Pleiotropic Roles of NOTCH1 Signaling in the Loss of Maturational Arrest of Human Osteoarthritic Chondrocytes

Notch signaling has been identified as a critical regulator of cartilage development and homeostasis. Its pivotal role was established by both several joint specific Notch signaling loss of function mouse models and transient or sustained overexpression. NOTCH1 is the most abundantly expressed NOTCH receptors in normal cartilage and its expression increases in osteoarthritis (OA), when chondrocytes exit from their healthy “maturation arrested state” and resume their natural route of proliferation, hypertrophy, and terminal differentiation. The latter are hallmarks of OA that are easily evaluated in vitro in 2-D or 3-D culture models. The aim of our study was to investigate the effect of NOTCH1 knockdown on proliferation (cell count and Picogreen mediated DNA quantification), cell cycle (flow cytometry), hypertrophy (gene and protein expression of key markers such as RUNX2 and MMP-13), and terminal differentiation (viability measured in 3-D cultures by luminescence assay) of human OA chondrocytes. NOTCH1 silencing of OA chondrocytes yielded a healthier phenotype in both 2-D (reduced proliferation) and 3-D with evidence of decreased hypertrophy (reduced expression of RUNX2 and MMP-13) and terminal differentiation (increased viability). This demonstrates that NOTCH1 is a convenient therapeutic target to attenuate OA progression.

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POS0042 NOTCH 1 INHIBITION INCREASES OSTEOCLAST PROGENITOR ACTIVITY IN THE MOUSE MODEL OF RHEUMATOID ARTHRITIS

Annals of the Rheumatic Diseases ◽

10.1136/annrheumdis-2021-eular.2601 ◽

2021 ◽

Vol 80 (Suppl 1) ◽

pp. 226.3-226

Author(s):

M. Filipović ◽

A. Šućur ◽

D. Flegar ◽

Z. Jajić ◽

M. Ikić Matijašević ◽

...

Keyword(s):

Flow Cytometry ◽

Notch Signaling ◽

Neutralizing Antibodies ◽

Osteoclast Differentiation ◽

Notch Receptor ◽

Notch 1 ◽

Collagen Induced Arthritis ◽

Notch Receptors

Background:Osteoclasts mediate periarticular and systemic bone loss in rheumatoid arthritis (RA). Osteoclast progenitor cells (OCPs) derived from the myeloid lineage are susceptible to regulation through Notch signaling. Murine bone marrow and splenic OCPs, identified as CD45+Ly6G-CD3-B220-NK1.1-CD11blo/+CD115+CCR2+ cells, are specifically increased in arthritis. We previously identified an increased frequency of OCPs expressing Notch receptors in arthritic mice.Objectives:Several studies suggested that Notch signaling modulation affects the course of experimental arthritis. We aimed to determine the effects of Notch receptor signaling inhibition on OCP activity and arthritis severity in murine collagen-induced arthritis (CIA).Methods:Male C57/Bl6 and DBA mice were immunized with chicken type II collagen and treated with i.p. injections of anti-Notch 1 neutralizing antibodies (1mg/kg). Notch receptor 1 through 4 expression on OCPs was analyzed by flow cytometry in periarticular bone marrow (PBM) and spleen (SPL). Gene expression of Notch receptors, ligands and transcription targets as well as osteoclast differentiation genes RANK, cFos and cFms was determined by qPCR from tissues and sorted OCPs. FACS sorted OCPs were stimulated by osteoclastogenic factors (M-CSF and RANKL), in control, IgG, Jagged (Jag)1 or Delta-like (DLL)1 coated wells, with or without anti-Notch 1 antibodies. Research was approved by the Ethics Committee.Results:We confirmed the expression of Notch receptors on OCPs by flow cytometry with Notch 1 and 2 being most abundantly expressed (around 25% and 40% positive OCPs in PBM and 35% and 20% in SPL respectively), with a significant increase of Notch 2 expression in arthritis. Seeding OCPs on DLL1 coated wells significantly increased while seeding on Jag1 coated wells significantly decreased osteoclastogenesis as reflected on the number of TRAP+ osteoclasts and expression of osteoclast differentiation genes. The addition of anti-Notch 1 antibodies to ligand-stimulated OCPs resulted in an increased number of TRAP+ osteoclasts, partially reversing Jag1 inhibition. In vivo treatment with anti-Notch 1 antibodies did not affect total OCP frequency, but increased expression of Notch 4 both in PBM and SPL as seen by flow cytometry and qPCR. Additionally, anti-Notch 1 treatment stimulated Notch transcription factors HES and HEY. Both PBM and SPL cultured OCPs from anti-Notch 1 treated mice produced a higher number of large TRAP+ osteoclasts, doubling the area covered with osteoclasts in the latter compared to untreated mice. Increased osteoclastogenesis in vitro was further confirmed by an increased expression of osteoclast differentiation genes in the treated group.Conclusion:Our results confirm that Notch signaling may represent an important therapeutic target for the regulation of osteoclast activity in arthritis. Both in vitro and in vivo anti-Notch 1 neutralizing antibodies enhanced osteoclastogenesis in CIA model, implying an inhibitory role of Notch 1 signaling in osteoclast differentiation. As Notch 2 expression is increased on OCPs of arthritic mice, we next plan to determine the effects of Notch 2 neutralization on osteoclast activity and arthritis severity.References:[1]Ikić Matijašević M, Flegar D, Kovačić N, Katavić V, Kelava T, Šućur A, et al. Increased chemotaxis and activity of circulatory myeloid progenitor cells may contribute to enhanced osteoclastogenesis and bone loss in the C57BL/6 mouse model of collagen-induced arthritis. Clin Exp Immunol. 2016;186(3):321–35.[2]Šućur A, Filipović M, Flegar D, Kelava T, Šisl D, Lukač N, et al. Notch receptors and ligands in inflammatory arthritis – a systematic review. Immunology Letters 2020 Vol. 223, p. 106–14.Acknowledgements:The work has been supported by Croatian Science Foundation projects IP-2018-01-2414, UIP-2017-05-1965 and DOK-2018-09-4276.Disclosure of Interests:None declared.

