GPT and Hepatic fibrosis: The CCl4 group mice developed serious liver fibrosis and knockout of Airn further aggravated the CCl4-induced liver fibrosis as demonstrated by macroscopic examination, hematoxylin and eosin (H&E), sirius red staining, serum ALT, AST level, and liver hydroxyproline content (Fig. 2A and Additional file 1: Table S2).