Objective To explore the effect and mechanism of protein kinase N1(PKN1)on the proliferation of mouse cardiomyocytes.Methods Two 1-day-old mice were anesthetized with isoflurane,and their cardiomyocytes were isolated and divided into the control group and the interference group.The cardiomyocytes in the interference group were transfected with PKN1 fragments,while the cardiomyocytes in the control group were transfected with control fragments.According to the random number table method,10 mice were divided into the normal group and the observation group,with 5 mice in each group.The mice in the observation group were injected with PKN1 adenovirus in situ in the heart,while the mice in the normal group were injected with empty adenovirus in situ in the heart.The Ki-67 positive expression in myocardial cells and tissues of mice in the four groups was detected by immunofluorescence assay,indicating the proliferation ability of cardiomyocytes.The PKN1 mRNA expression in cardiomyocytes of mice in the control group and interference group was measured by real-time fluorescence quan-titative polymerase chain reaction.The expression of PKN1 and cyclin D1 proteins in cardiomyocytes of mice in the control group and interference group was determined by Western blot.Results The positive expression rates of Ki-67 in myocardial cells of mice in the interference group was significantly lower than that in the control group(t=11.201,P＜0.01);the positive expression rate of Ki-67 in myocardial tissue of mice in the observation group was significantly lower than that in the normal group(t=11.851,P＜0.01).The relative expression level of PKN1 mRNA in cardiomyocytes of mice in the interference group was significantly lower than that in the control group(t=7.022,P＜0.01).The relative expression levels of PKN1 and cyclin D1 proteins in cardiomyocytes of mice in the interference group were significantly lower than those in the control group(t=5.762,6.884;P＜0.01).Conclusion The decreased expression of PKN1 in mouse cardiomyocytes can inhibit the expression of cyclin D1 protein,thereby restraining cardiomyocyte proliferation.

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.

To construct cellular senescence model by stimulating primary hepatocytes with hydrogen peroxide (H 2O 2). Primary hepatocytes were transfected with p53 siRNA, progerin siRNA or IGF-1 adenovirus vector. The number of SA-β-Gal stained positive cells and the expression of p53 and progerin were detected. The results showed that p53 siRNA and progerin siRNA had knocked-down the expression of p53 and progerin, and had alleviated the hepatocyte senescence. Transfection of insulin-like growth factor (IGF)-1 adenovirus vector into primary hepatocytes had overexpressed IGF-1, and had alleviated the number of SA-β-Gal-positive cells. The expression of p53 and progerin was down-regulated in the nucleus, while the expression of p53 was up-regulated in the cytoplasm. The co-precipitation and co-localization of p53 and progerin was decreased in the nuclear region of hepatocytes. IGF-1 overexpression can inhibit intranuclear p53 translocation, alleviate the interaction between p53-progerin, and alleviate hepatocyte senescence.