Nucleoredoxin promotes adipogenic differentiation through regulation of Wnt/β-catenin signaling

Nucleoredoxin (NRX) is a member of the thioredoxin family of proteins that controls redox homeostasis in cell. Redox homeostasis is a well-known regulator of cell differentiation into various tissue types. We found that NRX expression levels were higher in white adipose tissue of obese ob/ob mice and increased in the early adipogenic stage of 3T3-L1 preadipocyte differentiation. Knockdown of NRX decreased differentiation of 3T3-L1 cells, whereas overexpression increased differentiation. Adipose tissue-specific NRX transgenic mice showed increases in adipocyte size as well as number compared with WT mice. We further confirmed that the Wingless/int-1 class (Wnt)/β-catenin pathway was also involved in NRX-promoted adipogenesis, consistent with a previous report showing NRX regulation of this pathway. Genes involved in lipid metabolism were downregulated, whereas inflammatory genes, including those encoding macrophage markers, were significantly upregulated, likely contributing to the obesity in Adipo-NRX mice. Our results therefore suggest that NRX acts as a novel proadipogenic factor and controls obesity in vivo.     

Wnt/β-catenin signaling regulates neuronal differentiation of mesenchymal stem cells

Mesenchymal stem cells (MSCs) have been demonstrated to be able to differentiate into neuron-like cells, but the precise mechanisms controlling this process are unclear. Using neuron-specific enolase (NSE) and nestin as neuronal markers, we examined the role of Wnt/β-catenin signaling in MSC neuronal differentiation in present study. The results indicated that the expression of β-catenin increased markedly during the neuronal differentiation of MSCs. Blocking Wnt signaling by treating MSCs with β-catenin siRNA could decrease the differentiation of MSCs into neuron-like cells and up-regulation of Wnt signaling by treating MSCs with Wnt-3a could promote neuronal differentiation of MSCs. Above results suggest that Wnt/β-catenin signaling may play a pivotal role in neuronal differentiation of MSCs. Our data broaden the knowledge of molecular mechanisms involved in the neuronal differentiation of MSCs and provide a potential target for directing differentiation of MSCs for clinical application.     

Wnt/β-catenin signaling and disease

The WNT signal transduction cascade controls myriad biological phenomena throughout development and adult life of all animals. In parallel, aberrant Wnt signaling underlies a wide range of pathologies in humans. In this Review, we provide an update of the core Wnt/β-catenin signaling pathway, discuss how its various components contribute to disease, and pose outstanding questions to be addressed in the future.     

Parkin protects dopaminergic neurons from excessive Wnt/β-catenin signaling

Parkinson’s disease (PD) is caused by degeneration of the dopaminergic (DA) neurons of the substantia nigra but the molecular mechanisms underlying the degenerative process remain elusive. Several reports suggest that cell cycle deregulation in post-mitotic neurons could lead to neuronal cell death. We now show that Parkin, an E3 ubiquitin ligase linked to familial PD, regulates β-catenin protein levels in vivo. Stabilization of β-catenin in differentiated primary ventral midbrain neurons results in increased levels of cyclin E and proliferation, followed by increased levels of cleaved PARP and loss of DA neurons. Wnt3a signaling also causes death of post-mitotic DA neurons in parkin null animals, suggesting that both increased stabilization and decreased degradation of β-catenin results in DA cell death. These findings demonstrate a novel regulation of Wnt signaling by Parkin and suggest that Parkin protects DA neurons against excessive Wnt signaling and β-catenin-induced cell death.     

Mechanical stress regulates osteogenic differentiation and RANKL/OPG ratio in periodontal ligament stem cells by the Wnt/β-catenin pathway