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Reduction of Matrix Metallopeptidase 13 and Promotion of Chondrogenesis by Zeel T in Primary Human Osteoarthritic Chondrocytes

Frontiers in Pharmacology ◽

10.3389/fphar.2021.635034 ◽

2021 ◽

Vol 12 ◽

Author(s):

Christelle Sanchez ◽

Kathrin Hemmer ◽

Natascha Krömmelbein ◽

Bernd Seilheimer ◽

Jean-Emile Dubuc ◽

...

Keyword(s):

Differential Expression Analysis ◽

Type Ii Collagen ◽

Cartilage Degradation ◽

Alginate Beads ◽

Protein Quantification ◽

Type Ii ◽

Osteoarthritic Chondrocytes ◽

Matrix Metallopeptidase ◽

Oa Chondrocytes

Objectives: Zeel T (Ze14) is a multicomponent medicinal product. Initial preclinical data suggested a preventive effect on cartilage degradation. Clinical observational studies demonstrated that Ze14 reduced symptoms of osteoarthritis (OA), including stiffness and pain. This study aimed to explore these effects further to better understand the mode of action of Ze14 on human OA chondrocytes in vitro.Methods: Primary chondrocytes were obtained from the knees of 19 OA patients and cultured either as monolayers or in alginate beads. The cultures were treated with 20% or 10% (v/v) Ze14 or placebo. For RNA-seq, reads were generated with Illumina NextSeq5000 sequencer and aligned to the human reference genome (UCSC hg19). Differential expression analysis between Ze14 and placebo was performed in R using the DESeq2 package. Protein quantification by ELISA was performed on selected genes from the culture medium and/or the cellular fractions of primary human OA chondrocyte cultures.Results: In monolayer cultures, Ze14 20% (v/v) significantly modified the expression of 13 genes in OA chondrocytes by at least 10% with an adjusted p-value < 0.05: EGR1, FOS, NR4A1, DUSP1, ZFP36, ZFP36L1, NFKBIZ, and CCN1 were upregulated and ATF7IP, TXNIP, DEPP1, CLEC3A, and MMP13 were downregulated after 24 h Ze14 treatment. Ze14 significantly increased (mean 2.3-fold after 24 h, p = 0.0444 and 72 h, p = 0.0239) the CCN1 protein production in human OA chondrocytes. After 72 h, Ze14 significantly increased type II collagen pro-peptide production by mean 27% (p = 0.0147). For both time points CCN1 production by OA chondrocytes was correlated with aggrecan (r = 0.66, p = 0.0004) and type II collagen pro-peptide (r = 0.64, p = 0.0008) production. In alginate beads cultures, pro-MMP-13 was decreased by Ze14 from day 7–14 (from −16 to −25%, p < 0.05) and from day 17–21 (−22%, p = 0.0331) in comparison to controls.Conclusion: Ze14 significantly modified the expression of DUSP1, DEPP1, ZFP36/ZFP36L1, and CLEC3A, which may reduce MMP13 expression and activation. Protein analysis confirmed that Ze14 significantly reduced the production of pro-MMP-13. As MMP-13 is involved in type II collagen degradation, Ze14 may limit cartilage degradation. Ze14 also promoted extracellular matrix formation arguably through CCN1 production, a growth factor well correlated with type II collagen and aggrecan production.

