Chronic cardiotoxicity assessment of BMS-986094, a guanosine nucleotide analogue, using human iPS cell-derived cardiomyocytes.

Predicting drug-induced side effects in the cardiovascular system is very important because it can lead to the discontinuation of new drugs/candidates or the withdrawal of marketed drugs. Although chronic assessment of cardiac contractility is an important issue in safety pharmacology, an in vitro evaluation system has not been fully developed. We previously developed an imaging-based contractility assay system to detect acute cardiotoxicity using human iPS cell-derived cardiomyocytes (hiPSC-CMs). To extend the system to chronic toxicity assessment, we examined the effects of the anti-hepatitis C virus (HCV) drug candidate BMS-986094, a guanosine nucleotide analogue, which was withdrawn from phase 2 clinical trials because of unexpected contractility toxicities. Additionally, we examined sofosbuvir, another nucleotide analogue inhibitor of HCV that has been approved as an anti-HCV drug. Motion imaging analysis revealed the difference in cardiotoxicity between the cardiotoxic BMS-986094 and the less toxic sofosbuvir in hiPSC-CMs, with a minimum of 4 days of treatment. In addition, we found that BMS-986094-induced contractility impairment was mediated by a decrease in calcium transient. These data suggest that chronic treatment improves the predictive power for the cardiotoxicity of anti-HCV drugs. Thus, hiPSC-CMs can be a useful tool to assess drug-induced chronic cardiotoxicity in non-clinical settings.

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.

In-silico human electro-mechanical ventricular modelling and simulation for drug-induced pro-arrhythmia and inotropic risk assessment.

Human-based computational modelling and simulation are powerful tools to accelerate the mechanistic understanding of cardiac patho-physiology, and to develop and evaluate therapeutic interventions. The aim of this study is to calibrate and evaluate human ventricular electro-mechanical models for investigations on the effect of the electro-mechanical coupling and pharmacological action on human ventricular electrophysiology, calcium dynamics, and active contraction. The most recent models of human ventricular electrophysiology, excitation-contraction coupling, and active contraction were integrated, and the coupled models were calibrated using human experimental data. Simulations were then conducted using the coupled models to quantify the effects of electro-mechanical coupling and drug exposure on electrophysiology and force generation in virtual human ventricular cardiomyocytes and tissue. The resulting calibrated human electro-mechanical models yielded active tension, action potential, and calcium transient metrics that are in agreement with experiments for endocardial, epicardial, and mid-myocardial human samples. Simulation results correctly predicted the inotropic response of different multichannel action reference compounds and demonstrated that the electro-mechanical coupling improves the robustness of repolarisation under drug exposure compared to electrophysiology-only models. They also generated additional evidence to explain the partial mismatch between in-silico and in-vitro experiments on drug-induced electrophysiology changes. The human calibrated and evaluated modelling and simulation framework constructed in this study opens new avenues for future investigations into the complex interplay between the electrical and mechanical cardiac substrates, its modulation by pharmacological action, and its translation to tissue and organ models of cardiac patho-physiology.

Assessment of Drug Proarrhythmic Potential in Electrically Paced Human Induced Pluripotent Stem Cell-Derived Ventricular Cardiomyocytes Using Multielectrode Array.

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have been widely used for the assessment of drug proarrhythmic potential through multielectrode array (MEA). HiPSC-CM cultures beat spontaneously with a wide range of frequencies, however, which could affect drug-induced changes in repolarization. Pacing hiPSC-CMs at a physiological heart rate more closely resembles the state of in vivo ventricular myocytes and permits the standardization of test conditions to improve consistency. In this study, we systematically investigated the time window of stable ion currents in high-purity hiPSC-derived ventricular cardiomyocytes (hiPSC-vCMs) and confirmed that these cells could be used to correctly predict the proarrhythmic risk of Comprehensive In Vitro Proarrhythmia Assay (CiPA) reference compounds. To evaluate drug proarrhythmic potentials at a physiological beating rate, we used a MEA to electrically pace hiPSC-vCMs, and we recorded regular field potential waveforms in hiPSC-vCMs treated with DMSO and 10 CiPA reference drugs. Prolongation of field potential duration was detected in cells after exposure to high- and intermediate-risk drugs; in addition, drug-induced arrhythmia-like events were observed. The results of this study provide a simple and feasible method to investigate drug proarrhythmic potentials in hiPSC-CMs at a physiological beating rate.

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.

Video-based assessment of drug-induced effects on contractile motion properties using human induced pluripotent stem cell-derived cardiomyocytes.

