Ductular reaction-associated neutrophils promote biliary epithelium proliferation in chronic liver disease

Background & aims: Ductular reaction expansion is associated with poor prognosis in patients with advanced liver disease. However, the mechanisms promoting biliary cell proliferation are largely unknown. Here we identify neutrophils as drivers of biliary cell proliferation and defective wound-healing response.

Methods: Liver tissue location of neutrophil was evaluated in patients with chronic liver disease. Neutrophil dynamics was analyzed by intravital microscopy and neutrophil-labeling assays in DDC treated mice. Neutrophil depletion or recruitment inhibition was achieved using Ly6g antibody and CXCR1/2 inhibitor, respectively. Mice deficient in PAD4 and neutrophil Elastase (NE) were used to investigate the mechanisms underlying ductular reaction expansion.

Results: In this study we describe a population of ductular reaction-associated neutrophils (DRANs), which are in direct contact to the biliary epithelial cells in chronic liver diseases and their number increases along disease progression. We show that DRANs are immobilized at the ductular reaction for a prolonged period of time. In addition, liver neutrophils display a unique phenotypic and transcriptomic profile, showing a decreased phagocytic capacity and increased oxidative burst. Depletion of neutrophils or inhibition of their recruitment reduces DRANs and the expansion of ductular reaction, while mitigating liver fibrosis and angiogenesis. Mechanistically, neutrophils deficient in PAD4 and NE abrogate neutrophil-induced biliary cell proliferation, thus indicating the role of neutrophil extracellular traps and Elastase release in ductular reaction expansion.

Conclusions: Overall, our study reveals the accumulation of DRANs as a hallmark of advanced liver disease and a potential therapeutic target to mitigate ductular reaction and maladaptive wound-healing response.

Impact and implications: Our results indicate that neutrophils are highly plastic and can have an extended lifespan. Moreover, we identify a new role of neutrophils as triggers of expansion of the biliary epithelium. Overall, the results of this study indicate that ductular reaction-associated neutrophils (DRANs) are new players in maladaptive tissue healing response in chronic liver injury and may be a potential target for therapeutic interventions to reduce ductular reaction expansion and promoting tissue repair in advanced liver disease.

Biliary cells; Chronic injury; Ductular reaction; Elastase; Neutrophil extracellular traps; Neutrophils; Organoids.