Organ and species specificity in the stimulation of transitional epithelial cell growth by fibroblasts

Objectives: Culture of transitional epithelium for urinary tract reconstruc tion has been problematic due, in part, to the dependence of urothelial cel ls on a basal layer of bladder fibroblasts for growth. In vitro studies on the effect of bladder, ureter, and intestinal fibroblast cocultures and con ditioned media upon urothelial cell growth were conducted to better charact erize the dependence of urothelial cells of fibroblasts. Methods: Primary cultures of human and porcine bladder, ureter, and intesti nal fibroblasts and bladder and ureter urothelial cells were established. T he urothelial cells were incubated with fibroblasts in a coculture system a nd growth compared to that of individual fibroblast and urothelial cultures . Urothelium-specific medium was exposed to the fibroblast cultures for 6, 12, and 24 h. Urothelial cell growth in each of the fibroblast-conditioned media was evaluated. Results: Coculture of human urothelial cells with human bladder and ureter fibroblasts yielded increased cell growth when compared to the cells in ind ividual culture. This improvement was greatest for the bladder fibroblasts in coculture with bladder epithelial cells. The media exposed to bladder an d ureter fibroblasts for 24 h significantly increased bladder and ureter ur othelial growth compared to fresh medium. Coculture with intestinal fibrobl asts and exposure to intestinal fibroblast conditioned media did not signif icantly stimulate urothelial cell growth. Similarly, coculture and conditio ned media studies of porcine urothelial cells with porcine bladder and uret er fibroblasts (but not intestinal fibroblasts) yielded increased cell grow th when compared to the cells in individual culture, particularly with blad der fibroblasts. However, human urothelial cells were not stimulated by por cine bladder and ureter fibroblast conditioned media, nor were porcine urot helial cells stimulated by human bladder a nd ureter fibroblast conditioned media. Conclusions: The ability of urinary fibroblasts to stimulate urothelial cel l proliferation resides in an unidentified soluble factor secreted into the medium, independent of the presence of the fibroblasts, This factor is rel atively organ and species-specific. Copyright (C) 2001 S. Karger AG, Basel.