by Arlene Miles

Created on: August 20, 2010

The latest advances in heart stem cell research involve a study from the University of Miami published in the July 29, 2010 issue of Circulation Research that focuses on the effects of immature human stem cells extracted from bone marrow. Built upon another UM study published the previous December, the research helps explain how stem cells accelerate the heart’s healing process.

These studies found that stems cells helped hearts, first by actually turning into new health heart cells after they were injected into the body via catheter. The stem cells actually replaced cardiac cells damaged by coronaries. Other stem cells that didn’t turn into new heart muscle were found to induce stem cells already existing in the heart to multiply and build additional heart muscle. Cardiac stem cells work like those in hair follicles, which make hair regrow following a haircut.

Until recently, only embryonic stem cells were thought to be pluripotent, meaning that they are able to develop in more than one manner. According to the American Heart Association, other recent research has indicated that adult stem cells can be induced to be pluripotent, thus providing the potential to create patient-specific cell therapies that could reduce underlying complications found in therapies with embryonic stem cells.

As defined by the National Institutes of Health (NIH), induced pluripotent stem cells (iPSCs) are adult cells that have been genetically reprogrammed to an embryonic-like state by  being forced to express genes and factors important for maintaining properties of embryonic stem cells. Human iPSCs also express stem cell markers and are capable of generating cells characteristic of all three germ layers.

Also as noted by the NIH, a number of stem cell types, including embryonic stem cells (ES), cardiac stem cells residing within the heart, myoblasts (muscle stem cells), adult bone-marrow derived cells, endothelial progenitor cells, which give rise to the interior lining of blood vessels, and umbilical cord blood cells, have all been considered possible sources for regenerating damaged heart tissue. All have been explored through experiences with mice and rats, with some being tested on larger animals such as pigs.

Several small studies involving humans who have generally undergone open-heart surgery indicate that stem cells injected into the blood or directly into injured heart tissue appear to improve cardiac function and may promote formation ofr new capillaries.

Another area of stem cell research that the NIH indicates holds promise is that stem cells appear to be able to be coxed into developintg as new cardiomyocytes and vascular endothelial cells. This approach would have great advantages over heart transplant therapy. One stuedy showed that human adult stem cells taken from bone marrow can give rise to vascular endothelial cells when transplanted into rats. The cells were used to form new blood vessels in the damaged areas of rats who had suffered heart attacks. When injected into the bloodst4ream, these cells prevented the death of thickened but generally viable myocardial cells and reduced the formation of collagen fibers and scars.

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