Urinary tract is subjected to many varieties of pathologies since birth including congenital anomalies, trauma, inflammatory lesions, and malignancy. These diseases necessitate the replacement of involved organs and tissues. Shortage of organ donation, problems of immunosuppression, and complications associated with the use of nonnative tissues have urged clinicians and scientists to investigate new therapies, namely, tissue engineering. Tissue engineering follows principles of cell transplantation, materials science, and engineering. Epithelial and muscle cells can be harvested and used for reconstruction of the engineered grafts. These cells must be delivered in a well-organized and differentiated condition because water-seal epithelium and well-oriented muscle layer are needed for proper function of the substitute tissues. Synthetic or natural scaffolds have been used for engineering lower urinary tract. Harnessing autologous cells to produce their own matrix and form scaffolds is a new strategy for engineering bladder and urethra. This self-assembly technique avoids the biosafety and immunological reactions related to the use of biodegradable scaffolds. Autologous equivalents have already been produced for pigs (bladder) and human (urethra and bladder). The purpose of this paper is to present a review for the existing methods of engineering bladder and urethra and to point toward perspectives for their replacement.

The time needed to produce engineered tissue is critical. A self-assembly approach provided excellent results regarding biological functions and cell differentiation because it closely respected the microenvironment of cells. Nevertheless, the technique was time consuming for producing tissue equivalents with enough extracellular matrix to allow manipulations. Unlike L-arginine supplementation that only increased accumulation of collagen in cell culture supernatant in our model, addition of lysophosphatidic acid, a natural bioactive lipid, did not modify the amount of accumulated collagen in the cell culture supernatant; however, it enhanced the matrix deposition rate without inducing fibroblast hyperproliferation and tissue fibrosis.

Introduction: Many efforts are used to improve surgical techniques and graft materials for urethral reconstruction. We developed an endothelialized tubular structure for urethral reconstruction.Methods: Two tubular models were created in vitro. Human fibroblasts were cultured for 4 weeks to form fibroblast sheets. Then, endothelial cells (ECs) were seeded on the fibroblast sheets and wrapped around a tubular support to form a cylinder for the endothelialized tubular urethral model (ET). No ECs were added in the standard tubular model (T). After 21 days of maturation, urothelial cells were seeded into the lumen of both models. Constructs were placed under perfusion in a bioreactor for 1 week. At several times,histology and immunohistochemistry were performed on grafted nude mice to evaluate the impact of ECs on vascularization.Results: Both models produced an extracellular matrix, without exogenous material, and developed a pseudostratified urothelium. Seven days after the graft, mouse red blood cells were present only in the outer layers in T model, but in the full thickness of ET model. After 14 days, erythrocytes were present in both models, but in a greater proportion in ET model. At day 28, both models were well-vascularized, with capillary-like structures in the wholethickness of the tubes.Conclusion: Incorporating endothelial cells was associated with an earlier vascularization of the grafts, which could decrease the necrosis of the transplanted tissue. As those models can be elaborated with the patient’s cells, this tubular urethral graft would be unique in its autologous property.

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