 nM. Thus, it was possible to establish a cardiac effect rank order of the tested substances: neriifolin > oleandrin > digitoxigenin = peruvoside > digoxin > thevetin A.

A predictive in vitro risk assessment platform for pro-arrhythmic toxicity using human 3D cardiac microtissues

Cardiotoxicity of pharmaceutical drugs, industrial chemicals, and environmental toxicants can be severe, even life threatening, which necessitates a thorough evaluation of the human response to chemical compounds. Predicting risks for arrhythmia and sudden cardiac death accurately is critical for defining safety profiles. Currently available approaches have limitations including a focus on single select ion channels, the use of non-human species in vitro and in vivo, and limited direct physiological translation. We have advanced the robustness and reproducibility of in vitro platforms for assessing pro-arrhythmic cardiotoxicity using human induced pluripotent stem cell-derived cardiomyocytes and human cardiac fibroblasts in 3-dimensional microtissues. Using automated algorithms and statistical analyses of eight comprehensive evaluation metrics of cardiac action potentials, we demonstrate that tissue-engineered human cardiac microtissues respond appropriately to physiological stimuli and effectively differentiate between high-risk and low-risk compounds exhibiting blockade of the hERG channel (E4031 and ranolazine, respectively). Further, we show that the environmental endocrine disrupting chemical bisphenol-A (BPA) causes acute and sensitive disruption of human action potentials in the nanomolar range. Thus, this novel human 3D in vitro pro-arrhythmic risk assessment platform addresses critical needs in cardiotoxicity testing for both environmental and pharmaceutical compounds and can be leveraged to establish safe human exposure levels.

Human induced pluripotent stem cell (iPSC)-derived cardiomyocytes as an in vitro model in toxicology: strengths and weaknesses for hazard identification and risk characterization

INTRODUCTION

Human induced pluripotent stem cell (iPSC)-derived cardiomyocytes is one of the most widely used cell-based models that resulted from the discovery of how non-embryonic stem cells can be differentiated into multiple cell types. In just one decade, iPSC-derived cardiomyocytes went from a research lab to widespread use in biomedical research and preclinical safety evaluation for drugs and other chemicals.

AREAS COVERED

This manuscript reviews data on toxicology applications of human iPSC-derived cardiomyocytes. We detail the outcome of a systematic literature search on their use (i) in hazard assessment for cardiotoxicity liabilities, (ii) for risk characterization, (iii) as models for population variability, and (iv) in studies of personalized medicine and disease.

EXPERT OPINION

iPSC-derived cardiomyocytes are useful to increase the accuracy, precision, and efficiency of cardiotoxicity hazard identification for both drugs and non-pharmaceuticals, with recent efforts beginning to demonstrate their utility for risk characterization. Notable limitations include the needs to improve the maturation of cells in culture, to better understand their potential use identifying structural cardiotoxicity, and for additional case studies involving population-wide and disease-specific risk characterization. Ultimately, the greatest future benefits are likely for non-pharmaceutical chemicals, filling a critical gap where no routine testing for cardiotoxicity is currently performed.

Bioprinting 3D human cardiac tissue chips using the pin type printer 'microscopic painting device' and analysis for cardiotoxicity

In this study, three-dimensional (3D) cardiac tissue constructed using the pin type bioprinter 'microscopic painting device' and layer-by-layer cell coating technique was confirmed to have drug responsiveness by three different analytical methods for cardiotoxicity assay. Recently, increasing attention has been focused on biofabrication to create biomimetic 3D tissue. Although various tissues can be produced in vitro, there are many issues surrounding the stability and reproducibility of the preparation of 3D tissues. Thus, although many bioprinters have been developed, none can efficiently, reproducibly and precisely produce small 3D tissues (μm-mm order) such as spheroids, which are most commonly used in drug development. The 3D cardiac tissue chips were successfully constructed with a similar number of cells as conventional 2D tissue using a pin type bioprinter, and corresponding drug-induced cardiotoxicities were obtained with known compounds that induce cardiotoxicity. The 3D cardiac tissue chips displayed uniform cell density and completely synchronized electrophysiological properties as compared to 2D tissue. The 3D tissues constructed using a pin type bioprinter as a biofabrication device would be promising tools for cardiotoxicity assay as they are capable of obtaining stable and reproducible data, which cannot be obtained by 2D tissue.

