Aluminum adjuvant promotes liver inflammation and fibrosis in mice: A novel approach to establish a liver fibrosis animal model.

BACKGROUND AND AIMS: Liver fibrosis is a prevalent pathological stage of various chronic liver diseases and has the potential to progress to liver cirrhosis and hepatocellular carcinoma. However, experimental models for in vivo research are limited. Unexpectedly, increased liver inflammation and fibrosis were previously observed in mice treated with aluminum adjuvant (commercial Imject Alum, a mixture of Al(OH)3 and Mg(OH)2). Our study aimed to reveal the pathogenesis and pathological features of Imject Alum-induced liver injury and evaluate its potential as an experimental model of fibrotic liver disease.

METHODS AND MATERIALS: C57BL/6J mice were randomly divided into the following four groups: (i) control group, which received phosphate-buffered saline injections on days 1, 12, 26, 40, and 54; (ii) Imject Alum (Al(OH)3 160 mg/kg) D26 group, which was administered with Imject Alum (Al(OH)3 160 mg/kg) on days 1, 12, and 26; (iii) Imject Alum (Al(OH)3 80 mg/kg) D54; and (iv) Imject Alum (Al(OH)3 160 mg/kg) D54 groups, which were treated with 80 mg/kg and 160 mg/kg of Imject Alum (Al(OH)3), respectively, on days 1, 12, 26, 40, and 54. All reagents were delivered by intraperitoneal injection. Serum biochemical parameters, liver pathology, and expression of genes related to inflammation and fibrogenesis were evaluated. Transcriptome sequencing was performed. The genetic characteristics of the Imject Alum-induced liver lesions in the existing fibrosis model and patients with cirrhosis were determined.

RESULTS

Administration of Imject Alum (Al(OH)3 160 mg/kg) at certain points for 54 days led to extensive hepatic inflammation and fibrosis, accompanied by disturbed bile acid metabolism in mice. Moreover, Imject Alum aggravated liver inflammation and injury by activating the pyroptosis-related inflammasome pathway. Transcriptome analysis revealed that Imject Alum-induced liver lesions had differentially expressed genes that were significantly enriched in pathways related to inflammation, fibrogenesis, and multiple metabolic processes. Moreover, Imject Alum-induced liver lesions exhibited gene signatures similar to those of existing fibrosis models and patients with cirrhosis.

CONCLUSIONS

Aluminum adjuvant (Imject Alum; Al(OH)3 160 mg/kg) administration at certain points for 54 days resulted in notable liver injury, inflammation, and fibrosis. This model had similar gene expression characteristics with existing fibrosis models and liver samples from patients with cirrhosis. Overall, aluminum adjuvant (Imject Alum)-induced mouse model may be a novel approach for establishing a liver fibrosis animal model.