The Influence Of Co-culture Ex Vivo Of CD34~+ Cells From Different Two Units Cord Blood On The Homing And Differentiation Ability Of Each Other

Background and objective Umbilical cord blood (UCB) is a good source of hematopoietic stem cells (HSC), but the numbers of HSC are relatively small thus limiting its application in adults. The successful treatment for leukemia with double units umbilical cord blood transplantation (UCBT) aroused the research on the mechanism of interaction between the two units UCB. Previous research revealed dominancy of one of two units from the day of engraftment and the interaction between the two units may exist. Our research is to explore the influence of co-culture ex vivo of CD34~+ cells from different two units UCB on the homing and differentiation ability of each other. Methods Mesenchymal stem cells (MSCs) were obtained from human bone marrow and their morphology and phenotype were identified. Double units CB CD34~+ cells were co-culture on 12Gy X-Gy irradiated MSC layer. Their homing ability (CD26, CD44, CD54, CD62L, CD162,CD184) and differentiation ability (CD33, CD41, CD71) were assessed respectively by flow cytometry, Results 1. Establishment and identification of MSC layer After cultured for 12days, MSC integrated of 70% to 80% with a whirlpool-like growth. Cells were transferred to the third passage and then phenotype was identified. CD90, CD105, CD166, CD29, CD44, CD13 and CD49e are highly expressed on MSC with no expression of CD14, CD34, CD31, CD45 and HLA-DR. 2. The homing ability change of each unit CD34~+ cells The purity of the isolated CD34~+ cells was (98.25±0.93)%.After co-culture on MSC layer for 6 days, the proportion of CD34~+ cells of each unit was dropped to (60.4±6.32)% and (60.2±5.12)% respectively, but there was no significant difference from the control groups. The expressions of CD26, CD44, CD62L and CD184 on CD34~+ cells of each unit remained unaffected. The expression of CD162 was downregulated and CD54 was first increased but then dropped to the level before co-culture. But there was no significant difference between the experimental and control groups. 2. The differentiation ability change of each unit CD34~+ cells During the co-culture, the expression of CD33 on CD34~+ cells of each unit was gradually decreased and CD41 remained a low lever, but CD71 was gradually upregulated. However, there was still no significant difference from the control groups. Conclusion Co-culture with two units CD34~+ cells may have no effects on the homing and differentiation ability of each other. Therefore, we suppose the interaction between cord bloods may not be induced by the interaction between the CD34~+ cells.