INTRODUCTION: Drug-induced inotropic change is a risk factor in drug development; thus, de-risking is desired in the early stages of drug development. Unlike proarrhythmic risk assessment using human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs), few in vitro models were validated to predict cardiac contractility. Motion field imaging (MFI), a high-resolution block matching-based optical flow technique, was expected to possess high quantitative predictivity in the detection of contraction speed. We aimed to establish an in vitro model to assess drug-induced contractile changes using hiPSC-CMs and MFI. METHODS: MFI was designed to noninvasively characterize cardiomyocyte contractile behavior by analyzing light microscope video images, and maximum contraction speed (MCS) was used as the index of contractility. Using MFI, 9 inactive compounds, 10 negative inotropes, and 10 positive inotropes were tested. Two negative chronotropes, ZD7288 and ivabradine, were also tested. To determine the sensitivity and specificity of the assay, the minimum effective concentration of the MCS was compared with the human effective total therapeutic concentration for 28 compounds in clinical use. RESULTS: For 8 negative and 8 positive inotropes, the effects observed in in vivo and clinical studies were detected in MFI assay. MFI assay showed negative chronotropic changes without inotropic changes. MFI assay presented sufficient specificity (83%) and sensitivity (88%), and RNA-sequence analysis provided an insight into the relationship between occurrence of the false compounds and target gene expression. DISCUSSION: We demonstrated the utility of MFI assay using hiPSC-CMs to assess drug-induced contractile function. These results will facilitate the de-risking of compounds during early drug development.

Reversal of angiotensin-(1-12)-caused positive modulation on left ventricular contractile performance in heart failure: Assessment by pressure-volume analysis.

BACKGROUND: Angiotensin-(1-12) [Ang-(1-12)] is a renin-independent precursor for direct angiotensin-II production by chymase. Substantial evidence suggests that heart failure (HF) may alter cardiac Ang-(1-12) expression and activity; this novel Ang-(1-12)/chymase axis may be the main source for angiotensin-II deleterious actions in HF. We hypothesized that HF alters cardiac response to Ang-(1-12). Its stimulation may produce cardiac negative modulation and exacerbate left ventricle (LV) systolic and diastolic dysfunction. METHODS AND RESULTS: We assessed the effects of Ang-(1-12) (2 nmol/kg/min, iv, 10 min) on LV contractility, LV diastolic filling, and LV-arterial coupling (AVC) in 16 SD male rats with HF-induced by isoproterenol (3 mo after 170 mg/kg sq. for 2 consecutive days) and 10 age-matched male controls. In normal controls, versus baseline, Ang-(1-12) increased LV end-systolic pressure, without altering heart rate, arterial elastance (EA), LV end-diastolic pressure (PED), the time constant of LV relaxation (τ) and ejection fraction (EF). Ang-(1-12) significantly increased the slopes (EES) of LV end-systolic pressure (P)-volume (V) relations and the slopes (MSW) of LV stroke wok-end-diastolic V relations, indicating increased LV contractility. AVC (quantified as EES/EA) improved. In contrast, in HF, versus HF baseline, Ang-(1-12) produced a similar increase in PES, but significantly increased τ, EA, and PED. The early diastolic portion of LV PV loop was shifted upward with reduced in EF. Moreover, Ang-(1-12) significantly decreased EES and MSW, demonstrating decreased LV contractility. AVC was decreased by 43%. CONCLUSIONS: In both normal and HF rats, Ang-(1-12) causes similar vasoconstriction. In normal, Ang-(1-12) increases LV contractile function. In HF, Ang-(1-12) has adverse effects and depresses LV systolic and diastolic functional performance.

Cardiac safety assessment with motion field imaging analysis of human iPS cell-derived cardiomyocytes is improved by an integrated evaluation with cardiac ion channel profiling.

