Epsin1-mediated exosomal sorting of Dll4 modulates the tubular-macrophage crosstalk in diabetic nephropathy

Tubular epithelial cells (TECs) play critical roles in the development of diabetic nephropathy (DN), and can activate macrophages through the secretion of exosomes. However, the mechanism(s) of TEC-exosomes in macrophage activation under DN remains unknown. By mass spectrometry, 1,644 differentially expressed proteins, especially Dll4, were detected in the urine exosomes of DN patients compared with controls, which was confirmed by western blot assay. Elevated Epsin1 and Dll4/N1ICD expression was observed in kidney tissues in both DN patients and db/db mice and was positively associated with tubulointerstitial damage. Exosomes from high glucose (HG)-treated tubular cells (HK-2) with Epsin1 knockdown (KD) ameliorated macrophage activation, TNF-α, and IL-6 expression, and tubulointerstitial damage in C57BL/6 mice in vivo. In an in vitro study, enriched Dll4 was confirmed in HK-2 cells stimulated with HG, which was captured by THP-1 cells and promoted M1 macrophage activation. In addition, Epsin1 modulated the content of Dll4 in TEC-exosomes stimulated with HG. TEC-exosomes with Epsin1-KD significantly inhibited N1ICD activation and iNOS expression in THP-1 cells compared with incubation with HG alone. These findings suggested that Epsin1 could modulate tubular-macrophage crosstalk in DN by mediating exosomal sorting of Dll4 and Notch1 activation.

Matrix stiffness regulates Notch signaling activity in endothelial cells

Notch signaling is critical for many developmental and disease-related processes. It is widely accepted that Notch has a mechanotransduction module that regulates receptor cleavage. However, the role of biomechanical properties of the cellular environment in Notch signaling in general is still poorly understood. During angiogenesis, differentiation of endothelial cells into tip and stalk cells is regulated by Notch signaling, and remodeling of the extracellular matrix occurs. We investigated the influence of substrate stiffness on the Notch signaling pathway in endothelial cells. Using stiffness-tuned polydimethylsiloxane (PDMS) substrates, we show that activity of the Notch signaling pathway inversely correlates with a physiologically relevant range of substrate stiffness (i.e. increased Notch signaling activity on softer substrates). Trans-endocytosis of the Notch extracellular domain, but not the overall endocytosis, is regulated by substrate stiffness, and integrin cell-matrix connections are both stiffness dependent and influenced by Notch signaling. We conclude that mechanotransduction of Notch activation is modulated by substrate stiffness, highlighting the role of substrate rigidity as an important cue for signaling. This might have implications in pathological situations associated with stiffening of the extracellular matrix, such as tumor growth.

Delta-like ligand-4 regulates Notch-mediated maturation of second heart field progenitor-derived pharyngeal arterial endothelial cells

Mesodermal progenitors in the second heart field (SHF) express Delta‐like‐ligand 4 (Dll4) that regulates Notch‐mediated proliferation. As cells of SHF lineage mature to assume endocardial and myocardial cell fates, we have shown that Dll4 expression is lost, and the subsequent expression of another Notch ligand Jagged1 regulates Notch‐mediated maturation events in the developing heart. A subset of SHF progenitors also matures to form the pharyngeal arch artery (PAA) endothelium. Dll4 was originally identified as an arterial endothelial‐specific Notch ligand that plays an important role in blood vessel maturation, but its role in aortic arch maturation has not been studied to date secondary to the early lethality observed in Dll4 knockout mice. We show that, unlike in SHF‐derived endocardium and myocardium, Dll4 expression persists in SHF‐derived arterial endothelial cells. Using SHF‐specific conditional deletion of Dll4, we demonstrate that as SHF cells transition from their progenitor state to an endothelial fate, Dll4‐mediated Notch signalling switches from providing proliferative to maturation cues. Dll4 expression maintains arterial identity in the PAAs and plays a critical role in the maturation and re‐organization of the 4th pharyngeal arch artery, in particular. Haploinsufficiency of Dll4 in SHF leads to highly penetrant aortic arch artery abnormalities, similar to those observed in the clinic, primarily resulting from aberrant reorganization of bilateral 4th pharyngeal arch arteries. Hence, we show that cells of SHF lineage that assume an arterial endothelial fate continue to express Dll4 and the resulting Dll4‐mediated Notch signalling transitions from an early proliferative to a later maturation role during aortic arch development.

Notch signaling determines cell-fate specification of the two main types of vomeronasal neurons of rodents

The ability of terrestrial vertebrates to find food and mating partners, and to avoid predators, relies on the detection of chemosensory information. Semiochemicals responsible for social and sexual behaviors are detected by chemosensory neurons of the vomeronasal organ (VNO), which transmits information to the accessory olfactory bulb. The vomeronasal sensory epithelium of most mammalian species contains a uniform vomeronasal system; however, rodents and marsupials have developed a more complex binary vomeronasal system, containing vomeronasal sensory neurons (VSNs) expressing receptors of either the V1R or V2R family. In rodents, V1R/apical and V2R/basal VSNs originate from a common pool of progenitors. Using single cell RNA-sequencing, we identified differential expression of Notch1 receptor and Dll4 ligand between the neuronal precursors at the VSN differentiation dichotomy. Our experiments show that Notch signaling is required for effective differentiation of V2R/basal VSNs. In fact, Notch1 loss of function in neuronal progenitors diverts them to the V1R/apical fate, whereas Notch1 gain of function redirects precursors to V2R/basal. Our results indicate that Notch signaling plays a pivotal role in triggering the binary differentiation dichotomy in the VNO of rodents.

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

BACKGROUND AND PURPOSE

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.

EXPERIMENTAL APPROACH

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.

KEY RESULTS

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.

CONCLUSIONS AND IMPLICATIONS

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.

Preliminary Research of Main Components of Dll4/ Notch-VEGF Signaling Pathway Under High-Glucose Stimulation in vitro

PURPOSE

To establish a high-glucose (HG) stressed cell model and study the expression of main components of the Dll4/Notch-VEGF signaling pathway under high-glucose stimulation.

METHODS

A model of HG-conditioned cells (human umbilical vein endothelial cells, HUVECs) was first established, and then the expression of Dll4, Notch1, Notch4 and VEGF in HG-stressed cells with or without Notch pathway blockage was analyzed by RT-PCR and Western blot. To observe cell migration, we also evaluated the Transwell assay.

RESULTS

HUVECs stimulated with 30mmol/L HG was selected as a cell model. RT-PCR and Western blot results showed that HG stimulation induced the expression of Dll4, Notch1 and VEGF and downregulated Notch4. The expressions were reversed after Notch pathway blockage; meanwhile, the blockage of Notch pathway inhibited cell migration under HG condition.

CONCLUSION

The function of Notch4 in responses to HG stimulation deserves further researching. Combination therapy by blocking Dll4/Notch and VEGF pathways may provide us with a new way for anti-neovascularization.

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.

