Expansion of cord blood CD34+hematopoietic progenitor cells in coculture with autologous umbilical vein endothelial cells (HUVEC) is superior to cytokine-supplemented liquid culture

Expansion of hematopoietic progenitor cells ( HPC) in the presence of endothelium has been shown to result in grafts capable of restoring hematopoiesis in a myeloablated host. However, the use of xenogeneic endothelium or cell lines may carry risks in a clinical transplantation setting. We explored the feasibility of cord blood progenitor cell expansion in vitro in an autologous coculture system using umbilical vein endothelial cells ( HUVEC). CD34 + HPC and HUVEC were isolated from the same umbilical cord. For 3 days, HPC were maintained in serum- free medium supplemented with a single cytokine ( SCF) or a cytokine combination ( SCF, Flt3- ligand, IL- 6). Meanwhile, adherent HUVEC cultures were established. After addition of VEGF and IL- 1 at day 3, the cells were either added to HUVEC cultures or grown without endothelial cells for further 7 days. Total cells, CD34 + and clonogenic progenitors were significantly increased when coculture was compared to liquid culture. Long- term culture-initiating cells ( LTC- IC) and cobble stone area- forming cells ( CAFC, limiting dilution analysis) were detected more frequently after coculture with endothelial cells. Also precursors and mature myeloid cells were observed after expansion. We conclude that coculture with autologous HUVEC represents a feasable approach for ex vivo expansion of cord blood HPC.