Plasticity of the urothelial phenotype: effects of gastro-intestinal mesenchyme/stroma and implications for urinary tract reconstruction

Prognostic significance of E-Cadherin and B-Catenin in non-muscle invasive bladder cancer

Non muscle invasive bladder cancer (NMIBC) has unpredictable outcomes with a variable risk of recurrence and progression. Many clinic-pathological prognostic factors have been identified but remain insufficient, raising the need to investigate new biomarkers. The aim of our study was to assess the prognostic value of the immunohistochemical (IHC) markers E-Cadherin and B-Catenin in NMIBC. All cases of NMIBC were collected between 2008 and 2013. IHC analysis was performed using E-Cadherin and B-Catenin. Reduced or loss of E-Cadherin expression was assessed as abnormal. Only cases with B-Catenin intense membranous staining were considered normal. A correlation was found between abnormal E-Cadherin expression and stage (p = 0.001), grade (p = 0.0000000), recurrence (p = 0.0000000), progression (p = 0.01), recurrence-free survival (p = 0.00000001), and progression-free survival (p = 0.01). A statistically significant association was found between B-Catenin and stage (p = 0. 05), grade (p = 0.02), and recurrence (p = 0.02). The abnormal expression of these markers could help to identify a high-risk subgroup of NMIBC that might benefit from either more accurate follow-up or more aggressive treatment.

The role and function of PPARγ in bladder cancer

Peroxisome proliferator-activated receptor gamma (PPARγ), a member of the nuclear receptor superfamily, participates in multiple physiological and pathological processes. Extensive studies have revealed the relationship between PPARγ and various tumors. However, the expression and function of PPARγ in bladder cancer seem to be controversial. It has been demonstrated that PPARγ affects the occurrence and progression of bladder cancer by regulating proliferation, apoptosis, metastasis, and reactive oxygen species (ROS) and lipid metabolism, probably through PPARγ-SIRT1 feedback loops, the PI3K-Akt signaling pathway, and the WNT/β-catenin signaling pathway. Considering the frequent relapses after chemotherapy, some researchers have focused on the relationship between PPARγ and chemotherapy sensitivity in bladder cancer. Moreover, the feasibility of PPARγ ligands as potential therapeutic targets for bladder cancer has been uncovered. Taken together, this review summarizes the relevant literature and our findings to explore the complicated role and function of PPARγ in bladder cancer.

Heterogeneity of PTEN and PPAR-γ in cancer and their prognostic application to bladder cancer

The aim of the present study was to determine the prognostic value of peroxisome proliferator-activated receptor-γ (PPAR-γ) and phosphatase and tensin homologue deleted on chromosome ten (PTEN) for bladder cancer. Data were collected from The Cancer Genome Atlas (TCGA), a public database, and were analyzed to assess PTEN and PPAR-γ heterogeneity as well as distinct trends in bladder cancers. Furthermore, PPAR-γ and PTEN expression levels and their association with one another were evaluated. Finally, the prognostic significance of PPAR-γ and PTEN for bladder cancer was validated in vivo using clinical samples. Based on the TCGA database, PTEN levels were significantly increased in bladder cancers (P<0.001); whereas PPAR-γ expression was downregulated in the same samples (P<0.05). Furthermore, linear correlation analysis indicated that in bladder cancers, PPAR-γ and PTEN are inversely correlated (P<0.001). The assessment and analysis of clinical samples revealed that PPAR-γ was significantly elevated in tumor tissues (P<0.001); however, PTEN was downregulated in cancer tissues (P<0.001). Furthermore, PPAR-γ expression determined by immunohistochemistry grey level (P=0.002) was also elevated in high-grade and invasive bladder cancers compared with low-grade and superficial tumors, whereas PTEN levels exhibited the opposite in this analysis (P=0.001). In individuals with lymphoid metastasis, PPAR-γ was significantly increased (P<0.001), and PTEN was significantly decreased (P<0.001). Pearson analysis revealed a significant negative correlation between PPAR-γ and PTEN expression (r=-0.604, P<0.05). In conclusion, tissue heterogeneity was observed with respect to PPAR-γ and PTEN expression in bladder cancer. PTEN and PPAR-γ expression are negatively correlated and may be excellent indicators of bladder cancer tumorigenesis and progression.

Secondary Tumors After Urinary Diversion

It has been known that urinary diversions juxtaposing the urinary and intestinal tracts lead to increased incidence of secondary malignancies. Although tumorigenesis in ureterosigmoidostomies follows the typical course from adenomas to adenocarcinomas, secondary malignancies arising from isolated intestinal diversions are much more heterogeneous. Research over the last half century has unveiled patterns of incidence and progression, while also uncovering possible mechanisms driving the neoplastic changes. In this review, we summarize the current understanding of these unique tumors, with the hope that the knowledge gained may shed light on the etiologies of other cancers arising from the urinary and intestinal tracts.

