Measurement of Liver Stiffness using Atomic Force Microscopy Coupled with Polarization Microscopy

Area of Science:

• Biomedical Engineering
• Cell Biology
• Pathology

Background:

• Matrix stiffening is a key driver of liver fibrosis progression.
• Understanding tissue mechanics at the cellular level is crucial due to non-homogeneous changes in the liver.
• Collagen fibers contribute significantly to liver tissue stiffness.

Purpose of the Study:

• To present a protocol for measuring liver tissue elastic moduli with high spatial precision using atomic force microscopy (AFM).
• To investigate the changes in mechanical properties of collagen-rich areas in fibrotic liver tissues.
• To correlate tissue stiffness with fibrosis development.

Main Methods:

• Utilized atomic force microscopy (AFM) to measure local mechanical properties (elastic modulus) of liver tissue.
• Coupled AFM with polarization microscopy to identify collagen-rich areas based on birefringence.
• Applied the protocol to mildly fixed fibrotic and control mouse liver tissues.

Main Results:

• Demonstrated a prominent increase in the stiffness of collagen-positive areas in fibrotic livers compared to controls.
• The protocol enabled highly reproducible measurements of liver tissue stiffness.
• High spatial precision allowed for characterization of localized mechanical changes.

Conclusions:

• The developed AFM protocol provides a reproducible method for assessing liver tissue stiffness.
• Increased matrix stiffness is a significant feature of liver fibrosis.
• This method can advance understanding of how mechanical changes impact cell behavior during disease.