Fibroblast growth factor-10 is a mitogen for urothelial cells

Distinct effects of Fgf7 and Fgf10 on the terminal differentiation of murine bladder urothelium revealed using an organoid culture system

BACKGROUND

Dysregulation of the terminal differentiation of bladder urothelium is associated with the pathogenesis of urinary tract disorders. Fibroblast growth factor (Fgf)7 and Fgf10 stimulate urothelial proliferation; however, their roles in cellular differentiation remain unclear. In this study, we used an organoid system to investigate the roles of these Fgfs in regulating bladder urothelium differentiation and identify their distribution patterns in the mouse bladder.

METHODS

Adult bladder epithelia (AdBE) isolated from adult mouse bladder tissues (AdBTs) were used to culture adult bladder organoids (AdBOs) in the presence of Fgf7 and Fgf10. The differentiation status of the cells in AdBTs, AdBEs, AdBOs, and neonatal bladder tissues (NeoBTs) was analyzed via quantitative real-time-PCR for the presence of undifferentiated cell markers (Krt5, Trp63, and Krt14) and differentiated cell markers (Krt20, Upk1a, Upk2, and Upk3a). Organoid cell proliferation was assessed by counting cell numbers using the trypan blue method. The effects of Fgf7 and Fgf10 on organoid differentiation were assessed using different doses of Fgfs, and the involvement of peroxisome proliferator-activated receptor γ (PPARγ) signaling in these processes was tested by introducing a PPARγ agonist (Rosiglitazone) and antagonist (T0070907) to the culture. The expression patterns of Fgf7 and Fgf10 were examined via in situ hybridization of AdBTs.

RESULTS

AdBOs showed higher expression of undifferentiated cell markers and lower expression of differentiated cell markers than AdBTs, NeoBTs, and AdBEs, indicating the relatively immature state of AdBOs. Differentiation of AdBOs was enhanced by Rosiglitazone and Fgf7, suggesting an interplay of intracellular signals between Fgf7 and PPARγ. Co-addition of T0070907 suppressed Fgf7-mediated differentiation, demonstrating that PPARγ is activated downstream of Fgf7 to promote cellular differentiation into umbrella cells. Furthermore, we found that Fgf7 is predominantly expressed in the umbrella cells of the urothelium, whereas Fgf10 is predominantly expressed in the urothelium and stroma of AdBTs.

CONCLUSIONS

We demonstrated that unlike Fgf10, Fgf7 induces cellular differentiation via PPARγ activity and has a unique tissue distribution pattern in the adult bladder. Further studies on the Fgf7-PPARγ signaling axis would provide insights into the differentiation mechanisms toward functional umbrella cells and the pathogenesis of several urinary tract diseases.

Growth factor dependence of the proliferation and survival of cultured lacrimal gland epithelial cells isolated from late-embryonic mice

Epidermal growth factor (EGF) and hepatocyte growth factor (HGF) regulate the growth and morphogenesis of various exocrine glands with branched morphologies. Their roles in lacrimal gland (LG) development remain unknown, but fibroblast growth factor (FGF) 10 is crucial for early LG organogenesis. To clarify the roles of EGF, HGF, and FGF10 in LG development, LG epithelial cells were isolated from late-embryonic and neonatal mice; cultured; and treated with EGF, HGF, or FGF10 and their respective receptor tyrosine kinase (RTK) inhibitors AG1478, PHA665752, or SU5402. EGF and HGF increased the number of viable cells by enhancing DNA synthesis, FGF10 and SU5402 showed no such effect, and RTK inhibitors exhibited the opposite effect. EGF and HGF receptors were immunostained in cultured late-embryonic LG epithelial cells and terminal LG acini from late embryos and adult mice. HGF was detected in neonatal LG epithelial cell culture supernatants by western blotting. In the absence of EGF and HGF RTK inhibitors, growth factor addition increased the number of viable cells and suppressed cell death. However, when one RTK was inhibited and a growth factor targeting an intact RTK was added, the number of dead cells increased as the number of viable cells increased. No cells survived when both RTKs were inhibited. In explant cultures of LGs from embryos, AG1478 or PHA665752 decreased the number of Ki67-positive proliferating epithelial cells in terminal acini. Thus, EGF and HGF may function in a cooperative autocrine manner, supporting cell proliferation and survival during LG development in late-embryonic and neonatal mice.

FGFR2 signaling enhances the SHH-BMP4 signaling axis in early ureter development

The patterned array of basal, intermediate and superficial cells in the urothelium of the mature ureter arises from uncommitted epithelial progenitors of the distal ureteric bud. Urothelial development requires signaling input from surrounding mesenchymal cells, which, in turn, depend on cues from the epithelial primordium to form a layered fibro-muscular wall. Here, we have identified FGFR2 as a crucial component in this reciprocal signaling crosstalk in the murine ureter. Loss of Fgfr2 in the ureteric epithelium led to reduced proliferation, stratification, intermediate and basal cell differentiation in this tissue, and affected cell survival and smooth muscle cell differentiation in the surrounding mesenchyme. Loss of Fgfr2 impacted negatively on epithelial expression of Shh and its mesenchymal effector gene Bmp4. Activation of SHH or BMP4 signaling largely rescued the cellular defects of mutant ureters in explant cultures. Conversely, inhibition of SHH or BMP signaling in wild-type ureters recapitulated the mutant phenotype in a dose-dependent manner. Our study suggests that FGF signals from the mesenchyme enhance, via epithelial FGFR2, the SHH-BMP4 signaling axis to drive urothelial and mesenchymal development in the early ureter.

Association of fibroblast growth factor 10 with the fibrotic and inflammatory pathogenesis of Graves' orbitopathy

Purpose

The role of fibroblast growth factor (FGF) in orbital fibroblasts (OFs) is rarely known. In this study, we investigated the effect of FGF10 on fibrosis and the inflammation mechanism of Graves′ orbitopathy (GO).

Methods

Orbital tissue from GO (n = 15) and non-GO (n = 15) was obtained for this study. The mRNA and protein expression levels of FGF10 and FGF receptor 2b (FGFR2b) in orbital tissue were determined by real-time polymerase chain reaction, western blot analysis, and confocal microscopy. The effects of FGF10 on transforming growth factor (TGF)-β1 induced fibrotic proteins and interleukin (IL)-1β- or tumor necrosis factor (TNF)-α- induced inflammatory proteins were investigated using recombinant human (rh) FGF10 and small interfering (si) RNA transfection against FGF10.

Results

FGF10 and FGFR2b mRNA expression levels were significantly lower in GO orbital tissues than in non-GO orbital tissues (p = 0.009 and 0.005, respectively). Immunostaining of FGF10 in orbital adipose tissues showed differences in FGF10 expression between GO and control samples. Immunostaining of FGF10 was very weak in the orbital tissues of GO patients. TGF-β1-induced fibronectin, collagen Iα, α-smooth muscle actin protein expression in GO OFs was attenuated by rhFGF10 treatment and increased by knockdown of FGF10 via siFGF10 transfection. Similarly, IL-1β- or TNF-α-induced IL-6, IL-8, and cyclooxygenase-2 protein production in GO OFs was either blocked by rhFGF10 treatment or further upregulated by inhibition of FGF10 via siFGF10 transfection.

