Inhibition of GSK3beta enhances both adhesive and signalling activities of beta-catenin in mouse embryonic stem cells

Cadherin adhesion complexes direct cell aggregation in the epithelial transition of Wnt-induced nephron progenitor cells

In the developing mammalian kidney, nephron formation is initiated by a subset of nephron progenitor cells (NPCs). Wnt input activates a β-catenin (Ctnnb1)-driven, transcriptional nephrogenic program and the mesenchymal to epithelial transition (MET) of NPCs. Using an in vitro mouse NPC culture model, we observed that activation of the Wnt pathway results in the aggregation of induced NPCs, which is an initiating step in the MET program. Genetic removal showed aggregation was dependent on β-catenin. Modulating extracellular Ca2+ levels showed cell-cell contacts were Ca2+ dependent, suggesting a role for cadherin (Cdh)-directed cell adhesion. Molecular analysis identified Cdh2, Cdh4 and Cdh11 in NPCs, and the β-catenin directed upregulation of Cdh3 and Cdh4 accompanying the MET of induced NPCs. Mutational analysis of β-catenin supported a role for a Lef/Tcf-β-catenin-mediated transcriptional response in the cell aggregation process. Genetic removal of all four cadherins, and independent removal of α-catenin or of β-catenin-α-catenin interactions, abolished aggregation, but not the inductive response to Wnt pathway activation. These findings, and data in an accompanying article highlight the role of β-catenin in linking transcriptional programs to the morphogenesis of NPCs in mammalian nephrogenesis.

Adapting the endoplasmic reticulum proteostasis rescues epilepsy-associated NMDA receptor variants

The GRIN genes encoding N-methyl-D-aspartate receptor (NMDAR) subunits are remarkably intolerant to variation. Many pathogenic NMDAR variants result in their protein misfolding, inefficient assembly, reduced surface expression, and impaired function on neuronal membrane, causing neurological disorders including epilepsy and intellectual disability. Here, we investigated the proteostasis maintenance of NMDARs containing epilepsy-associated variations in the GluN2A subunit, including M705V and A727T. In the transfected HEK293T cells, we showed that the two variants were targeted to the proteasome for degradation and had reduced functional surface expression. We demonstrated that the application of BIX, a known small molecule activator of an HSP70 family chaperone BiP (binding immunoglobulin protein) in the endoplasmic reticulum (ER), dose-dependently enhanced the functional surface expression of the M705V and A727T variants in HEK293T cells. Moreover, BIX (10 μM) increased the surface protein levels of the M705V variant in human iPSC-derived neurons. We revealed that BIX promoted folding, inhibited degradation, and enhanced anterograde trafficking of the M705V variant by modest activation of the IRE1 pathway of the unfolded protein response. Our results suggest that adapting the ER proteostasis network restores the folding, trafficking, and function of pathogenic NMDAR variants, representing a potential treatment for neurological disorders resulting from NMDAR dysfunction.

Cadherin Adhesion Complexes Direct Cell Aggregation in the Epithelial Transition of Wnt-Induced Nephron Progenitor Cells

In the developing mammalian kidney, nephron formation is initiated by a subset of nephron progenitor cells (NPCs). Wnt input activates a β-catenin ( Ctnnb1 )-driven, transcriptional nephrogenic program. In conjunction, induced mesenchymal NPCs transition through a pre-tubular aggregate to an epithelial renal vesicle, the precursor for each nephron. How this critical mesenchymal-to-epithelial transition (MET) is regulated is unclear. In an in vitro mouse NPC culture model, activation of the Wnt pathway results in the aggregation of induced NPCs into closely-packed, cell clusters. Genetic removal of β-catenin resulted in a failure of both Wnt pathway-directed transcriptional activation and the formation of aggregated cell clusters. Modulating extracellular Ca 2+ levels showed cell-cell contacts were Ca 2+ -dependent, suggesting a role for cadherin (Cdh)-directed cell adhesion. Molecular analysis identified Cdh2 , Cdh4 and Cdh11 in uninduced NPCs and the up-regulation of Cdh3 and Cdh4 accompanying the Wnt pathway-induced MET. Genetic removal of all four cadherins, and independent removal of α-catenin, which couples Cdh-β-catenin membrane complexes to the actin cytoskeleton, abolished cell aggregation in response to Wnt pathway activation. However, the β-catenin driven inductive transcriptional program was unaltered. Together with the accompanying paper (Bugacov et al ., submitted), these data demonstrate that distinct cellular activities of β-catenin - transcriptional regulation and cell adhesion - combine in the mammalian kidney programs generating differentiated epithelial nephron precursors from mesenchymal nephron progenitors.

Summary statement

Our study highlights the role of Wnt-β-catenin pathway regulation of cadherin-mediated cell adhesion in the mesenchymal to epithelial transition of induced nephron progenitor cells.

Wnt signaling and the regulation of pluripotency

The role of Wnt signaling in stem cells has been mired in seemingly contradictory findings. On one hand, Wnt has been heralded as a self-renewal factor. On the other hand, Wnt's association with differentiation and lineage commitment is indisputable. This apparent contradiction is particularly evident in pluripotent stem cells, where Wnt promotes self-renewal as well as differentiation. To resolve this discrepancy one must delve into fundamental principles of pluripotency and gain an appreciation for the concept of pluripotency states, which exist in a continuum with intermediate metastable states, some of which have been stabilized in vitro. Wnt signaling is a critical regulator of transitions between pluripotent states. Here, we will discuss Wnt's roles in maintaining pluripotency, promoting differentiation, as well as stimulating reprogramming of somatic cells to an induced pluripotent state.

Wnt/β-catenin signaling stimulates the self-renewal of conjunctival stem cells and promotes corneal conjunctivalization

Limbal stem cell deficiency causes conjunctivalization characterized by the covering of the corneal surface with conjunctival epithelium. However, the driving force for the encroachment of these conjunctival cells is unclear. Conjunctival stem cells are bipotent stem cells that can proliferate and differentiate into conjunctival epithelial cells and goblet cells to maintain regeneration of the conjunctival epithelium. Here, we show a robust proliferative response of conjunctival stem cells and upregulation of Wnt2b and Wnt3a gene expression in the conjunctivae of mice with induced limbal stem cell deficiency. Topical application of the Wnt/β-catenin signaling activator CHIR resulted in increased proliferation of ΔNp63α-positive stem cells in the basal layers of the bulbar and forniceal conjunctivae and enhanced invasion of conjunctival epithelial and goblet cells into the corneal surface. We also found that in cultures of stem cells isolated from the human conjunctiva, Wnt/β-catenin pathway activation improved the expansion of the ΔNp63α/ABCG2 double-positive cell population by promoting the proliferation and preventing the differentiation of these cells. These expanded stem cells formed a stratified epithelium containing goblet cells under airlift culture conditions. Our data reveal that Wnt/β-catenin signaling contributes to the pathological process of limbal stem cell deficiency by promoting the self-renewal of conjunctival stem cells and suggest that these cells are a driving force in corneal conjunctivalization.

A major signaling pathway that regulates stem cell function acts as a key mediator of conjunctival invasion into the cornea following eye injuries. Using human tissue and mouse models, a team from South Korea led by Chang Rae Rho of Daejeon St. Mary’s Hospital and Jungmook Lyu of Konyang University, Daejon, showed how insults to the eye can spur the proliferation of stem cells found in the conjunctiva, the thin membrane covering the white part of the eyeball. This cell growth and self-renewal is driven by increased activity of the Wnt/β-catenin signaling pathway, leading to conjunctivalization of the cornea, the transparent outer layer of the eye, resulting in corneal opacity and loss of vision. Therapies that manipulate this signaling pathway could help improve vision for people with certain corneal diseases.

GSK3β Interacts With CRMP2 and Notch1 and Controls T-Cell Motility

The trafficking of T-cells through peripheral tissues and into afferent lymphatic vessels is essential for immune surveillance and an adaptive immune response. Glycogen synthase kinase 3β (GSK3β) is a serine/threonine kinase and regulates numerous cell/tissue-specific functions, including cell survival, metabolism, and differentiation. Here, we report a crucial involvement of GSK3β in T-cell motility. Inhibition of GSK3β by CHIR-99021 or siRNA-mediated knockdown augmented the migratory behavior of human T-lymphocytes stimulated via an engagement of the T-cell integrin LFA-1 with its ligand ICAM-1. Proteomics and protein network analysis revealed ongoing interactions among GSK3β, the surface receptor Notch1 and the cytoskeletal regulator CRMP2. LFA-1 stimulation in T-cells reduced Notch1-dependent GSK3β activity by inducing phosphorylation at Ser9 and its nuclear translocation accompanied by the cleaved Notch1 intracellular domain and decreased GSK3β-CRMP2 association. LFA-1-induced or pharmacologic inhibition of GSK3β in T-cells diminished CRMP2 phosphorylation at Thr514. Although substantial amounts of CRMP2 were localized to the microtubule-organizing center in resting T-cells, this colocalization of CRMP2 was lost following LFA-1 stimulation. Moreover, the migratory advantage conferred by GSK3β inhibition in T-cells by CHIR-99021 was lost when CRMP2 expression was knocked-down by siRNA-induced gene silencing. We therefore conclude that GSK3β controls T-cell motility through interactions with CRMP2 and Notch1, which has important implications in adaptive immunity, T-cell mediated diseases and LFA-1-targeted therapies.

