MESENCHYMAL-EPITHELIAL INTERACTIONS IN BLADDER SMOOTH MUSCLE DEVELOPMENT: EPITHELIAL SPECIFICITY

Increased Expression of p63 Protein and Sonic Hedgehog Signaling Molecule in Buccal Epithelial Holoclones

Construction of many tissues and organs de novo requires the use of external epithelial cell sources. In the present study, we optimized the isolation, expansion, and characterization of porcine oral epithelial cells from buccal tissue (Buccal Epithelial Cells, BECs). Additionally, we tested whether key markers [cytokeratin 14 (ck14), p63 protein, and sonic hedgehog molecule (shh)] expression profiles are correlated with three buccal epithelial clone types. Two digestion methods of BECs isolation [Method 1, M1 (collagenase IV/dispase and accutase) and Method 2, M2 (collagenase IV/dispase and trypsin/EDTA)] were compared. Cells obtained by more effective method were further cultured to the third passage and analyzed. Holoclone-, meroclone-, and paraclone-like colonies were identified based on BEC morphology. Immunofluorescent staining was performed to compare selected markers for the indicated buccal clone types. Comparative analysis demonstrated the advantage of isolation using M1 over M2. Cells from the third passage exhibited average 92.73% ± 2.27% presence of ck14. Real-time polymerase chain reaction confirmed expression of tested genes [cytokeratin 8 (ck8), ck14, integrin β1, and p63]. The highest level of ck14, shh and p63, was observed for holoclones. The comparable ck14 expression was observed in the mero- and paraclones. Meroclones expressed significantly lower levels of shh compared with paraclones. The weakest p63 expression was observed in the paraclone-like cells. It was demonstrated that holoclones are the richest in shh (+) and p63 (+) stem cells and these cells should appear to be a promising alternative for obtaining epithelial cells for tissue engineering purposes.

An update on clonality: what smooth muscle cell type makes up the atherosclerotic plaque?

Almost 50 years ago, Earl Benditt and his son John described the clonality of the atherosclerotic plaque. This led Benditt to propose that the atherosclerotic lesion was a smooth muscle neoplasm, similar to the leiomyomata seen in the uterus of most women. Although the observation of clonality has been confirmed many times, interest in the idea that atherosclerosis might be a form of neoplasia waned because of the clinical success of treatments for hyperlipemia and because animal models have made great progress in understanding how lipid accumulates in the plaque and may lead to plaque rupture. Four advances have made it important to reconsider Benditt's observations. First, we now know that clonality is a property of normal tissue development. Second, this is even true in the vessel wall, where we now know that formation of clonal patches in that wall is part of the development of smooth muscle cells that make up the tunica media of arteries. Third, we know that the intima, the "soil" for development of the human atherosclerotic lesion, develops before the fatty lesions appear. Fourth, while the cells comprising this intima have been called "smooth muscle cells", we do not have a clear definition of cell type nor do we know if the initial accumulation is clonal. As a result, Benditt's hypothesis needs to be revisited in terms of changes in how we define smooth muscle cells and the quite distinct developmental origins of the cells that comprise the muscular coats of all arterial walls. Finally, since clonality of the lesions is real, the obvious questions are do these human tumors precede the development of atherosclerosis, how do the clones develop, what cell type gives rise to the clones, and in what ways do the clones provide the soil for development and natural history of atherosclerosis?

Development of the human female reproductive tract

Development of the human female reproductive tract is reviewed from the ambisexual stage to advanced development of the uterine tube, uterine corpus, uterine cervix and vagina at 22 weeks. Historically this topic has been under-represented in the literature, and for the most part is based upon hematoxylin and eosin stained sections. Recent immunohistochemical studies for PAX2 (reactive with Müllerian epithelium) and FOXA1 (reactive with urogenital sinus epithelium and its known pelvic derivatives) shed light on an age-old debate on the derivation of vaginal epithelium supporting the idea that human vaginal epithelium derives solely from urogenital sinus epithelium. Aside for the vagina, most of the female reproductive tract is derived from the Müllerian ducts, which fuse in the midline to form the uterovaginal canal, the precursor of uterine corpus and uterine cervix an important player in vaginal development as well. Epithelial and mesenchymal differentiation markers are described during human female reproductive tract development (keratins, homeobox proteins (HOXA11 and ISL1), steroid receptors (estrogen receptor alpha and progesterone receptor), transcription factors and signaling molecules (TP63 and RUNX1), which are expressed in a temporally and spatially dynamic fashion. The utility of xenografts and epithelial-mesenchymal tissue recombination studies are reviewed.

Development of the human bladder and ureterovesical junction

The urinary bladder collects urine from the kidneys and stores it until the appropriate moment for voiding. The trigone and ureterovesical junctions are key to bladder function, by allowing one-way passage of urine into the bladder without obstruction. Embryological development of these structures has been studied in multiple animal models as well as humans. In this report we review the existing literature on bladder development and cellular signalling with particular focus on bladder development in humans. The bladder and ureterovesical junction form primarily during the fourth to eighth weeks of gestation, and arise from the primitive urogenital sinus following subdivision of the cloaca. The bladder develops through mesenchymal-epithelial interactions between the endoderm of the urogenital sinus and mesodermal mesenchyme. Key signalling factors in bladder development include shh, TGF-β, Bmp4, and Fgfr2. A concentration gradient of shh is particularly important in development of bladder musculature, which is vital to bladder function. The ureterovesical junction forms from the interaction between the Wolffian duct and the bladder. The ureteric bud arises from the Wolffian duct and is incorporated into the developing bladder at the trigone. It was previously thought that the trigonal musculature developed primarily from the Wolffian duct, but it has been shown to develop primarily from bladder mesenchyme. Following emergence of the ureters from the Wolffian ducts, extensive epithelial remodelling brings the ureters to their final trigonal positions via vitamin A-induced apoptosis. Perturbation of this process is implicated in clinical obstruction or urine reflux. Congenital malformations include ureteric duplication and bladder exstrophy.

TGFβ-1 and epithelial-mesenchymal interactions promote smooth muscle gene expression in bone marrow stromal cells: Possible application in therapies for urological defects

Purpose

For regenerative and cellular therapies of the urinary tract system, autologous bladder smooth muscle cells (SMCs) have several limitations, including constricted in vitro proliferation capacity and, more importantly, inability to be used in malignant conditions. The use of in vitro (pre-)differentiated multipotential adult progenitor cells may help to overcome the shortcomings associated with primary cells.

Methods

By mimicking environmental conditions of the bladder wall, we investigated in vitro effects of growth factor applications and epithelial-mesenchymal interactions on smooth muscle gene expression and on the morphological appearance of adherent bone marrow stromal cells (BMSCs).

Results

Transcription growth factor beta-1 (TGFβ-1) upregulated the transcription of myogenic gene desmin and smooth muscle actin-γ2 in cultured BMSCs. Stimulatory effects were significantly increased by coculture with urothelial cells. Prolonged stimulation times and epigenetic modifications further enhanced transcription levels, indicating a dose-response relationship. Immunocytochemical staining of in vitro-differentiated BMSCs revealed expression of myogenic protein α-smooth muscle actin and desmin, and changes in morphological appearance from a fusiform convex shape to a laminar flattened shape with filamentous inclusions similar to the appearance of bladder SMCs. In contrast to the TGFβ-1 action, application of vascular endothelial growth factor (VEGF) did not affect the cells.

