Bone tissue engineering is considered as one of the most promising way to treat large segmental bone defect. When constructing bone tissue engineering graft in vitro, suitable bioreactor is usually used to incubate cell-scaffold complex under perfusion to obtain bone tissue engineering graft with good repair efficiency. However, the theoretical model for growth rate of single cell (especially for stem cell) during this process still has many defects. The difference between stem cells and terminally differentiated cells is always ignored. Based on our previous studies, this study used self-made perfusion apparatus to apply different modes and strengths of fluid shear stress (FSS) to the cells seeded on scaffolds. The effects of FSS on the proliferation and osteogenic differentiation of mesenchymal stem cells (MSCs) were investigated. The regression analysis model of the effect of FSS on the single-cell growth rate of MSCs was further established. The results showed that 0.022 5 Pa oscillatory shear stress had stronger ability to promote proliferation and osteogenic differentiation of MSCs, and the growth rate of a single MSC cell under FSS was modified. This study is expected to provide theoretical guidance for optimizing the perfusion culture condition of bone tissue engineering grafts in vitro.
Objective To study the effects of pcDNA3/AFP/TK/Angio fusion gene targeting therapy for human primary liver cancer in nude mice implanted with SMMC-7721. Methods Human liver cancer cell line SMMC-7721 was implanted subcutaneously in nude mice to establish experiment model. Animals bearing liver cancer were randomly divided into five groups: control group， vector group， GCV (ganciclovir) group， pcDNA3/TK/Angio group; pcDNA3/AFP/TK/Angio group. Different plasmids were directly injected into tumors and GCV was intraperitoneally administrated simultaneously according to different groups. The growth of tumors was observed and the pathology was examined as well. Serum AFP level was measured by radioimmunology, the ultrastructural change of tumor cells was studied by using electron microscopy, the expressions of MVD and VEGF were respectively detected with immunohistochemistry and the cell apoptosis in situ was detected by TUNEL. Results The success rate to establish subcutaneous implanted liver cancer model in nude mice was 100%. The tumor volume, serum AFP level, VEGF and MVD expressions of pcDNA3/TK/Angio group and pcDNA3/AFP/TK/Angio group were lower than those in control group, vector group and GCV group (P＜0.05) and more apoptosis cells could be observed. While the tumor volume, serum AFP level, VEGF and MVD expressions of pcDNA3/AFP/TK/Angio group was lower than those in pcDNA3/TK/Angio group (P＜0.05); and apoptosis index was higher than that of the latter (P＜0.05).Conclusion pcDNA3/AFP/TK/Angio fusion gene inhibits the growth of tumor remarkably and becomes a promising new biological agent to treat human primary liver cancer.