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

Background: Following liver injury, mast cells (MCs) migrate into the liver and are activated in cholestatic patients. Inhibition of MC mediators decreases ductular reaction (DR) and liver fibrosis. TGF-β1 contributes to fibrosis and promotes liver disease.

Aim: To demonstrate that reintroduction of MCs induces cholestatic injury via TGF-β1.

Methods: Wild-type, KitW-sh (MC-deficient), and Mdr2-/- mice lacking l-histidine decarboxylase were injected with vehicle or PKH26-tagged murine MCs pretreated with 0.01% DMSO or the TGF-βR inhibitor, LY2109761 (TGF-βRi, 10 μM) three days prior to sac. Hepatic damage was assessed by H&E and serum chemistry. Injected MCs were detected in liver, spleen and lung by immunofluorescence (IF). DR was measured by CK-19 immunohistochemistry (IHC) and F4/80 staining coupled with qPCR for IL-1β, IL-33 and F4/80; biliary senescence evaluated by IF or qPCR for p16, p18 and p21. Fibrosis was evaluated by Sirius Red/Fast Green staining and IF for SYP-9, desmin and α-SMA. TGF-β1 secretion/expression was measured by EIA and qPCR. Angiogenesis was detected by IF for vonWillebrand Factor and VEGF-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 MTS and qPCR; HSC activation evaluated for α-SMA, SYP-9 and collagen type-1a expression.

Results: 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.

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

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S2704 LY2109761 LY2109761 is a novel selective TGF-β receptor type I/II (TβRI/II) dual inhibitor with Ki of 38 nM and 300 nM in a cell-free assay, respectively; shown to negatively affect the phosphorylation of Smad2. LY2109761 blocks autophagy and induces apoptosis. (103) (5)

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