Indoleamine 2, 3 Dioxygenase 1 Impairs Chondrogenic Differentiation of Mesenchymal Stem Cells in the Joint of Osteoarthritis Mice Model

Osteoarthritis (OA) is a serious joint inflammation that leads to cartilage degeneration and joint dysfunction. Mesenchymal stem cells (MSCs) are used as a cell-based therapy that showed promising results in promoting cartilage repair. However, recent studies and clinical trials explored unsatisfied outcomes because of slow chondrogenic differentiation and increased calcification without clear reasons. Here, we report that the overexpression of indoleamine 2,3 dioxygenase 1 (IDO1) in the synovial fluid of OA patients impairs chondrogenic differentiation of MSCs in the joint of the OA mice model. The effect of MSCs mixed with IDO1 inhibitor on the cartilage regeneration was tested compared to MSCs mixed with IDO1 in the OA animal model. Further, the mechanism exploring the effect of IDO1 on chondrogenic differentiation was investigated. Subsequently, miRNA transcriptome sequencing was performed for MSCs cocultured with IDO1, and then TargetScan was used to verify the target of miR-122-5p in the SF-MSCs. Interestingly, we found that MSCs mixed with IDO1 inhibitor showed a significant performance to promote cartilage regeneration in the OA animal model, while MSCs mixed with IDO1 failed to stimulate cartilage regeneration. Importantly, the overexpression of IDO1 showed significant inhibition to Sox9 and Collagen type II (COL2A1) through activating the expression of β-catenin, since inhibiting of IDO1 significantly promoted chondrogenic signaling of MSCs (Sox9, COL2A1, Aggrecan). Further, miRNA transcriptome sequencing of SF-MSCs that treated with IDO1 showed significant downregulation of miR-122-5p which perfectly targets Wnt1. The expression of Wnt1 was noticed high when IDO1 was overexpressed. In summary, our results suggest that IDO1 overexpression in the synovial fluid of OA patients impairs chondrogenic differentiation of MSCs and cartilage regeneration through downregulation of miR-122-5p that activates the Wnt1/β-catenin pathway.

SM04755, a small-molecule inhibitor of the Wnt pathway, as a potential topical treatment for tendinopathy

The Wnt pathway is upregulated in tendinopathy, affecting inflammation and tenocyte differentiation. Given its potential role in tendinopathy, this signaling pathway may be a relevant target for treatment. The current study examined the therapeutic potential of SM04755, a topical, small-molecule Wnt pathway inhibitor, for the treatment of tendinopathy using in vitro assays and animal models. In vitro, SM04755 decreased Wnt pathway activity, induced tenocyte differentiation, and inhibited catabolic enzymes and pro-inflammatory cytokines in human mesenchymal stem cells, rat tendon-derived stem cells, and human peripheral blood mononuclear cells. Evaluation of the mechanism of action of SM04755 by biochemical profiling and computational modeling identified CDC-like kinase 2 (CLK2) and dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A) as molecular targets. CLK and DYRK1A inhibition by siRNA knockdown or pharmacological inhibition induced tenocyte differentiation and reduced tenocyte catabolism. In vivo, topically applied SM04755 showed therapeutically relevant exposure in tendons with low systemic exposure and no detectable toxicity in rats. Moreover, SM04755 showed reduced tendon inflammation and evidence of tendon regeneration, decreased pain, and improved weight-bearing function in rat collagenase-induced tendinopathy models compared with vehicle control. Together, these data demonstrate that CLK2 and DYRK1A inhibition by SM04755 resulted in Wnt pathway inhibition, enhanced tenocyte differentiation and protection, and reduced inflammation. SM04755 has the potential to benefit symptoms and modify disease processes in tendinopathy.

Small-molecule inhibitors of the PDZ domain of Dishevelled proteins interrupt Wnt signalling

Dishevelled (Dvl) proteins are important regulators of the Wnt signalling pathway, interacting through their PDZ domains with the Wnt receptor Frizzled. Blocking the Dvl PDZ-Frizzled interaction represents a potential approach for cancer treatment, which stimulated the identification of small-molecule inhibitors, among them the anti-inflammatory drug Sulindac and Ky-02327. Aiming to develop tighter binding compounds without side effects, we investigated structure-activity relationships of sulfonamides. X-ray crystallography showed high complementarity of anthranilic acid derivatives in the GLGF loop cavity and space for ligand growth towards the PDZ surface. Our best binding compound inhibits Wnt signalling in a dose-dependent manner as demonstrated by TOP-GFP assays (IC50 ∼ 50  µ M ) and Western blotting of β -catenin levels. Real-time PCR showed reduction in the expression of Wnt-specific genes. Our compound interacted with Dvl-1 PDZ (KD = 2.4  µ M ) stronger than Ky-02327 and may be developed into a lead compound interfering with the Wnt pathway.

Glycogen synthase kinase-3ß supports serotonin transporter function and trafficking in a phosphorylation-dependent manner

Serotonin (5-HT) transporter (SERT) plays a crucial role in serotonergic transmission in the central nervous system, and any aberration causes serious mental illnesses. Nevertheless, the cellular mechanisms that regulate SERT function and trafficking are not entirely understood. Growing evidence suggests that several protein kinases act as modulators. Here, we delineate the molecular mechanisms by which glycogen synthase kinase-3ß (GSK3ß) regulates SERT. When mouse striatal synaptosomes were treated with the GSK3α/ß inhibitor CHIR99021, we observed a significant increase in SERT function, V_max , surface expression with a reduction in 5-HT K_m and SERT phosphorylation. To further study how the SERT molecule is affected by GSK3α/ß, we used HEK-293 cells as a heterologous expression system. As in striatal synaptosomes, CHIR99021 treatment of cells expressing wild-type hSERT (hSERT-WT) resulted in a time and dose-dependent elevation of hSERT function with a concomitant increase in the V_max and surface transporters because of reduced internalization and enhanced membrane insertion; silencing GSK3α/ß in these cells with siRNA also similarly affected hSERT. Converting putative GSK3α/ß phosphorylation site serine at position 48 to alanine in hSERT (hSERT-S48A) completely abrogated the effects of both the inhibitor CHIR99021 and GSK3α/ß siRNA. Substantiating these findings, over-expression of constitutively active GSK3ß with hSERT-WT, but not with hSERT-S48A, reduced SERT function, V_max , surface density, and enhanced transporter phosphorylation. Both hSERT-WT and hSERT-S48A were inhibited similarly by PKC activation or by inhibition of Akt, CaMKII, p38 MAPK, or Src kinase. These findings provide new evidence that GSK3ß supports basal SERT function and trafficking via serine-48 phosphorylation.

AICAR Stimulates the Pluripotency Transcriptional Complex in Embryonic Stem Cells Mediated by PI3K, GSK3β, and β-Catenin

Pluripotent stem cells maintain the property of self-renewal and differentiate into all cell types under clear environments. Though the gene regulatory mechanism for pluripotency has been investigated in recent years, it is still not completely understood. Here, we show several signaling pathways involved in the maintenance of pluripotency. To investigate whether AMPK is involved in maintaining the pluripotency in mouse embryonic stem cells (mESCs) and elucidating the possible molecular mechanisms, implicated D3 and R1/E mESC lines were used in this study. Cells were cultured in the absence or presence of LIF and treated with 1 mM and 0.5 mM 5-aminoimidazole-4-carboxamide-1-β-d-ribofuranoside (AICAR), 2 mM metformin, compound C, and the PI3K inhibitor LY294002 for 24, 72, and 120 h. The levels of Nanog, Oct3/4, and REX1 and Brachyury, Notch2, and Gata4 mRNAs and Nanog or OCT3/4 protein levels were analyzed. Alkaline phosphatase and the cellular cycle were determined. The pGSK3β, GSK3β, p-β-catenin, and β-catenin protein levels were also investigated. We found that AMPK activators such as AICAR and metformin increase mRNA expression of pluripotency markers and decrease mRNA expression of differentiation markers in R1/E and D3 ES cells. AICAR increases phosphatase activity and arrests the cellular cycle in the G1 phase in these cells. We describe that AICAR effects were mediated by AMPK activation using a chemical inhibitor or by silencing this gene. AICAR effects were also mediated by PI3K, GSK3β, and β-catenin in R1/E ES cells. According to our findings, we provide a mechanism by which AICAR increases and maintains a pluripotency state through enhanced Nanog expression, involving AMPK/PI3K and p-GSK3β Ser21/9 pathways backing up the AICAR function as a potential target for this drug controlling pluripotency. The highlights of this study are that AICAR (5-aminoimidazole-4-carboxamied-1-b-riboside), an AMP protein kinase (AMPK) activator, blocks the ESC differentiation and AMPK is a key enzyme for pluripotency and shows valuable data to clarify the molecular pluripotency mechanism.

