In a recent study, scientists have revealed that the neurohormone,oxytocin can play a crucial role in the activation of regenerative, repair mechanisms in the damaged hearts of zebrafish and human beings . This discovery led by researchers at Michigan State University can be used to promote the regeneration of the human heart after a heart attack.
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What is oxytocin?
Oxytocin is produced in the hypothalamus and released by the posterior pituitary. This peptide hormone is known for its crucial role in social bonding, the regulation of lactation and uterine contractions in women, and the regulation of ejaculation, sperm transport, and testosterone production in men.
Discovery of Oxytocin’s new function
Researchers were able to demonstrate that in cell cultures of human beings and zebrafish, oxytocin can activate heart-repairing mechanisms. Oxytocin can stimulate the migration of stem cells (derived from the epicardium, the heart’s outer layer) into the middle layer i.e.myocardium. In the myocardium, these cells develop into cardiomyocytes, muscle cells that generate heart contractions. Hence, these stem cells can regenerate cardiomyocytes. However, cardiomyocytes cannot replenish; thus, they die in large numbers during a heart attack.
Nonetheless, some cells in the epicardium can undergo reprogramming to become stem-like cells. These are Epicardium-derived Progenitor Cells (EpiPCs). EpiPCs are not only able to regenerate cardiomyocytes but also other types of heart cells.
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But the production of EpiPCs is inefficient for heart regeneration in humans under natural conditions. Thus, the researchers thought of using neurohormones to stimulate the growth of EpiPcs in artificial conditions. Considering zebrafish’s regenerative ability, researchers looked into the stimulating capacity of oxytocin.
What did the researchers find?
They found that in zebrafish, within three days after cryoinjury – injury due to freezing – to the heart, the expression of the messenger RNA for oxytocin increases up to 20-fold in the brain. This oxytocin travels to the epicardium of zebrafish and binds to the oxytocin receptor, triggering a molecular cascade and stimulating local cells to expand and develop into EpiPCs. These newly generated EpiPCs then migrated to the myocardium of the zebrafish, developing into cardiomyocytes, blood vessels, and other important heart cells to replace those which had been lost.
The authors used this discovery to show that oxytocin has a similar effect on human tissue in vitro. They compared the efficiency of oxytocin with other neurohormones in the stimulation of cultures of human Induced Pluripotent Stem Cells (hIPSCs) to become EpiPCs. Oxytocin stimulated the process at up to twice the basal rate compared to other molecules. Moreover, genetic knock-down of the oxytocin receptor prevented the regenerative activation of human EpiPCs in culture.
Concluding the research, lead author Aguirre comments that the results show the possibility that the stimulation by oxytocin of EpiPC production is evolutionary conserved in human beings to a significant extent. He adds oxytocin is widely used for clinical reasons to which replenishment after heart damage can also be added. Even if the heart regenerative properties are only partial, the benefits for patients could be enormous.
The research has been published in the journal Frontiers in Cell and Developmental Biology.