MKs sense FN-coated substrate stiffness. (A) MK adhesion for 2 hours onto PDMS substrate of various stiffness coated with FN 50 μg/mL using microcontact printing (circular patterns of 200 μm diameter). (Left) bright field image illustrating MK adhesion, bar is 50 μm; (right) quantification of the number of MK adhered per unit surface. (B) Effect of blebbistatin (100 μM) on MK adhesion. (A-B) Mean ± standard error of mean (SEM). Dots represent independent experiments (mean of 6-9 replicates); 2-way ANOVA analysis and Šidák multiple comparisons test, § indicates P < .0001, comparing the control condition with same substrate stiffness. (C-D) MK adhered for 5 hours and observed by bright field microscopy; (C) measurement of the visible surface of each MK measured; mean ± SEM, n = 3 independent experiments; statistics, ordinary 1-way ANOVA with Tukey multiple comparisons test. (D) Photomicrographs illustrating bright field microscopy observations; representative of at least 8 independent experiments; scale bar, 20 μm.