Mining fat tissue for cardiac repair

CHICAGO — Sifting stem cells from fatty tissue and shooting these nascent cells into the coronary arteries of people who just survived a heart attack may limit heart-tissue damage, researchers have found. The process, which takes a few hours, might rescue cells on the cusp of dying, said Henricus Duckers, an interventional cardiologist at Erasmus University in the Netherlands who presented the new findings November 16 at a meeting of the American Heart Association.

The small study is the first to reinfuse fat-derived stem cells into heart attack patients, he said.

Duckers and his colleagues recruited 14 people who had just survived a severe heart attack. All had undergone emergency treatment to reopen blocked coronary arteries. Surgeons removed fatty tissue from each patient’s abdomen and placed it in a machine that separates fat cells from stem cells.  The researchers then randomly assigned 10 of the patients to get the actual therapy, in which only the stem cells are injected within 24 hours into the individual’s coronary artery, where they flow downstream into damaged parts of the heart. The other four patients received placebo infusions.

Over six months, the scar size of the treated patients shrank from 31.6 percent of the left ventricle — the huge pumping chamber of the heart — to roughly 15.4 percent on average, magnetic resonance imaging showed. This reduction by half goes well beyond the 10 percent typically seen in heart attack patients, Duckers said. In those who received a placebo, ventricle scar size remained unchanged.

The rate at which blood was pumped out of the heart also improved somewhat in the group that got the cell therapy.

Eduardo Marbán, director of the Cedars-Sinai Heart Institute in Los Angeles, said that while several kinds of stem cells have been tried in heart therapy over the past decade, three stand out — fat-derived cells, bone marrow cells and cells taken from heart tissues themselves.

Most stem cells seem to work indirectly, he said. Once injected into the heart, the cells act more like role models than like replacement heart-muscle cells. “They send out danger signals to the rest of heart to activate endogenous repair mechanisms. New muscle may not be due directly to the new cells you put in, but more from this role model effect and recruitment effects,” Marbán said.

Duckers agreed. “We think that these [fat-derived stem] cells do not grow into new tissue,” he said. Rather, he suspects that they make growth factor proteins and recruit an inflammation-quelling immune protein called interleukin-10 to the damaged areas of the heart. The infusions seem to foster scar shrinkage, muscle recovery and even the growth of new blood vessels. Duckers said much of this benefit probably comes from preventing cells on the verge of dying from going under. “Adding the growth factors can tip that balance into a positive direction and they survive.”

Duckers said that larger trials of the fat-derived stem cells are planned in Europe.