Murine Model of Cardiac Defects Observed in Adams-Oliver Syndrome Driven by Delta-Like Ligand-4 Haploinsufficiency

Heterozygous loss-of-function mutation in Delta-like ligand-4 (Dll4) is an important cause of Adams-Oliver syndrome (AOS). Cardiac defects, in particular outflow tract (OFT) alignment defects, are observed in about one-fourth of patients with this syndrome. The mechanism underlying this genotype-phenotype correlation has not yet been established. Dll4-mediated Notch signaling is known to play a crucial role in second heart field (SHF) progenitor cell proliferation. We hypothesized that the depletion of the SHF progenitor pool of cells due to partial loss of Dll4 is responsible for the OFT alignment defects seen in AOS. To demonstrate this, we studied Dll4 expression by murine SHF progenitor cells around E9.5, a crucial time-point in SHF biology. We used SHF-specific (Islet1-Cre) conditional knockout of Dll4 to bypass the early embryonic lethality seen in global Dll4 heterozygotes. Dll4-mediated Notch signaling is critically required for SHF proliferation such that Dll4 knockout results in a 33% reduction in proliferation and a fourfold increase in apoptosis in SHF cells, leading to a 56% decline in the size of the SHF progenitor pool. A reduction in SHF cells available for incorporation into the developing heart leads to underdevelopment of the SHF-derived right ventricle and OFT. Similar to the clinical syndrome, 32% of SHF-specific Dll4 heterozygotes demonstrate foreshortened and misaligned OFT, resulting in a double outlet right ventricle. Our murine model provides a molecular mechanism to explain the cardiac defects observed in AOS and establishes a novel clinical role for Dll4-mediated Notch signaling in SHF progenitor biology.

NOTCH signalling in ovarian cancer angiogenesis

The Notch signalling pathway is involved in the new vessel formation process by regulating tip and stalk cells, which are key cells in the sprout formation. This process is essential in both normal ovary and cancer angiogenesis and is regulated by Notch-VEGF crosstalk. Furthermore, Notch has been linked in ovary with stem cell maintenance and epithelial mesenchymal transition processes. Dysregulation of the Notch pathway is frequent in ovarian cancer (OC) and it has been associated with impaired survival and advanced stages or lymph node involvement. Notch also plays a role in chemoresistance to platinum. In this context, this pathway has emerged as an attractive target for precision medicine in OC. Two main targets of this pathway concentrate the clinical development of compounds blocking Notch: gamma secretase and Delta-like ligand 4. Most of the clinical trials including OC patients have been developed in phase I or phase Ib. Despite being in an early phase, both of these compounds, navicixizumab or demcizumab, two monoclonal antibodies targeting Dll4, showed promising efficacy data in platinum-resistant OC patients in recent studies. This review will focus on the mechanisms of the Notch pathway with special interest in angiogenesis regulation and the implication of Notch as a potential therapeutic target in OC.

Endothelial Jagged1 Antagonizes Dll4/Notch Signaling in Decidual Angiogenesis during Early Mouse Pregnancy

Maternal spiral arteries and newly formed decidual capillaries support embryonic development prior to placentation. Previous studies demonstrated that Notch signaling is active in endothelial cells of both decidual capillaries and spiral arteries, however the role of Notch signaling in physiologic decidual angiogenesis and maintenance of the decidual vasculature in early mouse pregnancy has not yet been fully elucidated. We used the Cdh5-Cre^ERT2;Jagged1(Jag1)^flox/flox (Jag1∆EC) mouse model to delete Notch ligand, Jag1, in maternal endothelial cells during post-implantation, pre-placentation mouse pregnancy. Loss of endothelial Jag1 leads to increased expression of Notch effectors, Hey2 and Nrarp, and increased endothelial Notch signaling activity in areas of the decidua with remodeling angiogenesis. This correlated with an increase in Dll4 expression in capillary endothelial cells, but not spiral artery endothelial cells. Consistent with increased Dll4/Notch signaling, we observed decreased VEGFR2 expression and endothelial cell proliferation in angiogenic decidual capillaries. Despite aberrant Dll4 expression and Notch activation in Jag1∆EC mutants, pregnancies were maintained and the decidual vasculature was not altered up to embryonic day 7.5. Thus, Jag1 functions in the newly formed decidual capillaries as an antagonist of endothelial Dll4/Notch signaling during angiogenesis, but Jag1 signaling is not necessary for early uterine angiogenesis.

Macrophages fine-tune pupil shape during development

Tissue macrophages, which are ubiquitously present innate immune cells, play versatile roles in development and organogenesis. During development, macrophages prune transient or unnecessary synapses in neuronal development, and prune blood vessels in vascular development, facilitating appropriate tissue remodeling. In the present study, we identified that macrophages contributed to the development of pupillary morphology. Csf1^op/op mutant mice, in which ocular macrophages are nearly absent, exhibited abnormal pupillary edges, with abnormal protrusions of excess iris tissue into the pupillary space. Macrophages located near the pupillary edge engulfed pigmented debris, which likely consisted of unnecessary iris protrusions that emerge during smoothening of the pupillary edge. Indeed, pupillary edge macrophages phenotypically possessed some features of M2 macrophages, consistent with robust tissue engulfment and remodeling activities. Interestingly, protruding irises in Csf1^op/op mice were only detected in gaps between regressing blood vessels. Taken together, our findings uncovered a new role for ocular macrophages, demonstrating that this cell population is important for iris pruning during development.

Effects of Notch signaling components from breast cancer cells treated in culture with resveratrol

Resveratrol (Res) has an anti-tumor effect. Notch signaling components from breast cancer cells treated in culture with Resveratrol was investigated. MDA-MB-231cells were divided into control group (Res-untreated) and Res-treated groups including six concentrations 0 μM, 10 μM, 20 μM, 40 μM, 80 μM and 160 μM. Cytotoxicity test were evaluated by CCK-8. The mRNA and Protein expression levels of Notch1, Jagged1, Dll4 and Hes-5 were detected by RT-PCR and Western blot. The mRNA expression of Notch1, Jagged1, Hes-5 and Dll4 in the Res administration group decreased significantly (0.01 < p < .05), and Hes-5 and Dll4 were extremely significant (p < .01). Compared with the blank control group, the protein expression of Notch1 and Dll4 decreased significantly in each concentration Res group, but the decrease of protein expression of Jagged1 and Hes-5 was not significant. In conclusion, Res regulates mRNA and protein expression of Notch1, Dll4 of MDA-MB-231 cells via Notch pathway.

Notch ligand Dll4 impairs cell recruitment to aortic clusters and limits blood stem cell generation

Hematopoietic stem cells (HSCs) develop from the hemogenic endothelium in cluster structures that protrude into the embryonic aortic lumen. Although much is known about the molecular characteristics of the developing hematopoietic cells, we lack a complete understanding of their origin and the three-dimensional organization of the niche. Here, we use advanced live imaging techniques of organotypic slice cultures, clonal analysis, and mathematical modeling to show the two-step process of intra-aortic hematopoietic cluster (IACH) formation. First, a hemogenic progenitor buds up from the endothelium and undergoes division forming the monoclonal core of the IAHC. Next, surrounding hemogenic cells are recruited into the IAHC, increasing their size and heterogeneity. We identified the Notch ligand Dll4 as a negative regulator of the recruitment phase of IAHC. Blocking of Dll4 promotes the entrance of new hemogenic Gfi1⁺ cells into the IAHC and increases the number of cells that acquire HSC activity. Mathematical modeling based on our data provides estimation of the cluster lifetime and the average recruitment time of hemogenic cells to the cluster under physiologic and Dll4-inhibited conditions.

