Cells on Hydrogels with Micron-Scaled Stiffness Patterns Demonstrate Local Stiffness Sensing.

Area of Science:

• Cellular mechanics
• Biophysics
• Materials science

Background:

• Cell rigidity sensing is crucial for cellular adaptation to mechanical cues.
• Cells interact with their extracellular environment by exerting forces.
• In vivo, cells encounter diverse mechanical properties at multiple scales.

Purpose of the Study:

• To investigate cellular sensing of micron-scale stiffness textures.
• To measure forces transmitted by cells to the extracellular matrix on patterned substrates.
• To understand how cells adjust traction forces to local stiffness variations.

Main Methods:

• Fabrication of polyacrylamide hydrogels with micron-scale stiffness patterns and gradients using photochemistry.
• Development of a surface coating protocol for adhesion proteins to decouple or couple surface density from stiffness.
• Adaptation of traction force microscopy (TFM) with submicron resolution using a pyramidal optical flow algorithm for non-uniform substrates.

Main Results:

• Cells exert forces on their surroundings, adjusting stress levels in response to micron-scaled stiffness.
• Demonstrated ability of cells to sense and respond to stiffness textures at the micron scale.
• Validated a novel TFM approach for analyzing cellular forces on complex substrates.

Conclusions:

• Cells actively sense and respond to micron-scale stiffness heterogeneities in their environment.
• The developed methods enable precise control over substrate mechanics and cell-matrix interactions.
• Findings contribute to understanding the role of altered stiffness in diseases like cancer.