The VEGF family, the inside story

The construction of a microenvironment with the vascular network by co-culturing fibroblasts and endothelial cells

Introduction

Extracellular matrix (ECM) synthesis and deposition in fibroblasts, and vascularization via endothelial cells are essential for successful tissue regeneration. Fibroblasts can produce both ECM, physical support for maintaining homeostasis, and bioactive molecules, such as growth factors and cytokines. Endothelial cells can secrete growth factors and form vascular networks that enable the supply of nutrients and oxygen and remove metabolic products.

Methods

In this study, we focused on combining Human Periodontal Ligament Fibroblasts (HPLF) and Human Umbilical Vein Endothelial Cells (HUVEC) for tissue regeneration in clinical applications.

Results

The fibroblastic and angiogenic phenotypes were promoted in co-culture with HPLF and HUVEC at a ratio of 1:1 compared to HPLF or HUVEC mono-culture. The gene expression of ECM components and angiogenesis-related factors was also enhanced by HPLF/HUVEC co-culture. Despite an apparent increase in the expression of angiogenic factors, the levels of secreted growth factors decreased under co-culture conditions. These data suggest that ECM constructed by HPLF and HUVEC would act as a storage site for growth factors, which can later be released. Our results showed that cell-to-cell interactions between HPLF and HUVEC enhanced collagen synthesis and endothelial network formation, leading to the creation of highly vascularized constructs for periodontal tissue regeneration.

Conclusion

Successful periodontal tissue regeneration requires microenvironmental reconstruction and vascularization, which can be achieved using a co-culture system. In the present study, we found that fibroblastic and angiogenic phenotypes were enhanced by the co-culture of HPLF and HUVEC. The optimal culture conditions (1:1) could potentially accelerate tissue engineering, including ECM synthesis and EC tube formation, and these approaches can improve therapeutic efficacy after transplantation.

Thermodynamically stable ionic liquid microemulsions pioneer pathways for topical delivery and peptide application

Copper peptides (GHK-Cu) are a powerful hair growth promoter with minimal side effects when compared with minoxidil and finasteride; however, challenges in delivering GHK-Cu topically limits their non-invasive applications. Using theoretical calculations and pseudo-ternary phase diagrams, we designed and constructed a thermodynamically stable ionic liquid (IL)-based microemulsion (IL-M), which integrates the high drug solubility of ILs and high skin permeability of microemulsions, thus improving the local delivery of copper peptides by approximately three-fold while retaining their biological function. Experiments in mice validated the effectiveness of our proposed IL-M system. Furthermore, the exact effects of the IL-M system on the expression of growth factors, such as vascular endothelial growth factor, were revealed, and it was found that microemulsion increased the activation of the Wnt/β-catenin signaling pathway, which includes factors involved in hair growth regulation. Overall, the safe and non-invasive IL microemulsion system developed in this study has great potential for the clinical treatment of hair loss.

Cardiotoxicity of Selected Vascular Endothelial Growth Factor Receptor Tyrosine Kinase Inhibitors in Patients with Renal Cell Carcinoma

Renal cell carcinoma (RCC) is one of the most frequent malignant neoplasms of the kidney. The therapeutic options available for the treatment of advanced or metastatic RCC include vascular endothelial growth factor receptor (VEGFR)-targeted molecules, for example, tyrosine kinase inhibitors (TKI). Various VEGFR-TKIs proved to be effective in the treatment of patients with solid tumours. The combination of two drugs may prove most beneficial in the treatment of metastatic RCC; however, it also enhances the risk of toxicity compared to monotherapy. Specific VEGFR-TKIs (e.g., sunitinib, sorafenib or pazopanib) may increase the rate of cardiotoxicity in metastatic settings. VEGF inhibitors modulate multiple signalling pathways; thus, the identification of the mechanism underlying cardiotoxicity appears challenging. VEGF signalling is vital for the maintenance of cardiomyocyte homeostasis and cardiac function; therefore, its inhibition can be responsible for the reported adverse effects. Disturbed growth factor signalling pathways may be associated with endothelial dysfunction, impaired revascularization, the development of dilated cardiomyopathy, cardiac hypertrophies and altered peripheral vascular load. Patients at high cardiovascular risk at baseline could benefit from clinical follow-up in the first 2-4 weeks after the introduction of targeted molecular therapy; however, there is no consensus concerning the surveillance strategy.

