Figure 3.
Cells Elongate on Substrates of Intermediate Stiffness
(A) Example configurations of cells at 2000 MCS on substrates of 1, 50, and 50 kPa. Color ramp shows hydrostatic stress.
(B and C) (B) Cell eccentricity as a function of substrate stiffness, shaded regions: standard deviations over 25 simulations; (C) distribution of N, the number of integrin bonds per cluster, all FA at 2000 MCS from 25 simulations were pooled. Vertical line piece shows the median value of the FA sizes. Color coding for panel (C): see legend.
(D) The mechanism of cell elongation explained. Hot spots of ECM stress form under protrusions. If this stress is strong enough, the FA stabilizes here, obstructing cell retractions. Around these hot spots, forces will continue to build up and the force field polarizes. FAs continue to stabilize at the front and back, whereas adhesions at the sides of the cell remain small. This feedback loop allows the cell to elongate.