Smooth muscle contribution to vaginal viscoelastic response

Area of Science:

• Biomechanics
• Tissue Engineering
• Physiology

Background:

• Smooth muscle cells are crucial for soft tissue mechanics, but their role in viscoelastic responses under multiaxial loading is unclear.
• The vagina, a fibromuscular organ, experiences creep (geometric change under pressure) due to daily activities and childbirth.
• Vaginal smooth muscle may significantly contribute to this creep phenomenon, impacting tissue function.

Purpose of the Study:

• To develop and utilize extension-inflation tests to quantify smooth muscle's contribution to vaginal creep under multiaxial loading.
• To investigate the influence of smooth muscle activation and varying pressures on vaginal viscoelasticity.

Main Methods:

• Mouse vaginas were subjected to extension-inflation tests.
• Smooth muscle was stimulated using potassium chloride, and vaginal creep was measured under physiological pressures (7, 5, and 15 mmHg).
• Vaginal outer diameter was recorded in real-time using a laser micrometer; smooth muscle actin and myosin expression were assessed via immunofluorescence.

Main Results:

• Smooth muscle activation significantly increased vaginal creep compared to the relaxed state.
• Elevated pressure (15 mmHg) diminished the active creep response induced by smooth muscle contraction.
• Extension-inflation protocols effectively assessed smooth muscle's role in the viscoelasticity of tubular soft tissues.

Conclusions:

• Smooth muscle activity plays a key role in the viscoelastic behavior of the vagina, specifically influencing creep.
• The interplay between smooth muscle contraction and applied pressure modulates the tissue's creep response.
• This study validates extension-inflation methods for evaluating smooth muscle contributions to soft tissue biomechanics.