Prognostic role of expression of angiogenesis markers in hepatocellular carcinoma: A bioinformatics analysis

The expression of angiopoietin (ANGPT) 1, ANGPT2, vascular endothelial growth factor (VEGF) A, VEGFB, VEGFC, VEGFD, and placental growth factor (PGF) is significantly higher in tumor tissues than in normal tissues in both unpaired and paired hepatocellular carcinoma (HCC) samples. ANGPT2, VEGFB, VEGFC, and PGF are primarily involved in regulating the activation of the epithelial-mesenchymal transition pathway; ANGPT1 is primarily involved in regulating the activation of the RAS/mitogen-activated protein kinase and receptor tyrosine kinase (RTK) pathways; VEGFA is engaged in regulating the RTK activation pathway; and VEGFD is mainly involved in regulating the activation of the tuberous sclerosis protein/mammalian target of rapamycin pathway. There is a significant difference in overall survival between HCC patients with high and low expression of ANGPT2, PGF, VEGFA, and VEGFD. Disease free survival (DFS) is significantly shorter in HCC patients with high ANGPT2, PGF, and VEGFA expression than in those with low ANGPT2, PGF, and VEGFA expression.

Ocular surface mast cells promote inflammatory lymphangiogenesis

Mast cells, sentinel immune cells, are most abundantly expressed in vascularized tissues that interface the external environment, such as the skin and ocular surface. Our previous reports have shown mast cells reside closely with vascular endothelial cells and mediate the pathogenic angiogenic response. However, the contribution of mast cells and their underlying mechanisms on lymphangiogenesis have not been fully deciphered. Using a murine model of inflammatory corneal angiogenesis, we observed adjacent migration of activated mast cells with new lymph vessel growth. Our in vitro co-culture assays demonstrate that mast cells express high levels of of VEGF-D and directly promote lymphatic endothelial cell tube formation and proliferation. Moreover, our loss-of-function approaches, using mast cell knockout mice and cromolyn-mediated mast cell inhibition, showed mast cell deficiency suppresses the induction of inflammatory lymphangiogenesis and VEGF-D expression at the ocular surface following corneal tissue insult. Our findings suggest blockade of mast cells as a potential therapeutic strategy to inhibit pathological lymphangiogenesis.

Interferons Are Pro-Inflammatory Cytokines in Sheared-Stressed Human Aortic Valve Endothelial Cells

Calcific aortic valve disease (CAVD) is an athero-inflammatory process. Growing evidence supports the inflammation-driven calcification model, mediated by cytokines such as interferons (IFNs) and tumor necrosis factor (TNF)-α. Our goal was investigating IFNs' effects in human aortic valve endothelial cells (VEC) and the potential differences between aortic (aVEC) and ventricular (vVEC) side cells. The endothelial phenotype was analyzed by Western blot, qPCR, ELISA, monocyte adhesion, and migration assays. In mixed VEC populations, IFNs promoted the activation of signal transducers and activators of transcription-1 and nuclear factor-κB, and the subsequent up-regulation of pro-inflammatory molecules. Side-specific VEC were activated with IFN-γ and TNF-α in an orbital shaker flow system. TNF-α, but not IFN-γ, induced hypoxia-inducible factor (HIF)-1α stabilization or endothelial nitric oxide synthase downregulation. Additionally, IFN-γ inhibited TNF-α-induced migration of aVEC. Also, IFN-γ triggered cytokine secretion and adhesion molecule expression in aVEC and vVEC. Finally, aVEC were more prone to cytokine-mediated monocyte adhesion under multiaxial flow conditions as compared with uniaxial flow. In conclusion, IFNs promote inflammation and reduce TNF-α-mediated migration in human VEC. Moreover, monocyte adhesion was higher in inflamed aVEC sheared under multiaxial flow, which may be relevant to understanding the initial stages of CAVD.

Angiogenesis regulation by microRNAs and long non-coding RNAs in human breast cancer

MicroRNAs (miRNAs) and long non-coding RNAs (lncRNAs) are capable of regulating gene expression post-transcriptionally. Since the past decade, a number of in vitro, in vivo, and clinical studies reported the roles of these non-coding RNAs (ncRNAs) in regulating angiogenesis, an important cancer hallmark that is associated with metastases and poor prognosis. The specific roles of various miRNAs and lncRNAs in regulating angiogenesis in breast cancer, with particular focus on the downstream targets and signalling pathways regulated by these ncRNAs will be discussed in this review. In light of the recent trend in exploiting ncRNAs as cancer therapeutics, the potential use of miRNAs and lncRNAs as biomarkers and novel therapeutic agent against angiogenesis was also discussed.

Switching of vascular cells towards atherogenesis, and other factors contributing to atherosclerosis: a systematic review

Background

Onset, development and progression of atherosclerosis are complex multistep processes. Many aspects of atherogenesis are not yet properly known. This study investigates the changes in vasculature that contribute to switching of vascular cells towards atherogenesis, focusing mainly on ageing.

