Wnt and Frizzled RNA expression in human mesenchymal and embryonic (H7) stem cells

Investigation of the effect of belinostat on MCF-7 breast cancer stem cells via the Wnt, Notch, and Hedgehog signaling pathway

OBJECTIVES

To evaluate belinostat's (PXD101) activity on MCF-7 breast cancer stem cells (CSCs) via Wnt, Notch, and Hedgehog.

METHODS

This research study was carried out at the Department of Medical Biology, Necmettin Erbakan University, Konya, Turkey, from June 2017 to July 2019. The effect of PXD101 on MCF-7 cell viability was determined by cell proliferation kit (XTT). Following belinostat treatment, CD44+/CD24- MCF-7 CSCs were isolated by FACS. Ribonucleic acid isolation and copy-deoxyribonucleic acid synthesis were carried out using HEK-293 cells, MCF-7 cells, and MCF-7 CSCs. Expression changes of metastasis-related genes, Wnt, Hedgehog, Notch, and stem cell markers were analysed by quantitative polymerase chain reaction. The IC50 in MCF-7 cancer cells was 5 μM for 48 hours. The FACS analysis indicated that 2% of the MCF-7 cancer cells were CSCs. Following belinostat treatment, the MCF-7 cell count decreased by 44%, and the MCF-7 CD44+/CD24- CSC count decreased by 66%.

RESULTS

Belinostat treatment reduced the expression of metastasis, Wnt, Notch, Hedgehog, and stem cell marker genes.

CONCLUSION

Belinostat has a potential effect on the differentiation and self-renewal of breast CSCs.

Ethanolic Extract of Artemisia vulgaris Leaf Promotes Apoptotic Cell Death in Non-Small-Cell Lung Carcinoma A549 Cells through Inhibition of the Wnt Signaling Pathway

The Wnt signaling pathway is reported to be associated with lung cancer progression, metastasis and drug resistance, and thus it is an important therapeutic target for lung cancer. Plants have been shown as reservoirs of multiple potential anticancer agents. In the present investigation, the ethanolic leaf extract of Artemisia vulgaris (AvL-EtOH) was initially analyzed by means of gas chromatography-mass spectrometry (GC–MS) to identify the important phytochemical constituents. The GC–MS analysis of AvL-EtOH exhibited 48 peaks of various secondary metabolites such as terpenoids, flavonoids, carbohydrates, coumarins, amino acids, steroids, proteins, phytosterols, and diterpenes. It was found that the treatment with increasing doses of AvL-EtOH suppressed the proliferation and migration of lung cancer cells. Furthermore, AvL-EtOH induced prominent nuclear alteration along with a reduction in mitochondrial membrane potential and increased ROS (reactive oxygen species) generation in lung cancer cells. Moreover, AvL-EtOH-treated cells exhibited increased apoptosis, demonstrated by the activation of caspase cascade. AvL-EtOH also induced downregulation of Wnt3 and β-catenin expression along with cell cycle protein cyclin D1. Thus, the results of our study elucidated the potential of bioactive components of Artemisia vulgaris in the therapeutic management of lung cancer cells.

Wnt5A signaling supports antigen processing and CD8 T cell activation

Antigen processing and antigen-specific CD8 T cell activation form part and parcel of cell-mediated immunity to infections. Yet, several lacunae remain in our understanding of how antigen processing and CD8 T cell response are coordinated. In this study, using mouse bone marrow-derived dendritic cells (BMDC) as antigen-presenting cells and Ovalbumin (OVA)/DQ-Ovalbumin (DQ-OVA) as model antigen we demonstrated that Wnt5A signaling in BMDC supports antigen processing/presentation and concomitant CD8 T cell activation through regulation of actin and proteasome dynamics. Recombinant Wnt5A conditioning of BMDC and associated actin assembly facilitated DQ-OVA processing, which was inhibited by the proteasome inhibitor MG132. Moreover, Wnt5A depletion led to a significant reduction in OVA processing and presentation. Impaired DQ-OVA processing in Wnt5A depleted BMDC correlated with altered dynamics of both actin and the proteasome regulator PA28α-PA28β, and reduced association of DQ-OVA with actin and proteasome subunits. Inhibited OVA processing/presentation in the Wnt5A depleted BMDC also resulted in subdued activation of OVA-sensitized CD8 T cells in co-culture with the BMDC. In concurrence with these findings, we demonstrated reduced OVA processing and impaired CD8 T cell response to OVA immunization in Wnt5A heterozygous mice lacking a copy of the Wnt5A gene in comparison to the wild-type cohorts. Taken together, our results reveal a crucial requirement of Wnt5A signaling in antigen processing/presentation and CD8 T cell activation, thus unveiling a vital regulatory node of cell-mediated immunity, unidentified thus far.

