Modulators of hepatic response to TGF-ß mediated cellular injury in inbred mice: Identification of modifiers of fibrosis susceptibility

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Hepatic fibrosis is a non-specific response to chronic liver injury, the two most common causes being viral hepatitis or alcohol abuse. Twin studies and ethnic differences indicate that genetic factors play a role in predisposition to and progression of both types. In contrast to viral hepatitis, no firm associations between genetic variants and susceptibility to alcoholic liver fibrosis have been identified to date. Transforming growth factor (TGF)-β is considered the master pro-fibrogenic cytokine, driving fibrosis in response to various modes of injury. This central role makes every modifier locus of the response to TGF-β mediated hepatic injury a candidate gene for fibrosis susceptibility. The aim of this project is to identify the modifier genes of TGF-β mediated injury, using hepatocytes isolated from genetically distinct inbred mouse strains. Hepatocytes are highly responsive to TGF-β. Their demise leads to activation of Kupffer cells and subsequent release of inflammatory cytokines as well as activation of hepatic stellate cells with enhanced expression of growth factors and extracellular matrix components. Here, we propose to avail of a genetic reference population generated from progeny of inbred mouse lines C57BL/6J and DBA/2J, also known as BXD recombinant inbred lines. The genetically distinct hepatocytes from these mouse lines will be challenged with TGF-β, and phenotypic differences (cellular damage, gene expression) will be quantified to delineate differences in response. Quantitative trait locus mapping, i.e. linkage analysis in the BXD panel, will enable us to identify the genetic loci that underlie differential responses to TGF-β by allelic variation. This experimental framework will allow us to assess the orthologous human regions and candidate genes for contribution to fibrogenesis susceptibility in defined human cohorts.