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IL-15R-alpha controls hepatic stellate cell fibrogenic potential during murine chronic liver injury

ABSTRACT: Gene-expression profiles of hepatic stellate cells isolated from IL15R-alpha knockout mouse IL-15 and its high affinity receptor IL-15Rα are widely expressed in immune cells including dendritic cells and macrophages and non-immune cells such as hepatocytes, oval cells and hepatic stellate cells (HSC). IL-15 signaling has important functions in natural killers (NK), natural killers T (NKT) and cytotoxic T (CD8+T) cell homeostasis and also in liver regeneration. We hypothesized that IL-15 may have a protective role during liver fibrosis progression due to its role in NK cell homeostasis. We compared fibrosis progression in IL-15Rα knockout mice (IL-15RαKO) to wild type mice using two mechanistically distinct models, chronic carbon tetrachloride (CCl4) exposure and bile duct ligation (BDL). Enhanced fibrosis progression was observed in IL-15RαKO mice in both models. Furthermore, using congenic bone marrow transplantation (BMT), we demonstrated an unexpected role for IL-15 signaling in hepatic resident cells for the maintenance of liver NK and CD8+T cell populations. Using this approach, transplanting IL-15RKO hematopoietic cells results in NK defect that surprisingly is not reflected in a change of fibrosis progression. However, chimeric mice with defect of IL-15R on liver resident cells have similar NK defects and significant more fibrosis after CCL4 liver injury. This supports a direct protective, anti-fibrogenic role for IL-15R on one of the radioresistant liver cell populations (hepatocytes, HSC and sessile Kupffer cells). Microarray analysis of IL15RKO HSC suggests up-regulation of collagen transcripts and down-regulation of pathways involved in cell proliferation/survival. Finally, activated HSCs isolated from IL-15RKO mice show increased collagen secretion and as predicted, no changes in the growth curves. In summary, IL-15Rα signaling has an anti-fibrotic effect through both BM-derived and hepatic resident cells. These findings establish a rationale to explore IL-15 signaling in HSC as a potential therapeutic target in liver fibrogenesis.

ORGANISM(S): Mus musculus

PROVIDER: GSE45612 | GEO | 2016/09/21

SECONDARY ACCESSION(S): PRJNA195399

REPOSITORIES: GEO

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Project description:Activated hepatic stellate cells (HSC) that transdifferentiate to myofibroblasts in the injured liver are responsible for scar formation that leads to fibrosis and eventually cirrhosis. To investigate the gene expression profile during different stages of this process, we performed serial analysis of gene expression (SAGE), representing a quantitative and qualitative description of all expressed genes. Stellate cells were isolated from human livers and cultured. SAGE was performed on RNA isolated from quiescent, activated and transdifferentiated HSC. Comparison of the three resulting transcriptomes showed that less than 5% of all genes changed significantly in expression. Established markers of liver fibrosis showed enhanced expression in accordance with the transdifferentiation process. In addition, induction was seen for several genes not yet recognized to be involved in liver fibrosis, such as insulin-like growth factor binding proteins (IGFBP) and antagonists of bone morphogenic proteins: follistatin and gremlin. The induction of these genes was validated in vivo in mice developing liver fibrosis. The expression of IGFBPs and gremlin was measurable in the livers of these mice while it was low or undetectable in control mice without liver fibrosis. Since gremlin modulates the activity of bone morphogenic growth factors, it may represent a novel pathway and a target for therapeutic intervention and together with IGFBPs as a specific marker of liver fibrosis. In conclusion, the comparison of the three transcriptomes of (activated) stellate cells reveals novel genes involved in fibrogenesis and provides an appreciation of the sequence and timing of the fibrotic process in liver. Keywords: cell type comparison Human hepatic stellate cells (HSC) were isolated from wedge sections of normal human liver unsuitable for transplantation or from tumor-free human liver after partial hepatectomy as previously reported. Briefly, after a combined digestion with collagenase/pronase, HSC were separated from other liver nonparenchymal cells by ultracentrifugation over gradients of Larcoll (Sigma). The percentage of HSC in these isolates was > 90% as assessed by transmission microscopy, autofluorescence of vitamin A and immunofluorescence of vimentin. Immediately after isolation RNA was extracted for the construction of the SAGE library of quiescent HSC. To obtain activated stellate cells, these cells were cultured for 15 days on plastic culture dishes in modified Dulbecco's medium supplemented with 0.6 U/ml insulin, 2.0 mmol/L glutamine, 0.1 mmol/L nonessential amino acids, 1.0 mmol/L sodium pyruvate, antibiotic antifungal solution (Gibco) and 20% fetal bovine serum. To obtain fully transdifferentiated hepatic stellate cells, or myofibroblasts, the cells were cultured until they had reached passage 6 to 7. Myofibroblast phenotype was confirmed by detection of vimentin and ?-smooth muscle actin using immunofluorescence with monoclonal antibodies from Dako and Sigma, respectively. Medium was refreshed twice a week and at the indicated period RNA was extracted using Trizol (Quiagen)

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IL-15R-alpha controls hepatic stellate cell fibrogenic potential during murine chronic liver injury

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