Background: In an earlier study we demonstrated the feasibility to create tissue engineered venous scaffolds\nin vitro and in vivo. In this study we investigated the use of tissue engineered constructs for ureteral replacement in\na long term orthotopic minipig model. In many different projects well functional ureretal tissue was established\nusing tissue engineering in animals with short-time follow up (12 weeks). Therefore urothelial cells were harvested\nfrom the bladder, cultured, expanded in vitro, labelled with fluorescence and seeded onto the autologous veins,\nwhich were harvested from animals during a second surgery. Three days after cell seeding the right ureter was\nreplaced with the cell-seeded matrices in six animals, while further 6 animals received an unseeded vein for ureteral\nreplacement. The animals were sacrificed 12, 24, and 48 weeks after implantation. Gross examination, intravenous\npyelogram (IVP), H&E staining, Trichrome Masson�s Staining, and immunohistochemistry with pancytokeratin\nAE1/AE3, smooth muscle alpha actin, and von Willebrand factor were performed in retrieved specimens.\nResults: The IVP and gross examination demonstrated that no animals with tissue engineered ureters and all\nanimals of the control group presented with hydronephrosis after 12 weeks. In the 24-week group, one tissue\nengineered and one unseeded vein revealed hydronephrosis. After 48 weeks all tissue engineered animals and\nnone of the control group showed hydronephrosis on the treated side. Histochemistry and immunohistochemistry\nrevealed a multilayer of urothelial cells attached to the seeded venous grafts.\nConclusions: Venous grafts may be a potential source for ureteral reconstruction. The results of so far published\nureteral tissue engineering projects reveal data up to 12 weeks after implantation. Even if the animal numbers of\nthis study are small, there is an increasing rate of hydronephrosis revealing failure of ureteral tissue engineering\nwith autologous matrices in time points longer than 3 months after implantation. Further investigations have to\nprove adequate clinical outcome and appropriate functional long-term results.
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