Conclusions

Our data demonstrate that FGF10 has beneficial effects on the inflammatory and fibrotic mechanisms of GO in primary cultured OFs, providing new insights into GO pathology and the discovery of FGF10 as a promising novel therapeutic application for the treatment of GO.

Loss of Fibroblast Growth Factor Receptor 2 (FGFR2) Leads to Defective Bladder Urothelial Regeneration after Cyclophosphamide Injury

Cyclophosphamide may cause hemorrhagic cystitis and eventually bladder urothelial cancer. Genetic determinants for poor outcomes are unknown. We assessed actions of fibroblast growth factor receptor (FGFR) 2 in urothelium after cyclophosphamide exposure. Conditional urothelial deletion of Fgfr2 (Fgfr2KO) did not affect injury severity or proliferation of keratin 14⁺ (KRT14⁺) basal progenitors or other urothelial cells 1 day after cyclophosphamide exposure. Three days after cyclophosphamide exposure, Fgfr2KO urothelium had defective regeneration, fewer cells, larger basal cell bodies and nuclei, paradoxical increases in proliferation markers, and excessive replication stress versus controls. Fgfr2KO mice had evidence of pathologic basal cell endoreplication associated with absent phosphorylated ERK staining and decreased p53 expression versus controls. Mice with conditional deletion of Fgfr2 in urothelium enriched for KRT14⁺ cells reproduced Fgfr2KO abnormalities after cyclophosphamide exposure. Fgfr2KO urothelium had defects up to 6 months after injury versus controls, including larger basal cells and nuclei, more persistent basal and ectopic lumenal KRT14⁺ cells, and signs of metaplasia (attenuated E-cadherin staining). Mice missing one allele of Fgfr2 also had (less severe) regeneration defects and basal cell endoreplication 3 days after cyclophosphamide exposure versus controls. Thus, reduced FGFR2/ERK signaling apparently leads to abnormal urothelial repair after cyclophosphamide exposure from pathologic basal cell endoreplication. Patients with genetic variants in FGFR2 or its ligands may have increased risks of hemorrhagic cystitis or urothelial cancer from persistent and ectopic KRT14⁺ cells.

High HNRNPA3 expression is associated with lymph node metastasis and poor prognosis in patients treated with radical cystectomy

OBJECTIVE

We sought to identify heterogeneous nuclear ribonucleoprotein A3 (HNRNPA3) expression in bladder cancer and its relationship to clinicopathological findings and prognosis.

METHODS

Immunohistochemical staining for HNRNPA3 was performed on 122 archived radical cystectomy specimens, with immunoreactivity being stratified on a 0 to 3 scale. The percentage of HNRNPA3 expressing tumor cells was calculated and multiplied by the staining score over an average of 5 areas to obtain a semiquantitative H-score (maximum value: 300). HNRNPA3 expression was categorized as high (≥80) or low (<80).

RESULTS

The patients' median age was 70 years, and the median follow-up period was 39.4 months. High HNRNPA3 expression was significantly associated with lymph node metastasis (P= 0.014) and S100A8, S100A9 and uroplakin III expression (P= 0.028, 0.002, and 0.047, respectively). Log-rank tests indicated that high HNRNPA3 expression was significantly associated with disease progression and cancer-specific death (P= 0.013 and 0.006, respectively). In the Cox proportional hazards regression analysis, only lymph node metastasis was associated with disease progression and cancer-specific survival.

CONCLUSION

HNRNPA3 may be a new biomarker to predict biologically aggressive cancers and determine the appropriate treatment modality in patients after radical cystectomy.

Application of Adult and Pluripotent Stem Cells in Interstitial Cystitis/Bladder Pain Syndrome Therapy: Methods and Perspectives

Interstitial cystitis/bladder pain syndrome (IC/BPS) is a multifactorial, chronic disease without definite etiology characterized by bladder-related pelvic pain. IC/BPS is associated with pain that negatively affects the quality of life. There are various therapeutic approaches against IC/BPS. However, no efficient therapeutic agent against IC/BPS has been discovered yet. Urothelium dysfunction is one of the key factors of IC/BPS-related pathogenicity. Stem cells, including adult stem cells (ASCs) and pluripotent stem cells (PSCs), such as embryonic stem cells (ESCs) and induced PSCs (iPSCs), possess the abilities of self-renewal, proliferation, and differentiation into various cell types, including urothelial and other bladder cells. Therefore, stem cells are considered robust candidates for bladder regeneration. This review provides a brief overview of the etiology, pathophysiology, diagnosis, and treatment of IC/BPS as well as a summary of ASCs and PSCs. The potential of ASCs and PSCs in bladder regeneration via differentiation into bladder cells or direct transplantation into the bladder and the possible applications in IC/BPS therapy are described in detail. A better understanding of current studies on stem cells and bladder regeneration will allow further improvement in the approaches of stem cell applications for highly efficient IC/BPS therapy.

Overactivity or blockade of transforming growth factor-β each generate a specific ureter malformation

Transforming growth factor-β (TGFβ) has been reported to be dysregulated in malformed ureters. There exists, however, little information on whether altered TGFβ levels actually perturb ureter development. We therefore hypothesised that TGFβ has functional effects on ureter morphogenesis. Tgfb1, Tgfb2 and Tgfb3 transcripts coding for TGFβ ligands, as well as Tgfbr1 and Tgfbr2 coding for TGFβ receptors, were detected by quantitative polymerase chain reaction in embryonic mouse ureters collected over a wide range of stages. As assessed by in situ hybridisation and immunohistochemistry, the two receptors were detected in embryonic urothelia. Next, TGFβ1 was added to serum-free cultures of embryonic day 15 mouse ureters. These organs contain immature smooth muscle and urothelial layers and their in vivo potential to grow and acquire peristaltic function can be replicated in serum-free organ culture. Such organs therefore constitute a suitable developmental stage with which to define roles of factors that affect ureter growth and functional differentiation. Exogenous TGFβ1 inhibited growth of the ureter tube and generated cocoon-like dysmorphogenesis. RNA sequencing suggested that altered levels of transcripts encoding certain fibroblast growth factors (FGFs) followed exposure to TGFβ. In serum-free organ culture exogenous FGF10 but not FGF18 abrogated certain dysmorphic effects mediated by exogenous TGFβ1. To assess whether an endogenous TGFβ axis functions in developing ureters, embryonic day 15 explants were exposed to TGFβ receptor chemical blockade; growth of the ureter was enhanced, and aberrant bud-like structures arose from the urothelial tube. The muscle layer was attenuated around these buds, and peristalsis was compromised. To determine whether TGFβ effects were limited to one stage, explants of mouse embryonic day 13 ureters, more primitive organs, were exposed to exogenous TGFβ1, again generating cocoon-like structures, and to TGFβ receptor blockade, again generating ectopic buds. As for the mouse studies, immunostaining of normal embryonic human ureters detected TGFβRI and TGFβRII in urothelia. Collectively, these observations reveal unsuspected regulatory roles for endogenous TGFβ in embryonic ureters, fine-tuning morphogenesis and functional differentiation. Our results also support the hypothesis that the TGFβ up-regulation reported in ureter malformations impacts on pathobiology. Further experiments are needed to unravel the intracellular signalling mechanisms involved in these dysmorphic responses. © 2019 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Directed differentiation of human induced pluripotent stem cells into mature stratified bladder urothelium

