Peritoneal macrophages regulate distal wound healing via endocrine release of plasma fibronectin.

The peritoneal cavity contains a large population of GATA6-expressing large peritoneal macrophages (LPMs), known to support healing of intraabdominal organs. In this study, we aimed to explore their full sphere of influence by examining their ability to perform wound healing at distant sites outside the cavity. In a mouse model combining a remote skin injury with peritoneal stimulation we observed a significant acceleration of skin wound healing in response to LPM activation. Tracking GATA6-expressing LPMs, we demonstrated that LPMs do not migrate to distant wound sites following peritoneal activation. Using parabiosis experiments and administration of activated peritoneal contents indicated an important role of molecules secreted by LPMs in remote skin wound healing. More specifically, proteomic and transcriptomic analyses identified fibronectin as a key factor produced by activated LPMs. In fact, depletion of LPMs or genetic knockout of fibronectin in myeloid cells eliminated the enhanced healing effect. These findings highlight the endocrine function of LPMs in systemic tissue repair, challenging the traditional perspective of plasma fibronectin being exclusively liver derived. Our results suggest that LPMs, strategically positioned in the peritoneal cavity, serve as a source of circulating fibronectin, promoting matrix formation and accelerating wound healing at distant sites.