Development, regeneration and tumorigenesis of the urothelium

PPARG contributes to urothelial integrity in the murine ureter by activating the expression of Shh and superficial cell-specific genes

The urothelium is a stratified epithelium with an important barrier function in the urinary drainage system. The differentiation and maintenance of the three major urothelial cell types (basal, intermediate and superficial cells) is incompletely understood. Here, we show that mice with a conditional deletion of the transcription factor gene peroxisome proliferator activated receptor gamma (Pparg) in the ureteric epithelium have a dilated ureter at postnatal stages with a urothelium consisting of a layer of undifferentiated luminal cells and a layer of proliferating basal cells. Molecular analysis of fetal stages revealed that the expression of a large number of genes is not activated in superficial cells and that of a few genes, including Shh, is not activated in intermediate and basal cells. Pharmacological activation of SHH signaling in explant cultures of perinatal Pparg-deficient ureters reduced ureteral width and urothelial cell number to normal levels, increased the number of intermediate cells and slightly reduced basal cell proliferation. Our data suggest that PPARG independently activates the expression of structural genes in superficial cells and of Shh in basal and intermediate cells, and that both functions contribute to urothelial integrity.

Tumor involvement of the trigone and urethra at the time of robot-assisted radical cystectomy is associated with adverse oncological outcomes

INTRODUCTION

The trigone/urethra (T/U) has a distinct embryologic origin and a different histologic morphology compared to the rest of the urinary bladder. We sought to determine the association between tumors involved in the T/U and the presence of variant histology, pathologic, and oncologic outcomes in patients who underwent robot-assisted radical cystectomy (RARC).

METHODS

Tumor location was classified into 2 groups: tumors in the bladder walls only, or tumors in the T/U area, with or without involvement of other bladder walls. Univariable and multivariable Cox regression models were used to determine the association between T/U with recurrence-specific (RSS), cancer-specific (CSS), and overall survival (OS).

RESULTS

608 patients who underwent RARC were identified, T/U involvement occurred in 191 (31%). Patients in the T/U group were more likely to have pT3/pT4 (57% vs. 42%, P < 0.01), positive surgical margins (21% vs. 9%, P < 0.01), and received salvage chemotherapy more frequently (16% vs. 8%, P < 0.01). Squamous variant histology was more frequent in the T/U group (25% vs. 17%, P = 0.02). On multivariable analysis, T/U location was independently associated with RSS (HR1.63, 95% CI 1.23-2.16, P < 0.01) and CSS (HR1.50, 95% CI 1.04-2.16, P = 0.02) but not OS.

CONCLUSION

Residual T/U tumor involvement was associated with a higher risk of an advanced tumor stage, positive margin, cancer recurrence, and cancer-specific death.

Tracing the Evolution of Sex Hormones and Receptor-Mediated Immune Microenvironmental Differences in Prostate and Bladder Cancers: From Embryonic Development to Disease

The bladder and prostate originate from the urogenital sinus. However, bladder cancer (BC) is usually classified as an immune "hot" tumor, whereas prostate cancer (PCa) is deemed as an immune "cold" tumor according to the tumor microenvironment (TME) and clinical outcomes. To investigate the immune differences between BC and PCa, studies are compared focusing on immune regulation mediated by sex hormones and receptors to identify key genes and pathways responsible for the immune differences. From a developmental perspective, it is shown that PCa and BC activate genes and pathways similar to those in the developmental stage. During prostate development, the differential expression and function of the androgen receptor (AR) across cell types may contribute to its dual role in promoting and inhibiting immunity in different cells. Androgen deprivation therapy affects AR function in different cells within the TME, influencing immune cell infiltration and antitumor function. Additionally, estrogenα and estrogenβ exert contrasting effects in PCa and BC, which may hold the potential for modifying the "cold" and "hot" tumor phenotypes. Future research should target key genes and pathways involved in bladder development to clarify the immune regulatory similarities and differences between BC and PCa.

Vitamin A-Enriched Diet Increases Urothelial Cell Proliferation by Upregulating Itga3 and Areg After Cyclophosphamide-Induced Injury in Mice

Vitamin A (VitA) is an essential nutrient, affecting many cell functions, such as proliferation, apoptosis, and differentiation, all of which are important for the regeneration of various tissues. In this study, we investigated the effects of a VitA-enriched diet on the regeneration of the urothelium of the urinary bladder in mice after cyclophosphamide (CP)-induced injury. Female mice were fed VitA-enriched and normal diet for 1 week before receiving an intraperitoneal injection of CP (150 mg/kg). Urinary bladders were removed 1 and 3 days after CP. On Day 1, RNA sequencing showed that VitA upregulated two Kyoto Encyclopedia of Genes and Genomes (KEGG) signaling pathways: the cell cycle and the PI3K-Akt pathway. This was confirmed by qPCR, which showed significantly increased expression of the Itga3 and Areg genes. In addition, the effect of VitA on the proliferation of urothelial cells was analyzed by immunohistochemistry of Ki-67, which confirmed an increased proliferation rate. No significant effects of the VitA-enriched diet were observed on the expression of apoptosis-related genes and on differentiation-related markers of superficial urothelial cells. Our results suggest that a VitA-enriched diet improves early urothelial regeneration after CP-induced injury by promoting cell proliferation.

