Preliminary data from the largest CD34+ adult stem cell study for heart disease has shown the first evidence that delivering a potent form of autologous (patient-derived) adult stem cells into the heart muscle of patients with severe angina (chest pain due to blocked arteries) may result in less pain and improved exercise tolerance. The stem cells contribute to forming new angiogenic blood vessels that provide critical blood flow to oxygen-starved heart tissue. The findings were presented on March 28 as a late-breaking abstract at the American College of Cardiology's 58th annual scientific session in Orlando.

The prospective phase II, randomized, double blind, placebo-controlled, multi-center study included 167 adult patients who were on maximal medical therapy and were not suitable candidates for conventional procedures to improve blood flow to the heart, such as angioplasty, stents, or coronary artery bypass surgery. All patients were given a drug to stimulate release of CD34+ adult stem cells from the bone marrow; these cells were then collected from the bloodstream using a process called apheresis, and then separated from the other blood components.

The CD34+ adult stem cells were injected into 10 locations in the heart muscle of patients in the treatment group. Patients in the placebo group received saline injections. Researchers used a sophisticated electromechanical mapping technology to identify where the heart muscle was alive but not functioning because it was not receiving enough blood supply. “In this situation, the muscle hibernates because it wants to decrease energy consumption to stay alive," explained principal investigator Douglas Losordo, M.D. "It's not getting enough oxygenated blood to perform normally, so it shuts down its contractile function."

After the procedure, the autologous stem cell transplant patients were able to walk longer on a treadmill (60 seconds on average) than those in the placebo group. It also took longer until they experienced angina pain on a treadmill compared to the placebo group and, when they felt pain, it went away faster with rest. In addition, stem cell-treated patients had a reduction in the number of episodes of chest pain compared to the control group.

"The results from this study provide the first evidence that a patient's own stem cells could actually be used as a treatment for their heart disease," said Dr. Losordo, who is also the Eileen M. Foell Professor of Heart Research at the Feinberg School of Medicine and of the Program in Cardiovascular Regenerative Medicine at Northwestern Memorial Hospital. Northwestern Memorial Hospital was the lead site of the study, which was sponsored by Baxter International Inc. "The study provides potential hope for those patients with currently untreatable angina to be more active with less pain."

According to the Angiogenesis Foundation, about 300,000 out of the estimated one million people in the U.S. who suffer from chronic, severe angina cannot be helped by traditional medical treatment. The patients in the study were Canadian Classification System (CCS) class 3 or 4, meaning they experienced chest pain while performing normal to minimal activities such as brushing their teeth, or even while at rest. New treatments that stimulate coronary angiogenesis are a highly promising approach to this debilitating and life-threatening condition."

"In addition to the new vessels that adult stem cells help grow," stated William Li, M.D., President and Medical Director of the Angiogenesis Foundation, "this approach is likely to bring in crucial survival factors that promote recovery and possibly even regeneration of damaged heart tissue."

Dr. Losordo cautions that the findings of the 26-site trial, while encouraging, are not yet definitive and require verification in a larger randomized study. Analysis of this study’s efficacy at 12 months is pending.

By Roderick Smith, M.S.

References: Losordo DW. Randomized, double-blind placebo controlled phase 2 study of intramyocardial injection of autologous CD34+ cells for treatment of refractory angina. Presented at: American College of Cardiology Scientific Session/ i2 Summit. March 28, 2009; Orlando, FL.