a Concentration-dependent effect of fibronectin on hMSC sensing of substrate stiffness. While high fibronectin coating (10 μg/ml) led hMSCs to sense a ‘stiff’ environment, low fibronectin coating (1 μg/ml) led to sensing of a ‘soft’ microenvironment regardless of hydrogel stiffness. In the groups with 4 or 7 μg/ml fibronectin, YAP regulation was dependent on substrate stiffness, as shown in the conventional polyacrylamide hydrogel groups. Scale bar: 20 μm. b Quantification of nuclear YAP localization. Data are mean values; error bars are standard error of the mean. (n=14, ****p<0.0001, two-way ANOVA by Bonferroni’s multiple comparisons test. n.s. not significant)