Collective Cell Behavior in Mechanosensing of Substrate Thickness

Area of Science:

• Biomaterials Science
• Cell Biology
• Mechanobiology

Background:

• Extracellular matrix (ECM) stiffness influences cell behavior.
• Cells exert contractile forces and sense material stiffness, dependent on elastic modulus and thickness.
• Single cells can detect stiff substrates through thin ( <10 µm) soft hydrogels.

Purpose of the Study:

• To test if cohesive cell colonies exert more force and deform hydrogels more than single cells.
• To determine if cell colonies can mechanosense deeper into underlying materials compared to single cells.
• To investigate the role of Rho-associated protein kinase (ROCK) in colony-mediated depth-sensing.

Main Methods:

• Modulated thickness of soft (1 kPa) ECM-functionalized polyacrylamide hydrogels on glass substrates.
• Allowed MG63 cell colonies to form on hydrogels.
• Quantified cell morphology and hydrogel deformation using time-lapse fluorescence microscopy with fluorescent fiducial markers.

Main Results:

• Single-cell spreading increased with decreasing hydrogel thickness (half-maximal response at 3.2 µm).
• Colony-cell spreading also increased with decreasing hydrogel thickness (half-maximal response at 54 µm).
• Hydrogel deformation was greater on thick hydrogels and extended further from colony peripheries on thick compared to thin hydrogels.
• Depth-sensing was dependent on Rho-associated protein kinase (ROCK)-mediated contractility.

Conclusions:

• Collective cell action enables mechanosensing of rigid materials beneath elastic hydrogels at greater depths than individual cells.
• Cell colonies exhibit enhanced depth-sensing capabilities compared to single cells.
• Collective cell behavior may allow sensing of material property variations at larger distances.