OBJECTIVETo investigate the role of endothelial progenitor cell (EPC) injection in the restoration of vascular niche in bone marrow (BM) after allo-BMT in mice, and to observe its role on hematopoietic reconstitution.

METHODS6-8 weeks old female BALB/c (H-2(d)) were randomized to BMT (allo-BMT) group and combined EPC transplant (allo-BMT + EPC) group. For allo-BMT group, female BALB/c mice were lethally irradiated with 60Co source, and then were injected intravenously with 5×10(6) BM cells from donor mice. In allo-BMT + EPC group, recipient mice were injected intravenously with 5×10(6) BM cells and 5×10(5) EPC from donor mice. The recipients were monitored for histological changes of endothelial cells (EC) in BM. The recovery of hematopoiesis was determined by white blood cell counts and the proportion of reticulocytes in circulation and the proportion of hematopoietic stem cells (HSC) in BM. The histology of hematopoiesis in BM was also detected.

RESULTSThe in vitro induced EPC successfully homed to the bone marrow of recipients. The ECs of allo-BMT recipients were destructed severely, while the structures of ECs were restored in EPC treated recipients. 10 and 15 days after allo-BMT, the amount of Lin-c-kit(+)Sca-1(+) cells in the BM of the EPC treated group were (20.31 ± 2.65)×10(3) per mouse and (10.26 ± 2.19)×10(3) per mouse, while the allo-BMT group's were (9.61 ± 0.98)×10(3) per mouse and (4.09 ± 1.34)×10(3) per mouse; and 15 days after allo-BMT, the amount of white blood cell counts and proportion of reticulocytes of the EPC treated group were (1.20 ± 0.11)×10(9)/L and (2.35 ± 0.30)% comparing to the allo-BMT group which were (0.65 ± 0.10)×10(9)/L and (1.63 ± 0.20)%.

CONCLUSIONCo-transfer of donor EPC restores the ECs of bone marrow, which consequently promotes hematopoietic reconstitution in murine allo-BMT.