Screening of Apoptosis Pathway-Mediated Anti-Proliferative Activity of the Phytochemical Compound Furanodienone against Human Non-Small Lung Cancer A-549 Cells

Furanodienone (FDN), a major bioactive component of sesquiterpenes produced from Rhizoma Curcumae, has been repeatedly acknowledged for its intrinsic anticancer efficacy against different types of cancer. In this study, we aimed to investigate the cytotoxic potential of furanodienone against human lung cancer (NSCLC A549) cells in vitro, as well as its underlying molecular mechanisms in the induction of apoptosis. Herein, we found that FDN significantly inhibited the proliferation of A549 cells in a dose-dependent manner. In addition, treatment with FDN potentially triggered apoptosis in A549 cells via not only disrupting the nuclear morphology, but by activating capsase-9 and caspase-3 with concomitant modulation of the pro- and antiapoptotic gene expression as well. Furthermore, FDN revealed its competence in inducing cell cycle arrest at G0/G1 phase in A549 cells, which was associated with decreased expression of cyclin D1 and cyclin-dependent kinase 4 (CDK4), along with increased expression of CDK inhibitor p21Cip1. Intriguingly, FDN treatment efficiently downregulated the Wnt signaling pathway, which was correlated with increased apoptosis, as well as cell cycle arrest, in A549 cells. Collectively, FDN might represent a promising adjuvant therapy for the management of lung cancer.

CD8+ T cells mediate the regenerative PTH effect in hPDL cells via Wnt10b signaling

It was the aim of the present investigation to examine whether the stimulating effect of parathyroid hormone (PTH) on human periodontal ligament (hPDL) cell proliferation and differentiation would be enhanced by hPDL/T-cell interaction involving Wnt10b signaling as a mediating pathway. hPDL cells were cultured from healthy premolar tissues of three adolescent orthodontic patients and exposed to PTH(1-34) in monocultures or co-cultures with CD8⁺ T cells. At harvest, proliferation, alkaline phosphatase-specific activity (ALP), and osteocalcin production were determined by immunofluorescence cytochemistry, real-time PCR, biochemical assay, and ELISA. Wnt10b signaling was analyzed by the use of a specific WNT10b neutralizing antibody. PTH(1-34) stimulation of T cells significantly increased Wnt10b expression and production. Wnt10b exposure of hPDL cells enhanced proliferation and differentiation. PDL cells co-cultured with T cells showed a Wnt10b-dependent regulation of proliferation and differentiation parameters. The addition of a Wnt10b-neutralizing Ab to the co-culture medium resulted in a significant inhibition of the PTH(1-34) effect on proliferation, ALP-specific activity, and osteocalcin protein expression. Our findings provide novel insight into the mechanism of action of PTH on hPDL cells and establish the interplay of T cells and hPDL cells via the Wnt10b pathway as a modulating factor for the anabolic properties of the hormone in periodontal regeneration.

Identification of SSEA-1 expressing enhanced reprogramming (SEER) cells in porcine embryonic fibroblasts

Previous research has shown that a subpopulation of cells within cultured human dermal fibroblasts, termed multilineage-differentiating stress enduring (Muse) cells, are preferentially reprogrammed into induced pluripotent stem cells. However, controversy exists over whether these cells are the only cells capable of being reprogrammed from a heterogeneous population of fibroblasts. Similarly, there is little research to suggest such cells may exist in embryonic tissues or other species. To address if such a cell population exists in pigs, we investigated porcine embryonic fibroblast populations (pEFs) and identified heterogeneous expression of several key cell surface markers. Strikingly, we discovered a small population of stage-specific embryonic antigen 1 positive cells (SSEA-1+) in Danish Landrace and Göttingen minipig pEFs, which were absent in the Yucatan pEFs. Furthermore, reprogramming of SSEA-1+ sorted pEFs led to higher reprogramming efficiency. Subsequent transcriptome profiling of the SSEA-1+ vs. the SSEA-1neg cell fraction revealed highly comparable gene signatures. However several genes that were found to be upregulated in the SSEA-1+ cells were similarly expressed in mesenchymal stem cells (MSCs). We therefore termed these cells SSEA-1 Expressing Enhanced Reprogramming (SEER) cells. Interestingly, SEER cells were more effective at differentiating into osteocytes and chondrocytes in vitro. We conclude that SEER cells are more amenable for reprogramming and that the expression of mesenchymal stem cell genes is advantageous in the reprogramming process. This data provides evidence supporting the elite theory and helps to delineate which cell types and specific genes are important for reprogramming in the pig.

