Kinetic Imaging Cytometry of Stem Cell-Derived Cardiomyocytes Paced by Electrical Field Stimulation

Abstract

Human stem cell-derived cardiomyocytes provide a powerful model system for basic research studies, drug discovery and toxicology screening. Due to the electrical nature of their activity, cardiomyocytes are routinely studied using electrophysiological techniques. However, in addition to being very expensive and time-consuming, electrophysiology-based testing employs “one-cell-at-a-time” approach, which significantly limits the amount of the data collected during an experiment. Imaging methods, on the other hand, allow acquiring the enormous amount of information from many cells simultaneously, although they generally lack the ability to trigger the cellular activity in a physiological manner.To address this problem, our group has introduced an automated optical Calcium Transient Image Cytometer (CTIC) that is capable to physiologically activate cells via electrical field stimulation and to simultaneously monitor kinetic fluorescent signals from many cells in real time with the sub-cellular resolution.For proper assessment of the cardiomyocyte activity, cardiomyocytes have to be activated multiple times using the specific stimulation pattern. The need to preserve the viability of cardiomyocytes through the complicated multi-parameter stimulation experiments is imposing more stringent requirements on the cell-friendliness of the electrical stimulation. To achieve this challenging goal, we have developed a novel electrical stimulation module for the CTIC. By varying the configuration of electrodes and assay conditions we were able to achieve a highly reproducible cell-sparing electrical stimulation while decreasing the voltage required to initiate the response by ∼4 fold.These innovations in the design of the electrical stimulation module allowed us to perform high content screening of stem-cell-derived cardiomyocytes at the different stages of their maturation as well as to carry out the pharmacological studies of use-dependence mechanisms of different pharmacological agents.