Conclusions

The combined application of TGFβ-1 and epithelial-mesenchymal interactions promoted in vitro outgrowth of cells with a smooth muscle-like phenotype from a selected adherent murine bone marrow-derived cell population.

Systematic Review to Compare Urothelium Differentiation with Urethral Epithelium Differentiation in Fetal Development, as a Basis for Tissue Engineering of the Male Urethra

BACKGROUND

Tissue-engineered (TE) urethra is desirable in men with urethral disease (stricture or hypospadias) and shortage of local tissue. Although ideally a TE graft would contain urethral epithelium cells, currently, bladder epithelium (urothelium) is widely used, but morphologically different. Understanding the differences and similarities of urothelium and urethral epithelium could help design a protocol for in vitro generation of urethral epithelium to be used in TE grafts for the urethra.

PURPOSE

To understand the development toward urethral epithelium or urothelium to improve TE of the urethra.

METHODS

A literature search was done following PRISMA guidelines. Articles describing urethral epithelium and bladder urothelium development in laboratory animals and humans were selected.

RESULTS

Twenty-nine studies on development of urethral epithelium and 29 studies on development of urothelium were included. Both tissue linings derive from endoderm and although adult urothelium and urethral epithelium are characterized by different gene expression profiles, the signaling pathways underlying their development are similar, including Shh, BMP, Wnt, and FGF. The progenitor of the urothelium and the urethral epithelium is the early fetal urogenital sinus (UGS). The urethral plate and the urothelium are both formed from the p63+ cells of the UGS. Keratin 20 and uroplakins are exclusively expressed in urothelium, not in the urethral epithelium. Further research has to be done on unique markers for the urethral epithelium.

CONCLUSION

This review has summarized the current knowledge about embryonic development of urothelium versus urethral epithelium and especially focuses on the influencing factors that are potentially specific for the eventual morphological differences of both cell linings, to be a basis for developmental or tissue engineering of urethral tissue.

Effects of CYP-Induced Cystitis on Growth Factors and Associated Receptor Expression in Micturition Pathways in Mice with Chronic Overexpression of NGF in Urothelium

We have determined if cyclophosphamide (CYP)-induced cystitis produces additional changes in growth factor/receptors expression in the urinary bladder (urothelium, detrusor) and lumbosacral (L6-S1) dorsal root ganglia (DRG) in a transgenic mouse model with chronic urothelial overexpression of NGF (NGF-OE). Functionally, NGF-OE mice treated with CYP exhibit significant increases in voiding frequency above that observed in control NGF-OE mice (no CYP). Quantitative PCR was used to determine NGF, BDNF, VEGF, and receptors (TrkA, TrkB, p75(NTR)) transcripts expression in tissues from NGF-OE and wild-type (WT) mice with CYP-induced cystitis of varying duration (4 h, 48 h, 8 days). In urothelium of control NGF-OE mice, NGF mRNA was significantly (p ≤ 0.001) increased. Urothelial expression of NGF mRNA in NGF-OE mice treated with CYP (4 h, 48 h, 8 days) was not further increased but maintained with all durations of CYP treatment evaluated. In contrast, CYP-induced cystitis (4 h, 48 h, 8 days) in NGF-OE mice demonstrated significant (p ≤ 0.05) regulation in BDNF, VEGF, TrkA, TrkB, and P75(NTR) mRNA in urothelium and detrusor smooth muscle. Similarly, CYP-induced cystitis (4 h, 48 h, 8 days) in NGF-OE mice resulted in significant (p ≤ 0.05), differential changes in transcript expression for NGF, BDNF, and receptors (TrkA, TrkB, p75(NTR)) in S1 DRG that was dependent on the duration-of CYP-induced cystitis. In general, NGF, BDNF, TrkA, and TrkB protein content in the urinary bladder increased in WT and NGF-OE mice with CYP-induced cystitis (4 h). Changes in NGF, TrkA and TrkB expression in the urinary bladder were significantly (p ≤ 0.05) greater in NGF-OE mice with CYP-induced cystitis (4 h) compared to WT mice with cystitis (4 h). However, the magnitude of change between WT and NGF-OE mice was only significantly (p ≤ 0.05) different for TrkB expression in urinary bladder of NGF-OE mice treated with CYP. These studies are consistent with target-derived NGF and other inflammatory mediators affecting neurochemical plasticity with potential contributions to reflex function of micturition pathways.

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.

Transcriptome of the inner circular smooth muscle of the developing mouse intestine: Evidence for regulation of visceral smooth muscle genes by the hedgehog target gene, cJun

BACKGROUND

Digestion is facilitated by coordinated contractions of the intestinal muscularis externa, a bilayered smooth muscle structure that is composed of inner circular muscles (ICM) and outer longitudinal muscles (OLM). We performed transcriptome analysis of intestinal mesenchyme tissue at E14.5, when the ICM, but not the OLM, is present, to investigate the transcriptional program of the ICM.

RESULTS

We identified 3967 genes enriched in E14.5 intestinal mesenchyme. The gene expression profiles were clustered and annotated to known muscle genes, identifying a muscle-enriched subcluster. Using publically available in situ data, 127 genes were verified as expressed in ICM. Examination of the promoter and regulatory regions for these co-expressed genes revealed enrichment for cJUN transcription factor binding sites, and cJUN protein was enriched in ICM. cJUN ChIP-seq, performed at E14.5, revealed that cJUN regulatory regions contain characteristics of muscle enhancers. Finally, we show that cJun is a target of Hedgehog (Hh), a signaling pathway known to be important in smooth muscle development, and identify a cJun genomic enhancer that is responsive to Hh.

CONCLUSIONS

This work provides the first transcriptional catalog for the developing ICM and suggests that cJun regulates gene expression in the ICM downstream of Hh signaling. Developmental Dynamics 245:614-626, 2016. © 2016 Wiley Periodicals, Inc.

Maintenance of bladder urothelia integrity and successful urothelialization of various tissue-engineered mesenchymes in vitro

Tissue-engineering offers the opportunity to produce hybrid tissues in vitro. The induction of bladder urothelial cells (BUCs) differentiation in vitro has been assessed by several research groups to build bladder models for fundamental studies and clinical applications. However, BUC induction of advanced differentiation in culture remains a challenging task. To reach this goal, optimal culture conditions are required, notably the use of specific additives as well as proper mesenchymal support. The best positive control for BUCs functional state monitoring is native urothelium collected from healthy bladder samples. In order to establish the best culture conditions to maintain and promote BUC differentiated state, native urothelia were cultured on various mesenchymes. Native bladder mesenchymes were used as controls for the maintenance of native urothelia. Histological and ultrastructural analyses showed the necessity to have a cellularized mesenchyme for rapid formation of a pseudostratified urothelium, allowing apical membrane rearrangement of the superficial cells in culture. Taken together, the results strongly suggest that it is possible to conserve the integrity of urothelia in vitro and, thus, potentially use them for eventual clinical applications and pharmacological investigations.

