Progenitor cell expansion and impaired hepatocyte regeneration in explanted livers from alcoholic hepatitis

Abstract

Objective In alcoholic hepatitis (AH), development of targeted therapies is crucial and requires improved knowledge of cellular and molecular drivers in liver dysfunction. The unique opportunity of using explanted livers from patients with AH having undergone salvage liver transplantation allowed to perform more in-depth molecular translational studies. Design We studied liver explants from patients with AH submitted to salvage transplantation (n=16), from patients with alcoholic cirrhosis without AH (n=12) and fragments of normal livers (n=16). Hepatic cytokine content was quantified. Hepatocyte function and proliferation and the presence of hepatic progenitor cells (HPCs) were evaluated by immunohistochemistry, western blot or quantitative PCR. Mitochondrial morphology was evaluated by electron microscopy. Results Livers from patients with AH showed decreased cytokine levels involved in liver regeneration (tumour necrosis factor α and interleukin-6), as well as a virtual absence of markers of hepatocyte proliferation compared with alcoholic cirrhosis and normal livers. Electron microscopy revealed obvious mitochondrial abnormalities in AH hepatocytes. Importantly, livers from patients with AH showed substantial accumulation of HPCs that, unexpectedly, differentiate only into biliary cells. AH livers predominantly express laminin (extracellular matrix protein favouring cholangiocyte differentiation); consequently, HPC expansion is inefficient at yielding mature hepatocytes. Conclusions AH not responding to medical therapy is associated with lack of expression of cytokines involved in liver regeneration and profound mitochondrial damage along with lack of proliferative hepatocytes. Expansion of HPCs is inefficient to yield mature hepatocytes. Manoeuvres aimed at promoting differentiation of HPCs into mature hepatocytes should be tested in AH.

Alcohol stimulates macrophage activation through caspase-dependent hepatocyte derived release of CD40L containing extracellular vesicles

“…In the present study, hepatocyte-derived EV activated macrophages (both primary and cell lines) based on a number of readouts including macrophage adhesion and pro-inflammatory cytokines mRNA and protein levels. Interestingly, recent studies suggest that these responses may also be necessary for beneficial regenerative responses necessary for recovery [41]. …”

Alcohol, Diet and Drug Use Preceding Alcoholic Hepatitis

“…Given that AH is associated with marked dysregulation of progenitor cells and impaired liver regeneration [18, 19], this provides a biologically plausible hypothesis where alcohol cessation may conceivably cause short-term deterioration in liver function. This is consistent with our data that confirm that a proportion of patients have cut down or stopped drinking before coming unwell.…”

Pathogenesis and Management of Alcoholic Liver Disease

“…In the diseased state, in which hepatocyte proliferation is inhibited, pluripotent liver progenitor cells, also referred to as oval cells, or ductal hepatocytes, proliferate and differentiate to repopulate hepatocytes or biliary epithelial cells 56 . In the rodent model, alcohol attenuates regeneration of hepatocytes following partial surgical hepatectomy 57 , so despite a lack of human studies, it is reasonable to hypothesize that alcohol not only causes hepatocellular injury and death, but also prevents regeneration. While histologically, the presence of bilirubinostasis and severe fibrosis are associated with a poorer prognosis in alcoholic hepatitis, the presence of proliferating hepatocytes is associated with better prognosis 58 .…”