Development and evaluation of next-generation cardiotoxicity assay based on embryonic stem cell-derived cardiomyocytes

In accordance with requirements of the ICH S7B safety pharma-cology guidelines, numerous next-generation cardiotoxicity studies using human stem cell-derived cardiomyocytes (CMs) are being conducted globally. Although several stem cell-derived CMs are being developed for commercialization, there is insufficient research to verify if these CMs can replace animal experiments. In this study, in vitro high-efficiency CMs derived from human embryonic stem cells (hESC-CMs) were compared with Sprague-Dawley rats as in vivo experimental animals, and primary cultured in vitro rat-CMs for cardiotoxicity tests. In vivo rats were administrated with two consecutive injections of 100 mg/kg isoproterenol, 15 mg/kg doxorubicin, or 100 mg/kg nifedipine, while in vitro rat-CMs and hESC-CMs were treated with 5 µM isoproterenol, 5 µM doxorubicin, and 50 µM nifedipine. We have verified the equivalence of hESC-CMs assessments over various molecular biological markers, morphological analysis. Also, we have identified the advantages of hESC-CMs, which can distinguish between species variability, over electrophysiological analysis of ion channels against cardiac damage. Our findings demonstrate the possibility and advantage of high-effi-ciency hESC-CMs as next-generation cardiotoxicity assessment.

Integration of mechanical conditioning into a high throughput contractility assay for cardiac safety assessment

INDUCTION

Despite increasing acceptance of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) in safety pharmacology, controversy remains about the physiological relevance of existing in vitro models for their mechanical testing. We hypothesize that existing signs of immaturity of the cell models result from an improper mechanical environment. With the presented study, we aimed at validating the newly developed FLEXcyte96 technology with respect to physiological responses of hiPSC-CMs to pharmacological compounds with known inotropic and/or cardiotoxic effects.

METHODS

hiPSC-CMs were cultured in a 96-well format on hyperelastic silicone membranes imitating their native mechanical environment. Cardiomyocyte contractility was measured contact-free by application of capacitive displacement sensing of the cell-membrane biohybrids. Acute effects of positive inotropic compounds with distinct mechanisms of action were examined. Additionally, cardiotoxic effects of tyrosine kinase inhibitors and anthracyclines were repetitively examined during repeated exposure to drug concentrations for up to 5 days.

RESULTS

hiPSC-CMs grown on biomimetic membranes displayed increased contractility responses to isoproterenol, S-Bay K8644 and omecamtiv mecarbil without the need for additional stimulation. Tyrosine kinase inhibitor erlotinib, vandetanib, nilotinib, gefitinib, A-674563 as well as anthracycline idarubicin showed the expected cardiotoxic effects, including negative inotropy and induction of proarrhythmic events.

DISCUSSION

We conclude that the FLEXcyte 96 system is a reliable high throughput tool for invitro cardiac contractility research, providing the user with data obtained under physiological conditions which resemble the native environment of human heart tissue. We showed that the results obtained for both acute and sub-chronic compound administration are consistent with the respective physiological responses in humans.

Noninvasive optical coherence tomography imaging of three-dimensional cardiac tissues derived from human induced pluripotent stem cells

