Macrophages expressing Macrophage Receptor with Collagen Structure Attenuate Liver Fibrosis Through a Tissue Restoration Phenotype [macrophage_liverFibrosis_scRNA-seq]

Liver macrophages are central in maintaining hepatic homeostasis and mediating immune responses during liver injury, including fibrosis. Macrophages may have proinflammatory or anti-inflammatory properties, but which properties influence fibrosis remains unclear. To explore the role of macrophages in liver fibrosis, we performed single-cell RNA sequencing in a mouse model of liver injury and found that macrophage diversity was increased. A subset of macrophages expressing high levels of Marco gene was the most significantly upregulated after injury but was spatially segregated to non-fibrotic areas. The macrophage receptor with collagenous structure (MARCO) protein is a scavenger receptor expressed by specific subsets of macrophages, and its role in liver fibrosis is unclear. In vitro induction of Marco in bone marrow-derived macrophages decreased proinflammatory gene expression, increased anti-inflammatory and antifibrotic gene expression, and enhanced phagocytosis, indicating a restorative phenotype. Adoptive transfer of MARCO-positive macrophages in a mouse model of liver fibrosis reduced the expression of extracellular matrix (ECM)-associated genes in hepatic stellate cells (HSCs) and reduced collagen deposition, which did not occur with the transfer of MARCO-negative macrophages. Therefore, MARCO-positive macrophages have a tissue restorative role in the liver and attenuate fibrogenesis through interaction with HSCs, thereby providing a novel therapeutic pathway for liver fibrosis.