Expansion and long-term culture of differentiated normal rat urothelial cells in vitro

Urine-derived stem cells in neurological diseases: current state-of-the-art and future directions

Stem cells have potential applications in the field of neurological diseases, as they allow for the development of new biological models. These models can improve our understanding of the underlying pathologies and facilitate the screening of new therapeutics in the context of precision medicine. Stem cells have also been applied in clinical tests to repair tissues and improve functional recovery. Nevertheless, although promising, commonly used stem cells display some limitations that curb the scope of their applications, such as the difficulty of obtention. In that regard, urine-derived cells can be reprogrammed into induced pluripotent stem cells (iPSCs). However, their obtaining can be challenging due to the low yield and complexity of the multi-phased and typically expensive differentiation protocols. As an alternative, urine-derived stem cells (UDSCs), included within the population of urine-derived cells, present a mesenchymal-like phenotype and have shown promising properties for similar purposes. Importantly, UDSCs have been differentiated into neuronal-like cells, auspicious for disease modeling, while overcoming some of the shortcomings presented by other stem cells for these purposes. Thus, this review assesses the current state and future perspectives regarding the potential of UDSCs in the ambit of neurological diseases, both for disease modeling and therapeutic applications.

A Biomimetic Porcine Urothelial Model for Assessing Escherichia coli Pathogenicity

Urinary tract infections can be severe, sometimes fatal, diseases whose etiological pathogens are predominantly uropathogenic strains of E. coli (UPEC). To investigate the UPEC pathogenesis, several models have already been established with minor or major disadvantages. The aim was to develop a simple, fast, and inexpensive biomimetic in vitro model based on normal porcine urothelial (NPU) cells that are genetically and physiologically similar to human bladder urothelium and to perform basic studies of E. coli pathogenicity. Initially, the model was tested using a set of control E. coli strains and, subsequently, with human E. coli strains isolated either from patients with urinary infections or from the feces of healthy individuals. A drop in viability of NPU cells was used as a measure of the pathogenicity of the individual strain tested. To visualize the subcellular events, transmission and scanning electron microscopy was performed. The strains were tested for the presence of different virulence-associated genes, phylogroup, type of core lipid, O-serotype, and type of lipopolysaccharide and a statistical analysis of possible correlations between strains’ characteristics and the effect on the model was performed. Results showed that our model has the discriminatory power to distinguish pathogenic from non-pathogenic E. coli strains, and to identify new, potentially pathogenic strains.

Urine-Derived Stem Cells: Applications in Regenerative and Predictive Medicine

Despite being a biological waste, human urine contains a small population of cells with self-renewal capacity and differentiation potential into several cell types. Being derived from the convoluted tubules of nephron, renal pelvis, ureters, bladder and urethra, urine-derived stem cells (UDSC) have a similar phenotype to mesenchymal stroma cells (MSC) and can be reprogrammed into iPSC (induced pluripotent stem cells). Having simple, safer, low-cost and noninvasive collection procedures, the interest in UDSC has been growing in the last decade. With great potential in regenerative medicine applications, UDSC can also be used as biological models for pharmacology and toxicology tests. This review describes UDSC biological characteristics and differentiation potential and their possible use, including the potential of UDSC-derived iPSC to be used in drug discovery and toxicology, as well as in regenerative medicine. Being a new cellular platform amenable to noninvasive collection for disease stratification and personalized therapy could be a future application for UDSC.

Urothelium with barrier function differentiated from human urine-derived stem cells for potential use in urinary tract reconstruction

Background

Autologous urothelial cells are often obtained via bladder biopsy to generate the bio-engineered urethra or bladder, while urine-derived stem cells (USC) can be obtained by a non-invasive approach. The objective of this study is to develop an optimal strategy for urothelium with permeability barrier properties using human USC which could be used for tissue repair in the urinary tract system.

Methods

USC were harvested from six healthy adult individuals. To optimize urothelial differentiation, five different differentiation methods were studied. The induced cells were assessed for gene and protein expression markers of urothelial cells via RT-PCR, Western blotting, and immunofluorescent staining. Barrier function and ultrastructure of the tight junction were assessed with permeability assays and transmission electron microscopy (TEM). Induced cells were both cultured on trans-well membranes and small intestinal submucosa, then investigated under histology analysis.

