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Accumulation of duct cells with activated YAP parallels fibrosis progression in non-alcoholic fatty liver disease.

ABSTRACT: Mechanisms that regulate regeneration of injured livers are complex. YAP, a stem cell associated factor, controls liver growth in healthy adult mice. Increasing nuclear localization of YAP triggers accumulation of reactive-appearing ductular cells (YAP+RDC) with liver progenitor capabilities. The significance of YAP activation, and mechanisms involved, are unknown in diseased livers. We evaluated the hypothesis that YAP is more activated in injured livers that are scarring than in those that are regenerating effectively.Immunohistochemistry and qRT-PCR analysis were used to localize and quantify changes in YAP and RDC in 52 patients with non-alcoholic fatty liver disease (NAFLD) and two mouse models of diet-induced non-alcoholic steatohepatitis (NASH). Results were correlated with liver disease severity, metabolic risk factors, and factors proven to control NAFLD progression.YAP increased in NAFLD where it mainly localized in nuclei of RDC that expressed progenitor markers. Accumulation of YAP+RDC paralleled the severity of hepatocyte injury and accumulation of Sonic hedgehog, but not steatosis or metabolic risk factors. YAP+RDC expressed osteopontin, a Shh-regulated fibrogenic factor. Myofibroblast accumulation, fibrosis, and numbers of YAP+RDC strongly correlated. In murine NASH models, atrophic fibrotic livers contained significantly more YAP+RDC than livers with less severe NASH.YAP+RDC promote scarring, rather than effective regeneration, during NASH.

SUBMITTER: Machado MV

PROVIDER: S-EPMC4575842 | biostudies-other | 2015 Oct

REPOSITORIES: biostudies-other

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Accumulation of duct cells with activated YAP parallels fibrosis progression in non-alcoholic fatty liver disease.

Machado Mariana Verdelho MV Michelotti Gregory Alexander GA Pereira Thiago Almeida TA Xie Guanhua G Premont Richard R Cortez-Pinto Helena H Diehl Anna Mae AM

Journal of hepatology 20150610 4

<h4>Background & aims</h4>Mechanisms that regulate regeneration of injured livers are complex. YAP, a stem cell associated factor, controls liver growth in healthy adult mice. Increasing nuclear localization of YAP triggers accumulation of reactive-appearing ductular cells (YAP+RDC) with liver progenitor capabilities. The significance of YAP activation, and mechanisms involved, are unknown in diseased livers. We evaluated the hypothesis that YAP is more activated in injured livers that are scarr ...[more]

PMID: 26070409

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Project description:BackgroundNon-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease worldwide. Autophagy plays a vital role in NAFLD development and progression. We aimed to establish a novel autophagy-related gene (ARG) signature as a therapeutic target in NAFLD patients based on high-throughput sequencing data.MethodsARGs obtained from the HAMdb and high-sequencing data obtained from the Gene Expression Omnibus (GEO) database were analyzed to identify differentially expressed ARGs (DEARGs) between normal and NASH tissues. Then, gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were performed to explore potential biological and pathological functions of DEARGs. The protein-protein interaction (PPI) network of the DEARGs was established through the STRING website, and visualized by Cytoscape. In addition, hub genes were validated by an independent dataset GSE89632. Finally, we performed Gene Set Variation Analysis (GSVA) pathway-related analysis to identify the pivotal signaling pathways and genes for the progression of non-alcoholic fatty liver (NAFL) to non-alcoholic steatohepatitis (NASH).ResultsA total of 76 DEARGs were identified in the GSE126848 dataset, of which 45 genes were upregulated and 31 genes were downregulated. GO analysis showed that the biological functions of DEARGs focused primarily on autophagy, cellular response to external stimulus, fibroblast proliferation, late endosome, and ubiquitin protein ligase binding. KEGG pathway analysis showed that these DEARGs were mainly involved in the apoptosis, PI3K-Akt signaling pathway, and estrogen signaling pathway. Among DEGs, 9 most closely related genes were identified from the PPI network. Furthermore, NOS3, IGF1, VAMP8, FOS, and HMOX1 were verified in the GSE89632 dataset. At last, the MAPK signal pathway was identified as important pathway, and JUN was identified as a key gene involved in the progression from NAFL to NASH.ConclusionThis study may provide credible molecular biomarkers in terms of screening and diagnosis for NAFLD. Meanwhile, it also serves as a basis for exploring the molecular mechanisms underlying the progression of NAFL to NASH.

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Accumulation of duct cells with activated YAP parallels fibrosis progression in non-alcoholic fatty liver disease.

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Accumulation of duct cells with activated YAP parallels fibrosis progression in non-alcoholic fatty liver disease.

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