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Background and aims: Ductular reaction (DR) expands in chronic liver diseases and correlates with disease severity. Besides its potential role in liver regeneration, DR plays a role in the wound-healing response of the liver, promoting periductular fibrosis and inflammatory cell recruitment. However, there is no information regarding its role in intrahepatic angiogenesis. In the current study we investigated the potential contribution of DR cells to hepatic vascular remodeling during chronic liver disease. Approach and results: In mouse models of liver injury, DR cells express genes involved in angiogenesis. Among angiogenesis-related genes, the expression of Slit2 and its receptor Roundabout 1 (Robo1) was localized in DR cells and neoangiogenic vessels, respectively. The angiogenic role of the Slit2-Robo1 pathway in chronic liver disease was confirmed in ROBO1/2-/+ mice treated with 3,5-diethoxycarbonyl-1,4-dihydrocollidine, which displayed reduced intrahepatic neovascular density compared to wild-type mice. However, ROBO1/2 deficiency did not affect angiogenesis in partial hepatectomy. In patients with advanced alcohol-associated disease, angiogenesis was associated with DR, and up-regulation of SLIT2-ROBO1 correlated with DR and disease severity. In vitro, human liver-derived organoids produced SLIT2 and induced tube formation of endothelial cells. Conclusions: Overall, our data indicate that DR expansion promotes angiogenesis through the Slit2-Robo1 pathway and recognize DR cells as key players in the liver wound-healing response., Supported by grants from Fondo de Investigación Sanitaria Carlos III (FIS), cofinanced by Fondo Europeo de Desarrollo Regional (FEDER), Unión Europea, “Una manera de hacer Europa” (FIS PI20/00765, PI17/00673, to P.S.-B; FIS 18-PI18/00862, to I.G and M.C); from the National Institute on Alcohol Abuse and Alcoholism (1U01AA026972-01 and AGAUR 2017-SGR-01456, to P.S.-B.); and from the European Foundation for Alcohol Research (EA1653, to P.S.-B.). M.C. is funded by the Ramon y Cajal program from the Ministerio de Ciencia e Innovación RYC2019-026662-I. P.G. is funded by the Agencia de Gestió d'Ajuts Universitaris i de Recerca 2014 SGR 708, Centro de Investigaciónen Red Enfermedades Hepáticas y Digestivas (CIBERehd), and Institució Catalana de Recerca i Estudis Avançats. S.A. received a grant from the Ministerio de Educación, Cultura y Deporte (FPU17/04992). B.A.-B. is funded by the Instituto de Salud Carlos III (FI16/00203)

Background and aims Tolerance is transplantation's holy grail, as it denotes allograft health without immunosuppression and its toxicities. Our aim was to determine, among stable long-term pediatric liver transplant recipients, the efficacy and safety of immunosuppression withdrawal to identify operational tolerance. Approach and results We conducted a multicenter, single-arm trial of immunosuppression withdrawal over 36-48 weeks. Liver tests were monitored biweekly (year 1), monthly (year 2), and bimonthly (years 3-4). For-cause biopsies were done at investigators' discretion but mandated when alanine aminotransferase or gamma glutamyltransferase exceeded 100 U/L. All subjects underwent final liver biopsy at trial end. The primary efficacy endpoint was operational tolerance, defined by strict biochemical and histological criteria 1 year after stopping immunosuppression. Among 88 subjects (median age 11 years; 39 boys; 57 deceased donor grafts), 33 (37.5%; 95% confidence interval [CI] 27.4%, 48.5%) were operationally tolerant, 16 were nontolerant by histology (met biochemical but failed histological criteria), and 39 were nontolerant by rejection. Rejection, predicted by subtle liver inflammation in trial entry biopsies, typically (n = 32) occurred at ≤32% of the trial-entry immunosuppression dose and was treated with corticosteroids (n = 32) and/or tacrolimus (n = 38) with resolution (liver tests within 1.5 times the baseline) for all but 1 subject. No death, graft loss, or chronic, severe, or refractory rejection occurred. Neither fibrosis stage nor the expression level of a rejection gene set increased over 4 years for either tolerant or nontolerant subjects. Conclusions Immunosuppression withdrawal showed that 37.5% of selected pediatric liver-transplant recipients were operationally tolerant. Allograft histology did not deteriorate for either tolerant or nontolerant subjects. The timing and reversibility of failed withdrawal justifies future trials exploring the efficacy, safety, and potential benefits of immunosuppression minimization.

