Injecting stem cells sparks progress in repairing heart

ORLANDO — Researchers here reported small successes Wednesday in using stem cells to patch ailing hearts, an effort that has generated more debate than breakthroughs.

Stem cells are the building blocks of a variety of tissues, while embryonic stem cells can grow into any tissue in the body.

Researchers from Finland and California showed it is possible to inject heart attack patients with muscle stem cells and boost their hearts' pumping power. The studies, though preliminary, are the latest of several to open a window into the future of heart attack care.

"If we can do this, we are going to see a complete revolution in medicine, how we treat heart disease and heart attacks," says Nabil Dib of the University of California, San Diego Medical Center.

That day is years off. Doctors are still trying to figure out how to plant cells in the heart so they will take over for tissue that no longer functions. It won't be easy. The heart is complex with a built-in electrical system, blood supply and tireless cells.
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Over the past few years, researchers have carried out about two dozen trials in which stem cells were injected into the heart, most of them taken from adult tissues. Most yielded positive, though modest, results.

Scientists have yet to answer key questions. How long will stem cells survive after they're injected? Can they be tweaked to become heart cells? Such questions must be resolved before research takes off, says Joseph Wu of Stanford University.

Last year, three major studies showed mixed results. "One was positive, one was negative, and one was equivocal," Wu says. "Now we're back to the drawing board."

Scientific issues aren't the only obstacles. Others include ethical and religious concerns about the use of embryonic stem cells, which prompted the White House to restrict their use. "The added burden we have in the U.S. is that regulatory issues make it difficult to get anything off the ground," says Mariell Jessup of the University of Pennsylvania.

In the studies reported at a meeting of the American Heart Association:

•Doctors concluded it was feasible and safe to replace scarring from decade-old heart attack s with hundreds of thousands of custom-cultured cells taken from each patient's thigh muscle. The cells appear to take root and grow, but some scientists question that. The procedure likely would cost more than $100,000, says Jonathan Dinsmore of Mytogen, Inc., the company that cultures the cells.

•Doctors at two hospitals in Finland injected 39 patients with special bone marrow cells within a week of having a heart attack, boosting their pumping power compared with patients who did not get the treatment.

"There clearly is a signal that cell therapy can contribute to recovery in acute (heart attacks)," says Andreas Zeiher of the University of Frankfurt, lead investigator of a larger study released last year that yielded similar findings.

-USA Today