We validated a motion field imaging (MFI) assay with human induced pluripotent stem cell-derived cardiomyocytes (hiPS-CMs) as a model to assess multiple cardiac liabilities by comparing the guinea-pig Langendorff heart with hiPS-CMs using 4 reference compounds and 9 internal compounds. We investigated repolarization duration, beating rate (BR), conduction speed, contractility, and inhibitory profile of three cardiac ion channels: hERG, Cav1.2, and Nav1.5. For repolarization, the contraction-relaxation duration (CRDc) of hiPS-CMs was generally consistent with the QTc interval of Langendorff heart. However, 2 internal compounds shortened CRDc despite QTc prolongation in Langendorff heart. Cardiac ion channel profiling revealed that hiPS-CMs could not be used to detect QTc prolongation when the value of Cav1.2 IC50 / hERG IC50 for a compound was between 1 and 10, whereas hiPS-CMs showed responses largely consistent with Langendorff heart when Cav1.2 IC50 / hERG IC50 was below 1 or above 10. The accuracy of hiPS-CMs for the BR was not high, mainly because the BR of hiPS-CMs was increased by an inhibition of Cav1.2. The hiPS-CMs were highly sensitive to conduction speed and contractility, able to detect QRS widening caused by Nav1.5-inhibition, as well as decreased LVdP/dtmax caused by the inhibition of Cav1.2 and/or Nav1.5. In conclusion, the MFI assay with hiPS-CMs would be useful for evaluating multiple cardiac liabilities. The ion channel profile helps to interpret the results of MFI assay and correctly evaluate cardiac risks. Therefore, an integrated cardiac safety assessment with MFI and ion channel profiling is recommended.

Usefulness of myocardial work measurement in the assessment of left ventricular systolic reserve response to spironolactone in heart failure with preserved ejection fraction.

AIMS: Improvement in left ventricular (LV) systolic reserve, including exertional increase in global longitudinal strain (GLS), may contribute to the clinical benefit from therapeutic interventions in heart failure with preserved ejection fraction (HFpEF). However, GLS is an afterload-dependent parameter, and its measurements may not adequately reflect myocardial contractility recruitment with exercise. The estimation of myocardial work (MW) allows correction of GLS for changing afterload. We sought to investigate the associations of GLS and MW parameters with the response of exercise capacity to spironolactone in HFpEF. METHODS AND RESULTS: We analysed 114 patients (67 ± 8 years) participating in the STRUCTURE study (57 randomized to spironolactone and 57 to placebo). Resting and immediately post-exercise echocardiograms were performed at baseline and at 6-month follow-up. The following indices of MW were assessed: global work index (GWI), global constructive work (GCW), global wasted work, and global work efficiency. The amelioration of exercise intolerance at follow-up in the spironolactone group was accompanied by a significant improvement in exertional increase in GCW (P = 0.002) but not in GLS and other MW parameters. Increase in exercise capacity at 6 months was independently correlated with change in exertional increase in GCW from baseline to follow-up (ß = 0.24; P = 0.009) but not with GLS (P = 0.14); however, no significant interaction with the use of spironolactone on peak VO2 was found (P = 0.97). CONCLUSION: GCW as a measure of LV contractile response to exertion is a better determinant of exercise capacity in HFpEF than GLS. Improvement in functional capacity during follow-up is associated with improvement in exertional increment of GCW.

Contractile performance of the Alaska blackfish (Dallia pectoralis) ventricle: Assessment of the effects of temperature, pacing frequency, the role of the sarcoplasmic reticulum in contraction and adrenergic stimulation.

The air-breathing Alaska blackfish (Dallia pectoralis) experiences aquatic hypoxia, but restricted air-access in winter due to ice-cover. To lend insight into its overwintering strategy, we examined the effects of thermal acclimation (15 °C vs. 5 °C), acute temperature change (to 10 °C), increased pacing frequency, inhibition of sarcoplasmic reticulum (SR) Ca2+ release and uptake and adrenaline (1000 nmol l-1) on the contractile performance of isometrically-contracting, electrically-paced ventricular strips. At routine pacing frequencies, maximal developed force (Fmax) was equivalent at 5 °C (2.1 ±â€¯0.2 mN mm-2) and 15 °C (2.2 ±â€¯0.3 mN mm-2), whereas contraction durations were 2.2- to 2.4-times longer and contraction rates 2.4- to 3.5-times slower at 5 °C. Maximum contraction frequency was reduced by decreased temperature, being 0.91 ±â€¯0.04 Hz at 15 °C, 0.35 ±â€¯0.02 Hz at 5 °C and equivalent between acclimation groups at 10 °C (~0.8 Hz). 15 °C and 5 °C strips were insensitive to SR inhibition at routine stimulation frequencies, but SR function supported high contraction rates at 10 °C and 15 °C. Adrenaline shortened T0.5R and increased relaxation rate by 18-40% at 15 °C, whereas at 5 °C, adrenaline augmented Fmax by 15-25%, in addition to increasing contraction kinetics by 22-82% and decreasing contraction duration by 20%. Overall, the results reveal that ventricular contractility is suppressed in cold-acclimated Alaska blackfish largely by acute and perhaps direct effects of decreased temperature, which effectively preconditions the tissue for low energy supply during winter hypoxia. Additionally, the level of cardiac performance associated with maintained activity in winter is supported by enhanced inotropic responsiveness to adrenaline at 5 °C.

