The typical patient with peripheral arterial disease is a man in his 60s; he’s a smoker who has high blood pressure and possibly even diabetes. Because of a blockage in a major blood vessel in his leg, it’s painful when he walks or tries to exercise.
Ten percent of people with peripheral arterial disease experience this chronic leg pain, a symptom called intermittent claudication, according to the National Heart, Lung and Blood Institute, and this symptom markedly limits their ability to walk for even a few minutes. The University of Florida College of Medicine, and six other federally funded centers in the Cardiovascular Cell Therapy Research Network, is recruiting participants for a clinical trial to evaluate whether using stem cell therapy can provide relief.
“We view cardiovascular stem cell therapy as one of the most exciting advances in cardiovascular therapy and even, for that matter, diagnosis,” said Carl J. Pepine, M.D., UF center principal investigator.
Peripheral arterial disease is caused by plaque building up and partially blocking the arteries that transport blood to limbs and organs. In addition to the resulting pain and numbness, people with this disease are at high risk for heart attack or stroke.
Many of these patients are not good candidates for surgery due to their age or other medical factors, and the alternative treatments are often weak or unable to provide long-term relief, said Pepine, a professor emeritus of medicine. Enter stem cell therapy, which has been studied in patients with heart disease and severe peripheral arterial disease, but has yet to be evaluated in patients with intermittent claudication.
For the study, nicknamed PACE, Pepine’s team will treat patients with stem cells retrieved from their own bone marrow. These special bone marrow cells, called bright cells, contain an enzyme called aldehyde dehydrogenase that responds to signals from damaged tissue and may assist in tissue repair and blood vessel growth.
The goal of the study is to see if injecting a concentration of bright cells directly into the affected leg muscles will result in the formation of new blood vessels and improved blood flow. A better blood supply would reduce the pain caused by peripheral arterial disease and allow patients to walk longer distances.
“We are all endowed with the ability to repair ourselves, whether it’s a cut on your skin or a deep injury in one of your organs,” Pepine said. “What we’re doing is trying to capitalize on the body’s own processes and enhance that repair capacity.”
Study participants will be put under anesthesia for a few minutes while bone marrow is extracted, then their aldehyde dehydrogenase-bright cells will be selected, purified, concentrated and several days later injected into their leg muscles during one treatment of 10 injections.
In 2006, the UF College of Medicine became one of five centers in the Cardiovascular Cell Therapy Research Network when it helped conduct three trials in five years that used patients’ bone marrow stem cells to treat different symptoms of heart disease. In all three trials, UF enrolled the second-highest number of participants. In 2011, the network received funding for its second phase of studies and again chose UF to be one of its centers.
“These are very complex trials that require a highly skilled multidisciplinary team — we couldn’t do this alone,” Pepine said. “We are fortunate enough to have wonderful stem cell support at UF Health Shands. We have two stem cells laboratories with absolutely superb staff. We have world experts in stem cells as well as cardiovascular anesthesiologists and surgeons.”
The Cardiovascular Cell Therapy Research Network is sponsored and funded by the National Heart, Lung, and Blood Institute of the National Institutes of Health, and is made up of physicians, scientists and support staff from institutes and universities across the country — including the Minneapolis Heart Institute Foundation, the University of Minnesota, the Texas Heart Institute Stem Cell Center, the University of Louisville, the Vascular and Cardiac Center for Adult Stem Cell Therapy, the University of Miami and Stanford University.
The network is currently recruiting 80 patients over the age of 40 for the intermittent claudication clinical trial. In this double-blind study, patients will be divided into two groups — one that receives stem cell therapy and one that receives a placebo — and observed for a year.