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.

Analysis of the Sonic Hedgehog signaling pathway in normal and abnormal bladder development

In this study, we examined the expression of Sonic Hedgehog, Patched, Gli1, Gli2, Gli3 and Myocardin in the developing bladders of male and female normal and megabladder (mgb-/-) mutant mice at embryonic days 12 through 16 by in situ hybridization. This analysis indicated that each member of the Sonic Hedgehog signaling pathway as well as Myocardin displayed distinct temporal and spatial patterns of expression during normal bladder development. In contrast, mgb-/- bladders showed both temporal and spatial changes in the expression of Patched, Gli1 and Gli3 as well as a complete lack of Myocardin expression. These changes occurred primarily in the outer mesenchyme of developing mgb-/- bladders consistent with the development of an amuscular bladder phenotype in these animals. These results provide the first comprehensive analysis of the Sonic Hedgehog signaling pathway during normal bladder development and provide strong evidence that this key signaling cascade is critical in establishing radial patterning in the developing bladder. In addition, the lack of detrusor smooth muscle development observed in mgb-/- mice is associated with bladder-specific temporospatial changes in Sonic Hedgehog signaling coupled with a lack of Myocardin expression that appears to result in altered patterning of the outer mesenchyme and poor initiation and differentiation of smooth muscle cells within this region of the developing bladder.

Morphological and urodynamic evaluation of urinary bladder wall regeneration: muscles guarantee contraction but not proper function--a rat model research study

BACKGROUND

Numerous studies are ungoing to develop a substitute for the native urinary bladder wall. The principals of tissue engineering approaches to urinary bladder wall augmentation require a favorable environment for smooth muscle regeneration, which is crucial for bladder function. This study was performed to evaluate bone marrow mesenchymal stem cells (BMSC) seeded on to amniotic membranes fixed to Tachosil sponges as grafts for urinary bladder muscle layer augmentation in a syngenic rat model.

MATERIALS AND METHODS

Amniotic membranes seeded with BMSC and covered by Tachosil sponges were implanted as multilayer grafts into nine rats to regenerate the urinary bladder wall. The control group consisted of 12 healthy rats. Urodynamic examinations included contraction, elasticity, compliance, and urinary bladder motor activity. Hematocylin and eosin and Masson's trichrome stains were used to evaluate muscle regeneration; histological data were digitally analyzed with the ImageJ tool.

RESULTS

The area of muscle bundles ranged from 5% to 25% or 32% to 41% in control versus reconstructed bladders, respectively. Among nine animals with reconstructed urinary bladders, urodynamic evaluation revealed bladder motor hyperactivity with regular (n = 4) or irregular (n = 1) storage and voiding phases, as well as proper bladder motor activity with a large bladder capacity (n = 1). No bladder contractility was recorded in one case and large stones developed in two animals, which made functional studies impossible.

CONCLUSIONS

Regenerated smooth muscle cells created an autonomic cell population that was poorly assimilated to the rest of the urinary bladder wall. The histological presence of a regenerated muscle layer did not guarantee proper urinary bladder function.

Transforming growth factor β receptor type 1 is essential for female reproductive tract integrity and function

The transforming growth factor β (TGFβ) superfamily proteins are principle regulators of numerous biological functions. Although recent studies have gained tremendous insights into this growth factor family in female reproduction, the functions of the receptors in vivo remain poorly defined. TGFβ type 1 receptor (TGFBR1), also known as activin receptor-like kinase 5, is the major type 1 receptor for TGFβ ligands. Tgfbr1 null mice die embryonically, precluding functional characterization of TGFBR1 postnatally. To study TGFBR1–mediated signaling in female reproduction, we generated a mouse model with conditional knockout (cKO) of Tgfbr1 in the female reproductive tract using anti-Müllerian hormone receptor type 2 promoter-driven Cre recombinase. We found that Tgfbr1 cKO females are sterile. However, unlike its role in growth differentiation factor 9 (GDF9) signaling in vitro, TGFBR1 seems to be dispensable for GDF9 signaling in vivo. Strikingly, we discovered that the Tgfbr1 cKO females develop oviductal diverticula, which impair embryo development and transit of embryos to the uterus. Molecular analysis further demonstrated the dysregulation of several cell differentiation and migration genes (e.g., Krt12, Ace2, and MyoR) that are potentially associated with female reproductive tract development. Moreover, defective smooth muscle development was also revealed in the uteri of the Tgfbr1 cKO mice. Thus, TGFBR1 is required for female reproductive tract integrity and function, and disruption of TGFBR1–mediated signaling leads to catastrophic structural and functional consequences in the oviduct and uterus.

Approximately 20% of infertile couples in the United States have unexplained causes. Many vital aspects of female fertility are regulated by a family of growth factors called the transforming growth factor β (TGFβ) superfamily. These factors exert their functions via specific receptors and downstream signal mediators. Perturbation of components in this pathway can lead to reproductive dysfunction. We identified a novel role for a TGFβ receptor (called TGFBR1) in female fertility. We demonstrated that female mice with disruption of Tgfbr1 in the reproductive tract are unable to successfully conceive, although they can ovulate and produce fertilizable oocytes. Most importantly, these mice have a striking deformity in the oviduct, marked by the formation of oviductal outpouchings (diverticula) that prevent embryos from reaching the uterus. Concomitant aberrations in the uterine smooth muscle layers are additional features of mice lacking TGFBR1. Therefore, TGFBR1 is critical for the structural integrity and function of the female reproductive tract. Our model can be further exploited to study the development of smooth muscle cells of the female reproductive tract. Genetic mutations in TGFBR1 or other TGFβ signaling machinery may lead to fertility defects in women.

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.

Smooth muscle differentiation and patterning in the urinary bladder

Smooth muscle differentiation and patterning is a fundamental process in urinary bladder development that involves a complex array of local environmental factors, epithelial-mesenchymal interaction, and signaling pathways. An epithelial signal is necessary to induce smooth muscle differentiation in the adjacent bladder mesenchyme. The bladder epithelium (urothelium) also influences the spatial organization of the bladder wall. Sonic hedgehog (Shh), which is expressed by the urothelium, promotes mesenchymal proliferation and induces differentiation of smooth muscle from embryonic bladder mesenchyme. Shh, whose signal is mediated through various transcription factors including Gli2 and BMP4, is likely also important in the patterning of bladder smooth muscle. However, it is not known to what extent early mediators of mesenchymal migration, other Shh-associated transcription factors, and crosstalk between the Shh signaling cascade and other pathways are involved in the patterning of bladder smooth muscle. Here we review the role of epithelial-mesenchymal interaction and Shh signaling in smooth muscle differentiation and patterning in the bladder. We also discuss emerging signaling molecules, transcription factors, and mesenchyme properties that might be fruitful areas of future research in the process of smooth muscle formation in the bladder.

