Hemostimulating effects of umbilical blood
The aim of this study was to develop an experimental cultural model for detecting and evaluating the type of colony stimulating activity of the umbilical blood (UB) cell fraction. Immunophenotyping has shown polymorphic cell composition of the studied UB monolayer cell cultures, different in each specimen. Hemopoietic cells with CD45+ phenotype predominate in the majority of samples. In addition, cells phenotypically similar to endotheliocytes, hemopoietic stem cells (HSC), and mesenchymal stem cells (MSC) are sometimes present in different concentrations. Our data indicate that the monolayer culture of UB adhesive cell fraction is characterized by hemostimulating effects comparable to those of the standard leukocytic feeder, which confirms the hemostimulating activity of UB monolayer cell culture in this model. Analysis of the relationship between the UB cell monolay er colony stimulating activity and cell composition showed a positive correlation between the percentage of cells with CD45+ and CD14+ phenotype, on the one hand, and capacity of the granulocytic/macrophagal precursors to form large colonies (CFU GM) in a monolayer, on the other hand (r=0.703, p=0.035 and r=0.67, p=0.049, respectively). It was noted that cell population with CD45+CD61+ phenotype (presumably osteoclasts) also stimulated the proliferative potential of CFU GM (r=0.667, p=0.05). No colony stimulating effects of other populations of UB blood, such as HSC (CD34+CD45+, CD34+HLA DR , CD117+) or lympho cytes (CD3+, CD19+), were detected for this model. Of the cells belonging to nonhemopoietic cell fraction, CD90+CD31 cells (phenotype intrinsic of MSC) exhibited a positive effect on the colony stimulating activity of UB monolayer cell culture. Hence, UB cell culture is characterized by hemostimulating activity, its intensity being determined primarily by the phenotypical characteristics of cells among which the mesenchymal precursors and macrophages play the main role, releasing growth factors essential for the proliferation of CFU GM.