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Asian Cardiovasc Thorac Ann 2004;12:173-181
© 2004 Asia Publishing EXchange Ltd

REVIEW PAPER

Therapeutic Angiogenesis Using Vascular Endothelial Growth Factor

Lei Ye, MD, Husnain K Haider, PhD1, Shu-Jia Jiang, MD, Eugene KW Sim, FRCS

Department of Cardiothoracic and Vascular Surgery
1 National University Medical Institutes, Clinical Research Centre, National University of Singapore, Singapore

For reprint information contact: Eugene KW Sim, FRCS Tel: 65 6772 5214 Fax: 65 6776 6475 Email: sursimkw{at}nus.edu.sg Dept. of Cardiothoracic & Vascular Surgery, National University Hospital, 5 Lower Kent Ridge Road, Singapore 119074


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 VEGF LIGANDS AND RECEPTORS
 REGULATION OF VEGF EXPRESSION
 THERAPEUTIC ANGIOGENESIS...
 PROTEIN THERAPY
 BENEFITS OF VEGF THERAPY
 DELIVERY STRATEGY
 FUTURE PERSPECTIVES
 REFERENCES
 
Therapeutic angiogenesis using vascular endothelial growth factor can reduce tissue ischemia by simulating the natural process of angiogenesis. Vascular endothelial growth factor not only stimulates endothelial cells to proliferate and migrate, but also mobilizes endothelial progenitor cells and achieves vascular protection. Besides direct administration of angiogenic proteins, plasmids and viral vectors carrying angiogenic genes have been used. Animal experiments have shown promise with evidence of neovascularization and improved perfusion in the target myocardium. Initial phase I and II clinical trials results are encouraging and reflect the potential success of therapeutic angiogenesis as a clinical modality for the treatment of ischemic heart disease. This review discusses the role of vascular endothelial growth factor in therapeutic angiogenesis, along with the problems and considerations of this approach as a treatment strategy.


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
VEGF LIGANDS AND RECEPTORS
 REGULATION OF VEGF EXPRESSION
 THERAPEUTIC ANGIOGENESIS...
 PROTEIN THERAPY
 BENEFITS OF VEGF THERAPY
 DELIVERY STRATEGY
 FUTURE PERSPECTIVES
 REFERENCES
 
Angiogenesis is integral to embryogenesis and contributes to the development and progression of various physiological as well as pathological processes during postnatal life. Therapeutic angiogenesis is an outside intervention that mimics the natural process of new blood vessel formation to enhance neovascularization of the infarct area for the treatment of a failing heart and ischemic tissues.1 The introduction of exogenous angiogenic growth factors triggers neovascularization with enhanced collateral blood fl ow, and improves global heart function.2 The greatest interest and research have been concentrated on basic fibroblast growth factor and vascular endothelial growth factor (VEGF).3–9 Vascular endothelial growth factor is a key player in the angiogenic pathway, with a pivotal role in the physiological as well as pathophysiological development of new blood vessels. The safety and efficacy of VEGF165 and VEGF121 have been tested in several clinical phase I and II trials (Table 1Go). Apart from the earlier concept of direct administration of angiogenic proteins, plasmids, and viral vector carrying angiogenic genes, recent studies have suggested therapeutic angiogenesis through cell-mediated gene transfer. Transplantation of stem cells is an alternative strategy to derive new vessel formation, besides increasing the number of myocytes differentiated from stem cells. The purpose of this review is to discuss the role of VEGF in therapeutic angiogenesis, along with the problems and considerations of this approach as a treatment strategy.


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  		Table 1. Treatment of myocardial injury using vascular endothelial growth factor
 

   VEGF LIGANDS AND RECEPTORS
TOP
 ABSTRACT
 INTRODUCTION
 VEGF LIGANDS AND RECEPTORS
REGULATION OF VEGF EXPRESSION
 THERAPEUTIC ANGIOGENESIS...
 PROTEIN THERAPY
 BENEFITS OF VEGF THERAPY
 DELIVERY STRATEGY
 FUTURE PERSPECTIVES
 REFERENCES
 
