As important and durable as it is, the heart has quite a lot of difficulty in repairing itself after sustaining damage. But now, researchers from the University of Calgary have found a previously unidentified cell population in the fluid that surrounds the heart, which seems to help heal injuries.

Cardiovascular diseases are the leading cause of death around the world today, and the heart of the trouble is … well, the heart. Even if a person survives the initial cardiac arrest, this vital organ struggles to heal itself properly. The resulting scar tissue impedes the heart's ability to pump blood and further heart attacks are likely down the track.

Scientists have focused plenty of research onto finding ways to more effectively heal the heart. Bioengineered scaffolds could improve healing, as could reprogramming structural cells to become new beating cells. Stem cells of different types are also a promising avenue – cardiac progenitor cells have been used to regrow outer layers of the heart, placental stem cells have been shown to regenerate heart tissue, and stem cell "messengers" called exosomes have been found to induce the heart to self-repair.

For the new study, the Calgary team moved outside the heart to the fluid-filled sac that surrounds it. The pericardial fluid lubricates the organ to keep it beating smoothly decade after decade, and it was there that the researchers found a new population of cells that naturally help patch up the heart after an attack.

In tests on mice, the team noticed that cells called Gata6+ pericardial cavity macrophages gathered around the site of injury after a heart attack and appeared to be entering the heart tissue to remodel the structure. The researchers then removed the sac and the fluid in other mice, and found that much more scar tissue formed around their hearts.

While this study was conducted on mice, the team notes that the specific cells are also found in the pericardial fluid of humans. That means they could be a target for future studies to find ways to use them to improve our own recovery after heart attacks.

"Our discovery of a new cell that can help heal injured heart muscle will open the door to new therapies and hope for the millions of people who suffer from heart disease," says Paul Fedak, co-lead author of the study. "We always knew that the heart sits inside a sac filled with a strange fluid. Now we know that this pericardial fluid is rich with healing cells. These cells may hold the secret to repair and regeneration of new heart muscle. The possibilities for further discovery and innovative new therapies are exciting and important."

The research was published in the journal Immunity.

View gallery - 2 images