Comparative analysis of inflammation and fibrosis in MDR2/ HO-1 double knockout mice

R Barikbin; A Quaas; M Soares; G Tiegs; G Sass

doi:10.1055/s-0032-1331903

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Z Gastroenterol 2013; 51 - P_1_03
DOI: 10.1055/s-0032-1331903

Comparative analysis of inflammation and fibrosis in MDR2/ HO-1 double knockout mice

R Barikbin ¹, A Quaas ², M Soares ³, G Tiegs ¹, G Sass ¹

¹University Medical Center Hamburg Eppendorf, Department of Experimental Immunology and Hepatology, Hamburg, Germany
²University Medical Center Hamburg Eppendorf, Institute of Pathology, Hamburg, Germany
³Instituto Gulbenkian de Ciência, Apartado 14, Oeiras, Portugal

Congress Abstract

Background: Deletion of the multi drug resistance protein 2 (Mdr2) in mice causes hepatic inflammation and fibrosis with progression to hepatocellular carcinoma (HCC) at about 12 month of age (Mdr2 knockout mouse; Mdr2ko; FVB.129P2-Abcb4tm1Bor). We have recently shown that induction of heme oxygenase-1 (HO-1) in Mdr2ko mice interferes with liver inflammation, fibrosis formation and proliferation. We now established a double knockout mouse for Mdr2 and HO-1 (FVB/Mdr2/HO-1ko) to further investigate effects of HO-1 on chronic inflammation of the liver and its consequences.

Methods: Breeding pairs were heterozygous for HO-1ko, either in single HO-1 knockout or in Mdr2/HO-1 double knockout breeding pairs. The Mdr2ko was homozygous in Mdr2/HO-1 double ko and Mdr2ko breeding pairs. Liver damage was monitored by alanin aminotranferase (ALT) levels. Leukocyte infiltration was visualized by H&E staining of liver slices. Fibrosis was visualized by EVG staining. Real time RT-PCR was performed to proof knockout of Mdr2 and HO-1 and to exclude a possible up-regulation of HO-2 in consequence of the HO-1 knockout. Mice were investigated at the age of 12 weeks.

Results: Statistical analysis showed that birth rates of FVB/HO-1ko mice were very low (0.2%) while surprisingly, FVB/Mdr2/HO-1ko mice showed an improvement of birth rates to 4.2%. Among FVB/Mdr2/HO-1ko mice an elevated percentage of male offspring (57%) compared to FVB/Mdr2ko mice (47%) was detected. ALT levels were slightly elevated in FVB/Mdr2/HO-1ko mice compared to FVB/Mdr2ko mice. Leukocyte infiltration and fibrosis formation in FVB/Mdr2/HO-1ko was similar to FVB/Mdr2ko, although FVB/Mdr2/HO-1ko showed a partial loss of small bile ducts. MRNA expression for Mdr2 and HO-1 proofed the knockout of both genes. In addition HO-2 was not found to be up-regulated upon HO-1 knockout.

Conclusion: We established a new double knockout mouse model, the FVB/Mdr2/HO-1ko. Surprisingly these mice show an improved birth rate compared to single HO-1ko mice. Liver inflammation and fibrosis formation at the age of 12 weeks seems to be similar between FVB/Mdr2/HO-1ko and Mdr2ko mice. Further investigations will elucidate more similarities and differences between FVB/Mdr2/HO-1ko and FVB/Mdr2ko and reveal the impact of HO-1 on chronic liver inflammation.