IGF antagonizes the Wnt/β-Catenin pathway and promotes differentiation of extra-embryonic endoderm

Trophoblast Differentiation: Mechanisms and Implications for Pregnancy Complications

Placental development is a tightly controlled event, in which cell expansion from the trophectoderm occurs in a spatiotemporal manner. Proper trophoblast differentiation is crucial to the vitality of this gestational organ. Obstructions to its development can lead to pregnancy complications, such as preeclampsia, fetal growth restriction, and preterm birth, posing severe health risks to both the mother and offspring. Currently, the only known treatment strategy for these complications is delivery, making it an important area of research. The aim of this review was to summarize the known information on the development and mechanistic regulation of trophoblast differentiation and highlight the similarities in these processes between the human and mouse placenta. Additionally, the known biomarkers for each cell type were compiled to aid in the analysis of sequencing technologies.

Dynamic expression of IGFBP3 modulate dual actions of mineralization micro-environment during tooth development via Wnt/beta-catenin signaling pathway

BACKGROUND

Tooth development, as one of the major mineralized tissues in the body, require fine-tuning of mineralization micro-environment. The interaction between dental epithelium and mesenchyme plays a decisive role in this process. With epithelium-mesenchyme dissociation study, we found interesting expression pattern of insulin-like growth factor binding protein 3 (IGFBP3) in response to disruption of dental epithelium-mesenchyme interaction. Its action and related mechanisms as regulator of mineralization micro-environment during tooth development are investigated.

RESULTS

Expressions of osteogenic markers at early stage of tooth development are significantly lower than those at later stage. BMP2 treatment further confirmed a high mineralization micro-environment is disruptive at early stage, but beneficial at later stage of tooth development. In contrast, IGFBP3's expression increased gradually from E14.5, peaked at P5, and decreased afterwards, demonstrating an inverse correlation with osteogenic markers. RNA-Seq and Co-immunoprecipitation showed that IGFBP3 regulates the Wnt/beta-catenin signaling pathway activity by enhancing DKK1 expression and direct protein-protein interaction. The suppression of the mineralization microenvironment effectuated by IGFBP3 could be reversed by the DKK1 inhibitor WAY-262611, further demonstrating that IGFBP3 exerted its influence via DKK1.

CONCLUSION

A deeper understanding of tooth development mechanisms is essential for tooth regeneration, which have great implications for dental care. The current study demonstrated that the IGFBP3 expression is regulated in accordance with the needs of the mineralization microenvironment during tooth development, and IGFBP3 exerts its modulating action on osteogenic/odontogenic differentiation of hDPSCs by DKK1-Wnt/ beta-catenin axis.

Potential role of TREM2 in high cholesterol‑induced cell injury and metabolic dysfunction in SH‑SY5Y cells

Triggering receptor expressed on myeloid cells 2 (TREM2) is an important member of the immunoglobulin family of inflammatory stimulating receptors and is involved in a number of pathophysiological processes. The present study aimed to investigate the role of TREM2 in neurotoxicity induced by high cholesterol levels in SH-SY5Y cells and explore the potential mechanism. SH-SY5Y cells were routinely cultured and stimulated with a range of cholesterol concentrations. Cell viability was assessed using an MTT assay, morphological changes were observed, and the cell cycle distribution was measured using flow cytometry. Lipid deposition was measured by Oil red O staining, and the mRNA and protein expression levels of SRBEP-1 and SRBEP-2 were detected by quantitative PCR and western blotting, respectively. Moreover, the protein expression levels of BDNF, Copine-6, TREM1, TREM2, and key molecules of the Wnt signaling pathways were detected by western blotting. Finally, TREM2 was overexpressed to investigate its potential role in high cholesterol-induced neurotoxicity. The results showed that cell viability was significantly decreased in SH-SY5Y cells stimulated with cholesterol (0.1~100 µM) in a dose- and time-dependent manner. Stimulation with 100 µM cholesterol for 24 h resulted in morphological injuries, increased the proportion of SH-SY5Y cells at G0/G1, the degree of lipid accumulation, and the protein expression levels of sterol regulatory element binding protein (SREBP)1 and SREBP2, markedly decreased the protein expression levels of BDNF, Copine-6, and TREM2, and the p-β-catenin/β-catenin ratio, and increased the expression levels of nesfatin-1, TREM1 and the p-GSK3β/GSK3β ratio. Furthermore, the imbalanced expression of BDNF, Copine-6, nesfatin-1, and p-GSK3β induced by high cholesterol levels was reversed after overexpression of TREM2. These results suggest that a high concentration of cholesterol could induce cell injury and lipid deposition in SH-SY5Y cells and that the underlying mechanism may be associated with imbalanced TREM2 expression.