Results

Differentiated USC expressed significantly higher levels of urothelial-specific transcripts and proteins (Uroplakin III and Ia), epithelial cell markers (CK20 and AE1/AE3), and tight junction markers (ZO-1, ZO-2, E-cadherin, and Cingulin) in a time-dependent manner, compared to non-induced USC. In vitro assays using fluorescent dye demonstrated a significant reduction in permeability of differentiated USC. In addition, transmission electron microscopy confirmed appropriate ultrastructure of urothelium differentiated from USC, including tight junction formation between neighboring cells, which was similar to positive controls. Furthermore, multilayered urothelial tissues formed 2 weeks after USC were differentiated on intestine submucosal matrix.

Conclusion

The present study illustrates an optimal strategy for the generation of differentiated urothelium from stem cells isolated from the urine. The induced urothelium is phenotypically and functionally like native urothelium and has proposed uses in in vivo urological tissue repair or in vitro urethra or bladder modeling.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-1035-6) contains supplementary material, which is available to authorized users.

The use of mesenchymal stem cells in bladder augmentation

PURPOSE

To compare integration of bladder acellular matrix (BAM) with the bladder when seeded with mesenchymal stem cells (MSC) and when MSC are injected intravenously (IV).

METHODS

MSCs were isolated from bone marrow of EPM-1 Wistar male rats. Female rats were distributed into: Group A-BAM augmentation; Group B-BAM augmentation and MSCs IV administered; Group C-BAM-MSC seeded augmentation. Animals were killed on postoperative days 7, 14 and 28. Morphological analyses were performed using hematoxylin and eosin and Masson's trichrome, in addition to immunohistochemical staining with α-SMA and neurofilament for assessment of tissue repair. RNAm expression of the SRY gene was used to mark MSCs in the rats killed on postoperative day 28.

RESULTS

The muscle layer was best repaired in Groups B and C. No difference in the repair of the urothelium in the animals in any of the three groups was found. Group B presented the smallest inflammatory reaction and the best neural repair on postoperative day 28. None of the animals examined had MSCs in their bladder graft.

CONCLUSION

The MSCs were able to improve repair of the muscle layer and when injected intravenously, they were noted to initiate the neuronal regeneration process.

How to isolate urothelial cells? Comparison of four different methods and literature review

The aim of this study is to present the comparison of four different methods for urothelial cell isolation and culture and compare them to methods cited in the literature. Four different techniques were examined for urothelium isolation from rat bladders. Isolation effectiveness was calculated using trypan blue assay. Confirmation of isolated cell phenotype and comparison with native bladder tissue was confirmed using immunohistochemical (IHC), immunocytochemical (ICC) and immunofluorescence (IF) analysis. The method with bladder inversion and collagenase P digestion resulted in the highest number of isolated cells. These cells showed positive expression of cytokeratin 7, 8, 18, α6-integrin and p63. Our results and the literature review showed that the best method for urothelium bladder isolation is dissection of the epithelium layer from other bladder parts and digestion of mechanically prepared tissue in a collagenase solution.

Urothelial cell culture: stratified urothelial sheet and three-dimensional growth of urothelial structure

Urothelial cells line the urinary tract, including the renal pelvis, ureters, bladder, superior urethra, and the central ducts of the prostate. They are highly specialized epithelial cell types possessing unique features, imparting important functional roles in the urinary system. They act as a permeability barrier and protect underlying muscle tissues from the caustic effects of urine while also expanding with bladder filling to adjust urine pressures. The multilayered urothelium is typically structured with differentiated, mature surface cells and less mature basal cells. The basal cell layer contains tissue-specific stem cells able to self-renew for the lifetime of the mammal and also produces a pool of maturing cells for tissue homeostasis. Maintaining regenerative basal cells in a culture facilitates urothelial cell growth in vitro. Additionally, epithelial-mesenchymal communication, epithelial-matrix interactions, and cytokines/growth factors are required to maintain the normal structure and function of mature urothelial cells in vitro and to induce stem cell differentiation into urothelial cells. These cultures are useful to study the biology and physiology of the urinary tract, particularly for the development of cell-based tissue engineering strategies in urology. This chapter describes methods for the isolation of urothelial cells and their maintenance in monolayer culture, and methods for the production of multilayer urothelial cell sheets and three-dimensional cocultures of urothelial and mesenchymal cells.