Assessment of PKA and PKC inhibitors on force and kinetics of non-failing and failing human myocardium.

AIMS: Heart failure (HF) is a prevalent disease that is considered the foremost reason for hospitalization in the United States. Most protein kinases (PK) are activated in heart disease and their inhibition has been shown to improve cardiac function in both animal and human studies. However, little is known about the direct impact of PKA and PKC inhibitors on human cardiac contractile function. MATERIAL AND METHODS: We investigated the ex vivo effect of such inhibitors on force as well as on kinetics of left ventricular (LV) trabeculae dissected from non-failing and failing human hearts. In these experiments, we applied 0.5 µM of H-89 and GF109203X, which are PKA and PKC inhibitors, respectively, in comparison to their vehicle DMSO (0.05%). KEY FINDINGS AND CONCLUSION: Statistical analyses revealed no significant effect for H-89 and GF109203X on either contractile force or kinetics parameters of both non-failing and failing muscles even though they were used at a concentration higher than the reported IC50s and Kis. Therefore, several factors such as selectivity, concentration, and treatment time, which are related to these PK inhibitors according to previous studies require further exploration.

Experimental assessment of a myocyte-based multiscale model of cardiac contractile dysfunction.

Cardiac contractile dysfunction (CD) is a multifactorial syndrome caused by different acute or progressive diseases which hamper assessing the role of the underlying mechanisms characterizing a defined pathological condition. Mathematical modeling can help to understand the processes involved in CD and analyze their relative impact in the overall response. The aim of this study was thus to use a myocyte-based multiscale model of the circulatory system to simulate the effects of halothane, a volatile anesthetic which at high doses elicits significant acute CD both in isolated myocytes and intact animals. Ventricular chambers built using a human myocyte model were incorporated into a whole circulatory system represented by resistances and capacitances. Halothane-induced decreased sarco(endo)plasmic reticulum Ca2+ (SERCA2a) reuptake pump, transient outward K+ (Ito), Na+-Ca2+ exchanger (INCX) and L-type Ca2+ channel (ICaL) currents, together with ryanodine receptor (RyR2) increased open probability (Po) and reduced myofilament Ca2+ sensitivity, reproduced equivalent decreased action potential duration at 90% repolarization and intracellular Ca2+ concentration at the myocyte level reported in the literature. In the whole circulatory system, model reduction in mean arterial pressure, cardiac output and regional wall thickening fraction was similar to experimental results in open-chest sheep subjected to acute halothane overdose. Effective model performance indicates that the model structure could be used to study other changes in myocyte targets eliciting CD.

Single Versus Standard Multiview Assessment of Global Longitudinal Strain for the Diagnosis of Cardiotoxicity During Cancer Therapy.

OBJECTIVES: The goal of this study was to compare echocardiographic measurements of global longitudinal strain (GLS) (using 3 apical views) with single-view longitudinal strain (LS, 4- or 2-chamber [4CV_LS and 2CV_LS, respectively]) for detection of cancer-therapy related cardiotoxicity. BACKGROUND: GLS is useful for the detection of cardiotoxicity, but the need for repeated measurements poses a significant burden on busy echocardiography laboratories. A single-view LS measurement, possibly at point of care, could improve efficiency. METHODS: Seventeen international centers prospectively recruited 108 patients (mean age 54 ± 13 years) at high risk for cardiotoxicity as part of the ongoing SUCCOUR (Strain Surveillance for Improving Cardiovascular Outcomes During Chemotherapy) randomized controlled trial. Echocardiography performed at baseline and follow-up were analyzed in a core laboratory setting blinded to clinical information. Peak systolic GLS and LS were measured from raw data. Cardiotoxicity was defined by reduction in left ventricular ejection fraction >0.10 to <0.55 or a relative drop in GLS by ≥12%. RESULTS: Cardiotoxicity developed in 46 patients by either criteria. Baseline and follow-up 2-dimensional left ventricular ejection fraction were 61 ± 4% and 58 ± 5%, respectively (p < 0.001). The baseline GLS (-20.9 ± 2.4%) was not different from 4CV_LS (-20.7 ± 2.5%; p = 0.09) or 2CV_LS (-21.1 ± 3.1%; p = 0.25). The follow-up GLS (-19.5 ± 2.4%) was also similar to 4CV_LS (-19.5 ± 2.6%; p = 0.80) and 2CV_LS (-19.7 ± 3.1%; p = 0.19). There was good correlation between GLS and 4CV_LS at baseline (r = 0.86; p < 0.001) and follow-up (r = 0.89; p < 0.001) and with 2CV_LS at baseline (r = 0.87; p < 0.001) and follow-up (r = 0.88; p < 0.001). However, there was 15% to 22% disagreement between GLS and 4CV_LS or 2CV_LS for the detection of cardiotoxicity. The interobserver and intraobserver reproducibility was higher for GLS (intraclass correlation: 0.93 to 0.95; coefficient of variance: 2.9% to 3.7%) compared with either single-chamber-based LS measurement (intraclass correlation: 0.85 to 0.91; coefficient of variance: 4.1% to 4.8%). CONCLUSIONS: Although there was good correlation between GLS and single-view LS measurements, single-view LS measurement led to disagreement in the diagnosis of cardiotoxicity in up to 22% of patients. GLS measurements were more reproducible than single-view LS. GLS based on 3 apical views should remain the preferred technique for detection of cardiotoxicity. (Strain Surveillance for Improving Cardiovascular Outcomes During Chemotherapy [SUCCOUR]; ACTRN12614000341628).

