Hypoxic induction of vascular endothelial growth factor (VEGF) in human epithelial cells is mediated by increases in mRNA stability

Analysis of RNA Interference Targeted Against Human Antigen R (HuR) to Reduce Vascular Endothelial Growth Factor (VEGF) Protein Expression in Human Retinal Pigment Epithelial Cells

VEGF-A or vascular endothelial growth factor-A is an important factor in enabling neovascularization and angiogenesis. VEGF-A is regulated transcriptionally as well as post transcriptionally. Human antigen R (HuR) belonging to the embryonic lethal abnormal vision (ELAV) family is a key regulator promoting stabilization of VEGF-A mRNA. In this research we investigate, whether HuR targeted RNA interference would enable the reduction of the VEGF-A protein in human retinal pigment epithelial cells (ARPE-19) in-vitro, in normoxic conditions. Three siRNA molecules with sequences complementary to three regions of the HuR mRNA were designed. The three designed siRNA molecules were individually transfected in ARPE-19 cells using Lipofectamine™2000 reagent. Post-transfection (24 h, 48 h, 72 h), downregulation of HuR mRNA was estimated by real-time polymerase reaction, while HuR protein and VEGF-A protein levels were semi-quantitatively determined by western blotting techniques. VEGF-A protein levels were additionally quantified using ELISA techniques. All experiments were done in triplicate. The designed siRNA could successfully downregulate HuR mRNA with concomitant decreases in HuR and VEGF-A protein. The study reveals that HuR downregulation can prominently downregulate VEGF-A, making the protein a target for therapy against pathological angiogenesis conditions such as diabetic retinopathy.

VEGFR1 signaling in retinal angiogenesis and microinflammation

Five vascular endothelial growth factor receptor (VEGFR) ligands (VEGF-A, -B, -C, -D, and placental growth factor [PlGF]) constitute the VEGF family. VEGF-A binds VEGF receptors 1 and 2 (VEGFR1/2), whereas VEGF-B and PlGF only bind VEGFR1. Although much research has been conducted on VEGFR2 to elucidate its key role in retinal diseases, recent efforts have shown the importance and involvement of VEGFR1 and its family of ligands in angiogenesis, vascular permeability, and microinflammatory cascades within the retina. Expression of VEGFR1 depends on the microenvironment, is differentially regulated under hypoxic and inflammatory conditions, and it has been detected in retinal and choroidal endothelial cells, pericytes, retinal and choroidal mononuclear phagocytes (including microglia), Müller cells, photoreceptor cells, and the retinal pigment epithelium. Whilst the VEGF-A decoy function of VEGFR1 is well established, consequences of its direct signaling are less clear. VEGFR1 activation can affect vascular permeability and induce macrophage and microglia production of proinflammatory and proangiogenic mediators. However the ability of the VEGFR1 ligands (VEGF-A, PlGF, and VEGF-B) to compete against each other for receptor binding and to heterodimerize complicates our understanding of the relative contribution of VEGFR1 signaling alone toward the pathologic processes seen in diabetic retinopathy, retinal vascular occlusions, retinopathy of prematurity, and age-related macular degeneration. Clinically, anti-VEGF drugs have proven transformational in these pathologies and their impact on modulation of VEGFR1 signaling is still an opportunity-rich field for further research.

Tripeptide-based macroporous hydrogel improves the osteogenic microenvironment of stem cells

Due to the ability to combine multiple osteogenic induction "cues" at the same time, hydrogels are widely used in the three-dimensional (3D) culture of human mesenchymal stem cells (hMSCs) and osteoinduction. However, the survival and proliferation of stem cells in a 3D culture system are limited, which reduces their osteogenic differentiation efficiency. In addition, the cells inside the hydrogel are prone to apoptosis due to hypoxia, which is a serious challenge for tissue engineering based on stem cells. In this study, a tripeptide-based macroporous alginate hydrogel was prepared to improve the osteogenic microenvironment of stem cells. The arginine-glycine-aspartate (RGD) peptide promoted the adhesion and proliferation of stem cells, and the degradation of gelatin microspheres (GMs) produced a macroporous structure to enhance further the migration and aggregation of stem cells. Mesoporous silica nanoparticles (MSNs) sustained-release bone-forming peptide-1 (BFP-1) induced osteogenic differentiation, and the sustained release of the QK peptide from the GMs promoted angiogenesis. In vitro experiments have shown that this functionalized hydrogel stimulates the proliferation of hMSCs, encourages larger cell cluster formation, and enhances the osteogenic differentiation efficiency. The released QK facilitates the proliferation and migration of endothelial cells. In vivo experiments have also verified that this system has a better osteogenic effect, and more blood vessels were observed inside the hydrogel, than in other systems. In general, this research has led to the development of a tripeptide macroporous hydrogel that can simultaneously promote osteogenesis and angiogenesis, showing great promise for applications of 3D cultures and stem cell-based tissue engineering.

Mathematical Model of Chronic Dermal Wounds in Diabetes and Obesity

Chronic dermal-wound patients frequently suffer from diabetes type 2 and obesity; without treatment or early intervention, these patients are at risk of amputation. In this paper, we identified four factors that impair wound healing in these populations: excessive production of glycation, excessive production of leukotrient, decreased production of stromal derived factor (SDF-1), and insulin resistance. We developed a mathematical model of wound healing that includes these factors. The model consists of a system of partial differential equations, and it demonstrates how these four factors impair the closure of the wound, by reducing the oxygen flow into the wound area and by blocking the transition from pro-inflammatory macrophages to anti-inflammatory macrophages. The model is used to assess treatment by insulin injection and by oxygen infusion.

Metabolic labeling of RNA uncovers the contribution of transcription and decay rates on hypoxia-induced changes in RNA levels

Cells adapt to environmental changes, including fluctuations in oxygen levels, through the induction of specific gene expression programs. However, most transcriptomic studies do not distinguish the relative contribution of transcription, RNA processing, and RNA degradation processes to cellular homeostasis. Here we used metabolic labeling followed by massive parallel sequencing of newly transcribed and preexisting RNA fractions to simultaneously analyze RNA synthesis and decay in primary endothelial cells exposed to low oxygen tension. We found that changes in transcription rates induced by hypoxia are the major determinant of changes in RNA levels. However, degradation rates also had a significant contribution, accounting for 24% of the observed variability in total mRNA. In addition, our results indicated that hypoxia led to a reduction of the overall mRNA stability from a median half-life in normoxia of 8.7 h, to 5.7 h in hypoxia. Analysis of RNA content per cell confirmed a decrease of both mRNA and total RNA in hypoxic samples and that this effect is dependent on the EGLN/HIF/TSC2 axis. This effect could potentially contribute to fundamental global responses such as inhibition of translation in hypoxia. In summary, our study provides a quantitative analysis of the contribution of RNA synthesis and stability to the transcriptional response to hypoxia and uncovers an unexpected effect on the latter.

Visible light mediated PVA-tyramine hydrogels for covalent incorporation and tailorable release of functional growth factors

PVA-Tyr hydrogel facilitated covalent incorporation can control release of pristine growth factors while retaining their native bioactivity.

Pericytes: Problems and Promises for CNS Repair

Microvascular complications are often associated with slow and progressive damage of various organs. Pericytes are multi-functional mural cells of the microcirculation that control blood flow, vascular permeability and homeostasis. Whereas accumulating evidence suggests that these cells are also implicated in a variety of diseases, pericytes represent promising targets that can be manipulated for therapeutic gain. Here, we review the role of pericytes in angiogenesis, blood-brain barrier (BBB) function, neuroinflammation, tissue fibrosis, axon regeneration failure, and neurodegeneration. In addition, we outline strategies altering pericyte behavior to point out problems and promises for axon regeneration and central nervous system (CNS) repair following injury or disease.