BackgroundThe balance between osteoblastic and osteoclastic activity is critical in orthodontic tooth movement (OTM). Mesenchymal stem cells (MSCs) play an important role in maintaining bone homeostasis, and periodontal ligament stem cells (PDLSCs) are tissue-specific MSCs in the periodontal ligament. However, whether PDLSCs are required for periodontal tissue remodeling during OTM is not fully understood.MethodsHere, we used PDGFRα and Nestin to trace PDLSCs during OTM in rats. We treat human PDLSCs with 100 kpa static pressure for 1 h or 12 h in vitro, and examined the phenotypic changes and expression of RANKL and OPG in these cells.ResultsIn vivo, we found that positive signals of PDGFRα and Nestin in the PDL gradually increased and then decreased on the pressure side to which pressure was applied. In vitro, the osteogenic differentiation of PDLSCs was significantly increased after force treatment for 1 h relative to 12 h. In contrast, the expression ratio of RANKL/OPG was reduced at 1 h and significantly increased at 12 h. Furthermore, we found that the Wnt/β-catenin pathway was dynamically activated in the PDL and in PDLSCs after mechanical stimulation. Importantly, the canonical Wnt pathway inhibitor DKK1 blocked the osteogenesis effect and rescued the ratio of RANKL/OPG in PDLSCs under force treatment for 1 h.ConclusionsOur findings reveal that PDLSCs participate in OTM and that the Wnt/β-catenin pathway maintains bone homeostasis during tooth movement by regulating the balance between osteoblastic and osteoclastic activity.General significanceWe describe a novel potential mechanism related to tooth movement.     

Effects of TGF-β1 on the proliferation and differentiation of human periodontal ligament cells and a human periodontal ligament stem/progenitor cell line

Periodontal ligament (PDL) is a specialized connective tissue that influences the lifespan of the tooth. Transforming growth factor-β1 (TGF-β1) is a multifunctional cytokine, but little is known about the effects of TGF-β1 on PDL cells. Our aim has been to demonstrate the expression of TGF-β1 in rat PDL tissues and to evaluate its effects on the proliferation and gene expression in human PDL cells (HPLCs) and a human PDL stem/progenitor cell line, line 1-11, that we have recently developed. The expression of TGF-β1 in the entire PDL tissue was confirmed immunohistochemically, and both HPLCs and cell line 1-11 expressed mRNA from the TGF-β1, TGF-β type I receptor, and TGF-β type II receptor genes. Although exogenous TGF-β1 stimulated the proliferation of HPLCs, it did not upregulate the expression of alpha-smooth muscle actin (α-SMA), type I collagen (Col I), or fibrillin-1 (FBN1) mRNA or of α-SMA protein in HPLCs, whereas expression for these genes was attenuated by an anti-TGF-β1 neutralizing antibody. In contrast, exogenous TGF-β1 reduced the proliferation of cell line 1-11, although it upregulated the expression of α-SMA, Col I, and FBN1 mRNA and of α-SMA protein in this cell line. In addition, interleukin-1 beta stimulation significantly reduced the expression of TGF-β1 mRNA and protein in HPLCs. Thus, TGF-β1 seems to play an important role in inducing fibroblastic differentiation of PDL stem/progenitor cells and in maintaining the PDL apparatus under physiological conditions.     

Wnt/β-catenin signaling in hepatic organogenesis

Wnt/β-catenin signaling has come to the forefront of liver biology in recent years. This pathway regulates key pathophysiological events inherent to the liver including development, regeneration, and cancer, by dictating several biological processes such as proliferation, apoptosis, differentiation, adhesion, zonation and metabolism in various cells of the liver. This review will examine the studies that have uncovered the relevant roles of Wnt/β-catenin signaling during the process of liver development. We will discuss the potential roles of Wnt/β-catenin signaling during the phases of development, including competence, hepatic induction, expansion, and morphogenesis. In addition, we will discuss the role of negative and positive regulation of this pathway and how the temporal expression of Wnt/β-catenin can direct key processes during hepatic development. We will also identify some of the major deficits in the current understanding of the role of Wnt/β-catenin signaling in liver development in order to provide a perspective for future studies. Thus, this review will provide a contextual overview of the role of Wnt/β-catenin signaling during hepatic organogenesis.     

