Asian Cardiovasc Thorac Ann 2005;13:90-97
© 2005 Asia Publishing EXchange Ltd
Reappraisal of Recent Clinical Trials of Angiogenic Therapy in Myocardial Ischemia
Carolyn J Teng, MD,
Kevin Lachapelle, FRCSC,
Ray CJ Chiu, FRCSC
McGill University Health Centre, Royal Victoria Hospital, Montreal, Canada
For reprint information contact: Kevin Lachapelle, FRCSC Tel: 1 514 843 1519 Fax: 1 514 843 1603 Email: kevin.lachapelle{at}mcgill.ca, Royal Victoria Hospital, 687 Pine Ave West, Suite S8.30, Montreal H3A 1A1, Canada.
 |
ABSTRACT
|
|---|
We review the clinical trials of angiogenic therapy for myocardial ischemia, focusing on why the results are unsatisfactory in more recent larger and better designed trials. Critical reappraisal of such trials, in view of the pathophysiologic complexity of the angiogenic process at a molecular level, suggests that the strategy of therapies based on a single growth factor protein or gene may not be adequate for optimal therapeutic response.
|
INTRODUCTION
|
|---|
In recent years, there have been spectacular advances in our knowledge of myocardial angiogenesis, both in the physiology and in the molecular mechanisms of this complex biological process. Since myocardial ischemia continues to be the leading cause of morbidity and mortality in our society, it is of little surprise that attempts are being made to rapidly apply this knowledge clinically to benefit the vast number of patients who are candidates for this therapy. Unfortunately, in spite of the optimistic earlier findings of many pioneering clinical trials, more recent larger and better designed clinical trials have come up with disappointing results. In this review, we will attempt to critically reappraise the strategies used in these trials, and to suggest alternative approaches for future studies.
|
BRIEF REVIEW OF RECENT CLINICAL TRIAL RESULTS
|
|---|
There are many different growth factors implicated in the process of angiogenesis (Figure 1
). These factors, both the growth factor protein molecules and the genes encoding them, have been studied individually, in combination, or in sequence, using various animal models in vitro and in vivo. However, in human clinical trials, the studies have virtually all focused on a single growth factor for therapy, most commonly vascular endothelial growth factor (VEGF) or fibroblast growth factor (FGF).
View larger version (13K):
[in this window]
[in a new window]
|
Figure 1. Steps of angiogenesis and some of the growth factors that have been implicated. Ang = angiogenesis; BM = basement membrane; ECM = extracellular matrix; FGF = fibroblast growth factor; PDGF = platelet derived growth factor; TGF = transforming growth factor; TNF = tumor necrosis factor; VEGF = vascular endothelial growth factor.
|
|
|
VASCULAR ENDOTHELIAL GROWTH FACTOR
|
|---|
Many phase I clinical trials involved the administration of VEGF to a small number of patients suffering from ischemic heart disease (Table 1). Rosengart and colleagues1 used an E1–E3– adenovirus gene-transfer vector expressing human VEGF121. Patients received either VEGF121 alone or with concomitant coronary artery bypass grafting (CABG). The results showed a trend towards improvement as measured by coronary angiography and stress sestamibi assessment of wall motion 30 days after therapy. Patients also reported improvement of anginal class. Only the group with VEGF121 showed increased treadmill exercise times. The improvement in anginal class and exercise times persisted for the group with VEGF121 without CABG at the 6-month follow-up.1 Rosengart and colleagues1 point out that it is difficult to interpret data from the group that received both VEGF121 and CABG. To what extent the observed improvement can be attributed to the administration of VEGF121 rather than CABG-related watershed perfusion cannot be easily ascertained. Furthermore, this study lacked a control group so the possibility of a placebo effect exists.
Indeed, in a phase I trial in which assessment of safety is the primary focus, the ethical considerations of performing a minithoracotomy with no administration of the therapeutic agent make it difficult to include a control placebo group. Therefore, control groups were absent in many of the smaller trials that involved an operation such as a minithoracotomy for the administration of VEGF therapy. This is the case in several trials of VEGF165 in which naked plasmid DNA encoding VEGF165 or VEGF-2 was injected intramyocardially through a minithoracotomy.2–5,7 These trials, taken together, showed a decrease in anginal symptoms and amount of nitroglycerin used, which were accompanied by improved Canadian Cardiovascular Society (CCS) anginal class and increased exercise treadmill times. In addition to the clinical improvements, decreased defects on sestamibi scans and improved stress perfusion scores and collateral filling were also reported. However, myocardial viability did not change significantly on left ventricular electromechanical (NOGA) mapping. The improvements seen were statistically significant, but as stated earlier, there were no control groups in these studies using minithoracotomy, to account for variables other than the addition of naked plasmid DNA encoding for VEGF.