Delta-like 1 and Delta-like 4 differently require their extracellular domains for triggering Notch signaling in mice

Delta-like (Dll) 1 and Dll4 differently function as Notch ligands in a context-dependent manner. As these ligands share structural properties, the molecular basis for their functional difference is poorly understood. Here, we investigated the superiority of Dll4 over Dll1 with respect to induction of T cell development using a domain-swapping approach in mice. The DOS motif, shared by Notch ligands-except Dll4-contributes to enhancing the activity of Dll for signal transduction. The module at the N-terminus of Notch ligand (MNNL) of Dll4 is inherently advantageous over Dll1. Molecular dynamic simulation revealed that the loop structure in MNNL domain of Dll1 contains unique proline residues with limited range of motion. The Dll4 mutant with Dll1-derived proline residues showed reduced activity. These results suggest that the loop structure-present within the MNNL domain-with a wide range of motion ensures the superiority of Dll4 and uniquely contributes to the triggering of Notch signaling.

Antitumor and anti-angiogenic effects of artemisinin on breast tumor xenografts in nude mice

Breast cancer is a high incidence disease in humans. Artemisinin is an important extract that is widely used as an antimalarial drug which also serve as effective treatments for cancer. 32 nude mice were injected with 0.2 ml of MDA-MB-231 cell suspension of 2 × 10⁷ cells/ml respectively. The nude mice models were randomly divided into four groups of 8 in each group. Each group was given daily gavage, high dose group: 200 mg/kg/0.1 ml, middle dose group 100 mg/kg/0.1 ml, low dose group 50 mg/kg/0.1 ml, control group: 0.1 ml vegetable oil was fed continuously for 21 days. ELISA was used to detect serum vascular endothelial growth the content of factor VEGF and hypoxia-inducible factor HIF-1α were detected. The expression of Notch pathway-related factors in tumor tissue was detected by fluorescence quantitative assay. ELISA results showed that the serum VEGF decreased significantly in the high dose group compared with the control group (p < .01), while the other dose groups did not have significant (p > .05). The serum HIF-1α in the high dose group compared with the control group, the decrease in HIF-1α was significant (p < .05), and the other groups were not significant (p > .05). The result of fluorescence quantitative section showed that artemisinin could down-regulate the expression of notch signaling related factors notch1, Dll4 and Jagged1, and 200 mg/kg dose group had the most significant effect. It may inhibit the development of tumors by reducing serum angiogenesis-related factors VEGF, HIF-1ɑ and inhibiting the activity of notch1 signaling pathway related factors.

The Notch pathway: a novel therapeutic target for cardiovascular diseases?

Introduction: The Notch pathway is involved in determining cell fate during development and postnatally in continuously renewing tissues, such as the endothelium, the epithelium, and in the stem cells pool. The dysregulation of the Notch pathway is one of the causes of limited response, or resistance, to available cancer treatments and novel therapeutic strategies based on Notch inhibition are being investigated in preclinical and clinical studies in oncology. A large body of evidence now shows that the dysregulation of the Notch pathway is also involved in the pathophysiology of cardiovascular diseases (CVDs). Areas covered: This review discusses the molecular mechanisms involving Notch which underlie heart failure, aortic valve calcification, and aortic aneurysm. Expert opinion: Despite the existence of preventive, pharmacological and surgical interventions approaches, CVDs are the first causes of mortality worldwide. The Notch pathway is becoming increasingly recognized as being involved in heart failure, aortic aneurysm and aortic valve calcification, which are among the most common global causes of mortality due to CVDs. As already shown in cancer, the dissection of the biological processes and molecular mechanisms involving Notch should pave the way for new strategies to prevent and cure these diseases.

What makes cells move: Requirements and obstacles for leader cells in collective invasion

Most recently, mounting evidence has shown that cancer cells can invade as a cohesive and multicellular group with coordinated movement, which is called collective invasion. In this cohesive cancer cell group, cancer cells at the front of collective invasion are defined as leader cell that are responsible for many aspects of collective invasion, including sensing the microenvironment, determining the invasion direction, modifying the path of invasion and transmitting information to other cells. To fulfill their dispensable roles, leader cells are required to embark on some specific phenotypes with unusual expression of some proteins and it's very important to investigate into these proteins as they may serve as potential therapeutic targets. Here, in this review we will summarize current knowledge on four emerging proteins highly expressed in leader cells including K14, ΔNp63α, Dll4 and cysteine protease cathepsin B (CTSB), with a focus on their important roles in collective invasion and special mechanisms by which they promote collective invasion.

Lessons learned from a lncRNA odyssey for two genes with vascular functions, DLL4 and TIE1

Pervasive transcription is a feature of the human genome that requires better understanding. Over the last decade or so, RNA species longer than 200 nucleotides-dubbed long non-coding RNA (lncRNAs)-had been found in sense or anti-sense orientation within or outside of genes that encode proteins. Importantly, lncRNA-mediated gene regulation and the elements that control lncRNA expression are a source of fascination among molecular biologists. In vascular biology, a dozen or so lncRNAs had been identified, and progress occurs each day. In this review, we highlighted our laboratories' contribution to the lncRNA field by discussing lessons learned from two lncRNAs in the tyrosine kinase containing immunoglobulin and epidermal growth factor homology1 (Tie1) and delta-like 4 (Dll4) loci. These genes are responsible for basic vascular patterning and pathophysiological remodeling in angiogenesis.

Notch Signaling Regulates Immune Responses in Atherosclerosis

Atherosclerosis is a chronic autoimmune inflammatory disease that can cause coronary artery disease, stroke, peripheral artery disease, depending on which arteries are affected. At the beginning of atherosclerosis plasma lipoproteins accumulate in the sub-endothelial space. In response, monocytes migrate from the circulation through the endothelium into the intima where they differentiate into macrophages. These early events trigger a complex immune response that eventually involves many cellular subtypes of both innate and adaptive immunity. The Notch signaling pathway is an evolutionary conserved cell signaling system that mediates cell-to-cell communication. Recent studies have revealed that Notch modulate atherosclerosis by controlling macrophages polarization into M1 or M2 subtypes. Furthermore, it is known that Notch signaling controls differentiation and activity of T-helper and cytotoxic T-cells in inflammatory diseases. In this review, we will discuss the role of Notch in modulating immunity in the context of atherosclerosis and whether targeting Notch may represent a therapeutic strategy.

