AIMS: Angiocrine signaling by liver sinusoidal endothelial cells (LSEC) regulates liver functions such as liver growth, metabolic maturation, and regeneration . Recently, we identified GATA4 as the master regulator of LSEC specification during development . Here, we studied endothelial GATA4 in the adult liver and in hepatic disease pathogenesis .
METHODS: We generated adult Clec4g-icretg/0xGata4fl/fl (Gata4LSEC-KO) mice with deficiency of Gata4 in LSEC . Livers were analyzed by histology, electron microscopy, immunohistochemistry/immunofluorescence, in-situ hybridization, and by expression profiling, ChIP- and ATAC-sequencing of isolated LSEC . For liver regeneration, partial hepatectomy was performed . As models of liver fibrosis, CDAA diet and chronic CCl4 exposure were applied . Human single cell RNAseq data sets were analyzed for endothelial alterations in healthy and cirrhotic livers .
RESULTS: Genetic Gata4 deficiency in LSEC of adult mice caused perisinusoidal liver fibrosis, hepatopathy and impaired liver regeneration . Sinusoidal capillarization and LSEC-to-continuous endothelial transdifferentiation were accompanied by a profibrotic angiocrine switch including de novo endothelial expression of hepatic stellate cell-activating cytokine Pdgfb . Increased chromatin accessibility and amplification by activated MYC mediated angiocrine Pdgfb expression . In CDAA diet-induced perisinusoidal liver fibrosis, LSEC showed repression of GATA4, activation of MYC and the profibrotic angiocrine switch already detected in Gata4LSEC-KO mice . Comparison of CDAA-fed Gata4LSEC-KO and control mice demonstrated that endothelial GATA4 indeed protects from dietary-induced perisinusoidal liver fibrosis . In human cirrhotic livers, GATA4-positive LSEC and endothelial GATA4 target genes were reduced, while non-LSEC endothelial cells and MYC target genes including PDGFB were enriched .
CONCLUSIONS: Endothelial GATA4 protects from perisinusoidal liver fibrosis by repressing MYC activation and profibrotic angiocrine signaling on the chromatin level . Therapies targeting the GATA4/MYC/PDGFB/PDGFRß axis offer a promising strategy for prevention and treatment of liver fibrosis.