Oxytocin, the so-called love hormone, drives heart regeneration in zebrafish. It wakes up stem cells and turns them into Epicardium-derived Progenitor Cells (EpiPCs), the cells that heal the heart. A zebrafish can regrow its heart even after losing one-third of it. The human heart heals poorly, and a heart attack (myocardial infarction) is still a leading cause of death.
Heart disease, like heart attack (myocardial infarction), is still the top cause of death worldwide. The human heart does not heal well. But some animals, like zebrafish, can regrow whole organs. A zebrafish can regrow its heart even if one-third of it is gone. A new study shows how. The love hormone, oxytocin, wakes up stem cells and turns them into Epicardium-derived Progenitor Cells (EpiPCs). Those cells heal the heart.
Heart attack is still the top cause of death in the US and around the world. In heart disease, the blood vessels that feed the heart muscle get blocked. The muscle downstream starves and dies. That is called an infarction. If doctors do not open the blocked artery fast, with drugs or other tools, the heart muscle dies for good. The result is heart failure and death.
Doctors mostly work to open blocked arteries. They have no way to bring dead tissue back. If they could revive heart muscle and make it regrow, many lives could be saved. And regenerative medicine is not just about the heart. Researchers are looking for ways to help people recover from many illnesses and injuries, such as diabetic neuropathy pain and sciatica nerve pain. In humans, every organ can regrow to some degree. But for most organs, that power is weak. So when the damage is big, the organ fails.
Some animals regrow their organs far better than we do. The zebrafish is one. It can regrow its liver, its heart and more. It can rebuild its heart even after losing one-third of it to an injury. So researchers set out to find how. What they found surprised them. After a heart injury, zebrafish start making oxytocin, a love hormone that humans make too. Their oxytocin levels jump by more than 20 times.
This rise in oxytocin seems to wake up stem cells in the heart’s outer layer, the epicardium. Driven by oxytocin, those stem cells move into the muscle layer of the heart (the myocardium). There they turn into heart muscle cells (cardiomyocytes), and healing begins.
In humans, oxytocin does many jobs. The body releases it after sex, and it is tied to pleasure and bonding. It also controls ejaculation, milk letdown (lactation) and other body functions. Its effects reach across the body and shape how the brain works.
Stem cells sit in almost every tissue in the human body. The problem is that science still does not know how to control them. So researchers are hunting for ways to steer the stem cells in each body part. Learn to steer them, and you can regrow organs and speed healing.
Researchers at Michigan State University tested oxytocin and 15 other neuropeptides (small signaling proteins). Only oxytocin had the power to drive healing. Oxytocin seems to reprogram stem cells into Epicardium-derived Progenitor Cells (EpiPCs). Those cells can then rebuild the heart. In humans, though, EpiPC activity is low. That is why the human heart can barely repair itself.
Next, researchers tested oxytocin on human heart tissue. In an in vitro study (cells in a lab dish), oxytocin also pushed human induced pluripotent stem cells (hiPSCs) to become EpiPCs. This may be a key step in heart healing after a heart attack (myocardial infarction). And when oxytocin is knocked out, healing stops.
These findings are interesting as oxytocin is a readily available hormone for humans. Therefore, in the future, there is a need to find out if giving oxytocin to myocardial infarction patients can really help. Since oxytocin is approved for clinical use in other health conditions, testing it in heart patients would be relatively easier. If researchers can prove that it helps in clinical settings, we are likely to see its widespread use in heart patients in the near future.
Frequently asked questions
What does oxytocin do to your heart?
In zebrafish, oxytocin levels climb more than 20 times after a heart injury. The hormone wakes up stem cells in the heart’s outer layer, the epicardium. Those cells move into the muscle layer, the myocardium, and turn into new heart muscle cells, and healing begins. When researchers knocked out oxytocin, the healing stopped.
Can oxytocin heal a human heart after a heart attack?
Not yet proven. In a lab dish, oxytocin pushed human stem cells to become the same progenitor cells, EpiPCs, that rebuild the zebrafish heart. No one has yet shown that giving oxytocin to heart attack patients helps. Oxytocin is already approved for other uses. So testing it in heart patients should be fairly easy.
Can stem cells regenerate the heart?
The human heart heals poorly. Stem cells sit in almost every tissue in the body, but science still does not know how to control them. In people, the activity of heart progenitor cells is low, which is why a heart attack leaves dead muscle behind. Oxytocin was the only one of 16 hormone-like signals tested that turned stem cells into heart-rebuilding cells.
Why is oxytocin called the love hormone?
The body releases oxytocin after sex, and it is linked with pleasure and bonding. It also controls ejaculation and lactation and affects how the brain works. In the Michigan State University work, the same bonding hormone switched on heart repair in zebrafish.
Dr. Gurpreet Singh Padda, MD, MBA, MHP
