Altered extracellular matrix expression in the diverted fetal sheep bladder

Area of Science:

• Developmental Biology
• Urology
• Tissue Engineering

Background:

• Fetal bladder development is influenced by mechanical forces from filling and emptying.
• The role of these mechanical stimuli in regulating bladder wall development remains incompletely understood.

Purpose of the Study:

• To investigate the impact of urinary diversion (lack of filling and emptying) on fetal lamb bladder development.
• To determine if mechanical loading is essential for normal bladder wall maturation.

Main Methods:

• Urinary diversion was performed in fetal lambs, with transmural sections analyzed after 14 days.
• Tissue layer thickness, mRNA levels (collagens, growth factors), and protein levels (collagen subtypes) were quantified.

Main Results:

• Diverted bladders showed decreased mucosal and detrusor muscle thickness but increased serosal layer thickness.
• Significant increases in collagen mRNA and protein were observed in the serosal/detrusor layer.
• Specific gene expression changes (IGF-1, BCL-2, EGR-1, FN, WT-1) indicated altered cellular processes.

Conclusions:

• Absence of mechanical loading arrests detrusor smooth muscle growth and promotes serosal layer fibrosis.
• Growth factors and anti-apoptotic genes likely regulate smooth muscle phenotype changes in the detrusor.
• Mechanical forces are critical for normal fetal bladder wall development and maintenance.