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Heart Disease
In 1995:
 481,000 deaths related to Coronary Artery Disease (CAD)
 1,100,000 new or recurrent cases of CAD
 Estimated that 7.2 million people experienced angina to some
degree
Treatment
 434,000 angioplasties performed
 573,000 Bypasses performed
 60,000-100,000 patients not good candidates for
bypass/angioplasty
(Possibly up to 250,000 patients a year)
Use of Vascular
Endothelial Growth Factor
(VEGF) as a Treatment for
End Stage Coronary Artery
Disease (CAD)
By: Jeremy Gillis
Senior…Biochemistry and Molecular Biology
Current Treatments for CAD
Percutaneous Transluminal Coronary
Angioplasty or PTCA (434,000)
Coronary Artery Bypass Graft (CABG)
“cabbage” (573,000)
Vascular Stents (wire props for an
artery)
Rotational Atherectomy (much like a
drill)
Problems with Current Treatments
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Restenosis
Graft disease
Arterial puncture
Coronary thrombosis
How can we help people who don’t respond well
or are not good candidates for conventional
treatments?
It is thought that VEGF is involved in
Angiogenesis
Angiogenesis: the formation of new blood vessels (collaterals)
from existing microvessels
Contributes to the preservation of ischemic tissue and
myocardial pump function after myocardial infarction
Important in:
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Embryogenesis (called vasculogenesis)
Wound healing
Tumor growth and metastasization
Rheumatoid arthritis
Ischemic heart disease
Ischemic peripheral vascular disease
Inducing Angiogenesis
1. Need a stimulus
Hypoxic tissue, Ischemic tissue, Mechanically damaged tissue
2. Need expression of angiogenic molecules to initiate
angiogenesis
VEGF, FGF, TGF, PDGF
3. Need angiogenesis to occur
1. Proliferation and migration of endothelial cells from the
microvasculature
2. Controlled expression of proteolytic enzymes
3. Breakdown and reassembly of extracellular matrix
4. Morphogenic process of endothelial tube formation
Mechanism of Angiogenesis not completely known
Why use VEGF to Promote Angiogenesis?
VEGF (vascular endothelial growth factor)
Specific for only endothelial cells
May inhibit smooth muscle growth…reduce restenosis
FGF (fibroblast growth factor)
Associated with tumor angiogenesis
Can stimulate growth in other cells besides endothelial cells
Not as specific as VEGF
TGF- (transforming growth factor ß)
Indirect angiogenesis effect
Possibly induces VEGF expression (Protein Kinase C pathway)
PDGF (platelet derived growth factor)
Not well characterized in angiogenesis
Other VEGF Characteristics
 VEGF expressed by Macrophages, fibroblasts, smooth
muscle cells, endothelial cells (all are present in the
heart)
 Action is direct because of the exclusive specificity for
receptors (flt-1 and flk-1)
 Receptors only found on endothelial cells
 Causes activation of many other genes involved in
angiogenic response
How to Deliver VEGF
Protein Therapy
 Direct injection of protein
 Time delay delivery
 Local intercoronary bolus
Gene Therapy
Adenovirus vector
 Excellent specificity for endothelial cells
 Extended expression of VEGF
Direct gene transfer
 Involves direct injection of eukaryotic plasmid DNA
containing VEGF cDNA
Should VEGF administration prove effective, it is likely that
VEGF/VEGF DNA will be delivered on a catheter platform
Case Studies
Injection of naked VEGF cDNA contained in an
Eukaryotic Expression Vector
Jeffery Isner et al. St. Elizabeth’s Medical Center
Phase I clinical trial…designed to assess safety and
bioactivity of treatment methods
Limited sample…only 5 patients involved
 Prior Bypass and/or angioplasty
 Class 3-4 Angina
 No longer respond to additional treatment
Results
Age Lifestyle Before Treatment
67
Angina from Mild activity
Lifestyle After Treatment
 Angina virtually gone
 Able to resume swimming
 Nitroglycerin (NTG) no longer needed
 30 days post needed very little NTG
 60 days post could exercise for 30
minutes on a stationary bike
69
Angina after walking 10 yards
53
Angina after walking 50 yards
71
Angina from walking 100 yards  30 days NTG use decreased dramatically
 Returned to work part time
Daily Angina
 30 days later could walk up to ¼ mile
without pain
 Less need for supplemental oxygen
 2 episodes of angina/month
59
 60 days post could walk ½ mile
 Claims to have felt beneficial effects
after only two weeks
Also notable:
Nitroglycerin usage dropped from 7.7 pills per day
to 1.4 per day for the group (60 days post)
Effective biological outcomes despite low
transfection rates
Because of the condition of the patients in the
study, the improvements to health were not likely
random events
All 5 patients had remarkable gains in
quality of life post procedure
Animal Data:
Charles Mack et al. New York HospitalCornell Medical Center
Administration VEGF gene through
Adenovirus mediated gene therapy
Preclinical work to determine efficacy in an
animal model of ischemia
Model:
 Pig with a constrictor band around circumflex artery to induce
myocardial infarction and ischemia
 Eventually results in complete occlusion of circumflex artery
Vector:
 Adenovirus vector in E1a-, partial E1b-, and partial E3- mutations
(makes them replication deficient)
 Adenovirus used because of the natural selectivity for endothelial
cells
 Minimal inflammation detected in animals 4 weeks post therapy
 In vivo conformation of expression confirmed by ELISA 3 days
after injection
Results
Treatment Resulted in significantly reduced ischemic
area (area of oxygen starved tissue) and
Ischemic maximum (severity of ischemia) in treated
animals
Strength of heartbeat returned in treated animals
more than untreated animals
More vessels visible angiographically in treated
animals vs. untreated animals
Treated animals seemed to route around the
occlusion as demonstrated by the filling of branching
arteries
Why it works?
Placebo effect?
VEGF stimulates growth of “collateral”
vessels?
Microvessel growth due to physical
damage of heart?
Real or perceived Angiogenesis?
Problems:
 Doesn’t work as well on older patients with more
advanced disease
 VEGF may stimulate undetected cancer growth (tumors
cannot be larger than a few mm3 without
revascularization?
 Limited number of trials and patients
 Treatment kills some patients?
 What are the effects on women?
 No placebo substance given for ethical reasons
References
Battegay, E.J. Angiogenesis: mechanistic insights, neovascular diseases, and therapeutic
prospects. Journal of Molecular Medicine (1995) 73:333-346.
Losordo, Douglas W., et al. Gene therapy for Myocardial Angiogenesis: Initial Clinical Results
With Direct Myocardial Injection of phVEGF165 as Sole Therapy for Myocardial Ischemia.
Circulation (1998) 98:2800-2804.
Mack, Charles 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. Journal of
Thoracic and Cardiovascular Surgery (1998) 115:168-77.
Li, Jian, et al. Stretch-induced VEGF Expression in the Heart. Journal of Clinical Investigation
(1997) 100:18-24.
Seko, Yoshinori, et al. Serum levels of vascular endothelial growth factor in patients with acute
myocardial infarction undergoing reperfusion therapy. Clinical Science (1997) 92:453-454.
Lopez, John J., et al. VEGF administration in chronic myocardial ischemia in pigs.
Cardiovascular Research (1998) 40:272-281.
Metais, Caroline, et al. Effects of coronary artery disease on expression and microvascular
response to VEGF. American Journal of Physiology (1998) 275:H1411-H1418.