Applied Visualized Technology Of Atomic Force Microscope (AFM) In Stem Cell Research

Nowadays, atomic force microscopy (AFM) is more and more widely applied in the cell biological researches. On the other hand, stem cell research is on the front edge of life science in this century. In this study, AFM was applied to stem cell research. Some phenomena and mechanisms in cell biology which could not be done by other techniques were observed and discussed.In order to investigate the membrane surface ultrastructures of bone marrow CD34~+ hematopoietic stem cells (HSC), CD34~+ HSC from normal persons and leukemia patients were observed and compared by using AFM. With the region analysis function of IP2.1 software, the region of 2μm×2μm was selected and four parameters of the surface (maximum peak-to-valley distance, average roughness, root-mean-squared roughness and mean height) were measured. Values of the 4 parameters showed that the characteristic parameters of CD34~+ HSC from leukemia were higher than that of from normal person. It is concluded that AFM had specific advantages in analyzing the ultrastructure of CD34~+ HSC membrane from different source. Through the help of surface parameter analysis, AFM could be a helpful tool for fast leukemic diagnosis and CD34~+ HSC selection.In order to investigate the membrane morphologic change and its corresponding biologic signification during the differentiation of ES cells under the control of cell growth factors in vitro, the ES cell line mouse BALB/c was cultured and directional induced by Hepatocyte Growth factor (HGF) and Epidermal Growth factor (EGF). The cells' membrane morphologic changes in different period of such process were detected by AFM. Combined with the biological technologies of immunocyto--chemistry (ICC) , FACS, RT-PCR and transmission electron microscopy, we confirmed that the midterm phase of hepatic oval cells do occur during the course of the directional induction and differentiation of mouse embryonic stem cells into hepatic parenchyma cells for the first time. The contrast of the differentiation ratio ofhepatic oval cell between the induced group and the control group was significant, and the former was higher than the latter. Compared the structure parameter of cells' membrane in different phase during differentiation, we found that the roughness of the hepatic oval cells' membrane were decreased obviously. Such phenomena presumed that the membrane receptors of the hepatic oval cells were decreasing. AFM could visualize the quantitative changes of the membrane receptors, and reflect the developmental process of the stem cell in a direct way. AFM has extended the techniques of stem cell research and been propitious to the development of cell biologic theory and technology.Furthermore, with the help of ultra thin section technology, zoning scan and computer software analysis, this study has preliminarily solved two difficult problems during applied AFM in cell biological researches—the unobtaining of inner structure and the restriction of scanning range.