Juan E. Puche, Youngmin A. Lee, Jingjing Jiao, Costica Aloman, Maria I. Fiel, Ursula Muñoz, Thomas Kraus, Tingfang Lee, Hal F. Yee Jr., Scott L. Friedman
We have developed a novel model for depleting mouse HSCs that has allowed us to clarify their contributions to hepatic injury and fibrosis. Transgenic mice (TG) expressing the herpes simplex virus-Thymidine kinase gene (HSV-Tk) driven by the mouse GFAP promoter were used to render proliferating HSCs susceptible to killing in response to ganciclovir (GCV). Effects of GCV were explored in primary HSCs and in vivo. Panlobular damage was provoked to maximize HSC depletion by combining carbon tetrachloride (CCl4) (centrilobular injury) with allyl alcohol (AA) (periportal injury), as well as in a bile duct ligation (BDL) model. Cell depletion in situ was quantified using dual-immunofluorescence (IF) for desmin and GFAP. In primary HSCs isolated from both untreated wild type (WT) and TG mice, GCV induced cell death in ∼50% of HSCs from TG but not WT mice. In TG mice treated with CCl4+AA+GCV, there was a significant decrease in GFAP & desmin positive cells compared to WT mice (∼65% reduction, p<0.01), which was accompanied by a decrease in the expression of HSC activation markers (α-SMA, β-PDGFR and collagen I). Similar results were seen following BDL. Associated with HSC depletion in both fibrosis models, there was marked attenuation of fibrosis and liver injury, as indicated by Sirius Red/Fast Green, H quantification and serum ALT/AST. Hepatic expression of IL-10 and IFN-γ was increased following HSC depletion. No toxicity of GCV in either WT or TG mice accounted for the differences in injury. Conclusion: Activated HSCs significantly amplify the hepatic response to liver injury, further expanding this cell type's repertoire in orchestrating hepatic injury and repair.