One study did use a control group to assess the effects of percutaneous intramyocardial injection of VEGF-2.2 After NOGA mapping was performed, a modified mapping catheter with a 27-gauge needle on the tip was advanced through a femoral artery introducer sheath into the left ventricle. The needle was advanced 4 to 6 mm into the myocardium, and the naked plasmid DNA encoding VEGF-2 or a placebo was injected. There was a statistically significant improvement in CCS angina class in the treatment group compared to the placebo group. Trends favoring the efficacy of VEGF-2 versus placebo were found in exercise duration, functional improvement by 
2 CCS classes, and Seattle Angina Questionnaire; however, these trends did not reach statistical significance.
Other studies using percutaneous methods of VEGF administration have been reported.8–10 In these cases, recombinant DNA encoding VEGF165 (rhVEGF) was injected into the right and left coronaries rather than intramyocardially. The two smaller trials showed decreased summed rest scores but no change in summed stress scores. There was a trend towards angiographic improvement, but only high-dose rhVEGF showed improvement in resting myocardial perfusion. Again, these smaller trials had no control groups. In contrast, the more recent VIVA trial involved 178 patients randomized to receive placebo, low-dose, or high-dose rhVEGF.10 The results of this randomized controlled trial for VEGF, with the largest sample size, showed no evidence of treatment effect on the primary endpoint of change in exercise treadmill test at 60 days. In addition, no significant difference was noted in myocardial perfusion. A trend of improved exercise treadmill time was seen at 120 days in the high-dose group, but this was not statistically significant. It is of particular interest to note that the placebo and treatment groups all showed significant improvement of anginal class with no significant difference between the groups at 60 days.
|
FIBROBLAST GROWTH FACTOR
|
|---|
In the first clinical trial of fibroblast growth factor (FGF), 40 patients with triple-vessel disease undergoing CABG were injected with either genetically engineered FGF-1 or denatured FGF-1 (Table 2).11 Angiography at 12 weeks showed increased contrast medium at the site of injection and in the distal areas supplied by the left anterior descending coronary artery in patients who received FGF-1 compared to those who had denatured FGF-1. Electronic data processing-assisted digital gray value analysis for the quantification of neoangiogenesis was higher in patients given FGF-1 compared to controls. However, no statistics were provided to show whether the differences were indeed significant, and a correlation between collateral blush and functional improvement was not made. Three-year follow-up of these patients demonstrated a sustained increase in the amount of contrast medium at angiography, as well as improved ejection fraction and clinical improvement in New York Heart Association (NYHA) classification.12 Again, no statistical data were provided to prove significance for the differences between the study and control groups, although there appeared to be a strong trend.
Administration of basic FGF (bFGF) via a slow-release preparation using heparin-alginate devices implanted in the epicardial fat during a concomitant CABG procedure was employed in 8 patients.13 Of the 7 patients examined by stress perfusion scans at 3 months, 3 had clear enhancement of perfusion in the un-revascularized myocardium that was implanted with bFGF. The absence of a control group and the presence of a concomitant procedure again make it difficult to interpret these data. A randomized double-blind study using FGF-2 was subsequently conducted by the same investigators.14 Twenty-four patients were randomized to receive either FGF-2 or placebo delivered to ungraftable myocardium via heparin-alginate capsules during CABG. The CCS class improved significantly in all groups; however, FGF-treated patients had significantly more freedom from angina than the placebo group. The overall sum of left ventricular stress perfusion defect scores was also lower in FGF-treated patients compared to controls. Left ventricular ejection fraction was not significantly different; however, there was a trend favoring the FGF-treated groups. The fact that all groups, including the control group, displayed significant improvement in CCS class, re-emphasizes the importance of a control group to minimize the confounding role of the placebo effect. The extent to which the concomitant CABG procedure played a role in the improvements seen is not clear, but the inclusion of a control group in this experiment allows a better assessment.