Vascular endothelial growth factor, also termed vascular permeability factor, exists in 6 isoforms: VEGF-A, VEGF-B, VEGF-C, VEGF-D, VEGF-E, and placental growth factor.32 The members of the VEGF family and their receptors are listed in Table 2Go. There are 5 isoforms of VEGF-A which are products of alternative exon splicing of the VEGF-A gene and referred to as VEGF121, VEGF145, VEGF165, VEGF189, and VEGF206; VEGF165 and VEGF121 are the predominant forms. These variants of VEGF play pivotal roles in vascular development. The loss of a single VEGF-A allele may disrupt the development of a normal vascular system, leading to a fatal outcome.33,34


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  		Table 2. Identified endothelial-cell-specific receptors / ligands*
 
The biological activity of VEGF isoforms is affected via 3 cell surface expressed receptors: VEGF receptor-1 (VEGFR-1 or Flt-1), VEGF receptor-2 (VEGFR-2 or Flk-1), and VEGF receptor-3 (VEGFR-3); VEGFR-1 and VEGFR-2 are mainly expressed on endothelial cells, VEGFR-3 is mainly found in the lymphatic endothelium.35–38 In the absence of VEGFR-1, a vascular defect is due to an increase in the number of hemangioblasts.39 The expression of these receptors is influenced by many factors including hypoxia-responsive elements.40,41 These receptors have different signal transduction properties: VEGFR-1 mainly promotes endothelial cell differentiation, whereas VEGFR-2 mediates endothelial proliferation.42 The promotion of endothelial cell differentiation is regulated by limiting VEGFR-2-mediated endothelial cell proliferation through the nitric oxide (NO) pathway.43 The mutants of VEGF that may bind selectively to VEGFR-2 induce mitogenesis and chemotaxis in normal endothelium, whereas VEGFR-1-selective mutants are devoid of such activities.44,45 Moreover, neuropilin-1 receptor binds VEGF165 and potentiates VEGF-induced endothelial cell migration.46,47


   REGULATION OF VEGF EXPRESSION
TOP
 ABSTRACT
 INTRODUCTION
 VEGF LIGANDS AND RECEPTORS
 REGULATION OF VEGF EXPRESSION
THERAPEUTIC ANGIOGENESIS...
 PROTEIN THERAPY
 BENEFITS OF VEGF THERAPY
 DELIVERY STRATEGY
 FUTURE PERSPECTIVES
 REFERENCES
 
HYPOXIA
Hypoxia is the major driving force for angiogenesis through the induction of hypoxia-inducible factor (HIF).48 Hypoxic conditions induce elevated HIF-1{alpha} expression (HIF-1{alpha} is a subunit of HIF-1) which regulates VEGF at its transcriptional and post-transcriptional level.48,49 The increased HIF-1{alpha} and VEGF messenger RNA expression depend on the activity of phosphoinositide 3-kinase, antiapoptotic protein kinase, and the downstream kinase FRAP (FKBP-rapamycin-associated protein).50 Sodhi and colleagues51 suggested that two divergent signaling pathways emerging from Ras may cooperatively but independently regulate the activity of HIF-1{alpha}, thereby promoting the expression of VEGF.51

GROWTH FACTORS AND CYTOKINES
Endothelial growth factor, transforming growth factor-ß, and keratinocyte growth factor-1 up-regulate VEGF messenger RNA expression.52 Insulin-like growth factor-1, thyroid-stimulating hormone, and angiotensin-II also induce VEGF expression.53–55 Interleukin-1 and prostaglandin E2 induce VEGF expression in cultured synovial fibroblasts, and interleukin-6 induces angiogenesis indirectly by inducing VEGF expression.56,57 Nitric oxide induces VEGF synthesis in vascular smooth muscle cells, tumor cells, and keratinocytes.58–61 Nitric oxide is not only a downstream mediator of VEGF signaling in endothelial cells, it also operates in an upstream direction and induces VEGF synthesis, which implies that the regulation between VEGF and NO is reciprocal.62

MISCELLANEOUS
Apart from hypoxia and cytokines, some other factors also trigger neovascularization. Nicotine increases endothelial cell number, increases capillary network formation, and reduces apoptosis in-vitro.63 Nicotine potentiates the angiogenic response to inflammation, ischemia, atherosclerosis, and neoplasia. The pro-angiogenic effects of nicotine involve the elaboration of NO and VEGF. It is suggested that tissue acidosis independent of hypoxia is another important stimulus for up-regulation of VEGF expression. Similarly, neuropeptide Y may stimulate multiple steps of angiogenesis, such as proliferation and capillary formation through a NO-dependent pathway.64


