Mechanics regulates ATP-stimulated collective calcium response in fibroblast cells

Cells constantly sense their chemical and mechanical environments. We study the effect ofmechanics on theATP-induced collective calciumresponse of fibroblast cells in experiments that mimic various tissue environments.We find that closely packed two-dimensional cell cultures on a soft polyacrylamide gel (Young'smodulus E = 690 Pa) containmore cells exhibiting calciumoscillations than cultures on a rigid substrate (E = 36 000 Pa). Calciumresponses of cells on soft substrates show a slower decay of calcium level relative to those on rigid substrates. Actin enhancement and disruption experiments for the cell cultures allow us to conclude that actin filaments determine the collective Ca2+ oscillatory behaviour in the culture. Inhibition of gap junctions results in a decrease of the oscillation period and reduced correlation of calciumresponses, which suggests additional complexity of signalling upon cell-cell contact. Moreover, the frequency of calcium oscillations is independent of the rigidity of the substrate but depends on ATP concentration. We compare our results with those from similar experiments on individual cells. Overall, our observations show that collective chemical signalling in cell cultures via calcium depends critically on the mechanical environment.