Single-cell RNA sequencing reveals the heterogeneity and intercellular communication of hepatic stellate cells and macrophages during liver fibrosis.

Uncontrolled and excessive progression of liver fibrosis is thought to be the prevalent pathophysiological cause of liver cirrhosis and hepatocellular cancer, and there are currently no effective antifibrotic therapeutic options available. Intercellular communication and cellular heterogeneity in the liver are involved in the progression of liver fibrosis, but the exact nature of the cellular phenotypic changes and patterns of interregulatory remain unclear. Here, we performed single-cell RNA sequencing on nonparenchymal cells (NPCs) isolated from normal and fibrotic mouse livers. We identified eight main types of cells, including endothelial cells, hepatocytes, dendritic cells, B cells, natural killer/T (NK/T) cells, hepatic stellate cells (HSCs), cholangiocytes and macrophages, and revealed that macrophages and HSCs exhibit the most variance in transcriptional profile. Further analyses of HSCs and macrophage subpopulations and ligand-receptor interaction revealed a high heterogeneity characterization and tightly interregulated network of these two groups of cells in liver fibrosis. Finally, we uncovered a profibrotic Thbs1+ macrophage subcluster, which expands in mouse and human fibrotic livers, activating HSCs via PI3K/AKT/mTOR signaling pathway. Our findings decode unanticipated insights into the heterogeneity of HSCs and macrophages and their intercellular crosstalk at a single-cell level, and may provide potential therapeutic strategies in liver fibrosis.