Many studies have used intracoronary injection as the route of administration of FGF, including the larger randomized controlled trials.15–19 The study by Laham and colleagues15 in which 52 patients received an intracoronary injection of rFGF-2 demonstrated an improvement in quality of life as measured by the Seattle Angina Questionnaire, an increase in exercise treadmill time, increased regional wall thickening, and a decrease in the extent of the ischemic area on magnetic resonance imaging. However, no dose response was seen and there was no overall improvement in left ventricular ejection fraction. A similar study by Udelson and colleagues16 in which 59 patients received an intracoronary injection of rFGF-2 showed improvements in resting perfusion and decreased per-segment reversibility scores, reflecting the magnitude of inducible ischemia. Nevertheless, no consistent improvement in global stress perfusion or inducible ischemia was shown. Instead, changes were only demonstrated with ischemic segment analysis. Neither this study nor the one by Laham and colleagues15 included a placebo group, and as seen in studies involving intramyocardial administration of FGF, there can be a significant placebo effect.
The need for a control group is also quite evident from the study by Unger and colleagues17 in which either bFGF or a placebo was injected into the left main coronary artery of 25 patients. No significant difference in exercise treadmill time compared to baseline was seen in either the placebo or FGF group. However, no definitive conclusion can be drawn as this study was designed to show safety rather than efficacy.
The FIRST and AGENT trials are the largest randomized controlled trials using intracoronary injection of FGF. The FIRST trial involved 337 patients randomized to receive a single intracoronary injection of rFGF-2 or placebo. The results of this study showed an increase in exercise treadmill times in all groups, including the placebo group, with no significant difference between treatment and placebo. The administration of rFGF-2 diminished anginal symptoms significantly compared to the control group, as measured by the Seattle Angina Questionnaire; however, this effect was not sustained at 180 days because of continued improvement in the control group. The CCS class also showed nonsustained improvement. Nuclear perfusion imaging demonstrated no significant difference in rest or stress perfusion between placebo or rFGF-2 groups at 90 or 180 days.
Results were similar in the AGENT trial in which FGF-4 was injected into the coronaries using an adenovirus vector. Seventy-nine patients were randomized to receive FGF-4 or placebo. A trend toward improved exercise treadmill time at 4 weeks was shown, but this did not reach significance. No significant difference in exercise treadmill time was seen in any treatment dose groups compared to the controls. No significant difference was found in stress-induced wall motion scores by echocardiography between baseline and 4 weeks or 12 weeks. No dose-response relationship in the anti-ischemic effect was seen.
|
CRITICAL REAPPRAISAL
|
|---|
A detailed discussion of the issues of study design in angiogenic therapy has been presented by Kutryk and Stewart.20 Here we will revisit some of these issues briefly and focus particularly on why in angiogenic therapy, even in the best designed trials to date, the outcome has been disappointing.
|
PLACEBO EFFECT
|
|---|
The early prospective studies were phase I trials, and as such, were designed to establish safety rather than determine efficacy. Although they did show trends and some even demonstrated statistically significant improvements with the administration of angiogenic growth factor when comparing baseline to post-therapeutic measurements, there were no control groups in most of these trials. The possibility of a placebo effect has been raised to account for the improvements in anginal scores and nitroglycerin use. Other possibilities to account for the improvement seen, not only in such subjective indices, but in more objective SPECT-sestamibi, angiography, magnetic resonance imaging, and NOGA data, could be due to an increase in the body’s own intrinsic expression of growth factors. The intramyocardial administration of any therapeutic agent may cause local tissue damage and an inflammatory response with associated angiogenesis at the sites of injection due to inflammatory-mediated upregulation of growth factors.21–25 In most cases, multiple injection sites are used, which may stimulate the intrinsic upregulation of multiple growth factors to initiate angiogenesis, leading to improvement post-therapy, which is not attributable to the particular growth factor administered. When this is accounted for by including a control group, i.e. multiple injections of a placebo, the positive effects of treatment with a single agent may not be as robust as they appear.
|
PROTEIN VS. GENE THERAPY
|
|---|
Protein administration has been used in a number of the above studies. The advantages of the use of protein include the ability to modify the dose and length of effect, given the short half-life of most proteins. However, a short half-life may necessitate multiple administrations in order to prolong the effect. The use of single-dose administration of protein, as in a number of studies reported, may not be as effective in providing a significant and sustained response.