Artificial three-dimensional (3D) tissues have the potential to be used in regenerative medicine or in vitro screening. In particular, the fabrication of 3-D cardiac tissues is greatly anticipated. However, hierarchical organization of 3-D tissues is still unknown. In regenerative medicine and drug discovery, noninvasive evaluation methods of 3-D tissues including inside of it play a key role. In this study, we report on noninvasive methods of analyzing bio-fabricated 3-D cardiac tissues using optical coherence tomography (OCT) and image analysis. Three-dimensional cardiac tissues were fabricated by coating of extracellular matrix nanofilms onto a cell surface using a layer-by-layer (LbL) technique. At first, we investigated the relationship between surface beating and its thickness to assess the value of internal analysis. The results showed that the surface beating was influenced by the thickness. Next, we tried to quantitatively evaluate the internal beating of 3-D cardiac tissues. We also confirmed the methods by changing the beating properties through the administration of isoproterenol. Our results demonstrated that the beating properties of 3-D cardiac tissues differed by depth. The results of this study suggest that information on the internal properties of 3-D cardiac tissue was necessary to understand how it functions. The combination of OCT and image analysis can be used to evaluate the internal beating properties, including changes in beating induced by a drug. It is suggested that OCT and image analysis have the potential to be used as noninvasive methods in regenerative medicine and pharmaceutical applications.

Dominant rule of community effect in synchronized beating behavior of cardiomyocyte networks

Exploiting the combination of latest microfabrication technologies and single cell measurement technologies, we can measure the interactions of single cells, and cell networks from "algebraic" and "geometric" perspectives under the full control of their environments and interactions. However, the experimental constructive single cell-based approach still remains the limitations regarding the quality and condition control of those cells. To overcome these limitations, mathematical modeling is one of the most powerful complementary approaches. In this review, we first explain our on-chip experimental methods for constructive approach, and we introduce the results of the "community effect" of beating cardiomyocyte networks as an example of this approach. On-chip analysis revealed that (1) synchronized interbeat intervals (IBIs) of cell networks were followed to the more stable beating cells even their IBIs were slower than the other cells, which is against the conventional faster firing regulation or "overdrive suppression," and (2) fluctuation of IBIs of cardiomyocyte networks decreased according to the increase of the number of connected cells regardless of their geometry. The mathematical simulation of this synchronous behavior of cardiomyocyte networks also fitted well with the experimental results after incorporating the fluctuation-dissipation theorem into the oscillating stochastic phase model, in which the concept of spatially arranged cardiomyocyte networks was involved. The constructive experiments and mathematical modeling indicated the dominant rule of synchronization behavior of beating cardiomyocyte networks is a kind of stability-oriented synchronization phenomenon as the "community effect" or a fluctuation-dissipation phenomenon. Finally, as a practical application of this approach, the predictive cardiotoxicity is introduced.

Quantitative Systems Pharmacology for Neuroscience Drug Discovery and Development: Current Status, Opportunities, and Challenges

The substantial progress made in the basic sciences of the brain has yet to be adequately translated to successful clinical therapeutics to treat central nervous system (CNS) diseases. Possible explanations include the lack of quantitative and validated biomarkers, the subjective nature of many clinical endpoints, and complex pharmacokinetic/pharmacodynamic relationships, but also the possibility that highly selective drugs in the CNS do not reflect the complex interactions of different brain circuits. Although computational systems pharmacology modeling designed to capture essential components of complex biological systems has been increasingly accepted in pharmaceutical research and development for oncology, inflammation, and metabolic disorders, the uptake in the CNS field has been very modest. In this article, a cross-disciplinary group with representatives from academia, pharma, regulatory, and funding agencies make the case that the identification and exploitation of CNS therapeutic targets for drug discovery and development can benefit greatly from a system and network approach that can span the gap between molecular pathways and the neuronal circuits that ultimately regulate brain activity and behavior. The National Institute of Neurological Disorders and Stroke (NINDS), in collaboration with the National Institute on Aging (NIA), National Institute of Mental Health (NIMH), National Institute on Drug Abuse (NIDA), and National Center for Advancing Translational Sciences (NCATS), convened a workshop to explore and evaluate the potential of a quantitative systems pharmacology (QSP) approach to CNS drug discovery and development. The objective of the workshop was to identify the challenges and opportunities of QSP as an approach to accelerate drug discovery and development in the field of CNS disorders. In particular, the workshop examined the potential for computational neuroscience to perform QSP-based interrogation of the mechanism of action for CNS diseases, along with a more accurate and comprehensive method for evaluating drug effects and optimizing the design of clinical trials. Following up on an earlier white paper on the use of QSP in general disease mechanism of action and drug discovery, this report focuses on new applications, opportunities, and the accompanying limitations of QSP as an approach to drug development in the CNS therapeutic area based on the discussions in the workshop with various stakeholders.

