Research on Gene Expression of CXCL9 and Its Receptor CXCR3 in Hepatic Fibrosis
|School||Shanghai Jiaotong University|
|Course||Animal Genetic Breeding and Reproduction|
|Keywords||Hepatic Fibrosis Chemokines CXCL9 CXCR3|
Hepatic fibrosis is overly exuberant wound healing in which excessive connective tissue builds up in the liver, forming fibrous scar. Cirrhosis is consequence of chronic liver disease characterized by presence of fibrous scar tissues and regenerative nodules in the liver. Regeneration after fibrosis was considered impossible since long but recently hepatic cells are considered to be capable of regeneration, and lots of studies regarding liver regeneration are being conducted around the globe. The development of liver fibrosis, particularly in the cirrhosis stage, is associated with high morbidity and mortality rates and at present the only curative treatment for end stage liver cirrhosis is organ transplantation. So, modeling liver fibrosis in laboratory animals is very important as mechanisms of fibrogenesis and regression of fibrogenesis has not yet been defined clearly. In this thesis, the lab animals will be modeled for the study of progression and regression of fibrosis process and their histopathological, chemical, genetic and biological changes will be collected and interpreted in relation with the progression of fibrosis and regeneration from it. The change in the expression level of CXCL9, its receptor CXCR3 will be accessed during liver fibrogenesis and recovery.Chemokines are a class of small chemotactic molecules with cytokine-like functions, which are well known to orchestrate inflammatory responses within different organs. In recent years, accumulating functional and genetic evidence suggests that chemokines play a critical role in acute and chronic liver diseases, mediating the infiltration of immune cells （monocytes, T-cells） into the injured liver along a concentration gradient. However, chemokines can also directly affect the biology of liver resident cells, such as hepatic stellatecells and hepatocytes during inflammatory and fibrogenic tissue responses. Although the chemokine system has long been considered highly redundant, studies in knockout animals have convincingly demonstrated that single chemokines and chemokine receptors strongly affect the phenotype of toxic and inflammatory liver disease in vivo.Liver fibrosis was induced in rats by injecting 2ml carbon tetrachloride （CCl4） mixed in olive oil （1:1） for first 2 weeks followed by 1ml solution per Kg body weight, intraperitoneally, twice a week and allowed. Throughout the experiment. Control groups were injected with vehicle only. At different designated times, a group of the experimental animals were allowed to self-regenerate their liver back to normal histology by ceasing CCl4 administration. Animals were sacrificed to collect livers and blood, and histology, immunohistology were performed. Quantitative PCR technique was used to quantify the gene expression level in liver. Blood of self-regenerating rats was collected biweekly for the quantitation of biomarkers of liver fibrosis. Then there was an attempt to set up a model for genetic modified mice, which in our case is the CXCR3-/- type.The fibrosis was more severe with the prolonged administration of CCl4 with the increase in deposition of extracellular matrix, which at the end of 12 weeks claimed almost 40% of the hepatic tissues. The highly proliferating hepatic tissues were constantly trying to restore their normal hepatic architecture by degradation of the extracellular matrix, which could be seen prominently after the hepatotoxin injection was withdrawn and the animals were allowed to self-recover. The collagen percentage declined to a low level （nearly 8% from 40%） and the number of proliferating hepatocytes was also decreased to minimum level. During the progression of fibrosis and recovery process, the CXCL9 gene and its receptor CRCR3 showed change in the expression, which was an immediate increase in transcription level and reaching a peak of at the highest severity point. Then we well established the Partial Hepatectomy Model for CXCR3-/- Mice and summarized the crucial control points in the surgical procedure of mice from our own experience and others, which has presented a good layout for the incoming related research for CXCL9 and its receptor CXCR3.