For augmentation or reconstruction of urinary bladder after cystectomy, bladder urothelium derived from human induced pluripotent stem cells (hiPSCs) has recently received focus. However, previous studies have only shown the emergence of cells expressing some urothelial markers among derivatives of hiPSCs, and no report has demonstrated the stratified structure, which is a particularly important attribute of the barrier function of mature bladder urothelium. In present study, we developed a method for the directed differentiation of hiPSCs into mature stratified bladder urothelium. The caudal hindgut, from which the bladder urothelium develops, was predominantly induced via the high-dose administration of CHIR99021 during definitive endoderm induction, and this treatment subsequently increased the expressions of uroplakins. Terminal differentiation, characterized by the increased expression of uroplakins, CK13, and CK20, was induced with the combination of Troglitazone + PD153035. FGF10 enhanced the expression of uroplakins and the stratification of the epithelium, and the transwell culture system further enhanced such stratification. Furthermore, the barrier function of our urothelium was demonstrated by a permeability assay using FITC-dextran. According to an immunohistological analysis, the stratified uroplakin II-positive epithelium was observed in the transwells. This method might be useful in the field of regenerative medicine of the bladder.

Mouse and human urothelial cancer organoids: A tool for bladder cancer research

Bladder cancer is a common malignancy that has a relatively poor outcome. Lack of culture models for the bladder epithelium (urothelium) hampers the development of new therapeutics. Here we present a long-term culture system of the normal mouse urothelium and an efficient culture system of human bladder cancer cells. These so-called bladder (cancer) organoids consist of 3D structures of epithelial cells that recapitulate many aspects of the urothelium. Mouse bladder organoids can be cultured efficiently and genetically manipulated with ease, which was exemplified by creating genetic knockouts in the tumor suppressors Trp53 and Stag2. Human bladder cancer organoids can be derived efficiently from both resected tumors and biopsies and cultured and passaged for prolonged periods. We used this feature of human bladder organoids to create a living biobank consisting of bladder cancer organoids derived from 53 patients. Resulting organoids were characterized histologically and functionally. Organoid lines contained both basal and luminal bladder cancer subtypes based on immunohistochemistry and gene expression analysis. Common bladder cancer mutations like TP53 and FGFR3 were found in organoids in the biobank. Finally, we performed limited drug testing on organoids in the bladder cancer biobank.

Regulation of FGF10 Signaling in Development and Disease

Fibroblast Growth Factor 10 (FGF10) is a multifunctional mesenchymal-epithelial signaling growth factor, which is essential for multi-organ development and tissue homeostasis in adults. Furthermore, FGF10 deregulation has been associated with human genetic disorders and certain forms of cancer. Upon binding to FGF receptors with heparan sulfate as co-factor, FGF10 activates several intracellular signaling cascades, resulting in cell proliferation, differentiation, and invasion. FGF10 activity is modulated not only by heparan sulfate proteoglycans in the extracellular matrix, but also by hormones and other soluble factors. Despite more than 20 years of research on FGF10 functions, context-dependent regulation of FGF10 signaling specificity remains poorly understood. Emerging modes of FGF10 signaling regulation will be described, focusing on the role of FGF10 trafficking and sub-cellular localization, heparan sulfate proteoglycans, and miRNAs. Systems biology approaches based on quantitative proteomics will be considered for globally investigating FGF10 signaling specificity. Finally, current gaps in our understanding of FGF10 functions, such as the relative contribution of receptor isoforms to signaling activation, will be discussed in the context of genetic disorders and tumorigenesis.

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.

FGFR2IIIb-MAPK Activity Is Required for Epithelial Cell Fate Decision in the Lower Müllerian Duct

Cell fate of lower Müllerian duct epithelium (MDE), to become uterine or vaginal epithelium, is determined by the absence or presence of ΔNp63 expression, respectively. Previously, we showed that SMAD4 and runt-related transcription factor 1 (RUNX1) were independently required for MDE to express ΔNp63. Here, we report that vaginal mesenchyme directs vaginal epithelial cell fate in MDE through paracrine activation of fibroblast growth factor (FGF) receptor-MAPK pathway. In the developing reproductive tract, FGF7 and FGF10 were enriched in vaginal mesenchyme, whereas FGF receptor 2IIIb was expressed in epithelia of both the uterus and vagina. When Fgfr2 was inactivated, vaginal MDE underwent uterine cell fate, and this differentiation defect was corrected by activation of MEK-ERK pathway. In vitro, FGF10 in combination with bone morphogenetic protein 4 and activin A (ActA) was sufficient to induce ΔNp63 in MDE, and ActA was essential for induction of RUNX1 through SMAD-independent pathways. Accordingly, inhibition of type 1 receptors for activin in neonatal mice induced uterine differentiation in vaginal epithelium by down-regulating RUNX1, whereas conditional deletion of Smad2 and Smad3 had no effect on vaginal epithelial differentiation. In conclusion, vaginal epithelial cell fate in MDE is induced by FGF7/10-MAPK, bone morphogenetic protein 4-SMAD, and ActA-RUNX1 pathway activities, and the disruption in any one of these pathways results in conversion from vaginal to uterine epithelial cell fate.

Epithelial-Mesenchymal Interactions in Urinary Bladder and Small Intestine and How to Apply Them in Tissue Engineering

Reciprocal interactions between the epithelium and mesenchyme are essential for the establishment of proper tissue morphology during organogenesis and tissue regeneration as well as for the maintenance of cell differentiation. With this review, we highlight the importance of epithelial-mesenchymal cross talk in healthy tissue and further discuss its significance in engineering functional tissues in vitro. We focus on the urinary bladder and small intestine, organs that are often compromised by disease and are as such in need of research that would advance effective treatment or tissue replacement. To date, the understanding of epithelial-mesenchymal reciprocal interactions has enabled the development of in vitro biomimetic tissue equivalents that have provided many possibilities in treating defective, damaged, or even cancerous tissues. Although research of the past several years has advanced the field of bladder and small intestine tissue engineering, one must be aware of its current limitations in successfully and above all safely introducing tissue-engineered constructs into clinical practice. Special attention is in particular needed when treating cancerous tissues, as initially successful tumor excision and tissue reconstruction may later on result in cancer recurrence due to oncogenic signals originating from an altered stroma. Recent rather poor outcomes in pioneering clinical trials of bladder reconstructions should serve as a reminder that recreating a functional organ to replace a dysfunctional one is an objective far more difficult to reach than initially foreseen. When considering effective tissue engineering approaches for diseased tissues in humans, it is imperative to introduce animal models with dysfunctional or, even more importantly, cancerous organs, which would greatly contribute to predicting possible complications and, hence, reducing risks when translating to the clinic.

