VEGF function for upregulation of endogenous PlGF expression during FGF-2-mediated therapeutic angiogenesis

Metamorphic Effect of Angiogenic Switch in Tumor Development: Conundrum of Tumor Angiogenesis Toward Progression and Metastatic Potential

Our understanding of angiogenesis has significantly expanded over the past five decades. More recently, research has focused on this process at a more molecular level, looking at it through the signaling pathways that activate it and its non-direct downstream effects. This review discusses current findings in molecular angiogenesis, focusing on its impact on the immune system. Moreover, the impairment of this process in cancer progression and metastasis is highlighted, and current anti-angiogenic treatments and their effects on tumor growth are discussed.

Design of a dual-function agent by fusing a designed anti-VEGF-A binder and CPG-2 enzyme

Anti-VEGF therapies are common for the treatment of cancer. Carboxypeptidase G (CPG-2) enzyme is a zinc-dependent metalloenzyme that metabolizes non-toxic synthetic 'benzoic mustard prodrugs' to cytotoxic moieties in tumor cells. In this study, we designed a dual-activity agent by combining a designed anti-VEGF- and CPG-2 enzyme to convert methotrexate (MTX). VEGF-A was docked against a set of scaffolds, and suitable inverse rotamers were made. Rosetta design was used for the interface design. The top 1200 binders were chosen by flow cytometry and displayed in yeast. The activity of CPG-2 enzyme was analyzed at different temperature conditions and in the presence of the substrate, MTX. Optimal binders were selected and protein was eluted using immobilized metal affinity chromatography and size-exclusion chromatography. Both, native PAGE and on-yeast flow cytometry confirmed the binding of the binder to VEGF-A. The activity of truncated enzymes was slightly lower than that of full-length enzymes linked to VEGF-A. The method should be generally useful as a dual-activity agent for targeting VEGF-A and combination therapy with the enzyme CPG-2 for metabolizing non-toxic prodrugs to cytotoxic moieties.Communicated by Ramaswamy H. Sarma.

Evaluation of the Effect of the Fibroblast Growth Factor Type 2 (FGF-2) Administration on Placental Gene Expression in a Murine Model of Preeclampsia Induced by L-NAME

The abnormal implantation of the trophoblast during the first trimester of pregnancy precedes the appearance of the clinical manifestations of preeclampsia (PE), which is a hypertensive disorder of pregnancy. In a previous study, which was carried out in a murine model of PE that was induced by NG-nitro-L-arginine methyl ester (L-NAME), we observed that the intravenous administration of fibroblast growth factor 2 (FGF2) had a hypotensive effect, improved the placental weight gain and attenuated the fetal growth restriction, and the morphological findings that were induced by L-NAME in the evaluated tissues were less severe. In this study, we aimed to determine the effect of FGF2 administration on the placental gene expression of the vascular endothelial growth factor (VEGFA), VEGF receptor 2 (VEGFR2), placental growth factor, endoglin (ENG), superoxide dismutase 1 (SOD1), catalase (CAT), thioredoxin (TXN), tumor protein P53 (P53), BCL2 apoptosis regulator, Fas cell surface death receptor (FAS), and caspase 3, in a Sprague Dawley rat PE model, which was induced by L-NAME. The gene expression was determined by a real-time polymerase chain reaction using SYBR green. Taking the vehicle or the L-NAME group as a reference, there was an under expression of placental VEGFA, VEGFR2, ENG, P53, FAS, SOD1, CAT, and TXN genes in the group of L-NAME + FGF2 (p < 0.05). The administration of FGF2 in the murine PE-like model that was induced by L-NAME reduced the effects that were generated by proteinuria and the increased BP, as well as the response of the expression of genes that participate in angiogenesis, apoptosis, and OS. These results have generated valuable information regarding the identification of molecular targets for PE and provide new insights for understanding PE pathogenesis.

RNF213 gene silencing upregulates transforming growth factor β1 expression in bone marrow-derived mesenchymal stem cells and is involved in the onset of Moyamoya disease

Moyamoya disease (MMD) is a chronic and progressive cerebrovascular occlusion disease, the precise etiology of which is poorly understood. Ring finger protein 213 (RNF213) has been previously identified as a susceptibility gene that serves an important role in angiogenesis, where it has been shown to be closely associated with the onset of MMD. Patients with MMD exhibit increased expression levels of various pro-inflammatory molecules and angiogenic factors. Under certain conditions, bone marrow mesenchymal stem cells (BMSCs) have the ability to differentiate to form neuron-like and microglia-like cells. In the present study, a total of 40 MMD patients and 40 healthy individuals were enrolled. ELISA assays revealed that the expression of serum vascular endothelial growth factor (VEGF) and transforming growth factor β1 (TGF-β1) were higher than that in healthy controls. Furthermore, rat BMSCs (rBMSCs) were isolated and cultured using the whole bone marrow adherence method, which were then phenotyped using flow cytometry. Osteogenic and adipogenic differentiation were determined by using Alizarin red and oil red O staining, respectively. RNF213 was knocked-down using a lentivirus-mediated short hairpin RNA system in passage three rBMSCs, and successful transfection of the RNF213 was confirmed by RT-qPCR and fluorescence imaging. The expression levels of VEGF and TGF-β1 in these rBMSCs were measured on days 7 and 14, respectively. The results demonstrated that RNF213 knockdown upregulated TGF-β1 at both protein and mRNA levels, but did not exert any effect on VEGF gene expression. In conclusion, these findings suggested that that RNF213 knockdown may contribute to aberrant TGF-β1 expression via a pathway that remains to be unidentified, indicating that quantitative changes in RNF213 gene expression may serve an important role in the pathogenesis of MMD.

