A team of researchers from the Temple University School of Medicine (TUSM) has conducted a study involving the use of communications modules secreted by stem cells to help limit the damage caused by a heart attack. The team performed tests on mice, with extremely promising results.
During a heart attack, the tissue of the vital organ is often badly damaged, and it has little innate ability to repair itself. Instead, it compensates by growing large and flabby, which can lead to congestive heart failure, which in turn is currently responsible for one in nine deaths in the United States.
To combat the pressing issue, the TUSM team turned to exosomes – tiny sacks secreted by cells that act as messengers, allowing different cells in the body to communicate. While these extracellular vesicles are secreted by nearly all types of cell, the researchers believed that exosomes from stem cells, which have the unique ability to grow into any type of cell in the human body, might well be a useful tool in mitigating damage caused by heart attacks. 
Previous studies have shown that injecting damaged hearts with stem cells is ineffective, and due to the nature of the cells, can run the risk of creating a tumor made up of a mass of cells of different tissue types, known as a teratoma. So the team looked to approach the problem from a slightly different angle, injecting only the exosomes from stem cells. It was known that this would avoid the teratoma problem, and could have positive effects on damaged heart tissue.
The team conducted a study on mice with myocardial infraction heart attacks, with one group receiving exosomes from stem cells, and another – the control group – being injected with fibroblast exosomes.
The results were extremely promising, with the stem cell exosome mice exhibiting improved heart function, less scar tissue, lower levels of programmed cell death and better capillary development around the damaged area. There was also a higher presence of cardiac progenitor cells – the heart's own stem cells – in the stem cell exosome-injected mice. Overall, the heartbeat of the mice was stronger than those in the control group, with less unhealthy enlargement of the organ. 
The researchers then took things a little further, isolating an abundant gene-regulating molecule (microRNA) from the exosomes, known as miR-294, and introducing it to cardiac stem cells in a laboratory setting. The results indicate that many of the positive effects of the stem cell exosomes seen in the animal study were mimicked here.
The team intends to continue its research, studying the effect of individual microRNAs on damaged heart tissue. 
"Our work shows that the best way to regenerate the heart is to augment the self-repair capabilities and increase the heart's own capacity to heal," says researcher Dr Mohsin Khan. "This way, we're avoiding risks associated with teratoma formation and other potential complications of using full stem cells. It's an exciting development in the field of heart disease."
The researchers published the findings of the study in the journal Circulation Research.
Source: TUSM