CD44 expression in the bile duct epithelium is related to hepatic fibrosis in nonalcoholic steatohepatitis rats induced by a choline-deficient, methionine-lowered, L-amino acid diet

Nonalcoholic steatohepatitis is a lifestyle-related disease and an increasing threat worldwide. Hepatic fibrosis, which results from chronic hepatic diseases including nonalcoholic steatohepatitis, is closely correlated with mortality among hepatic lesions, such as steatosis and inflammation. Thus, it is important to identify factors that can serve as diagnostic and therapeutic targets for hepatic fibrosis. In this study, we examined the function of CD44 in the development of hepatic fibrosis in choline-deficient, methioninelowered, L-amino-acid diet-fed rats, especially with respect to the proliferation of bile duct epithelium. Male Fischer 344 rats were fed a choline-deficient, methionine-lowered, L-amino-acid diet for 2, 4, 13, or 26 weeks. This diet decreased the body weight; increased the levels of serum parameters indicating liver injury, such as aspartate and alanine aminotransferase; upregulated inflammation-and fibrosis-related gene expression in the liver; and resulted in the development of hepatic lesions, including fatty changes in hepatocytes, inflammatory cell infiltration, and fibrosis. Hepatic hyaluronan was synthesized and deposited in the liver tissue. The expression of both CD44 mRNA and protein was significantly increased throughout the experimental period. CD44 protein was observed in some of the bile duct epithelium, around which hyaluronic acid was deposited, and these bile duct lesions were concordant with the area of hepatic fibrosis. Thus, CD44 expressed in the bile duct epithelium may be a target for controlling nonalcoholic steatohepatitis-related hepatic fibrosis. (DOI: 10.1293/tox.2021-0069; J Toxicol Pathol 2022; 35: 149-157)

Automated summary

Nonalcoholic steatohepatitis is a lifestyle-related disease that poses an increasing threat worldwide. This study investigates the role of CD44 in the development of hepatic fibrosis, particularly in the proliferation of bile duct epithelium. The experiment used a rat model fed a choline-deficient, methionine-lowered, L-amino-acid diet and found that the expression of CD44 protein significantly increased throughout the experimental period. CD44 protein was mainly present in the bile duct epithelium, which overlapped with the area of hepatic fibrosis.