| Human mesenchymal stem cells(MSCs) are thought to be multipotent cells, which are present in adult bone marrow, that can replicate as undifferentiated cells and that have the potential to differentiate to lineages of mesenchymal tissues, including bone, cartilage, fat, tendon, muscle, and marrow stroma. The isolation, expansion, and characterization of MSCs have been reported recently. With the development of histocell engineering and genetic engineering, many research has focused on the appliance of multi-differentiating potential of MSCs in histoengineering, gene therpy and organ transplanting. However, little research has been done about the function of MSCs in blood vesselengineering and the relationship between MSCs and endothelial cells.MSCs have phenotype of endothelial cells in some extent, so it is important to characterize MSCs in culture,expandition and differentiation, which will give advantage to some disease related to endothelial cells, but also bring great changes to blood vesselengineering. MSCs have some characteristics and advantages as seeding cells in blood vesselengineering: ①It was convenient to draw the materials and lightly injure, which avoided of unnecessary second trauma on the patients; ②The autologous expanded MSCs had no histocompatibility when induced to ECs; ③The proliferation of mature EC was limited and had the tumorigenic tendency of de-differentiation. MSCs had the highly ability of proliferation and maintained un-differentiation on 25 passages on the condition of no inducer. Meanwhile, MSCs had immunoregulation and no occurrence of tumor in Vivo; ④The degraded artificial synthetic materials such as PGA, PLA, PLLA binding with MSCs, which bring about the surprising prospect of application for the vessel-tissue engineering. Therefore, MSCs became a novel seeding cells, exploring the mechanism of EC differentiation possessed the important theory sense.The initiation and process of cell differentiation procedures is the result of orderly opening and shut-off of multi-genes or regulation of gene expression, which is also influenced by the interaction between cell and cell as well as cell and extracellar matrix. Cytokines play an important role in signal transduction between cell and cell as well as cell and extracellar matrix. Flt-1/VEGF and Flk-1/VEGF systems are important in endothelial cells proliferation, differentiation,migration and tube formation. Changes of extracellar matrix may also affects MSCs, differentiation because certain message exocell will be convested to stem cell by extracellar matrix, which will trigger transmembrane signal conduction and control some gene expression. Such process may not only alter stem cell,s cleavage manier, but also activate stem cell,s multipotent to differentiate to committed progenitor. To examine roles of VEGF on MSCs differentiation to endothelial cells, immunofluorescence, whole cell patch clamp technology, Bodyen chamber technology, tube formation in vitro, confocal laser scanning microscopy real-time monitoring and three-dimension figures recombination were used to study the actions in morphology, cell biology and electric physiology. To investigate MSCs differentiation mechanisms and identify differentially expressed genes between MSCs and endothelial cells, especially specified genes expressed in endothelial cells, a cDNA subtractive library of endothelial cells was constructed using suppression subtractive hybridization (SSH) technique.Results:1.Cells that have the characteristics of human mesenchymal stem cells were isolated from bone marrow aspirates of volunteer donors using density gradient and adherence to plastic dishes method combined with sieve filtering technique, which eliminate unwanted big and flat cells and keep undifferentiation state to highly homologous population. Different from obvious research, the mesenchymal cells were negative for CD29 .MSCs comprised a single phenotypic population (93.26±2.48%) by flow cytometric analysis of expressed surface antigens CD44 indicating...
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