(190ao) Hyper-Activation of Cellular Rigidity Sensing By Solid Surface Tension of Biomaterials and Silicone Breast Implants

Silicone materials have been used as implants and breast prostheses for decades in aesthetic and constructive plastic surgery, yet it has not been extensively studied how rupture and leakage of implants could affect cellular functions. Cells physically interrogate their extracellular environment to make decisions related to cell proliferation, migration and other critical processes. In addition to biochemical signals, physical properties of the extracellular matrix, including its stiffness, are key regulators for cell behaviors. Typically, on stiff substrates, cells display large spreading areas, assemble robust integrin-based adhesion complexes, whereas on soft substrates these functions are suppressed. However, cell behaviors that defy expectations based on substrate rigidity alone have been observed.

It has been recently illustrated that solid surface tension can have a dominant role in the mechanical behaviors of soft materials with vanishingly small elasticity. We proposed and have now demonstrated that cells interacting with soft materials with high surface tension primarily sense and respond to surface tension and not the bulk elastic moduli of the materials. Our results are consistent with theory that predicts that solid surface tension can dominate over elasticity at cellular length scales. On silicone materials with appreciable surface tension, cells assemble robust adhesion complexes and cytoskeleton stress fibers, spread over large areas, upregulate canonical integrin-based signal transduction, proliferate and migrate efficiently. Grown directly on the interior materials of silicone breast implants, cells showed drastic cell spreading as well as robust nuclear localization of gene transcriptional factor YAP, which was observed for the very first time.

Together, our results indicate that material surface tension is important criteria for the design of soft biomaterial scaffolds in tissue engineering.