title: Deletion of Wntless in myeloid cells exacerbates liver fibrosis and the ductular reaction in chronic liver injury.
abstract: BACKGROUND
  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 also 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 by conditionally deleting Wntless expression, which encodes a chaperone essential for Wnt protein secretion, in LysM-Cre-expressing myeloid cells (LysM-Wls mice).
  
  
  RESULTS
  Fibrosis and HPC activation were exacerbated in LysM-Wls mice compared to littermate controls, in the absence of an apparent increase in myofibroblast activation or interstitial collagen mRNA expression, in both the TAA and CDE models of chronic liver disease. Increased Epcam mRNA levels paralleled the increased HPC activation and more mature ductular reactions, in LysM-Wls mice. Increased Epcam expression in LysM-Wls HPC was also observed, consistent with a more cholangiocytic phenotype. No differences in the mRNA expression levels of key pro-inflammatory and pro-fibrotic cytokines or the macrophage-derived HPC mitogen, Tweak, were observed. LysM-Wls mice exhibited increased expression of Timp1, encoding the key Mmp inhibitor Timp1 that blocks interstitial collagen degradation, and, in the TAA model, reduced expression of the anti-fibrotic matrix metalloproteinases, Mmp12 and Mmp13, suggesting a role for macrophage-derived Wnt proteins in restraining fibrogenesis during ongoing liver injury.
  
  
  CONCLUSIONS
  In summary, these data suggest that macrophage-derived Wnt proteins possess anti-fibrogenic potential in chronic liver disease, which may be able to be manipulated for therapeutic benefit.
authors.affiliation: Centre for Liver Disease Research, School of Medicine, The University of Queensland, Translational Research Institute, 37 Kent St, Brisbane, 4102 Australia.
authors.forename: Katharine M
authors.initials: KM
authors.lastname: Irvine
authors.affiliation: Centre for Liver Disease Research, School of Medicine, The University of Queensland, Translational Research Institute, 37 Kent St, Brisbane, 4102 Australia.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Clouston
authors.affiliation: Centre for Liver Disease Research, School of Medicine, The University of Queensland, Translational Research Institute, 37 Kent St, Brisbane, 4102 Australia.
authors.forename: Victoria L
authors.initials: VL
authors.lastname: Gadd
authors.affiliation: Centre for Liver Disease Research, School of Medicine, The University of Queensland, Translational Research Institute, 37 Kent St, Brisbane, 4102 Australia.
authors.forename: Gregory C
authors.initials: GC
authors.lastname: Miller
authors.affiliation: Centre for Liver Disease Research, School of Medicine, The University of Queensland, Translational Research Institute, 37 Kent St, Brisbane, 4102 Australia.
authors.forename: Weng-Yew
authors.initials: WY
authors.lastname: Wong
authors.affiliation: QIMR Berghofer Medical Research Institute, Brisbane, Australia.
authors.forename: Michelle
authors.initials: M
authors.lastname: Melino
authors.affiliation: The University of Queensland Diamantina Institute, Translational Research Institute, Brisbane, Australia.
authors.forename: Muralidhara Rao
authors.initials: MR
authors.lastname: Maradana
authors.affiliation: QIMR Berghofer Medical Research Institute, Brisbane, Australia.
authors.forename: Kelli
authors.initials: K
authors.lastname: MacDonald
authors.affiliation: Visual Systems Group, Cincinnati Children's Hospital Medical Center, Cincinnati, OH USA.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Lang
authors.affiliation: Institute for Molecular Bioscience and the Centre for Inflammation and Disease Research, The University of Queensland, Brisbane, Australia.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Sweet
authors.affiliation: The University of Queensland Diamantina Institute, Translational Research Institute, Brisbane, Australia.|Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, Australia.
authors.forename: Antje
authors.initials: A
authors.lastname: Blumenthal
authors.affiliation: Centre for Liver Disease Research, School of Medicine, The University of Queensland, Translational Research Institute, 37 Kent St, Brisbane, 4102 Australia.
authors.forename: Elizabeth E
authors.initials: EE
authors.lastname: Powell
keywords: CDE; Ductular reaction; Liver fibrosis; Macrophages; Matrix remodelling; TAA