‘Love hormone’ revealed to have heart healing properties

(Frontiers) - The neurohormone oxytocin is well-known for promoting social bonds and generating pleasurable feelings, for example from art, exercise, or sex. But the hormone has many other functions, such as the regulation of lactation and uterine contractions in females, and the regulation of ejaculation, sperm transport, and testosterone production in males.

Now, researchers from Michigan State University show that in zebrafish and human cell cultures, oxytocin has yet another, unsuspected, function: it stimulates stem cells derived from the heart’s outer layer (epicardium) to migrate into its middle layer (myocardium) and there develop into cardiomyocytes, muscle cells that generate heart contractions. This discovery could one day be used to promote the regeneration of the human heart after a heart attack. The results are published in Frontiers in Cell and Developmental Biology.

“Here we show that oxytocin, a neuropeptide also known as the love hormone, is capable of activating heart repair mechanisms in injured hearts in zebrafish and human cell cultures, opening the door to potential new therapies for heart regeneration in humans,” said Dr Aitor Aguirre, an assistant professor at the Department of Biomedical Engineering of Michigan State University, and the study’s senior author. Cardiomyocetes typically die off in great numbers after a heart attack. Because they are highly specialized cells, they can’t replenish themselves. But previous studies have shown that a subset of cells in the epicardium can undergo reprogramming to become stem-like cells, called Epicardium-derived Progenitor Cells (EpiPCs), which can regenerate not only cardiomyocytes, but also other types of heart cells.

“Think of the EpiPCs as the stonemasons that repaired cathedrals in Europe in the Middle Ages,” explained Aguirre.

Unfortunately for us, the production of EpiPCs is inefficient for heart regeneration in humans under natural conditions.

Enter the zebrafish: famous for their extraordinary capacity for regenerating organs, including the brain, retina, internal organs, bone, and skin. They don’t suffer heart attacks, but its many predators are happy to take a bite out of any organ, including the heart – so zebrafish can regrow their heart when as much as a quarter of it has been lost. This is done partly by proliferation of cardiomyocytes, but also by EpiPCs. But how do the EpiPCs of zebrafish repair the heart so efficiently? And can we find a ‘magic bullet’ in zebrafish that could artificially boost the production of EpiPCs in humans?