Distinctive Roles of Wnt Signaling in Chondrogenic Differentiation of BMSCs under Coupling of Pressure and Platelet-Rich Fibrin

BACKGROUND

Although newly formed constructs of feasible pressure-preadjusted bone marrow mesenchymal stem cells (BMSCs) and platelet-rich fibrin (PRF) showed biomechanical flexibility and superior capacity for cartilage regeneration, it is still not very clear how BMSCs and seed cells feel mechanical stimuli and convert them into biological signals, and the difference in signal transduction underlying mechanical and chemical cues is also unclear.

METHODS

To determine whether mechanical stimulation (hydrostatic pressure) and chemical cues (platelet-rich fibrin, PRF) activate canonical or noncanonical Wnt signaling in BMSCs, BMSCs cocultured with PRF were subjected to hydrostatic pressure loading, and the activation of the Wnt signaling molecules and expression of cartilage-associated proteins and genes were determined by western blotting and polymerase chain reaction (PCR). Inhibitors of canonical or noncanonical Wnt signaling, XVX-939 or L690,330, were adopted to investigate the role of Wnt signaling molecules in mechanically promoted chondrogenic differentiation of BMSCs.

RESULTS

Hydrostatic pressure of 120 kPa activated both Wnt/β-catenin signaling and Wnt/Ca²⁺ signaling, with the the maximum promotion effect at 60 min. PRF exerted no synergistic effect on Wnt/β-catenin signaling activation. However, the growth factors released by PRF might reverse the promotion effects of pressure on Wnt/Ca²⁺ signaling. Real-time PCR and Western blotting results showed that pressure could activate the expression of Col-II, Sox9, and aggrecan in BMSCs cocultured with PRF. Blocking experiment found a positive role of Wnt/β-catenin signaling, and a negative role of Wnt/Ca²⁺ signaling in chondrogenic differentiation of the BMSCs. Mutual inhibition exists between canonical and noncanonical Wnt signaling in BMSCs under pressure.

CONCLUSION

Wnt signaling participates in the pressure-promoted chondrogenesis of the BMSCs co-cultured with PRF, with canonical and noncanonical pathways playing distinct roles during the process.

Wnt/β-catenin signaling pathway in uterine leiomyoma: role in tumor biology and targeting opportunities

Uterine leiomyoma is the most common tumor of the female reproductive system and originates from a single transformed myometrial smooth muscle cell. Despite the immense medical, psychosocial, and financial impact, the exact underlying mechanisms of leiomyoma pathobiology are poorly understood. Alterations of signaling pathways are thought to be instrumental in leiomyoma biology. Wnt/β-catenin pathway appears to be involved in several aspects of the genesis of leiomyomas. For example, Wnt5b is overexpressed in leiomyoma, and the Wnt/β-catenin pathway appears to mediate the role of MED12 mutations, the most common mutations in leiomyoma, in tumorigenesis. Moreover, Wnt/β-catenin pathway plays a paracrine role where estrogen/progesterone treatment of mature myometrial or leiomyoma cells leads to increased expression of Wnt11 and Wnt16, which induces proliferation of leiomyoma stem cells and tumor growth. Constitutive activation of β-catenin leads to myometrial hyperplasia and leiomyoma-like lesions in animal models. Wnt/β-catenin signaling is also closely involved in mechanotransduction and extracellular matrix regulation and relevant alterations in leiomyoma, and crosstalk is noted between Wnt/β-catenin signaling and other pathways known to regulate leiomyoma development and growth such as estrogen, progesterone, TGFβ, PI3K/Akt/mTOR, Ras/Raf/MEK/ERK, IGF, Hippo, and Notch signaling. Finally, evidence suggests that inhibition of the canonical Wnt pathway using β-catenin inhibitors inhibits leiomyoma cell proliferation. Understanding the molecular mechanisms of leiomyoma development is essential for effective treatment. The specific Wnt/β-catenin pathway molecules discussed in this review constitute compelling candidates for therapeutic targeting.

