Fig. 4: Overexpression of Fgf18 in hepatocytes promotes liver fibrosis.

a Strategy for liver-specific expression of Fgf18. Deletion of the stop codon by albumin-Cre recombinase results in the expression of Fgf18 in hepatocytes. b–n Non-Tg and Fgf18 Tg mice were analyzed at the indicated times after birth. Body weight (b) and calculated liver/body weight ratios (%) of mice (c) are shown. Results are mean ± SE (n = 5 mice). Representative photos of the macroscopic appearance of the livers of 6- to 8-week-old mice (n = 10 mice) are shown (d). Hepatocytes and NPCs were isolated from 4-week-old non-Tg and Fgf18 Tg mice, and the expression of Fgf18 at both the mRNA (e) and protein levels (f) was analyzed by qPCR and Western blotting, respectively. Results are mean ± SE (n = 3 mice) (e). Each number indicates an individual mouse. mFGF18 indicates recombinant murine FGF18. Hepatocytes and NPCs were isolated as in (e) and cultured for 72 h (g). The concentrations of FGF18 were determined by the in-house ELISA. Results are mean ± SD of triplicate samples. Results are representative of two or three independent experiments (e–g). The ALT, AST, and ALP concentrations in the sera of mice (h). Results are mean ± SE (n = 5 mice). Liver sections were stained with H&E (n = 5 mice) (i). The right panel is an enlarged image of the left red box. A, artery; BD, bile duct; PV, portal vein. Liver sections were stained with Sirius Red (j), and the Sirius Red⁺ areas were quantified and expressed as in Fig. 1f (k). Results are mean ± SE. n = 5 (6–8 weeks) or n = 4 (18–24 weeks) mice. The hydroxyproline content was determined (l). Results are mean ± SE (n = 5 mice). Liver sections were stained with anti-CK19 (m) antibody, and the CK19⁺ areas were quantified and expressed as in Fig. 1f (n). The expression of Krt19 was determined by qPCR (o). Results are mean ± SE. n = 5 (non-Tg and Fgf18 Tg at 6–8 weeks and non-Tg at 18–24 weeks) or n = 7 (Fgf18 Tg at 18–24 weeks) mice for m, n, o. Pooled results from two to three independent experiments (b, c, h, k, l, n, o). Statistical significance was determined by the two-tailed unpaired Student’s t test (b, c, e, h, k, l, n, o) or two-way ANOVA with Tukey’s multiple comparison (g). Source data are provided as a Source Data file.