Hepcidin knockout mice as a model of iron-overload associated liver fibrosis development

Abstract

Background and aims: Hepcidin is the central regulator of iron homeostasis. Disrupted hepcidin signalling results in hereditary hemochromatosis and iron overload in chronic liver disorders. While the association between iron overload and development of end-stage liver disease is well established, the understanding of the underlying pathomechanisms is hampered by the lack of a suitable animal model. To circumvent this problem, we studied hepcidin-knockout (KO) mice as a model of iron-overload associated liver disease. Methods: 6 and 12 month-old hepcidin-KO and -wild type (WT) mice fed 3% iron carbonyl-containing diet (Fe-diet) since four weeks of age were compared to age-matched WT and KO animals kept on standard diet. The liver phenotype was quantified serologically as well as morphometrically based on hematoxylin & eosin, Prussian blue and Sirius red stainings. Liver iron content was determined by atomic mass absorption. Liver fibrosis development was determined by collagen RT-PCR and hydroxyproline assay. Results: 6 month Fe-fed hepcidin KO mice (compared to WTs) exhibited (i) increased iron liver contents (2543±114 vs. 1493±136 p<0,005); (ii) elevated AST and serum iron levels (AST: KO 261±15, WT 142±34 p<0,05; serum iron: KO 95±3, WT 46±5, p<0,0005); (iii) increased liver inflammation and hepatocellular apoptosis; and (iv) elevated markers of hepatic stellate cell activation (collagen and α-smooth muscle actin mRNA), but no detectable liver fibrosis. 12 month Fe-fed hepcidin KO mice (compared to WTs) also showed increased liver injury markers as well as marked iron accumulation. In addition, they developed significantly stronger liver fibrosis than their wildtype counterparts as suggested by collagen RT-PCR, hydroxyproline assay and morphometrical evaluation. Conclusions: Iron-fed hepcidin KOs develop not only a mild chronic liver injury, but also liver fibrosis and therefore represent unique tool to study the mechanism of iron overload-related liver diseases