   THERAPEUTIC ANGIOGENESIS MEDIATED BY VEGF DELIVERY
TOP
 ABSTRACT
 INTRODUCTION
 VEGF LIGANDS AND RECEPTORS
 REGULATION OF VEGF EXPRESSION
 THERAPEUTIC ANGIOGENESIS...
PROTEIN THERAPY
 BENEFITS OF VEGF THERAPY
 DELIVERY STRATEGY
 FUTURE PERSPECTIVES
 REFERENCES
 
Use of VEGF is being considered for therapeutic relief of coronary heart disease and other forms of tissue ischemia. The most common methods of employing VEGF to achieve neovascularization include direct introduction of VEGF protein, application of plasmid, or injection of recombinant viral vectors or nonviral vectors carrying gene encoding for VEGF. The applications of VEGF with reference to myocardial angiogenesis are listed in Table 1Go.


   PROTEIN THERAPY
TOP
 ABSTRACT
 INTRODUCTION
 VEGF LIGANDS AND RECEPTORS
 REGULATION OF VEGF EXPRESSION
 THERAPEUTIC ANGIOGENESIS...
 PROTEIN THERAPY
BENEFITS OF VEGF THERAPY
 DELIVERY STRATEGY
 FUTURE PERSPECTIVES
 REFERENCES
 
The recombinant angiogenic proteins constitute a potential form of therapy for patients with limb ischemia.65,66 The results of these studies have revealed an interesting dose-response relationship. Low-dose administration for an extended duration shows a better prognosis with fewer side effects compared to a higher dose for shorter time. Banai and colleagues14 have documented enhanced collateral blood flow to ischemic myocardium in a canine heart model of chronic ischemia using 45-µg doses daily for 4 weeks. Even when the recombinant VEGF (rVEGF) dose was reduced to 20 µg for 3 weeks, significant angiogenesis with improved regional perfusion was still observed.19 Contrary to this, administration of 2 mg of rVEGF intravenously in a pig model of chronic ischemia resulted in severe hypotension in 50% of the animals.18 Hendel and colleagues67 administrated 4 doses (low doses: 0.005 and 0.017 µg·kg–1, high doses: 0.05 and 0.167 µg·kg–1) via a coronary artery in 14 patients. Single-photon emission computed tomography (SPECT) showed improvement in 4 of the 7 patients who received high-dose rVEGF at 60 days after the treatment. The dose-dependent response underscores the need for an optimal dosage to achieve angiogenesis and avoid hypotension during injection. The route of administration also significantly influences the outcome of angiogenic protein therapy. Saito and colleagues68 documented the efficiency of intracoronary infusion of rVEGF165 compared to intravenous injection. Moreover, site-specific delivery of rVEGF may augment blood flow to ischemic myocardium with fewer side effects. Recently, Henry and colleagues22 assessed the safety and efficacy of intracoronary and intravenous infusions of rVEGF in 178 patients in a double-blind placebo-controlled trial. Two doses of rVEGF (low dose: 17 ng·kg–1·min–1, high dose: 50 ng·kg–1·min–1) were administered. An improvement in angina class was observed only in the high-dose group at 120 days after treatment.

NAKED DNA INJECTION
One shortcoming of angiogenic protein therapy is the limited duration of the therapeutic effect due to the short biological half-life of VEGF. Repeated administration of VEGF is needed to maintain the serum level within the therapeutic window. To overcome this problem, exogenous gene transfer encoding for one or more angiogenic factors has been studied as an alternative strategy. The advantage of gene transfer is to achieve a fairly long-term expression of the gene in an injured heart. In addition, gene therapy may potentially avoid systemic hypotension. The angiogenic gene therapy strategies are based on direct transfer of plasmids or viral vector constructs expressing VEGF.15,17,21,23,24,26–29,69,70

The feasibility and safety of intramyocardial plasmid human VEGF (phVEGF) in patients was first studied by Losordo and colleagues.23 Five patients each received 125 µg of phVEGF165 by intramyocardial administration. The treatment caused no changes in heart rate, systolic or diastolic blood pressure. Ventricular arrhythmia was limited to unifocal premature beats at the moment of injection. A similar study involving 20 patients confirmed the efficacy of the procedure.70 The phVEGF165 was injected directly with no perioperative myocardial infarction, hemodynamic instability, or change in ventricular function. A reduction in ischemic defects on SPECT was observed in 13 of the 16 patients followed to day 90. Angiographic evidence of improved collateral filling of at least one occluded vessel was observed in all patients evaluated on day 60. The improvement was observed to be more consistent with a high dose compared to a low dose.

