Location-dependent correlation between tissue structure and the mechanical behaviour of the urinary bladder

Area of Science:

• Biomedical Engineering
• Tissue Mechanics
• Urology

Background:

• The mechanical properties of the urinary bladder wall are crucial for its filling and voiding functions.
• Understanding regional heterogeneities and microstructure is vital for diagnosing and treating bladder diseases.

Purpose of the Study:

• To investigate the regional differences in mechanical properties and microstructure of the porcine urinary bladder wall.
• To correlate structural variations with observed mechanical behaviors.

Main Methods:

• Mechanical testing (equibiaxial) of 90 porcine bladder wall samples from nine distinct locations.
• Histological analysis using Picro-Sirius red staining to differentiate tissue components (smooth muscle, ECM, fat).

Main Results:

• The bladder wall displays non-linear stress-stretch behavior with hysteresis and softening.
• Significant regional variations in mechanical response and microstructure were identified.
• The trigone region showed higher peak stresses and a thinner muscularis layer.
• Ventral bladder regions exhibited anisotropic behavior, while the dorsal side was isotropic, correlating with smooth muscle fiber orientation.

Conclusions:

• Urinary bladder wall mechanics and microstructure are heterogeneous across the organ.
• Observed regional differences, particularly in the trigone and ventral/dorsal regions, are linked to smooth muscle arrangement.
• Findings are relevant for constitutive modeling, whole bladder mechanics, and tissue engineering applications.