Reconstruction of the urinary bladder mucosa in three-dimensional collagen gel culture: fibroblast-extracellular matrix interactions on the differentiation of transitional epithelial cells.

The purpose of this study was to reconstruct a urinary bladder mucosa in three-dimensional collagen gel culture conditions that included fibroblasts. Transitional epithelial cells and fibroblasts, isolated respectively from the epithelial and lamina propria layers of porcine urinary bladder, were cultured in monolayer. These fibroblasts were embedded and cultured within a collagen gel matrix to reconstruct a lamina propria. The isolated transitional epithelial cells were then seeded in vitro on this reconstructed lamina propria on which the transitional epithelial cells formed a stratified urothelium composed of basal, intermediate and superficial layers. Urothelial differentiation was observed only on the fibroblast-containing collagen matrix. Differentiation did not occur on a cell-free collagen matrix through use of fibroblast conditioned medium. Thus, urothelial differentiation depended upon a fibroblast-extracellular matrix interaction. The differentiated transitional epithelial cell layer thus produced closely resembled a urothelium in vivo. This culture model may provide a useful system in which to study various diseases of the urinary bladder.