Effect of insulin-like growth factor 1 on hepatocyte senescence in carbon tetrachloride-induced liver fibrosis rats

Abstract

Objective To investigate the development of hepatocyte senescence during liver fibrogenesis and to explore the effect and possible mechanism of insulin-like growth factor 1 (IGF-1) on hepatocyte senescence and liver fibrosis. Methods A total of 42 male Sprague Dawley (SD) rats were selected. Eighteen rats were induced by carbon tetrachloride (CCl4) to establish the rat model of liver fibrosis. On the day 0, six and 28 after the establishment of the model, six rats were executed respectively to analyze the liver fibrosis and hepatocyte senescence in CCl4-induced liver fibrosis rat models. Twenty-four rats were divided into control group, CCl4 group, CCl4+ lentivirus vector (LV-CTR) group and CCl4+ LV-IGF-1 group, with six rats in each group.The rats were sacrificed on the 28th day after the establishment of the model. The liver tissues were obtained and the inferior vena cava blood was collected to analyze the effect of IGF-1 overexpression on liver fibrosis and hepatocyte senescence. Analysis variance (ANOVA), least significant difference (LSD) and Dunnett T3 test were performed for statistical analysis. Results Steatohepatitis on the 6th day and early stage of hepatic fibrosis on the 28th day, which indicated the model was successfully established. The results of the effects of IGF-1 overexpression on hepatic fibrosis and hepatocyte senescence showed that on the 28th day, compared with those of control group, both the score of Ishak liver inflammation and necrosis and the score of Ishak liver fibrosis were increased in the CCl4 group, CCl4+ LV-CTR group and CCl4+ LV-IGF-1 group (0, 14.55±1.94, 15.43±2.19 and 10.29±1.47, respectively; 0, 3.51±0.51, 3.21±0.79 and 1.32±0.40, respectively). The area of liver tissues by Masson staining (0.45±0.40, 5.62±1.08, 6.03±0.65 and 2.88±1.54), SA-β-Gal staining (1.75±0.80, 4.28±1.19, 4.92±1.14, 3.11±0.79), p53 (2.02±0.81, 4.36±1.02, 4.72±0.72 and 3.58±0.70) and progerin (0.72±0.40, 4.52±1.01, 4.01±1.25 and 2.66±0.80) all were increased. The levels of serum IGF-1 all were decreased ((632.00±6.04), (503.00±40.42), (508.00±21.94) and (572.40±5.94) ng/L). However the levels of ALT all were increased ((11.20±5.97), (214.00±73.90), (245.00±76.06) and (30.00±5.00) U/L). The relative expression levels of p53 (0.58±0.06, 1.78±0.18, 1.72±0.10 and 1.23±0.22) and progerin (0.12±0.02, 0.78±0.15, 1.32±0.20 and 0.81±0.16) in the primary hepatocytes were increased. The differences were all statistically significant (F=91.674, 90.778, 32.982, 9.726, 10.640, 17.029, 103.910, 30.059, 64.707 and 97.457, all P<0.05). Compared with those of CCl4+ LV-CTR group, the score of Ishak liver inflammation and necrosis and the score of Ishak liver fibrosis were decreased in the rats′ liver tissues of CCl4+ LV-IGF-1 group, the areas of Masson staining, SA-β-Gal staining, p53 and progerin in the liver tissues were decreased, the level of serum IGF-1 was increased, the level of ALT was decreased, and the relative expression levels of p53 and progerin in primary hepatocytes both were decreased. The differences were all statistically significant (all P<0.05, respectively). Conclusions Hepatocyte senescence increases in the process of liver fibrosis induced by CCl4. Overexpression of IGF-1 may alleviate liver injury, improve hepatocyte senescence and liver fibrogenesis by regulating the nuclear p53/progerin pathway. Key words: Liver cirrhosis; Insulin-like growth factor 1; Hepatocyte senescence; p53; Rat