Frizzled gene expression and negative regulation of canonical WNT-β-catenin signaling in mouse F9 teratocarcinoma cells

Mouse F9 cells differentiate into primitive endoderm (PrE) following the activation of the canonical WNT-β-catenin pathway. The upregulation of Wnt6 and activation of β-catenin-TCF-LEF-dependent transcription is known to accompany differentiation, but the Frizzled (FZD) receptor responsible for transducing the WNT6 signal is not known. Eight of the 10 Fzd genes were found to be expressed in F9 cells, with Fzd7 being the most highly expressed, and chosen for further analysis. To alter steady-state Fzd7 levels and test the effect this has on differentiation, siRNA and overexpression approaches were used to knock-down and ectopically express the Fzd7 message, respectively. siRNA knock-down of Fzd7 resulted in reduced DAB2 levels, and the overexpression activated a TCF-LEF reporter, but neither approach affected differentiation. Our focus turned to how canonical WNT6 signaling was attenuated to allow PrE cells to form parietal endoderm (PE). Dkk1, encoding a WNT antagonist, was examined and results showed that its expression increased in F9 cells treated with retinoic acid (RA) or overexpressing Wnt6. F9 cells overexpressing human DKK1 or treated with DKK1-conditioned medium and then treated with RA failed to differentiate, indicating that a negative feedback loop involving WNT6 and DKK1 attenuates canonical WNT-β-catenin signaling, thereby allowing PE cells to differentiate.

Different Impact Of Antiretroviral Drugs On Bone Differentiation In An In Vitro Model

Recently increasing emphasis is placed on preventive health and management of chronic comorbidities avoiding long-term toxicities of antiretroviral therapy (ART). Drawing from this background we decided to use the Saos-2, osteosarcoma cell line, as a cellular model, to evaluate the effects of some antiretroviral drugs such as abacavir (ABC), tenofovir (TDF), efavirenz (EFV), etravirine (ETR), and darunavir (DRV), on bone differentiation related pathways. According to our observation, treatment with TDF and ABC affects the ability of the cells to produce calcium deposits with a reduced expression of type I collagen gene and p21 mRNA, also increasing the activity of Wnt3a related pathway. On the other hand treatment with EFV and DRV was not related to any significant reduction of calcium deposits but displayed a decrease in the expression of Wnt3a at day 14 and Type I Collagen at day 7 compared with untreated cells, even if this last down regulation was not confirmed at day 14. Instead ETR administration to Saos-2 cells increases the calcium deposits collagen type I production, as a result of Wnt3a mRNA overexpression, and of an upregulation of collagen type I expression, being also the only drug able to increase the expression of p21 cdk inhibitor as further marker of terminal differentiation. In summary these data suggest the potential negative interference of TDF and ABC on bone differentiation. DRV and EFV partially affect collagen type I production, instead ETR facilitates a positive bone balance as a result of an increased osteoblasts terminal differentiation.

[Effect of irradiated human lung fibroblasts on activation of canonical Wnt/β-catenin signaling pathway in mesenchymal stem cells]

OBJECTIVE

To investigate the effect of irradiated human lung fibroblasts (HLFs) on the canonical Wnt/β-catenin signaling pathway in human umbilical cord mesenchymal stem cells (HUMSCs).

METHODS

HUMSCs were cultured alone (single group) or co-cultured with HLFs exposed to 5Gy X-rays (co-culture group). The protein levels of GSK-3β, p-GSK-3β, FRAT1 and β-catenin in HUMSCs were examined by Western blotting 3 days after culture or co-culture. WISP-1 protein levels in conditioned medium were examined by ELISA.

