| Hepatocellular carcinoma(HCC) is among the most common malignancy in the world. According to WHO statistics, HCC death toll already arrange in the 4th in the world in 2007. In China, both the urban and country resident HCC mortality account for 2nd of cancer cause of death in 2007. At present, the synthesis giving first place to operation is the main way of curing disease such as later period liver cancer and hepar failure. Orthotopic liver transplantation(OLT) is the idealest cure means. But OLT is restricted by many factors such as deficiency of liver, using the immune depressor in the long time, expensive cost. Meanwhile, Liver cell transplantation (LCT) is the ideal alternative of OLT. LCT has these merits like the relative rich source, bearable immune and relatively cheap cost. The Stem/progenitor cells having the differentiation potency of liver cells is considered as the optimum source of LCT. But it has the latent danger.Recent years, with the development of studying of microenvironment, more and more researchers find microenvironment is an important factor of tumor occurrence and development. The mutation of stem cells to cancer stem cells is considered the origin of carcinogenesis. The stem cell niche is the key to maintaining homeostasis. In general, proliferation signals and inhibiting proliferation signals have an active balance. Lost balance, Lost control. Stem cell proliferation will be uncontrolled, becoming the target of several gene events. Microenvironment plays an important role in the early period of carcinogenesis. Tumor has its own microenvironment that could protect and support it. Many researches show that tumor cells have more vulnerable to fast-breeder at the appropriate microenvironment. So microenvironment is an important field of tumor research.Fetal Liver Cells as a kind of liver stem/progenitor Cells, is also regarded as one of the cell sources of transplantation. A great quantity about Fetal Liver Cells property, has been studied on the animal especially rat. Fetal liver cells in the study are the liver cells of fetal rats of 14 days of pregnancy period, and they are also regarded as fetal liver stem/progenitor cells (FLPC/FLSPC). Fetal liver cells own the features of liver cells and also present great proliferative activity which is probably induced by bilateral potential stem/progenitor cells accounting for 3% of the total fetal liver cells. Fetal liver cells proliferate so rapidly that show competition in growth with jacent recipient liver cells, which could result in death of adjacent cells. Thus, we can take advantage of fetal liver cells to study the effects of liver stem cells transplantation on recipient.This study consists of two parts:Part 1 The effects of fetal liver cells on formation of liver cancer in rats1. Effects of fetal liver cells interference in various time point on life span of rats induced liver cancerFirstly, we identified the sex of fetal liver by detecting Y chromosome-specific SPY gene with PCR reaction, and then set up sex-crossing fetal liver cell transplant model, by which we achieve the interference in liver cancer formation and development in different time points in rats who have accepted DEN inducement to observe its effects on rats'life span. Study shows that life span of rats in early interference group is greatly shortened compared with control group, while there is no significant difference between middle-late interference group and control group.2. Effect on tumor growth of early fetal liver cell interference in rats of induced liver cancerTo judge whether it is because fetal liver cells accelerate tumorigenesis that early interference exerts effects on life span, we adopted methods of advancing execution of rats in early interference group and shortening DEN feeding time. Researches show that the shortening life span by early fetal liver cell interference may attribute to its promoting effects on tumorigenesis which leads to the overall antedisplacement of the period for successfully inducing rat liver cancer with DEN.Part 2 Study on mechanism of fetal live cells promoting rat liver cancer occurrenceIn this part, we investigate the promoting mechanism. First, with SRY gene as the mark for fetal liver cells, we use real time PCR to identify the induced cancer cell resource in early interference group and make clear that there is no tumorigenesis originated from fetal liver cell which may lead to the conclusion that fetal liver cell would probably just has the effects of acceleration instead of directly causing cancer formation. Next, we use serum indexes and tunel to study on how transplanted fetal liver cell exert influence on recipient liver, and we found that it intensify the impairment of recipient liver. At last, with investigation on conditioned medium of fetal liver cell, we find out that cytokine secreted by fetal liver cell have the effects of enhancing proliferation of tumor cells.Conclusion:1. Early fetal liver cell interference in rats with induced liver cancer by DEN shortens rats life span, which probably is due to its promoting effects on tumor formation and development resulting in overall antedisplacement of the period for successfully inducing rat liver cancer with DEN.2. Instead of directly causing tumorigenesis, fetal liver cells just enhance the formation and development of liver cancer induced in rats by DEN through the mechanism of aggravating liver impairment and facilitating the growth of adjacent tumor cells.
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