Characterisation of cardiomyocytes derived from human induced pluripotent stem cells as monolayers

Abstract

BackgroundHuman myocardial tissue for use in physiological research is difficult to obtain, and differences between human cardiac tissue and that used in animal models preclude full understanding of mechanisms of human arrhythmia. Stem-cell-derived cardiomyocytes might offer an alternative source of tissue. Therefore we aimed to explore the physiological features of cardiac tissue produced from human induced pluripotent stem (iPS) cells in monolayer form and investigated its response to β-adrenergic modulation. MethodsCardiomyocyte monolayers were produced as per the protocol of Burridge and colleagues. Monolayers were loaded with a calcium-sensitive dye (Fluo 4-AM, 5 μM) and imaged with fluorescence microscopy. Isoprenaline was used for β agonism and propranolol for β antagonism. Images were analysed with custom-written MatLab software to calculate relevant physiological variables. Ethics approval was not required because iPS cell lines were transformed. FindingsSeven monolayers were produced. They stained positive for troponin T and exhibited spontaneous contraction. Mean cycle length and calcium transient duration were 4·04 s (SD 2·90) and 1·88 s (1·18), respectively. Both variables were shortened on addition of isoprenaline (0·3 μM): cycle length 2·27 s (2·02) (p=0·0063) and duration 1·26 s (1·05) (p=0·0041). Propranolol (50 μM) reversed the effect of isoprenaline: cycle length 6·14 s (6·14) (p=0·045) and duration 2·43 s (1·04) (p=0·0009). The calcium transient amplitude reduced with cycle length because of a rise in baseline intracellular calcium (p=0·0138). In an additional monolayer, spiral waves were seen, which provided focal sources of excitation at higher frequencies than those in monolayers driven by non re-entrant mechanisms (cycle length 1·34 s [0·49], p=0·0497). InterpretationCardiomyocytes were successfully derived from human iPS cells and showed a chronotropic response to β-adrenergic modulation. The data support the plausibility of understanding arrhythmogenesis by use of human iPS derived cardiomyocytes. The immaturity of the derived cells is a potential limitation of the study. The presence of spiral waves in one case was notable since spiral waves or rotors are thought to drive arrhythmias such as atrial fibrillation. FundingBritish Heart Foundation.