High‐throughput sequencing identifies aetiology‐dependent differences in ductular reaction in human chronic liver disease

Abstract

Ductular reaction (DR) represents the activation of hepatic progenitor cells (HPCs) and has been associated with features of advanced chronic liver disease; yet it is not clear whether these cells contribute to disease progression and how the composition of their micro‐environment differs depending on the aetiology. This study aimed to identify HPC‐associated signalling pathways relevant in different chronic liver diseases using a high‐throughput sequencing approach. DR/HPCs were isolated using laser microdissection from patient samples diagnosed with HCV or primary sclerosing cholangitis (PSC), as models for hepatocellular or biliary regeneration. Key signals were validated at the protein level for a cohort of 56 patients (20 early and 36 advanced stage). In total, 330 genes were significantly differentially expressed between the HPCs in HCV and PSC. Recruitment and homing of inflammatory cells were distinctly different depending on the aetiology. HPCs in PSC were characterised by a response to oxidative stress (e.g. JUN, VNN1) and neutrophil‐attractant chemokines (CXCL5, CXCL6, IL‐8), whereas HPCs in HCV were identified by T‐ and B‐lymphocyte infiltration. Moreover, we found that communication between HPCs and macrophages was aetiology driven. In PSC, a high frequency of CCL28‐positive macrophages was observed in the portal infiltrate, already in early disease in the absence of advanced fibrosis, while in HCV, HPCs showed a strong expression of the macrophage scavenger receptor MARCO. Interestingly, DR/HPCs in PSC showed more deposition of ECM (e.g. FN1, LAMC2, collagens) compared to HCV, where an increase of pro‐invasive genes (e.g. PDGFRA, IGF2) was observed. Additionally, endothelial cells in the vicinity of DR/HPCs showed differential immunopositivity (e.g. IGF2 and INHBA expression). In conclusion, our data shine light on the role of DR/HPCs in immune signalling, fibrogenesis and angiogenesis in chronic liver disease. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

The Spectrum of Reactive Cholangiocytes in Primary Sclerosing Cholangitis

“…Indeed, in different pathologic settings, they have been shown to originate from reactive cholangiocytes, hepatic and biliary progenitor/stem cells (HPCs), or transdifferentiated hepatocytes/hybrid hepatocytes (sex‐determining region Y‐box 9–positive [Sox9 + ] hepatocyte nuclear factor 4 alpha–positive) . This heterogeneity has rendered the identification of common, specific markers of DRCs quite challenging as different DRCs can express different markers depending on their origin and the nature of the injury . On the other hand, frequently used markers to identify DRCs, such as epithelial cell adhesion molecule, SOX9, and cytokeratins 7 and 19, lack specificity as they are not exclusively expressed by DRCs but also by normal cholangiocytes and, in some cases, SCs.…”

“…This etiology‐dependent origin of DRCs likely affects their interaction with nonparenchymal cells within the ductular reaction, as demonstrated by a recent study that compared the transcriptomic profile of DRCs/HPCs from hepatitis C virus–infected and PSC livers as models for hepatocellular or biliary injury, respectively. The study identified significant differences in the expression of over 300 genes between the DRCs of the two diseases and defined how these differences influence the recruiting and homing of inflammatory cells …”

Bile ductular reactions in the liver: similarities are only skin deep

“…The contribution of the ductular reactions (DRs) to liver regeneration has been more problematic – a scenario described by Govaere et al in a recent issue of The Journal of Pathology . Many models of murine liver injury have targeted either the biliary epithelium or hepatocytes, but genetic lineage tracing has found that most of this regeneration was accomplished through hepatocyte replication, even though DRs were very prominent.…”

“…The validation cohort of 56 formalin‐fixed paraffin‐embedded (FFPE) samples had equal numbers of HCV and PSC cases with 10 being early stage fibrosis (F0–F1) and 18 being advanced stage (F3–F4) for each disease. When comparing HPCs with their neighbouring hepatocytes, RNA‐seq identified 2451 genes in HCV and 1696 genes in PSC that were differentially expressed .…”

“…The factors controlling the behaviour of DRs are slowly becoming apparent. The study of Govaere et al has highlighted the pro‐ and anti‐inflammatory profiles DRs can present, with DR expansion positively correlating with disease progression and short‐term survival in alcoholic liver disease, where there is also expression of neutrophil‐recruiting chemokines . Likewise, in many other liver diseases the extent of liver fibrosis correlates with DR expansion, undoubtedly reflecting the close anatomical association between hepatic stellate cells and the DR .…”