VEGF-A Is Associated With the Degree of TILs and PD-L1 Expression in Primary Breast Cancer

BACKGROUND/AIM

Vascular endothelial growth factor-A (VEGF-A), an important angiogenic factor, has been reported to effect cancer growth and development. Recent reports indicated that anti-VEGF therapy has an important effect of enhancing anti-tumor immunity in various cancers. In the current study, we investigated the relationship between VEGF-A expression and immunological factors, including programmed cell death ligand 1 (PD-L1) and the degrees of stromal tumor-infiltrating lymphocytes (TILs) in breast cancer.

PATIENTS AND METHODS

This study enrolled 97 cases with invasive breast cancer who had undergone surgery without preoperative therapy. The grades of stromal-TILs were evaluated using the criteria of the International Working Group for TILs in breast cancer: low, intermediate, and high. VEGF-A and PD-L1 positivity were evaluated by immunohistochemistry. The relationship between VEGF-A expression and the expression of PD-L1 and TILs was investigated.

RESULTS

Among the 97 cases, 37 (38.1%) had positive VEGF-A expression in the breast tumor. We divided the cases in two groups based on the VEGF-A expression levels. The analysis revealed that PD-L1 positivity was significantly associated with VEGF-A expression in the breast tumor (29.7% vs. 10.0%, p=0.014). Among the cases with positive PD-L1, 36.7% of VEGF-positive cases and none of VEGF-negative cases had low TILs in the breast tumor.

CONCLUSION

VEGF-A expression in breast cancer may reflect PD-L1 expression in the tumor. VEGF-A may act as a negative biomarker of TILs in PD-L1-positive breast cancer. Our results suggest that VEGF-A may be predictive of immunological features and may serve as a useful biomarker for immuno-targeting therapy in patients with breast cancer.

Hypoxia Promotes Adipose-Derived Stem Cells to Protect Human Dermal Microvascular Endothelial Cells Against Hypoxia/Reoxygenation Injury

BACKGROUND

Microcirculation is important for regulating ischemia-reperfusion (I/R) injury associated with skin flap transplantation surgery. We investigated whether co-culture with adipose-derived stem cells (ADSCs) could protect human dermal microvascular endothelial cells (HDMECs) from I/R injury by inhibiting cell apoptosis and enhancing cell proliferation. We also investigated the effects of hypoxic preconditioning on ADSCs.

MATERIALS AND METHODS

HDMECs were divided into four groups, control, HDMECs in normoxic culture conditions; hypoxia/reoxygenation (H/R), HDMECs in a hypoxic incubator for 8 h then in saturated aerobic culture medium for 24 h; H/R + ADSC(N), HDMECs treated similar to the H/R group then co-cultured with normoxic ADSCs; and H/R + ADSC(H), HDMECs treated similar to the H/R group then co-cultured with hypoxia preconditioned ADSCs.

RESULTS

The rate of HDMECs apoptosis significantly increased in the H/R group, but decreased upon co-culture with ADSCs for 24 h, especially in the H/R + ADSC(H) group. Co-culture with ADSCs, especially hypoxia preconditioned ADSCs, significantly enhanced cell proliferation ability compared with that of the H/R group after 48 h and 72 h, but not after 24 h. Vascular endothelial growth factor levels were significantly higher in the H/R + ADSC(N) and H/R + ADSC(H) groups than in the H/R group.

CONCLUSIONS

ADSCs attenuated H/R injury in endothelial cells by promoting proliferation ability and reducing apoptosis, with an increase in Vascular endothelial growth factor level, especially in the context of hypoxic preconditioning. This approach suggests the potential for an easy and safe method to reduce I/R injury associated with skin flap transplantation surgery.

Therapeutic Angiogenesis with Somatic Stem Cell Transplantation

Therapeutic angiogenesis is an important strategy to rescue ischemic tissues in patients with critical limb ischemia having no other treatment option such as endovascular angioplasty or bypass surgery. Studies indicated so far possibilities of therapeutic angiogenesis using autologous bone marrow mononuclear cells, CD34⁺ cells, peripheral blood mononuclear cells, adipose-derived stem/progenitor cells, and etc. Recent studies indicated that subcutaneous adipose tissue contains stem/progenitor cells that can give rise to several mesenchymal lineage cells. Moreover, these mesenchymal progenitor cells release a variety of angiogenic growth factors including vascular endothelial growth factor, fibroblast growth factor, hepatocyte growth factor and chemokine stromal cell-derived factor-1. Subcutaneous adipose tissues can be harvested by less invasive technique. These biological properties of adipose-derived regenerative cells (ADRCs) implicate that autologous subcutaneous adipose tissue would be a useful cell source for therapeutic angiogenesis in humans. In this review, I would like to discuss biological properties and future perspective of ADRCs-mediated therapeutic angiogenesis.