RESULTS

The levels of p-GSK3β/GSK3β (0.15 ± 0.05), FRAT1 (0.48 ± 0.07) and β-catenin (0.50 ± 0.07) in co-cultured HUMSCs significantly decreased compared to those in single group (0.55 ± 0.05, 1.16 ± 0.13 and 2.39 ± 0.15, all P<0.05). The supernatant level of WISP-1 in co-culture group was significantly decreased [(602.23 ± 161.47) ng/mL], compared to the single group [(977.77 ± 110.56) ng/mL, P<0.05].

CONCLUSION

Irradiated HLFs attenuate the activation of canonical Wnt/β-catenin signaling pathway in HUMSCs in vitro.

AP2 suppresses osteoblast differentiation and mineralization through down-regulation of Frizzled-1

AP2 is an important transcription factor in bone development. AP2 binds to the human Frizzled 1 (FZD1) promoter and down-regulates FZD1 expression in osteoblasts. In addition, AP2 negatively regulates osteoblast differentiation and mineralization in part through down-regulation of FZD1 expression.

Mesenchymal Stem Cells Increase Hippocampal Neurogenesis and Neuronal Differentiation by Enhancing the Wnt Signaling Pathway in an Alzheimer's Disease Model

Neurogenesis in the subgranular zone of the hippocampal dentate gyrus may act as an endogenous repair mechanism in Alzheimer's disease (AD), and the Wnt signaling pathway has been suggested to closely modulate neurogenesis in amyloid-β (Aβ)-related AD models. The present study investigated whether mesenchymal stem cells (MSCs) would modulate hippocampal neurogenesis via modulation of the Wnt signaling pathway in a model of AD. In Aβ-treated neuronal progenitor cells (NPCs), the coculture with MSCs increased significantly the expression of Ki-67, GFAP, SOX2, nestin, and HuD compared to Aβ treatment alone. In addition, MSC treatment in Aβ-treated NPCs enhanced the expression of β-catenin and Ngn1 compared to Aβ treatment alone. MSC treatment in Aβ-treated animals significantly increased the number of BrdU-ir cells in the hippocampus at 2 and 4 weeks compared to Aβ treatment alone. In addition, quantitative analysis showed that the number of BrdU and HuD double-positive cells in the dentate gyrus was significantly higher in the MSC-treated group than in controls or after Aβ treatment alone. These results demonstrate that MSC administration significantly augments hippocampal neurogenesis and enhances the differentiation of NPCs into mature neurons in AD models by augmenting the Wnt signaling pathway. The use of MSCs to modulate endogenous adult neurogenesis may have a significant impact on future strategies for AD treatment.

Human embryonic stem cell-derived cardiomyocytes migrate in response to gradients of fibronectin and Wnt5a

An improved understanding of the factors that regulate the migration of human embryonic stem cell-derived cardiomyocytes (hESC-CMs) would provide new insights into human heart development and suggest novel strategies to improve their electromechanical integration after intracardiac transplantation. Since nothing has been reported as to the factors controlling hESC-CM migration, we hypothesized that hESC-CMs would migrate in response to the extracellular matrix and soluble signaling molecules previously implicated in heart morphogenesis. To test this, we screened candidate factors by transwell assay for effects on hESC-CM motility, followed by validation via live-cell imaging and/or gap-closure assays. Fibronectin (FN) elicited a haptotactic response from hESC-CMs, with cells seeded on a steep FN gradient showing nearly a fivefold greater migratory activity than cells on uniform FN. Studies with neutralizing antibodies indicated that adhesion and migration on FN are mediated by integrins α-5 and α-V. Next, we screened 10 soluble candidate factors by transwell assay and found that the noncanonical Wnt, Wnt5a, elicited an approximately twofold increase in migration over controls. This effect was confirmed using the gap-closure assay, in which Wnt5a-treated hESC-CMs showed approximately twofold greater closure than untreated cells. Studies with microfluidic-generated Wnt5a gradients showed that this factor was chemoattractive as well as chemokinetic, and Wnt5a-mediated responses were inhibited by the Frizzled-1/2 receptor antagonist, UM206. In summary, hESC-CMs show robust promigratory responses to FN and Wnt5a, findings that have implications on both cardiac development and cell-based therapies.

