Optical Method to Quantify Mechanical Contraction and Calcium Transients of Human Pluripotent Stem Cell-Derived Cardiomyocytes.

Differentiation of human pluripotent stem cells into cardiomyocytes (hPS-CMs) holds promise for myocardial regeneration therapies, drug discovery, and models of cardiac disease. Potential cardiotoxicities may affect hPS-CM mechanical contraction independent of calcium signaling. Herein, a method using an image capture system is described to measure hPS-CM contractility and intracellular calcium concurrently, with high spatial and temporal resolution. The image capture system rapidly alternates between brightfield and epifluorescent illumination of contracting cells. Mechanical contraction is quantified by a speckle tracking algorithm applied to brightfield image pairs, whereas calcium transients are measured by a fluorescent calcium reporter. This technique captured changes in contractile strain, calcium transients, and beat frequency of hPS-CMs over 21 days in culture, as well as acute responses to isoproterenol and Cytochalasin D. The technique described above can be applied without the need to alter the culture platform, allowing for determination of hPS-CM behavior over weeks in culture for drug discovery and myocardial regeneration applications.