Internet-based image analysis quantifies contractile behavior of individual fibroblasts inside model tissue.

Area of Science:

• Biophysics
• Cell Biology
• Biomaterials Science

Background:

• Quantifying cell-gel mechanics is crucial for understanding tissue development and disease.
• Existing methods often lack the resolution to capture localized cellular forces and their transmission through the extracellular matrix.

Purpose of the Study:

• To develop and validate a novel method for quantifying cell-gel mechanics in situ using intrinsic collagen fiber structure.
• To investigate the role of fibroblast contractile machinery and cytoskeletal dynamics in mediating cell-gel interactions and strain transmission.

Main Methods:

• Utilizing differential interference contrast (DIC) microscopy to visualize intrinsic collagen fiber structure as an in situ strain gauge.
• Employing optical sections of fluorescent protein distribution (e.g., GFP-alpha-actinin) to capture cytoskeletal kinematics.
• Applying automated image analysis using the Deformation Quantification and Analysis (DQA) software package for mechanics quantification.

Main Results:

• Demonstrated that intrinsic fiber structure in collagen gels can serve as a reliable in situ strain gauge.
• Observed fibroblast contractile machinery localized within pseudopods, with GFP-alpha-actinin concentrating at pseudopod tips and cortex.
• Characterized complex strain patterns around individual cells, revealing both elastic and inelastic strain transmission.

Conclusions:

• The developed method accurately quantifies cell-gel mechanics and cytoskeletal kinematics.
• Fibroblast contractility within pseudopods plays a significant role in localized matrix deformation.
• Observed strain patterns suggest a mechanism for long-range cell alignment mediated by cell-generated forces and matrix remodeling.