A novel mouse model of non-alcoholic steatohepatitis suggests that liver fibrosis initiates around lipid-laden macrophages

Various cells such as macrophages and hepatic stellate cells interact in the generation of fibrosis in nonalcoholic steatohepatitis (NASH), but the mechanism remains unclear. We employed a high fat/cholesterol/cholate (HFCC) diet to generate a model of NASH-related fibrosis and investigate the pathogenesis of fibrosis. Two mouse strains differing in susceptibility to obesity, the susceptible strain C57BL/6J (B6) and the relatively resistant strain A/J, developed hepatic histological features of NASH including fat deposition, intralobular inflammation, hepatocyte ballooning, and fibrosis after 9 weeks of HFCC diet feeding. The severity of hepatic inflammation and fibrosis was greater in A/J mice than in B6 mice. A/J mice fed the HFCC diet exhibited characteristic CD204-positive lipid-laden macrophage aggregation in hepatic parenchyma. Polarized light visualized the Maltese cross, namely cholesterol crystals within the aggregated macrophages. Moreover, fibrosis developed in a ring-shape from the periphery of the aggregated macrophages, i.e., the starting point of fibrosis could be visualized histologically. Furthermore, matrix assisted laser desorption/ionization mass spectrometry imaging analysis detected a molecule at m/z 772.462, which corresponds to the protonated ion of phosphatidylcholine (P-18:1 (11Z)/18:0) and phosphatidylethanolamine (18:0/20:2 (11Z, 14Z)), in aggregated macrophages in adjacent to the fibrotic lesions. In conclusion, the present HFCC diet-fed A/J model provides an ideal tool to study fibrogenesis and enables novel insights into the pathophysiology of NASH-related fibrosis.

© 2021. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/