Objective     To investigate the effect of human umbilical cord blood-derived stromal cells (hUCBDSCs) on early homing efficiency and engraftment capability of hematopoietic cells.       Methods     CCK-8 method and Transwell method were utilized to compare the effects

of hUCBDSCs and human bone marrow stromal cells (hBMSCs) on

in vitro

adhesion and migration capability of human umbilical cord blood-mononuclear cells (hUCB-MNCs). RT-PCR assay was employed to detect the expression of homing-associated factors in hUCBDSCs. BABL/c mice were irradiated by

60

Co γ-ray at a lethal dose

and then hUCB-MNCs were transplanted into some of the BABL/c mice alone and into others in combination with hUCBDSCs or hBMSCs. The engraftment rates of human CD45

+

cells in mouse bone marrow were measured by flow cytometry. The

in vivo

  migration of CM-DiI-labeled hUCB-MNCs after transplantation was traced

and homing rates were compared accordingly.     Results     Both hUCBDSCs and hBMSCs promoted the adhesion of hUCB-MNCs and significantly enhance the migration of hUCB-MNCs (

P

<

0.05). The hUCBDSCs expressed a series of homing-associated adhesion molecules and cytokines

and increased the engraftment rate of hUCB-MNCs

particularly when hUCB-MNCs were transplanted at a low dose (2×10

6

hUCB-MNCs and 2×10

6

hUCBDSCs per mouse) (P

<

0.01). The CM-DiI-labeled hUCB-MNCs mainly homed to the bone marrow and spleen

in vivo

. The hUCB-MNCs showed a higher homing rate when transplanted in combination with hUCBDSCs than when transplanted alone or in combination with hBMSCs at 48 h after transplantation [(43.49±3.06)%

vs

(31.99±7.26)% and (21.46±6.88)%

]

(

P

<

0.05).      Conclusion      hUCBDSCs can effectively promote the migration

homing

and engraftment of hUCB-MNCs.