Bladder cell culture on small intestinal submucosa as bioscaffold: Experimental study on engineered urothelial grafts

Objectives: To investigate the feasibility to perform primary urothelial cell culture using porcine small intestinal submucosa as a delivery scaffold both in vitro and after in vivo implantation in a rabbit model. Materials and methods: Bladder mucosa samples were aseptically obtained from a group of eight male rabbits. The mucosa was cut into fragments and placed on small intestinal submucosa matrices for selective urothelial cell culture. After complete in vitro epithelization the matrices were shaped into tubes and placed in the subcutaneous tissue and subdartos of donor rabbits. The pattern of cell growth and delivery was evaluated on retrieved grafts using histology and immunostaining at the end of the in vitro phase; then 5, 10 and 20 days after implantation. Results: Histological and immunohistochemical analysis of the in vitro primary culture showed the acellular matrices covered with a thin uninterrupted monolayer of urothelial cells. The implants examined on the day 5 mantained the epithelial configuration of the cultured grafts in all samples retrieved. On the day 10 the urothelium showed increased thickness taking on a bilayer configuration. On day 20, all grafts presented the transitional cells arranged in a double layer closely resembling the natural urothelium. The immunostaining pattern displayed the mantaining of urothelial cell phenotype. No differences in epithelium growth and delivery were noted between the two sites of implantation. Five days after implantation, the histological analysis of small intestinal submucosa showed a medium degree tissue reaction with the presence of acute inflammatory cells. Angiogenesis was demonstrated by the development of several new vessels inside the matrix. After twenty days, small intestinal submucosa was gradually replaced with host tissue. Conclusion: The small intestinal submucosa proved to function as a means of delivering of autologous urothelial cells cultured in vitro. After ectopic in vivo implantation the bioscaffold maintained viability and growth of the surrounding cells until its degradation.