Urothelial differentiation of human amniotic fluid stem cells by urothelium specific conditioned medium

Human amniotic fluid stem cells (HAFSCs) have a high proliferative capacity and a good differentiation potential, and may thus be suitable for regenerative medicine. To date, urothelial differentiation mechanisms of HAFSCs are poorly understood. We have investigated the urothelial differentiation potential of HAFSCs so that they can be therapeutically applied to cure defective diseases of bladder. To induce the stem cell differentiation, HAFSCs were cultured in a bladder cancer-derived conditioned medium. After 2 weeks of culture, HAFSCs began to express the urothelial lineage-specific markers (UPII, CK8 and FGF10). Meanwhile, pluripotency markers (Oct-4, Sox-2 and Nanog) were downregulated at both RNA and protein levels in the differentiated HAFSCs. Immunocytochemistry data revealed that differentiated HAFSCs expressed urothelial markers of UPII and CK8. We have screened the receptor tyrosine kinase arrays with the differentiated HAFSCs. The screening showed that MuSK, Tie-1 and EphA4 receptor tyrosine kinases were upregulated, whereas EphA7 and FGF R1 kinases were downregulated in HAFSCs. The data suggest that HAFSCs can be an important urothelium cell source, which can be used for urinary tract engineering.

Coordinated activity of Spry1 and Spry2 is required for normal development of the external genitalia

Development of the mammalian external genitalia is controlled by a network of signaling molecules and transcription factors. Because FGF signaling plays a central role in this complicated morphogenetic process, we investigated the role of Sprouty genes, which are important intracellular modulators of FGF signaling, during embryonic development of the external genitalia in mice. We found that Sprouty genes are expressed by the urethral epithelium during embryogenesis, and that they have a critical function during urethral canalization and fusion. Development of the genital tubercle (GT), the anlage of the prepuce and glans penis in males and glans clitoris in females, was severely affected in male embryos carrying null alleles of both Spry1 and Spry2. In Spry1(-/-);Spry2(-/-) embryos, the internal tubular urethra was absent, and urothelial morphology and organization was abnormal. These effects were due, in part, to elevated levels of epithelial cell proliferation in Spry1(-/-);Spry2(-/-) embryos. Despite changes in overall organization, terminal differentiation of the urothelium was not significantly affected. Characterization of the molecular pathways that regulate normal GT development confirmed that deletion of Sprouty genes leads to elevated FGF signaling, whereas levels of signaling in other cascades were largely preserved. Together, these results show that levels of FGF signaling must be tightly regulated during embryonic development of the external genitalia in mice, and that this regulation is mediated in part through the activity of Sprouty gene products.

Bladder cancer cell in co-culture induces human stem cell differentiation to urothelial cells through paracrine FGF10 signaling

Fibroblast growth factor 10 (FGF10) is required for embryonic epidermal morphogenesis including brain development, lung morphogenesis, and initiation of limb bud formation. In this study, we investigated the role of FGF10 as a lead induction factor for stem cell differentiation toward urothelial cell. To this end, human multipotent stem cell in vitro system was employed. Human amniotic fluid stem cells were co-cultured with immortalized bladder cancer lines to induce directed differentiation into urothelial cells. Urothelial markers, uroplakin II, III, and cytokeratin 8, were monitored by RT-PCR, immunocytochemistry, and Western blot analysis. Co-cultured stem cells began to express uroplakin II, III, and cytokeratin 8. Targeted FGF10 gene knockdown from bladder cancer cells abolished the directed differentiation. In addition, when FGF10 downstream signaling was blocked with the Mek inhibitor, the co-culture system lost the capacity to induce urothelial differentiation. Exogenous addition of recombinant FGF10 protein promoted stem cell differentiation into urothelium cell lineage. Together, this report suggests that paracrine FGF10 signaling stimulates the differentiation of human stem cell into urothelial cells. Current study provides insight into the potential role of FGF10 as a lead growth factor for bladder regeneration and its therapeutic application for bladder transplantation.

Involvement of the WNT and FGF signaling pathways in non-isolated anorectal malformations: sequencing analysis of WNT3A, WNT5A, WNT11, DACT1, FGF10, FGFR2 and the T gene

Anorectal malformations (ARMs) comprise a broad spectrum of anomalies, including anal atresia, congenital anal fistula and persistence of the cloaca. Research suggests that genetic factors play an important role in ARM development. However, few genetic variants have been identified. Embryogenesis is orchestrated by crosstalk of the wingless-type MMTV integration site family (WNT) and fibroblast growth factor (FGF) signaling pathways in a process that involves several intracellular cascades. Studies in mice have implicated several genes from these pathways in the etiology of ARMs. We performed sequencing analysis of seven of these previously reported genes in 78 patients with ARMs occurring within the context of at least one additional congenital anomaly. No associations were identified with variants in WNT3A, WNT5A, WNT11, DACT1, FGF10 or the T gene. In the FGFR2 gene, three novel heterozygous nucleotide substitutions were identified. Further investigations, including the study of family members, revealed that these variants were not causally related to the phenotype in the present ARM cohort. Mutations in the seven investigated genes may nonetheless be a cause of ARMs in rare cases. However, further studies should consider genes encoding other proteins in the WNT/FGF signaling pathways as possible candidates.

Nuclear translocation of FGF8 and its implication to induce Sprouty2

Fibroblast growth factor 8 (FGF8) functions as a local organizing signal for the tectum and cerebellum. FGF8 activates Ras-ERK signaling pathway to induce cerebellar development. We paid attention to the difference in the expression pattern of the molecules that are induced by FGF8 in the mid-hind brain region during normal development and after FGF8 misexpression; some are expressed in the area corresponding to the ERK activation domain but the others are expressed corresponding to the Fgf8 expression domain. Since some of the FGF family members are localized in the nucleus, we wondered if FGF8 could localize in the nuclei and function in the nucleus. We first show that in cultured NIH3T3 cells transfected FGF8b could localize in the nucleus. Transfected FGF8b could also localize in the nucleus of the cells in the chick neural tube. In mouse embryonic neural tube, we detected endogenous FGF8 in the nuclei. Implantation of an FGF8b-soaked bead showed that exogenous FGF8b could be translocated to the nuclei in the isthmus. Furthermore, signal-peptide-deletion mutant of FGF8b mainly localized in the nuclei, and induced Sprouty2 without activating ERK in the mesencephalon. Signal-peptide-deletion mutant of FGF8b could not induce Pax2 expression. Taken together, we concluded that FGF8b could be translocated to the nuclei, and that the nuclear FGF8 could function as transcriptional regulator to induce Sprouty2 in the isthmus.

