Optogenetic Modulation of Action-Potential Morphology in Human Induced Pluripotent Stem Cell Models

Background and Aims:

The cardiac action potential (AP) relies on delicate balance among ionic currents. Any deviation from the conserved physiological state might affect the AP morphology and increase the risk for lethal arrhythmias. Here, we aimed to apply the emerging optogenetics technology to modulate (prolong or shorten) the cardiac AP in healthy, long QT syndrome (LQTS), and short QT syndrome (SQTS) patient-specific human induced pluripotent stem cell derived cardiomyocyte (hiPSC-CM) models.

Methods and Results:

Somatic cells from patients were reprogrammed to generate hiPSC lines, coaxed to differentiate into cardiomyocytes, transduced to express the relevant light-sensitive proteins (opsins) and subjected to patch-clamp and optical imaging experiments. Our results demonstrate the ability of carefully designed synchronized optical stimuli could to either shorten or prolong AP duration (APD) of hiPSC-CMs. Interestingly, the light-sensitive depolarizing cationic channel, ChR2, displayed a bidirectional ability to affect the APD. Light-activation of ChR2 during the late-stages of the AP significantly prolonged APD, and a strong correlation (r²=0.998) was noted between the duration of the optical stimulus and the measured APD80. In contrast, APD80 could be shortened from 286±21ms to 253±14ms (p<0.05) when ChR2 was activated at early phase 2 of the AP. Importantly, light-activation of the anionic channel GtACR2 was able to robustly shorten APD80 during both early and late AP phases. Finally, appropriate light stimulation protocols were able to restore normal APD80 in hiPSC models of inherited LQTS and SQTS and to supress arrhythmic activity.

Conclusions:

Carefully synchronized optical stimuli can either shorten or prolong (APD of hiPSC-CMs and to rescue the abnormal AP phenotype. in hiPSC models of the LQTS and SQTS.