Vascular permeability factor/vascular endothelial growth factor inhibits anchorage-disruption-induced apoptosis in microvessel endothelial cells by inducing scaffold formation

An appraisal of vascular endothelial growth factor (VEGF): the dynamic molecule of wound healing and its current clinical applications

Angiogenesis is a critical step of wound healing, and its failure leads to chronic wounds. The idea of restoring blood flow to the damaged tissues by promoting neo-angiogenesis is lucrative and has been researched extensively. Vascular endothelial growth factor (VEGF), a key dynamic molecule of angiogenesis has been investigated for its functions. In this review, we aim to appraise its biology, the comprehensive role of this dynamic molecule in the wound healing process, and how this knowledge has been translated in clinical application in various types of wounds. Although, most laboratory research on the use of VEGF is promising, its clinical applications have not met great expectations. We discuss various lacunae that might exist in making its clinical application unsuccessful for commercial use, and provide insight to the foundation for future research.

The Give-and-Take Interaction Between the Tumor Microenvironment and Immune Cells Regulating Tumor Progression and Repression

A fundamental concern of the majority of cancer scientists is related to the identification of mechanisms involved in the evolution of neoplastic cells at the cellular and molecular level and how these processes are able to control cancer cells appearance and death. In addition to the genome contribution, such mechanisms involve reciprocal interactions between tumor cells and stromal cells within the tumor microenvironment (TME). Indeed, tumor cells survival and growth rely on dynamic properties controlling pro and anti-tumorigenic processes. The anti-tumorigenic function of the TME is mainly regulated by immune cells such as dendritic cells, natural killer cells, cytotoxic T cells and macrophages and normal fibroblasts. The pro-tumorigenic function is also mediated by other immune cells such as myeloid-derived suppressor cells, M2-tumor-associated macrophages (TAMs) and regulatory T (Treg) cells, as well as carcinoma-associated fibroblasts (CAFs), adipocytes (CAA) and endothelial cells. Several of these cells can show both, pro- and antitumorigenic activity. Here we highlight the importance of the reciprocal interactions between tumor cells and stromal cells in the self-centered behavior of cancer cells and how these complex cellular interactions control tumor progression and repression.

Placental mitochondrial function as a driver of angiogenesis and placental dysfunction

The placenta is a highly vascularized and complex foetal organ that performs various tasks, crucial to a healthy pregnancy. Its dysfunction leads to complications such as stillbirth, preeclampsia, and intrauterine growth restriction. The specific cause of placental dysfunction remains unknown. Recently, the role of mitochondrial function and mitochondrial adaptations in the context of angiogenesis and placental dysfunction is getting more attention. The required energy for placental remodelling, nutrient transport, hormone synthesis, and the reactive oxygen species leads to oxidative stress, stemming from mitochondria. Mitochondria adapt to environmental changes and have been shown to adjust their oxygen and nutrient use to best support placental angiogenesis and foetal development. Angiogenesis is the process by which blood vessels form and is essential for the delivery of nutrients to the body. This process is regulated by different factors, pro-angiogenic factors and anti-angiogenic factors, such as sFlt-1. Increased circulating sFlt-1 levels have been linked to different preeclamptic phenotypes. One of many effects of increased sFlt-1 levels, is the dysregulation of mitochondrial function. This review covers mitochondrial adaptations during placentation, the importance of the anti-angiogenic factor sFlt-1in placental dysfunction and its role in the dysregulation of mitochondrial function.

Facilitated vascularization and enhanced bone regeneration by manipulation hierarchical pore structure of scaffolds

Sufficient vascularization is quite important for preventing cell death and promoting host integration during the repair of the critical sized bone defects. Porous structure providing enough space for the ingrowth of vessels is an essential consideration during the scaffold's development. In this study, we designed and fabricated three kinds of porous structured scaffolds based on poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx), such as mono-structured PHBHHx scaffolds with macro pores (PH-1), di-structured PHBHHx scaffolds with macro-meso pores (PHS-2), and tri-structured PHBHHx scaffolds with macro-micro-meso pores (PHS-3), respectively. In vitro effects of the hierarchical porous scaffolds on human umbilical vein endothelial cells (HUVECs), such as cell attachment, glucose and lactate detection, relative gene expressions of endothelial markers were investigated. The PHS-3 scaffolds exhibited preferential potency of inducing better angiogenesis in vitro. Consequently, the hierarchical porous scaffolds were applied to load rhBMP-2 and repair the critical sized bone defect (15 mm) in rabbits. Microangiography analysis by three dimensional micro-computed tomographic (micro-CT) demonstrated that the volume of blood vessels within the defect area was higher in the rhBMP-2 loaded PHS-3 (PHS-3/rhBMP-2) than that in other rhBMP-2 loaded porous scaffolds with simplex or double scaled pores (PH-1/rhBMP-2 or PHS-2/rhBMP-2) at 4 weeks and 8 weeks, which implied that multi-level porous structure was conducive to nutrition transmission and revascularization. Further investigations of orthotopic bone formation by micro-CT, histological and immunohistochemistry analysis confirmed the most accelerated new bone formation rate in the PHS-3/rhBMP-2 group. The maximum load value of the regenerated bone induced by PHS-3/rhBMP-2 at 12 weeks was 258.47 ± 14.77 N which did not show significant difference from the normal bone of 268.81 ± 12.05 N. These results highlighted that introducing multi-level pores into the biocompatible scaffolds may be an effective approach to promote angiogenesis and bone regeneration.

Pro-angiogenic therapeutics for preeclampsia

Preeclampsia is a pregnancy-induced hypertensive disorder resulting from abnormal placentation, which causes factors such as sFlt-1 to be released into the maternal circulation. Though anti-hypertensive drugs and magnesium sulfate can be given in an effort to moderate symptoms, the syndrome is not well controlled. A hallmark characteristic of preeclampsia, especially early-onset preeclampsia, is angiogenic imbalance resulting from an inappropriately upregulated sFlt-1 acting as a decoy receptor binding vascular endothelial growth factor (VEGF) and placental growth factor (PlGF), reducing their bioavailability. Administration of sFlt-1 leads to a preeclamptic phenotype, and several models of preeclampsia also have elevated levels of plasma sFlt-1, demonstrating its role in driving the progression of this disease. Treatment with either VEGF or PlGF has been effective in attenuating hypertension and proteinuria in multiple models of preeclampsia. VEGF, however, may have overdose toxicity risks that have not been observed in PlGF treatment, suggesting that PlGF is a potentially safer therapeutic option. This review discusses angiogenic balance as it relates to preeclampsia and the studies which have been performed in order to alleviate the imbalance driving the maternal syndrome.

STAT3 Protein Regulates Vascular Smooth Muscle Cell Phenotypic Switch by Interaction with Myocardin

The JAK-STAT3 signaling pathway is one of the critical pathways regulating cell proliferation, differentiation, and apoptosis. Myocardin is regarded as a key mediator for the change of smooth muscle phenotypes. However, the relationship between STAT3 and myocardin in the vascular smooth muscle cell (VSMC) phenotypic switch has not been investigated. The goal of this study was to investigate the molecular mechanism by which STAT3 affects the myocardin-regulated VSMC phenotypic switch. Data presented in this study demonstrated that STAT3 was rapidly up-regulated after stimulation with VEGF. Inhibition of the STAT3 activation process impaired VSMC proliferation and enhanced the expression of VSMC contractile genes by increasing serum-response factor binding to the CArG-containing regions of VSMC-specific contractile genes. In contrast, the interaction between serum-response factor and its co-activator myocardin was reduced by overexpression of STAT3. In addition, treated VEGF inhibited the transcription activity of myocardin, and overexpression of STAT3 inhibited myocardin-induced up-regulation of VSMC contractile phenotype-specific genes. Although myocardin and STAT3 are negatively correlated, interestingly, both of them can enhance the expression of VEGF, suggesting a feedback loop to regulate the VSMC phenotypic switch. Taken together, these results indicate that the JAK-STAT3 signaling pathway plays a key role in controlling the phenotypic switch of VSMCs through the interactions between STAT3 and myocardin by various coordinated gene regulation pathways and feedback loops.