Dual sources of vitronectin in the human lower urinary tract: synthesis by urothelium vs. extravasation from the bloodstream

Vitronectin (VN), secreted into the bloodstream by liver hepatocytes, is known to anchor epithelial cells to basement membranes through interactions with cell surface integrin receptors. We report here that VN is also synthesized by urothelial cells of urothelium in vivo and in vitro. In situ hybridization, dideoxy sequencing, immunohistochemistry, and ELISA of urothelial cell mRNA, cDNA, tissue, and protein extracts demonstrated that the VN gene is active in vivo and in vitro. The expression of VN by urothelium is hypothesized to constitute one of several pathways that anchor basal cells to an underlying substratum and explains why urothelial cells adhere to glass and propagate under serum-free conditions. Therefore, two sources of VN in the human urinary bladder are recognized: 1) localized synthesis by urothelial cells and 2) extravasation of liver VN through fenestrated capillaries. When human plasma was fractionated by denaturing heparin affinity chromatography, VN was isolated in a biologically active form that supported rapid spreading of urothelial cells in vitro under serum-free conditions. This activity was inhibited by the matricellular protein SPARC via direct binding of VN to SPARC through a Ca(+2)-dependent mechanism. A novel form of VN, isolated from the same heparin affinity chromatography column and designated as the VN(c) chromatomer, also supported cell spreading but failed to interact with SPARC. Therefore, the steady-state balance among urothelial cells, their extracellular milieu, and matricellular proteins constitutes a principal mechanism by which urothelia are anchored to an underlying substrata in the face of constant bladder cycling.

Fibroblast growth factor-10 signals development of von Brunn's nests in the exstrophic bladder

von Brunn's nests have long been recognized as precursors of benign lesions of the urinary bladder mucosa. We report here that von Brunn's nests are especially prevalent in the exstrophic bladder, a birth defect that predisposes the patient to formation of bladder cancer. Cells of von Brunn's nest were found to coalesce into a stratified, polarized epithelium which surrounds itself with a capsule-like structure rich in types I, III, and IV collagen. Histocytochemical analysis and keratin profiling demonstrated that nested cells exhibited a phenotype similar, but not identical, to that of urothelial cells of transitional epithelium. Immunostaining and in situ hybridization analysis of exstrophic tissue demonstrated that the FGF-10 receptor is synthesized and retained by cells of von Brunn's nest. In contrast, FGF-10 is synthesized and secreted by mesenchymal fibroblasts via a paracrine pathway that targets basal epithelial cells of von Brunn's nests. Small clusters of 10pRp cells, positive for both FGF-10 and its receptor, were observed both proximal to and inside blood vessels in the lamina propria. The collective evidence points to a mechanism where von Brunn's nests develop under the control of the FGF-10 signal transduction system and suggests that 10pRp cells may be the original source of nested cells.

Identification of a bladder cancer-specific ligand using a combinatorial chemistry approach

OBJECTIVES

To develop bladder cancer-specific ligands using a combinatorial chemistry approach.

MATERIALS AND METHODS

We performed a high-throughput one-bead one-compound combinatorial chemistry approach to identify ligands that bound to bladder transitional cell carcinoma cells. The whole-cell binding assay allowed successful identification of a few peptides that bound selectively to bladder cancer cells. Single cell suspensions derived from clinical bladder cancer specimens and cell lines were used to determine the binding specificity. Studies with mouse xenografts were performed to determine the in vivo binding and targeting efficiency, specificity, and biodistribution of one of the ligands.

RESULTS

One cyclic peptide named PLZ4 (amino acid sequence: cQDGRMGFc) was identified that could selectively bind to bladder cancer cell lines and all of the 5 primary bladder cancer cells from human patients, but not to normal urothelial cells, cell mixtures from normal bladder specimens, fibroblasts, and blood cells. Comparison of PLZ4 binding to cell lines of different cancer origins showed that it was bladder cancer-specific (P < 0.05). PLZ4 could bind to tumor cells treated with urine at pH 6.0, but not to noncancerous cells collected from the urine of 4 patients actively being treated with intravesical Bacillus Calmette-Guerin therapy. In vivo and ex vivo imaging studies showed that PLZ4 linked to Cy5.5 fluorescent dye administered via tail vein injection was specifically taken up in mouse xenografts developed from excised fresh human bladder cancer specimens. Several ligands contain the same DGR motif, but only PLZ4 was bladder cancer-specific. We performed alanine walk and rainbow bead coding experiments, and found that the C-terminal GF residues were also important for cell binding and modulated the binding specificity.

CONCLUSIONS

PLZ4 has the potential to be used for targeted therapy and imaging detection during diagnosis and follow-up/surveillance of noninvasive and advanced bladder cancer.

Thr-114 is an important functional residue of fibroblast growth factor 10 identified by structure-based mutational analysis

Fibroblast growth factor 10 (FGF10) plays important roles in vertebrate limb development, lung branching morphogenesis, and epidermis regeneration. The receptor (FGFR2b) binding specificity is an essential element in regulating the diverse functions of FGF10. Analyzing the FGF10:FGFR2b complex we found that Thr-114 in beta4 of FGF10 could form specific interactions with D3 of FGFR2b. To investigate the role of Thr-114 played on functions of FGF10, two mutants of FGF10 were constructed, named TA (Thr-114-->Ala) and TR (Thr-114-->Arg), respectively. The biological activity assays showed that the receptor-binding affinity, the stimulating growth effect on rat tracheal epithelium (RTE) cells, and the inducing ability in receptor phosphorylation of both mutants were decreased, which were consistent with the interaction analysis of the TA:FGFR2b and TR:FGFR2b complexes. These results suggested that Thr-114 is a crucial functional residue for FGF10, and mutating Thr-114 to Ala or Arg would lead to great decrease in receptor-binding affinity and biological activity of FGF10.

Construction and characterization of a high activity mutant of human keratinocyte growth factor-2

Keratinocyte growth factor-2 (KGF-2) plays an important role in vertebrate limb development, lung branching morphogenesis, regeneration and reconstruction of the epidermis. Previous studies have used the wild type factor. Here, we have constructed a double-site mutant of human KGF-2, named STEA. STEA possesses higher receptor binding affinity and promotes better proliferation activity on rat tracheal epithelium (RTE) cells than recombinant human KGF-2. These results suggest that the simultaneous mutation of Ser115 to Thr and Glu117 to Ala improves the biological activity of KGF-2.

Investigation of FGF10 as a candidate gene in patients with anorectal malformations and exstrophy of the cloaca

The spectrum of anorectal malformations (ARM) comprises anal stenosis, ectopic anus, recto-urogenital fistula, persistent cloaca, multisystem VACTERL (VATER associations including cardiac and limb anomalies) associations, and exstrophy of the cloaca (CE). The latter also constitutes the most severe form of the bladder exstrophy epispadias complex. Since recent data revealed that fibroblast growth factor 10 (fgf-10) invalidation in mice resulted in a genetically reproducible urorectal defect, we considered FGF10 a suitable candidate gene for ARM and CE, as the protein seems to be involved in the development of this primary developmental field. A total of 20 patients (ten with ARM and VACTERL association, respectively, and ten with CE) were analysed for genomic mutations in the coding regions and exon-intron boundaries of FGF10. Aside from a common FGF10 variant no deviation from the wild-type sequence could be detected and data obtained is not supportive of FGF10 as a genetic cause of ARMs or CE in the patients investigated. Nonetheless, mutations in possibly further upstream located promoter regions and/or unknown regulatory sequences or non-coding regions cannot be excluded. Furthermore, it cannot be ruled out that other genes involved in the signalling pathway of FGF10 may contribute to the formation of these congenital malformations.

