Embryonic Stem Cells Rebuild Damaged Heart

Researchers have transformed embryonic stem cells into functional cardiac cells and transplanted them into damaged regions of the myocardium in rats, where they were integrated into the infarct and provided rapid and robust improvements, maintained over a three-month period. The results were reported in the August 2004 issue of the American Journal of Physiology-Heart and Circulatory Physiology.

The researchers used a murine embryonic stem cell line and engineered a cell clone to express fluorescent proteins so they could easily identify the location of the newly generated cardiac cells. After testing, they collected the cells with high potential for becoming cardiomyocytes. Rats that had been induced with myocardial infarction were injected either with the stem cells or a sham product.

Three weeks later, the cardiac contractile function of both groups was tested by echocardiography. The stem-cell treated group's left ventricular pumping was not only significantly stronger than the sham group but its heartbeat reacted favorably to a stress test, unlike the sham group. The improvements lasted for the three weeks of the study. Upon examination, the researchers found the cardiac cells stayed in the heart, and did not
spread to the brain, kidney, or liver. They also took on the distinctive striations indicating proper development of contractile apparatus. These hearts also showed normal cardiac ultrastructure, in contrast to the sham hearts.

In addition, the stem cell treated hearts showed that the wall or muscle had been "rebuilt,” compared with the sham-treated hearts, which remained "eaten-up,” with a decayed, thin look, including the formation of aneurysms.

"By generating diseased myocardium and prompting cardiac repair, embryonic stem cells provide a unique therapeutic modality that has the potential to reduce the morbidity and mortality of this prevalent heart disease,” said the authors, from the Mayo Clinic (Rochester, MN, USA).




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