Expression and localization of HSD17B13 along mouse urinary tract

17β-Hydroxysteroid dehydrogenase-13 (HSD17B13), a newly identified lipid droplet-associated protein, plays an important role in the development of nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH). Emerging evidence demonstrates that NASH is an independent risk factor for chronic kidney disease, which is frequently accompanied by renal lipid accumulation. In addition, the HSD17B13 rs72613567 variant is associated with lower levels of albuminuria in patients with biopsy-proven NAFLD. At present, the role of HSD17B13 in lipid accumulation in the kidney is unclear. This study utilized bioinformatic and immunostaining approaches to examine the expression and localization of HSD17B13 along the mouse urinary tract. We found that HSD17B13 is constitutively expressed in the kidney, ureter, and urinary bladder. Our findings reveal for the first time, to our knowledge, the precise localization of HSD17B13 in the mouse urinary system, providing a basis for further studying the pathogenesis of HSD17B13 in various renal and urological diseases.NEW & NOTEWORTHY HSD17B13, a lipid droplet-associated protein, is crucial in nonalcoholic fatty liver disease (NAFLD) development. NAFLD also independently raises chronic kidney disease (CKD) risk, often with renal lipid buildup. However, HSD17B13's role in CKD-related lipid accumulation is unclear. This study makes the first effort to examine HSD17B13 expression and localization along the urinary system, providing a basis for exploring its physiological and pathophysiological roles in the kidney and urinary tract.

Human Pluripotent Stem Cell Derived Organoids Reveal a Role for WNT Signaling in Dorsal-Ventral Patterning of the Hindgut

The cloaca is a transient structure that forms in the terminal hindgut giving rise to the rectum dorsally and the urogenital sinus ventrally. Similarly, human hindgut cultures derived from human pluripotent stem cells generate human colonic organoids (HCOs) which also contain co-developing urothelial tissue. In this study, our goal was to identify pathways involved in cloacal patterning and apply this to human hindgut cultures. RNA-seq data comparing dorsal versus ventral cloaca in e10.5 mice revealed that WNT signaling was elevated in the ventral versus dorsal cloaca. Inhibition of WNT signaling in hindgut cultures biased their differentiation towards a colorectal fate. WNT activation biased differentiation towards a urothelial fate, giving rise to human urothelial organoids (HUOs). HUOs contained cell types present in human urothelial tissue. Based on our results, we propose a mechanism whereby WNT signaling patterns the ventral cloaca, prior to cloacal septation, to give rise to the urogenital sinus.

Transcription factor Tcf21 modulates urinary bladder size and differentiation

Urinary bladder organogenesis requires coordinated cell growth, specification, and patterning of both mesenchymal and epithelial compartments. Tcf21, a gene that encodes a helix-loop-helix transcription factor, is specifically expressed in the mesenchyme of the bladder during development. Here we show that Tcf21 is required for normal development of the bladder. We found that the bladders of mice lacking Tcf21 were notably hypoplastic and that the Tcf21 mutant mesenchyme showed increased apoptosis. There was also a marked delay in the formation of visceral smooth muscle, accompanied by a defect in myocardin (Myocd) expression. Interestingly, there was also a marked delay in the formation of the basal cell layer of the urothelium, distinguished by diminished expression of Krt5 and Krt14. Our findings suggest that Tcf21 regulates the survival and differentiation of mesenchyme cell-autonomously and the maturation of the adjacent urothelium non-cell-autonomously during bladder development.

Bladder cancer

Bladder cancer is a global health issue with sex differences in incidence and prognosis. Bladder cancer has distinct molecular subtypes with multiple pathogenic pathways depending on whether the disease is non-muscle invasive or muscle invasive. The mutational burden is higher in muscle-invasive than in non-muscle-invasive disease. Commonly mutated genes include TERT, FGFR3, TP53, PIK3CA, STAG2 and genes involved in chromatin modification. Subtyping of both forms of bladder cancer is likely to change considerably with the advent of single-cell analysis methods. Early detection signifies a better disease prognosis; thus, minimally invasive diagnostic options are needed to improve patient outcomes. Urine-based tests are available for disease diagnosis and surveillance, and analysis of blood-based cell-free DNA is a promising tool for the detection of minimal residual disease and metastatic relapse. Transurethral resection is the cornerstone treatment for non-muscle-invasive bladder cancer and intravesical therapy can further improve oncological outcomes. For muscle-invasive bladder cancer, radical cystectomy with neoadjuvant chemotherapy is the standard of care with evidence supporting trimodality therapy. Immune-checkpoint inhibitors have demonstrated benefit in non-muscle-invasive, muscle-invasive and metastatic bladder cancer. Effective management requires a multidisciplinary approach that considers patient characteristics and molecular disease characteristics.

