Reconstitution of human urothelium from monolayer cultures.

PURPOSE: We established a 3-dimensional organ culture model of urinary tract tissue in which to study the effects of seeding cultured urothelial cells onto de-epithelialized urothelial stroma.
MATERIALS AND METHODS: Normal human urinary tract tissues were placed in organ culture or used to establish urothelial cell cultures. At passage 2 cell cultures were harvested and used to reconstitute autologous organ cultures by seeding onto de-epithelialized stroma. Organ cultures were harvested at intervals and analyzed by immunohistology with a panel of antibodies against differentiation associated antigens, cytokeratins, cell adhesion molecules, extracellular matrix components and proliferation associated antigens.
RESULTS: Human urothelial tissues were maintained in organ culture for at least 18 weeks and they retained a transitional epithelial morphology with expression of normal in situ antigenic characteristics. Within 2 weeks of reconstitution recombined organ cultures formed a stratified, polarized, transitional-like neo-epithelium that expressed many of the phenotypic and differentiated characteristics of normal tissue. Basement membrane formed at sites of direct contact between urothelial cells and stroma. After an initial stabilization period the proliferation rate of the urothelium of intact and reconstituted organ cultures decreased to the low turnover rate characteristic of normal urothelium in situ, indicating that the cells were responsive to normal growth regulatory controls.
CONCLUSIONS: Normal human urothelial cells, which express a proliferative nondifferentiated phenotype in monolayer culture, retain the capacity to differentiate and reform a slow turnover, stratified transitional epithelium.