Urethral replacement using epidermal cell-seeded tubular acellular bladder collagen matrix

To investigate the feasibility of replacing urinary epithelium cells with foreskin epidermal cells to reconstruct engineered anterior urethra with an acellular collagen matrix. Acellular collagen matrices were generated from allogeneic rabbit bladder submucosa. In nine rabbits, autologous foreskin epidermal cells were isolated, expanded in vitro, and labelled with 5-bromo2'-deoxy-uridine (BrdU) before seeding onto a tubular acellular collagen matrix (1.5 x 1 cm). In male rabbits, a urethral mucosal defect was created, and urethroplasty performed with a tubular acellular collagen matrix seeded with epidermal cells (nine rabbits) or with a matrix with no cell seeding (nine rabbits; control group). Urethrography was done at 1, 2 and 6 months after grafting. The urethral grafts were harvested and analysed grossly and histologically. In the control group, gross views and urethrography revealed stricture of repaired defects at the different sample times. In the experimental group, a wide urethral calibre was maintained with no sign of strictures. Histology in the control group showed a single layer of epithelium cells with disorganized muscle fibre bundles in the submucosa layer at 1 month after grafting, and a transitional cell layer surrounded by disorganized muscle fibre bundles at 2 and at 6 months. Grafts seeded with epidermal cells formed a single-layer structure by 1 month, and at 2 and 6 months there were several layers of epidermal cells with abundant vessels in the submucosa. There was an evident margin between graft epidermal cells and host epithelium at 6 months. The implanted cells expressed keratin, shown by staining with anti-pancytokeratins. Immunofluorescence for BrdU confirmed the presence of implanted epidermal cells at 1 month after grafting; there were fewer positive cells at the implantation site at 2 months. At 6 months, there were several layers of epidermal cells with no signs of BrdU staining. Urethral reconstruction was better with an acellular collagen matrix seeded with epidermal cells than with the acellular collagen matrix alone. Foreskin epidermal cells seem adequate in replacing urethral epithelium cells for urethral reconstruction.