Clinical Research

Angiogenesis: Four Approaches to Restoring Cardiac Function

Growth of new vascular branches in response to angiogenic growth factors: Left, vascular anatomy of mouse peritoneum, with control vehicle stimulation; Right, stimulated growth of interarterial vessels in the presence of slow-release angiogenic growth factors

Few fields have advanced as dramatically over the last two decades as cardiology and cardiothoracic surgery. Yet, for people whose blood vessels are unsuitable for angioplasty, endovascular stenting, brachytherapy, or bypass surgery–people with "malignant" heart disease– modern medicine offers no treatment options.

If only these failing hearts could grow new blood vessels.

"That is the hope and the dream of angiogenesis," says Judah Z. Weinberger, MD, PhD, Director of Interventional Cardiology at CUMC and Associate Professor of Medicine and Pharmacology at Columbia University.

In 1971, surgeon Judah Folkman hypothesized that angiogenesis was a major factor in enabling malignant tumors to grow. He was ridiculed at first by clinicians and basic scientists, but today his ideas are widely accepted and have fostered development of antiangiogenic therapies that are proving effective in reducing malignant tumors.

Inspired by the possibilities initiated by Folkman's work, heart researchers today are working to stimulate, rather than block, angiogenesis. They face a prodigious task: the mechanisms that trigger blood vessel growth are complex, and they must be carefully controlled to avoid unwanted outcomes that can come with an oversupply of blood vessels, which is seen in such disorders as rheumatoid arthritis, psoriasis, and diabetes.

Despite the complexity, however, the research has shown highly promising results thus far, especially in these four approaches.

Dr. Silviu Itescu: Using Adult Stem Cells to Promote Angiogenesis

Essentially, Dr. Itescu's method stimulates new blood vessel growth within damaged or "at risk" cardiac tissue, thereby protecting and even causing regeneration of heart muscle. The team is now studying ways by which a variety of biological agents can further augment the cardiac regenerative capacity of adult bone marrow stem cells, including enhancing migration and targeting to thedamaged heart.

Above: New capillary formation adjacent to hypertrophied rat cardiac myocytes at the peri-infarct rim after intravenous injection of human adult bone marrow angioblasts Below: Salvage of cardiac muscle and prevention of left ventricular remodeling and fibrous replacement in rat heart at 15 weeks after intravenous injection of human adult bone marrow angioblasts (right) compared with animal receiving saline (left)

In treating the sickest heart failure patients during the past decade, Dr. Itescu faced significant limitations with all therapeutic options. The severe shortage of donor hearts renders transplantation impossible for most patients, and mechanical devices (LVADs and artificial hearts) and xenotransplantation both produce significant immune responses that lead to immune deficiency and frequent infections.

Unsatisfied with these options, Dr. Itescu began searching for a new solution. His approach: to stimulate the growth of new blood vessels, thereby providing a pathway to deliver nutrients and blood flow, and restoring and maintaining function of the heart tissue itself.

In his preliminary investigations of bone marrow stem cells, Dr. Itescu achieved remarkable success in three short years. He published the first evidence, in Nature Medicine in April 2001, that certain bone marrow cells (cells that express the c-Kit protein) can be manipulated to become angioplasts. When injected into the tails of rats with simulated heart attacks, these highly differentiated cells migrated directly to the area of heart damage, halted the remodeling process, and helped regenerate blood vessel tissue. The protective effect was clear: in this trial, the technique resulted in up to 40% improvement in heart function in the animals studied. This marked a major therapeutic achievement compared to the 10% improvement typically expected with current medical management.

Dr. Itescu's approach differs from that of other researchers who are working to stimulate the growth of heart tissue itself. Regenerated heart tissue is of limited value if the blood vessels supporting it are inadequate. Furthermore, the team's efforts thus far demonstrate that regeneration of blood vessels actually promotes the development of heart muscle cells too. "The capillary network must be able to meet the increased demands of the post-infarction heart," Dr. Itescu explains. "What we are doing is trying to enhance a naturally occurring process."

On the basis of his groundbreaking work, Dr. Itescu was awarded a 5-year NIH RO1 grant for over $2 million in direct and indirect funding to begin examining the function of bone marrow stem cells from human heart disease patients. He has obtained ethics committee approval to begin a protocol trial testing the safety and potential efficacy of procedures to harvest and subsequently reinfuse adult bone marrow stem cells. This trial sets the stage for upcoming randomized clinical trials of the efficacy of progenitor cells in repairing the human heart.

In this 12-month trial, the researchers are collecting, processing, and re-infusing endothelial stem cells systemically in about 25 patients of various ages who have angina, who have suffered a heart attack, or who have heart failure. The administration of granulocyte stimulating factor (G-CSF) induces the migration of the cells from the bone marrow to the blood, where they are obtained. The team then purifies, concentrates, and stains the cells with radioactive dye before reinfusion. Whereas in this study the stem cells will be reinfused systemically, in subsequent studies Dr. Itescu will evaluate whether injecting the cells directly into the heart or through a catheter might be more effective for certain clinical indications such as congestive heart failure. The initial trial is designed to evaluate the safety of this process so that it may be employed in subsequent efficacy trials using adult stem cells to restore cardiac function.

