Metabolic reprogramming in livers of mice with chronic liver disease

Metabolic zonation of healthy liver lobules is extensively studied. However, little is known how chronic liver disease (CLD) influences lobular zonation. To bridge this gap, we studied metabolic zonation in two mouse models of CLD: repeated intoxication with carbon tetrachloride (CCl4; 1 gram/kg) twice a week up to one year, and bile duct ligation (BDL) for 21 days. Disease progression and its impact on metabolic zonation was analysed by histopathology, immunohistochemistry, image analyses, RT-PCR, as well as RNA-sequencing (RNA-seq) techniques.

Repeated CCl4 intoxication triggered centro-centro bridging pattern of fibrosis that was detected already at 2 months. At late stages (1 year), progression to cirrhosis with presence of regenerative and neoplastic nodules was detected. RNA-seq analysis revealed downregulation of the pericentral and upregulation of the periportal genetic programs, respectively. Furthermore, immunohistochemistry analysis revealed spatio-temporal alterations of the pericentral and the periportal proteins. At the early stage (2 – 6 months), the pericentral proteins, e.g. CYP450 enzymes and glutamine synthetase, showed decreased diameter of the positive area and centro-centro bridging pattern. At the late stage (1 year), the expression of the pericentral proteins was almost completely lost. In contrast, the territory of the periportal proteins, e.g. the urea cycle enzymes, was increased time-dependently to cover almost the entire liver parenchyma. To check whether the loss of pericentral gene expression occurs because CCl4 intoxication targets the pericentral hepatocytes, the same analyses was done after BDL; a model of periportal fibrosis. Interestingly, the pattern of periportalization of the liver lobule was also consistent in the BDL model. Biostatistical analysis of the RNA-seq data suggested that periportalization of the liver lobule in CLD was due to a loss of Wnt/β-catenin signalling pathway. In order to check the functional consequences of this altered zonation, mice on day 21 post BDL or on one year of repeated CCl4 intoxication were challenged with 200 mg/kg acetaminophen (APAP). Interestingly, both mouse models were almost completely resistant to APAP intoxication.

In conclusion, CLD strongly alters zonation of the liver lobule where the periportal genetic program becomes dominant, forming a "periportal-like" lobule.