Mesenchymal stem cells improve cardiac conduction by upregulation of connexin 43 through paracrine signaling

Mesenchymal stem cells (MSCs) were shown to improve cell survival and alleviate cardiac arrhythmias when transplanted into cardiac tissue; however, little is known about the mechanism by which MSCs modify the electrophysiological properties of cardiac tissue. We aimed to distinguish the influence of cell-cell coupling between myocytes and MSCs from that of MSC-derived paracrine factors on the spontaneous activity and conduction velocity (θ) of multicellular cardiomyocyte preparations. HL-1 cells were plated on microelectrode arrays and their spontaneous activity and θ was determined from field potential recordings. In heterocellular cultures of MSCs and HL-1 cells the beating frequency was attenuated (t(0h): 2.26 ± 0.18 Hz; t(4h): 1.98 ± 0.26 Hz; P < 0.01) concomitant to the intercellular coupling between MSCs and cardiomyocytes. In HL-1 monolayers supplemented with MSC conditioned media (ConM) or tyrode (ConT) θ significantly increased in a time-dependent manner (ConT: t(0h): 2.4 cm/s ± 0.2; t(4h): 3.1 ± 0.4 cm/s), whereas the beating frequency remained constant. Connexin (Cx)43 mRNA and protein expression levels also increased after ConM or ConT treatment over the same time period. Enhanced low-density lipoprotein receptor-related protein 6 (LRP6) phosphorylation after ConT treatment implicates the Wnt signaling pathway. Suppression of Wnt secretion from MSCs (IWP-2; 5 μmol/l) reduced the efficacy of ConT to induce phospho-LRP6 and to increase θ. Inhibition of β-catenin (cardamonin; 10 μmol/l) or GSK3-α/β (LiCl; 5 mmol/l) also suppressed changes in θ, further supporting the hypothesis that MSC-mediated Cx43 upregulation occurs in part through secreted Wnt ligands and activation of the canonical Wnt signaling pathway.

Redundant sources of Wnt regulate intestinal stem cells and promote formation of Paneth cells

BACKGROUND & AIMS

Wnt signaling regulates multiple aspects of intestinal physiology, including stem cell maintenance. Paneth cells support stem cells by secreting Wnt, but little is known about the exact sources and primary functions of individual Wnt family members.

METHODS

We analyzed intestinal tissues and cultured epithelial cells from adult mice with conditional deletion of Wnt3 (Vil-CreERT2;Wnt3fl/fl mice). We also analyzed intestinal tissues and cells from Atoh1 mutant mice, which lack secretory cells.

RESULTS

Unexpectedly, Wnt3 was dispensable for maintenance of intestinal stem cells in mice, indicating a redundancy of Wnt signals. By contrast, cultured crypt organoids required Paneth cell-derived Wnt3. Addition of exogenous Wnt, or coculture with mesenchymal cells, restored growth of Vil-CreERT2;Wnt3fl/fl crypt organoids. Intestinal organoids from Atoh1 mutant mice did not grow or form Paneth cells; addition of Wnt3 allowed growth in the absence of Paneth cells. Wnt signaling had a synergistic effect with the Lgr4/5 ligand R-spondin to induce formation of Paneth cells. Mosaic expression of Wnt3 in organoids using a retroviral vector promoted differentiation of Paneth cells in a cell-autonomous manner.

CONCLUSIONS

Wnt is part of a signaling loop that affects homeostasis of intestinal stem and Paneth cells in mice. Wnt3 signaling is required for growth and development of organoid cultures, whereas nonepithelial Wnt signals could provide a secondary physiological source of Wnt.

WNT10A plays an oncogenic role in renal cell carcinoma by activating WNT/β-catenin pathway