Dickkopf 2-Expressing Adenovirus Increases the Survival of Random-Pattern Flaps and Promotes Vasculogenesis in a Rat Model

BACKGROUND

Dickkopf 2 (DKK2) has important roles in vertebrate development; it inhibits Wnt signaling-related processes, such as axial patterning, limb development, somitogenesis, and eye formation. However, DKK2 also acts as a Wnt signaling agonist. Dickkopf 2, induced during endothelial cell morphogenesis, promotes angiogenesis in cultured human endothelial cells. In this study, we explored the effect of DKK2-expressing adenovirus on random-pattern flaps using a rodent model.

METHODS

A DKK2-expressing (dE1-RGD/DKK2) adenovirus was generated and 20 Sprague-Dawley rats were randomly divided into 2 groups: a DKK2 group and a control group. Each group was intradermally injected with 1 × 10 plaque-forming units of DKK2-expressing adenovirus (DKK2 group) or control virus (control group) 48 hours before and immediately before surgery. Then, random-pattern dorsal cutaneous flaps of 3 × 9 cm were elevated. Flap survival rates and cutaneous blood flow were measured over time, and immunohistochemical staining was performed 10 days after surgery to detect CD31 and vascular endothelial growth factor (VEGF).

RESULTS

Immunofluorescence staining confirmed the expression of DKK2 in the DKK2 group. The flap survival rate was higher in the DKK2 group (80.0 ± 4.49%) than in the control group (57.5 ± 4.21%; P < 0.05). Blood flow to the most distal compartment was higher in the DKK2 group than the control group during the early postoperative period. Although vascular density was greater in the DKK2 group, there was no difference in the VEGF concentration between groups.

CONCLUSIONS

The findings of the present study suggest that the DKK2-expressing adenovirus increases the survival of the random-pattern cutaneous flap independently of VEGF. The administration of the DKK2-expressing adenovirus into elevated skin flaps increased the number of capillaries and blood flow, thereby improving skin flap survival.

Combination of laser and human adipose-derived stem cells in repair of rabbit anal sphincter injury: a new therapeutic approach

Background

Anal sphincter injury leads to fecal incontinence. Based on the regenerative capability of laser and human adipose-derived stem cells (hADSCs), this study was designed to assess the effects of co-application of these therapies on anal sphincter recovery after injury.

Design

Male rabbits were assigned to equal groups (n = 7) including control, sphincterotomy, sphincterotomy treated with laser (660 nm, 90 s, immediately after sphincterotomy, daily, 14 days), hADSCs (2 × 10⁶ hADSCs injected into injured area of the sphincter immediately after sphincterotomy), and laser + hADSCs. Ninety days after sphincterotomy, manometry and electromyography were performed, sphincter collagen content was evaluated, and Ki67, myosin heavy chain (MHC), skeletal muscle alpha-actin (ACTA1), vascular endothelial growth factor A (VEGFA), and vimentin mRNA gene expression were assessed.

Results

The laser + hADSCs group had a higher resting pressure compared with the sphincterotomy (p < 0.0001), laser (p < 0.0001), and hADSCs (p = 0.04) groups. Maximum squeeze pressure was improved in all treated animals compared with the sphincterotomized animals (p < 0.0001), without a significant difference between treatments (p > 0.05). In the laser + hADSCs group, motor unit numbers were higher than those in the laser group (p < 0.0001) but did not differ from the hADSCs group (p = 0.075). Sphincterotomy increased collagen content, but the muscle content (p = 0.36) and collagen content (p = 0.37) were not significantly different between the laser + hADSCs and control groups. Laser + hADSCs increased ACTA1 (p = 0.001) and MHC (p < 0.0001) gene expression compared with laser or hADSCs alone and was associated with increased VEGFA (p = 0.009) and Ki67 mRNA expression (p = 0.01) and decreased vimentin mRNA expression (p < 0.0001) compared with laser.

Conclusion

The combination of laser and hADSCs appears more effective than either treatment alone for promoting myogenesis, angiogenesis, and functional recovery after anal sphincterotomy.

Genetic variants of VEGFR-1 gene promoter in acute myocardial infarction

BACKGROUND

Coronary artery disease (CAD) including acute myocardial infarction (AMI) is a common complex disease caused by atherosclerosis. Vascular epithelial growth factor receptor-1 (VEGFR-1) stimulates angiogenesis and vascular permeability, and functions as a decoy to sequester VEGF and prevent initiation of intracellular signaling. VEGFR-1 knockout mice exhibit significantly higher mortality due to heart failure, cardiac hypertrophy, and cardiac dysfunction. An evident increase in macrophage infiltration and cardiac fibrosis are also observed after transverse aortic constriction. Therefore, VEGFR-1 gene variants may be involved in CAD. In this study, VEGFR-1 gene promoter was genetically and functionally analyzed in large cohorts of AMI patients and ethnic-matched controls.

RESULTS

A total of 16 DNA sequence variants (DSVs) including six single-nucleotide polymorphisms (SNPs) were found in the VEGFR-1 gene promoter and 5'-untranslated region. Five novel DSVs and one SNP were only identified in AMI patients group. These DSVs and SNP significantly altered the transcriptional activity of the VEGFR-1 gene promoter in both HEK-293 and H9c2 cells (P < 0.05). Further electrophoretic mobility shift assay indicated that the DSVs and SNPs evidently affected the binding of transcription factors.

CONCLUSIONS

The genetic variants in VEGFR-1 gene identified in AMI patients may alter the transcriptional activity of the VEGFR-1 gene promoter and change VEGFR-1 level, contributing to AMI development.

Oxygen and nutrient delivery in tissue engineering: Approaches to graft vascularization

The field of tissue engineering is making great strides in developing replacement tissue grafts for clinical use, marked by the rapid development of novel biomaterials, their improved integration with cells, better-directed growth and differentiation of cells, and improved three-dimensional tissue mass culturing. One major obstacle that remains, however, is the lack of graft vascularization, which in turn renders many grafts to fail upon clinical application. With that, graft vascularization has turned into one of the holy grails of tissue engineering, and for the majority of tissues, it will be imperative to achieve adequate vascularization if tissue graft implantation is to succeed. Many different approaches have been developed to induce or augment graft vascularization, both in vitro and in vivo. In this review, we highlight the importance of vascularization in tissue engineering and outline various approaches inspired by both biology and engineering to achieve and augment graft vascularization.

Human antigen R protein modulates vascular endothelial growth factor expression in human corneal epithelial cells under hypoxia

PURPOSE

Corneal avascularity is critical for corneal transparency; therefore, a tailored process has been presumed to minimize corneal neovascularization (NV). In most cell types, the transcription of vascular endothelial growth factor (VEGF) is up-regulated, and the stability of VEGF mRNA is sustained by human antigen R (HuR) during hypoxia; however, whether such response applies to corneal epithelial cells is unclear.

METHODS

Human corneal epithelial cells (HCECs) and MCF-7 cells that serves as the control were incubated under 0.5% oxygen, and the levels of VEGF and HuR were examined time-dependently. The alteration of HuR was also examined in vivo using the closed-eye contact lens-induced corneal neovascularization rabbit model and immunohistochemistry. Additionally, the expression of HuR was modulated by transfection of plasmids encoding HuR or siRNA targeting HuR to validate the role of HuR in VEGF expression.