Glycogen synthase kinase 3β inhibitor- CHIR 99021 augments the differentiation potential of mesenchymal stem cells

AIM

Mesenchymal stem cells (MSCs) are immunomodulatory, non-teratogenic and multipotent alternatives to embryonic or induced pluripotent stem cells (ESCs or iPSCs). However, the potency of MSCs is not equivalent to the pluripotency of ESCs or iPSCs. We used CHIR 99021 to improve current protocols and methods of differentiation for the enhanced transdifferentiation potency of MSCs.

MAIN METHODS

We used Flurescence activated cell sorter (FACS) for MSC immunophenotyping and biochemical assay for demonstrating the trilineage potential of MSCs. We used real-time polymerase chain reaction, immunocytochemistry and Western blotting assay for analyzing the expression of lineage-specific markers.

KEY FINDINGS

CHIR 99021 treatment of MSCs resulted in enhanced transdifferentiation into neurological, hepatogenic and cardiomyocyte lineages with standardized protocols of differentiation. CHIR 99021-treated MSCs showed increased nuclear localization of β-catenin. These MSCs showed a significantly increased deposition of active histone marks (H3K4Me3, H3K36Me3), whereas no change was observed in repressive marks (H3K9Me3, H3K27Me3). Differential methylation profiling showed demethylation of the transcription factor OCT4 promoter region with subsequent analysis revealing increased gene expression and protein content. The HLA-DR antigen was absent in CHIR 99021-treated MSCs and their differentiated cell types, indicating their immune-privileged status. Karyotyping analysis showed that CHIR 99021-treated MSCs were genomically stable. Teratoma analysis of nude mice injected with CHIR 99021-treated MSCs showed the increased presence of cell types of mesodermal origin at the site of injection.

SIGNIFICANCE

MSCs pretreated with CHIR 99021 can be potent, abundant alternative sources of stem cells with enhanced differentiation capabilities that are well suited to cell-based regenerative therapy.

Cyclin G2 suppresses Wnt/β-catenin signaling and inhibits gastric cancer cell growth and migration through Dapper1

BACKGROUND

Gastric cancer is one of the most common malignant tumors. Cyclin G2 has been shown to be associated with the development of multiple types of tumors, but its underlying mechanisms in gastric tumors is not well-understood. The aim of this study is to investigate the role and the underlying mechanisms of cyclin G2 on Wnt/β-catenin signaling in gastric cancer.

METHODS

Real-time PCR, immunohistochemistry and in silico assay were used to determine the expression of cyclin G2 in gastric cancer. TCGA datasets were used to evaluate the association between cyclin G2 expression and the prognostic landscape of gastric cancers. The effects of ectopic and endogenous cyclin G2 on the proliferation and migration of gastric cancer cells were assessed using the MTS assay, colony formation assay, cell cycle assay, wound healing assay and transwell assay. Moreover, a xenograft model and a metastasis model of nude mice was used to determine the influence of cyclin G2 on gastric tumor growth and migration in vivo. The effects of cyclin G2 expression on Wnt/β-catenin signaling were explored using a TOPFlash luciferase reporter assay, and the molecular mechanisms involved were investigated using immunoblots assay, yeast two-hybrid screening, immunoprecipitation and Duolink in situ PLA. Ccng2-/- mice were generated to further confirm the inhibitory effect of cyclin G2 on Wnt/β-catenin signaling in vivo. Furthermore, GSK-3β inhibitors were utilized to explore the role of Wnt/β-catenin signaling in the suppression effect of cyclin G2 on gastric cancer cell proliferation and migration.

RESULTS

We found that cyclin G2 levels were decreased in gastric cancer tissues and were associated with tumor size, migration and poor differentiation status. Moreover, overexpression of cyclin G2 attenuated tumor growth and metastasis both in vitro and in vivo. Dpr1 was identified as a cyclin G2-interacting protein which was required for the cyclin G2-mediated inhibition of β-catenin expression. Mechanically, cyclin G2 impacted the activity of CKI to phosphorylate Dpr1, which has been proved to be a protein that acts as a suppressor of Wnt/β-catenin signaling when unphosphorylated. Furthermore, GSK-3β inhibitors abolished the cyclin G2-induced suppression of cell proliferation and migration.

CONCLUSIONS

This study demonstrates that cyclin G2 suppresses Wnt/β-catenin signaling and inhibits gastric cancer cell growth and migration through Dapper1.

Autophagy induces G0/G1 arrest and apoptosis in menstrual blood-derived endometrial stem cells via GSK3-β/β-catenin pathway

BACKGROUND/AIMS

Menstrual blood-derived endometrial stem cells (MenSCs) emerge as an ideal source for cell-based treatment in regenerative medicine and immunotherapy. However, the major obstacle is the low survival rate in tissues and the limited expansion number. Autophagy is an intracellular metabolic self-degradative process which plays important roles in normal cellular division and survival, and the present study aimed to explore the related mechanisms between autophagy and survival of MenSCs in vitro and in vivo.

METHODS

The MenSCs were obtained from menstrual blood procured from healthy female donors. In vitro, MenSCs were exposed to rapamycin and Earle's balanced salts solution (EBSS). We evaluated the MenSCs immunophenotypic cell cycle distribution by propidium iodide (PI) staining and cell apoptosis by Annexin V/PI staining as well as their proliferative potential by the MTT assay. We also assessed the expression of genes associated with the cell cycle and Gsk3β signaling pathway by western blot analysis. We depressed Atg5 and Gsk3β expression by short hairpin RNA (shRNA) and undertook the experiments. Moreover, the labeled MenSCs were observed and counted with DiI after transplantation into the mice via the tail vein by microscopy in vivo.

RESULTS

In vitro, rapamycin and starvation induced autophagy of MenSCs. Hyperactive autophagy significantly induced G0/G1 arrest and slightly promoted apoptosis of MenSCs. Meanwhile, autophagy could stimulate p-GSK3β expression in MenSCs. Further, knockdown GSK3β can accelerate the proliferation of MenSCs by shRNA and CHIR99021. Moreover, the shGSK3β MenSCs showed strong proliferative activity in vitro and in vivo.

CONCLUSIONS

Our results indicate that autophagy induced G0/G1 arrest and apoptosis of MenSCs via GSK3β/β-catenin pathway. Inhibiting autophagy or reduced GSK3β levels may improve survival rate in vivo, thus playing roles in MenSCs therapy.

Inhibition of GSK3 and MEK induced cancer stem cell generation via the Wnt and MEK signaling pathways

Cancer stem cells (CSCs) are considered to be tumor-initiating cells, responsible for tumor invasive growth and dissemination to distant organ sites. Typically, radiation treatment and chemotherapy should target CSCs. However, current research investigating CSCs is impeded by the difficulty of isolating pure CSCs and maintaining them in vitro. In the present study, the synergistic inhibition of glycogen synthase kinase 3 and mitogen-activated protein kinase kinase using small molecules, CHIR99021 and PD184352, efficiently generated CSCs from immortalized human mammary epithelial cells (HMLEs) and resulted in the acquisition of mesenchymal traits and the expression of epithelial-mesenchymal transition markers. The cell proliferation, invasion and migration of HMLE cells were significantly promoted by CHIR99021 and PD184352 (P<0.05). Furthermore, the cell cycle was shifted from the G0/G1 phase to the G2/M phase, and the apoptotic rate was suppressed in HMLE cells following treatment with CHIR99021 and PD184352. Compared with control group, the stimulated cells exhibited an increased ability to form mammospheres and regenerate a tumor. In addition to these properties, the induced cells also exhibited notable chemotherapy resistance. In vivo, the treatment of cells with CHIR99021 and PD184352 promoted the growth of HMLE-engrafted tumor types. These results provide a practical strategy for the generation of CSCs using small molecules in vitro, which provides a cell resource that may be used for drug screening. Additionally, the present results additionally highlighted the synergistic functions of Wnt and mitogen-activated protein kinase kinase signaling pathways in tumorigenesis.

Wnt activation followed by Notch inhibition promotes mitotic hair cell regeneration in the postnatal mouse cochlea

Hair cell (HC) loss is the main cause of permanent hearing loss in mammals. Previous studies have reported that in neonatal mice cochleae, Wnt activation promotes supporting cell (SC) proliferation and Notch inhibition promotes the trans-differentiation of SCs into HCs. However, Wnt activation alone fails to regenerate significant amounts of new HCs, Notch inhibition alone regenerates the HCs at the cost of exhausting the SC population, which leads to the death of the newly regenerated HCs. Mitotic HC regeneration might preserve the SC number while regenerating the HCs, which could be a better approach for long-term HC regeneration. We present a two-step gene manipulation, Wnt activation followed by Notch inhibition, to accomplish mitotic regeneration of HCs while partially preserving the SC number. We show that Wnt activation followed by Notch inhibition strongly promotes the mitotic regeneration of new HCs in both normal and neomycin-damaged cochleae while partially preserving the SC number. Lineage tracing shows that the majority of the mitotically regenerated HCs are derived specifically from the Lgr5⁺ progenitors with or without HC damage. Our findings suggest that the co-regulation of Wnt and Notch signaling might provide a better approach to mitotically regenerate HCs from Lgr5⁺ progenitor cells.

