AUTHOR=Uzun Ahmet U. , Mannhardt Ingra , Breckwoldt Kaja , Horváth András , Johannsen Silke S. , Hansen Arne , Eschenhagen Thomas , Christ Torsten 

TITLE=Ca2+-Currents in Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes Effects of Two Different Culture Conditions

JOURNAL=Frontiers in Pharmacology

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/pharmacology/articles/10.3389/fphar.2016.00300

DOI=10.3389/fphar.2016.00300

ISSN=1663-9812

ABSTRACT=<p>Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) provide a unique opportunity to study human heart physiology and pharmacology and repair injured hearts. The suitability of hiPSC-CM critically depends on how closely they share physiological properties of human adult cardiomyocytes (CM). Here we investigated whether a 3D engineered heart tissue (EHT) culture format favors maturation and addressed the L-type Ca<sup>2+</sup>-current (I<sub>Ca,L</sub>) as a readout. The results were compared with hiPSC-CM cultured in conventional monolayer (ML) and to our previous data from human adult atrial and ventricular CM obtained when identical patch-clamp protocols were used. HiPSC-CM were two- to three-fold smaller than adult CM, independently of culture format [capacitance ML 45 ± 1 pF (<italic>n</italic> = 289), EHT 45 ± 1 pF (<italic>n</italic> = 460), atrial CM 87 ± 3 pF (<italic>n</italic> = 196), ventricular CM 126 ± 8 pF (<italic>n</italic> = 50)]. Only 88% of ML cells showed I<sub>Ca</sub>, but all EHT. Basal I<sub>Ca</sub> density was 10 ± 1 pA/pF (<italic>n</italic> = 207) for ML and 12 ± 1 pA/pF (<italic>n</italic> = 361) for EHT and was larger than in adult CM [7 ± 1 pA/pF (<italic>p</italic> &lt; 0.05, <italic>n</italic> = 196) for atrial CM and 6 ± 1 pA/pF (<italic>p</italic> &lt; 0.05, <italic>n</italic> = 47) for ventricular CM]. However, ML and EHT showed robust T-type Ca<sup>2+</sup>-currents (I<sub>Ca,T</sub>). While (−)-Bay K 8644, that activates I<sub>Ca,L</sub> directly, increased I<sub>Ca,L</sub>to the same extent in ML and EHT, β<sub>1</sub>- and β<sub>2</sub>-adrenoceptor effects were marginal in ML, but of same size as (−)-Bay K 8644 in EHT. The opposite was true for serotonin receptors. Sensitivity to β<sub>1</sub> and β<sub>2</sub>-adrenoceptor stimulation was the same in EHT as in adult CM (−logEC<sub>50</sub>: 5.9 and 6.1 for norepinephrine (NE) and epinephrine (Epi), respectively), but very low concentrations of Rp-8-Br-cAMPS were sufficient to suppress effects (−logEC<sub>50</sub>: 5.3 and 5.3 respectively for NE and Epi). Taken together, hiPSC-CM express I<sub>Ca,L</sub> at the same density as human adult CM, but, in contrast, possess robust I<sub>Ca,T</sub>. Increased effects of catecholamines in EHT suggest more efficient maturation.</p>