Activated hepatic stellate cells promote expansion of LGR5-positive progenitor cells in fibrotic human liver disease

Abstract

Background Liver regeneration is compromised in advanced fibrosis or cirrhosis, where progenitor cell therapy is being considered as a therapeutic option. Little is known about the presence and potential role of leucine-rich-repeat-containing G protein-coupled receptor 5-expressing (LGR5+) progenitor cells in chronically injured human liver. In this study, we analyzed LGR5 expression in fibrotic and cirrhotic human livers and studied the interaction between human liver organoids and hepatic stellate cells (HSC) in vitro. Methods Control and fibrotic human liver tissues were combined in a tissue microaarray and sections were stained with H&E or Sirius red, or immune-stained for LGR5 and various liver cell type markers. Adult LGR5+ progenitor cell-derived human liver organoids were co-cultured with human LX-2 HSC or exposed to LX-2 conditioned medium and analyzed by q-PCR and immuno-microscopy. Results LGR5 mRNA were significantly enhanced in fibrotic liver tissue and LGR5+ cell numbers positively correlated with the stage of fibrosis. LGR5+ cells accumulated close to the fibrotic bands and co-expressed hepatocyte markers, but not cholangiocyte markers. TGFβ1-activated LX-2 cells enhanced LGR5 expression in organoids and organoid growth, results that were replicated by exposing organoids to LX-2-conditioned medium. Blocking LX-2 activation by dimethyloxalylglycine prevented all these effects on liver organoids. Conclusion LGR5+ progenitor cells are abundantly present in human liver fibrosis. Activated HSC induce LGR5 expression and growth of human liver organoids. Treatment of advanced liver fibrosis may therefore not strongly benefit from adding exogenous progenitor cells, but rather from promoting expansion and differentiation of the endogenous LGR5+ cells.