Transdifferentiation of adult rat stem Leydig cells into prostatic and uterine epithelium, but not epidermis

Stem Leydig cells (SLCs), precursors of testicular Leydig cells that secrete testosterone required for male sexual differentiation, spermatogenesis, and fertility, were recently identified in rat testes. Various types of stem cells have shown the ability to differentiate into other tissues, but there is no information on the plasticity of adult rat SLCs (rSLCs). This study investigated the ability of rSLCs to transdifferentiate into cell types from all three germ layers-prostatic epithelium (endoderm), uterine epithelium (mesoderm), and epidermis (ectoderm)-under the influence of inductive mesenchyme from fetal and neonatal tissues. To differentiate rSLCs into cells of other lineages, mesenchyme from green fluorescent protein (GFP)-expressing mice was used. Tissue recombinants of urogenital sinus mesenchyme (a potent prostate inducer) and rSLCs grafted into adult male hosts formed ductal structures resembling prostate after 5 weeks. Prostate epithelium was of rSLC origin as determined by absence of GFP expression, and expressed characteristic markers of prostatic epithelium. Similarly, uterine mesenchyme + rSLCs tissue recombinants contained a simple columnar epithelium that was histologically similar to normal uterine epithelium and expressed typical uterine epithelial markers, but was of rSLC origin. In contrast, epidermal tissue was absent in fetal dermis + rSLCs recombinants, suggesting rSLCs did not form skin epithelium. Thus, rSLCs can transdifferentiate into uterine and prostatic epithelium, mesodermal, and endodermal derivatives, respectively, but they may have a limited transdifferentiation potential, as shown by their inability to form epidermis, an ectodermal derivative.

Hierarchical transcriptional profile of urothelial cells development and differentiation

The urothelial lining of the lower urinary tract is the most efficient permeability barrier in animals, exhibiting a highly differentiated phenotype and a remarkable regenerative capacity upon wounding. During development and possibly during repair, cells undergo a sequence of hierarchical transcriptional events that mark the transition of these cells from the least differentiated urothelial phenotype characteristic of the basal cell layer, to the most differentiated cellular phenotype characteristic of the superficial cell layer. Unraveling normal urothelial differentiation program is essential to uncover the underlying causes of many congenital abnormalities and for the development of an appropriate differentiation niche for stem cells, for future use in urinary tract tissue engineering and organ reconstruction. Kruppel like factor-5 appears to be at the top of the hierarchy activating several downstream transcription factors, the most prominent of which is peroxisome proliferator activator receptor-γ. Eventually those lead to the activation of transcription factors that directly regulate the expression of uroplakin proteins along with other proteins that mediate the permeability function of the urothelium. In this review, we discuss the most recent findings in the area of urothelial cellular differentiation and transcriptional regulation, aiming for a comprehensive overview that aids in a refined understanding of this process.

Mesenchymal-epithelial interaction techniques

This paper reviews the importance of mesenchymal-epithelial interactions in development and gives detailed technical protocols for investigating these interactions. Successful analysis of mesenchymal-epithelial interactions requires knowing the ages in which embryonic, neonatal and adult organs can be separated into mesenchymal and epithelial tissues. Methods for separation of mesenchymal and epithelial tissues and preparation of tissue recombinants are described.

Organ-specific matrix self-assembled by mesenchymal cells improves the normal urothelial differentiation in vitro

PURPOSE

Enterocystoplasty is the gold standard to perform bladder reconstruction. Since this technique has a high morbidity rate, several matrix scaffolds have been proposed to support the urothelial maturation. Unfortunately, epithelial cells failed to fully integrate the cell-matrix interactions and therefore appropriate signalling pathways of normal differentiation. Based on these observations, we proposed to culture bladder urothelial cells (BUC) onto a matrix self-assembled by bladder mesenchymal cells (BMC), to form a vesical model (VM).

METHODS

Different serum proportions were assessed to obtain a manipulable matrix deposited by BMC. The BUC were then seeded onto the BMC's matrix to evolve in a three-dimensional culture. Haematoxylin-eosin staining, immunolabeling, scanning electron microscopy, western blot and matrix metalloproteinases analysis were performed for the VM characterization.

RESULTS

We were able to obtain an original matrix made of collagen-I and presenting specific organization. Matrix remodelling was observed and led to a cellular compartmentalization. The reconstructed urothelium developed in a pseudostratified arrangement, displaying an adequate cellular polarity and apical membrane remodelling of superficial cells. Like native bladder, cytokeratin 14 immunolabeling was not observed in our VM, which indicate the conformity of the development sequence taken by BUC under the influence of the BMC's matrix.

CONCLUSION

Thus, it was possible to elaborate a VM without the use of exogenous matrices. The particular characteristics of the BMC's matrix permitted the development of an urothelium that shared the phenotype of native tissue. The autologous character of our VM, and its appropriate urothelial maturation, could potentially promote a better integration after grafting.

