Israeli researchers appear to have accidentally stumbled upon the answer to one of the mysteries of the heart and its uncanny ability to self-heal.
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Researchers from Hadassah University Hospital, Ein Karem had been conducting a study on sheep in which they implanted a stent from the heart's left ventricle to the left atrial appendage when, "suddenly, tissue was seen growing inside the stent."
"The tissue had a structural resemblance to tissue that was known to grow inside the atrial appendage," Professor Ronen Beeri, the director of the Cardiovascular Research Center at Hadassah and one of the study's partners, reported in the scientific journal PLOS ONE.
After conducting a follow-up experiment on the hearts of adult mice, the Hadassah researchers discovered that what they were looking at was really stem cells hidden in the left atrial appendage which can stimulate the heart to repair itself.
Their findings, presented last month at the Israel Heart Society's annual conference, support the rather revolutionary view among scientists in recent years that the heart contains stem cells that help heal diseased tissue. Beeri’s partners in the experiment included Dr. Jussi Leinonen, Dr. Avishag Korkus-Emanuelov and Dr. Sara Hoss of Hadassah University Hospital.
In the follow-up study, the left atria of the mice’s hearts were sealed and placed on a platform used for growing stem cells. To the researchers' surprise, round cells appeared that resembled the structure of stem cells found in the heart. Their analysis of the cells confirmed their hopes: The cells were found to contain certain proteins that serve as markers for the fetal development of cardiac cells.
What this means is that the cells had the ability to regenerate and turn into not only cardiac muscle cells but also other kinds of cells in the heart, such as blood vessels, connective tissue, and, most importantly, a certain kind of cardiac tissue that is important for the body's immune system. In other words, these stem cells can turn into other cells with the ability to stimulate an injured heart to heal itself.
The researchers' findings are also curious because they shed light on the function of the mysterious left atrial appendage.
The function of this appendage – a kind of pocket on the heart's upper left side that receives oxygenated blood from the lungs through the pulmonary vein – has long baffled physicians. But while its purpose is generally unclear, the damage it can cause is not: Blood accumulates in the left atrial appendage, and patients who suffer from arrhythmic disturbances such as atrial fibrillation are at risk of forming fatal blood clots.