Z Gastroenterol 2011; 49 - P1_27
DOI: 10.1055/s-0030-1269477

New targets of miR-29 in cell communication during liver fibrogenesis

M Kwiecinski 1, N Elfimova 1, A Noetel 1, U Töx 2, I Strack 1, M Steffen 2, HP Dienes 1, M Odenthal 3
  • 1Institute for Pathology, University Hospital of Cologne, Cologne
  • 2Department of Gastroenterology and Hepatology, Cologne
  • 3Institut für Pathologie, Universität Köln, Köln

Aims: MicroRNAs (miRNA) are small noncoding RNAs that regulate gene expression by targeting mRNAs through translational repression or RNA degradation. Since hepatic stellate cells (HSC) represent the central cell type of liver fibrogenesis, we have analysed the miRNA pattern in HSC and demonstrated recently, that miR-29a/b reduce collagen expression in HSC. In the present study, we identified additional targets of miR-29 and investigated the role of miR-29 in fibrogenic cell communication.

Methods: Putative targets of miR-29 were analysed by reporter assays after cloning the 3´UTR sequences in fusion to the luciferase coding sequence. Interactions between miR-29 and putative targets were detected by luminescence assays. In order to check specificity of miR-29, binding 3´UTR variants were constructed and miR-29 binding was compared to variants with mutations within the binding side. Synthesis of identified targets in HSC was determined by Real Time PCR, Western Blot and ELISA after transfection with miR-29 mimics. Expression of miRNA and of the identified targets was analysed by Real Time PCR in rat livers (N=13) after bile-duct obstruction (BDO).

Results: Screening of different databases revealed novel putative miR-29 target sequences in transcripts of PDGF-B, PDGF-C, IGF-I and VEGF-A. Specific binding of miR-29 to the 3´UTR of PDGF-C, VEGF-A and IGF-I mRNA but not to the respective mutants, was proven, miR-29 treated HSC resulted in a prominent repression of PDGF-C and IGF-I synthesis on transcript and protein level. After BDO-induced fibrosis miR-29a/b expression was shown to be reduced, but IGF-I and PDGF-C expression was upregulated correlating inversely to the miR-29 pattern.

Conclusion: The profibrogenic mediators PDGF-C and IGF-I, inducing HSC proliferation and collagen synthesis are regulated by miR-29. Therefore miR-29 affects not only fibrogenesis by direct collagen repression but also by interfering with the profibrotic cell communication.