Estimating Cell Mechanical Anisotropy Via Spherical Indentation and F-Actin Imaging

Area of Science:

• Cellular mechanics and mechanobiology
• Biophysics of cytoskeletal dynamics
• Tissue engineering and biomaterials

Background:

• Cellular mechanical properties indicate physiological state.
• Standard Young's modulus (Es) does not capture mechanical anisotropy.
• F-actin alignment is a key determinant of cell mechanical behavior.

Purpose of the Study:

• To assess if standard indentation and F-actin alignment can estimate anisotropic cell elastic moduli (E1, E2).
• To correlate F-actin alignment with cell anisotropy in different cell types.
• To develop a predictive model for anisotropic moduli based on F-actin alignment and isotropic modulus.

Main Methods:

• Performed toroidal indentation on porcine aortic valvular interstitial cells (PAVICs) and dermal fibroblasts.
• Quantified F-actin alignment using fluorescent microscopy.
• Developed a multivariable regression model incorporating F-actin alignment and finite element-simulated Young's modulus (Es).

Main Results:

• Moderate correlation between F-actin alignment and cell anisotropy (E1/E2) observed in PAVICs, but not dermal fibroblasts.
• Grouping PAVICs by aspect ratio significantly improved correlation and predictive accuracy at the group level.
• Individual cell mechanical properties showed high variation, limiting predictive accuracy for single cells.

Conclusions:

• Average anisotropic elastic moduli can be accurately predicted for groups of cells with similar morphology.
• Direct measurement is necessary for individual cell mechanical anisotropy due to high variability.
• Clarifies the relationship between F-actin structure, isotropic Young's modulus, and anisotropic elastic moduli in cells.