Soft Hyaluronic Gels Promote Cell Spreading, Stress Fibers, Focal Adhesion, and Membrane Tension by Phosphoinositide Signaling, Not Traction Force.

Cells respond to both physical and chemical aspects of their substrate. Whether intracellular signals initiated by physical stimuli are fundamentally different from those elicited by chemical stimuli is an open question. Here, we show that the requirement for a stiff substrate (and, therefore, high cellular tension) for cells to produce large focal adhesions and stress fibers is obviated when a soft substrate contains both hyaluronic acid (HA) and an integrin ligand (collagen I).