Study Of The Tumoriyenesis Of Embryonic Stem Cells In Liver Microenvironment

For its promising applications in biomedical research and regenerative medicine,embryonic stem cells (ESCs) have drawn wide attractione to this field since they have beenfound. As the growing knowledge for ontogeny development, the methods of inducing ESCsto various kinds of adult cells become more sophisticated. However, there are still manybarriers that these ESCs-derived adult cells must conquer before they can be really appliedinto clinical approaches: First, it is the crisis of teratomas when the ESCs are transplanted inits undifferentiated state. If differentiate the ESCs in advance and enrich for desired celltypes, it would sufficiently avoid the risk of teratomas formation. But these methods areunable to meet the need of clinical application. Other types of safety concerns are related toadult cell grafts, which may cause aberrant activities of normal tissue or organs. Besides,cell-death pathways initiated by multiple stresses associated with transplantation causeslarge numbers of death of transplanted cells, discounting the efficiency of celltransplantation. According the “Embryonic rest theory”, cancer stem cells are derived from“embryonal rests”, the remaining ESCs deteriorate and form cancer when their environmentchanged. In our pevious study, when ESCs were transplanted in to body several times,culturied in vitro measwhile, cells derived from teratomas have dramatic change in geneticand appeared malignancy.In our study, by transplanting mESCs in mouse liver to form teratomas, screeningteratomas stem cells and culturing in N2B27+3i Medium, and replanting these cells intomouse liver–and maximizing the influence of liver microenvironment, we gothepatocyte-like cells G2-H. G2-H was unable to passage in N2B27+3i Medium or2D/F12+10%serum but can passage in F-medium. Its appearance and growing pace have bothchanged as well. According to the result of Semi-Quantitative RT-PCR, the marker genes for mESCs and that are linked to stem cell tumorigenesis, including OCT4, SOX2, and Nanog,do not express in G2-H cells. This indicated that the molecular processes of self-renewal ofG2-H cells were rather different from those of ES or teratomas cells derived from otherlocations. The presence of AFP, albumin, transthyretin, CK18, and fumarylacetoacetatehydroxylase as shown by Western blot analysis, ELISA, and immunocytochemistry revealedESC-derived G2-H cells acquired characteristics under the influence of livermicroenvironment. If transplanted into mouse liver again, these cells were not able to formteratomas. Therefore, we get a hepatocy-like cell by re-transplanting ESCs in mouse liver,while it keeps passage in long-term and do not generate teratomas.In conclusion, though ESCs are able to generate teratomas in liver, their tumorigenesiswill decline greatly with the affect of liver microenvironment. Combining the influence ofliver microenvironment and culture in vitro, it may induce ESCs into hepatocy-like cells thatcan passage for a long time and express hepatocy related protein, which suggests these cellshave less safety problems because of their low tumorigenesis.