OBJECTIVETo explore the potential of human bone marrow stromal cells (MSCs) as the feeding-layer to promote ex vivo expansion of cord blood CD34+ cells and engraftment of the expanded cells in NOD/SCID mice.

METHODSHuman MSCs were routinely isolated and cultured. MSCs at passage 3 were used as feeding-layer for the expansion of cord blood CD34+ cell in the presence of thrombopoietin (TPO), flt3/flk2 ligand (FL), stem cell factor (SCF) and granulocyte-colony stimulating factor (G-CSF). The engraftment potential between unexpanded and expanded cord blood cells transplanted into NOD/SCID mice was compared.

RESULTSThe total nucleated cells (TNC), CD34 cells and colony forming units (CFUs) in the MSC feeding culture were increased by 111.6-, 19.3- and 58-fold after 1 week expansion and 532.8-, 41.3- and 563.5- fold increased after 2 weeks expansion respectively as compared with that in non MSC feeding culture. In transplant experiment, the percentage of human CD45+ cells (45.3% -59.1%) in bone marrow of recipient mice transplanted with the MSC feeding expanded cells was the highest in all the groups at six weeks after transplantation.

CONCLUSIONHuman MSCs enhance CB CD34+ cells in vitro expansion and their capacity of short-term engraftment in NOD/SCID mice.