Urothelium-derived Sonic hedgehog promotes mesenchymal proliferation and induces bladder smooth muscle differentiation

Induction of smooth muscle differentiation from bladder mesenchyme depends on signals that originate from the urothelium. We hypothesize Sonic hedgehog (Shh) is the urothelial signal that promotes bladder mesenchymal proliferation and induces bladder smooth muscle differentiation. Pregnant FVB mice were euthanized on embryonic day (E) 12.5 and fetal bladders were harvested. Two experimental protocols were utilized: Specimens were sized by serial sectioning. Cell counts were performed after trypsin digestion. Immunohistochemistry was performed to detect smooth muscle-specific protein expression. alpha-Actin expression was quantified using Western blot. All specimens were viable at 72h. BLM cultured without Shh survived but did not grow or undergo smooth muscle differentiation. IB cultured without Shh and BLM cultured with Shh grew and expressed smooth muscle proteins at 72h. IB cultured with Shh were larger and contained more cells than IB cultured without Shh (all p<0.05). Increasing Shh concentration from 48 to 480nM did not change bladder size, cell counts, or the level of alpha-actin expression. Prior to culture, IB did not express alpha-actin. After culture of IB in Shh-deficient media, alpha-actin was detected throughout the mesenchyme except in the submucosal layer. The IB submucosa was thinner after culture with 48nM Shh and smooth muscle completely obliterated the submucosa after culture with 480nM Shh. In fetal mouse bladders, urothelium-derived Shh is necessary for mesenchymal proliferation and smooth muscle differentiation. Shh concentration affects mesenchymal proliferation and patterning of bladder smooth muscle.

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.

Prostate epithelial cell fate

Androgen receptor (AR) within prostatic mesenchymal cells, with the absence of AR in the epithelium, is still sufficient to induce prostate development. AR in the luminal epithelium is required to express the secretory markers associated with differentiation. Nkx3.1 is expressed in the epithelium in early prostatic embryonic development and expression is maintained in the adult. Induction of the mouse prostate gland by the embryonic mesenchymal cells results in the organization of a sparse basal layer below the luminal epithelium with rare neuroendocrine cells that are interdispersed within this basal layer. The human prostate shows similar glandular organization; however, the basal layer is continuous. The strong inductive nature of embryonic prostatic and bladder mesenchymal cells is demonstrated in grafts where embryonic stem (ES) cells are induced to differentiate and organize as a prostate and bladder, respectively. Further, the ES cells can be driven by the correct embryonic mesenchymal cells to form epithelium that differentiates into secretory prostate glands and differentiated bladders that produce uroplakin. This requires the ES cells to mature into endoderm that gives rise to differentiated epithelium. This process is control by transcription factors in both the inductive mesenchymal cells (AR) and the responding epithelium (FoxA1 and Nkx3.1) that allows for organ development and differentiation. In this review, we explore a molecular mechanism where the pattern of transcription factor expression controls cell determination, where the cell is assigned a developmental fate and subsequently cell differentiation, and where the assigned cell now emerges with it's own unique character.

Terminal Urothelium Differentiation of Engineered Neoureter After In Vivo Maturation in the “Omental Bioreactor”

OBJECTIVE

Long ureteric defects may theoretically be repaired with the use of tissue-engineered neoureter. However, attempts to construct such a neoureter in animal models have failed because of major inflammatory response. Avoidance of such inflammation requires a well-differentiated urothelium. We investigated whether omental maturation of a seeded construct in a pig model could achieve terminal differentiation of the urothelium to allow construction of a stricture-free neoureter.

MATERIAL AND METHOD

Bladder biopsies were taken to allow urothelial and smooth muscle cell cultures. These cultured cells were used to seed small intestinal submucosa (SIS) matrix. After 2 wk of cell growth, the in vitro SIS-seeded construct was shaped around a silicone drain and wrapped by the omentum to obtain neoureters. These neoureters were left in the omentum without any contact with urine, and then harvested 3 wk later for histologic and immunohistochemical studies.

RESULTS

Before implantation, the in vitro constructs were composed of a mono- or bilayer of undifferentiated urothelium overlying a monolayer of smooth muscle cells. After 3 wk of omental maturation, these constructs were vascularized and comprised a terminally differentiated multilayered urothelium with umbrella cells over connective tissue and smooth muscle cells, with no evidence of fibrosis or inflammation.

CONCLUSION

We obtained, for the first time, with this model of in vivo maturation in the omentum, a mature neoureter composed of a well-differentiated multilayered urothelium.

Urothelial Inhibition of Transforming Growth Factor-β in a Bladder Tissue Recombination Model

PURPOSE

We examined the role of transforming growth factor-beta in urothelial and bladder development. Transforming growth factor-beta signaling was attenuated in the urothelial compartment and the subsequent effects were examined in a tissue recombination model.

MATERIALS AND METHODS

Urothelium was cultured from adult rat bladders and transfected with control vector C7Delta or mutant DNIIR (dominant negative transforming growth factor-beta receptor II). Grafts were created by recombining transfected urothelium plus embryonic day 18 bladder mesenchyma and placed beneath the renal capsule of athymic mouse hosts. Grafts were harvested at 21 and 42 days. Final tissues were evaluated with staining and immunohistochemistry using hematoxylin and eosin, Gomori's trichrome strain, broad-spectrum uroplakin, smooth muscle actin-alpha, phosphorylated SMAD2 and Ki67 antigen. Bladder structures were defined as having smooth muscle, suburothelial connective tissue and mature urothelium expressing uroplakin. Urothelial compartment diameters were measured and subcategorized as small--0.10 to 0.40, medium--0.41 to 1.0 and large--greater than 1.1 mm.

RESULTS

At 21 days 14 C7Delta control and 15 DNIIR grafts were evaluated. No bladder tissue was seen in the C7Delta grafts vs 49 in DNIIR tissue, including 30 small, 9 medium and 10 large tissues. At 42 days 14 C7Delta and 12 DNIIR grafts were evaluated. Six bladder structures (5 small and 1 medium) were seen in the C7Delta cohort vs 27 (14 small, 7 medium and 6 large) in the DNIIR group. Immunohistochemical detection of phosphorylated-SMAD2 was significantly attenuated in DNIIR tissue. In addition, Ki67 proliferative indexes were 4.0-fold higher in the DNIIR cohort compared to those in C7Delta tissues.

CONCLUSIONS

We successfully observed that primary urothelium cultures can be genetically manipulated and recombined with undifferentiated mesenchyma to grow bladder tissue. By attenuating transforming growth factor-beta signaling in the urothelium superior bladder tissue growth occurred, suggesting that transforming growth factor-beta is a growth inhibitor in this organ system.

