Deletion of Wntless in myeloid cells exacerbates liver fibrosis and the ductular reaction in chronic liver injury

Abstract

BackgroundMacrophages 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).ResultsFibrosis 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.ConclusionIn 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.Electronic supplementary materialThe online version of this article (doi:10.1186/s13069-015-0036-7) contains supplementary material, which is available to authorized users.

Multiplex Serum Protein Analysis Identifies Novel Biomarkers of Advanced Fibrosis in Patients with Chronic Liver Disease with the Potential to Improve Diagnostic Accuracy of Established Biomarkers

“…In contrast to the increase in MMP7, advanced fibrosis was associated with reduced serum MMP1, which may suggest a perturbation in the balance between matrix deposition and degradation contributes to progressive fibrosis. In support of this, MMP1 levels were previously reported to be elevated in patients with mild fibrosis compared to healthy controls, but diminished in cirrhosis[26], and we recently demonstrated exacerbated fibrosis in mice deficient in macrophage Wnt production which was associated with reduced Mmp13 expression (the murine ortholog of MMP1)[28]. AFP, a hepatoblast marker, is used clinically as a biomarker for HCC, although an association with fibrosis has previously been observed in chronic HBV[29], and reduced AFP levels were associated with fibrosis regression following interferon therapy in patients with chronic HCV[30].…”

WNT ligands contribute to the immune response during septic shock and amplify endotoxemia-driven inflammation in mice

“…One previous report showed TLR4-and TRIF-dependent induction of Wisp1 expression and WISP1-driven inflammation in a liver ischemiareperfusion injury model. 43 As we and others have implicated WNT proteins in the liver injury response, 15,53,54 it will be informative to assess whether the effect of TRIF-deficiency on WISP1-driven liver inflammation is a consequence of impaired TRIF-mediated WNT ligand expression.…”

“…[11][12][13][14] Studies in patients and animal models suggest WNT proteins shape inflammation and tissue repair. 11,12,[15][16][17][18][19][20] The current paradigm suggests WNT ligands exert pro-inflammatory or immune-modulatory functions, depending on whether they activate b-catenin-independent or b-catenin-dependent signaling. This model largely relies on studies using the prototypical WNT ligands WNT5A and WNT3A as triggers for b-catenin-independent and b-catenin-dependent signaling, respectively.…”

Non-canonical Wnt signalling initiates scarring in biliary disease

“…Two previous reports (32,42) have demonstrated differing effects of myeloid Wnts in mouse models of cholestatic damage. Our data, deleting Wnt5a from myeloid cells, appears to support the conclusions drawn by Okabe et al, who showed that loss of myeloid Wnt production through the loss of Wls resulted in a reduced fibrotic response in DDC model of biliary injury.…”

“…Previous studies have shown that loss of Wnt ligand export in myeloid (using LysM--Cre) (32,42) or epithelial (using Albumin--Cre)(32) cells through Wls deletion, can alter the number of regenerating ductules or levels of fibrosis in biliary disease. However it remains unclear whether this effect is due to altered canonical or non--canonical Wnt signalling.…”