FIG. 2.

dFBs demonstrate the influence of a CD90-positive cell type upon hiPSC-CM electrophysiology. (A) Analysis of CD90 expression in dFBs by flow cytometry. (B) Optical tracings of negative change in fluorescence over fluorescence (-ΔF/F) permit analysis of AP properties of CMs, including APD₅₀ (AP duration at 50% repolarization, horizontal red dotted line), APD₉₀ (horizontal blue dotted line), amplitude (black line), and maximum upstroke velocity (V_max, not shown). (C–G) Analysis of AP amplitude (C), V_max (D), APD₅₀ (E), APD₉₀ (F), and APD₉₀/APD₅₀ (G) for 1:9 (1 part dFB to 9 parts CM) and 1:1 co-cultures. Data were collected from two different hiPSC-CM clones on day 40 of differentiation. 1:9: n = 22 cells; 7:3: n = 22 cells. Heavier dashed lines within each violin indicate medians and lighter dashed lines indicate interquartile range. P values were calculated by either Student's t-test (AP amplitude, APD₅₀, APD₉₀) or Mann-Whitney U test (V_max, APD₉₀/APD₅₀). AP, action potential; APD₅₀, action potential duration at 50% repolarization; APD₉₀, Action potential duration at 90% repolarization; dFBs, dermal fibroblasts; hiPSC-CM, human induced pluripotent stem cell-derived cardiomyocyte.