Roles of Wnt/β-catenin signaling in epithelial differentiation of mesenchymal stem cells

Bone marrow-derived mesenchymal stem cells (MSCs) have been demonstrated to be able to differentiate into epithelial lineage, but the precise mechanisms controlling this process are unclear. Our aim is to explore the roles of Wnt/β-catenin in the epithelial differentiation of MSCs. Using indirect co-culture of rat MSCs with rat airway epithelial cells (RTE), MSCs expressed several airway epithelial markers (cytokeratin 18, tight junction protein occudin, cystic fibrosis transmembrance regulator). The protein levels of some important members in Wnt/β-catenin signaling were determined, suggested down-regulation of Wnt/β-catenin with epithelial differentiation of MSCs. Furthermore, Wnt3α can inhibit the epithelial differentiation of MSCs. A loss of β-catenin induced by Dickkopf-1 can enhance MSCs differentiation into epithelial cells. Lithium chloride transiently activated β-catenin expression and subsequently decreased β-catenin level and at last inhibited MSCs to differentiate into airway epithelium. Taken together, our study indicated that RTE cells can trigger epithelial differentiation of MSCs. Blocking Wnt/β-catenin signaling may promote MSCs to differentiate towards airway epithelial cells.     

IL-1β favors osteoclastogenesis via supporting human periodontal ligament fibroblasts

The balance between bone formation and bone resorption in inflammatory diseases is often disturbed. Periodontitis, a chronic inflammation of the tooth gums, leads to unwanted bone loss as a response to inflammatory compounds such as interleukin‐1β (IL‐1β). This excessive bone loss reflects an increased osteoclast formation and activity. Osteoclast formation is a multistep process driven by osteoclastogenesis supporting cells such as periodontal ligament fibroblasts. The inflammatory factors can induce osteoclastogenesis, probably also by affecting the periodontal ligament fibroblast. In this study we investigated how pre‐culture of periodontal ligament fibroblasts with IL‐1β affected osteoclastogenesis. Fibroblasts were pre‐cultured with IL‐1β and/or dexamethasone, a commonly used anti‐inflammatory compound, before being co‐cultured with peripheral blood mononuclear cells (PBMCs). Pre‐culture with IL‐1β (1–100 ng/ml) resulted in an increased number of adhered PBMCs as well as an increased mRNA expression of intercellular adhesion molecule‐1 (ICAM‐1), macrophage colony stimulating factor (M‐CSF) and IL‐1β. Pre‐culture with IL‐1β also caused retraction of fibroblasts and an augmented formation of TRACP⁺ multinucleated cells. Our data suggest that stimulation of fibroblasts with IL‐1β has a long‐lasting effect, leading to a significantly increased osteoclastogenesis. These results provide new insights for understanding excessive bone loss in periodontitis. J. Cell. Biochem. 112: 1890–1897, 2011. © 2011 Wiley‐Liss, Inc.     

Wnt/β-catenin signaling pathway in severe preeclampsia

This study aims to elucidate the mechanisms of Wnt/β-catenin signaling pathway in the development of preeclampsia (PE). The mRNA levels of Wnt1, β-catenin, c-myc and cyclinD1 were determined by real-time PCR in the placentas. Moreover, the expression levels of Wnt1, β-catenin, Dickkopf-1 (DKK1) and glycogen synthase kinase 3β (GSK-3β) proteins were detected by Western blot. Immunohistochemistry was used in placental tissue microarray to localize the expression of Wnt1, β-catenin, DKK1 proteins in the placentas of two groups. Compared with the control placentas, the mRNA levels of Wnt1, β-catenin, c-myc and cyclinD1 were decreased in the severe preeclamptic placentas. The Western blot results showed that the expression levels of Wnt1, β-catenin, and GSK-3β proteins were significantly elevated in the control group, while the expression level of DKK1 was significantly decreased. In addition, the staining intensity of Wnt1, β-catenin were weaker in the placentas of the severe PE group while the staining intensity of DKK1 was significantly stronger in the placentas of the severe PE group. Wnt/β-catenin signaling pathway may play a significant role in the pathogenesis of PE by regulating the invasion and proliferation of trophoblast.     

Small molecule modulators of Wnt/β-catenin signaling

The Wnt signal transduction pathway is dysregulated in many highly prevalent diseases, including cancer. Unfortunately, drug discovery efforts have been hampered by the paucity of targets and drug-like lead molecules amenable to drug discovery. Recently, we reported the FDA-approved anthelmintic drug Niclosamide inhibits Wnt/β-catenin signaling by a unique mechanism, though the target responsible remains unknown. We interrogated the mechanism and structure–activity relationships to understand drivers of potency and to assist target identification efforts. We found inhibition of Wnt signaling by Niclosamide appears unique among the structurally-related anthelmintic agents tested and found the potency and functional response was dependent on small changes in the chemical structure of Niclosamide. Overall, these findings support efforts to identify the target of Niclosamide inhibition of Wnt/β-catenin signaling and the discovery of potent and selective modulators to treat human disease.     

