A Visible Light-Responsive Hydrogel to Study the Effect of Dynamic Tissue Stiffness on Cellular Mechanosensing

Abstract

Dynamic changes in elasticity during tissue development, remodeling, and aging influence cell behavior through mechanotransduction, yet most studies rely on hydrogels with fixed mechanical properties. Although photoresponsive azobenzene-based hydrogels can control substrate stiffness dynamically, they require UV light, which can damage cells and DNA. This makes it difficult to determine whether cellular responses are due to mechanical changes or UV-induced damage. This study develops a polyacrylamide-azobenzene hydrogel system (PAMA) responsive to biocompatible blue and green light, enabling unambiguous investigation of cellular mechanosensing dynamics. The hydrogel system achieves rapid and reversible switching between physiologically relevant stiffness values (19 to 4 kPa), triggering immediate responses in mesenchymal stromal cells (MSCs) including changes in cell shape and yes-associated protein (YAP) localization. When exposed to fluctuating substrate stiffness, early-passage MSCs demonstrate rapid adaptive responses through cell spreading, while late-passage MSCs exhibit delayed spreading and pronounced nuclear lamina wrinkling, indicating impaired mechanosensitivity. These findings provide new insights into cellular mechanosensing dynamics, particularly with respect to cellular aging. With the ability to simulate tissue development, homeostasis, aging, and pathological conditions such as fibrosis or tumorigenesis, this platform also offers exciting potential across multiple fields, from regenerative medicine to cancer research.