Triggering of a Dll4-Notch1 loop impairs wound healing in diabetes

Diabetic foot ulcerations (DFUs) represent a major medical, social, and economic problem. Therapeutic options are restricted due to a poor understanding of the pathogenic mechanisms. The Notch pathway plays a pivotal role in cell differentiation, proliferation, and angiogenesis, processes that are profoundly disturbed in diabetic wounds. Notch signaling is activated upon interactions between membrane-bound Notch receptors (Notch 1-4) and ligands (Jagged 1-2 and Delta-like 1, 3, 4), resulting in cell-context-dependent outputs. Here, we report that Notch1 signaling is activated by hyperglycemia in diabetic skin and specifically impairs wound healing in diabetes. Local inhibition of Notch1 signaling in experimental wounds markedly improves healing exclusively in diabetic, but not in nondiabetic, animals. Mechanistically, high glucose levels activate a specific positive Delta-like 4 (Dll4)-Notch1 feedback loop. Using loss-of-function genetic approaches, we demonstrate that Notch1 inactivation in keratinocytes is sufficient to cancel the repressive effects of the Dll4-Notch1 loop on wound healing in diabetes, thus making Notch1 signaling an attractive locally therapeutic target for the treatment of DFUs.

MicroRNA-30a as a candidate underlying sex-specific differences in neonatal hyperoxic lung injury: implications for BPD

Premature male neonates are at a greater risk of developing bronchopulmonary dysplasia (BPD). The reasons underlying sexually dimorphic outcomes in premature neonates are not known. The role of miRNAs in mediating sex biases in BPD is understudied. Analysis of the pulmonary transcriptome revealed that a large percentage of angiogenesis-related differentially expressed genes are miR-30a targets. We tested the hypothesis that there is differential expression of miR-30a in vivo and in vitro in neonatal human pulmonary microvascular endothelial cells (HPMECs) upon exposure to hyperoxia. Neonatal male and female mice (C57BL/6) were exposed to hyperoxia [95% fraction of inspired oxygen (FiO2), postnatal day ( PND) 1-5] and euthanized on PND 7 and 21. HPMECs (18-24-wk gestation donors) were subjected to hyperoxia (95% O2 and 5% CO2) or normoxia (air and 5% CO2) up to 72 h. miR-30a expression was increased in both males and females in the acute phase ( PND 7) after hyperoxia exposure. However, at PND 21 (recovery phase), female mice showed significantly higher miR-30a expression in the lungs compared with male mice. Female HPMECs showed greater expression of miR-30a in vitro upon exposure to hyperoxia. Delta-like ligand 4 (Dll4) was an miR-30a target in HPMECs and showed sex-specific differential expression. miR-30a increased angiogenic sprouting in vitro in female HPMECs. Lastly, we show decreased expression of miR-30a and increased expression of DLL4 in human BPD lung samples compared with controls. These results support the hypothesis that miR-30a could, in part, contribute to the sex-specific molecular mechanisms in play that lead to the sexual dimorphism in BPD.

Muscle Satellite Cell Cross-Talk with a Vascular Niche Maintains Quiescence via VEGF and Notch Signaling

Skeletal muscle is a complex tissue containing tissue resident muscle stem cells (satellite cells) (MuSCs) important for postnatal muscle growth and regeneration. Quantitative analysis of the biological function of MuSCs and the molecular pathways responsible for a potential juxtavascular niche for MuSCs is currently lacking. We utilized fluorescent reporter mice and muscle tissue clearing to investigate the proximity of MuSCs to capillaries in 3 dimensions. We show that MuSCs express abundant VEGFA, which recruits endothelial cells (ECs) in vitro, whereas blocking VEGFA using both a vascular endothelial growth factor (VEGF) inhibitor and MuSC-specific VEGFA gene deletion reduces the proximity of MuSCs to capillaries. Importantly, this proximity to the blood vessels was associated with MuSC self-renewal in which the EC-derived Notch ligand Dll4 induces quiescence in MuSCs. We hypothesize that MuSCs recruit capillary ECs via VEGFA, and in return, ECs maintain MuSC quiescence though Dll4.

Sulodexide inhibits angiogenesis via decreasing Dll4 and Notch1 expression in mouse proepicardial explant cultures

Sulodexide (SDX) is a mixed drug containing low-molecular-weight heparin sulfate and dermatan sulfate. It exerts mild anticoagulant action but can also affect leukocytes, macrophages, and cell-cell adhesion and may interact with growth factors although its direct influence on endothelial cells is not well described. Clinically, SDX is used for the treatment of cardiovascular diseases, where it exerts anti-inflammatory and endothelial protective effects. The aim of this study was to determine the influence of SDX on tubule formation and angiogenesis-related proteins' mRNA expression in endothelial cell line C166 and mouse proepicardial explants. C166 cells and explants were stimulated with a proangiogenic cocktail containing bFGF/VEGF-A₁₂₀ /VEGF-A₁₆₄ enriched with SDX. After stimulation, the number and morphology of tubules stained with anti-CD31 antibody were examined under confocal microscope and expression of mRNA for VEGF-A, VEGF-B, VEGF-C, bFGF, IGF-1, Dll4, and Notch1 was measured with real-time PCR. In C166 cell line, there was no difference in tubule formation and mRNA expression, but in proepicardial explants, we observed reduction in tubule number and in mRNA level for DLL4 and Notch1 after SDX administration. In conclusion, SDX indirectly inhibits angiogenesis in mouse proepicardial explant cultures but has no direct effect on the C166 endothelial cell line.

Pentoxifylline inhibits angiogenesis via decreasing Dll4 and Notch1 expression in mouse proepicardial explant cultures

Pentoxifylline (PTX), a non-specific inhibitor of cAMP phosphodiesterases, is commonly used for treatment of peripheral vascular disorders although its direct action on endothelial cells is not well described. The aim of this study was to determine the influence of PTX on tubule formation and mRNA expression for angiogenesis-related proteins in endothelial cell line C166 and mouse proepicardial explants cultured on collagen. C166 cells and explants were stimulated with proangiogenic cocktail containing bFGF/VEGF-A₁₂₀/VEGF-A₁₆₄ and with proangiogenic cocktail enriched with PTX. After stimulation the number and morphology of tubules stained with anti-CD31 antibody was examined under a confocal microscope and expression of mRNA for VEGF-A, VEGF-B, VEGF-C, bFGF, IGF-1, Dll4 and Notch1 was measured with RealTime PCR. In C166 cell line there was no significant difference in tubule formation and mRNA expression, but in proepicardial explants we observed a considerable reduction in tubule number and in mRNA levels for Dll4 and Notch1 after PTX administration. In conclusion, PTX indirectly inhibits angiogenesis in mouse proepicardial explant cultures but has no significant effect on C166 endothelial cell line.

