Premature senescence of the liver in Alagille patients

Alagille syndrome (ALGS) is an autosomal dominant disease characterized by a multisystem involvement including bile duct paucity and cholestasis, caused by JAG1 or NOTCH2 mutations in most of the cases. Jagged1-Notch2 interactions are known to be crucial for intrahepatic biliary tract development, but the Notch signaling pathway is also involved in the juxtacrine transmission of senescence and in the induction and modulation of the senescence-associated secretory phenotype (SASP).

Our aim was to investigate premature senescence and SASP in ALGS livers.

Liver tissue from ALGS patients was prospectively obtained at the time of liver transplantation (n = 5) and compared to control livers (n = 5).

We evidenced advanced premature senescence in the livers of five JAG1 mutated ALGS pediatric patients through increased senescence-associated beta-galactosidase activity (p<0.05), increased p16 and p21 gene expression (p<0.01), and increased p16 and γH2AX protein expression (p<0.01). Senescence was located in hepatocytes of the whole liver parenchyma as well as in remaining bile ducts. The classical SASP markers TGF-β1, IL-6, and IL-8 were not overexpressed in the livers of our patients.

We demonstrate for the first time that ALGS livers display important premature senescence despite Jagged1 mutation, underlying the complexity of senescence and SASP development pathways.