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The β-catenin/TCF-4 pathway regulates the expression of OPN in human osteoarthritic chondrocytes

10.21203/rs.2.24706/v3 ◽

2020 ◽

Author(s):

Jian Tian ◽

Shu-Guang Gao ◽

Yu-Sheng Li ◽

Chao Cheng ◽

Zhen-Han Deng ◽

...

Keyword(s):

Cartilage Destruction ◽

Transient Transfection ◽

Human Chondrocytes ◽

Mrna Levels ◽

Osteoarthritic Chondrocytes ◽

Mrna And Protein Expression ◽

Oa Chondrocytes ◽

Canonical Wnt ◽

Dickkopf 1

Abstract Background: Cartilage destruction is the main characteristic of osteoarthritis (OA), and osteopontin (OPN) is elevated in OA articular cartilage; however, the reason for the increased OPN level is not determined. In addition, Wnt/β-catenin signaling participates in the progression of OA. The aim of the present study was to evaluate whether canonical Wnt signaling could regulate the expression of OPN in human chondrocytes in vitro.Methods: Human chondrocytes were cultured in vitro, and we first assayed the mRNA levels of OPN and β-catenin in chondrocytes. Next, we performed transient transfection of TCF 4 shRNA into chondrocytes to inhibit TCF 4 expression and explore changes in the OPN level. Then, the Wnt/β-catenin signaling inhibitor Dickkopf-1 (Dkk-1) was incubated with chondrocytes, and we assayed the changes in β-catenin and OPN.Results: Our results showed that the expression of both β-catenin and OPN was increased in OA chondrocytes, but there were no correlations between β-catenin and OPN expression. TCF4 shRNA downregulated the expression of TCF 4 and OPN in chondrocytes, while after treatment with rDKK-1 at a concentration of 400 ng/ml for 24 h, the mRNA and protein expression of both β-catenin and OPN was significantly decreased in chondrocytes.Conclusions: Elevated OPN expression might be regulated by the β-catenin/TCF-4 pathway, and the Wnt/β-catenin inhibitor DKK1 could inhibit the expression of β-catenin and OPN in OA chondrocytes.

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AP-2 factors act in concert with Notch to orchestrate terminal differentiation in skin epidermis

The Journal of Cell Biology ◽

10.1083/jcb.200804030 ◽

2008 ◽

Vol 183 (1) ◽

pp. 37-48 ◽

Cited By ~ 59

Author(s):

Xuan Wang ◽

H. Amalia Pasolli ◽

Trevor Williams ◽

Elaine Fuchs

Keyword(s):

Transcription Factors ◽

Notch Signaling ◽

Terminal Differentiation ◽

Hair Follicles ◽

Structural Genes ◽

Enhancer Binding Protein ◽

Basal Proliferation ◽

Skin Epidermis

The mechanisms by which mammalian epidermal stem cells cease to proliferate and embark upon terminal differentiation are still poorly understood. By conditionally ablating two highly expressed transcription factors, AP-2α and AP-2γ, we unmasked functional redundancies and discovered an essential role for AP-2s in the process. In vivo and in vitro, AP-2 deficiency is accompanied by surprisingly minimal changes in basal gene expression but severely perturbed terminal differentiation and suppression of additional transcription factors and structural genes involved. In dissecting the underlying molecular pathways, we uncover parallel pathways involving AP-2 and Notch signaling, which converge to govern CCAAT/enhancer binding protein genes and orchestrate the transition from basal proliferation to suprabasal differentiation. Finally, we extend the striking similarities in compromising either Notch signaling or AP-2α/AP-2γ in developing skin to that in postnatal skin, where all hair follicles and sebaceous gland differentiation are also repressed and overt signs of premalignant conversion emerge.