An Empirically Derived Pediatric Cardiac Inotrope Score Associated With Pediatric Heart Surgery.

We aimed to empirically derive an inotrope score to predict real-time outcomes using the doses of inotropes after pediatric cardiac surgery. The outcomes evaluated included in-hospital mortality, prolonged hospital length of stay, and composite poor outcome (mortality or prolonged hospital length of stay). The study population included patients <18 years of age undergoing heart operations (with or without cardiopulmonary bypass) of varying complexity. To create this novel pediatric cardiac inotrope score (PCIS), we collected the data on the highest doses of 4 commonly used inotropes (epinephrine, norepinephrine, dopamine, and milrinone) in the first 24 hours after heart operation. We employed a hierarchical framework by representing discrete probability models with continuous latent variables that depended on the dosage of drugs for a particular patient. We used Bayesian conditional probit regression to model the effects of the inotropes on the mean of the latent variables. We then used Markov chain Monte Carlo simulations for simulating posterior samples to create a score function for each of the study outcomes. The training dataset utilized 1030 patients to make the scientific model. An online calculator for the tool can be accessed at https://soipredictiontool.shinyapps.io/InotropeScoreApp. The newly proposed empiric PCIS demonstrated a high degree of discrimination for predicting study outcomes in children undergoing heart operations. The newly proposed empiric PCIS provides a novel measure to predict real-time outcomes using the doses of inotropes among children undergoing heart operations of varying complexity.

Usefulness of cardiotoxicity assessment using calcium transient in human induced pluripotent stem cell-derived cardiomyocytes.

Monitoring dramatic changes in intracellular calcium ion levels during cardiac contraction and relaxation, known as calcium transient, in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) would be an attractive strategy for assessing compounds on cardiac contractility. In addition, as arrhythmogenic compounds are known to induce characteristic waveform changes in hiPSC-CMs, it is expected that calcium transient would allow evaluation of not only compound-induced effects on cardiac contractility, but also compound arrhythmogenic potential. Using a combination of calcium transient in hiPSC-CMs and a fast kinetic fluorescence imaging detection system, we examined in this study changes in calcium transient waveforms induced by a series of 17 compounds that include positive/negative inotropic agents as well as cardiac ion channel activators/inhibitors. We found that all positive inotropic compounds induced an increase in peak frequency and/or peak amplitude. The effects of a negative inotropic compound could clearly be detected in the presence of a ß-adrenergic receptor agonist. Furthermore, most arrhythmogenic compounds raised the ratio of peak decay time to peak rise time (D/R ratio) in calcium transient waveforms. Compound concentrations at which these parameters exceeded cutoff values correlated well with systemic exposure levels at which arrhythmias were reported to be evoked. In conclusion, we believe that peak analysis of calcium transient and determination of D/R ratio are reliable methods for assessing compounds' cardiac contractility and arrhythmogenic potential, respectively. Using these approaches would allow selection of compounds with low cardiotoxic potential at the early stage of drug discovery.

From the Cover: High-Throughput Imaging of Cardiac Microtissues for the Assessment of Cardiac Contraction during Drug Discovery.

