Umbrella Cell

A term for a multinucleated superficial cell of the bladder’s transitional epithelium, which has vacuolated cytoplasm. Umbrella cells are thin but cover multiple underlying transitional cells in a parasol-like fashion. They can be identified immunohistochemically by the presence of uroplakins—Ia, Ib, II, and III
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50) The normal urothelium shows CK20 positivity confined to the umbrella cell layer, CD44 positivity in the basal cell layer, and a weak and patchy p53 nuclear staining.
It is composed of 3 types of cells: (1) the basal cells, which are cylindrical to flat and in contact with the underlying fibroconnective tissue or lamina propria--the basal cell layer is thought to harbor urothelial stem cells; (2) the intermediate cells, which are cuboidal to columnar cells, overlie the basal cells, and usually have the same orientation toward the bladder lumen; and (3) the umbrella cells, which are larger flat eosinophilic cells, with ample pink cytoplasm and variable nuclear reactive/degenerative atypia such as binucleation, smudging, and nucleoli.
The normal constituents of the urothelium are present, including basal cells, intermediate cells, and umbrella cells.
Although outside the scope of the present study, findings with the rabbit primary culture system (29) suggest that further manipulation of the cell culture technique could modify the level of differentiation of the UROtsa cell cultures toward either the highly differentiated umbrella cell or the undifferentiated basal cell.
These superficial cells were identified as umbrella cells based on their ability to form junctional complexes, possession of an asymmetric unit membrane, expression of uroplakins and a 27-kDa urothelial cell-specific antigen that assembled into detergent-resistant asymmetric unit membrane particles.
However, the organization of the sealing strands was not complex enough, nor did the cells possess an asymmetric unit membrane, to suggest that the UROtsa cultures have characteristics similar to that of the most apically located umbrella cells.
In reactive urothelium, p53 is absent to focal staining, CD44 shows diffuse or patchy staining of all layers, and CK20 stains only the umbrella cell layer.
Typical umbrella cells can be displaced so they are not on the surface, mimicking CIS.
Intravesical chemotherapy (thiotepa [N,N'N"-triethyle nethiophosphoramide] and mitomycin C) induces atypical changes, primarily on the surface umbrella cells, which show nuclear enlargement, multinucleation, smudged chromatin, and cytoplasmic vacuolization.
Due to slow turnover of the umbrella cells, post-injury inflammation and hyperplasia, ethical drawbacks and animal cost, the in vivo study of urothelial differentiation and development is difficult.
However, terminal differentiation of urothelium was obtained only with BSCs-based equivalents, as CK20 is specific for umbrella cells in normal bladder and the marker of final differentiation for superficial cells.