The long-term culture of porcine urothelial cells and induction of urothelial stratification

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.

What's in the Pipeline about Bladder Reconstructive Surgery? Some Remarks on the State of the Art

The fusion of engineering with cell biology and advances in biomaterials may lead to de novo construction of implantable organs. Engineering of neobladder from autologous urothelial and smooth muscle cells cultured on biocompatible, either synthetic or naturally-derived substrates, is now feasible in preclinical studies and may have clinical applicability in the near future. The development of a bioartificial bladder would warrant the prevention of both the metabolic and neoplastic shortcomings of the intestinal neobladder. Two tissue-engineering techniques for bladder reconstruction have been tested on animals: 1) the in vivo technique involves the use of naturally-derived biomaterials for functional native bladder regeneration 2) the in vitro technique involves the establishment of autologous urothelial and smooth muscle cell culture from the host's urinary tract, after which the cells are seeded on the biodegradable matrix-scaffold to create a composite graft that is implanted into the same host for complete histotectonic regeneration. Waiting for the creation of a complete tissue-engineered bladder with a trigone-shaped base, we suggest, in surgical oncology after radical cystectomy, the realization of conduit or continent pouch using tissue-engineered material.

Co-culturing porcine normal urothelial cells, urinary bladder fibroblasts and smooth muscle cells for tissue engineering research

New strategies for culturing and co-culturing of the main types of urinary bladder cells are essential for successful establishment of biomimetic in vitro models, which could be applied for research into, and management of, diverse urological disorders. Porcine normal urothelial cells are available in nearly unlimited amounts and have many properties equivalent to human urothelial cells. In the present study, we established normal differentiated porcine urothelial cells in co-cultures with porcine urinary bladder normal fibroblasts and/or smooth muscle cells. The optimal culture medium for establishment of differentiated urothelial cells, demonstrated by positive immunofluorescence of uroplakins, cytokeratins (CK 7, CK 20), zonula occludens 1 (ZO-1), claudin 4, claudin 8, and E-cadherin, was the medium composed of equal parts of Advanced Dulbecco's modified Eagle's medium (A-DMEM) and MCDB 153 medium with physiological calcium concentration of 2.5 mM and without fetal bovine serum, named UroM (+Ca²⁺  - S). This medium was also proven to be suitable for culturing of bladder fibroblasts and smooth muscle cells and co-culturing of urothelial cells with these mesenchymal cells. Urothelial cell differentiation was optimal in UroM (+Ca²⁺  - S) medium in all co-culture conditions and when compared to all conditioned-media combinations. To summarize, these strategies for culturing and co-culturing of urinary bladder urothelial cells with mesenchymal cells could be used as new in vitro models for future basic and applicable research of the urinary bladder and thus potentially also for translational tissue engineering studies.

Optimization of porcine urothelial cell cultures: Best practices, recommendations, and threats

Many experimental approaches have been conducted in order to isolate urothelial cells from bladder tissue biopsies, but each method described has utilized different protocols and sources of bladder tissue. In this study, we compared the different methods of urothelial cell isolation available in literature together with standardized methods in order to obtain more unified results. Five methods for primary porcine urothelial culture establishment were compared: tissue explants and four enzymatic methods utilizing collagenase II, dispase II, combination of dispase II and trypsin, and trypsin alone. The average number of isolated cells, cell morphology, success of established culture, average number of cells from the first passage, expression of p63 and pancytokeratin and the characterization of urothelial cell growth, and aging were analyzed during the in vitro culture. The method utilizing dispase II was the most efficient and reproducible method for the isolation and culture of porcine urothelial cells when compared to the other tested methods. Urothelial cells obtained by this method grew considerably well and the cultures were established with high efficiency, which enabled us in obtaining a large quantity of cells with normal morphology. Contamination with fibroblasts in this method was the lowest. The utilization of a proper method for urothelial cell isolation is a critical step in the urinary tract regeneration when using tissue engineering techniques. In summary, this study demonstrated that by utilizing the described method with dispase II, a suitable number of cells was achieved, proving the method useful for tissue regeneration.

