Microindentation of Fluid-Filled Cellular Domes Reveals the Contribution of RhoA-ROCK Signaling to Multicellular Mechanics

Cellular mechanics encompass both mechanical properties that resist forces applied by the external environment and internally generated forces applied at the location of cell-cell and cell-matrix junctions. Here, the authors demonstrate that microindentation of cellular domes formed by cell monolayers that locally lift off the substrate provides insight into both aspects of cellular mechanics in multicellular structures. Using a modified Hertz contact equation, the force-displacement curves generated by a micro-tensiometer are used to measure an effective dome stiffness. The results indicate the domes are consistent with the Laplace-Young relationship for elastic membranes, regardless of biochemical modulation of the RhoA-ROCK signaling axis. In contrast, activating RhoA, and inhibiting ROCK both alter the relaxation dynamics of the domes deformed by the micro-tensiometer, revealing an approach to interrogate the role of RhoA-ROCK signaling in multicellular mechanics. A finite element model incorporating a Mooney-Rivlin hyperelastic constitutive equation to describe monolayer mechanics predicts effective stiffness values that are consistent with the micro-tensiometer measurements, verifying previous measurements of the response of cell monolayers to tension. Overall, these studies establish microindentation of fluid-filled domes as an avenue to investigate the contribution of cell-generated forces to the mechanics of multicellular structures.