Comprehensive Cardiac Safety Assessment using hiPS-cardiomyocytes (Consortium for Safety Assessment using Human iPS Cells: CSAHi)

Current cardiac safety assessment platforms (in vitro hERG-centric, APD, and/or in vivo animal QT assays) are not fully predictive of drug-induced Torsades de Pointes (TdP) and do not address other mechanism-based arrhythmia, including ventricular tachycardia or ventricular fibrillation, or cardiac safety liabilities such as contractile and structural cardiotoxicity which are another growing safety concerns. We organized the Consortium for Safety Assessment using Human iPS cells (CSAHi; http://csahi.org/en/) in 2013, based on the Japan Pharmaceutical Manufacturers Association (JPMA), to verify the application of human iPS/ES cell-derived cardiomyocytes for drug safety evaluation. The CSAHi HEART team focused on comprehensive screening strategies to predict a diverse range of cardiotoxicities using recently introduced platforms such as the Multi-Electrode Array (MEA), cellular impedance, Motion Field Imaging (MFI), and optical imaging of Ca transient to identify strengths and weaknesses of each platform. Our study showed that hiPS-CMs used in these platforms could detect pharmacological responses that were more relevant to humans compared to existing hERG, APD, or Langendorff (MAPD/contraction) assays. Further, MEA and other methods such as impedance, MFI, and Ca transient assays provided paradigm changes of platforms for predicting drug-induced QT risk and/or arrhythmia or contractile dysfunctions. In contrast, since discordances such as overestimation (false positive) of arrhythmogenicity, oversight, or opposite conclusions in positive inotropic and negative chronotropic activities to some compounds were also confirmed, possibly due to their functional immaturity of hiPS-CMs, hiPS-CMs should be used in these platforms for cardiac safety assessment based upon their advantages and disadvantages.

hiPSCs Derived Cardiac Cells for Drug and Toxicity Screening and Disease Modeling: What Micro- Electrode-Array Analyses Can Tell Us

Human induced pluripotent stem cell (iPSC)-derived cardiomyocytes (CM) have been intensively used in drug development and disease modeling. Since iPSC-cardiomyocyte (CM) was first generated, their characterization has become a major focus of research. Multi-/micro-electrode array (MEA) systems provide a non-invasive user-friendly platform for detailed electrophysiological analysis of iPSC cardiomyocytes including drug testing to identify potential targets and the assessment of proarrhythmic risk. Here, we provide a systematical overview about the physiological and technical background of micro-electrode array measurements of iPSC-CM. We introduce the similarities and differences between action- and field potential and the advantages and drawbacks of MEA technology. In addition, we present current studies focusing on proarrhythmic side effects of novel and established compounds combining MEA systems and iPSC-CM. MEA technology will help to open a new gateway for novel therapies in cardiovascular diseases while reducing animal experiments at the same time.

Population-based toxicity screening in human induced pluripotent stem cell-derived cardiomyocytes

The potential for cardiotoxicity is carefully evaluated for pharmaceuticals, as it is a major safety liability. However, environmental chemicals are seldom tested for their cardiotoxic potential. Moreover, there is a large variability in both baseline and drug-induced cardiovascular risk in humans, but data are lacking on the degree to which susceptibility to chemically-induced cardiotoxicity may also vary. Human induced pluripotent stem cell (iPSC)-derived cardiomyocytes have become an important in vitro model for drug screening. Thus, we hypothesized that a population-based model of iPSC-derived cardiomyocytes from a diverse set of individuals can be used to assess potential hazard and inter-individual variability in chemical effects on these cells. We conducted concentration-response screening of 134 chemicals (pharmaceuticals, industrial and environmental chemicals and food constituents) in iPSC-derived cardiomyocytes from 43 individuals, comprising both sexes and diverse ancestry. We measured kinetic calcium flux and conducted high-content imaging following chemical exposure, and utilized a panel of functional and cytotoxicity parameters in concentration-response for each chemical and donor. We show reproducible inter-individual variability in both baseline and chemical-induced effects on iPSC-derived cardiomyocytes. Further, chemical-specific variability in potency and degree of population variability were quantified. This study shows the feasibility of using an organotypic population-based human in vitro model to quantitatively assess chemicals for which little cardiotoxicity information is available. Ultimately, these results advance in vitro toxicity testing methodologies by providing an innovative tool for population-based cardiotoxicity screening, contributing to the paradigm shift from traditional animal models of toxicity to in vitro toxicity testing methods.