Methods

Databases including PubMed, MEDLINE and Google Scholar were searched for published articles without any date restrictions, involving atherogenesis, vascular homeostasis, aging, gene expression, signaling pathways, angiogenesis, vascular development, vascular cell differentiation and maintenance, vascular stem cells, endothelial and vascular smooth muscle cells.

Results

Atherogenesis is a complex multistep process that unfolds in a sequence. It is caused by alterations in: epigenetics and genetics, signaling pathways, cell circuitry, genome stability, heterotypic interactions between multiple cell types and pathologic alterations in vascular microenvironment. Such alterations involve pathological changes in: Shh, Wnt, NOTCH signaling pathways, TGF beta, VEGF, FGF, IGF 1, HGF, AKT/PI3K/ mTOR pathways, EGF, FOXO, CREB, PTEN, several apoptotic pathways, ET - 1, NF-κB, TNF alpha, angiopoietin, EGFR, Bcl - 2, NGF, BDNF, neurotrophins, growth factors, several signaling proteins, MAPK, IFN, TFs, NOs, serum cholesterol, LDL, ephrin, its receptor pathway, HoxA5, Klf3, Klf4, BMPs, TGFs and others.This disruption in vascular homeostasis at cellular, genetic and epigenetic level is involved in switching of the vascular cells towards atherogenesis. All these factors working in pathologic manner, contribute to the development and progression of atherosclerosis.

Conclusion

The development of atherosclerosis involves the switching of gene expression towards pro-atherogenic genes. This happens because of pathologic alterations in vascular homeostasis. When pathologic alterations in epigenetics, genetics, regulatory genes, microenvironment and vascular cell biology accumulate beyond a specific threshold, then the disease begins to express itself phenotypically. The process of biological ageing is one of the most significant factors in this aspect as it is also involved in the decline in homeostasis, maintenance and integrity.The process of atherogenesis unfolds sequentially (step by step) in an interconnected loop of pathologic changes in vascular biology. Such changes are involved in 'switching' of vascular cells towards atherosclerosis.

Aqueous humour outflow imaging: seeing is believing

Elevated intraocular pressure (IOP) is the primary risk factor for blindness in glaucoma. IOP is determined by many factors including aqueous humour production and aqueous humour outflow (AHO), where AHO disturbance represents the primary cause of increased IOP. With the recent development of new IOP lowering drugs and Minimally Invasive Glaucoma Surgeries (MIGS), renewed interest has arisen in shedding light on not only how but where AHO is occurring for the trabecular/conventional, uveoscleral/unconventional, and subconjunctival outflow pathways. Historical studies critical to understanding outflow anatomy will be presented, leading to the development of modern imaging methods. New biological behaviours uncovered by modern imaging methods will be discussed with relevance to glaucoma therapies emphasized.

Bone marrow-derived mesenchymal stem cells improve cognitive impairment in an Alzheimer's disease model by increasing the expression of microRNA-146a in hippocampus

Alzheimer's disease (AD) is characterized by the accumulation of amyloid-β and tau. We previously reported that administration of bone marrow mesenchymal stem cells (BM-MSCs) ameliorates diabetes-induced cognitive impairment by transferring exosomes derived from these cells into astrocytes. Here, we show that intracerebroventricularly injected BM-MSCs improve cognitive impairment in AD model mice by ameliorating astrocytic inflammation as well as synaptogenesis. Although AD model mice showed an increase in NF-κB in the hippocampus, BM-MSC-treated AD model mice did not show this increase but showed an increase in levels of microRNA (miR)-146a in the hippocampus. Intracerebroventricularly injected BM-MSCs were attached to the choroid plexus in the lateral ventricle, and thus, BM-MSCs may secrete exosomes into the cerebrospinal fluid. In vitro experiments showed that exosomal miR-146a secreted from BM-MSCs was taken up into astrocytes, and an increased level of miR-146a and a decreased level of NF-κB were observed in astrocytes. Astrocytes are key cells for the formation of synapses, and thus, restoration of astrocytic function may have led to synaptogenesis and correction of cognitive impairment. The present study indicates that exosomal transfer of miR-146a is involved in the correction of cognitive impairment in AD model mice.

