Enhanced maturation of iPSC-CMs strongly improves their sensitivity to cardioactive drugs

Mario Schubert (Dresden)1, W. Li (Dresden)1, K. Fischer (Dresden)1, J. Pöche (Dresden)1, K. Guan (Dresden)1

1Medizinische Fakultät Carl Gustav Carus der TU Dresden Institut für Pharmakologie und Toxikologie Dresden, Deutschland


Human model systems based on induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) with patient-specific characteristics have the potential to revolutionize biomedical as well as translational cardiovascular research. Due to their human origin, high availability, and application possibilities in long-term culture, iPSC-CMs have decisive advantages over animal models or primary cells. One aspect represents the establishment of iPSC-CM-based drug screening platforms to identify pro-arrhythmogenic or cardiotoxic molecules. However, the use of iPSC-CM in vitro models to ultimately guide the selection of particular drugs for individual patients in the clinic remains a vision. A major limitation is the immature phenotype of iPSC-CMs, which affects their response to physiological stimuli and to cardioactive drugs, in comparison to adult CMs.

We have recently established an advanced culture protocol, which combines the use of a lipid-supplemented maturation medium (MM), nanopatterning surface (NP) and electrical stimulation (ES), to generate iPSC-CMs with strongly improved structural, metabolic as well as functional properties. In this study, we aimed to investigate whether the enhanced maturation state of iPSC-CMs correlates with an altered response to cardioactive drugs and thus better reflects clinical safety. Multi-electrode array (MEA) measurements revealed a step-wise increase in conduction velocity and spike amplitude by MM, MM+NP and MM+NP+ES, in comparison to iPSC-CMs cultured in widely used RPMI/B27 standard medium. These results demonstrate a significantly increased maturation state of iPSC-CMs cultivated under the influence of MM+NP+ES (mat-CMs) versus iPSC-CMs in RPMI/B27 medium (imm-CMs). To investigate the influence of the maturation state on drug response, we performed MEA recordings to study the effect of different cardioactive substances in mat-CMs in comparison to imm-CMs. We tested the influence of isoprenaline and found that mat-CMs had a stronger chronotropic response and higher sensitivity (decreased EC50) to β-adrenergic stimulation. As MEA allows detection of field potential duration (FPDc) as a surrogate for the clinically relevant QT-interval and thus arrhythmogenic potential, we examined the influence of the hERG-channel blocker E-4031. Although E-4031 prolonged the FPDc in both imm-CMs and mat-CMs, this effect was more pronounced in mat-CMs, indicating that mat-CMs have a higher sensitivity for the identification of proarrhythmic compounds. Moreover, testing of TTX demonstrated that the beating activity of mat-CMs was diminished in the presence of low concentrations of TTX, while the imm-CMs still beat spontaneously. As these findings point towards different mechanisms underlying depolarization of imm-CMs and mat-CMs, we investigated the effect of the L-type calcium channel (LTCC) blocker verapamil. Interestingly, verapamil diminished spontaneous beating activity in imm-CMs but not in mat-CMs, demonstrating that LTCC is important for depolarization of imm-CMs. In contrast, depolarization of mat-CMs mainly relied on sodium channel activity, better resembling the behavior of adult CMs.

Taken together, we demonstrated that the maturation of iPSC-CMs under the combined influence of MM, NP and ES strongly improves their electrophysiological functionality and drug response profile, which may provide the basis for iPSC-CM-based drug screening platforms with high translational potential.
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