Engineering functional epithelium for regenerative medicine and in vitro organ models: a review

Recent advances in the fields of microfabrication, biomaterials, and tissue engineering have provided new opportunities for developing biomimetic and functional tissues with potential applications in disease modeling, drug discovery, and replacing damaged tissues. An intact epithelium plays an indispensable role in the functionality of several organs such as the trachea, esophagus, and cornea. Furthermore, the integrity of the epithelial barrier and its degree of differentiation would define the level of success in tissue engineering of other organs such as the bladder and the skin. In this review, we focus on the challenges and requirements associated with engineering of epithelial layers in different tissues. Functional epithelial layers can be achieved by methods such as cell sheets, cell homing, and in situ epithelialization. However, for organs composed of several tissues, other important factors such as (1) in vivo epithelial cell migration, (2) multicell-type differentiation within the epithelium, and (3) epithelial cell interactions with the underlying mesenchymal cells should also be considered. Recent successful clinical trials in tissue engineering of the trachea have highlighted the importance of a functional epithelium for long-term success and survival of tissue replacements. Hence, using the trachea as a model tissue in clinical use, we describe the optimal structure of an artificial epithelium as well as challenges of obtaining a fully functional epithelium in macroscale. One of the possible remedies to address such challenges is the use of bottom-up fabrication methods to obtain a functional epithelium. Modular approaches for the generation of functional epithelial layers are reviewed and other emerging applications of microscale epithelial tissue models for studying epithelial/mesenchymal interactions in healthy and diseased (e.g., cancer) tissues are described. These models can elucidate the epithelial/mesenchymal tissue interactions at the microscale and provide the necessary tools for the next generation of multicellular engineered tissues and organ-on-a-chip systems.

Deficiency in metabolic regulators PPARγ and PTEN cooperates to drive keratinizing squamous metaplasia in novel models of human tissue regeneration

Hindgut-derived endoderm can differentiate into rectal, prostatic, and bladder phenotypes. Stromal-epithelial interactions are crucial for this development; however, the precise mechanisms by which epithelium responds to stromal cues remain unknown. We have previously reported ectopic expression of peroxisome proliferator-activated receptor-γ2 (PPARγ2) increased androgen receptor expression and promoted differentiation of mouse prostate epithelium. PPARγ is also implicated in urothelial differentiation. Herein we demonstrate that knockdown of PPARγ2 in benign human prostate epithelial cells (BHPrEs) promotes urothelial transdifferentiation. Furthermore, in vitro and in vivo heterotypic tissue regeneration models with embryonic bladder mesenchyme promoted urothelial differentiation of PPARγ2-deficient BHPrE cells, and deficiency of both PPARγ isoforms 1 and 2 arrested differentiation. Because PTEN deficiency is cooperative in urothelial pathogenesis, we engineered BHPrE cells with combined knockdown of PPARγ and PTEN and performed heterotypic recombination experiments using embryonic bladder mesenchyme. Whereas PTEN deficiency alone induced latent squamous differentiation in BHPrE cells, combined PPARγ and PTEN deficiency accelerated the development of keratinizing squamous metaplasia (KSM). We further confirmed via immunohistochemistry that gene expression changes in metaplastic recombinants reflected human urothelium undergoing KSM. In summary, these data suggest that PPARγ isoform expression provides a molecular basis for observations that adult human epithelium can be transdifferentiated on the basis of heterotypic mesenchymal induction. These data also implicate PPARγ and PTEN inactivation in the development of KSM.

Bladder expression of CD cell surface antigens and cell-type-specific transcriptomes

Many cell types have no known functional attributes. In the bladder and prostate, basal epithelial and stromal cells appear similar in cytomorphology and share several cell surface markers. Their total gene expression (transcriptome) should provide a clear measure of the extent to which they are alike functionally. Since urologic stromal cells are known to mediate organ-specific tissue formation, these cells in cancers might exhibit aberrant gene expression affecting their function. For transcriptomes, cluster designation (CD) antigens have been identified for cell sorting. The sorted cell populations can be analyzed by DNA microarrays. Various bladder cell types have unique complements of CD molecules. CD9(+) urothelial, CD104(+) basal and CD13(+) stromal cells of the lamina propria were therefore analyzed, as were CD9(+) cancer and CD13(+) cancer-associated stromal cells. The transcriptome datasets were compared by principal components analysis for relatedness between cell types; those with similarity in gene expression indicated similar function. Although bladder and prostate basal cells shared CD markers such as CD104, CD44 and CD49f, they differed in overall gene expression. Basal cells also lacked stem cell gene expression. The bladder luminal and stromal transcriptomes were distinct from their prostate counterparts. In bladder cancer, not only the urothelial but also the stromal cells showed gene expression alteration. The cancer process in both might thus involve defective stromal signaling. These cell-type transcriptomes provide a means to monitor in vitro models in which various CD-isolated cell types can be combined to study bladder differentiation and bladder tumor development based on cell-cell interaction.