Functional, structural, and molecular identification of lymphatic outflow from subconjunctival blebs

The purpose of this study is to evaluate outflow pathways from subconjunctival blebs and to identify their identity. Post-mortem porcine (n = 20), human (n = 1), and bovine (n = 1) eyes were acquired, and tracers (fluorescein, indocyanine green, or fixable/fluorescent dextrans) were injected into the subconjunctival space to create raised blebs where outflow pathways were visualized qualitatively and quantitatively. Rodents with fluorescent reporter transgenes were imaged for structural comparison. Concurrent optical coherence tomography (OCT) was obtained to study the structural nature of these pathways. Using fixable/fluorescent dextrans, tracers were trapped to the bleb outflow pathway lumen walls for histological visualization and molecular identification using immunofluorescence against lymphatic and blood vessel markers. Bleb outflow pathways could be observed using all tracers in all species. Quantitative analysis showed that the nasal quadrant had more bleb-related outflow pathways compared to the temporal quadrant (nasal: 1.9±0.3 pathways vs. temporal: 0.7±0.2 pathways; p = 0.003). However, not all blebs resulted in an outflow pathway (0-pathways = 18.2%; 1-pathway = 36.4%; 2-pathways = 38.6%; and 3-pathways = 6.8%). Outflow signal was validated as true luminal pathways using optical coherence tomography and histology. Bicuspid valves were identified in the direction of flow in porcine eyes. Immunofluorescence of labeled pathways demonstrated a lymphatic (Prox-1 and podoplanin) but not a blood vessel (CD31) identity. Therefore, subconjunctival bleb outflow occurs in discrete luminal pathways. They are lymphatic as assessed by structural identification of valves and molecular identification of lymphatic markers. Better understanding of lymphatic outflow may lead to improved eye care for glaucoma surgery and ocular drug delivery.

Expressions of vascular endothelial growth factor receptors, Flk1 and Flt1, in rat skin mast cells during development

Vascular endothelial growth factor-A (VEGF-A) is a principal regulator of hematopoiesis as well as angiogenesis. However, the functions of VEGF-A and its receptors (VEGFRs) in the differentiation of mast cells (MCs) in the skin remain unclear. The aim of this study was to determine the expression patterns of two VEGFRs (Flk1 and Flt1) in the skin MCs during development and maturation in rats. From the 17th days of embryonic development (E17) to 1 day after birth (Day 1), most of skin MCs were immature cells containing predominant alcian blue (AB)⁺ rather than safranin O (SO)⁺ granules (AB>SO MCs). AB>SO MC proportions gradually decreased, while mature AB<SO MC proportions increased from Day 7 to 28. Flk1⁺ MC proportions increased from E20 and reached to approximately 90% from Day 1 to 21, thereafter decreased to about 10% at Day 60 and 90. Flk1⁺ MC proportions changed almost in parallel with the numbers of MCs and Ki67⁺ MC proportions from E17 to Day 90. The proportions of MCs with both nuclear and cytoplasmic Flt1-immunoreactivity were markedly increased at Day 28, when the proportions of nuclear Flk1⁺, Ki67⁺, and AB>SO MCs had significantly decreased, and AB<SO MC proportions significantly increased. Considering that the main function of Flt1 is suppression of Flk1 effects, our results indicated that cross-talk between Flk1 and Flt1 regulates the proliferation and maturation of the skin MCs during late embryonic and neonatal development in rats.

Role of Macrophages in Pregnancy and Related Complications

Macrophages (MФs) are the leukocytes produced from differentiation of monocytes and are located in almost all tissues of human body. They are involved in various processes, such as phagocytosis, innate and adaptive immunity, proinflammatory (M1) and anti-inflammatory (M2) activity, depending on the tissue microenvironment. They play a crucial role in pregnancy, and their dysfunction or alteration of polarity is involved in pregnancy disorders, like preeclampsia, recurrent spontaneous abortion, infertility, intrauterine growth restriction, and preterm labor. About 50-60% of decidual leukocytes are natural killer (NK) cells followed by MФs (the second largest population). MФs are actively involved in trophoblast invasion, tissue and vascular remodeling during early pregnancy, besides their role as major antigen-presenting cells in the decidua. These cells have different phenotypes and polarities in different stages of pregnancy. They have also been observed to enhance tumor growth by their anti-inflammatory activity (M2 type) and prevent immunogenic rejection. Targeted alteration of polarity (M1-M2 or vice versa) could be a major focus in the future treatment of pregnancy complications. This review is focused on the role of MФs in pregnancy, their involvement in pregnancy disorders, and decidual MФs as possible therapeutic targets for the treatment of pregnancy complications.

