Virus-free hiPSCs differentiate efficiently into cardiomyocytes with cardiac-specific molecular, structural, and functional properties that recapitulate the developmental ontogeny of cardiogenesis. These results, coupled with the potential to generate patient-specific hiPSC lines, hold great promise for the development of an in vitro platform for drug pharmacogenomics, disease modelling, and regenerative medicine.
Development of pharmaceutical agents for cardiac indication demands elaborate safety screening in which assessing repolarization of cardiac cells remains a critical path in risk evaluations. An efficient platform for evaluating cardiac repolarization in vitro significantly facilitates drug developmental programs. In a proof of principle study, we examined the effect of antiarrhythmogenic drugs (Vaughan Williams class I-IV) and noncardiac active drugs (terfenadine and cisapride) on the repolarization profile of viral-free human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). Extracellular field potential (FP) recording using microelectrode arrays demonstrated significant delayed repolarization as prolonged corrected FP durations (cFPDs) by class I (quinidine and flecainide), class III (sotalol and amiodarone), and class IV (verapamil), whereas class II drugs (propranolol and nadolol) had no effects. Consistent with their sodium channel-blocking ability, class I drugs also significantly reduced FPmin and conduction velocity. Although lidocaine (class IB) had no effects on cFPDs, verapamil shortened cFPD and FPmin by 25 and 50%, respectively. Furthermore, verapamil reduced beating frequencies drastically. Importantly, the examined drugs exhibited dose-response curve on prolongation of cFPDs at an effective range that correlated significantly with therapeutic plasma concentrations achieved clinically. Consistent with clinical outcomes, drug-induced arrhythmia of tachycardia and bigeminy-like waveforms by quinidine, flecainide, and sotalol was demonstrated at supraphysiological concentrations. Furthermore, off-target effects of terfenadine and cisapride on cFPD and Na( + ) channel blockage were similarly revealed. These results suggest that hiPSC-CMs may be useful for safety evaluation of cardioactive and noncardiac acting drugs for personalized medicine.
Brugada syndrome (BrS) is an inherited cardiac arrhythmia commonly associated with SCN5A mutations, yet its ionic mechanisms remain unclear due to a lack of cellular models. Here, we used human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) from a BrS patient (BrS1) to evaluate the roles of Na+ currents (INa) and transient outward K+ currents (Ito) in BrS induced action potential (AP) changes. To understand the role of these current changes in repolarization we employed dynamic clamp to “electronically express” IK1 and restore normal resting membrane potentials and allow normal recovery of the inactivating currents, INa, ICa and Ito. HiPSC-CMs were generated from BrS1 with a compound SCN5A mutation (p. A226V & p. R1629X) and a healthy sibling control (CON1). Genome edited hiPSC-CMs (BrS2) with a milder p. T1620M mutation and a commercial control (CON2) were also studied. CON1, CON2 and BrS2, had unaltered peak INa amplitudes, and normal APs whereas BrS1, with over 75% loss of INa, displayed a loss-of-INa basal AP morphology (at 1.0 Hz) manifested by a reduced maximum upstroke velocity (by ~80%, p < 0.001) and AP amplitude (p < 0.001), and an increased phase-1 repolarization pro-arrhythmic AP morphology (at 0.1 Hz) in ~25% of cells characterized by marked APD shortening (~65% shortening, p < 0.001). Moreover, Ito densities of BrS1 and CON1 were comparable and increased from 1.0 Hz to 0.1 Hz by ~ 100%. These data indicate that a repolarization deficit could be a mechanism underlying BrS.
Prostacyclin (PGI2) is known as a short-lived, potent vasodilator and platelet anti-aggregatory eicosanoid. This work attempts to selectively augment PGI2 synthesis in neuron-glia cultures by adenoviral (Ad) gene transfer of PGI synthase (PGIS) or bicistronic cyclooxygenase 1 (COX-1)/PGIS and examines whether PGI2 confers protection against lipopolysaccharide (LPS) stimulation. Cultures released low levels of eicosanoids. Upon Ad-PGIS or Ad-COX-1/PGIS infection, cultures selectively increased prostacyclin release. Both PGIS- and COX-1/PGIS-overexpressed cultures contained fewer microglial numbers. Further, they significantly attenuated LPS-induced iNOS expression and lactate, nitric oxide, and TNF-alpha production. Taken together, enhanced prostacyclin synthesis in neuron-glial cultures reduced microglia number and suppressed LPS stimulation.
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