Too much fat around the waist may be bad for your health, but the stem cells it contains might one day save your life. Starting this month, a new European trial aims to determine whether stem cells harvested from a person’s own fat, delivered shortly after a heart attack, could prevent some of the cardiac muscle damage that results from blocked arteries.
During a heart attack, blood vessels that deliver blood to the heart muscle are blocked, and the lack of oxygen slowly kills the tissue. San Diego-based Cytori Therapeutics has developed a treatment that aims to prevent much of that muscle damage before it starts. It works by injecting a concentrated slurry of stem cells and other regenerative cells isolated from the patient’s body directly into the heart’s main artery within 24 hours after an attack. “Time is muscle. The quicker you get in, the better,” says Christopher Calhoun, Cytori’s chief executive officer. “You can’t do anything about dead tissue, but tissue that’s bruised and damaged—that’s revitalizable. If you can get new blood flow in there, that tissue comes back to life.”
Adult stem cells, which exist in small populations throughout the body, can differentiate to form specific tissue types and are responsible for repairing injuries and replacing dying cells. The prospect of using them to heal damaged heart muscle has tantalized biomedical researchers for more than two decades. If the stem cells come from a patient’s own body, there is no risk of rejection. A number of clinical trials in recent years have focused on using stem cells collected from bone marrow, since this potent population can differentiate into both cardiac muscle cells and blood vessel cells, among other types. But marrow stem cells are difficult to collect and somewhat scarce; they must be isolated and then grown in culture before they’re injected back into an injured heart. The process can take weeks.
Over the last decade, however, researchers have discovered that fat tissue has its own population of stem cells that are more easily accessible and far more abundant than the ones in bone marrow. A typical sample of bone marrow yields about 5,000 stem cells; a sample of fat, gathered quickly through liposuction, can provide up to 200 times that amount. Fat also contains other cells that may aid the healing process. “My belief is that you need that mixed population of cells in order for this therapy to be effective,” says Stuart Williams, director of the Cardiovascular Innovation Institute in Louisville, Kentucky, who is not affiliated with Cytori. “Everybody who is now seeing success with the use of these cells—almost all of them—are using a mixed population.”
Cytori has created a portable machine that, in less than an hour, can reduce a sample of fat “about the size of a can of Coke,” Calhoun says, to less than a teaspoon of concentrated slurry that Cytori believes contains its most vital elements: stem cells, smooth muscle cells, cells that line blood vessels, and a number of other regenerative cells that can promote growth healing.
“Fat tissue has been used for years by very astute surgeons, who just pulled pieces of fat into areas that weren’t healing well,” Williams says. “All the data so far has shown that these cells are safe, but beyond that, what are these cells doing? We just don’t know.”
One benefit of Cytori’s therapy is that unlike stem cells derived from bone marrow, it can be used immediately after a heart attack, before much tissue damage has occurred. The regenerative cells from fat appear to release growth factors and other chemicals that prevent cell death, Calhoun says, “by sending out signals that say, ‘Don’t commit suicide—the cavalry’s coming.’” He believes that it’s the mixture of different cells, rather than just the stem cells, that are important for repair: “I think it’s a group of cells that are reacting to the local environment, signaling back and forth, that help stimulate new blood vessels.”