Probe Sensitivity to Cortical versus Intracellular Cytoskeletal Network Stiffness

Area of Science:

• Cellular biomechanics
• Biophysics
• Cellular biology

Background:

• Cellular biomechanical properties are crucial in development, wound healing, and pathology.
• Understanding how different experimental probes measure these properties in heterogeneous cell regions is essential.

Purpose of the Study:

• To comprehensively compare four distinct probe technologies for measuring cell biomechanical properties.
• To define the relative sensitivity of each probe to different cellular structures.

Main Methods:

• Studied Schlemm's canal endothelial cells and mouse embryonic fibroblasts (MEFs).
• Utilized four probe technologies: sharp-tip AFM, round-tip AFM, optical magnetic twisting cytometry (OMTC), and traction microscopy (TM).
• Employed finite-element analysis to interpret results.

Main Results:

• Sharp-tip AFM and TM detected increased stiffness and traction in perturbed Schlemm's canal cells, while round-tip AFM and OMTC showed minimal changes.
• Vimentin knockout in MEFs reduced traction (TM) and stiffness (sharp-tip and round-tip AFM) but paradoxically increased OMTC stiffness, attributed to reduced cell thickness.
• Results suggest vimentin influences both intracellular network and cortex stiffness.

Conclusions:

• AFM sharp tip and TM primarily reflect the properties of the actin-rich cell cortex.
• Round-tip AFM and OMTC are more sensitive to the noncortical intracellular network.
• Probe selection is critical for accurately assessing specific cellular biomechanical properties.