Capsule induction technique in a rat model for bladder wall replacement: an overview

The search for a reliable technique for functional genitourinary tissue replacement remains a challenging task. The most recent advances in cell biology and tissue engineering have utilized various avascular and acellular collagen scaffolds with or without seeded cells. These techniques, however, are frequently complicated by tissue necrosis, contracture and resorption due to limited vascularization. We employed a new three-stage, evolving animal model with stage I optimizing the culture delivery vehicle, stage II employing a seeded vascularized capsule flap, and stage III adding a contractile matrix in the form of pedicled gracilis muscle prelaminated with autologous, in vitro-expanded urothelial cells to reconstruct an entire supratrigonal bladder-wall defect in rats.Specimens stained with hematoxylin and eosin (H&E), alpha(1)-actin staining, and a specific immunohistochemical staining (AE(1)&AE(3)-anticytoceratin monoclonal antibody stain) showed a continuous, multilayered, functioning urothelial lining along the transposed prelaminated gracilis flap in the animals of the final-stage experiment. Successful urinary reconstruction requires a contractile neoreservoir resistant to resorption over time and a stable, protective urothelial lining. We demonstrated that a gracilis muscle flap can be seeded with autologous cultured urothelial cells suspended in fibrin glue. This prelaminated flap can be safely transposed onto its pedicle and become successfully integrated into the remaining bladder wall, demonstrating urothelial lining and the potential to contract. Further studies in larger animals with urodynamic assessment is warranted to determine if this type of bladder-wall replacement technique is suitable for urinary reconstruction in humans.