title: Epigenetic Changes during Hepatic Stellate Cell Activation.
abstract: OBJECTIVE
  Hepatic stellate cells (HSC), which can participate in liver regeneration and fibrogenesis, have recently been identified as liver-resident mesenchymal stem cells. During their activation HSC adopt a myofibroblast-like phenotype accompanied by profound changes in the gene expression profile. DNA methylation changes at single genes have been reported during HSC activation and may participate in the regulation of this process, but comprehensive DNA methylation analyses are still missing. The aim of the present study was to elucidate the role of DNA methylation during in vitro activation of HSC.
  
  
  RESULTS
  The analysis of DNA methylation changes by antibody-based assays revealed a strong decrease in the global DNA methylation level during culture-induced activation of HSC. To identify genes which may be regulated by DNA methylation, we performed a genome-wide Methyl-MiniSeq EpiQuest sequencing comparing quiescent and early culture-activated HSC. Approximately 400 differentially methylated regions with a methylation change of at least 20% were identified, showing either hypo- or hypermethylation during activation. Further analysis of selected genes for DNA methylation and expression were performed revealing a good correlation between DNA methylation changes and gene expression. Furthermore, global DNA demethylation during HSC activation was investigated by 5-bromo-2-deoxyuridine assay and L-mimosine treatment showing that demethylation was independent of DNA synthesis and thereby excluding a passive DNA demethylation mechanism.
  
  
  CONCLUSIONS
  In summary, in vitro activation of HSC initiated strong DNA methylation changes, which were associated with gene regulation. These results indicate that epigenetic mechanisms are important for the control of early HSC activation. Furthermore, the data show that global DNA demethylation during activation is based on an active DNA demethylation mechanism.
authors.affiliation: Clinic of Gastroenterology, Hepatology and Infectious Diseases, Heinrich Heine University, Düsseldorf, Germany.
authors.forename: Silke
authors.initials: S
authors.lastname: Götze
authors.affiliation: Clinic of Gastroenterology, Hepatology and Infectious Diseases, Heinrich Heine University, Düsseldorf, Germany.
authors.forename: Eva C
authors.initials: EC
authors.lastname: Schumacher
authors.affiliation: Clinic of Gastroenterology, Hepatology and Infectious Diseases, Heinrich Heine University, Düsseldorf, Germany.
authors.forename: Claus
authors.initials: C
authors.lastname: Kordes
authors.affiliation: Clinic of Gastroenterology, Hepatology and Infectious Diseases, Heinrich Heine University, Düsseldorf, Germany.
authors.forename: Dieter
authors.initials: D
authors.lastname: Häussinger
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D019175:DNA Methylation / Q000187:drug effects / Q000502:physiology*; D015224:Dideoxynucleosides / Q000494:pharmacology; D044127:Epigenesis, Genetic / Q000187:drug effects / Q000502:physiology*; D055106:Genome-Wide Association Study; D055166:Hepatic Stellate Cells / Q000166:cytology / Q000378:metabolism*; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D008297:Male; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000378:metabolism*; D008898:Mimosine / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar
chemical_list: D015224:Dideoxynucleosides; C073006:5-bromo-2',3'-dideoxyuridine; D008898:Mimosine