Bone marrow stem cells do not convert into heart muscle cells in mice, according to a study by UW researchers. These results contradict a study conducted elsewhere that had prompted human clinical trials for such stem cell therapy in the treatment of heart attack.

Charles Murry, associate professor of pathology, led a team of researchers at the UW and at the Wells Center for Pediatric Research at Indiana University during a two-year study of stem cell therapy. They injected hematopoietic stem cells, which typically form blood cells, into the wall of the heart in both normal mice and in mice with hearts damaged by heart attacks.

Murry and his colleagues found that the stem cells did not convert into heart muscle cells in either group, and the damaged heart muscle tissue did not regenerate. Murry's results will be published in an upcoming issue of the journal Nature, and are available online on the journal's Web site.

The results represent a break from previous research, including a study published three years ago in Nature that indicated such stem cells could help regenerate damaged heart muscle tissue after a myocardial infarction. The work of that group is not reproducible, Murry said.

The group's research prompted a series of premature clinical trials for the treatment of acute heart attacks, Murry said, and those trials are still going on now. However, since the trials appear to be safe, Murry thinks it is worthwhile continuing them to see whether the stem cell therapy is effective.

Despite the absence of muscle regeneration from stem cell therapy, Murry thinks there could still be potential benefits from the therapy in damaged hearts. The cells could help increase blood flow in the vessels surrounding damaged cardiac tissue, or the cells could help prevent remodeling in the heart, which is when the heart dilates after a heart attack. That dilation can damage the heart muscle, Murry said, so preventing the dilation could help avoid the damage.