Biomimickry of UPEC Cytoinvasion: A Novel Concept for Improved Drug Delivery in UTI

Urinary tract infections (UTIs) are among the most common bacterial infections. In an increasing number of cases, pathogen (multi-)resistance hampers durable treatment success via the standard therapies. On the functional level, the activity of urinary excreted antibiotics is compromized by the efficient tissue colonization mechanism of uropathogenic Escherichia coli (UPEC). Advanced drug delivery systems aim at exploiting a glycan-mediated targeting mechanism, similar to the UPEC invasion pathway, to increase bioavailability. This may be realized by conjugation of intravesically applied drugs or drug carriers to chosen plant lectins. Higher local drug concentrations in or nearby bacterial reservoirs may be gained, with higher chances for complete eradication. In this study, preliminary parameters to clarify the potential of this biorecognitive approach were evaluated. Glycan-triggered interaction cascades and uptake processes of several plant lectins with distinct carbohydrate specificities were characterized, and wheat germ agglutinin (WGA) could be identified as the most promising targeter for crossing the urothelial membrane barrier. In partially differentiated primary cells, intracellular accumulation sites were largely identical for GlcNAc- and Mannose-specific lectins. This indicates that WGA-mediated delivery may also enter host cells via the FimH-dependent uptake pathway.

Potential in two types of collagen scaffolds for urological tissue engineering applications – Are there differences in growth behaviour of juvenile and adult vesical cells?

The aging society has a deep impact on patient care in urology. The number of patients in need of partial or whole bladder wall replacement is increasing simultaneously with the number of cancer incidents. Therefore, urological research requires a model of bladder wall replacement in adult and elderly people. Two types of porcine collagen I/III scaffolds were used in vitro for comparison of cell growth of two different pig breeds at different growth stages. Scaffolds were characterised with scanning electron and laser scanning microscopy. Urothelial and detrusor smooth muscle cells were isolated from 15 adult Göttingen minipigs and 15 juvenile German Landrace pigs. Growth behaviour was examined in cell culture and seeded onto the collagen scaffolds via immunohistochemistry, two-photon laser scanning microscopy and a viability assay. The collagen scaffolds showed different structured surfaces which are appropriate for seeding of the two different cell types. Moisturisation of the scaffolds resulted in a change of the structure. Cell growth of German Landrace urothelial cells and smooth muscle cells was significantly higher than cell growth of the Göttingen minipig cells. Seeding of scaffolds with both cell types from both pig races was possible which could be shown by immunohistochemistry and two-photon laser scanning microscopy. Growth behaviour on the scaffolds was significantly increased for the German Landrace compared to Göttingen minipig. Nevertheless, seeding with the adult Göttingen minipig cells resulted in a closed layer on the surface and urothelial cells and smooth muscle cells showed increasing growth until day 14. The results show that these collagen scaffolds are adequate for the seeding with vesical cells. Moreover, they seem appropriate for the use as an in vitro model for the adult or elderly as the cells of the adult Göttingen minipig too, show good growth behaviour.

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.

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.

Induction of proliferation and differentiation of cultured urothelial cells on acellular biomaterials

OBJECTIVE

To determine the optimum conditions for the proliferation of urothelial cells, leading to the confluent coverage of large surfaces of biocompatible membranes, and for their terminal differentiation.

MATERIALS AND METHODS

Porcine and human urothelial cells were cultured on different matrices under different growth conditions. Proliferative activity and the viability of cells were evaluated using fluorescent markers for nuclei and cytoplasm. Growth and differentiation were assessed by histological, histochemical and immunohistochemical methods.

RESULTS

Under fibroblastic induction and supplementation of 5% fetal calf serum (FCS), urothelial cells showed more proliferation than in other conditions tested. Terminal differentiation of superficial cells was achieved by lowering the concentration of FCS to 1% at the air-liquid interface.

CONCLUSIONS

The mitogenic effects of the extracellular matrix content of biological membranes and fibroblastic inductive factors are synergistic with each other, and can compensate for a low FCS concentration and the absence of other additives. Lowering the FCS concentration to 1% inhibits the proliferation of urothelial cells and permits their terminal differentiation.

