Ubiquitin hydrolase (protein gene product 9.5) in the obstructed bladder: evidence for tissue remodelling involving a subset of interstitial cells

OBJECTIVE To examine the expression of ubiquitin hydrolase (UH), an enzyme which is part of the ubiquitin‐proteasome system involved in the regulation of cell growth and differentiation, to gain an insight into the cell types and processes underlying the tissue remodelling that occur after bladder neck damage. MATERIALS AND METHODS Three groups of male guinea pigs were used, comprising controls (not operated, four), sham (five) and obstructed (six). The bladder outlet was obstructed by implanting a silver ring around the urethra, which was left in situ for 2–4 weeks. Sham‐operated guinea pigs had the same operative procedure but no ring was implanted. The bladders were removed and incubated in Krebs’ solution at 36 °C, gassed with 95% O2 and 5% CO2, Tissues were then fixed in 4% depolymerized paraformaldehyde and processed for immunohistochemistry. We used antibodies raised against UH, cyclooxygenase type I and vimentin. Specific antibody binding was visualized using the appropriate secondary antibodies. RESULTS Staining with an antibody to UH showed the presence of both sensory and motor nerves in control, sham and obstructed bladders. In the control bladders this was the predominant staining pattern. In the sham and obstructed bladders UH staining revealed additional positive cell types; cells associated with the outermost layers of the urothelium (the umbrella cells), in the lamina propria (the lamina propria interstitial cells (lp‐ICs), on the surface of the muscle bundles (surface muscle, sm‐ICs) and on the serosal surface (muscle coat, mc‐ICs). All ICs stained with vimentin. The ICs within the muscle bundles (intramuscular, im‐ICs) did not stain with UH. The number and density of the UH‐positive cells was greater in the obstructed than in the sham bladders, suggesting a change in relation to the severity of damage to the bladder neck. CONCLUSION The expression of UH implies the re‐targeting of proteins marked for degradation in the proteasome. Increased expression of UH in the lp‐ICs and sm‐ICs shows that these cells are active in the early and late stages of the tissue remodelling resulting from obstruction. These results show a further subset of ICs that might be involved in the increased deposition of extracellular material and tissue remodelling.