Gene administration results in more sustained secretion of growth factor than administration of protein. Although length of time of expression of the added gene can result in prolonged presence of the growth factor, there is the possibility that overexpression may continue on into a phase of vessel maturation in which it is no longer advantageous to have that particular growth factor present. Oncogenicity to produce hemangiomas has been reported experimentally. In addition, the possibility of uptake of vectors for gene therapy at distant sites could cause unwanted and potentially dangerous effects.
|
ROUTE OF ADMINISTRATION
|
|---|
The route through which an agent is administered may greatly affect the efficacy of that agent. As with the choice of agent, there are advantages and disadvantages that must be weighed in order to select an appropriate route. Intravenous injections are easy to perform and minimally invasive, but the amount of growth factor which reaches the target myocardium can be small and variable. Intramyocardial injections have the advantage of control over the site of administration and maximization of the amount of growth factor delivered to the desired site. However, a disadvantage lies in the fact that they usually require an invasive approach.
Due to the difficulties of including a control group in studies involving intramyocardial injections, the larger placebo-controlled trials used intracoronary infusion of growth factors.10,18,19 This brings up a few points that may possibly explain the negative results seen. All of the patients undergoing intracoronary infusion have coronary artery disease, therefore, the possibility exists that the amount of growth factor reaching the sites most affected by coronary stenosis or occlusion is sub-optimal. Hence, no significant effect is seen, given that the areas that would most benefit from angiogenesis receive the least amount of growth factor. When this is coupled with the fact that < 1% of growth factor remains in the myocardium 1 hour after intracoronary administration, and < 0.05% at 24 hours, one must seriously question the actual amount of growth factor reaching the ischemic sites.26
|
SENSITIVE AND OBJECTIVE MEASUREMENTS OF IMPROVEMENT
|
|---|
In the AGENT trial, FGF was infused through patent coronaries or bypass grafts, thus tempering the concern that FGF distribution was hampered by injection through a stenosed or obstructed conduit. However, patients with severe triple-vessel disease, and thus at high risk of adverse events, were excluded from this study, and only patients with mild to moderate angina were included. This may contribute to negative results in a number of ways. The patients’ high exercise tolerance may make it difficult to show significant improvement given high baseline scores. In addition, there is the possibility that ischemic areas caused by severe coronary stenosis or occlusion are, in fact, the areas that show improvement from growth factor administration. By excluding patients with severe disease, those most likely to show a response are excluded. Previous studies showed significant improvement only in segments of myocardium with severe perfusion defects, even when no global improvement could be demonstrated.16 It seems unlikely that there would be a need for increased angiogenesis in areas of relatively normal myocardium, or that even with increased angiogenesis, areas that are already functioning well would benefit significantly from more blood vessels.27 As the authors of the AGENT study point out, both the presence of FGF and repeated bouts of ischemia may be necessary to significantly increase angiogenesis. Perhaps this underlies the importance of evoking an increase in the other growth factors, in this case through repeated ischemic episodes, in order to show increased development of collateral vessels.
A test must also be an objective measure of myocardial perfusion, as well as being a sensitive measure. If there is no established correlation between the results of a test and the physiologic effect, then it is difficult to draw a conclusion as to the efficacy of the treatment. The "coronary blush" seen in patients injected with FGF may not translate into an actual improvement in myocardial perfusion or function.11,12 In this case, other measures are needed to validate whether or not this constitutes a reasonable surrogate for collateral formation in ischemic myocardium.
|
SINGLE GROWTH FACTOR ADMINISTRATION — AN OVERSIMPLIFICATION?
|
|---|
Given the many different growth factors involved in angiogenesis, it is perhaps unreasonable to assume that providing just one will result in an optimal angiogenic response. The lack of a dose-dependent response, as seen in some studies, may be due to the choice of doses or the sensitivity of the tests used to measure changes. Another possibility is that overdriving one step of the pathway may increase the products from that step, but the rate-limiting factor may be upstream or downstream. In the case of VEGF and FGF, there may be an increase in immature vessel formation, but without an increase in subsequent growth factor activity, these nascent vessels will not mature. This may explain the fact that some of the improvements seen with single growth factor administration are neither sustained nor functionally effective. There may be an initial increase in capillary formation, but then regression of these nascent vessels occurs without further stimulation to facilitate their development into mature vessels. Results from work with transgenic mice have revealed the importance of numerous growth factors in the formation and maturation of blood vessels in both vasculogenesis and angiogenesis.28–34 Given the importance of each growth factor and the defects caused by the loss of their gene expression, amplification of gene expression in only one of these growth factors would appear to be inadequate for optimal promotion of angiogenesis.
