Substrate Mechanics Dictates Cell-Cell Communication via Gap Junction in Stem Cells from Human Apical Papilla

It is recognized that the interaction between cells and their physical microenvironment plays a fundamental role in controlling cell behaviours and even in determining cell fate. Any change in the physical properties of the extracellular matrix (ECM), such as its topography, geometry or stiffness, controls this interaction. In the current study, we revealed a novel connection between the cell-matrix interaction and cell-cell communication that is mediated by interface stiffness, and elucidated this process in stem cells from human apical papilla (hSCAPs) in terms of mechanosensing, mechanotransduction and gap junction-mediated cell-cell communication. We first fabricated polydimethylsiloxane (PDMS) substrates with the same topography and geometry but different stiffnesses and found that the cell morphology of the hSCAPs actively changed to adapt to the difference in substrate stiffness, and we also found that the hSCAPs secreted more fibronectin in response to the stiff substrate. The focal adhesion plaques were changed by altering the expression of focal adhesion kinase (FAK) and paxillin. The FAK and paxillin bound to connexin 43 and, as a result, altered the gap junction formation. By a Lucifer yellow transfer assay, we further confirmed that the interface stiffness mediated cell-cell communication in living hSCAPs via changes in gap junction tunnels. The novel mechanics that mediated cell-cell communication through extracellular stiffness that was observed in this study show the great influence of the interaction between cells and their external physical microenvironment and stress the importance of microenvironmental mechanics in organ development and diseases.