Development of a Human iPSC Cardiomyocyte-Based Scoring System for Cardiac Hazard Identification in Early Drug Safety De-risking

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have emerged as a promising cardiac safety platform, demonstrated by numerous validation studies using drugs with known cardiac adverse effects in humans. However, the challenge remains to implement hiPSC-CMs into cardiac de-risking of new chemical entities (NCEs) during preclinical drug development. Here, we used the calcium transient screening assay in hiPSC-CMs to develop a hazard score system for cardiac electrical liabilities. Tolerance interval calculations and evaluation of different classes of cardio-active drugs enabled us to develop a weighted scoring matrix. This approach allowed the translation of various pharmacological effects in hiPSC-CMs into a single hazard label (no, low, high, or very high hazard). Evaluation of 587 internal NCEs and good translation to ex vivo and in vivo models for a subset of these NCEs highlight the value of the cardiac hazard scoring in facilitating the selection of compounds during early drug safety screening.

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Scoring system identifies different degrees of cardiac hazard

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Can be applied within R&D to cardiac safety screening of NCEs

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Controls and reference drugs are essential for development of scoring matrix

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Analysis can be applied to other in vitro drug safety assays

Considerations for an In Vitro, Cell-Based Testing Platform for Detection of Drug-Induced Inotropic Effects in Early Drug Development. Part 2: Designing and Fabricating Microsystems for Assaying Cardiac Contractility With Physiological Relevance Using Human iPSC-Cardiomyocytes

Contractility of the myocardium engines the pumping function of the heart and is enabled by the collective contractile activity of its muscle cells: cardiomyocytes. The effects of drugs on the contractility of human cardiomyocytes in vitro can provide mechanistic insight that can support the prediction of clinical cardiac drug effects early in drug development. Cardiomyocytes differentiated from human-induced pluripotent stem cells have high potential for overcoming the current limitations of contractility assays because they attach easily to extracellular materials and last long in culture, while having human- and patient-specific properties. Under these conditions, contractility measurements can be non-destructive and minimally invasive, which allow assaying sub-chronic effects of drugs. For this purpose, the function of cardiomyocytes in vitro must reflect physiological settings, which is not observed in cultured cardiomyocytes derived from induced pluripotent stem cells because of the fetal-like properties of their contractile machinery. Primary cardiomyocytes or tissues of human origin fully represent physiological cellular properties, but are not easily available, do not last long in culture, and do not attach easily to force sensors or mechanical actuators. Microengineered cellular systems with a more mature contractile function have been developed in the last 5 years to overcome this limitation of stem cell-derived cardiomyocytes, while simultaneously measuring contractile endpoints with integrated force sensors/actuators and image-based techniques. Known effects of engineered microenvironments on the maturity of cardiomyocyte contractility have also been discovered in the development of these systems. Based on these discoveries, we review here design criteria of microengineered platforms of cardiomyocytes derived from pluripotent stem cells for measuring contractility with higher physiological relevance. These criteria involve the use of electromechanical, chemical and morphological cues, co-culture of different cell types, and three-dimensional cellular microenvironments. We further discuss the use and the current challenges for developing and improving these novel technologies for predicting clinical effects of drugs based on contractility measurements with cardiomyocytes differentiated from induced pluripotent stem cells. Future research should establish contexts of use in drug development for novel contractility assays with stem cell-derived cardiomyocytes.