When urothelial differentiation pathways go wrong: implications for bladder cancer development and progression

Differentiation is defined as the ability of a cell to acquire full functional behavior. For instance, the function of bladder urothelium is to act as a barrier to the diffusion of solutes into or out of the urine after excretion by the kidney. The urothelium also serves to protect the detrusor muscle from toxins present in stored urine. A major event in the initiation and progression of bladder cancer is loss of urothelial differentiation. This is important because less differentiated urothelial tumors (higher histologic tumor grade) are typically associated with increased biologic and clinical aggressiveness. The differentiation status of urothelial carcinomas can be assessed by histopathologic examination and is reflected in the assignment of a histologic grade (low-grade or high-grade). Although typically limited to morphologic evaluation in most routine diagnostic practices, tumor grade can also be assessed using biochemical markers. Indeed, current pathological analysis of tumor specimens is increasingly reliant on molecular phenotyping. Thus, high priorities for bladder cancer research include identification of (1) biomarkers that will enable the identification of high grade T1 tumors that pose the most threat and require the most aggressive treatment; (2) biomarkers that predict the likelihood that a low grade, American Joint Committee on Cancer stage pTa bladder tumor will progress into an invasive carcinoma with metastatic potential; (3) biomarkers that indicate which pTa tumors are most likely to recur, thus enabling clinicians to prospectively identify patients who require aggressive treatment; and (4) how these markers might contribute to biological processes that underlie tumor progression and metastasis, potentially through loss of terminal differentiation. This review will discuss the proteins associated with urothelial cell differentiation, with a focus on those implicated in bladder cancer, and other proteins that may be involved in neoplastic progression. It is hoped that ongoing discoveries associated with the study of these differentiation-promoting proteins can be translated into the clinic to positively impact patient care.

Uroplakins in urothelial biology, function, and disease

Urothelium covers the inner surfaces of the renal pelvis, ureter, bladder, and prostatic urethra. Although morphologically similar, the urothelia in these anatomic locations differ in their embryonic origin and lineages of cellular differentiation, as reflected in their different uroplakin content, expandability during micturition, and susceptibility to chemical carcinogens. Previously thought to be an inert tissue forming a passive barrier between the urine and blood, urothelia have recently been shown to have a secretory activity that actively modifies urine composition. Urothelial cells express a number of ion channels, receptors, and ligands, enabling them to receive and send signals and communicate with adjoining cells and their broader environment. The urothelial surface bears specific receptors that not only allow uropathogenic E. coli to attach to and invade the bladder mucosa, but also provide a route by which the bacteria ascend through the ureters to the kidney to cause pyelonephritis. Genetic ablation of one or more uroplakin genes in mice causes severe retrograde vesicoureteral reflux, hydronephrosis, and renal failure, conditions that mirror certain human congenital diseases. Clearly, abnormalities of the lower urinary tract can impact the upper tract, and vice versa, through the urothelial connection. In this review, we highlight recent advances in the field of urothelial biology by focusing on the uroplakins, a group of urothelium-specific and differentiation-dependent integral membrane proteins. We discuss these proteins' biochemistry, structure, assembly, intracellular trafficking, and their emerging roles in urothelial biology, function, and pathological processes. We also call attention to important areas where greater investigative efforts are warranted.

Urothelium patterns bladder smooth muscle location

Smooth muscle differentiation is induced in the embryonic bladder by the centrally located urothelium in the undifferentiated mesenchyme in the periphery adjacent to the serosa. We hypothesize that under the appropriate signal the entire undifferentiated bladder mesenchyme is capable of smooth muscle differentiation and that the urothelium patterns fibromuscular development. Embryonic bladders of wild-type and Green Fluorescent Protein mice were separated into urothelial and mesenchymal components before smooth muscle differentiation (E12.5-E13). The urothelial layer green fluorescent protein was recombined and grafted with the mesenchyme (wild-type) in an orthotopic position, heterotopic position and ectopic position. In all cases, a zone of smooth muscle inhibition was observed adjacent to the epithelium whether the urothelium was in an orthotopic or heterotypic position. Bladder mesenchyme and bladder epithelium grafted alone did not grow. In conclusion, the full thickness of bladder mesenchyme is capable of smooth muscle differentiation dependent on the location of urothelium. These experiments support the hypothesis that urothelium secretes a diffusible factor that at high concentrations inhibits smooth muscle and at low concentrations induces smooth muscle, thus patterning mesenchymal cell differentiation across the full thickness of the fibromuscular bladder wall.

Different matrix micro-environments in colon cancer and diverticular disease

BACKGROUND AND AIMS

The extracellular matrix and the interactive signalling between its components are thought to play a pivotal role for tumour development and metastasis formation. An altered matrix composition as potential underlying pathology for the development of colorectal cancer was hypothesized.