Model of vascular desmoplastic multispecies tumor growth

We present a three-dimensional nonlinear tumor growth model composed of heterogeneous cell types in a multicomponent-multispecies system, including viable, dead, healthy host, and extra-cellular matrix (ECM) tissue species. The model includes the capability for abnormal ECM dynamics noted in tumor development, as exemplified by pancreatic ductal adenocarcinoma, including dense desmoplasia typically characterized by a significant increase of interstitial connective tissue. An elastic energy is implemented to provide elasticity to the connective tissue. Cancer-associated fibroblasts (myofibroblasts) are modeled as key contributors to this ECM remodeling. The tumor growth is driven by growth factors released by these stromal cells as well as by oxygen and glucose provided by blood vasculature which along with lymphatics are stimulated to proliferate in and around the tumor based on pro-angiogenic factors released by hypoxic tissue regions. Cellular metabolic processes are simulated, including respiration and glycolysis with lactate fermentation. The bicarbonate buffering system is included for cellular pH regulation. This model system may be of use to simulate the complex interactions between tumor and stromal cells as well as the associated ECM and vascular remodeling that typically characterize malignant cancers notorious for poor therapeutic response.

Aligned nanofibrillar collagen scaffolds - Guiding lymphangiogenesis for treatment of acquired lymphedema

Secondary lymphedema is a common disorder associated with acquired functional impairment of the lymphatic system. The goal of this study was to evaluate the therapeutic efficacy of aligned nanofibrillar collagen scaffolds (BioBridge) positioned across the area of lymphatic obstruction in guiding lymphatic regeneration. In a porcine model of acquired lymphedema, animals were treated with BioBridge scaffolds, alone or in conjunction with autologous lymph node transfer as a source of endogenous lymphatic growth factor. They were compared with a surgical control group and a second control group in which the implanted BioBridge was supplemented with exogenous vascular endothelial growth factor-C (VEGF-C). Three months after implantation, immunofluorescence staining of lymphatic vessels demonstrated a significant increase in lymphatic collectors within close proximity to the scaffolds. To quantify the functional impact of scaffold implantation, bioimpedance was used as an early indicator of extracellular fluid accumulation. In comparison to the levels prior to implantation, the bioimpedance ratio was significantly improved only in the experimental BioBridge recipients with or without lymph node transfer, suggesting restoration of functional lymphatic drainage. These results further correlated with quantifiable lymphatic collectors, as visualized by contrast-enhanced computed tomography. They demonstrate the therapeutic potential of BioBridge scaffolds in secondary lymphedema.

Making microvascular networks work: angiogenesis, remodeling, and pruning

The adequate and efficient functioning of the microcirculation requires not only numerous vessels providing a large surface area for transport but also a structure that provides short diffusion distances from capillaries to tissue and efficient distribution of convective blood flow. Theoretical models show how a combination of angiogenesis, remodeling, and pruning in response to hemodynamic and metabolic stimuli, termed "angioadaptation," generates well organized, functional networks.

Analysis of constant tissue remodeling in Syrian hamster Harderian gland: intra-tubular and inter-tubular syncytial masses

The Syrian hamster Harderian gland (HG) has a marked sexual dimorphism and exhibits an extraordinary rate of porphyrinogenesis. The physiological oxidative stress, derived from constant porphyrin production, is so high that the HG needs additional survival autophagic mechanisms to fight against this chronic exposure, provoking the triggering of a holocrine secretion in female glands that forms two types of secretory masses: intra-tubular-syncytial and inter-tubular-syncytial masses. The aim of this work was to study the development of this inter-tubular holocrine secretion. To approach this task, we have considered that the steps developed during the formation of the so-called invasive masses consist of the growth of epithelial cells, cell detachment from the basal lamina and invasion of surrounding tissues. The presence of these masses, particularly in the female HG, are closely linked to sexual dimorphism in redox balance and to alterations in the expression of certain factors such as cytokeratins, P-cadherin, matrix metalloproteinases, cathepsin H, proliferating cell nuclear antigen, p53, CD-31 and vascular endothelial growth factor, which seem to be involved in tissue remodeling. The results document unusual mechanisms of secretion in Syrian hamster HG: an extraordinary system of massive secretion through the conjunctive tissue, disrupting the branched structure of the gland.

Differential effects of a soluble or immobilized VEGFR-binding peptide

Regulating endothelial cell behavior is a key step in understanding and controlling neovascularization for both pro-angiogenic and anti-angiogenic therapeutic strategies. Here, we characterized the effects of a covalently immobilized peptide mimic of vascular endothelial growth factor, herein referred to as VEGF receptor-binding peptide (VR-BP), on human umbilical vein endothelial cell (HUVEC) behavior. Self-assembled monolayer arrays presenting varied densities of covalently immobilized VR-BP and varied densities of the fibronectin-derived cell adhesion peptide Gly-Arg-Gly-Asp-Ser-Pro (GRGDSP) were used to probe for changes in HUVEC attachment, proliferation and tubulogenesis. In a soluble form, VR-BP exhibited pro-angiogenic effects in agreement with previous studies, indicated by increases in HUVEC proliferation. However, when presented to cells in an insoluble context, covalently immobilized VR-BP inhibited several pro-angiogenic HUVEC behaviors, including attachment and proliferation, and also inhibited HUVEC response to soluble recombinant VEGF protein. Furthermore, substrates with covalently immobilized VR-BP also modulated HUVEC tubulogenesis when a matrigel overlay assay was used to provide cells with a pseudo-three dimensional environment. Taken together, these results demonstrate that the context in which ligands are presented to cell surface receptors strongly influences their effects, and that the same ligand can be an agonist or an antagonist depending on the manner of presentation to the cell.

