This study describes two experimental models for the in vitro reconstitution of the human bladder mucosa (neo-bladder): human urothelial stabilized cell lines were cultured on three-dimensional matrices, collagen or platelet-fibrin gels, containing murine fibroblast 3T3-J2 cells. Low-density seeding (2x10(4) cells/ml) of both normal (TCA-48) and neoplastic cell lines (TCA-47) on collagen matrix gave rise to isolated papillar colonies, while high-density seeding (3.75x10(6) cells/ml) led to the formation of wide pluristratified epithelial sheets, resembling the normal transitional epithelium. In contrast, high-density seeding (5x10(5) cells/ml) on platelet-fibrin matrix did not allow the formation of epithelial sheets: only isolated voluminous colonies of normal TCA-48 cells, and sparse and small colonies of neoplastic TCA-47 could be observed. Growth assays and cytotoxicity reduction tests showed that the growth inhibitory effect of platelet-fibrin gel on urothelial cells was probably due to the aspecific activation of the complement contained in the plasmatic fraction, whose precipitation forms fibrin-glue. Collectively, these findings allow us to draw the following conclusions: i) neobladders obtained by culturing urothelial cells on collagen matrix reproduce normal bladder mucosa and could be utilized in pharmacological studies; and ii) platelet-fibrin gels, that specifically inhibit neoplastic urothelial cell growth, could be used as scaffolds in surgical bladder reconstitution.