METHODS

In a retrospective study of patients with colon cancer, the extracellular matrix in tumour-free bowel specimen was investigated in comparison with non-infected bowel specimen from patients operated on for colonic diverticulosis. The following matrix parameters with known associations to tumour formation, cell proliferation, invasion and metastasis were analysed by immunohistochemistry and quantified by a scoring system: VEGF, TGF-beta, ESDN, CD117, c-erb-2, cyclin D1, p53, p27, COX-2, YB-1, collagen I/III, MMP-13, PAI and uPAR. Expression profiles and correlations were calculated.

RESULTS

The comparison of the two groups revealed a significantly decreased immunostaining for CD117 and TGF-beta in the cancer group (8.5+/-2.6 vs 10.3+/-2,1 and 4.9+/-1.5 vs 8.1+/-3, respectively), whereas PAI scores were significantly higher than in patients with diverticular disease (8.1+/-1.6 vs 6.2+/-0.9). Overall correlation patterns of matrix parameters indicated pronounced differences between tumour-free tissue in cancer patients compared with patients with diverticular disease.

CONCLUSIONS

Our results indicate distinct differences in the colonic tissue architecture between cancer patients and patients with diverticulitis that support the notion of an altered matrix composition predisposing to the development of colon cancer.

Anatomic demarcation by positional variation in fibroblast gene expression programs

Fibroblasts are ubiquitous mesenchymal cells with many vital functions during development, tissue repair, and disease. Fibroblasts from different anatomic sites have distinct and characteristic gene expression patterns, but the principles that govern their molecular specialization are poorly understood. Spatial organization of cellular differentiation may be achieved by unique specification of each cell type; alternatively, organization may arise by cells interpreting their position along a coordinate system. Here we test these models by analyzing the genome-wide gene expression profiles of primary fibroblast populations from 43 unique anatomical sites spanning the human body. Large-scale differences in the gene expression programs were related to three anatomic divisions: anterior-posterior (rostral-caudal), proximal-distal, and dermal versus nondermal. A set of 337 genes that varied according to these positional divisions was able to group all 47 samples by their anatomic sites of origin. Genes involved in pattern formation, cell-cell signaling, and matrix remodeling were enriched among this minimal set of positional identifier genes. Many important features of the embryonic pattern of HOX gene expression were retained in fibroblasts and were confirmed both in vitro and in vivo. Together, these findings suggest that site-specific variations in fibroblast gene expression programs are not idiosyncratic but rather are systematically related to their positional identities relative to major anatomic axes.

Altered phenotype of cultured urothelial and other stratified epithelial cells: implications for wound healing

The differentiation of cultured stratified epithelial cells can deviate significantly from that of normal epithelium, leading to suggestions that cultured cells undergo abnormal differentiation, or a truncated differentiation. Thus cultured epidermal and corneal epithelial cells stop synthesizing their tissue-specific keratin pair K1/K10 and K3/K12, respectively. The replacement of these keratins in the suprabasal compartment by K6/K16 keratins that are made by all stratified squamous epithelia during hyperplasia rules out a truncated differentiation. Importantly, the keratin pattern of in vivo corneal epithelium undergoing wound repair mimics that of cultured rabbit corneal epithelial cells. Although cultured urothelial cells continue to synthesize uroplakins, which normally form two-dimensional crystalline urothelial plaques covering almost the entire apical urothelial surface, these proteins do not assemble into crystals in cultured cells. Cultured epithelial cells can, however, rapidly regain normal differentiation on the removal of mitogenic stimuli, the use of a suitable extracellular matrix, or the transplantation of the cells to an in vivo, nonmitogenic environment. These data suggest that cultured epithelial cells adopt altered differentiation patterns mimicking in vivo regenerating or hyperplastic epithelia. Blocking the synthesis of tissue-specific differentiation products, such as the K1 and K10 keratins designed to form extensive disulfide cross-links in cornified cells, or the assembly of uroplakin plaques allows epithelial cells to better migrate and proliferate, activities that are of overriding importance during wound repair. Cultured urothelial and other stratified epithelial cells provide excellent models for studying the regulation of the synthesis and assembly of differentiation products, a key cellular process during epithelial wound repair.

Cellular basis of urothelial squamous metaplasia: roles of lineage heterogeneity and cell replacement

Although the epithelial lining of much of the mammalian urinary tract is known simply as the urothelium, this epithelium can be divided into at least three lineages of renal pelvis/ureter, bladder/trigone, and proximal urethra based on their embryonic origin, uroplakin content, keratin expression pattern, in vitro growth potential, and propensity to keratinize during vitamin A deficiency. Moreover, these cells remain phenotypically distinct even after they have been serially passaged under identical culture conditions, thus ruling out local mesenchymal influence as the sole cause of their in vivo differences. During vitamin A deficiency, mouse urothelium form multiple keratinized foci in proximal urethra probably originating from scattered K14-positive basal cells, and the keratinized epithelium expands horizontally to replace the surrounding normal urothelium. These data suggest that the urothelium consists of multiple cell lineages, that trigone urothelium is closely related to the urothelium covering the rest of the bladder, and that lineage heterogeneity coupled with cell migration/replacement form the cellular basis for urothelial squamous metaplasia.