Renal cell carcinoma (RCC) is a malignancy with poor prognosis. WNT/β-catenin signaling dysregulation, especially β-catenin overactivation and WNT antagonist silencing, is associated with RCC carcinogenesis and progression. However, the role of WNT ligands in RCC has not yet been determined. We screened 19 WNT ligands from normal kidney and RCC cell lines and tissues and found that WNT10A was significantly increased in RCC cell lines and tissues as compared to that in normal controls. The clinical significance of increase in WNT10A was evaluated by performing an immunohistochemical association study in a 19-year follow-up cohort comprising 284 RCC and 267 benign renal disease (BRD) patients. The results of this study showed that WNT10A was dramatically upregulated in RCC tissues as compared to that in BRD tissues. This result suggests that WNT10A, nuclear β-catenin, and nuclear cyclin D1 act as independent risk factors for RCC carcinogenesis and progression, with accumulative risk effects. Molecular validation of cell line models with gain- or loss-of-function designs showed that forced WNT10A expression induced RCC cell proliferation and aggressiveness, including higher chemoresistance, cell migration, invasiveness, and cell transformation, due to the activation of β-catenin-dependent signaling. Conversely, WNT10A siRNA knockdown decreased cell proliferation and aggressiveness of RCC cells. In conclusion, we showed that WNT10A acts as an autocrine oncogene both in RCC carcinogenesis and progression by activating WNT/β-catenin signaling.

Embryonic stem cell markers

Embryonic stem cell (ESC) markers are molecules specifically expressed in ES cells. Understanding of the functions of these markers is critical for characterization and elucidation for the mechanism of ESC pluripotent maintenance and self-renewal, therefore helping to accelerate the clinical application of ES cells. Unfortunately, different cell types can share single or sometimes multiple markers; thus the main obstacle in the clinical application of ESC is to purify ES cells from other types of cells, especially tumor cells. Currently, the marker-based flow cytometry (FCM) technique and magnetic cell sorting (MACS) are the most effective cell isolating methods, and a detailed maker list will help to initially identify, as well as isolate ESCs using these methods. In the current review, we discuss a wide range of cell surface and generic molecular markers that are indicative of the undifferentiated ESCs. Other types of molecules, such as lectins and peptides, which bind to ESC via affinity and specificity, are also summarized. In addition, we review several markers that overlap with tumor stem cells (TSCs), which suggest that uncertainty still exists regarding the benefits of using these markers alone or in various combinations when identifying and isolating cells.

Wnt2 inhibits enteric bacterial-induced inflammation in intestinal epithelial cells

BACKGROUND

Wnt signaling plays an essential role in gastrointestinal epithelial proliferation. Most investigations have focused on developmental and immune responses. Bacterial infection can be chronic and increases the risk of inflammatory bowel disease and colitis-associated cancer. However, we lack studies on how bacteria regulate Wnt proteins and how Wnts modulate the host responses to enteric bacteria. This study investigated the effects of Salmonella and Escherichia coli on Wnt2, one of the Wnt family members, in intestinal epithelia cells.

METHODS

Using cultured epithelial cells, a Salmonella-colitis mouse model, and a gnotobiotic mouse model, we found that Wnt2 mRNA and protein expression levels were elevated after bacterial infection. Enteric bacteria regulate Wnt2 location in the intestine. Furthermore, we found that elevation of Wnt2 was a strategy for host defense by inhibiting cell apoptosis and inflammatory responses to infection.

RESULTS

Using Wnt2 siRNA analysis, we show enhanced inflammatory cytokine IL-8 in epithelial cells. Cells overexpressed Wnt2 had less bacterial-induced IL-8 secretion. AvrA is a bacterial protein that inhibits inflammation by stabilizing β-catenin, the downstream target of Wnt. We found that the stabilization of Wnt2 was regulated through ubiquitination. Moreover, the bacterial protein AvrA from Salmonella and E. coli stabilized Wnt2 protein expression in vivo. In an ex-germ-free system, E. coli F18 expressing AvrA increased Wnt2 expression and changed Wnt2 distribution in intestine.

CONCLUSIONS

Wnt2 contributes to host protection in response to enteric bacteria. Our findings thus reveal a previously undefined role of Wnt for host-pathogen interaction and inflammation.

Physiological inhibitors of Wnt signaling

Wnt signaling is crucial for cell proliferation and differentiation. It represents a complex network with mechanisms of self-regulation through positive and negative feedback. Recent increasing interest in this signaling pathway has led to the discovery of many new proteins that down-regulate Wnt activity. Here, we provide a short description of the most important and best-studied inhibitors, group them according to the target molecule within the Wnt cascade, and discuss their clinical potential. Although most of the inhibitors discussed here may also interact with proteins from other signaling pathways, we focus only on their ability to modulate Wnt signaling.