RESULTS

We found that, unlike in control cells, the level of VEGF was not up-regulated, and the HuR expression was declined in HCECs following hypoxia. The HuR immunostaining intensities were decreased in corneal epithelial cells of rabbits wearing contact lenses. In addition, HuR overexpression restored the ability of HCECs to up-regulate VEGF under hypoxia; however, knockdown of HuR suppressed hypoxia-induced VEGF in control cells but did not further decrease VEGF in HCECs. These findings suggest that HCECs may modulate HuR to suppress hypoxia-mediated up-regulation of VEGF.

CONCLUSION

Our study revealed a distinct regulation of VEGF via HuR in HCECs following hypoxia, which likely contributes to minimizing corneal NV and/or maintenance of corneal avascularity.

Ultrasound imaging and on-demand therapy of peripheral arterial diseases using H2O2-Activated bubble generating anti-inflammatory polymer particles

Muscles of peripheral artery disease (PAD) patients are under oxidative stress associated with a significantly elevated level of reactive oxygen species (ROS) including hydrogen peroxide (H₂O₂). Curcumin is a major active constituent of turmeric and is well known for its highly potent antioxidant, anti-inflammatory and angiogenic effects. We previously reported antioxidant vanillyl alcohol-incorporated copolyoxalate (PVAX) which is designed to rapidly scavenge H₂O₂ and release bioactive vanillyl alcohol and CO₂ in a H₂O₂-triggered manner. In this work, we developed curcumin-loaded PVAX (CUR-PVAX) nanoparticles as contrast-enhanced ultrasound imaging agents as well as on-demand therapeutic agents for ischemic injuries based on the hypothesis that PVAX nanoparticles generate echogenic CO₂ bubbles through H₂O₂-triggered oxidation of peroxalate esters and the merger of curcumin and PVAX exerts H₂O₂-activatable synergistic therapeutic actions. CUR-PVAX nanoparticles also displayed the drastic ultrasound signal in ischemic areas by generating CO₂ bubbles. CUR-PVAX nanoparticles exhibited significantly higher antioxidant and anti-inflammatory activities than empty PVAX nanoparticles and equivalent curcumin in vascular endothelial cells. A mouse model of ischemic injury was used to evaluate the potential of CUR-PVAX nanoparticles as ultrasound imaging agents and on-demand therapeutic agents. CUR-PVAX nanoparticles significantly suppressed the expression of pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β). Moreover, CUR-PVAX nanoparticles significantly enhanced the level of vascular endothelial growth factor (VEGF) and platelet endothelial cell adhesion molecule-1 (PECAM-1, also known as CD31), leading to blood perfusion into ischemic tissues. We, therefore, believe that CUR-PVAX nanoparticles hold great translational potential as novel theranostic agents for ischemic diseases such as PAD.

Positive and Negative Regulation of Angiogenesis by Soluble Vascular Endothelial Growth Factor Receptor-1

Vascular endothelial growth factor receptor (VEGFR)-1 exists in different forms, derived from alternative splicing of the same gene. In addition to the transmembrane form, endothelial cells produce a soluble VEGFR-1 (sVEGFR-1) isoform, whereas non-endothelial cells produce both sVEGFR-1 and a different soluble molecule, known as soluble fms-like tyrosine kinase (sFlt)1-14. By binding members of the vascular endothelial growth factor (VEGF) family, the soluble forms reduce the amounts of VEGFs available for the interaction with their transmembrane receptors, thereby negatively regulating VEGFR-mediated signaling. In agreement with this activity, high levels of circulating sVEGFR-1 or sFlt1-14 are associated with different pathological conditions involving vascular dysfunction. Moreover, sVEGFR-1 and sFlt1-14 have an additional role in angiogenesis: they are deposited in the endothelial cell and pericyte extracellular matrix, and interact with cell membrane components. Interaction of sVEGFR-1 with &alpha;5&beta;1 integrin on endothelial cell membranes regulates vessel growth, triggering a dynamic, pro-angiogenic phenotype. Interaction of sVEGFR-1/sFlt1-14 with cell membrane glycosphingolipids in lipid rafts controls kidney cell morphology and glomerular barrier functions. These cell⁻matrix contacts represent attractive novel targets for pharmacological intervention in addition to those addressing interactions between VEGFs and their receptors.

Endothelial cell metabolism in health and disease: impact of hypoxia

In contrast to the general belief, endothelial cell (EC) metabolism has recently been identified as a driver rather than a bystander effect of angiogenesis in health and disease. Indeed, different EC subtypes present with distinct metabolic properties, which determine their function in angiogenesis upon growth factor stimulation. One of the main stimulators of angiogenesis is hypoxia, frequently observed in disease settings such as cancer and atherosclerosis. It has long been established that hypoxic signalling and metabolism changes are highly interlinked. In this review, we will provide an overview of the literature and recent findings on hypoxia-driven EC function and metabolism in health and disease. We summarize evidence on metabolic crosstalk between different hypoxic cell types with ECs and suggest new metabolic targets.

Limb ischemia and vessel regeneration: Is there a role for VEGF?

Vascular endothelial growth factor (VEGF), as an endothelial cell-specific mitogen, is crucial for new blood vessels formation. Atherosclerosis affecting the cardiovascular system causes ischemia and functio laesa in tissues supplied by the occluded vessels. When such a situation occurs in the lower extremities, it causes critical limb ischemia (CLI) often requiring leg amputation. Low oxygen tension leads to upregulation of hypoxia-regulated genes (i.e. VEGF), that should help to restore the impaired blood flow. In CLI these rescue mechanisms are, however, often inefficient. Moreover, there are many contradictory reports showing either induction, no changes or even down-regulation of VEGF in specimens taken from patients with CLI, as well as in samples collected from animals subjected to hindlimb ischemia. Additionally, taking into account numerous experimental and clinical data demonstrating rather insufficient therapeutic potential of VEGF, we called into question the role of this protein in limb ischemia and vessel regeneration. In this review we are also summarizing several aspects which can influence VEGF expression and its measurement in the ischemic tissues.

Vascular Endothelial Growth Factor Activation of Intramembranous Absorption: A Critical Pathway for Amniotic Fluid Volume Regulation

OBJECTIVE

The purpose of this review is to propose a critical role for vascular endothelial growth factor (VEGF) in mediating the transfer of amniotic fluid from the amniotic compartment through the fetal membranes and fetal surface of the placenta into fetal blood.

METHODS

Experimental findings in humans and animal models on the action of VEGF in mediating fluid transfer are reviewed and interpreted in order to postulate a proposed mechanism for VEGF regulation of amniotic fluid absorption through the fetal membranes and placenta.

RESULTS

Recent scientific advances suggest that up-regulation of VEGF gene expression in the amnion and chorion is associated with increased transfer of amniotic fluid into fetal blood. The possible mechanisms of action for VEGF appear to involve regulation of intramembranous blood vessel proliferation and membrane transport via passive permeation as well as nonpassive transcytotic vesicular movement of fluid.

CONCLUSION

Currently evolving concepts suggest that amniotic fluid volume is regulated through modulation of the rate of intramembranous absorption of amniotic fluid by both passive and nonpassive mechanisms. The permeability factor VEGF appears to be a critical regulator of amniotic fluid transport in the fetal membranes.

VEGF: From Discovery to Therapy: The Champalimaud Award Lecture

Purpose

Intraocular vascular diseases are leading causes of adult vision loss, and in the mid-1900s, I. C. Michaelson postulated that the retina releases a soluble, diffusible factor that causes abnormal vascular growth and leakage. What became known as “Factor X” eluded investigators for decades.