Heart failure associated with sunitinib: lessons learned from animal models

Sunitinib is a highly potent, multitargeted anticancer agent. However, there is growing clinical evidence that sunitinib induces cardiac dysfunction. Disruption of multiple signaling pathways, which are important in the maintenance of adult cardiac function, is likely to result in cardiovascular toxicity. Basic and translational evidence implicates a potential role for specific growth factor signaling pathways. This review discusses the relevant translational data from animal models of heart failure, focusing on three key pathways that are inhibited by sunitinib: AMP-activated protein kinase (AMPK), platelet-derived growth factor receptors (PDGFRs), and the vascular endothelial growth factor receptors (VEGFRs) 1, 2, and 3. We hypothesize that disruption of these pathways by sunitinib results in cardiotoxicity, and present direct and indirect evidence to support the notion that sunitinib-induced cardiac dysfunction likely involves a variety of molecular mechanisms that are critical for cardiac homeostasis.

9-cis retinoic acid promotes lymphangiogenesis and enhances lymphatic vessel regeneration: therapeutic implications of 9-cis retinoic acid for secondary lymphedema

BACKGROUND

The lymphatic system plays a key role in tissue fluid homeostasis and lymphatic dysfunction caused by genetic defects, or lymphatic vessel obstruction can cause lymphedema, disfiguring tissue swelling often associated with fibrosis and recurrent infections with no available cures to date. In this study, retinoic acids (RAs) were determined to be a potent therapeutic agent that is immediately applicable to reduce secondary lymphedema.

METHODS AND RESULTS

We report that RAs promote proliferation, migration, and tube formation of cultured lymphatic endothelial cells by activating fibroblast growth factor receptor signaling. Moreover, RAs control the expression of cell-cycle checkpoint regulators such as p27(Kip1), p57(Kip2), and the aurora kinases through both an Akt-mediated nongenomic action and a transcription-dependent genomic action that is mediated by Prox1, a master regulator of lymphatic development. Moreover, 9-cisRA was found to activate in vivo lymphangiogenesis in animals in mouse trachea, Matrigel plug, and cornea pocket assays. Finally, we demonstrate that 9-cisRA can provide a strong therapeutic efficacy in ameliorating experimental mouse tail lymphedema by enhancing lymphatic vessel regeneration.

CONCLUSION

These in vitro and animal studies demonstrate that 9-cisRA potently activates lymphangiogenesis and promotes lymphatic regeneration in an experimental lymphedema model, presenting it as a promising novel therapeutic agent to treat human lymphedema patients.

The vascular marker soluble fms-like tyrosine kinase 1 is associated with disease severity and adverse outcomes in chronic heart failure

OBJECTIVES

We sought to evaluate placental growth factor (PlGF) and soluble Fms-like tyrosine kinase 1 (sFlt-1) as clinical biomarkers in chronic heart failure (HF).

BACKGROUND

Vascular remodeling is a crucial compensatory mechanism in chronic HF. The angiogenic ligand PlGF and its target receptor fms-like tyrosine kinase 1 modulate vascular growth and function, but their relevance in human HF is undefined.

METHODS

We measured plasma PlGF and sFlt-1 in 1,403 patients from the Penn Heart Failure Study, a multicenter cohort of chronic systolic HF. Subjects were followed for death, cardiac transplantation, or ventricular assist device placement over a median follow-up of 2 years.

RESULTS

The sFlt-1 was independently associated with measures of HF severity, including New York Heart Association functional class (p < 0.01) and B-type natriuretic peptide (p < 0.01). Patients in the 4th quartile of sFlt-1 (>379 pg/ml) had a 6.17-fold increased risk of adverse outcomes (p < 0.01). This association was robust, even after adjustment for the Seattle Failure Model (hazard ratio: 2.54, 95% confidence interval [CI]: 1.76 to 2.27, p < 0.01) and clinical confounders including HF etiology (hazard ratio: 1.67, 95% CI: 1.06 to 2.63, p = 0.03). Combined assessment of sFlt-1 and B-type natriuretic peptide exhibited high predictive accuracy at 1 year (area under the receiver-operator characteristic curve: 0.791, 95% CI: 0.752 to 0.831) that was greater than either marker alone (p < 0.01 and p = 0.03, respectively). In contrast, PlGF was not an independent marker of disease severity or outcomes.

