Electrophysiological Analysis of human Pluripotent Stem Cell-derived Cardiomyocytes (hPSC-CMs) Using Multi-electrode Arrays (MEAs).

Cardiomyocytes can now be derived with high efficiency from both human embryonic and human induced-Pluripotent Stem Cells (hPSC). hPSC-derived cardiomyocytes (hPSC-CMs) are increasingly recognized as having great value for modeling cardiovascular diseases in humans, especially arrhythmia syndromes. They have also demonstrated relevance as in vitro systems for predicting drug responses, which makes them potentially useful for drug-screening and discovery, safety pharmacology and perhaps eventually for personalized medicine. This would be facilitated by deriving hPSC-CMs from patients or susceptible individuals as hiPSCs. For all applications, however, precise measurement and analysis of hPSC-CM electrical properties are essential for identifying changes due to cardiac ion channel mutations and/or drugs that target ion channels and can cause sudden cardiac death. Compared with manual patch-clamp, multi-electrode array (MEA) devices offer the advantage of allowing medium- to high-throughput recordings. This protocol describes how to dissociate 2D cell cultures of hPSC-CMs to small aggregates and single cells and plate them on MEAs to record their spontaneous electrical activity as field potential. Methods for analyzing the recorded data to extract specific parameters, such as the QT and the RR intervals, are also described here. Changes in these parameters would be expected in hPSC-CMs carrying mutations responsible for cardiac arrhythmias and following addition of specific drugs, allowing detection of those that carry a cardiotoxic risk.

Integrating cardiomyocytes from human pluripotent stem cells in safety pharmacology: has the time come?

Cardiotoxicity is a severe side effect of drugs that induce structural or electrophysiological changes in heart muscle cells. As a result, the heart undergoes failure and potentially lethal arrhythmias. It is still a major reason for drug failure in preclinical and clinical phases of drug discovery. Current methods for predicting cardiotoxicity are based on guidelines that combine electrophysiological analysis of cell lines expressing ion channels ectopically in vitro with animal models and clinical trials. Although no new cases of drugs linked to lethal arrhythmias have been reported since the introduction of these guidelines in 2005, their limited predictive power likely means that potentially valuable drugs may not reach clinical practice. Human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) are now emerging as potentially more predictive alternatives, particularly for the early phases of preclinical research. However, these cells are phenotypically immature and culture and assay methods not standardized, which could be a hurdle to the development of predictive computational models and their implementation into the drug discovery pipeline, in contrast to the ambitions of the comprehensive pro-arrhythmia in vitro assay (CiPA) initiative. Here, we review present and future preclinical cardiotoxicity screening and suggest possible hPSC-CM-based strategies that may help to move the field forward. Coordinated efforts by basic scientists, companies and hPSC banks to standardize experimental conditions for generating reliable and reproducible safety indices will be helpful not only for cardiotoxicity prediction but also for precision medicine. LINKED ARTICLES: This article is part of a themed section on New Insights into Cardiotoxicity Caused by Chemotherapeutic Agents. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.21/issuetoc.

Readthrough-Promoting Drugs Gentamicin and PTC124 Fail to Rescue Nav1.5 Function of Human-Induced Pluripotent Stem Cell-Derived Cardiomyocytes Carrying Nonsense Mutations in the Sodium Channel Gene SCN5A.

BACKGROUND: Several compounds have been reported to induce translational readthrough of premature stop codons resulting in the production of full-length protein by interfering with ribosomal proofreading. Here we examined the effect of 2 of these compounds, gentamicin and PTC124, in human-induced pluripotent stem cell (hiPSC)-derived cardiomyocytes bearing nonsense mutations in the sodium channel gene SCN5A, which are associated with conduction disease and potential lethal arrhythmias. METHODS AND RESULTS: We generated hiPSC from 2 patients carrying the mutations R1638X and W156X. hiPSC-derived cardiomyocytes from both patients recapitulated the expected electrophysiological phenotype, as evidenced by reduced Na+ currents and action potential upstroke velocities compared with hiPSC-derived cardiomyocytes from 2 unrelated control individuals. While we were able to confirm the readthrough efficacy of the 2 drugs in Human Embryonic Kidney 293 cells, we did not observe rescue of the electrophysiological phenotype in hiPSC-derived cardiomyocytes from the patients. CONCLUSIONS: We conclude that these drugs are unlikely to present an effective treatment for patients carrying the loss-of-function SCN5A gene mutations examined in this study.

Recessive cardiac phenotypes in induced pluripotent stem cell models of Jervell and Lange-Nielsen syndrome: disease mechanisms and pharmacological rescue.

Jervell and Lange-Nielsen syndrome (JLNS) is one of the most severe life-threatening cardiac arrhythmias. Patients display delayed cardiac repolarization, associated high risk of sudden death due to ventricular tachycardia, and congenital bilateral deafness. In contrast to the autosomal dominant forms of long QT syndrome, JLNS is a recessive trait, resulting from homozygous (or compound heterozygous) mutations in KCNQ1 or KCNE1. These genes encode the α and ß subunits, respectively, of the ion channel conducting the slow component of the delayed rectifier K(+) current, IKs. We used complementary approaches, reprogramming patient cells and genetic engineering, to generate human induced pluripotent stem cell (hiPSC) models of JLNS, covering splice site (c.478-2A>T) and missense (c.1781G>A) mutations, the two major classes of JLNS-causing defects in KCNQ1. Electrophysiological comparison of hiPSC-derived cardiomyocytes (CMs) from homozygous JLNS, heterozygous, and wild-type lines recapitulated the typical and severe features of JLNS, including pronounced action and field potential prolongation and severe reduction or absence of IKs. We show that this phenotype had distinct underlying molecular mechanisms in the two sets of cell lines: the previously unidentified c.478-2A>T mutation was amorphic and gave rise to a strictly recessive phenotype in JLNS-CMs, whereas the missense c.1781G>A lesion caused a gene dosage-dependent channel reduction at the cell membrane. Moreover, adrenergic stimulation caused action potential prolongation specifically in JLNS-CMs. Furthermore, sensitivity to proarrhythmic drugs was strongly enhanced in JLNS-CMs but could be pharmacologically corrected. Our data provide mechanistic insight into distinct classes of JLNS-causing mutations and demonstrate the potential of hiPSC-CMs in drug evaluation.