Dll4 Expression Research Articles

P106 Macrophages as a source of NOTCH Ligands in Crohn’s disease: implications in fibrosis

Abstract Background Fibrosis constitute the main complications associated to Crohn′s disease (CD). NOTCH signalling has been implicated in lung, kidney, liver and cardiac fibrosis. Macrophages contribute to fibrosis through the release of different mediators and the pattern of secretion may vary according to their microenvironment. The aim of the present study is to analyze the role of NOTCH ligands derived from macrophages in the complications of CD. Methods The aim of the present study is to analyze the role of NOTCH ligands derived from macrophages in the complications of CD. We have analyzed: the protein expression of NOTCH ligands and receptors in CD patients with fistulizing (B3) and stenting pattern (B2), the protein expression of NOTCH ligands in macrophages treated with the main cytokines present in CD patients (IFNγ-, IL10-, IL4, TNFα-U937 treated cells), the protein expression of HES1 and fibrosis markers in DLL4-HT29 and DLL3-HT29 treated cells. Results are expressed as fold induction (mean±SEM). Statistical analysis was performed with one-way ANOVA followed by Newman-Keuls test or t-tet. Results The expression of DLL4 and NOTCH4 were significantly higher in intestinal samples from B3 CD patients (3,2 ± 0,6 N=4* and 3,8 ± 0,6 N=8*, respectively) than in B2 patients (1,6 ± 0,2 N=4 and 1,7 ± 0,3 N=8, respectively) and controls (1,0 ± 0,1N=3 and 1,0 ± 0,1 N=8, respectively). IFNγ-U937 treated cells increased significantly the protein expression of DLL3 and DLL4 (1,6 ± 0,09 N=6* and 1,3 ± 0,1 N=7*, respectively) respect vehicle; IL4 increased significantly the expression of DLL4 (1,4 ± 0,1 N=7*) and TNFα increased significantly the expression of DLL3 (1,4 ± 0,1 N=5*), respect vehicle. DLL4-HT29 treated cells increased significantly fibrosis markers (VIMENTIN: 1,7 ± 0,1 N=3*; SNAIL: 2,2 ± 0,2 N=3*) and HES1 (1,4 ± 0,06 N=3*), respect vehicle (1,0 ± 0,07 N=6; 1,0 ± 0,05 N=6; and 1,0 ± 0,05 N=6, respectively). DLL3-HT29 treated cells only produced a reduction in the protein expression of ECADHERIN (0,4 ± 0,1 N=3*), respect vehicle (1,0 ± 0,09 N=6). Conclusion Macrophages may act as a source of NOTCH ligands who could act as fibrosis mediators in CD patients with a fistulizing (B3) behavior. The microenvironment rich in IFNγ could activate the fibrosis process in epithelial cells by favoring the expression of DLL4 and DLL3 in macrophages. DLL4 mainly activates transcription factors involved in mesenchymal epithelial transition in colonic epithelial cells (SNAIL), while DLL3 seems to have a more relevant role in cell-cell junction modification (ECADHERIN).

Two distinct Notch signals, Delta-like 4/Notch1 and Jagged-1/Notch2, antagonistically regulate chemical hepatocarcinogenesis in mice

Notch signaling is one of the most common drivers of carcinogenesis in many types of cancers, including hepatocellular carcinoma (HCC); however, it occasionally suppresses tumor progression. Moreover, it is virtually unknown how different sets of Notch ligands and receptors regulate the HCC development. In this study, we demonstrate that the expression of the Notch ligands, Delta-like 4 (Dll4) and Jagged-1 (Jag1), is upregulated during diethylnitrosamine-induced hepatocarcinogenesis. Dll4 is detected in the preneoplastic hepatocytes and HCC cells, but not in the normal hepatocytes, while Jag1 is expressed in the desmin-positive mesenchymal cells. Hepatocyte-specific Dll4 knockout abolishes the Notch1 signaling and suppresses the tumor progression. In contrast, Jag1 deletion induces the ectopic expression of Dll4 in hepatocytes along with the loss of Notch2 signaling, leading to the tumor progression. These results indicate that the two distinct Notch signals, Dll4/Notch1 and Jag1/Notch2, are antagonistic to each other, exerting opposite effects on HCC progression.

Advanced Glycation End Products Induce Atherosclerosis via RAGE/TLR4 Signaling Mediated-M1 Macrophage Polarization-Dependent Vascular Smooth Muscle Cell Phenotypic Conversion.

