| Stem cells are self-renewing, unspecialized cells that can give rise to multiple types of all specialized cells of the body. Stem cells can be obtained from the embryo, the fetus and the adult. The importance of research in stem cell lies in two aspects. First, for basic research purposes, it is important to understand the genetic and molecular basis by which these cells continue to make many copies of themselves over long periods of time. Second, if the cells are to be manipulated and used for transplantation, it is important to have sufficient quantities of cells that can be directed to differentiate into the desired cell type(s) and used to treat the many patient that may be suffering from a particular disease. Directed differentiation is the key for research and application of stem cell.Cranial neural crest-derived ecto-mesenchymal cells may be pluripotent stem cells which can give rise to odontoblasts, pulp cells, osteoblasts and chondrocytes forming the oro-facial tissues. In vivo experimental approaches have reinforced this view, but only limited information on cell lineage diversity is available from in vitro experiments. The fate of the ecto-mesenchyme appears to be determined in part by intrinsic genetic programs and also, by the influence of extracellular signals in the local environment. A number of studies have demonstrated the multipotency of cranial neural crest in vivo and in vitro and the potential role of growth factors in signaling cell fate. Respectively, neural crest cell had been induced to differentiate to neuron by BMP-2/4, to glial cellby GGF, to smooth muscle cell by TGFP 1,2,3 in vitro. The ecto-mesenchymal cells may have the potency to differentiate into most cell types of oro-facial tissues.Normal human cells exhibit a limited replicative potential, eventually succumbing to senescence in vitro. The catalytic subunit of telomerase (human telomerase reverse transcriptase, hTERT), the enzyme that elongates telomeres, has been implicated as an important participant in the immortalization process. In general, human somatic cells have little or no hTERT expression or telomerase activity. In rare cells which overcome crisis and become immortal, the hTERT gene and telomerase usually are spontaneously up-regulated and telomere shorting is arrested. So far, hTERT is the most safety gene for immortalization. Ecto-mesenchymal stem cell immortalized by transfecting hTERT gene can overcome the shorting of cell for research and application purposes.The aim of the present study was to test the hypothesis that ecto-mesenchymal stem cells of the first branchial arch show properties of pluripotent stem cells, the lineage of which may be directed by specific molecular signaling, and to establish the immortalized ecto-mesenchymal stem cells by transfecting hTERT gene. Part 1, Culture and identification of undifferentiated ecto-mesenchymal stem cells isolated from the first branchial arch of human embryo.Ecto-mesenchymal stem cells were enzymatically isolated from the first branchial arch of human embryo for 50 days and maintained in an undifferentiated state whilst cultured with leukemia inhibitor factor (LIF). Immunocytochemistry assay was used to identify the source and the state of ecto-mesenchymal stem cells. The cells expressed HNK-1, which is the marker.of migrating neural crest cell. Also Vimentin was expressed. FactorVIII was expressed weakly. Cells didn't expressed NF, GFAP, a -SMA and CK. The evidence suggests that the cells cultured were undifferentiatedecto-mesenchymal stem cells.Part 2, Spontaneously differentiation of ecto-mesenchymal stem cells.Undifferentiate state of stem cell was maintained by inhibitor. Stem cells will differentiate spontaneously without inhibitor. 2 days after being omitted LIF, about 65% cells spontaneously differentiated to smooth muscle cells. 2 weeks later, about 1% cells expressed neural filament and few cells expressed GFAP. That meant EMSC had high tendency to differentiate spontaneously to smooth muscle cell. Injected ecto-m...
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