Expression of tumor necrosis factor-alpha and vascular endothelial growth factor in different zones of fetal membranes: a possible relation to onset of labor

This study aimed to explore whether the altered expression of tumor necrosis factor-alpha (TNF-α), vascular endothelial growth factor (VEGF) and apoptotic changes in mid zone (MZ) and rupture zone (RZ) of fetal membranes (FM) are regulatory mechanisms associated with labor at term. Fifteen FM specimens were collected after vaginal deliveries and 13 specimens after elective caesarian section. Histological and immunohistochemical analysis were employed. Area percent of TNF-α and VEGF immunostaining and apoptotic index (AI) were evaluated using image analysis. The statistical data revealed significantly higher area % for TNF-α, VEGF immunoexpression and AI in labor compared to non-labor specimens (p < 0.0001). There was a significantly higher percentage of TNF-α immunoexpressed area in MZ compared with RZ in both groups (p < 0.0001). VEGF expression in RZ of both groups proved nearly double or triple the area % of expression relative to MZ with highly significant difference (p < 0.0001). quantitative analysis revealed near two fold increase in the AI in RZ (13.42% ± 1.2 in labor; 11.20% ± 0.96 in non-labor groups) when compared to MZ (7.20% ± 0.6 in labor; 5.08% ± 0.76 in non-labor groups) with highly significant zonal difference (p < 0.0001). Correlation analysis revealed significant correlation between apoptotic indices and area % of TNF-α (r = 0.575, p = 0.002 in non-labor; r = 0.652, p < 0.0001 in labor) and VEGF (r = 0.795, p < 0.0001 in non-labor; r = 0.668, p < 0.0001 in labor). In conclusion, Apoptosis may be regulated by TNF-α and VEGF expression in FM at labor. MZ is a step back from RZ and could participate actively in rupture of the FM during labor. TNF-α and VEGF increase with onset of labor and differentially expressed in the RZ and the MZ. These findings call for further study with tissue cultures or animal models.

Bio-hybrid silk fibroin/calcium phosphate/PLGA nanocomposite scaffold to control the delivery of vascular endothelial growth factor

This study investigated the efficacy of bio-hybrid silk fibroin/Calcium phosphate/PLGA nanocomposite scaffold as vascular endothelial growth factor (VEGF) delivery system. The scaffold was fabricated using freeze-drying and electrospinning. Here, we highlight the structural changes of the scaffold using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and differential scanning calorimetry (DSC). The uniform dispersion of calcium phosohate (CaP) powder within silk fibroin (SF) solution was also confirmed using Zeta potential analysis. Moreover, good biocompatibility of osteoblast cells next to the scaffold was approved by cell adhesion, proliferation and alkaline phosphatase production. The release profile of VEGF during 28 days has established the efficacy of the scaffold as a sustained delivery system. The bioactivity of the released VEGF was maintained about 83%. The histology analysis has shown that the new bone tissue formation happened in the defected site after 10 weeks of implantation. Generally, our data showed that the fabricated scaffold could be considered as an effective scaffold for bone tissue engineering applications.

Angiogenesis and lymphangiogenesis as prognostic factors after therapy in patients with cervical cancer

AIM OF THE STUDY

This retrospective study attempts to evaluate the influence of serum vascular endothelial growth factor C (VEGF-C), microvessel density (MVD) and lymphatic vessel density (LMVD) on the result of tumour treatment in women with cervical cancer.

MATERIAL AND METHODS

The research was carried out in a group of 58 patients scheduled for brachytherapy for cervical cancer. All women were patients of the Department and University Hospital of Oncology and Brachytherapy, Collegium Medicum in Bydgoszcz of Nicolaus Copernicus University in Toruń. VEGF-C was determined by means of a quantitative sandwich enzyme immunoassay using a human antibody VEGF-C ELISA produced by Bender MedSystem, enzyme-linked immunosorbent detecting the activity of human VEGF-C in body fluids. The measure for the intensity of angiogenesis and lymphangiogenesis in immunohistochemical reactions is the number of blood vessels within the tumour. Statistical analysis was done using Statistica 6.0 software (StatSoft, Inc. 2001). The Cox proportional hazards model was used for univariate and multivariate analyses. Univariate analysis of overall survival was performed as outlined by Kaplan and Meier. In all statistical analyses p < 0.05 (marked red) was taken as significant.

RESULTS

In 51 patients who showed up for follow-up examination, the influence of the factors of angiogenesis, lymphangiogenesis, patients' age and the level of haemoglobin at the end of treatment were assessed. Selected variables, such as patients' age, lymph vessel density (LMVD), microvessel density (MVD) and the level of haemoglobin (Hb) before treatment were analysed by means of Cox logical regression as potential prognostic factors for lymph node invasion. The observed differences were statistically significant for haemoglobin level before treatment and the platelet number after treatment. The study revealed the following prognostic factors: lymph node status, FIGO stage, and kind of treatment. No statistically significant influence of angiogenic and lymphangiogenic factors on the prognosis was found.

CONCLUSION

Angiogenic and lymphangiogenic factors have no value in predicting response to radiotherapy in cervical cancer patients.

A myocardial patch made of collagen membranes loaded with collagen-binding human vascular endothelial growth factor accelerates healing of the injured rabbit heart

Tissue-engineered myocardial patches could be useful in the repair of myocardial injuries. The aim of the present study was to evaluate a collagen targeting delivery system for myocardial repair. A specific peptide collagen-binding domain (CBD) was fused to human vascular endothelial growth factor (VEGF) to enhance the binding of VEGF to collagen. In this study, collagen membranes loaded with CBD-VEGF, natural VEGF, or phosphate-buffered saline are used as cardiac patches to repair the infarcted myocardium in a rabbit model. CBD-VEGF/collagen group could effectively induce more cells to penetrate into the collagen membrane after 4 weeks and promote more vascularization in infarcted myocardium after 12 weeks compared with the other two control groups. Echocardiography and hemodynamic studies both show cardiac function improvement in the CBD-VEGF/collagen group. These results reveal that implantation of CBD-VEGF collagen membrane patch into the infarcted myocardium could effectively improve left ventricle cardiac function and increase the vascular density.

Improved cellularization and angiogenesis using collagen scaffolds chemically conjugated with vascular endothelial growth factor

Much research has focused on developing vascular endothelial growth factor (VEGF) delivery systems to enhance angiogenesis in wound repair and in tissue engineering. Collagen can be used as a delivery system because of its biocompatibility, but its fast degradation rate and limited affinity with growth factors are disadvantageous for maintaining a sufficient growth factor concentration at injury sites. To enhance VEGF binding to collagen scaffolds and reduce the collagen degradation rate we found a simple way to modify porous collagen scaffolds by chemical addition of sulfhydryl groups, which then allow both cross-linking of the collagen fibers with each other and the immobilization of more VEGF in the scaffold after treatment with sulfo-SMCC. We demonstrated that cross-linking led to a slower degradation rate of the collagen scaffolds, while cellularization was improved by both cross-linking and the presence of VEGF. On the other hand, angiogenesis was increased only moderately by cross-linking, but significantly more by the presence of immobilized VEGF. We conclude that collagen scaffolds chemically conjugated to VEGF by Traut's reagent and sulfo-SMCC is an effective delivery system in wound repair and tissue engineering.

Relationship between RPE and choriocapillaris in age-related macular degeneration

PURPOSE

The purpose of this study was to examine the relationships between choriocapillaris (CC) and retinal pigment epithelial changes in age-related macular degeneration (AMD). Morphologic changes in the retinal pigment epithelium (RPE)/choriocapillaris complex were quantified in dry and wet forms of AMD, and the results were compared with those in aged control eyes without maculopathy.

METHODS

Postmortem choroids from three aged control subjects, five subjects with geographic atrophy (GA), and three subjects with wet AMD were analyzed using a semiquantitative computer-assisted morphometric technique developed to measure the percentages of retinal pigment epithelial and CC areas in choroidal wholemounts incubated for alkaline phosphatase activity. The tissues were subsequently embedded in methacrylate and were sectioned so that structural changes could be examined.

RESULTS

There was a linear relationship between the loss of RPE and CC in GA. A 50% reduction in vascular area was found in regions of complete retinal pigment epithelial atrophy. Extreme constriction of remaining viable capillaries was found in areas devoid of RPE. Adjacent to active choroidal neovascularization (CNV) in wet AMD, CC dropout was evident in the absence of retinal pigment epithelial atrophy, resulting in a 50% decrease in vascular area. Lumenal diameters of the remaining capillaries in wet AMD eyes were similar to those in control eyes.

CONCLUSIONS

The primary insult in GA appears to be at the level of the RPE, and there is an intimate relationship between retinal pigment epithelial atrophy and secondary CC degeneration. CC degeneration occurs in the presence of viable RPE in wet AMD. The RPE in regions of vascular dropout are presumably hypoxic, which may result in an increase in VEGF production by the RPE and stimulation of CNV.

