The structural features of the matrix surrounding the cells play a crucial role in regulating their behavior.

Multifocal plane microscopy allows for capturing images at different focal planes simultaneously. Using a proprietary prism which splits the emitted light into paths of different lengths, images at 8 different focal depths were obtained, covering a volume of 50x50x4 µm3. The position of single emitters was retrieved using a phasor-based approach across the different imaging planes, with better than 10 nm precision in the axial direction. We validated the accuracy of this approach by tracking fluorescent beads in 3D to calculate water viscosity. The fast acquisition rate (>100 fps) also enabled us to follow the capturing of 0.2 µm fluorescent beads into an optical trap.

Cells continuously sense external forces from their microenvironment, the extracellular matrix (ECM). In turn, they generate contractile forces, which stiffen and remodel this matrix. Although this bidirectional mechanical exchange is crucial for many cell functions, it remains poorly understood. Key challenges are that the majority of available matrices for such studies, either natural or synthetic, are difficult to control or lack biological relevance. Here, we use a synthetic, yet highly biomimetic hydrogel based on polyisocyanide (PIC) polymers to investigate the effects of the fibrous architecture and the nonlinear mechanics on cell–matrix interactions. Live-cell rheology was combined with advanced microscopy-based approaches to understand the mechanisms behind cell-induced matrix stiffening and plastic remodeling. We demonstrate how cell-mediated fiber remodeling and the propagation of fiber displacements are modulated by adjusting the biological and mechanical properties of this material. Moreover, we validate the biological relevance of our results by demonstrating that cellular tractions in PIC gels develop analogously to those in the natural ECM. This study highlights the potential of PIC gels to disentangle complex bidirectional cell–matrix interactions and to improve the design of materials for mechanobiology studies.

No abstract

The interactions between cells and their direct environment are crucial for cell fate but biochemically and mechanically highly complex, and therefore, poorly understood. Despite recent advances that exposed the impact of a range of different factors, real progress remains challenging, since appropriate controllable matrices and quantitative analysis techniques that cover a range of time and length scales are unavailable. Here, we use a synthetic fibrous hydrogel with nonlinear mechanics to mimic and tailor the bi-directional cell-matrix interactions. Using advanced microscopy-based approaches, we acquire a comprehensive picture of how cellular traction forces, fiber remodeling, matrix stiffening, matrix properties and cellular behavior interact, highlighting for instance, the importance of a fibrous architecture and nonlinear mechanics of the matrix. Complete mapping of cell-matrix interactions at the cellular length scale provides indispensable information for the rational design of biomimetic materials to recreate realistic in vitro cell environments.