Purpose: Expression of the proteoglycan core proteins biglycan, decorin, perlecan and syndecan-1, and differentiation related markers of keratins 18 and 20 were examined to determine the origins of the loss of the glycosaminoglycan layer and investigate more fully the altered differentiation of the urothelium in interstitial cystitis.
Materials and methods: Formalin fixed biopsies from 27 patients with interstitial cystitis and 5 controls were immunohistochemically labeled for the described proteins and scored using a modification of previous scoring for other markers. Inflammation was scored from hematoxylin and eosin stained slides. By combining previous with new data, cluster analysis showed the relationships among the markers and samples.
Results: Interstitial cystitis specimens clustered into 4 groups, ranging from most biomarkers abnormal to most biomarkers normal, but all clustered separately from normal controls. One group of interstitial cystitis specimens mainly showed aberrant expression of E-cadherin, which might represent an early abnormality. The biomarkers fell into 2 major groupings. One group consisted of chondroitin sulfate, perlecan, biglycan, decorin and the tight junction protein ZO-1. A second cluster consisted of uroplakin, the epithelial marker keratin 18 and 20, and the morphology of the layer. E-cadherin and syndecan-1 showed little relation to the other 2 clusters or to each other. Inflammation correlated moderately with syndecan-1 but to no other marker.
Conclusions: Findings strongly suggest abnormal differentiation in the interstitial cystitis urothelium with a loss of barrier function markers and altered differentiation markers being independent and occurring independently of inflammation. Loss of the glycosaminoglycan layer was associated with a loss of biglycan and perlecan on the luminal layer.