Physicians at Emory University School of Medicine are conducting a clinical trial using stem cells generated within the bone marrow to grow new blood vessels that could improve circulation in patients with blockages in the arteries of their legs -- a condition called peripheral vascular disease (PVD). Individuals with PVD have decreased blood flow to the muscles of the legs, especially during exercise, which causes pain, aching, cramping or fatigue in the muscles of their legs when they walk. This condition also is called "intermittent claudication."
The Emory team, led by cardiologist Arshed A. Quyyumi, MD, and cardiology fellow Veerappan Subramaniyam, MD, is using colony stimulating factors (growth factors), to prod the bone marrow to release a type of stem cells called endothelial progenitor cells, which are used by the body to form new blood vessels or to repair damaged ones.
Decreased blood flow in the legs is caused by the blockage or narrowing of the arteries due to build-up of cholesterol. Normally, with exercise, the blood vessels dilate (get bigger), but clogged blood vessels constrict during exercise. In some individuals the vascular system corrects the problem on its own either by forming new blood vessels, called "collaterals," that bypass the blockages, or by repairing the diseased blood vessels. This repair process results in improved circulation even during exercise. Some people are not able to repair their own vessels, however, and physicians don't completely understand the reasons why.
Recent studies show that when muscles do not receive enough blood, the body makes growth factors that stimulate the bone marrow to release stem cells that "home" to the muscle that is not getting enough blood. These stem cells include endothelial progenitor cells (EPCs), which is the type of cell needed to make new blood vessels and to repair damaged ones.
Patients in the clinical trial will be given an injection of either a growth factor called GM-CSF (granulocyte-macrophage colony stimulating factor) or placebo (sterile salt water) three times a week for two weeks. The level of EPCs in the volunteers' blood will be measured before, during and after administration of the drug or placebo. The study is randomized and blinded, which means that volunteers will not know whether they are receiving the study drug or the placebo.
The goal of the study is to determine if and how much GM-CSF will increase the number of circulating EPCs in patients with peripheral vascular disease. Another goal is to find out whether or not increasing the number of circulating EPCs results in improved blood flow to the leg, improved blood vessel function and improvement of patients' symptoms.
Currently, GM-CSF is approved by the FDA for several uses, including in cancer patients to increase the number of white blood cells to fight infection after chemotherapy; in healthy individuals serving as bone marrow donors to stimulate the bone marrow to release stem cells; and in patients who have had a bone marrow transplant to increase the number of white blood cells. It is still considered experimental, however, for use to increase the level of EPCs in patients with peripheral vascular disease.
The investigators are seeking patients in whom prior treatments, including surgery or angioplasty, have been unsuccessful, or patients for whom those treatments are not options. To find out more about the study and eligibility, call 404-712-0170.
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