Translocation of fibroblast growth factor-10 and its receptor into nuclei of human urothelial cells

Fibroblast growth factor-10 (FGF-10), a mitogen for the epithelial cells lining the lower urinary tract, has been identified inside urothelial cells, despite its acknowledged role as an extracellular signaling ligand. Recombinant (r)FGF-10 was determined by fluorescence microscopy optical sectioning to localize strongly to nuclei inside cultured urothelial cells. To clarify the possible role of a nuclear localization signal (NLS) in this translocation, a variant of rFGF-10 was constructed which lacked this sequence. rFGF-10(no NLS) was found in cytoplasm to a far greater degree than rFGF-10, identifying this motif as a possible NLS. Furthermore, this variant displayed poor or non-existent bioactivity compared to the wild-type protein in triggering mitogenesis in quiescent urothelial cells. The presence of rFGF-10(no NLS) in the nucleus suggested that additional interactions were also responsible for the nuclear accumulation of rFGF-10. The FGF-10 receptor was observed in cell nuclei regardless of the presence or concentration of exogenous rFGF-10 ligand. Co-localization studies between rFGF-10 and the FGF-10 receptor revealed a strong intracellular relationship between the two. This co-localization was seen in nuclei for both rFGF-10 and for rFGF-10(no NLS), although the correlation was weaker for rFGF-10(no NLS). These data show that an NLS-like motif of rFGF-10 is a partial determinant of its intracellular distribution and is necessary for its mitogenic activity. These advancements in the understanding of the activity of FGF-10 present an opportunity to engineer the growth factor as a therapeutic agent for the healing of damaged urothelial tissue.

Abnormal expression of differentiation related proteins and proteoglycan core proteins in the urothelium of patients with interstitial cystitis

PURPOSE

Expression of the proteoglycan core proteins biglycan, decorin, perlecan and syndecan-1, and differentiation related markers of keratins 18 and 20 were examined to determine the origins of the loss of the glycosaminoglycan layer and investigate more fully the altered differentiation of the urothelium in interstitial cystitis.

MATERIALS AND METHODS

Formalin fixed biopsies from 27 patients with interstitial cystitis and 5 controls were immunohistochemically labeled for the described proteins and scored using a modification of previous scoring for other markers. Inflammation was scored from hematoxylin and eosin stained slides. By combining previous with new data, cluster analysis showed the relationships among the markers and samples.

RESULTS

Interstitial cystitis specimens clustered into 4 groups, ranging from most biomarkers abnormal to most biomarkers normal, but all clustered separately from normal controls. One group of interstitial cystitis specimens mainly showed aberrant expression of E-cadherin, which might represent an early abnormality. The biomarkers fell into 2 major groupings. One group consisted of chondroitin sulfate, perlecan, biglycan, decorin and the tight junction protein ZO-1. A second cluster consisted of uroplakin, the epithelial marker keratin 18 and 20, and the morphology of the layer. E-cadherin and syndecan-1 showed little relation to the other 2 clusters or to each other. Inflammation correlated moderately with syndecan-1 but to no other marker.

CONCLUSIONS

Findings strongly suggest abnormal differentiation in the interstitial cystitis urothelium with a loss of barrier function markers and altered differentiation markers being independent and occurring independently of inflammation. Loss of the glycosaminoglycan layer was associated with a loss of biglycan and perlecan on the luminal layer.

Extracellular matrix protein coatings for facilitation of urothelial cell attachment

Synthetic urothelium is an important goal for the tissue-engineering field that would have great utility for treating diseases and congenital defects affecting the urinary tract. A key step in the development of synthetic tissue is optimizing the conditions for coating biomaterials with cells of interest. Initial cell attachment is an important consideration when designing tissue-engineering scaffolds. The scaffold environment must also be conducive to cell proliferation and differentiation. The most popular materials for tissue-engineering scaffold often have suboptimal properties when analyzed for cell attachment and growth. It would then be of interest to know, for urinary tract tissue-engineering applications, which extracellular matrix protein coatings can facilitate urothelial cell attachment and encourage growth. Cells grown on 96-well cycloolefin plates coated with type IV or type I collagen exhibited improved initial attachment over plates coated with fibronectin or laminin. After 20 h, deoxyribonucleic acid synthesis was found to increase in cultures grown on type IV collagen, fibronectin, and laminin. Total metabolic activity of urothelial cell cultures was also monitored, and no difference was seen between any protein-coating conditions. The development of such reliable assays will be beneficial in monitoring the fate of scaffolds seeded with human urothelial cells.

Compensatory paracrine mechanisms that define the urothelial response to injury in partial bladder outlet obstruction

Diseases and conditions affecting the lower urinary tract are a leading cause of dysfunctional sexual health, incontinence, infection, and kidney failure. The growth, differentiation, and repair of the bladder's epithelial lining are regulated, in part, by fibroblast growth factor (FGF)-7 and -10 via a paracrine cascade originating in the mesenchyme (lamina propria) and targeting the receptor for FGF-7 and -10 within the transitional epithelium (urothelium). The FGF-7 gene is located at the 15q15-q21.1 locus on chromosome 15 and four exons generate a 3.852-kb mRNA. Five duplicated FGF-7 gene sequences that localized to chromosome 9 were predicted not to generate functional protein products, thus validating the use of FGF-7-null mice as an experimental model. Recombinant FGF-7 and -10 induced proliferation of human urothelial cells in vitro and transitional epithelium of wild-type and FGF-7-null mice in vivo. To determine the extent that induction of urothelial cell proliferation during the bladder response to injury is dependent on FGF-7, an animal model of partial bladder outlet obstruction was developed. Unbiased stereology was used to measure the percentage of proliferating urothelial cells between obstructed groups of wild-type and FGF-7-null mice. The stereological analysis indicated that a statistical significant difference did not exist between the two groups, suggesting that FGF-7 is not essential for urothelial cell proliferation in response to partial outlet obstruction. In contrast, a significant increase in FGF-10 expression was observed in the obstructed FGF-7-null group, indicating that the compensatory pathway that functions in this model results in urothelial repair.

