**Acknowledgements**

complete synthesis, its good folding and its appropriate localization. But these preliminary results encourage the integration of mechanical phase in the process of engineered bladder. This is why we designed a bioreactor which is scheduled to reproduce the physiological intravesical pressures at the fetal stage, and replace the air/liquid phase used for our selfassembled model. Briefly, our self-assembled vesical tissue is placed between two chambers, with urothelial side face to the pressure chamber. To mimic the low pressure maintained during filling phase, 5 cm H2O is applied during few hours. In the last hour the pressure slowly increase until 15 cm H2O, and then decline quickly to zero in a few seconds in order to simulate the voiding and complete the urination cycle. Compared to static condition, short-term dynamic culture significantly improves the urothelial development and the watertightness profile of the self-assembled substitute [129]. These results are in conformity with outcomes related in our dynamical engineered urethra which displayed an increase of uroplakins immunostaining at urothelial cells surface [130]. Whatever the substitute model, the mechan‐ ical stimulations must take more importance within protocols of in vitro bladder reconstruc‐ tion. When must the dynamic phase intervene? How long time must it intervene? Should the pressure cycle follow a constant scheme or must it evolved during the process? Better under‐ standing of bladder cells mechanotransduction may ameliorate the setting up of a dynamical environment appropriate to the reconstruction of a mature and functional vesical tissue.

Bladder exposition to diverse pathologies could jeopardize its function of elastic and water‐ tight reservoir. To date, the clinical technique for bladder repair is associated to a high level of morbidity. Based on the well documented post-operative complications, it is appear that the ideal bladder substitute must combine the compliance conferred by the nature and architecture of the matrix support, with a urinary barrier provided by the differentiation degree of urothelium. Natural and synthetic scaffolds were investigated to reproduce the bladder abilities and some successes were furthered the urological tissue-engineering domain. But due to their poor mechanical stability, immune responses, and incomplete cellular maturation, these models remain insufficiently developed to be used in clinical application. At present, teams which support the acellularised or polymeric substitute are working on the next generation of engineered bladder model. For example, nanodimensional surface features would be included in order to imitate the nanometer topography of native tissue, and therefore, to enhance interactions between bladder cells and the proposed environment. Among all biotechnologies, the self-assembly method proves to be a promising approach to elaborate a vesical substitute comparable to the structure and function of native tissue. The good water‐ tightness of reconstructed mucosa and its autologous character will permit a suitable integra‐ tion in vivo, and promote the cellular expansion. The application of appropriate culture method, such as dynamical regime, will lead to the maturation of the reconstructed connective tissue and its urothelium. The capacity of the self-assembled tissue to be pre-endothelialized might avoid the necrosis of the graft attributed to the lack of synchronized neovascularization. Another aspect which is rarely taking into account is the capacity for a graft to growth with

**5. Conclusion**

586 Regenerative Medicine and Tissue Engineering

The authors thank Kenza Bouhout for her useful discussions and her participation in the illustration of this chapter.
