The missing link? the role of mast cells in post-transplant ischaemic cholangiopathy

Mast cells (MC), historically affiliated with allergic disease have been overlooked and underestimated. Recent literature has reported a role for MC in liver fibrogenesis.1 In addition, an increase in MC has been noted in a range of liver diseases, most notably cholangiopathies (Primary Biliary Cirrhosis and Primary Sclerosing Cholangitis)2–6 and are proposed to have a pathogenic role. Ischaemic cholangiopathy (IC) is a common complication post liver transplantation, the pathogenesis of IC is not well understood.7 We hypothesised there will be an increase in MC in IC and that they play a key role in the disease pathogenesis. Patients who were re-transplanted for IC were identified from online records at University Hospitals Birmingham. Explants from twelve patients who were re-transplanted for IC and seven normal liver samples (controls) were examined with immunohistochemistry staining. Formalin-fixed, paraffin-embedded peripheral tissue blocks were sectioned and stained using a rabbit polyclonal anti-CD117 antibody. A minimum of 10 portal tracts were identified per case and examined at 200x magnification. The total MC counts per one high powered field (hpf = 0.42 mm2) was identified and the mean MC count was calculated. The level of fibrosis was assessed using the Ishak score (0–6). Results were analysed using Mann Whitney and Wilcoxon tests. MC were predominantly located in portal tracts. The mean mast cell count per hpf for IC cases was 11.07, this was significantly higher than the mean mast cell count for control samples (p < 0.05). There was no difference in mean mast cell counts based on primary liver disease, such as immune mediated liver disease compared with alcohol and hepatitis C (p = 0.88). The density of MC infiltrate significantly correlated to the Ishak score (p < 0.05), with increasing MC density associated with higher Ishak score. In line with our hypothesis there is a significant increase in mast cells in portal tracts, predominantly the peri-biliary region in patients with IC. The level of MC infiltrate strongly corelates to the level of fibrosis. This is the first study to demonstrate MC in IC and adds to the emerging literature on the importance of mast cells in liver fibrogenesis and cholangiopathy. Mouse models have shown that MC stabilising medications are effective in reducing the severity of fibrosis after liver injury.8–9 This is an exciting development which could guide future research and potentially management of this condition. References 1. Weiskirchen R, Meurer SK, Liedtke C, Huber M. Mast Cells in Liver Fibrogenesis. Cells . 2019; 8 (11):1429. Published 2019 Nov 13. doi:10.3390/cells8111429. 2. Ishii M, Iwai M, Harada Y, Morikawa T, Okanoue T, Kishikawa T, Tsuchihashi Y, Hanai K, Arizono N. A role of mast cells for hepatic fibrosis in primary sclerosing cholangitis. Hepatol Res . 2005 Mar; 31 (3):127–31. doi: 10.1016/j.hepres.2005.01.007. 3. González MI, Vannan DT, Eksteen B, Flores-Sotelo I, Reyes JL. Mast Cells in ImmuneMediated Cholangitis and Cholangiocarcinoma. Cells . 2022 Jan 22; 11 (3):375. doi: 10.3390/cells11030375. 4. Veronica Jarido, Lindsey Kennedy, Laura Hargrove, Jennifer Demieville, Joanne Thomson, Kristen Stephenson, and Heather Francis. The emerging role of mast cells in liver disease. Am. J. Physiol. Gastrointest. Liver Physiol . 2017; 313 :2, G89–G101 5. Satomura K, Yin M, Shimizu S, Kato Y, Nagano T, Komeichi H, Ohsuga M, Katsuta Y, Aramaki T, Omoto Y. Increased chymase in livers with autoimmune disease: colocalization with fibrosis. J Nippon Med Sch . 2003 Dec; 70 (6):490–5. doi: 10.1272/jnms.70.490. 6. Kennedy L, Meadows V, Kundu D, Yang Z, Invernizzi P, Carbone M, Liangpunsakul S, Alpini G, Francis H. Mast cell (MC) activation and histamine (HA) signalling promotes atypical ductular reaction, biliary senescence and liver fibrosis during advanced stage primary biliary cholangitis (PBC). The FASEB Journal 2020; 34 :1. [https://doi.org/10.1096/fasebj.2020.34.s1.02713][1] 7. Yvonne de Vries, Fien A von Meijenfeldt, Robert J Porte. Post-transplant cholangiopathy: Classification, pathogenesis, and preventive strategies. Biochimica et Biophysica Acta (BBA) – Molecular Basis of Disease, 2018; 1864 (4, Part B):1507–1515. 8. Jones H, Hargrove L, Kennedy L, et al . Inhibition of mast cell-secreted histamine decreases biliary proliferation and fibrosis in primary sclerosing cholangitis Mdr2(-/-) mice. Hepatology . 2016; 64 (4):1202–1216. doi:10.1002/hep.28704 9. Hargrove L, Graf-Eaton A, Kennedy L, et al . Isolation and characterization of hepatic mast cells from cholestatic rats. Lab Invest 2016; 96 :1198–1210. https://doi.org/10.1038/labinvest.2016.89. [1]: http://