The motif of SPARC that inhibits DNA synthesis is not a nuclear localization signal

SPARC (secreted protein acidic and rich in cysteine), although primarily known as a secreted, matricellular protein, has also been identified in urothelial cell nuclei. Many biological activities, including inhibition of cell adhesion and repression of DNA synthesis, have been ascribed to SPARC, but the influence of its intracellular localization on each of these activities is unknown. When exposed by epitope retrieval and nuclear matrix unmasking techniques, endogenous SPARC was found to localize strongly to the nuclei and the nuclear matrix of cultured urothelial cells. Live-cell time-lapse imaging revealed that exogenous fluorescently labeled recombinant (r) SPARC was taken up from medium over a 16 h period and accumulated inside cells. Two variants of rSPARC with alterations in its putative nuclear localization signal (NLS) were generated to investigate the existence and effects of the NLS. These variants demonstrated similar biophysical characteristics as the wild-type protein. Visualization by a variety of techniques, including live-cell imaging, deconvolution microscopy, and cell fractionation, all concurred that exogenous rSPARC was not able to localize to cell nuclei, but instead accumulated as perinuclear clusters. Localization of the rSPARC NLS variants was no different than wild-type, arguing against the presence of an active NLS in rSPARC. Imaging experiments showed that only permeabilized, dead cells avidly took up rSPARC into their nuclei. The rSPARC(no NLS) variant proved ineffective at inhibiting DNA synthesis, whereas the rSPARC(strong NLS) variant was a more potent inhibitor of DNA synthesis than was wild-type rSPARC. The motif of SPARC that inhibits the synthesis of urothelial cell DNA is therefore not a nuclear localization signal, but its manipulation holds therapeutic potential to generate a "Super-SPARC" that can quiesce proliferative tissues.

Immortalization of human urothelial cells by human papillomavirus type 16 E6 and E7 genes in a defined serum-free system

Normal human epithelial cell cultures exhibit a limited (although different between tissues) lifespan in vitro. In previous studies, urothelial cell cultures were immortalized using retroviral transformation with human papillomavirus type 16 E6 and E7 genes, in undefined culture systems containing serum or bovine pituitary extract.

OBJECTIVE

Due to the variability of results in such systems, we instead developed a procedure for the immortalization of urothelial cells using a defined, serum-free culture system.

METHOD AND RESULTS

Immortalization through retroviral transformation with human papillomavirus type 16 E6 and E7 was successful, and transformation of urothelial cells conferred an extended over normal lifespan and restored telomerase activity. Transformed cells retained typical morphology and exhibited a similar growth rate, cytokeratin immunoreactivity pattern, and response to growth factors as observed in untransformed cells. Karyotype analysis revealed a gradual accumulation of genetic mutations that are consistent with previously reported mutations in epithelial cells transformed with human papillomavirus type 16 E6 and E7.

CONCLUSION

The ability to extend the in vitro lifespan of cells holds the potential to reduce the continuous need for tissue samples and to enable complete investigations with one cell line.

Fibroblast growth factor 10 is required for survival and proliferation but not differentiation of intestinal epithelial progenitor cells during murine colon development

Epithelial-mesenchymal interactions that govern the development of the colon from the primitive gastrointestinal tract are still unclear. In this study, we determine the temporal-spatial expression pattern of Fibroblast growth factor 10 (Fgf10), a key developmental gene, in the colon at different developmental stages. We found that Fgf10 is expressed in the mesenchyme of the distal colon, while its main receptor Fgfr2-IIIb is expressed throughout the entire intestinal epithelium. We demonstrate that Fgf10 inactivation leads to decreased proliferation and increased cell apoptosis in the colonic epithelium at E10.5, therefore resulting in distal colonic atresia. Using newly described Fgf10 hypomorphic mice, we show that high levels of FGF10 are dispensable for the differentiation of the colonic epithelium. Our work unravels for the first time the pivotal role of FGF10 in the survival and proliferation of the colonic epithelium, biological activities which are essential for colonic crypt formation.

FGF-10 and its receptor exhibit bidirectional paracrine targeting to urothelial and smooth muscle cells in the lower urinary tract

Control of the regenerative properties of urothelial tissue would greatly aid the clinician in the management of urinary tract disease and disorders. Fibroblast growth factor 10 (FGF-10) is a mitogen which is particularly promising as a protein therapy for urothelial injury. The spatial synthesis, transport, targeting, and mechanistic pathway of FGF-10 and its receptor were studied in a human urothelial cell culture model and in fixed sections of lower urinary tract tissue. Synthesis of FGF-10 was restricted to mesenchymal fibroblasts, and secreted FGF-10 exhibited paracrine transport to two proximal sites, transitional epithelium and smooth muscle cell bundles, both of which were also the exclusive sites of FGF-10 receptor synthesis. The addition of recombinant FGF-10 to quiescent urothelial cells in vitro was sufficient to stimulate DNA synthesis. This stimulation was through a pathway independent of the epidermal growth factor receptor pathway. Deconvolution, light and transmission electron microscopic studies captured FGF-10 and its receptor in association with the urothelial cell surface, in cytoplasm, and within nuclei, observations that describe the mechanism that transduces the mitogenic signal in these tissues. Localization of the FGF-10 receptor to the superficial urothelial layer is clinically significant because intravesical administration of FGF-10 may provide the clinician a means to control the turnover of transitional epithelium in bladder disorders such as interstitial cystitis.

LADD syndrome is caused by FGF10 mutations

Lacrimo-auriculo-dento-digital syndrome [LADD (MIM 149730)] is an autosomal-dominant multiple congenital anomaly disorder characterized by aplasia, atresia or hypoplasia of the lacrimal and salivary systems, cup-shaped ears, hearing loss, and dental and digital anomalies. Loss of function mutations in FGF10 were recently described in aplasia of the lacrimal and salivary glands [ALSG (MIM 180920; MIM 103420)] (Entesarian et al., Nat Genet 2005: 37: 125-127, Milunsky et al., American College of Medical Genetics Annual Meeting, Dallas, TX, 2005: A100). Due to the significant phenotypic overlap between LADD syndrome and ALSG and the variable expressivity of both the disorders, we hypothesized that FGF10 mutations could also result in LADD syndrome. A de novo missense mutation was found in exon 3 of FGF10 in a 3-year-old female (Family 1) with LADD syndrome. This missense mutation, resulting in a non-conservative amino acid change, was confirmed by restriction enzyme digestion and was not found in 500 control chromosomes. A nonsense mutation was also found in exon 2 of FGF10 (Family 2) in a 19-year-old mother with ALSG and her 2-year-old daughter with LADD syndrome. Previous studies of FGF10 mutant mice have demonstrated abnormalities consistent with ALSG and LADD syndrome. We conclude that ALSG and LADD syndrome may represent variable presentations of the same clinical spectrum caused by FGF10 mutations.

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.

Development of the mammalian urethra is controlled by Fgfr2-IIIb

Development of external genitalia in mammalian embryos requires tight coordination of a complex series of morphogenetic events involving outgrowth,proximodistal and dorsoventral patterning, and epithelial tubulogenesis. Hypospadias is a congenital defect of the external genitalia that results from failure of urethral tube closure. Although this is the second most common birth defect in humans, affecting one in every 250 children, the molecular mechanisms that regulate morphogenesis of the mammalian urethra are poorly understood. We report that mice lacking the IIIb isoform of fibroblast growth factor receptor 2 (Fgfr2) exhibit severe hypospadias. Urethral signaling regions, as indicated by Shh and Fgf8 expression, are established in Fgfr2-IIIb null mice; however, cell proliferation arrests prematurely and maturation of the urethral epithelium is disrupted. Fgfr2-IIIb-/- mutants fail to maintain the progenitor cell population required for uroepithelial renewal during tubular morphogenesis. In addition, we show that antagonism of the androgen receptor (AR) leads to loss of Fgfr2-IIIb and Fgf10 expression in the urethra, and an associated hypospadias phenotype, suggesting that these genes are downstream targets of AR during external genital development. Genitourinary defects resulting from disruption of AR activity, by either genetic or environmental factors, may therefore involve negative regulation of the Fgfr2 pathway. This represents the first example of how the developing genitourinary system integrates cues from systemically circulating steroid hormones with a locally expressed growth factor pathway.

