Fig. 2: Characterization of cell morphology reveals heterogeneities in populations of hiPSC-CMs.
a Left: Schematic of hiPSC-CM culture, differentiation, micropatterning and experimental groups. Right: brightfield image of a single micropatterned hiPSC-CM and corresponding fluorescence image; the ECM micropattern (GFP-labelled gelatin + Matrigel) printed on polyacrylamide hydrogel with embedded red-fluorescent. Brightfield images were systematically recorded for each single measured hiPSC-CM. The corresponding protein micropattern were imaged in > 5 independent experiments and in other studies in our lab, but was not systematically imaged by fluorescence microscopy for each hiPSC-CM. Abbreviation: M16lac: lactate-rich and M16glu: glucose-rich) media. b Single hiPSC-CMs adopt an elongated morphology when adhered onto the ECM micropatterns (7:1 aspect ratio). Green line: theoretical trend for the area of a cell filling the whole width of the micropatterned while elongating along the micropattern (Eq. 1). Red dashed line, linear regression; dotted lines: median values for spread area and aspect ratio. Sample number n is provided in the figure panel and were analyzed from five differentiation batches in independent experiments. Linear regression model was tested against the null hypothesis using an F test, with p values < 0.001 against the null hypothesis of zero-slopes for the models and a p-value of 0.0599 when comparing the slopes. c Stiffness, maturation medium, and experimental day influence the distributions of spread area and cellular aspect ratio. Normality versus lognormality tests were performed using multiple tests including D’Agostino-Pearson omnibus, Anderson-Darling, Shapiro-Wilk, and Kolmogorov-Smirnov tests for normality with an alpha coefficient of 0.05, indicating a lognormal distribution. Unpaired t-test using parametric test were performed on the log value of the data using a two-tailed P value at confidence level of 95%. d and e see Figure S1 In all panels, *p < 0.05, **p < 0.005, ***p < 0.001, ****p < 0.0001. ns, not significant.