Divergent effects of Wnt/β-catenin signaling modifiers on the preservation of human limbal epithelial progenitors according to culture condition

Wnt signaling plays an important role in the regulation of self-renewal in stem cells. Here we investigated the effect of CHIR99021, the primary transducer of the Wnt signaling canonical pathway, and IWP2, a wide action Wnt signal blocker, on the growth and differentiation of the limbal epithelial progenitor cells when these cells are cultured in two different, common culture approaches, outgrowth from limbal biopsy explants and isolated cell seeded in low calcium medium. Consistent with their expected effects, irrespective of the culture system, IWP2 decreased total β-catenin while CHIR99021 increased it in nuclear localization. However, IWP2 increased stem/progenitor cell marker (p63α and ABCG2) content and clonogenic capacity in the explants but had opposite effects on isolated cells. CHIR99021 reduced the growth rate, stem/progenitor cell marker content and clonogenic capacity in the explants but also had the opposite effect on the isolated cells. These results show that the outcome of Wnt/β-catenin signaling modification is dependent on the culture systems. Transplantation of limbal epithelial sheets from explant cultures is one of the standard treatments of limbal stem cell deficiency. Our study shows that Wnt-associated activity has a strong negative impact on stem/progenitor cell preservation in limbal explant cultures.

An ongoing role for Wnt signaling in differentiating melanocytes in vivo

A role for Wnt signaling in melanocyte specification from neural crest is conserved across vertebrates, but possible ongoing roles in melanocyte differentiation have received little attention. Using a systems biology approach to investigate the gene regulatory network underlying stable melanocyte differentiation in zebrafish highlighted a requirement for a positive-feedback loop involving the melanocyte master regulator Mitfa. Here, we test the hypothesis that Wnt signaling contributes to that positive feedback. We show firstly that Wnt signaling remains active in differentiating melanocytes and secondly that enhanced Wnt signaling drives elevated transcription of mitfa. We show that chemical activation of the Wnt signaling pathway at early stages of melanocyte development enhances melanocyte specification as expected, but importantly that at later (differentiation) stages, it results in altered melanocyte morphology, although melanisation is not obviously affected. Downregulation of Wnt signaling also results in altered melanocyte morphology and organization. We conclude that Wnt signaling plays a role in regulating ongoing aspects of melanocyte differentiation in zebrafish.

In Vitro Generated Hepatocyte-Like Cells: A Novel Tool in Regenerative Medicine and Drug Discovery

Hepatocyte-like cells (HLCs) are generated from either various human pluripotent stem cells (hPSCs) including induced pluripotent stem cells (iPSCs) and embryonic stem cells (ESCs), or direct cell conversion, mesenchymal stem cells as well as other stem cells like gestational tissues. They provide potential cell sources for biomedical applications. Liver transplantation is the gold standard treatment for the patients with end stage liver disease, but there are many obstacles limiting this process, like insufficient number of donated healthy livers. Meanwhile, the number of patients receiving a liver organ transplant for a better life is increasing. In this regard, HLCs may provide an adequate cell source to overcome these shortages. New molecular engineering approaches such as CRISPR/ Cas system applying in iPSCs technology provide the basic principles of gene correction for monogenic inherited metabolic liver diseases, as another application of HLCs. It has been shown that HLCs could replace primary human hepatocytes in drug discovery and hepatotoxicity tests. However, generation of fully functional HLCs is still a big challenge; several research groups have been trying to improve current differentiation protocols to achieve better HLCs according to morphology and function of cells. Large-scale generation of functional HLCs in bioreactors could make a new opportunity in producing enough hepatocytes for treating end-stage liver patients as well as other biomedical applications such as drug studies. In this review, regarding the biomedical value of HLCs, we focus on the current and efficient approaches for generating hepatocyte-like cells in vitro and discuss about their applications in regenerative medicine and drug discovery.

miR302 regulates SNAI1 expression to control mesangial cell plasticity

Cell fate decisions are controlled by the interplay of transcription factors and epigenetic modifiers, which together determine cellular identity. Here we elaborate on the role of miR302 in the regulation of cell plasticity. Overexpression of miR302 effected silencing of the TGFβ type II receptor and facilitated plasticity in a manner distinct from pluripotency, characterized by increased expression of Snail. miR302 overexpressing mesangial cells also exhibited enhanced expression of EZH2 coincident with Snail upregulation. esiRNA silencing of each component suggest that Smad3 and EZH2 are part of a complex that regulates plasticity and that miR302 regulates EZH2 and Snail independently. Subsequent manipulation of miR302 overexpressing cells demonstrated the potential of using this approach for reprogramming as evidenced by de novo expression of the tight junction components ZO-1 and E-cadherin and the formation of ZO-1 containing tight junctions. Understanding the processes through which dynamic epigenetic silencing is controlled in adults cells will allow us to address the epigenetic state of acquired disease and whether original states, regenerative in nature, can be restored with therapy.

Autocrine Wnt regulates the survival and genomic stability of embryonic stem cells

Wnt signaling plays an important role in the self-renewal and differentiation of stem cells. The secretion of Wnt ligands requires Evi (also known as Wls). Genetically ablating Evi provides an experimental approach to studying the consequence of depleting all redundant Wnt proteins, and overexpressing Evi enables a nonspecific means of increasing Wnt signaling. We generated Evi-deficient and Evi-overexpressing mouse embryonic stem cells (ESCs) to analyze the role of autocrine Wnt production in self-renewal and differentiation. Self-renewal was reduced in Evi-deficient ESCs and increased in Evi-overexpressing ESCs in the absence of leukemia inhibitory factor, which supports the self-renewal of ESCs. The differentiation of ESCs into cardiomyocytes was enhanced when Evi was overexpressed and teratoma formation and growth of Evi-deficient ESCs in vivo were impaired, indicating that autocrine Wnt ligands were necessary for ESC differentiation and survival. ESCs lacking autocrine Wnt signaling had mitotic defects and showed genomic instability. Together, our study demonstrates that autocrine Wnt secretion is important for the survival, chromosomal stability, differentiation, and tumorigenic potential of ESCs.

Allelic Imbalance in Regulation of ANRIL through Chromatin Interaction at 9p21 Endometriosis Risk Locus

Genome-wide association studies (GWASs) have discovered numerous single nucleotide polymorphisms (SNPs) associated with human complex disorders. However, functional characterization of the disease-associated SNPs remains a formidable challenge. Here we explored regulatory mechanism of a SNP on chromosome 9p21 associated with endometriosis by leveraging “allele-specific” functional genomic approaches. By re-sequencing 1.29 Mb of 9p21 region and scrutinizing DNase-seq data from the ENCODE project, we prioritized rs17761446 as a candidate functional variant that was in perfect linkage disequilibrium with the original GWAS SNP (rs10965235) and located on DNase I hypersensitive site. Chromosome conformation capture followed by high-throughput sequencing revealed that the protective G allele of rs17761446 exerted stronger chromatin interaction with ANRIL promoter. We demonstrated that the protective allele exhibited preferential binding affinities to TCF7L2 and EP300 by bioinformatics and chromatin immunoprecipitation (ChIP) analyses. ChIP assays for histone H3 lysine 27 acetylation and RNA polymerase II reinforced the enhancer activity of the SNP site. The allele specific expression analysis for eutopic endometrial tissues and endometrial carcinoma cell lines showed that rs17761446 was a cis-regulatory variant where G allele was associated with increased ANRIL expression. Our work illuminates the allelic imbalances in a series of transcriptional regulation from factor binding to gene expression mediated by chromatin interaction underlie the molecular mechanism of 9p21 endometriosis risk locus. Functional genomics on common disease will unlock functional aspect of genotype-phenotype correlations in the post-GWAS stage.

A large number of variants associated with human complex diseases have been discovered by genome-wide association studies (GWASs). These discoveries have been anticipated to be translated into the definitive understanding of disease pathogeneses; however, functional characterization of the disease-associated SNPs remains a formidable challenge. Here we explored regulatory mechanism of a variant on chromosome 9p21 associated with endometriosis, a common gynecological disorder. By scrutinizing linkage disequilibrium structure and DNase I hypersensitive sites across the risk locus, we prioritized rs17761446 as a candidate causal variant. The results of our “allele-specific” functional genomic approaches sheds light on regulatory mechanisms underlying 9p21 endometriosis risk locus, in which preferential bindings of TCF7L2 and its coactivator EP300 to the protective G allele of rs17761446 lead to stronger chromatin interaction with the promoter of ANRIL, which in turn activate transcription of the non-coding RNA. Motivated by the fact that TCF7L2 was a key transcription factor of Wnt signaling pathway, we postulated that the induction of Wnt signaling activated expression levels of ANRIL and cell cycle inhibitors, CDKN2A/2B. Functional genomics on common disease will unlock functional aspect of genotype-phenotype correlations in the post-GWAS stage.