Cardiotoxicity is a common cause of attrition in preclinical and clinical drug development. Current in vitro approaches have two main limitations, they either are limited to low throughput methods not amendable to drug discovery or lack the physiological responses to allow an integrated risk assessment. A human 3D cardiac microtissue containing human-induced pluripotent stem cell-derived cardiomyocytes (hiPS-CMs), cardiac endothelial cells and cardiac fibroblast were used to assess their suitability to detect drug induced changes in cardiomyocyte contraction. These cardiac microtissues, have a uniform size, spontaneously beat, lack a hypoxic core, and contain key markers of each cell type. Application of field stimulation and measurement of cardiac contraction confirm cardiac microtissues to be a suitable model to investigate drug-induced changes in cardiomyocyte contractility. Using a bespoke image acquisition work flow and optical flow analysis method to test 29 inotroptic and 13 non-inotroptic compounds in vivo We report that cardiac microtissues provide a high-throughput experimental model that is both able to detect changes in cardiac contraction with a sensitivity and specificity of 80 and 91%, respectively, and provide insight into the direction of the inotropic response. Allowing improved in vitro cardiac contractility risk assessment. Moreover, our data provide evidence of the detection of this liability at therapeutically relevant concentrations with a throughput amenable to drug discovery.

Clinical Assessment of Histidine-Tryptophan-Ketoglutarate Solution and Modified St. Thomas' Solution in Pediatric Cardiac Surgery of Tetralogy of Fallot.

The objective of this study is to compare the myocardium protective effect of Bretschneider's histidine-tryptophan-ketoglutarate (HTK) solution versus Modified St. Thomas' (STH) solution in pediatric cardiac surgery of Tetralogy of Fallot (TOF). Seventy-seven pediatric patients of TOF who received the total surgical repair were reviewed, from January 2014 to October 2015. A horizontal comparison between HTK solution and modified STH solution has been made since the HTK solutions were started to be used in our hospital. The patients were divided into the HTK group (n = 35) and the STH group (n = 33). The perioperative values of the groups were assessed in this study. The primary endpoints including spontaneous cardiac re-beating time, intensive care unit (ICU) stay, overall stay, mechanical ventilation postoperation, postoperation stay, overall stay, and perioperative echocardiographic results were analyzed in this study. We found that spontaneous cardiac re-beating time of the HTK group was significantly shorter than that of the STH group (0.26 min ± 0.56 vs. 1.33 ± 1.02, P < 0.001). There were no significant differences between the two groups in ICU stay (P = 0.29), postoperative mechanical ventilation time (P = 0.84), overall stay (0.73); and the mortalities of the two groups were similar (2.9 vs. 3.0%). Aimed at pediatric cardiac surgery of TOF, this study suggests that with similar aorta cross-clamping time, modified STH solution is as safe as HTK solution.

Promising approach for the preclinical assessment of cardiac risks using left ventricular pressure-volume loop analyses in anesthetized monkeys.

INTRODUCTION: Load-independent cardiac parameters obtained from the ventricular pressure-volume relationship are recognized as gold standard indexes for evaluating cardiac inotropy. In this study, for better analyses of cardiac risks, load-independent pressure-volume loop parameters were assessed in addition to load-dependent inotropic, hemodynamic and electrocardiographic changes in isoflurane-anesthetized monkeys. METHODS: The animals were given milrinone (a PDE 3 inhibitor), metoprolol (a ß-blocker), or dl-sotalol (a ß+IKr blocker) intravenously over 10min at two dose levels including clinically relevant doses (n=5/drug). RESULTS: Milrinone and metoprolol produced positive and negative inotropy, respectively. These effects were detected as changes in the slope of the preload-recruitable stroke work, which is a load-independent inotropic parameter. However, dl-sotalol did not alter the slope of the preload-recruitable stroke work. That means dl-sotalol produced no inotropy, although it decreased load-dependent inotropic parameters, including maximal upstroke velocity of left ventricular pressure, attributable to decreased heart rate and blood pressure. Other typical pharmacological effects of the compounds tested were also detected. Both ß-blockers produced PR prolongation, decreased left ventricular end-systolic pressure, increased left ventricular end-diastolic pressure, and increased maximal descending velocity of left ventricular pressure and time constant for isovolumic relaxation. dl-Sotalol also prolonged heart-rate-corrected QT interval. Milrinone induced reflex tachycardia, PR shortening, and decreased left ventricular end-diastolic pressure. DISCUSSION: The overall assessment by not only load-dependent inotropic parameters but also load-independent parameters obtained from the ventricular pressure-volume loop analysis using monkeys can provide further appropriate information for the assessment of drug-induced cardiac risks.