Chronic liver diseases are characterized by the expansion of ductular reaction (DR) cells and the expression of liver progenitor cell (LPC) markers. In alcoholic hepatitis (AH), the degree of DR expansion correlates with disease progression and short-term survival. However, little is known about the biological properties of DR cells, their impact on the pathogenesis of human liver disease, and their contribution to tissue repair. In this study, we have evaluated the transcriptomic profile of DR cells by laser capture microdissection in patients with AH and assessed its association with disease progression. The transcriptome analysis of cytokeratin 7-positive (KRT7(+)) DR cells uncovered intrinsic gene pathways expressed in DR and genes associated with alcoholic liver disease progression. Importantly, DR presented a proinflammatory profile with expression of neutrophil recruiting C-X-C motif chemokine ligand (CXC) and C-C motif chemokine ligand chemokines. Moreover, LPC markers correlated with liver expression and circulating levels of inflammatory mediators such as CXCL5. Histologically, DR was associated with neutrophil infiltration at the periportal area. In order to model the DR and to assess its functional role, we generated LPC organoids derived from patients with cirrhosis. Liver organoids mimicked the transcriptomic and proinflammatory profile of DR cells. Conditioned medium from organoids induced neutrophil migration and enhanced cytokine expression in neutrophils. Likewise, neutrophils promoted the proinflammatory profile and the expression of chemokines of liver organoids. CONCLUSION: Transcriptomic and functional analysis of KRT7(+) cells indicate that DR has a proinflammatory profile and promote neutrophil recruitment. These results indicate that DR may be involved in the liver inflammatory response in AH, and suggest that therapeutic strategies targeting DR cells may be useful to mitigate the inflammatory cell recruitment in AH.

Liver transplantation (LT) is a successful treatment for patients with liver failure. However, organ shortage results in over 11% of patients losing their chance of a transplant attributed to liver decompensation (LD) and death. Ischemia/reperfusion injury (IRI) following conventional cold storage (CS) is a major cause of injury leading to graft loss after LT. Normothermic machine perfusion (NMP), a method of organ preservation, provides oxygen and nutrition during preservation and allows aerobic metabolism. NMP has recently been shown to enable improved organ utilization and posttransplant outcomes following a phase I and a phase III randomized trial. The aim of the present study is to assess the impact of NMP on reducing IRI and to define the underlying mechanisms. We transplanted and compared 12 NMP with 27 CS-preserved livers by performing gene microarray, immunoprofiling of hepatic lymphocytes, and immunochemistry staining of liver tissues for assessing necrosis, platelet deposition, and neutrophil infiltration, and the status of steatosis after NMP or CS prereperfusion and postreperfusion. Recipients receiving NMP grafts showed significantly lower peak aspartate aminotransferase (AST) levels than those receiving CS grafts. NMP altered gene-expression profiles of liver tissue from proinflammation to prohealing and regeneration. NMP also reduced the number of interferon gamma (IFN-γ) and interleukin (IL)-17–producing T cells and enlarged the CD4 pos CD25 high CD127 neg FOXP3 pos regulatory T cell (Treg) pool. NMP liver tissues showed less necrosis and apoptosis in the parenchyma and fewer neutrophil infiltration compared to CS liver tissues. Conclusion: Reduced IRI in NMP recipients was the consequence of the combination of inhibiting inflammation and promoting graft regeneration.

