Fig. 7
Analysis of the effect of viscoelasticity on 3T3 cell stiffness and hepatic stellate cell differentiation. a Young’s modulus of 3T3 fibroblasts as a function of G”. Cells were incubated for 24 h on 5 kPa elastic (G” = 0 Pa) and viscoelastic (G” = 500 Pa) gels coated with collagen I (left) or fibronectin (right). Sample size: Collagen I gels NHS 0 Pa n = 76 cells, NHS 500 Pa n = 68 cells, sulfoSANPAH 0 Pa n = 112 cells, sulfoSANPAH 500 Pa n = 104 cells; fibronectin gels NHS 0 Pa n = 187 cells, NHS 500 Pa n = 176 cells, sulfoSANPAH 0 Pa n = 149 cells, sulfoSANPAH 500 Pa n = 139 cells. b The evolution over 7 days of the projected area of hepatic stellate cells on elastic (left) and viscoelastic gels (middle and right). The distribution of cell area values becomes broader over time. This shift toward greater values is characteristic of the differentiation of part of the cell population into myofibroblasts. Sample size: 5 kPa 0 Pa gel day 1 n = 114 cells, day 2 n = 117 cells, day 4 n = 117 cells, day 7 n = 70 cells; 5 kPa 200 Pa gel day 1 n = 112 cells, day 2 n = 108 cells, day 4 n = 119 cells, day 7 = 114 cells; 5 kPa 500 Pa gel day 1 n = 113 cells, day 2 n = 95 cells, day 4 n = 107 cells, day 7 = 106 cells. c Bright field images of myofibroblasts incubated for 24 h on elastic and viscoelastic PAA gels coated with collagen I. Myofibroblasts have a smaller area on viscoelastic gels; on the gels with G” = 500 Pa, cell morphology is similar to that of undifferentiated cells. Scale bar = 50 µm. d Fluorescence images of myofibroblasts incubated for 24 h on elastic and viscoelastic PAA gels coated with collagen I. Nuclei (blue) are stained with Hoechst, α-smooth muscle actin (magenta) has been stained by immunofluorescence and lipid droplets (green) were stained with Bodipy® 493/503. Scale bar = 20 μm. ***Statistically significant differences with a p-value of <0.01, as calculated by non-parametric Tukey's tests; “ns” indicates no statistical difference
