Primary cultures of human urothelial cells for genotoxicity testing

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.

Recurrent Urinary Tract Infection: A Mystery in Search of Better Model Systems

Urinary tract infections (UTIs) are among the most common infectious diseases worldwide but are significantly understudied. Uropathogenic E. coli (UPEC) accounts for a significant proportion of UTI, but a large number of other species can infect the urinary tract, each of which will have unique host-pathogen interactions with the bladder environment. Given the substantial economic burden of UTI and its increasing antibiotic resistance, there is an urgent need to better understand UTI pathophysiology - especially its tendency to relapse and recur. Most models developed to date use murine infection; few human-relevant models exist. Of these, the majority of in vitro UTI models have utilized cells in static culture, but UTI needs to be studied in the context of the unique aspects of the bladder's biophysical environment (e.g., tissue architecture, urine, fluid flow, and stretch). In this review, we summarize the complexities of recurrent UTI, critically assess current infection models and discuss potential improvements. More advanced human cell-based in vitro models have the potential to enable a better understanding of the etiology of UTI disease and to provide a complementary platform alongside animals for drug screening and the search for better treatments.

Adipose-derived stem cells-seeded bladder acellular matrix graft-silk fibroin enhances bladder reconstruction in a rat model

The unfavourable clinical outcomes of host cell-seeded scaffolds for bladder augmentation warrant improved bioactive biomaterials. This study aimed to examine the feasibility of adipose-derived stem cells (ASCs)-seeded bilayer bladder acellular matrix graft (BAMG)-silk fibroin (SF) scaffold in enhancing bladder reconstruction. Sprague Dawley rats were randomly divided into three groups: the BAMG-SF-ASCs group, the acellular BAMG-SF group and the cystotomy group. The BAMG-SF-ASCs group was sampled at 2, 4 and 12 weeks, and compared with the other groups at 12 weeks. In the BAMG-SF-ASCs group, the normal bladder contour was reformed similar to that in the cystotomy group, with abundant urothelium and smooth muscle regeneration, as well as a suitable scaffold degradation speed, and trivial fibrosis and inflammation. The ASCs seeded in BAMG-SF were maintained in the regenerated region during the 12-week experimental period and significantly enhanced the vessel density, nerve regeneration and bladder function compared with acellular BAMG-SF. In addition, the BAMG-SF-ASCs group presented elevated levels of SDF-1α, VEGF and their receptors, with an obvious increase in ERK 1/2 phosphorylation. BAMG-SF is a promising biomaterial for ASCs seeding to facilitate bladder augmentation and demonstrated an enhanced angiogenic potential possibly related to the SDF-1α/CXCR4 pathway via ERK 1/2 activation.

Micro-brushing-based technique to gain fresh urothelial cells for gene expression analysis

The gold standard of saving fresh tissue in liquid nitrogen has some serious disadvantages in that this process is not available in daily medical routine practices even in many tumor centers. Our approach of a new minimally invasive technique is obtaining urothelial cells via micro-brushing the urinary bladder on the occasion of urological routine methods such as transurethral resection (TUR). Urothelial cells were obtained from 25 patients via two different micro-brushes from tumor tissue and from macroscopically healthy tissue during TUR. These cells were immediately transferred into RNA stabilization reagent and stored at -20°C. Later, mRNA was isolated, transcribed into cDNA, and amplified. cDNA was stored at -20°C until analysis. The mean RNA quantity was 99.5 ng/μl from tumor tissues and 66.3 ng/μl from macroscopically tumor-free tissue, enabling a considerable number of analyses. The quality of the gained cDNA allowed semi-quantitative PCR analysis of GSTM1 expression as well as quantitative PCR analysis of c-Myc expression. The new technique presents several important advantages. First, staging and grading of the stained tumor sample can be examined immediately, whereas fresh frozen sample is not examined until some days later. Further, this method can be applied in hospitals with no access to liquid nitrogen or without capability to provide an additional examination of frozen tumor sample by a pathologist. This presented minimally invasive method enables investigation of gene expression in the urinary bladder without disadvantages of the need for storage of fresh tissues in liquid nitrogen.