Activated STAT3 is a mediator and biomarker of VEGF endothelial activation

STAT3 plays important roles in cell proliferation and survival signaling and is often constitutively activated in transformed cells. In this study, we examined STAT3 activation in endothelial cells (EC) during angiogenic activation and therapeutic angiogenesis inhibition. VEGF stimulation of cultured EC induced STAT3 phosphorylation by a VEGFR2- and Src-dependent mechanism. FGF2 but not PlGF also induced EC STAT3 activation in vitro. Activated STAT3 mediated VEGF induction of EC Bcl-2 and contributed to VEGF protection of EC from apoptosis. In vivo, p-STAT3 was absent by immunohistological staining in the vascular EC of most normal mouse organs but was present in the vessels of mouse and human tumors. Tumor vascular p-STAT3 increased as tumors were induced to overexpress VEGF, indicating that VEGF is an activator of EC p-STAT3 in vivo. Tumor vascular p-STAT3 decreased during angiogenesis inhibition by antagonists of VEGF-VEGFR signaling, VEGF Trap and SU5416, indicating that VEGF contributed to the EC STAT3 activation seen in the tumors prior to treatment and that p-STAT3 may be used to monitor therapy. These studies show that p-STAT3 is a mediator and biomarker of endothelial activation that reports VEGF-VEGFR2 activity and may be useful for studying the pharmacodynamics of targeted angiogenesis inhibitors.

Hydroxysafflor yellow A enhances survival of vascular endothelial cells under hypoxia via upregulation of the HIF-1 alpha-VEGF pathway and regulation of Bcl-2/Bax

Hydroxysafflor yellow A (HSYA) is a component of the flower Carthamus tinctorius L. The present investigation determines whether HSYA can modify the effects of hypoxia on vascular endothelial cells (EC) and its mechanisms. Human EC line (EAhy926) viability was determined using the MTT assay. EC cycle phase distribution was done with PI staining and flow cytometric analysis, and EC apoptosis was done by AnnexinV-FITC detection and the TUNEL assay. The protein levels of VEGF, Bcl-2, Bax, and HIF-1 alpha were determined by ELISA or Western blot analysis, and the mRNA expression of these genes by RT-PCR analysis. HIF-1 alpha transcriptional activity was measured using a reporter gene assay. HSYA improved cell viability under hypoxia in a concentration-dependent manner by attenuating its cycle arrest and inhibiting its apoptosis. HSYA upregulated the bcl-2/bax ratio, which is downregulated under hypoxia, increased VEGF protein concentration and VEGF mRNA expression and enhanced HIF-1 alpha protein accumulation and its transcriptional activity. In conclusion, HSAY could enhance the survival of ECs under hypoxia, which may be correlated with its effect of upregulating the bcl-2/bax ratio and promoting HIF-1 alpha protein accumulation, which increases VEGF. These findings provide evidence for the mechanisms by which HSYA maintains EC survival under hypoxia.

RGD peptide-induced cell death of chondrocytes and synovial cells

BACKGROUND

Small peptides including the Arg-Gly-Asp (RGD) motif have been used in studies on cell-extracellular matrix (ECM) attachment due to their ability to disturb integrin-mediated attachment on the cell surface. As another biological action of RGD peptides, several reports have shown that RGD peptides are incorporated into cytoplasm and induce apoptosis by direct activation of caspase-3. This study evaluated the effect of RGD peptides on chondrocytes and synovial cells and studied the involvement of caspases.

METHODS

Chondrocytes and synovial cells were isolated and cultured from the knee joints of New Zealand White rabbits. Cells were incubated in serum-free medium with peptides (RGD, RGDS, GRGDSP, GRGDNP, RGES), and the survival rates were evaluated. The rate of apoptotic cells was measured by flow cytometry in cells treated with RGDS, GRGDSP, and RGES. Caspase-3, -8 and -9 activity was measured in cells treated with RGDS and GRGDSP. Osteochondral explants harvested from rabbits were also incubated with RGD peptides (RGDS, GRGDSP, and GRGDNP), and the survival rate of chondrocytes was evaluated.

RESULTS

The survival rate of cultured chondrocytes was significantly decreased in the GRGDSP- and GRGDNP-treated groups. The survival rate of synovial cells was significantly decreased with four of the RGD peptides (RGD, RGDS, GRGDSP, and GRGDNP) at 5 mM, and in the RGDS- and GRGDSP-treated groups at 1 mM. Flow cytometric assay revealed increases of apoptotic chondrocytes with GRGDSP and increases of apoptotic synovial cells with RGDS and GRGDSP. Caspase-3 was activated in chondrocytes treated with GRGDSP and it was also activated in synovial cells treated with RGDS and GRGDSP. Caspases-8 and -9 were not activated in chondrocytes or in synovial cells. The survival rate of chondrocytes in explants decreased in the superficial layer with all three RGD peptides (RGDS, GRGDSP, and GRGDNP) and in the middle layer with GRGDSP.

CONCLUSIONS

RGD peptides induced apoptosis in cultured chondrocytes as well as in cells in cartilage explants and synovial cells, presumably through direct activation of caspase-3.

VEGF-A and the induction of pathological angiogenesis

Tumors, wounds, and chronic inflammatory disorders generate a new vascular supply by a process known as pathological angiogenesis. Whereas formation of the normal blood vasculature requires the interaction of many different agonists and inhibitors, including vascular endothelial growth factor-A (VEGF-A) and other members of the vascular permeability factor/VEGF family, pathological angiogenesis is a cruder, simpler process that can be replicated by a single VEGF-A isoform, VEGF-A(164/5). VEGF-A(164/5) induces the formation of several distinctly different types of new blood vessels that differ from normal blood vessels with respect to organization, structure, and function. Elucidating the properties of these new vessels has led to a better understanding of angiogenesis and will hopefully lead to new approaches to antiangiogenic therapy.

The role of vascular endothelial growth factor in wound healing

BACKGROUND

A chronic wound is tissue with an impaired ability to heal. This is often a consequence of one of the following etiologies: diabetes, venous reflux, arterial insufficiency sickle cell disease, steroids, and/or pressure. Healing requires granulation tissue depending on epithelialization and angiogenesis. Currently no growth factor is available to treat patients with impaired healing that stimulates both epithelialization and angiogenesis. The objective is to review is the multiple mechanisms of vascular endothelial growth factor (VEGF) in wound healing.

MATERIALS AND METHODS

The authors reviewed the literature on the structure and function of VEGF, including its use for therapeutic angiogenesis. Particular attention is given to the specific role of VEGF in the angiogenesis cascade, its relationship to other growth factors and cells in a healing wound.

RESULTS

VEGF is released by a variety of cells and stimulates multiple components of the angiogenic cascade. It is up-regulated during the early days of healing, when capillary growth is maximal. Studies have shown the efficacy of VEGF in peripheral and cardiac ischemic vascular disease with minimal adverse effects. Experimental data supports the hypothesis that VEGF stimulates epithelialization and collagen deposition in a wound.

CONCLUSION

VEGF stimulates wound healing through angiogenesis, but likely promotes collagen deposition and epithelialization as well. Further study of the molecule by utilizing the protein itself, or novel forms of delivery such as gene therapy, will increase its therapeutic possibilities to accelerate closure of a chronic wound.

Antiangiogenic and antitumor effects of SRC inhibition in ovarian carcinoma

Src, a nonreceptor tyrosine kinase, is a key mediator for multiple signaling pathways that regulate critical cellular functions and is often aberrantly activated in a number of solid tumors, including ovarian carcinoma. The purpose of this study was to determine the role of activated Src inhibition on tumor growth in an orthotopic murine model of ovarian carcinoma. In vitro studies on HeyA8 and SKOV3ip1 cell lines revealed that Src inhibition by the Src-selective inhibitor, AP23846, occurred within 1 hour and responded in a dose-dependent manner. Furthermore, Src inhibition enhanced the cytotoxicity of docetaxel in both chemosensitive and chemoresistant ovarian cancer cell lines, HeyA8 and HeyA8-MDR, respectively. In vivo, Src inhibition by AP23994, an orally bioavailable analogue of AP23846, significantly decreased tumor burden in HeyA8 (P = 0.02), SKOV3ip1 (P = 0.01), as well as HeyA8-MDR (P < 0.03) relative to the untreated controls. However, the greatest effect on tumor reduction was observed in combination therapy with docetaxel (P < 0.001, P = 0.002, and P = 0.01, for the above models, respectively). Proliferating cell nuclear antigen staining showed that Src inhibition alone (P = 0.02) and in combination with docetaxel (P = 0.007) significantly reduced tumor proliferation. In addition, Src inhibition alone and in combination with docetaxel significantly down-regulated tumoral production of vascular endothelial growth factor and interleukin 8, whereas combination therapy decreased the microvessel density (P = 0.02) and significantly affected vascular permeability (P < 0.05). In summary, Src inhibition with AP23994 has potent antiangiogenic effects and significantly reduces tumor burden in preclinical ovarian cancer models. Thus, Src inhibition may be an attractive therapeutic approach for patients with ovarian carcinoma.

