Istituto Nazionale Genetica Molecolare, Padiglione Romeo ed Enrica Invernizzi, IRCCS Ospedale Maggiore Policlinico, Milan, Italy.
Institute of Pathology, University Hospital Basel, Basel, Switzerland.
Liver Int. 2019 Nov;39(11):2124-2135. doi: 10.1111/liv.14128. Epub 2019 May 15.
Primary biliary cholangitis is an autoimmune biliary disease characterized by injury of bile ducts, eventually leading to cirrhosis and death. In most cases, anti-mitochondrial antibodies and persistently elevated serum alkaline phosphatase are the basis for the serological diagnosis. Anti-nuclear antibodies are also useful and may indicate a more aggressive diseases course. In patients in which anti-mitochondrial antibodies are not detected, an accurate diagnosis requires liver histology. This study aims at identifying specific biomarkers for the serological diagnosis of primary biliary cholangitis.
Sera from patients affected by primary biliary cholangitis, primary sclerosing cholangitis, hepatitis C virus (with and without cryoglobulinemia), hepatocarcinoma and healthy donors were tested on a protein array representing 1658 human proteins. The most reactive autoantigens were confirmed by DELFIA analysis on expanded cohorts of the same mentioned serum classes, and on autoimmune hepatitis sera, using anti-PDC-E2 as reference biomarker.
Two autoantigens, SPATA31A3 and GARP, showed high reactivity with primary biliary cholangitis sera, containing or not anti-mitochondrial antibodies. Their combination with PDC-E2 allowed to discriminate primary biliary cholangitis from all tested control classes with high sensitivity and specificity. We found that GARP expression is upregulated upon exposure to biliary salts in human cholangiocytes, an event involving EGFR and insulin pathways. GARP expression was also detected in biliary duct cells of PBC patients.
This study highlighted SPATA31A3 and GARP as new biomarkers for primary biliary cholangitis and unravelled molecular stimuli underlying GARP expression in human cholangiocytes.
原发性胆汁性胆管炎是一种自身免疫性肝胆疾病，其特征为胆管损伤，最终导致肝硬化和死亡。在大多数情况下，抗线粒体抗体和持续升高的血清碱性磷酸酶是血清学诊断的基础。抗核抗体也很有用，可能表明疾病更具侵袭性。对于未检测到抗线粒体抗体的患者，准确的诊断需要肝组织学检查。本研究旨在确定原发性胆汁性胆管炎血清学诊断的特异性生物标志物。
使用代表 1658 个人类蛋白的蛋白质芯片检测原发性胆汁性胆管炎、原发性硬化性胆管炎、丙型肝炎病毒（伴或不伴冷球蛋白血症）、肝癌和健康供体患者的血清。在相同血清类别中扩大的队列以及自身免疫性肝炎血清中，通过 DELFIA 分析对最具反应性的自身抗原进行确认，使用抗 PDC-E2 作为参考生物标志物。
两种自身抗原 SPATA31A3 和 GARP 与原发性胆汁性胆管炎血清具有高反应性，无论是否含有抗线粒体抗体。它们与 PDC-E2 的组合可实现对原发性胆汁性胆管炎与所有测试对照类别的高灵敏度和特异性区分。我们发现，人胆管细胞暴露于胆汁盐会导致 GARP 表达上调，这一事件涉及 EGFR 和胰岛素途径。在 PBC 患者的胆管细胞中也检测到 GARP 的表达。
本研究强调了 SPATA31A3 和 GARP 作为原发性胆汁性胆管炎的新生物标志物，并揭示了人类胆管细胞中 GARP 表达的分子刺激。
