P615 DIFFERENTIAL DNA METHYLATION OF GENES INVOLVED IN FIBROSIS PROGRESSION IN NAFLD AND ALD

Abstract

Background and Aims: Fibrosis is determined by genetic and exogenous factors. We observed that administration of carbon tetrachloride (CCl4) induces fibrosis in liver and heart. To dissect common and organ-specific mechanisms of fibrosis, we employed BXD recombinant inbred lines as a genetic reference population (GRP). Our aim was to identify potential candidate genes for hepatic and cardiac fibrogenesis. Methods: Thirty BXD lines were used as GRP for quantitative trait loci (QTL)-analyses. Fibrosis was induced by CCl4 (1.4mg/kg/week, 12 i.p. injections). Coinciding liver and heart loci linked to collagen accumulation were screened for locally regulated genes (cisQTGs) by expression QTL (eQTL)-analysis, availing of transcriptomic data of CCl4-treated BXD lines. In-silico analyses affirmed Rafkinase inhibitor 1 (Rkip1) as a potential candidate gene. Hence, we compared collagen accumulation in CCl4-challenged Rkip1knockout (Rkip) and wild-type mice after Sirius red staining of liver and heart sections. Results: We observed significant differences for hepatic and cardiac fibrosis among the BXD lines. These were conferred by common QTLs as well as organ-specific QTLs on chromosomes 4, 5, and 18. Rkip1 was identified as major cis-QTG (LRS = 64.6). CCl4-challenged Rkip mice showed significant (p < 0.05) less cardiac collagen accumulation, whereas no differences were observed in liver. Conclusions: This study reveals that CCl4-induced fibrosis is a systemic model allowing comparative analysis of fibrosis in liver and heart. QTL-analysis of hepatic and cardiac fibrosis identified common and organ-specific QTLs of fibrogenesis. Rkip1 deficiency has anti-fibrotic effects in heart, but not in liver pointing to organspecific mechanisms of fibrosis progression in this model.