Objective The objective of this study was to investigate the involved mechanisms of advanced glycation end product- (AGE-) exacerbated atherosclerosis (AS). Methods Toll-like receptor 4 (TLR4) inhibitor was administrated to type 2 diabetes mellitus (T2DM) AS rats. Atherosclerotic plaque, M1 macrophage infiltration, and VSMCs phenotypes were evaluated. AGE-exposed primary macrophages were treated with specific siRNAs knocking down receptor for AGEs (RAGE) and TLR4. Phenotypes of M1 macrophage and VSMCs were identified by fluorescent stains. Contact and noncontact coculture models were established. VSMCs and macrophages were cocultured in these models. ELISA was used to detect inflammatory cytokine concentrations. Relative mRNA expression levels were determined by real-time PCR. Relative protein expression and phosphorylation levels were evaluated by Western blots assays. Results TLR4 inhibitor treatment significantly reduced arterial stenosis, infiltration of M1 polarized macrophages, and contractile-to-synthetic phenotype conversion of VSMCs in DM AS animals. RAGE and TLR4 silencing dramatically reduced AGE-induced macrophage M1 polarization, inflammatory cytokine secretion, and RAGE/TLR4/forkhead box protein C2 (FOXC2)/signaling which inhibited delta-like ligand 4 (Dll4) expression in macrophages. AGE-treated macrophages induced VSMC phenotypic conversion via activating Notch pathway in a contact coculture model rather than a noncontact model. The VSMC phenotypic conversion induction capability of macrophages was attenuated by RAGE and TLR4 silencing. Conclusions AGEs induced activation of RAGE/TLR4/FOXC2 signaling, which featured macrophage with Dll4 high expression during M1 polarization. These macrophages promoted contractile-synthetic phenotypic conversion of VSMCs through the Dll4/Notch pathway after direct cell-to-cell contacts.

A novel peptide inhibitor of Dll4-Notch1 signalling and its pro-angiogenic functions.

The Dll4-Notch1 signalling pathway plays an important role in sprouting angiogenesis, vascular remodelling and arterial or venous specificity. Genetic or pharmacological inhibition of Dll4-Notch1 signalling leads to excessive sprouting angiogenesis. However, transcriptional inhibitors of Dll4-Notch1 signalling have not been described. We designed a new peptide targeting Notch signalling, referred to as TAT-ANK, and assessed its effects on angiogenesis. In vitro, tube formation and fibrin gel bead assay were carried out, using human umbilical vein endothelial cells (HUVECs). In vivo, Matrigel plug angiogenesis assay, a developmental retinal model and tumour models in mice were used. The mechanisms underlying TAT-ANK activity were investigated by immunochemistry, western blotting, immunoprecipitation, RT-qPCR and luciferase reporter assays. The amino acid residues 179-191 in the G-protein-coupled receptor-kinase-interacting protein-1 (GIT1-ankyrin domain) are crucial for GIT1 binding to the Notch transcription repressor, RBP-J. We designed the peptide TAT-ANK, based on residues 179-191 in GIT1. TAT-ANK significantly inhibited Dll4 expression and Notch 1 activation in HUVECs by competing with activated Notch1 to bind to RBP-J. The analyses of biological functions showed that TAT-ANK promoted angiogenesis in vitro and in vivo by inhibiting Dll4-Notch1 signalling. We synthesized and investigated the biological actions of TAT-ANK peptide, a new inhibitor of Notch signalling. This peptide will be of significant interest to research on Dll4-Notch1 signalling and to clinicians carrying out clinical trials using Notch signalling inhibitors. Furthermore, our findings will have important conceptual and therapeutic implications for angiogenesis-related diseases.

Relationship of Notch Signal, Surfactant Protein A, and Indomethacin in Cervix During Preterm Birth: Mast Cell and Jagged-2 May Be Key in Understanding Infection-mediated Preterm Birth.

Although it is thought that there is a close relationship between Notch signal and preterm birth, the functioning of this mechanism in the cervix is unknown. The efficacy of surfactants and prostaglandin inhibitors in preterm labor is also still unclear. In this study, 48 female CD-1 mice were distributed to pregnant control (PC), Sham, PBS, indomethacin (2 mg/kg; intraperitoneally), lipopolysaccharides (LPS) (25 μg/100 μl; intrauterine), LPS + IND, and Surfactant Protein A Block (SP-A Block: SP-A B; the anti-SP-A antibody was applied 20 µg/100μl; intrauterine) groups. Tissues were examined by immunohistochemistry, immunofluorescence, and Western blot analysis. LPS administration increased the expression of N1 Dll-1 and Jagged-2 (Jag-2). Although Toll-like receptor (Tlr)-2 significantly increased in the LPS-treated and SP-A-blocked groups, Tlr-4 significantly increased only in the LPS-exposed groups. It was observed that Jag-2 is specifically expressed by mast cells. Overall, this experimental model shows that some protein responses increase throughout the uterus, starting at a specific point on the cervix epithelium. Surfactant Protein A, which we observed to be significantly reduced by LPS, may be associated with the regulation of the epithelial response, especially during preterm delivery due to infection. On the contrary, prostaglandin inhibitors can be considered an option to delay infection-related preterm labor with their dose-dependent effects. Finally, the link between mast cells and Jag-2 could potentially be a control switch for preterm birth.

Notch1 and Notch3 coordinate for pericyte-induced stabilization of vasculature.

