Decreased expression of a glycoprotein component of bladder surface mucin (GP1) in interstitial cystitis

Interstitial cystitis is a disease of unknown etiology characterized by unremitting urinary frequency, urgency and suprapubic pain. Recently, a change in urothelial permeability has been identified in interstitial cystitis patients that is presumably mediated by aberrations in bladder surface mucin. For this study we evaluated qualitative changes in a previously defined glycoprotein component of this layer (GP1) as it occurs in interstitial cystitis patients and normal controls. Paraffinized bladder biopsies were obtained from 23 interstitial cystitis patients (all meeting National Institutes of Health inclusion criteria) and 11 normal controls. All biopsy tissue was stained with hematoxylin and eosin, and periodic acid, Schiff reaction. The tissues were examined immunohistochemically for GP1 using an anti-GP1 serum. Periodic acid, Schiff staining clearly identified bladder surface proteoglycans in all specimens. Moderate GP1 reactivity was noted in all normal control specimens. Alternatively, GP1 expression was absent in 35% of the interstitial cystitis patient biopsies and decreased in 61%. These data demonstrate qualitative GP1 changes in a majority of interstitial cystitis patients. It is unknown whether these differences have an impact on the pathogenesis of interstitial cystitis. However, our findings suggest that the absence or decreased expression of GP1 in interstitial cystitis bladder biopsies may serve as a marker to characterize the disease further in conjunction with clinical findings.