studies

878A AASLD ABSTRACTS HEPATOLOGY, October, 2015
Disclosures:
The following authors have nothing to disclose: Lin Wang
1361
Liver fatty acid-binding protein is required for Perilipin
5 to restore lipid droplets in activated hepatic stellate
cells
Jianguo Lin 1 , Elizabeth P. Newberry 2 , Nicholas O. Davidson 2 ,
Anping Chen 1 ; 1 Pathology, Saint Louis University, St. Louis, MO;
2 Medicine, Washington University in St. Louis, St. Louis, MO
Hepatic stellate cell (HSC) activation is coupled to the loss of
lipid droplets (LDs) which are specialized organelles composed
of neutral lipids surrounded by perilipins (Plins), among which
Plin5 plays a key role in regulating aspects of intracellular
trafficking, signaling and cytoskeletal organization in hepatocytes.
Recent work in Plin5 ko mice suggests a role in high fat
diet induced hepatic lipotoxicity. We now show that high fat
diet induced liver fibrosis is accompanied by >70% reduction
in HSC Plin5 and that spontaneous activation of primary
HSCs produces temporally coincident loss of Plin5 expression
and LD depletion. Since modulating lipid content in HSCs is
a suggested strategy for inhibiting HSC activation and treatment
of hepatic fibrosis we asked whether exogenous Plin5
expression in primary HSCs would reverse the activation phenotype
and promote LD formation. Lentiviral Plin5 expression
in primary wild type (WT) mouse HSCs restored LDs, increased
lipid content and suppressed activation (~2-fold reduced procollagen
expression), coincident with ~2 fold upregulation of
both PPARgamma and L-Fabp expression. Since HSC specific
expression of L-Fabp promotes FA accumulation and LDs and
inhibits HSC activation in vitro, we next asked if L-Fabp expression
is required for Plin5 rescue of the activated phenotype.
Lentiviral Plin5 transduction of HSCs from L-Fabp –/– mice failed
to restore lipogenic enzyme expression (FAS, SREBP1c) and
showed significantly attenuated induction of PPARgamma (WT
~5-fold induction vs KO ~2.5 fold). Lentiviral Plin5 transduction
also failed to induce LD formation in HSCs from L-Fabp –/– mice
and failed to reverse the activation phenotype (no change in
aSMA or procollagen 1 mRNA, vs significant ~2-fold reduction
in WT HSCs). To further verify the functional role of L-Fabp in
Plin5 mediated pathways, we introduced adenoviral L-Fabp
into HSCs from L-Fabp –/– mice, which completely rescued the
ability of lentiviral Plin5 to restore LD formation and increase
lipid content. Control, lacZ transduced HSCs from L-Fabp –/–
mice failed to demonstrate increased lipid content or visible LDs
after lentiviral Plin5 transduction. Taken together, our results
indicate that Plin5 expression in HSCs plays a critical role in
the activation phenotype both in vivo and in vitro. Furthermore,
our findings demonstrate that HSC L-Fabp has a critical role in
the pathways by which Plin5 modulates lipogenic gene expression,
restoring LD formation and overall lipid content and in
turn modulating HSC activation.
Disclosures:
The following authors have nothing to disclose: Jianguo Lin, Elizabeth P. Newberry,
Nicholas O. Davidson, Anping Chen
1362
Deletion of Wntless in macrophages exacerbates liver
fibrosis and the ductular reaction in chronic liver injury
Katharine Irvine 1 , Andrew D. Clouston 1 , Antje Blumenthal 3 , Elizabeth
E. Powell 1,2 ; 1 Centre for Liver Disease Research, The University
of Queensland, Brisbane, QLD, Australia; 2 Department of
Gastroenterology and Hepatology, Princess Alexandra Hospital,
Brisbane, QLD, Australia; 3 UQ Diamantina Institute, The University
of Queensland, Brisbane, QLD, Australia
Introduction: Macrophages play critical roles in liver regeneration,
fibrosis development and resolution. They are among the
first responders to liver injury, and are implicated in orchestrating
the fibrogenic response via multiple mechanisms. Macrophages
are intimately associated with the activated hepatic
progenitor cell (HPC) niche, or ductular reaction, that develops
in parallel with fibrosis. Among the many macrophage-derived
mediators implicated in liver disease progression, a key role
for macrophage-derived Wnt proteins in driving pro-regenerative
HPC activation towards a hepatocellular fate has been
suggested. Wnt proteins, in general, however, have been
associated with both pro- and anti-fibrogenic activities in the
liver and other organs. We investigated the role of macrophage-derived
Wnt proteins in fibrogenesis and HPC activation
in murine models of chronic liver disease. Methods: We
generated mice deficient in Wnt secretion from macrophages
(MΦ) by deleting the Wls gene, which is essential for Wnt
secretion, in LysM-Cre-expressing cells. Liver injury and fibrosis
were induced by administration of thioacetamide (TAA, 12
wks) in drinking water, or a choline-deficient ethionine-supplemented
diet (CDE, 6 wks). Fibrosis and the ductular reaction
were assessed histologically, and gene expression in whole
liver and flow cytometry-sorted macrophages and HPC was
assessed in MΦ-Wls-knockout mice and littermate controls.
Results: Fibrosis and HPC activation were exacerbated in
MΦ-Wls mice compared to littermate controls in TAA and CDE
treated mice (TAA, p