Urothelial cell culture

This chapter reviews the use of urothelial cells as a means to enhance tissue regeneration and wound healing in urinary tract system. It addresses the properties of urothelial cells, including their role as a permeability barrier to protect underlying muscle tissue from the caustic effects of urine and as one of the main cell types, along with smooth muscle cells, that are used in urethral or bladder tissue engineering today. This description includes a general overview of various isolation techniques and culture methods that have been developed to improve urinary tract reconstruction in vivo and aid the characterization of growth factor expression in vitro. The chapter then describes various applications using urothelial cells, including production of multilayer urothelial sheets, tissue engineered bladder mucosa, tissue engineered urethra, and tissue engineered bladder. It also outlines the advantages of sandwich and layered coculture of these cells and the effects of epithelial-stromal cell interactions during tissue regeneration or wound healing processes in the urinary tract.

Hair follicle stem cells can be driven into a urothelial-like phenotype: an experimental study

The aim of this study was to show that conditioned medium might induce transdifferentiation of hair follicle stem cells into urothelial-like cells. Several conditioned media and culture conditions (skeletal muscle cell conditioned medium, smooth muscle cell conditioned medium, fibroblast conditioned medium, transforming growth factor-conditioned medium, urothelial cell conditioned medium, and co-culture of hair follicle stem cells and urothelial cells) were used. The hair follicle stem cells phenotype from rat whisker hair follicles was checked by using flow cytometry and immunofluorescence. Cytokeratins 7, 8, 15 and 18 were used as markers. Urothelial cell conditioned medium increased the expression of urothelial markers (cytokeratin 7, cytokeratin 8, cytokeratin 18), whereas it decreased a hair follicle stem cells marker (cytokeratin 15) after 2 weeks of culture. This process depended on the time of cultivation. This medium was able to sustain the epithelial phenotype of the culture. Other media including a co-culture system failed to induce similar changes. Smooth muscle conditioned medium resulted in a loss of cells in culture. Hair follicle stem cells are capable of differentiating into urothelial-like cells in vitro when exposed to a bladder-specific microenvironment.

The effect of hyperosmolar stimuli and cyclophosphamide on the culture of normal rat urothelial cells in vitro

Highly concentrated urine may induce a harmful effect on the urinary bladder. Therefore, we considered osmolarity of the urine as a basic pathomechanism of mucosal damage. The influence of both cyclophosphamide (CYP) and hyperosmolar stimuli (HS) on the urothelium are not well described. The purpose was to evaluate the effect of CYP and HS on rat urothelial cultured cells (RUCC). 15 Wistar rats were used for RUCC preparation. RUCC were exposed to HS (2080 and 3222 mOsm/l NaCl) for 15 min and CYP (1 mg/ml) for 4 hrs. APC-labelled annexin V was used to quantitatively determine the percentage of apoptotic cells and propidium iodide (PI) as a standard flow cytometric viability probe to distinguish necrotic cells from viable ones. Annexin V-APC (+), annexin V-APC and PI (+), and PI (+) cells were analysed as apoptotic, dead, and necrotic cells, respectively. The results were presented in percentage values. The flow cytometric analysis was done on a FACSCalibur Flow Cytometer using Cell-Quest software. Treatment with 2080 and 3222 mOsm/l HS resulted in 23.7 ± 3.9% and 26.0 ± 1.5% apoptotic cells, respectively, 14.3 ± 1.4% and 19.4 ± 2.7% necrotic cells, respectively and 60.5 ± 1.4% and 48.6 ± 5.3% dead cells, respectively. The effect of CYP on RUCC was similar to the effect of HS. After CYP the apoptotic and necrotic cells were 23.1 ± 0.3% and 17.9 ± 7.4%, respectively. The percentage of dead cells was 57.7 ± 10.8%. CYP and HS induced apoptosis and necrosis in RUCC. 3222 mOsm/l HS had the most harmful effect based on the percentage of necrotic and apoptotic cells.

Re-epithelialization of demucosalized stomach patch with tissue-engineered urothelial mucosa combined with Botox A in bladder augmentation

Re-epithelialization demucosa stomach patch is important to prevent the patch being exposed to urine that might cause patch shrinkage and fibrosis formation due to urine-derived chemical irritation. Additionally, Botox A acts by blocking the transmission of nerve impulses to smooth muscles and so paralysing the muscles, which is commonly used to relax muscle for treatment of oesophageal achalasia due to overactive smooth muscle and sphincters of gastrointestinal tract. We fabricated in vitro tissue engineered urothelial mucosa with multi-layers of urothelium and smooth muscle layers seeded on SIS scaffold and then used this cell-scaffold construct to cover nuke gastro patch combining with Botox A for gastrocystoplasty in a canine model.