Methods

The field of cancer research, where Judah Folkman pioneered the concept of angiogenesis, provided the inspiration for the work honored by the 2014 Champalimaud Vision Award. Recognizing that tumors recruit their own blood supply to achieve critical mass, Dr Folkman proposed that angiogenic factors could be therapeutic targets in cancer. Napoleone Ferrara identified vascular endothelial growth factor (VEGF) as such an angiogenic agent: stimulated by hypoxic tumor tissue, secreted, and able to induce neovascularization. VEGF also was a candidate for Factor X, and the 2014 Champalimaud Laureates and colleagues worked individually and collaboratively to identify the role of VEGF in ocular disease.

Results

The Champalimaud Laureates correlated VEGF with ocular neovascularization in animal models and in patients. Moreover, they showed that VEGF not only was sufficient, but it also was required to induce neovascularization in normal animal eyes, as VEGF inhibition abolished ocular neovascularization in key animal models.

Conclusions

The identification of VEGF as Factor X altered the therapeutic paradigms for age-related macular degeneration (AMD), diabetic retinopathy, retinal vein occlusion, and other retinal disorders.

Translational Relevance

The translation of VEGF from discovery to therapy resulted in the most successful applications of antiangiogenic therapy to date. Annually, over one million patients with eye disease are treated with anti-VEGF agents.

Cotton Wool Spots after Anti-Vascular Endothelial Growth Factor Therapy for Macular Edema Associated with Central Retinal Vein Occlusion

PURPOSE

To report a case series, whereby we encountered a transient increase in retinal cotton wool spots (CWS) following anti-vascular endothelial growth factor (anti-VEGF) therapy for the treatment of macular edema secondary to central retinal vein occlusion (CRVO).

METHODS

Eighteen eyes were treated with intravitreal aflibercept (IVA), and 5 were treated with intravitreal ranibizumab (IVR). Fundus photographs obtained 1 month after initial IVA or IVR injections were retrospectively evaluated for the presence of CWS.

RESULTS

Twenty-one (91.3%) patients had the following systemic diseases: hypertension, diabetes mellitus without retinopathy, dyslipidemia, or chronic renal failure requiring dialysis. One month after treatment, reduced macular edema was observed in 21 (91.3%) eyes. Initial injections facilitated complete resolution in 14 eyes, and CWS gradually became fainter with additional injections.

CONCLUSION

Some eyes with CRVO-related macular edema can show a transient increase in CWS after initial anti-VEGF therapy; however, macular edema, retinal hemorrhage, and visual acuity were improved in almost every case.

Acute and chronic effect of sprint interval training combined with postexercise blood-flow restriction in trained individuals

This investigation assessed the efficacy of sprint interval training (SIT) combined with postexercise blood-flow restriction as a novel approach to enhance maximal aerobic physiology and performance. In study 1, a between-groups design was used to determine whether 4 weeks (2 days per week) of SIT (repeated 30 s maximal sprint cycling) combined with postexercise blood-flow restriction (BFR) enhanced maximal oxygen uptake (V̇(O2max)) and 15 km cycling time-trial performance (15 km TT) compared with SIT alone (CON) in trained individuals. The V̇(O2max) increased after BFR by 4.5% (P = 0.01) but was unchanged after CON. There was no difference in 15 km TT performance after CON or BFR. In study 2, using a repeated-measures design, participants performed an acute bout of either BFR or CON. Muscle biopsies were taken before and after exercise to examine the activation of signalling pathways regulating angiogenesis and mitochondrial biogenesis. Phosphorylation of p38MAPK(Thr180/Tyr182) increased by a similar extent after CON and BFR. There was no difference in the magnitude of increase in PGC-1α, VEGF and VEGFR-2 mRNA expression between protocols; however, HIF-1α mRNA expression increased (P = 0.04) at 3 h only after BFR. We have demonstrated the potency of combining BFR with SIT in increasing V̇(O2max) in trained individuals, but this did not translate to an enhanced exercise performance. Sprint interval training alone did not induce any observable adaptation. Although the mechanisms are not fully understood, we present preliminary evidence that BFR leads to enhanced HIF-1α-mediated cell signalling.

Regulation of vascular endothelial growth factor in prostate cancer

Prostate cancer (PCa) is the most common malignancy affecting men in the western world. Although radical prostatectomy and radiation therapy can successfully treat PCa in the majority of patients, up to ~30% will experience local recurrence or metastatic disease. Prostate carcinogenesis and progression is typically an androgen-dependent process. For this reason, therapies for recurrent PCa target androgen biosynthesis and androgen receptor function. Such androgen deprivation therapies (ADT) are effective initially, but the duration of response is typically ≤24 months. Although ADT and taxane-based chemotherapy have delivered survival benefits, metastatic PCa remains incurable. Therefore, it is essential to establish the cellular and molecular mechanisms that enable localized PCas to invade and disseminate. It has long been accepted that metastases require angiogenesis. In the present review, we examine the essential role for angiogenesis in PCa metastases, and we focus in particular on the current understanding of the regulation of vascular endothelial growth factor (VEGF) in localized and metastatic PCa. We highlight recent advances in understanding the role of VEGF in regulating the interaction of cancer cells with tumor-associated immune cells during the metastatic process of PCa. We summarize the established mechanisms of transcriptional and post-transcriptional regulation of VEGF in PCa cells and outline the molecular insights obtained from preclinical animal models of PCa. Finally, we summarize the current state of anti-angiogenesis therapies for PCa and consider how existing therapies impact VEGF signaling.

Gelatin-chondroitin-6-sulfate-hyaluronic acid scaffold seeded with vascular endothelial growth factor 165 modified hair follicle stem cells as a three-dimensional skin substitute

INTRODUCTION

In the field of skin tissue engineering, gelatin-chondroitin-6-sulfate-hyaluronic acid (Gel-C6S-HA) stents are a suitable bio skin substitute. The purpose was to investigate the effect of genetically-modified hair follicle stem cells (HFSCs), combined with Gel-C6S-HA scaffolds, on the vascularization of tissue-engineered skin.

METHODS

Three-dimensional (3D) Gel-C6S-HA scaffolds were prepared by freeze-drying. Vascular endothelial growth factor (VEGF) 165 gene-modified rat HFSCs (rHFSCs) were inoculated into the scaffolds and cultured for 7 days. Two bilateral full-thickness skin defects were created on the back of 18 Sprague-Dawley rats. Rats were randomly divided into four groups: Group A, HFSCs transduced with VEGF165 seeded onto Gel-C6S-HA scaffolds; Group B, HFSCs transduced with empty vector seeded onto Gel-C6S-HA scaffolds; Group C, Gel-C6S-HA scaffold only; Group D, Vaseline gauze dressing. These compositions were implanted onto the defects and harvested at 7, 14 and 21 days. Wound healing was assessed and compared among groups according to hematoxylin-eosin staining, CD31 expression, alpha smooth muscle actin (α-SMA) and major histocompatibility complex class I (MHC-I) immunohistochemistry, and microvessel density (MVD) count, to evaluate the new blood vessels.

RESULTS

SEM revealed the Gel-C6S-HA scaffold was spongy and 3D, with an average pore diameter of 133.23 ± 43.36 μm. Cells seeded on scaffolds showed good adherent growth after 7 days culture. No significant difference in rHFSC morphology, adherence and proliferative capacity was found before and after transfection (P >0.05). After 14 and 21 days, the highest rate of wound healing was observed in Group A (P <0.05). Histological and immunological examination showed that after 21 days, MVD also reached a maximum in Group A (P <0.05). Therefore, the number of new blood vessels formed within the skin substitutes was greatest in Group A, followed by Group B. In Group C, only trace amounts of mature subcutaneous blood vessels were observed, and few subcutaneous tissue cells migrated into the scaffolds.

