Abstract

Background:

Non-alcoholic steatohepatitis (NASH) is prevalent, yet lacks for effective treatments to hinder rapid fibrosis progression, which is the main factor that limits patient prognosis. The role of Hypoxia-inducible factor 1α (HIF-1α) in NASH progression remains unclear. This study investigates the impact and mechanism of hepatocyte-specific HIF-1α deletion on NASH fibrosis, aiming to uncover a novel therapeutic target.

Methods:

Hepatocyte-specific HIF-1α-knockout mice were generated using the Cre-Lox system and non-alcoholic steatohepatitis (NASH) models were established via a methionine choline-deficient (MCD) diet or Gubra-Amylin NASH (GAN) diet. During the study, mouse food intake and weight changes were monitored, and biochemical indices were evaluated. Liver specimens were obtained for weighing, quantitative measurements of TC and TG, histopathological examination via H&E staining, Oil Red O staining, Sirius Red staining, and immunohistochemical staining. RNA-seq, histological techniques, flow cytometry, and co-culture experiments were employed to screen for and characterize the expression and functionality of GPMNB-positive macrophages.

Results:

Hepatocyte-specific HIF-1α knockout mice, compared with the Flox control group, demonstrated significantly exacerbated hepatic steatosis and increased formation of fatty granulomas when subjected to MCD and GAN diet-induced NASH models. However, knockout mice exhibited no significant difference in physiological parameters such as weight change and serum biochemistry under normal dietary conditions, compared to wild-type mice. HIF-1α-knockout mice characterized an earlier onset of hepatic fibrosis, accompanied by significantly upregulated mRNA expression of fibrosis-related genes. Recruitment of GPNMB⁺ macrophages was observed in the HIF-1α-depleted liver. Single-cell sequencing data of the liver tissues indicated that GPNMB was predominantly expressed in macrophages. Furthermore, the GPNMB protein stimulated hepatic stellate cell activation, suggesting that GPNMB⁺ macrophages might hasten the progression of NASH to liver fibrosis.

Conclusion:

Hepatocyte-specific HIF-1α deficiency accelerates NASH progression to liver fibrosis through the recruitment of GPNMB⁺ macrophages. Targeting GPNMB might provide a promising strategy to curb fibrosis progression and benefit NASH prognosis.