FIGURE 5.

Analysis of cell mechanical properties by AFM and RT‐DC. (a) Superposition of multiple force‐indentation curves from AFM‐based colloidal force spectroscopy obtained from two biological replicates of cardiac progenitor cells (CPC), immature (iCM) and more differentiated (mCM) cardiomyocytes across different sample conditions of negative control (control), DMSO vehicle control (vehicle), and 1 µM cytochalasin D (CytoD). Dotted lines represent isoelasticity lines and serve as reference to compare data between plots. (b) Example of a single force indentation curve (shown in red) plotted together with isoelasticity lines (dotted) annotated for their corresponding Young's modulus. The inclination of the curve is proportional to the stiffness of the probed area. (c) Comparison of AFM measurements for negative control samples of CPC, iCM and mCM showing significant differences in Young's modulus between the iCM and either CPC or mCM, but not between CPC and mCM. (d) AFM measurements to probe the effect of 1 µM CytoD (CytoD) compared with vehicle control (vehicle) shows a significant decrease in the Young's modulus for CPC and iCM, but not for mCM. (e) Typical RT‐DC scatter plots of deformation as a function of cell size for the CPC (left), iCM (centre) and mCM (right) show that while changes in deformation appear subtle, there are clear differences in the size of the different cell types. (f) Evaluation of RT‐DC data from three biological replicates show a significant increase in cell size and Young's modulus that positively correlates with the extent of cardiomyocyte differentiation. The total number of single measurements were: 10,761 for CPC, 4451 for iCM, and 5087 for mCM. In boxplots, boxes indicate interquartile range, error bars show standard deviation. Bar charts show estimated marginal means and error bars represent standard error of means. Statistical analysis was performed using linear mixed‐effect models (*p < 0.05; ***p < 0.001; n.s., non‐significant)