The Notch pathway regulates complex patterning events in many species and is critical for the proper formation and function of the vasculature. Despite this importance, how the various components of the Notch pathway work in concert is still not well understood. For example, NOTCH1 stabilizes homotypic endothelial junctions, but the role of NOTCH1 in heterotypic interactions is not entirely clear. NOTCH3, on the other hand, is essential for heterotypic interactions of pericytes with the endothelium, but how NOTCH3 signaling in pericytes impacts the endothelium remains elusive. Here, we use in vitro vascular models to investigate whether pericyte-induced stabilization of the vasculature requires the cooperation of NOTCH1 and NOTCH3. We observe that both pericyte NOTCH3 and endothelial NOTCH1 are required for the stabilization of the endothelium. Loss of either NOTCH3 or NOTCH1 decreases the accumulation of VE-cadherin at endothelial adherens junctions and increases the frequency of wider, more motile junctions. We found that DLL4 was the key ligand for simulating NOTCH1 activation in endothelial cells and observed that DLL4 expression in pericytes is dependent on NOTCH3. Altogether, these data suggest that an interplay between pericyte NOTCH3 and endothelial NOTCH1 is critical for pericyte-induced vascular stabilization.

MiR-130b suppresses the invasion and migration of prostate cancer via inhibiting DLL1 and regulating the PI3K/Akt pathways.

Prostate cancer occurs in the prostatic epithelium and poses a threat to the health of middle-aged and older males. The objective of the present study was to explore the roles of microRNA (miRNA/miR)-130b in prostate cancer and potential molecular mechanisms in order to control the migration and invasion of prostate cancer. For this purpose, reverse transcription-PCR was performed to evaluate the mRNA levels of DLL1, phosphoinositide-3 kinase (PI3K), protein kinase B (Akt) and matrix metalloproteinase (MMP)9, and western blot analysis was carried out to detect the protein expression levels of DLL1, phosphorylated (p)-PI3K, p-Akt and MMP9. A Transwell assay was conducted to examine the invasion rate of prostate cancer cells. Furthermore, a scratch wound assay was performed to examine the migration rate of prostate cancer cells. A luciferase assay was performed to examine the interaction between miRNA and its target mRNA. The results revealed that miR-130b had abnormal (low) expression in tumor tissues compared with that in the adjacent normal tissue. An miR-130b mimic suppressed the expression of DLL1. The expression of p-PI3K, p-Akt and MMP9 in prostate cancer cells transfected with the miR-130b mimic was decreased in comparison to the negative control and control groups. Furthermore, migration and invasion were significantly suppressed in the miR-130b mimic group. In conclusion, a novel pathway interlinking miR-130b and MMP9, p-Akt and p-PI3K, which regulates the migration and invasion of prostate cancer cells, was identified. These findings provide an intriguing biomarker and treatment strategy for patients with prostate cancer.

Rivaroxaban Suppresses Atherosclerosis by Inhibiting FXa-Induced Macrophage M1 Polarization-Mediated Phenotypic Conversion of Vascular Smooth Muscle Cells.

Background: Factor Xa (FXa) is a mediator initiating and accelerating atherosclerosis (AS). Both macrophage and vascular smooth muscle cells (VSMCs) participate in AS progression. This study was aimed to investigate the mechanisms underlying the effects of the FXa inhibitor rivaroxaban on AS.Methods: Rivaroxaban was administered to AS mice. Primary macrophages were exposed to FXa, treated with rivaroxaban, and transfected with siRNA silencing protease-activated receptor 2 (PAR2), hypoxia-inducible factor 1α (HIF1α), delta-like receptor 4 (Dll4), and Akt. Interaction between macrophages and VSMCs was assessed by co-culturing systems. Atherosclerotic lesions were evaluated by oil red O stain. Fluorescent staining was used to determine the cell phenotypes. Secretions of inflammatory cytokines and collagen were assessed by ELISA and Sircol assays. Western blotting was used to evaluate the protein expression and phosphorylation levels.Results: Rivaroxaban reduced lesion area, accumulation of M1 macrophages, and contractile-synthetic phenotypic conversion of VSMCs in atherosclerotic plaques. FXa exposure induced polarization of macrophages toward M1 and Dll4 high expression, which were inhibited by PAR2, Akt1, and HIF1α silencing. Rivaroxaban treatment inhibited PAR2/Akt/HIF1α signaling activation and Dll4 expression in FXa-exposed macrophages. By cell-to-cell contact, M1 macrophages induced Notch signaling activation in VSMCs which committed contractile-synthetic conversion. Rivaroxaban treatment and Dll4 silencing incapacitated macrophage in inducing phenotypic conversion of VSMCs upon cell-to-cell contact.Conclusion: Rivaroxaban suppresses AS by inhibiting FXa-induced PAR2/Akt/HIF1α signaling activation-mediated macrophage M1 polarization and high Dll4 expression. These macrophages facilitated VSMCs to perform contractile-synthetic phenotypic conversion upon macrophage-VSMCs cell-to-cell contact.

Intratumoral Heterogeneity Promotes Collective Cancer Invasion through NOTCH1 Variation.