Distinct downstream signaling and the roles of VEGF and PlGF in high glucose-mediated injuries of human retinal endothelial cells in culture

Vascular endothelial growth factor (VEGF) and placental growth factor (PlGF) plays a crucial role in breakdown of the blood-retinal barrier due to hyperpermeability in diabetic retinopathy (DR). However, the distinct signaling driven by VEGF and PlGF in the pathogenesis of DR remains unclear. In this study, we investigated VEGF- and PlGF- related signaling pathways and their roles in cultured human microvascular retinal endothelial cells (hRECs) under high glucose conditions (HG; 25 mM). Apoptotic cell death was evaluated, and FITC conjugated bovine serum albumin across monolayer hRECs served as an index of permeability. Western blots were used to assess the protein levels of VEGF and PlGF, as well as the phosphorylation of p38MAPK, STAT1 and Erk1/2. Knockdown of VEGF and PlGF was performed by using siRNA. Following HG treatment, increases of VEGF and PlGF as well as PKC activity were detected in hRECs. Increased phosphorylations of p38MAPK^{Thr180/Thr182}, STAT1^Ser727, and Erk1/2^{Tyr202/Tyr185} as well as VEGFR1^Tyr1213 and VEGFR2^Tyr1175 were also detected in HG-treated hRECs. Inhibition of PKC activity by Go 6976 prevented HG-induced increases of phosphor-Erk1/2 and nitric oxide synthase (NOS1) expressions as well as hyperpermeability, whereas inhibition of p38MAPK pathway by SB203580 selectively suppressed activation of STAT1 and decreased apoptotic cell death under HG conditions. Moreover, VEGF knockdown predominantly inhibited activation of VEGFR2, and phosphorylation of p38MAPK and STAT1, as well as apoptotic cell death in HG-treated hRECs. Nevertheless, PlGF knockdown mainly suppressed phosphorylation of VEGFR1, PKC, and Erk1/2, as well as NOS1 expressions and hyperpermeability. Taken together, we provide evidence demonstrating that HG-induced elevation of PlGF is responsible for hyperpermeability mainly through increasing activation of PKC-Erk1/2-NOS axis via VEGFR1, while HG-induced elevation of VEGF is associated with induction of apoptotic cell death mainly through increasing activation of p38MAPK/STAT1 signaling via VEGFR2.

Combination antitumor immunotherapy with VEGF and PIGF siRNA via systemic delivery of multi-functionalized nanoparticles to tumor-associated macrophages and breast cancer cells

Given that vascular endothelial growth factor (VEGF) and placental growth factor (PIGF), over-expressed in breast cancer cells and M2-like tumor-associated macrophages (M2-TAMs) within tumor microenvironment (TME), work synergistically and independently in mediating tumor progression and immunosuppression, combinatorial immune-based approaches targeting them are expected to be a potent therapeutic modality for patients. Here, polyethylene glycol (PEG) and mannose doubly modified trimethyl chitosan (PEG = MT) along with citraconic anhydride grafted poly (allylamine hydrochloride) (PC)-based nanoparticles (NPs) (PEG = MT/PC NPs) with dual pH-responsiveness were developed to deliver VEGF siRNA (siVEGF)/PIGF siRNA (siPIGF) to both M2-TAMs and breast cancer cells for antitumor immunotherapy. With prolonged blood circulation and intelligent pH-sensitivity, PEG = MT/PC NPs were highly accumulated in tumor tissues and then internalized in M2-TAMs and breast cancer cells via mannose-mediated active targeting and passive targeting, respectively. With the charge-reversal of PC, PEG = MT/PC NPs presented effective endosomal/lysosomal escape and intracellular siRNA release, resulting in efficient gene silencing. Due to the synergism between siVEGF and siPIGF in anti-proliferation of tumor cells and reversal of the TME from pro-oncogenic to anti-tumoral, PEG = MT/PC/siVEGF/siPIGF NPs (PEG = MT/PC/siV-P NPs) exerted robust suppression of breast tumor growth and lung metastasis. This combination strategy may provide a promising alternative for breast cancer therapy.

Ginsenoside Rd regulates the Akt/mTOR/p70S6K signaling cascade and suppresses angiogenesis and breast tumor growth

Blockade of angiogenesis is an important approach for cancer treatment and prevention. In the present study, we investigated the effect of ginsenoside Rd (Rd) on angiogenesis in vitro and in vivo. Our results demonstrated that Rd inhibited vascular endothelial growth factor (VEGF)-induced migration, tube formation and proliferation of primary cultured human umbilical vascular endothelial cells (HUVECs) dose‑dependently. Furthermore, Rd abrogated VEGF-induced sprouting of the vessels from aortic rings, and inhibited vascular formation in the Matrigel plug assay in vivo. Under normoxic or hypoxic conditions, Rd suppressed VEGF‑induced activation of Akt/mammalian target of rapamycin (mTOR) signaling transduction cascades in HUVECs. When intraperitoneally administered to mice bearing human breast cancer (MDA‑MB-231) cell xenografts, Rd significantly decreased the volume and the weight of solid tumors in a dose-dependent manner, and decreased tumor angiogenesis as less Ki67- and CD31-positive cells were found. Additionally, we found that Rd inhibited proliferation and induced apoptosis as well as the inhibition of Akt/mTOR/P70S6 kinase signaling in breast cancer cells. Collectively, our findings revealed that Rd may be a promising anti-angiogenic drug with significant antitumor activity in human breast cancer.