If the process works in humans, the ability to grow new blood vessels through infusions of adult stem cells carries enormous potential for reducing morbidity and mortality associated with cardiovascular disease. Dr. Itescu is confident that not only will the harvesting and delivery process prove safe, but that evidence of efficacy may even become apparent in this initial trial. Once safety is demonstrated, he will begin clinical efficacy trials in which the effects on the heart will be studied.

	Silviu Itescu, MD si5@columbia.edu Phone: 212.305.7176
	Silviu Itescu, MD is Director of Transplant Immunology at Columbia University Medical Center and Assistant Professor, Division of Surgical Science at Columbia University College of Physicians & Surgeons.

Dr. Jay Edelberg: Restoring Endogenous Pathways to the Aging Heart

The size of myocardial infarctions in aging rat hearts is reduced by injection of the cardiac muscle with platelet-derived growth factor (PDGF) as compared with saline (control). Adapted from: Edelberg et al. Circulation 2002, 105:608

His goal is to prevent and even reverse cardiovascular disease in the elderly, and to reduce morbidity and mortality after MI. He focuses specifically on the aging heart, because "that's where most cardiac disease occurs."

Dr. Edelberg's approach is twofold. On the one hand, his team is conducting basic research into the molecular and cellular pathways that govern angiogenesis and vascular function, and the basic causes of dysregulation in the older heart. Aging patients suffer a markedly decreased capacity to develop new blood vessels following MI; by understanding the biological reasons why angiogenesis is impaired, the researchers hope to develop targeted therapies to reverse such impairment.

Simultaneously, the team is also working to restore endogenous pathways to the aging heart via transplantation of adult bone marrow stem cells. Cornell research has shown that alterations in the migration of endothelial cells may contribute to the depressed angiogenic potential in the senescent heart. Systemic approaches such as restoring bone marrow capacity may prove to restore the body's natural ability to generate blood vessels and thereby protect the aging heart from infarction-induced damage.

Aging cardiac endothelial cells exhibit different transport behavior from young ones, and Dr. Edelberg believes that restoring the cellular pathway might be a key factor in reversing angiogenic decline. Indeed, his work has shown already that young endothelial cells restore the cellular communication in aging animal hearts, resulting in improved heart function. For his work demonstrating this, and to support his ongoing research in this area, Dr. Edelberg was awarded the prestigious $450,000 Beeson Award in 2001.

Dr. Edelberg's delivery system is via systemic bone marrow transplantation. "Whether using cytokines or stem cell approaches, the key is to address the fundamental changes in the aging heart as a way to develop long-lasting targeted therapies," he states. "One way is by restoring bone marrow stem cell capacity." At this time, Dr. Edelberg is working with animal subjects. If his research demonstrates efficacy, it could lead to human trials of therapy aimed at promoting the growth of cardiac blood vessels. This would represent a significant potential to reduce the incidence of cardiovascular disease among aging patients.

	Jay M. Edelberg, MD, PhD jme2002@med.cornell.edu Phone: 212.746.1361
	Jay M. Edelberg, MD, PhD is Assistant Professor of Medicine at the Weill Medical College of Cornell University.

Dr. Judah Weinberger: Angiogenic Growth Factors

"We are studying the ability of these factors to stimulate the growth of collaterals and new blood vessels," he says. "We see this process occurring naturally in the earliest stages of the life cycle, as the fetus and embryo grow new blood vessels during the development of the organism." Dr. Weinberger has recently identified and isolated genetic materials from bone marrow and muscle cells. "I am hopeful that this recent addition to our technical and cognitive armamentarium, or general approach, will help us in our understanding of the angiogenic process," he says. He predicts that it will be another year or two before he is ready to begin clinical trials that apply this research.

	Judah Z. Weinberger MD, PhD jzw1@columbia.edu Phone: 212.305.1581
	Judah Z. Weinberger MD, PhD is Director of Interventional Cardiology at Columbia University Medical Center and Associate Professor of Medicine and Pharmacology at Columbia University College of Physicians & Surgeons.

Summary of the 4 Approaches to Angiogenesis

Dr. Leonard Lee: Gene Therapy for "Biologic Bypass"

Ex-vivo coronary angiography following AdVEGF121 administration

Their group conducted a Phase I clinical safety trial with 21 human subjects in 1999, shuttling the genetic material, specifically vascular endothelial growth factor (VEGF), directly into the heart via the Ad_GVVEGF121.10 adenovirus.

As reported in Circulation and Annals of Surgery, 15 of the 21 patients underwent conventional coronary bypass in addition to gene therapy, and 6 received gene therapy as the sole treatment. "At 6 months' post-treatment, these individuals showed no adverse effects," Dr. Lee says. "By all of our criteria, we found gene therapy to be very safe." However, as the group was about to verify its results with a new trial, the FDA halted gene therapy research nationwide after the death of a research subject in an unrelated project at another university. That embargo has recently been lifted, and Drs. Lee, Rosengart, and Crystal are now ready to go ahead with an FDA-approved Phase I/Phase II safety and efficacy trial to promote angiogenesis using gene therapy, to be conducted at NewYork-Presbyterian and Evanston.

	Leonard Y. Lee, MD lyl2003@med.cornell.edu Phone: 212.746.5172
	Leonard Y. Lee, MD is Assistant Professor of Cardiothoracic Surgery at Weill Medical College of Cornell University.