Urothelial cell detachment and differentiation in urinary bladder.

In developing and in repairing bladder, proliferation of the transitional urothelium is followed by cell detachment--desquamation or apoptosis. Proliferation results in formation of terminally differentiated superficial cells and this process may be followed by checking the cells on the presence of differentiation markers. The formation of an asymmetric unit membrane (AUM) structure (plaque) on the cell surface is in correlation with urothelial differentiation. Thus, the microstructure of the luminal surface of the urinary bladder provides a very convenient differentiation biomarker. The surface of immature cells showed a pattern of microvilli. The progress of differentiation was associated with microvili arranged in rows finally forming the characteristic pattern of ridges in terminally differentiated cells. These results demonstrate that the characteristic surface pattern and the AUM plaque formation in the apical plasma membrane of superficial urothelial cells are associated with specific morphology, and patterns and thus help detect differentiation level of cell.