Thorough QT/QTc in a Dish: An In Vitro Human Model That Accurately Predicts Clinical Concentration-QTc Relationships

"Thorough QT/corrected QT (QTc)" (TQT) studies are cornerstones of clinical cardiovascular safety assessment. However, TQT studies are resource intensive, and preclinical models predictive of the threshold of regulatory concern are lacking. We hypothesized that an in vitro model using induced pluripotent stem cell (iPSC)-derived cardiomyocytes from a diverse sample of human subjects can serve as a "TQT study in a dish." For 10 positive and 3 negative control drugs, in vitro concentration-QTc, computed using a population Bayesian model, accurately predicted known in vivo concentration-QTc. Moreover, predictions of the percent confidence that the regulatory threshold of 10 ms QTc prolongation would be breached were also consistent with in vivo evidence. This "TQT study in a dish," consisting of a population-based iPSC-derived cardiomyocyte model and Bayesian concentration-QTc modeling, has several advantages over existing in vitro platforms, including higher throughput, lower cost, and the ability to accurately predict the in vivo concentration range below the threshold of regulatory concern.

Combining stem cell-derived hepatocytes with impedance sensing to better predict human drug toxicity

Background: The liver plays a central role in human drug metabolism. To model drug metabolism, the major cell type of the liver, the hepatocyte, is commonly used. Hepatocytes can be derived from human and animal sources, including pluripotent stem cells. Cell-based models have shown promise in modeling human drug exposure. The assays used in those studies are normally 'snap-shot' in nature, and do not provide the complete picture of human drug exposure. Research design and methods: In this study, we employ stem cell-derived hepatocytes and impedance sensing to model human drug toxicity. This impedance-based stem cell assay reports hepatotoxicity in real time after treatment with compounds provided by industry. Results: Using electric cell-substrate impedance Sensing (ECIS), we were able to accurately measure drug toxicity post-drug exposure in real time and more quickly than gold standard biochemical assays. Conclusions: ECIS is robust and non-destructive methodology capable of monitoring human drug exposure with superior performance to current gold standard 'snapshot' assays. We believe that the methodology presented within this article could prove valuable in the quest to better predict off-target effects of drugs in humans.

Application of human pluripotent stem cells and pluripotent stem cell-derived cellular models for assessing drug toxicity

Introduction: Human pluripotent stem cells (hPSCs) are capable of differentiating into all types of cells in the body and so provide suitable toxicology screening systems even for hard-to-obtain human tissues. Since hPSCs can also be generated from differentiated cells and current gene editing technologies allow targeted genome modifications, hPSCs can be applied for drug toxicity screening both in normal and disease-specific models. Targeted hPSC differentiation is still a challenge but cardiac, neuronal or liver cells, and complex cellular models are already available for practical applications. Areas covered: The authors review new gene-editing and cell-biology technologies to generate sensitive toxicity screening systems based on hPSCs. Then the authors present the use of undifferentiated hPSCs for examining embryonic toxicity and discuss drug screening possibilities in hPSC-derived models. The authors focus on the application of human cardiomyocytes, hepatocytes, and neural cultures in toxicity testing, and discuss the recent possibilities for drug screening in a 'body-on-a-chip' model system. Expert opinion: hPSCs and their genetically engineered derivatives provide new possibilities to investigate drug toxicity in human tissues. The key issues in this regard are still the selection and generation of proper model systems, and the interpretation of the results in understanding in vivo drug effects.

