Abnormal expression of differentiation related proteins and proteoglycan core proteins in the urothelium of patients with interstitial cystitis

Abstract

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.

Fig. 1

Examples of normal and abnormal distributions of marker molecules. (There is no photo shown for Decorin +1 because none of the samples displayed this pattern).

Fig. 2

Dendrograms of hierarchical clustering of patient samples and marker distributions. Similarity is indicated by the length of the line segments connecting the elements in the dendrogram with short line segments indicating high similarity. The numerical value of correlation is shown by the scales shown on the figures. The dendrogram on the left shows the clustering observed without inclusion of inflammation. On the right is shown clustering including inflammation. Because some of the biopsies had been exhausted, some data were missing. This was most significant for inflammation, the last marker examined, and to prevent the missing data from driving the clustering, specimens with more than 2 missing data points were excluded from clustering analysis. Interestingly, all those excluded came from the least severe group.