Thus, it would appear that the use of single agent growth factor therapy, regardless of the route of administration or the dosage, would be unlikely to lead to optimal treatment of ischemic myocardial disease. The actual pathophysiology during an ischemic event is highly complex. As discussed by Jain,35 it is thought that in the presence of hypoxia, a number of different genes are upregulated. Nitric oxide causes dilation of existing blood vessels. The vessels then become leaky in response to VEGF.36 Proteases dissolve the basement membrane and extracellular matrix, allowing plasma proteins through to form the provisional matrix that interacts with integrins to signal endothelial cell migration. These cells will then proliferate and form sprouts in the presence of angiopoietin (Ang) and VEGF. The formation of vascular loops and networks is a result of sprout anastomosis. Several growth factors also play a role in the stabilization of immature vessels. Platelet-derived growth factor, which is secreted by endothelial cells, in the presence of VEGF, promotes recruitment of mural cells by proliferation and migration.37 The interaction of Tie-1 and Tie-2 receptors with Ang-1 and Ang-2 also contributes to vessel formation and stabilization.38,39 Ang-1 helps to make newly formed blood vessels leak-resistant, and in so doing, it may facilitate communication between the mural and endothelial cells.36 Transforming growth factor TGF-ß stimulates extracellular matrix production and differentiation of mesenchymal cells to mural cells.40,41
|
FUTURE DIRECTIONS
|
|---|
What seemed so promising in smaller clinical trials has yielded less conclusive evidence when examined in larger-scale trials. In order to understand the possible implications of this discrepancy, it is necessary to re-examine a number of issues described above in relation to experimental designs; but there may be more fundamental conceptual flaws in our approach. We should begin to think of angiogenesis as more than just the production of new blood vessels, as its name implies. Instead, those newly formed capillaries must also mature. Without all of the steps involved in maturation, they risk regression, apoptosis, and death after the initial signal for formation has subsided. Thus, simply augmenting a single growth factor may not be sufficient. Conversely, "dumping" many different growth factors at the same time may not lead to an optimal response either. Inhibitory as well as synergistic relationships exist between growth factors. For example, growth factors enhancing the leakiness of vessels may not be advantageous when the vessels are maturing and becoming more leak-resistant in order to facilitate mural and endothelial cell communication. Given this more complex view of angiogenesis, the importance of understanding the sequence and timing of growth factor activities becomes paramount in developing strategies to deliver signals that will result in improved tissue perfusion in ischemic heart disease. What appears to be necessary for new blood vessels is a reason to form (a signal such as hypoxia), substrates from which to form (surrounding endothelial and mural cells), the tools to proliferate and mature (genes encoding growth factors and other cell mitogens), and possibly a gene that acts as a master switch to start the well-timed cascade of events. Thus, angiogenesis is like a complex symphony of events that leads from the formation of nascent vessels to the development of mature vessels. An orchestra of different growth factors, each specifically timed to play their part, and perhaps, a master gene that acts as a conductor to let them know when it is appropriate to start and stop. Upon understanding the music better, we may finally learn to play it well using all the instruments needed.