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SEL-10 Is an Inhibitor of Notch Signaling That Targets Notch for Ubiquitin-Mediated Protein Degradation

Molecular and Cellular Biology ◽

10.1128/mcb.21.21.7403-7415.2001 ◽

2001 ◽

Vol 21 (21) ◽

pp. 7403-7415 ◽

Cited By ~ 226

Author(s):

Guangyu Wu ◽

Svetlana Lyapina ◽

Indranil Das ◽

Jinhe Li ◽

Mark Gurney ◽

...

Keyword(s):

Notch Signaling ◽

Protein Degradation ◽

Notch Receptor ◽

Dominant Negative ◽

Intracellular Domain ◽

Notch Receptors ◽

Intracellular Domains ◽

Wd40 Repeats ◽

In Cells

ABSTRACT Notch receptors and their ligands play important roles in both normal animal development and pathogenesis. We show here that the F-box/WD40 repeat protein SEL-10 negatively regulates Notch receptor activity by targeting the intracellular domain of Notch receptors for ubiquitin-mediated protein degradation. Blocking of endogenous SEL-10 activity was done by expression of a dominant-negative form containing only the WD40 repeats. In the case of Notch1, this block leads to an increase in Notch signaling stimulated by either an activated form of the Notch1 receptor or Jagged1-induced signaling through Notch1. Expression of dominant-negative SEL-10 leads to stabilization of the intracellular domain of Notch1. The Notch4 intracellular domain bound to SEL-10, but its activity was not increased as a result of dominant-negative SEL-10 expression. SEL-10 bound Notch4 via the WD40 repeats and bound preferentially to a phosphorylated form of Notch4 in cells. We mapped the region of Notch4 essential for SEL-10 binding to the C-terminal region downstream of the ankyrin repeats. When this C-terminal fragment of Notch4 was expressed in cells, it was highly labile but could be stabilized by the expression of dominant-negative SEL-10. Ubiquitination of Notch1 and Notch4 intracellular domains in vitro was dependent on SEL-10. Although SEL-10 interacts with the intracellular domains of both Notch1 and Notch4, these proteins respond differently to interference with SEL-10 function. Thus, SEL-10 functions to promote the ubiquitination of Notch proteins; however, the fates of these proteins may differ.

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A Novel Notch Pathway Inhibitor Blocks Osteoclast Activity and Synergistically Induces Apoptosis with the Proteasome Inhibitor Bortezomib in Multiple Myeloma Cells.

Blood ◽

10.1182/blood.v110.11.1522.1522 ◽

2007 ◽

Vol 110 (11) ◽

pp. 1522-1522

Author(s):

Franziska Jundt ◽

Rolf Schwarzer ◽

Martin Kaiser ◽

Oezlem Acikgoez ◽

Ulrike Heider ◽

...

Keyword(s):

Cell Growth ◽

Notch Signaling ◽

Proteasome Inhibitor ◽

Notch Pathway ◽

Growth And Survival ◽

Osteoclast Activity ◽

Notch Receptors ◽

Induced Apoptosis

Abstract Notch pathway inhibition in multiple myeloma (MM) cells is a promising new therapeutic approach since it controls myeloma cell growth as we previously demonstrated (Blood. 2004; 103:3511–3515). Notch signaling is involved in the tight interactions between myeloma cells and the bone marrow microenvironment and induces tumor cell growth in MM. We provided evidence that Notch receptors are expressed on MM cells and that Notch ligands on MM and bone marrow stromal cells activate Notch signaling through homotypic as well as heterotypic interactions in MM cells. In this study, we analyzed whether Notch signaling might be activated in osteoclasts, which express Notch receptors but not the ligands. To that end, we co-cultured MM cells and human osteoclasts, which were generated from mononuclear hematopoietic precursors of healthy donors using in vitro RANKL/M-CSF stimulation. Co-cultivation specifically activated Notch in osteoclasts and induced osteoclast activity as measured by mRNA expression of the tartrate-resistant acid phosphatase. The novel Notch pathway inhibitor, so called γ-secretase inhibitor 1 (GSI1), that we recently identified by structural comparison of known inhibitors with unknown compounds by data bank screening, specifically inhibited Notch signaling in osteoclasts and blocked their activity in this co-cultivation assay. In addition, GSI1 induced apoptosis in osteoclasts in higher concentrations. We suggest from our data that GSI treatment controls MM cell growth and concomitantly aberrant osteoclast activity in vitro and possibly in vivo, that is under current investigation. We further hypothesized that GSI1 can be combined with the proteasome inhibitor bortezomib, which has been known to have in vitro and in vivo activity against MM. We evaluated the activity of the combination of GSI1 and bortezomib against MM cell growth and survival. Proliferation of MM cell lines treated with GSI, bortezomib and their combination was determined by CellTiter-Glo® luminescent cell viability assay. AnnexinV-FITC/PI staining and cleaved poly (ADP-ribose) polymerase (PARP) staining were used to determine the degree of apoptosis. Although treatment of MM cell lines (OPM2, LP1) with either drug alone significantly inhibited proliferation and induced apoptosis with concentrations of GSI1 (30–60 μM) and bortezomib (1–4 nM), the combination resulted in synergistic inhibition of cell growth and survival. Our data suggest that combination of GSI1 and bortezomib is a rational novel treatment option in MM that simultaneously targets different proliferative and anti-apoptotic pathways. Whether this combination might also have synergistic activity against aberrant osteoclast activity in MM will be further investigated.