The feasibility of intramyocardial administration of phVEGF was assessed using an electromechanical left ventricular mapping system (NOGA) in 13 patients.26 Mean left ventricular ejection fraction improved from 31.3% ± 2.7% to 36.9% ± 2.3% after treatment, and there was a marked reduction in the area of ischemic myocardium. The efficacy of intracoronary delivery of a high dose of 1 mg of phVEGF was assessed in 10 patients as an adjunct to percutaneous transluminal coronary angioplasty.24 The results showed no VEGF plasmid or recombinant VEGF protein in the systemic circulation after the gene transfer. Freedman and colleagues28 assessed the kinetics of VEGF protein release into the systemic circulation after phVEGF gene transfer in patients with peripheral or coronary artery disease. They found that intramuscular and intramyocardial phVEGF injections resulted in modest elevations of circulating gene product for < 14 days, with no relationship to the injected dose.

Follow-up of more than 2 years in patients treated with intramyocardial gene transfer of phVEGF165 showed the feasibility and safety of therapeutic angiogenesis using naked plasmid in patients, with poor transduction efficiency.27 This approach is, however, afflicted with the problem of poor transduction efficiency. To overcome this problem, viral vectors carrying the angiogenic gene have been designed and assessed for safety and efficiency in animal models and human studies.

VIRAL VECTOR DELIVERY
Mack and colleagues21 used adenovirus carrying VEGF121 (Ad-VEGF121) gene for neovascularization in a porcine heart model of ischemia. The Ad-VEGF121 was administered intramyocardially at 10 sites in the circumflex distribution, with 108 plaque-forming units per site. Single-photon emission computed tomography revealed significant improvements in both myocardial perfusion and functional collateral vessel formation 4 weeks after administration. Angiography revealed collateral vessel development which was significantly greater in Ad-VEGF121-treated animals than in the control animals. Similar observations have also been documented in rabbit and canine ischemic heart models.15,17

Besides animal studies, human studies have shown the safety and tolerance of direct injection of Ad-VEGF121 for myocardial therapeutic angiogenesis in patients with coronary artery disease.29,30 Direct injection of Ad-VEGF121 in 21 patients as an adjunct to coronary bypass grafting or as a sole therapy showed no evidence of dose-related abnormalities in blood parameters or hypotension related to adenoviral vector injection. Hedman and colleagues31 carried out a randomized placebo-controlled double-blind phase-II study using adenoviral-vector-carrying VEGF for the treatment of chronic myocardial ischemia in 103 patients. Myocardial perfusion was significantly improved in the treated patients after 6 months. No serious adverse events were detected. This study demonstrated that gene transfer for coronary artery disease using adenoviral vector was feasible and well tolerated.

CELLULAR ANGIOGENESIS
A novel strategy to achieve angiogenesis is combining cell transplantation and angiogenesis. Primary myoblasts have been commonly used as a platform for gene delivery to the target organ. Koh and colleagues71 assessed the ability of genetically modified myoblasts for long-term delivery of recombinant transforming growth factor-ß (TGF-ß) to the myocardium. The C2C12 stable myoblast cell line constitutively secreted active TGF-ß. These genetically modified myoblasts were transplanted intramyocardially in a syngenic C3Heb/FeJ host for long-term delivery of recombinant molecules to the heart. Viable grafts were observed as long as 3 months after implantation. Regions of apparent neovascularization were found in the myocardium that bordered grafts expressing TGF-ß. A later study assessed the efficiency of rat myoblasts carrying human VEGF165 for improvement of the injured heart.13 Myocardial VEGF levels in the VEGF group rose significantly 2–14 days after transplantation. Both systolic and diastolic function were better preserved after myocardial infarction in the VEGF group. Enhanced angiogenesis with a larger number of mature capillaries was observed in the VEGF group, with no angioma formation.

