[Long-term observation of prefabricated urethra with buccal mucosa in expanded capsule].

Objective: To investigate the histological and keratinous variation of prefabricated urethra in the capsule with micro-mucosa and gelatin sponge compound graft.
Methods: Five 8-week-old Guizhou miniature pigs (2 females and 3 males) weighing 20-25 kg were used. Eight tissue expanders were bilaterally inserted into subcutaneous position on the dorsal thorax of each pig. Forty inserted expanders were randomized into two groups (n=20 per group). For the experimental group, the free buccal mucosa was cut into particles less than 1 mm in diameter, spread onto the gelatin sponge (3 cm x 2 cm) and then transplanted to the capsule; the area expansion ratio of autogenous micro-mucosa was 8 : 1. For the control group, soft tissue expander without mucosa graft was implanted. The pressure in inserted expander was about 40 mm Hg (1 mm Hg=0.133 kPa). Inflation should be stopped when the injected saline volume reached 15 mL. The animals were killed 1 and 2 weeks and 1, 2, and 4 months after the implant to receive examination. Microscope, histology, and immunohistochemistry changes were observed.
Results: All the animals survived to the end of the experiment and the wounds healed by first intention. There was no obvious degeneration of gelatin sponge, and some of the mucosa survived 1 week after implant. The gelatin sponge was partly absorbed, most of the mucosa survived 2 weeks after implant. Visual examination showed complete epithelialization of the entire cavity 1 month after implant. The experimental group at 2 and 4 months were similar to that of at 1 month in gross observations. The neo-mucosa was not found in the control group at different time points after implant. Histology examination revealed that compound implant was mainly infiltrated by inflammatory cells and the micro-mucosa survived well 1 week after implant in the experimental group. The stratified squamous epithelium presented obvious polarity and the submucous neovascularization was abundant 2 weeks after implant. The compound implant achieved complete epithelialization 1 month after implant. The epithelium degeneration occurred 2 months after implant. The stratified squamous epithelium presented no abovious polarity 4 months after implant. No neo-mucosa was evident in control group at different time points. The experimental group was positive for the pan-cytokeratin staining at 1, 2 weeks, and 1, 2 months after implant, but negative at 4 months after implant. The pan-cytokeratin staining was negative in the control group at different time points.
Conclusion: The buccal micromucosa and gelatin sponge compound graft can grow well on the expanded capsule 1 month after implant and the epithelium degeneration is evident 2 months after implant. Environment of implanted mucosa has great influence on epithelium mucosa.