Z Gastroenterol 2015; 53 - A1_44
DOI: 10.1055/s-0034-1397085

Riboflavin Kinase Inhibitor 1 (RKIP1): A Potential Modifier of Fibrogenesis in Liver and Heart

RA Hall 1, A Kazakov 2, U Laufs 2, M Böhm 2, F Lammert 1
  • 1Saarland University Medical Center, Department of Medicine II, Homburg, Germany
  • 2Saarland University Medical Center, Department of Medicine III, Homburg, Germany

Background: Recently we observed that long-term administration of carbon tetrachloride (CCl4) induces fibrosis in both liver and heart in the mouse. To dissect common and organ-specific mechanisms of fibrosis, we challenged BXD recombinant inbred lines with CCl4. BXD lines represent a genetic reference population (GRP) that is genetically mosaic but homozygous for all loci. Our aim was to identify potential candidate genes with effects on hepatic and cardiac fibrogenesis.

Methods and results: Thirty BXD lines were used as a GRP for genome-wide quantitative trait loci (QTL)-analyses. Fibrosis was induced by CCl4 for six weeks (0.7 ml/kg, 12 i.p. injections). We observed significant differences for hepatic and cardiac fibrosis among the BXD lines and using a genome-wide marker panel, we mapped co-localizing loci linked to collagen accumulation for liver and heart on chromosomes 5 and 18. These QTL were further screened for candidate genes by expression QTL (eQTL)-mapping. Hence, gene expression levels (Affy 1.0 ST whole genome arrays) were included into the mapping analysis as quantitative traits. Among all locally regulated quantitative trait genes (cis-QTGs) within the QTL on chromosome 5, Rkip1was identified as major cis-QTG (LRS= 64.6) and further in silico analyses affirmed it as a potential candidate gene. Therefore, we compared fibrosis progression in CCl4-challenged Rkip1-knockout (Rkip-/-) and C57Bl/6N wild-type mice by quantification of collagen accumulation in liver and heart. After six weeks of fibrosis induction, Rkip-/- mice showed significantly less cardiac collagen accumulation (p < 0.05), as assessed by Sirius red staining. However, in the liver hydroxyproline levels were enhanced (p < 0.001) in Rkip-/- mice, and so were Col1a2 expression levels (p < 0.05).

Conclusions: This study reveals that CCl4-induced fibrosis is a systemic model that allows comparative analysis of fibrosis mechanisms in liver and heart in genetically identical individuals. Genome-wide analysis of hepatic and cardiac fibrosis identified common and regulatory QTLs of fibrogenesis. Rkip1 deficiency appears to have anti-fibrotic effects in heart but not liver, pointing to organ-specific mechanisms of fibrosis progression.

Corresponding author: Hall, Rabea A.

E-Mail: rabea.hall@uks.eu