Nitric Oxide Prevents Mouse Embryonic Stem Cell Differentiation Through Regulation of Gene Expression, Cell Signaling, and Control of Cell Proliferation

Nitric oxide (NO) delays mouse embryonic stem cell (mESC) differentiation by regulating genes linked to pluripotency and differentiation. Nevertheless, no profound study has been conducted on cell differentiation regulation by this molecule through signaling on essential biological functions. We sought to demonstrate that NO positively regulates the pluripotency transcriptional core, enforcing changes in the chromatin structure, in addition to regulating cell proliferation, and signaling pathways with key roles in stemness. Culturing mESCs with 2 μM of the NO donor diethylenetriamine/NO (DETA/NO) in the absence of leukemia inhibitory factor (LIF) induced significant changes in the expression of 16 genes of the pluripotency transcriptional core. Furthermore, treatment with DETA/NO resulted in a high occupancy of activating H3K4me3 at the Oct4 and Nanog promoters and repressive H3K9me3 and H3k27me3 at the Brachyury promoter. Additionally, the activation of signaling pathways involved in pluripotency, such as Gsk3-β/β-catenin, was observed, in addition to activation of PI3 K/Akt, which is consistent with the protection of mESCs from cell death. Finally, a decrease in cell proliferation coincides with cell cycle arrest in G2/M. Our results provide novel insights into NO-mediated gene regulation and cell proliferation and suggest that NO is necessary but not sufficient for the maintenance of pluripotency and the prevention of cell differentiation. J. Cell. Biochem. 117: 2078-2088, 2016. © 2016 Wiley Periodicals, Inc.

A Small-Molecule Antagonist of the β-Catenin/TCF4 Interaction Blocks the Self-Renewal of Cancer Stem Cells and Suppresses Tumorigenesis

Wnt/β-catenin signaling is a highly conserved pathway essential for embryogenesis and tissue homeostasis. However, deregulation of this pathway can initiate and promote human malignancies, especially of the colon and head and neck. Therefore, Wnt/β-catenin signaling represents an attractive target for cancer therapy. We performed high-throughput screening using AlphaScreen and ELISA techniques to identify small molecules that disrupt the critical interaction between β-catenin and the transcription factor TCF4 required for signal transduction. We found that compound LF3, a 4-thioureido-benzenesulfonamide derivative, robustly inhibited this interaction. Biochemical assays revealed clues that the core structure of LF3 was essential for inhibition. LF3 inhibited Wnt/β-catenin signals in cells with exogenous reporters and in colon cancer cells with endogenously high Wnt activity. LF3 also suppressed features of cancer cells related to Wnt signaling, including high cell motility, cell-cycle progression, and the overexpression of Wnt target genes. However, LF3 did not cause cell death or interfere with cadherin-mediated cell-cell adhesion. Remarkably, the self-renewal capacity of cancer stem cells was blocked by LF3 in concentration-dependent manners, as examined by sphere formation of colon and head and neck cancer stem cells under nonadherent conditions. Finally, LF3 reduced tumor growth and induced differentiation in a mouse xenograft model of colon cancer. Collectively, our results strongly suggest that LF3 is a specific inhibitor of canonical Wnt signaling with anticancer activity that warrants further development for preclinical and clinical studies as a novel cancer therapy.

Rapid and robust generation of long-term self-renewing human neural stem cells with the ability to generate mature astroglia

Induced pluripotent stem cell bear the potential to differentiate into any desired cell type and hold large promise for disease-in-a-dish cell-modeling approaches. With the latest advances in the field of reprogramming technology, the generation of patient-specific cells has become a standard technology. However, directed and homogenous differentiation of human pluripotent stem cells into desired specific cell types remains an experimental challenge. Here, we report the development of a novel hiPSCs-based protocol enabling the generation of expandable homogenous human neural stem cells (hNSCs) that can be maintained under self-renewing conditions over high passage numbers. Our newly generated hNSCs retained differentiation potential as evidenced by the reliable generation of mature astrocytes that display typical properties as glutamate up-take and expression of aquaporin-4. The hNSC-derived astrocytes showed high activity of pyruvate carboxylase as assessed by stable isotope assisted metabolic profiling. Moreover, using a cell transplantation approach, we showed that grafted hNSCs were not only able to survive but also to differentiate into astroglial in vivo. Engraftments of pluripotent stem cells derived from somatic cells carry an inherent tumor formation potential. Our results demonstrate that hNSCs with self-renewing and differentiation potential may provide a safer alternative strategy, with promising applications especially for neurodegenerative disorders.

Divergent Androgen Receptor and Beta-Catenin Signaling in Prostate Cancer Cells

Despite decades of effort to develop effective therapy and to identify promising new drugs, prostate cancer is lethal once it progresses to castration-resistant disease. Studies show mis-regulation of multiple pathways in castration-resistant prostate cancer (CRPC), reflecting the heterogeneity of the tumors and also hinting that targeting androgen receptor (AR) pathway alone might not be sufficient to treat CRPC. In this study, we present evidence that the Wnt/β-catenin pathway might be activated in prostate cancer cells after androgen-deprivation to promote androgen-independent growth, partly through enhanced interaction of β-catenin with TCF4. Androgen-independent prostate cancer cells were more prone to activate a Wnt-reporter, and inhibition of the Wnt/β-catenin pathway increased sensitivity of these cells to the second-generation antiandrogen, enzalutamide. Combined treatment of enzalutamide and Wnt/β-catenin inhibitor showed increased growth repression in both androgen-dependent and -independent prostate cancer cells, suggesting therapeutic potential for this approach.

Regulation of autophagic cell death by glycogen synthase kinase-3β in adult hippocampal neural stem cells following insulin withdrawal

Background

Neural stem cells (NSCs) hold great potential for the treatment of neurodegenerative diseases. However, programmed cell death (PCD) provoked by the harsh conditions evident in the diseased brain greatly undermines the potential of NSCs. Currently, the mechanisms of PCD that effect NSCs remain largely unknown.

Results

We have previously reported that hippocampal neural stem (HCN) cells derived from the adult rat brain undergo autopahgic cell death (ACD) following insulin withdrawal without hallmarks of apoptosis despite their normal apoptotic capabilities. In this study, we demonstrate that glycogen synthase kinase 3β (GSK-3β) induces ACD in insulin-deprived HCN cells. Both pharmacological and genetic inactivation of GSK-3β significantly decreased ACD, while activation of GSK-3β increased autophagic flux and caused more cell death without inducing apoptosis following insulin withdrawal. In contrast, knockdown of GSK-3α barely affected ACD, lending further support to the critical role of GSK-3β.

Conclusion

Collectively, these data demonstrate that GSK-3β is a key regulator of ACD in HCN cells following insulin withdrawal. The absence of apoptotic indices in GSK-3β-induced cell death in insulin-deprived HCN cells corroborates the notion that HCN cell death following insulin withdrawal represents the genuine model of ACD in apoptosis-intact mammalian cells and identifies GSK-3β as a key negative effector of NSC survival downstream of insulin signaling.

In vitro culture of stem-like cells derived from somatic cell nuclear transfer bovine embryos of the Korean beef cattle species, HanWoo

We established and maintained somatic cell nuclear transfer embryo-derived stem-like cells (SCNT-eSLCs) from the traditional Korean beef cattle species, HanWoo (Bos taurus coreanae). Each SCNT blastocyst was placed individually on a feeder layer with culture medium containing three inhibitors of differentiation (3i). Primary colonies formed after 2-3 days of culture and the intact colonies were passaged every 5-6 days. The cells in each colony showed embryonic stem cell-like morphologies with a distinct boundary and were positive to alkaline phosphatase staining. Immunofluorescence and reverse transcription-polymerase chain reaction analyses also confirmed that these colonies expressed pluripotent markers. The colonies were maintained over 50 passages for more than 270 days. The cells showed normal karyotypes consisting of 60 chromosomes at Passage 50. Embryoid bodies were formed by suspension culture to analyse in vitro differentiation capability. Marker genes representing the differentiation into three germ layers were expressed. Typical embryonal carcinoma was generated after injecting cells under the testis capsule of nude mice, suggesting that the cultured cells may also have the potential of in vivo differentiation. In conclusion, we generated eSLCs from SCNT bovine embryos, using a 3i system that sustained stemness, normal karyotype and pluripotency, which was confirmed by in vitro and in vivo differentiation.

Small-molecule-driven hepatocyte differentiation of human pluripotent stem cells

The differentiation of pluripotent stem cells to hepatocytes is well established, yet current methods suffer from several drawbacks. These include a lack of definition and reproducibility, which in part stems from continued reliance on recombinant growth factors. This has remained a stumbling block for the translation of the technology into industry and the clinic for reasons associated with cost and quality. We have devised a growth-factor-free protocol that relies on small molecules to differentiate human pluripotent stem cells toward a hepatic phenotype. The procedure can efficiently direct both human embryonic stem cells and induced pluripotent stem cells to hepatocyte-like cells. The final population of cells demonstrates marker expression at the transcriptional and protein levels, as well as key hepatic functions such as serum protein production, glycogen storage, and cytochrome P450 activity.

