Architecture-Dependent Anisotropic Hysteresis in Smooth Muscle Cells

Area of Science:

• Cellular mechanics
• Biophysics
• Tissue engineering

Background:

• Mechanically dynamic tissues like arteries experience constant force and deformation.
• Pathologies such as aneurysms involve complex cellular force transduction, leading to maladaptive growth.
• Understanding cellular responses to mechanical stress is crucial for tissue health.

Purpose of the Study:

• To determine the dynamic mechanical properties of vascular smooth muscle cells (VSMCs) under biaxial load.
• To investigate the influence of load orientation and actin organization on VSMC hysteresis.
• To develop models capable of describing observed cellular mechanical behaviors.

Main Methods:

• Cellular micro-biaxial stretching microscopy was employed.
• Large-strain anisotropic stress-strain hysteresis of VSMCs was measured.
• A Hill-type active fiber model was developed and validated.

Main Results:

• VSMC hysteresis is highly dependent on load orientation and actin organization.
• Elongated VSMCs exhibited reverse hysteresis under cyclic loading, where unloading stress exceeded loading stress.
• Traditional quasilinear viscoelasticity models failed to replicate this reverse hysteresis.

Conclusions:

• VSMCs in organized tissues display strongly anisotropic responses to complex mechanical loads.
• The developed active fiber model accurately describes experimentally observed reverse hysteresis.
• These findings have significant implications for understanding mechanotransduction in arterial pathologies.