Heart, Heal Thyself?

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Within two months, the patients demonstrated improved heart function, with almost double the pumping motion in those parts where the cells were injected.

When one of those patients died 11 months after treatment, of unrelated causes, the doctors discovered during an autopsy that there was clear evidence of new blood vessel formation to the heart.

The team is now conducting a U.S. trial with 25 patients, and recently won approval for another trial. "We realize that we've not identified the best stem cells, or the best method of administration," says Willerson. "We don't want to be part of the hype, but this is an exciting time."

SMALL SAMPLE.

Willerson and Perin are using the patient's own adult stem cells to avoid rejection by the body's immune system. But a small biotech in Baltimore, Osiris Therapeutics, is aiming to come up with a more universal approach by using donated mesenchymal stem cells (MSC).

These are universal to everyone, so they do not set off an immune reaction. Animal studies indicate that the MSCs are prompted by inflammatory signals to head to the site of an injury, and Osiris recently started a Food & Drug Administration-sanctioned clinical trial to test the therapy in heart attack patients.

Then there are stem cells that actually originate in the heart, discovered only two years ago. These cardiac stem cells exist in very small numbers, but doctors at Johns Hopkins School of Medicine have figured out how to harvest them by taking a small tissue sample from the heart and then growing them in culture.

FIRST PAGE.

The cells have not yet been tested in humans, but when injected into animals they appear to go straight to the heart and regenerate tissue, says Dr. Eduardo Marban, chief of cardiology at Johns Hopkins. "The mystery is: If these cells do work to heal the heart, how do they work?" questions Marban. "We're reading the first page of a very long book here."

Long it may be, but Marban speculates that there could be evidence of whether or not adult stem cells work in humans in a year or two. It will certainly take longer to figure out why. There are many scientists in the field who believe the stem cells may be merely "good neighbors" that are prompting the heart's own healing process to kick into high gear.

That wouldn't be such a bad discovery, says Dr. David T. Scadden, co-director of Harvard University's Stem Cell Institute. "In the short term the stem cells may be providing something that reverses damage, but that could lead to a whole new generation of studies into an off-the-shelf drug that would perform the same function." In that dreamscape, heart attack victims could just visit the pharmacy instead of the hospital.

Arnst is a senior writer for BusinessWeek in New York.