Mutations in the gene encoding fibroblast growth factor 10 are associated with aplasia of lacrimal and salivary glands

Autosomal dominant aplasia of lacrimal and salivary glands (ALSG; OMIM 180920 and OMIM 103420) is a rare condition characterized by irritable eyes and dryness of the mouth. We mapped ALSG to 5p13.2-5q13.1, which coincides with the gene fibroblast growth factor 10 (FGF10). In two extended pedigrees, we identified heterozygous mutations in FGF10 in all individuals with ALSG. Fgf10(+/-) mice have a phenotype similar to ALSG, providing a model for this disorder. We suggest that haploinsufficiency for FGF10 during a crucial stage of development results in ALSG.

Cellular and molecular mechanisms of development of the external genitalia

The limb and external genitalia are appendages of the body wall. Development of these structures differs fundamentally in that masculine development of the external genitalia is androgen dependent, whereas development of the limb is not. Despite this fundamental difference in developmental regulation, epithelial-mesenchymal interactions play key roles in the development of both structures, and similar regulatory molecules are utilized as mediators of morphogenetic cell-cell interactions during development of both the limb and external genitalia. Given the relatively high incidence of hypospadias, a malformation of penile development, it is appropriate and timely to review the morphological, endocrine, and molecular mechanisms of development of the genital tubercle (GT), the precursor of the penis in males and the clitoris in females. Morphological observations comparing development of the GT in humans and mouse emphasize the validity of the mouse as an animal model of GT development and validate the results of experimental studies. Accordingly, the use of mutant mice provides important insights into the roles of specific regulatory molecules in development of the external genitalia. While our current understanding of the morphological and molecular mechanisms of mammalian external genitalia development is still rudimentary, this review summarizes the current state of our knowledge and whenever possible draws from the rich experimental embryology literature on other relevant organs such as the developing limb. Future research on the hormonal and molecular mechanisms of GT development may yield strategies to prevent or reduce the incidence of hypospadias and to elucidate the molecular genetic mechanisms of GT morphogenesis, especially in relation to common organogenetic pathways utilized in other organ systems.

Repifermin (keratinocyte growth factor-2) reduces the severity of graft-versus-host disease while preserving a graft-versus-leukemia effect

Graft-versus-host disease (GVHD) is the principal complication after allogeneic bone marrow transplantation (BMT). Reductions in systemic GVHD are frequently associated with a corresponding diminishment of the graft-versus-leukemia (GVL) response. In this study, we tested the effects of a novel recombinant human keratinocyte growth factor, repifermin (keratinocyte growth factor-2), on the induction of GVHD in a well-defined murine BMT model (B6 --> B6D2F1). Administration of repifermin (5 mg/kg/d) to allogeneic BMT recipients resulted in a significant decrease in both systemic GVHD and target organ histopathology. Repifermin treatment also reduced serum levels of tumor necrosis factor alpha and lipopolysaccharide compared with control mice. In contrast, repifermin did not affect T-cell proliferation, cytokine production, or cytotoxic responses to host antigens. When 2000 host-derived P815 (H-2(d)) leukemia cells were added to the bone marrow inoculum, repifermin preserved GVL effects and resulted in significantly delayed mortality compared with control-treated allogeneic BMT recipients. Collectively, these data suggest that repifermin administration may represent a novel strategy to separate the toxicity of GVHD from the beneficial GVL effects after allogeneic BMT.

Intracellular renin and the nature of intracrine enzymes

Recently, the binding of renin and prorenin to cellular receptors with the subsequent generation of second messengers and the production of physiological effects has been demonstrated. In addition, the internalization of prorenin by target cells has been associated with increased cellular synthesis of angiotensin and cardiac pathology. Also, a renin transcript lacking the sequences encoding a secretory signal has been reported, and this transcript appears to produce a renin that acts in the cell that synthesized it. Some years ago, we coined the term intracrine for a peptide hormone or factor that acts in the intracellular space either after internalization or retention in its cell of synthesis. Thus defined, a wide variety of peptides display intracrine functionality, including hormones, growth factors, transcription factors, and enzymes. For example, considerable evidence indicates that angiotensin II is an intracrine. Also, general principles of intracrine functionality have been developed. Thus, recent evidence demonstrates that the prorenin/renin molecule is an intracrine enzyme. Here, the actions of intracrine enzymes (angiogenin, phosphoglucose isomerase, phospholipase A2, granzyme A and B, thioredoxin, platelet-derived endothelial growth factor, and serine protease inhibitors) are reviewed. The relation of prorenin/renin to other intracrine enzymes, and to intracrines in general, is discussed.

Specific molecular interactions of oversulfated chondroitin sulfate E with various heparin-binding growth factors. Implications as a physiological binding partner in the brain and other tissues

We previously observed that the cortical neuronal cell adhesion mediated by midkine (MK), a heparin (Hep)-binding growth factor, is specifically inhibited by oversulfated chondroitin sulfate-E (CS-E) (Ueoka, C., Kaneda, N., Okazaki, I., Nadanaka, S., Muramatsu, T., and Sugahara, K. (2000) J. Biol. Chem. 275, 37407-37413) and that CS-E exhibits neurite outgrowth promoting activities toward embryonic rat hippocampal neurons. We have also shown oversulfated CS chains in embryonic chick and rat brains and demonstrated that the CS disaccharide composition changes during brain development. In view of these findings, here we tested the possibility of CS-E interacting with Hep-binding growth factors during development, using squid cartilage CS-E. The binding ability of Hep-binding growth factors (MK, pleiotrophin (PTN), fibroblast growth factor-1 (FGF-1), FGF-2, Hep-binding epidermal growth factor-like growth factor (HB-EGF), FGF-10, FGF-16, and FGF-18) toward [(3)H]CS-E was first tested by a filter binding assay, which demonstrated direct binding of all growth factors, except FGF-1, to CS-E. The bindings were characterized further in an Interaction Analysis system, where all of the growth factors, except FGF-1, gave concentration-dependent and specific bindings. The kinetic constants k(a), k(d), and K(d) suggested that MK, PTN, FGF-16, FGF-18, and HB-EGF bound strongly to CS-E, in comparable degrees to the binding to Hep, whereas the intensity of binding of FGF-2 and FGF-10 toward CS-E was lower than that for Hep. These findings suggest the possibility of CS-E being a binding partner, a coreceptor, or a genuine receptor for various Hep-binding growth factors in the brain and possibly also in other tissues.