Mir-135a enhances cellular proliferation through post-transcriptionally regulating PHLPP2 and FOXO1 in human bladder cancer

Background

Bladder cancer is the most common malignancy in urinary system and the ninth most common malignancy in the world. MicroRNAs (miRNAs) are small, non-coding RNAs that regulate gene expression by targeted repression of transcription and translation and play essential roles during cancer development. We investigated the expression of miR-135a in bladder cancer and explored its bio-function during bladder cancer progression.

Methods

The expression of miR-135a in bladder cancer cells and tissues are performed by using Real-time PCR assay. Cell viability assay (MTT assay), colony formation assay, anchorage-independent growth ability assay and Bromodeoxyuridine labeling and immunofluorescence (BrdUrd) assay are used to examine cell proliferative capacity and tumorigenicity. Flow cytometry analysis is used to determine cell cycle progression. The expressions of p21, p27, CyclinD1, Ki67, PHLPP2 and FOXO1 are measured by Western blotting assay. Luciferase assay is used to confirm whether FOXO1 is the direct target of miR-135a.

Results

miR-135a is upregulated in bladder cancer cells and tissues. Enforced expression of miR-135a promotes bladder cancer cells proliferation, whereas inhibition of miR-135a reverses the function. Furthermore, for the first time we demonstrated PHLPP2 and FOXO1 are direct targets of miR-135a and transcriptionally down-regulated by miR-135a. Suppression of PHLPP2 or FOXO1 by miR-135a, consisted with dysregulation of p21, p27, Cyclin D1 and Ki67, play important roles in bladder cancer progression.

Conclusion

Our study demonstrates that miR-135a promotes cell proliferation in bladder cancer by targeting PHLPP2 and FOXO1, and is performed as an onco-miR.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0438-8) contains supplementary material, which is available to authorized users.

Biomimetic urothelial tissue models for the in vitro evaluation of barrier physiology and bladder drug efficacy

The bladder is an important tissue in which to evaluate xenobiotic drug interactions and toxicities due to the concentration of parent drug and hepatic/enteric-derived metabolites in the urine as a result of renal excretion. Breaching of the barrier provided by the bladder epithelial lining (the urothelium) can expose the underlying tissues to urine and cause harmful effects (e.g., cystitis or cancer). Human urothelium is most commonly represented in vitro as immortalized or established cancer-derived cell lines, but the compromised ability of such cells to undergo differentiation and barrier formation means that nonimmortalized, normal human urothelial (NHU) cells provide a more relevant cell culture system. The impressive capacity for urothelial self-renewal in vivo can be harnessed in vitro to generate experimentally-useful quantities of NHU cells, which can subsequently be differentiated to form a functional or "biomimetic" urothelium. When seeded onto permeable membranes, these barrier-forming human urothelial tissue models enable the modeling of serum and luminal (intravesical) exposure to drugs and metabolites, thus supporting efficacy/toxicity assessments. Biomimetic human urothelial constructs provide a potential step along the preclinical trail and may support the extrapolation from rodent in vivo data to determine human relevance. Early evidence is beginning to demonstrate that human urothelium in vitro can provide information that supersedes conventional rodent studies, but further validation is needed to support widespread adoption.

Bladder tissue regeneration using acellular bi-layer silk scaffolds in a large animal model of augmentation cystoplasty