CONCLUSIONS

Tissue-engineered skin constructs, using 3D Gel-C6S-HA scaffolds seeded with VEGF165-modified rHFSCs, resulted in promotion of angiogenesis during wound healing and facilitation of vascularization in skin substitutes. This may be a novel approach for tissue-engineered skin substitutes.

Preliminary study on retinal vascular and oxygen-related changes after long-term silicone oil and foldable capsular vitreous body tamponade

Silicone oil has been the only long-term vitreous substitute used in the treatment of retinal detachment since 1962 by Cibis. Nevertheless, its effects on retinal vascular morphology and oxygen supply to the retina are ambiguous in current research. We previously invented a foldable capsular vitreous body (FCVB) to use as a new vitreous substitute in the treatment of severe retinal detachment, but its effects on the retinal vessel were unknown. Therefore, in this study, a standard three-port pars plana vitrectomy (PPV) was performed on the right eye of each rabbit and then silicone oil and FCVB were injected into the vitreous cavity as vitreous substitutes. After 180 days of retention, the retinal vascular morphology did not display any distinct abnormalities, and hypoxia-induced factor-1alpha (HIF-1α) and vascular endothelial growth factor (VEGF) did not vary markedly during the observation period in silicone oil tamponade- and FCVB-implanted eyes. This study may suggest that silicone oil and FCVB tamponade in rabbit eyes did not cause retinal vascular pathologic changes or retinal hypoxia for 180 days.

Manipulation of the HIF-Vegf pathway rescues methyl tert-butyl ether (MTBE)-induced vascular lesions

Methyl tert-butyl ether (MTBE) has been shown to be specifically anti-angiogenic in piscine and mammalian model systems at concentrations that appear non-toxic in other organ systems. The mechanism by which MTBE targets developing vascular structures is unknown. A global transcriptome analysis of zebrafish embryos developmentally exposed to 0.00625-5mM MTBE suggested that hypoxia inducible factor (HIF)-regulated pathways were affected. HIF-driven angiogenesis via vascular endothelial growth factor (vegf) is essential to the developing vasculature of an embryo. Three rescue studies were designed to rescue MTBE-induced vascular lesions: pooled blood in the common cardinal vein (CCV), cranial hemorrhages (CH), and abnormal intersegmental vessels (ISV), and test the hypothesis that MTBE toxicity was HIF-Vegf dependent. First, zebrafish vegf-a over-expression via plasmid injection, resulted in significantly fewer CH and ISV lesions, 46 and 35% respectively, in embryos exposed to 10mM MTBE. Then HIF degradation was inhibited in two ways. Chemical rescue by N-oxaloylglycine significantly reduced CCV and CH lesions by 30 and 32% in 10mM exposed embryos, and ISV lesions were reduced 24% in 5mM exposed zebrafish. Finally, a morpholino designed to knock-down ubiquitin associated von Hippel-Lindau protein, significantly reduced CCV lesions by 35% in 10mM exposed embryos. In addition, expression of some angiogenesis related genes altered by MTBE exposure were rescued. These studies demonstrated that MTBE vascular toxicity is mediated by a down regulation of HIF-Vegf driven angiogenesis. The selective toxicity of MTBE toward developing vasculature makes it a potentially useful chemical in the designing of new drugs or in elucidating roles for specific angiogenic proteins in future studies of vascular development.

The Harvard angiogenesis story

I shall discuss the work of researchers at Harvard Medical School who came together in the early 1990s. Scattered across various Harvard-affiliated hospitals and research centers, these individuals were unified by their interest in ocular neovascularization. Together and separately, they investigated models of ocular neovascularization, exploring tumor angiogenesis in eye development and disease.

Effects of deferoxamine on blood–brain barrier disruption and VEGF in focal cerebral ischemia

OBJECTIVE

Deferoxamine, an iron chelator, is reported to induce hypoxia-inducible factor 1 (HIF-1) that leads to transcriptional activation of numerous genes including vascular endothelial growth factor (VEGF) that is known to increase blood-brain barrier (BBB) permeability. This study was performed to test whether deferoxamine would disrupt BBB further in focal cerebral ischemia by altering the level of VEGF.

METHODS

Rats were injected intraperitoneally with normal saline (control group), 300 mg/kg deferoxamine mesylate 18 (deferoxamine 18 group) or 48 (deferoxamine 48 group) hours before middle cerebral artery (MCA) occlusion. The transfer coefficient (Ki) of 14C-alpha-aminoisobutyric acid (14C-AIB) and the volume of 3H-dextran distribution were determined to measure the degree of BBB disruption 1 hour after MCA occlusion. Immunohistochemistry using a monoclonal VEGF antibody was performed to determine the protein level of VEGF.

RESULTS

In all groups of animals, the Ki of the ischemic cortex (IC) was higher than that of the corresponding contralateral cortex (CC). In the deferoxamine 18 group, the Ki of the IC was significantly higher than that in the control group (+52%, p<0.05) or deferoxamine 48 group (+72%, p<0.05). The Ki of the CC of all experimental groups were similar. The volume of dextran distribution of the IC was significantly higher than that of the CC only in the deferoxamine 18 group. The number of areas that were stained with VEGF antibody in the deferoxamine 18 group (106 +/- 5/mm2) was significantly higher than that in the control group (54 +/- 2/mm2) or deferoxamine 48 group (58 +/- 1/mm2).

DISCUSSION

Our data suggest that deferoxamine induced an increase in VEGF but that its effect depends on the time of administration. The increase in VEGF by deferoxamine could aggravate the disruption of BBB in focal cerebral ischemia.

VEGF-A mRNA processing, stability and translation: a paradigm for intricate regulation of gene expression at the post-transcriptional level

Vascular Endothelial Growth Factor A (VEGF-A) is a potent secreted mitogen crucial for physiological and pathological angiogenesis. Post-transcriptional regulation of VEGF-A occurs at multiple levels. Firstly, alternative splicing gives rise to different transcript variants encoding diverse isoforms that exhibit distinct biological properties with regard to receptor binding and extra-cellular localization. Secondly, VEGF-A mRNA stability is regulated by effectors such as hypoxia or growth factors through the binding of stabilizing and destabilizing proteins at AU-rich elements located in the 3′-untranslated region. Thirdly, translation of VEGF-A mRNA is a controlled process involving alternative initiation codons, internal ribosome entry sites (IRESs), an upstream open reading frame (uORF), miRNA targeting and a riboswitch in the 3′ untranslated region. These different levels of regulation cooperate for the crucial fine-tuning of the expression of VEGF-A variants. This review will be focused on our current knowledge of the complex post-transcriptional regulatory switches that modulate the cellular VEGF-A level, a paradigmatic model of post-transcriptional regulation.

A novel synergistic effect of iron depletion on antiangiogenic cancer therapy

Iron is an essential element for both normal and cancer cells in humans. Treatment to reduce iron levels has been shown to suppress tumor growth in vivo. However, iron depletion monotherapy by iron decreased treatment has not been thought to be superior to ordinary chemotherapy and is not part of the standard therapeutic strategy for the treatment of cancer. Iron depletion is also known to reduce serum hemoglobin and oxygen supply to the tissue, which indicates that iron depletion may induce angiogenesis. Therefore, we hypothesized that iron depletion with antiangiogenic therapy can have a novel therapeutic effect in the treatment of cancer. Human nonsmall cell carcinoma cell lines A549 and H1299 were used in our study. An iron-deficient diet and an iron chelator were used to simulate an iron-depleted condition. The antitumor effects of iron depletion and antiangiogenic therapy were determined on A549 xenograft mice. The iron-depleted condition produced by an iron-deficient diet suppressed tumor growth. Tumor tissue from the iron-deficient diet group showed that cancer cell proliferation was suppressed and hypoxia was induced. Microvessel density of this group was increased which suggested that the iron-depleted condition induced angiogenesis. Bevacizumab administration had a synergetic effect on inhibiting the tumor growth on Day 39. An iron-depleted condition inhibited cancer cell proliferation and reciprocally induced angiogenesis. Bevacizumab synergistically enhanced the iron-depleted antitumor effect. Treatment to deplete iron levels combined with anti-angiogenic therapy could induce a novel therapeutic effect in the treatment of cancer.