Cellular and molecular heterogeneity within tumors has long been associated with the progression of cancer to an aggressive phenotype and a poor prognosis. However, how such intratumoral heterogeneity contributes to the invasiveness of cancer is largely unknown. Here, using a tumor bioengineering approach, we investigate the interaction between molecular subtypes within bladder microtumors and the corresponding effects on their invasiveness. Our results reveal heterogeneous microtumors formed by multiple molecular subtypes possess enhanced invasiveness compared to individual cells, even when both cells are not invasive individually. To examine the molecular mechanism of intratumoral heterogeneity mediated invasiveness, live single cell biosensing, RNA interference, and CRISPR-Cas9 gene editing approaches were applied to investigate and control the composition of the microtumors. An agent-based computational model was also developed to evaluate the influence of NOTCH1 variation on DLL4 expression within a microtumor. The data indicate that intratumoral variation in NOTCH1 expression can lead to upregulation of DLL4 expression within the microtumor and enhancement of microtumor invasiveness. Overall, our results reveal a novel mechanism of heterogeneity mediated invasiveness through intratumoral variation of gene expression.

Using Spatial Transcriptomics to Reveal Fetal Liver Hematopoietic Stem Cell-Niche Interactions

The hematopoietic stem cell (HSC) microenvironment, termed the niche, supports the proliferation, self-renewal, and differentiation abilities of HSCs. The definitive HSCs emerge from the hemogenic endothelium in the aorta-gonad-mesonephros (AGM) region after E11.5, and then migrate to the fetal liver after E12.5 for expansion. After E17.5, HSCs migrate to the bone marrow and reside in the bone marrow for the postnatal stage and adulthood. Because the fetal liver is thought to be a harbor for the rapid expansion of HSCs, numerous studies have focused on the fetal liver HSC niche in the search for novel niche factors and niche cells that support HSC expansion. However, to our knowledge, there are no successes in translating the niche factors to a clinical application for the expansion of HSCs ex vivo. In this study, we are using cutting-edge spatial transcriptomics to comprehensively study the transcriptomics and interactions between HSCs and the niche cells in the fetal liver, and in search of the niche cells and factors for HSC expansion.To understand the spatial distribution and interactions between HSCs and niche cells in the fetal liver, we introduced 2 spatial transcriptomic methods, slide-seq, and 10x Visium, in our study on E14.5 mouse fetal liver. By integrating with a parallel single-cell sequencing analysis, we revealed the spatial transcriptomics of HSCs and potential niche cells, including hepatoblasts, endothelium cells, macrophages, megakaryocytes, and hepatic stellate cells/perivascular mesenchymal cells (PMCs) in E14.5 mouse fetal liver. Interestingly, we found that the PMCs were characterized by enriched N-cadherin expression. Both slide-seq and 10x Visium showed that the N-cadherin-expressing PMCs are enriched in the portal vessel area. Importantly, the majority of fetal liver HSCs are in close proximity to N-cadherin-expressing PMCs, indicating a supportive role of N-cadherin-expressing PMCs in HSC maintenance. Subsequent CellPhoneDB (CPDB) analysis demonstrated that the N-cadherin-expressing PMCs are major niche-signaling senders with an enriched expression of niche factors, such as CXCL12 and KITL, and stemness pathway-related ligands, such as IGF1, IGF2, TGFβ2, TGFβ3, JAG2, and DLK1, indicating N-cadherin-expressing PMCs could be the major niche cells in supporting HSCs in the fetal liver. This finding was consistent with our previous finding that N-cadherin-expressing bone and marrow stromal progenitor cells can maintain reserve HSCs in the adult bone marrow. Moreover, CPDB analysis indicated that other potential niche cells, such as endothelium cells, macrophages, and megakaryocytes, may support HSCs in different signal transduction pathways. For example, endothelium cells have an enriched expression of KITL, IGF2, DLL1, TGFβ1, and TGFβ2; macrophages have enriched expression of KITL, IFNγ, and TGFβ1; megakaryocytes have enriched expression of PF4, JAG2 and TGFβ1. Intriguingly, our previous studies showed that megakaryocytes could promote HSC expansion under stress conditions in the bone marrow. To investigate the potential role of N-cadherin-expressing cells in supporting fetal liver HSCs, we generated an N-cad CreER;Cxcl12 and an N-cad CreER;Scf mouse model to conditionally knockout the well-studied niche factors, CXCL12 and SCF, in N-cadherin-expressing cells. Conditional knockout of either Cxcl12 or Scf in N-cadherin-expressing cells resulted in an increase in the number of HSCs. Moreover, conditional knockout of Cxcxl12 in N-cadherin-expressing cells also resulted in a myeloid-biased differentiation. We postulate that the knockout of Cxcl12 or Scf in N-cadherin-expressing cells leads to the migration of HSCs towards other potential niche cells, such as macrophages and megakaryocytes, which may induce HSC expansion and biased differentiation.In summary, by using cutting-edge spatial transcriptomics, we revealed a comprehensive spatial transcriptomics of HSCs and niche cells in E14.5 mouse fetal liver. The N-cadherin-expressing cells in the fetal liver is a major niche in maintaining HSCs, while other potential niches may be responsible for the expansion of HSCs. In the future, we will use multiple approaches, such as spatial transcriptomics and fluorescence in situ hybridization (FISH), to verify the distribution changes of HSCs in N-cad CreER;Cxcl12 mouse, and to reveal the niches in support of the expansion of HSCs. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Substrate stiffness modulates endothelial cell function via the YAP-Dll4-Notch1 pathway