Urothelial sonic hedgehog signaling plays an important role in bladder smooth muscle formation

During bladder development, primitive mesenchyme differentiates into smooth muscle (SM) under the influence of urothelium. The gene(s) responsible for this process have not been elucidated. We propose that the Sonic hedgehog (Shh) signaling pathway is critical in bladder SM formation. Herein, we examine the role of the Shh-signaling pathway during SM differentiation in the embryonic mouse bladder. Genes in the Shh pathway and SM expression in mouse embryonic (E) bladders (E12.5, 13.5, and 14.5) were examined by immunohistochemistry (IHC), in situ hybridization, and reverse transcription polymerase chain reaction (RT-PCR). To examine the effects of disrupting Shh signaling, bladder tissues were isolated at E12.5 and E14.5, that is, before and after bladder SM induction. The embryonic bladders were cultured on membranes floating on medium with and without 10 muM of cyclopamine, an Shh inhibitor. After 3 days, SM expression was examined by assessing the following: SM alpha-actin (SMAA), SM gamma-actin (SMGA), SM-myosin heavy chain (SM-MHC), Patched, GLI1, bone morphogenic protein 4 (BMP4), and proliferating cell nuclear antigen (PCNA) by IHC and RT-PCR. SM-related genes and proteins were not expressed in E12.5 mouse embryonic bladder before SM differentiation, but were expressed by E13.5 when SM differentiation was initiated. Shh was expressed in the urothelium in E12.5 bladders. Shh-related gene expression at E12.5 was significantly higher than at E14.5. In cyclopamine-exposed cultures of E12.5 tissue, SMAA, SMGA, GLI1, and BMP4 gene expression was significantly decreased compared with controls, but PCNA gene expression did not change. In cyclopamine-exposed E14.5 cultures, SMGA and SM-MHC gene expression did not change compared with controls. Using an in vitro embryonic bladder culture model, we were able to define the kinetics of SM- and Shh-related gene expression. Cyclopamine inhibited detrusor SM actin induction, but did not inhibit SM-MHC induction. SMAA and SMGA genes appear to be induced by Shh-signaling pathways, but the SM-MHC gene is not. Based on Shh expression by urothelium and the effects of Shh inhibition on bladder SM induction, we hypothesize that urothelial-derived Shh orchestrates induction of SM in the fetal mouse bladder.

Bladder tissue formation from cultured bladder urothelium

Tissue recombination is a powerful method to evaluate the paracrine-signaling events that orchestrate the development of organs using the in vivo environment of a host rodent. Studies have reported the successful generation of primary cultures of rodent bladder urothelium, but none have reported their use to recapitulate bladder tissue with tissue recombination. We propose that primary cultured bladder urothelium, when recombined with inductive embryonic bladder mesenchyme, will form bladder tissue in a recombination model. Adult rat bladders were isolated and urothelium obtained. Sheets of bladder urothelium were re-suspended in collagen and maintained in tissue culture. After expansion (>20 passages), the urothelium was recombined with embryonic day-14 mouse bladder mesenchyme, then grafted beneath the renal capsule of immunocompromised mouse hosts. Grafts were harvested after 28 days. Control grafts were performed with bladder mesenchyme alone, cultured bladder urothelium alone, and collagen matrix alone. Final tissues were evaluated with staining and immunohistochemistry (H&E, Gomori's trichrome, broad-spectrum uroplakin, and smooth muscle actin alpha and gamma). Immunocytochemistry on cultured urothelium for broad-spectrum keratin, vimentin, and broad-spectrum uroplakin confirmed pure populations, void of mesenchymal contaminants. Staining of recombinant grafts demonstrated bladder tissue with mature urothelium and stromal differentiation. Control tissues were void of bladder tissue formation. We have successfully demonstrated that a chimeric bladder is formed from primary cultured bladder urothelium recombined with embryonic bladder mesenchyme. This is a powerful new tool for investigating the molecular mechanisms of bladder development and disease. Future applications may include the in vitro genetic manipulation of urothelium and examining those effects on growth and development in an in vivo environment.

Stem cells for regeneration of urological structures

OBJECTIVES

This review focuses on advances in regenerative therapies using stem cells in urology.

METHODS

A detailed literature search was performed using the PubMed database of the National Center of Biotechnology Information. Publications of experimental investigations and clinical trials using stem cells in reconstructive urology have been summarized and critically reviewed.

RESULTS

Tissue engineering and autologous cell therapy techniques have been developed to generate prostheses for different urological tissues and organ systems. During the last decade, increasing numbers of studies have described stem cells in the context of therapeutic tools. The ability of adult and embryonic stem cells as well as progenitors to improve bladder wall architecture, improve renal tubule formation, or promote restoration of spermatogenesis or recovery of continence has been investigated in several animal models. Although results have been encouraging, only a myoblast-based therapy of incontinence has reached clinical trials.

CONCLUSIONS

Several populations of adult stem cells and progenitor cells have been studied as useful cellular sources in the treatment and reconstruction of urological organs. However, considerable basic research still needs to be performed to ensure the controlled differentiation and long-term fate of stem cells following transplantation.

Directed differentiation of embryonic stem cells into bladder tissue

Manipulatable models of bladder development which interrogate specific pathways are badly needed. Such models will allow a systematic investigation of the multitude of pathologies which result from developmental defects of the urinary bladder. In the present communication, we describe a model in which mouse embryonic stem (ES) cells are directed to differentiate to form bladder tissue by specific interactions with fetal bladder mesenchyme. This model allows us to visualize the various stages in the differentiation of urothelium from ES cells, including the commitment to an endodermal cell lineage, with the temporal profile characterized by examining the induction of specific endodermal transcription factors (Foxa1 and Foxa2). In addition, final functional urothelial differentiation was characterized by examining uroplakin expression. It is well established that ES cells will spontaneously develop teratomas when grown within immunocompromised mouse hosts. We determined the specific mesenchymal to ES cell ratios necessary to dictate organ-specific differentiation while completely suppressing teratomatous growth. Embryonic mesenchyme is well established as an inductive tissue which dictates organ-specific programming of epithelial tissues. The present study demonstrates that embryonic bladder mesenchyme can also steer ES cells towards developing specific endodermal derived urothelium. These approaches allow us to capture specific stages of stem cell differentiation and to better define stem cell hierarchies.

Serum response factor, its cofactors, and epithelial-mesenchymal signaling in urinary bladder smooth muscle formation

Little is known about the mechanism of bladder smooth muscle differentiation. We hypothesize that epithelial-mesenchymal signaling induces the expression of smooth muscle proteins in bladder mesenchyme resulting in smooth muscle differentiation. We confirmed that smooth muscle differentiation in the mouse urinary bladder occurs first at gestational day 14 (E14) based upon immunohistochemical localization of smooth muscle alpha-actin (SMAA). To investigate murine bladder smooth muscle differentiation and epithlelial-mesenchymal signaling in the developing bladder, we analyzed gene expression profiles of intact embryonic murine bladders and separated epithelial and mesenchymal components at embryonic days E13, E14, E15, E16, and postnatal day 1 (P1). Using cDNA microarray, we identified regulators of vascular smooth muscle differentiation in bladder mesenchyme, including serum response factor (SRF) and its cofactors, ELK1 and SRF accessory protein (SAP)1, as well as two SRF-associated pathways, angiotension receptor II and transforming growth factor- beta2. Immunohistochemistry showed diffuse expression of SRF in the bladder at E12 with localization of expression to the peripheral mesenchyme at E13 and E14. Our results suggest that bladder smooth muscle differentiation may share a similar gene expression program as occurs during vascular smooth muscle differentiation. The unique structure of the urinary bladder makes it an ideal model for studies of smooth muscle differentiation and epithelial-mesenchymal signaling.