Ischemia-driven angiogenesis

New blood vessels usually develop in places where they are most needed. A prime example of neovascularization representing a positive feedback response to insufficient perfusion is the development of collateral blood vessels in the ischemic myocardium and leg. The recent discoveries of hypoxia-inducible transcription and angiogenic factors have provided important mechanistic links between the metabolic consequences of ischemia and compensatory angiogenesis. Vascular endothelial growth factor (VEGF) has emerged as the key mediator of ischemia-driven angiogenesis. Environmental stresses, including hypoxia, hypoglycemia, and hypoferremia, upregulate VEGF expression at both the transcriptional and posttranscriptional levels. VEGF acts in turn on adjacent vascular beds expressing cognate receptors and induces sprouting and capillary growth toward the ischemic tissue. In addition to expanding the vasculature at sites where existing vessels have been occluded or obliterated, VEGF also functions to match the vascular density according to development and physiologic increases in oxygen consumption. Fine adjustment of the vasculature includes a step of oxygen-regulated vascular pruning mediated by VEGF in its capacity as a survival factor for newly formed vessels. Pathologic settings of ischemia-driven angiogenesis include a major component of stress-induced angiogenesis during tumor neovascularization and abnormal vessel growth associated with retinopathies. The latter represents an excessive angiogenic response to conditions of severe retinal ischemia. Further insights into the mechanism of stress-induced angiogenesis are likely to suggest new ways to augment growth of collateral vessels and to restrain unwarranted neovascularization in tumors and retinopathies. (Trends Cardiovasc Med 1997;7:289-294). © 1997, Elsevier Science Inc.

Vascular endothelial growth factor expression following ischemic conditioning of the gastric conduit

The partial devascularization of the stomach, necessary for esophageal reconstruction with a gastric conduit, impairs microcirculation in the anastomotic region of the gastric fundus. Ischemic conditioning of the gastric tube is considered as a possible approach to improve microcirculation in the gastric mucosa. The aim of this study was to investigate whether ischemic conditioning induces neo-angiogenesis in the gastric fundus by expression of vascular endothelial growth factor (VEGF). Twenty patients with an esophageal carcinoma scheduled for esophagectomy and gastric reconstruction were included. To compare VEGF expression before and after ischemic conditioning, preoperative endoscopic biopsies were taken from the gastric fundus. The surgical procedure consisted of two separate steps, the complete gastric mobilization including partial devascularization of the stomach and after a delay of 4-5 days high transthoracic esophagectomy with intrathoracic gastric reconstruction (Ivor-Lewis procedure). The second tissue sample was obtained from the donut of the stapled esophagogastrostomy. For further work-up, preoperative biopsies and the gastric donuts were fixed in liquid nitrogen. Preoperative and intraoperative VEGF expression was measured by quantitative real-time reverse transcription-polymerase chain reaction (VEGF×100/β-actin) and results were compared using Wilcoxon test for paired samples. In all 40 specimens, a distinct expression of VEGF could be detected. Comparing the level of VEGF expression of the preoperative biopsies and postoperative tissue sample, no significant difference could be demonstrated following ischemic conditioning. In this model of ischemic conditioning with delayed reconstruction of 4-5 days, no induction of neo-angiogenesis could be demonstrated by measurement of VEGF expression.

Improvement of a long random skin flap survival by application of vascular endothelial growth factor in various ways of local administration in a rat model

Background:

Vascular endothelial growth factor (VEGF) is a heparin-binding glycoprotein which plays a significant role in angiogenesis and vascular permeability. The effect of various ways of local administration of VEGF on random skin flap survival was studied, using flaps with a relatively high length (L) to width (W) ratio (5:1).

Materials and Methods:

An 1.5 × 7.5 cm dorsal skin flap with the pedicle orientated, centered, and remaining attached between the lower angles of the scapulae was elevated in 45 Wistar rats in different phases, depending on the group. Rats were divided in five groups of nine. In group A, injections of saline were administered, in equally divided spaces, into flap's fascia and transposed to a created skin defect. In group B, injections of VEGF were applied subdermally, in equally divided spaces, within the limits of a predesigned flap, a week prior to flap dissection and transposition. In group C, injections of VEGF were applied into a recipient bed's fascia just before flap raising and transposition. In group D, injections of VEGF were applied subdermally, only in the distal third of the flap and then the flap was transposed to a recipient area. Finally, in group E, injections of VEGF were applied in the flap intrafascially and in equally divided spaces and then again, the flap was transposed to a recipient area. A week after final flap raising and positioning, rats were euthanatised and flaps were excised. Specimens were photographed, measured, put in formalin 10% and were sent for histological and image analysis.

Results:

Mean flap survival percentage was 35.4% in group A, and 33.7% in group B. In groups C and D, the mean survival area was 56.3% and 80.4%, respectively. In group E, the mean flap survival percentage was 28.3%. Histological analysis demonstrated increased angiogenesis in groups C and D.

Conclusions:

VEGF application improved skin flap survival when injected subdermally in the distal third of a random skin flap or into the fascia of a recipient area even though the length-to-width ratio was high.

Recombinant vascular endothelial growth factor165 gene therapy improves anastomotic healing in an animal model of ischemic esophagogastrostomy

Proper anastomotic healing is dependent upon many factors including adequate blood flow to healing tissue. The aim of this study was to investigate the impact of vascular endothelial growth factor (VEGF(165)) transfection on anastomotic healing in an ischemic gastrointestinal anastomosis model. Utilizing an established opossum model of esophagogastrectomy followed by esophageal-gastric anastomosis, the gastric fundus was transfected with recombinant human vascular endothelial growth factor via direct injection of a plasmid-based nonviral delivery system. Twenty-nine animals were divided into three groups: two concentrations of VEGF and a control group. Outcomes included VEGF mRNA transcript levels, neovascularization, tissue blood flow, and anastomotic bursting pressure. To determine whether local injection resulted in a systemic effect, distant tissues were evaluated for VEGF transcript levels. Successful gene transfection was demonstrated by quantitative polymerase chain reaction analysis of anastomotic tissue, with significantly higher VEGF mRNA expression in treated animals compared to controls. At the gastric side of the anastomosis, there was significantly increased neovascularization, blood flow, and bursting pressure in experimental animals compared to controls. There were no differences in outcome measures between low- and high-dose VEGF groups; however, the high-dose group demonstrated increased VEGF mRNA expression across the anastomosis. VEGF production was not increased at distant sites in treated animals. In this animal model, VEGF gene therapy increased VEGF transcription at a healing gastrointestinal anastomosis without systemic VEGF upregulation. This treatment led to improved healing and strength of the acutely ischemic anastomosis. These findings suggest that VEGF gene therapy has the potential to reduce anastomotic morbidity and improve surgical outcomes in a wide array of patients.

Where it's at really matters: in situ in vivo vascular endothelial growth factor spatially correlates with electron paramagnetic resonance pO2 images in tumors of living mice

Purpose

Tumor microenvironments show remarkable tumor pO₂ heterogeneity, as seen in prior EPR pO₂ images (EPROI). pO₂ correlation with hypoxia response proteins is frustrated by large rapid pO₂ changes with position.