Comprehensive human stem cell differentiation in a 2D and 3D mode to cardiomyocytes for long-term cultivation and multiparametric monitoring on a multimodal microelectrode array setup

Human pluripotent stem cell derived cardiomyocytes are a promising cell source for research and clinical applications like investigation of cardiomyopathies and therefore, identification and testing of novel therapeutics as well as for cell based therapy approaches. However, actually it´s a challenge to generate matured adult cardiomyocyte-like phenotype in a reasonable time. Moreover, there is a lack of applicable non-invasive label-free monitoring techniques providing quantitative parameters for analysing the culture stability and maturation status. In this context, we established an efficient protocol based on a combined differentiation of hiPSC in 2D cultures followed by a forced reaggregation step that leads to highly enriched (>90% cardiomyocytes) cardiomyocyte clusters. Interestingly, 3D cultures revealed an accelerated maturation as well as phenotype switch from atrial to ventricular cardiomyocytes. More strikingly using combined impedimetric and electrophysiological monitoring the high functionality and long-term stability of 3D cardiomyocyte cultures, especially in comparison to 2D cultures could be demonstrated. Additionally, chronotropic as well as QT-prolongation causing reference compounds were used for validating the cardio specific and sensitive reaction over the monitored time range of more than 100 days. Thus, the approach of multiparametric bioelectronic monitoring offers capabilities for the long-term quantitative analysis of hiPS derived cardiomyocyte culture functionality and long-term stability. Moreover, the same multiparametric bioelectronic platform can be used in combination with validated long-term stable cardiomyocyte cultures for the quantitative detection of compound induced effects. This could pave the way for more predictive in vitro chronic/repeated dose cardiotoxicity testing assays.

On-chip spatiotemporal electrophysiological analysis of human stem cell derived cardiomyocytes enables quantitative assessment of proarrhythmia in drug development

We examined a simultaneous combined spatiotemporal field potential duration (FPD) and cell-to-cell conduction time (CT) in lined-up shaped human embryonic stem cell-derived cardiomyocytes (hESC-CMs) using an on-chip multielectrode array (MEA) system to evaluate two origins of lethal arrhythmia, repolarization and depolarization. The repolarization index, FPD, was prolonged by E-4031 and astemizole, and shortened by verapamil, flecainide and terfenadine at 10 times higher than therapeutic plasma concentrations of each drug, but it did not change after lidocaine treatment up to 100 μM. CT was increased by astemizol, flecainide, terfenadine, and lidocaine at equivalent concentrations of Nav1.5 IC50, suggesting that CT may be an index of cardiac depolarization because the increase in CT (i.e., decrease in cell-to-cell conduction speed) was relevant to Nav1.5 inhibition. Fluctuations (short-term variability; STV) of FPD and CT, STVFPD and STVCT also discriminated between torsadogenic and non-torsadogenic compounds with significant increases in their fluctuation values, enabling precise prediction of arrhythmogenic risk as potential new indices.

Toxicological evaluation of convulsant and anticonvulsant drugs in human induced pluripotent stem cell-derived cortical neuronal networks using an MEA system

Functional evaluation assays using human induced pluripotent stem cell (hiPSC)-derived neurons can predict the convulsion toxicity of new drugs and the neurological effects of antiepileptic drugs. However, differences in responsiveness depending on convulsant type and antiepileptic drugs, and an evaluation index capable of comparing in vitro responses with in vivo responses are not well known. We observed the difference in synchronized burst patterns in the epileptiform activities induced by pentylentetrazole (PTZ) and 4-aminopryridine (4-AP) with different action mechanisms using multi-electrode arrays (MEAs); we also observed that 100 µM of the antiepileptic drug phenytoin suppressed epileptiform activities induced by PTZ, but increased those induced by 4-AP. To compare in vitro results with in vivo convulsive responses, frequency analysis of below 250 Hz, excluding the spike component, was performed. The in vivo convulsive firing enhancement of the high γ wave and β wave component were observed remarkably in in vitro hiPSC-derived neurons with astrocytes in co-culture. MEA measurement of hiPSC-derived neurons in co-culture with astrocytes and our analysis methods, including frequency analysis, appear effective for predicting convulsion toxicity, side effects, and their mechanism of action as well as the comparison of convulsions induced in vivo.