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Functional Characterization of POFUT1 Variants Associated with Colorectal Cancer

Cancers ◽

10.3390/cancers12061430 ◽

2020 ◽

Vol 12 (6) ◽

pp. 1430 ◽

Cited By ~ 1

Author(s):

Marlène Deschuyter ◽

Florian Pennarubia ◽

Emilie Pinault ◽

Sébastien Legardinier ◽

Abderrahman Maftah

Keyword(s):

Colorectal Cancer ◽

Notch Signaling ◽

Functional Characterization ◽

Missense Mutations ◽

Colorectal Tumors ◽

Protein Targets ◽

E Coli ◽

Notch Receptors

Background: Protein O-fucosyltransferase 1 (POFUT1) overexpression, which is observed in many cancers such as colorectal cancer (CRC), leads to a NOTCH signaling dysregulation associated with the tumoral process. In rare CRC cases, with no POFUT1 overexpression, seven missense mutations were found in human POFUT1. Methods: Recombinant secreted forms of human WT POFUT1 and its seven mutated counterparts were produced and purified. Their O-fucosyltransferase activities were assayed in vitro using a chemo-enzymatic approach with azido-labeled GDP-fucose as a donor substrate and NOTCH1 EGF-LD26, produced in E. coli periplasm, as a relevant acceptor substrate. Targeted mass spectrometry (MS) was carried out to quantify the O-fucosyltransferase ability of all POFUT1 proteins. Findings: MS analyses showed a significantly higher O-fucosyltransferase activity of six POFUT1 variants (R43H, Y73C, T115A, I343V, D348N, and R364W) compared to WT POFUT1. Interpretation: This study provides insights on the possible involvement of these seven missense mutations in colorectal tumors. The hyperactive forms could lead to an increased O-fucosylation of POFUT1 protein targets such as NOTCH receptors in CRC patients, thereby leading to a NOTCH signaling dysregulation. It is the first demonstration of gain-of-function mutations for this crucial glycosyltransferase, modulating NOTCH activity, as well as that of other potential glycoproteins.

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The Deubiquitinase OTUD3 Stabilizes ACTN4 to Activate NF-κB Signaling Pathway in Hepatocellular Carcinoma

10.21203/rs.3.rs-139689/v1 ◽

2021 ◽

Author(s):

Peiyi Xie ◽

Yanglin Chen ◽

Hongfei Zhang ◽

Guichao Zhou ◽

Qing Chao ◽

...

Keyword(s):

Hepatocellular Carcinoma ◽

Signaling Pathway ◽

Protein Level ◽

Loss Of Function ◽

Downstream Target ◽

Gene And Protein Expression ◽

Hcc Cells

Abstract Background: OTUD3, a deubiquitinating enzyme, has emerged as important role in some cancer. It showed that OTUD3 plays suppressive role in breast cancer whereas oncogenic role in lung cancer. However, the function and mechanism of OTUD3 in hepatocellular carcinoma (HCC) progression remain elusive. Methods: Gene and protein expression of OTUD3 in HCC tissues were determined by qRT-PCR, western blot and immunohistochemistry. A series of gain- and loss-of-function assays were used to investigated the role of OTUD3 in HCC cells progression. Moreover, mass spectroscopic analysis and RNA-seq were used to identify the downstream targets of OTUD3 in HCC cells. The interaction between OTUD3 and ACTN4 was examined through co-IP experiment and in vitro ubiquitination assay.Results: In our research, OTUD3 was significantly overexpressed in HCC tissues and higher OTUD3 expression was correlated with bigger tumor size, more distant metastasis, and worse TNM stage. Additionally, OTUD3 promoted HCC cells growth and metastasis in vitro and in vivo. Furthermore, ACTN4 was identified as a downstream target of OTUD3 and ACTN4 protein level was significantly related to OTUD3 expression. Rescue experiments indicated that ACTN4 was essential for OTUD3-mediated HCC proliferation and metastasis in vitro and in vivo. Moreover, we identified that NF-κB signaling pathway was activated by OTUD3 through ACTN4 to promote HCC cells progression. Importantly, OTUD3 protein level was correlated with ACTN4 protein level and activity of NF-κB signaling pathway in HCC tissues. Conclusion: Our findings identify the oncogenic role of OTUD3 in HCC and suggest that OTUD3 can be considered as a pivotal prognostic biomarker and a potential therapeutic target.

