Bladder urothelium in PBS/IC shows distinct differences in keratin profiles

Research groups from the Netherlands and Denmark led by Pilar Laguna studied urothelial involvement in PBS/IC by characterizing the keratin phenotype of bladder urothelium in 18 patients with the disorder.

They used a panel of 11 keratin antibodies recognizing simple keratins found in columnar epithelia and keratins associated with basal cell compartments of squamous epithelia. The goal of this descriptive study was to establish whether the keratin phenotype of urothelium in PBS/IC is in any way altered from what has been reported for normal urothelium.

The study demonstrated distinct changes in the keratin phenotype of urothelium in patients with PBS/IC that can be categorized as follows: 1) In a considerable number of PBS/IC cases, the urothelium loses its "keratin-urothelial phenotype" and keratin makeup shifts to a phenotype associated with squamous type epithelium. Interestingly, this is not evident morphologically. 2) Variability of keratin 20 expression is present. This may indicate a defect in the urothelial permeability barrier and/or impairment of urothelial response to mechanical stress.

The keratin phenotype was not related to mucosal inflammation, and, in all cases, the urothelium was light microscopically normal. Electron microscopic studies in IC report intracellular canals, epithelial edema, and degeneration. This interesting study gives further credence to the theory that PBS/IC is associated with a urothelial cell defect, even in patients with a normal histology by light microscopy. Whether these changes are primary or secondary to another underlying condition remains to be determined.

Written by Philip M. Hanno, MD - UroToday

Am J Clin Pathol, 2006; 125:105-110