BACKGROUND :
We examined an ex vivo expansion system for cord blood (CB) hematopoietic progenitor cells, which is based upon a co-culture of CD34+cells with human umbilical endothelial cells (HUVECs) in the presence of stromal cell-derived factor-1 (SDF-1) and hematopoietic growth factors.
METHODS :
Cord blood CD34+cells were either incubated a liquid suspension culture or co-cultured on HUVEC monolayers with hematopoietic growth factors in the presence or absence of SDF-1. After 7~14 days of culture, cells were harvested and analyzed for fold- increase in nucleated cells, CD34+ cells, and colony-forming cells (CFCs) and apoptosis.
RESULTS : Seven-day suspension culture of CD34+ cells in the presence of a cytokine combination consisting of throbmopoietin, flk-2 ligand, and kit-ligand (TFK) led to a 43-fold increase of nucleated cells, a 19-fold increase of CD34+ cells, and 14-fold increase of CFCs, respectively. The addition of SDF-1 to TFK slightly further increased this expansion. A co-culture of CD34+ cells with HUVECs significantly enhanced the expansion of both CD34+ cells and CFCs compared with a liquid suspension culture. This was further increased by the addition of SDF-1. A co-culture of CD34+ cells on HUVECs transfected with null-adenoviral vector led to a better fold increase of haemtopoietic progenitor cells compared with a culture with non-transfected HUVECs. Adding SDF-1 to the co-culture diminished the annexn V- positive cells both in the supernatant and adherent cell layers.
CONCLUSION :
A co-culture of cord blood cells with HUVECs in the presence of hematopoietic growth factors and SDF-1 could be a new model for the efficient expansion of hematopoietic progenitors.

Keywords: Cord blood, Hematopoietic progenitor cells, Ex vivo expansion, Human umbilical endothelial cells, Co-culture