Anticancer effect of rapamycin on MCF-7 via downregulation of VEGF expression

The importance of mTOR signaling in tumor biology is widely accepted and a number of agents that selectively target mTOR are being developed in cancer therapy. On the other hand, it has been demonstrated that mTOR can act as an angiogenic agent. Thus, we hypothesized that the mTOR inhibitor-induced anticancer effect is affected by expression of a key angiogenic factor, vascular endothelial growth factor (VEGF) and investigated the anticancer effect underlying mTOR using an in vitro assay. The mTOR inhibitor rapamycin dose-dependently reduced the cell viability of the breast cancer cell line, MCF-7, but did not reduce the cell viability of the colon cancer cell line, HT-29. Rapamycin reduced the VEGF expression in the culture medium of MCF-7, while rapamycin did not contribute VEGF expression in the culture medium of HT-29. VEGF stimulated cell viability and VEGF inhibition reduced cell viability of MCF-7, and rapamycin dose-dependently restored the cell viability of MCF-7 reduced by rapamycin. These findings suggest that mTOR acts as a direct anticancer agent and that the mTOR-inhibitor-induced anticancer effect involved the reduced expression of VEGF in MCF-7. Our results imply that mTOR regulates the expression of VEGF and is involved in breast cancer progression.

Adequate Selection of a Therapeutic Site Enables Efficient Development of Collateral Vessels in Angiogenic Treatment With Bone Marrow Mononuclear Cells

Background

Induction of angiogenic mechanisms to promote development of collateral vessels is considered promising for the treatment of peripheral arterial diseases. Collateral vessels generally develop from preexisting arteriolar connections, bypassing the diseased artery. We speculated that induction of angiogenic mechanisms should be directed to such arteriolar connections to achieve efficient collateral development. The aim of this study was to verify this hypothesis using autologous transplantation of bone marrow mononuclear cells in the rabbit model of chronic limb ischemia.

Methods and Results

The left femoral artery was excised to induce limb ischemia in male rabbits. In this model, arteriolar connections in the left coccygeofemoral muscle tend to develop into collateral vessels, although this transformation is insufficient to alleviate the limb ischemia. In contrast, arteriolar connections in the closely located adductor muscle do not readily develop into collateral vessels. At 21 days after ischemia initiation, a sufficient number of automononuclear cells were selectively injected in the left coccygeofemoral muscle (coccygeo group) or left adductor muscle (adductor group). Evaluation of calf blood pressure ratios, blood flow in the left internal iliac artery, and angiographic scores at day 28 after injection revealed that collateral development and improvement of limb ischemia were significantly more efficient in the coccygeo group than in the adductor group. Morphometric analysis of the coccygeofemoral muscle at day 14 showed similar results.

Conclusions

Specific delivery of mononuclear cells to the coccygeofemoral but not the adductor muscle effectively improves collateral circulation in the rabbit model of limb ischemia and suggests that adequate site selection can facilitate therapeutic angiogenesis.

Placenta growth factor and vascular endothelial growth factor a have differential, cell-type specific patterns of expression in vascular cells

OBJECTIVE

PLGF, a VEGF-A related protein, mediates collateral enlargement via monocytes but plays little role in capillary proliferation. In contrast, VEGF-A mediates both collateral enlargement and capillary proliferation. PLGF has been less thoroughly studied than VEGF-A, and questions remain regarding its regulation and function. Therefore, our goal was to characterize the expression of PLGF by vascular cells. We hypothesized that vascular SMC would express more PLGF than EC, since VEGF-A is primarily expressed by non-EC.

METHODS

We compared PLGF and VEGF-A across eight EC and SMC lines, then knocked down PLGF and evaluated cell function. We also assessed the effect of hypoxia on PLGF expression and promoter activity.

RESULTS

PLGF was most highly expressed in EC, whereas VEGF-A was most highly expressed in SMC. PLGF knockdown did not affect EC number, migration, or tube formation, but reduced monocyte migration toward EC. Monocyte migration was rescued by exogenous PLGF. Hypoxia increased PLGF protein without activating PLGF gene transcription.

CONCLUSIONS

PLGF and VEGF-A have distinct patterns of expression in vascular cells. EC derived PLGF may function primarily in communication between EC and circulating cells. Hypoxia increases EC PLGF expression posttranscriptionally.

Y-tocotrienol inhibits angiogenesis-dependent growth of human hepatocellular carcinoma through abrogation of AKT/mTOR pathway in an orthotopic mouse model

Angiogenesis is one of the key hallmarks of cancer. In this study, we investigated whether γ-tocotrienol can abrogate angiogenesis-mediated tumor growth in hepatocellular carcinoma (HCC) and if so, through what molecular mechanisms. We observed that γ-tocotrienol inhibited vascular endothelial growth factor (VEGF)-induced migration, invasion, tube formation and viability of HUVECs in vitro. Moreover, γ-tocotrienol reduced the number of capillary sprouts from matrigel embedded rat thoracic aortic ring in a dose-dependent manner. Also, in chick chorioallantoic membrane assay, γ-tocotrienol significantly reduced the blood vessels formation. We further noticed that γ-tocotrienol blocked angiogenesis in an in vivo matrigel plug assay. Furthermore, γ-tocotrienol inhibited VEGF-induced autophosphorylation of VEGFR2 in HUVECs and also suppressed the constitutive activation of AKT/mammalian target of rapamycin (mTOR) signal transduction cascades in HUVECs as well as in HCC cells. Interestingly, γ-tocotrienol was also found to significantly reduce the tumor growth in an orthotopic HCC mouse model and inhibit tumor-induced angiogenesis in HCC patient xenografts through the suppression of various biomarkers of proliferation and angiogenesis. Taken together, our findings strongly suggest that γ-tocotrienol might be a promising anti-angiogenic drug with significant antitumor activity in HCC.

