Comparing the tissue properties of human buccal mucosa and penile skin flap: insights for urethral graft substitution.

Objectives: To compare the histological features, biomechanical properties, water permeability, and osmotic stress responses of human buccal mucosa and penile skin flaps to evaluate their suitability as urethral graft substitutes.

Methods: Buccal mucosa (n = 53) and penile skin flap (n = 59) were prepared for histological assessment of tissue structural characteristics and vascular patterns using H&E staining and immunofluorescence. Biomechanical properties were evaluated through mechanical testing, water permeability through deuterium oxide diffusion assays, and osmotic stress responses under hypo-, iso-, and hypertonic conditions.

Results: H&E staining revealed that the buccal mucosa epithelium was significantly thicker (628.8 ± 213.3 μm) than that of the penile skin flap (148.2 ± 62.1 μm; p < 0.05). Mechanical testing demonstrated that the buccal mucosa had significantly higher elastic modulus and tensile strength and lower tensile strain compared with penile skin flap (p < 0.05). Water permeability testing revealed that the cumulative diffusion of deuterium oxide (D₂O) through the buccal mucosa was consistently higher at all time points compared to the penile skin flap (p < 0.05). In the Hypo group, the ratio of variation in epithelial thickness was significantly higher in the penile skin flap compared to the buccal mucosa. No statistical differences in the ratio of epithelial thickness variation were observed under Iso (p = 0.43) and Hyper (p = 0.07) conditions. The primary limitation of this study is the relatively small sample size. Additionally, the in vitro model lacks the ability to fully replicate the urethral microenvironment, where multiple interacting factors influence graft survival.

Conclusion: This study presents the first comprehensive comparison of the tissue properties of buccal mucosa and penile skin flaps. Our findings provide valuable insights for surgical decision-making, postoperative management, personalized treatment strategies, and the advancement of bioengineered urethral substitutes.