Focal adhesion kinase mediates β-catenin signaling in periodontal ligament cells

Periodontal ligament (PDL) cells convert the orthodontic forces into biological responses by secreting signaling molecules to induce modeling of alveolar bone and tooth movement. Beta-catenin pathway is activated in response to mechanical loading in PDL cells. The upstream signaling pathways activated by mechanical loading resulting in the activation of β-catenin pathway through Wnt-independent mechanism remains to be characterized. We hypothesized that mechanical loading induces activation of β-catenin signaling by mechanisms that dependent on focal adhesion kinase (FAK) and nitric oxide (NO). We found that mechanical or pharmacological activation of β-catenin signaling in PDL cells upregulated the expression of β-catenin target genes. Pre-treatment of PDL cells with FAK inhibitor-14 prior to mechanical loading abolished the mechanical loading-induced phosphorylation of Akt and dephosphorylation of β-catenin. PDL cells pre-treated with NO donor or NO inhibitor and subjected to mechanical loading. Western blot analysis showed that the mechanical loading or pre-treatment with NO donor increased the levels of dephosphorylated β-catenin, pAkt, and pGSK-3β. Pre-treatment with NO inhibitor blocked the mechanical loading-induced phosphorylation of Akt and dephosphorylation of β-catenin. These data indicate that mechanical loading-induced β-catenin stabilization in PDL cells involves phosphorylation of Akt by two parallel pathways requiring FAK and NO.     

Podocan affects C2C12 myogenic differentiation by enhancing Wnt/β-catenin signaling

Podocan, a small leucine-rich repeat protein, is a negative regulator of cell proliferation. In this study, we demonstrated that podocan is involved in the differentiation of C2C12 murine myoblasts. Podocan expression increased with the progression of C2C12 differentiation. As expect, siRNA-mediated podocan knockdown inhibited C2C12 differentiation, as indicated by inhibition of MYOG, MYH2, and desmin expression, as well as reductions in the differentiation and fusion indices. Overexpression of podocan using dCas9 technology promoted C2C12 cell differentiation. In addition, supplementation of culture medium with podocan influenced C2C12 differentiation. Podocan knockdown reduced Wnt/β-catenin signaling, characterized by a reduction in the nuclear translocation of β-catenin, whereas podocan overexpression had the opposite effect. Furthermore, treatment with XAV939, an inhibitor of Wnt/β-catenin, reduced the podocan-mediated promotion of C2C12 differentiation. Induction of muscle injury in mice by bupivacaine administration suggested that podocan may play a role in muscle regeneration. In summary, our results suggest that podocan is required for normal C2C12 differentiation and that its role in myogenesis is mediated by the Wnt/β-catenin pathway.     

Promoting osteogenic differentiation of human-induced pluripotent stem cells by releasing Wnt/β-catenin signaling activator from the nanofibers

Implants that can enhance the stem cells differentiation in the absence of the chemical osteogenic growth factors will attract the great interest of orthopedic scientists. Inorganic polyphosphate (poly-P), as a ubiquitous biological polymer, is one of the factors that can be an alternative for osteogenic growth factors via activating Wnt/β-catenin signaling. In this study, poly-P was incorporated at the blend of polycaprolactone (PCL)/poly (l -lactic acid) (PLLA) electrospun nanofibers and then osteogenic differentiation potential of human-induced pluripotent stem cells (iPSCs) was investigated by the important bone markers. 3-[4, 5-dimethylthiazol-2-yl]-2, 5 diphenyl tetrazolium bromide (MTT) and scanning electron microscopy results confirmed the biocompatibility of the fabricated nanofibers, while higher proliferation rate of iPSCs was detected in PCL-PLLA(poly-P) group compared with the PCL-PLLA and tissue culture plate groups. Alkaline phosphatase activity, calcium content, and gene expression results demonstrated that osteogenic differentiation of iPSCs was increased when cultured on PCL-PLLA(poly-P) in comparison with other groups. According to the results, PCL-PLLA(poly-P) could be considered as a promising candidate for use as bone implants.