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The aim of this study was to detect DNA damage during expansion ex vivo of umbilical cord blood (UCB) hematopoietic cells and explore the optimal harvest time for culture of CB hematopoietic cells. Mononuclear cells (MNCs) separated from UCB were cultured in a serum-free system supplemented with cytokines and colony forming units were assessed by semisolid culture at the same time. On day 0, 7, 14 and 21 cells were collected for single cell gel electrophoresis (SCGE) analysis and CFUs were also assayed by SCGE, CD34+ cells and CD133+ cells were quantitated by fluorescence-activated cell sorting (FACS). The results showed that the percentage of CD34+ and CD133+ cells was found to be highest after short-term culture (<14 days) and the cord blood DNA damage rate was observed to be less than 5.0% at earlier time points, but at day 21 the DNA damage rate was 28.2%, which was higher than that at day 0 (p=0.000), the tail length of the DNA comet was longer than that at day 0 (p=0.000). The tail lengths of DNA damage on other time points were not significantly different from that at day 0. It is concluded that the DNA damage rate is less than 5.0% after short-term (<14 days) culture of UCB cells ex vivo by using this method. After 14 days DNA damage rate increases significantly. The optimal harvest time of cord blood cells after culture ex vivo would be within 14 days.

The aim of this study was to expand hematopoietic progenitor cells at large scale by magnet stirred culture system. Mononuclear cell from umbilical cord blood were cultured in serum-free medium with stem cell factor, FIT-3 ligand and thrombopoietin. Firstly, the role of magnet on cell growth and colony-forming was studied by static culture on 0, 25 and 50 mT. Then the expansion multiple of cells, colony-forming and expression of surface markers were studied in magnet stirred culture by cell counting, colony-forming assay and flow cytometry. The results indicated that there was no difference in multiple of total cell expansion and numbers of hematopoietic colonies between 0, 25 and 50 mT groups and spinner groups (all p > 0.05). After 7 day cultures, the multiple of total cell expansion in magnet stirred culture was higher than that in static culture (p < 0.01). The numbers of CFU-GM (colony-forming unit-granulocyte/macrophage) and CFU-E (erythroid colony forming unit) in magnet stirred culture were higher than those in static culture, (p < 0.05). The primitive cells (CD34(+), CD34(+)/CD38(-) or CD133(+)) of the expanded cells in magnet stirred culture were less than those in static culture (p < 0.05). However, the CD184(+) or CD62L(+) expanded cells were more than that in static culture (p < 0.05). It is concluded that magnet stirred culture favors the expansion of hematopoietic progenitor cells. The results will be finally confirmed in further in vivo experiments and clinical applications.

To investigate whether lymphocyte function-associated antigen 1 (LFA-1) and very late antigen 4 (VLA-4) are involved in vasoendothelial adhesion and transendothelial migration of high proliferative potential endothelial progenitor cells (HPP-EPCs), flow cytometry was used to analyze the expression of integrin beta1 and beta2, the expression of intercellular adhesion molecule (ICAM-1, 2) and vascular cell adhesion molecule (VCAM-1) in mouse bone marrow endothelial cells (mBMECs). The adhesion and transmigration through endothelial cells of the HPP-EPCs blocked by functional grade neutralizing antibodies of VLA-4 and LFA-1 were studied in vitro. The results revealed that HPP-EPCs were positive for CD11a and CD49d in HPP-EPCs. The expression of ICAM-1and VCAM-1 of mBMECs increased after activated by IL-1beta and TNF-alpha. The results of adhesion in vitro revealed that the numbers of the adhered and migrated cells in the CD11a antibody group, in the CD49d antibody group and in the combinational antibody group were less than those in the isotype control antibody group. Furthermore, the number of adhered and migrated cells in the combinational antibody group was less than that in the CD11a or the CD49d antibody group (p < 0.05). It is concluded that both LFA-1 and VLA-4 are involved in vasoendothelial adhesion and transendothelial migration of HPP-EPCs.

The aim of this study was to establish the method of isolating and culturing endothelial progenitor cells (EPCs) from human umbilical cord blood. Mononuclear cells (MNCs) from human umbilical cord blood were cultured by using culture system supplemented with endothelial cell-conditioned medium. The obtained two types of cells were purified by picking up colonies, identified by uptake of acetylated low-density lipoprotein (Ac-LDL) and binding to lectin [Ulex European Agglatinin (UEA-1)], and were analyzed for the expression of markers by flow cytometry. The results showed that there were significant differences between two types of cells in proliferation, so they were referred as circulating angiogenic cells (CACs) and high proliferative potential endothelial progenitor cells (HPP-EPCs), respectively. They were in accordance with the standards of EPCs, could uptake DiI-Ac-LDL and bind to UEA-1, and expressed the markers of endothelial cells, such as CD31, CD144 and vWF detected by immunocytochemistry. The transcription of CD31, KDR, CD144 and ENOS in both of them could be detected by RT-PCR, but FACS analysis showed significant differences of surface marker expression between them. In conclusion, two types of EPCs are successfully obtained by culturing MNCs isolated from human umbilical cord blood using endothelial cell-conditioned medium.