Liver stromal cells restrict macrophage maturation and stromal IL-6 limits the differentiation of cirrhosis-linked macrophages

Abstract

Background & aims Myeloid cells are key regulators of cirrhosis, a major cause of mortality worldwide. Because stromal cells can modulate the functionality of myeloid cells in vitro, targeting stromal-myeloid interactions has become an attractive potential therapeutic strategy. We aimed to investigate how human liver stromal cells impact myeloid cell properties and to understand the utility of a stromal-myeloid coculture system to study these interactions in the context of cirrhosis. Methods Single-cell RNA-sequencing analyses of non-cirrhotic (n = 7) and cirrhotic (n = 5) human liver tissue were correlated to the bulk RNA-sequencing results of in vitro cocultured human CD14 + and primary liver stromal cells. Complimentary mechanistic experiments and flow cytometric analysis were performed on human liver stromal-myeloid coculture systems. Results We found that stromal-myeloid coculture reduces the frequency CD14 + cell subsets transcriptionally similar to liver macrophages, showing that stromal cells inhibit the maturation of monocytes into macrophages. Stromal cells also influenced in vitro macrophage differentiation by skewing away from cirrhosis-linked CD9 + scar-associated macrophage-like cells and towards CD163 + Kupffer cell-like macrophages. We identify IL-6 production as a mechanism by which stromal cells limit CD9 + macrophage differentiation and find that local IL-6 levels are decreased in early-stage human liver disease compared to healthy liver tissue, suggesting…