Chronic cadmium exposure induces transcriptional activation of the Wnt pathway and upregulation of epithelial-to-mesenchymal transition markers in mouse kidney

The transition metal cadmium (Cd) is an environmental pollutant which damages the kidneys. Chronic Cd exposure may induce renal fibrosis and/or cancer, but the signaling pathways involved are not understood. The Wnt pathway is a key signaling cascade responsible for renal development, fibrosis and cancer. Hence the effect of chronic in vivo Cd exposure (100 mg/l drinking water for 12 weeks) on transcriptional activation of the Wnt pathway and markers of epithelial-to-mesenchymal transition (EMT) was investigated in mouse kidneys. Cd exposure increased kidney Cd content from 0.023+/-0.001 microg/g to 61+/-7 microg/g wet weight (means+/-S.D. of 6-7 animals). This was accompanied by increased expression of Wnt ligands (Wnt3a/6/7a/7b/9a/9b/10a/11), as determined by RT-PCR. The Wnt receptors Frizzled (Fz1/2/4,5,7-10) were also upregulated, as were the co-receptors low-density lipoprotein receptor-related proteins 5/6. Immunoblots with Wnt10a and Fz7 antibodies also revealed increased protein expression induced by Cd exposure. In contrast, Wnt antagonists were largely unaffected. Upregulation of Wnt signaling components induced by Cd was corroborated by increased expression of Wnt target genes, i.e. cell proliferation and survival genes c-Myc, cyclin D1 and the multidrug transporter P-glycoprotein Abcb1b, which promote malignancy. Lastly the EMT markers Twist, fibronectin and collagen I, but not alpha-smooth muscle actin, were also upregulated, suggesting that Cd-induced changes of renal epithelial tissue characteristics towards fibrosis and cancer may be mediated by Wnt signaling.

G protein coupled receptors in embryonic stem cells: a role for Gs-alpha signaling

Background

Identification of receptor mediated signaling pathways in embryonic stem (ES) cells is needed to facilitate strategies for cell replacement using ES cells. One large receptor family, largely uninvestigated in ES cells, is G protein coupled receptors (GPCRs). An important role for these receptors in embryonic development has been described, but little is known about GPCR expression in ES cells.

Methodology/Principal Findings

We have examined the expression profile of 343 different GPCRs in mouse ES cells demonstrating for the first time that a large number of GPCRs are expressed in undifferentiated and differentiating ES cells, and in many cases at high levels. To begin to define a role for GPCR signaling in ES cells, the impact of activating Gs-alpha, one of the major alpha subunits that couples to GPCRs, was investigated. Gs-alpha activation resulted in larger embryoid bodies (EBs), due, in part, to increased cell proliferation and prevented the time-related decline in expression of transcription factors important for maintaining ES cell pluripotency.

Significance/Conclusions

These studies suggest that Gs-alpha signaling contributes to ES cell proliferation and pluripotency and provide a framework for further investigation of GPCRs in ES cells.

Effects of age and gender on WNT gene expression in human bone marrow stromal cells

WNT signaling pathways play important roles in the behavior of human bone marrow stromal cells. Although WNT expression has been examined in human bone marrow stromal cells (hMSCs) with limited numbers of subjects or from commercial sources, there are conflicting results on WNT gene expression in hMSCs. Furthermore, the effects of age and gender on WNT expression in hMSCs are largely unknown. In this study, we evaluated RNA expression of all the WNT genes in hMSCs from 19 subjects, 12 women and 7 men, aged from 36 to 85 years. Analysis of WNT gene expression in young and old groups indicated that WNT7B and 14 were expressed significantly higher in the young group. WNT2 and WNT13 showed a trend of higher expression in young group. WNT7B, 13, and 14 were inversely correlated with age. Further analysis for gender-specific difference indicated that WNT16 was expressed significantly higher in men than in women. WNT11 showed a trend of higher expression in hMSCs from women. For the hMSCs from women, WNT13 was inversely correlated with age and WNT4 was positively correlated with age. For the hMSCs from men, WNT7B and WNT14 were inversely correlated with age. These data indicated that most of the age-related WNT genes belong to the canonical WNT signaling pathway. Further, there are gender-specific differences in the expression of WNT4, 7B, 13, 14, and 16 in hMSCs. Age and gender account for many of the sample-to-sample variations in WNT gene expression in human marrow stromal cells.