Inhibition of mast cell-secreted histamine decreases biliary proliferation and fibrosis in primary sclerosing cholangitis Mdr2 ^−/− mice

Abstract

Background and Aim

Hepatic fibrosis is marked by activation of hepatic stellate cells (HSCs). Cholestatic injury precedes liver fibrosis and cholangiocytes interact with HSCs promoting fibrosis. Mast cells (MCs) infiltrate following liver injury and release histamine increasing biliary proliferation. We evaluated if inhibition of MC-derived histamine decreases biliary proliferation and fibrosis.

Methods

WT and Mdr2 ^−/− mice (9-11 weeks) were treated with cromolyn sodium for 1 week to block MC-derived histamine. Biliary mass and proliferation were evaluated by immunohistochemistry for CK-19 and Ki-67. Bile flow, bicarbonate excretion and total bile acids were measured in all mice. Fibrosis was evaluated by Sirius Red/Fast Green staining and by qPCR for α-SMA, fibronectin, collagen type 1a and TGF-β1. HSC activation was evaluated by qPCR in total liver and immunofluorescent staining in tissues for synaptophysin 9. Histamine serum secretion was measured by EIA. Mouse liver and human liver samples from control or PSC patients were evaluated for MC markers by qPCR and immunohistochemistry. In vitro, cultured MCs were transfected with HDC shRNA to decrease histamine secretion and subsequently co-cultured with cholangiocytes or HSCs prior to measuring fibrosis markers, proliferation and TGF-β1 secretion.

Results

Treatment with cromolyn sodium decreased biliary proliferation, fibrosis, histamine secretion, and bile flow in Mdr2 ^−/− mice. PSC mice and patients have increased MCs. Knockdown of MC HDC decreased cholangiocyte and HSC proliferation/activation.

Conclusion

MCs are recruited to proliferating cholangiocytes and promote fibrosis. Inhibition of MC-derived histamine decreases fibrosis and regulation of MC mediators may be a therapeutic for PSC.