Generation of a functional humanized Delta-like ligand 4 transgenic mouse model

Humanized mouse models are important tools in many areas of biological drug development including, within oncology research, the development of antagonistic antibodies that have the potential to block tumor growth by controlling vascularization and are key to the generation of in vivo proof-of-concept efficacy data. However, due to cross reactivity between human antibodies and mouse target such studies regularly require mouse models expressing only the human version of the target molecule. Such humanized knock-in/knock-out, KIKO, models are dependent upon the generation of homozygous mice expressing only the human molecule, compensating for loss of the mouse form. However, KIKO strategies can fail to generate homozygous mice, even though the human form is expressed and the endogenous mouse locus is correctly targeted. A typical strategy for generating KIKO mice is by ATG fusion where the human cDNA is inserted downstream of the endogenous mouse promoter elements. However, when adopting this strategy it is possible that the mouse promoter fails to express the human form in a manner compensating for loss of the mouse form or alternatively the human protein is incompatible in the context of the mouse pathway being investigated. So to understand more around the biology of KIKO models, and to overcome our failure with a number of ATG fusion strategies, we developed a range of humanized models focused on Delta-like 4 (Dll4), a target where we initially failed to generate a humanized model. By adopting a broader biologic strategy, we successfully generated a humanized DLL4 KIKO which led to a greater understanding of critical biological aspects for consideration when developing humanized models.

Endothelial Dll4 overexpression reduces vascular response and inhibits tumor growth and metastasization in vivo

BACKGROUND

The inhibition of Delta-like 4 (Dll4)/Notch signaling has been shown to result in excessive, nonfunctional vessel proliferation and significant tumor growth suppression. However, safety concerns emerged with the identification of side effects resulting from chronic Dll4/Notch blockade. Alternatively, we explored the endothelial Dll4 overexpression using different mouse tumor models.

METHODS

We used a transgenic mouse model of endothelial-specific Dll4 overexpression, previously produced. Growth kinetics and vascular histopathology of several types of solid tumors was evaluated, namely Lewis Lung Carcinoma xenografts, chemically-induced skin papillomas and RIP1-Tag2 insulinomas.

RESULTS

We found that increased Dll4/Notch signaling reduces tumor growth by reducing vascular endothelial growth factor (VEGF)-induced endothelial proliferation, tumor vessel density and overall tumor blood supply. In addition, Dll4 overexpression consistently improved tumor vascular maturation and functionality, as indicated by increased vessel calibers, enhanced mural cell recruitment and increased network perfusion. Importantly, the tumor vessel normalization is not more effective than restricted vessel proliferation, but was found to prevent metastasis formation and allow for increased delivery to the tumor of concomitant chemotherapy, improving its efficacy.

CONCLUSIONS

By reducing endothelial sensitivity to VEGF, these results imply that Dll4/Notch stimulation in tumor microenvironment could be beneficial to solid cancer patient treatment by reducing primary tumor size, improving tumor drug delivery and reducing metastization. Endothelial specific Dll4 overexpression thus appears as a promising anti-angiogenic modality that might improve cancer control.

The role of Notch signalling in ovarian angiogenesis

In adults, the ovary is characterized with extensive angiogenesis and regular intervals of rapid growth. Ovarian function is dependent on the network of angiogenic vessels which enable the follicle and/or corpus luteum to receive oxygen, nutrients and hormonal support. Abnormal angiogenesis is involved in the induction and development of pathological ovary, such as polycystic ovary syndrome and ovarian cancer. Notch signalling pathway is one of the primary regulators of angiogenesis and a therapeutic target for ovarian diseases. Here, we will review literatures on the expression pattern of Notch pathway components in the ovary and on the role of Notch signalling pathway on ovarian angiogenesis.

Enhancement of vascular endothelial growth factor's angiogenic capacity by the therapeutic modulation of notch signalling improves tram flap survival in rats submitted to nicotine

BACKGROUND

Smoke of cigarettes, and specifically nicotine, has been shown to diminish pedicled transverse rectus abdominis musculocutaneous (TRAM) flap survival. Considering that Notch signalling through its ligand Delta-like 4 (Dll4) functions as anti-angiogenic factor by inhibiting the pro-angiogenic effects of vascular endothelial growth factor (VEGF), it is hypothesised that inhibition of the Notch would promote angiogenesis and increase TRAM flap survival in rats submitted to nicotine.

METHODS

Twenty rats were treated with nicotine for 28 days preoperatively. Thereafter, a pedicled TRAM flap was created in all animals. The Notch inhibitor N-[N-(3,5-difluorophenacetyl)-1-alanyl]-S-phenylglycine-t-butyl-ester was administered in animals of the treatment group. Animals in the control group were given the same amount of solvent. Five days after the surgery, viable flap areas were determined. Skin samples were evaluated for VEGF and Dll4 mRNA levels. Immunohistochemical analysis was used for the assessment of endothelial Dll4 expression. Vascular density was determined histologically. Plasma levels of VEGF and Dll4 were measured.

RESULTS

A significant improvement in TRAM flap surviving area was observed in the treatment group (53.50 ± 14.25%) compared with the controls (32.20 ± 9.15%). Immunohistochemical analysis revealed a significant increase in the number of Dll4 stained vessels in animals of the treatment group (9.2 ± 1.6) in comparison with the controls (5.7 ± 1.9). VEGF mRNA levels (0.22 ± 0.08) in the treatment group were significantly lower than those in the control group (0.36 ± 0.09).

CONCLUSION

Notch inhibition significantly improved TRAM flap survival in animals exposed to nicotine by promoting VEGF-induced angiogenesis.

Release of endothelial cell associated VEGFR2 during TGF-β modulated angiogenesis in vitro

Background

Sprouting angiogenesis requires vascular endothelial proliferation, migration and morphogenesis. The process is regulated by soluble factors, principally vascular endothelial growth factor (VEGF), and via bidirectional signaling through the Jagged/Notch system, leading to assignment of tip cell and stalk cell identity. The cytokine transforming growth factor beta (TGF-β) can either stimulate or inhibit angiogenesis via its differential surface receptor signaling. Here we evaluate changes in expression of angiogenic signaling receptors when bovine aortic endothelial cells were exposed to TGF-β1 under low serum conditions.

Results

TGF-β1 induced a dose dependent inhibition of tip cell assignment and subsequent angiogenesis on Matrigel, maximal at 5.0 ng/ml. This occurred via ALK5-dependent pathways and was accompanied by significant upregulation of the TGF-β co-receptor endoglin, and SMAD2 phosphorylation, but no alteration in Smad1/5 activation. TGF-β1 also induced ALK5-dependent downregulation of Notch1 but not of its ligand delta-like ligand 4. Cell associated VEGFR2 (but not VEGFR1) was significantly downregulated and accompanied by reciprocal upregulation of VEGFR2 in conditioned medium. Quantitative polymerase chain reaction analysis revealed that this soluble VEGFR2 was not generated by a selective shift in mRNA isoform transcription. This VEGFR2 in conditioned medium was full-length protein and was associated with increased soluble HSP-90, consistent with a possible shedding of microvesicles/exosomes.

Conclusions

Taken together, our results suggest that endothelial cells exposed to TGF-β1 lose both tip and stalk cell identity, possibly mediated by loss of VEGFR2 signaling. The role of these events in physiological and pathological angiogenesis requires further investigation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12860-017-0127-y) contains supplementary material, which is available to authorized users.