Distinct effects of Fgf7 and Fgf10 on the terminal differentiation of murine bladder urothelium revealed using an organoid culture system

BACKGROUND

Dysregulation of the terminal differentiation of bladder urothelium is associated with the pathogenesis of urinary tract disorders. Fibroblast growth factor (Fgf)7 and Fgf10 stimulate urothelial proliferation; however, their roles in cellular differentiation remain unclear. In this study, we used an organoid system to investigate the roles of these Fgfs in regulating bladder urothelium differentiation and identify their distribution patterns in the mouse bladder.

METHODS

Adult bladder epithelia (AdBE) isolated from adult mouse bladder tissues (AdBTs) were used to culture adult bladder organoids (AdBOs) in the presence of Fgf7 and Fgf10. The differentiation status of the cells in AdBTs, AdBEs, AdBOs, and neonatal bladder tissues (NeoBTs) was analyzed via quantitative real-time-PCR for the presence of undifferentiated cell markers (Krt5, Trp63, and Krt14) and differentiated cell markers (Krt20, Upk1a, Upk2, and Upk3a). Organoid cell proliferation was assessed by counting cell numbers using the trypan blue method. The effects of Fgf7 and Fgf10 on organoid differentiation were assessed using different doses of Fgfs, and the involvement of peroxisome proliferator-activated receptor γ (PPARγ) signaling in these processes was tested by introducing a PPARγ agonist (Rosiglitazone) and antagonist (T0070907) to the culture. The expression patterns of Fgf7 and Fgf10 were examined via in situ hybridization of AdBTs.

RESULTS

AdBOs showed higher expression of undifferentiated cell markers and lower expression of differentiated cell markers than AdBTs, NeoBTs, and AdBEs, indicating the relatively immature state of AdBOs. Differentiation of AdBOs was enhanced by Rosiglitazone and Fgf7, suggesting an interplay of intracellular signals between Fgf7 and PPARγ. Co-addition of T0070907 suppressed Fgf7-mediated differentiation, demonstrating that PPARγ is activated downstream of Fgf7 to promote cellular differentiation into umbrella cells. Furthermore, we found that Fgf7 is predominantly expressed in the umbrella cells of the urothelium, whereas Fgf10 is predominantly expressed in the urothelium and stroma of AdBTs.

CONCLUSIONS

We demonstrated that unlike Fgf10, Fgf7 induces cellular differentiation via PPARγ activity and has a unique tissue distribution pattern in the adult bladder. Further studies on the Fgf7-PPARγ signaling axis would provide insights into the differentiation mechanisms toward functional umbrella cells and the pathogenesis of several urinary tract diseases.

Treatment Outcomes of Intravesical Botulinum Toxin A Injections on Patients with Interstitial Cystitis/Bladder Pain Syndrome

Botulinum toxin A (BoNT-A) is effective in reducing bladder hypersensitivity and increasing capacity through the effects of anti-inflammation in the bladder urothelium; however, studies on the treatment outcome of interstitial cystitis/bladder pain syndrome (IC/BPS) are lacking. We investigated the treatment outcome in IC/BPS patients receiving intravesical BoNT-A injections. This retrospective study included IC/BPS patients who had 100U BoNT-A intravesical injections in the past 20 years. The treatment outcomes at 6 months following the BoNT-A treatment were evaluated using the global response assessment (GRA) scale. The treatment outcomes according to the GRA scale include clinical symptoms, urodynamic parameters, cystoscopic characteristics, and urinary biomarkers, and it was these predictive factors for achieving satisfactory outcomes which were investigated. Among the 220 enrolled patients (180 women, 40 men) receiving BoNT-A injections, only 87 (40%) had significantly satisfactory treatment outcomes. The satisfactory group showed significantly larger voided volumes, and lower levels of both the urinary inflammatory protein MCP-1 and the oxidative stress biomarker 8-isoprostane in comparison to the unsatisfactory group. The IC severity and detrusor pressure are predictive factors of BoNT-A treatment outcomes. IC/BPS patients with less bladder inflammation showed satisfactory outcomes with intravesical BoNT-A injections. Patients with severe bladder inflammation might require more intravesical BoNT-A injections to achieve a satisfactory outcome.

The urothelium: a multi-faceted barrier against a harsh environment

All mucosal surfaces must deal with the challenge of exposure to the outside world. The urothelium is a highly specialized layer of stratified epithelial cells lining the inner surface of the urinary bladder, a gruelling environment involving significant stretch forces, osmotic and hydrostatic pressures, toxic substances, and microbial invasion. The urinary bladder plays an important barrier role and allows the accommodation and expulsion of large volumes of urine without permitting urine components to diffuse across. The urothelium is made up of three cell types, basal, intermediate, and umbrella cells, whose specialized functions aid in the bladder's mission. In this review, we summarize the recent insights into urothelial structure, function, development, regeneration, and in particular the role of umbrella cells in barrier formation and maintenance. We briefly review diseases which involve the bladder and discuss current human urothelial in vitro models as a complement to traditional animal studies.