Abstract
Introduction: Tissue engineering is a potential source of urethral substitutes to treat severe urethral defects. Our aim was to create tissue-engineered urethras by harvesting autologous cells obtained by bladder washes and then using these cells to create a neourethra in a chronic large urethral defect in a rabbit model.Methods: A large urethral defect was first created in male New Zealand rabbits by resecting an elliptic defect (70 mm2) in the ventral penile urethra and then letting it settle down as a chronic defect for 5–6 weeks. Urothelial cells were harvested noninvasively by washing the bladder with saline and isolating urothelial cells. Neourethras were created by seeding urothelial cells on a commercially available decellularized intestinal submucosa matrix (Biodesign® Cook-Biotech®). Twenty-two rabbits were divided into three groups. Group-A (n = 2) is a control group (urethral defect unrepaired). Group-B (n = 10) and group-C (n = 10) underwent on-lay urethroplasty, with unseeded matrix (group-B) and urothelial cell-seeded matrix (group-C). Macroscopic appearance, radiology, and histology were assessed.Results: The chronic large urethral defect model was successfully created. Stratified urothelial cultures attached to the matrix were obtained. All group-A rabbits kept the urethral defect size unchanged (70 ± 2.5 mm2). All group-B rabbits presented urethroplasty dehiscence, with a median defect of 61 mm2 (range 34–70). In group-C, five presented complete correction and five almost total correction with fistula, with a median defect of 0.3 mm2 (range 0–12.5), demonstrating a significant better result (p = 7.85 × 10−5). Urethrography showed more fistulas in group-B (10/10, versus 5/10 in group-C) (p = 0.04). No strictures were found in any of the groups. Group-B histology identified the absence of ventral urethra in unrepaired areas, with squamous cell metaplasia in the edges toward the defect. In group-C repaired areas, ventral multilayer urothelium was identified with cells staining for urothelial cell marker cytokeratin-7.Conclusions: The importance of this study is that we used a chronic large urethral defect animal model and clearly found that cell-seeded transplants were superior to nonseeded. In addition, bladder washing was a feasible method for harvesting viable autologous cells in a noninvasive way. There is a place for considering tissue-engineered transplants in the surgical armamentarium for treating complex urethral defects and hypospadias cases.
Highlights
Tissue engineering is a potential source of urethral substitutes to treat severe urethral defects
We can summarize three main findings: we were successful in establishing a reproducible and chronic large urethral defect animal model in rabbits; TEUs were successfully created, using the bladder washing technique as source of cells and small intestinal submucosa matrix (SIS) matrix as scaffold; and reconstructive urethroplasty using TEUs was superior to the use of acellular scaffolds of SIS matrix in the rabbit model
The chronic large urethral defect model created was harmless to the rabbit, reproducible and stable over time, and may be suitable for use for further development of urethroplasty models and tissue engineering techniques
Summary
Tissue engineering is a potential source of urethral substitutes to treat severe urethral defects. Mild case (distal hypospadias) repair is usually successful with numerous techniques, but severe case (proximal hypospadias) treatment may be challenging due to the lack of healthy tissue for the urethral reconstruction. In these cases, multiple urethral tissue substitutes have, so far, been described for creating a neourethra, such as the inner prepuce, buccal mucosa, bladder mucosa, postauricular grafts, among others [4,5,6,7,8,9]. These substitutes have well documented side effects such as donor site morbidity and present mechanical and biological differences compared with the native urethra, and sometimes may not even be available due to multiple previous surgical interventions
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