|
REFERENCES
|
|---|
- Rosengart TK, Lee LY, Patel SR, Kligfield PD, Okin PM, Hackett NR, et al. Six-month assessment of a phase I trial of angiogenic gene therapy for the treatment of coronary artery disease using direct intramyocardial administration of an adenovirus vector expressing the VEGF121 cDNA. Ann Surg
1999;230:466–70.[Medline]
- 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]
- Symes JF, Losordo DW, Vale PR, Lathi KG, Esakof DD, Mayskiy M, et al. Gene therapy with vascular endothelial growth factor for inoperable coronary artery disease. Ann Thorac Surg
1999;68:830–6.[Abstract/Free Full Text]
- Vale PR, Losordo DW, Milliken CE, Maysky M, Esakof DD, Symes JF, et al. Left ventricular electromechanical mapping to assess efficacy of phVEGF165 gene transfer for therapeutic angiogenesis in chronic myocardial ischemia. Circulation
2000;102:965–74.[Abstract/Free Full Text]
- Lathi KG, Vale PR, Losordo DW, Cespedes RM, Symes JF, Esakof DD, et al. Gene therapy with vascular endothelial growth factor for inoperable coronary artery disease: anesthetic management and results. Anesth Analg
2001;92:19–25.[Abstract/Free Full Text]
- Losordo DW, Vale PR, Hendel RC, Milliken CE, Fortuin FD, Cummings N, et al. Phase 1/2 placebo-controlled, double-blind, dose-escalating trial of myocardial vascular endothelial growth factor 2 gene transfer by catheter delivery in patients with chronic myocardial ischemia. Circulation
2002;105:2012–8.[Abstract/Free Full Text]
- 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]
- Hendel RC, Henry TD, Rocha-Singh K, Isner JM, Kereiakes DJ, Giordano FJ, et al. Effect of intracoronary recombinant human vascular endothelial growth factor on myocardial perfusion: evidence for a dose-dependent effect [see comment]. Circulation
2000;101:118–21.[Abstract/Free Full Text]
- Henry TD, Rocha-Singh K, Isner JM, Kereiakes DJ, Giordano FJ, Simons M, et al. Intracoronary administration of recombinant human vascular endothelial growth factor to patients with coronary artery disease. Am Heart J
2001;142:872–80.[Medline]
- Henry TD, Annex BH, McKendall GR, Azrin MA, Lopez JJ, Giordano FJ, et al. The VIVA trial: Vascular endothelial growth factor in Ischemia for Vascular Angiogenesis. Circulation
2003;107:1359–65.[Abstract/Free Full Text]
- Schumacher B, Pecher P, von Specht BU, Stegmann T. Induction of neoangiogenesis in ischemic myocardium by human growth factors: first clinical results of a new treatment of coronary heart disease [see comment]. Circulation
1998;97:645–50.[Abstract/Free Full Text]
- Pecher P, Schumacher BA. Angiogenesis in ischemic human myocardium: clinical results after 3 years [see comment]. Ann Thorac Surg
2000;69:1414–9.[Abstract/Free Full Text]
- Sellke FW, Laham RJ, Edelman ER, Pearlman JD, Simons M. Therapeutic angiogenesis with basic fibroblast growth factor: technique and early results. Ann Thorac Surg
1998;65:1540–4.[Abstract/Free Full Text]
- Ruel M, Laham RJ, Parker JA, Post MJ, Ware JA, Simons M, et al. 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]
- Laham RJ, Chronos NA, Pike M, Leimbach ME, Udelson JE, Pearlman JD, et al. Intracoronary basic fibroblast growth factor (FGF-2) in patients with severe ischemic heart disease: results of a phase I open-label dose escalation study. J Am Coll Cardiol
2000;36:2132–9[Abstract/Free Full Text]
- Udelson JE, Dilsizian V, Laham RJ, Chronos N, Vansant J, Blais M, et al. Therapeutic angiogenesis with recombinant fibroblast growth factor-2 improves stress and rest myocardial perfusion abnormalities in patients with severe symptomatic chronic coronary artery disease. Circulation
2000;102:1605–10.[Abstract/Free Full Text]
- Unger EF, Goncalves L, Epstein SE, Chew EY, Trapnell CB, Cannon RO, 3rd, et al. Effects of a single intracoronary injection of basic fibroblast growth factor in stable angina pectoris. Am J Cardiol
2000;85:1414–9.[Medline]
- Simons M, Annex BH, Laham RJ, Kleiman N, Henry T, Dauerman H, 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]
