The goal of this research is to identify the role of engineered cell-cell signals on how cells sense material properties. Mesenchymal stem cells (MSCs) are adult cells whose behavior is regulated by matrix mechanosensing, which is characterized by stiffness-dependent changes in cell shape and the nuclear localization of mechano-transducer proteins including YAP (Yes-associated Protein). MSC area and nuclear YAP translocation increase with increasing stiffness, and although low levels of N-cadherin-based cell-cell signaling reduce this effect, two fundamental questions remain: (1) do engineered cell-cell signals at higher concentrations further reduce matrix mechanosensing, and (2) does N-cadherin signaling affect MSC adaptation to dynamic materials. To answer these questions, a stiffening hydrogel system was developed to independently control stiffness and HAVDI, a peptide that mimics cell-cell signaling. High concentrations of HAVDI (2 mM) reduce matrix mechanosensing on static hydrogels as seen by a decrease in area and nuclear YAP. The area of MSCs on soft HAVDI hydrogels that are stiffened does not change, but surprisingly nuclear YAP increases post-stiffening. These studies demonstrate that competing stiffness and cell-cell signals regulate matrix mechanosensing, and these insights are critical towards developing in vitro platforms to study ailments attributed to tissue stiffening including cancer, fibrosis, and aging