Functional and pathological improvements of the hearts in diabetes model by the combined therapy of bFGF-loaded nanoparticles with ultrasound-targeted microbubble destruction

Diabetic cardiomyopathy (DCM) is the leading cause of morbidity and mortality among the diabetic patients and currently there is no effective means to reverse its pathological progress. Basic fibroblast growth factor (bFGF) has shown promise as a molecular therapy for DCM, but its delivery is inefficient and non-specific. In the present study, a therapy combining nanoparticle (NP) carrier and ultrasound-targeted microbubble destruction (UTMD) was reported the first time for bFGF delivery to the heart of diabetic rats. bFGF-loaded NP (bFGF-NP) were prepared with Poloxamer 188-grafted heparin copolymer using water-in-water technique, and the morphology, encapsulation efficiency, and bioactivity of bFGF-NP were studied. The cellular uptake and cytotoxicity of bFGF-NP were evaluated with primary cultures of the left ventricular (LV) cardiomyocytes in vitro. Therapeutic effects of bFGF-NP/UTMD on the heart of DCM rats were studied by measuring LV systolic and diastolic functions, hemodynamic characteristics and indicators of cardiac remodeling including myocardial collagen volume fraction and capillary density. Results demonstrated that bFGF-NP showed good round morphology, efficient bFGF encapsulation and stable bioactivity of bFGF in vitro. bFGF-NP/UTMD combined treatment significantly enhanced the efficiency of bFGF cellular uptake (P<0.05) without obvious cytotoxicity. Significant improvements (P<0.05) in both cardiac functions and tissue morphology in the DCM rats were observed in bFGF-NP/UTMD group. These were not achievable using free bFGF, bFGF-NP or UTMD treatment alone. Our results show that combining a non-viral vector with UTMD technique is an effective strategy to deliver bFGF to the heart, and the resulting growth factor therapy has demonstrated potential to reverse the progress of DCM by restoring the cardiac functions and even the structure of damaged cardiac tissues.

Human urine-derived stem cells alone or genetically-modified with FGF2 Improve type 2 diabetic erectile dysfunction in a rat model

Aim

The aim of this study was to determine the possibility of improving erectile dysfunction using cell therapy with either human urine-derived stem cells (USCs) or USCs genetically-modified with FGF2 in a type 2 diabetic rat model.

Methods

Human USCs were collected from 3 healthy donors. USCs were transfected with FGF2 (USCs-FGF2). Sixty-five SD male rats were divided into five groups (G). A control group of normal rats (G1, n = 10), and four other test groups of type 2 diabetic erectile dysfunction rats: PBS as a negative control (G2, n = 10), USCs (G3, n = 15), lentivirus-FGF2 (G4, n = 15), and USCs-FGF2 (G5, n = 15). Diabetes was induced in the rats via a high fat diet for 28 days and a subsequent intraperitoneal injection of streptozotocin (35 mg/kg). Erectile dysfunction was screened with apomorphine (100 μg/kg). Cell injections in the test groups (G2–G5) occurred directly into the corpora cavernosa. The implanted cells were tracked at 7 days (n = 5 animals/G) and 28 days (n = 10 animals/G) post injection. Mean arterial pressure (MAP), intracavernosal pressure (ICP), expression of endothelial markers (CD31, VEGF and eNOS), smooth muscle markers (desmin and smoothelin), histological changes and erectile function were assessed for each group.

Results

USCs expressed mesenchymal stem cell markers, and secreted a number of proangiogenic growth factors. USCs expressed endothelial cell markers (CD31 and vWF) after transfection with FGF2. Implanted USCs or USCs-FGF2 displayed a significantly raised ICP and ICP/MAP ratio (p<0.01) 28 days after intracavernous injection. Although few cell were detected within the implanted sites, histological and western blot analysis demonstrated an increased expression of endothelial and smooth muscle markers within the cavernous tissue following USC or USC-FGF2 injection.

Conclusions

The paracrine effect of USCs or USCs-FGF2 induced improvement of erectile function in type 2 diabetic rats by recruiting resident cells and increasing the endothelial expression and contents of smooth muscle.

Instruction of circulating endothelial progenitors in vitro towards specialized blood-brain barrier and arterial phenotypes

OBJECTIVE

The vascular system is adapted to specific functions in different tissues and organs. Vascular endothelial cells are important elements of this adaptation, leading to the concept of 'specialized endothelial cells'. The phenotype of these cells is highly dependent on their specific microenvironment and when isolated and cultured, they lose their specific features after few passages, making models using such cells poorly predictive and irreproducible. We propose a new source of specialized endothelial cells based on cord blood circulating endothelial progenitors (EPCs). As prototype examples, we evaluated the capacity of EPCs to acquire properties characteristic of cerebral microvascular endothelial cells (blood-brain barrier (BBB)) or of arterial endothelial cells, in specific inducing culture conditions.