Neonatal lung side population cells demonstrate endothelial potential and are altered in response to hyperoxia-induced lung simplification

Lung side population (SP) cells are resident lung precursor cells with both epithelial and mesenchymal potential that are believed to play a role in normal lung development and repair. Neonatal hyperoxic exposure impairs lung development leading to a long-term decrease in gas exchange surfaces. The hypothesis that lung SP cells are altered during impaired lung development has not been studied. To address this issue, we characterized the endothelial potential of neonatal lung SP and subsets of lung SP from neonatal mice following hyperoxic exposure during room air recovery. Lung SP cells were isolated and sorted on the basis of their capacity to efflux Hoechst 33342. The lung SP was further sorted based on expression of Flk-1 and CD45. In vitro, both CD45pos/Flk-1pos and CD45neg/Flk-1pos bind isolectin B4 and incorporate LDL and form networks in matrigel, indicating that these populations have endothelial cell characteristics. Hyperoxic exposure of neonatal mice resulted in subtle changes in vascular and alveolar density on P13, which persisted with room air recovery to P41. During room air recovery, a decrease in lung SP cells was detected in the hyperoxic-exposed group on postnatal day 13 followed by an increase on day 41. Within this group, the lung SP subpopulation of cells expressing CD45 increased on day 21, 41, and 55. Here, we show that lung SP cells demonstrate endothelial potential and that the population distribution changes in number as well as composition following hyperoxic exposure. The hyperoxia-induced changes in lung SP cells may limit their ability to effectively contribute to tissue morphogenesis during room air recovery.

Modulation of angiogenic phenotype alters tumorigenicity in rat ovarian epithelial cells

Vascular endothelial growth factor (VEGF) expression correlates with microvessel density, stage, malignant ascites, metastasis, and survival in ovarian cancer. By transducing VEGF165 into a nontumorigenic rat ovarian surface epithelial cell line (ROSE199), we investigated the direct effect of an angiogenic phenotype on tumor development. The neu oncogene, which is overexpressed in >30% of ovarian cancers, was used in comparison. Neu-transfected ROSE199 cells showed phenotypic characteristics of transformation in vitro with an abundance of focus-forming units in monolayer cultures and anchorage-independent growth in soft agar. In contrast, VEGF-secreting ROSE199 cells (VR) retained normal morphology and in vitro growth characteristics (e.g., proliferation rate) compared with parental ROSE199 cells. Interestingly, injection of VR cells into athymic mice formed malignant ascites in 100% of the animals when injected into the peritoneum and developed vascularized tumors in 85% of the mice when injected s.c. Furthermore, blocking VEGF-mediated signaling by the Flk-1/KDR receptor kinase inhibitor SU5416 significantly inhibited the growth of VR tumors. To validate that the proangiogenic switch is responsible for tumor development, the angiogenic phenotype was balanced by the inducible coexpression of endostatin under the control of Tet-activated promoter. Coexpression of endostatin along with VEGF reversed the tumorigenic phenotype of VR cells. These studies show that alterations in the angiogenic characteristics of ovarian surface epithelium may play an important role in the etiology of ovarian cancer, and that inhibition of angiogenesis can be effective in the treatment of epithelial ovarian cancer.

Decreased endothelial progenitor cells in umbilical cord blood in severe preeclampsia

BACKGROUND/AIMS

We compared the numbers of endothelial progenitor cells (EPCs) in umbilical cord blood in severe preeclampsia and normal pregnancy, along with the cord blood plasma levels of free VEGF and sVEGFR-1.

METHODS

Umbilical cord blood EPC counts in severe preeclampsia (n = 15) and gestationally matched normal pregnant women (n = 30) were retrospectively analyzed. Cord plasma free VEGF and sVEGFR-1 levels were measured by enzyme immunoassay.

RESULTS

Significantly higher systolic blood pressure, lower birth weight, and higher rate of small for gestational age were noted in the severe preeclampsia group. Circulating EPCs in cord blood and umbilical cord plasma free VEGF were significantly decreased in severe preeclampsia compared to the control group (p = 0.009 and 0.04, respectively).

CONCLUSION

In severe preeclampsia, cord blood EPCs were reduced markedly and this was accompanied by a significant decrease in cord plasma free VEGF which is known to play a role in EPC mobilization.

Recombinant protein-co-PEG networks as cell-adhesive and proteolytically degradable hydrogel matrixes. Part II: biofunctional characteristics

We present here the biological performance in supporting tissue regeneration of hybrid hydrogels consisting of genetically engineered protein polymers that carry specific features of the natural extracellular matrix, cross-linked with reactive poly(ethylene glycol) (PEG). Specifically, the protein polymers contain the cell adhesion motif RGD, which mediates integrin receptor binding, and degradation sites for plasmin and matrix-metalloproteinases, both being proteases implicated in natural matrix remodeling. Biochemical assays as well as in vitro cell culture experiments confirmed the ability of these protein-PEG hydrogels to promote specific cellular adhesion and to exhibit degradability by the target enzymes. Cell culture experiments demonstrated that proteolytic sensitivity and suitable mechanical properties were critical for three-dimensional cell migration inside these synthetic matrixes. In vivo, protein-PEG matrixes were tested as a carrier of bone morphogenetic protein (rhBMP-2) to heal critical-sized defects in a rat calvarial defect model. The results underscore the importance of fine-tuning material properties of provisional therapeutic matrixes to induce cellular responses conducive to tissue repair. In particular, a lack of rhBMP or insufficient degradability of the protein-PEG matrix prevented healing of bone defects or remodeling and replacement of the artificial matrix. This work confirms the feasibility of attaining desired biological responses in vivo by engineering material properties through the design of single components at the molecular level. The combination of polymer science and recombinant DNA technology emerges as a powerful tool for the development of novel biomaterials.

Efficacy and antivascular effects of EphA2 reduction with an agonistic antibody in ovarian cancer

BACKGROUND

EphA2 is an oncoprotein and tyrosine kinase receptor that is overexpressed in ovarian and many other cancers. We investigated the effects of reduced EphA2 levels on tumor growth and the tumor microenvironment in an orthotopic ovarian cancer model.

METHODS

The effect of the EphA2-agonistic monoclonal antibody EA5, alone or in combination with paclitaxel, on the growth of ovarian cancer cells (SKOV3ip1, HeyA8, and HeyA8MDR [taxane-platinum resistant]) was determined in vitro and in vivo by immunoblotting, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay, and immunohistochemical analysis. Expression of EphA2 and markers of angiogenesis (CD31, vascular endothelial growth factor [VEGF], and basic fibroblast growth factor), proliferation (proliferating cell nuclear antigen), and endothelial cell apoptosis (CD31-terminal deoxynucleotidyl transferase biotin-deoxyuridine triphosphate nick-end labeling colocalization) and phosphorylation of Src were analyzed by immunoblotting, immunohistochemistry, immunofluorescence, and in situ hybridization in tumors from treated mice. Statistical tests were two-sided.

RESULTS

EA5 antibody treatment led to a more than 90% reduction in EphA2 expression in HeyA8 tumors in vivo. In mice bearing orthotopic SKOV3ip1 or HeyA8 tumors, 4 weeks of EA5 treatment resulted in tumors that weighed 31% and 45% less, respectively, than those in control (IgG-treated) mice (95% confidence interval [CI] = -0.09% to 71% and 20% to 70%, P = .27 and .01, respectively). Combination therapy with EA5 and paclitaxel reduced tumor weight by 77% and 80% (95% CI = 63% to 91% and 68% to 91%), respectively, compared with paclitaxel alone and by 92% and 88% (95% CI = 87% to 97% and 80% to 94%), respectively, compared with IgG alone. Combination therapy also reduced the weight of HeyA8MDR tumors by 47% (95% CI = 24% to 72%) compared with paclitaxel. Mice bearing SKOV3ip1 or HeyA8 tumors that were treated with combination therapy survived longer than those treated with paclitaxel alone (median survival = 144 versus 69 days and 46 versus 37 days, respectively). EA5-treated tumors had reduced microvascular density, proliferation, and VEGF protein and mRNA levels, with increased endothelial cell apoptosis. EphA2 was associated with Src, which was rapidly dephosphorylated after EA5 treatment.

CONCLUSIONS

EA5 in combination with paclitaxel decreased tumor growth in an orthotopic ovarian cancer mouse model through antiangiogenic mechanisms associated with reduced levels of VEGF and phosphorylated Src. Humanized antibody constructs against EphA2 are worthy of future study.

