Babies regenerate heart tissue efficiently, while adults develop scars after injuries.
Scientists have long been intrigued by the body’s ability to heal itself, particularly when it comes to the heart. While newborn hearts can recover from injuries with little to no lasting damage, adults often face permanent scarring that can lead to heart failure. A recent study from Northwestern Medicine may help explain why this happens, highlighting key differences in how immune cells respond to injury at different ages.
The research focuses on macrophages, a type of immune cell that plays a major role in healing. In newborns, these cells quickly clean up dying tissue and send out signals that help new heart cells grow. In adults, however, macrophages don’t work as efficiently, making it harder for the heart to repair itself after a heart attack.
The study, conducted in mice, compared how newborn and adult hearts responded to injury. Scientists found that newborn macrophages were better at recognizing and removing dead cells thanks to a specific receptor called MerTK. This cleanup process triggered the production of a molecule called thromboxane A2, which then signaled heart muscle cells to multiply and repair the damaged tissue. In contrast, adult macrophages produced much less of this molecule, leading to weaker repair signals and more scar tissue.
To test their findings, researchers blocked the MerTK receptor in newborn mice. When they did, the mice lost their ability to regenerate heart tissue, making their healing process resemble that of an adult. This confirmed that the way macrophages behave early in life plays a major role in heart regeneration.
Further analysis revealed another key factor—how heart muscle cells in newborns respond to thromboxane A2. Unlike in adults, these cells are primed to react to the molecule by shifting their metabolism to support growth and repair. This additional step in the healing process makes newborn hearts much better at regenerating compared to adult hearts.
One of the biggest takeaways from this study is the potential for new treatments. If scientists can find a way to boost thromboxane A2 production in adults, they might be able to improve heart healing after a heart attack. Instead of scar tissue forming, the heart could regenerate healthier muscle, reducing the risk of long-term complications. Researchers are now exploring whether certain drugs or gene therapies could stimulate macrophages in adults to behave more like those in newborns.
While these findings are still in the early stages, they open the door for future research into ways to “reprogram” the immune system. If doctors could tweak macrophage behavior in adults, it might change how heart disease is treated, offering hope for millions of people living with heart conditions.
The study will be published in the journal Immunity, with researchers continuing to explore how immune cells influence healing. As they learn more, there’s a chance that what’s been discovered in newborns could one day lead to life-changing therapies for adults struggling with heart damage. Scientists believe that by understanding and replicating the natural healing mechanisms of newborns, they might be able to develop groundbreaking treatments that could change the way heart disease is managed.
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Study explores why newborns regenerate heart tissue better than adults
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