"We know that if you have a major loss of blood, the spleen is turned on to supplement the bone marrow in replenishing your blood supply. We may find that the spleen kicks in to help with many more biological emergencies. What has been considered a practically unnecessary organ may actually provide critical healing cells," In addition to regeneration of islets, these cells might also produce bone cells-suggested by findings from other researchers-or potentially even cells of the nervous system.
Emory Study Tests Bone Marrow Stem Cells To Improve Circulation In The Legs
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 bypbutt 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.
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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.
Adapted from the following source: Emory University School of Medicine
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Spleen May Be Source Of Versatile Stem Cells
A year ago, Mbuttachusetts General Hospital (MGH) researchers discovered that the spleen might be a source of adult stem cells that could regenerate the insulin-producing islets of the pancreas. In a follow-up to that unexpected finding, members of the same team now report that these potential adult stem cells produce a protein previously believed to be present only during the embryonic development of mammals.
The finding both supports the existence of these splenic stem cells and also suggests they may be able to produce an even greater variety of tissues. The report appears in the January 19 issue of SAGE KE, an online resource on the science of aging from the publishers of the journal Science.
"There may be a previously undiscovered pocket of primitive stem cells in the spleen that are important for healing several types of damage or injury," says Denise Faustman, MD, PhD, director of the MGH Immunobiology Laboratory and senior author of the SAGE KE report. "If so, these cells could have much broader therapeutic applications than suggested by our earlier work."
The researchers also note that the spleen develops from embryonic tissue that is known not only to generate precursors to many types of blood cells, a function shared by the bone marrow, but potentially to form such diverse organs as the small intestine, uterus, vascular system and lung. They theorize that a pocket of these uncommitted cells might remain in the spleen though adulthood. In addition to regeneration of islets, these cells might also produce bone cells-suggested by findings from other researchers-or potentially even cells of the nervous system.
"We know that if you have a major loss of blood, the spleen is turned on to supplement the bone marrow in replenishing your blood supply. We may find that the spleen kicks in to help with many more biological emergencies. What has been considered a practically unnecessary organ may actually provide critical healing cells," says Faustman, an buttociate professor of Medicine at Harvard Medical School.
Adapted from the following source: Mbuttachusetts General Hospital
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