Human hepatic sinusoidal endothelial cells can be distinguished by expression of phenotypic markers related to their specialised functions in vivo

The hepatic sinusoids are lined by a unique population of hepatic sinusoidal endothelial cells (HSEC), which is one of the first hepatic cell populations to come into contact with blood components. However, HSEC are not simply barrier cells that restrict the access of blood-borne compounds to the parenchyma. They are functionally specialised endothelial cells that have complex roles, including not only receptor-mediated clearance of endotoxin, bacteria and other compounds, but also the regulation of inflammation, leukocyte recruitment and host immune responses to pathogens. Thus understanding the differentiation and function of HSEC is critical for the elucidation of liver biology and pathophysiology. This article reviews methods for isolating and studying human hepatic endothelial cell populations using in vitro models. We also discuss the expression and functions of phenotypic markers, such as the presence of fenestrations and expression of VAP-1, Stabilin-1, L-SIGN, which can be used to identify sinusoidal endothelium and to permit discrimination from vascular and lymphatic endothelial cells.

Induction of three-dimensional assembly and increase in apoptosis of human endothelial cells by simulated microgravity: impact of vascular endothelial growth factor

Endothelial cells play a crucial role in the pathogenesis of many diseases and are highly sensitive to low gravity conditions. Using a three-dimensional random positioning machine (clinostat) we investigated effects of simulated weightlessness on the human EA.hy926 cell line (4, 12, 24, 48 and 72 h) and addressed the impact of exposure to VEGF (10 ng/ml). Simulated microgravity resulted in an increase in extracellular matrix proteins (ECMP) and altered cytoskeletal components such as microtubules (alpha-tubulin) and intermediate filaments (cytokeratin). Within the initial 4 h, both simulated microgravity and VEGF, alone, enhanced the expression of ECMP (collagen type I, fibronectin, osteopontin, laminin) and flk-1 protein. Synergistic effects between microgravity and VEGF were not seen. After 12 h, microgravity further enhanced all proteins mentioned above. Moreover, clinorotated endothelial cells showed morphological and biochemical signs of apoptosis after 4 h, which were further increased after 72 h. VEGF significantly attenuated apoptosis as demonstrated by DAPI staining, TUNEL flow cytometry and electron microscopy. Caspase-3, Bax, Fas, and 85-kDa apoptosis-related cleavage fragments were clearly reduced by VEGF. After 72 h, most surviving endothelial cells had assembled to three-dimensional tubular structures. Simulated weightlessness induced apoptosis and increased the amount of ECMP. VEGF develops a cell-protective influence on endothelial cells exposed to simulated microgravity.

Heat shock protein 70, heat shock protein 32, and vascular endothelial growth factor production and their effects on lipopolysaccharide-induced apoptosis in porcine aortic endothelial cells

Lipopolysaccharide (LPS) is a highly proactive molecule that causes in vivo a systemic inflammatory response syndrome and activates in vitro the inflammatory pathway in different cellular types, including endothelial cells (EC). Because the proinflammatory status could lead to EC injury and apoptosis, the expression of proinflammatory genes must be finely regulated through the induction of protective genes. This study aimed at determining whether an LPS exposure is effective in inducing apoptosis in primary cultures of porcine aortic endothelial cells and in stimulating heat shock protein (Hsp)70 and Hsp32 production as well as vascular endothelial growth factor (VEGF) secretion. Cells between third and eighth passage were exposed to 10 microg/mL LPS for 1, 7, 15, and 24 hours (time-course experiments) or to 1, 10, and 100 microg/mL LPS for 7 and 15 hours (dose-response experiments). Apoptosis was not affected by 1 microg/mL LPS but significantly increased in a dose-dependent manner with the highest LPS doses. Furthermore, apoptosis rate increased only till 15 hours of LPS exposure. LPS stimulated VEGF secretion in a dose-dependent manner; its effect became significant after 7 hours and reached a plateau after 15 hours. Both Hsp70 and Hsp32 expressions were induced by LPS in a dose-dependent manner after 7 hours. Subsequent studies were addressed to evaluate the protective role of Hsp32, Hsp70, and VEGF. Hemin, an Hsp32 inducer (5, 20, 50 microM), and recombinant VEGF (100 and 200 ng/mL), were added to the culture 2 hours before LPS (10 microg/mL for 24 hours); to induce Hsp70 expression, cells were heat shocked (42 degrees C for 1 hour) 15 hours before LPS (10 microg/mL for 24 hours). Hemin exposure upregulated Hsp32 expression in a dose-dependent manner and protected cells against LPS-induced apoptosis. Heat shock (HS) stimulated Hsp70 expression but failed to reduce LPS-induced apoptosis; VEGF addition did not protect cells against LPS-induced apoptosis at any dose tested. Nevertheless, when treatments were associated, a reduction of LPS-induced apoptosis was always observed; the reduction was maximal when all the treatments (HS + Hemin + VEGF) were associated. In conclusion, this study demonstrates that LPS is effective in evoking "the heat shock response" with an increase of nonspecific protective molecules (namely Hsp70 and Hsp32) and of VEGF, a specific EC growth factor. The protective role of Hsp32 was also demonstrated. Further investigations are required to clarify the synergic effect of Hsp32, Hsp70, and VEGF, thus elucidating the possible interaction between these molecules.

Constitutive and inducible expression and regulation of vascular endothelial growth factor

Vascular endothelial growth factor (VEGF), which was originally discovered as vascular permeability factor, is critical to human cancer angiogenesis through its potent functions as a stimulator of endothelial cell survival, mitogenesis, migration, differentiation and self-assembly, as well as vascular permeability, immunosuppression and mobilization of endothelial progenitor cells from the bone marrow into the peripheral circulation. Genetic alterations and a chaotic tumor microenvironment, such as hypoxia, acidosis, free radicals, and cytokines, are clearly attributed to numerous abnormalities in the expression and signaling of VEGF and its receptors. These perturbations confer a tremendous survival and growth advantage to vascular endothelial cells as manifested by exuberant tumor angiogenesis and a consequent malignant phenotype. Understanding the regulatory mechanisms of both inducible and constitutive VEGF expression will be crucial in designing effective therapeutic strategies targeting VEGF to control tumor growth and metastasis. In this review, molecular regulation of VEGF expression in tumor cells is discussed.

Protective effect of vascular endothelial growth factor/vascular permeability factor 165 and 121 on glomerular endothelial cell injury in the rat

Vascular endothelial growth factor/vascular permeability factor (VEGF/VPF) promotes the repair of injured vessels by stimulating angiogenesis. VEGF/VPF reportedly has cytoprotective activity but no study has shown the protective effect of VEGF/VPF on glomerular endothelial cells. We examined whether recombinant VEGF/VPF121 and VEGF/VPF165 isoforms could prevent injury of glomerular endothelial cells. Mild glomerular injury was induced in rats by an intravenous-injection of a limited dose of anti-Thy-1.1 antibody to obtain lesions similar to those found in the human disease. Recombinant VEGF/VPF165, VEGF/VPF121 or BSA was administered 4 h before the injection of the antibody, and once daily for 3 days. In the BSA-injected rats, mesangial cell lysis and endothelial cell injury in dilated capillary tufts were evident without endothelial cell apoptosis on days 1-4. Thereafter, cell proliferation and repair began and remodeling of the glomeruli was completed by day 28. Macrophages but not polymorphonuclear leukocytes accumulated significantly in the glomeruli on days 1-4. Treatment with VEGF/VPF isoform protected endothelial cells but not mesangial cells from destruction on day 1, and accelerated the repair of both types of cells, which was completed by day 18, 10 days earlier than that of the control animals. The results indicate that VEGF/VPF121 or VEGF/VPF165 can protect glomerular endothelial cells against injury, independent of apoptosis-inhibition activity, thereby promoting reconstruction of glomeruli. The protective effect of VEGF/VPF on endothelial cells suggests that it could provide therapeutic benefit for certain kidney diseases.

Pathology of pulmonary hypertension

This article briefly discusses the traditional concepts of severe pulmonary hypertension and then details how the concept of severe pulmonary hypertension has moved from a vasoconstrictive to an angioproliferative disorder.

EGF-Like domain of tenascin-C is proapoptotic for cultured smooth muscle cells

OBJECTIVE

Based on our previous observations on the expression of Tenascin-C (Tn-C) in human atherosclerotic plaques and its colocalization with macrophages, we explored whether Tn-C undergoes fragmentation and the potential pathobiological significance of this fragmentation.