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Development of small-molecule-driven hepatocyte differentiation procedure for hPSCs

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Small-molecule-derived hepatocytes demonstrate key hepatic functions

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Significantly reduces the cost of hepatocyte differentiation

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Procedure is applicable to multiple human pluripotent stem cell lines

GSK3 inhibitors CHIR99021 and 6-bromoindirubin-3'-oxime inhibit microRNA maturation in mouse embryonic stem cells

Wnt/β-catenin signalling plays a prominent role in maintaining self-renewal and pluripotency of mouse embryonic stem cells (mESCs). microRNAs (miRNAs) have critical roles in maintaining pluripotency and directing reprogramming. To investigate the effect of GSK3 inhibitors on miRNA expression, we analysed the miRNA expression profile of J1 mESCs in the absence or presence of CHIR99021 (CHIR) or 6-bromoindirubin-3'-oxime (BIO) by small RNA deep-sequencing. The results demonstrate that CHIR and BIO decrease mature miRNAs of most miRNA species, 90.4% and 98.1% of the differentially expressed miRNAs in BIO and CHIR treated cells were downregulated respectively. CHIR and BIO treatment leads to a slight upregulation of the primary transcripts of the miR-302-367 cluster and miR-181 family of miRNAs, these miRNAs are activated by Wnt/β-catenin signalling. However, the precursor and mature form of the miR-302-367 cluster and miR-181 family of miRNAs are downregulated by CHIR, suggesting CHIR inhibits maturation of primary miRNA. Western blot analysis shows that BIO and CHIR treatment leads to a reduction of the RNase III enzyme Drosha in the nucleus. These data suggest that BIO and CHIR inhibit miRNA maturation by disturbing nuclear localisation of Drosha. Results also show that BIO and CHIR induce miR-211 expression in J1 mESCs.

Disruption of cell-cell contact-mediated notch signaling via hydrogel encapsulation reduces mesenchymal stem cell chondrogenic potential: winner of the Society for Biomaterials Student Award in the Undergraduate Category, Charlotte, NC, April 15 to 18, 2015

Cell-cell contact-mediated Notch signaling is essential for mesenchymal stem cell (MSC) chondrogenesis during development. However, subsequent deactivation of Notch signaling is also required to allow for stem cell chondrogenic progression. Recent literature has shown that Notch signaling can also influence Wnt/β-catenin signaling, critical for MSC differentiation, through perturbations in cell-cell contacts. Traditionally, abundant cell-cell contacts, consistent with development, are emulated in vitro using pellet cultures for chondrogenesis. However, cells are often encapsulated within biomaterials-based scaffolds, such as hydrogels, to improve therapeutic cell localization in vivo. To explore the role of Notch and Wnt/β-catenin signaling in the context of hydrogel-encapsulated MSC chondrogenesis, we compared signaling and differentiation capacity of MSCs in both hydrogels and traditional pellet cultures. We demonstrate that encapsulation within poly(ethylene glycol) hydrogels reduces cell-cell contacts, and both Notch (7.5-fold) and Wnt/β-catenin (84.7-fold) pathway activation. Finally, we demonstrate that following establishment of cell-cell contacts and transient Notch signaling in pellet cultures, followed by Notch signaling deactivation, resulted in a 1.5-fold increase in MSC chondrogenesis. Taken together, these findings support that cellular condensation, and establishment of initial cell-cell contacts is critical for MSC chondrogenesis, and this process is inhibited by hydrogel encapsulation.

Insulin-like growth factor-I induces epithelial to mesenchymal transition via GSK-3β and ZEB2 in the BGC-823 gastric cancer cell line

Metastasis is the most common cause of mortality in patients with gastric cancer. Epithelial-to-mesenchymal transition (EMT), which may be stimulated by insulin-like growth factor-I (IGF-I) is involved in the metastasis of numerous tumors; however, the molecular mechanism by which IGF-I may induce tumor cell EMT remains to be elucidated in gastric cancer. The present study aimed to investigate the induction of EMT in BGC-823 gastric cancer cells. It was identified that IGF-I induced EMT by upregulating the levels of ZEB2 transcription factor, and this was dependent on the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway in these cells. In addition, glycogen synthase kinase 3β (GSK-3β), an intracellular downstream effector of PI3K/Akt, sustained the epithelial phenotype by repressing ZEB2 expression and the subsequent inhibition of EMT induced by IGF-I, suggesting the involvement of a potential PI3K/Akt-GSK-3β-ZEB2 signaling pathway in IGF-I-induced EMT in gastric cancer BGC-823 cells. Overall, the results of the present study suggest that IGF-I induced EMT by the activation of a PI3K/Akt-GSK-3β-ZEB2 signaling pathway in gastric cancer BGC-823 cells. Therefore, this study may provide more useful information regarding the mechanism of gastric cancer metastasis.

The roles of Notch3 on the cell proliferation and apoptosis induced by CHIR99021 in NSCLC cell lines: a functional link between Wnt and Notch signaling pathways

Wnt and Notch signaling pathways both play essential roles and interact closely in development and carcinogenesis, but their interaction in non-small-cell lung cancer (NSCLC) is poorly unknown. Here we investigated the effects of CHIR99021, a Wnt signaling agonist, or Notch3-shRNA, or the combined application of CHIR99021 and Notch3-shRNA on cell proliferation and apoptosis, as well as the expressions of Notch3, its downstream genes, cyclinA and caspase-3. Our results showed that CHIR99021 up-regulated the expression of Notch3 protein and HES1 and HEYL mRNA. CHIR99021 promoted cell proliferation and the expression of cyclinA, which were inhibited by Notch3-shRNA in these three cell lines. Moreover, Notch3-shRNA significantly attenuated the positive effects of CHIR99021 on cell proliferation and cyclinA in H460 and H157. As for apoptosis, Notch3-shRNA induced cell apoptosis and increased the expression of caspase-3, whereas CHIR99021 showed the different effects in these three cell lines. The inhibitory effect of CHIR99021 on apoptosis was significantly weakened by Notch3-shRNA only in H460. Overall, although the effects of CHIR99021 and the combined application of CHIR99021 and Notch3-shRNA on the cell proliferation and apoptosis aren’t completely similar in the three cell lines, our findings still indicate that Notch3 signaling can be activated by canonical Wnt signaling and a functional link between Wnt and Notch signaling pathways exists in NSCLC, at least, which partially is associated with their regulations on the expressions of cyclinA and caspase-3.

Wnt/β-catenin signaling directs the regional expansion of first and second heart field-derived ventricular cardiomyocytes

In mammals, cardiac development proceeds from the formation of the linear heart tube, through complex looping and septation, all the while increasing in mass to provide the oxygen delivery demands of embryonic growth. The developing heart must orchestrate regional differences in cardiomyocyte proliferation to control cardiac morphogenesis. During ventricular wall formation, the compact myocardium proliferates more vigorously than the trabecular myocardium, but the mechanisms controlling such regional differences among cardiomyocyte populations are not understood. Control of definitive cardiomyocyte proliferation is of great importance for application to regenerative cell-based therapies. We have used murine and human pluripotent stem cell systems to demonstrate that, during in vitro cellular differentiation, early ventricular cardiac myocytes display a robust proliferative response to β-catenin-mediated signaling and conversely accelerate differentiation in response to inhibition of this pathway. Using gain- and loss-of-function murine genetic models, we show that β-catenin controls ventricular myocyte proliferation during development and the perinatal period. We further demonstrate that the differential activation of the Wnt/β-catenin signaling pathway accounts for the observed differences in the proliferation rates of the compact versus the trabecular myocardium during normal cardiac development. Collectively, these results provide a mechanistic explanation for the differences in localized proliferation rates of cardiac myocytes and point to a practical method for the generation of the large numbers of stem cell-derived cardiac myocytes necessary for clinical applications.

CHIR99021 promotes self-renewal of mouse embryonic stem cells by modulation of protein-encoding gene and long intergenic non-coding RNA expression

Embryonic stem cells (ESCs) can proliferate indefinitely in vitro and differentiate into cells of all three germ layers. These unique properties make them exceptionally valuable for drug discovery and regenerative medicine. However, the practical application of ESCs is limited because it is difficult to derive and culture ESCs. It has been demonstrated that CHIR99021 (CHIR) promotes self-renewal and enhances the derivation efficiency of mouse (m)ESCs. However, the downstream targets of CHIR are not fully understood. In this study, we identified CHIR-regulated genes in mESCs using microarray analysis. Our microarray data demonstrated that CHIR not only influenced the Wnt/β-catenin pathway by stabilizing β-catenin, but also modulated several other pluripotency-related signaling pathways such as TGF-β, Notch and MAPK signaling pathways. More detailed analysis demonstrated that CHIR inhibited Nodal signaling, while activating bone morphogenetic protein signaling in mESCs. In addition, we found that pluripotency-maintaining transcription factors were up-regulated by CHIR, while several developmental-related genes were down-regulated. Furthermore, we found that CHIR altered the expression of epigenetic regulatory genes and long intergenic non-coding RNAs. Quantitative real-time PCR results were consistent with microarray data, suggesting that CHIR alters the expression pattern of protein-encoding genes (especially transcription factors), epigenetic regulatory genes and non-coding RNAs to establish a relatively stable pluripotency-maintaining network.

