In a paper, published in the Journal of Molecular and Cellular Cardiology, a team led by Timothy J. Kamp at the University of Wisconsin-Madison reports that all-purpose embryonic stem cells, transplanted into mouse hearts damaged by experimentally induced heart attacks, shift gears and morph into functional forms of the major types of cells that compose the healthy heart.

The study's results are important because they demonstrate that blank-slate embryonic stem cells can be introduced to damaged heart tissue, develop into heart muscle and into cells that form the heart's blood vessels. If perfected, such therapy could provide a practical, less-invasive alternative to current therapies such as surgery, improve the quality of life for many patients and reduce the number of deaths attributed to heart disease, now estimated at about 700,000 deaths per year in the United States.

In their experiments, when stem cells were introduced directly to tissue damaged by a heart attack, three critical types of cells formed: cardiomyocytes or heart muscle; vascular smooth muscle and endothelial cells.

" There are multiple components," Kamp explains. "But ( in these experiments ) we see the three most important types of cells forming. It didn't completely repair the heart, but it was encouraging."

Kamp emphasized that although results of the study show promise for using stem cells to repair diseased and damaged tissue, clinical application remains a distant hope. Further studies in mice, primates and, ultimately, humans will be required to ensure efficacy and safety.

The experiments were aimed at answering critical questions relative to repairing hearts that have been damaged by heart attacks: Would the cells be driven to repair the heart at the site of the injury, and what kinds of cells would they become ?

The group's finding showed that the cells did indeed migrate to the site of the injury and developed into the critical cell types. Perhaps most importantly, the transplanted cells improved the function of the damaged heart.

" The heart ballooned out less, and its ability to contract improved," Kamp says. " The transplanted cells seemed to respond to the area of active injury. There is something about the injury that favors engraftment and incorporation of those cells."

One intriguing result of the study is that the implanted cells did not result in tumor formation, one of the primary safety concerns for stem cell therapy. Like cancer cells, embryonic stem cells have a capacity to reproduce indefinitely and scientists must perfect cell transplant methods that are safe before the therapy can be attempted in human patients.

Source: University of Wisconsin-Madison, 2005


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