Delta-like 4/Notch signaling promotes Apc Min/+ tumor initiation through angiogenic and non-angiogenic related mechanisms

Background

Delta like 4 (Dll4)/Notch signaling is a key regulator of tumor angiogenesis. Additionally, the role of Dll4 has been studied on tumor stem cells. However, as these cells are implicated in tumor angiogenesis, it is conceivable that the effect of Dll4 on these cells may be a consequence of its angiogenic function. Our aim was to evaluate the expression and dissect the functions of Dll4 in the Apc^Min/+ model of colorectal cancer.

Methods

We evaluated the protein expression pattern of Dll4 and other Notch members in the Apc^Min/+ tumors relatively to the normal gut and compared endothelial-specific with ubiquitous Dll4 knockout mice on an Apc^Min/+ background.

Results

All Notch pathway members were present in the normal small and large intestine and in the adenomas of the same regions. Dll4, all Notch receptors and Hes1 expression seemed upregulated in the tumors, with some regional differences. The same members and Hes5, instead of Hes1, presented ectopic expression in the tumor parenchyma. Dll4 expression was most pronounced in the tumor cells but it was also present in the tumor blood vessels and in other stromal cells. Ubiquitous and endothelial-specific Dll4 deletion led to an equivalent reduction of tumor growth because of a similarly marked tumoral angiogenic phenotype promoting non-productive vasculature and consequently hypoxia and apoptosis. The ubiquitous Dll4 inhibition led to a stronger decrease of tumor multiplicity than the endothelial-specific deletion by further reducing tumor proliferation and tumor stem cell density through upregulation of the cyclin-dependent kinase inhibitors 1C and 1B and downregulation of Myc, Cyclin D1 and D2 independently of β-catenin activation. This phenotype was associated to the observed increased epithelial differentiation deviated towards the secretory lineages by Atoh1 and Klf4 upregulation only in the ubiquitous Dll4 mutants.

Conclusions

Dll4 seems to promote Apc^Min/+ tumorigenesis through both angiogenic and non-angiogenic related mechanisms.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-3036-0) contains supplementary material, which is available to authorized users.

Vascular Notch proteins and Notch signaling in the peri-implantation mouse uterus

Background

Angiogenesis is essential for uterine decidualization, the progesterone-mediated transformation of the uterus allowing embryo implantation and initiation of pregnancy. In the current study, we define the vasculature, expression of Notch proteins and Notch ligands, and Notch activity in both endothelial cells and vascular-associated mural cells of blood vessels in the pre-implantation endometrium and post-implantation decidua of the mouse uterus.

Methods

We used immunofluorescence to determine the expression of Notch in endothelial cells and mural cells by co-staining for the endothelial cell marker, CD31, the pan-mural cell marker, platelet-derived growth factor receptor beta (PDGFR-β), the pericyte markers, neural/glial antigen 2 (NG2) and desmin, or the smooth muscle cell marker, alpha smooth muscle actin (SMA). A fluorescein isothiocyanate-labeled dextran tracer, was used to identify functional peri-implantation vasculature. CBF:H2B-Venus Notch reporter transgenic mice were used to determine Notch activity.

Results

Notch signaling is observed in endothelial cells and pericytes in the peri-implantation uterus. Prior to implantation, Notch1, Notch2 and Notch4 and Notch ligand, Delta-like 4 (Dll4) are expressed in capillary endothelial cells, while Notch3 is expressed in the pericytes. Jagged1 is expressed in both capillary endothelial cells and pericytes. After implantation, Notch1, Notch4 and Dll4 are expressed in endothelial cells of newly formed decidual capillaries. Jagged1 is expressed in endothelial cells of spiral arteries and a subset of decidual pericytes. Notch proteins are not expressed in lymphatic vessels or macrophages in the peri-implantation uterus.

Conclusions

We show Notch activity and distinct expression patterns for Notch proteins and ligands, suggesting unique roles for Notch1, Notch4, Dll4, and Jag1 during decidual angiogenesis and early placentation. These data set the stage for loss-of-function and gain-of-function studies that will determine the cell-type specific requirements for Notch proteins in decidual angiogenesis and placentation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13221-015-0034-y) contains supplementary material, which is available to authorized users.

PET Imaging of Dll4 Expression in Glioblastoma and Colorectal Cancer Xenografts Using (64)Cu-Labeled Monoclonal Antibody 61B

Delta-like ligand 4 (Dll4) expressed in tumor cells plays a key role to promote tumor growth of numerous cancer types. Based on a novel antihuman Dll4 monoclonal antibody (61B), we developed a (64)Cu-labeled probe for positron emission tomography (PET) imaging of tumor Dll4 expression. In this study, 61B was conjugated with the (64)Cu-chelator DOTA through lysine on the antibody. Human IgG (hIgG)-DOTA, which did not bind to Dll4, was also prepared as a control. The Dll4 binding activity of the probes was evaluated through the bead-based binding assay with Dll4-alkaline phosphatase. The resulting PET probes were evaluated in U87MG glioblastoma and HT29 colorectal cancer xenografts in athymic nude mice. Our results demonstrated that the 61B-DOTA retained (77.2 ± 3.7) % Dll4 binding activity of the unmodified 61B, which is significantly higher than that of hIgG-DOTA (0.06 ± 0.03) %. Confocal microscopy analysis confirmed that 61B-Cy5.5, but not IgG-Cy5.5, predominantly located within the U87MG and HT29 cells cytoplasm. U87MG cells showed higher 61B-Cy5.5 binding as compared to HT29 cells. In U87MG xenografts, 61B-DOTA-(64)Cu demonstrated remarkable tumor accumulation (10.5 ± 1.7 and 10.2 ± 1.2%ID/g at 24 and 48 h postinjection, respectively). In HT29 xenografts, tumor accumulation of 61B-DOTA-(64)Cu was significantly lower than that of U87MG (7.3 ± 1.3 and 6.6 ± 1.3%ID/g at 24 and 48 h postinjection, respectively). The tumor accumulation of 61B-DOTA-(64)Cu was significantly higher than that of hIgG-DOTA-(64)Cu in both xenografts models. Immunofluorescence staining of the tumor tissues further confirmed that tumor accumulation of 61B-Cy5.5 was correlated well with in vivo PET imaging data using 61B-DOTA-(64)Cu. In conclusion, 61B-DOTA-(64)Cu PET probe was successfully synthesized and demonstrated prominent tumor uptake by targeting Dll4. 61B-DOTA-(64)Cu has great potential to be used for noninvasive Dll4 imaging, which could be valuable for tumor detection, Dll4 expression level evaluation, and Dll4-based treatment monitoring.

Notch signaling: a hero or villain in the war against cancer?

The Notch signal transduction pathway regulates cell fate decisions throughout embryonic development. The mechanisms through which Notch signaling maintains cellular integrity are well understood. However, Notch signaling is more complex than previously thought as Notch is also involved in cancer where it functions as both an oncogene and tumor suppressor depending on the cellular context. Aberrant activation of oncogenic Notch is found in various cancers prompting the search for therapeutic agents to attenuate constitutively active Notch. However, there is also substantial evidence that Notch signaling suppresses tumor growth and progression, suggesting that Notch activators might be of therapeutic benefit in other cancers. This editorial describes the dual role of Notch signaling observed within and across multiple cancers. We highlight a study in non-small cell lung cancer cells (NSCLC) revealing a tumor suppressive role for endothelial cell Dll4-activated Notch1 and the underlying molecular mechanism involving suppression of PI3K signaling.

