Abstract
With their properties of self-renewal and differentiation, embryonic stem (ES) cells hold great promises for regenerative therapy. However, teratoma formation and ethical concerns of ES cells may restrict their potential clinical applications. Currently, parthenogenetic embryonic stem (pES) cells have attracted the interest of researchers for its self-renewing and pluripotent differentiation while eliciting less ethic concerns. In this study, we established a model with ES and pES cells both stably transfected with a double-fusion reporter gene containing renilla luciferase (Rluc) and red fluorescent protein (RFP) to analyze the mechanisms of teratoma formation. Transgenic Vegfr2-luc mouse, which expresses firefly luciferase (Fluc) under the promoter of vascular endothelial growth factor receptor 2 (Vegfr2-luc), was used to trace the growth of new blood vessel recruited by transplanted cells. Bioluminescence imaging (BLI) of Rluc/Fluc provides an effective tool in estimating the growth and angiogenesis of teratoma in vivo. We found that the tumorigenesis and angiogenesis capacity of ES cells were higher than those of pES cells, in which VEGF/VEGFR2 signal pathway plays an important role. In conclusion, pES cells have the decreased potential of teratoma formation but meanwhile have similar differentiating capacity compared with ES cells. These data demonstrate that pES cells provide an alternative source for ES cells with the risk reduction of teratoma formation and without ethical controversy.
Highlights
embryonic stem (ES) cells are unique among all stem cell populations owing to their high pluripotency and differentiation capacity, which makes them one of the most promising cells for regenerative medicine [1, 2]
The parthenogenetic embryonic stem (pES) cell lines are similar to ES cells in terms of proliferation, expression of pluripotency markers, and capacity to differentiate into several cell lines including tenocyte-like cells [11], osteogenic cells [12], and neural cells [12]
The expression of red fluorescent protein (RFP) in reporter gene-labeled cells was observed with an inverted fluorescence microscope; the activity of renilla luciferase (Rluc) in these cells was measured by bioluminescence imaging (BLI)
Summary
ES cells are unique among all stem cell populations owing to their high pluripotency and differentiation capacity, which makes them one of the most promising cells for regenerative medicine [1, 2]. Parthenogenetic embryonic stem (pES) cells have attracted the interest of researchers for their pluripotent differentiation without ethical issues [8]. These cells can be derived from embryos resulted from artificial activation of oocytes without fertilization [9, 10]. Monitoring the processes of teratoma angiogenesis may provide novel approach for inhibiting the formation of teratoma and direct future clinical translational application of pES cells. We developed a teratoma model to monitor the behavior of pES and ES cells in transgenic mice by molecular imaging. Molecular imaging provides the possibility to visually monitor the cellular processes after transplantation, including proliferation and angiogenesis. Transgenic Vegfr2-luc mice expressing Fluc under the promoter of Vegfr2-luc allow us to capture and quantify teratoma angiogenesis in vivo
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