Human Heart Can Regrow Muscle After a Heart Attack, Australian Study Reveals

The human heart can grow new muscle cells after a heart attack. A world-first study from the University of Sydney confirms this and it rewrites a medical belief held for decades.

The research, published in the journal Circulation Research, shows that cardiomyocytes (heart muscle cells) actively divide and regenerate in damaged human heart tissue. This process, called mitosis, had only ever been seen in animals like mice. Now, for the first time, scientists have confirmed it happens in humans.

The discovery gives new hope to millions living with heart disease worldwide. It also sets the stage for future therapies that could reverse heart failure a condition that currently has no cure except a transplant.

What Happens to the Heart During a Heart Attack

A heart attack (myocardial infarction, or MI) occurs when a blood clot blocks a coronary artery. This cuts off oxygen to heart muscle, causing cells to die within minutes. The body responds by forming scar tissue over the damaged area.

Scar tissue does not beat. It does not contract. This means the heart pumps less blood with every beat. Over time, this leads to heart failure, arrhythmia, or a second, more severe heart attack.

Medical students have been taught for generations that cardiomyocytes cannot divide after birth. The cells you are born with are, largely, the cells you die with. A heart attack destroys up to one-third of them permanently or so the thinking went.

The Australian Study: What Researchers Found

The study was led by Dr. Robert Hume, a cardiologist and research fellow at the University of Sydney’s Charles Perkins Centre and the Baird Institute for Applied Heart and Lung Research. Senior author Professor Sean Lal a heart failure cardiologist at Royal Prince Alfred Hospital oversaw the research alongside a multi-institution team.

Researchers used 3 distinct tissue sources to reach their findings:

• A full human heart from a brain-dead donor
• Living tissue samples from patients undergoing coronary artery bypass graft (CABG) surgery
• Advanced RNA sequencing, protein analysis, and metabolic profiling of oxygen-deprived heart cells

Key finding: 7% to 8% of cardiomyocytes in damaged heart tissue showed active mitosis. Full repair would require 25% to 50% mitosis, so the regeneration is limited but it is real, measurable, and reproducible.

The team also identified specific biological signals in the damaged tissue that appear to trigger this cell division. These included transcripts, proteins, and metabolites previously linked to heart regeneration in rodent studies. In short, the oxygen-starved environment of a heart attack may itself activate a dormant repair programme.

Why This Finding Is Bigger Than It Sounds

Most competitor coverage treats this as a “hopeful” but distant science story. That misses the precision of what was found. Here is why the data matters:

• First human proof of post-MI mitosis. Previous research showed this in zebrafish (complete regeneration) and mice (partial). Humans were assumed to lack this ability entirely.
• Living tissue model created. The team developed a reproducible lab system using real human heart tissue. This gives future researchers a reliable platform to test drugs and therapies.
• Hypoxia as a trigger. Low oxygen levels during a heart attack appear to activate the same regeneration signals seen in fetal hearts, which develop in a naturally low-oxygen womb.
• Mechanical pumps boost repair. Patients using Left Ventricular Assist Devices (LVADs) showed cell renewal rates of 3.1% per year six times higher than healthy hearts. Reducing heart workload appears to amplify natural repair.

Dr. Hume stated: “Our research shows that while the heart is left scarred after a heart attack, it produces new muscle cells, which opens up new possibilities.”

Heart Failure: The Scale of the Problem

Cardiovascular disease (CVD) kills more people globally than any other cause. It accounts for nearly 24% of all deaths in Australia and roughly 17.9 million deaths per year worldwide, according to the World Health Organization.

In Australia alone, around 144,000 people live with heart failure. Only about 115 heart transplants are performed each year in the country. That gap between those who need a new heart and those who can get one is where this research becomes urgent.

Heart failure has no cure except transplantation. Drug therapies manage symptoms. Mechanical pumps (LVADs) extend life. But neither regenerates damaged muscle. This study points toward a third path: amplifying what the heart already tries to do on its own.

In the United States, 805,000 heart attacks occur every year one every 40 seconds. Globally, the burden on healthcare systems from post-MI heart failure costs hundreds of billions of dollars annually.

What the Research Does Not Mean

This discovery is not a cure. Professor Lal was direct about that:

“Although this new discovery of regrowing muscle cells is exciting, it isn’t enough to prevent the devastating effects of a heart attack,” he said.

The 7% to 8% mitosis rate observed falls far short of the 25% to 50% needed to meaningfully repair a damaged heart. Scar tissue still forms. The heart is still weakened. Patients still face serious risk after a major MI.

What the research does is identify a biological mechanism that, if amplified through drugs, gene therapy, or other interventions, could one day reduce or reverse heart failure. That process from discovery to clinical therapy typically takes 10 to 20 years.