METHODS AND RESULTS

Using cultured human smooth muscle cells (SMCs), we found that Tn-C upregulates expression of matrix metalloproteinases (MMPs). Western blot analysis revealed that Tn-C substrate is fragmented and most of the cleavage products have fibronectin-like and epidermal growth factor-like (EGF-like) domains of Tn-C. One fragment that contains an EGF-like domain was found in some human atherosclerotic plaques. Cell culture studies revealed that the recombinant EGF-like domain inhibits growth, induces apoptosis of SMCs in a dose-dependent, time-dependent, and caspase-dependent manner, and activates caspase-3 before SMC detachment. Conversely, the caspase inhibitor z-YVAD.cmk, serum, and protease inhibitors blocked cell apoptosis conferred by the EGF-like domain. In addition, these inhibitors blocked EGF-like domain-induced caspase-3 activation. In contrast to this EGF-like domain, intact Tn-C, its fibronectin-like, and its fibrinogen-like domains were inactive.

CONCLUSIONS

Together with our previous observations, our data suggest that Tn-C upregulates MMP expression that cleaves Tn-C into fragments containing the EGF-like domain. This domain has proapoptotic activity for SMCs.

Carboplatin selectively induces the VEGF stress response in endothelial cells: Potentiation of antitumor activity by combination treatment with antibody to VEGF

Vascular Endothelial Growth Factor (VEGF) functions as a key regulator in tumor angiogenesis. In addition, VEGF is an important survival factor for endothelial cells under chemical or physical stress. In our report, we show that treatment of endothelial cells with the chemotherapeutic agent carboplatin significantly increased the expression of VEGF. Furthermore, neutralization of secreted VEGF with specific polyclonal anti-VEGF antibodies or monoclonal antibody sensitized endothelial cells to carboplatin treatment and increased apoptosis several-fold. Interestingly, carboplatin treatment did not alter VEGF expression in tumor cells. Similarly, antibody to VEGF did not change the chemosensitivity of tumor cells to this drug. Most importantly, tumor-bearing animals treated with carboplatin showed an increase in VEGF immunoreactivity in the tumor vasculature, confirming the in vitro studies. Based on these observations, we determined whether neutralization of VEGF could enhance the anti-tumor activity of carboplatin in an in vivo ovarian cancer model system. A combination therapy consisting of a suboptimal dose of carboplatin (32.5 mg/kg/inj., q3d x 5; i.p.) and polyclonal anti-VEGF antibody (2 mg/inj., q3d x 10; i.p.) significantly enhanced solid tumor growth inhibition over individual monotherapies and included multiple complete responses. These findings suggest that VEGF is a critical endothelial cell specific survival factor that is induced by carboplatin and contributes to the protection of tumor vasculature during chemotherapy treatment. In addition, these results provide evidence for a potential mechanism that underlies enhanced anti-tumor activity achieved with chemotherapy and anti-VEGF antibody combination treatment regimens as recently reported in a number of clinical trials. We conclude that a similar type of combination therapy may be applicable to many types of malignancies since VEGF expression was differentially induced in the tumor host environment (i.e., tumor vasculature) and not in the tumor cells themselves; hence, this phenomenon may be independent of the type and origin of the primary cancer.

Neutralization of circulating vascular endothelial growth factor (VEGF) by anti-VEGF antibodies and soluble VEGF receptor 1 (sFlt-1) induces proteinuria

There are about 2.5 million glomeruli in the kidneys each consisting of a barrel of glomerular basement membrane surrounded by glomerular endothelial cells on the inside and glomerular epithelial cells with established foot processes (podocytes) on the outside. Defects in this filtration apparatus lead to glomerular vascular leak or proteinuria. The role of vascular endothelial growth factor (VEGF) in the regulation of glomerular vascular permeability is still unclear. Recent studies indicate that patients receiving anti-VEGF antibody therapy may have an increased incidence of proteinuria. In a different setting, pregnancies complicated by preeclampsia are associated with elevated soluble VEGF receptor 1 protein (sFlt-1), endothelial cell dysfunction and proteinuria. These studies suggest that neutralization of physiologic levels of VEGF, a key endothelial survival factor, may lead to proteinuria. In the present study, we evaluated the potential of anti-VEGF neutralizing antibodies and sFlt-1 in the induction of proteinuria. Our studies demonstrate that anti-VEGF antibodies and sFlt-1 cause rapid glomerular endothelial cell detachment and hypertrophy, in association with down-regulation of nephrin, a key epithelial protein in the glomerular filtration apparatus. These studies suggest that down-regulation or neutralization of circulating VEGF may play an important role in the induction of proteinuria in various kidney diseases, some forms of cancer therapy and also in women with preeclampsia.

Effects of blocking platelet-derived growth factor-receptor signaling in a mouse model of experimental prostate cancer bone metastases

BACKGROUND

Expression of platelet-derived growth factor (PDGF) and activation (by autophosphorylation) of its receptor (PDGF-R), a tyrosine kinase, are associated with the growth of metastatic prostate tumor cells in the bone parenchyma. The tyrosine kinase inhibitor STI571 blocks the PDGF signaling pathway by inhibiting PDGF-R autophosphorylation. We examined the effects of STI571, given alone or with paclitaxel (Taxol), on tumor growth in a mouse model of prostate cancer metastasis.

METHODS

Human prostate cancer PC-3MM2 cells were injected into the tibias of male nude mice. Three days later the mice (20 per group) were randomly assigned to 5 weeks of treatment with oral and injected water (control), daily oral STI571, weekly injected paclitaxel, or STI571 plus paclitaxel. Lesions in bone and the surrounding muscles were then harvested and analyzed by histology, western blotting (for PDGF-R phosphorylation), immunohistochemistry (for expression of proangiogenic molecules), and double immunofluorescence (to identify endothelial cells and apoptotic tumor cells). Growth of bone lesions was monitored by digital radiography. Bone lesions from control mice were used to establish short-term cell cultures for analysis of PDGF-R phosphorylation. All statistical tests were two-sided.

RESULTS

PC-3MM2 cells cultured from bone lesions and treated in vitro with STI571 had less phosphorylated PDGF-R than untreated cells. In control mice, bone lesions expressed high levels of PDGF and activated (i.e., phosphorylated) PDGF-R, whereas lesions in the adjacent musculature did not. Activated PDGF-R was present on the surface of endothelial cells within the bone lesions but not in endothelial cells of uninjected bone. Mice treated with STI571 or STI571 plus paclitaxel had a lower tumor incidence, smaller tumors, and less bone lysis and lymph node metastasis than mice treated with water or paclitaxel alone (P<.001 for all). Mice treated with STI571 or STI571 plus paclitaxel had less phosphorylated PDGF-R on tumor cells and tumor-associated endothelial cells, less tumor cell proliferation, statistically significantly more apoptotic tumor cells (all P<.001), and fewer tumor-associated endothelial cells (P<.001) than control mice.

CONCLUSIONS

Endothelial cells appear to express phosphorylated PDGF-R when they are exposed to tumor cells that express PDGF. Using STI571 to inhibit PDGF-R phosphorylation may, especially in combination with paclitaxel, produce substantial therapeutic effects against prostate cancer bone metastasis.

Differential assessment of angiogenic activity and of vascular survival ability (VSA) in breast cancer

Recent reports provide evidence that some growth factors behave as inhibitors of the apoptosis of the endothelial cells, bringing forward the concept of vascular survival as a post-angiogenesis process. At least two different vasculature development processes occur within a tumor: the angiogenic (formation of new vessels) and the vascular survival pathway, which is devoted to the preservation of the newly-formed vessels in layers that lose contact with the adjacent normal tissue. We developed a method to assess these processes in tissue samples. We noted that differences among tumors may exist not only in the tumor angiogenic activity (TAA) but also in the vascular survival ability (VSA). One third of the highly angiogenic breast cancer cases examined had a poor ability to maintain high vessel density in inner tumor areas. Both parameters are independently related to prognosis, while VSA was directly related to tumor dimensions and node involvement. Patients with high TAA and VSA had a particularly poor prognosis. It is suggested that although cancer angiogenic activity is important for the local invasion and dissemination into vessels and lymphatics, the VSA may be important for the effective formation of viable tumor foci in lymph nodes or distant organs. Recognition and quantification of the vascular survival ability in human tumors may significantly improve the prognostic value of the assessment of tumor vasculature, and may help to stratify patients for clinical trials with novel anti-angiogenic or angiotoxic drugs. Elucidation of the pathways may provide additional targets for antiangiogenic therapy.