Role of fucosyltransferase IV in epithelial-mesenchymal transition in breast cancer cells

Epithelial–mesenchymal transition (EMT) is a crucial step in tumor progression and has an important role during cancer invasion and metastasis. Although fucosyltransferase IV (FUT4) has been implicated in the modulation of cell migration, invasion and cancer metastasis, its role during EMT is unclear. This study explores the molecular mechanisms of the involvement of FUT4 in EMT in breast cancer cells. Breast cancer cell lines display increased expression of FUT4, which is accompanied by enhanced appearance of the mesenchymal phenotype and which can be reversed by knockdown of endogenous FUT4. Moreover, FUT4 induced activation of phosphatidylinositol 3-kinase (PI3K)/Akt, and inactivation of GSK3β and nuclear translocation of NF-κB, resulting in increased Snail and MMP-9 expression and greater cell motility. Taken together, these findings indicate that FUT4 has a role in EMT through activation of the PI3K/Akt and NF-κB signaling systems, which induce the key mediators Snail and MMP-9 and facilitate the acquisition of a mesenchymal phenotype. Our findings support the possibility that FUT4 is a novel regulator of EMT in breast cancer cells and a promising target for cancer therapy.

Agonism of Wnt-β-catenin signalling promotes mesenchymal stem cell (MSC) expansion

Promoting mesenchymal stem cell (MSC) proliferation has numerous applications in stem cell therapies, particularly in the area of regenerative medicine. In order for cell-based regenerative approaches to be realized, MSC proliferation must be achieved in a controlled manner without compromising stem cell differentiation capacities. Here we demonstrate that 6-bromoindirubin-3'-oxime (BIO) increases MSC β-catenin activity 106-fold and stem cell-associated gene expression ~33-fold, respectively, over untreated controls. Subsequently, BIO treatment increases MSC populations 1.8-fold in typical 2D culture conditions, as well as 1.3-fold when encapsulated within hydrogels compared to untreated cells. Furthermore, we demonstrate that BIO treatment does not reduce MSC multipotency where MSCs maintain their ability to differentiate into osteoblasts, chondrocytes and adipocytes using standard conditions. Taken together, our results demonstrate BIO's potential utility as a proliferative agent for cell transplantation and tissue regeneration.

Nuclear expression of glycogen synthase kinase-3β and lack of membranous β-catenin is correlated with poor survival in colon cancer

Dysregulation of Wnt/β-catenin signaling is a hallmark of colon cancer. Glycogen synthase kinase-3β (GSK-3β) can be a positive regulator of survival and proliferation of cultured colon cancer cell but its role in clinical colon cancer is unknown. Our objectives were to evaluate the role of GSK-3β in colon cancer. A tumor tissue microarray of primary colon cancers and metastases was used to evaluate expression and subcellular localization of GSK-3β and β-catenin. In total, 85 primary colon cancer samples were evaluated by immunohistochemistry. Immunoreactivity was correlated to known markers of adverse prognosis. Overall survival was the primary end-point. We found nuclear accumulation of GSK-3β in 39% (33/85) of evaluated tumors. Nuclear GSK-3β was significantly associated with shorter overall survival (p = 0.008), larger tumor size (p = 0.015), distant metastasis (p = 0.029) and loss of membranous β-catenin (p = 0.007). Loss of membranous β-catenin occurred in 37% (30/82) of the tumors and was associated with poor survival (p = 0.016). The combination of nuclear GSK-3β and lack of membrane β-catenin occurred in a total of 26% of the studied tumors (21/61) and was significantly and independently associated with poor prognosis. Our results suggest that nuclear expression of GSK-3β and loss of membrane β-catenin identify a subset of colon carcinomas with worse prognosis.

Emerging ideas: Engineering the periosteum: revitalizing allografts by mimicking autograft healing

BACKGROUND

To fulfill the need for large volumes, devitalized allografts are used to treat massive bone defects despite a 60%, 10-year postimplantation fracture rate. Allograft healing is inferior to autografts where the periosteum orchestrates remodeling.

HYPOTHESIS

By augmenting allografts with a tissue engineered periosteum consisting of tunable and degradable, poly(ethylene glycol) (PEG) hydrogels for mesenchymal stem cell (MSC) transplantation, the functions critical for periosteum-mediated healing will be identified and emulated.

METHOD OF STUDY

PEG hydrogels will be designed to emulate periosteum-mediated autograft healing to revitalize allografts. We will exploit murine femoral defect models for these approaches. Critical-sized, 5-mm segmental defects will be created and filled with decellularized allograft controls or live autograft controls. Alternatively, defects will be treated with our experimental approaches: decellularized allografts coated with MSCs transplanted via degradable PEG hydrogels to mimic progenitor cell densities and persistence during autograft healing. Healing will be evaluated for 9 weeks using microcomputed tomography, mechanical testing, and histologic analysis. If promising, MSC densities, hydrogel compositions, and genetic methods will be used to isolate critical aspects of engineered periosteum that modulate healing. Finally, hydrogel biochemical characteristics will be altered to initiate MSC and/or host-material interactions to further promote remodeling of allografts.

SIGNIFICANCE

This approach represents a novel tissue engineering strategy whereby degradable, synthetic hydrogels will be exploited to emulate the periosteum. The microenvironment, which will mediate MSC transplantation, will use tunable PEG hydrogels for isolation of critical allograft revitalization factors. In addition, hydrogels will be modified with biochemical cues to further augment allografts to reduce or eliminate revision surgeries associated with allograft failures.

Use of insulin to increase epiblast cell number: towards a new approach for improving ESC isolation from human embryos

Human embryos donated for embryonic stem cell (ESC) derivation have often been cryopreserved for 5-10 years. As a consequence, many of these embryos have been cultured in media now known to affect embryo viability and the number of ESC progenitor epiblast cells. Historically, these conditions supported only low levels of blastocyst development necessitating their transfer or cryopreservation at the 4-8-cell stage. As such, these embryos are donated at the cleavage stage and require further culture to the blastocyst stage before hESC derivation can be attempted. These are generally of poor quality, and, consequently, the efficiency of hESC derivation is low. Recent work using a mouse model has shown that the culture of embryos from the cleavage stage with insulin to day 6 increases the blastocyst epiblast cell number, which in turn increases the number of pluripotent cells in outgrowths following plating, and results in an increased capacity to give rise to ESCs. These findings suggest that culture with insulin may provide a strategy to improve the efficiency with which hESCs are derived from embryos donated at the cleavage stage.

A framework for the establishment of a cnidarian gene regulatory network for "endomesoderm" specification: the inputs of ß-catenin/TCF signaling

Understanding the functional relationship between intracellular factors and extracellular signals is required for reconstructing gene regulatory networks (GRN) involved in complex biological processes. One of the best-studied bilaterian GRNs describes endomesoderm specification and predicts that both mesoderm and endoderm arose from a common GRN early in animal evolution. Compelling molecular, genomic, developmental, and evolutionary evidence supports the hypothesis that the bifunctional gastrodermis of the cnidarian-bilaterian ancestor is derived from the same evolutionary precursor of both endodermal and mesodermal germ layers in all other triploblastic bilaterian animals. We have begun to establish the framework of a provisional cnidarian “endomesodermal” gene regulatory network in the sea anemone, Nematostella vectensis, by using a genome-wide microarray analysis on embryos in which the canonical Wnt/ß-catenin pathway was ectopically targeted for activation by two distinct pharmaceutical agents (lithium chloride and 1-azakenpaullone) to identify potential targets of endomesoderm specification. We characterized 51 endomesodermally expressed transcription factors and signaling molecule genes (including 18 newly identified) with fine-scale temporal (qPCR) and spatial (in situ) analysis to define distinct co-expression domains within the animal plate of the embryo and clustered genes based on their earliest zygotic expression. Finally, we determined the input of the canonical Wnt/ß-catenin pathway into the cnidarian endomesodermal GRN using morpholino and mRNA overexpression experiments to show that NvTcf/canonical Wnt signaling is required to pattern both the future endomesodermal and ectodermal domains prior to gastrulation, and that both BMP and FGF (but not Notch) pathways play important roles in germ layer specification in this animal. We show both evolutionary conserved as well as profound differences in endomesodermal GRN structure compared to bilaterians that may provide fundamental insight into how GRN subcircuits have been adopted, rewired, or co-opted in various animal lineages that give rise to specialized endomesodermal cell types.

Cnidarians (anemones, corals, and “jellyfish”) are an animal group whose adults possess derivatives of only two germ layers: ectoderm and a bifunctional (absorptive and contractile) gastrodermal (gut) layer. Cnidarians are the closest living relatives to bilaterally symmetrical animals that possess all three germ layers (ecto, meso, and endoderm); and compelling molecular, genomic, developmental, and evolutionary evidence exists to demonstrate that the cnidarian gastrodermis is evolutionarily related to both endodermal and mesodermal germ layers in all other triploblastic bilaterian animals. Little is known about endomesoderm specification in cnidarians. In this study, we constructed the framework of a cnidarian endomesodermal gene regulatory network in the sea anemone, Nematostella vectensis, using a combination of experimental approaches. We identified and characterized by both qPCR and in situ hybridization 51 genes expressed in defined domains within the presumptive endomesoderm. In addition, we functionally demonstrate that Wnt/Tcf signaling is crucial for regionalized expression of a defined subset of these genes prior to gut formation and endomesoderm maintenance. Our results support the idea of an ancient gene regulatory network underlying endomesoderm specification that involves inputs from multiple signaling pathways (Wnt, FGF, BMP, but not Notch) early in development, that are temporarily uncoupled in bilaterian animals.