APPROACH AND RESULTS

First, we demonstrated that EPC-derived endothelial cells (EPDCs) co-cultured with astrocytes acquired several BBB phenotypic characteristics, such as restricted paracellular diffusion of hydrophilic solutes and the expression of tight junction proteins. Second, we observed that culture of the same EPDCs in a high concentration of VEGF resulted, through activation of Notch signaling, in an increase of expression of most arterial endothelial markers.

CONCLUSIONS

We have thus demonstrated that in vitro culture of early passage human cord blood EPDCs under specific conditions can induce phenotypic changes towards BBB or arterial phenotypes, indicating that these EPDCs maintain enough plasticity to acquire characteristics of a variety of specialized phenotypes. We propose that this property of EPDCs might be exploited for producing specialized endothelial cells in culture to be used for drug testing and predictive in vitro assays.

Inhibition of stromal PlGF suppresses the growth of prostate cancer xenografts

The growth and vascularization of prostate cancer is dependent on interactions between cancer cells and supporting stromal cells. The primary stromal cell type found in prostate tumors is the carcinoma-associated fibroblast, which produces placental growth factor (PlGF). PlGF is a member of the vascular endothelial growth factor (VEGF) family of angiogenic molecules and PlGF mRNA levels increase after androgen deprivation therapy in prostate cancer. In this study, we show that PlGF has a direct dose-dependent proliferative effect on human PC-3 prostate cancer cells in vitro and fibroblast-derived PlGF increases PC-3 proliferation in co-culture. In xenograft tumor models, intratumoral administration of murine PlGF siRNA reduced stromal-derived PlGF expression, reduced tumor burden and decreased the number of Ki-67 positive proliferating cells associated with reduced vascular density. These data show that targeting stromal PlGF expression may represent a therapeutic target for the treatment of prostate cancer.

PlGF: a multitasking cytokine with disease-restricted activity

Placental growth factor (PlGF) is a member of the vascular endothelial growth factor (VEGF) family that also comprises VEGF-A (VEGF), VEGF-B, VEGF-C, and VEGF-D. Unlike VEGF, PlGF is dispensable for development and health but has diverse nonredundant roles in tissue ischemia, malignancy, inflammation, and multiple other diseases. Genetic and pharmacological gain-of-function and loss-of-function studies have identified molecular mechanisms of this multitasking cytokine and characterized the therapeutic potential of delivering or blocking PlGF for various disorders.

Macrophage β2 integrin-mediated, HuR-dependent stabilization of angiogenic factor-encoding mRNAs in inflammatory angiogenesis

HuR is a member of the Drosophila Elav protein family that binds mRNA degradation sequences and prevents RNase-mediated degradation. Such HuR-mediated mRNA stabilization, which is stimulated by integrin engagement and is controlled at the level of HuR nuclear export, is critically involved in T-cell cytokine production. However, HuR's role in macrophage soluble factor production, in particular in response to angiogenic stimuli, has not yet been established. We show that the labile transcripts that encode vascular endothelial growth factor and matrix metalloproteinase-9 are stabilized when murine macrophages adhere to the β(2) integrin ligand intercellular adhesion molecule-1. This mRNA stabilization response was absent in bone marrow-derived macrophages obtained from conditional macrophage-specific HuR knockout mice. The microvascular angiogenic response to an inflammatory stimulus (ie, subcutaneous polyvinyl alcohol sponge implantation) was markedly diminished in these macrophage HuR knockout mice despite the equal levels of macrophage localization to those observed in littermate wild-type controls. Furthermore, blood flow recovery and ischemic muscle neovascularization after femoral artery ligation were impaired in the conditional macrophage-specific HuR knockout mice. These results demonstrate that dynamic effects on mRNA, mediated by the RNA-binding and RNA-stabilizing protein HuR, are required for macrophage production of angiogenic factors, which play critical roles in the neovascular responses to a variety of stimuli, including tissue ischemia.

Cathepsin L derived from skeletal muscle cells transfected with bFGF promotes endothelial cell migration

Gene transfer of basic fibroblast growth factor (bFGF) has been shown to induce significant endothelial migration and angiogenesis in ischemic disease models. Here, we investigate what factors are secreted from skeletal muscle cells (SkMCs) transfected with bFGF gene and whether they participate in endothelial cell migration. We constructed replication-defective adenovirus vectors containing the human bFGF gene (Ad/bFGF) or a control LacZ gene (Ad/LacZ) and obtained conditioned media, bFGF-CM and LacZ-CM, from SkMCs infected by Ad/bFGF or Ad/LacZ, respectively. Cell migration significantly increased in HUVECs incubated with bFGF-CM compared to cells incubated with LacZ-CM. Interestingly, HUVEC migration in response to bFGF-CM was only partially blocked by the addition of bFGF-neutralizing antibody, suggesting that bFGF-CM contains other factors that stimulate endothelial cell migration. Several proteins, matrix metalloproteinase-1 (MMP-1), plasminogen activator inhibitor-1 (PAI-1), and cathepsin L, increased in bFGF-CM compared to LacZ-CM; based on 1-dimensional gel electrophoresis and mass spectrometry. Their increased mRNA and protein levels were confirmed by RT-PCR and immunoblot analysis. The recombinant human bFGF protein induced MMP-1, PAI-1, and cathepsin L expression in SkMCs. Endothelial cell migration was reduced in groups treated with bFGF-CM containing neutralizing antibodies against MMP-1 or PAI-1. In particular, HUVECs treated with bFGF-CM containing cell-impermeable cathepsin L inhibitor showed the most significant decrease in cell migration. Cathepsin L protein directly promotes endothelial cell migration through the JNK pathway. These results indicate that cathepsin L released from SkMCs transfected with the bFGF gene can promote endothelial cell migration.