Endothelial cells adapt their functions as a consequence of sensing extracellular substrate stiffness; these alterations allow them to maintain their vascular structure and function. Substrate stiffness-mediated yes-associated protein 1 (YAP) activation plays an important role in mechano-transduction and pro-angiogenic phenotype of endothelial cells, and Delta-like ligand 4 (Dll4)-Notch1 signaling is closely related to angiogenesis; however, the impact of substrate stiffness-mediated interrelation of these pathways on endothelial cell functions remains elusive. We confirmed that endothelial cells on softer substrates not only elongate cellular aspects but also attenuate YAP activation compared to cells on stiffer substrates. Endothelial cells on softer substrates also upregulate the vascular endothelial growth factor receptor 1 (VEGFR1) and VEGFR2 mRNA expression that is enhanced by VEGF stimulation. We determined that endothelial cells on softer substrates increased Dll4 expression, but not Notch1 expression, via YAP signaling. Moreover, endothelial cells on soft substrates induced not only VEGFRs upregulation but also suppression of pro-inflammatory interleukin-6 and plasminogen activator inhibitor-1 mRNA expression and the facilitation of anti-coagulant thrombomodulin and pro-coagulant tissue factor mRNA expression. Our results suggest that endothelial cells activate the YAP-Dll4-Notch signaling pathway in response to substrate stiffness and dictate cellular function.

Feedback regulation of Notch signaling and myogenesis connected by MyoD-Dll1 axis.

Muscle precursor cells known as myoblasts are essential for muscle development and regeneration. Notch signaling is an ancient intercellular communication mechanism that plays prominent roles in controlling the myogenic program of myoblasts. Currently whether and how the myogenic cues feedback to refine Notch activities in these cells are largely unknown. Here, by mouse and human gene gain/loss-of-function studies, we report that MyoD directly turns on the expression of Notch-ligand gene Dll1 which activates Notch pathway to prevent precautious differentiation in neighboring myoblasts, while autonomously inhibits Notch to facilitate a myogenic program in Dll1 expressing cells. Mechanistically, we studied cis-regulatory DNA motifs underlying the MyoD–Dll1–Notch axis in vivo by characterizing myogenesis of a novel E-box deficient mouse model, as well as in human cells through CRISPR-mediated interference. These results uncovered the crucial transcriptional mechanism that mediates the reciprocal controls of Notch and myogenesis.

Effect of the Notch4/Dll4 signaling pathway in early gestational intrauterine infection on lung development.

Intrauterine infection is an important risk factor for bronchopulmonary dysplasia (BPD). BPD is characterized by arrested lung alveolarization and impaired pulmonary vascularization. The Notch4 signaling pathway is a key regulator of vascular remodeling and angiogenesis. Therefore, the presents study investigated the expression of Notch4, delta-like canonical Notch ligand 4 (Dll4) and related factors in an in vivo rat model and in rat pulmonary microvascular endothelial cells (PMVECs) in vitro, to study the mechanisms by which intrauterine infection affects rat lung development. A rat model of intrauterine infection was established by endocervical inoculation with Escherichia scoli on embryonic day 15. The date of birth was counted as postnatal day 0 (P0). Then, the lung tissues were collected from pups at days P3-P14. The expression of Notch4, Dll4 and related factors was measured by reverse transcription-quantitative PCR and western blotting. In addition, the γ-secretase inhibitor DAPT was used to examine the effect of Notch4 signaling on PMVECs. Intrauterine E. coli infection impaired normal lung development, as indicated by decreased microvessel density, fewer alveoli, fewer secondary septa, and larger alveoli compared with the control group. Furthermore, Notch4, Dll4 and NF-κB levels were significantly increased in the E. coli-infected group at P3 compared with the control group. Similarly, the mRNA expression levels of fetal liver kinase 1 (Flk-1, a VEGF receptor) were significantly increased in the E. coli-infected group at P3 and P7. In PMVECs, the inhibition of Notch4 signaling contributed to decreases in lipopolysaccharide (LPS)-induced expression of VEGF and its receptors. Furthermore, the inhibition of Notch4/Dll4 signaling accelerated cell proliferation and decreased the apoptosis rate of LPS-induced PMVECs. LPS-induced NF-κB expression in PMVECs was also attenuated by the Notch4/Dll4 inhibitor. In conclusion, intrauterine E. coli infection impaired normal lung development, possibly through Notch4/Dll4 signaling and effects on VEGF and its receptors.

The effect induced by alternated mechanical loading on Notch-1 in mandibular condylar cartilage of growing rabbits.