CONCLUSIONS

Our findings support a role for sFlt-1 in the biology of human HF. With additional study, circulating sFlt-1 might emerge as a clinically useful biomarker to assess the influence of vascular remodeling on clinical outcomes.

C/EBP-δ regulates VEGF-C autocrine signaling in lymphangiogenesis and metastasis of lung cancer through HIF-1α

CCAAT/enhancer-binding protein-δ (C/EBP-δ), a transcription factor, is elevated in carcinoma compared with that in normal tissue. This study reports a novel function of C/EBP-δ in lymphangiogenesis and tumor metastasis. Genetic deletion of C/EBP-δ in mice resulted in a significant reduction of lymphangiogenesis and pulmonary metastases, with a dramatic reduction of vascular endothelial growth factor-C (VEGF-C) and its cognate receptor VEGF receptor-3 (VEGFR3) in lymphatic endothelial cells (LECs). By contrast, no difference of VEGF-C in tumor tissues and bone marrow was observed between null and wild-type mice. Consistently, forced expression of C/EBP-δ increased VEGF-C and VEGFR3 expression in cultured LECs. These findings suggest a specific and important role of C/EBP-δ in the regulation of VEGFR3 signaling in LECs. Furthermore, expression of C/EBP-δ in cultured LECs significantly increased cell motility, and knockdown of C/EBP-δ inhibited cell motility and lymphatic vascular network formation in vitro. Forced expression of VEGF-C, but not recombinant VEGF-C, rescued the knockdown of C/EBP-δ-induced cell apoptosis, indicative of autonomous VEGF-C autocrine signaling essential for LEC survival. Moreover, hypoxia induces C/EBP-δ expression and C/EBP-δ regulates HIF-1α expression. Blocking HIF-1α activity totally blocked CEBP-δ-induced VEGF-C and VEGFR3 expression in LECs. Together, these findings uncover a new function of CEBP-δ in lymphangiogenesis through regulation of VEGFR3 signaling in LECs.

Effect of vegf gene knockdown on growth of the murine sarcoma cell line MS-K

The murine sarcoma cell line MS-K was previously established as a Ki-ras-positive cell line. Inoculation of this cell line under the flank of C3H/HeN mice results in the growth of large tumors with well-developed blood vessels within day 30 of transplantation without any metastasis because MS-K cells produce vascular endothelial growth factor (VEGF). To elucidate the role of VEGF in tumor formation in vivo, stable vegf-knockdown-MS-K clones were obtained using plasmid-based knockdown vectors. Interestingly, tumorigenesis was completely suppressed in a vegf-A-knockdown-MS-K clone [designated MS-K (A-KD)]. Proliferation and colony formation capacity of the MS-K (A-KD) cells in a semi-solid medium under low serum conditions was significantly lower than that of control MS-K (SCR) cells; however, the expression of vegf-receptor 1 (vegf-r-1) was not changed. Addition of the recombinant VEGF-A(165) partially restored the colony formation capacity of MS-K (A-KD) cells and caused the phosphorylation of VEGF-r-1 (Flt-1) in MS-K (Normal) cells. Furthermore, tumorigenicity of the vegf-r-1-knockdown-MS-K clone [designated MS-K (R1-KD)] had obviously delayed or strongly suppressed compared with the MS-K (Normal). These results indicate that Vascular endothelial growth factor-A, produced from MS-K, acts as a growth factor for MS-K cells itself and supports tumor formation in vivo by inducing the blood vessel formation.

Spliceostatin A blocks angiogenesis by inhibiting global gene expression including VEGF

Spliceostatin A (SSA) is a methylated derivative of an antitumor natural product FR901464, which specifically binds and inhibits the SF3b spliceosome sub-complex. To investigate the selective antitumor activity of SSA, we focused on the regulation of vascular endothelial growth factor (VEGF) mRNA, since VEGF is a key regulatory component in tumor angiogenesis and known for the intricate regulation of mRNA processing, such as alternative splicing. We found that in HeLa cells SSA reduced the amount of both mRNA and protein of VEGF. Spliceostatin A not only inhibited the splicing reaction of VEGF pre-mRNA but also reduced the total amount of VEGF's transcripts, while SSA affected GAPDH mRNA to a lesser extent. Given a significant reduction in VEGF gene expression, SSA was expected to possess anti-angiogenic activity in vivo. Indeed, SSA inhibited cancer cell-derived angiogenesis in vivo in a chicken chorioallantoic membrane (CAM) assay. The inhibition of angiogenesis with SSA was abolished by addition of exogenous VEGF. We also performed global gene expression analyses of HeLa cells and found that the expression levels of 38% of total genes including VEGF decreased to <50% of the basal levels following 16 h of SSA treatment. These results suggest that the global interference of gene expression including VEGF in tumor cells is at least one of the mechanisms by which SSA (or FR901464) exhibits its strong antitumor activity.

