Examining the link between the ductular reaction and fibrosis in fatty liver disease

Boyd, Alexander D (2025). Examining the link between the ductular reaction and fibrosis in fatty liver disease. University of Birmingham. M.D.

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Abstract

The ductular reaction (DR) is a structural remodelling which takes place within and around the portal tracts in response to liver injury. There is known to be a positive correlation between the magnitude of the DR and the amount of liver fibrosis, particularly within the realm of biliary
disease. The propensity of DR cells to directly drive fibrosis has been demonstrated in some murine models of biliary injury, however the degree to which this plays out within the sphere of metabolic dysfunction-associated steatotic liver disease (MASLD), particularly in humans, remains
unknown.

Two murine models of MASLD (methionine and choline deficient (MCD) and choline deficient, L�amino acid defined (CDAA) diet) were compared for their ability to induce a DR and fibrosis, and the gene expression profile of DR cells was analysed. An in vitro co-culture model was set-up to
assess any activating effect on hepatic stellate cells (HSC) following co-culture with biliary epithelial cells (BEC). A protocol was developed to freshly isolate human biliary/DR cells using fluorescence-activated cell sorting from donor and non-alcohol related steatohepatitis (NASH)
explant livers and bulk RNA sequencing undertaken to perform transcriptomic analysis.

The CDAA model was shown to better recapitulate some features of human NASH. DR cells from injured mice were shown to upregulate gene expression of platelet derived growth factor beta (Pdgfβ) and connective tissue growth factor (Ctgf), known HSC activating ligands.
Immunohistochemical staining was used to demonstrate increased expression of the PDGFβ receptor in both murine and human MASLD, and dual immunofluorescent staining showed co�localisation between DR cells and activated HSC/fibroblasts. Co-culture with alcohol-related liver
disease-derived BEC was shown to activate HSC in vitro, whereas co-culture with donor-derived BEC had the opposite effect. Transcriptomic analysis via geneset enrichment of biliary/DR cells from NASH and donor human livers showed differential regulation of pathways including tumour necrosis factor alpha signalling via nuclear factor kappa-light-chain-enhancer of activated B cells, epithelial mesenchymal transition and inflammatory response.

This is the first report directly comparing the gene expression profile of biliary/DR cells in healthy versus NASH human livers. The findings support a potential role of DR cells in activating HSC and driving fibrosis within the realm of human MASLD. This work has helped to streamline protocols
for biliary/DR cell isolation to facilitate future single-cell RNA sequencing techniques.

Type of Work:

Thesis (Doctorates > M.D.)

Award Type:

Doctorates > M.D.

Supervisor(s):