Characterization of liver disease regression in murine models of liver fibrosis and portal hypertension.

Characterization of toxin-induced mouse models of regressive liver disease, focusing on the detecting of a suitable therapeutic window during fibrosis and portal hypertension (PH) regression. C57BL/6JRj mice were studied when exposed to thioacetamide (TAA) or carbon tetrachloride (CCl4) for 8 or 12 weeks (8w/12w) and after one/two (+R1/+R2) week(s) of TAA/CCl4-free regression. Healthy controls received NaCl or olive oil (OO). Primary readouts included liver fibrosis (collagen proportionate area, CPA), portal pressure (PP), serum transaminases and hepatic fibrosis-related gene expression. The diseased models (8wTAA/12wTAA/8wCCl4/12wCCl4) showed significant fibrosis (CPA: 3.03/3.87/8.53/16.90%; vs. NaCl/OO: 0.87/1.15%) and PH (PP: 6.8/7.7/8.5/10.0 mmHg; vs. NaCl/OO: 5.5/5.1 mmHg). CPA significantly regressed in 8wTAA+R1 (2.60%; p = 0.01) and 12wCCl4+R1 (10.9%; p = 0.01), but not in 12wTAA+R1/8wCCl4+R1. CPA regression was significant in all +R2-groups (p < 0.001) but not in 8wCCl4+R2 (p = 0.30). Significant PP regression was found at 8wCCl4+R1 (5.8 mmHg; p = 0.004) and 12wCCl4+R1 (8.4 mmHg; p = 0.01), but not in the 8w/12w TAA models. All +R2-groups showed significant PP regression: 8wTAA+R2 (6.0 mmHg; p ≤ 0.001), 12wTAA+R2 (6.0 mmHg), 8wCCl4+R2 (6.0 mmHg, p = 0.004) and 12wCCl4+R2 (7.9 mmHg, p = 0.008). Serum AST/ALT levels at +R1/+R2 returned to levels of healthy controls. Hepatic Col1a1 and Timp1 gene expression peaked in 12w-groups and showed a gradual decrease at +R1/+R2: Col1a1 (12wTAA+R1/+R2: -14%/-29%, p = 0.002; 12wCCl4+R1/R2: -28%/-23%, p = 0.05) and Timp1 (12wTAA+R1/+R2: -41%/-61%, p ≤ 0.001; 12wCCl4+R1/R2: -43%/-40%, p ≤ 0.001). While liver disease regressed in all models/timepoints, both liver fibrosis (CPA) and PP remained increased in the 12wCCl4+R1/R2 settings - qualifying this model as suitable for pre-clinical testing of therapeutic strategies aimed at promoting liver fibrosis and PH regression.