Evidence of corneal lymphangiogenesis in dry eye disease: a potential link to adaptive immunity?

OBJECTIVE

To determine the effect of desiccating stress on corneal angiogenic responses in dry eye disease (DED) using a murine model.

METHODS

Dry eye was induced in murine eyes using high-flow desiccated air. Corneas were double stained with CD31 (panendothelial marker) and LYVE-1 (lymphatic endothelial marker). Real-time polymerase chain reaction was performed to quantify expression of vascular endothelial growth factors (VEGF-A, VEGF-C, and VEGF-D) and their receptors (VEGFR-2 and VEGFR-3) in the cornea on days 6, 10, and 14. Enumeration of CD11b(+)/LYVE-1(+) monocytic cells was performed in corneas with DED on day 14. Flow cytometric evaluation of the draining lymph nodes in normal mice and mice with DED was performed to determine whether DED is associated with homing of mature (major histocompatibility complex class II(hi)) antigen-presenting cells to the lymphoid compartment.

RESULTS

Lymphatic vessels unaccompanied by blood vessels were seen growing toward the center of corneas with DED. Significant increases in lymphatic area (P < .001) and lymphatic caliber (P < .02) were seen on day 14 of disease. Lymphangiogenic-specific VEGF-D and VEGFR-3 levels increased earliest on day 6 followed by increased VEGF-C, VEGF-A, and VEGFR-2 levels. Increased recruitment of CD11b(+)/LYVE-1(+) monocytic cells to the cornea and homing of mature CD11b(+) antigen-presenting cells to the draining lymph nodes were also associated with DED.

CONCLUSION

Low-grade inflammation associated with DED is an inducer of lymphangiogenesis without accompanying hemangiogenesis.

Lymphatic vessel density and function in experimental bladder cancer

BACKGROUND

The lymphatics form a second circulatory system that drains the extracellular fluid and proteins from the tumor microenvironment, and provides an exclusive environment in which immune cells interact and respond to foreign antigen. Both cancer and inflammation are known to induce lymphangiogenesis. However, little is known about bladder lymphatic vessels and their involvement in cancer formation and progression.

METHODS

A double transgenic mouse model was generated by crossing a bladder cancer-induced transgenic, in which SV40 large T antigen was under the control of uroplakin II promoter, with another transgenic mouse harboring a lacZ reporter gene under the control of an NF-kappaB-responsive promoter (kappaB-lacZ) exhibiting constitutive activity of beta-galactosidase in lymphatic endothelial cells. In this new mouse model (SV40-lacZ), we examined the lymphatic vessel density (LVD) and function (LVF) during bladder cancer progression. LVD was performed in bladder whole mounts and cross-sections by fluorescent immunohistochemistry (IHC) using LYVE-1 antibody. LVF was assessed by real-time in vivo imaging techniques using a contrast agent (biotin-BSA-Gd-DTPA-Cy5.5; Gd-Cy5.5) suitable for both magnetic resonance imaging (MRI) and near infrared fluorescence (NIRF). In addition, IHC of Cy5.5 was used for time-course analysis of co-localization of Gd-Cy5.5 with LYVE-1-positive lymphatics and CD31-positive blood vessels.

RESULTS

SV40-lacZ mice develop bladder cancer and permitted visualization of lymphatics. A significant increase in LVD was found concomitantly with bladder cancer progression. Double labeling of the bladder cross-sections with LYVE-1 and Ki-67 antibodies indicated cancer-induced lymphangiogenesis. MRI detected mouse bladder cancer, as early as 4 months, and permitted to follow tumor sizes during cancer progression. Using Gd-Cy5.5 as a contrast agent for MRI-guided lymphangiography, we determined a possible reduction of lymphatic flow within the tumoral area. In addition, NIRF studies of Gd-Cy5.5 confirmed its temporal distribution between CD31-positive blood vessels and LYVE-1 positive lymphatic vessels.

CONCLUSION

SV40-lacZ mice permit the visualization of lymphatics during bladder cancer progression. Gd-Cy5.5, as a double contrast agent for NIRF and MRI, permits to quantify delivery, transport rates, and volumes of macromolecular fluid flow through the interstitial-lymphatic continuum. Our results open the path for the study of lymphatic activity in vivo and in real time, and support the role of lymphangiogenesis during bladder cancer progression.