Cytoarchitecture modifications of the human uterine endocervical mucosa in long-term three-dimensional organotypic culture

We assayed the effects of phenol red (pr), estrogen (Es), and progesterone (Pg) in three-dimensional organotypic cultures of human uterine endocervix. Small intact fragments deposited on sponges submerged in DMEM with 10% fetal bovine serum were cultured in three different conditions: with pr (DMEM(pr+)), without pr (DMEM(pr-)), and without pr but with the addition of physiological concentrations of Es and Pg [DMEM(pr-)(Es+Pg)]. Cell viability and cellular responses were assayed after 4, 10, and 21 days using immunohistochemistry for the expression and distribution of the following markers: mucins and mucopolysaccharides (PAS staining), pan-cytokeratins (AE1/AE3), CK19, p63, Ki-67, vimentin, estrogen receptor-alpha (ER-alpha), and progesterone receptor (PR). The fragments cultivated in DMEM(pr+) showed a cuboidal, poorly differentiated epithelial phenotype and signs of stroma degeneration. In DMEM(pr-), both tissue architecture and cellular heterogeneity were much better preserved: epithelial cells showed a more columnar shape, and stroma was very well conserved, maintaining cell density. The addition of Es and Pg further improved the histology and physiology of the fragments: in DMEM(pr-)(Es+Pg), epithelial cells retained a columnar shape, secreted mucins, and formed areas of squamous hyperplasia.

Induction of the urothelial differentiation program in the absence of stromal cues

PURPOSE

The urothelial stroma is presumed to have a critical role in the formation and homeostasis of normal urothelium. To determine the intrinsic capacity of urothelial cells to initiate urothelial differentiation human urothelial cell were cultured under conditions that promote differentiation in the absence of stromal signaling.

MATERIALS AND METHODS

Immortalized and primary human urothelial cells were cultured in semisolid medium. Recovered cells were then analyzed by immunofluorescence, flow cytometry and immunoblotting for expression of the differentiation specific keratins K18 and K8, and cyclin-cyclin-dependent kinase inhibitors. The expression of these markers in cells following semisolid culture was then compared with that in normal bladder and ureteral mucosa as well as in synthetic urothelium generated by 3-dimensional organotypic raft cultures.

RESULTS

Organotypic raft culture of primary and immortalized urothelial cells generated full-thickness epithelium that resembled human bladder and ureteral urothelium, and expressed K8 and K18 in superficial layers. Suspension culture in semisolid medium induced K18 expression approximately 9-fold at 24 hours. p21 and p27 expression were induced by 6 hours and yet p21 expression subsided within 12 hours, while p27 expression persisted.

CONCLUSIONS

These results indicate that primary and immortalized human urothelial cells have the capacity to enter the urothelial differentiation program and such entry does not require inductive signals from stroma. Furthermore, these data suggest that p21 and p27 have distinct roles in regulating the urothelial cell cycle.

Molecular, cellular and developmental biology of urothelium as a basis of bladder regeneration

Urinary bladder malfunction and disorders are caused by congenital diseases, trauma, inflammation, radiation, and nerve injuries. Loss of normal bladder function results in urinary tract infection, incontinence, renal failure, and end-stage renal dysfunction. In severe cases, bladder augmentation is required using segments of the gastrointestinal tract. However, use of gastrointestinal mucosa can result in complications such as electrolyte imbalance, stone formation, urinary tract infection, mucous production, and malignancy. Recent tissue engineering techniques use acellular grafts, cultured cells combined with biodegradable scaffolds, and cell sheets. These techniques are not all currently applicable for human bladder reconstruction. However, new avenues for bladder reconstruction maybe facilitated by a better understanding of urogenital development, the cellular and molecular biology of urothelium, and cell-cell interactions, which modulate tissue repair, homeostasis, and disease progression.

Promising directions for the diagnosis and management of gynecological cancers

Diagnosis and management of cancer requires tools with both high sensitivity and specificity. The minimally invasive cervical smear has demonstrated how a test, even one with low specificity, can change the public health profile of a cancer from a late stage deadly disease to early diagnosis with rare tumor-related deaths. The benefit of such a test is best demonstrated by the low frequency of cervix cancer and its good outcome in countries where this test is readily available and used with appropriate secondary follow up. Early and specific symptoms, and identification and prevention for high risk groups has had similar impact for endometrial cancer. Neither a robust test, nor reliable or specific early symptoms are available for ovarian cancer, making clinical and scientific advances in this area a critical world-wide need. Current approaches testing one protein or gene marker at a time will not address this crisis expeditiously. New sensitive, specific, accurate, and reliable technologies that can be implemented using high throughput mechanisms are needed at as low a cost as possible. Ideally, these technologies should be focused on readily available patient resources, such as blood or urine, or as in the case of cervix cancer, minimally invasive informative approaches such as cervical smears. Techniques that allow data mining from a large input database overcome the slow advances of one protein-one gene investigation, and further address the multi-faceted carcinogenesis process occurring even in germ line mutation-associated malignancy. Proteomics, the study of the cellular proteins and their activation states, has led the progress in biomarker development for ovarian and other cancers and is being applied to management assessment. Amenable to high throughput, internet interface, and representative of the proteome spectrum, proteomic technology is the newest and most promising direction for translational developments in gynecologic cancers.

