INTEGRATION OF ENGINEERED "SPARK-CELL" SPHEROIDS FOR OPTICAL PACING OF CARDIAC TISSUE
Optogenetic methods for pacing of cardiac tissue can be realized by direct genetic modification of the cardiomyocytes to express light-sensitive actuators, such as channelrhodopsin-2, ChR2, or by introduction of light-sensitized non-myocytes that couple to the cardiac cells and yield responsiveness to optical pacing. In this study, we engineer three-dimensional "spark cells" spheroids, composed of ChR2-expressing human embryonic kidney cells, and characterize their morphology as function of cell density and time. These "spark-cell" spheroids are then deployed to demonstrate site-specific optical pacing of human stem-cell-derived cardiomyocytes (hiPSC-CMs) in 96-well format using non-localized light application and all-optical electrophysiology. We show that the spheroids can be handled using liquid pipetting and can confer optical responsiveness of cardiac tissue earlier than direct viral or liposomal genetic modification of the cardiomyocytes, with 24% providing reliable stimulation of the iPSC-CMs within 6 hours and >80% within 24 hours. Our results demonstrate a scalable, cost-effective method to achieve contactless optical stimulation of cardiac cell constructs that can be integrated in a robotics-amenable workflow for high-throughput drug testing. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=180 SRC="FIGDIR/small/428177v1_ufig1.gif" ALT="Figure 1"> View larger version (58K): org.highwire.dtl.DTLVardef@156108org.highwire.dtl.DTLVardef@1956092org.highwire.dtl.DTLVardef@1f7237eorg.highwire.dtl.DTLVardef@3b37a4_HPS_FORMAT_FIGEXP M_FIG C_FIG