AimsThe aim of our study is to investigate the effect induced by alternated mechanical loading on Notch-1 in mandibular condylar cartilage (MCC) of growing rabbits.MethodsA total of 64 ten-day-old rabbits were randomly divided into two groups according to dietary hardness: normal diet group (pellet) and soft diet group (powder). In each group, the rabbits were further divided into four subgroups by feeding time: two weeks, four weeks, six weeks, and eight weeks. Animals would be injected 5-bromo-2′-deoxyuridine (BrdU) every day for one week before sacrificing. Histomorphometric analysis of MCC thickness was performed through haematoxylin and eosin (HE) staining. Immunochemical analysis was done to test BrdU and Notch-1. The quantitative real-time polymerase chain reaction (qRT-PCR) and western blot were used to measure expression of Notch-1, Jagged-1, and Delta-like 1 (Dll-1).ResultsThe thickness of MCC in the soft diet group was thinner than the one in normal diet group. Notch-1 was restricted in fibrous layer, proliferative layer, and hypertrophic layer. The expression of Notch-1 increased from two weeks to six weeks and then fell down. Notch-1 in normal diet group was higher than that in soft diet group in anterior part of MCC. The statistical differences of Notch-1 were shown at two, four, and six weeks (p < 0.05). The result of western blot and quantitative real-time PCR (qRT-PCR) showed the expression of Dll-1 and Jagged-1 rose from two to four weeks and started to decrease at four weeks. BrdU distributed in all layers of cartilage and subchondral bone. The number of BrdU-positive cells, which were less in soft diet group, was decreasing along with the experiment period. The significant difference was found at four, six, and eight weeks in anterior and posterior parts (p < 0.05).ConclusionThe structure and proliferation of MCC in rabbits were sensitive to dietary loading changes. The proper mechanical loading was essential for transduction of Notch signalling pathway and development of mandibular condylar cartilage.Cite this article: Bone Joint Res 2021;10(7):437–444.

Notch Signaling Promotes the Differentiation of Human CLEC9A+ Dendritic Cells from Hematopoietic Stem and Progenitor Cells

Human CLEC9A+ dendritic cells (also known as CD141+ DCs, XCR1+ DCs, and cDC1) are an endogenous DC subset with constitutive ability to traffic to secondary lymphoid tissues, efficiently cross-present cellular antigens, and prime CD4+ and CD8+ antiviral and antitumor T cell responses. As such, CLEC9A+ DCs have been proposed as ideal candidates for adoptive cell immunotherapy, however their rarity in vivo and a lack of knowledge regarding their development have thus far precluded their therapeutic use.We used in vitro differentiation approaches to identify novel microenvironmental cues that regulate the development of CLEC9A+ DCs from human CD34+ hematopoietic stem and progenitor cells (HSPCs). Our findings reveal a previously unknown role for Notch signaling as a key regulatory pathway in CLEC9A+ DC differentiation from HSPCs. Exposure of HSPCs to the Notch ligand DLL1 expressed by MS5 stromal cells, together with the DC-promoting cytokines FLT3L and GM-CSF, markedly enhanced the generation of CLEC9A+ DCs relative to control cultures lacking DLL1 expression. Resulting CLEC9A+ DC frequency was on average 66% of total cells in DLL1 cultures, compared with 6% in control cultures at 20 days (p < 0.0001). Promotion of CLEC9A+ DC development was accompanied by statistically significant decreases in monocyte, CD1c+ DC, and plasmacytoid DC frequencies and cell numbers, with granulocytic differentiation relatively unaffected. Similar changes were seen when DLL1 was substituted for the Notch ligands DLL4 or JAG1, and abrogated by gamma secretase inhibition. Furthermore, promotion of CLEC9A+ DC differentiation was mimicked by transduction of HSPCs with intracellular Notch1, consistent with a cell-intrinsic role for Notch in CLEC9A+ DC development.The effect of Notch signaling on CLEC9A+ DC development was conserved between HSPCs isolated from human cord blood (CB), bone marrow (BM), or G-CSF mobilized peripheral blood (MPB). Furthermore, highly purified BM monocyte/dendritic cell progenitors (MDP) or common dendritic cell progenitors (CDP) cultured in the presence of DLL1 preferentially generated CLEC9A+ DCs with loss of alternative lineage outputs, supporting a mechanism by which Notch signaling skews lineage commitment to the CLEC9A+ DC lineage at the level of multipotent DC progenitors.Notch-induced CLEC9A+ DCs derived from HSPCs were phenotypically and functionally similar to primary CLEC9A+ DCs isolated from the blood. Whole transcriptome profiling by RNAseq of Notch-induced CLEC9A+ DCs confirmed lineage-specific upregulation of key CLEC9A+ DC genes including XCR1, CADM1, BATF3, and IRF8 . Furthermore, global gene expression profiles were similar between Notch-induced CLEC9A+ DCs generated from HSPCs isolated from CB or MPB. Notch-induced CLEC9A+ DCs expressed high levels of CD62L and CCR7, and underwent efficient chemotaxis in response to CCL21 in transwell migration assays, suggesting lymph node-homing capacity. Compared to primary blood CLEC9A+ DCs, Notch-induced CLEC9A+ DCs exhibited higher basal surface expression of T cell costimulatory molecules including CD80, CD83, and CD86, reminiscent of dermal CLEC9A+ DCs, and these were further upregulated in response to the TLR agonists poly(I:C) or R848. Notch-induced CLEC9A+ DCs exhibited potent CD4+ and CD8+ immunostimulatory activity in mixed lymphocyte reactions, and induced antigen-specific CD8+ T cell responses to an HLA-A*0201-restricted NY-ESO-1 epitope through either cross-presentation of cellular antigen acquired from necrotic tumor cells, or endogenous presentation of antigen transduced at the CD34+ HSPC stage.In conclusion, we have identified a novel role for Notch signaling in the differentiation of CLEC9A+ DCs from HSPCs. We propose Notch signaling enforces CLEC9A+ DC lineage commitment in multipotent DC progenitors, and RNAseq studies addressing the molecular basis of Notch-induced CLEC9A+ DC commitment are in progress. Importantly, the identification of Notch as a critical regulatory pathway in human CLEC9A+ DC development allows robust in vitro differentiation of large numbers of highly functional CLEC9A+ DCs. Taken together our findings provide insight into the development of this important DC lineage and permit the preclinical development of next generation cellular vaccine strategies using in vitro derived CLEC9A+ DCs. DisclosuresMontel-Hagen:Kite Pharma: Research Funding. Kohn:Kite Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees; Biogen IDEC: Research Funding; BioMarin Pharmaceutical: Research Funding; Orchard Therapeutics Ltd.: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Crooks:Kite Pharma: Research Funding.