Advanced technique for long term culture of epithelia in a continuous luminal-basal medium gradient

The majority of epithelia in our organism perform barrier functions on being exposed to different fluids at the luminal and basal sides. To simulate this natural situation under in vitro conditions for biomaterial testing and tissue engineering the epithelia have to withstand mechanical and fluid stress over a prolonged period of time. Leakage, edge damage and pressure differences in the culture system have to be avoided so that the epithelial barrier function is maintained. Besides, the environmental influences on important cell biological features such as, sealing or transport functions, have to remain upregulated and a loss of characteristics by dedifferentiation is prevented. Our aim is to expose embryonic renal collecting duct (CD) epithelia as model tissue for 14 days to fluid gradients and to monitor the development of tissue-specific features. For these experiments, cultured embryonic epithelia are placed in tissue carriers and in gradient containers, where different media are superfused at the luminal and basal sides. Epithelia growing on the tissue carriers act as a physiological barrier during the whole culture period. To avoid mechanical damage of the tissue and to suppress fluid pressure differences between the luminal and basal compartments improved transport of the medium and an elimination of unilaterally accumulated gas bubbles in the gradient container compartments by newly developed gas expander modules is introduced. By the application of these tools the yield of embryonic renal collecting duct epithelia with intact barrier function on a fragile natural support material could be increased significantly as compared to earlier experiments. Epithelia treated with a luminal NaCl load ranging from 3 to 24 mmol l were analyzed by immunohistochemical methods to determine the degree of differentiation. The tissue showed an upregulation of individual CD cell features as compared to embryonic epithelia in the neonatal kidney.

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

The objective of this study is to establish a reliable cell culture system for the long-term culture of rat urothelial cells (RUC), in which the cells multiply in vitro and form stratified polarized urothelium. Urothelial cells were harvested by the enzymatic digestion of the urothelium exposed by the eversion of resected rat bladders. Primary cultures were initiated in keratinocyte serum-free medium (KSFM) for selective proliferation of urothelial cells. Subsequently, the cells were propagated in a mixture of conditioned medium (CM) derived from Swiss 3T3 cell culture supernatant and KSFM (CM-KSFM). Mean population doubling time was 13.8 +/- 0.9 h. RUC were successfully maintained for 18 passages over a period of 4-5 mo. Detailed investigations of culture conditions showed that CM-KSFM yielded a differentiated multilayer structure. The stratified urothelial sheets measuring 4 x 6 cm2 could be formed and then detached using dispase. Cytokeratin pattern in both the cultured urothelial monolayer and engineered stratified layers was similar to those seen in vivo, as assessed with monoclonal antibody against cytokeratin 17. Ultrastructural morphology showed microvilli, basal cell layer, and desmosomes between adjacent cells in the stratified urothelium.

In vitro engineering of human stratified urothelium: analysis of its morphology and function

PURPOSE

Gastric or intestinal patches, commonly used for reconstructive cystoplasty, may induce severe metabolic complications. The use of bladder tissues reconstructed in vitro could avoid these complications. We compared cellular differentiation and permeability characteristics of human native with in vitro cultured stratified urothelium.

MATERIALS AND METHODS

Human stratified urothelium was induced in vitro. Morphology was studied with light and electron microscopy and expression of key cellular proteins was assessed using immunohistochemistry. Permeability coefficients were determined by measuring water, urea, ammonia and proton fluxes across the urothelium.

RESULTS

As in native urothelium the stratified urothelial construct consisted of basal membrane and basal, intermediate and superficial cell layers. The apical membrane of superficial cells formed villi and glycocalices, and tight junctions and desmosomes were developed. Immunohistochemistry showed similarities and differences in the expression of cytokeratins, integrin and cellular adhesion proteins. In the cultured urothelium cytokeratin 20 and integrin subunits alpha6 and beta4 were absent, and symplekin was expressed diffusely in all layers. Uroplakins were clearly expressed in the superficial umbrella cells of the urothelial constructs, however, they were also present in intermediate and basal cells. Symplekin and uroplakins were expressed only in the superficial cells of native bladder tissue. The urothelial constructs showed excellent viability, and functionally their permeabilities for water, urea and ammonia were no different from those measured in native human urothelium. Proton permeability was even lower in the constructs compared to that of native urothelium.

CONCLUSIONS

Although the in vitro cultured human stratified urothelium did not show complete terminal differentiation of its superficial cells, it retained the same barrier characteristics against the principal urine components. These results indicate that such in vitro cultured urothelium, after being grown on a compliant degradable support or in coculture with smooth muscle cells, is suitable for reconstructive cystoplasty.