Heart DiseaseHeart DiseaseIn 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 GillisSenior…Biochemistry and Molecular Biology

Current Treatments for CADCurrent 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 Problems with Current TreatmentsTreatments

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 It is thought that VEGF is involved in Angiogenesisin 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: Embryogenesis (called vasculogenesis) Wound healing Tumor growth and metastasization Rheumatoid arthritis Ischemic heart disease Ischemic peripheral vascular disease

Inducing AngiogenesisInducing Angiogenesis

1. Need a stimulusHypoxic tissue, Ischemic tissue, Mechanically damaged tissue

2. Need expression of angiogenic molecules to initiate angiogenesisVEGF, FGF, TGF, PDGF3. Need angiogenesis to occur1. Proliferation and migration of endothelial cells from the microvasculature2. Controlled expression of proteolytic enzymes3. Breakdown and reassembly of extracellular matrix4. Morphogenic process of endothelial tube formation

Mechanism of Angiogenesis not completely known

Why use VEGF to Promote Angiogenesis?Why use VEGF to Promote Angiogenesis?VEGF (vascular endothelial growth factor)Specific for only endothelial cellsMay inhibit smooth muscle growth…reduce restenosis

FGF (fibroblast growth factor)

Associated with tumor angiogenesisCan stimulate growth in other cells besides endothelial cellsNot as specific as VEGF

TGF- (transforming growth factor ß) Indirect angiogenesis effectPossibly induces VEGF expression (Protein Kinase C pathway)

PDGF (platelet derived growth factor)

Not well characterized in angiogenesis

Other VEGF CharacteristicsOther 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 VEGFHow to Deliver VEGFProtein Therapy

Direct injection of protein Time delay delivery Local intercoronary bolus

Gene TherapyAdenovirus vector

Excellent specificity for endothelial cells Extended expression of VEGFDirect 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 StudiesCase 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

Age Lifestyle Before Treatment Lifestyle After Treatment67 Angina from Mild activity ⟨ Angina virtually gone

⟨ Able to resume swimming⟨ Nitroglycerin (NTG) no longer needed

69 Angina after walking 10 yards ⟨ 30 days post needed very little NTG⟨ 60 days post could exercise for 30

minutes on a stationary bike

53 Angina after walking 50 yards ⟨ 60 days post could walk ? mile⟨ Claims to have felt beneficial effects

after only two weeks

71 Angina from walking 100 yards ⟨ 30 days NTG use decreased dramatically⟨ Returned to work part time

59 Daily Angina ⟨ 30 days later could walk up to ? milewithout pain

⟨ Less need for supplemental oxygen⟨ 2 episodes of angina/month

ResultsResults

Also notable: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:Animal Data:

Charles Mack et al. New York Hospital-Cornell Medical Center

Administration VEGF gene through Adenovirus mediated gene therapy

Preclinical work to determine efficacy in an animal model of ischemia

Model:Model: Pig with a constrictor band around circumflex artery to

induce myocardial infarction and ischemia Eventually results in complete occlusion of circumflex

artery

Vector: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

ResultsResults

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?Why it works?

Placebo effect?VEGF stimulates growth of

“collateral” vessels?Microvessel growth due to physical

damage of heart?Real or perceived Angiogenesis?

Problems: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

ReferencesReferencesBattegay, 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.