Dengue virus up-regulates expression of notch ligands Dll1 and Dll4 through interferon-β signalling pathway

The Notch signalling pathway is involved in multiple cellular processes and has been recently indicated to modulate the host immune response. However, the role of the Notch pathway in dengue virus (DENV) infection remains unknown. Our study has screened the expression profile of Notch receptors, ligands and target genes in human monocytes, macrophages and dendritic cells in response to DENV infection. The real-time PCR data showed that Notch ligand Dll1 was significantly induced in DENV-infected monocytes; and receptor Notch4, ligands Dll1 and Dll4, and target Hes1 were dramatically enhanced in DENV-infected macrophages and dendritic cells. In macrophages, induction of Dll1 and Dll4 mediated by DENV2 was increased by treatment with interferon-β (IFN-β), and was impaired by neutralization of IFN-β. The DENV-induced Dll1 and Dll4 expression level was decreased by silencing key innate immune molecules, including Toll-like receptor 3 (TLR3), MyD88, RIG-I and IPS-I. In IFN-receptor-depleted macrophages, the Dll1 and Dll4 induction was significantly alleviated. Functionally, activation of Notch signalling by Dll1 in CD4(+) T cells enhanced the expression of a T helper type 1 (Th1) cytokine IFN-γ, while Notch activation in macrophages had no direct effect on replication of DENV. Our data revealed that the expressions of Notch ligands in antigen-presenting cells were differentially induced by DENV via innate immune signalling, which is important for Th1/Th2 differentiation during adaptive immune response.

Delta-like ligand 4-targeted nanomedicine for antiangiogenic cancer therapy

Tumor angiogenesis is a multistep process involved with multiple molecular events in cancer microenvironment. Several molecular-targeted agents aiming to suppress tumor angiogenesis have been successfully translated into cancer clinic. However, new strategies are still urgently desired to be excavated to overcome the poor response and resistance in some antiangiogenic therapies. Recently, Delta-like ligand 4 (Dll4) is identified to be specifically over-expressed on tumor vascular endothelial cells (EC), and the Dll4-Notch pathway serves as a critical regulator in the development and maintenance of tumor angiogenesis. The intensively up-regulated phenotype of Dll4 on the membrane of tumor vascular EC implies that Dll4 may act as a targetable address for drug delivery system (DDS) to achieve targeted antiangiogenic cancer therapy. Here, a nano-DDS, GD16 peptide (H2N-GRCTNFHNFIYICFPD-CONH2, containing a disulfide bond between Cys3 and Cys13) conjugated nanoparticles loading paclitaxel (GD16-PTX-NP), which can specifically target the angiogenic marker Dll4, was fabricated for the investigation of antiangiogenic therapeutic efficacy in human head and neck cancer FaDu (Dll4-negative) xenograft in nude mice. The results demonstrate that GD16-PTX-NP achieved controlled drug release and exhibited favorable in vivo long-circulating feature. GD16-PTX-NP exerted enhanced antiangiogenic activity in the inhibition of human umbilical vein endothelial cell (HUVEC) viability, motility, migration, and tube formation, and in the Matrigel plug model as well, which can be definitely ascribed to the active internalization mediated by the interaction of GD16 and the over-expressed Dll4 on EC. GD16-PTX-NP showed accurate in vivo tumor neovasculature targeting property in FaDu tumor, where the paclitaxel was specifically delivered into the tumor vascular EC, leading to significant apoptosis of tumor vascular EC and necrosis of tumor tissues. The antiangiogenic activity of GD16-PTX-NP significantly contributed to its in vivo anticancer efficacy in Fadu tumor; moreover, no overt toxicity to the mice was observed. Our research firstly presents the potency and significance of a Dll4-targeted nanomedicine in antiangiogenic cancer therapy.

Selective neuronal lineages derived from Dll4-expressing progenitors/precursors in the retina and spinal cord

BACKGROUND

During retinal and spinal cord neurogenesis, Notch signaling plays crucial roles in regulating proliferation and differentiation of progenitor cells. One of the Notch ligands, Delta-like 4 (Dll4), has been shown to be expressed in subsets of retinal and spinal cord progenitors/precursors and involved in neuronal subtype specification. However, it remains to be determined whether Dll4 expression has any progenitor/precursor-specificity contributing to its functional specificity during neural development.

RESULTS

We generated a Dll4-Cre BAC transgenic mouse line that drives Cre recombinase expression mimicking that of the endogenous Dll4 in the developing retina and spinal cord. By fate-mapping analysis, we found that Dll4-expressing progenitors/precursors give rise to essentially all cone, amacrine and horizontal cells, a large portion of rod and ganglion cells, but only few bipolar and Müller cells. In the spinal cord, Dll4-expressing progenitors/precursors generate almost all V2a and V2c cells while producing only a fraction of the cells for other interneuron and motor neuron subtypes along the dorsoventral axis.

CONCLUSIONS

Our data suggest that selective expression of Dll4 in progenitors/precursors contributes to its functional specificity in neuronal specification and that the Dll4-Cre line is a valuable tool for gene manipulation to study Notch signaling.

IFNγ-responsiveness of endothelial cells leads to efficient angiostasis in tumours involving down-regulation of Dll4

Although IFNγ is regarded as a key cytokine in angiostatic response, our poor understanding of its effective cellular target drastically limits its clinical trials against angiogenesis-related disorders. Here, we investigated the effect of IFNγ on endothelial cells (ECs) and possible molecular mechanisms in angiostasis. By employing Tie2(IFNγR) mice, in which IFNγR expression was reconstituted under the control of Tie2 promoter in IFNγR-deficient mice, we found that the response of ECs to IFNγ was highly effective in inhibiting blood supply and retarding tumour growth. Interestingly, the expression of IFNγR on Tie2(-) cells did not inhibit, but promoted tumour growth in control wild-type mice. Mechanism studies showed that IFNγ reacting on ECs down-regulated the delta-like ligand 4 (Dll4)/Notch signalling pathway. Accordingly, overexpression of Dll4 in human ECs diminished the effect of IFNγ on ECs. This study demonstrates that the action of IFNγ on ECs, but not other cells, is highly effective for tumour angiostasis, which involves down-regulating Dll4. It provides insights for EC-targeted angiostatic therapy in treating angiogenesis-associated disorders in the clinic.