Increased cytoplasmic expression of DLL4 is associated with favorable prognosis in colorectal cancer.

Aims: DLL4 of the Notch pathway is a key regulator of VEGF expression, which mediates tumor neovascularization and stem cell self-renewal in colorectal cancer (CRC). The authors investigated the association of DLL4 expression with the clinicopathological characteristics and survival outcomes of CRC patients. Methods: DLL4 expression level was evaluated in 199 CRC samples using immunohistochemistry analysis of tissue microarrays. Results: The high expression of DLL4 was inversely associated with distant metastasis (p <0.029), tumor recurrence (p <0.04) and longer overall survival following curative surgery compared with those with low DLL4 expression with 95% CI(log-rank test: p =0.050). In univariate analysis, histological grade (hazard ratio: 3.859; 95% CI: 1.081-13.784; p =0.038) was a strong prognostic risk factor, affecting the overall survival of CRC patients. Conclusion: The authors' results demonstrate that DLL4 expression might be considered a favorable prognostic factor for overall survival in CRC patients.

Notch signaling supports the appearance of follicular helper T cells in the Peyer's patches concomitantly with the reduction of regulatory T cells.

The intracellular fragment of Notch1, a mediator of Notch signaling that is frequently detected in thymic immigrants, is critical for specifying T-cell fate in the thymus, where Delta-like 4 (Dll4) functions as a Notch ligand on the epithelium. However, as such Notch signaling has not been detected in mature T cells, how Notch signaling contributes to their response in secondary lymphoid organs has not yet been fully defined. Here, we detected the marked expression of Dll4 on the stromal cells and the active fragment of Notch1 (Notch1 intracellular domain, N1ICD) in CD4+ T cells in the follicles of Peyer's patches (PPs). In addition, N1ICD-bearing T cells were found in the T-cell zone of PPs, especially in the transcription factor Foxp3+ regulatory T (Treg) cells, with slight expression of Dll4 on the stromal cells. These fragments disappeared in Dll4-deficient conditions. It was also found that Notch1- and Notch2-deficient T cells preferentially differentiated into Treg cells in PPs, but not CXCR5+PD-1+ follicular helper T (Tfh) cells. Moreover, these phenotypes were also observed in chimeric mice reconstituted with the control and T-cell-specific Notch1/2-deficient bone marrow or Treg cells. These results demonstrated that Dll4-mediated Notch signaling in PPs is required for the efficient appearance of Tfh cells in a Treg cell-prone environment, which is common among the gut-associated lymphoid tissues, and is critical for the generation of Tfh-mediated germinal center B cells.

P051 Macrophages as a source of Notch Ligands in Crohn’s disease: implications in fibrosis