The histone methyltransferase inhibitor BIX01294 enhances the cardiac potential of bone marrow cells

Bone marrow (BM) has long been considered a potential stem cell source for cardiac repair due to its abundance and accessibility. Although previous investigations have generated cardiomyocytes from BM, yields have been low, and far less than produced from ES or induced pluripotent stem cells (iPSCs). Since differentiation of pluripotent cells is difficult to control, we investigated whether BM cardiac competency could be enhanced without making cells pluripotent. From screens of various molecules that have been shown to assist iPSC production or maintain the ES cell phenotype, we identified the G9a histone methyltransferase inhibitor BIX01294 as a potential reprogramming agent for converting BM cells to a cardiac-competent phenotype. BM cells exposed to BIX01294 displayed significantly elevated expression of brachyury, Mesp1, and islet1, which are genes associated with embryonic cardiac progenitors. In contrast, BIX01294 treatment minimally affected ectodermal, endodermal, and pluripotency gene expression by BM cells. Expression of cardiac-associated genes Nkx2.5, GATA4, Hand1, Hand2, Tbx5, myocardin, and titin was enhanced 114, 76, 276, 46, 635, 123, and 5-fold in response to the cardiogenic stimulator Wnt11 when BM cells were pretreated with BIX01294. Immunofluorescent analysis demonstrated that BIX01294 exposure allowed for the subsequent display of various muscle proteins within the cells. The effect of BIX01294 on the BM cell phenotype and differentiation potential corresponded to an overall decrease in methylation of histone H3 at lysine9, which is the primary target of G9a histone methyltransferase. In summary, these data suggest that BIX01294 inhibition of chromatin methylation reprograms BM cells to a cardiac-competent progenitor phenotype.

GSK3 inhibitor-BIO regulates proliferation of female germline stem cells from the postnatal mouse ovary

OBJECTIVE

It is widely believed that in most female mammalian neonates, all germ cells enter meiosis to form the primary oocyte at the end of foetal development, and as a result, the postnatal mammalian ovary harbours only a limited supply of oocytes that cannot be regenerated. However, this idea has been challenged by the discovery of the existence of female germline stem cells (FGSCs) in postnatal mammalian ovaries.

MATERIALS AND METHODS

We have isolated ovarian GSCs from neonatal and adult mouse ovaries and expanded them in the same culture conditions as embryonic stem cells (ESCs).

RESULTS

LIF and BIO were beneficial for formation of FGSC colonies. BIO promoted proliferation of FGSCs through activation of β-catenin and up-regulation of E-cadherin. The FGSCs formed compact round colonies with unclear borders, maintained ESC characteristics and alkaline phosphatase (AP) activity, expressing germ-cell markers-Vasa, and stem-cell markers: Oct4, Klf4, C-myc, Nanog, CD49f, Sox2, CD133, SSEA1 and SSEA4. These cells had the ability to form embryoid bodies (EBs), which expressed specific markers for all three germ layers. Then we induced EBs to differentiate into neurons, cardiomyocytes, pancreatic cells and germ cells, which showed the expression of specific markers, β-III-tubulin, cardiac a-actin, Pdx1 and Zps respectively.

DISCUSSION AND CONCLUSION

This study reveals the existence of FGSCs in postnatal mouse ovary with multipotent characteristics. BIO played an important role in regulation of proliferation and maintenance of the FGSCs. This could help provide a better understanding of causes of ovarian infertility, prevention and potential treatment of infertility.

Glycogen synthase kinase 3 (GSK3) inhibitor, SB-216763, promotes pluripotency in mouse embryonic stem cells

Canonical Wnt/β-catenin signaling has been suggested to promote self-renewal of pluripotent mouse and human embryonic stem cells. Here, we show that SB-216763, a glycogen synthase kinase-3 (GSK3) inhibitor, can maintain mouse embryonic stem cells (mESCs) in a pluripotent state in the absence of exogenous leukemia inhibitory factor (LIF) when cultured on mouse embryonic fibroblasts (MEFs). MESCs maintained with SB-216763 for one month were morphologically indistinguishable from LIF-treated mESCs and expressed pluripotent-specific genes Oct4, Sox2, and Nanog. Furthermore, Nanog immunostaining was more homogenous in SB-216763-treated colonies compared to LIF. Embryoid bodies (EBs) prepared from these mESCs expressed early-stage markers for all three germ layers, and could efficiently differentiate into cardiac-like cells and MAP2-immunoreactive neurons. To our knowledge, SB-216763 is the first GSK3 inhibitor that can promote self-renewal of mESC co-cultured with MEFs for more than two months.

Pleiotropy of glycogen synthase kinase-3 inhibition by CHIR99021 promotes self-renewal of embryonic stem cells from refractory mouse strains

Background

Inhibition of glycogen synthase kinase-3 (GSK-3) improves the efficiency of embryonic stem (ES) cell derivation from various strains of mice and rats, as well as dramatically promotes ES cell self-renewal potential. β-catenin has been reported to be involved in the maintenance of self-renewal of ES cells through TCF dependent and independent pathway. But the intrinsic difference between ES cell lines from different species and strains has not been characterized. Here, we dissect the mechanism of GSK-3 inhibition by CHIR99021 in mouse ES cells from refractory mouse strains.

Methodology/Principal Findings

We found that CHIR99021, a GSK-3 specific inhibitor, promotes self-renewal of ES cells from recalcitrant C57BL/6 (B6) and BALB/c mouse strains through stabilization of β-catenin and c-Myc protein levels. Stabilized β-catenin promoted ES self-renewal through two mechanisms. First, β-catenin translocated into the nucleus to maintain stem cell pluripotency in a lymphoid-enhancing factor/T-cell factor–independent manner. Second, β-catenin binds plasma membrane-localized E-cadherin, which ensures a compact, spherical morphology, a hallmark of ES cells. Further, elevated c-Myc protein levels did not contribute significantly to CH-mediated ES cell self-renewal. Instead, the role of c-Myc is dependent on its transformation activity and can be replaced by N-Myc but not L-Myc. β-catenin and c-Myc have similar effects on ES cells derived from both B6 and BALB/c mice.

Conclusions/Significance

Our data demonstrated that GSK-3 inhibition by CH promotes self-renewal of mouse ES cells with non-permissive genetic backgrounds by regulation of multiple signaling pathways. These findings would be useful to improve the availability of normally non-permissive mouse strains as research tools.

Insulin increases epiblast cell number of in vitro cultured mouse embryos via the PI3K/GSK3/p53 pathway

High-quality embryos give rise to embryonic stem cells (ESCs) at greater efficiencies than poor-quality embryos. However, most embryos available for human ESC derivation are of a reduced quality as a result of culture in relatively simple media up to 10 years earlier, before cryopreservation, or before compaction. In the present study, we used a mouse model to determine whether a culture with insulin from the 8-cell stage could increase the number of ESC progenitor epiblast cells in blastocysts, as well as endeavor to determine the molecular mechanism of the insulin's effect. Culture in media containing 1.7 ρM insulin increased epiblast cell number (determined by Oct4 and Nanog co-expression), and proportion in day 6 blastocysts. The inhibition of phosphoinositide 3 kinase (PI3K) (via LY294002), an early second messenger of the insulin receptor, blocked this effect. The inhibition of glycogen synthase kinase 3 (GSK3) or p53, 2 s messengers inactivated by insulin signaling (via CT99021 or pifithrin-α, respectively), increased epiblast cell numbers. When active, GSK3 and p53 block the transcription of Nanog, which is important for maintaining pluripotency. A simultaneous inhibition of GSK3 and p53 had no synergistic effects on epiblast cell number. The induced activation of GSK3 and p53, via the inhibition of proteins responsible for their inactivation (PKA via H-89 and SIRT-1 via nicotinamide, respectively), blocked the insulin's effect on the epiblast.From our findings, we conclude that insulin increases epiblast cell number via the activation of PI3K, which ultimately inactivates GSK3 and p53. Furthermore, we suggest that the inclusion of insulin in culture media could be used as a strategy for increasing the efficiency with which the ESC lines can be derived from cultured embryos.

GSK3 inhibitor-BIO regulates proliferation of immortalized pancreatic mesenchymal stem cells (iPMSCs)

Background

The small molecule 6-bromoindirubin-30-oxime (BIO), a glycogen synthase kinase 3 (GSK3) inhibitor, is a pharmacological agent known to maintain self-renewal in human and mouse embryonic stem cells (ESCs). However, the precise role of GSK3 in immortalized pancreatic mesenchymal stem cells (iPMSCs) growth and survival is not completely understood at present.

Results

To determine whether this molecule is involved in controlling the proliferation of iPMSCs, we examined the effect of BIO on iPMSCs. We found that the inactivation of GSK3 by BIO can robustly stimulate iPMSCs proliferation and mass formation as shown by QRT-PCR, western blotting, 5-Bromo-2-deoxyuridine (BrdU) immunostaining assay and tunel assay. However, we did not find the related roles of BIO on β cell differentiation by immunostaining, QRT-PCR assay, glucose-stimulated insulin release and C-peptide content analysis.

Conclusions

These results suggest that BIO plays a key role in the regulation of cell mass proliferation and maintenance of the undifferentiated state of iPMSCs.