OBJECTIVETo compare the in vivo homing potential of human hematopoietic stem/progenitor cells (HS/PCs) derived from fresh umbilical cord blood (UCB), cryopreserved UCB, mobilized peripheral blood (mPB) and bone marrow (BM) in xenotransplanted NOD/SCID mouse model, and to explore the relationship between the homing potential of HS/PCs and their expression levels of membrane receptor CXCR4.

METHODSThe expression levels of membrane CXCR4 on HS/PCs were assessed by flow cytometric analysis (FACS). CFSE-labeled human HS/PCs from different sources were transplanted into irradiated NOD/SCID mice. Human CD34 cells home in bone marrow and spleen of recipient mice were determined 20 hours after xenotransplantation by FACS and the homing efficiencies were calculated. Tissue sections of the recipient mice femurs were made and the distribution of CFSE-labeled human CD34 cells were observed under fluorescence microscope.

RESULTSThe expression levels of membrane CXCR4 on CD34+ cells from fresh UCB, cryopreserved UCB, mPB and BM were (49.52 +/- 1.12)%, (46.12 +/- 2.29)%, (48.50 +/- 2.48)% and (65.39 +/- 1.27)%, respectively. The homing efficiencies of CD34+ cells from fresh UCB, cryopreserved UCB, mPB and BM in recipient mice BM were (3.00 +/- 0.44)%, (2.84 +/- 0.46)%, (4.06 +/- 0.70)% and (5.76 +/- 0.52)% , respectively. Human CD34+ cells mainly located within endosteal region of recipient mice femurs.

CONCLUSIONCD34+ cells from UCB express lower levels of membrane CXCR4 than those from mPB and BM. The level of membrane CXCR4 on UCB CD34+ cells is down-regulated after freezing and thawing procedures. The homing efficiency of human CD34 cells from UCB in recipient mice is lower than that of mPB and BM.