OBJECTIVE

To evaluate the demucosalized stomach patch covered with tissue-engineered urothelium for gastrocystoplasty and to determine whether or not injections of Botox A into the re-epithelialized stomach patch can protect the graft from contraction in a canine bladder reconstruction model.

MATERIALS AND METHODS

Gastrocystoplasty was performed in 10 adult beagles after hemi-cystectomy using five types of stomach patch (n = 2 per group): entire stomach patches (group I); demucosalized patches (group II); demucosalized patches covered with cell-free small intestinal submucosa (SIS) (group III); demucosalized patches with urothelial and smooth muscle cell-seeded SIS (group IV); and demucosalized patches with the cell-seeded SIS combined with injections of Botox A (group V). The bladder volume/pressure and the graft sizes were measured before surgery and again 10 weeks after bladder augmentation. The graft tissues were examined both histologically and using immunohistochemistry.

RESULTS

All dogs survived and their gastric grafts were all vital with a good blood supply. Gastric metaplasia of urothelium appeared on the top of stomach mucosa patches in two animals in group I. There was calcification formation at the centre of the graft in one animal in group II. As compared with urothelium that was partially covered over with stomach patches in groups II and III, stratified urothelium completely covered the demucosalized gastric patches in groups IV and V. There was less shrinkage of the stomach grafts in groups I and V, which shrank to half of their original size, than of the stomach grafts in groups II, III, and IV, which shrank significantly to one-quarter of their original sizes.

CONCLUSIONS

Botox A injections appear to protect the graft contraction in the re-epithelialized stomach flaps. The gastrocystoplasty using demucosalized patches covered with tissue-engineered urothelial mucosa combined with an injection of Botox A could have clinical potential for use in bladder reconstruction.

Scaffold Characteristics for Functional Hollow Organ Regeneration

Many medical conditions require surgical reconstruction of hollow organs. Tissue engineering of organs and tissues is a promising new technique without harvest site morbidity. An ideal biomaterial should be biocompatible, support tissue formation and provide adequate structural support. It should degrade gradually and provide an environment allowing for cell-cell interaction, adhesion, proliferation, migration, and differentiation. Although tissue formation is feasible, functionality has never been demonstrated. Mainly the lack of proper innervation and vascularisation are hindering contractility and normal function. In this chapter we critically review the current state of engineering hollow organs with a special focus on innervation and vascularisation.

The TRPV4 cation channel mediates stretch-evoked Ca2+ influx and ATP release in primary urothelial cell cultures

Transient receptor potential channels have recently been implicated in physiological functions in a urogenital system. In this study, we investigated the role of transient receptor potential vanilloid 4 (TRPV4) channels in a stretch sensing mechanism in mouse primary urothelial cell cultures. The selective TRPV4 agonist, 4alpha-phorbol 12,13-didecanoate (4alpha-PDD) evoked Ca(2+) influx in wild-type (WT) urothelial cells, but not in TRPV4-deficient (TRPV4KO) cells. We established a cell-stretch system to investigate stretch-evoked changes in intracellular Ca(2+) concentration and ATP release. Stretch stimulation evoked intracellular Ca(2+) increases in a stretch speed- and distance-dependent manner in WT and TRPV4KO cells. In TRPV4KO urothelial cells, however, the intracellular Ca(2+) increase in response to stretch stimulation was significantly attenuated compared with that in WT cells. Stretch-evoked Ca(2+) increases in WT urothelium were partially reduced in the presence of ruthenium red, a broad TRP channel blocker, whereas that in TRPV4KO cells did not show such reduction. Potent ATP release occurred following stretch stimulation or 4alpha-PDD administration in WT urothelial cells, which was dramatically suppressed in TRPV4KO cells. Stretch-dependent ATP release was almost completely eliminated in the presence of ruthenium red or in the absence of extracellular Ca(2+). These results suggest that TRPV4 senses distension of the bladder urothelium, which is converted to an ATP signal in the micturition reflex pathway during urine storage.

Urine derived cells are a potential source for urological tissue reconstruction

PURPOSE

Contemporary approaches to tissue engineering and cell therapy for urinary tract reconstruction require invasive tissue biopsies to obtain autologous cells. However, these procedures are associated with potential complications. We determined whether the cells present in urine have characteristics of normal bladder cells and investigated their potential uses for urological reconstructive procedures.

MATERIALS AND METHODS

A total of 55 urine samples were collected from 15 healthy individuals and 8 patients with vesicoureteral reflux. Urine derived cells were isolated, expanded and tested for progenitor and differentiated cell specific markers using flow cytometry, immunofluorescence and Western immunoblotting. The chromosomal stability of cultured urine derived cells was determined by karyotype analysis.