The authors have studied the potential of human myoblasts carrying human VEGF165 for concurrent myogenesis and angiogenesis for the treatment of myocardial infarction in a porcine heart model.72 Human myoblasts were transduced with replication-defective adenovirus carrying the human VEGF165 gene. Enzyme-linked immunosorbent assay revealed that the level of in-vitro secreted VEGF165 from VEGF165-transfected myoblasts was 25 ng·mL–1, which was significantly higher than that of null-adenovirus transfected myoblasts. The transfected myoblasts secreted VEGF165 for at least 18 days, with a peak at day 7 (37 ± 3 ng·mL–1). The secreted VEGF165 was biologically functional as assayed by human umbilical vein endothelial cell proliferation and thymidine incorporation assays. When transplanted into porcine heart, the cells survived to differentiate into multinucleated myotubes. Histological studies revealed improved neovascularization at the site of the cell graft (Figure 1Go).




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  		Figure 1. Photomicrographs of porcine heart model of myocardial infarction 12 weeks post transplantation of (A) human myoblasts as a control, and (B) human myoblasts transduced with adenoviral vector carrying human VEGF165. The histological tissue sections were immunostained for von Willebrand factor-VIII expression using rhodamine labeled antibodies. The capillary count was significantly higher in VEGF transduced myoblast transplanted group of animals as compared with the myoblast transplanted controls animals ( p < 0.005).

 
More recently, endothelial progenitor cells (EPC) have attracted attention for therapeutic angiogenesis in the treatment of myocardial infarction. Kawamoto and colleagues73 injected EPC into ischemic myocardium under the guidance of a NOGA system. They found that capillary density in ischemic myocardium was greater in the treated group than the control group. This study suggested the feasibility of EPC injection for treatment of myocardial infarction. The same group further demonstrated that stromal cell-derived factor-1 augmented the recruitment and improved the survival of EPC in ischemic tissues.74


   BENEFITS OF VEGF THERAPY
TOP
 ABSTRACT
 INTRODUCTION
 VEGF LIGANDS AND RECEPTORS
 REGULATION OF VEGF EXPRESSION
 THERAPEUTIC ANGIOGENESIS...
 PROTEIN THERAPY
 BENEFITS OF VEGF THERAPY
DELIVERY STRATEGY
 FUTURE PERSPECTIVES
 REFERENCES
 
The results of animal studies and recent human trials underscore the usefulness of VEGF for therapeutic angiogenesis. The beneficial effects of VEGF are firstly due to neovascularization which is mediated through endothelial cell activation, migration, proliferation, and formation of new endothelial tubes. The neovascularization is mainly achieved by endothelial cell proliferation triggered through VEGF receptors, especially VEGFR-2.75 Secondly, vascular protection is achieved via NO and prostacyclin pathways.76 The induction of NO by VEGF involves activation of endothelial nitric oxide synthase through prostaglandin-I2 stimulation.77 These two mediators cause vasodilatation, inhibition of smooth muscle proliferation, anti-platelet-accumulation, and inhibition of leukocyte adhesion, leading to a vascular protection effect. Finally, it mobilizes endothelial progenitor cells. In one human study, direct transfection of ischemic myocardium with plasmid DNA encoding VEGF165 (250 µg per patient) in 13 patients mobilized endothelial progenitor cells for 9 weeks after treatment.25 Flow cytometry showed that these cells expressed CD34, KDR, CD62E (endothelial cell markers) and vascular endothelial cadherin. In a recent study, Laguens and colleagues20 registered an increased cardiomyocyte mitotic index in a pig model of chronic myocardial ischemia after direct intramyocardial injection of plasmids encoding for human VEGF165. The finding may potentially widen the therapeutic spectrum of VEGF gene transfer.

Although VEGF has significant clinical implications and stimulates neovascularization in patients with ischemic heart disease, VEGF therapy has been shown to precipitate the progression of atherosclerosis and inappropriate blood vessel growth.10 Unregulated continuous high-level expression of VEGF level is associated with a high rate of failure to thrive and angioma formation.10,12 Masaki and colleagues78 demonstrated that VEGF is necessary, but unregulated and over-expression of VEGF results in accelerated limb loss in murine critical limb ischemia. These results underscore the importance of controlled VEGF expression for therapeutic angiogenesis.


