Figure 3. Basic Characterization of Human PSC-derived Cardiomyocytes.
A) Flow cytometry provides a quantitative method to evaluate the relative yield and purity of CMs resulting from differentiation protocols by measuring the number of cells expressing cardiac-specific proteins such as cardiac troponin T (cTnT). B) RT-PCR can be used as a first assessment for changes in gene expression typical of cardiogenesis by assaying for the expression of cardiac transcription factors, myofilament proteins, and Ca2+-cycling proteins. C) Immunofluorescence microscopy using antibodies specific for myofilament proteins determine if cells exhibit organized sarcomeres typical of CMs. D) Functional assessment of CMs can be provided by cellular electrophysiology measurements to determine if cardiac action potentials typical of different types of CMs are present. E) Extracellular field potential measurements by multielectrode arrays provide another method to detect spontaneous electrical activity in the CMs preparations. F) Detection of Ca2+ transients typical of CMs provides another assessment of the functional integrity of the differentiating CMs. Cells loaded with the Ca2+ indicator Fluo-3 were imaged using laser scanning confocal microscopy in the line scan mode with Ca2+ transients displayed and time versus normalized Ca2+ transient intensity (F/F0) shown below. (Panels B and D modified from Zhang et al., 2009)