RESULTS

Clones were successfully established from primary cultures of urine derived cells. Isolated cells showed 3 phenotypes, including fully differentiated, differentiating and progenitor-like cells. Some urine derived cells stained positive for the surface markers c-Kit, SSEA4, CD105, CD73, CD91, CD133 and CD44. Two to 7 cells per 100 ml urine were multipoint progenitors that could expand extensively in culture. Single progenitor cells had the ability to differentiate into the cell lineages expressing urothelial, smooth muscle, endothelial and interstitial cell markers. The expression of lineage markers was characterized by Western blot and immunofluorescence analysis. Urine derived cells also maintained a normal karyotype after serial culture.

CONCLUSIONS

A subpopulation of cells isolated from urine had progenitor cell features and the potential to differentiate into several bladder cell lineages. Urine derived cells could serve as an alternative cell source for urinary tract tissue engineering and reconstruction.

Heterogeneity of muscarinic receptor-mediated Ca2+ responses in cultured urothelial cells from rat

Muscarinic receptors (mAChRs) have been identified in the urothelium, a tissue that may be involved in bladder sensory mechanisms. This study investigates the expression and function of mAChRs using cultured urothelial cells from the rat. RT-PCR established the expression of all five mAChR subtypes. Muscarinic agonists acetylcholine (ACh; 10 microM), muscarine (Musc; 20 microM), and oxotremorine methiodide (OxoM; 0.001-20 microM) elicited transient repeatable increases in the intracellular calcium concentration ([Ca(2+)](i)) in approximately 50% of cells. These effects were blocked by the mAChR antagonist atropine methyl nitrate (10 microM). The sources of [Ca(2+)](i) changes included influx from external milieu in 63% of cells and influx from external milieu plus release from internal stores in 27% of cells. The use of specific agonists and antagonists (10 microM M(1) agonist McN-A-343; 10 microM M(2), M(3) antagonists AF-DX 116, 4-DAMP) revealed that M(1), M(2), M(3) subtypes were involved in [Ca(2+)](i) changes. The PLC inhibitor U-73122 (10 microM) abolished OxoM-elicited Ca(2+) responses in the presence of the M(2) antagonist AF-DX 116, suggesting that M(1), M(3), or M(5) mediates [Ca(2+)](i) increases via PLC pathway. ACh (0.1 microM), Musc (10 microM), oxotremorine sesquifumarate (20 microM), and McN-A-343 (1 muM) acting on M(1), M(2), and M(3) mAChR subtypes stimulated ATP release from cultured urothelial cells. In summary, cultured urothelial cells express functional M(1), M(2), and M(3) mAChR subtypes whose activation results in ATP release, possibly through mechanisms involving [Ca(2+)](i) changes.

Corneal epithelial cell cultures as a tool for research, drug screening and testing

Understanding of visual system function and the development of new therapies for corneal diseases and damages depend upon comprehension of the biological roles of the tissue. The in vitro cultivation of corneal epithelial cells and cell lines derived from them has become a powerful tool to analyze and understand such issues. Currently, researchers have developed well-defined and precisely described culture protocols and a collection of corneal epithelial cell lines. These cell lines have been obtained through different experimental approaches: (1) the ectopic expression of oncogenes, (2) the inactivation of p16 and p53 pathways and hTERT expression, and (3) the spontaneous establishment after serial cultivation of cells. The advantages or disadvantages for these approaches are discussed. In conclusion, the availability of several culture protocols and immortalized cell lines that express corneal epithelial phenotype will be useful for investigating issues such as gene regulation and tissue development, or for validating alternative methods in toxicology.

The permeability of SPION over an artificial three-layer membrane is enhanced by external magnetic field

Background

Sensorineural hearing loss, a subset of all clinical hearing loss, may be correctable through the use of gene therapy. We are testing a delivery system of therapeutics through a 3 cell-layer round window membrane model (RWM model) that may provide an entry of drugs or genes to the inner ear. We designed an in vitro RWM model similar to the RWM (will be referred to throughout the paper as RWM model) to determine the feasibility of using superparamagnetic iron oxide (Fe₃O₄) nanoparticles (SPION) for targeted delivery of therapeutics to the inner ear.

