Morphological characterization of the liver in a murine non‐alcoholic fatty liver disease model

Abstract

Non‐alcoholic fatty liver disease (NAFLD) is increasing and may progress to hepatocellular carcinomas. We sought to clarify the morphological and functional characteristics of the hepatic changes in a murine NAFLD model. Nine‐week(wk)‐old male C57BL/6 mice were fed an MCD (methionine‐chorine deficient) diet up to 30 wk (group M). Recovery model mice (group R) were prepared by feeding normal control diet for two weeks after the termination of MCD diet feeding for 8, 16, 30 wk. Serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels were measured and liver cryosections were made. A multiple‐immunostaining technique for various markers was employed for the 3‐dimentional imaging by the confocal laser‐scanning microscopy. Serum AST was elevated from 2 wk (Wk 2) to Wk 16, but decreased at Wk 30 in group M. Oil red O staining also indicated that the group M caused fat accumulation in hepatocytes from Wk 2 to Wk 16. Fibrosis started from Wk 10 and progressed thereafter in group M. In group Rs, serum AST decreased and the fat deposition and fibrosis improved. The immunohistochemical data revealed swollen CD68 positive cells appeared and increased after Wk 16. In semi‐thin sections, these cells contained various‐shaped contents including dead cell fragments, and they remained in group R. The significance of these CD68 positive cells in the pathogenesis of the hepatic changes caused by the MCD diet is discussed.