Researchers are the first to discover a previously unidentified cell population in the pericardial fluid found inside the sac around the heart. The discovery could lead to new treatments for patients with injured hearts. journal Immunity.

The collaborative study found that a specific cell, a Gata6+ pericardial cavity macrophage, helps heal an injured heart in mice. The cell was discovered in the pericardial fluid (sac around the heart) of a mouse with heart injury.  

Following experimental MI, these macrophages invaded the epicardium and lost Gata6 expression but continued to perform anti-fibrotic functions. Loss of this specialized macrophage population enhanced interstitial fibrosis after ischemic injury.

The same cells were also found within the human pericardium of people with injured hearts, confirming that the repair cells offer the promise of a new therapy for patients with heart disease.

Heart doctors had never before explored the possibility that cells just outside the heart could participate in healing and repair of hearts after injury. Unlike other organs, the heart has a very limited capacity to repair itself which is why heart disease is the number one cause of death in North America.

"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. 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," says one of the lead authors.

https://www.cell.com/immunity/fulltext/S1074-7613(19)30280-8