   DELIVERY STRATEGY
TOP
 ABSTRACT
 INTRODUCTION
 VEGF LIGANDS AND RECEPTORS
 REGULATION OF VEGF EXPRESSION
 THERAPEUTIC ANGIOGENESIS...
 PROTEIN THERAPY
 BENEFITS OF VEGF THERAPY
 DELIVERY STRATEGY
FUTURE PERSPECTIVES
 REFERENCES
 
The choice of the angiogenic protein or gene delivery system has a significant bearing on the outcome of the procedure.79 Currently, data on the safety and effectiveness of the delivery strategy to achieve clinically significant therapeutic angiogenesis is limited. More research including larger-scale clinical trials are needed before deciding whether VEGF therapy either as a gene or a recombinant slow-release protein formulation can be offered to patients who cannot be treated with conventional revascularization. There are many more issues that need to be settled, including the delivery strategy and route of administration. The delivery of the recombinant growth factor proteins and their genes has been accomplished until now through different routes and each one of these routes has its own limitations and advantages.

ENDOVASCULAR ADMINISTRATION
Endovascular administration includes intracoronary and intravenous injection. The intravenous injection of angiogenic protein has been shown to be less effective in inducing angiogenesis compared to intracoronary administration.14,16,68,80 One potential side effect related to endovascular administration of VEGF protein is hypotension which is mediated by NO following administration.18 Furthermore, the beneficial effects may be short lived due to the short biological half-life. Catheter-based endovascular administration of VEGF protein and gene transfer using plasmid/liposome or viral vector adjunct to angioplasty has been tested and shown to be safe, well tolerated, and potentially applicable for the prevention of restenosis and myocardial ischemia in patients.17

INTRAMYOCARDIAL ADMINISTRATION
Intramyocardial administration includes epimyocardial and endomyocardial injections. Injection of naked human VEGF plasmid into the ischemic myocardium of patients has shown the safety of this procedure.23,26 The epimyocardial injection of adenoviral vector-mediated VEGF121 induced collateral vessel development in ischemic myocardium with significant improvement in collateral vessel formation, and improved regional perfusion and function without any evidence of adverse reactions related to vector administration.21,25,29,30 Intramyocardial administration is a more efficient delivery route than intracoronary administration of VEGF gene delivery. Lee and colleagues11 compared the expression efficiency of exogenous VEGF delivered to the myocardium via intracoronary and intramyocardial routes. Adenoviral vector genome and VEGF protein levels in the injected area were 1,000-fold and 90-fold higher, respectively, than in other myocardial regions. In comparison, intracoronary injection yielded higher myocardial adenoviral vector genome and VEGF protein levels than intramyocardial delivery. Endomyocardial administration through the NOGA system was achieved by Vale and colleagues.26 Their 13 patients showed improved ejection fractions after treatment, along with a marked reduction in the area of ischemic myocardium.


   FUTURE PERSPECTIVES
TOP
 ABSTRACT
 INTRODUCTION
 VEGF LIGANDS AND RECEPTORS
 REGULATION OF VEGF EXPRESSION
 THERAPEUTIC ANGIOGENESIS...
 PROTEIN THERAPY
 BENEFITS OF VEGF THERAPY
 DELIVERY STRATEGY
 FUTURE PERSPECTIVES
REFERENCES
 