Acellular scaffolds derived from Bombyx mori silk fibroin were investigated for their ability to support functional tissue regeneration in a porcine model of augmentation cystoplasty. Two bi-layer matrix configurations were fabricated by solvent-casting/salt leaching either alone (Group 1) or in combination with silk film casting (Group 2) to yield porous foams buttressed by heterogeneous surface pore occlusions or homogenous silk films, respectively. Bladder augmentation was performed with each scaffold group (6 × 6 cm(2)) in juvenile Yorkshire swine for 3 m of implantation. Augmented animals exhibited high rates of survival (Group 1: 5/6, 83%; Group 2: 4/4, 100%) and voluntary voiding over the course of the study period. Urodynamic evaluations demonstrated mean increases in bladder capacity over pre-operative levels (Group 1: 277%; Group 2: 153%) which exceeded nonsurgical control gains (144%) encountered due to animal growth.In addition, animals augmented with both matrix configurations displayed increases in bladder compliance over pre-operative levels(Group 1: 357%; Group 2: 338%) similar to growth-related elevations observed in non-surgical controls (354%) [corrected]. Gross tissue evaluations revealed that both matrix configurations supported extensive de novo tissue formation throughout the entire original implantation site which exhibited ultimate tensile strength similar to nonsurgical counterparts. Histological and immunohistochemical analyses showed that both implant groups promoted comparable extents of smooth muscle regeneration and contractile protein (α-smooth muscle actin and SM22α) expression within defect sites similar to controls. Parallel evaluations demonstrated the formation of a transitional, multi-layered urothelium with prominent cytokeratin, uroplakin, and p63 protein expression in both matrix groups. De novo innervation and vascularization processes were evident in all regenerated tissues indicated by synaptophysin-positive neuronal cells and vessels lined with CD31 expressing endothelial cells. Ex vivo organ bath studies demonstrated that regenerated tissues supported by both silk matrices displayed contractile responses to carbachol, α,β-methylene-ATP, KCl, and electrical field stimulation similar to controls. Our data detail the ability of acellular silk scaffolds to support regeneration of innervated, vascularized smooth muscle and urothelial tissues within 3 m with structural, mechanical, and functional properties comparable to native tissue in a porcine model of bladder repair.

Supportive development of functional tissues for biomedical research using the MINUSHEET® perfusion system

Functional tissues generated under in vitro conditions are urgently needed in biomedical research. However, the engineering of tissues is rather difficult, since their development is influenced by numerous parameters. In consequence, a versatile culture system was developed to respond the unmet needs.

Optimal adhesion for cells in this system is reached by the selection of individual biomaterials. To protect cells during handling and culture, the biomaterial is mounted onto a MINUSHEET® tissue carrier. While adherence of cells takes place in the static environment of a 24 well culture plate, generation of tissues is accomplished in one of several available perfusion culture containers. In the basic version a continuous flow of always fresh culture medium is provided to the developing tissue. In a gradient perfusion culture container epithelia are exposed to different fluids at the luminal and basal sides. Another special container with a transparent lid and base enables microscopic visualization of ongoing tissue development. A further container exhibits a flexible silicone lid to apply force onto the developing tissue thereby mimicking mechanical load that is required for developing connective and muscular tissue. Finally, stem/progenitor cells are kept at the interface of an artificial polyester interstitium within a perfusion culture container offering for example an optimal environment for the spatial development of renal tubules.

The system presented here was evaluated by various research groups. As a result a variety of publications including most interesting applications were published. In the present paper these data were reviewed and analyzed. All of the results point out that the cell biological profile of engineered tissues can be strongly improved, when the introduced perfusion culture technique is applied in combination with specific biomaterials supporting primary adhesion of cells.

Exposure of primary porcine urothelial cells to benzo(a)pyrene: in vitro uptake, intracellular concentration, and biological response

More than 90 % of all bladder cancers are transitional cell carcinomas arising from the cells lining the inside of the hollow organ (uroepithelium). Cell cultures from primary urinary bladder epithelial cells (PUBEC) of pigs were established to assess the uptake, intracellular concentration, and subcellular distribution of the environmental pollutant benzo(a)pyrene (BaP). During treatment of the cells with 0.5 μM BaP for up to 24 h, intracellular concentration of BaP increased without saturation but with marked differences between various PUBEC pools. Analysis of BaP uptake by laser scanning microscopy indicated that BaP is rapidly partitioned into the cell membrane, while only a slight but significant increase in BaP fluorescence intensity was observed in the cytosol and nucleus. Spectrofluorometric quantification of BaP in PUBEC using ex situ calibration revealed a strong accumulation of BaP, leading to intracellular concentrations ranging from 7.28 to 35.70 μM in cells exposed to 0.5 μM BaP and from 29.9 to 406.64 μM in cells exposed to 10 μM BaP. These results were confirmed by gas chromatographic mass spectrometric analysis. Apoptotic cell nuclei were assessed by TUNEL analysis to see whether BaP exposure at the given concentrations results in a toxic effect. While apoptotic cells were barely detectable in control epithelial cells, there was a marked elevation in apoptosis in the BaP-exposed cells. In conclusion, a comprehensive study on uptake and quantification of BaP in epithelial cells from pig bladder is reported for the first time. The study may be helpful in understanding the pattern of BaP uptake and distribution in bladder and its possible implication in bladder cancer development.