Procedures

To overcome this limitation, biopsies stereotactically located in the EPROI were used to explore the relationship between vascular endothelial growth factor A (VEGF) concentrations in living mouse tumors and the local EPROI pO₂.

Results

Quantitative ELISA VEGF concentrations correlated (p = 0.0068 to 0.019) with mean pO₂, median pO₂, and the fraction of voxels in the biopsy volume with pO₂ less than 3, 6, and 10 Torr.

Conclusions

This validates EPROI hypoxic fractions at the molecular level and provides a new paradigm for the assessment of the relationship, in vivo, between hypoxia and hypoxia response proteins. When translated to human subjects, this will enhance understanding of human tumor pathophysiology and cancer response to therapy.

Probing high affinity sequences of DNA aptamer against VEGF165

Vascular endothelial growth factor (VEGF₁₆₅) is a potent angiogenic mitogen commonly overexpressed in cancerous cells. It contains two main binding domains, the receptor-binding domain (RBD) and the heparin-binding domain (HBD). This study attempted to identify the specific sequences of the VEa5 DNA aptamer that exhibit high binding affinity towards the VEGF₁₆₅ protein by truncating the original VEa5 aptamer into different segments. Using surface plasmon resonance (SPR) spectroscopy for binding affinity analysis, one of the truncated aptamers showed a >200-fold increase in the binding affinity for HBD. This truncated aptamer also exhibited high specificity to HBD with negligible binding affinity for VEGF₁₂₁, an isoform of VEGF lacking HBD. Exposing colorectal cancer cells to the truncated aptamer sequence further confirmed the binding affinity and specificity of the aptamer to the target VEGF₁₆₅ protein. Hence, our approach of aptamer truncation can potentially be useful in identifying high affinity aptamer sequences for the biological molecules and targeting them as antagonist for cancer cell detection.

RSUME is implicated in HIF-1-induced VEGF-A production in pituitary tumour cells

The recently cloned small RWD-domain containing protein RSUME was shown to increase protein levels of hypoxia-inducible factor-1α (HIF-1α). The latter is the oxygen-regulated subunit of HIF-1, the most important transcription factor of the cellular adaptive processes to hypoxic conditions. It is also a major regulator of vascular endothelial growth factor-A (VEGF-A), which is critically involved in the complex process of tumour neovascularisation. In this study, the expression and role of RSUME in pituitary tumours was studied. We found that RSUME mRNA was up-regulated in pituitary adenomas and significantly correlated with HIF-1α mRNA levels. Hypoxia (1% O(2)) or treatment with hypoxia-mimicking CoCl(2) enhanced RSUME and HIF-1α expression, induced translocation of HIF-1α to the nuclei and stimulated VEGF-A production both in pituitary tumour cell lines and primary human pituitary adenoma cell cultures. When RSUME expression was specifically down-regulated by siRNA, the CoCl(2)-induced increase VEGF-A secretion was strongly reduced which was shown to be a consequence of the RSUME knockdown-associated reduction of HIF-1α synthesis. Thus, RSUME plays an important role in initiating pituitary tumour neovascularisation through regulating HIF-1α levels and subsequent VEGF-A production and may therefore be critically involved in pituitary adenoma progression.

Phosphatidylinositol 3′-kinase signaling pathway is essential for Rac1-induced hypoxia-inducible factor-1α and vascular endothelial growth factor expression

We have previously demonstrated the roles of RhoA, Rac1, and Cdc42 in hypoxia-driven angiogenesis. However, the role of oncogenes in hypoxia signaling is poorly understood. Given the importance of Rho proteins in the hypoxic response, we hypothesized that Rho family members could act as mediators of hypoxic signal transduction. We investigated the cross-talk between hypoxia and oncogene-driven signal transduction pathways and explored the role of Rac1 on hypoxia-induced hypoxia-inducible factor (HIF)-1α and VEGF expression. Since the phosphatidylinositol 3′-kinase (PI3K) pathway is involved in signal transduction of many oncogenes, we explored the role of PI3K on Rac1-mediated expression of HIF-1α and VEGF in hypoxia. We showed that LY-294002, a PI3K inhibitor, suppressed HIF-1α and VEGF induction under hypoxic conditions by up to 50%. Activation of Rac1 resulted in an upregulation of hypoxia-induced HIF-1α expression, which was blocked by LY-294002. These data suggested that Rac1 is an intermediate in the PI3K-mediated induction of HIF-1α. Interestingly, there was a significant downregulation of the tumor suppressor genes p53 and von Hippel-Lindau tumor suppressor (VHL) in cells expressing a constitutively active form of Rac1. Rac1-mediated inhibition of p53 and VHL could therefore be implicated in the upregulation of HIF-1α expression.

Bevasiranib for the treatment of wet, age-related macular degeneration

Age- related Macular Degeneration (AMD) is the leading cause of severe visual impairment in people 65 years and older in industrialized nations. Exudative, or “wet”, AMD is a late form of AMD (as distinguished from atrophic, so-called dry, AMD) and is responsible for over 60% of all cases of blindness due to AMD. It is widely accepted that vascular endothelial growth factor (VEGF) is a key component in the pathogenesis of choroidal neo-vascularization (CNV), which is a precursor to wet AMD. The current gold-standard for treating wet AMD is the monoclonal antibody fragment ranibizumab (trade name Lucentis), which targets VEGF. Other agents used to treat wet AMD include pegaptanib (Macugen), bevacizumab (Avastin; off-label use), and several other experimental agents. The advent of small interfering RNA (siRNA) has presented a whole new approach to inhibiting VEGF. This article reviews the status of a novel siRNA-based therapeutic, bevasiranib, for the treatment of wet AMD. Bevasiranib is believed to work by down regulating VEGF production in the retina. Studies in human cell-lines and animal models have shown that VEGF siRNAs are effective in inhibiting VEGF production. Although there is a lack of sufficient published data on human studies supporting the use of bevasiranib for wet AMD, available data indicates that due to its unique mechanism of action, bevasiranib might hold some promise as a primary or adjunct treatment for wet AMD.

Controlling matrix formation and cross-linking by hypoxia in cardiovascular tissue engineering

In vivo functionality of cardiovascular tissue engineered constructs requires in vitro control of tissue development to obtain a well developed extracellular matrix (ECM). We hypothesize that ECM formation and maturation is stimulated by culturing at low oxygen concentrations. Gene expression levels of monolayers of human vascular-derived myofibroblasts, exposed to 7, 4, 2, 1, and 0.5% O(2) (n = 9 per group) for 24 h, were measured for vascular endothelial growth factor (VEGF), procollagen α1(I) and α1(III), elastin, and cross-link enzymes lysyl oxidase (LOX) and lysyl hydroxylase 2 (LH2). After 4 days of exposure to 7, 2, and 0.5% O(2) (n = 3 per group), protein synthesis was evaluated. All analyses were compared with control cultures at 21% O(2). Human myofibroblasts turned to hypoxia-driven gene expression, indicated by VEGF expression, at oxygen concentrations of 4% and lower. Gene expression levels of procollagen α1(I) and α1(III) increased to 138 ± 26 and 143 ± 19%, respectively, for all oxygen concentrations below 4%. At 2% O(2), LH2 and LOX gene expression levels were higher than control cultures (340 ± 53 and 136 ± 29%, respectively), and these levels increased even further with decreasing oxygen concentrations (611 ± 176 and 228 ± 45%, respectively, at 0.5% O(2)). Elastin gene expression levels remained unaffected. Collagen synthesis and LH2 protein levels increased at oxygen concentrations of 2% and lower. Oxygen concentrations below 4% induce enhanced ECM production by human myofibroblasts. Implementation of these results in cardiovascular tissue engineering approaches enables in vitro control of tissue development.