Uncontrolled neovascularization plays a critical role in various pathological process such as solid tumor formation, metastasis, childhood hemangiomas and psoriasis as well as inflammation-related diseases. Hence, it is crucial to find safer and more efficient ways to take advantage of therapeutic angiogenesis. In future studies, gene therapy via transcript factors or mediators in the signaling pathway of angiogenesis will introduce new targets for therapeutic angiogenesis.81–83 Transcription factors in milieu may regulate the expression of angiogenic factor to avoid over-expression. Considering angiogenesis is a cascade reaction with multiple angiogenic factors contributing, combinations of several angiogenic factors may be preferable in future. This strategy may not only stimulate angiogenesis more efficiently, but also reduce side effects. The combination of VEGF with angiopoietin-1 may be more efficient.84 These two factors have been documented to play pivotal roles at different stages of angiogenesis. The synergy between various angiogenic cytokines may lead to more efficiency. Shyu and colleagues85 reported a synergistic effect of VEGF with angiopoietin-1. A greater improvement in angiogenesis was observed when both growth factors were co-administered, compared to the administration of either alone, at 30 days after treatment. Cao and colleagues86 reported that the combination of a platelet-derived growth factor and a fibroblast growth factor synergistically induced the development of vascular networks.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 VEGF LIGANDS AND RECEPTORS
 REGULATION OF VEGF EXPRESSION
 THERAPEUTIC ANGIOGENESIS...
 PROTEIN THERAPY
 BENEFITS OF VEGF THERAPY
 DELIVERY STRATEGY
 FUTURE PERSPECTIVES
 REFERENCES
 

  1. Khan TA, Sellke FW, Laham RJ. Gene therapy progress and prospects: therapeutic angiogenesis for limb and myocardial ischemia. Gene Ther 2003;10:285 91.[Medline]

  2. Stegmann TJ, Hoppert T, Schneider A, Gemeinhardt S, Kocher M, Ibing R, et al. Induction of myocardial neo-angiogenesis by human growth factors. A new therapeutic approach in coronary heart disease. Herz 2000;25:589–99.[Medline]

  3. Ruel M, Laham RJ, Parker JA, Post MJ, Ware JA, Simons M, Sellke FW. Long-term effects of surgical angiogenic therapy with fibroblast growth factor 2 protein. J Thorac Cardiovasc Surg 2002;124:28–34.[Abstract/Free Full Text]

  4. Simons M, Annex BH, Laham RJ, Kleiman N, Henry T, Dauerman H, Udelson JE, et al. Pharmacological treatment of coronary artery disease with recombinant fibroblast growth factor-2: double-blind, randomized, controlled clinical trial. Circulation 2002;105:788–93.[Abstract/Free Full Text]

  5. Rajanayagam MA, Shou M, Thirumurti V, Lazarous DF, Quyyumi AA, Goncalves L, et al. Intracoronary basic fibroblast growth factor enhances myocardial collateral perfusion in dogs. J Am Coll Cardiol 2000;35:19–26.[Abstract/Free Full Text]

  6. Iwakura A, Fujita M, Ikemoto M, Hasegawa K, Nohara R, Sasayama S, et al. Myocardial ischemia enhances the expression of acidic fibroblast growth factor in human pericardial fluid. Heart Vessels 2000;15:112–6.[Medline]

  7. Kusumanto YH, Hospers GA, Mulder NH, Tio RA. Therapeutic angiogenesis with vascular endothelial growth factor in peripheral and coronary artery disease: a review. Int J Cardiovasc Intervent 2003;5:27–34.[Medline]

  8. Laham RJ, Li J, Tofukuji M, Post M, Simons M, Sellke FW. Spatial heterogeneity in VEGF-induced vasodilation: VEGF dilates microvessels but not epicardial and systemic arteries and veins. Ann Vasc Surg 2003;17:245–2.[Medline]

  9. Fortuin FD, Vale P, Losordo DW, Symes J, DeLaria GA, Tyner JJ, et al. One-year follow-up of direct myocardial gene transfer of vascular endothelial growth factor-2 using naked plasmid deoxyribonucleic acid by way of thoracotomy in no-option patients. Am J Cardiol 2003;92:436–9.[Medline]

  10. Lee RJ, Springer ML, Blanco-Bose WE, Shaw R, Ursell PC, Blau HM. VEGF gene delivery to myocardium: deleterious effects of unregulated expression. Circulation 2000;102:898–901.[Abstract/Free Full Text]

  11. Lee LY, Patel SR, Hackett NR, Mack CA, Polce DR, El-Sawy T, et al. Focal angiogenic therapy using intramyocardial delivery of an adenovirus vector coding for vascular endothelial growth factor 121. Ann Thorac Surg 2000;69:14–23.[Abstract/Free Full Text]

  12. Schwarz ER, Speakman MT, Patterson M, Hale SS, Isner JM, Kedes LH, et al. Evaluation of the effects of intramyocardial injection of DNA expressing vascular endothelial growth factor (VEGF) in a myocardial infarction model in the rat – angiogenesis and angioma formation. J Am Coll Cardiol 2000;35:1323–30.[Abstract/Free Full Text]

  13. Suzuki K, Murtuza B, Smolenski RT, Sammut IA, Suzuki N, Kaneda Y, et al. Cell transplantation for the treatment of acute myocardial infarction using vascular endothelial growth factor-expressing skeletal myoblasts. Circulation 2001;104 (Suppl I):207–12.