Urothelium regeneration using viable cultured urothelial cell sheets grafted on demucosalized gastric flaps

OBJECTIVE

To evaluate urothelium regeneration by grafting viable cultured urothelial cell sheets, harvested from temperature-responsive culture surfaces, on demucosalized gastric flaps in a dog model.

MATERIALS AND METHODS

Viable urothelium was obtained from eight beagle dogs by partial cystectomy. Harvested urothelial cells were seeded on temperature-responsive culture dishes modified with the thermally sensitive polymer, poly(N-isopropylacrylamide). Urothelial cells cultured for 3 weeks generated contiguous urothelial cell sheets that were noninvasively harvested with no enzymatic treatment from these dishes, by reducing culture temperature. Urothelial cell sheets were autografted onto surgically demucosalized gastric flaps. Three weeks after autografting the dogs were killed and the gastric flaps with the urothelial cell sheets were examined. Cell and tissue characteristics were compared between these urothelial cell sheet-grafted gastric flaps and native urothelium. Ultrafine structures were also examined by electron microscopy.

RESULTS

Five of the eight urothelial cell sheet-grafted flaps showed viable urothelial regeneration. Urothelial cell sheets attached spontaneously to demucosalized tissue surfaces completely, with no suture or fixing, and developed into a stratified viable epithelium very similar to native urothelium. Regenerated urothelium remained unstained by antiproton pump antibody, which typically stains epithelial cells positively in gastric mucosal layers. On three of the eight flaps where there were severe haematomas, grafted cell sheets were not adherent and there was no urothelial regeneration.

CONCLUSIONS

Urothelial cell sheets were autografted onto dog demucosalized gastric flaps successfully, with no suture or fixation, generating a multilayered urothelium in vivo. The novel intact cell-sheet grafting method rapidly produces native-like epithelium in vivo. This versatile technology should prove useful in urinary tract tissue engineering and surgical reconstruction.

A surgical model of composite cystoplasty with cultured urothelial cells: a controlled study of gross outcome and urothelial phenotype

OBJECTIVES

To study the outcome of composite cystoplasty using cultured urothelial cells combined with de-epithelialized colon or uterus in a porcine surgical model, using appropriate controls, and to characterize the neo-epithelium created by composite cystoplasty.

MATERIALS AND METHODS

Urothelial cells were isolated and propagated in vitro from open bladder biopsies taken from nine female minipigs. Cohesive sheets of confluent urothelial cells were transferred to polyglactin carrier meshes and sutured to de-epithelialized autologous colon in four animals and de-epithelialized autologous uterus in five. These composite segments were then used for augmentation cystoplasty. Conventional colocystoplasty, de-epithelialized colocystoplasty and sham operations were carried out in six control animals. After killing the animals at approximately 90 days the bladders were removed for examination and immunohistochemical analysis, using a panel of antibodies against cytokeratins and urothelial differentiation-associated antigens.

RESULTS

Macroscopically, the bladders augmented with composite segments derived from uterine muscle had no evidence of shrinkage or contracture. Histological analysis showed that in four of five composite uterocystoplasties, the neo-urothelium was stratified and had a transitional morphology, although in some areas coverage was incomplete. Immunohistochemical analysis showed evidence of squamous differentiation in both native and augmented segments. All composite and de-epithelialized colonic segments showed significant contraction with poor urothelial coverage, reflecting the unsuitability of the thin-walled porcine colon for de-epithelialization.

CONCLUSIONS

The functional and macroscopic outcome of bladder augmentation with a composite derived from cultured urothelium and de-epithelialized smooth muscle of uterine origin endorses the feasibility of composite cystoplasty.

Urothlelium Facilitates the Recruitment and Trans-Differentiation of Fibroblasts into Smooth Muscle in Acellular Matrix

PURPOSE

Tissue engineering has shown promise for patients requiring bladder reconstruction secondary to diverse diseases such as spina bifida and tuberculosis. In this study we addressed whether urothelium in conjunction with an acellular bladder matrix is necessary for the recruitment of host cells to repopulate the graft and whether the urothelium facilitates trans-differentiation of host fibroblastic cells into bladder smooth muscle type cells.

MATERIALS AND METHODS

Urothelium from embryonic mice and rats (E18) was microdissected from bladder stroma after enzymatic digestion with 10 mM ethylenediaminetetraacetic acid. Acellular bladder matrix was prepared from postnatal day 1 rat and mouse pups using a combination of membrane disruption and DNA digestion. Urothelium was placed inside the bladder matrix and then grown either underneath the renal capsule or subcutaneously in athymic mice for 2 to 24 weeks. Grafts were sectioned and immunocytochemistry was performed with antibodies for alpha-actin smooth muscle, uroplakin, cytokeratins and vimentin to assess for the development of detrusor muscle.

