Fig. 4: Force imbalance drives the detachment adhesion and further “snap-back” process.

a, b Adhesion forces of hMSCs on static soft (2.2 kPa) and rigid (13.0 kPa) PYP hydrogels and on PYP hydrogel with fast cyclic rigidity change (1 min cycle) over 12 h. To better represent the average cell force, the results are presented as traction forces per unit area (N m^-2), also known as traction stress (Pa). Scale bar is 50 µm for all panels. In b, n = 215, 212 and 204 (2.2 kPa, 1 min cycle, and 13.0 kPa) cells were examined, each from 3 independent experiments. c, d Mechnosignalling protein pMyosin IIa level of hMSCs on static soft (2.2 kPa) and rigid (13.0 kPa) PYP hydrogels and on PYP hydrogel with fast cyclic rigidity change (1 min cycle) over 12 h. Scale bar is 50 µm for all panels. In d, n = 213, 205 and 214 (2.2 kPa, 1 min cycle, and 13.0 kPa) cells were examined, each from 3 independent experiments. e Time series of images of hMSCs migration on PYP hydrogels with fast cyclic rigidity change with (OE Talin) overexpressing Talin. The far-right panel shows the trajectories of ~20 randomly selected migrating cells under the condition over 12 h. Times are indicated in hour:minute: second. Scale bar is 50 µm for all panels. f Time series of images of hMSCs migration on PYP hydrogels with fast cyclic rigidity change with the addition of non-phototoxic Blebbistatin inhibitors (25 μM, –pMyosin). The far-right panel shows the trajectories of ~20 randomly selected migrating cells under the condition over 12 h. Times are indicated in hour:minute:second. Scale bar is 50 µm for all panels. g Average cell migration speed on PYP hydrogels with fast cyclic rigidity change with and without (Ctrl) overexpressing Talin (OE Talin) and addition of non-phototoxic Blebbistatin inhibitors (–pMyosin). In g, n = 204, 202, and 222 (Ctrl, OE Talin, and –pMyosin) cells were examined, each from 3 independent experiments. In all graphs, *** = p < 0.01, n.s. = p > 0.1, unpaired, two-tailed t-test. Source data are provided as a Source Data file.