Constructing a Tissue-Engineered Ureter Using a Decellularized Matrix with Cultured Uroepithelial Cells and Bone Marrow-Derived Mononuclear Cells

This study investigated the efficacy of the ureteral decellularized matrix (UDM) as a scaffold material for a tissue-engineered ureter, and the effect of bone marrow-derived mononuclear cells (BM-MNC) on the neovascularization of the scaffold. Canine ureters were treated with deoxycholic acid to remove all cells. Uroepithelial cells (UEC) were obtained from canine bladders, cultured, and then seeded onto the inner surface of the UDM before transplantation into the subcutaneous space of nude mice or the omentum of nude rats. The cultured UECs began showing vacuolar degeneration 3 days after transplantation and gradually disappeared thereafter. To facilitate neovascularization in the implant, BM-MNCs were seeded around the UDM before transplantation. This facilitated the survival of the UECs, which formed three to five cellular layers after 14 days. The mean microvessel density was significantly increased in tissues seeded with BM-MNCs. However, cell-tracking experiments revealed that the increased number of capillaries in the experimental group was not due to the direct differentiation of transplanted endothelial progenitor cells. Our results demonstrate that the UDM is a useful scaffold for a tissue-engineered ureter, especially when seeded with BM-MNCs to enhance angiogenesis.

Structural changes of smooth muscle in congenital ureteropelvic junction obstruction

BACKGROUND/PURPOSE

Ureteropelvic junction (UPJ) obstruction is the most common cause of congenital hydronephrosis. Previous studies have reported that the excess amount of collagen restricting mobility and resiliency of the UPJ is the result of an impaired collagen production by anomalous smooth muscle cells (SMCs). Our purpose was to evaluate the role of SMC differentiation in the pathogenesis of UPJ obstruction.

METHODS

Surgical specimens of UPJ from 21 patients (8 girls/13 boys) who were subjected to dismembered pyeloplasty were examined immunohistochemically using monoclonal antibodies against smooth muscle (SM) myosin heavy chain isoforms including SM1, SM2, and SMemb. The age ranged from 1 month to 13 years. Ureteropelvic walls taken from 14 forensic autopsy cases, with no urological abnormalities, served as age-matched control group.

RESULTS

The immunohistochemical expression of SM1 and SM2 in UPJ obstruction was significantly increased when compared with controls (P < .05). In contrast, there was no statistical difference of expression of SMemb.

CONCLUSION

Our findings supported the hypothesis that the primary anomaly in UPJ obstruction may be attributed to a malfunction of SMCs in the ureter.

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.

Bowel imbrication in the management of anorectal anomalies

Four patients who had imbrication of their proximal rectum and distal sigmoid colon as part of the management of constipation following an anorectoplasty for an anorectal anomaly. Three children with an anorectal anomaly presented with constipation and marked dilation of the rectosigmoid portion of the large bowel; each had longitudinal imbrication of the dilated segment, via a left iliac fossa incision. The forth was born with a cloacal anomaly with associated colonic atresia. The small bowel was used to construct the anorectum following a redo anorectoplasty. Subsequently, the small bowel became ectatic, resulting in the patient developing persistent watery diarrhoea and severe perianal excoriation, which was managed with a 30 cm longitudinal imbrication of the distal bowel during an extensive laparotomy. All 4 have patients now have near normal bowel motions with minimal medication, after only a short hospital stay. Residual problematic dilatation of the rectosigmoid colon in patients with a high anorectal anomaly, in the presence of constipation, can be successfully managed by imbrication of the dilated segment, if carefully selected.

Creation of luminal tissue covered with urothelium by implantation of cultured urothelial cells into the peritoneal cavity

PURPOSE

We established the culture condition of seeding urothelial cells onto a scaffold for implantation into the peritoneal cavity and evaluated the histology of implanted urothelial cells.

MATERIALS AND METHODS

In part 1 of the study cultured porcine bladder urothelial cells were seeded onto 3 types of collagen gel made on microporous membrane, including collagen gel with or without cultured porcine bladder fibroblasts, or a feeder layer. The macroscopic and microscopic appearance of the gel with urothelial cells were examined in vitro. As an in vivo study, cultured porcine bladder urothelial cells were seeded onto a collagen gel/sponge matrix with or without cultured fibroblasts, or a feeder layer. Urothelial cell survival on each matrix was evaluated 28 days after implantation onto the omentum or mesentery of nude rats. In part 2 of the study rat urothelial cells were cultured and seeded onto fibrin gel/atelocollagen sponge matrix as an autologous implantation model. After 7 days of cultivation the matrix was folded with urothelial cells inside, implanted onto the mesentery and serially evaluated.

RESULTS

Gel containing cultured fibroblasts was shrunken and basement membrane formation was observed on the gel with cultured fibroblasts or the feeder layer in vitro. Urothelial cells cultured with the feeder layer better survived on the collagen based matrix and formed a hollow-like lumen when implanted into the peritoneal cavity. The regenerated urothelium in an autologous implantation showed the same histological features as normal bladder urothelium.

CONCLUSIONS

Selection of less degradable matrix and formation of basement membrane are critical for survival of implanted urothelial cells. The regenerated urothelium in an autologous implantation model seems to have the similar properties to the normal urothelium.

Evidence that bone morphogenetic protein 4 has multiple biological functions during kidney and urinary tract development

BACKGROUND

We have suggested that bone morphogenetic protein 4 (BMP4), acting on the Wolffian duct and ureter epithelium, determines the budding site of the ureter by locally antagonizing ubiquitous inductive signal(s) from the metanephric mesenchyme. In the present study, we examine the effect of BMP4 on the development of metanephric and periureteral mesenchymal cells, which express the BMP type I receptor gene, Bmpr1a (Alk3).

METHODS

Urogenital tissues obtained from Bmp4 heterozygous null mutant (Bmp4+/-) embryos at different stages, and metanephric and ureteral tissue explants cultured in the presence of recombinant BMP4 were subjected to morphologic, immunohistochemical and in situ hybridization analyses. To examine the chemotactic activity of BMP4 for periureteral mesenchymal cells, a modified Boyden chamber assay was performed.

RESULTS

Many of the kidneys of newborn Bmp4+/- mice contained multicystic dysplastic regions. This morphology was preceded by abnormally high apoptotic activity in the metanephric mesenchyme of mutant embryos at E14.5. In whole metanephric explants, BMP4 uniformly promoted the expansion of the Pax2-negative and weakly Foxd1 (previously Bf2) -positive peripheral stromal compartment of metanephric mesenchyme in the presence of fibroblast growth factor 2 (FGF2). In addition, in isolated metanephric mesenchyme, BMP4-loaded beads prevented apoptosis locally. Thus, BMP4 prevents cell death and promotes the growth of the metanephric mesenchyme. The effect of BMP4 on periureteral mesenchyme is different from its effect on metanephric mesenchyme. In utero, periureteral mesenchymal cells condense around the ureter epithelium, followed by differentiation into smooth muscle cells at a site where Bmp4 is intensely expressed. Analysis of Bmp4+/- ureters at E15.5 reveals that the alpha-smooth muscle actin (alpha-SMA)-positive cells are low in number. In vitro, BMP4-loaded beads promote the accumulation of periureteral mesenchymal cells to form several cell layers surrounding the beads. In addition, in a Boyden chamber assay, BMP4 increases the migration of periureteral mesenchymal cells through the filter. Thus, BMP4 can serve as a chemoattractant for periureteral mesenchymal cells and induce locally the smooth muscle layer of the ureter at Bmp4-expressing sites.