- Grines CL, Watkins MW, Helmer G, Penny W, Brinker J, Marmur JD, et al. Angiogenic Gene Therapy (AGENT) trial in patients with stable angina pectoris [see comment]. Circulation
2002;105:1291–7.[Abstract/Free Full Text]
- Kutryk MJ, Stewart DJ. Angiogenesis of the heart [review]. Microsc Res Tech
2003;60:138–58.[Medline]
- McMahon JM, Wells KE, Bamfo JE, Cartwright MA, Wells DJ. Inflammatory responses following direct injection of plasmid DNA into skeletal muscle. Gene Ther
1998;5:1283–90.[Medline]
- Hiromatsu Y, Toda S. Mast cells and angiogenesis [review]. Microsc Res Tech
2003;60:64–9.[Medline]
- Iijima K, Yoshikawa N, Nakamura H. Activation-induced expression of vascular permeability factor by human peripheral T cells: a non-radioisotopic semiquantitative reverse transcription-polymerase chain reaction assay. J Immunol Methods
1996;196:199–209.[Medline]
- Scapini P, Calzetti F, Cassatella MA. On the detection of neutrophil-derived vascular endothelial growth factor (VEGF). J Immunol Methods
1999;232:121–9.[Medline]
- Gaudry M, Bregerie O, Andrieu V, El Benna J, Pocidalo MA, Hakim J. Intracellular pool of vascular endothelial growth factor in human neutrophils. Blood
1997;90:4153–61.[Abstract/Free Full Text]
- Laham RJ, Rezaee M, Post M, Sellke FW, Braeckman RA, Hung D, et al. Intracoronary and intravenous administration of basic fibroblast growth factor: myocardial and tissue distribution. Drug Metab Dispos
1999;27:821–6.[Abstract/Free Full Text]
- 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]
- Shalaby F, Rossant J, Yamaguchi TP, Gertsenstein M, Wu XF, Breitman ML, et al. Failure of blood-island formation and vasculogenesis in Flk-1-deficient mice. Nature
1995;376:62–6.[Medline]
- Fong GH, Zhang L, Bryce DM, Peng J. Increased hemangioblast commitment, not vascular disorganization, is the primary defect in flt-1 knock-out mice. Development
1999;126:3015–25.[Abstract]
- Dumont DJ, Gradwohl G, Fong GH, Puri MC, Gertsenstein M, Auerbach A, et al. Dominant-negative and targeted null mutations in the endothelial receptor tyrosine kinase, tek, reveal a critical role in vasculogenesis of the embryo. Genes Dev
1994;8:1897–909.[Abstract/Free Full Text]
- Sato TN, Tozawa Y, Deutsch U, Wolburg-Buchholz K, Fujiwara Y, Gendron-Maguire M, et al. Distinct roles of the receptor tyrosine kinases Tie-1 and Tie-2 in blood vessel formation. Nature
1995;376:70–4.[Medline]
- Suri C, Jones PF, Patan S, Bartunkova S, Maisonpierre PC, Davis S, et al. Requisite role of angiopoietin-1, a ligand for the TIE2 receptor, during embryonic angiogenesis [see comment]. Cell
1996;87:1171–80.[Medline]
- Maisonpierre PC, Suri C, Jones PF, Bartunkova S, Wiegand SJ, Radziejewski C, et al. Angiopoietin-2, a natural antagonist for Tie2 that disrupts in vivo angiogenesis [see comment]. Science
1997;277:55–60.[Abstract/Free Full Text]
- Schattemann GC, Loushin C, Li T, Hart CE. PDGF-A is required for normal murine cardiovascular development. Dev Biol
1996;176:133–42.[Medline]
- Jain RK. Molecular regulation of vessel maturation [review]. Nat Med
2003;9:685–93.[Medline]
- Thurston G, Suri C, Smith K, McClain J, Sato TN, Yancopoulos GD, et al. Leakage-resistant blood vessels in mice transgenically overexpressing angiopoietin-1. Science
1999;286:2511–4.[Abstract/Free Full Text]
- Hellstrom M, Gerhardt H, Kalen M, Li X, Eriksson U, Wolburg H, et al. Lack of pericytes leads to endothelial hyperplasia and abnormal vascular morphogenesis. J Cell Biol
2001;153:543–53.[Abstract/Free Full Text]
- Loughna S, Sato TN. Angiopoietin and Tie signaling pathways in vascular development [review]. Matrix Biol
2001;20:319–25.[Medline]
- Yancopoulos GD, Davis S, Gale NW, Rudge JS, Wiegand SJ, Holash J. Vascular-specific growth factors and blood vessel formation [review]. Nature
2000;407:242–8.[Medline]
- Chambers RC, Leoni P, Kaminski N, Laurent GJ, Heller RA. Global expression profiling of fibroblast responses to transforming growth factor-beta1 reveals the induction of inhibitor of differentiation-1 and provides evidence of smooth muscle cell phenotypic switching. Am J Pathol
2003;162:533–46.[Abstract/Free Full Text]
TOP
ABSTRACT
INTRODUCTION
