title: Application of human stem cell-derived cardiomyocytes in safety pharmacology requires caution beyond hERG.
abstract: Human embryonic stem cell-derived cardiomyocytes (hESC-CM) have been proposed as a new model for safety pharmacology. So far, a thorough description of their basic electrophysiology and extensive testing, and mechanistic explanations, of their overall pro-arrhythmic ability is lacking. Under standardized conditions, we have evaluated the sensitivity of hESC-CM to proarrhythmic provocations by blockade of hERG and other channels. Using voltage patch clamp, some ion current densities (pA/pF) in hESC-CM were comparable to adult CM: I(Kr) (-12.5 ± 6.9), I(Ks) (0.65 ± 0.12), I(Na,peak) (-72 ± 21), I(Na,late) (-1.10 ± 0.36), and I(Ca,L) (-4.3 ± 0.6). I(f) density was larger (-10 ± 1.1) and I(K1) not existent or very small (-2.67 ± 0.3). The low I(K1) density was corroborated by low KCNJ2 mRNA levels. Effects of pro-arrhythmic compounds on action potential (AP) parameters and provocation of early afterdepolarizations (EADs) revealed that Chromanol293B (100 μmol/l) and Bay K8644 (1 μmol/l) both significantly prolonged APD(90). ATX-II (<1 μmol/l ) and BaCl(2) (10 μmol/l ) had no effect on APD. The only compound that triggered EADs was hERG blocker Cisapride. Computer simulations and AP clamp showed that the immature AP of hESC-CM prevents proper functioning of I(Na)-channels, and result in lower peak/maximal currents of several other channels, compared to the adult situation. Lack of functional I(K1) channels and shifted I(Na) channel activation cause a rather immature electrophysiological phenotype in hESC-CM, and thereby limits the potential of this model to respond accurately to pro-arrhythmic triggers other than hERG block. Maturation of the electrical phenotype is a prerequiste for future implementation of the model in arrhythmogenic safety testing.
authors.affiliation: Department of Medical Physiology, Division Heart & Lungs, University Medical Center Utrecht, Utrecht, The Netherlands. m.k.b.jonsson@umcutrecht.nl
authors.forename: Malin K B
authors.initials: MK
authors.lastname: Jonsson
authors.forename: Marc A
authors.initials: MA
authors.lastname: Vos
authors.forename: Gary R
authors.initials: GR
authors.lastname: Mirams
authors.forename: Göran
authors.initials: G
authors.lastname: Duker
authors.forename: Peter
authors.initials: P
authors.lastname: Sartipy
authors.forename: Teun P
authors.initials: TP
authors.lastname: de Boer
authors.forename: Toon A B
authors.initials: TA
authors.lastname: van Veen
mesh_terms: D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000200:Action Potentials; D001145:Arrhythmias, Cardiac / Q000188:drug therapy / Q000473:pathology; D001552:Benzazepines / Q000494:pharmacology; D002120:Calcium Channel Agonists / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020013:Calcium Signaling; D002478:Cells, Cultured; D020117:Cisapride / Q000494:pharmacology; D004353:Drug Evaluation, Preclinical; D000072237:ERG1 Potassium Channel; D053595:Embryonic Stem Cells / Q000502:physiology*; D051638:Ether-A-Go-Go Potassium Channels / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006801:Humans; D032383:Myocytes, Cardiac / Q000187:drug effects*; D009543:Nifedipine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D015222:Sodium Channels / Q000378:metabolism
chemical_list: D001552:Benzazepines; D002120:Calcium Channel Agonists; D002121:Calcium Channel Blockers; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; C000606913:KCNH2 protein, human; D015222:Sodium Channels; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D009543:Nifedipine; C043636:zatebradine; D020117:Cisapride