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.