Quantitative polarization microscopy as a potential tool for quantification of mechanical stresses within 3D matrices

Area of Science:

• Biophysics
• Biomaterials Science
• Cellular Mechanics

Background:

• 3D mechanical stresses in tissues and extracellular matrices (ECMs) are crucial for physiological and pathological processes.
• Quantifying these stresses is challenging due to the nonlinear and heterogeneous nature of fibrous matrices.
• Existing methods like 3D traction force microscopy have limitations.

Purpose of the Study:

• To introduce quantitative polarization microscopy (QPOL) as a non-invasive, label-free technique for 3D mechanical stress quantification in matrices.
• To demonstrate the correlation between QPOL retardance signals and mechanical parameters in 3D collagen hydrogels.
• To establish QPOL as a viable tool for understanding mechanobiology.

Main Methods:

• Utilized quantitative polarization microscopy (QPOL) on collagen hydrogels.
• Applied external loads using cantilever-collagen systems.
• Correlated QPOL retardance signals with applied forces and computational finite element (FE) model-derived shear stresses.
• Measured retardance around spheroids with varying contractility.

Main Results:

• QPOL retardance signals positively correlated with applied external loads on collagen hydrogels.
• Retardance values aligned with maximum shear stress derived from FE models.
• Retardance distribution around embedded spheroids reflected cellular contractility-induced stress distribution.

Conclusions:

• QPOL provides a framework for accurate, non-invasive quantification of 3D mechanical stresses in ECMs.
• The technique is computationally efficient and does not require matrix material model assumptions.
• QPOL offers a valuable tool for mechanobiology research and potential therapeutic development.