title: MicroRNAs interfere with DNA methylation in rheumatoid arthritis synovial fibroblasts.
abstract: BACKGROUND
  The DNA of rheumatoid arthritis synovial fibroblasts (RASF) is globally hypomethylated; this contributes to an aggressive behaviour. In an attempt to remethylate these cells, we supplemented with methyl donors. We investigated the possible interference of microRNAs (miRs).
  
  
  METHODS
  RASF were treated with L-methionine or betaine. Transcripts of de novo methyltransferases (DNMTs) and miRs were measured by real-time PCR, and a transcription PCR array was performed. Levels of homocysteine, matrix metalloproteinase-1 (MMP-1) and global DNA methylation were determined. Transfection with lipofectamine was performed with specific pre-miRs and anti-miRs, such as miR29 and let7f.
  
  
  RESULTS
  L-methionine was more efficient to increase DNA methylation than betaine. This was associated with a reduced expression of DNMT3A mRNA in betaine-treated RASF. Betaine increases the expression of miR29 in RASF which targets DNMT3A, thereby limiting the remethylation process. Nevertheless, betaine inhibited the expression of multiple transcription factors, decreased the release of MMP-1, biosynthesis of homocysteine and cell migration.
  
  
  CONCLUSIONS
  Alterations in cellular miRs profiles, in particular the upregulation of miR29, which targets DNMT3A, may limit the efficiency of betaine if it is used as DNA remethylating agent. However, L-methionine also has similar impact on miR29 expression. On the other hand, betaine has multiple other beneficial effects on the activated phenotype of RASF; it is not excluded that the effect of betaine on DNMT3A is, at least in part, indirect. Clinical trials with betaine could be promising.
authors.affiliation: Centre of Experimental Rheumatology, University Hospital , Zurich , Switzerland.
authors.forename: Niharika
authors.initials: N
authors.lastname: Gaur
authors.affiliation: Centre of Experimental Rheumatology, University Hospital , Zurich , Switzerland.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Karouzakis
authors.affiliation: Centre of Experimental Rheumatology, University Hospital , Zurich , Switzerland.
authors.forename: Selene
authors.initials: S
authors.lastname: Glück
authors.affiliation: Department of Regenerative Medicine , State Research Institute Centre for Innovative Medicine , Vilnius , Lithuania.
authors.forename: Edvardas
authors.initials: E
authors.lastname: Bagdonas
authors.affiliation: Centre of Experimental Rheumatology, University Hospital , Zurich , Switzerland.
authors.forename: Astrid
authors.initials: A
authors.lastname: Jüngel
authors.affiliation: Centre of Experimental Rheumatology, University Hospital , Zurich , Switzerland.
authors.forename: Beat A
authors.initials: BA
authors.lastname: Michel
authors.affiliation: Centre of Experimental Rheumatology, University Hospital , Zurich , Switzerland.
authors.forename: Renate E
authors.initials: RE
authors.lastname: Gay
authors.affiliation: Centre of Experimental Rheumatology, University Hospital , Zurich , Switzerland.
authors.forename: Steffen
authors.initials: S
authors.lastname: Gay
authors.affiliation: Centre of Experimental Rheumatology, University Hospital , Zurich , Switzerland.
authors.forename: Mojca
authors.initials: M
authors.lastname: Frank-Bertoncelj
authors.affiliation: Centre of Experimental Rheumatology, University Hospital , Zurich , Switzerland.
authors.forename: Michel
authors.initials: M
authors.lastname: Neidhart
keywords: Fibroblasts; Pharmacogenetics; Rheumatoid Arthritis; Synovitis