Upregulated hypoxia inducible factor-1alpha and -2alpha pathway in rheumatoid arthritis and osteoarthritis

The pathogenesis of rheumatoid arthritis (RA) and osteoarthritis (OA) remains obscure, although angiogenesis appears to play an important role. We recently confirmed an overexpression of two angiogenic factors, namely vascular endothelial growth factor (VEGF) and platelet-derived endothelial cell growth factor (PD-ECGF), by the lining and stromal cells of the synovium in both conditions. Because hypoxia inducible factor (HIF)-1alpha and HIF-2alpha are essential in regulating transcription of the VEGF gene, active participation of HIF-alpha molecules in the pathogenesis of these arthritides is anticipated. We investigated the immunohistochemical expression of HIF-1alpha and HIF-2alpha in the synovium of 22 patients with RA, 34 patients with OA and 22 'normal' nonarthritic individuals, in relation to VEGF, VEGF/KDR (kinase insert domain protein receptor) vascular activation, PD-ECGF and bcl-2. A significant cytoplasmic and nuclear overexpression of HIF-1alpha and HIF-2alpha was noted in the synovial lining and stromal cells of both diseases relative to normal. Overexpression of HIF-alphas was related to high microvessel density, high PD-ECGF expression and high VEGF/KDR receptor activation, suggesting HIF-alpha-dependent synovial angiogenesis in OA. By contrast, the activation of the angiogenic VEGF/KDR pathway was persistently increased in RA, as indeed was microvessel density and the expression of PD-ECGF, irrespective of the extent of HIF-alpha expression, indicating a cytokine-dependent angiogenesis. In all cases, the VEGF/KDR vascular activation was significantly lower in OA than in RA, suggesting a relative failure of the HIF-alpha pathway to effectively produce a viable vasculature for OA, which is consistent with the degenerative nature of the disease. The activation of the HIF-alpha pathway occurs in both RA and OA, although for unrelated reasons.

Aplidine, a new anticancer agent of marine origin, inhibits vascular endothelial growth factor (VEGF) secretion and blocks VEGF-VEGFR-1 (flt-1) autocrine loop in human leukemia cells MOLT-4

The mechanism by which aplidine, a marine natural product in early clinical development as an anticancer agent, induces cell growth inhibition and apoptosis has been investigated in the human leukemia cell line MOLT-4. This cell line is characterized not only by the ability to secrete VEGF, but also for the presence on its surface of the VEGF receptor-1 (VEGFR-1). Previous studies from our laboratory concerned with evaluating early changes in gene expression induced by aplidine in MOLT-4 cells have shown that the drug decreases the expression of VEGFR-1 (Marchini et al. Proc Am Assoc Cancer Res 2000; 41: 833). Here, we report the ability of aplidine to block the VEGF/VEGFR-1 loop. We found that aplidine blocked VEGF secretion that was temporally followed by a decrease in both VEGF and VEGFR-1 production. Aplidine did not directly affect either VEGF transcription or stabilization of its mRNA. Transfection of MOLT-4 cells with an antisense VEGF cDNA construct, resulted in inhibition of colony formations. One clone, transfected with sense VEGF cDNA, secreting 8-10 times more VEGF than parental cells, was less sensitive to aplidine-induced cytotoxicity and apoptosis than control cells. Moreover, addition of VEGF in the medium decreased the activity of aplidine in MOLT-4 cells. These data demonstrate that aplidine inhibits the growth and induces apoptosis in MOLT-4 cells through the inhibition of VEGF secretion which blocks the VEGF/VEGFR-1 autocrine loop necessary for the growth of these cells.

Redox signaling in vascular angiogenesis

Angiogenesis is thought to be regulated by several growth factors (EGF, TGF-alpha, beta-FGF, VEGF). Induction of these angiogenic factors is triggered by various stresses. For instance, tissue hypoxia exerts its pro-angiogenic action through various angiogenic factors, the most notable being vascular endothelial growth factor, which has been mainly associated with initiating the process of angiogenesis through the recruitment and proliferation of endothelial cells. Recently, reactive oxygen species (ROS) have been found to stimulate angiogenic response in the ischemic reperfused hearts. Short exposure to hypoxia/reoxygenation, either directly or indirectly, produces ROS that induce oxidative stress which is associated with angiogenesis or neovascularization. ROS can cause tissue injury in one hand and promote tissue repair in another hand by promoting angiogenesis. It thus appears that after causing injury to the cells, ROS promptly initiate the tissue repair process by triggering angiogenic response.

Blockade of epidermal growth factor receptor signaling on tumor cells and tumor-associated endothelial cells for therapy of human carcinomas

The purpose of this study was to determine whether the expression of epidermal growth factor receptor (EGF-R) and activated EGF-R by tumor-associated endothelial cells is influenced by interaction with specific growth factors in the microenvironment. Different human carcinoma cell lines expressing EGF-R with low or high levels of EGF/transforming growth factor (TGF)-alpha were implanted into orthotopic organs of nude mice. In the EGF/TGF-alpha-positive bladder cancer (253J-BV), pancreatic cancer (L3.6pl), and renal cancer (RBM1-IT) but not in the EGF/TGF-alpha-negative renal cancer SN12-PM6, tumor-associated endothelial cells expressed EGF-R and activated EGF-R. Mice were implanted with human 253J-BV bladder tumors (EGF+) or human SN12-PM6 renal tumors (EGF-). Treatment with oral PKI 166 (a specific inhibitor of EGF-R phosphorylation) alone, intraperitoneal paclitaxel alone (253J-BV), gemcitabine alone (SN12-PM6), or combination of PKI 166 and chemotherapy produced a 60%, 32%, or 81% reduction in the volume of 253J-BV bladder tumors, respectively, and 26%, 23%, or 51% reduction in the volume of SN12-PM6 kidney tumors, respectively. Immunohistochemical analyses demonstrated down-regulation of activated EGF-R in EGF/TGF-alpha-positive and EGF/TGF-alpha-negative lesions from mice treated with PKI 166, although apoptosis of tumor-associated endothelial cells was found only in EGF/TGF-alpha-positive tumors. Collectively, these data suggest that expression of activated EGF-R by tumor-associated endothelial cells provides an important target for therapy.

Matrix regulation of skeletal cell apoptosis II: role of Arg-Gly-Asp-containing peptides

This investigation was based on the assumption that arg-gly-asp (RGD)-containing peptides are released from the extracellular matrix of bone and cartilage during the remodeling cycle. We asked the question: Can RGD peptides influence skeletal cell viability? Primary human osteoblasts, mouse MC-3T3-E1 cells, and chick chondrocytes were incubated with purified RGD-containing peptides and cell viability was determined. The RGD peptide did not kill osteoblasts, chondrocytes, or MC-3T3-E1 cells. In contrast, RGDS and GRGDSP peptides killed all three cell types. Osteoblast death was quite rapid, occurring within 6 h of treatment. transferase uridyl mediated nick end labeling (TUNEL) and transmission electron microscopy (TEM) analysis indicated that death was mediated by apoptosis. To learn if mitochondria transduced the death signal, cells were treated with RGDS and organelle function was evaluated using a voltage-sensitive fluorescent probe. It was observed that there was no net loss of fluorescence and, hence, it was concluded that mitochondria were not the primary effectors of the apoptotic response. Experiments were performed with enzyme inhibitors to determine the import of the caspase pathway on RGDS-mediated osteoblast apoptosis. Results of these studies, as well as a study conducted using a fluorescent substrate, pointed to caspase 3 mediating the effector stage of the apoptotic process. Finally, using a purified labeled-RGDS peptide, we showed that the molecule was not restricted by the plasma membrane because it was accumulated in the cytosolic compartment. Results of the investigation support the view that resorption of the extracellular matrix generates peptide products that can induce apoptosis of vicinal cells.

Differential mitogenic responses of human macrovascular and microvascular endothelial cells to cytokines underline their phenotypic heterogeneity

A variety of growth factors promote the complex multistep process of angiogenesis. The mitogenic activity of vascular endothelial growth factors (VEGFs) and placental growth factors (PlGFs), known as cytokines acting predominantly on endothelial cells, was tested on human umbilical vein endothelial cells (HUVEC) and microvascular endothelial cells (MIEC) and compared with the potency of the universally acting basic fibroblast growth factor (FGF-2). The cells were seeded at different cell numbers and incubated with various doses of growth factors for a period of 24-72 h in culture medium +/- serum. Proliferation was determined by measuring the optical density after staining the cells with the tetrazolium salt WST-1. VEGF121 and VEGF165 increased the number of HUVEC and MIEC at low and high seeding densities various doses and incubation times. The efficiency of FGF-2 was less pronounced at high seeding densities of the cells under serum-free conditions. PlGF-1 and PlGF-2 stimulated mitogenesis on HUVEC only at low cell numbers and after a short incubation time by 125 +/- 3% and 102 +/- 5% (P < 0.001), respectively. Longer incubation times with the lower seeding density in the absence of FCS did not induce a significant stimulatory effect of the PlGFs. MIEC responded stronger to all growth factors. In particular under serum free conditions, PlGF-1 and PlGF-2 effectively stimulated cell proliferation by 247 +/- 54% (P < 0.01) and 288 +/- 40% (P < 0.05) at low cell numbers, and by 81 +/- 13% (P < 0.05) and 49 +/- 13% (P < 0.01), respectively, at high cell numbers. The addition of fetal calf serum caused a reduced proliferative response of all growth factors on both cell types related to the controls. In conclusion, MIEC and HUVEC differ in their proliferative response to VEGFs, PlGFs and FGF-2.