IGF-1R/β-catenin signaling axis is implicated in streptozotocin exacerbating bone impairment in ovariectomized rats

OBJECTIVE

The aim of this study was to investigate the role of the insulin-like growth factor-1 receptor (IGF-1R)/β-catenin signaling axis in bone impairment induced by hyperglycemia in ovariectomized rats.

METHODS

Rats were divided into four groups. The sham group received sham operation and a single intraperitoneal administration of vehicle. The ovariectomy (OVX) group was subjected to bilateral OVX and vehicle injection. The streptozotocin (STZ) group received sham operation and a single STZ injection to induce hyperglycemia. The OVX + STZ group received bilateral OVX and a single STZ injection. Dual-energy X-ray absorptiometry measurement, bone biomechanics test, micro-computed tomography scan, and hematoxylin-eosin staining were performed to evaluate bone alteration in this model. The expression of relevant signals including IGF-1R, glycogen synthase kinase-3β (GSK-3β), and β-catenin were examined by quantitative real-time polymerase chain reaction and western blot.

RESULTS

The OVX, STZ, and OVX + STZ groups induced bone loss, attenuated bone strength, and impaired microarchitecture compared with the sham group, respectively. Compared with OVX, more serious bone damage was found in the OVX + STZ group, which showed enhanced phosphorylation of IGF-1R, GSK-3β, and β-catenin.

CONCLUSION

OVX plus STZ induced more serious bone impairment than OVX alone, which involves the IGF-1R/β-catenin signaling axis in the pathogenesis. This may provide a potential target for treatment of postmenopausal diabetic osteoporosis.

IGF-1R/β-catenin signaling axis is involved in type 2 diabetic osteoporosis

Insulin-like growth factor-1 receptor (IGF-1R) is involved in both glucose and bone metabolism. IGF-1R signaling regulates the canonical Wnt/β-catenin signaling pathway. In this study, we investigated whether the IGF-1R/ β-catenin signaling axis plays a role in the pathogenesis of diabetic osteoporosis (DOP). Serum from patients with or without DOP was collected to measure the IGF-1R level using enzyme-linked immunosorbent assay (ELISA). Rats were given streptozotocin following a four-week high-fat diet induction (DOP group), or received vehicle after the same period of a normal diet (control group). Dual energy X-ray absorption, a biomechanics test, and hematoxylin-eosin (HE) staining were performed to evaluate bone mass, bone strength, and histomorphology, respectively, in vertebrae. Quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting were performed to measure the total and phosphorylation levels of IGF-1R, glycogen synthase kinase-3β (GSK-3β), and β-catenin. The serum IGF-1R level was much higher in patients with DOP than in controls. DOP rats exhibited strikingly reduced bone mass and attenuated compression strength of the vertebrae compared with the control group. HE staining showed that the histomorphology of DOP vertebrae was seriously impaired, which manifested as decreased and thinned trabeculae and increased lipid droplets within trabeculae. PCR analysis demonstrated that IGF-1R mRNA expression was significantly up-regulated, and western blotting detection showed that phosphorylation levels of IGF-1R, GSK-3β, and β-catenin were enhanced in DOP rat vertebrae. Our results suggest that the IGF-1R/β-catenin signaling axis plays a role in the pathogenesis of DOP. This may contribute to development of the underlying therapeutic target for DOP.

