[Preliminary study on prefabricated urethra in expander capsule].

Objective: To investigate the feasibility of prefabricating urethra in the expander capsule with gelatin sponge and micro-mucosa compound transplantation.
Methods: Eight 8-week-old Guizhou miniature pigs (male and/or female) weighing 20-25 kg were used. Six expanders (15 mL) were placed subcutaneously on the dorsal thorax of each miniature pig. Autologous oral mucosa of every pig was harvested 2 weeks later to prepare micro-mucosa with a diameter less than 1 mm. Gelatin sponge 3 cm x 2 cm in size was transplanted to the expander capsule after being coated by the autologous micro-mucosa at the area expansion ratio of 4 : 1 (group A), 8 : 1 (group B), and 16 : 1 (group C), respectively (n = 2 per group). The implantation of gelatin sponge served as the blank control (group D, n = 2). Physiological saline was injected into the expander immediately after operation, and the pressure in the expander was 40 mm Hg (1 mm Hg = 0.133 kPa). The postoperative general condition of the animals was observed. At 1, 2, and 3 weeks after operation, the animals were killed to receive general, HE staining, and immunohistochemistry staining observations.
Results: All animals survived till the end of the experiment. The wounds healed well. General observation: in groups A, B, and C at 1 week after operation, there was no obvious degeneration of gelatin, the mucous was survived partially, and there were significant differences among three groups in terms of mucosa healing rate (P < 0.05), groups A and B were better than group C, and group A was better than group B; at 2 weeks, the gelatin sponge was partly absorbed, most of the mucosa survived, and the mucosa healing rate of groups A and B was better than that of group C (P < 0.05); at 3 weeks, the gelatin sponge was still not absorbed completely, the wound reached epithelialization approximately, and there were no significant differences among three groups in terms of mucosa healing rate (P > 0.05). No neo-mucosa was evident in group D at each time point. Histology and immunohistochemistry staining observation: at each time point, the mucosa epithelium survival, inflammatory cell infiltration, and pan-cytokeratin were evident in groups A, B, and C; at 3 weeks after operation, the stratified squamous epithelium presented obvious polarity and the submucous neovascularization was abundant in groups A, B, and C. There was no mucosa epithelium and positive stained pan-cytokeratin in group D. For the percentage of positive pan-cytokeratin stained area, there were significant differences among groups A, B, and C 1 week after operation (P < 0.05); at 2 and 3 weeks after operation, there was significant difference between group A and group C, and between group B and group C (P < 0.05); but no significant difference was evident between group A and group B (P > 0.05).
Conclusion: Micro-mucosa and gelatin spongy compound transplantation on the expander capsule can form mucosal lining, achieve complete epithelialization in 2 weeks, and contribute to maintain the normal function of prefabricated urethra.