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The β-catenin/TCF-4 pathway regulates the expression of OPN in human osteoarthritic chondrocytes

10.21203/rs.2.24706/v1 ◽

2020 ◽

Author(s):

Jian Tian ◽

Shu-Guang Gao ◽

Yu-Sheng Li ◽

Chao Cheng ◽

Zhen-Han Deng ◽

...

Keyword(s):

Cartilage Destruction ◽

Transient Transfection ◽

Human Chondrocytes ◽

Mrna Levels ◽

In Vitro Methods ◽

Osteoarthritic Chondrocytes ◽

Mrna And Protein Expression ◽

Oa Chondrocytes ◽

Canonical Wnt

Abstract Background Cartilage destruction is the main characteristic of osteoarthritis (OA), and osteopontin (OPN) is elevated in OA articular cartilage; however, the reason for the increased OPN level is not determined. In addition, Wnt/β-catenin signaling participates in the progression of OA. The aim of the present study was to evaluate whether canonical Wnt signaling could regulate the expression of OPN in human chondrocytes in vitro. Methods Human chondrocytes were cultured in vitro, and we first assayed the mRNA levels of OPN and β-catenin in chondrocytes. Next, we performed transient transfection of TCF 4 shRNA into chondrocytes to inhibit TCF 4 expression and explore changes in the OPN level. Then, the Wnt/β-catenin signaling inhibitor dinkkopf-1 (Dkk-1) was incubated with chondrocytes, and we assayed the changes in β-catenin and OPN. Results Our results showed that the expression of both β-catenin and OPN was increased in OA chondrocytes, but there were no correlations between β-catenin and OPN expression. TCF4 shRNA downregulated the expression of TCF 4 and OPN in chondrocytes, while after treatment with rDKK-1 at a concentration of 400 ng/ml for 24 h, the mRNA and protein expression of both β-catenin and OPN was significantly decreased in chondrocytes. Conclusions Elevated OPN expression might be regulated by the β-catenin/TCF-4 pathway, and the Wnt/β-catenin inhibitor DKK1 could inhibit the expression of β-catenin and OPN in OA chondrocytes.

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Inhibition of Dll4-mediated signaling induces proliferation of immature vessels and results in poor tissue perfusion

Blood ◽

10.1182/blood-2006-12-063933 ◽

2007 ◽

Vol 109 (11) ◽

pp. 4753-4760 ◽

Cited By ~ 171

Author(s):

Jeffrey S. Scehnet ◽

Weidong Jiang ◽

S. Ram Kumar ◽

Valery Krasnoperov ◽

Alexandre Trindade ◽

...

Keyword(s):

Notch Signaling ◽

Network Formation ◽

Critical Role ◽

Notch Pathway ◽

Tissue Perfusion ◽

Soluble Form ◽

Loss Of Function ◽

Vascular Perfusion ◽

Notch Receptors ◽

Vascular Proliferation

Abstract Vascular development is dependent on various growth factors and certain modifiers critical for providing arterial or venous identity, interaction with the surrounding stroma and tissues, hierarchic network formation, and recruitment of pericytes. Notch receptors and ligands (Jagged and Delta-like) play a critical role in this process in addition to VEGF. Dll4 is one of the Notch ligands that regulates arterial specification and maturation events. In the current study, we have shown that loss of function by either targeted allele deletion or use of a soluble form of Dll4 extracellular domain leads to inhibition of Notch signaling, resulting in increased vascular proliferation but defective maturation. Newly forming vessels have thin caliber, a markedly reduced vessel lumen, markedly reduced pericyte recruitment, and deficient vascular perfusion. sDll4 similarly induced defective vascular response in tumor implants leading to reduced tumor growth. Interference with Dll4-Notch signaling may be particularly desirable in tumors that have highly induced Dll4-Notch pathway.

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