Local nascent protein deposition and remodelling guide mesenchymal stromal cell mechanosensing and fate in three-dimensional hydrogels.

Hydrogels serve as valuable tools for studying cell-extracellular matrix interactions in three-dimensional environments that recapitulate aspects of native extracellular matrix. However, the impact of early protein deposition on cell behaviour within hydrogels has largely been overlooked. Using a bio-orthogonal labelling technique, we visualized nascent proteins within a day of culture across a range of hydrogels. In two engineered hydrogels of interest in three-dimensional mechanobiology studies-proteolytically degradable covalently crosslinked hyaluronic acid and dynamic viscoelastic hyaluronic acid hydrogels-mesenchymal stromal cell spreading, YAP/TAZ nuclear translocation and osteogenic differentiation were observed with culture. However, inhibition of cellular adhesion to nascent proteins or reduction in nascent protein remodelling reduced mesenchymal stromal cell spreading and nuclear translocation of YAP/TAZ, resulting in a shift towards adipogenic differentiation. Our findings emphasize the role of nascent proteins in the cellular perception of engineered materials and have implications for in vitro cell signalling studies and application to tissue repair.