CONCLUSION

Depending on local context, BMP4 has several biological actions on the morphogenesis of different portions of the excretory system, namely, the development of the ureterovesical junction, the ureter, and the kidney.

Changes of phenotypic expression of prostatic antigen in secondary transitional cell carcinoma of the prostate: evidence for induction phenomenon as a mechanism for acquisition of prostatic antigens in prostatic transitional cell carcinoma

BACKGROUND

In vitro and experimental studies of mesenchymal-epithelial interaction for the prostatic stroma have demonstrated that the prostatic stroma is capable of inducing the nonprostatic epithelium to acquire many features of prostatic epithelium. We investigated whether this phenomenon could be observed in vivo in human prostatic stroma. MATERIALS AND METHODS Sixty transitional cell carcinoma (TCC) of the urinary bladder: (a) 20 with glandular lumen; (b) 20 without glandular lumen: (c) 10 mixed TCC-adenocarcinoma (ACA); and (d) 10 with synchronous or metachronous TCC of the prostate; and three primary TCC of the prostate were examined and submitted for immunostaining for prostatic acid phosphatase (PAP) and prostatic specific antigen (PSA).

RESULTS

There was a spectrum of immunostaining for PSA ranging from negative reactivity in TCC without glandular lumen of the urinary bladder, to focal and weak reactivity in single cells with varying degrees of nonmucinous glandular differentiation and to strong reactivity in groups of cells in primary and synchronous or metachronous TCC in the prostate. The areas of carcinoma geographically closest to the prostate and with the most extensive nonmucinous glandular differentiation displayed the most frequent and strongest immunoreactivity for PSA. The immunoreactivity for PAP was usually stronger than for PSA. Four cases of TCC and mixed TCC-ACA were immunoreactive only for PAP. Furthermore, there was a change in the phenotype of TCC in the urinary bladder as it spread into the prostate. For 10 TCC in the urinary bladder with synchronous or metachronous tumor in the prostate, all TCC in the urinary bladder were negative for PAP and PSA, whereas six TCC in the prostate were focally positive.

CONCLUSIONS

The spectrum of immunoreactivity for PAP and PSA and the change in immunoreactivity of TCC of the urinary bladder as it spreads into the prostate are likely induced by the prostatic stroma through the mechanism of mesenchymal-epithelial interaction. Prostate 47:172-182, 2001.

Ontogeny of bladder agenesis in rats induced by adriamycin

OBJECTIVES

To determine the anatomical steps leading to bladder agenesis in rats prenatally exposed as fetuses on gestational days (GD) 6-9 to adriamycin.

MATERIALS AND METHODS

Timed-pregnant Sprague-Dawley rats were injected intraperitoneally with adriamycin at 2 mg/kg (n = 28) on GD 6-9 (vaginal plug = day 0). The control group (n = 21) received saline. Fetuses were harvested on GD 10, 11, 12, 13, 14, 15 and 16. Serial paraffin sections were prepared from a minimum of 10 experimental and five control fetuses at each gestational age, and stained with either trichrome or haematoxylin and eosin, and examined by light microscopy.

RESULTS

In the control group the urorectal septum first became visible and the mesonephric ducts apparently abutting the anterior cloaca on GD 12. The presumptive urinary bladder was clearly defined on GD 14. On GD 15, the common excretory ducts became incorporated into the newly formed urogenital sinus and the ureters opened into the bladder. In the treated animals, beginning on GD 11, the undivided cloaca was noticeably smaller and by GD 13-14, the vesical extension of the urogenital sinus was conspicuously absent. Instead, opposite ureters joined to drain directly into the proximal blind-ending urethra or the persistent distal urogenital sinus.

CONCLUSIONS

Prenatal exposure of rat fetuses to adriamycin resulted in primary agenesis rather than secondary resorption of the bladder. The ontogeny showed that the mechanism underpinning bladder development is unique and is under the influence of factors that can be targeted by adriamycin. Further work will elucidate the unique nature of bladder organogenesis and should have important applications in future research into artificial bladders.

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

The present study tests the hypothesis that heterotypic stromal-epithelial interactions cause phenotypic changes in urothelium. The rational for the experimental design is to simulate heterotypic stromal-epithelial interactions that are created at the anastomotic site of intestinal-bladder augmentations and internal urinary diversions where the urothelium is in direct contact with the gastro-intestinal tract tissues. Tissue recombination experiments were performed by combining 14-day embryonic rat and mouse rectal mesenchyme with urothelium from embryonic, newborn, and adult mice or rats. All tissue recombinants were grown beneath the renal capsule of athymic mouse hosts for 6-16 weeks. Analyses were performed to detect expression of uroplakins, cytokeratin 7, 14, 19 and mucin secreting epithelial cells via Periodic Acid-Schiff (PAS). The phenotype of both mouse and rat urothelium was changed to a glandular morphology under the influence of rectal mesenchyme. Immunohistochemical staining revealed a loss of the urothelial specific uroplakins and cytokeratins 7, 14, and 19 (characteristic of urothelium). Histologic analysis revealed the presence of mucin secreting glandular structures which stained positive for PAS. The urothelial transdifferentiation into glandular epithelium was not a function of epithelial age and occurred in the embryonic, newborn and adult urothelium. Likewise, rectal mesenchyme from embryonic, neonatal, and adult animals was able to induce glandular differentiation in bladder epithelium. Urothelium exhibits the plasticity to change into an intestinal like epithelium as a result of mesenchymal/stromal stimulation from the gastro-intestinal tract. This experimental result is germane to heterotypic stromal-epithelial interactions that are created in patients with urinary tract reconstructions (intestinal augmentations, de-mucosalized urothelial lined bladder patches, and internal urinary diversion such as ureterosigmoidostomies). We propose that heterotypic stromal-epithelial interactions may play a role in determining histodifferentiation of urothelial cells at the anastomotic site between bowel and bladder tissue in patients with gastro-intestinal urothelial reconstructions.

Coculture of bladder urothelial and smooth muscle cells on small intestinal submucosa: potential applications for tissue engineering technology

PURPOSE

Small intestinal submucosa is a xenogenic, acellular, collagen rich membrane with inherent growth factors that has previously been shown to promote in vivo bladder regeneration. We evaluate in vitro use of small intestinal submucosa to support the individual and combined growth of bladder urothelial cells and smooth muscle cells for potential use in tissue engineering techniques, and in vitro study of the cellular mechanisms involved in bladder regeneration.

