Development of a seeded scaffold in the great omentum:: Feasibility of an in vivo bioreactor for bladder tissue engineering

Objectives: Tissue engineering is very promising in bladder reconstruction. However, one of the main problems is to limit the development of ischaernic fibrosis during tissue maturation. We describe a model using the omenturn as an in vivo bioreactor for a previously seeded scaffold. Methods: Bladder biopsies were taken from five female pigs, from which both urothelial and smooth muscle cells cultures were made. These cultured cells were used to seed a sphere-shaped small intestinal submucosa (SIS) matrix, which was transferred into the omenturn after 3 wk of cell growth. The grafts were harvested 3 wk later and histologic, immunohistochemical, and functional studies were performed. Results: We obtained a highly vascularized tissue-engineered construct that contracted in response to acetylcholine stimulation. The wall thickness was 4 mm, on average. Histologic and immunostaining analysis of the construct confirmed the presence of a multilayer urothelium on the luminal aspect and deeper fascicles organised tissue composed of differentiated smooth muscle cells and mature fibroblasts without evidence of inflammation or necrosis. Large- and small-diameter vessels were clearly identified histologically in the tissue obtained. Conclusion: The omenturn permitted in vivo maturation of seeded scaffolds with the development of a dense vascularisation that is anticipated to prevent fibrosis and loss of contractility. This in vivo maturation into the omenturn could be the first step before in situ implantation of the construct. (c) 2007 European Association of Urology. Published by Elsevier B.V. All rights reserved.