Uroplakin 1b is critical in urinary tract development and urothelial differentiation and homeostasis

Proper development and maintenance of urothelium is critical to its function. Uroplakins are expressed in developing and mature urothelium where they establish plaques associated with the permeability barrier. Their precise functional role in development and disease is unknown. Here, we disrupted Upk1b in vivo where its loss resulted in urothelial plaque disruption in the bladder and kidney. Upk1b(RFP/RFP) bladder urothelium appeared dysplastic with expansion of the progenitor cell markers, Krt14 and Krt5, increased Shh expression, and loss of terminal differentiation markers Krt20 and uroplakins. Upk1b(RFP/RFP) renal urothelium became stratified with altered cellular composition. Upk1b(RFP/RFP) mice developed age-dependent progressive hydronephrosis. Interestingly, 16% of Upk1b(RFP/RFP) mice possessed unilateral duplex kidneys. Our study expands the role of uroplakins, mechanistically links plaque formation to urinary tract development and function, and provides a tantalizing connection between congenital anomalies of the kidney and urinary tract along with functional deficits observed in a variety of urinary tract diseases. Thus, kidney and bladder urothelium are regionally distinct and remain highly plastic, capable of expansion through tissue-specific progenitor populations. Furthermore, Upk1b plays a previously unknown role in early kidney development representing a novel genetic target for congenital anomalies of the kidney and urinary tract.

Heterogeneity of uroplakin localization in human normal urothelium, papilloma and papillary carcinoma

Background

Uroplakins are differentiation-related membrane proteins of urothelium. We compared uroplakin expression and ultrastructural localization in human normal urothelium, papilloma and papillary carcinoma. Because of high recurrence rate of these tumours, treated by transurethral resection, we investigated urothelial tumour, resection border and uninvolved urothelium.

Patients and methods

Urinary bladder samples were obtained from tumour free control subjects and patients with papilloma and papillary carcinoma. Immunohistochemical and immunoelectron labelling of uroplakins were performed.

Results

In normal human urothelium with continuous uroplakin-positive superficial cell layer uroplakins were localized to flattened mature fusiform vesicles and apical plasma membrane of umbrella cells. Diverse uroplakin expression was found in papilloma and papillary carcinoma. Three aberrant differentiation stages of urothelial cells, not found in normal urothelium, were recognized in tumours. Diverse uroplakin expression and aberrant differentiation were occasionally found in resection border and in uninvolved urothelium.

Conclusions

We demonstrated here that uroplakin expression and localization in urothelial tumours is altered when compared to normal urothelium. In patients with papilloma and papillary carcinoma immunolabelling of uroplakins at ultrastructural level shows aberrant urothelial differentiation. It is possible that aberrant differentiation stages of urothelial cells in resection border and in uninvolved urothelium contribute to high recurrence rate.

Increased mRNA expression of genes involved in pronociceptive inflammatory reactions in bladder tissue of interstitial cystitis

PURPOSE

We assayed mRNA expression of the TRP family of channels and ASIC1 in bladder tissue from patients with interstitial cystitis.

MATERIALS AND METHODS

Bladder biopsies of 1) nonclassic interstitial cystitis, 2) nonulcerative portions of classic interstitial cystitis, 3) ulcerative portions of classic interstitial cystitis and 4) noncancerous portions of bladder cancer as the control were placed immediately in ice-cold RNAlater® and subjected to real-time reverse transcriptase-polymerase chain reaction. We compared the mRNA expression of TRP channels, ASIC1, NGF, CXCL9 and UPK3A with that of controls, and correlated expression with symptom severity.

RESULTS

We analyzed specimens from 17 patients with nonclassic interstitial cystitis, 22 with classic interstitial cystitis and 11 controls. In nonclassic interstitial cystitis samples TRPV2 and NGF showed significantly increased expression. In classic interstitial cystitis samples nonulcerative portions demonstrated a significant increase in the expression of TRPA1, TRPM2 and 8, TRPV1 and 2, ASIC1, NGF and CXCL9, and a significant decrease in UPK3A and TRPV4. Ulcerative portions showed similar changes for TRPM2, TRPV1, 2 and 4, CXCL9 and UPK3A. Increased expression of TRPM2, first noted in interstitial cystitis tissue, was the most pronounced one of the TRP family. All symptom measures correlated with TRPM2 and TRPV2 expression, and partially with that of the other genes.

CONCLUSIONS

This study showed increased expression of the genes involved in pronociceptive inflammatory reactions in interstitial cystitis, including TRPV1, 2 and 4, ASIC1, NGF and CXCL9, and to our knowledge TRPM2 for the first time. The different expression patterns suggest distinct pathophysiologies for classic and nonclassic interstitial cystitis. The genes and their products are potential candidates for use as biomarkers or novel therapy targets.

Adipose-derived stromal cells for the reconstruction of a human vesical equivalent

Despite a wide panel of tissue-engineering models available for vesical reconstruction, the lack of a differentiated urothelium remains their main common limitation. For the first time to our knowledge, an entirely human vesical equivalent, free of exogenous matrix, has been reconstructed using the self-assembly method. Moreover, we tested the contribution of adipose-derived stromal cells, an easily available source of mesenchymal cells featuring many potential advantages, by reconstructing three types of equivalent, named fibroblast vesical equivalent, adipose-derived stromal cell vesical equivalent and hybrid vesical equivalent--the latter containing both adipose-derived stromal cells and fibroblasts. The new substitutes have been compared and characterized for matrix composition and organization, functionality and mechanical behaviour. Although all three vesical equivalents displayed adequate collagen type I and III expression, only two of them, fibroblast vesical equivalent and hybrid vesical equivalent, sustained the development of a differentiated and functional urothelium. The presence of uroplakins Ib, II and III and the tight junction marker ZO-1 was detected and correlated with impermeability. The mechanical resistance of these tissues was sufficient for use by surgeons. We present here in vitro tissue-engineered vesical equivalents, built without the use of any exogenous matrix, able to sustain mechanical stress and to support the formation of a functional urothelium, i.e. able to display a barrier function similar to that of native tissue.

Involvement of vps33a in the fusion of uroplakin-degrading multivesicular bodies with lysosomes

The apical surface of the terminally differentiated mouse bladder urothelium is largely covered by urothelial plaques, consisting of hexagonally packed 16-nm uroplakin particles. These plaques are delivered to the cell surface by fusiform vesicles (FVs) that are the most abundant cytoplasmic organelles. We have analyzed the functional involvement of several proteins in the apical delivery and endocytic degradation of uroplakin proteins. Although FVs have an acidified lumen and Rab27b, which localizes to these organelles, is known to be involved in the targeting of lysosome-related organelles (LROs), FVs are CD63 negative and are therefore not typical LROs. Vps33a is a Sec1-related protein that plays a role in vesicular transport to the lysosomal compartment. A point mutation in mouse Vps33a (Buff mouse) causes albinism and bleeding (Hermansky-Pudlak syndrome) because of abnormalities in the trafficking of melanosomes and platelets. These Buff mice showed a novel phenotype observed in urothelial umbrella cells, where the uroplakin-delivering FVs were almost completely replaced by Rab27b-negative multivesicular bodies (MVBs) involved in uroplakin degradation. MVB accumulation leads to an increase in the amounts of uroplakins, Lysosomal-associated membrane protein (LAMP)-1/2, and the activities of beta-hexosaminidase and beta-glucocerebrosidase. These results suggest that FVs can be regarded as specialized secretory granules that deliver crystalline arrays of uroplakins to the cell surface, and that the Vps33a mutation interferes with the fusion of MVBs with mature lysosomes thus blocking uroplakin degradation.