The RWM model is a 3 cell-layer model with epithelial cells cultured on both sides of a small intestinal submucosal (SIS) matrix and fibroblasts seeded in between. Dextran encapsulated nanoparticle clusters 130 nm in diameter were pulled through the RWM model using permanent magnets with flux density 0.410 Tesla at the pole face. The SIS membranes were harvested at day 7 and then fixed in 4% paraformaldehyde. Transmission electron microscopy and fluorescence spectrophotometry were used to verify transepithelial transport of the SPION across the cell-culture model. Histological sections were examined for evidence of SPION toxicity, as well to generate a timeline of the position of the SPION at different times. SPION also were added to cells in culture to assess in vitro toxicity.

Results

Transepithelial electrical resistance measurements confirmed epithelial confluence, as SPION crossed a membrane consisting of three co-cultured layers of cells, under the influence of a magnetic field. Micrographs showed SPION distributed throughout the membrane model, in between cell layers, and sometimes on the surface of cells. TEM verified that the SPION were pulled through the membrane into the culture well below. Fluorescence spectrophotometry quantified the number of SPION that went through the SIS membrane. SPION showed no toxicity to cells in culture.

Conclusion

A three-cell layer model of the human round window membrane has been constructed. SPION have been magnetically transported through this model, allowing quantitative evaluation of prospective targeted drug or gene delivery through the RWM. Putative in vivo carrier superparamagnetic nanoparticles may be evaluated using this model.

Bladder acellular matrix as a substrate for studying in vitro bladder smooth muscle-urothelial cell interactions

The objective of this study was to evaluate the ability of bladder acellular matrix (BAM) to support the individual and combined growth of primary porcine bladder smooth muscle (SMC) and urothelial (UEC) cells. An in vitro co-culture system was devised to evaluate the effect of UEC on (i) SMC-mediated contraction of BAM discs, and (ii) SMC invasiveness into BAM. Cells were seeded onto BAM discs under 4 different culture conditions. Constructs were incubated for 1, 7, 14 and 28 days. Samples were then harvested for evaluation of matrix contraction. Immunohistochemistry (IHC) was utilized to examine cellular organization within the samples and conditioned media supernatants analyzed for net gelatinase activity. BAM contraction was significantly increased with co-culture. The same side co-culture configuration lead to a greater reduction in surface area than opposite side co-culture. IHC revealed enhanced SMC infiltration into BAM when co-culture was utilized. A significant increase in net gelatinase activity was also observed with the co-culture configuration. Enhanced infiltration and contractile ability of bladder SMCs with UEC co-culture may, in part, be due to an increase in gelatinase activity. The influence of bladder UECs on SMC behaviour in vitro indicates that BAM may contain some key inductive factors that serve to promote important bladder cell-cell and cell-matrix interactions.

Nrf2 Is Essential for the Chemopreventive Efficacy of Oltipraz against Urinary Bladder Carcinogenesis

The induction of phase 2 detoxifying enzymes, such as UDP-glucuronosyltransferases (UGTs), in response to an array of naturally occurring and synthetic agents, such as oltipraz (4-methyl-5-[2-pyrazinyl]-1,2-dithiole-3-thione), provides an effective means of protection against a variety of carcinogens. Transcription factor Nrf2 is an essential regulator of the inducible expression of detoxifying enzyme genes by chemopreventive agents. In this study, we investigated in Nrf2-deficient mice the susceptibility to the urinary bladder-specific carcinogen N-nitrosobutyl(4-hydroxybutyl)amine (BBN) and the chemopreventive efficacy of oltipraz. The incidence of urinary bladder carcinoma by BBN was significantly higher in Nrf2-/- mice than in wild-type mice; invasive carcinoma was found in 24.0 and 38.5% of wild-type and Nrf2-/- mice, respectively. Oltipraz induced the phase 2 enzymes responsible for BBN detoxification in the liver and urinary bladder in an Nrf2-dependent manner. As expected, therefore, oltipraz decreased the incidence of urinary bladder carcinoma by BBN in wild-type mice but had little effect in Nrf2-/- mice. In wild-type mouse liver, oltipraz significantly induced BBN glucuronidation and decreased the urinary concentration of N-nitrosobutyl(3-carboxypropyl)amine, a proximate carcinogen of BBN. Importantly, BBN was found to suppress the expression of UGT1A specifically in the urinary bladder. This suppression was counteracted by oltipraz in wild-type mice but not in Nrf2-/- mice. These results show that Nrf2 and its downstream target genes are responsible for BBN detoxification. Furthermore, oltipraz prevents carcinogenesis by BBN by enhancing detoxification of this carcinogen in the liver and urinary bladder.