Characterization of murine excisional wounds based on atomic force microscopy indentation

Area of Science:

• Biomedical Engineering
• Tissue Mechanics
• Wound Healing Research

Background:

• Mechanical factors significantly influence skin wound healing and scar formation.
• Quantitative characterization of the extracellular matrix's mechanical environment during healing is incomplete.
• Atomic Force Microscopy (AFM) is a key tool for micrometer-scale mechanical tissue analysis.

Purpose of the Study:

• To map mechanical properties of different regions within murine skin wounds at two healing time points.
• To compare the efficacy of various stiffness measures in differentiating tissue compartments.
• To investigate the impact of constitutive models and surface topography on AFM indentation results.

Main Methods:

• AFM-based indentation was performed on murine excisional wounds and adjacent skin at day 7 and day 14 post-wounding.
• Data analysis involved extracting and comparing different stiffness measures.
• Finite element analysis using a biphasic constitutive model was employed to simulate indentation experiments and assess surface roughness effects.

Main Results:

• At day 7, the hyperproliferative epithelium was stiffer than granulation tissue, which was softer than adjacent skin; these differences diminished by day 14.
• Shear stiffness derived from AFM data can be up to 50% higher than conventional elastic modulus measurements.
• Surface roughness can lead to an underestimation of local stiffness by up to 50%.

Conclusions:

• AFM indentation provides quantitative insights into the mechanical changes during skin wound healing.
• The study resolves contradictions regarding wound deformability and offers a more accurate interpretation of AFM data.
• The findings are crucial for understanding mechanobiology in wound healing and improving biomaterial design.