Glycosylation Engineering Combined with CD26 Inhibitor Enhances Umbilical Blood Cells Engraftment In the NOD/SCID Mouse

Abstract 4687

Given the tremendous need for and potential of umbilical cord blood (UCB) to be utilized as a donor source for hematopoietic stem cell (HSC) transplantation in adults, there is a strong push to overcome the constraints created by the limited volumes and subsequent limited HSC and hematopoietic progenitor cell (HPC) numbers available for HSC transplantation from a single collection. Hematopoietic stem cell homing is believed to be critical for the development of methodologies to improve transplant efficiency and subsequently immune reconstitution during hematopoietic stem cell transplantation in clinical setting. We have previously described the functional defect of partial homing receptor in cord blood stem cell (the higher activity of CD26 and the lower expression of P/E-selectin ligand) in vitro. Respectively, we had confirmed that using of glycosylation engineering and CD26 inhibitor can fix the defect of stem cell homing. However, there is no evidence can prove whether the combination would improve the ability of homing. In present study, to explore the use of glycosylation combined with CD26 inhibitor as a method of improving the transplant efficiency of CB CD34⁺ hematopoietic stem cells (expressing CD45), we utilized the xenotransplanted nonobese diabetic/severe combined immunodeficient (NOD/SCID) mouse model in vivo. 6–8 weeks age of NOD/SCID mice were divided into 5 groups (8 mice per group): blank control group (without stem cells infusion); control group (CD34+ cells infusion alone); glycosylation engineering group; CD26 inhibitor group and combination group (glycosylation engineering combined CD26 inhibitor group). Purified CD34+ stem cells (5×10⁵ per mice) derived from fresh UCB by immunomagnetic beads were injected into lethally irradiated NOD/SCID mice intravenously. To investigate the effect of early engraftment in vivo, we monitored the expression of CD45 in peripheral blood and the overall viability rate weekly until the fourth week by flow cytometry. One week after transplantation, there is no expression of CD45 in peripheral blood in any group, but we observed 2.52±1.41% and 4.8% expression in bone marrow of recipient mice respectively in control and glycosylation engineering groups. All mice in the blank control group were dead and overall viability rate were almost the same for the other four groups (80% in control group,80% in glycosylation engineering group, 100% in CD26 inhibitor group and 100% in combination group). The second week, there is only expression of CD45 in recipient mice for combination group 0.63±0.37%. The overall survival rate among control were significantly lower than the other four groups (40% in control group,80% in glycosylation engineering group, 100% in CD26 inhibitor group and 100% in combination group, P<0.05). In the third week, all groups except the blank control group expressed CD45 in peripheral blood, we observed 0.81±0.12%, 2.81±0.14%, 3.12±0.53% and 7.05±0.87% in peripheral blood of recipient mice for control, glycosylation engineering, CD26 inhibitor treated and combination group. The overall survival rate among CD26 inhibitor treated and combination groups were significantly higher than the other three groups. (40% in control group,40% in glycosylation engineering group, 80% in CD26 inhibitor group and 80% in combination group, P<0.05). In the fourth week, we observed 15.87±0.21%, 30.51±0.62%, 34.33±0.82% and 40.22±1.62% in peripheral blood of recipient mice for control, glycosylation engineering, CD26 inhibitor treated and combination group. The overall survival rate among CD26 inhibitor treated and combination groups were significantly higher than the other three groups. (40% in control group,40% in glycosylation engineering group, 80% in CD26 inhibitor group and 80% in combination group, P<0.05). These results provide the evidence that the combination of two methods have better effect on early implantation than use them respectively. Our results also supported the potential use of CD26 inhibitor combined with glycosylation engineering to treat the umbilical blood which the number of stem cell is less than bone marrow and peripheral blood during hematopoietic stem cell transplantation as a method to improve the transplant efficiency. Furthermore, we aimed to investigate the long-term implantation effect of combination of glycosylation engineering and inhibition of CD26 in vivo.