Mast cells (MCs) induce ductular reaction mimicking liver injury in mice via MC-derived TGF-β1 signaling

Abstract

Background and aims: Following liver injury, mast cells (MCs) migrate into the liver and are activated in patients with cholestasis. Inhibition of MC mediators decreases ductular reaction (DR) and liver fibrosis. Transforming growth factor beta 1 (TGF-β1) contributes to fibrosis and promotes liver disease. Our aim was to demonstrate that reintroduction of MCs induces cholestatic injury through TGF-β1.

Approach and results: Wild-type, KitW-sh (MC-deficient), and multidrug resistance transporter 2/ABC transporter B family member 2 knockout mice lacking l-histidine decarboxylase were injected with vehicle or PKH26-tagged murine MCs pretreated with 0.01% dimethyl sulfoxide (DMSO) or the TGF-β1 receptor inhibitor (TGF-βRi), LY2109761 (10 μM) 3 days before sacrifice. Hepatic damage was assessed by hematoxylin and eosin (H&E) and serum chemistry. Injected MCs were detected in liver, spleen, and lung by immunofluorescence (IF). DR was measured by cytokeratin 19 (CK-19) immunohistochemistry and F4/80 staining coupled with real-time quantitative PCR (qPCR) for interleukin (IL)-1β, IL-33, and F4/80; biliary senescence was evaluated by IF or qPCR for p16, p18, and p21. Fibrosis was evaluated by sirius red/fast green staining and IF for synaptophysin 9 (SYP-9), desmin, and alpha smooth muscle actin (α-SMA). TGF-β1 secretion/expression was measured by enzyme immunoassay and qPCR. Angiogenesis was detected by IF for von Willebrand factor and vascular endothelial growth factor C qPCR. In vitro, MC-TGF-β1 expression/secretion were measured after TGF-βRi treatment; conditioned medium was collected. Cholangiocytes and hepatic stellate cells (HSCs) were treated with MC-conditioned medium, and biliary proliferation/senescence was measured by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium and qPCR; HSC activation evaluated for α-SMA, SYP-9, and collagen type-1a expression. MC injection recapitulates cholestatic liver injury characterized by increased DR, fibrosis/TGF-β1 secretion, and angiogenesis. Injection of MC-TGF-βRi reversed these parameters. In vitro, MCs induce biliary proliferation/senescence and HSC activation that was reversed with MCs lacking TGF-β1.

Conclusions: Our study demonstrates that reintroduction of MCs mimics cholestatic liver injury and that MC-derived TGF-β1 may be a target in chronic cholestatic liver disease.