Oxygen saturation in premature infants at risk for threshold retinopathy of prematurity

PURPOSE

We aimed to determine if oxygen saturation, desaturations, and saturation variability play a role in progression of retinopathy of prematurity (ROP) and need for laser treatment.

METHODS

This was a retrospective case-control study. We performed chart review of premature infants in a university hospital neonatal intensive care unit consecutively examined for ROP between May 2000 and December 2001. We compared birthweight, postmenstrual age, and oxygen saturation for 3 weeks before laser treatment for threshold ROP in group 1 (n=19) (average weight at treatment 2508 grams) and group 2 (n=18) before they reached 2500 grams. Outcome measures were retinopathy progression and need for treatment.

RESULTS

Adjusting for birthweight and postmenstrual age, known predictors of ROP progression, we found that babies requiring laser treatment (group 1) had lower average daily oxygen saturation levels in the study period, significantly on 5/20 days (25%). These babies had saturations below 95% on 18/20 days (90%). Babies not requiring laser (group 2) had saturations below 95% on 2/20 days (10%). The last day on which pretreatment saturations differed significantly was 2 days before laser. Group 1 had more desaturations below 80% (6.0±3.2) than group 2 (3.2±1.2), p=0.0002 (independent samples t tests). Saturations varied more for individual group 1 infants.

CONCLUSIONS

Decreased oxygen saturation as early as 3 weeks and as late as 2 days before laser, increased number of desaturations, and saturation variability were seen in babies eventually requiring laser treatment for ROP.

Inhibition of experimental choroidal neovascularization in mice by anti-VEGFA/VEGFR2 or non-specific siRNA

Choroidal neovascularization (CNV) is one of the severe pathological consequences of the end-stage of age-related macular degeneration (AMD). Several lines of evidence implicate increased levels of vascular endothelial growth factor (VEGF) in the retinas of AMD patients. Current available agents for the inhibition of VEGF protein such as bevacizumab show significant promise for the treatment of exudative AMD. However, this compound still has limited efficacy and requires multiple administrations; thus, it is associated with a variety of ocular complications, including endophthalmitis and retinal detachment. In this study, we used anti-VEGFA/VEGFR2 or non-specific siRNA and evaluated their suppression of laser-induced choroidal neovascularization (CNV) in mice. Male adult C57BL/6J mice were used in the study. The mice were subjected to laser rupture of Bruch's membrane to induce CNV and then randomized to five groups with six mice per group. The five groups were blank control, vehicle control (5% glucose solution, GS), VEGFA.siRNA, VEGFR2.siRNA, and non-specific siRNA. Two days after laser photocoagulation, each group, with the exception of the blank control group, received 1 microl of the appropriate agent by intravitreal injection to both eyes. Seven days later, after taking fundus photography and fundus fluorescein angiography (FFA), the mice were killed for tissue sampling. Six eyes from three mice in each group were used for choroidal flatmounts to examine CNV. Six eyes from three mice in each group were subjected to RNA extraction for VEGF mRNA quantification by qRT-PCR. Retinal tissue from 2 mice without laser treatment was harvested as the assay reference. The incidence of burns which showed fluorescein leakage was 80.0% in blank control, 75.0% in GS, 55.0% in VEGFA.siRNA, 40.0% in VEGFR2.siRNA and 30.0% in non-specific siRNA group. The flatmounted specimens showed that the retinal pigment epithelium (RPE) was visualized as a uniform hexagonal array in nonlasered areas. On day 7 after laser burn, well-defined isolectin-B4 labeled CNV networks were shown within the burn spots of the 2 control groups. The inhibitory effects of the 3 siRNAs on CNV formation were statistically significant as compared to the 2 control groups. Compared to the control groups, the ocular expression of VEGF mRNA was decreased significantly in the 3 siRNA treated groups. The areas of CNV correlated with the expression of VEGF mRNA. Anti-VEGFA/VEGFR2 or non-specific siRNA can inhibit CNV and attenuate VEGF mRNA expression in a laser-induced mouse model of CNV. We conclude that the siRNAs may be an option for treating patients with exudative AMD, and more studies are needed to test the possible side-effects of the treatment.

PRH/Hhex controls cell survival through coordinate transcriptional regulation of vascular endothelial growth factor signaling

The proline-rich homeodomain protein (PRH) plays multiple roles in the control of gene expression during embryonic development and in the adult. Vascular endothelial growth factor (VEGF) is a mitogen that stimulates cell proliferation and survival via cell surface receptors including VEGFR-1 and VEGFR-2. VEGF signaling is of critical importance in angiogenesis and hematopoiesis and is elevated in many tumors. Here we show that PRH binds directly to the promoter regions of the Vegf, Vegfr-1, and Vegfr-2 genes and that in each case PRH represses transcription. We demonstrate that overexpression or knockdown of PRH directly impinges on the survival of both leukemic and tumor cells and that the modulation of VEGF and VEGF receptor signaling by PRH mediates these effects. Our findings demonstrate that PRH is a key regulator of the VEGF signaling pathway and describe a mechanism whereby PRH plays an important role in tumorigenesis and leukemogenesis.

The function of vascular endothelial growth factor

Vascular endothelial growth factor (VEGF) is considered the master regulator of angiogenesis during growth and development, as well as in disease states such as cancer, diabetes, and macular degeneration. This review details our current understanding of VEGF signaling and discusses the benefits and unexpected side effects of promising anti-angiogenic therapeutics that are currently being used to inhibit neovacularization in tumors.

A new dawn for the use of traditional Chinese medicine in cancer therapy

Although traditional Chinese medicine has benefitted one fifth of the world's population in treating a plethora of diseases, its acceptance as a real therapeutic option by the West is only now emerging. In light of a new wave of recognition being given to traditional Chinese medicine by health professionals and regulatory bodies in the West, an understanding of their molecular basis and highlighting potential future applications of a proven group of traditional Chinese medicine in the treatment of a variety of cancers is crucial – this is where their calling holds much hope and promise in both animal and human trials. Furthermore, the rationale for combining conventional agents and modern biotechnological approaches to the delivery of traditional Chinese medicine is an avenue set to revolutionize the future practice of cancer medicine – and this may well bring on a new dawn of therapeutic strategies where East truly meets West.

Vascular endothelial growth factor (VEGF)-C - a potent risk factor in children diagnosed with stadium 4 neuroblastoma

To evaluate the immunohistochemical expression of VEGF-C, CD34 and VEGFR-2 in cancer tissue of children diagnosed with stadium 4 neuroblastoma (NB) and correlate their presence with the survival rate of children diagnosed with that stage of the disease. Eighteen children assigned to stadium 4 composed the study group. Fourteen patients (allocated to stadium 3) formed a control group. VEGF-C, CD34 and VEGFR-2 expressions were evaluated by immunohistochemical assay. Consecutive slides incubated with anti-CD34 and anti-VEGFR-2 antibodies revealed that the two markers were colocalized within endothelial layer of the blood vessels. On the other hand, VEGF-C was expressed exclusively in tumour cells. As demonstrated by Fisher's exact test, the risk of NB treatment failure (progression or relapse) as well as tumour related death, when all the patients were considered, was found to be significant in VEGF-C positive patients. VEGF-C expression in NB constitutes a potent risk factor and may direct future anti-angiogenic treatment strategy. The proximity of VEGF-C and CD34/VEGFR-2 of NB could be the equivalent of a potentially interesting VEGF-C fashion involving a tumour cell invasion into the blood vessels in an early phase of metastases promoting.