Transcriptome 3'end organization by PCF11 links alternative polyadenylation to formation and neuronal differentiation of neuroblastoma

Diversification at the transcriptome 3'end is an important and evolutionarily conserved layer of gene regulation associated with differentiation and dedifferentiation processes. Here, we identify extensive transcriptome 3'end-alterations in neuroblastoma, a tumour entity with a paucity of recurrent somatic mutations and an unusually high frequency of spontaneous regression. Utilising extensive RNAi-screening we reveal the landscape and drivers of transcriptome 3'end-diversification, discovering PCF11 as critical regulator, directing alternative polyadenylation (APA) of hundreds of transcripts including a differentiation RNA-operon. PCF11 shapes inputs converging on WNT-signalling, and governs cell cycle, proliferation, apoptosis and neurodifferentiation. Postnatal PCF11 down-regulation induces a neurodifferentiation program, and low-level PCF11 in neuroblastoma associates with favourable outcome and spontaneous tumour regression. Our findings document a critical role for APA in tumorigenesis and describe a novel mechanism for cell fate reprogramming in neuroblastoma with potentially important clinical implications. We provide an interactive data repository of transcriptome-wide APA covering > 170 RNAis, and an APA-network map with regulatory hubs.

A Boolean network of the crosstalk between IGF and Wnt signaling in aging satellite cells

Aging is a complex biological process, which determines the life span of an organism. Insulin-like growth factor (IGF) and Wnt signaling pathways govern the process of aging. Both pathways share common downstream targets that allow competitive crosstalk between these branches. Of note, a shift from IGF to Wnt signaling has been observed during aging of satellite cells. Biological regulatory networks necessary to recreate aging have not yet been discovered. Here, we established a mathematical in silico model that robustly recapitulates the crosstalk between IGF and Wnt signaling. Strikingly, it predicts critical nodes following a shift from IGF to Wnt signaling. These findings indicate that this shift might cause age-related diseases.

Tbx3-dependent amplifying stem cell progeny drives interfollicular epidermal expansion during pregnancy and regeneration

The skin surface area varies flexibly in response to body shape changes. Skin homeostasis is maintained by stem cells residing in the basal layer of the interfollicular epidermis. However, how the interfollicular epidermal stem cells response to physiological body shape changes remains elusive. Here, we identify a highly proliferative interfollicular epidermal basal cell population in the rapidly expanding abdominal skin of pregnant mice. These cells express Tbx3 that is necessary for their propagation to drive skin expansion. The Tbx3+ basal cells are generated from Axin2+ interfollicular epidermal stem cells through planar-oriented asymmetric or symmetric cell divisions, and express transit-amplifying cell marker CD71. This biased division of Axin2+ interfollicular epidermal stem cells is induced by Sfrp1 and Igfbp2 proteins secreted from dermal cells. The Tbx3+ basal cells promote wound repair, which is enhanced by Sfrp1 and Igfbp2. This study elucidates the interfollicular epidermal stem cell/progeny organisation during pregnancy and suggests its application in regenerative medicine.The abdominal skin expands rapidly during pregnancy. Here the authors show that a population of highly proliferative stem cell progenies expressing the transcription factor Tbx3 is required for abdominal skin expansion in pregnant mice.

NOX1 and NOX4 are required for the differentiation of mouse F9 cells into extraembryonic endoderm

Mouse F9 cells differentiate to primitive endoderm (PrE) when treated with retinoic acid (RA). Differentiation is accompanied by increased reactive oxygen species (ROS) levels, and while treating F9 cells with antioxidants attenuates differentiation, H₂O₂ treatment alone is sufficient to induce PrE. We identified the NADPH oxidase (NOX) complexes as candidates for the source of this endogenous ROS, and within this gene family, and over the course of differentiation, Nox1 and Nox 4 show the greatest upregulation induced by RA. Gata6, encoding a master regulator of extraembryonic endoderm is also up-regulated by RA and we provide evidence that NOX1 and NOX4 protein levels increase in F9 cells overexpressing Gata6. Pan-NOX and NOX1-specific inhibitors significantly reduced the ability of RA to induce PrE, and this was recapitulated using a genetic approach to knockdown Nox1 and/or Nox4 transcripts. Interestingly, overexpressing either gene in untreated F9 cells did not induce differentiation, even though each elevated ROS levels. Thus, the data suggests that ROS produced during PrE differentiation is dependent in part on increased NOX1 and NOX4 levels, which is under the control of GATA6. Furthermore, these results suggest that the combined activity of multiple NOX proteins is necessary for the differentiation of F9 cells to primitive endoderm.

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

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