MATERIALS AND METHODS

Primary cultures of human bladder urothelial cells and smooth muscle cells were established using standard enzymatic digestion or explant techniques. Cultured cells were then seeded on small intestinal submucosa at a density of 1 x 105 cells per cm.2, incubated and harvested at 3, 7, 14 and 28 days. The 5 separate culture methods evaluated were urothelial cells seeded alone on the mucosal surface of small intestinal submucosa, smooth muscle cells seeded alone on the mucosal surface, layered coculture of smooth muscle cells seeded on the mucosal surface followed by urothelial cells 1 hour later, sandwich coculture of smooth muscle cells seeded on the serosal surface followed by seeding of urothelial cells on the mucosal surface 24 hours later, and mixed coculture of urothelial cells and smooth muscle cells mixed and seeded together on the mucosal surface. Following harvesting at the designated time points small intestinal submucosa cell constructs were formalin fixed and processed for routine histology including Masson trichrome staining. Specific cell growth characteristics were studied with particular attention to cell morphology, cell proliferation and layering, cell sorting, presence of a pseudostratified urothelium and matrix penetrance. To aid in the identification of smooth muscle cells and urothelial cells in the coculture groups, immunohistochemical analysis was performed with antibodies to alpha-smooth muscle actin and cytokeratins AE1/AE3.

RESULTS

Progressive 3-dimensional growth of urothelial cells and smooth muscle cells occurred in vitro on small intestinal submucosa. When seeded alone urothelial cells and smooth muscle cells grew in several layers with minimal to no matrix penetration. In contrast, layered, mixed and sandwich coculture methods demonstrated significant enhancement of smooth muscle cell penetration of the membrane. The layered and sandwich coculture techniques resulted in organized cell sorting, formation of a well-defined pseudostratified urothelium and multilayered smooth muscle cells with enhanced matrix penetration. With the mixed coculture technique there was no evidence of cell sorting although matrix penetrance by the smooth muscle cells was evident. Immunohistochemical studies demonstrated that urothelial cells and smooth muscle cells maintain the expression of the phenotypic markers of differentiation alpha-smooth muscle actin and cytokeratins AE1/AE3.

CONCLUSIONS

Small intestinal submucosa supports the 3-dimensional growth of human bladder cells in vitro. Successful combined growth of bladder cells on small intestinal submucosa with different seeding techniques has important future clinical implications with respect to tissue engineering technology. The results of our study demonstrate that there are important smooth muscle cell-epithelial cell interactions involved in determining the type of in vitro cell growth that occurs on small intestinal submucosa. Small intestinal submucosa is a valuable tool for in vitro study of the cell-cell and cell-matrix interactions that are involved in regeneration and various disease processes of the bladder.

Diffusable growth factors induce bladder smooth muscle differentiation

Bladder smooth muscle differentiation is dependent on the presence of bladder epithelium. Previously, we have shown that direct contact between the epithelium and bladder mesenchyme (BLM) is necessary for this interaction. In this study, we tested the hypothesis that bladder smooth muscle can be induced via diffusable growth factors. Fourteen-day embryonic rat bladders were separated into bladder mesenchyme (prior to smooth muscle differentiation) and epithelium by enzymatic digestion and microdissection. Six in vitro experiments were performed with either direct cellular contact or no contact (1) 14-d embryonic bladder mesenchyme (BLM) alone (control), (Contact) (2) 14-d embryonic bladders intact (control), (3) 14-d embryonic bladder mesenchyme combined with BPH-1 cells (an epithelial prostate cell line) in direct contact, (4) 14-d embryonic bladder mesenchyme with recombined bladder epithelium (BLE) in direct contact, (No Contact) (5) 14-d embryonic bladder mesenchyme with BPH-1 prostatic epithelial cells cocultured in type 1 collagen gel on the bottom of the well, and (6) 14-d embryonic bladder mesenchyme with BPH-1 epithelium cultured in a monolayer on a transwell filter. In each case the bladder tissue was cultured on Millicell-CM 0.4-microm membranes for 7 d in plastic wells using serum free medium. Growth was assessed by observing the size of the bladder organoids in histologic cross section as well as the vertical height obtained in vitro. Immunohistochemical analysis of the tissue explants was performed to assess cellular differentiation with markers for smooth muscle alpha-actin and pancytokeratin to detect epithelial cells. Control (1) bladder mesenchyme grown alone did not exhibit growth or smooth muscle and epithelial differentiation. Contact experiments (2) intact embryonic bladder, (3) embryonic bladder mesenchyme recombined with BPH-1 cells, and (4) embryonic bladder mesenchyme recombined with urothelium each exhibited excellent growth and bladder smooth muscle and epithelial differentiation. Both noncontact experiments (5) and (6) exhibited growth as well as bladder smooth muscle and epithelial differentiation but to a subjectively lesser degree than the contact experiments. Direct contact of the epithelium with bladder mesenchyme provides the optimal environment for growth and smooth muscle differentiation. Smooth muscle growth and differentiation can also occur without direct cell to cell contact and is not specific to urothelium. This data supports the hypothesis that epithelium produces diffusable growth factors that induce bladder smooth muscle.

BMP-4 affects the differentiation of metanephric mesenchyme and reveals an early anterior-posterior axis of the embryonic kidney

Bone morphogenetic protein-4 (BMP4), a member of the transforming growth factor-beta (TGF-beta) family, regulates several developmental processes during animal development. We have now studied the effects of BMP-4 in the metanephric kidney differentiation by using organ culture technique. Human recombinant BMP-4 diminishes the number of ureteric branches and changes the branching pattern. Our data suggest that BMP-4 affects the ureteric branching indirectly via interfering with the differentiation of the nephrogenic mesenchyme. The clear positional preference of the defects to posterior mesenchyme might reflect an early anterior-posterior patterning of the metanephric mesenchyme. The smooth muscle alpha-actin expressing cell population around the ureteric stalk, highly expressing Bmp-4 mRNA, is also expanded in kidneys treated with BMP-4. Thus, BMP-4 may be a physiological regulator of the development of the periureteric smooth muscle layer and ureteric elongation.

Understanding bladder regeneration: smooth muscle ontogeny

PURPOSE

We determined the origin of smooth muscle cells in acellular bladder matrix grafts.

MATERIALS AND METHODS

A total of 15 female Sprague-Dawley rats underwent partial cystectomy and grafting with an acellular matrix derived from rat bladder. The grafts were examined 1, 2, 3 and 4 weeks after grafting by immunohistochemical studies for smooth muscle markers and by transmission electron microscopy for smooth muscle morphology. Bladder matrix and bladder epithelium recombinants were created and grafted subcutaneously and under the renal capsule in nude mice. Recombinants were examined 1, 2, 3 and 4 weeks postoperatively by immunohistochemical studies for bladder epithelium and bladder smooth muscle.

RESULTS

Smooth muscle ingrowth into acellular matrix was initially seen at 2 weeks. The immunohistochemical and electron microscopic characteristics of the cells were similar to those of fetal smooth muscle 2 weeks and newborn smooth muscle 4 weeks after grafting. Matrix epithelium recombinants displayed mature bladder epithelium with 3 to 7 layers but they did not support the ingrowth of smooth muscle cells.

CONCLUSIONS

Mature bladder smooth muscle cells undergo dedifferentiation, migration and redifferentiation to repopulate an acellular matrix graft. It is unlikely that adult fibroblasts from the surrounding tissue are induced by epithelium and matrix to form smooth muscle. The contractile behavior of bladder substitute materials likely reflects the properties of the host bladder.