Differential regulation of diverse physiological responses to VEGF in pulmonary endothelial cells

The mechanisms responsible for the divergent physiological responses of endothelial cells to vascular endothelial growth factor (VEGF) are incompletely understood. We hypothesized that VEGF elicits increased endothelial permeability and cell migration via differential activation of intracellular signal transduction pathways. To test this hypothesis, we established a model of VEGF-induced endothelial barrier dysfunction and chemotaxis with bovine pulmonary endothelial cells. We compared the effects of VEGF on transendothelial electrical resistance (TER), actin cytoskeletal remodeling, and chemotaxis of lung endothelial cells and then evaluated the role of the mitogen-activated protein kinases (MAPKs) p38 and extracellular signal-regulated kinase (ERK)1/2 in VEGF-mediated endothelial responses. The dose response of pulmonary arterial and lung microvascular endothelial cells to VEGF differed when barrier regulation and chemotaxis were evaluated. Inhibition of tyrosine kinase, phosphoinositol 3-kinase, or p38 MAPK significantly attenuated VEGF-mediated TER, F-actin remodeling, and chemotaxis. VEGF-mediated decreased TER was also significantly attenuated by inhibition of ERK1/2 MAPK but not by inhibition of fetal liver kinase-1 (flk-1) or Src kinase. In contrast, VEGF-mediated endothelial migration was not attenuated by ERK1/2 inhibition but was abolished by inhibition of either flk-1 or Src kinase. These data suggest potential mechanisms by which VEGF may differentially mediate physiological responses in vivo.

Suppression of angiogenesis and therapy of human colon cancer liver metastasis by systemic administration of interferon-alpha

The purpose of this study was to determine whether systemic administration of interferon-alpha (IFN-alpha) can inhibit liver metastasis produced in nude mice by human colon cancer cells. KM12L4 (IFN-alpha-sensitive) or KM12L4 IFN(R) (IFN-alpha-resistant) cells were injected into the spleen of nude mice. Seven days later, the mice were treated with subcutaneous (s.c.) injections of IFN-alpha (70,000 units/week) at different dosing schedules (1, 2, or 7 times/week). Significant inhibition of tumor growth, vascularization and expression of basic fibroblast growth factor (bFGF) or matrix metalloproteinase-9 (MMP-9) mRNA and protein occurred in mice given daily injections of IFN-alpha. Kinetic analysis of therapy showed that daily s.c. administrations of 10,000 units of IFN-alpha induced apoptosis in liver metastasis-associated endothelial cells, followed by inhibition of tumor cell division and apoptosis of tumor cells. These data suggest that the antiangiogenic activity of IFN-alpha-2a depends on frequent administration of the optimal biologic dose.

Respiratory syncytial virus stimulation of vascular endothelial cell growth Factor/Vascular permeability factor

We hypothesized that respiratory syncytial virus (RSV)-induced pathologies could be mediated, in part, by vascular active cytokines elaborated during virus infection. To address this hypothesis, we determined whether RSV stimulated vascular endothelial cell growth factor (VEGF)/vascular permeability factor (VPF) elaboration in vitro. Supernatants from unstimulated A549 cells and normal human bronchial epithelial cells contained modest levels of VEGF. In contrast, supernatants from RSV-infected cells contained elevated levels of VEGF/VPF. This stimulation was seen after as little as 2 h, was still prominent after 48 h, and, by immunoblot, was specific for the 165- and 121-amino acid isoforms of VEGF/VPF. It was not associated with significant cell cytotoxicity or alterations in VEGF messenger RNA. It did, however, require new protein biosynthesis. In accordance with these findings, the 165- and 121-amino acid isoforms of VEGF/VPF were also found in the nasal washings from patients with RSV infections. These studies demonstrate that RSV is a potent stimulator of VEGF/VPF elaboration and that, in vitro, this stimulation is mediated via a noncytotoxic translational and/or post-translational biosynthetic mechanism. VEGF/VPF may play an important role in the pathogenesis of RSV-induced disorders.

'Invading edge vs. inner' (edvin) patterns of vascularization: an interplay between angiogenic and vascular survival factors defines the clinical behaviour of non-small cell lung cancer

Neo-angiogenesis during neoplastic growth involves endothelial mitogenic and migration stimuli produced by cancer or tumour stromal cells. Although this active angiogenesis takes place in the tumour periphery, the process of vessel growth and survival in inner areas and its clinical role remain largely unexplored. The present study compared the microvessel score (MS) as well as the single endothelial cell score (ECS) in the invading edge and in inner areas of non-small cell lung carcinomas (NSCLCs). Three different patterns of vascular growth were distinguished: the edvin (edge vs. inner) type 1, where a low MS was observed in both peripheral and inner tumour areas; the edvin type 2, where a high MS was noted in the invading front but a low MS in inner areas; and the edvin type 3, where both peripheral and inner tumour areas had a high MS. The ECS was high in the invading edge in edvin type 2 and 3 cases and was sharply decreased in both types in inner areas, suggesting that endothelial cell migration is unlikely to contribute to the angiogenic process in areas away from the tumour front. Expression of the vascular endothelial growth factor (VEGF) and of thymidine phosphorylase (TP) was associated with a high MS in the invading edge. VEGF was associated with a high MS in inner areas (edvin 3), while TP expression was associated with edvin type 2, showing that VEGF (and not TP) contributes to the preservation of the inner vasculature. Both edvin type 2 and 3 cases showed an increased incidence of node metastasis, but edvin type 3 cases had a poorer prognosis, even in the N1-stage group. The present study suggests that tumour factors regulating angiogenesis and vascular survival are not identical. A possible method is reported to quantify these two parameters by comparing the MS in the invading edge and inner areas (edvin types). This observation may contribute to the evaluation of the effectiveness of different therapeutic approaches, namely vascular targeting vs. anti-angiogenesis.

Apoptosis in the vasculature: mechanisms and functional importance

Apoptotic death has now been recognized in a number of common and threatening vascular diseases, including atherosclerosis. Interest in apoptosis research relates to the fact that apoptosis, in contrast to oncosis, is a highly regulated process of cell death which raises the hope for the development of specific therapeutic strategies to alter disease progression. This review summarizes the mechanisms involved in vascular endothelial and smooth muscle cell survival/apoptosis, and the potential roles of apoptotic death in atherosclerosis and restenosis. The potential effects of modulation of apoptosis in these diseases are also discussed.

Regulation of placental vascular endothelial growth factor (VEGF) and placenta growth factor (PIGF) and soluble Flt-1 by oxygen--a review

Morphological studies show poor placental vascular development and an increase in the mitotic index of cytotrophoblast cells in intrauterine growth restriction (IUGR). We hypothesized that the reported relatively high oxygen level in the intervillous space in contact with IUGR placental villi will limit angiogenesis by changes in vascular endothelial growth factor (VEGF) and placenta growth factor (PIGF) expression and function. Western immunoblot analysis demonstrates a diametric expression of PIGF and VEGF proteins throughout pregnancy, with P1GF levels increasing and VEGF levels decreasing, consistent with placental oxygenation. PIGF mRNA and protein is increased in IUGR as compared to gestationally matched normal placentae. Increasing oxygen tension upregulates P1GF protein in term placental villous explants, whereas hypoxia downregulates P1GF and VEGFR-1 (Flt-1) autophosphorylation in term trophoblast choriocarcinoma cell line (BeWo). Levels of soluble Flt-1 (sFlt-1) protein in supernatant of term villous explants were upregulated by 1 per cent hypoxia, whereas hyperoxia (40 per cent) decreased sFlt-1 levels, indicating that under conditions of increasing oxygen tension, PlGF function may remain unopposed. The addition of PlGF-1 to a spontaneously transformed first trimester cytotrophoblast cell line (ED27) stimulated cell proliferation while PlGF-2 had little effect. In contrast, the addition of PlGF-1 had little effect on endothelial cell proliferation while this was inhibited by PIGF-2. Taken together these changes provide a molecular explanation for the observed poor angiogenesis in the pathogenesis of IUGR.