Immune cells in organ cavities play essential role in fast tissue repair

Immune cells in organ cavities play essential role in fast tissue repair

While scientists have known for many years that there are cells living in the cavities surrounding various organs such as the heart, lung and liver, their function has remained unknown.

Among a few types of immune cells found in body cavities, the study looked specifically at macrophages - immune cells that play a key role in clearing the body of harmful substances and microbes, such as toxins and bacteria, as well as clearing away dead tissue. Looking at cells in the abdominal cavity surrounding the liver, the study demonstrated the macrophages patrol within the cavity, and upon organ damage, adhere themselves to the damaged area for quick repair.

Using animal models, researchers used intravital imaging technology to view the cells in real time, and observed their behavior in response to both thermal injury and toxin induced injury. The cells behaved in the same way for both types of injury.

In response to a sterile injury in liver, a reservoir of fully mature F4/80hiGATA6+ peritoneal cavity macrophages rapidly invaded into afflicted tissue via direct recruitment across the mesothelium. The invasion was dependent on CD44 and DAMP molecule ATP and resulted in rapid replication and switching of macrophage toward an alternatively activated phenotype.

These macrophages dismantled the nuclei of necrotic cells releasing DNA and forming a cover across the injury site. Further to the observation, when the macrophage supply was depleted in the abdominal cavity, tissue repair did not take place as quickly. When the cells were reinfused back into the animal models, they resumed their role.

Rapid invasion of mature macrophages from body cavity with capacity for induction of reparative phenotype may impact altered tissues ranging from trauma to infections to cancer.

Author says while the study only looked at the cells in the abdominal cavity and how they responded to liver injury, it's reasonable to hypothesize that cells in other body cavities, such as the pleural cavity surrounding the lungs, and the pericardium cavity surrounding the heart, would perform similar functions. And while the Cell study was conducted in animal models, author says this research could have implications for humans as well.