Abstract Background Fibrosis constitute the main complications associated to Crohn’s disease (CD). Notch signalling has been implicated in lung, kidney, liver and cardiac fibrosis. Macrophages contribute to fibrosis through the release of different mediators and the pattern of secretion may vary according to their microenvironment. The aim of the present study is to analyze the role of Notch ligands derived from macrophages in the complications of CD. Methods We have analyzed: the mRNA expression of cytokines and Notch ligands in CD patients with fistulizing and stenting pattern, the mRNA and protein expression of macrophage markers and Notch ligands in macrophages treated with the main cytokines present in CD patients (IFNγ-, IL10-, IL4, TNFα-U937 treated cells), the mRNA expression of fibrosis markers of DLL4-HT29 treated cells. Results are expressed as fold induction (mean±SEM, n≥4). Statistical analysis was performed with one-way ANOVA followed by Newman-Keuls test. Correlations were analyzed with the Spearman coefficient. Results The mRNA expression of IFNγ, TNFα, IL4, IL6 and IL10 was significantly higher in intestinal samples from B2- and B3-CD patients (11.4±1.6, 6.9±1.3, 16.4±3.9, 4.1±0.4, and 5.0±1.0 respectively for B2, and 14.2±1.8, 9.6±2.6, 21.5±4.1, 6.3±1.0 and 9.2±1.7 respectively for B3) than in controls (1.0±0.09, 1.1±0.2, 1.2±0.1, 1.1±0.1 and 1.0±0.1 respectively). The mRNA expression of DLL3 and DLL4 was significantly higher in intestinal samples from B2 (6.1±1.3 and 9.3±2.4, respectively) than in B3 CD patients (4.4±1.0 and 1.8±0.7, respectively) and in controls (0.9±0.2 and 0.7±1.2 respectively). IFNγ-U937 treated cells increased significantly the mRNA expression of DLL3 and DLL4 (2,9±0,6 N=5 N=4 and 3,7±1,1 N=4, respectively) respect vehicle; IL1β increased significantly the expression of DLL4 (1,8±0,01 N=4) and TNFα increased significantly the expression of DLL3 (7,1±2,2 N=4), respect vehicle. DLL4-HT29 treated cells increased significantly fibrosis markers (VIMENTIN (4,6±0,6 N=6), α-SMA (20,9±8,2 N=6), SNAIL1 (1,8±0,4 N=6), SNAIL2 (8,3±1,3 N=6), ZEB1 (8,2±4,3 N=6) and ZEB2 (4,3±0,2 N=6), respect vehicle. Conclusion Macrophages may act as a source of Notch ligands who could act as fibrosis mediators in CD patients with a stenting (B2) behavior. The microenvironment rich in IFNγ could activate the fibrosis process in epithelial cells by favoring the expression of DLL4 in macrophages.

Mycobacterium tuberculosis modulates DC-T cell cross-talk and Th17 polarization by dampening Notch signaling

Abstract Tuberculosis (TB) is among the leading causes of death worldwide. While IFN-γ and CD4+ Th1 T cell responses are necessary to mount an immune response to Mycobacterium tuberculosis (Mtb), the causative agent of TB, they are not sufficient to provide protection. Studies from several groups, including our own, have highlighted an important role for IL-17 and Th17 responses in immunity to Mtb infection. Previous research from the laboratory has shown that Mtb restricts Th17 responses by dampening dendritic cell (DC) responses and has identified CD40-mediated co-stimulation as critical for generating Th17 responses in response to Mtb. We showed that exogenous CD40 engagement on Mtb-infected DCs enhances Th17 polarization and reduces Mtb burden in the lungs in a vaccination model. However, the DC mechanisms that mediate CD40-dependent Th17 polarization and protection have not been defined. Here we show that Notch signaling in DCs modulates DC-T cell crosstalk and influences T cell polarization during infection. Engaging the CD40 pathway on Mtb-infected DCs increases the mRNA and protein expression of Notch ligands DLL4 and Jagged1 over the course of infection. Blockade of Jagged1 during a DC-T cell co-culture lowers Th1 responses while blockade of both DLL4 and Jagged1 significantly limits Th17 polarization. These results reveal that during infection, Mtb restricts expression of Notch ligands, which impedes Th17 responses during TB. Insights from this study could be applied to designing more efficacious TB vaccines and adjuvants.

Unique Cholangiocyte-Targeted IgM Autoantibodies Correlate With Poor Outcome in Biliary Atresia.

The etiology of biliary atresia (BA) is not known and is likely multifactorial, including a genetic predisposition, a viral or environmental trigger, an aberrant autoimmune response targeting cholangiocytes, and unique susceptibilities of the neonatal bile ducts to injury. Damaged cholangiocytes may express neo self-antigens and elicit autoreactive T-cell-mediated inflammation and B-cell production of autoantibodies. The aim of this study was to discover autoantibodies in BA that correlated with outcomes. An autoantigen microarray encompassing approximately 9,500 autoantigens was used to screen for serum immunoglobulin M (IgM) and immunoglobulin G (IgG) autoantibodies in patients with BA or other liver disease controls. Validation of candidate autoantibodies by enzyme-linked immunosorbent assay on a second cohort of subjects (6-12months following Kasai portoenterostomy) and correlations of autoantibodies with outcomes were performed (serum bilirubin levels and need for liver transplant in first 2years of life). Mean anti-chitinase 3-like 1 (CHI3L1), anti-delta-like ligand (DLL-4), and antisurfactant protein D (SFTPD) IgM autoantibodies in BA were significantly higher compared with controls, and IgM autoantibody levels positively correlated with worse outcomes. Immunofluorescence revealed cholangiocyte-predominant expression of CHI3L1, DLL-4, and SFTPD. The humoral autoantibody response was associated with C3d complement activation and T-cell autoimmunity, based on detection of cholangiocyte-predominant C3d co-staining and peripheral blood autoreactive T cells specific to CHI3L1, DLL-4 and SFTPD, respectively. BA is associated with cholangiocyte-predominant IgM autoantibodies in the first year after Kasai portoenterostomy. Anti-CHI3L1, anti-DLL-4, and anti-SFTPD IgM autoantibody correlations with worse outcomes and the detection of C3d on cholangioctyes and antigen-specific autoreactive T cells suggest that autoimmunity plays a role in the ongoing bile duct injury and progression of disease.