Murry thinks that while the finding is promising, it needs to be confirmed in larger animals such as sheep or pigs, because their hearts beat slower. Rat hearts beat 450 times a minute, while the human heart beats about 70 times a minute. "So, there may be problems that were not predicted with the rat model," he acknowledged.
One expert thinks that while the results of this study are promising, there are still many problems to be overcome before stem cells can be used to treat humans after a heart attack.
"This study makes the case that you can use embryonic stem cells after a heart attack, and shows that there is an improvement in cardiac function," said Dr. Kenneth R. Chien, a member of the Harvard Stem Cell Institute.
In contrast to adult stem cells, these embryonic heart cells appear to actually be heart muscle. Experiments with adult stem cells seem to show improved heart function by creating blood vessels, Chien explained.
Chien noted that long-term follow-up is needed to be sure the heart muscle continues to function and that some of these cells don't become cancer cells, as has been the case with adult stem cells.
"The other issue is whether these cells will survive over a long time and how efficiently are they grafted in with the neighboring cells," Chien said. "In addition, because rat hearts beat so fast, they are resistant to arrhythmias. When you put this into an animal with a slower heart rate, would there be arrhythmias over the long term?"
"Clinical applications are many years away," Chien said. "But this is an important step."
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