Heart cells discovery raises treatment hopes
Scientists announced yesterday the discovery of cells in the heart that can create new muscle cells, raising hopes that doctors may find dramatic new ways to treat heart disease, the nation's leading cause of death.
The team, led by Dr. Kenneth Chien at the University of California at San Diego, showed that the cells, which are similar to stem cells, can be expanded from just a few hundred in a laboratory dish to more than a million, and these cells can be guided into becoming the pulsing muscle cells that power the heart. The finding, published in today's issue of the journal Nature, will probably yield new insights into the heart's development, and might further the quest to regenerate damaged heart tissue -- an idea once thought impossible.
"I think this is a very important paper," said Dr. Leonard Zon, a scientist at Children's Hospital Boston and president of the International Society for Stem Cell Research. "People have not been able to find these cells, and they have been trying very hard."
Yesterday's announcement held extra interest for local researchers because Chien, the senior scientist behind the work, is in the midst of a somewhat surprising move to Massachusetts. Local stem cell biologists have been worrying that the November passage of a $3 billion stem cell program in California is going to make it difficult to recruit top talent. But Chien, a biologist, will begin working this summer as director of the Cardiovascular Research Center at Massachusetts General Hospital and a member of the Harvard Stem Cell Institute. Chien's recruitment was an intense effort, according to a scientist involved, and means that he will bring the new cells, and the research program based on them, to Boston.
"I am sure that there are a lot of people in California who will be sad to see him go," said Dr. Doris Taylor, director of the Center for Cardiovascular Repair at the University of Minnesota.
The new type of cell contributes to a broad change in how biologists view the heart. For decades, the heart was viewed as similar to the brain: a vital organ unable to repair itself. Over the last decade, neuroscience has been profoundly altered by the realization that the brain is surprisingly malleable, and now a similar trend is rocking cardiac science.
These changes have been driven by rapid strides in the understanding of stem cells -- powerful cells that have the ability to multiply nearly indefinitely and also transform into more specialized cells. Stem cells play a crucial role in maintaining and repairing some parts of the body, such as the skin, and scientists are hoping to harness stem cells to repair many kinds of damage that the body cannot repair itself.
Because heart disease claims so many victims, some 700,000 annually in the United States alone, the search for cardiac stem cells has been particularly intense. Chien's team has found cells that play a crucial role in the development of the heart, and have the ability to form different types of cardiac muscle cells, according to the paper. But the cells are called "progenitor cells," not stem cells, because the team has not shown that they have the ability to multiply nearly indefinitely, Chien said.
Other scientific teams have claimed to find cardiac stem cells, but the claims have been controversial because critics do not believe that the evidence has been conclusive. The work announced yesterday uses a different method for marking and tracking cells. The method makes the conclusions more compelling, according to Dr. Jonathan Epstein, a professor of medicine at the University of Pennsylvania who wrote a review of heart stem cell research scheduled to appear tomorrow in the journal Cell.
Chien has been a vocal critic of what he considers the rush to start human clinical trials of stem cell treatments for the heart, saying that the biology is not understood well enough. Trials are underway, using bone marrow, which is rich with the stem cells that form the blood. A paper published last year challenged the idea that such cells could form heart muscle cells, but there have been early indications from the trials that the treatment is helping patients. Just last week, researchers led by Dr. Douglas W. Losordo, chief of cardiovascular research at Caritas St. Elizabeth's Medical Center in Brighton, published a study indicating that a type of human stem cell found in bone marrow can mend rat hearts.
The cells announced yesterday, however, reside in the heart itself, and play a role in building muscle early in the heart's development, according to Eric N. Olson, chairman of the department of molecular biology at the University of Texas Southwestern Medical Center at Dallas. The team found the cells in the hearts of newborn mice, rats, and humans, and they successfully transformed them into muscle cells in the laboratory. What the researchers have not shown is whether the cells can be used to repair a damaged heart.
Chien said that there were probably too few cells in the heart for them to be part of any natural repair mechanism. But, he said, he planned to aggressively pursue the possibility that the cells could be harnessed for treatments. Chien said that Boston has a wealth of top stem cell biologists, and that this was one of the great appeals of coming here. But he said that he, too, is worrying about what the money in California could do to the community here.
"This is a pivotal point for the state," Chien said.
Gareth Cook can be reached at cook@globe.com.