N-Acetylation of p-aminobenzoic acid and p-phenylenediamine in primary porcine urinary bladder epithelial cells and in the human urothelial cell line 5637

N-Acetyltransferases (NAT) are important enzymes in the metabolism of certain carcinogenic arylamines, as N-acetylation decreases or prevents their bioactivation via N-hydroxylation. To study such processes in the bladder, cell culture models may be used, but metabolic competence needs to be characterized. This study focused on the N-acetylation capacity of two urothelial cell systems, using p-aminobenzoic acid (PABA) and the hair dye precursor p-phenylenediamine (PPD), two well-known substrates of the enzyme NAT1. The constitutive NAT1 activity was investigated using primary cultures of porcine urinary bladder epithelial cells (PUBEC) and in the human urothelial cell line 5637 to assess their suitability for further in vitro studies on PABA and PPD-induced toxicity. N-Acetylation of PABA and PPD was determined by high-performance liquid chromatography (HPLC) analysis in cytosols of the two cell systems upon incubation with various substrate levels for up to 60 min. The primary PUBEC revealed higher N-acetylation rates (2.5-fold for PABA, 5-fold for PPD) compared to the 5637 cell line, based on both PABA conversion to its acetylated metabolite and formation of mono- and diacetylated PPD. The urothelial cell systems may thus be useful as a tool for further studies on the N-acetylation of aromatic amines via NAT1.

Immunocytochemical characterisation of cultures of human bladder mucosal cells

Background

The functional role of the bladder urothelium has been the focus of much recent research. The bladder mucosa contains two significant cell types: urothelial cells that line the bladder lumen and suburothelial interstitial cells or myofibroblasts. The aims of this study were to culture these cell populations from human bladder biopsies and to perform immunocytochemical characterisation.

Methods

Primary cell cultures were established from human bladder biopsies (n = 10). Individual populations of urothelial and myofibroblast-like cells were isolated using magnetic activated cell separation (MACS). Cells were slow growing, needing 3 to 5 weeks to attain confluence.

Results

Cytokeratin 20 positive cells (umbrella cells) were isolated at primary culture and also from patients' bladder washings but these did not proliferate. In primary culture, proliferating cells demonstrated positive immunocytochemical staining to cytokeratin markers (AE1/AE3 and A0575) as well fibroblasts (5B5) and smooth muscle (αSMA) markers. An unexpected finding was that populations of presumptive urothelial and myofibroblast-like cells, isolated using the MACS beads, stained for similar markers. In contrast, staining for cytokeratins and fibroblast or smooth muscle markers was not co-localised in full thickness bladder sections.

Conclusions

Our results suggest that, in culture, bladder mucosal cells may undergo differentiation into a myoepithelial cell phenotype indicating that urothelial cells have the capacity to respond to environmental changes. This may be important pathologically but also suggests that studies of the physiological function of these cells in culture may not give a reliable indicator of human physiology.

Comparison of a poly-L-lactide-co-ε-caprolactone and human amniotic membrane for urothelium tissue engineering applications

The reconstructive surgery of urothelial defects, such as severe hypospadias is susceptible to complications. The major problem is the lack of suitable grafting materials. Therefore, finding alternative treatments such as reconstruction of urethra using tissue engineering is essential. The aim of this study was to compare the effects of naturally derived acellular human amniotic membrane (hAM) to synthetic poly-L-lactide-co-ε-caprolactone (PLCL) on human urothelial cell (hUC) viability, proliferation and urothelial differentiation level. The viability of cells was evaluated using live/dead staining and the proliferation was studied using WST-1 measurement. Cytokeratin (CK)7/8 and CK19 were used to confirm that the hUCs maintained their phenotype on different biomaterials. On the PLCL, the cell number significantly increased during the culturing period, in contrast to the hAM, where hUC proliferation was the weakest at 7 and 14 days. In addition, the majority of cells were viable and maintained their phenotype when cultured on PLCL and cell culture plastic, whereas on the hAM, the viability of hUCs decreased with time and the cells did not maintain their phenotype. The PLCL membranes supported the hUC proliferation significantly more than the hAM. These results revealed the significant potential of PLCL membranes in urothelial tissue engineering applications.