RESULTS

Embryonic bladder urothelium resulted in ingrowth of fibroblasts into acellular matrix in greater than 85% of 60 grafts consisting of acellular matrix and bladder urothelium. Moreover, there was apparent trans-differentiation of these fibroblasts into a smooth muscle phenotype. This smooth muscle development occurred in a graded, incremental fashion starting as early as 3 weeks and resulting in almost complete repopulation of the matrix at 6 months.

CONCLUSIONS

These data support the hypothesis that epithelial mesenchymal signaling is important for the differentiation of bladder smooth muscle. Smooth muscle development during augmentation with acellular matrix is facilitated by the placement of epithelia onto the surface of the matrix.

The relationship between aging and carcinogenesis: a critical appraisal

The incidence of cancer increases with age in humans and in laboratory animals alike. There are different patterns of age-related distribution of tumors in different organs and tissues. Aging may increase or decrease the susceptibility of various tissues to initiation of carcinogenesis and usually facilitates promotion and progression of carcinogenesis. Aging may predispose to cancer by several mechanisms: (1) tissue accumulation of cells in late stages of carcinogenesis; (2) alterations in homeostasis, in particular, alterations in immune and endocrine system and (3) telomere instability linking aging and increased cancer risk. Increased susceptibility to the effects of tumor promoters is found both in aged animals and aged humans, as predicted by the multistage model of carcinogenesis. Available evidence supporting the relevance of replicative senescence of human cells and telomere biology to human cancer seems quite strong, however, the evidence linking cellular senescence to human aging is controversial and required additional studies. Data on the acceleration of aging by carcinogenic agents as well as on increased cancer risk in patients with premature aging are critically discussed. In genetically modified mouse models (transgenic, knockout or mutant) characterized by the aging delay, the incidence of tumors usually similar to those in controls, whereas the latent period of tumor development is increased. Practically all models of accelerated of aging in genetically modified animals show the increase in the incidence and the reduction in the latency of tumors. Strategies for cancer prevention must include not only measures to minimize exposure to exogenous carcinogenic agents, but also measures to normalize the age-related alterations in internal milieu. Life-span prolonging drugs (geroprotectors) may either postpone population aging and increase of tumor latency or decrease the mortality in long-living individuals in populations and inhibit carcinogenesis. At least some geroprotectors may increase the survival of a short-living individuals in populations but increase the incidence of malignancy.

Surgical management of the neurogenic bladder and bowel

Spina bifida and myelodysplasia are associated with neurogenic abnormalities of the bladder and bowel function. All children with myelodysplasia require an evaluation of their urinary tract with ultrasound and urodynamics to confirm normal bladder and kidney function. Patients with anatomical and functional abnormalities require treatment, the mainstay being intermittent catheterization and anticholinergic medication. The treatment goals for patients with a neurogenic bladder are the preservation of the upper urinary tract, bladder and bowel continence, independence, autonomy, and facilitation of self-esteem. A minority of children will not respond to conservative therapy and will ultimately require surgical intervention. This review will discuss the surgical options for bladder augmentation, bladder neck reconstruction and closure, as well as the methods for the creation of continent catheterizable stomas. The timing, indications, and description for each procedure will be addressed. Finally, the antegrade continence enema procedure will be described for the management of refractory fecal incontinence.

22 week assessment of bladder acellular matrix as a bladder augmentation material in a porcine model

Previous studies on the reconstruction of porcine bladder using bladder acellular matrix allograft (BAMA) have indicated positive preliminary results with respect to graft shrinkage and cellular repopulation. The current study was conducted to investigate the feasibility of using BAMA in a similar model of bladder reconstruction out to longer time frames (22 weeks). At predetermined time points, the macroscopic, histological and mechanical properties of explanted native and BAMA tissues were evaluated and compared. Macroscopically, contracture of the BAMA was observed. The peripheral regions of the grafts experienced extensive cellular repopulation. Towards the centre however, all grafts were consistently devoid of organized smooth muscle bundles and a well-developed urothelium. An alteration in both the amount and organization of collagen was also observed within this region. Significant differences (p < 0.05) in the rupture strain and the elastic modulus of the BAMA compared to native bladder tissue appear to correlate with macroscopic graft contracture as well as the fibroproliferative tissue response of the matrix.

The microenvironment of the tumour-host interface

Throughout the entire process of cancer aetiology, progression and metastasis, the microenvironment of the local host tissue can be an active participant. Invasion occurs within a tumour-host microecology, where stroma and tumour cells exchange enzymes and cytokines that modify the local extracellular matrix, stimulate migration, and promote proliferation and survival. A new class of cancer therapies that targets this pathological communication interface between tumour cells and host cells is currently under development.