A constrained mixture model for developing mouse aorta.

Area of Science:

• Biomedical Engineering
• Vascular Biology
• Computational Modeling

Background:

• Mechanical stresses are critical for blood vessel development and function.
• Vessel walls remodel to maintain homeostatic mechanical stresses after perturbations.
• Existing models for adult vessel remodeling are insufficient for developing vessels due to continuous force changes.

Purpose of the Study:

• To present a constrained mixture model for postnatal development of mouse aorta.
• To investigate the role of smooth muscle cell (SMC) responses and age-dependent material properties in vascular remodeling.
• To approximate experimental data on the mechanical properties and dimensions of developing aortas.

Main Methods:

• Developed a constrained mixture model for postnatal mouse aorta development.
• Incorporated multiple step increases in pressure, axial length, and blood flow.
• Modified baseline assumptions regarding SMC response and age-dependent material properties (stretch ratios, passive constants) to match experimental data.

Main Results:

• The baseline model, assuming immediate SMC response and age-independent properties, failed to predict experimental data.
• Altering assumptions to include a constant SMC dilation and age-dependent homeostatic stretch ratios and material constants improved model accuracy.
• The modified model successfully approximated experimental data for mouse aorta mechanical properties and dimensions from 3 to 30 days old.

Conclusions:

• Vascular remodeling during development is influenced by age-dependent changes in smooth muscle cell behavior and material properties.
• Constrained mixture models, when adapted for developmental specifics, can accurately predict vascular growth and remodeling.
• This model provides a foundation for understanding vascular diseases and designing tissue-engineered blood vessels.