The bladder wall of the rat is composed of three layers of tissue, including the mucosal layer, the muscular layer and the outer membrane. Among them, the mucosa is a very thin layer of transitional epithelial tissue, which is connected with the ureter and urethral mucosa. In vitro culture of bladder epithelial cells is not only a necessary means of cell implantation for tissue engineered bladder and urethra, but also the basis and premise for the study of the genesis and treatment of transitional epithelial cell tumors.