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Twenty years ago, Dr. François A. Auger, the founder of the Laboratory of Experimental Organogenesis (LOEX), introduced the self-assembly technique. This innovative technique relies on the ability of dermal fibroblasts to produce and assemble their own extracellular matrix, differing from all other tissue-engineering techniques that use preformed synthetic scaffolds. Nevertheless, the use of the self-assembly technique was limited for a long time due to its main drawbacks: time and cost. Recent scientific breakthroughs have addressed these limitations. New protocol modifications that aim at increasing the rate of extracellular matrix formation have been proposed to reduce the production costs and laboratory handling time of engineered tissues. Moreover, the introduction of vascularization strategies in vitro permits the formation of capillary-like networks within reconstructed tissues. These optimization strategies enable the large-scale production of inexpensive native-like substitutes using the self-assembly technique. These substitutes can be used to reconstruct three-dimensional models free of exogenous materials for clinical and fundamental applications.

Cells obtained from a patient's biopsy have to be expanded after extraction to produce autologous tissues, but standard cell culture conditions often limit their growth or lifespan and could induce early and inadequate cell differentiation. Moreover, it has previously been reported that the air-liquid interface, that induces maturation of the urothelium, stimulated inadequate differentiation associated with aberrant keratin-14 expression. The aim of this study was to test the benefits of hypoxia during expansion of urothelial cells and maturation of the bladder epithelium in the context of tissue engineering. Bladder mucosa substitutes were reconstructed using the self-assembly method with urothelial cells (UCs) expanded in normoxia or hypoxia. Hypoxia improved UCs expansion until passage P7, whereas normoxic conditions limited the use of UCs to passage P4. Maturation of the urothelium was also compared in normoxic vs. hypoxic conditions. Using laminin V, p63, Ki-67, keratin-5 and -14, Claudin-4 and zonula occludens protein-1, we show a better organization of the basal UC layer in hypoxia despite a thinner intermediate layer. Finally, barrier function was assessed by permeation tests. Cell culture in hypoxia allowed the generation of bioengineered urological tissue closer to native bladder characteristics, which represents a promising avenue to circumvent the lack of adequate tissues for reconstructive surgery. Copyright © 2017 John Wiley & Sons, Ltd.

Although the self-assembly approach is an efficient method for the production of engineered physiological and pathological tissues, avoiding the use of exogenous materials, it nevertheless remains expensive and requires dexterity, which are features incompatible with large-scale production. We propose a modification to this technique to make easier the production of mesenchymal compartment, to reduce the cost and to improve the histological quality of the self-assembled tissues. The stroma produced by this novel approach allowed epithelial cell differentiation, resulting in a pseudostratified epithelium that shared several features with native tissues. The incorporation of endothelial cells in the reconstructed mesenchyme formed a three-dimensional capillary-like network, positive for CD31 and von Willebrand factor and surrounded by NG2 positive cells. It could limit self-contraction of the resulting tissue by recruiting α-Smooth Muscle Actin positive cells. With this new technique, which is relatively inexpensive and easy to use in a research laboratory set-up, near-native stromas can now be produced with minimal handling time. Copyright © 2015 John Wiley & Sons, Ltd.

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. Copyright © 2013 John Wiley & Sons, Ltd.

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.