Text Box: ENHANCED HEMATOPOIETIC STEM CELL ENGRAFTMENT IN ADULT MURINE RECIPIENTS BY SEQUENTIAL NEAR-TERM FETAL AND NEONATAL MURINE PERIPHERAL BLOOD TRANSPLANTATION Xu H-G, Fang J-P, Huang S-L, Wei Q, Huang W-G, Mai H-R Hematopoietic Stem Cell Transplantation Center, Department of Pediatrics, Sun Yat-sen Memorial Hospital, Guangzhou, China Objective: To explore a more practical and useful method in the engraftment with a murine model of unrelated umbilical cord blood transplantation (UR-UCBT). Methods: Adult BALB/c （H-2d）mice were transplanted intravenously after the regimen of cyclophosphamide (380mg/Kg ip) with near-term fetal and neonatal murine peripheral blood (FNPB) form C57BL/6 （H-2b）mice either a total nucleated cells transfused in one time (single transplantation group, SiTG) or the same or lower nucleated cells in 4 consecutive days (sequential transplantation group,SqTG). The biology of FNPB was evaluated, and the survival rate, hematopoietic and immunological reconstruction, flow cytometric chimeric analysis and graft versus host disease (GVHD) were compared between two groups. Results: The percentage of Sca-1+CD34－cells in FNPB (15.5±4.0%) was higher than that in BM (9.2±4.8%) (p=0.02) ,and the number of CFU-GEMM in FNPB was about twofold higher than that in BM (40.6±10.2/2×105MNC vs 22.0±9.8/2×105MNC, p<0.05). Both the SqTG by 4×0.125×106 FNPBs and SiTG by 1×106 FNPBs had the near survival rate (27% vs 30%), but much lower than that of SqTG by 4×0.25×106 FNPBs (56%). Moreover, the recovery of peripheral WBC and PLT, the reconstitution of hematopoietic and immunological function of SiTG were also delayed than that in SqTG by 4×0.25×106 FNPBs. Flow cytometric chimeric analysis demonstrated the engraftment of donor cells. Acute GVHD was absent in two groups. Conclusion: The results suggest that Murine FNPB grafts were an ideal animal model for UR-UCBT. Sequential FNPB transplantation has enhanced the engraftment, which may be helpful to improve the clinical outcome of UCBT.

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