Increased endometrial placenta growth factor (PLGF) gene expression in women with successful implantation

OBJECTIVE

To analyze the vascularization of the endometrium via hysteroscopy and to assess its correlation with angiogenic factor gene expression and embryo implantation rate.

DESIGN

Cross-sectional study.

SETTING

Public university hospital.

PATIENT(S)

Patients undergoing hysteroscopy for supposed infertility.

INTERVENTION(S)

Endometrial quality assessment according to Sakumoto-Masamoto, performed in the early secretory phase of the cycle. Collection of an endometrial tissue biopsy.

MAIN OUTCOME MEASURE(S)

RNA extraction, reverse transcription, and determination of gene expression of angiogenesis- and implantation-relevant factors using quantitative polymerase chain reaction. Retrieval of pregnancy information from the medical records.

RESULT(S)

Good quantity/quality RNA with infertility history was obtained from 63 participating women. Those with a "good" endometrium and subsequent pregnancy showed increased gene expression for placenta growth factor when compared with patients with a "bad" endometrium and who did not succeed with pregnancy to date. Nonpregnant women with a "good" endometrium presented an intermediate result. No significant differences were observed for several other genes tested, but trends in the same direction were observed.

CONCLUSION(S)

This study demonstrates for the first time that endometrial PLGF expression corresponds to the hysteroscopic appearance of the endometrium, and therefore has potential as a clinically relevant prognosticator for infertility treatment success.

Increased perfusion and angiogenesis in a hindlimb ischemia model with plasmid FGF-2 delivered by noninvasive electroporation

Gene therapy approaches delivering fibroblast growth factor-2 (FGF-2) have shown promise as a potential treatment for increasing blood flow to ischemic limbs. Currently, effective noninvasive techniques to deliver plasmids encoding genes of therapeutic interest, such as FGF-2, are limited. We sought to determine if intradermal injection of plasmid DNA encoding FGF-2 (pFGF) followed by noninvasive cutaneous electroporation (pFGFE+) could increase blood flow and angiogenesis in a rat model of hindlimb ischemia. pFGFE+ or control treatments were administered on postoperative day 0. Compared to injection of pFGF alone (pFGFE-), delivery of pFGFE+ significantly increased FGF-2 expression for 10 days. Further, the increase in FGF-2 expression with pFGFE+ was sufficient to significantly increase ischemic limb blood flow, measured by laser Doppler perfusion imaging, beginning on postoperative day 3. Ischemic limb blood flow in the pFGFE+ treatment group remained significantly higher than all control groups through the end point of the study, postoperative day 14. Immunohistochemical staining of gastrocnemius cross sections determined there was a twofold increase in capillary density in the pFGFE+ treatment group. Our results suggest that pFGFE+ is a potential noninvasive, nonviral therapeutic approach to increase perfusion and angiogenesis for the treatment of limb ischemia.

Regulation of the expression balance of angiopoietin-1 and angiopoietin-2 by Shh and FGF-2

Sonic hedgehog (Shh) is a typical morphogen to regulate epithelial-mesenchymal interactions during embryonic development. Shh is also an indirect angiogenic agent upregulating other angiogenic factors, including angiopoietin-1 (Ang-1). Recent studies revealed that angiogenesis induced by Shh is characterized by distinct large-diameter vessels with less branching. Ang-1 promotes blood vessel maturation, and angiopoietin-2 (Ang-2) counteracts Ang-1 activity and regulates vascular branching. Thus, we hypothesized that Shh-induced angiogenesis is affected by expression of Ang-1 and Ang-2, and we investigated the regulatory system of angiopoietins by Shh in vitro. Shh enhanced Ang-1 expression but did not enhance vascular endothelial growth factor in fibroblasts. The upregulation of Ang-1 expression by Shh was significantly decreased by fibroblast growth factor-2 (FGF-2), a potent angiogenic factor. Furthermore, FGF-2 increased the expression of Ang-2 in endothelial cells. These findings suggest that Shh and FGF-2 regulate the expression balance of vascular morphogens Ang-1 and Ang-2 and are involved in angiogenesis.

Site-specific connexin phosphorylation is associated with reduced heterocellular communication between smooth muscle and endothelium

BACKGROUND/AIMS

Myoendothelial junctions (MEJs) represent a specialized signaling domain between vascular smooth muscle cells (VSMC) and endothelial cells (EC). The functional consequences of phosphorylation state of the connexins (Cx) at the MEJ have not been explored.

