IL-22 Contributes To Liver Regeneration In Mice With Hepatitis After Hepatectomy

Liver disease is a serious threat to human health in the world, including various causes of hepatitis(such as fat, viral, alcohol and autoimmune), liver fibrosis and liver cancer. IL-22(Interleukin-22) cytokines as a new CD4+ Th cell factor, expressed as a dual effect of pro-inflammatory and promoting tissue repair in liver disease. IL-22 is involved in pathological processes mediated by the immune system, with diverse roles in the occurrence and development of diseases and so on, it has gradually been understood in liver disease, but the specific mechanism is not very clear. IL-22 may have a wide range of biological activities. At present, the research is still in the initial stage, whether there is close contact of IL-22 and other cytokines, it need to be researched with immunology, molecular biology and related disciplines of knowledge and technology. In recent years, the study of IL-22 has laid a foundation for the application of IL-22 in the treatment of liver diseases. IL-22 is expected to be a new target for the treatment of liver diseases.Part 1: Modifications of a 70%partial hepatectomy mice modelObject: To establish an effective and convenient model of 70%partial hepatectomy In mice, and provide a basis for investigating the underlying cellular and molecular mechanisms and pathophysiological significance of liver regeneration.Methods: 8 to 12 weeks old C57BL/6 mice(20–25g) were randomly divided into two groups: classic group: liver resection was performed after ligation of hepatic lobe's pedicle; and improved group: hepatic branch inflow vessels were ligated before resecting the liver lobes. The two methods were used respectively for 70%partial hepatectomy In mice. After surgery, the status of remnant liver regeneration and the mouse survival rate were investigated.Results: The survival rate of improved group(97.3%) was superior to the classic group(86.7%). The complications of postoperative bleeding, bile leakage and vena cava stenosis was significantly reduced in the improved group than the classic group. However there is no significant difference on liver regeneration(increased weight of remnant liver) between the two groups.Conclusion: We have successfully established an improved 70 % partial hepatectomy model in mice by ligating hepatic branch inflow vessels before liver resection. This method resects liver volume precisely, conveniently and gained increased survival rate and complications. It's an ideal animal model for the liver regeneration study.Part 2: The role of interleukin-22 in liver regeneration after partial hepatectomy with Con A(Concanavalin A)-mediated liver injury in miceObjective: To study the therapeutic effects and mechanisms of interleukin-22 in liver regeneration after partial hepatectomy with Con A(Concanavalin A)-mediated liver injury in mice.Methods: C57BL/6 were divided into four groups with 25 mice per group: PHX group, Con A group,PHX+Con A group, and PHX+Con A+IL-22 group.The serum and liver tissue at 32 h, 40 h, 48 h, 1w and 2w after resection were obtained.Before sampling liver were weighted and calculated liver regeneration rate. liver function(ALT, AST, ALB) changes of different time were tested by blood biochemical analysis and pathological changes were observed by hematoxylin-eosin staining. The expression and index of proliferating cell nuclear antigen(PCNA) in liver tissue were tested by immunohistochemical method. The level of Cyclin D1 and STAT3( Signal transducer and activator of transcription 3) signaling pathway detected by Western blot analysis and the expression of AFPm RNA were tested by real-time quantitative polymerase chain reaction(RQ-PCR)ananlysis. All changes of four groups were compared by t-test and linear correlation analysis.Results:With administration of exogenous interleukin-22, the liver weight/body increased significantly, compared with Con A+PH group(2.95±0.14, 3.09±0.14, 3.78±0.10, 4.89±0.12), Con A+PH+IL-22 group(3.16±0.17, 3.34±0.13, 4.19±0.14, 5.14±0.16) increased and reached statistical significance at 40 h, 48 h, 1w or 2w. Histopathology indicated that liver injury in mice of the treatment group was markedly alleviated. Furthermore, western blotting revealed that in the four groups, STAT3 and Cyclin D1 level as well as AFPm RNA are the most significantly increased in the Con A+PH+IL-22 group as well as the least significantly increased in the Con A+PH group at all the time points.Conclusions:Interleukin-22 acts as a protective cytokine to attenuate liver injury in the model of hepatectomy in T cell-mediated hepatitis induced by concanavalin A. This effect of interleukin-22 might be mediated by enhancing pro-growth pathways via STAT3 activation and then inducing the expression of genes important for cell cycle progression(such as cyclin D1 and AFPm RNA).