Contractility dominates adhesive ligand density in regulating cellular de-adhesion and retraction kinetics

Area of Science:

• Cell Biology
• Biophysics
• Biomaterials Science

Background:

• Cell detachment from substrates leads to rapid rounding due to unopposed cytoskeletal tension.
• Previous work linked retraction kinetics to cortical stiffness, suggesting potential for mechanical property screening.
• A key limitation is the potential rate-limiting role of matrix adhesion severance during retraction.

Purpose of the Study:

• To differentiate the contributions of cell contractility and adhesion to de-adhesion and retraction kinetics.
• To validate the use of cell de-adhesion measurements for assessing cell mechanical properties.
• To investigate these dynamics under controlled serum-free and standard serum-rich conditions.

Main Methods:

• Developed serum-free culture conditions for U373 MG glioma cells on fibronectin-coated substrates.
• Manipulated extracellular matrix (ECM) protein density and stimulated cell contractility using lysophosphatidic acid (LPA).
• Measured cell spreading area, cortical stiffness, and retraction kinetics post-enzymatic detachment.

Main Results:

• Cell spreading area increased with ECM density, but cortical stiffness and retraction time constants did not.
• LPA stimulation significantly accelerated retraction, independent of initial ECM density or spreading area.
• Retraction time constants correlated more strongly with cortical stiffness than with adhesive ligand density or cell spreading.

Conclusions:

• Cell contractility, not adhesion strength or cell spreading, is the primary determinant of retraction kinetics.
• Cell de-adhesion measurements are a viable method for high-throughput screening of cell mechanical properties.
• These findings hold true in both serum-free and conventional serum-rich cell culture media.