Severe liver diseases are characterized by expansion of liver progenitor cells (LPC), which correlates with disease severity. However, the origin and role of LPC in liver physiology and in hepatic injury remains a contentious topic. We found that ductular reaction cells in human cirrhotic livers express hepatocyte nuclear factor 1 homeobox B (HNF1β). However, HNF1β expression was not present in newly generated epithelial cell adhesion molecule (EpCAM)-positive hepatocytes. In order to investigate the role of HNF1β-expressing cells we used a tamoxifen-inducible Hnf1βCreER/R26RYfp/LacZ mouse to lineage-trace Hnf1β+ biliary duct cells and to assess their contribution to LPC expansion and hepatocyte generation. Lineage tracing demonstrated no contribution of HNF1β+ cells to hepatocytes during liver homeostasis in healthy mice or after loss of liver mass. After acute acetaminophen or carbon tetrachloride injury no contribution of HNF1β+ cells to hepatocyte was detected. We next assessed the contribution of Hnf1β+-derived cells following two liver injury models with LPC expansion, a diethoxycarbonyl-1,4-dihydro-collidin (DDC)-diet and a choline-deficient ethionine-supplemented (CDE)-diet. The contribution of Hnf1β+ cells to liver regeneration was dependent on the liver injury model. While no contribution was observed after DDC-diet treatment, mice fed with a CDE-diet showed a small population of hepatocytes derived from Hnf1β+ cells that were expanded to 1.86% of total hepatocytes after injury recovery. Genome-wide expression profile of Hnf1β+-derived cells from the DDC and CDE models indicated that no contribution of LPC to hepatocytes was associated with LPC expression of genes related to telomere maintenance, inflammation, and chemokine signaling pathways. Conclusion: HNF1β+ biliary duct cells are the origin of LPC. HNF1β+ cells do not contribute to hepatocyte turnover in the healthy liver, but after certain liver injury, they can differentiate to hepatocytes contributing to liver regeneration. (Hepatology 2014;60:1367–1377)

Prohibitin 1 (PHB1) is a highly conserved, ubiquitously expressed protein that participates in diverse processes including mitochondrial chaperone, growth and apoptosis. The role of PHB1 in vivo is unclear and whether it is a tumor suppressor is controversial. Mice lacking methionine adenosyltransferase 1A (MAT1A) have reduced PHB1 expression, impaired mitochondrial function, and spontaneously develop hepatocellular carcinoma (HCC). To see if reduced PHB1 expression contributes to the Mat1a knockout (KO) phenotype, we generated liver-specific Phb1 KO mice. Expression was determined at the messenger RNA and protein levels. PHB1 expression in cells was varied by small interfering RNA or overexpression. At 3 weeks, KO mice exhibit biochemical and histologic liver injury. Immunohistochemistry revealed apoptosis, proliferation, oxidative stress, fibrosis, bile duct epithelial metaplasia, hepatocyte dysplasia, and increased staining for stem cell and preneoplastic markers. Mitochondria are swollen and many have no discernible cristae. Differential gene expression revealed that genes associated with proliferation, malignant transformation, and liver fibrosis are highly up-regulated. From 20 weeks on, KO mice have multiple liver nodules and from 35 to 46 weeks, 38% have multifocal HCC. PHB1 protein levels were higher in normal human hepatocytes compared to human HCC cell lines Huh-7 and HepG2. Knockdown of PHB1 in murine nontransformed AML12 cells (normal mouse hepatocyte cell line) raised cyclin D1 expression, increased E2F transcription factor binding to cyclin D1 promoter, and proliferation. The opposite occurred with PHB1 overexpression. Knockdown or overexpression of PHB1 in Huh-7 cells did not affect proliferation significantly or sensitize cells to sorafenib-induced apoptosis. Conclusion: Hepatocyte-specific PHB1 deficiency results in marked liver injury, oxidative stress, and fibrosis with development of HCC by 8 months. These results support PHB1 as a tumor suppressor in hepatocytes. (HEPATOLOGY 2010.)