Distinct expression patterns of Notch ligands, Dll1 and Dll4, in normal and inflamed mice intestine

Reports have suggested that the two Notch ligands, Dll1 and Dll4, are indispensable to maintain the homeostasis of the intestinal epithelium. However, within the intestinal epithelium, the precise distribution of the cells that express those ligands at the protein level remains largely unknown. Here, we show a series of immunohistochemical analysis through which we successfully identified mice intestinal epithelial cells (IECs) that endogenously express Dll1 or Dll4. Results showed that Dll1-positive (Dll1+ve) IECs reside exclusively within the crypt, whereas Dll4-positive (Dll4+ve) IECs can locate both in the crypt and in the villus of the small intestine. Also in the colon, Dll1+ve IECs resided at the lower part of the crypt, whereas Dll4+ve IECs resided at both upper and lower part of the crypt, including the surface epithelium. Both Dll1+ve and Dll4+ve IECs were ATOH1-positive, but Hes1-negative cells, and located adjacent to Hes1-positive cells within the crypts. A sub-population of both Dll1+ve and Dll4+ve IECs appeared to co-express Muc2, but rarely co-expressed other secretory lineage markers. However, as compared to Dll1+ve IECs, Dll4+ve IECs included larger number of Muc2-postive IECs, suggesting that Dll4 is more preferentially expressed by goblet cells. Also, we identified that Dll4 is expressed in the Paneth cells of the small intestine, whereas Dll1 and Dll4 is expressed in the c-kit-positive IECs of the colon, indicating that Dll1+ve and Dll4+ve IECs may contribute to constitute the intestinal stem cell niche. Compared to the normal colon, analysis of DSS-colitis showed that number of Dll1+ve IECs significantly decrease in the elongated crypts of the inflamed colonic mucosa. In sharp contrast, number of Dll4+ve IECs showed a significant increase in those crypts, which was accompanied by the increase in number of Hes1-positive IECs. Those Dll4+ve IECs were mostly found adjacent to the Hes1-positive IECs, suggesting that Dll4 may act as a major Notch ligand in the crypts of the inflamed colonic mucosa. Our results illustrate distinct expression patterns of Dll1 and Dll4 within the intestinal epithelium, and suggest that these two ligands may have different roles in normal and inflamed mucosa.

Age-related changes in angiogenesis in human dermis

Present research is aimed to examine the number of dermal blood vessels, vascular endothelial growth factor (VEGF), delta-like ligand 4(Dll4) and Jagged-1 (Jag-1) in dermal blood vessels of human from 20weeks of pregnancy to 85years old. Numbers and proliferative activity of dermal fibroblast-like cells were also examined. Blood vessels were viewed with immunohistochemical staining for von Willebrand factor or CD31. VEGF, Dll4, Jag-1, and proliferating cell nuclear antigen (PCNA) were detected immunohistochemically. Results showed that the numbers of fibroblast-like cells, PCNA positive fibroblast-like cells, von Willebrand factor positive or CD31 positive blood vessels in dermis are dramatically decreased with age. The intensity of immunohistochemical staining for VEGF or Jag-1 in blood vessels of dermis is increased from antenatal to deep old period. The degree of immunohistochemical staining of dermal blood vessels for Dll4 has gone up from 20-40weeks of pregnancy to early life period (0-20years), and further decreased below antenatal values. Age-related decrease in the number of dermal blood vessels is suggested to be due to an impairment of VEGF signaling and to be mediated by Dll4 and Jag-1. It may be supposed that diminishing in blood supply of dermis occurring with age is a cause of a decrease in the number and proliferative pool of dermal fibroblasts.

Inhibition of Delta-like 4 mediated signaling induces abortion in mice due to deregulation of decidual angiogenesis

OBJECTIVE

To explore whether the Dll4/Notch1 pathway plays a key role in regulating the vascular endothelial growth factor (VEGF)/VEGF receptor 2 (VEGFR2) driven decidual angiogenesis and related pregnancy through induction of a tip/stalk phenotype.

METHODS

Progesterone-replaced ovariectomized pregnant mice received a single injection of YW152F (Dll4 blocking antibody, BAb) or placebo at embryonic day (E) 4.5. Animals were sacrificed at different time points; blood and uterus were collected for further analysis. Number of embryos and implantation site, uteri weight, and serum progesterone levels were assessed. Alterations in the tip/stalk phenotype were determined by quantitative immunofluorescent analysis of vascularization, Dll4 expression, cellular proliferation and apoptosis in uterine sections.

RESULTS

Abrogation of Dll4 signaling leads to a promiscuous expression of Dll4, increased cell proliferation, apoptosis and vascularization at E 6.5. Such an abrogation was associated with a dramatic disruption of embryo growth and development starting at E 9.5.

DISCUSSION

The observed promiscuous expression of Dll4 and the increase in cell proliferation, apoptosis and vascularization are events compatible with loss of the tip/stalk phenotype. Excessive (although very likely defective) decidual angiogenesis due to such vascular alterations is the most likely cause of subsequent interruption of embryo development and related pregnancy in Dll4 treated mice.

CONCLUSIONS

Dll4 plays a key role in regulating decidual angiogenesis and related pregnancy through induction of a tip/stalk phenotype.

Role of vascular endothelial progenitor cells in construction of new vascular loop

Since bone marrow-derived endothelial progenitor cells (EPCs) have been detected in adult peripheral blood, the mode of vasculogenesis in the adult tissue has caught attention in field of vascularization research. To confirm the role of EPCs in construction of new vascular loop, we took the biomaterial scaffold implanted into adult rat as an experimental model to observe and examine the actions of the EPCs in neovascularization of the material by immunohistochemistry and transmission electron microscopy. Additionally, by establishing a chemotactic migration model for vascular endothelial cells (ECs) and EPCs, the migrations of ECs and EPCs were explored in simulations. The results of 20,000 simulations showed that the number of the vascular loops assisted by the EPCs was 2-5 times that of the vascular sprouts being naturally joined. Based on the results of experiments and simulations, we conclude that the EPCs are able to assist the angiogenic sprouts in joining under the condition of plenty of the EPCs being mobilized, which aggregate at sites close to sprout tips, forming a cell cord and differentiating to ECs in situ, and become vessel segments between neighboring sprouts. This suggests that there is a difference between the adult and embryo in the manner of vasculogenesis and that a small number of EPCs can play an important role to make the new blood vessels achieve rapid functionalization.

Notch signaling in developmental and tumor angiogenesis

The discovery that Notch, a key regulator of cell fate determination, is functional in the vasculature has greatly improved our understanding of differentiation and specialization of vessels. Notch signaling has been proven to be critical for arterial specification, sprouting angiogenesis, and vessel maturation. In newly forming vascular sprouts, Notch promotes the distinction between the leading "tip" endothelial cell and the growing "stalk" cell, the endothelial cells that eventually form a new capillary. Notch signaling has also been implicated in vessel stability by regulating vascular mural cell function. More recently, macrophages carrying an activated Notch have been implicated in shaping the course of new sprout formation. Tumor vessels abide by similar principles and use Notch signaling in similar ways. An exciting discovery, made by several researchers, shows that blocking Notch function in tumor vasculature provides a means by which to suppress tumor growth. The authors discuss the developmental and physiological role of Notch in the vasculature and apply this knowledge to an overview of how Notch targeting in the tumor environment can affect tumor angiogenesis and growth.