An in Vitro Assay of hERG K + Channel Potency for a New EGFR Inhibitor FHND004

FHND004 is a newly synthesized epidermal growth factor receptor (EGFR) inhibitor for the treatment of non-small cell lung cancer (NSCLC). The aim of the present study was to investigate the impacts of FHND004 on human ether-à-go-go-related gene (hERG) K⁺ channels and the molecular mechanisms underlying of its action. Whole-cell patch clamp recording was performed on wild type (WT), mutant hERG channels heterologously expressed in human embryonic kidney (HEK) 293 cells or I_Kr endogenously expressed in HL-1 cells, respectively. FHND004 inhibited hERG K⁺ currents in a concentration-dependent manner with IC₅₀ values of 8.46 ± 0.33 μM in HEK293 cells and 7.52 ± 1.27 μM in HL-1 cells, respectively. However, the inhibitory potency of FHND004 on hERG channels was significantly less than its precursor AZD9291. FHND004-induced inhibition was state-dependent with a preference within open state, but did not alter other kinetics including activation, inactivation, and recovery from inactivation or deactivation. In addition, FHND004 exhibited more potent inhibitory effects on WT/A422T and WT/H562P-hERG, two known long QT syndrome (LQTS) associated KCNH2 mutations, than WT alone. Mutations of the residues at pore regions (F656C, Y652A, S624A, and F557L) in hERG channels attenuated block effects of FHND004. Taken together, our results demonstrate the evidence that FHND004 is a less potent hERG blocker than its precursor AZD9291. There is, however, a need for caution in the potential use of FHND004 for treating NSCLC patients, especially in those with other concurrent triggering factors.

Detection of synchronized burst firing in cultured human induced pluripotent stem cell-derived neurons using a 4-step method

Human induced pluripotent stem cell-derived neurons are promising for use in toxicity evaluations in nonclinical studies. The multi-electrode array (MEA) assay is used in such evaluation systems because it can measure the electrophysiological function of a neural network noninvasively and with high throughput. Synchronized burst firing (SBF) is the main analytic parameter of pharmacological effects in MEA data, but an accurate method for detecting SBFs has not been established. In this study, we present a 4-step method that accurately detects a target SBF confirmed by the researcher's interpretation of a raster plot. This method calculates one set parameter per step, in the following order: the inter-spike interval (ISI), the number of spikes in an SBF, the inter-SBF interval, and the number of spikes in an SBF again. We found that the 4-step method is advantageous over the conventional method because it determines the preferable duration of an SBF, accurately distinguishes continuous SBFs, detects weak SBFs, and avoids false detection of SBFs. We found also that pharmacological evaluations involving SBF analysis may differ depending on whether the 4-step or conventional threshold method is used. This 4-step method may contribute to improving the accuracy of drug toxicity and efficacy evaluations using human induced pluripotent stem cell-derived neurons.

CSAHi study-2: Validation of multi-electrode array systems (MEA60/2100) for prediction of drug-induced proarrhythmia using human iPS cell-derived cardiomyocytes: Assessment of reference compounds and comparison with non-clinical studies and clinical information

With the aim of reconsidering ICH S7B and E14 guidelines, a new in vitro assay system has been subjected to worldwide validation to establish a better prediction platform for potential drug-induced QT prolongation and the consequent TdP in clinical practice. In Japan, CSAHi HEART team has been working on hiPS-CMs in the MEA (hiPS-CMs/MEA) under a standardized protocol and found no inter-facility or lot-to-lot variability for proarrhythmic risk assessment of 7 reference compounds. In this study, we evaluated the responses of hiPS-CMs/MEA to another 31 reference compounds associated with cardiac toxicities, and gene expression to further clarify the electrophysiological characteristics over the course of culture period. The hiPS-CMs/MEA assay accurately predicted reference compounds potential for arrhythmogenesis, and yielded results that showed better correlation with target concentrations of QTc prolongation or TdP in clinical setting than other current in vitro and in vivo assays. Gene expression analyses revealed consistent profiles in all samples within and among the testing facilities. This report would provide CiPA with informative guidance on the use of the hiPS-CMs/MEA assay, and promote the establishment of a new paradigm, beyond conventional in vitro and in vivo assays for cardiac safety assessment of new drugs.