Repairing the heart without using stem cells

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Published April 27, 2012

| FoxNews.com

When a person suffers a heart attack, scar tissue forms over the damaged areas of the heart, reducing the organ’s function.  However, in a recent study, scientists successfully turned this scar tissue into working heart muscle without the use of stem cells.

Duke University researchers used molecules called microRNAs to convert scar tissue (called fibroblasts) into heart muscle cells in a living mouse, improving the heart’s ability to pump blood.  

According to the scientists, this process is much simpler than stem cell transplants and has none of the ethical concerns, making it a potential turning point in the science of tissue regeneration.

“Right now, there’s no good evidence stem cells can do the job,” senior author Dr. Victor Dzau, a James B. Duke professor of medicine and chancellor of health affairs at Duke University, told FoxNews.com.  

Scientists believe embryonic stem cells are the best to use for tissue regeneration because they are pluripotent—meaning they can become any type of cell in the body.  However, Dzau said there have not been enough experiments done to prove how functional the stem cells are in regenerating tissues and whether or not they may form deadly tumors.

Additionally, there are ethical concerns about using cells derived from a human embryo, he said.

Meanwhile, adult stem cells avoid the controversy surrounding embryonic stem cells but have a limited capacity to form other types of cells.  The results of using these adult stem cells for tissue regeneration are “not as satisfying as one would like,” Dzau said.

Rather than stem cells, the new method developed by Dzau’s team uses microRNA molecules—which typically control gene activity—and delivers them into the scar tissue that develops after a heart attack.  The microRNAs are able to reprogram, or trick, the scar tissue into becoming heart muscle again instead.  

Testing is still in its early stages, but so far, the method appears to be relatively easy, and the data looks very promising, according to the researchers.

“It’s a much simplified, feasible way of causing regeneration; very easy to use as therapy,” Dzau said.  “With stem cells, you have to take them from the embryo or tissue in the body, grow them in culture, and re-inject them—and then there can be technical and biological problems.

“With microRNA, after a heart attack you can simply convert some of the fibroblasts and tell them to become the right cell type and regenerate,” he said.

The method also has the potential to treat stroke, spinal cord injuries, chronic conditions such as heart disease—and even the normal damage that can come with aging.  It can feasibly be used for any type of organ in the body, though the process of converting the cells may be different for each organ.

“Right now, our work is proof of concept,” Dzau said, adding that the method must still be tested in then larger animals, and if successful there, it can move onto human clinical trials.  “But one could think about all these things of possibilities.  Could you use it to treat the disease of aging and losing brain cells?  Can you convert other cells in the brain to working brain cells?  

“It’s a significant finding because it changes the way we think about regenerating tissues,” Dzau said.  “It breaks open a whole new area.”

The study was funded in part by the National Heart, Lung and Blood Institute and published Thursday in the journal Circulation Research.

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