METHODS/RESULTS

Application of adenosine 3',5'-cyclic monophosphate sodium (pCPT) to mouse cremasteric arterioles reduces the detection of connexin 43 (Cx43) phosphorylated at its carboxyl terminal serine 368 site (S368) at the MEJ in vivo. After single-cell microinjection of a VSMC in mouse cremaster arterioles, only in the presence of pCPT was dye transfer to EC observed. We used a vascular cell co-culture (VCCC) and applied the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (PMA) or fibroblast growth factor-2 (FGF-2) to induce phosphorylation of Cx43 S368. This phosphorylation event was associated with a significant reduction in dye transfer and calcium communication. Using a novel method to monitor increases in intracellular calcium across the in vitro MEJ, we noted that PMA and FGF-2 both inhibited movement of inositol 1,4,5-triphosphate (IP(3)), but to a lesser extent Ca(2+).

CONCLUSION

These data indicate that site-specific connexin phosphorylation at the MEJ can potentially regulate the movement of solutes between EC and VSMC in the vessel wall.

The effect of adipose-derived stem cells on ischemia-reperfusion injury: immunohistochemical and ultrastructural evaluation

BACKGROUND

Advances in the treatment of reperfusion injury have created an opportunity for plastic surgeons to apply these treatments to flaps and implanted tissues. The authors examined the direct and indirect effects of adipose-derived stem cells on ischemia-reperfusion injury on a skin flap model to determine the in vivo differentiation of adipose-derived stem cells to endothelial cells; the levels of vascular endothelial growth factor (VEGF), transforming growth factor-beta, and fibroblast growth factor; and the ultrastructural changes apparent with scanning electron microscopy to clarify the initial events and the following cascades.

METHODS

Two identical cranial based random flaps with a dimension of 1 x 5 cm were elevated on the dorsums of 20 ICR mice. The left flap was designated as the control and the right flap was injected with adipose-derived stem cells. The flaps were then subjected to 6 hours of ischemia by clamping the pedicle, and then reperfusion.

RESULTS

The mean viable flap length in the control and experimental groups was 15.2 +/- 3.4 mm and 24.4 +/- 2.9 mm, respectively. The mean viable flap area in the control and experimental groups was 12.9 +/- 4.1 mm and 21.8 +/- 3.7 mm, respectively. The in vivo differentiation of adipose-derived stem cells to endothelial cells was observed. The immunohistochemical stainings, VEGF, transforming growth factor-beta, and fibroblast growth factor revealed increased levels in the experimental groups. Scanning electron microscopy indicated mild injury in the experimental group.

CONCLUSIONS

The adipose-derived stem cells could prevent ischemia-reperfusion injury, mainly by regulating the growth factors. Although VEGF was the foremost inhibitor of injury, the overall cascade was enhanced by adipose-derived stem cells, with the help of the other growth factors.

Positive and negative modulation of angiogenesis by VEGFR1 ligands

Vascular endothelial growth factor-A (VEGF-A) is a key target for new antiangiogenic drugs for the treatment of both malignant and nonmalignant human diseases. Vascular effects of VEGF family members are mainly mediated by VEGF receptor 2 (VEGFR2). Conversely, the function and signaling of VEGFR1, which is present on endothelial and nonendothelial cells, are poorly understood. Intriguingly, two of five members in the VEGF family--VEGF-B and placental growth factor (PlGF)--are exclusive ligands for VEGFR1 and do not interact with the other VEGFRs, VEGFR2 and VEGFR3. These VEGFR1-specific ligands may be important therapeutic targets for the treatment of cancer. This Review discusses the distinctive roles of VEGFR1 and its ligands PlGF and VEGF-B in the mediation of angiogenic signaling and considers the therapeutic potential of targeting these particular vascular factors.

Autologous adipose tissue as a new source of progenitor cells for therapeutic angiogenesis

Therapeutic angiogenesis is an important means for salvaging tissues from severe ischemic diseases in patients with no option for other vascular interventions. A number of recent studies examined the possibilities of cell transplantation-mediated angiogenesis using autologous bone marrow mononuclear cells, CD34(+) cells, peripheral mononuclear cells, etc. Subcutaneous adipose tissue can be harvested by relatively easy technology. Recent studies indicate that adipose tissue contains progenitor cells that can give rise to several mesenchymal lineages. Moreover, these progenitor cells can release multiple angiogenic growth factors including vascular endothelial growth factor, hepatocyte growth factor, and chemokine stromal cell-derived factor. The combination of these biological properties of adipose-derived regenerative cells indicates that autologous adipose tissue will be a useful cell source for therapeutic angiogenesis.

FLT1 and its ligands VEGFB and PlGF: drug targets for anti-angiogenic therapy?

Less than 5 years ago, it was still not clear whether anti-angiogenic drugs would prove successful in the clinic. After numerous patients with cancer or age-related macular degeneration have been treated with these drugs, they have now become part of the standard range of therapeutic tools. Despite this milestone, anti-angiogenic therapy still faces a number of clinical hurdles, such as improving efficacy, avoiding escape and resistance, and minimizing toxicity. Hopefully, other agents with complementary mechanisms, such as those that target placental growth factor, will offer novel opportunities for improved treatment.