To evaluate the histological integration process of the buccal mucosa onlay graft applied on the dorsal corpora cavernosa for urethroplasty in an experimental study in rabbits, as well as to preliminarily investigate potential mechanism of the survival of the buccal mucosa and the impact of the tunica and corpus cavernos.

Six New Zealand rabbits were fed with finasteride powder(10 mg/kg, 7 d)from 19th days of gestation, and the rabbit model of congenital hypospadias was established.At the age of 4 months, after releasing the chordee of the dorsal corpora cavernosa, the urethral defect was created by applying buccal mucosa onlay graft for the penile urethral reconstruction. The animals were sacrificed at 1, 2, 4, 12, 24 and 36 weeks post surgery and their genitals were subjected to morphological observation and histological assessment with hematoxyiin-eosin (HE), Masson and Stirus staining.

A total of 23 male rabbits were obtained from natural childbirth, 1 of them were normal rabbits, and the other 22 were hypospadias(1 glandular hypospadias, 15 penile hypospadias and 6 scrotal-perineal type). The buccal mucosa graft showed complete uptake in all animals the location of the graft was macroscopically identifiable, demonstrating its good integration. The typical squamous epithelium of buccal mucosa was observed. One week post operation, the tunica albuginea layer and the submucosa were blurred, with inflammatory cells infiltration. Two weeks after surgery, the epithelial layer was getting thick, few neovascularity and young fibroblasts were observed in the subepithelial layer. Gradual arrangement of epithelial layer was visible, the young fibroblasts were increasing and areas of mature collagen could be seen four weeks post operation. The typical squamous epithelium of buccal mucosa and minimal inflammatory cell infiltration in the subepithelial tissues were observed at the grafted mucosa twelve weeks after surgery. It was distinguishable to identify the cell level of subepithelial layer and the tunica of corpus cavernos. Twenty-four weeks after surgery, the epithelial layer was well integrated with adjacent urethral mucosa. Accentuated fibrosis was noticed with extensive mature collagen and without signs of inflammation and scar proliferation of the grafts.

The animal model of congenital hypospadias in rabbits could be established using Finasteride. It was feasible to use the animal model to carry out the experimental study of buccal mucosa grafts. The minimal inflammatory cell infiltrations in the subepithelial tissues were observed at the grafted mucosa twelve weeks after surgery. It was distinguishable to identify the cell level of subepithelial layer and the tunica albuginea of corpus cavernos. Buccal mucosa grafting had no obvious limitation effect on the tunica albuginea and the corpus cavernos development.

Hypospadias; Oral mucosa; Autologous transplantation; Animal model; Histopathology