What Comes Next: The Road to Regenerative Therapy

The University of Sydney team now has a working lab model using living human heart tissue. Their next steps involve 4 areas of investigation:

• Protein targets. Several proteins already identified in the study have previously been shown to drive heart regeneration in mice. The team will attempt to replicate that effect in human tissue.
• Hypoxia pathways. Understanding exactly which oxygen-deprivation signals trigger mitosis could allow drug developers to mimic those signals safely after a heart attack.
• LVAD-assisted regeneration. The 3.1% annual renewal rate seen in LVAD patients suggests that reducing mechanical load on the heart enhances natural repair. Future therapies may combine mechanical support with biological regeneration.
• Gene therapy potential. Longer-term, modifying the genetic pathways controlling cardiomyocyte division could enable more substantial cardiac regeneration.

Similar work is underway at institutions including the Harvard Stem Cell Institute and the European Society of Cardiology, where researchers have been exploring stem cell-based and gene therapy approaches to cardiac repair. The Sydney study adds crucial human evidence that the heart’s own biology not just external intervention can be the starting point.

Context: Previous Research on Cardiac Regeneration

Science did not arrive here overnight. A growing body of work over the past 20 years built the foundation for this discovery:

• 2002 Anversa et al. published early (later controversial) claims about cardiac stem cells regenerating the human heart, sparking two decades of debate.
• 2013 Research confirmed that adult humans replace roughly 0.5% of heart muscle cells per year through a slow baseline turnover process.
• 2018 Studies on neonatal mice confirmed that newborn hearts can fully regenerate within the first week of life but this ability disappears quickly after birth.
• 2024 Multiple groups identified zebrafish cardiac regeneration genes that may have human analogues.
• 2026 Hume, Lal et al. confirm, for the first time in humans, that mitosis increases measurably in heart tissue following a myocardial infarction.

The HIV treatment story offers a useful parallel: decades of research turned a death sentence into a manageable condition. Read how science transformed HIV care in our article on HIV Treatment Now Comparable to Chronic Conditions Like Diabetes. A similar transformation may be possible for heart failure.

A Broader Picture: Science Rewriting What the Body Can Do

This heart study fits a wider pattern of discoveries challenging old assumptions about the human body’s limits.

Taiwan scientists recently developed a hair regrowth serum that showed measurable results in 20 days read about it here: Taiwan Scientists Develop New Hair Regrowth Serum That Shows Results in Just 20 Days. Earlier, a Spanish research team reported elimination of pancreatic cancer in laboratory mice using a targeted treatment: Spanish Scientist Develops Treatment That Eliminates Pancreatic Cancer in Lab Mice.

Each of these advances in hair regrowth, cancer treatment, and cardiac repair shares a common thread: the body already contains mechanisms for healing that science is only beginning to decode and amplify.

FAQs: Human Heart Repair After a Heart Attack

Q: Can the human heart heal itself after a heart attack?

Yes. New research from the University of Sydney confirms that human cardiomyocytes undergo mitosis (cell division) after a myocardial infarction. However, the rate 7% to 8% is too low to prevent significant damage. Full repair would require 25% to 50% mitosis.

Q: What is mitosis in heart cells?

Mitosis is the process by which a cell divides to produce 2 identical daughter cells. In heart muscle, this means damaged cardiomyocytes can in limited numbers replicate to replace lost cells. Before this study, mitosis in human heart cells after a heart attack had never been confirmed.

Q: Why did doctors previously believe the heart could not repair itself?

Heart muscle cells were thought to be terminally differentiated meaning they lost the ability to divide after birth. No direct evidence of post-MI mitosis in humans existed before this Australian study.

Q: What triggers heart cell regeneration?

Hypoxia (low oxygen) during a heart attack appears to activate biological signals that promote cardiomyocyte division. These include specific proteins, RNA transcripts, and metabolites linked to regeneration in animal studies. The oxygen-deprived environment may mimic the low-oxygen womb where fetal hearts actively grow.

Q: Who led the study?

Dr. Robert Hume (first author, University of Sydney / Baird Institute) and Professor Sean Lal (senior author, University of Sydney / Royal Prince Alfred Hospital). The study was conducted by the Baird Institute for Applied Heart and Lung Research and was published in Circulation Research in January 2026.

Q: When will heart regeneration therapy be available?

No timeline exists yet. The researchers describe this as a starting point. Drug development and clinical trials for therapies based on this mechanism could take 10 to 20 years, following standard medical research timelines.

Q: Do mechanical heart pumps help the heart regenerate?

Yes. Patients using Left Ventricular Assist Devices (LVADs) show cardiomyocyte renewal rates of 3.1% per year six times higher than healthy hearts. Reducing the workload on the heart appears to allow natural repair mechanisms to function more effectively.

Q: How common are heart attacks globally?

Cardiovascular disease kills approximately 17.9 million people per year worldwide. In the US, a heart attack occurs every 40 seconds, totalling 805,000 per year. In Australia, around 144,000 people live with heart failure at any given time.

The Bottom Line

The human heart is not as permanent in its damage as medicine once assumed. This Australian study does not promise a cure but it proves the biological door to cardiac repair is open. The goal now is to push it wider.

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