  14. Banai S, Jaklitsch MT, Shou M, Lazarous DF, Scheinowitz M, Biro S, et al. Angiogenic-induced enhancement of collateral blood flow to ischemic myocardium by vascular endothelial growth factor in dogs. Circulation 1994;89:2183–9.[Abstract/Free Full Text]

  15. Tanaka E, Hattan N, Ando K, Ueno H, Sugio Y, Mohammed MU, et al. Amelioration of microvascular myocardial ischemia by gene transfer of vascular endothelial growth factor in rabbits. J Thorac Cardiovasc Surg 2000;120:720–8.[Abstract/Free Full Text]

  16. Lazarous DF, Shou M, Scheinowitz M, Hodge E, Thirumurti V, Kitsiou AN, et al. Comparative effects of basic fibroblast growth factor and vascular endothelial growth factor on coronary collateral development and the arterial response to injury. Circulation 1996;94:1074–82.[Abstract/Free Full Text]

  17. Lazarous DF, Shou M, Stiber JA, Hodge E, Thirumurti V, Goncalves L, et al. Adenoviral-mediated gene transfer induces sustained pericardial VEGF expression in dogs: effect on myocardial angiogenesis. Cardiovasc Res 1999;44:294–302.[Abstract/Free Full Text]

  18. Hariawala MD, Horowitz JR, Esakof D, Sheriff DD, Walter DH, Keyt B, et al. VEGF improves myocardial blood flow but produces EDRF-mediated hypotension in porcine hearts. J Surg Res 1996;63:77–82.[Medline]

  19. Lopez JJ, Laham RJ, Stamler A, Pearlman JD, Bunting S, Kaplan A, et al. VEGF administration in chronic myocardial ischemia in pigs. Cardiovasc Res 1998;40:272–81.[Abstract/Free Full Text]

  20. Laguens R, Cabeza Meckert P, Vera Janavel G, Del Valle H, Lascano E, Negroni J, et al. Entrance in mitosis of adult cardiomyocytes in ischemic pig hearts after plasmid-mediated rhVEGF165 gene transfer. Gene Ther 2002;9:1676–81.[Medline]

  21. Mack CA, Patel SR, Schwarz EA, Zanzonico P, Hahn RT, Ilercil A, et al. Biologic bypass with the use of adenovirus-mediated gene transfer of the complementary deoxyribonucleic acid for vascular endothelial growth factor 121 improves myocardial perfusion and function in the ischemic porcine heart. J Thorac Cardiovasc Surg 1998;115:168–76.[Abstract/Free Full Text]

  22. Henry TD, Annex BH, McKendall GR, Azrin MA, Lopez JJ, Giordano FJ, et al. VIVA Investigators. The VIVA trial: Vascular endothelial growth factor in Ischemia for Vascular Angiogenesis. Circulation 2003;107:1359–65.[Abstract/Free Full Text]

  23. Losordo DW, Vale PR, Symes JF, Dunnington CH, Esakof DD, Maysky M, et al. Gene therapy for myocardial angiogenesis: initial clinical results with direct myocardial injection of phVEGF165 as sole therapy for myocardial ischemia. Circulation 1998;98:2800–4.[Abstract/Free Full Text]

  24. Laitinen M, Hartikainen J, Hiltunen MO, Eranen J, Kiviniemi M, Narvanen O, et al. Catheter mediated vascular endothelial growth factor gene transfer to human coronary arteries after angioplasty. Hum Gene Ther 2000;11:263–70.[Medline]

  25. Kalka C, Tehrani H, Laudenberg B, Vale PR, Isner JM, Asahara T, et al. VEGF gene transfer mobilizes endothelial progenitor cells in patients with inoperable coronary disease. Ann Thorac Surg 2000;70:829–34.[Abstract/Free Full Text]

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