Inhibition of lncPostn Alleviates Oxidative Stress and Cardiac Fibrosis after Myocardial Infarction ​

When the heart suffers a major injury, such as a heart attack, it does not simply heal like a cut on the skin. Instead, the damaged area is filled with a tough, scar-like tissue. This process, known as cardiac fibrosis, is the heart's attempt to patch the hole left by dead muscle cells. While this scar prevents the heart from rupturing, it is stiff and cannot pump blood. Over time, this excessive scarring spreads, making the heart rigid and weak, often leading to heart failure. For decades, scientists have known that a specific type of stress, called oxidative stress, plays a major role in driving this scarring. This stress occurs when the body produces too many unstable molecules that damage cells, much like rust corroding metal. However, the precise molecular switches that turn on this damaging process in the heart's repair cells have remained elusive, leaving doctors with few ways to stop the scarring once it begins.

A new study from researchers at Soochow University in China has identified one of these critical switches. The team focused on a molecule called lncPostn, which is a long strand of genetic material that does not code for proteins but instead acts as a regulator. They discovered that this molecule is abundant in the heart's fibroblasts, the cells responsible for building the scar tissue. By using a specialized virus to silence lncPostn in mice that had suffered a heart attack, the researchers found that the scarring was significantly reduced, and the heart's ability to pump blood was preserved. This suggests that lncPostn is a key driver of the harmful remodeling that follows a heart attack, and that turning it off could protect the heart.

To understand how this works, the researchers first had to confirm that lncPostn was indeed the culprit. They created a model where mice received a virus designed to block lncPostn specifically in heart fibroblasts before the heart attack occurred. When these mice were compared to others that did not receive the treatment, the treated mice had much smaller scars and better heart function three weeks after the injury. The team then tested if this approach could work as a treatment rather than just a prevention. They administered the virus two days after the heart attack, mimicking a scenario where a patient arrives at the hospital after the event. Even with this delayed treatment, the mice showed improved heart function and less scarring. This finding is significant because it suggests that targeting lncPostn could be effective not just for preventing damage, but for treating it after the injury has already happened.

The researchers then dug deeper to find out how lncPostn causes this damage. They discovered that the molecule works by increasing oxidative stress within the mitochondria, the tiny power plants inside cells. In the treated mice, blocking lncPostn reduced the levels of harmful reactive oxygen species, which are the unstable molecules responsible for the oxidative stress. To prove that this stress was the direct cause of the scarring, the team added a powerful antioxidant called MitoQ, which targets the mitochondria. When they gave MitoQ to mice with high levels of lncPostn, it reversed the damage, reducing both the oxidative stress and the scar formation. This confirmed that lncPostn drives fibrosis by creating a toxic environment inside the cell's power plants.

The final piece of the puzzle was identifying the specific protein that lncPostn manipulates to create this stress. The team found that lncPostn binds directly to a protein called Nox4. Under normal conditions, the body has a mechanism to break down Nox4 when it is no longer needed, keeping its levels in check. However, lncPostn acts like a shield, binding to Nox4 and preventing it from being broken down. This causes Nox4 to accumulate and become more stable, leading to a surge in the production of harmful oxygen molecules. The researchers showed that when they blocked Nox4 using a specific drug or genetic tools, the negative effects of lncPostn disappeared. The heart cells stopped producing excessive stress, and the scarring was halted. This establishes a clear chain of events: lncPostn protects Nox4 from destruction, Nox4 builds up and creates oxidative stress, and this stress triggers the fibroblasts to lay down excessive scar tissue.

This study provides a detailed map of a new pathway that leads to heart failure after a heart attack. By identifying lncPostn as the upstream regulator that stabilizes Nox4, the researchers have highlighted a potential new target for therapy. The fact that blocking this molecule worked both before and after the heart attack in mice suggests that it could be a powerful tool for preserving heart function in humans. While the research is currently limited to animal models, the clarity of the mechanism offers a promising direction for future treatments. Instead of trying to manage the symptoms of heart failure, doctors might one day be able to intervene at the molecular level to stop the scarring process itself, keeping the heart flexible and strong even after a major injury.